[platform/upstream/btrfs-progs.git] / cmds-check.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <getopt.h>
#include <uuid/uuid.h>
#include "ctree.h"
#include "volumes.h"
#include "repair.h"
#include "disk-io.h"
#include "print-tree.h"
#include "task-utils.h"
#include "transaction.h"
#include "utils.h"
#include "commands.h"
#include "free-space-cache.h"
#include "free-space-tree.h"
#include "btrfsck.h"
#include "qgroup-verify.h"
#include "rbtree-utils.h"
#include "backref.h"
#include "kernel-shared/ulist.h"
#include "hash.h"
#include "help.h"

enum task_position {
        TASK_EXTENTS,
        TASK_FREE_SPACE,
        TASK_FS_ROOTS,
        TASK_NOTHING, /* have to be the last element */
};

struct task_ctx {
        int progress_enabled;
        enum task_position tp;

        struct task_info *info;
};

static u64 bytes_used = 0;
static u64 total_csum_bytes = 0;
static u64 total_btree_bytes = 0;
static u64 total_fs_tree_bytes = 0;
static u64 total_extent_tree_bytes = 0;
static u64 btree_space_waste = 0;
static u64 data_bytes_allocated = 0;
static u64 data_bytes_referenced = 0;
static LIST_HEAD(duplicate_extents);
static LIST_HEAD(delete_items);
static int no_holes = 0;
static int init_extent_tree = 0;
static int check_data_csum = 0;
static struct btrfs_fs_info *global_info;
static struct task_ctx ctx = { 0 };
static struct cache_tree *roots_info_cache = NULL;

enum btrfs_check_mode {
        CHECK_MODE_ORIGINAL,
        CHECK_MODE_LOWMEM,
        CHECK_MODE_UNKNOWN,
        CHECK_MODE_DEFAULT = CHECK_MODE_ORIGINAL
};

static enum btrfs_check_mode check_mode = CHECK_MODE_DEFAULT;

struct extent_backref {
        struct rb_node node;
        unsigned int is_data:1;
        unsigned int found_extent_tree:1;
        unsigned int full_backref:1;
        unsigned int found_ref:1;
        unsigned int broken:1;
};

static inline struct extent_backref* rb_node_to_extent_backref(struct rb_node *node)
{
        return rb_entry(node, struct extent_backref, node);
}

struct data_backref {
        struct extent_backref node;
        union {
                u64 parent;
                u64 root;
        };
        u64 owner;
        u64 offset;
        u64 disk_bytenr;
        u64 bytes;
        u64 ram_bytes;
        u32 num_refs;
        u32 found_ref;
};

#define ROOT_DIR_ERROR          (1<<1)  /* bad ROOT_DIR */
#define DIR_ITEM_MISSING        (1<<2)  /* DIR_ITEM not found */
#define DIR_ITEM_MISMATCH       (1<<3)  /* DIR_ITEM found but not match */
#define INODE_REF_MISSING       (1<<4)  /* INODE_REF/INODE_EXTREF not found */
#define INODE_ITEM_MISSING      (1<<5)  /* INODE_ITEM not found */
#define INODE_ITEM_MISMATCH     (1<<6)  /* INODE_ITEM found but not match */
#define FILE_EXTENT_ERROR       (1<<7)  /* bad FILE_EXTENT */
#define ODD_CSUM_ITEM           (1<<8)  /* CSUM_ITEM error */
#define CSUM_ITEM_MISSING       (1<<9)  /* CSUM_ITEM not found */
#define LINK_COUNT_ERROR        (1<<10) /* INODE_ITEM nlink count error */
#define NBYTES_ERROR            (1<<11) /* INODE_ITEM nbytes count error */
#define ISIZE_ERROR             (1<<12) /* INODE_ITEM size count error */
#define ORPHAN_ITEM             (1<<13) /* INODE_ITEM no reference */
#define NO_INODE_ITEM           (1<<14) /* no inode_item */
#define LAST_ITEM               (1<<15) /* Complete this tree traversal */
#define ROOT_REF_MISSING        (1<<16) /* ROOT_REF not found */
#define ROOT_REF_MISMATCH       (1<<17) /* ROOT_REF found but not match */
#define DIR_INDEX_MISSING       (1<<18) /* INODE_INDEX not found */
#define DIR_INDEX_MISMATCH      (1<<19) /* INODE_INDEX found but not match */
#define DIR_COUNT_AGAIN         (1<<20) /* DIR isize should be recalculated */

static inline struct data_backref* to_data_backref(struct extent_backref *back)
{
        return container_of(back, struct data_backref, node);
}

static int compare_data_backref(struct rb_node *node1, struct rb_node *node2)
{
        struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
        struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
        struct data_backref *back1 = to_data_backref(ext1);
        struct data_backref *back2 = to_data_backref(ext2);

        WARN_ON(!ext1->is_data);
        WARN_ON(!ext2->is_data);

        /* parent and root are a union, so this covers both */
        if (back1->parent > back2->parent)
                return 1;
        if (back1->parent < back2->parent)
                return -1;

        /* This is a full backref and the parents match. */
        if (back1->node.full_backref)
                return 0;

        if (back1->owner > back2->owner)
                return 1;
        if (back1->owner < back2->owner)
                return -1;

        if (back1->offset > back2->offset)
                return 1;
        if (back1->offset < back2->offset)
                return -1;

        if (back1->found_ref && back2->found_ref) {
                if (back1->disk_bytenr > back2->disk_bytenr)
                        return 1;
                if (back1->disk_bytenr < back2->disk_bytenr)
                        return -1;

                if (back1->bytes > back2->bytes)
                        return 1;
                if (back1->bytes < back2->bytes)
                        return -1;
        }

        return 0;
}

/*
 * Much like data_backref, just removed the undetermined members
 * and change it to use list_head.
 * During extent scan, it is stored in root->orphan_data_extent.
 * During fs tree scan, it is then moved to inode_rec->orphan_data_extents.
 */
struct orphan_data_extent {
        struct list_head list;
        u64 root;
        u64 objectid;
        u64 offset;
        u64 disk_bytenr;
        u64 disk_len;
};

struct tree_backref {
        struct extent_backref node;
        union {
                u64 parent;
                u64 root;
        };
};

static inline struct tree_backref* to_tree_backref(struct extent_backref *back)
{
        return container_of(back, struct tree_backref, node);
}

static int compare_tree_backref(struct rb_node *node1, struct rb_node *node2)
{
        struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
        struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
        struct tree_backref *back1 = to_tree_backref(ext1);
        struct tree_backref *back2 = to_tree_backref(ext2);

        WARN_ON(ext1->is_data);
        WARN_ON(ext2->is_data);

        /* parent and root are a union, so this covers both */
        if (back1->parent > back2->parent)
                return 1;
        if (back1->parent < back2->parent)
                return -1;

        return 0;
}

static int compare_extent_backref(struct rb_node *node1, struct rb_node *node2)
{
        struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
        struct extent_backref *ext2 = rb_node_to_extent_backref(node2);

        if (ext1->is_data > ext2->is_data)
                return 1;

        if (ext1->is_data < ext2->is_data)
                return -1;

        if (ext1->full_backref > ext2->full_backref)
                return 1;
        if (ext1->full_backref < ext2->full_backref)
                return -1;

        if (ext1->is_data)
                return compare_data_backref(node1, node2);
        else
                return compare_tree_backref(node1, node2);
}

/* Explicit initialization for extent_record::flag_block_full_backref */
enum { FLAG_UNSET = 2 };

struct extent_record {
        struct list_head backrefs;
        struct list_head dups;
        struct rb_root backref_tree;
        struct list_head list;
        struct cache_extent cache;
        struct btrfs_disk_key parent_key;
        u64 start;
        u64 max_size;
        u64 nr;
        u64 refs;
        u64 extent_item_refs;
        u64 generation;
        u64 parent_generation;
        u64 info_objectid;
        u32 num_duplicates;
        u8 info_level;
        unsigned int flag_block_full_backref:2;
        unsigned int found_rec:1;
        unsigned int content_checked:1;
        unsigned int owner_ref_checked:1;
        unsigned int is_root:1;
        unsigned int metadata:1;
        unsigned int bad_full_backref:1;
        unsigned int crossing_stripes:1;
        unsigned int wrong_chunk_type:1;
};

static inline struct extent_record* to_extent_record(struct list_head *entry)
{
        return container_of(entry, struct extent_record, list);
}

struct inode_backref {
        struct list_head list;
        unsigned int found_dir_item:1;
        unsigned int found_dir_index:1;
        unsigned int found_inode_ref:1;
        u8 filetype;
        u8 ref_type;
        int errors;
        u64 dir;
        u64 index;
        u16 namelen;
        char name[0];
};

static inline struct inode_backref* to_inode_backref(struct list_head *entry)
{
        return list_entry(entry, struct inode_backref, list);
}

struct root_item_record {
        struct list_head list;
        u64 objectid;
        u64 bytenr;
        u64 last_snapshot;
        u8 level;
        u8 drop_level;
        struct btrfs_key drop_key;
};

#define REF_ERR_NO_DIR_ITEM             (1 << 0)
#define REF_ERR_NO_DIR_INDEX            (1 << 1)
#define REF_ERR_NO_INODE_REF            (1 << 2)
#define REF_ERR_DUP_DIR_ITEM            (1 << 3)
#define REF_ERR_DUP_DIR_INDEX           (1 << 4)
#define REF_ERR_DUP_INODE_REF           (1 << 5)
#define REF_ERR_INDEX_UNMATCH           (1 << 6)
#define REF_ERR_FILETYPE_UNMATCH        (1 << 7)
#define REF_ERR_NAME_TOO_LONG           (1 << 8) // 100
#define REF_ERR_NO_ROOT_REF             (1 << 9)
#define REF_ERR_NO_ROOT_BACKREF         (1 << 10)
#define REF_ERR_DUP_ROOT_REF            (1 << 11)
#define REF_ERR_DUP_ROOT_BACKREF        (1 << 12)

struct file_extent_hole {
        struct rb_node node;
        u64 start;
        u64 len;
};

struct inode_record {
        struct list_head backrefs;
        unsigned int checked:1;
        unsigned int merging:1;
        unsigned int found_inode_item:1;
        unsigned int found_dir_item:1;
        unsigned int found_file_extent:1;
        unsigned int found_csum_item:1;
        unsigned int some_csum_missing:1;
        unsigned int nodatasum:1;
        int errors;

        u64 ino;
        u32 nlink;
        u32 imode;
        u64 isize;
        u64 nbytes;

        u32 found_link;
        u64 found_size;
        u64 extent_start;
        u64 extent_end;
        struct rb_root holes;
        struct list_head orphan_extents;

        u32 refs;
};

#define I_ERR_NO_INODE_ITEM             (1 << 0)
#define I_ERR_NO_ORPHAN_ITEM            (1 << 1)
#define I_ERR_DUP_INODE_ITEM            (1 << 2)
#define I_ERR_DUP_DIR_INDEX             (1 << 3)
#define I_ERR_ODD_DIR_ITEM              (1 << 4)
#define I_ERR_ODD_FILE_EXTENT           (1 << 5)
#define I_ERR_BAD_FILE_EXTENT           (1 << 6)
#define I_ERR_FILE_EXTENT_OVERLAP       (1 << 7)
#define I_ERR_FILE_EXTENT_DISCOUNT      (1 << 8) // 100
#define I_ERR_DIR_ISIZE_WRONG           (1 << 9)
#define I_ERR_FILE_NBYTES_WRONG         (1 << 10) // 400
#define I_ERR_ODD_CSUM_ITEM             (1 << 11)
#define I_ERR_SOME_CSUM_MISSING         (1 << 12)
#define I_ERR_LINK_COUNT_WRONG          (1 << 13)
#define I_ERR_FILE_EXTENT_ORPHAN        (1 << 14)

struct root_backref {
        struct list_head list;
        unsigned int found_dir_item:1;
        unsigned int found_dir_index:1;
        unsigned int found_back_ref:1;
        unsigned int found_forward_ref:1;
        unsigned int reachable:1;
        int errors;
        u64 ref_root;
        u64 dir;
        u64 index;
        u16 namelen;
        char name[0];
};

static inline struct root_backref* to_root_backref(struct list_head *entry)
{
        return list_entry(entry, struct root_backref, list);
}

struct root_record {
        struct list_head backrefs;
        struct cache_extent cache;
        unsigned int found_root_item:1;
        u64 objectid;
        u32 found_ref;
};

struct ptr_node {
        struct cache_extent cache;
        void *data;
};

struct shared_node {
        struct cache_extent cache;
        struct cache_tree root_cache;
        struct cache_tree inode_cache;
        struct inode_record *current;
        u32 refs;
};

struct block_info {
        u64 start;
        u32 size;
};

struct walk_control {
        struct cache_tree shared;
        struct shared_node *nodes[BTRFS_MAX_LEVEL];
        int active_node;
        int root_level;
};

struct bad_item {
        struct btrfs_key key;
        u64 root_id;
        struct list_head list;
};

struct extent_entry {
        u64 bytenr;
        u64 bytes;
        int count;
        int broken;
        struct list_head list;
};

struct root_item_info {
        /* level of the root */
        u8 level;
        /* number of nodes at this level, must be 1 for a root */
        int node_count;
        u64 bytenr;
        u64 gen;
        struct cache_extent cache_extent;
};

/*
 * Error bit for low memory mode check.
 *
 * Currently no caller cares about it yet.  Just internal use for error
 * classification.
 */
#define BACKREF_MISSING         (1 << 0) /* Backref missing in extent tree */
#define BACKREF_MISMATCH        (1 << 1) /* Backref exists but does not match */
#define BYTES_UNALIGNED         (1 << 2) /* Some bytes are not aligned */
#define REFERENCER_MISSING      (1 << 3) /* Referencer not found */
#define REFERENCER_MISMATCH     (1 << 4) /* Referenceer found but does not match */
#define CROSSING_STRIPE_BOUNDARY (1 << 4) /* For kernel scrub workaround */
#define ITEM_SIZE_MISMATCH      (1 << 5) /* Bad item size */
#define UNKNOWN_TYPE            (1 << 6) /* Unknown type */
#define ACCOUNTING_MISMATCH     (1 << 7) /* Used space accounting error */
#define CHUNK_TYPE_MISMATCH     (1 << 8)

static void *print_status_check(void *p)
{
        struct task_ctx *priv = p;
        const char work_indicator[] = { '.', 'o', 'O', 'o' };
        uint32_t count = 0;
        static char *task_position_string[] = {
                "checking extents",
                "checking free space cache",
                "checking fs roots",
        };

        task_period_start(priv->info, 1000 /* 1s */);

        if (priv->tp == TASK_NOTHING)
                return NULL;

        while (1) {
                printf("%s [%c]\r", task_position_string[priv->tp],
                                work_indicator[count % 4]);
                count++;
                fflush(stdout);
                task_period_wait(priv->info);
        }
        return NULL;
}

static int print_status_return(void *p)
{
        printf("\n");
        fflush(stdout);

        return 0;
}

static enum btrfs_check_mode parse_check_mode(const char *str)
{
        if (strcmp(str, "lowmem") == 0)
                return CHECK_MODE_LOWMEM;
        if (strcmp(str, "orig") == 0)
                return CHECK_MODE_ORIGINAL;
        if (strcmp(str, "original") == 0)
                return CHECK_MODE_ORIGINAL;

        return CHECK_MODE_UNKNOWN;
}

/* Compatible function to allow reuse of old codes */
static u64 first_extent_gap(struct rb_root *holes)
{
        struct file_extent_hole *hole;

        if (RB_EMPTY_ROOT(holes))
                return (u64)-1;

        hole = rb_entry(rb_first(holes), struct file_extent_hole, node);
        return hole->start;
}

static int compare_hole(struct rb_node *node1, struct rb_node *node2)
{
        struct file_extent_hole *hole1;
        struct file_extent_hole *hole2;

        hole1 = rb_entry(node1, struct file_extent_hole, node);
        hole2 = rb_entry(node2, struct file_extent_hole, node);

        if (hole1->start > hole2->start)
                return -1;
        if (hole1->start < hole2->start)
                return 1;
        /* Now hole1->start == hole2->start */
        if (hole1->len >= hole2->len)
                /*
                 * Hole 1 will be merge center
                 * Same hole will be merged later
                 */
                return -1;
        /* Hole 2 will be merge center */
        return 1;
}

/*
 * Add a hole to the record
 *
 * This will do hole merge for copy_file_extent_holes(),
 * which will ensure there won't be continuous holes.
 */
static int add_file_extent_hole(struct rb_root *holes,
                                u64 start, u64 len)
{
        struct file_extent_hole *hole;
        struct file_extent_hole *prev = NULL;
        struct file_extent_hole *next = NULL;

        hole = malloc(sizeof(*hole));
        if (!hole)
                return -ENOMEM;
        hole->start = start;
        hole->len = len;
        /* Since compare will not return 0, no -EEXIST will happen */
        rb_insert(holes, &hole->node, compare_hole);

        /* simple merge with previous hole */
        if (rb_prev(&hole->node))
                prev = rb_entry(rb_prev(&hole->node), struct file_extent_hole,
                                node);
        if (prev && prev->start + prev->len >= hole->start) {
                hole->len = hole->start + hole->len - prev->start;
                hole->start = prev->start;
                rb_erase(&prev->node, holes);
                free(prev);
                prev = NULL;
        }

        /* iterate merge with next holes */
        while (1) {
                if (!rb_next(&hole->node))
                        break;
                next = rb_entry(rb_next(&hole->node), struct file_extent_hole,
                                        node);
                if (hole->start + hole->len >= next->start) {
                        if (hole->start + hole->len <= next->start + next->len)
                                hole->len = next->start + next->len -
                                            hole->start;
                        rb_erase(&next->node, holes);
                        free(next);
                        next = NULL;
                } else
                        break;
        }
        return 0;
}

static int compare_hole_range(struct rb_node *node, void *data)
{
        struct file_extent_hole *hole;
        u64 start;

        hole = (struct file_extent_hole *)data;
        start = hole->start;

        hole = rb_entry(node, struct file_extent_hole, node);
        if (start < hole->start)
                return -1;
        if (start >= hole->start && start < hole->start + hole->len)
                return 0;
        return 1;
}

/*
 * Delete a hole in the record
 *
 * This will do the hole split and is much restrict than add.
 */
static int del_file_extent_hole(struct rb_root *holes,
                                u64 start, u64 len)
{
        struct file_extent_hole *hole;
        struct file_extent_hole tmp;
        u64 prev_start = 0;
        u64 prev_len = 0;
        u64 next_start = 0;
        u64 next_len = 0;
        struct rb_node *node;
        int have_prev = 0;
        int have_next = 0;
        int ret = 0;

        tmp.start = start;
        tmp.len = len;
        node = rb_search(holes, &tmp, compare_hole_range, NULL);
        if (!node)
                return -EEXIST;
        hole = rb_entry(node, struct file_extent_hole, node);
        if (start + len > hole->start + hole->len)
                return -EEXIST;

        /*
         * Now there will be no overlap, delete the hole and re-add the
         * split(s) if they exists.
         */
        if (start > hole->start) {
                prev_start = hole->start;
                prev_len = start - hole->start;
                have_prev = 1;
        }
        if (hole->start + hole->len > start + len) {
                next_start = start + len;
                next_len = hole->start + hole->len - start - len;
                have_next = 1;
        }
        rb_erase(node, holes);
        free(hole);
        if (have_prev) {
                ret = add_file_extent_hole(holes, prev_start, prev_len);
                if (ret < 0)
                        return ret;
        }
        if (have_next) {
                ret = add_file_extent_hole(holes, next_start, next_len);
                if (ret < 0)
                        return ret;
        }
        return 0;
}

static int copy_file_extent_holes(struct rb_root *dst,
                                  struct rb_root *src)
{
        struct file_extent_hole *hole;
        struct rb_node *node;
        int ret = 0;

        node = rb_first(src);
        while (node) {
                hole = rb_entry(node, struct file_extent_hole, node);
                ret = add_file_extent_hole(dst, hole->start, hole->len);
                if (ret)
                        break;
                node = rb_next(node);
        }
        return ret;
}

static void free_file_extent_holes(struct rb_root *holes)
{
        struct rb_node *node;
        struct file_extent_hole *hole;

        node = rb_first(holes);
        while (node) {
                hole = rb_entry(node, struct file_extent_hole, node);
                rb_erase(node, holes);
                free(hole);
                node = rb_first(holes);
        }
}

static void reset_cached_block_groups(struct btrfs_fs_info *fs_info);

static void record_root_in_trans(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root)
{
        if (root->last_trans != trans->transid) {
                root->track_dirty = 1;
                root->last_trans = trans->transid;
                root->commit_root = root->node;
                extent_buffer_get(root->node);
        }
}

static u8 imode_to_type(u32 imode)
{
#define S_SHIFT 12
        static unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
                [S_IFREG >> S_SHIFT]    = BTRFS_FT_REG_FILE,
                [S_IFDIR >> S_SHIFT]    = BTRFS_FT_DIR,
                [S_IFCHR >> S_SHIFT]    = BTRFS_FT_CHRDEV,
                [S_IFBLK >> S_SHIFT]    = BTRFS_FT_BLKDEV,
                [S_IFIFO >> S_SHIFT]    = BTRFS_FT_FIFO,
                [S_IFSOCK >> S_SHIFT]   = BTRFS_FT_SOCK,
                [S_IFLNK >> S_SHIFT]    = BTRFS_FT_SYMLINK,
        };

        return btrfs_type_by_mode[(imode & S_IFMT) >> S_SHIFT];
#undef S_SHIFT
}

static int device_record_compare(struct rb_node *node1, struct rb_node *node2)
{
        struct device_record *rec1;
        struct device_record *rec2;

        rec1 = rb_entry(node1, struct device_record, node);
        rec2 = rb_entry(node2, struct device_record, node);
        if (rec1->devid > rec2->devid)
                return -1;
        else if (rec1->devid < rec2->devid)
                return 1;
        else
                return 0;
}

static struct inode_record *clone_inode_rec(struct inode_record *orig_rec)
{
        struct inode_record *rec;
        struct inode_backref *backref;
        struct inode_backref *orig;
        struct inode_backref *tmp;
        struct orphan_data_extent *src_orphan;
        struct orphan_data_extent *dst_orphan;
        struct rb_node *rb;
        size_t size;
        int ret;

        rec = malloc(sizeof(*rec));
        if (!rec)
                return ERR_PTR(-ENOMEM);
        memcpy(rec, orig_rec, sizeof(*rec));
        rec->refs = 1;
        INIT_LIST_HEAD(&rec->backrefs);
        INIT_LIST_HEAD(&rec->orphan_extents);
        rec->holes = RB_ROOT;

        list_for_each_entry(orig, &orig_rec->backrefs, list) {
                size = sizeof(*orig) + orig->namelen + 1;
                backref = malloc(size);
                if (!backref) {
                        ret = -ENOMEM;
                        goto cleanup;
                }
                memcpy(backref, orig, size);
                list_add_tail(&backref->list, &rec->backrefs);
        }
        list_for_each_entry(src_orphan, &orig_rec->orphan_extents, list) {
                dst_orphan = malloc(sizeof(*dst_orphan));
                if (!dst_orphan) {
                        ret = -ENOMEM;
                        goto cleanup;
                }
                memcpy(dst_orphan, src_orphan, sizeof(*src_orphan));
                list_add_tail(&dst_orphan->list, &rec->orphan_extents);
        }
        ret = copy_file_extent_holes(&rec->holes, &orig_rec->holes);
        if (ret < 0)
                goto cleanup_rb;

        return rec;

cleanup_rb:
        rb = rb_first(&rec->holes);
        while (rb) {
                struct file_extent_hole *hole;

                hole = rb_entry(rb, struct file_extent_hole, node);
                rb = rb_next(rb);
                free(hole);
        }

cleanup:
        if (!list_empty(&rec->backrefs))
                list_for_each_entry_safe(orig, tmp, &rec->backrefs, list) {
                        list_del(&orig->list);
                        free(orig);
                }

        if (!list_empty(&rec->orphan_extents))
                list_for_each_entry_safe(orig, tmp, &rec->orphan_extents, list) {
                        list_del(&orig->list);
                        free(orig);
                }

        free(rec);

        return ERR_PTR(ret);
}

static void print_orphan_data_extents(struct list_head *orphan_extents,
                                      u64 objectid)
{
        struct orphan_data_extent *orphan;

        if (list_empty(orphan_extents))
                return;
        printf("The following data extent is lost in tree %llu:\n",
               objectid);
        list_for_each_entry(orphan, orphan_extents, list) {
                printf("\tinode: %llu, offset:%llu, disk_bytenr: %llu, disk_len: %llu\n",
                       orphan->objectid, orphan->offset, orphan->disk_bytenr,
                       orphan->disk_len);
        }
}

static void print_inode_error(struct btrfs_root *root, struct inode_record *rec)
{
        u64 root_objectid = root->root_key.objectid;
        int errors = rec->errors;

        if (!errors)
                return;
        /* reloc root errors, we print its corresponding fs root objectid*/
        if (root_objectid == BTRFS_TREE_RELOC_OBJECTID) {
                root_objectid = root->root_key.offset;
                fprintf(stderr, "reloc");
        }
        fprintf(stderr, "root %llu inode %llu errors %x",
                (unsigned long long) root_objectid,
                (unsigned long long) rec->ino, rec->errors);

        if (errors & I_ERR_NO_INODE_ITEM)
                fprintf(stderr, ", no inode item");
        if (errors & I_ERR_NO_ORPHAN_ITEM)
                fprintf(stderr, ", no orphan item");
        if (errors & I_ERR_DUP_INODE_ITEM)
                fprintf(stderr, ", dup inode item");
        if (errors & I_ERR_DUP_DIR_INDEX)
                fprintf(stderr, ", dup dir index");
        if (errors & I_ERR_ODD_DIR_ITEM)
                fprintf(stderr, ", odd dir item");
        if (errors & I_ERR_ODD_FILE_EXTENT)
                fprintf(stderr, ", odd file extent");
        if (errors & I_ERR_BAD_FILE_EXTENT)
                fprintf(stderr, ", bad file extent");
        if (errors & I_ERR_FILE_EXTENT_OVERLAP)
                fprintf(stderr, ", file extent overlap");
        if (errors & I_ERR_FILE_EXTENT_DISCOUNT)
                fprintf(stderr, ", file extent discount");
        if (errors & I_ERR_DIR_ISIZE_WRONG)
                fprintf(stderr, ", dir isize wrong");
        if (errors & I_ERR_FILE_NBYTES_WRONG)
                fprintf(stderr, ", nbytes wrong");
        if (errors & I_ERR_ODD_CSUM_ITEM)
                fprintf(stderr, ", odd csum item");
        if (errors & I_ERR_SOME_CSUM_MISSING)
                fprintf(stderr, ", some csum missing");
        if (errors & I_ERR_LINK_COUNT_WRONG)
                fprintf(stderr, ", link count wrong");
        if (errors & I_ERR_FILE_EXTENT_ORPHAN)
                fprintf(stderr, ", orphan file extent");
        fprintf(stderr, "\n");
        /* Print the orphan extents if needed */
        if (errors & I_ERR_FILE_EXTENT_ORPHAN)
                print_orphan_data_extents(&rec->orphan_extents, root->objectid);

        /* Print the holes if needed */
        if (errors & I_ERR_FILE_EXTENT_DISCOUNT) {
                struct file_extent_hole *hole;
                struct rb_node *node;
                int found = 0;

                node = rb_first(&rec->holes);
                fprintf(stderr, "Found file extent holes:\n");
                while (node) {
                        found = 1;
                        hole = rb_entry(node, struct file_extent_hole, node);
                        fprintf(stderr, "\tstart: %llu, len: %llu\n",
                                hole->start, hole->len);
                        node = rb_next(node);
                }
                if (!found)
                        fprintf(stderr, "\tstart: 0, len: %llu\n",
                                round_up(rec->isize,
                                         root->fs_info->sectorsize));
        }
}

static void print_ref_error(int errors)
{
        if (errors & REF_ERR_NO_DIR_ITEM)
                fprintf(stderr, ", no dir item");
        if (errors & REF_ERR_NO_DIR_INDEX)
                fprintf(stderr, ", no dir index");
        if (errors & REF_ERR_NO_INODE_REF)
                fprintf(stderr, ", no inode ref");
        if (errors & REF_ERR_DUP_DIR_ITEM)
                fprintf(stderr, ", dup dir item");
        if (errors & REF_ERR_DUP_DIR_INDEX)
                fprintf(stderr, ", dup dir index");
        if (errors & REF_ERR_DUP_INODE_REF)
                fprintf(stderr, ", dup inode ref");
        if (errors & REF_ERR_INDEX_UNMATCH)
                fprintf(stderr, ", index mismatch");
        if (errors & REF_ERR_FILETYPE_UNMATCH)
                fprintf(stderr, ", filetype mismatch");
        if (errors & REF_ERR_NAME_TOO_LONG)
                fprintf(stderr, ", name too long");
        if (errors & REF_ERR_NO_ROOT_REF)
                fprintf(stderr, ", no root ref");
        if (errors & REF_ERR_NO_ROOT_BACKREF)
                fprintf(stderr, ", no root backref");
        if (errors & REF_ERR_DUP_ROOT_REF)
                fprintf(stderr, ", dup root ref");
        if (errors & REF_ERR_DUP_ROOT_BACKREF)
                fprintf(stderr, ", dup root backref");
        fprintf(stderr, "\n");
}

static struct inode_record *get_inode_rec(struct cache_tree *inode_cache,
                                          u64 ino, int mod)
{
        struct ptr_node *node;
        struct cache_extent *cache;
        struct inode_record *rec = NULL;
        int ret;

        cache = lookup_cache_extent(inode_cache, ino, 1);
        if (cache) {
                node = container_of(cache, struct ptr_node, cache);
                rec = node->data;
                if (mod && rec->refs > 1) {
                        node->data = clone_inode_rec(rec);
                        if (IS_ERR(node->data))
                                return node->data;
                        rec->refs--;
                        rec = node->data;
                }
        } else if (mod) {
                rec = calloc(1, sizeof(*rec));
                if (!rec)
                        return ERR_PTR(-ENOMEM);
                rec->ino = ino;
                rec->extent_start = (u64)-1;
                rec->refs = 1;
                INIT_LIST_HEAD(&rec->backrefs);
                INIT_LIST_HEAD(&rec->orphan_extents);
                rec->holes = RB_ROOT;

                node = malloc(sizeof(*node));
                if (!node) {
                        free(rec);
                        return ERR_PTR(-ENOMEM);
                }
                node->cache.start = ino;
                node->cache.size = 1;
                node->data = rec;

                if (ino == BTRFS_FREE_INO_OBJECTID)
                        rec->found_link = 1;

                ret = insert_cache_extent(inode_cache, &node->cache);
                if (ret)
                        return ERR_PTR(-EEXIST);
        }
        return rec;
}

static void free_orphan_data_extents(struct list_head *orphan_extents)
{
        struct orphan_data_extent *orphan;

        while (!list_empty(orphan_extents)) {
                orphan = list_entry(orphan_extents->next,
                                    struct orphan_data_extent, list);
                list_del(&orphan->list);
                free(orphan);
        }
}

static void free_inode_rec(struct inode_record *rec)
{
        struct inode_backref *backref;

        if (--rec->refs > 0)
                return;

        while (!list_empty(&rec->backrefs)) {
                backref = to_inode_backref(rec->backrefs.next);
                list_del(&backref->list);
                free(backref);
        }
        free_orphan_data_extents(&rec->orphan_extents);
        free_file_extent_holes(&rec->holes);
        free(rec);
}

static int can_free_inode_rec(struct inode_record *rec)
{
        if (!rec->errors && rec->checked && rec->found_inode_item &&
            rec->nlink == rec->found_link && list_empty(&rec->backrefs))
                return 1;
        return 0;
}

static void maybe_free_inode_rec(struct cache_tree *inode_cache,
                                 struct inode_record *rec)
{
        struct cache_extent *cache;
        struct inode_backref *tmp, *backref;
        struct ptr_node *node;
        u8 filetype;

        if (!rec->found_inode_item)
                return;

        filetype = imode_to_type(rec->imode);
        list_for_each_entry_safe(backref, tmp, &rec->backrefs, list) {
                if (backref->found_dir_item && backref->found_dir_index) {
                        if (backref->filetype != filetype)
                                backref->errors |= REF_ERR_FILETYPE_UNMATCH;
                        if (!backref->errors && backref->found_inode_ref &&
                            rec->nlink == rec->found_link) {
                                list_del(&backref->list);
                                free(backref);
                        }
                }
        }

        if (!rec->checked || rec->merging)
                return;

        if (S_ISDIR(rec->imode)) {
                if (rec->found_size != rec->isize)
                        rec->errors |= I_ERR_DIR_ISIZE_WRONG;
                if (rec->found_file_extent)
                        rec->errors |= I_ERR_ODD_FILE_EXTENT;
        } else if (S_ISREG(rec->imode) || S_ISLNK(rec->imode)) {
                if (rec->found_dir_item)
                        rec->errors |= I_ERR_ODD_DIR_ITEM;
                if (rec->found_size != rec->nbytes)
                        rec->errors |= I_ERR_FILE_NBYTES_WRONG;
                if (rec->nlink > 0 && !no_holes &&
                    (rec->extent_end < rec->isize ||
                     first_extent_gap(&rec->holes) < rec->isize))
                        rec->errors |= I_ERR_FILE_EXTENT_DISCOUNT;
        }

        if (S_ISREG(rec->imode) || S_ISLNK(rec->imode)) {
                if (rec->found_csum_item && rec->nodatasum)
                        rec->errors |= I_ERR_ODD_CSUM_ITEM;
                if (rec->some_csum_missing && !rec->nodatasum)
                        rec->errors |= I_ERR_SOME_CSUM_MISSING;
        }

        BUG_ON(rec->refs != 1);
        if (can_free_inode_rec(rec)) {
                cache = lookup_cache_extent(inode_cache, rec->ino, 1);
                node = container_of(cache, struct ptr_node, cache);
                BUG_ON(node->data != rec);
                remove_cache_extent(inode_cache, &node->cache);
                free(node);
                free_inode_rec(rec);
        }
}

static int check_orphan_item(struct btrfs_root *root, u64 ino)
{
        struct btrfs_path path;
        struct btrfs_key key;
        int ret;

        key.objectid = BTRFS_ORPHAN_OBJECTID;
        key.type = BTRFS_ORPHAN_ITEM_KEY;
        key.offset = ino;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        btrfs_release_path(&path);
        if (ret > 0)
                ret = -ENOENT;
        return ret;
}

static int process_inode_item(struct extent_buffer *eb,
                              int slot, struct btrfs_key *key,
                              struct shared_node *active_node)
{
        struct inode_record *rec;
        struct btrfs_inode_item *item;

        rec = active_node->current;
        BUG_ON(rec->ino != key->objectid || rec->refs > 1);
        if (rec->found_inode_item) {
                rec->errors |= I_ERR_DUP_INODE_ITEM;
                return 1;
        }
        item = btrfs_item_ptr(eb, slot, struct btrfs_inode_item);
        rec->nlink = btrfs_inode_nlink(eb, item);
        rec->isize = btrfs_inode_size(eb, item);
        rec->nbytes = btrfs_inode_nbytes(eb, item);
        rec->imode = btrfs_inode_mode(eb, item);
        if (btrfs_inode_flags(eb, item) & BTRFS_INODE_NODATASUM)
                rec->nodatasum = 1;
        rec->found_inode_item = 1;
        if (rec->nlink == 0)
                rec->errors |= I_ERR_NO_ORPHAN_ITEM;
        maybe_free_inode_rec(&active_node->inode_cache, rec);
        return 0;
}

static struct inode_backref *get_inode_backref(struct inode_record *rec,
                                                const char *name,
                                                int namelen, u64 dir)
{
        struct inode_backref *backref;

        list_for_each_entry(backref, &rec->backrefs, list) {
                if (rec->ino == BTRFS_MULTIPLE_OBJECTIDS)
                        break;
                if (backref->dir != dir || backref->namelen != namelen)
                        continue;
                if (memcmp(name, backref->name, namelen))
                        continue;
                return backref;
        }

        backref = malloc(sizeof(*backref) + namelen + 1);
        if (!backref)
                return NULL;
        memset(backref, 0, sizeof(*backref));
        backref->dir = dir;
        backref->namelen = namelen;
        memcpy(backref->name, name, namelen);
        backref->name[namelen] = '\0';
        list_add_tail(&backref->list, &rec->backrefs);
        return backref;
}

static int add_inode_backref(struct cache_tree *inode_cache,
                             u64 ino, u64 dir, u64 index,
                             const char *name, int namelen,
                             u8 filetype, u8 itemtype, int errors)
{
        struct inode_record *rec;
        struct inode_backref *backref;

        rec = get_inode_rec(inode_cache, ino, 1);
        BUG_ON(IS_ERR(rec));
        backref = get_inode_backref(rec, name, namelen, dir);
        BUG_ON(!backref);
        if (errors)
                backref->errors |= errors;
        if (itemtype == BTRFS_DIR_INDEX_KEY) {
                if (backref->found_dir_index)
                        backref->errors |= REF_ERR_DUP_DIR_INDEX;
                if (backref->found_inode_ref && backref->index != index)
                        backref->errors |= REF_ERR_INDEX_UNMATCH;
                if (backref->found_dir_item && backref->filetype != filetype)
                        backref->errors |= REF_ERR_FILETYPE_UNMATCH;

                backref->index = index;
                backref->filetype = filetype;
                backref->found_dir_index = 1;
        } else if (itemtype == BTRFS_DIR_ITEM_KEY) {
                rec->found_link++;
                if (backref->found_dir_item)
                        backref->errors |= REF_ERR_DUP_DIR_ITEM;
                if (backref->found_dir_index && backref->filetype != filetype)
                        backref->errors |= REF_ERR_FILETYPE_UNMATCH;

                backref->filetype = filetype;
                backref->found_dir_item = 1;
        } else if ((itemtype == BTRFS_INODE_REF_KEY) ||
                   (itemtype == BTRFS_INODE_EXTREF_KEY)) {
                if (backref->found_inode_ref)
                        backref->errors |= REF_ERR_DUP_INODE_REF;
                if (backref->found_dir_index && backref->index != index)
                        backref->errors |= REF_ERR_INDEX_UNMATCH;
                else
                        backref->index = index;

                backref->ref_type = itemtype;
                backref->found_inode_ref = 1;
        } else {
                BUG_ON(1);
        }

        maybe_free_inode_rec(inode_cache, rec);
        return 0;
}

static int merge_inode_recs(struct inode_record *src, struct inode_record *dst,
                            struct cache_tree *dst_cache)
{
        struct inode_backref *backref;
        u32 dir_count = 0;
        int ret = 0;

        dst->merging = 1;
        list_for_each_entry(backref, &src->backrefs, list) {
                if (backref->found_dir_index) {
                        add_inode_backref(dst_cache, dst->ino, backref->dir,
                                        backref->index, backref->name,
                                        backref->namelen, backref->filetype,
                                        BTRFS_DIR_INDEX_KEY, backref->errors);
                }
                if (backref->found_dir_item) {
                        dir_count++;
                        add_inode_backref(dst_cache, dst->ino,
                                        backref->dir, 0, backref->name,
                                        backref->namelen, backref->filetype,
                                        BTRFS_DIR_ITEM_KEY, backref->errors);
                }
                if (backref->found_inode_ref) {
                        add_inode_backref(dst_cache, dst->ino,
                                        backref->dir, backref->index,
                                        backref->name, backref->namelen, 0,
                                        backref->ref_type, backref->errors);
                }
        }

        if (src->found_dir_item)
                dst->found_dir_item = 1;
        if (src->found_file_extent)
                dst->found_file_extent = 1;
        if (src->found_csum_item)
                dst->found_csum_item = 1;
        if (src->some_csum_missing)
                dst->some_csum_missing = 1;
        if (first_extent_gap(&dst->holes) > first_extent_gap(&src->holes)) {
                ret = copy_file_extent_holes(&dst->holes, &src->holes);
                if (ret < 0)
                        return ret;
        }

        BUG_ON(src->found_link < dir_count);
        dst->found_link += src->found_link - dir_count;
        dst->found_size += src->found_size;
        if (src->extent_start != (u64)-1) {
                if (dst->extent_start == (u64)-1) {
                        dst->extent_start = src->extent_start;
                        dst->extent_end = src->extent_end;
                } else {
                        if (dst->extent_end > src->extent_start)
                                dst->errors |= I_ERR_FILE_EXTENT_OVERLAP;
                        else if (dst->extent_end < src->extent_start) {
                                ret = add_file_extent_hole(&dst->holes,
                                        dst->extent_end,
                                        src->extent_start - dst->extent_end);
                        }
                        if (dst->extent_end < src->extent_end)
                                dst->extent_end = src->extent_end;
                }
        }

        dst->errors |= src->errors;
        if (src->found_inode_item) {
                if (!dst->found_inode_item) {
                        dst->nlink = src->nlink;
                        dst->isize = src->isize;
                        dst->nbytes = src->nbytes;
                        dst->imode = src->imode;
                        dst->nodatasum = src->nodatasum;
                        dst->found_inode_item = 1;
                } else {
                        dst->errors |= I_ERR_DUP_INODE_ITEM;
                }
        }
        dst->merging = 0;

        return 0;
}

static int splice_shared_node(struct shared_node *src_node,
                              struct shared_node *dst_node)
{
        struct cache_extent *cache;
        struct ptr_node *node, *ins;
        struct cache_tree *src, *dst;
        struct inode_record *rec, *conflict;
        u64 current_ino = 0;
        int splice = 0;
        int ret;

        if (--src_node->refs == 0)
                splice = 1;
        if (src_node->current)
                current_ino = src_node->current->ino;

        src = &src_node->root_cache;
        dst = &dst_node->root_cache;
again:
        cache = search_cache_extent(src, 0);
        while (cache) {
                node = container_of(cache, struct ptr_node, cache);
                rec = node->data;
                cache = next_cache_extent(cache);

                if (splice) {
                        remove_cache_extent(src, &node->cache);
                        ins = node;
                } else {
                        ins = malloc(sizeof(*ins));
                        BUG_ON(!ins);
                        ins->cache.start = node->cache.start;
                        ins->cache.size = node->cache.size;
                        ins->data = rec;
                        rec->refs++;
                }
                ret = insert_cache_extent(dst, &ins->cache);
                if (ret == -EEXIST) {
                        conflict = get_inode_rec(dst, rec->ino, 1);
                        BUG_ON(IS_ERR(conflict));
                        merge_inode_recs(rec, conflict, dst);
                        if (rec->checked) {
                                conflict->checked = 1;
                                if (dst_node->current == conflict)
                                        dst_node->current = NULL;
                        }
                        maybe_free_inode_rec(dst, conflict);
                        free_inode_rec(rec);
                        free(ins);
                } else {
                        BUG_ON(ret);
                }
        }

        if (src == &src_node->root_cache) {
                src = &src_node->inode_cache;
                dst = &dst_node->inode_cache;
                goto again;
        }

        if (current_ino > 0 && (!dst_node->current ||
            current_ino > dst_node->current->ino)) {
                if (dst_node->current) {
                        dst_node->current->checked = 1;
                        maybe_free_inode_rec(dst, dst_node->current);
                }
                dst_node->current = get_inode_rec(dst, current_ino, 1);
                BUG_ON(IS_ERR(dst_node->current));
        }
        return 0;
}

static void free_inode_ptr(struct cache_extent *cache)
{
        struct ptr_node *node;
        struct inode_record *rec;

        node = container_of(cache, struct ptr_node, cache);
        rec = node->data;
        free_inode_rec(rec);
        free(node);
}

FREE_EXTENT_CACHE_BASED_TREE(inode_recs, free_inode_ptr);

static struct shared_node *find_shared_node(struct cache_tree *shared,
                                            u64 bytenr)
{
        struct cache_extent *cache;
        struct shared_node *node;

        cache = lookup_cache_extent(shared, bytenr, 1);
        if (cache) {
                node = container_of(cache, struct shared_node, cache);
                return node;
        }
        return NULL;
}

static int add_shared_node(struct cache_tree *shared, u64 bytenr, u32 refs)
{
        int ret;
        struct shared_node *node;

        node = calloc(1, sizeof(*node));
        if (!node)
                return -ENOMEM;
        node->cache.start = bytenr;
        node->cache.size = 1;
        cache_tree_init(&node->root_cache);
        cache_tree_init(&node->inode_cache);
        node->refs = refs;

        ret = insert_cache_extent(shared, &node->cache);

        return ret;
}

static int enter_shared_node(struct btrfs_root *root, u64 bytenr, u32 refs,
                             struct walk_control *wc, int level)
{
        struct shared_node *node;
        struct shared_node *dest;
        int ret;

        if (level == wc->active_node)
                return 0;

        BUG_ON(wc->active_node <= level);
        node = find_shared_node(&wc->shared, bytenr);
        if (!node) {
                ret = add_shared_node(&wc->shared, bytenr, refs);
                BUG_ON(ret);
                node = find_shared_node(&wc->shared, bytenr);
                wc->nodes[level] = node;
                wc->active_node = level;
                return 0;
        }

        if (wc->root_level == wc->active_node &&
            btrfs_root_refs(&root->root_item) == 0) {
                if (--node->refs == 0) {
                        free_inode_recs_tree(&node->root_cache);
                        free_inode_recs_tree(&node->inode_cache);
                        remove_cache_extent(&wc->shared, &node->cache);
                        free(node);
                }
                return 1;
        }

        dest = wc->nodes[wc->active_node];
        splice_shared_node(node, dest);
        if (node->refs == 0) {
                remove_cache_extent(&wc->shared, &node->cache);
                free(node);
        }
        return 1;
}

static int leave_shared_node(struct btrfs_root *root,
                             struct walk_control *wc, int level)
{
        struct shared_node *node;
        struct shared_node *dest;
        int i;

        if (level == wc->root_level)
                return 0;

        for (i = level + 1; i < BTRFS_MAX_LEVEL; i++) {
                if (wc->nodes[i])
                        break;
        }
        BUG_ON(i >= BTRFS_MAX_LEVEL);

        node = wc->nodes[wc->active_node];
        wc->nodes[wc->active_node] = NULL;
        wc->active_node = i;

        dest = wc->nodes[wc->active_node];
        if (wc->active_node < wc->root_level ||
            btrfs_root_refs(&root->root_item) > 0) {
                BUG_ON(node->refs <= 1);
                splice_shared_node(node, dest);
        } else {
                BUG_ON(node->refs < 2);
                node->refs--;
        }
        return 0;
}

/*
 * Returns:
 * < 0 - on error
 * 1   - if the root with id child_root_id is a child of root parent_root_id
 * 0   - if the root child_root_id isn't a child of the root parent_root_id but
 *       has other root(s) as parent(s)
 * 2   - if the root child_root_id doesn't have any parent roots
 */
static int is_child_root(struct btrfs_root *root, u64 parent_root_id,
                         u64 child_root_id)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        int has_parent = 0;
        int ret;

        btrfs_init_path(&path);

        key.objectid = parent_root_id;
        key.type = BTRFS_ROOT_REF_KEY;
        key.offset = child_root_id;
        ret = btrfs_search_slot(NULL, root->fs_info->tree_root, &key, &path,
                                0, 0);
        if (ret < 0)
                return ret;
        btrfs_release_path(&path);
        if (!ret)
                return 1;

        key.objectid = child_root_id;
        key.type = BTRFS_ROOT_BACKREF_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(NULL, root->fs_info->tree_root, &key, &path,
                                0, 0);
        if (ret < 0)
                goto out;

        while (1) {
                leaf = path.nodes[0];
                if (path.slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root->fs_info->tree_root, &path);
                        if (ret)
                                break;
                        leaf = path.nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.objectid != child_root_id ||
                    key.type != BTRFS_ROOT_BACKREF_KEY)
                        break;

                has_parent = 1;

                if (key.offset == parent_root_id) {
                        btrfs_release_path(&path);
                        return 1;
                }

                path.slots[0]++;
        }
out:
        btrfs_release_path(&path);
        if (ret < 0)
                return ret;
        return has_parent ? 0 : 2;
}

static int process_dir_item(struct extent_buffer *eb,
                            int slot, struct btrfs_key *key,
                            struct shared_node *active_node)
{
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 name_len;
        u32 data_len;
        int error;
        int nritems = 0;
        u8 filetype;
        struct btrfs_dir_item *di;
        struct inode_record *rec;
        struct cache_tree *root_cache;
        struct cache_tree *inode_cache;
        struct btrfs_key location;
        char namebuf[BTRFS_NAME_LEN];

        root_cache = &active_node->root_cache;
        inode_cache = &active_node->inode_cache;
        rec = active_node->current;
        rec->found_dir_item = 1;

        di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
        total = btrfs_item_size_nr(eb, slot);
        while (cur < total) {
                nritems++;
                btrfs_dir_item_key_to_cpu(eb, di, &location);
                name_len = btrfs_dir_name_len(eb, di);
                data_len = btrfs_dir_data_len(eb, di);
                filetype = btrfs_dir_type(eb, di);

                rec->found_size += name_len;
                if (cur + sizeof(*di) + name_len > total ||
                    name_len > BTRFS_NAME_LEN) {
                        error = REF_ERR_NAME_TOO_LONG;

                        if (cur + sizeof(*di) > total)
                                break;
                        len = min_t(u32, total - cur - sizeof(*di),
                                    BTRFS_NAME_LEN);
                } else {
                        len = name_len;
                        error = 0;
                }

                read_extent_buffer(eb, namebuf, (unsigned long)(di + 1), len);

                if (key->type == BTRFS_DIR_ITEM_KEY &&
                    key->offset != btrfs_name_hash(namebuf, len)) {
                        rec->errors |= I_ERR_ODD_DIR_ITEM;
                        error("DIR_ITEM[%llu %llu] name %s namelen %u filetype %u mismatch with its hash, wanted %llu have %llu",
                        key->objectid, key->offset, namebuf, len, filetype,
                        key->offset, btrfs_name_hash(namebuf, len));
                }

                if (location.type == BTRFS_INODE_ITEM_KEY) {
                        add_inode_backref(inode_cache, location.objectid,
                                          key->objectid, key->offset, namebuf,
                                          len, filetype, key->type, error);
                } else if (location.type == BTRFS_ROOT_ITEM_KEY) {
                        add_inode_backref(root_cache, location.objectid,
                                          key->objectid, key->offset,
                                          namebuf, len, filetype,
                                          key->type, error);
                } else {
                        fprintf(stderr, "invalid location in dir item %u\n",
                                location.type);
                        add_inode_backref(inode_cache, BTRFS_MULTIPLE_OBJECTIDS,
                                          key->objectid, key->offset, namebuf,
                                          len, filetype, key->type, error);
                }

                len = sizeof(*di) + name_len + data_len;
                di = (struct btrfs_dir_item *)((char *)di + len);
                cur += len;
        }
        if (key->type == BTRFS_DIR_INDEX_KEY && nritems > 1)
                rec->errors |= I_ERR_DUP_DIR_INDEX;

        return 0;
}

static int process_inode_ref(struct extent_buffer *eb,
                             int slot, struct btrfs_key *key,
                             struct shared_node *active_node)
{
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 name_len;
        u64 index;
        int error;
        struct cache_tree *inode_cache;
        struct btrfs_inode_ref *ref;
        char namebuf[BTRFS_NAME_LEN];

        inode_cache = &active_node->inode_cache;

        ref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
        total = btrfs_item_size_nr(eb, slot);
        while (cur < total) {
                name_len = btrfs_inode_ref_name_len(eb, ref);
                index = btrfs_inode_ref_index(eb, ref);

                /* inode_ref + namelen should not cross item boundary */
                if (cur + sizeof(*ref) + name_len > total ||
                    name_len > BTRFS_NAME_LEN) {
                        if (total < cur + sizeof(*ref))
                                break;

                        /* Still try to read out the remaining part */
                        len = min_t(u32, total - cur - sizeof(*ref),
                                    BTRFS_NAME_LEN);
                        error = REF_ERR_NAME_TOO_LONG;
                } else {
                        len = name_len;
                        error = 0;
                }

                read_extent_buffer(eb, namebuf, (unsigned long)(ref + 1), len);
                add_inode_backref(inode_cache, key->objectid, key->offset,
                                  index, namebuf, len, 0, key->type, error);

                len = sizeof(*ref) + name_len;
                ref = (struct btrfs_inode_ref *)((char *)ref + len);
                cur += len;
        }
        return 0;
}

static int process_inode_extref(struct extent_buffer *eb,
                                int slot, struct btrfs_key *key,
                                struct shared_node *active_node)
{
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 name_len;
        u64 index;
        u64 parent;
        int error;
        struct cache_tree *inode_cache;
        struct btrfs_inode_extref *extref;
        char namebuf[BTRFS_NAME_LEN];

        inode_cache = &active_node->inode_cache;

        extref = btrfs_item_ptr(eb, slot, struct btrfs_inode_extref);
        total = btrfs_item_size_nr(eb, slot);
        while (cur < total) {
                name_len = btrfs_inode_extref_name_len(eb, extref);
                index = btrfs_inode_extref_index(eb, extref);
                parent = btrfs_inode_extref_parent(eb, extref);
                if (name_len <= BTRFS_NAME_LEN) {
                        len = name_len;
                        error = 0;
                } else {
                        len = BTRFS_NAME_LEN;
                        error = REF_ERR_NAME_TOO_LONG;
                }
                read_extent_buffer(eb, namebuf,
                                   (unsigned long)(extref + 1), len);
                add_inode_backref(inode_cache, key->objectid, parent,
                                  index, namebuf, len, 0, key->type, error);

                len = sizeof(*extref) + name_len;
                extref = (struct btrfs_inode_extref *)((char *)extref + len);
                cur += len;
        }
        return 0;

}

static int count_csum_range(struct btrfs_root *root, u64 start,
                            u64 len, u64 *found)
{
        struct btrfs_key key;
        struct btrfs_path path;
        struct extent_buffer *leaf;
        int ret;
        size_t size;
        *found = 0;
        u64 csum_end;
        u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);

        btrfs_init_path(&path);

        key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
        key.offset = start;
        key.type = BTRFS_EXTENT_CSUM_KEY;

        ret = btrfs_search_slot(NULL, root->fs_info->csum_root,
                                &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        if (ret > 0 && path.slots[0] > 0) {
                leaf = path.nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path.slots[0] - 1);
                if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
                    key.type == BTRFS_EXTENT_CSUM_KEY)
                        path.slots[0]--;
        }

        while (len > 0) {
                leaf = path.nodes[0];
                if (path.slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root->fs_info->csum_root, &path);
                        if (ret > 0)
                                break;
                        else if (ret < 0)
                                goto out;
                        leaf = path.nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
                    key.type != BTRFS_EXTENT_CSUM_KEY)
                        break;

                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.offset >= start + len)
                        break;

                if (key.offset > start)
                        start = key.offset;

                size = btrfs_item_size_nr(leaf, path.slots[0]);
                csum_end = key.offset + (size / csum_size) *
                           root->fs_info->sectorsize;
                if (csum_end > start) {
                        size = min(csum_end - start, len);
                        len -= size;
                        start += size;
                        *found += size;
                }

                path.slots[0]++;
        }
out:
        btrfs_release_path(&path);
        if (ret < 0)
                return ret;
        return 0;
}

static int process_file_extent(struct btrfs_root *root,
                                struct extent_buffer *eb,
                                int slot, struct btrfs_key *key,
                                struct shared_node *active_node)
{
        struct inode_record *rec;
        struct btrfs_file_extent_item *fi;
        u64 num_bytes = 0;
        u64 disk_bytenr = 0;
        u64 extent_offset = 0;
        u64 mask = root->fs_info->sectorsize - 1;
        int extent_type;
        int ret;

        rec = active_node->current;
        BUG_ON(rec->ino != key->objectid || rec->refs > 1);
        rec->found_file_extent = 1;

        if (rec->extent_start == (u64)-1) {
                rec->extent_start = key->offset;
                rec->extent_end = key->offset;
        }

        if (rec->extent_end > key->offset)
                rec->errors |= I_ERR_FILE_EXTENT_OVERLAP;
        else if (rec->extent_end < key->offset) {
                ret = add_file_extent_hole(&rec->holes, rec->extent_end,
                                           key->offset - rec->extent_end);
                if (ret < 0)
                        return ret;
        }

        fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
        extent_type = btrfs_file_extent_type(eb, fi);

        if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                num_bytes = btrfs_file_extent_inline_len(eb, slot, fi);
                if (num_bytes == 0)
                        rec->errors |= I_ERR_BAD_FILE_EXTENT;
                rec->found_size += num_bytes;
                num_bytes = (num_bytes + mask) & ~mask;
        } else if (extent_type == BTRFS_FILE_EXTENT_REG ||
                   extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                num_bytes = btrfs_file_extent_num_bytes(eb, fi);
                disk_bytenr = btrfs_file_extent_disk_bytenr(eb, fi);
                extent_offset = btrfs_file_extent_offset(eb, fi);
                if (num_bytes == 0 || (num_bytes & mask))
                        rec->errors |= I_ERR_BAD_FILE_EXTENT;
                if (num_bytes + extent_offset >
                    btrfs_file_extent_ram_bytes(eb, fi))
                        rec->errors |= I_ERR_BAD_FILE_EXTENT;
                if (extent_type == BTRFS_FILE_EXTENT_PREALLOC &&
                    (btrfs_file_extent_compression(eb, fi) ||
                     btrfs_file_extent_encryption(eb, fi) ||
                     btrfs_file_extent_other_encoding(eb, fi)))
                        rec->errors |= I_ERR_BAD_FILE_EXTENT;
                if (disk_bytenr > 0)
                        rec->found_size += num_bytes;
        } else {
                rec->errors |= I_ERR_BAD_FILE_EXTENT;
        }
        rec->extent_end = key->offset + num_bytes;

        /*
         * The data reloc tree will copy full extents into its inode and then
         * copy the corresponding csums.  Because the extent it copied could be
         * a preallocated extent that hasn't been written to yet there may be no
         * csums to copy, ergo we won't have csums for our file extent.  This is
         * ok so just don't bother checking csums if the inode belongs to the
         * data reloc tree.
         */
        if (disk_bytenr > 0 &&
            btrfs_header_owner(eb) != BTRFS_DATA_RELOC_TREE_OBJECTID) {
                u64 found;
                if (btrfs_file_extent_compression(eb, fi))
                        num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
                else
                        disk_bytenr += extent_offset;

                ret = count_csum_range(root, disk_bytenr, num_bytes, &found);
                if (ret < 0)
                        return ret;
                if (extent_type == BTRFS_FILE_EXTENT_REG) {
                        if (found > 0)
                                rec->found_csum_item = 1;
                        if (found < num_bytes)
                                rec->some_csum_missing = 1;
                } else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        if (found > 0)
                                rec->errors |= I_ERR_ODD_CSUM_ITEM;
                }
        }
        return 0;
}

static int process_one_leaf(struct btrfs_root *root, struct extent_buffer *eb,
                            struct walk_control *wc)
{
        struct btrfs_key key;
        u32 nritems;
        int i;
        int ret = 0;
        struct cache_tree *inode_cache;
        struct shared_node *active_node;

        if (wc->root_level == wc->active_node &&
            btrfs_root_refs(&root->root_item) == 0)
                return 0;

        active_node = wc->nodes[wc->active_node];
        inode_cache = &active_node->inode_cache;
        nritems = btrfs_header_nritems(eb);
        for (i = 0; i < nritems; i++) {
                btrfs_item_key_to_cpu(eb, &key, i);

                if (key.objectid == BTRFS_FREE_SPACE_OBJECTID)
                        continue;
                if (key.type == BTRFS_ORPHAN_ITEM_KEY)
                        continue;

                if (active_node->current == NULL ||
                    active_node->current->ino < key.objectid) {
                        if (active_node->current) {
                                active_node->current->checked = 1;
                                maybe_free_inode_rec(inode_cache,
                                                     active_node->current);
                        }
                        active_node->current = get_inode_rec(inode_cache,
                                                             key.objectid, 1);
                        BUG_ON(IS_ERR(active_node->current));
                }
                switch (key.type) {
                case BTRFS_DIR_ITEM_KEY:
                case BTRFS_DIR_INDEX_KEY:
                        ret = process_dir_item(eb, i, &key, active_node);
                        break;
                case BTRFS_INODE_REF_KEY:
                        ret = process_inode_ref(eb, i, &key, active_node);
                        break;
                case BTRFS_INODE_EXTREF_KEY:
                        ret = process_inode_extref(eb, i, &key, active_node);
                        break;
                case BTRFS_INODE_ITEM_KEY:
                        ret = process_inode_item(eb, i, &key, active_node);
                        break;
                case BTRFS_EXTENT_DATA_KEY:
                        ret = process_file_extent(root, eb, i, &key,
                                                  active_node);
                        break;
                default:
                        break;
                };
        }
        return ret;
}

struct node_refs {
        u64 bytenr[BTRFS_MAX_LEVEL];
        u64 refs[BTRFS_MAX_LEVEL];
        int need_check[BTRFS_MAX_LEVEL];
};

static int update_nodes_refs(struct btrfs_root *root, u64 bytenr,
                             struct node_refs *nrefs, u64 level);
static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path,
                            unsigned int ext_ref);

/*
 * Returns >0  Found error, not fatal, should continue
 * Returns <0  Fatal error, must exit the whole check
 * Returns 0   No errors found
 */
static int process_one_leaf_v2(struct btrfs_root *root, struct btrfs_path *path,
                               struct node_refs *nrefs, int *level, int ext_ref)
{
        struct extent_buffer *cur = path->nodes[0];
        struct btrfs_key key;
        u64 cur_bytenr;
        u32 nritems;
        u64 first_ino = 0;
        int root_level = btrfs_header_level(root->node);
        int i;
        int ret = 0; /* Final return value */
        int err = 0; /* Positive error bitmap */

        cur_bytenr = cur->start;

        /* skip to first inode item or the first inode number change */
        nritems = btrfs_header_nritems(cur);
        for (i = 0; i < nritems; i++) {
                btrfs_item_key_to_cpu(cur, &key, i);
                if (i == 0)
                        first_ino = key.objectid;
                if (key.type == BTRFS_INODE_ITEM_KEY ||
                    (first_ino && first_ino != key.objectid))
                        break;
        }
        if (i == nritems) {
                path->slots[0] = nritems;
                return 0;
        }
        path->slots[0] = i;

again:
        err |= check_inode_item(root, path, ext_ref);

        /* modify cur since check_inode_item may change path */
        cur = path->nodes[0];

        if (err & LAST_ITEM)
                goto out;

        /* still have inode items in thie leaf */
        if (cur->start == cur_bytenr)
                goto again;

        /*
         * we have switched to another leaf, above nodes may
         * have changed, here walk down the path, if a node
         * or leaf is shared, check whether we can skip this
         * node or leaf.
         */
        for (i = root_level; i >= 0; i--) {
                if (path->nodes[i]->start == nrefs->bytenr[i])
                        continue;

                ret = update_nodes_refs(root,
                                path->nodes[i]->start,
                                nrefs, i);
                if (ret)
                        goto out;

                if (!nrefs->need_check[i]) {
                        *level += 1;
                        break;
                }
        }

        for (i = 0; i < *level; i++) {
                free_extent_buffer(path->nodes[i]);
                path->nodes[i] = NULL;
        }
out:
        err &= ~LAST_ITEM;
        if (err && !ret)
                ret = err;
        return ret;
}

static void reada_walk_down(struct btrfs_root *root,
                            struct extent_buffer *node, int slot)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        u64 bytenr;
        u64 ptr_gen;
        u32 nritems;
        int i;
        int level;

        level = btrfs_header_level(node);
        if (level != 1)
                return;

        nritems = btrfs_header_nritems(node);
        for (i = slot; i < nritems; i++) {
                bytenr = btrfs_node_blockptr(node, i);
                ptr_gen = btrfs_node_ptr_generation(node, i);
                readahead_tree_block(fs_info, bytenr, ptr_gen);
        }
}

/*
 * Check the child node/leaf by the following condition:
 * 1. the first item key of the node/leaf should be the same with the one
 *    in parent.
 * 2. block in parent node should match the child node/leaf.
 * 3. generation of parent node and child's header should be consistent.
 *
 * Or the child node/leaf pointed by the key in parent is not valid.
 *
 * We hope to check leaf owner too, but since subvol may share leaves,
 * which makes leaf owner check not so strong, key check should be
 * sufficient enough for that case.
 */
static int check_child_node(struct extent_buffer *parent, int slot,
                            struct extent_buffer *child)
{
        struct btrfs_key parent_key;
        struct btrfs_key child_key;
        int ret = 0;

        btrfs_node_key_to_cpu(parent, &parent_key, slot);
        if (btrfs_header_level(child) == 0)
                btrfs_item_key_to_cpu(child, &child_key, 0);
        else
                btrfs_node_key_to_cpu(child, &child_key, 0);

        if (memcmp(&parent_key, &child_key, sizeof(parent_key))) {
                ret = -EINVAL;
                fprintf(stderr,
                        "Wrong key of child node/leaf, wanted: (%llu, %u, %llu), have: (%llu, %u, %llu)\n",
                        parent_key.objectid, parent_key.type, parent_key.offset,
                        child_key.objectid, child_key.type, child_key.offset);
        }
        if (btrfs_header_bytenr(child) != btrfs_node_blockptr(parent, slot)) {
                ret = -EINVAL;
                fprintf(stderr, "Wrong block of child node/leaf, wanted: %llu, have: %llu\n",
                        btrfs_node_blockptr(parent, slot),
                        btrfs_header_bytenr(child));
        }
        if (btrfs_node_ptr_generation(parent, slot) !=
            btrfs_header_generation(child)) {
                ret = -EINVAL;
                fprintf(stderr, "Wrong generation of child node/leaf, wanted: %llu, have: %llu\n",
                        btrfs_header_generation(child),
                        btrfs_node_ptr_generation(parent, slot));
        }
        return ret;
}

/*
 * for a tree node or leaf, if it's shared, indeed we don't need to iterate it
 * in every fs or file tree check. Here we find its all root ids, and only check
 * it in the fs or file tree which has the smallest root id.
 */
static int need_check(struct btrfs_root *root, struct ulist *roots)
{
        struct rb_node *node;
        struct ulist_node *u;

        if (roots->nnodes == 1)
                return 1;

        node = rb_first(&roots->root);
        u = rb_entry(node, struct ulist_node, rb_node);
        /*
         * current root id is not smallest, we skip it and let it be checked
         * in the fs or file tree who hash the smallest root id.
         */
        if (root->objectid != u->val)
                return 0;

        return 1;
}

/*
 * for a tree node or leaf, we record its reference count, so later if we still
 * process this node or leaf, don't need to compute its reference count again.
 */
static int update_nodes_refs(struct btrfs_root *root, u64 bytenr,
                             struct node_refs *nrefs, u64 level)
{
        int check, ret;
        u64 refs;
        struct ulist *roots;

        if (nrefs->bytenr[level] != bytenr) {
                ret = btrfs_lookup_extent_info(NULL, root, bytenr,
                                       level, 1, &refs, NULL);
                if (ret < 0)
                        return ret;

                nrefs->bytenr[level] = bytenr;
                nrefs->refs[level] = refs;
                if (refs > 1) {
                        ret = btrfs_find_all_roots(NULL, root->fs_info, bytenr,
                                                   0, &roots);
                        if (ret)
                                return -EIO;

                        check = need_check(root, roots);
                        ulist_free(roots);
                        nrefs->need_check[level] = check;
                } else {
                        nrefs->need_check[level] = 1;
                }
        }

        return 0;
}

static int walk_down_tree(struct btrfs_root *root, struct btrfs_path *path,
                          struct walk_control *wc, int *level,
                          struct node_refs *nrefs)
{
        enum btrfs_tree_block_status status;
        u64 bytenr;
        u64 ptr_gen;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_buffer *next;
        struct extent_buffer *cur;
        int ret, err = 0;
        u64 refs;

        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);

        if (path->nodes[*level]->start == nrefs->bytenr[*level]) {
                refs = nrefs->refs[*level];
                ret = 0;
        } else {
                ret = btrfs_lookup_extent_info(NULL, root,
                                       path->nodes[*level]->start,
                                       *level, 1, &refs, NULL);
                if (ret < 0) {
                        err = ret;
                        goto out;
                }
                nrefs->bytenr[*level] = path->nodes[*level]->start;
                nrefs->refs[*level] = refs;
        }

        if (refs > 1) {
                ret = enter_shared_node(root, path->nodes[*level]->start,
                                        refs, wc, *level);
                if (ret > 0) {
                        err = ret;
                        goto out;
                }
        }

        while (*level >= 0) {
                WARN_ON(*level < 0);
                WARN_ON(*level >= BTRFS_MAX_LEVEL);
                cur = path->nodes[*level];

                if (btrfs_header_level(cur) != *level)
                        WARN_ON(1);

                if (path->slots[*level] >= btrfs_header_nritems(cur))
                        break;
                if (*level == 0) {
                        ret = process_one_leaf(root, cur, wc);
                        if (ret < 0)
                                err = ret;
                        break;
                }
                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);

                if (bytenr == nrefs->bytenr[*level - 1]) {
                        refs = nrefs->refs[*level - 1];
                } else {
                        ret = btrfs_lookup_extent_info(NULL, root, bytenr,
                                        *level - 1, 1, &refs, NULL);
                        if (ret < 0) {
                                refs = 0;
                        } else {
                                nrefs->bytenr[*level - 1] = bytenr;
                                nrefs->refs[*level - 1] = refs;
                        }
                }

                if (refs > 1) {
                        ret = enter_shared_node(root, bytenr, refs,
                                                wc, *level - 1);
                        if (ret > 0) {
                                path->slots[*level]++;
                                continue;
                        }
                }

                next = btrfs_find_tree_block(fs_info, bytenr, fs_info->nodesize);
                if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
                        free_extent_buffer(next);
                        reada_walk_down(root, cur, path->slots[*level]);
                        next = read_tree_block(root->fs_info, bytenr, ptr_gen);
                        if (!extent_buffer_uptodate(next)) {
                                struct btrfs_key node_key;

                                btrfs_node_key_to_cpu(path->nodes[*level],
                                                      &node_key,
                                                      path->slots[*level]);
                                btrfs_add_corrupt_extent_record(root->fs_info,
                                                &node_key,
                                                path->nodes[*level]->start,
                                                root->fs_info->nodesize,
                                                *level);
                                err = -EIO;
                                goto out;
                        }
                }

                ret = check_child_node(cur, path->slots[*level], next);
                if (ret) {
                        free_extent_buffer(next);
                        err = ret;
                        goto out;
                }

                if (btrfs_is_leaf(next))
                        status = btrfs_check_leaf(root, NULL, next);
                else
                        status = btrfs_check_node(root, NULL, next);
                if (status != BTRFS_TREE_BLOCK_CLEAN) {
                        free_extent_buffer(next);
                        err = -EIO;
                        goto out;
                }

                *level = *level - 1;
                free_extent_buffer(path->nodes[*level]);
                path->nodes[*level] = next;
                path->slots[*level] = 0;
        }
out:
        path->slots[*level] = btrfs_header_nritems(path->nodes[*level]);
        return err;
}

static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path,
                            unsigned int ext_ref);

/*
 * Returns >0  Found error, should continue
 * Returns <0  Fatal error, must exit the whole check
 * Returns 0   No errors found
 */
static int walk_down_tree_v2(struct btrfs_root *root, struct btrfs_path *path,
                             int *level, struct node_refs *nrefs, int ext_ref)
{
        enum btrfs_tree_block_status status;
        u64 bytenr;
        u64 ptr_gen;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_buffer *next;
        struct extent_buffer *cur;
        int ret;

        WARN_ON(*level < 0);
        WARN_ON(*level >= BTRFS_MAX_LEVEL);

        ret = update_nodes_refs(root, path->nodes[*level]->start,
                                nrefs, *level);
        if (ret < 0)
                return ret;

        while (*level >= 0) {
                WARN_ON(*level < 0);
                WARN_ON(*level >= BTRFS_MAX_LEVEL);
                cur = path->nodes[*level];

                if (btrfs_header_level(cur) != *level)
                        WARN_ON(1);

                if (path->slots[*level] >= btrfs_header_nritems(cur))
                        break;
                /* Don't forgot to check leaf/node validation */
                if (*level == 0) {
                        ret = btrfs_check_leaf(root, NULL, cur);
                        if (ret != BTRFS_TREE_BLOCK_CLEAN) {
                                ret = -EIO;
                                break;
                        }
                        ret = process_one_leaf_v2(root, path, nrefs,
                                                  level, ext_ref);
                        cur = path->nodes[*level];
                        break;
                } else {
                        ret = btrfs_check_node(root, NULL, cur);
                        if (ret != BTRFS_TREE_BLOCK_CLEAN) {
                                ret = -EIO;
                                break;
                        }
                }
                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);

                ret = update_nodes_refs(root, bytenr, nrefs, *level - 1);
                if (ret)
                        break;
                if (!nrefs->need_check[*level - 1]) {
                        path->slots[*level]++;
                        continue;
                }

                next = btrfs_find_tree_block(fs_info, bytenr, fs_info->nodesize);
                if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
                        free_extent_buffer(next);
                        reada_walk_down(root, cur, path->slots[*level]);
                        next = read_tree_block(fs_info, bytenr, ptr_gen);
                        if (!extent_buffer_uptodate(next)) {
                                struct btrfs_key node_key;

                                btrfs_node_key_to_cpu(path->nodes[*level],
                                                      &node_key,
                                                      path->slots[*level]);
                                btrfs_add_corrupt_extent_record(fs_info,
                                                &node_key,
                                                path->nodes[*level]->start,
                                                fs_info->nodesize,
                                                *level);
                                ret = -EIO;
                                break;
                        }
                }

                ret = check_child_node(cur, path->slots[*level], next);
                if (ret < 0) 
                        break;

                if (btrfs_is_leaf(next))
                        status = btrfs_check_leaf(root, NULL, next);
                else
                        status = btrfs_check_node(root, NULL, next);
                if (status != BTRFS_TREE_BLOCK_CLEAN) {
                        free_extent_buffer(next);
                        ret = -EIO;
                        break;
                }

                *level = *level - 1;
                free_extent_buffer(path->nodes[*level]);
                path->nodes[*level] = next;
                path->slots[*level] = 0;
        }
        return ret;
}

static int walk_up_tree(struct btrfs_root *root, struct btrfs_path *path,
                        struct walk_control *wc, int *level)
{
        int i;
        struct extent_buffer *leaf;

        for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
                leaf = path->nodes[i];
                if (path->slots[i] + 1 < btrfs_header_nritems(leaf)) {
                        path->slots[i]++;
                        *level = i;
                        return 0;
                } else {
                        free_extent_buffer(path->nodes[*level]);
                        path->nodes[*level] = NULL;
                        BUG_ON(*level > wc->active_node);
                        if (*level == wc->active_node)
                                leave_shared_node(root, wc, *level);
                        *level = i + 1;
                }
        }
        return 1;
}

static int walk_up_tree_v2(struct btrfs_root *root, struct btrfs_path *path,
                           int *level)
{
        int i;
        struct extent_buffer *leaf;

        for (i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
                leaf = path->nodes[i];
                if (path->slots[i] + 1 < btrfs_header_nritems(leaf)) {
                        path->slots[i]++;
                        *level = i;
                        return 0;
                } else {
                        free_extent_buffer(path->nodes[*level]);
                        path->nodes[*level] = NULL;
                        *level = i + 1;
                }
        }
        return 1;
}

static int check_root_dir(struct inode_record *rec)
{
        struct inode_backref *backref;
        int ret = -1;

        if (!rec->found_inode_item || rec->errors)
                goto out;
        if (rec->nlink != 1 || rec->found_link != 0)
                goto out;
        if (list_empty(&rec->backrefs))
                goto out;
        backref = to_inode_backref(rec->backrefs.next);
        if (!backref->found_inode_ref)
                goto out;
        if (backref->index != 0 || backref->namelen != 2 ||
            memcmp(backref->name, "..", 2))
                goto out;
        if (backref->found_dir_index || backref->found_dir_item)
                goto out;
        ret = 0;
out:
        return ret;
}

static int repair_inode_isize(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root, struct btrfs_path *path,
                              struct inode_record *rec)
{
        struct btrfs_inode_item *ei;
        struct btrfs_key key;
        int ret;

        key.objectid = rec->ino;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = (u64)-1;

        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
        if (ret < 0)
                goto out;
        if (ret) {
                if (!path->slots[0]) {
                        ret = -ENOENT;
                        goto out;
                }
                path->slots[0]--;
                ret = 0;
        }
        btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
        if (key.objectid != rec->ino) {
                ret = -ENOENT;
                goto out;
        }

        ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
                            struct btrfs_inode_item);
        btrfs_set_inode_size(path->nodes[0], ei, rec->found_size);
        btrfs_mark_buffer_dirty(path->nodes[0]);
        rec->errors &= ~I_ERR_DIR_ISIZE_WRONG;
        printf("reset isize for dir %Lu root %Lu\n", rec->ino,
               root->root_key.objectid);
out:
        btrfs_release_path(path);
        return ret;
}

static int repair_inode_orphan_item(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root,
                                    struct btrfs_path *path,
                                    struct inode_record *rec)
{
        int ret;

        ret = btrfs_add_orphan_item(trans, root, path, rec->ino);
        btrfs_release_path(path);
        if (!ret)
                rec->errors &= ~I_ERR_NO_ORPHAN_ITEM;
        return ret;
}

static int repair_inode_nbytes(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct btrfs_path *path,
                               struct inode_record *rec)
{
        struct btrfs_inode_item *ei;
        struct btrfs_key key;
        int ret = 0;

        key.objectid = rec->ino;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto out;
        }

        /* Since ret == 0, no need to check anything */
        ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
                            struct btrfs_inode_item);
        btrfs_set_inode_nbytes(path->nodes[0], ei, rec->found_size);
        btrfs_mark_buffer_dirty(path->nodes[0]);
        rec->errors &= ~I_ERR_FILE_NBYTES_WRONG;
        printf("reset nbytes for ino %llu root %llu\n",
               rec->ino, root->root_key.objectid);
out:
        btrfs_release_path(path);
        return ret;
}

static int add_missing_dir_index(struct btrfs_root *root,
                                 struct cache_tree *inode_cache,
                                 struct inode_record *rec,
                                 struct inode_backref *backref)
{
        struct btrfs_path path;
        struct btrfs_trans_handle *trans;
        struct btrfs_dir_item *dir_item;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        struct btrfs_disk_key disk_key;
        struct inode_record *dir_rec;
        unsigned long name_ptr;
        u32 data_size = sizeof(*dir_item) + backref->namelen;
        int ret;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        fprintf(stderr, "repairing missing dir index item for inode %llu\n",
                (unsigned long long)rec->ino);

        btrfs_init_path(&path);
        key.objectid = backref->dir;
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = backref->index;
        ret = btrfs_insert_empty_item(trans, root, &path, &key, data_size);
        BUG_ON(ret);

        leaf = path.nodes[0];
        dir_item = btrfs_item_ptr(leaf, path.slots[0], struct btrfs_dir_item);

        disk_key.objectid = cpu_to_le64(rec->ino);
        disk_key.type = BTRFS_INODE_ITEM_KEY;
        disk_key.offset = 0;

        btrfs_set_dir_item_key(leaf, dir_item, &disk_key);
        btrfs_set_dir_type(leaf, dir_item, imode_to_type(rec->imode));
        btrfs_set_dir_data_len(leaf, dir_item, 0);
        btrfs_set_dir_name_len(leaf, dir_item, backref->namelen);
        name_ptr = (unsigned long)(dir_item + 1);
        write_extent_buffer(leaf, backref->name, name_ptr, backref->namelen);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(&path);
        btrfs_commit_transaction(trans, root);

        backref->found_dir_index = 1;
        dir_rec = get_inode_rec(inode_cache, backref->dir, 0);
        BUG_ON(IS_ERR(dir_rec));
        if (!dir_rec)
                return 0;
        dir_rec->found_size += backref->namelen;
        if (dir_rec->found_size == dir_rec->isize &&
            (dir_rec->errors & I_ERR_DIR_ISIZE_WRONG))
                dir_rec->errors &= ~I_ERR_DIR_ISIZE_WRONG;
        if (dir_rec->found_size != dir_rec->isize)
                dir_rec->errors |= I_ERR_DIR_ISIZE_WRONG;

        return 0;
}

static int delete_dir_index(struct btrfs_root *root,
                            struct inode_backref *backref)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_dir_item *di;
        struct btrfs_path path;
        int ret = 0;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        fprintf(stderr, "Deleting bad dir index [%llu,%u,%llu] root %llu\n",
                (unsigned long long)backref->dir,
                BTRFS_DIR_INDEX_KEY, (unsigned long long)backref->index,
                (unsigned long long)root->objectid);

        btrfs_init_path(&path);
        di = btrfs_lookup_dir_index(trans, root, &path, backref->dir,
                                    backref->name, backref->namelen,
                                    backref->index, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                btrfs_release_path(&path);
                btrfs_commit_transaction(trans, root);
                if (ret == -ENOENT)
                        return 0;
                return ret;
        }

        if (!di)
                ret = btrfs_del_item(trans, root, &path);
        else
                ret = btrfs_delete_one_dir_name(trans, root, &path, di);
        BUG_ON(ret);
        btrfs_release_path(&path);
        btrfs_commit_transaction(trans, root);
        return ret;
}

static int __create_inode_item(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root, u64 ino, u64 size,
                               u64 nbytes, u64 nlink, u32 mode)
{
        struct btrfs_inode_item ii;
        time_t now = time(NULL);
        int ret;

        btrfs_set_stack_inode_size(&ii, size);
        btrfs_set_stack_inode_nbytes(&ii, nbytes);
        btrfs_set_stack_inode_nlink(&ii, nlink);
        btrfs_set_stack_inode_mode(&ii, mode);
        btrfs_set_stack_inode_generation(&ii, trans->transid);
        btrfs_set_stack_timespec_nsec(&ii.atime, 0);
        btrfs_set_stack_timespec_sec(&ii.ctime, now);
        btrfs_set_stack_timespec_nsec(&ii.ctime, 0);
        btrfs_set_stack_timespec_sec(&ii.mtime, now);
        btrfs_set_stack_timespec_nsec(&ii.mtime, 0);
        btrfs_set_stack_timespec_sec(&ii.otime, 0);
        btrfs_set_stack_timespec_nsec(&ii.otime, 0);

        ret = btrfs_insert_inode(trans, root, ino, &ii);
        ASSERT(!ret);

        warning("root %llu inode %llu recreating inode item, this may "
                "be incomplete, please check permissions and content after "
                "the fsck completes.\n", (unsigned long long)root->objectid,
                (unsigned long long)ino);

        return 0;
}

static int create_inode_item_lowmem(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root, u64 ino,
                                    u8 filetype)
{
        u32 mode = (filetype == BTRFS_FT_DIR ? S_IFDIR : S_IFREG) | 0755;

        return __create_inode_item(trans, root, ino, 0, 0, 0, mode);
}

static int create_inode_item(struct btrfs_root *root,
                             struct inode_record *rec, int root_dir)
{
        struct btrfs_trans_handle *trans;
        u64 nlink = 0;
        u32 mode = 0;
        u64 size = 0;
        int ret;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                return ret;
        }

        nlink = root_dir ? 1 : rec->found_link;
        if (rec->found_dir_item) {
                if (rec->found_file_extent)
                        fprintf(stderr, "root %llu inode %llu has both a dir "
                                "item and extents, unsure if it is a dir or a "
                                "regular file so setting it as a directory\n",
                                (unsigned long long)root->objectid,
                                (unsigned long long)rec->ino);
                mode = S_IFDIR | 0755;
                size = rec->found_size;
        } else if (!rec->found_dir_item) {
                size = rec->extent_end;
                mode =  S_IFREG | 0755;
        }

        ret = __create_inode_item(trans, root, rec->ino, size, rec->nbytes,
                                  nlink, mode);
        btrfs_commit_transaction(trans, root);
        return 0;
}

static int repair_inode_backrefs(struct btrfs_root *root,
                                 struct inode_record *rec,
                                 struct cache_tree *inode_cache,
                                 int delete)
{
        struct inode_backref *tmp, *backref;
        u64 root_dirid = btrfs_root_dirid(&root->root_item);
        int ret = 0;
        int repaired = 0;

        list_for_each_entry_safe(backref, tmp, &rec->backrefs, list) {
                if (!delete && rec->ino == root_dirid) {
                        if (!rec->found_inode_item) {
                                ret = create_inode_item(root, rec, 1);
                                if (ret)
                                        break;
                                repaired++;
                        }
                }

                /* Index 0 for root dir's are special, don't mess with it */
                if (rec->ino == root_dirid && backref->index == 0)
                        continue;

                if (delete &&
                    ((backref->found_dir_index && !backref->found_inode_ref) ||
                     (backref->found_dir_index && backref->found_inode_ref &&
                      (backref->errors & REF_ERR_INDEX_UNMATCH)))) {
                        ret = delete_dir_index(root, backref);
                        if (ret)
                                break;
                        repaired++;
                        list_del(&backref->list);
                        free(backref);
                        continue;
                }

                if (!delete && !backref->found_dir_index &&
                    backref->found_dir_item && backref->found_inode_ref) {
                        ret = add_missing_dir_index(root, inode_cache, rec,
                                                    backref);
                        if (ret)
                                break;
                        repaired++;
                        if (backref->found_dir_item &&
                            backref->found_dir_index) {
                                if (!backref->errors &&
                                    backref->found_inode_ref) {
                                        list_del(&backref->list);
                                        free(backref);
                                        continue;
                                }
                        }
                }

                if (!delete && (!backref->found_dir_index &&
                                !backref->found_dir_item &&
                                backref->found_inode_ref)) {
                        struct btrfs_trans_handle *trans;
                        struct btrfs_key location;

                        ret = check_dir_conflict(root, backref->name,
                                                 backref->namelen,
                                                 backref->dir,
                                                 backref->index);
                        if (ret) {
                                /*
                                 * let nlink fixing routine to handle it,
                                 * which can do it better.
                                 */
                                ret = 0;
                                break;
                        }
                        location.objectid = rec->ino;
                        location.type = BTRFS_INODE_ITEM_KEY;
                        location.offset = 0;

                        trans = btrfs_start_transaction(root, 1);
                        if (IS_ERR(trans)) {
                                ret = PTR_ERR(trans);
                                break;
                        }
                        fprintf(stderr, "adding missing dir index/item pair "
                                "for inode %llu\n",
                                (unsigned long long)rec->ino);
                        ret = btrfs_insert_dir_item(trans, root, backref->name,
                                                    backref->namelen,
                                                    backref->dir, &location,
                                                    imode_to_type(rec->imode),
                                                    backref->index);
                        BUG_ON(ret);
                        btrfs_commit_transaction(trans, root);
                        repaired++;
                }

                if (!delete && (backref->found_inode_ref &&
                                backref->found_dir_index &&
                                backref->found_dir_item &&
                                !(backref->errors & REF_ERR_INDEX_UNMATCH) &&
                                !rec->found_inode_item)) {
                        ret = create_inode_item(root, rec, 0);
                        if (ret)
                                break;
                        repaired++;
                }

        }
        return ret ? ret : repaired;
}

/*
 * To determine the file type for nlink/inode_item repair
 *
 * Return 0 if file type is found and BTRFS_FT_* is stored into type.
 * Return -ENOENT if file type is not found.
 */
static int find_file_type(struct inode_record *rec, u8 *type)
{
        struct inode_backref *backref;

        /* For inode item recovered case */
        if (rec->found_inode_item) {
                *type = imode_to_type(rec->imode);
                return 0;
        }

        list_for_each_entry(backref, &rec->backrefs, list) {
                if (backref->found_dir_index || backref->found_dir_item) {
                        *type = backref->filetype;
                        return 0;
                }
        }
        return -ENOENT;
}

/*
 * To determine the file name for nlink repair
 *
 * Return 0 if file name is found, set name and namelen.
 * Return -ENOENT if file name is not found.
 */
static int find_file_name(struct inode_record *rec,
                          char *name, int *namelen)
{
        struct inode_backref *backref;

        list_for_each_entry(backref, &rec->backrefs, list) {
                if (backref->found_dir_index || backref->found_dir_item ||
                    backref->found_inode_ref) {
                        memcpy(name, backref->name, backref->namelen);
                        *namelen = backref->namelen;
                        return 0;
                }
        }
        return -ENOENT;
}

/* Reset the nlink of the inode to the correct one */
static int reset_nlink(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct btrfs_path *path,
                       struct inode_record *rec)
{
        struct inode_backref *backref;
        struct inode_backref *tmp;
        struct btrfs_key key;
        struct btrfs_inode_item *inode_item;
        int ret = 0;

        /* We don't believe this either, reset it and iterate backref */
        rec->found_link = 0;

        /* Remove all backref including the valid ones */
        list_for_each_entry_safe(backref, tmp, &rec->backrefs, list) {
                ret = btrfs_unlink(trans, root, rec->ino, backref->dir,
                                   backref->index, backref->name,
                                   backref->namelen, 0);
                if (ret < 0)
                        goto out;

                /* remove invalid backref, so it won't be added back */
                if (!(backref->found_dir_index &&
                      backref->found_dir_item &&
                      backref->found_inode_ref)) {
                        list_del(&backref->list);
                        free(backref);
                } else {
                        rec->found_link++;
                }
        }

        /* Set nlink to 0 */
        key.objectid = rec->ino;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = -ENOENT;
                goto out;
        }
        inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                    struct btrfs_inode_item);
        btrfs_set_inode_nlink(path->nodes[0], inode_item, 0);
        btrfs_mark_buffer_dirty(path->nodes[0]);
        btrfs_release_path(path);

        /*
         * Add back valid inode_ref/dir_item/dir_index,
         * add_link() will handle the nlink inc, so new nlink must be correct
         */
        list_for_each_entry(backref, &rec->backrefs, list) {
                ret = btrfs_add_link(trans, root, rec->ino, backref->dir,
                                     backref->name, backref->namelen,
                                     backref->filetype, &backref->index, 1, 0);
                if (ret < 0)
                        goto out;
        }
out:
        btrfs_release_path(path);
        return ret;
}

static int get_highest_inode(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_path *path,
                                u64 *highest_ino)
{
        struct btrfs_key key, found_key;
        int ret;

        btrfs_init_path(path);
        key.objectid = BTRFS_LAST_FREE_OBJECTID;
        key.offset = -1;
        key.type = BTRFS_INODE_ITEM_KEY;
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret == 1) {
                btrfs_item_key_to_cpu(path->nodes[0], &found_key,
                                path->slots[0] - 1);
                *highest_ino = found_key.objectid;
                ret = 0;
        }
        if (*highest_ino >= BTRFS_LAST_FREE_OBJECTID)
                ret = -EOVERFLOW;
        btrfs_release_path(path);
        return ret;
}

static int repair_inode_nlinks(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct btrfs_path *path,
                               struct inode_record *rec)
{
        char *dir_name = "lost+found";
        char namebuf[BTRFS_NAME_LEN] = {0};
        u64 lost_found_ino;
        u32 mode = 0700;
        u8 type = 0;
        int namelen = 0;
        int name_recovered = 0;
        int type_recovered = 0;
        int ret = 0;

        /*
         * Get file name and type first before these invalid inode ref
         * are deleted by remove_all_invalid_backref()
         */
        name_recovered = !find_file_name(rec, namebuf, &namelen);
        type_recovered = !find_file_type(rec, &type);

        if (!name_recovered) {
                printf("Can't get file name for inode %llu, using '%llu' as fallback\n",
                       rec->ino, rec->ino);
                namelen = count_digits(rec->ino);
                sprintf(namebuf, "%llu", rec->ino);
                name_recovered = 1;
        }
        if (!type_recovered) {
                printf("Can't get file type for inode %llu, using FILE as fallback\n",
                       rec->ino);
                type = BTRFS_FT_REG_FILE;
                type_recovered = 1;
        }

        ret = reset_nlink(trans, root, path, rec);
        if (ret < 0) {
                fprintf(stderr,
                        "Failed to reset nlink for inode %llu: %s\n",
                        rec->ino, strerror(-ret));
                goto out;
        }

        if (rec->found_link == 0) {
                ret = get_highest_inode(trans, root, path, &lost_found_ino);
                if (ret < 0)
                        goto out;
                lost_found_ino++;
                ret = btrfs_mkdir(trans, root, dir_name, strlen(dir_name),
                                  BTRFS_FIRST_FREE_OBJECTID, &lost_found_ino,
                                  mode);
                if (ret < 0) {
                        fprintf(stderr, "Failed to create '%s' dir: %s\n",
                                dir_name, strerror(-ret));
                        goto out;
                }
                ret = btrfs_add_link(trans, root, rec->ino, lost_found_ino,
                                     namebuf, namelen, type, NULL, 1, 0);
                /*
                 * Add ".INO" suffix several times to handle case where
                 * "FILENAME.INO" is already taken by another file.
                 */
                while (ret == -EEXIST) {
                        /*
                         * Conflicting file name, add ".INO" as suffix * +1 for '.'
                         */
                        if (namelen + count_digits(rec->ino) + 1 >
                            BTRFS_NAME_LEN) {
                                ret = -EFBIG;
                                goto out;
                        }
                        snprintf(namebuf + namelen, BTRFS_NAME_LEN - namelen,
                                 ".%llu", rec->ino);
                        namelen += count_digits(rec->ino) + 1;
                        ret = btrfs_add_link(trans, root, rec->ino,
                                             lost_found_ino, namebuf,
                                             namelen, type, NULL, 1, 0);
                }
                if (ret < 0) {
                        fprintf(stderr,
                                "Failed to link the inode %llu to %s dir: %s\n",
                                rec->ino, dir_name, strerror(-ret));
                        goto out;
                }
                /*
                 * Just increase the found_link, don't actually add the
                 * backref. This will make things easier and this inode
                 * record will be freed after the repair is done.
                 * So fsck will not report problem about this inode.
                 */
                rec->found_link++;
                printf("Moving file '%.*s' to '%s' dir since it has no valid backref\n",
                       namelen, namebuf, dir_name);
        }
        printf("Fixed the nlink of inode %llu\n", rec->ino);
out:
        /*
         * Clear the flag anyway, or we will loop forever for the same inode
         * as it will not be removed from the bad inode list and the dead loop
         * happens.
         */
        rec->errors &= ~I_ERR_LINK_COUNT_WRONG;
        btrfs_release_path(path);
        return ret;
}

/*
 * Check if there is any normal(reg or prealloc) file extent for given
 * ino.
 * This is used to determine the file type when neither its dir_index/item or
 * inode_item exists.
 *
 * This will *NOT* report error, if any error happens, just consider it does
 * not have any normal file extent.
 */
static int find_normal_file_extent(struct btrfs_root *root, u64 ino)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_file_extent_item *fi;
        u8 type;
        int ret = 0;

        btrfs_init_path(&path);
        key.objectid = ino;
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = 0;

        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0) {
                ret = 0;
                goto out;
        }
        if (ret && path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                ret = btrfs_next_leaf(root, &path);
                if (ret) {
                        ret = 0;
                        goto out;
                }
        }
        while (1) {
                btrfs_item_key_to_cpu(path.nodes[0], &found_key,
                                      path.slots[0]);
                if (found_key.objectid != ino ||
                    found_key.type != BTRFS_EXTENT_DATA_KEY)
                        break;
                fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                    struct btrfs_file_extent_item);
                type = btrfs_file_extent_type(path.nodes[0], fi);
                if (type != BTRFS_FILE_EXTENT_INLINE) {
                        ret = 1;
                        goto out;
                }
        }
out:
        btrfs_release_path(&path);
        return ret;
}

static u32 btrfs_type_to_imode(u8 type)
{
        static u32 imode_by_btrfs_type[] = {
                [BTRFS_FT_REG_FILE]     = S_IFREG,
                [BTRFS_FT_DIR]          = S_IFDIR,
                [BTRFS_FT_CHRDEV]       = S_IFCHR,
                [BTRFS_FT_BLKDEV]       = S_IFBLK,
                [BTRFS_FT_FIFO]         = S_IFIFO,
                [BTRFS_FT_SOCK]         = S_IFSOCK,
                [BTRFS_FT_SYMLINK]      = S_IFLNK,
        };

        return imode_by_btrfs_type[(type)];
}

static int repair_inode_no_item(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root,
                                struct btrfs_path *path,
                                struct inode_record *rec)
{
        u8 filetype;
        u32 mode = 0700;
        int type_recovered = 0;
        int ret = 0;

        printf("Trying to rebuild inode:%llu\n", rec->ino);

        type_recovered = !find_file_type(rec, &filetype);

        /*
         * Try to determine inode type if type not found.
         *
         * For found regular file extent, it must be FILE.
         * For found dir_item/index, it must be DIR.
         *
         * For undetermined one, use FILE as fallback.
         *
         * TODO:
         * 1. If found backref(inode_index/item is already handled) to it,
         *    it must be DIR.
         *    Need new inode-inode ref structure to allow search for that.
         */
        if (!type_recovered) {
                if (rec->found_file_extent &&
                    find_normal_file_extent(root, rec->ino)) {
                        type_recovered = 1;
                        filetype = BTRFS_FT_REG_FILE;
                } else if (rec->found_dir_item) {
                        type_recovered = 1;
                        filetype = BTRFS_FT_DIR;
                } else if (!list_empty(&rec->orphan_extents)) {
                        type_recovered = 1;
                        filetype = BTRFS_FT_REG_FILE;
                } else{
                        printf("Can't determine the filetype for inode %llu, assume it is a normal file\n",
                               rec->ino);
                        type_recovered = 1;
                        filetype = BTRFS_FT_REG_FILE;
                }
        }

        ret = btrfs_new_inode(trans, root, rec->ino,
                              mode | btrfs_type_to_imode(filetype));
        if (ret < 0)
                goto out;

        /*
         * Here inode rebuild is done, we only rebuild the inode item,
         * don't repair the nlink(like move to lost+found).
         * That is the job of nlink repair.
         *
         * We just fill the record and return
         */
        rec->found_dir_item = 1;
        rec->imode = mode | btrfs_type_to_imode(filetype);
        rec->nlink = 0;
        rec->errors &= ~I_ERR_NO_INODE_ITEM;
        /* Ensure the inode_nlinks repair function will be called */
        rec->errors |= I_ERR_LINK_COUNT_WRONG;
out:
        return ret;
}

static int repair_inode_orphan_extent(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root,
                                      struct btrfs_path *path,
                                      struct inode_record *rec)
{
        struct orphan_data_extent *orphan;
        struct orphan_data_extent *tmp;
        int ret = 0;

        list_for_each_entry_safe(orphan, tmp, &rec->orphan_extents, list) {
                /*
                 * Check for conflicting file extents
                 *
                 * Here we don't know whether the extents is compressed or not,
                 * so we can only assume it not compressed nor data offset,
                 * and use its disk_len as extent length.
                 */
                ret = btrfs_get_extent(NULL, root, path, orphan->objectid,
                                       orphan->offset, orphan->disk_len, 0);
                btrfs_release_path(path);
                if (ret < 0)
                        goto out;
                if (!ret) {
                        fprintf(stderr,
                                "orphan extent (%llu, %llu) conflicts, delete the orphan\n",
                                orphan->disk_bytenr, orphan->disk_len);
                        ret = btrfs_free_extent(trans,
                                        root->fs_info->extent_root,
                                        orphan->disk_bytenr, orphan->disk_len,
                                        0, root->objectid, orphan->objectid,
                                        orphan->offset);
                        if (ret < 0)
                                goto out;
                }
                ret = btrfs_insert_file_extent(trans, root, orphan->objectid,
                                orphan->offset, orphan->disk_bytenr,
                                orphan->disk_len, orphan->disk_len);
                if (ret < 0)
                        goto out;

                /* Update file size info */
                rec->found_size += orphan->disk_len;
                if (rec->found_size == rec->nbytes)
                        rec->errors &= ~I_ERR_FILE_NBYTES_WRONG;

                /* Update the file extent hole info too */
                ret = del_file_extent_hole(&rec->holes, orphan->offset,
                                           orphan->disk_len);
                if (ret < 0)
                        goto out;
                if (RB_EMPTY_ROOT(&rec->holes))
                        rec->errors &= ~I_ERR_FILE_EXTENT_DISCOUNT;

                list_del(&orphan->list);
                free(orphan);
        }
        rec->errors &= ~I_ERR_FILE_EXTENT_ORPHAN;
out:
        return ret;
}

static int repair_inode_discount_extent(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_path *path,
                                        struct inode_record *rec)
{
        struct rb_node *node;
        struct file_extent_hole *hole;
        int found = 0;
        int ret = 0;

        node = rb_first(&rec->holes);

        while (node) {
                found = 1;
                hole = rb_entry(node, struct file_extent_hole, node);
                ret = btrfs_punch_hole(trans, root, rec->ino,
                                       hole->start, hole->len);
                if (ret < 0)
                        goto out;
                ret = del_file_extent_hole(&rec->holes, hole->start,
                                           hole->len);
                if (ret < 0)
                        goto out;
                if (RB_EMPTY_ROOT(&rec->holes))
                        rec->errors &= ~I_ERR_FILE_EXTENT_DISCOUNT;
                node = rb_first(&rec->holes);
        }
        /* special case for a file losing all its file extent */
        if (!found) {
                ret = btrfs_punch_hole(trans, root, rec->ino, 0,
                                       round_up(rec->isize,
                                                root->fs_info->sectorsize));
                if (ret < 0)
                        goto out;
        }
        printf("Fixed discount file extents for inode: %llu in root: %llu\n",
               rec->ino, root->objectid);
out:
        return ret;
}

static int try_repair_inode(struct btrfs_root *root, struct inode_record *rec)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_path path;
        int ret = 0;

        if (!(rec->errors & (I_ERR_DIR_ISIZE_WRONG |
                             I_ERR_NO_ORPHAN_ITEM |
                             I_ERR_LINK_COUNT_WRONG |
                             I_ERR_NO_INODE_ITEM |
                             I_ERR_FILE_EXTENT_ORPHAN |
                             I_ERR_FILE_EXTENT_DISCOUNT|
                             I_ERR_FILE_NBYTES_WRONG)))
                return rec->errors;

        /*
         * For nlink repair, it may create a dir and add link, so
         * 2 for parent(256)'s dir_index and dir_item
         * 2 for lost+found dir's inode_item and inode_ref
         * 1 for the new inode_ref of the file
         * 2 for lost+found dir's dir_index and dir_item for the file
         */
        trans = btrfs_start_transaction(root, 7);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_init_path(&path);
        if (rec->errors & I_ERR_NO_INODE_ITEM)
                ret = repair_inode_no_item(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_FILE_EXTENT_ORPHAN)
                ret = repair_inode_orphan_extent(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_FILE_EXTENT_DISCOUNT)
                ret = repair_inode_discount_extent(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_DIR_ISIZE_WRONG)
                ret = repair_inode_isize(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_NO_ORPHAN_ITEM)
                ret = repair_inode_orphan_item(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_LINK_COUNT_WRONG)
                ret = repair_inode_nlinks(trans, root, &path, rec);
        if (!ret && rec->errors & I_ERR_FILE_NBYTES_WRONG)
                ret = repair_inode_nbytes(trans, root, &path, rec);
        btrfs_commit_transaction(trans, root);
        btrfs_release_path(&path);
        return ret;
}

static int check_inode_recs(struct btrfs_root *root,
                            struct cache_tree *inode_cache)
{
        struct cache_extent *cache;
        struct ptr_node *node;
        struct inode_record *rec;
        struct inode_backref *backref;
        int stage = 0;
        int ret = 0;
        int err = 0;
        u64 error = 0;
        u64 root_dirid = btrfs_root_dirid(&root->root_item);

        if (btrfs_root_refs(&root->root_item) == 0) {
                if (!cache_tree_empty(inode_cache))
                        fprintf(stderr, "warning line %d\n", __LINE__);
                return 0;
        }

        /*
         * We need to repair backrefs first because we could change some of the
         * errors in the inode recs.
         *
         * We also need to go through and delete invalid backrefs first and then
         * add the correct ones second.  We do this because we may get EEXIST
         * when adding back the correct index because we hadn't yet deleted the
         * invalid index.
         *
         * For example, if we were missing a dir index then the directories
         * isize would be wrong, so if we fixed the isize to what we thought it
         * would be and then fixed the backref we'd still have a invalid fs, so
         * we need to add back the dir index and then check to see if the isize
         * is still wrong.
         */
        while (stage < 3) {
                stage++;
                if (stage == 3 && !err)
                        break;

                cache = search_cache_extent(inode_cache, 0);
                while (repair && cache) {
                        node = container_of(cache, struct ptr_node, cache);
                        rec = node->data;
                        cache = next_cache_extent(cache);

                        /* Need to free everything up and rescan */
                        if (stage == 3) {
                                remove_cache_extent(inode_cache, &node->cache);
                                free(node);
                                free_inode_rec(rec);
                                continue;
                        }

                        if (list_empty(&rec->backrefs))
                                continue;

                        ret = repair_inode_backrefs(root, rec, inode_cache,
                                                    stage == 1);
                        if (ret < 0) {
                                err = ret;
                                stage = 2;
                                break;
                        } if (ret > 0) {
                                err = -EAGAIN;
                        }
                }
        }
        if (err)
                return err;

        rec = get_inode_rec(inode_cache, root_dirid, 0);
        BUG_ON(IS_ERR(rec));
        if (rec) {
                ret = check_root_dir(rec);
                if (ret) {
                        fprintf(stderr, "root %llu root dir %llu error\n",
                                (unsigned long long)root->root_key.objectid,
                                (unsigned long long)root_dirid);
                        print_inode_error(root, rec);
                        error++;
                }
        } else {
                if (repair) {
                        struct btrfs_trans_handle *trans;

                        trans = btrfs_start_transaction(root, 1);
                        if (IS_ERR(trans)) {
                                err = PTR_ERR(trans);
                                return err;
                        }

                        fprintf(stderr,
                                "root %llu missing its root dir, recreating\n",
                                (unsigned long long)root->objectid);

                        ret = btrfs_make_root_dir(trans, root, root_dirid);
                        BUG_ON(ret);

                        btrfs_commit_transaction(trans, root);
                        return -EAGAIN;
                }

                fprintf(stderr, "root %llu root dir %llu not found\n",
                        (unsigned long long)root->root_key.objectid,
                        (unsigned long long)root_dirid);
        }

        while (1) {
                cache = search_cache_extent(inode_cache, 0);
                if (!cache)
                        break;
                node = container_of(cache, struct ptr_node, cache);
                rec = node->data;
                remove_cache_extent(inode_cache, &node->cache);
                free(node);
                if (rec->ino == root_dirid ||
                    rec->ino == BTRFS_ORPHAN_OBJECTID) {
                        free_inode_rec(rec);
                        continue;
                }

                if (rec->errors & I_ERR_NO_ORPHAN_ITEM) {
                        ret = check_orphan_item(root, rec->ino);
                        if (ret == 0)
                                rec->errors &= ~I_ERR_NO_ORPHAN_ITEM;
                        if (can_free_inode_rec(rec)) {
                                free_inode_rec(rec);
                                continue;
                        }
                }

                if (!rec->found_inode_item)
                        rec->errors |= I_ERR_NO_INODE_ITEM;
                if (rec->found_link != rec->nlink)
                        rec->errors |= I_ERR_LINK_COUNT_WRONG;
                if (repair) {
                        ret = try_repair_inode(root, rec);
                        if (ret == 0 && can_free_inode_rec(rec)) {
                                free_inode_rec(rec);
                                continue;
                        }
                        ret = 0;
                }

                if (!(repair && ret == 0))
                        error++;
                print_inode_error(root, rec);
                list_for_each_entry(backref, &rec->backrefs, list) {
                        if (!backref->found_dir_item)
                                backref->errors |= REF_ERR_NO_DIR_ITEM;
                        if (!backref->found_dir_index)
                                backref->errors |= REF_ERR_NO_DIR_INDEX;
                        if (!backref->found_inode_ref)
                                backref->errors |= REF_ERR_NO_INODE_REF;
                        fprintf(stderr, "\tunresolved ref dir %llu index %llu"
                                " namelen %u name %s filetype %d errors %x",
                                (unsigned long long)backref->dir,
                                (unsigned long long)backref->index,
                                backref->namelen, backref->name,
                                backref->filetype, backref->errors);
                        print_ref_error(backref->errors);
                }
                free_inode_rec(rec);
        }
        return (error > 0) ? -1 : 0;
}

static struct root_record *get_root_rec(struct cache_tree *root_cache,
                                        u64 objectid)
{
        struct cache_extent *cache;
        struct root_record *rec = NULL;
        int ret;

        cache = lookup_cache_extent(root_cache, objectid, 1);
        if (cache) {
                rec = container_of(cache, struct root_record, cache);
        } else {
                rec = calloc(1, sizeof(*rec));
                if (!rec)
                        return ERR_PTR(-ENOMEM);
                rec->objectid = objectid;
                INIT_LIST_HEAD(&rec->backrefs);
                rec->cache.start = objectid;
                rec->cache.size = 1;

                ret = insert_cache_extent(root_cache, &rec->cache);
                if (ret)
                        return ERR_PTR(-EEXIST);
        }
        return rec;
}

static struct root_backref *get_root_backref(struct root_record *rec,
                                             u64 ref_root, u64 dir, u64 index,
                                             const char *name, int namelen)
{
        struct root_backref *backref;

        list_for_each_entry(backref, &rec->backrefs, list) {
                if (backref->ref_root != ref_root || backref->dir != dir ||
                    backref->namelen != namelen)
                        continue;
                if (memcmp(name, backref->name, namelen))
                        continue;
                return backref;
        }

        backref = calloc(1, sizeof(*backref) + namelen + 1);
        if (!backref)
                return NULL;
        backref->ref_root = ref_root;
        backref->dir = dir;
        backref->index = index;
        backref->namelen = namelen;
        memcpy(backref->name, name, namelen);
        backref->name[namelen] = '\0';
        list_add_tail(&backref->list, &rec->backrefs);
        return backref;
}

static void free_root_record(struct cache_extent *cache)
{
        struct root_record *rec;
        struct root_backref *backref;

        rec = container_of(cache, struct root_record, cache);
        while (!list_empty(&rec->backrefs)) {
                backref = to_root_backref(rec->backrefs.next);
                list_del(&backref->list);
                free(backref);
        }

        free(rec);
}

FREE_EXTENT_CACHE_BASED_TREE(root_recs, free_root_record);

static int add_root_backref(struct cache_tree *root_cache,
                            u64 root_id, u64 ref_root, u64 dir, u64 index,
                            const char *name, int namelen,
                            int item_type, int errors)
{
        struct root_record *rec;
        struct root_backref *backref;

        rec = get_root_rec(root_cache, root_id);
        BUG_ON(IS_ERR(rec));
        backref = get_root_backref(rec, ref_root, dir, index, name, namelen);
        BUG_ON(!backref);

        backref->errors |= errors;

        if (item_type != BTRFS_DIR_ITEM_KEY) {
                if (backref->found_dir_index || backref->found_back_ref ||
                    backref->found_forward_ref) {
                        if (backref->index != index)
                                backref->errors |= REF_ERR_INDEX_UNMATCH;
                } else {
                        backref->index = index;
                }
        }

        if (item_type == BTRFS_DIR_ITEM_KEY) {
                if (backref->found_forward_ref)
                        rec->found_ref++;
                backref->found_dir_item = 1;
        } else if (item_type == BTRFS_DIR_INDEX_KEY) {
                backref->found_dir_index = 1;
        } else if (item_type == BTRFS_ROOT_REF_KEY) {
                if (backref->found_forward_ref)
                        backref->errors |= REF_ERR_DUP_ROOT_REF;
                else if (backref->found_dir_item)
                        rec->found_ref++;
                backref->found_forward_ref = 1;
        } else if (item_type == BTRFS_ROOT_BACKREF_KEY) {
                if (backref->found_back_ref)
                        backref->errors |= REF_ERR_DUP_ROOT_BACKREF;
                backref->found_back_ref = 1;
        } else {
                BUG_ON(1);
        }

        if (backref->found_forward_ref && backref->found_dir_item)
                backref->reachable = 1;
        return 0;
}

static int merge_root_recs(struct btrfs_root *root,
                           struct cache_tree *src_cache,
                           struct cache_tree *dst_cache)
{
        struct cache_extent *cache;
        struct ptr_node *node;
        struct inode_record *rec;
        struct inode_backref *backref;
        int ret = 0;

        if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
                free_inode_recs_tree(src_cache);
                return 0;
        }

        while (1) {
                cache = search_cache_extent(src_cache, 0);
                if (!cache)
                        break;
                node = container_of(cache, struct ptr_node, cache);
                rec = node->data;
                remove_cache_extent(src_cache, &node->cache);
                free(node);

                ret = is_child_root(root, root->objectid, rec->ino);
                if (ret < 0)
                        break;
                else if (ret == 0)
                        goto skip;

                list_for_each_entry(backref, &rec->backrefs, list) {
                        BUG_ON(backref->found_inode_ref);
                        if (backref->found_dir_item)
                                add_root_backref(dst_cache, rec->ino,
                                        root->root_key.objectid, backref->dir,
                                        backref->index, backref->name,
                                        backref->namelen, BTRFS_DIR_ITEM_KEY,
                                        backref->errors);
                        if (backref->found_dir_index)
                                add_root_backref(dst_cache, rec->ino,
                                        root->root_key.objectid, backref->dir,
                                        backref->index, backref->name,
                                        backref->namelen, BTRFS_DIR_INDEX_KEY,
                                        backref->errors);
                }
skip:
                free_inode_rec(rec);
        }
        if (ret < 0)
                return ret;
        return 0;
}

static int check_root_refs(struct btrfs_root *root,
                           struct cache_tree *root_cache)
{
        struct root_record *rec;
        struct root_record *ref_root;
        struct root_backref *backref;
        struct cache_extent *cache;
        int loop = 1;
        int ret;
        int error;
        int errors = 0;

        rec = get_root_rec(root_cache, BTRFS_FS_TREE_OBJECTID);
        BUG_ON(IS_ERR(rec));
        rec->found_ref = 1;

        /* fixme: this can not detect circular references */
        while (loop) {
                loop = 0;
                cache = search_cache_extent(root_cache, 0);
                while (1) {
                        if (!cache)
                                break;
                        rec = container_of(cache, struct root_record, cache);
                        cache = next_cache_extent(cache);

                        if (rec->found_ref == 0)
                                continue;

                        list_for_each_entry(backref, &rec->backrefs, list) {
                                if (!backref->reachable)
                                        continue;

                                ref_root = get_root_rec(root_cache,
                                                        backref->ref_root);
                                BUG_ON(IS_ERR(ref_root));
                                if (ref_root->found_ref > 0)
                                        continue;

                                backref->reachable = 0;
                                rec->found_ref--;
                                if (rec->found_ref == 0)
                                        loop = 1;
                        }
                }
        }

        cache = search_cache_extent(root_cache, 0);
        while (1) {
                if (!cache)
                        break;
                rec = container_of(cache, struct root_record, cache);
                cache = next_cache_extent(cache);

                if (rec->found_ref == 0 &&
                    rec->objectid >= BTRFS_FIRST_FREE_OBJECTID &&
                    rec->objectid <= BTRFS_LAST_FREE_OBJECTID) {
                        ret = check_orphan_item(root->fs_info->tree_root,
                                                rec->objectid);
                        if (ret == 0)
                                continue;

                        /*
                         * If we don't have a root item then we likely just have
                         * a dir item in a snapshot for this root but no actual
                         * ref key or anything so it's meaningless.
                         */
                        if (!rec->found_root_item)
                                continue;
                        errors++;
                        fprintf(stderr, "fs tree %llu not referenced\n",
                                (unsigned long long)rec->objectid);
                }

                error = 0;
                if (rec->found_ref > 0 && !rec->found_root_item)
                        error = 1;
                list_for_each_entry(backref, &rec->backrefs, list) {
                        if (!backref->found_dir_item)
                                backref->errors |= REF_ERR_NO_DIR_ITEM;
                        if (!backref->found_dir_index)
                                backref->errors |= REF_ERR_NO_DIR_INDEX;
                        if (!backref->found_back_ref)
                                backref->errors |= REF_ERR_NO_ROOT_BACKREF;
                        if (!backref->found_forward_ref)
                                backref->errors |= REF_ERR_NO_ROOT_REF;
                        if (backref->reachable && backref->errors)
                                error = 1;
                }
                if (!error)
                        continue;

                errors++;
                fprintf(stderr, "fs tree %llu refs %u %s\n",
                        (unsigned long long)rec->objectid, rec->found_ref,
                         rec->found_root_item ? "" : "not found");

                list_for_each_entry(backref, &rec->backrefs, list) {
                        if (!backref->reachable)
                                continue;
                        if (!backref->errors && rec->found_root_item)
                                continue;
                        fprintf(stderr, "\tunresolved ref root %llu dir %llu"
                                " index %llu namelen %u name %s errors %x\n",
                                (unsigned long long)backref->ref_root,
                                (unsigned long long)backref->dir,
                                (unsigned long long)backref->index,
                                backref->namelen, backref->name,
                                backref->errors);
                        print_ref_error(backref->errors);
                }
        }
        return errors > 0 ? 1 : 0;
}

static int process_root_ref(struct extent_buffer *eb, int slot,
                            struct btrfs_key *key,
                            struct cache_tree *root_cache)
{
        u64 dirid;
        u64 index;
        u32 len;
        u32 name_len;
        struct btrfs_root_ref *ref;
        char namebuf[BTRFS_NAME_LEN];
        int error;

        ref = btrfs_item_ptr(eb, slot, struct btrfs_root_ref);

        dirid = btrfs_root_ref_dirid(eb, ref);
        index = btrfs_root_ref_sequence(eb, ref);
        name_len = btrfs_root_ref_name_len(eb, ref);

        if (name_len <= BTRFS_NAME_LEN) {
                len = name_len;
                error = 0;
        } else {
                len = BTRFS_NAME_LEN;
                error = REF_ERR_NAME_TOO_LONG;
        }
        read_extent_buffer(eb, namebuf, (unsigned long)(ref + 1), len);

        if (key->type == BTRFS_ROOT_REF_KEY) {
                add_root_backref(root_cache, key->offset, key->objectid, dirid,
                                 index, namebuf, len, key->type, error);
        } else {
                add_root_backref(root_cache, key->objectid, key->offset, dirid,
                                 index, namebuf, len, key->type, error);
        }
        return 0;
}

static void free_corrupt_block(struct cache_extent *cache)
{
        struct btrfs_corrupt_block *corrupt;

        corrupt = container_of(cache, struct btrfs_corrupt_block, cache);
        free(corrupt);
}

FREE_EXTENT_CACHE_BASED_TREE(corrupt_blocks, free_corrupt_block);

/*
 * Repair the btree of the given root.
 *
 * The fix is to remove the node key in corrupt_blocks cache_tree.
 * and rebalance the tree.
 * After the fix, the btree should be writeable.
 */
static int repair_btree(struct btrfs_root *root,
                        struct cache_tree *corrupt_blocks)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_path path;
        struct btrfs_corrupt_block *corrupt;
        struct cache_extent *cache;
        struct btrfs_key key;
        u64 offset;
        int level;
        int ret = 0;

        if (cache_tree_empty(corrupt_blocks))
                return 0;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                fprintf(stderr, "Error starting transaction: %s\n",
                        strerror(-ret));
                return ret;
        }
        btrfs_init_path(&path);
        cache = first_cache_extent(corrupt_blocks);
        while (cache) {
                corrupt = container_of(cache, struct btrfs_corrupt_block,
                                       cache);
                level = corrupt->level;
                path.lowest_level = level;
                key.objectid = corrupt->key.objectid;
                key.type = corrupt->key.type;
                key.offset = corrupt->key.offset;

                /*
                 * Here we don't want to do any tree balance, since it may
                 * cause a balance with corrupted brother leaf/node,
                 * so ins_len set to 0 here.
                 * Balance will be done after all corrupt node/leaf is deleted.
                 */
                ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
                if (ret < 0)
                        goto out;
                offset = btrfs_node_blockptr(path.nodes[level],
                                             path.slots[level]);

                /* Remove the ptr */
                ret = btrfs_del_ptr(root, &path, level, path.slots[level]);
                if (ret < 0)
                        goto out;
                /*
                 * Remove the corresponding extent
                 * return value is not concerned.
                 */
                btrfs_release_path(&path);
                ret = btrfs_free_extent(trans, root, offset,
                                root->fs_info->nodesize, 0,
                                root->root_key.objectid, level - 1, 0);
                cache = next_cache_extent(cache);
        }

        /* Balance the btree using btrfs_search_slot() */
        cache = first_cache_extent(corrupt_blocks);
        while (cache) {
                corrupt = container_of(cache, struct btrfs_corrupt_block,
                                       cache);
                memcpy(&key, &corrupt->key, sizeof(key));
                ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
                if (ret < 0)
                        goto out;
                /* return will always >0 since it won't find the item */
                ret = 0;
                btrfs_release_path(&path);
                cache = next_cache_extent(cache);
        }
out:
        btrfs_commit_transaction(trans, root);
        btrfs_release_path(&path);
        return ret;
}

static int check_fs_root(struct btrfs_root *root,
                         struct cache_tree *root_cache,
                         struct walk_control *wc)
{
        int ret = 0;
        int err = 0;
        int wret;
        int level;
        struct btrfs_path path;
        struct shared_node root_node;
        struct root_record *rec;
        struct btrfs_root_item *root_item = &root->root_item;
        struct cache_tree corrupt_blocks;
        struct orphan_data_extent *orphan;
        struct orphan_data_extent *tmp;
        enum btrfs_tree_block_status status;
        struct node_refs nrefs;

        /*
         * Reuse the corrupt_block cache tree to record corrupted tree block
         *
         * Unlike the usage in extent tree check, here we do it in a per
         * fs/subvol tree base.
         */
        cache_tree_init(&corrupt_blocks);
        root->fs_info->corrupt_blocks = &corrupt_blocks;

        if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
                rec = get_root_rec(root_cache, root->root_key.objectid);
                BUG_ON(IS_ERR(rec));
                if (btrfs_root_refs(root_item) > 0)
                        rec->found_root_item = 1;
        }

        btrfs_init_path(&path);
        memset(&root_node, 0, sizeof(root_node));
        cache_tree_init(&root_node.root_cache);
        cache_tree_init(&root_node.inode_cache);
        memset(&nrefs, 0, sizeof(nrefs));

        /* Move the orphan extent record to corresponding inode_record */
        list_for_each_entry_safe(orphan, tmp,
                                 &root->orphan_data_extents, list) {
                struct inode_record *inode;

                inode = get_inode_rec(&root_node.inode_cache, orphan->objectid,
                                      1);
                BUG_ON(IS_ERR(inode));
                inode->errors |= I_ERR_FILE_EXTENT_ORPHAN;
                list_move(&orphan->list, &inode->orphan_extents);
        }

        level = btrfs_header_level(root->node);
        memset(wc->nodes, 0, sizeof(wc->nodes));
        wc->nodes[level] = &root_node;
        wc->active_node = level;
        wc->root_level = level;

        /* We may not have checked the root block, lets do that now */
        if (btrfs_is_leaf(root->node))
                status = btrfs_check_leaf(root, NULL, root->node);
        else
                status = btrfs_check_node(root, NULL, root->node);
        if (status != BTRFS_TREE_BLOCK_CLEAN)
                return -EIO;

        if (btrfs_root_refs(root_item) > 0 ||
            btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
                path.nodes[level] = root->node;
                extent_buffer_get(root->node);
                path.slots[level] = 0;
        } else {
                struct btrfs_key key;
                struct btrfs_disk_key found_key;

                btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
                level = root_item->drop_level;
                path.lowest_level = level;
                if (level > btrfs_header_level(root->node) ||
                    level >= BTRFS_MAX_LEVEL) {
                        error("ignoring invalid drop level: %u", level);
                        goto skip_walking;
                }
                wret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
                if (wret < 0)
                        goto skip_walking;
                btrfs_node_key(path.nodes[level], &found_key,
                                path.slots[level]);
                WARN_ON(memcmp(&found_key, &root_item->drop_progress,
                                        sizeof(found_key)));
        }

        while (1) {
                wret = walk_down_tree(root, &path, wc, &level, &nrefs);
                if (wret < 0)
                        ret = wret;
                if (wret != 0)
                        break;

                wret = walk_up_tree(root, &path, wc, &level);
                if (wret < 0)
                        ret = wret;
                if (wret != 0)
                        break;
        }
skip_walking:
        btrfs_release_path(&path);

        if (!cache_tree_empty(&corrupt_blocks)) {
                struct cache_extent *cache;
                struct btrfs_corrupt_block *corrupt;

                printf("The following tree block(s) is corrupted in tree %llu:\n",
                       root->root_key.objectid);
                cache = first_cache_extent(&corrupt_blocks);
                while (cache) {
                        corrupt = container_of(cache,
                                               struct btrfs_corrupt_block,
                                               cache);
                        printf("\ttree block bytenr: %llu, level: %d, node key: (%llu, %u, %llu)\n",
                               cache->start, corrupt->level,
                               corrupt->key.objectid, corrupt->key.type,
                               corrupt->key.offset);
                        cache = next_cache_extent(cache);
                }
                if (repair) {
                        printf("Try to repair the btree for root %llu\n",
                               root->root_key.objectid);
                        ret = repair_btree(root, &corrupt_blocks);
                        if (ret < 0)
                                fprintf(stderr, "Failed to repair btree: %s\n",
                                        strerror(-ret));
                        if (!ret)
                                printf("Btree for root %llu is fixed\n",
                                       root->root_key.objectid);
                }
        }

        err = merge_root_recs(root, &root_node.root_cache, root_cache);
        if (err < 0)
                ret = err;

        if (root_node.current) {
                root_node.current->checked = 1;
                maybe_free_inode_rec(&root_node.inode_cache,
                                root_node.current);
        }

        err = check_inode_recs(root, &root_node.inode_cache);
        if (!ret)
                ret = err;

        free_corrupt_blocks_tree(&corrupt_blocks);
        root->fs_info->corrupt_blocks = NULL;
        free_orphan_data_extents(&root->orphan_data_extents);
        return ret;
}

static int fs_root_objectid(u64 objectid)
{
        if (objectid == BTRFS_TREE_RELOC_OBJECTID ||
            objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
                return 1;
        return is_fstree(objectid);
}

static int check_fs_roots(struct btrfs_fs_info *fs_info,
                          struct cache_tree *root_cache)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct walk_control wc;
        struct extent_buffer *leaf, *tree_node;
        struct btrfs_root *tmp_root;
        struct btrfs_root *tree_root = fs_info->tree_root;
        int ret;
        int err = 0;

        if (ctx.progress_enabled) {
                ctx.tp = TASK_FS_ROOTS;
                task_start(ctx.info);
        }

        /*
         * Just in case we made any changes to the extent tree that weren't
         * reflected into the free space cache yet.
         */
        if (repair)
                reset_cached_block_groups(fs_info);
        memset(&wc, 0, sizeof(wc));
        cache_tree_init(&wc.shared);
        btrfs_init_path(&path);

again:
        key.offset = 0;
        key.objectid = 0;
        key.type = BTRFS_ROOT_ITEM_KEY;
        ret = btrfs_search_slot(NULL, tree_root, &key, &path, 0, 0);
        if (ret < 0) {
                err = 1;
                goto out;
        }
        tree_node = tree_root->node;
        while (1) {
                if (tree_node != tree_root->node) {
                        free_root_recs_tree(root_cache);
                        btrfs_release_path(&path);
                        goto again;
                }
                leaf = path.nodes[0];
                if (path.slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(tree_root, &path);
                        if (ret) {
                                if (ret < 0)
                                        err = 1;
                                break;
                        }
                        leaf = path.nodes[0];
                }
                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type == BTRFS_ROOT_ITEM_KEY &&
                    fs_root_objectid(key.objectid)) {
                        if (key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
                                tmp_root = btrfs_read_fs_root_no_cache(
                                                fs_info, &key);
                        } else {
                                key.offset = (u64)-1;
                                tmp_root = btrfs_read_fs_root(
                                                fs_info, &key);
                        }
                        if (IS_ERR(tmp_root)) {
                                err = 1;
                                goto next;
                        }
                        ret = check_fs_root(tmp_root, root_cache, &wc);
                        if (ret == -EAGAIN) {
                                free_root_recs_tree(root_cache);
                                btrfs_release_path(&path);
                                goto again;
                        }
                        if (ret)
                                err = 1;
                        if (key.objectid == BTRFS_TREE_RELOC_OBJECTID)
                                btrfs_free_fs_root(tmp_root);
                } else if (key.type == BTRFS_ROOT_REF_KEY ||
                           key.type == BTRFS_ROOT_BACKREF_KEY) {
                        process_root_ref(leaf, path.slots[0], &key,
                                         root_cache);
                }
next:
                path.slots[0]++;
        }
out:
        btrfs_release_path(&path);
        if (err)
                free_extent_cache_tree(&wc.shared);
        if (!cache_tree_empty(&wc.shared))
                fprintf(stderr, "warning line %d\n", __LINE__);

        task_stop(ctx.info);

        return err;
}

/*
 * Find the @index according by @ino and name.
 * Notice:time efficiency is O(N)
 *
 * @root:       the root of the fs/file tree
 * @index_ret:  the index as return value
 * @namebuf:    the name to match
 * @name_len:   the length of name to match
 * @file_type:  the file_type of INODE_ITEM to match
 *
 * Returns 0 if found and *@index_ret will be modified with right value
 * Returns< 0 not found and *@index_ret will be (u64)-1
 */
static int find_dir_index(struct btrfs_root *root, u64 dirid, u64 location_id,
                          u64 *index_ret, char *namebuf, u32 name_len,
                          u8 file_type)
{
        struct btrfs_path path;
        struct extent_buffer *node;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        struct btrfs_key location;
        char name[BTRFS_NAME_LEN] = {0};

        u32 total;
        u32 cur = 0;
        u32 len;
        u32 data_len;
        u8 filetype;
        int slot;
        int ret;

        ASSERT(index_ret);

        /* search from the last index */
        key.objectid = dirid;
        key.offset = (u64)-1;
        key.type = BTRFS_DIR_INDEX_KEY;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0)
                return ret;

loop:
        ret = btrfs_previous_item(root, &path, dirid, BTRFS_DIR_INDEX_KEY);
        if (ret) {
                ret = -ENOENT;
                *index_ret = (64)-1;
                goto out;
        }
        /* Check whether inode_id/filetype/name match */
        node = path.nodes[0];
        slot = path.slots[0];
        di = btrfs_item_ptr(node, slot, struct btrfs_dir_item);
        total = btrfs_item_size_nr(node, slot);
        while (cur < total) {
                ret = -ENOENT;
                len = btrfs_dir_name_len(node, di);
                data_len = btrfs_dir_data_len(node, di);

                btrfs_dir_item_key_to_cpu(node, di, &location);
                if (location.objectid != location_id ||
                    location.type != BTRFS_INODE_ITEM_KEY ||
                    location.offset != 0)
                        goto next;

                filetype = btrfs_dir_type(node, di);
                if (file_type != filetype)
                        goto next;

                if (len > BTRFS_NAME_LEN)
                        len = BTRFS_NAME_LEN;

                read_extent_buffer(node, name, (unsigned long)(di + 1), len);
                if (len != name_len || strncmp(namebuf, name, len))
                        goto next;

                btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
                *index_ret = key.offset;
                ret = 0;
                goto out;
next:
                len += sizeof(*di) + data_len;
                di = (struct btrfs_dir_item *)((char *)di + len);
                cur += len;
        }
        goto loop;

out:
        btrfs_release_path(&path);
        return ret;
}

/*
 * Find DIR_ITEM/DIR_INDEX for the given key and check it with the specified
 * INODE_REF/INODE_EXTREF match.
 *
 * @root:       the root of the fs/file tree
 * @key:        the key of the DIR_ITEM/DIR_INDEX, key->offset will be right
 *              value while find index
 * @location_key: location key of the struct btrfs_dir_item to match
 * @name:       the name to match
 * @namelen:    the length of name
 * @file_type:  the type of file to math
 *
 * Return 0 if no error occurred.
 * Return DIR_ITEM_MISSING/DIR_INDEX_MISSING if couldn't find
 * DIR_ITEM/DIR_INDEX
 * Return DIR_ITEM_MISMATCH/DIR_INDEX_MISMATCH if INODE_REF/INODE_EXTREF
 * and DIR_ITEM/DIR_INDEX mismatch
 */
static int find_dir_item(struct btrfs_root *root, struct btrfs_key *key,
                         struct btrfs_key *location_key, char *name,
                         u32 namelen, u8 file_type)
{
        struct btrfs_path path;
        struct extent_buffer *node;
        struct btrfs_dir_item *di;
        struct btrfs_key location;
        char namebuf[BTRFS_NAME_LEN] = {0};
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 data_len;
        u8 filetype;
        int slot;
        int ret;

        /* get the index by traversing all index */
        if (key->type == BTRFS_DIR_INDEX_KEY && key->offset == (u64)-1) {
                ret = find_dir_index(root, key->objectid,
                                     location_key->objectid, &key->offset,
                                     name, namelen, file_type);
                if (ret)
                        ret = DIR_INDEX_MISSING;
                return ret;
        }

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, key, &path, 0, 0);
        if (ret) {
                ret = key->type == BTRFS_DIR_ITEM_KEY ? DIR_ITEM_MISSING :
                        DIR_INDEX_MISSING;
                goto out;
        }

        /* Check whether inode_id/filetype/name match */
        node = path.nodes[0];
        slot = path.slots[0];
        di = btrfs_item_ptr(node, slot, struct btrfs_dir_item);
        total = btrfs_item_size_nr(node, slot);
        while (cur < total) {
                ret = key->type == BTRFS_DIR_ITEM_KEY ?
                        DIR_ITEM_MISMATCH : DIR_INDEX_MISMATCH;

                len = btrfs_dir_name_len(node, di);
                data_len = btrfs_dir_data_len(node, di);

                btrfs_dir_item_key_to_cpu(node, di, &location);
                if (location.objectid != location_key->objectid ||
                    location.type != location_key->type ||
                    location.offset != location_key->offset)
                        goto next;

                filetype = btrfs_dir_type(node, di);
                if (file_type != filetype)
                        goto next;

                if (len > BTRFS_NAME_LEN) {
                        len = BTRFS_NAME_LEN;
                        warning("root %llu %s[%llu %llu] name too long %u, trimmed",
                        root->objectid,
                        key->type == BTRFS_DIR_ITEM_KEY ?
                        "DIR_ITEM" : "DIR_INDEX",
                        key->objectid, key->offset, len);
                }
                read_extent_buffer(node, namebuf, (unsigned long)(di + 1),
                                   len);
                if (len != namelen || strncmp(namebuf, name, len))
                        goto next;

                ret = 0;
                goto out;
next:
                len += sizeof(*di) + data_len;
                di = (struct btrfs_dir_item *)((char *)di + len);
                cur += len;
        }

out:
        btrfs_release_path(&path);
        return ret;
}

/*
 * Prints inode ref error message
 */
static void print_inode_ref_err(struct btrfs_root *root, struct btrfs_key *key,
                                u64 index, const char *namebuf, int name_len,
                                u8 filetype, int err)
{
        if (!err)
                return;

        /* root dir error */
        if (key->objectid == BTRFS_FIRST_FREE_OBJECTID) {
                error(
        "root %llu root dir shouldn't have INODE REF[%llu %llu] name %s",
                      root->objectid, key->objectid, key->offset, namebuf);
                return;
        }

        /* normal error */
        if (err & (DIR_ITEM_MISMATCH | DIR_ITEM_MISSING))
                error("root %llu DIR ITEM[%llu %llu] %s name %s filetype %u",
                      root->objectid, key->offset,
                      btrfs_name_hash(namebuf, name_len),
                      err & DIR_ITEM_MISMATCH ? "mismatch" : "missing",
                      namebuf, filetype);
        if (err & (DIR_INDEX_MISMATCH | DIR_INDEX_MISSING))
                error("root %llu DIR INDEX[%llu %llu] %s name %s filetype %u",
                      root->objectid, key->offset, index,
                      err & DIR_ITEM_MISMATCH ? "mismatch" : "missing",
                      namebuf, filetype);
}

/*
 * Insert the missing inode item.
 *
 * Returns 0 means success.
 * Returns <0 means error.
 */
static int repair_inode_item_missing(struct btrfs_root *root, u64 ino,
                                     u8 filetype)
{
        struct btrfs_key key;
        struct btrfs_trans_handle *trans;
        struct btrfs_path path;
        int ret;

        key.objectid = ino;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        btrfs_init_path(&path);
        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = -EIO;
                goto out;
        }

        ret = btrfs_search_slot(trans, root, &key, &path, 1, 1);
        if (ret < 0 || !ret)
                goto fail;

        /* insert inode item */
        create_inode_item_lowmem(trans, root, ino, filetype);
        ret = 0;
fail:
        btrfs_commit_transaction(trans, root);
out:
        if (ret)
                error("failed to repair root %llu INODE ITEM[%llu] missing",
                      root->objectid, ino);
        btrfs_release_path(&path);
        return ret;
}

/*
 * The ternary means dir item, dir index and relative inode ref.
 * The function handles errs: INODE_MISSING, DIR_INDEX_MISSING
 * DIR_INDEX_MISMATCH, DIR_ITEM_MISSING, DIR_ITEM_MISMATCH by the follow
 * strategy:
 * If two of three is missing or mismatched, delete the existing one.
 * If one of three is missing or mismatched, add the missing one.
 *
 * returns 0 means success.
 * returns not 0 means on error;
 */
int repair_ternary_lowmem(struct btrfs_root *root, u64 dir_ino, u64 ino,
                          u64 index, char *name, int name_len, u8 filetype,
                          int err)
{
        struct btrfs_trans_handle *trans;
        int stage = 0;
        int ret = 0;

        /*
         * stage shall be one of following valild values:
         *      0: Fine, nothing to do.
         *      1: One of three is wrong, so add missing one.
         *      2: Two of three is wrong, so delete existed one.
         */
        if (err & (DIR_INDEX_MISMATCH | DIR_INDEX_MISSING))
                stage++;
        if (err & (DIR_ITEM_MISMATCH | DIR_ITEM_MISSING))
                stage++;
        if (err & (INODE_REF_MISSING))
                stage++;

        /* stage must be smllarer than 3 */
        ASSERT(stage < 3);

        trans = btrfs_start_transaction(root, 1);
        if (stage == 2) {
                ret = btrfs_unlink(trans, root, ino, dir_ino, index, name,
                                   name_len, 0);
                goto out;
        }
        if (stage == 1) {
                ret = btrfs_add_link(trans, root, ino, dir_ino, name, name_len,
                               filetype, &index, 1, 1);
                goto out;
        }
out:
        btrfs_commit_transaction(trans, root);

        if (ret)
                error("fail to repair inode %llu name %s filetype %u",
                      ino, name, filetype);
        else
                printf("%s ref/dir_item of inode %llu name %s filetype %u\n",
                       stage == 2 ? "Delete" : "Add",
                       ino, name, filetype);

        return ret;
}

/*
 * Traverse the given INODE_REF and call find_dir_item() to find related
 * DIR_ITEM/DIR_INDEX.
 *
 * @root:       the root of the fs/file tree
 * @ref_key:    the key of the INODE_REF
 * @path        the path provides node and slot
 * @refs:       the count of INODE_REF
 * @mode:       the st_mode of INODE_ITEM
 * @name_ret:   returns with the first ref's name
 * @name_len_ret:    len of the name_ret
 *
 * Return 0 if no error occurred.
 */
static int check_inode_ref(struct btrfs_root *root, struct btrfs_key *ref_key,
                           struct btrfs_path *path, char *name_ret,
                           u32 *namelen_ret, u64 *refs_ret, int mode)
{
        struct btrfs_key key;
        struct btrfs_key location;
        struct btrfs_inode_ref *ref;
        struct extent_buffer *node;
        char namebuf[BTRFS_NAME_LEN] = {0};
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 name_len;
        u64 index;
        int ret;
        int err = 0;
        int tmp_err;
        int slot;
        int need_research = 0;
        u64 refs;

begin:
        err = 0;
        cur = 0;
        refs = *refs_ret;

        /* since after repair, path and the dir item may be changed */
        if (need_research) {
                need_research = 0;
                btrfs_release_path(path);
                ret = btrfs_search_slot(NULL, root, ref_key, path, 0, 0);
                /* the item was deleted, let path point to the last checked item */
                if (ret > 0) {
                        if (path->slots[0] == 0)
                                btrfs_prev_leaf(root, path);
                        else
                                path->slots[0]--;
                }
                if (ret)
                        goto out;
        }

        location.objectid = ref_key->objectid;
        location.type = BTRFS_INODE_ITEM_KEY;
        location.offset = 0;
        node = path->nodes[0];
        slot = path->slots[0];

        memset(namebuf, 0, sizeof(namebuf) / sizeof(*namebuf));
        ref = btrfs_item_ptr(node, slot, struct btrfs_inode_ref);
        total = btrfs_item_size_nr(node, slot);

next:
        /* Update inode ref count */
        refs++;
        tmp_err = 0;
        index = btrfs_inode_ref_index(node, ref);
        name_len = btrfs_inode_ref_name_len(node, ref);

        if (name_len <= BTRFS_NAME_LEN) {
                len = name_len;
        } else {
                len = BTRFS_NAME_LEN;
                warning("root %llu INODE_REF[%llu %llu] name too long",
                        root->objectid, ref_key->objectid, ref_key->offset);
        }

        read_extent_buffer(node, namebuf, (unsigned long)(ref + 1), len);

        /* copy the first name found to name_ret */
        if (refs == 1 && name_ret) {
                memcpy(name_ret, namebuf, len);
                *namelen_ret = len;
        }

        /* Check root dir ref */
        if (ref_key->objectid == BTRFS_FIRST_FREE_OBJECTID) {
                if (index != 0 || len != strlen("..") ||
                    strncmp("..", namebuf, len) ||
                    ref_key->offset != BTRFS_FIRST_FREE_OBJECTID) {
                        /* set err bits then repair will delete the ref */
                        err |= DIR_INDEX_MISSING;
                        err |= DIR_ITEM_MISSING;
                }
                goto end;
        }

        /* Find related DIR_INDEX */
        key.objectid = ref_key->offset;
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = index;
        tmp_err |= find_dir_item(root, &key, &location, namebuf, len,
                            imode_to_type(mode));

        /* Find related dir_item */
        key.objectid = ref_key->offset;
        key.type = BTRFS_DIR_ITEM_KEY;
        key.offset = btrfs_name_hash(namebuf, len);
        tmp_err |= find_dir_item(root, &key, &location, namebuf, len,
                            imode_to_type(mode));
end:
        if (tmp_err && repair) {
                ret = repair_ternary_lowmem(root, ref_key->offset,
                                            ref_key->objectid, index, namebuf,
                                            name_len, imode_to_type(mode),
                                            tmp_err);
                if (!ret) {
                        need_research = 1;
                        goto begin;
                }
        }
        print_inode_ref_err(root, ref_key, index, namebuf, name_len,
                            imode_to_type(mode), tmp_err);
        err |= tmp_err;
        len = sizeof(*ref) + name_len;
        ref = (struct btrfs_inode_ref *)((char *)ref + len);
        cur += len;
        if (cur < total)
                goto next;

out:
        *refs_ret = refs;
        return err;
}

/*
 * Traverse the given INODE_EXTREF and call find_dir_item() to find related
 * DIR_ITEM/DIR_INDEX.
 *
 * @root:       the root of the fs/file tree
 * @ref_key:    the key of the INODE_EXTREF
 * @refs:       the count of INODE_EXTREF
 * @mode:       the st_mode of INODE_ITEM
 *
 * Return 0 if no error occurred.
 */
static int check_inode_extref(struct btrfs_root *root,
                              struct btrfs_key *ref_key,
                              struct extent_buffer *node, int slot, u64 *refs,
                              int mode)
{
        struct btrfs_key key;
        struct btrfs_key location;
        struct btrfs_inode_extref *extref;
        char namebuf[BTRFS_NAME_LEN] = {0};
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 name_len;
        u64 index;
        u64 parent;
        int ret;
        int err = 0;

        location.objectid = ref_key->objectid;
        location.type = BTRFS_INODE_ITEM_KEY;
        location.offset = 0;

        extref = btrfs_item_ptr(node, slot, struct btrfs_inode_extref);
        total = btrfs_item_size_nr(node, slot);

next:
        /* update inode ref count */
        (*refs)++;
        name_len = btrfs_inode_extref_name_len(node, extref);
        index = btrfs_inode_extref_index(node, extref);
        parent = btrfs_inode_extref_parent(node, extref);
        if (name_len <= BTRFS_NAME_LEN) {
                len = name_len;
        } else {
                len = BTRFS_NAME_LEN;
                warning("root %llu INODE_EXTREF[%llu %llu] name too long",
                        root->objectid, ref_key->objectid, ref_key->offset);
        }
        read_extent_buffer(node, namebuf, (unsigned long)(extref + 1), len);

        /* Check root dir ref name */
        if (index == 0 && strncmp(namebuf, "..", name_len)) {
                error("root %llu INODE_EXTREF[%llu %llu] ROOT_DIR name shouldn't be %s",
                      root->objectid, ref_key->objectid, ref_key->offset,
                      namebuf);
                err |= ROOT_DIR_ERROR;
        }

        /* find related dir_index */
        key.objectid = parent;
        key.type = BTRFS_DIR_INDEX_KEY;
        key.offset = index;
        ret = find_dir_item(root, &key, &location, namebuf, len, mode);
        err |= ret;

        /* find related dir_item */
        key.objectid = parent;
        key.type = BTRFS_DIR_ITEM_KEY;
        key.offset = btrfs_name_hash(namebuf, len);
        ret = find_dir_item(root, &key, &location, namebuf, len, mode);
        err |= ret;

        len = sizeof(*extref) + name_len;
        extref = (struct btrfs_inode_extref *)((char *)extref + len);
        cur += len;

        if (cur < total)
                goto next;

        return err;
}

/*
 * Find INODE_REF/INODE_EXTREF for the given key and check it with the specified
 * DIR_ITEM/DIR_INDEX match.
 * Return with @index_ret.
 *
 * @root:       the root of the fs/file tree
 * @key:        the key of the INODE_REF/INODE_EXTREF
 * @name:       the name in the INODE_REF/INODE_EXTREF
 * @namelen:    the length of name in the INODE_REF/INODE_EXTREF
 * @index_ret:  the index in the INODE_REF/INODE_EXTREF,
 *              value (64)-1 means do not check index
 * @ext_ref:    the EXTENDED_IREF feature
 *
 * Return 0 if no error occurred.
 * Return >0 for error bitmap
 */
static int find_inode_ref(struct btrfs_root *root, struct btrfs_key *key,
                          char *name, int namelen, u64 *index_ret,
                          unsigned int ext_ref)
{
        struct btrfs_path path;
        struct btrfs_inode_ref *ref;
        struct btrfs_inode_extref *extref;
        struct extent_buffer *node;
        char ref_namebuf[BTRFS_NAME_LEN] = {0};
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 ref_namelen;
        u64 ref_index;
        u64 parent;
        u64 dir_id;
        int slot;
        int ret;

        ASSERT(index_ret);

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, key, &path, 0, 0);
        if (ret) {
                ret = INODE_REF_MISSING;
                goto extref;
        }

        node = path.nodes[0];
        slot = path.slots[0];

        ref = btrfs_item_ptr(node, slot, struct btrfs_inode_ref);
        total = btrfs_item_size_nr(node, slot);

        /* Iterate all entry of INODE_REF */
        while (cur < total) {
                ret = INODE_REF_MISSING;

                ref_namelen = btrfs_inode_ref_name_len(node, ref);
                ref_index = btrfs_inode_ref_index(node, ref);
                if (*index_ret != (u64)-1 && *index_ret != ref_index)
                        goto next_ref;

                if (cur + sizeof(*ref) + ref_namelen > total ||
                    ref_namelen > BTRFS_NAME_LEN) {
                        warning("root %llu INODE %s[%llu %llu] name too long",
                                root->objectid,
                                key->type == BTRFS_INODE_REF_KEY ?
                                        "REF" : "EXTREF",
                                key->objectid, key->offset);

                        if (cur + sizeof(*ref) > total)
                                break;
                        len = min_t(u32, total - cur - sizeof(*ref),
                                    BTRFS_NAME_LEN);
                } else {
                        len = ref_namelen;
                }

                read_extent_buffer(node, ref_namebuf, (unsigned long)(ref + 1),
                                   len);

                if (len != namelen || strncmp(ref_namebuf, name, len))
                        goto next_ref;

                *index_ret = ref_index;
                ret = 0;
                goto out;
next_ref:
                len = sizeof(*ref) + ref_namelen;
                ref = (struct btrfs_inode_ref *)((char *)ref + len);
                cur += len;
        }

extref:
        /* Skip if not support EXTENDED_IREF feature */
        if (!ext_ref)
                goto out;

        btrfs_release_path(&path);
        btrfs_init_path(&path);

        dir_id = key->offset;
        key->type = BTRFS_INODE_EXTREF_KEY;
        key->offset = btrfs_extref_hash(dir_id, name, namelen);

        ret = btrfs_search_slot(NULL, root, key, &path, 0, 0);
        if (ret) {
                ret = INODE_REF_MISSING;
                goto out;
        }

        node = path.nodes[0];
        slot = path.slots[0];

        extref = btrfs_item_ptr(node, slot, struct btrfs_inode_extref);
        cur = 0;
        total = btrfs_item_size_nr(node, slot);

        /* Iterate all entry of INODE_EXTREF */
        while (cur < total) {
                ret = INODE_REF_MISSING;

                ref_namelen = btrfs_inode_extref_name_len(node, extref);
                ref_index = btrfs_inode_extref_index(node, extref);
                parent = btrfs_inode_extref_parent(node, extref);
                if (*index_ret != (u64)-1 && *index_ret != ref_index)
                        goto next_extref;

                if (parent != dir_id)
                        goto next_extref;

                if (ref_namelen <= BTRFS_NAME_LEN) {
                        len = ref_namelen;
                } else {
                        len = BTRFS_NAME_LEN;
                        warning("root %llu INODE %s[%llu %llu] name too long",
                                root->objectid,
                                key->type == BTRFS_INODE_REF_KEY ?
                                        "REF" : "EXTREF",
                                key->objectid, key->offset);
                }
                read_extent_buffer(node, ref_namebuf,
                                   (unsigned long)(extref + 1), len);

                if (len != namelen || strncmp(ref_namebuf, name, len))
                        goto next_extref;

                *index_ret = ref_index;
                ret = 0;
                goto out;

next_extref:
                len = sizeof(*extref) + ref_namelen;
                extref = (struct btrfs_inode_extref *)((char *)extref + len);
                cur += len;

        }
out:
        btrfs_release_path(&path);
        return ret;
}

static void print_dir_item_err(struct btrfs_root *root, struct btrfs_key *key,
                               u64 ino, u64 index, const char *namebuf,
                               int name_len, u8 filetype, int err)
{
        if (err & (DIR_ITEM_MISMATCH | DIR_ITEM_MISSING)) {
                error("root %llu DIR ITEM[%llu %llu] name %s filetype %d %s",
                      root->objectid, key->objectid, key->offset, namebuf,
                      filetype,
                      err & DIR_ITEM_MISMATCH ? "mismath" : "missing");
        }

        if (err & (DIR_INDEX_MISMATCH | DIR_INDEX_MISSING)) {
                error("root %llu DIR INDEX[%llu %llu] name %s filetype %d %s",
                      root->objectid, key->objectid, index, namebuf, filetype,
                      err & DIR_ITEM_MISMATCH ? "mismath" : "missing");
        }

        if (err & (INODE_ITEM_MISSING | INODE_ITEM_MISMATCH)) {
                error(
                "root %llu INODE_ITEM[%llu] index %llu name %s filetype %d %s",
                      root->objectid, ino, index, namebuf, filetype,
                      err & INODE_ITEM_MISMATCH ? "mismath" : "missing");
        }

        if (err & INODE_REF_MISSING)
                error(
                "root %llu INODE REF[%llu, %llu] name %s filetype %u missing",
                      root->objectid, ino, key->objectid, namebuf, filetype);

}

/*
 * Call repair_inode_item_missing and repair_ternary_lowmem to repair
 *
 * Returns error after repair
 */
static int repair_dir_item(struct btrfs_root *root, u64 dirid, u64 ino,
                           u64 index, u8 filetype, char *namebuf, u32 name_len,
                           int err)
{
        int ret;

        if (err & INODE_ITEM_MISSING) {
                ret = repair_inode_item_missing(root, ino, filetype);
                if (!ret)
                        err &= ~(INODE_ITEM_MISMATCH | INODE_ITEM_MISSING);
        }

        if (err & ~(INODE_ITEM_MISMATCH | INODE_ITEM_MISSING)) {
                ret = repair_ternary_lowmem(root, dirid, ino, index, namebuf,
                                            name_len, filetype, err);
                if (!ret) {
                        err &= ~(DIR_INDEX_MISMATCH | DIR_INDEX_MISSING);
                        err &= ~(DIR_ITEM_MISMATCH | DIR_ITEM_MISSING);
                        err &= ~(INODE_REF_MISSING);
                }
        }
        return err;
}

static int __count_dir_isize(struct btrfs_root *root, u64 ino, int type,
                u64 *size_ret)
{
        struct btrfs_key key;
        struct btrfs_path path;
        u32 len;
        struct btrfs_dir_item *di;
        int ret;
        int cur = 0;
        int total = 0;

        ASSERT(size_ret);
        *size_ret = 0;

        key.objectid = ino;
        key.type = type;
        key.offset = (u64)-1;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0) {
                ret = -EIO;
                goto out;
        }
        /* if found, go to spacial case */
        if (ret == 0)
                goto special_case;

loop:
        ret = btrfs_previous_item(root, &path, ino, type);

        if (ret) {
                ret = 0;
                goto out;
        }

special_case:
        di = btrfs_item_ptr(path.nodes[0], path.slots[0], struct btrfs_dir_item);
        cur = 0;
        total = btrfs_item_size_nr(path.nodes[0], path.slots[0]);

        while (cur < total) {
                len = btrfs_dir_name_len(path.nodes[0], di);
                if (len > BTRFS_NAME_LEN)
                        len = BTRFS_NAME_LEN;
                *size_ret += len;

                len += btrfs_dir_data_len(path.nodes[0], di);
                len += sizeof(*di);
                di = (struct btrfs_dir_item *)((char *)di + len);
                cur += len;
        }
        goto loop;

out:
        btrfs_release_path(&path);
        return ret;
}

static int count_dir_isize(struct btrfs_root *root, u64 ino, u64 *size)
{
        u64 item_size;
        u64 index_size;
        int ret;

        ASSERT(size);
        ret = __count_dir_isize(root, ino, BTRFS_DIR_ITEM_KEY, &item_size);
        if (ret)
                goto out;

        ret = __count_dir_isize(root, ino, BTRFS_DIR_INDEX_KEY, &index_size);
        if (ret)
                goto out;

        *size = item_size + index_size;

out:
        if (ret)
                error("failed to count root %llu INODE[%llu] root size",
                      root->objectid, ino);
        return ret;
}

/*
 * Traverse the given DIR_ITEM/DIR_INDEX and check related INODE_ITEM and
 * call find_inode_ref() to check related INODE_REF/INODE_EXTREF.
 *
 * @root:       the root of the fs/file tree
 * @key:        the key of the INODE_REF/INODE_EXTREF
 * @path:       the path
 * @size:       the st_size of the INODE_ITEM
 * @ext_ref:    the EXTENDED_IREF feature
 *
 * Return 0 if no error occurred.
 * Return DIR_COUNT_AGAIN if the isize of the inode should be recalculated.
 */
static int check_dir_item(struct btrfs_root *root, struct btrfs_key *di_key,
                          struct btrfs_path *path, u64 *size,
                          unsigned int ext_ref)
{
        struct btrfs_dir_item *di;
        struct btrfs_inode_item *ii;
        struct btrfs_key key;
        struct btrfs_key location;
        struct extent_buffer *node;
        int slot;
        char namebuf[BTRFS_NAME_LEN] = {0};
        u32 total;
        u32 cur = 0;
        u32 len;
        u32 name_len;
        u32 data_len;
        u8 filetype;
        u32 mode = 0;
        u64 index;
        int ret;
        int err;
        int tmp_err;
        int need_research = 0;

        /*
         * For DIR_ITEM set index to (u64)-1, so that find_inode_ref
         * ignore index check.
         */
        if (di_key->type == BTRFS_DIR_INDEX_KEY)
                index = di_key->offset;
        else
                index = (u64)-1;
begin:
        err = 0;
        cur = 0;

        /* since after repair, path and the dir item may be changed */
        if (need_research) {
                need_research = 0;
                err |= DIR_COUNT_AGAIN;
                btrfs_release_path(path);
                ret = btrfs_search_slot(NULL, root, di_key, path, 0, 0);
                /* the item was deleted, let path point the last checked item */
                if (ret > 0) {
                        if (path->slots[0] == 0)
                                btrfs_prev_leaf(root, path);
                        else
                                path->slots[0]--;
                }
                if (ret)
                        goto out;
        }

        node = path->nodes[0];
        slot = path->slots[0];

        di = btrfs_item_ptr(node, slot, struct btrfs_dir_item);
        total = btrfs_item_size_nr(node, slot);
        memset(namebuf, 0, sizeof(namebuf) / sizeof(*namebuf));

        while (cur < total) {
                data_len = btrfs_dir_data_len(node, di);
                tmp_err = 0;
                if (data_len)
                        error("root %llu %s[%llu %llu] data_len shouldn't be %u",
                              root->objectid,
              di_key->type == BTRFS_DIR_ITEM_KEY ? "DIR_ITEM" : "DIR_INDEX",
                              di_key->objectid, di_key->offset, data_len);

                name_len = btrfs_dir_name_len(node, di);
                if (name_len <= BTRFS_NAME_LEN) {
                        len = name_len;
                } else {
                        len = BTRFS_NAME_LEN;
                        warning("root %llu %s[%llu %llu] name too long",
                                root->objectid,
                di_key->type == BTRFS_DIR_ITEM_KEY ? "DIR_ITEM" : "DIR_INDEX",
                                di_key->objectid, di_key->offset);
                }
                (*size) += name_len;
                read_extent_buffer(node, namebuf, (unsigned long)(di + 1),
                                   len);
                filetype = btrfs_dir_type(node, di);

                if (di_key->type == BTRFS_DIR_ITEM_KEY &&
                    di_key->offset != btrfs_name_hash(namebuf, len)) {
                        err |= -EIO;
                        error("root %llu DIR_ITEM[%llu %llu] name %s namelen %u filetype %u mismatch with its hash, wanted %llu have %llu",
                        root->objectid, di_key->objectid, di_key->offset,
                        namebuf, len, filetype, di_key->offset,
                        btrfs_name_hash(namebuf, len));
                }

                btrfs_dir_item_key_to_cpu(node, di, &location);
                /* Ignore related ROOT_ITEM check */
                if (location.type == BTRFS_ROOT_ITEM_KEY)
                        goto next;

                btrfs_release_path(path);
                /* Check relative INODE_ITEM(existence/filetype) */
                ret = btrfs_search_slot(NULL, root, &location, path, 0, 0);
                if (ret) {
                        tmp_err |= INODE_ITEM_MISSING;
                        goto next;
                }

                ii = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                    struct btrfs_inode_item);
                mode = btrfs_inode_mode(path->nodes[0], ii);
                if (imode_to_type(mode) != filetype) {
                        tmp_err |= INODE_ITEM_MISMATCH;
                        goto next;
                }

                /* Check relative INODE_REF/INODE_EXTREF */
                key.objectid = location.objectid;
                key.type = BTRFS_INODE_REF_KEY;
                key.offset = di_key->objectid;
                tmp_err |= find_inode_ref(root, &key, namebuf, len,
                                          &index, ext_ref);

                /* check relative INDEX/ITEM */
                key.objectid = di_key->objectid;
                if (key.type == BTRFS_DIR_ITEM_KEY) {
                        key.type = BTRFS_DIR_INDEX_KEY;
                        key.offset = index;
                } else {
                        key.type = BTRFS_DIR_ITEM_KEY;
                        key.offset = btrfs_name_hash(namebuf, name_len);
                }

                tmp_err |= find_dir_item(root, &key, &location, namebuf,
                                         name_len, filetype);
                /* find_dir_item may find index */
                if (key.type == BTRFS_DIR_INDEX_KEY)
                        index = key.offset;
next:

                if (tmp_err && repair) {
                        ret = repair_dir_item(root, di_key->objectid,
                                              location.objectid, index,
                                              imode_to_type(mode), namebuf,
                                              name_len, tmp_err);
                        if (ret != tmp_err) {
                                need_research = 1;
                                goto begin;
                        }
                }
                btrfs_release_path(path);
                print_dir_item_err(root, di_key, location.objectid, index,
                                   namebuf, name_len, filetype, tmp_err);
                err |= tmp_err;
                len = sizeof(*di) + name_len + data_len;
                di = (struct btrfs_dir_item *)((char *)di + len);
                cur += len;

                if (di_key->type == BTRFS_DIR_INDEX_KEY && cur < total) {
                        error("root %llu DIR_INDEX[%llu %llu] should contain only one entry",
                              root->objectid, di_key->objectid,
                              di_key->offset);
                        break;
                }
        }
out:
        /* research path */
        btrfs_release_path(path);
        ret = btrfs_search_slot(NULL, root, di_key, path, 0, 0);
        if (ret)
                err |= ret > 0 ? -ENOENT : ret;
        return err;
}

/*
 * Check file extent datasum/hole, update the size of the file extents,
 * check and update the last offset of the file extent.
 *
 * @root:       the root of fs/file tree.
 * @fkey:       the key of the file extent.
 * @nodatasum:  INODE_NODATASUM feature.
 * @size:       the sum of all EXTENT_DATA items size for this inode.
 * @end:        the offset of the last extent.
 *
 * Return 0 if no error occurred.
 */
static int check_file_extent(struct btrfs_root *root, struct btrfs_key *fkey,
                             struct extent_buffer *node, int slot,
                             unsigned int nodatasum, u64 *size, u64 *end)
{
        struct btrfs_file_extent_item *fi;
        u64 disk_bytenr;
        u64 disk_num_bytes;
        u64 extent_num_bytes;
        u64 extent_offset;
        u64 csum_found;         /* In byte size, sectorsize aligned */
        u64 search_start;       /* Logical range start we search for csum */
        u64 search_len;         /* Logical range len we search for csum */
        unsigned int extent_type;
        unsigned int is_hole;
        int compressed = 0;
        int ret;
        int err = 0;

        fi = btrfs_item_ptr(node, slot, struct btrfs_file_extent_item);

        /* Check inline extent */
        extent_type = btrfs_file_extent_type(node, fi);
        if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                struct btrfs_item *e = btrfs_item_nr(slot);
                u32 item_inline_len;

                item_inline_len = btrfs_file_extent_inline_item_len(node, e);
                extent_num_bytes = btrfs_file_extent_inline_len(node, slot, fi);
                compressed = btrfs_file_extent_compression(node, fi);
                if (extent_num_bytes == 0) {
                        error(
                "root %llu EXTENT_DATA[%llu %llu] has empty inline extent",
                                root->objectid, fkey->objectid, fkey->offset);
                        err |= FILE_EXTENT_ERROR;
                }
                if (!compressed && extent_num_bytes != item_inline_len) {
                        error(
                "root %llu EXTENT_DATA[%llu %llu] wrong inline size, have: %llu, expected: %u",
                                root->objectid, fkey->objectid, fkey->offset,
                                extent_num_bytes, item_inline_len);
                        err |= FILE_EXTENT_ERROR;
                }
                *end += extent_num_bytes;
                *size += extent_num_bytes;
                return err;
        }

        /* Check extent type */
        if (extent_type != BTRFS_FILE_EXTENT_REG &&
                        extent_type != BTRFS_FILE_EXTENT_PREALLOC) {
                err |= FILE_EXTENT_ERROR;
                error("root %llu EXTENT_DATA[%llu %llu] type bad",
                      root->objectid, fkey->objectid, fkey->offset);
                return err;
        }

        /* Check REG_EXTENT/PREALLOC_EXTENT */
        disk_bytenr = btrfs_file_extent_disk_bytenr(node, fi);
        disk_num_bytes = btrfs_file_extent_disk_num_bytes(node, fi);
        extent_num_bytes = btrfs_file_extent_num_bytes(node, fi);
        extent_offset = btrfs_file_extent_offset(node, fi);
        compressed = btrfs_file_extent_compression(node, fi);
        is_hole = (disk_bytenr == 0) && (disk_num_bytes == 0);

        /*
         * Check EXTENT_DATA csum
         *
         * For plain (uncompressed) extent, we should only check the range
         * we're referring to, as it's possible that part of prealloc extent
         * has been written, and has csum:
         *
         * |<--- Original large preallocated extent A ---->|
         * |<- Prealloc File Extent ->|<- Regular Extent ->|
         *      No csum                         Has csum
         *
         * For compressed extent, we should check the whole range.
         */
        if (!compressed) {
                search_start = disk_bytenr + extent_offset;
                search_len = extent_num_bytes;
        } else {
                search_start = disk_bytenr;
                search_len = disk_num_bytes;
        }
        ret = count_csum_range(root, search_start, search_len, &csum_found);
        if (csum_found > 0 && nodatasum) {
                err |= ODD_CSUM_ITEM;
                error("root %llu EXTENT_DATA[%llu %llu] nodatasum shouldn't have datasum",
                      root->objectid, fkey->objectid, fkey->offset);
        } else if (extent_type == BTRFS_FILE_EXTENT_REG && !nodatasum &&
                   !is_hole && (ret < 0 || csum_found < search_len)) {
                err |= CSUM_ITEM_MISSING;
                error("root %llu EXTENT_DATA[%llu %llu] csum missing, have: %llu, expected: %llu",
                      root->objectid, fkey->objectid, fkey->offset,
                      csum_found, search_len);
        } else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC && csum_found > 0) {
                err |= ODD_CSUM_ITEM;
                error("root %llu EXTENT_DATA[%llu %llu] prealloc shouldn't have csum, but has: %llu",
                      root->objectid, fkey->objectid, fkey->offset, csum_found);
        }

        /* Check EXTENT_DATA hole */
        if (!no_holes && *end != fkey->offset) {
                err |= FILE_EXTENT_ERROR;
                error("root %llu EXTENT_DATA[%llu %llu] interrupt",
                      root->objectid, fkey->objectid, fkey->offset);
        }

        *end += extent_num_bytes;
        if (!is_hole)
                *size += extent_num_bytes;

        return err;
}

/*
 * Set inode item nbytes to @nbytes
 *
 * Returns  0     on success
 * Returns  != 0  on error
 */
static int repair_inode_nbytes_lowmem(struct btrfs_root *root,
                                      struct btrfs_path *path,
                                      u64 ino, u64 nbytes)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_inode_item *ii;
        struct btrfs_key key;
        struct btrfs_key research_key;
        int err = 0;
        int ret;

        btrfs_item_key_to_cpu(path->nodes[0], &research_key, path->slots[0]);

        key.objectid = ino;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                err |= ret;
                goto out;
        }

        btrfs_release_path(path);
        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
        if (ret > 0)
                ret = -ENOENT;
        if (ret) {
                err |= ret;
                goto fail;
        }

        ii = btrfs_item_ptr(path->nodes[0], path->slots[0],
                            struct btrfs_inode_item);
        btrfs_set_inode_nbytes(path->nodes[0], ii, nbytes);
        btrfs_mark_buffer_dirty(path->nodes[0]);
fail:
        btrfs_commit_transaction(trans, root);
out:
        if (ret)
                error("failed to set nbytes in inode %llu root %llu",
                      ino, root->root_key.objectid);
        else
                printf("Set nbytes in inode item %llu root %llu\n to %llu", ino,
                       root->root_key.objectid, nbytes);

        /* research path */
        btrfs_release_path(path);
        ret = btrfs_search_slot(NULL, root, &research_key, path, 0, 0);
        err |= ret;

        return err;
}

/*
 * Set directory inode isize to @isize.
 *
 * Returns 0     on success.
 * Returns != 0  on error.
 */
static int repair_dir_isize_lowmem(struct btrfs_root *root,
                                   struct btrfs_path *path,
                                   u64 ino, u64 isize)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_inode_item *ii;
        struct btrfs_key key;
        struct btrfs_key research_key;
        int ret;
        int err = 0;

        btrfs_item_key_to_cpu(path->nodes[0], &research_key, path->slots[0]);

        key.objectid = ino;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                err |= ret;
                goto out;
        }

        btrfs_release_path(path);
        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
        if (ret > 0)
                ret = -ENOENT;
        if (ret) {
                err |= ret;
                goto fail;
        }

        ii = btrfs_item_ptr(path->nodes[0], path->slots[0],
                            struct btrfs_inode_item);
        btrfs_set_inode_size(path->nodes[0], ii, isize);
        btrfs_mark_buffer_dirty(path->nodes[0]);
fail:
        btrfs_commit_transaction(trans, root);
out:
        if (ret)
                error("failed to set isize in inode %llu root %llu",
                      ino, root->root_key.objectid);
        else
                printf("Set isize in inode %llu root %llu to %llu\n",
                       ino, root->root_key.objectid, isize);

        btrfs_release_path(path);
        ret = btrfs_search_slot(NULL, root, &research_key, path, 0, 0);
        err |= ret;

        return err;
}

/*
 * Wrapper function for btrfs_add_orphan_item().
 *
 * Returns 0     on success.
 * Returns != 0  on error.
 */
static int repair_inode_orphan_item_lowmem(struct btrfs_root *root,
                                           struct btrfs_path *path, u64 ino)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_key research_key;
        int ret;
        int err = 0;

        btrfs_item_key_to_cpu(path->nodes[0], &research_key, path->slots[0]);

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                err |= ret;
                goto out;
        }

        btrfs_release_path(path);
        ret = btrfs_add_orphan_item(trans, root, path, ino);
        err |= ret;
        btrfs_commit_transaction(trans, root);
out:
        if (ret)
                error("failed to add inode %llu as orphan item root %llu",
                      ino, root->root_key.objectid);
        else
                printf("Added inode %llu as orphan item root %llu\n",
                       ino, root->root_key.objectid);

        btrfs_release_path(path);
        ret = btrfs_search_slot(NULL, root, &research_key, path, 0, 0);
        err |= ret;

        return err;
}

/*
 * Check INODE_ITEM and related ITEMs (the same inode number)
 * 1. check link count
 * 2. check inode ref/extref
 * 3. check dir item/index
 *
 * @ext_ref:    the EXTENDED_IREF feature
 *
 * Return 0 if no error occurred.
 * Return >0 for error or hit the traversal is done(by error bitmap)
 */
static int check_inode_item(struct btrfs_root *root, struct btrfs_path *path,
                            unsigned int ext_ref)
{
        struct extent_buffer *node;
        struct btrfs_inode_item *ii;
        struct btrfs_key key;
        u64 inode_id;
        u32 mode;
        u64 nlink;
        u64 nbytes;
        u64 isize;
        u64 size = 0;
        u64 refs = 0;
        u64 extent_end = 0;
        u64 extent_size = 0;
        unsigned int dir;
        unsigned int nodatasum;
        int slot;
        int ret;
        int err = 0;
        char namebuf[BTRFS_NAME_LEN] = {0};
        u32 name_len = 0;

        node = path->nodes[0];
        slot = path->slots[0];

        btrfs_item_key_to_cpu(node, &key, slot);
        inode_id = key.objectid;

        if (inode_id == BTRFS_ORPHAN_OBJECTID) {
                ret = btrfs_next_item(root, path);
                if (ret > 0)
                        err |= LAST_ITEM;
                return err;
        }

        ii = btrfs_item_ptr(node, slot, struct btrfs_inode_item);
        isize = btrfs_inode_size(node, ii);
        nbytes = btrfs_inode_nbytes(node, ii);
        mode = btrfs_inode_mode(node, ii);
        dir = imode_to_type(mode) == BTRFS_FT_DIR;
        nlink = btrfs_inode_nlink(node, ii);
        nodatasum = btrfs_inode_flags(node, ii) & BTRFS_INODE_NODATASUM;

        while (1) {
                ret = btrfs_next_item(root, path);
                if (ret < 0) {
                        /* out will fill 'err' rusing current statistics */
                        goto out;
                } else if (ret > 0) {
                        err |= LAST_ITEM;
                        goto out;
                }

                node = path->nodes[0];
                slot = path->slots[0];
                btrfs_item_key_to_cpu(node, &key, slot);
                if (key.objectid != inode_id)
                        goto out;

                switch (key.type) {
                case BTRFS_INODE_REF_KEY:
                        ret = check_inode_ref(root, &key, path, namebuf,
                                              &name_len, &refs, mode);
                        err |= ret;
                        break;
                case BTRFS_INODE_EXTREF_KEY:
                        if (key.type == BTRFS_INODE_EXTREF_KEY && !ext_ref)
                                warning("root %llu EXTREF[%llu %llu] isn't supported",
                                        root->objectid, key.objectid,
                                        key.offset);
                        ret = check_inode_extref(root, &key, node, slot, &refs,
                                                 mode);
                        err |= ret;
                        break;
                case BTRFS_DIR_ITEM_KEY:
                case BTRFS_DIR_INDEX_KEY:
                        if (!dir) {
                                warning("root %llu INODE[%llu] mode %u shouldn't have DIR_INDEX[%llu %llu]",
                                        root->objectid, inode_id,
                                        imode_to_type(mode), key.objectid,
                                        key.offset);
                        }
                        ret = check_dir_item(root, &key, path, &size, ext_ref);
                        err |= ret;
                        break;
                case BTRFS_EXTENT_DATA_KEY:
                        if (dir) {
                                warning("root %llu DIR INODE[%llu] shouldn't EXTENT_DATA[%llu %llu]",
                                        root->objectid, inode_id, key.objectid,
                                        key.offset);
                        }
                        ret = check_file_extent(root, &key, node, slot,
                                                nodatasum, &extent_size,
                                                &extent_end);
                        err |= ret;
                        break;
                case BTRFS_XATTR_ITEM_KEY:
                        break;
                default:
                        error("ITEM[%llu %u %llu] UNKNOWN TYPE",
                              key.objectid, key.type, key.offset);
                }
        }

out:
        /* verify INODE_ITEM nlink/isize/nbytes */
        if (dir) {
                if (repair && (err & DIR_COUNT_AGAIN)) {
                        err &= ~DIR_COUNT_AGAIN;
                        count_dir_isize(root, inode_id, &size);
                }
                if (nlink != 1) {
                        err |= LINK_COUNT_ERROR;
                        error("root %llu DIR INODE[%llu] shouldn't have more than one link(%llu)",
                              root->objectid, inode_id, nlink);
                }

                /*
                 * Just a warning, as dir inode nbytes is just an
                 * instructive value.
                 */
                if (!IS_ALIGNED(nbytes, root->fs_info->nodesize)) {
                        warning("root %llu DIR INODE[%llu] nbytes should be aligned to %u",
                                root->objectid, inode_id,
                                root->fs_info->nodesize);
                }

                if (isize != size) {
                        if (repair)
                                ret = repair_dir_isize_lowmem(root, path,
                                                              inode_id, size);
                        if (!repair || ret) {
                                err |= ISIZE_ERROR;
                                error(
                "root %llu DIR INODE [%llu] size %llu not equal to %llu",
                                      root->objectid, inode_id, isize, size);
                        }
                }
        } else {
                if (nlink != refs) {
                        err |= LINK_COUNT_ERROR;
                        error("root %llu INODE[%llu] nlink(%llu) not equal to inode_refs(%llu)",
                              root->objectid, inode_id, nlink, refs);
                } else if (!nlink) {
                        if (repair)
                                ret = repair_inode_orphan_item_lowmem(root,
                                                              path, inode_id);
                        if (!repair || ret) {
                                err |= ORPHAN_ITEM;
                                error("root %llu INODE[%llu] is orphan item",
                                      root->objectid, inode_id);
                        }
                }

                if (!nbytes && !no_holes && extent_end < isize) {
                        err |= NBYTES_ERROR;
                        error("root %llu INODE[%llu] size (%llu) should have a file extent hole",
                              root->objectid, inode_id, isize);
                }

                if (nbytes != extent_size) {
                        if (repair)
                                ret = repair_inode_nbytes_lowmem(root, path,
                                                         inode_id, extent_size);
                        if (!repair || ret) {
                                err |= NBYTES_ERROR;
                                error(
        "root %llu INODE[%llu] nbytes %llu not equal to extent_size %llu",
                                      root->objectid, inode_id, nbytes,
                                      extent_size);
                        }
                }
        }

        return err;
}

/*
 * Insert the missing inode item and inode ref.
 *
 * Normal INODE_ITEM_MISSING and INODE_REF_MISSING are handled in backref * dir.
 * Root dir should be handled specially because root dir is the root of fs.
 *
 * returns err (>0 or 0) after repair
 */
static int repair_fs_first_inode(struct btrfs_root *root, int err)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_key key;
        struct btrfs_path path;
        int filetype = BTRFS_FT_DIR;
        int ret = 0;

        btrfs_init_path(&path);

        if (err & INODE_REF_MISSING) {
                key.objectid = BTRFS_FIRST_FREE_OBJECTID;
                key.type = BTRFS_INODE_REF_KEY;
                key.offset = BTRFS_FIRST_FREE_OBJECTID;

                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        goto out;
                }

                btrfs_release_path(&path);
                ret = btrfs_search_slot(trans, root, &key, &path, 1, 1);
                if (ret)
                        goto trans_fail;

                ret = btrfs_insert_inode_ref(trans, root, "..", 2,
                                             BTRFS_FIRST_FREE_OBJECTID,
                                             BTRFS_FIRST_FREE_OBJECTID, 0);
                if (ret)
                        goto trans_fail;

                printf("Add INODE_REF[%llu %llu] name %s\n",
                       BTRFS_FIRST_FREE_OBJECTID, BTRFS_FIRST_FREE_OBJECTID,
                       "..");
                err &= ~INODE_REF_MISSING;
trans_fail:
                if (ret)
                        error("fail to insert first inode's ref");
                btrfs_commit_transaction(trans, root);
        }

        if (err & INODE_ITEM_MISSING) {
                ret = repair_inode_item_missing(root,
                                        BTRFS_FIRST_FREE_OBJECTID, filetype);
                if (ret)
                        goto out;
                err &= ~INODE_ITEM_MISSING;
        }
out:
        if (ret)
                error("fail to repair first inode");
        btrfs_release_path(&path);
        return err;
}

/*
 * check first root dir's inode_item and inode_ref
 *
 * returns 0 means no error
 * returns >0 means error
 * returns <0 means fatal error
 */
static int check_fs_first_inode(struct btrfs_root *root, unsigned int ext_ref)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_inode_item *ii;
        u64 index;
        u32 mode;
        int err = 0;
        int ret;

        key.objectid = BTRFS_FIRST_FREE_OBJECTID;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        /* For root being dropped, we don't need to check first inode */
        if (btrfs_root_refs(&root->root_item) == 0 &&
            btrfs_disk_key_objectid(&root->root_item.drop_progress) >=
            BTRFS_FIRST_FREE_OBJECTID)
                return 0;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = 0;
                err |= INODE_ITEM_MISSING;
        } else {
                ii = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                    struct btrfs_inode_item);
                mode = btrfs_inode_mode(path.nodes[0], ii);
                if (imode_to_type(mode) != BTRFS_FT_DIR)
                        err |= INODE_ITEM_MISMATCH;
        }

        /* lookup first inode ref */
        key.offset = BTRFS_FIRST_FREE_OBJECTID;
        key.type = BTRFS_INODE_REF_KEY;
        /* special index value */
        index = 0;

        ret = find_inode_ref(root, &key, "..", strlen(".."), &index, ext_ref);
        if (ret < 0)
                goto out;
        err |= ret;

out:
        btrfs_release_path(&path);

        if (err && repair)
                err = repair_fs_first_inode(root, err);

        if (err & (INODE_ITEM_MISSING | INODE_ITEM_MISMATCH))
                error("root dir INODE_ITEM is %s",
                      err & INODE_ITEM_MISMATCH ? "mismatch" : "missing");
        if (err & INODE_REF_MISSING)
                error("root dir INODE_REF is missing");

        return ret < 0 ? ret : err;
}

static struct tree_backref *find_tree_backref(struct extent_record *rec,
                                                u64 parent, u64 root)
{
        struct rb_node *node;
        struct tree_backref *back = NULL;
        struct tree_backref match = {
                .node = {
                        .is_data = 0,
                },
        };

        if (parent) {
                match.parent = parent;
                match.node.full_backref = 1;
        } else {
                match.root = root;
        }

        node = rb_search(&rec->backref_tree, &match.node.node,
                         (rb_compare_keys)compare_extent_backref, NULL);
        if (node)
                back = to_tree_backref(rb_node_to_extent_backref(node));

        return back;
}

static struct data_backref *find_data_backref(struct extent_record *rec,
                                                u64 parent, u64 root,
                                                u64 owner, u64 offset,
                                                int found_ref,
                                                u64 disk_bytenr, u64 bytes)
{
        struct rb_node *node;
        struct data_backref *back = NULL;
        struct data_backref match = {
                .node = {
                        .is_data = 1,
                },
                .owner = owner,
                .offset = offset,
                .bytes = bytes,
                .found_ref = found_ref,
                .disk_bytenr = disk_bytenr,
        };

        if (parent) {
                match.parent = parent;
                match.node.full_backref = 1;
        } else {
                match.root = root;
        }

        node = rb_search(&rec->backref_tree, &match.node.node,
                         (rb_compare_keys)compare_extent_backref, NULL);
        if (node)
                back = to_data_backref(rb_node_to_extent_backref(node));

        return back;
}
/*
 * Iterate all item on the tree and call check_inode_item() to check.
 *
 * @root:       the root of the tree to be checked.
 * @ext_ref:    the EXTENDED_IREF feature
 *
 * Return 0 if no error found.
 * Return <0 for error.
 */
static int check_fs_root_v2(struct btrfs_root *root, unsigned int ext_ref)
{
        struct btrfs_path path;
        struct node_refs nrefs;
        struct btrfs_root_item *root_item = &root->root_item;
        int ret;
        int level;
        int err = 0;

        /*
         * We need to manually check the first inode item(256)
         * As the following traversal function will only start from
         * the first inode item in the leaf, if inode item(256) is missing
         * we will just skip it forever.
         */
        ret = check_fs_first_inode(root, ext_ref);
        if (ret < 0)
                return ret;
        err |= !!ret;

        memset(&nrefs, 0, sizeof(nrefs));
        level = btrfs_header_level(root->node);
        btrfs_init_path(&path);

        if (btrfs_root_refs(root_item) > 0 ||
            btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
                path.nodes[level] = root->node;
                path.slots[level] = 0;
                extent_buffer_get(root->node);
        } else {
                struct btrfs_key key;

                btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
                level = root_item->drop_level;
                path.lowest_level = level;
                ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
                if (ret < 0)
                        goto out;
                ret = 0;
        }

        while (1) {
                ret = walk_down_tree_v2(root, &path, &level, &nrefs, ext_ref);
                err |= !!ret;

                /* if ret is negative, walk shall stop */
                if (ret < 0) {
                        ret = err;
                        break;
                }

                ret = walk_up_tree_v2(root, &path, &level);
                if (ret != 0) {
                        /* Normal exit, reset ret to err */
                        ret = err;
                        break;
                }
        }

out:
        btrfs_release_path(&path);
        return ret;
}

/*
 * Find the relative ref for root_ref and root_backref.
 *
 * @root:       the root of the root tree.
 * @ref_key:    the key of the root ref.
 *
 * Return 0 if no error occurred.
 */
static int check_root_ref(struct btrfs_root *root, struct btrfs_key *ref_key,
                          struct extent_buffer *node, int slot)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_root_ref *ref;
        struct btrfs_root_ref *backref;
        char ref_name[BTRFS_NAME_LEN] = {0};
        char backref_name[BTRFS_NAME_LEN] = {0};
        u64 ref_dirid;
        u64 ref_seq;
        u32 ref_namelen;
        u64 backref_dirid;
        u64 backref_seq;
        u32 backref_namelen;
        u32 len;
        int ret;
        int err = 0;

        ref = btrfs_item_ptr(node, slot, struct btrfs_root_ref);
        ref_dirid = btrfs_root_ref_dirid(node, ref);
        ref_seq = btrfs_root_ref_sequence(node, ref);
        ref_namelen = btrfs_root_ref_name_len(node, ref);

        if (ref_namelen <= BTRFS_NAME_LEN) {
                len = ref_namelen;
        } else {
                len = BTRFS_NAME_LEN;
                warning("%s[%llu %llu] ref_name too long",
                        ref_key->type == BTRFS_ROOT_REF_KEY ?
                        "ROOT_REF" : "ROOT_BACKREF", ref_key->objectid,
                        ref_key->offset);
        }
        read_extent_buffer(node, ref_name, (unsigned long)(ref + 1), len);

        /* Find relative root_ref */
        key.objectid = ref_key->offset;
        key.type = BTRFS_ROOT_BACKREF_KEY + BTRFS_ROOT_REF_KEY - ref_key->type;
        key.offset = ref_key->objectid;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret) {
                err |= ROOT_REF_MISSING;
                error("%s[%llu %llu] couldn't find relative ref",
                      ref_key->type == BTRFS_ROOT_REF_KEY ?
                      "ROOT_REF" : "ROOT_BACKREF",
                      ref_key->objectid, ref_key->offset);
                goto out;
        }

        backref = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                 struct btrfs_root_ref);
        backref_dirid = btrfs_root_ref_dirid(path.nodes[0], backref);
        backref_seq = btrfs_root_ref_sequence(path.nodes[0], backref);
        backref_namelen = btrfs_root_ref_name_len(path.nodes[0], backref);

        if (backref_namelen <= BTRFS_NAME_LEN) {
                len = backref_namelen;
        } else {
                len = BTRFS_NAME_LEN;
                warning("%s[%llu %llu] ref_name too long",
                        key.type == BTRFS_ROOT_REF_KEY ?
                        "ROOT_REF" : "ROOT_BACKREF",
                        key.objectid, key.offset);
        }
        read_extent_buffer(path.nodes[0], backref_name,
                           (unsigned long)(backref + 1), len);

        if (ref_dirid != backref_dirid || ref_seq != backref_seq ||
            ref_namelen != backref_namelen ||
            strncmp(ref_name, backref_name, len)) {
                err |= ROOT_REF_MISMATCH;
                error("%s[%llu %llu] mismatch relative ref",
                      ref_key->type == BTRFS_ROOT_REF_KEY ?
                      "ROOT_REF" : "ROOT_BACKREF",
                      ref_key->objectid, ref_key->offset);
        }
out:
        btrfs_release_path(&path);
        return err;
}

/*
 * Check all fs/file tree in low_memory mode.
 *
 * 1. for fs tree root item, call check_fs_root_v2()
 * 2. for fs tree root ref/backref, call check_root_ref()
 *
 * Return 0 if no error occurred.
 */
static int check_fs_roots_v2(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *cur_root = NULL;
        struct btrfs_path path;
        struct btrfs_key key;
        struct extent_buffer *node;
        unsigned int ext_ref;
        int slot;
        int ret;
        int err = 0;

        ext_ref = btrfs_fs_incompat(fs_info, EXTENDED_IREF);

        btrfs_init_path(&path);
        key.objectid = BTRFS_FS_TREE_OBJECTID;
        key.offset = 0;
        key.type = BTRFS_ROOT_ITEM_KEY;

        ret = btrfs_search_slot(NULL, tree_root, &key, &path, 0, 0);
        if (ret < 0) {
                err = ret;
                goto out;
        } else if (ret > 0) {
                err = -ENOENT;
                goto out;
        }

        while (1) {
                node = path.nodes[0];
                slot = path.slots[0];
                btrfs_item_key_to_cpu(node, &key, slot);
                if (key.objectid > BTRFS_LAST_FREE_OBJECTID)
                        goto out;
                if (key.type == BTRFS_ROOT_ITEM_KEY &&
                    fs_root_objectid(key.objectid)) {
                        if (key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
                                cur_root = btrfs_read_fs_root_no_cache(fs_info,
                                                                       &key);
                        } else {
                                key.offset = (u64)-1;
                                cur_root = btrfs_read_fs_root(fs_info, &key);
                        }

                        if (IS_ERR(cur_root)) {
                                error("Fail to read fs/subvol tree: %lld",
                                      key.objectid);
                                err = -EIO;
                                goto next;
                        }

                        ret = check_fs_root_v2(cur_root, ext_ref);
                        err |= ret;

                        if (key.objectid == BTRFS_TREE_RELOC_OBJECTID)
                                btrfs_free_fs_root(cur_root);
                } else if (key.type == BTRFS_ROOT_REF_KEY ||
                                key.type == BTRFS_ROOT_BACKREF_KEY) {
                        ret = check_root_ref(tree_root, &key, node, slot);
                        err |= ret;
                }
next:
                ret = btrfs_next_item(tree_root, &path);
                if (ret > 0)
                        goto out;
                if (ret < 0) {
                        err = ret;
                        goto out;
                }
        }

out:
        btrfs_release_path(&path);
        return err;
}

static int do_check_fs_roots(struct btrfs_fs_info *fs_info,
                          struct cache_tree *root_cache)
{
        int ret;

        if (!ctx.progress_enabled)
                fprintf(stderr, "checking fs roots\n");
        if (check_mode == CHECK_MODE_LOWMEM)
                ret = check_fs_roots_v2(fs_info);
        else
                ret = check_fs_roots(fs_info, root_cache);

        return ret;
}

static int all_backpointers_checked(struct extent_record *rec, int print_errs)
{
        struct extent_backref *back, *tmp;
        struct tree_backref *tback;
        struct data_backref *dback;
        u64 found = 0;
        int err = 0;

        rbtree_postorder_for_each_entry_safe(back, tmp,
                                             &rec->backref_tree, node) {
                if (!back->found_extent_tree) {
                        err = 1;
                        if (!print_errs)
                                goto out;
                        if (back->is_data) {
                                dback = to_data_backref(back);
                                fprintf(stderr, "Data backref %llu %s %llu"
                                        " owner %llu offset %llu num_refs %lu"
                                        " not found in extent tree\n",
                                        (unsigned long long)rec->start,
                                        back->full_backref ?
                                        "parent" : "root",
                                        back->full_backref ?
                                        (unsigned long long)dback->parent:
                                        (unsigned long long)dback->root,
                                        (unsigned long long)dback->owner,
                                        (unsigned long long)dback->offset,
                                        (unsigned long)dback->num_refs);
                        } else {
                                tback = to_tree_backref(back);
                                fprintf(stderr, "Tree backref %llu parent %llu"
                                        " root %llu not found in extent tree\n",
                                        (unsigned long long)rec->start,
                                        (unsigned long long)tback->parent,
                                        (unsigned long long)tback->root);
                        }
                }
                if (!back->is_data && !back->found_ref) {
                        err = 1;
                        if (!print_errs)
                                goto out;
                        tback = to_tree_backref(back);
                        fprintf(stderr, "Backref %llu %s %llu not referenced back %p\n",
                                (unsigned long long)rec->start,
                                back->full_backref ? "parent" : "root",
                                back->full_backref ?
                                (unsigned long long)tback->parent :
                                (unsigned long long)tback->root, back);
                }
                if (back->is_data) {
                        dback = to_data_backref(back);
                        if (dback->found_ref != dback->num_refs) {
                                err = 1;
                                if (!print_errs)
                                        goto out;
                                fprintf(stderr, "Incorrect local backref count"
                                        " on %llu %s %llu owner %llu"
                                        " offset %llu found %u wanted %u back %p\n",
                                        (unsigned long long)rec->start,
                                        back->full_backref ?
                                        "parent" : "root",
                                        back->full_backref ?
                                        (unsigned long long)dback->parent:
                                        (unsigned long long)dback->root,
                                        (unsigned long long)dback->owner,
                                        (unsigned long long)dback->offset,
                                        dback->found_ref, dback->num_refs, back);
                        }
                        if (dback->disk_bytenr != rec->start) {
                                err = 1;
                                if (!print_errs)
                                        goto out;
                                fprintf(stderr, "Backref disk bytenr does not"
                                        " match extent record, bytenr=%llu, "
                                        "ref bytenr=%llu\n",
                                        (unsigned long long)rec->start,
                                        (unsigned long long)dback->disk_bytenr);
                        }

                        if (dback->bytes != rec->nr) {
                                err = 1;
                                if (!print_errs)
                                        goto out;
                                fprintf(stderr, "Backref bytes do not match "
                                        "extent backref, bytenr=%llu, ref "
                                        "bytes=%llu, backref bytes=%llu\n",
                                        (unsigned long long)rec->start,
                                        (unsigned long long)rec->nr,
                                        (unsigned long long)dback->bytes);
                        }
                }
                if (!back->is_data) {
                        found += 1;
                } else {
                        dback = to_data_backref(back);
                        found += dback->found_ref;
                }
        }
        if (found != rec->refs) {
                err = 1;
                if (!print_errs)
                        goto out;
                fprintf(stderr, "Incorrect global backref count "
                        "on %llu found %llu wanted %llu\n",
                        (unsigned long long)rec->start,
                        (unsigned long long)found,
                        (unsigned long long)rec->refs);
        }
out:
        return err;
}

static void __free_one_backref(struct rb_node *node)
{
        struct extent_backref *back = rb_node_to_extent_backref(node);

        free(back);
}

static void free_all_extent_backrefs(struct extent_record *rec)
{
        rb_free_nodes(&rec->backref_tree, __free_one_backref);
}

static void free_extent_record_cache(struct cache_tree *extent_cache)
{
        struct cache_extent *cache;
        struct extent_record *rec;

        while (1) {
                cache = first_cache_extent(extent_cache);
                if (!cache)
                        break;
                rec = container_of(cache, struct extent_record, cache);
                remove_cache_extent(extent_cache, cache);
                free_all_extent_backrefs(rec);
                free(rec);
        }
}

static int maybe_free_extent_rec(struct cache_tree *extent_cache,
                                 struct extent_record *rec)
{
        if (rec->content_checked && rec->owner_ref_checked &&
            rec->extent_item_refs == rec->refs && rec->refs > 0 &&
            rec->num_duplicates == 0 && !all_backpointers_checked(rec, 0) &&
            !rec->bad_full_backref && !rec->crossing_stripes &&
            !rec->wrong_chunk_type) {
                remove_cache_extent(extent_cache, &rec->cache);
                free_all_extent_backrefs(rec);
                list_del_init(&rec->list);
                free(rec);
        }
        return 0;
}

static int check_owner_ref(struct btrfs_root *root,
                            struct extent_record *rec,
                            struct extent_buffer *buf)
{
        struct extent_backref *node, *tmp;
        struct tree_backref *back;
        struct btrfs_root *ref_root;
        struct btrfs_key key;
        struct btrfs_path path;
        struct extent_buffer *parent;
        int level;
        int found = 0;
        int ret;

        rbtree_postorder_for_each_entry_safe(node, tmp,
                                             &rec->backref_tree, node) {
                if (node->is_data)
                        continue;
                if (!node->found_ref)
                        continue;
                if (node->full_backref)
                        continue;
                back = to_tree_backref(node);
                if (btrfs_header_owner(buf) == back->root)
                        return 0;
        }
        BUG_ON(rec->is_root);

        /* try to find the block by search corresponding fs tree */
        key.objectid = btrfs_header_owner(buf);
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;

        ref_root = btrfs_read_fs_root(root->fs_info, &key);
        if (IS_ERR(ref_root))
                return 1;

        level = btrfs_header_level(buf);
        if (level == 0)
                btrfs_item_key_to_cpu(buf, &key, 0);
        else
                btrfs_node_key_to_cpu(buf, &key, 0);

        btrfs_init_path(&path);
        path.lowest_level = level + 1;
        ret = btrfs_search_slot(NULL, ref_root, &key, &path, 0, 0);
        if (ret < 0)
                return 0;

        parent = path.nodes[level + 1];
        if (parent && buf->start == btrfs_node_blockptr(parent,
                                                        path.slots[level + 1]))
                found = 1;

        btrfs_release_path(&path);
        return found ? 0 : 1;
}

static int is_extent_tree_record(struct extent_record *rec)
{
        struct extent_backref *node, *tmp;
        struct tree_backref *back;
        int is_extent = 0;

        rbtree_postorder_for_each_entry_safe(node, tmp,
                                             &rec->backref_tree, node) {
                if (node->is_data)
                        return 0;
                back = to_tree_backref(node);
                if (node->full_backref)
                        return 0;
                if (back->root == BTRFS_EXTENT_TREE_OBJECTID)
                        is_extent = 1;
        }
        return is_extent;
}


static int record_bad_block_io(struct btrfs_fs_info *info,
                               struct cache_tree *extent_cache,
                               u64 start, u64 len)
{
        struct extent_record *rec;
        struct cache_extent *cache;
        struct btrfs_key key;

        cache = lookup_cache_extent(extent_cache, start, len);
        if (!cache)
                return 0;

        rec = container_of(cache, struct extent_record, cache);
        if (!is_extent_tree_record(rec))
                return 0;

        btrfs_disk_key_to_cpu(&key, &rec->parent_key);
        return btrfs_add_corrupt_extent_record(info, &key, start, len, 0);
}

static int swap_values(struct btrfs_root *root, struct btrfs_path *path,
                       struct extent_buffer *buf, int slot)
{
        if (btrfs_header_level(buf)) {
                struct btrfs_key_ptr ptr1, ptr2;

                read_extent_buffer(buf, &ptr1, btrfs_node_key_ptr_offset(slot),
                                   sizeof(struct btrfs_key_ptr));
                read_extent_buffer(buf, &ptr2,
                                   btrfs_node_key_ptr_offset(slot + 1),
                                   sizeof(struct btrfs_key_ptr));
                write_extent_buffer(buf, &ptr1,
                                    btrfs_node_key_ptr_offset(slot + 1),
                                    sizeof(struct btrfs_key_ptr));
                write_extent_buffer(buf, &ptr2,
                                    btrfs_node_key_ptr_offset(slot),
                                    sizeof(struct btrfs_key_ptr));
                if (slot == 0) {
                        struct btrfs_disk_key key;
                        btrfs_node_key(buf, &key, 0);
                        btrfs_fixup_low_keys(root, path, &key,
                                             btrfs_header_level(buf) + 1);
                }
        } else {
                struct btrfs_item *item1, *item2;
                struct btrfs_key k1, k2;
                char *item1_data, *item2_data;
                u32 item1_offset, item2_offset, item1_size, item2_size;

                item1 = btrfs_item_nr(slot);
                item2 = btrfs_item_nr(slot + 1);
                btrfs_item_key_to_cpu(buf, &k1, slot);
                btrfs_item_key_to_cpu(buf, &k2, slot + 1);
                item1_offset = btrfs_item_offset(buf, item1);
                item2_offset = btrfs_item_offset(buf, item2);
                item1_size = btrfs_item_size(buf, item1);
                item2_size = btrfs_item_size(buf, item2);

                item1_data = malloc(item1_size);
                if (!item1_data)
                        return -ENOMEM;
                item2_data = malloc(item2_size);
                if (!item2_data) {
                        free(item1_data);
                        return -ENOMEM;
                }

                read_extent_buffer(buf, item1_data, item1_offset, item1_size);
                read_extent_buffer(buf, item2_data, item2_offset, item2_size);

                write_extent_buffer(buf, item1_data, item2_offset, item2_size);
                write_extent_buffer(buf, item2_data, item1_offset, item1_size);
                free(item1_data);
                free(item2_data);

                btrfs_set_item_offset(buf, item1, item2_offset);
                btrfs_set_item_offset(buf, item2, item1_offset);
                btrfs_set_item_size(buf, item1, item2_size);
                btrfs_set_item_size(buf, item2, item1_size);

                path->slots[0] = slot;
                btrfs_set_item_key_unsafe(root, path, &k2);
                path->slots[0] = slot + 1;
                btrfs_set_item_key_unsafe(root, path, &k1);
        }
        return 0;
}

static int fix_key_order(struct btrfs_root *root, struct btrfs_path *path)
{
        struct extent_buffer *buf;
        struct btrfs_key k1, k2;
        int i;
        int level = path->lowest_level;
        int ret = -EIO;

        buf = path->nodes[level];
        for (i = 0; i < btrfs_header_nritems(buf) - 1; i++) {
                if (level) {
                        btrfs_node_key_to_cpu(buf, &k1, i);
                        btrfs_node_key_to_cpu(buf, &k2, i + 1);
                } else {
                        btrfs_item_key_to_cpu(buf, &k1, i);
                        btrfs_item_key_to_cpu(buf, &k2, i + 1);
                }
                if (btrfs_comp_cpu_keys(&k1, &k2) < 0)
                        continue;
                ret = swap_values(root, path, buf, i);
                if (ret)
                        break;
                btrfs_mark_buffer_dirty(buf);
                i = 0;
        }
        return ret;
}

static int delete_bogus_item(struct btrfs_root *root,
                             struct btrfs_path *path,
                             struct extent_buffer *buf, int slot)
{
        struct btrfs_key key;
        int nritems = btrfs_header_nritems(buf);

        btrfs_item_key_to_cpu(buf, &key, slot);

        /* These are all the keys we can deal with missing. */
        if (key.type != BTRFS_DIR_INDEX_KEY &&
            key.type != BTRFS_EXTENT_ITEM_KEY &&
            key.type != BTRFS_METADATA_ITEM_KEY &&
            key.type != BTRFS_TREE_BLOCK_REF_KEY &&
            key.type != BTRFS_EXTENT_DATA_REF_KEY)
                return -1;

        printf("Deleting bogus item [%llu,%u,%llu] at slot %d on block %llu\n",
               (unsigned long long)key.objectid, key.type,
               (unsigned long long)key.offset, slot, buf->start);
        memmove_extent_buffer(buf, btrfs_item_nr_offset(slot),
                              btrfs_item_nr_offset(slot + 1),
                              sizeof(struct btrfs_item) *
                              (nritems - slot - 1));
        btrfs_set_header_nritems(buf, nritems - 1);
        if (slot == 0) {
                struct btrfs_disk_key disk_key;

                btrfs_item_key(buf, &disk_key, 0);
                btrfs_fixup_low_keys(root, path, &disk_key, 1);
        }
        btrfs_mark_buffer_dirty(buf);
        return 0;
}

static int fix_item_offset(struct btrfs_root *root, struct btrfs_path *path)
{
        struct extent_buffer *buf;
        int i;
        int ret = 0;

        /* We should only get this for leaves */
        BUG_ON(path->lowest_level);
        buf = path->nodes[0];
again:
        for (i = 0; i < btrfs_header_nritems(buf); i++) {
                unsigned int shift = 0, offset;

                if (i == 0 && btrfs_item_end_nr(buf, i) !=
                    BTRFS_LEAF_DATA_SIZE(root)) {
                        if (btrfs_item_end_nr(buf, i) >
                            BTRFS_LEAF_DATA_SIZE(root)) {
                                ret = delete_bogus_item(root, path, buf, i);
                                if (!ret)
                                        goto again;
                                fprintf(stderr, "item is off the end of the "
                                        "leaf, can't fix\n");
                                ret = -EIO;
                                break;
                        }
                        shift = BTRFS_LEAF_DATA_SIZE(root) -
                                btrfs_item_end_nr(buf, i);
                } else if (i > 0 && btrfs_item_end_nr(buf, i) !=
                           btrfs_item_offset_nr(buf, i - 1)) {
                        if (btrfs_item_end_nr(buf, i) >
                            btrfs_item_offset_nr(buf, i - 1)) {
                                ret = delete_bogus_item(root, path, buf, i);
                                if (!ret)
                                        goto again;
                                fprintf(stderr, "items overlap, can't fix\n");
                                ret = -EIO;
                                break;
                        }
                        shift = btrfs_item_offset_nr(buf, i - 1) -
                                btrfs_item_end_nr(buf, i);
                }
                if (!shift)
                        continue;

                printf("Shifting item nr %d by %u bytes in block %llu\n",
                       i, shift, (unsigned long long)buf->start);
                offset = btrfs_item_offset_nr(buf, i);
                memmove_extent_buffer(buf,
                                      btrfs_leaf_data(buf) + offset + shift,
                                      btrfs_leaf_data(buf) + offset,
                                      btrfs_item_size_nr(buf, i));
                btrfs_set_item_offset(buf, btrfs_item_nr(i),
                                      offset + shift);
                btrfs_mark_buffer_dirty(buf);
        }

        /*
         * We may have moved things, in which case we want to exit so we don't
         * write those changes out.  Once we have proper abort functionality in
         * progs this can be changed to something nicer.
         */
        BUG_ON(ret);
        return ret;
}

/*
 * Attempt to fix basic block failures.  If we can't fix it for whatever reason
 * then just return -EIO.
 */
static int try_to_fix_bad_block(struct btrfs_root *root,
                                struct extent_buffer *buf,
                                enum btrfs_tree_block_status status)
{
        struct btrfs_trans_handle *trans;
        struct ulist *roots;
        struct ulist_node *node;
        struct btrfs_root *search_root;
        struct btrfs_path path;
        struct ulist_iterator iter;
        struct btrfs_key root_key, key;
        int ret;

        if (status != BTRFS_TREE_BLOCK_BAD_KEY_ORDER &&
            status != BTRFS_TREE_BLOCK_INVALID_OFFSETS)
                return -EIO;

        ret = btrfs_find_all_roots(NULL, root->fs_info, buf->start, 0, &roots);
        if (ret)
                return -EIO;

        btrfs_init_path(&path);
        ULIST_ITER_INIT(&iter);
        while ((node = ulist_next(roots, &iter))) {
                root_key.objectid = node->val;
                root_key.type = BTRFS_ROOT_ITEM_KEY;
                root_key.offset = (u64)-1;

                search_root = btrfs_read_fs_root(root->fs_info, &root_key);
                if (IS_ERR(root)) {
                        ret = -EIO;
                        break;
                }


                trans = btrfs_start_transaction(search_root, 0);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        break;
                }

                path.lowest_level = btrfs_header_level(buf);
                path.skip_check_block = 1;
                if (path.lowest_level)
                        btrfs_node_key_to_cpu(buf, &key, 0);
                else
                        btrfs_item_key_to_cpu(buf, &key, 0);
                ret = btrfs_search_slot(trans, search_root, &key, &path, 0, 1);
                if (ret) {
                        ret = -EIO;
                        btrfs_commit_transaction(trans, search_root);
                        break;
                }
                if (status == BTRFS_TREE_BLOCK_BAD_KEY_ORDER)
                        ret = fix_key_order(search_root, &path);
                else if (status == BTRFS_TREE_BLOCK_INVALID_OFFSETS)
                        ret = fix_item_offset(search_root, &path);
                if (ret) {
                        btrfs_commit_transaction(trans, search_root);
                        break;
                }
                btrfs_release_path(&path);
                btrfs_commit_transaction(trans, search_root);
        }
        ulist_free(roots);
        btrfs_release_path(&path);
        return ret;
}

static int check_block(struct btrfs_root *root,
                       struct cache_tree *extent_cache,
                       struct extent_buffer *buf, u64 flags)
{
        struct extent_record *rec;
        struct cache_extent *cache;
        struct btrfs_key key;
        enum btrfs_tree_block_status status;
        int ret = 0;
        int level;

        cache = lookup_cache_extent(extent_cache, buf->start, buf->len);
        if (!cache)
                return 1;
        rec = container_of(cache, struct extent_record, cache);
        rec->generation = btrfs_header_generation(buf);

        level = btrfs_header_level(buf);
        if (btrfs_header_nritems(buf) > 0) {

                if (level == 0)
                        btrfs_item_key_to_cpu(buf, &key, 0);
                else
                        btrfs_node_key_to_cpu(buf, &key, 0);

                rec->info_objectid = key.objectid;
        }
        rec->info_level = level;

        if (btrfs_is_leaf(buf))
                status = btrfs_check_leaf(root, &rec->parent_key, buf);
        else
                status = btrfs_check_node(root, &rec->parent_key, buf);

        if (status != BTRFS_TREE_BLOCK_CLEAN) {
                if (repair)
                        status = try_to_fix_bad_block(root, buf, status);
                if (status != BTRFS_TREE_BLOCK_CLEAN) {
                        ret = -EIO;
                        fprintf(stderr, "bad block %llu\n",
                                (unsigned long long)buf->start);
                } else {
                        /*
                         * Signal to callers we need to start the scan over
                         * again since we'll have cowed blocks.
                         */
                        ret = -EAGAIN;
                }
        } else {
                rec->content_checked = 1;
                if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
                        rec->owner_ref_checked = 1;
                else {
                        ret = check_owner_ref(root, rec, buf);
                        if (!ret)
                                rec->owner_ref_checked = 1;
                }
        }
        if (!ret)
                maybe_free_extent_rec(extent_cache, rec);
        return ret;
}

#if 0
static struct tree_backref *find_tree_backref(struct extent_record *rec,
                                                u64 parent, u64 root)
{
        struct list_head *cur = rec->backrefs.next;
        struct extent_backref *node;
        struct tree_backref *back;

        while(cur != &rec->backrefs) {
                node = to_extent_backref(cur);
                cur = cur->next;
                if (node->is_data)
                        continue;
                back = to_tree_backref(node);
                if (parent > 0) {
                        if (!node->full_backref)
                                continue;
                        if (parent == back->parent)
                                return back;
                } else {
                        if (node->full_backref)
                                continue;
                        if (back->root == root)
                                return back;
                }
        }
        return NULL;
}
#endif

static struct tree_backref *alloc_tree_backref(struct extent_record *rec,
                                                u64 parent, u64 root)
{
        struct tree_backref *ref = malloc(sizeof(*ref));

        if (!ref)
                return NULL;
        memset(&ref->node, 0, sizeof(ref->node));
        if (parent > 0) {
                ref->parent = parent;
                ref->node.full_backref = 1;
        } else {
                ref->root = root;
                ref->node.full_backref = 0;
        }

        return ref;
}

#if 0
static struct data_backref *find_data_backref(struct extent_record *rec,
                                                u64 parent, u64 root,
                                                u64 owner, u64 offset,
                                                int found_ref,
                                                u64 disk_bytenr, u64 bytes)
{
        struct list_head *cur = rec->backrefs.next;
        struct extent_backref *node;
        struct data_backref *back;

        while(cur != &rec->backrefs) {
                node = to_extent_backref(cur);
                cur = cur->next;
                if (!node->is_data)
                        continue;
                back = to_data_backref(node);
                if (parent > 0) {
                        if (!node->full_backref)
                                continue;
                        if (parent == back->parent)
                                return back;
                } else {
                        if (node->full_backref)
                                continue;
                        if (back->root == root && back->owner == owner &&
                            back->offset == offset) {
                                if (found_ref && node->found_ref &&
                                    (back->bytes != bytes ||
                                    back->disk_bytenr != disk_bytenr))
                                        continue;
                                return back;
                        }
                }
        }
        return NULL;
}
#endif

static struct data_backref *alloc_data_backref(struct extent_record *rec,
                                                u64 parent, u64 root,
                                                u64 owner, u64 offset,
                                                u64 max_size)
{
        struct data_backref *ref = malloc(sizeof(*ref));

        if (!ref)
                return NULL;
        memset(&ref->node, 0, sizeof(ref->node));
        ref->node.is_data = 1;

        if (parent > 0) {
                ref->parent = parent;
                ref->owner = 0;
                ref->offset = 0;
                ref->node.full_backref = 1;
        } else {
                ref->root = root;
                ref->owner = owner;
                ref->offset = offset;
                ref->node.full_backref = 0;
        }
        ref->bytes = max_size;
        ref->found_ref = 0;
        ref->num_refs = 0;
        if (max_size > rec->max_size)
                rec->max_size = max_size;
        return ref;
}

/* Check if the type of extent matches with its chunk */
static void check_extent_type(struct extent_record *rec)
{
        struct btrfs_block_group_cache *bg_cache;

        bg_cache = btrfs_lookup_first_block_group(global_info, rec->start);
        if (!bg_cache)
                return;

        /* data extent, check chunk directly*/
        if (!rec->metadata) {
                if (!(bg_cache->flags & BTRFS_BLOCK_GROUP_DATA))
                        rec->wrong_chunk_type = 1;
                return;
        }

        /* metadata extent, check the obvious case first */
        if (!(bg_cache->flags & (BTRFS_BLOCK_GROUP_SYSTEM |
                                 BTRFS_BLOCK_GROUP_METADATA))) {
                rec->wrong_chunk_type = 1;
                return;
        }

        /*
         * Check SYSTEM extent, as it's also marked as metadata, we can only
         * make sure it's a SYSTEM extent by its backref
         */
        if (!RB_EMPTY_ROOT(&rec->backref_tree)) {
                struct extent_backref *node;
                struct tree_backref *tback;
                u64 bg_type;

                node = rb_node_to_extent_backref(rb_first(&rec->backref_tree));
                if (node->is_data) {
                        /* tree block shouldn't have data backref */
                        rec->wrong_chunk_type = 1;
                        return;
                }
                tback = container_of(node, struct tree_backref, node);

                if (tback->root == BTRFS_CHUNK_TREE_OBJECTID)
                        bg_type = BTRFS_BLOCK_GROUP_SYSTEM;
                else
                        bg_type = BTRFS_BLOCK_GROUP_METADATA;
                if (!(bg_cache->flags & bg_type))
                        rec->wrong_chunk_type = 1;
        }
}

/*
 * Allocate a new extent record, fill default values from @tmpl and insert int
 * @extent_cache. Caller is supposed to make sure the [start,nr) is not in
 * the cache, otherwise it fails.
 */
static int add_extent_rec_nolookup(struct cache_tree *extent_cache,
                struct extent_record *tmpl)
{
        struct extent_record *rec;
        int ret = 0;

        BUG_ON(tmpl->max_size == 0);
        rec = malloc(sizeof(*rec));
        if (!rec)
                return -ENOMEM;
        rec->start = tmpl->start;
        rec->max_size = tmpl->max_size;
        rec->nr = max(tmpl->nr, tmpl->max_size);
        rec->found_rec = tmpl->found_rec;
        rec->content_checked = tmpl->content_checked;
        rec->owner_ref_checked = tmpl->owner_ref_checked;
        rec->num_duplicates = 0;
        rec->metadata = tmpl->metadata;
        rec->flag_block_full_backref = FLAG_UNSET;
        rec->bad_full_backref = 0;
        rec->crossing_stripes = 0;
        rec->wrong_chunk_type = 0;
        rec->is_root = tmpl->is_root;
        rec->refs = tmpl->refs;
        rec->extent_item_refs = tmpl->extent_item_refs;
        rec->parent_generation = tmpl->parent_generation;
        INIT_LIST_HEAD(&rec->backrefs);
        INIT_LIST_HEAD(&rec->dups);
        INIT_LIST_HEAD(&rec->list);
        rec->backref_tree = RB_ROOT;
        memcpy(&rec->parent_key, &tmpl->parent_key, sizeof(tmpl->parent_key));
        rec->cache.start = tmpl->start;
        rec->cache.size = tmpl->nr;
        ret = insert_cache_extent(extent_cache, &rec->cache);
        if (ret) {
                free(rec);
                return ret;
        }
        bytes_used += rec->nr;

        if (tmpl->metadata)
                rec->crossing_stripes = check_crossing_stripes(global_info,
                                rec->start, global_info->nodesize);
        check_extent_type(rec);
        return ret;
}

/*
 * Lookup and modify an extent, some values of @tmpl are interpreted verbatim,
 * some are hints:
 * - refs              - if found, increase refs
 * - is_root           - if found, set
 * - content_checked   - if found, set
 * - owner_ref_checked - if found, set
 *
 * If not found, create a new one, initialize and insert.
 */
static int add_extent_rec(struct cache_tree *extent_cache,
                struct extent_record *tmpl)
{
        struct extent_record *rec;
        struct cache_extent *cache;
        int ret = 0;
        int dup = 0;

        cache = lookup_cache_extent(extent_cache, tmpl->start, tmpl->nr);
        if (cache) {
                rec = container_of(cache, struct extent_record, cache);
                if (tmpl->refs)
                        rec->refs++;
                if (rec->nr == 1)
                        rec->nr = max(tmpl->nr, tmpl->max_size);

                /*
                 * We need to make sure to reset nr to whatever the extent
                 * record says was the real size, this way we can compare it to
                 * the backrefs.
                 */
                if (tmpl->found_rec) {
                        if (tmpl->start != rec->start || rec->found_rec) {
                                struct extent_record *tmp;

                                dup = 1;
                                if (list_empty(&rec->list))
                                        list_add_tail(&rec->list,
                                                      &duplicate_extents);

                                /*
                                 * We have to do this song and dance in case we
                                 * find an extent record that falls inside of
                                 * our current extent record but does not have
                                 * the same objectid.
                                 */
                                tmp = malloc(sizeof(*tmp));
                                if (!tmp)
                                        return -ENOMEM;
                                tmp->start = tmpl->start;
                                tmp->max_size = tmpl->max_size;
                                tmp->nr = tmpl->nr;
                                tmp->found_rec = 1;
                                tmp->metadata = tmpl->metadata;
                                tmp->extent_item_refs = tmpl->extent_item_refs;
                                INIT_LIST_HEAD(&tmp->list);
                                list_add_tail(&tmp->list, &rec->dups);
                                rec->num_duplicates++;
                        } else {
                                rec->nr = tmpl->nr;
                                rec->found_rec = 1;
                        }
                }

                if (tmpl->extent_item_refs && !dup) {
                        if (rec->extent_item_refs) {
                                fprintf(stderr, "block %llu rec "
                                        "extent_item_refs %llu, passed %llu\n",
                                        (unsigned long long)tmpl->start,
                                        (unsigned long long)
                                                        rec->extent_item_refs,
                                        (unsigned long long)tmpl->extent_item_refs);
                        }
                        rec->extent_item_refs = tmpl->extent_item_refs;
                }
                if (tmpl->is_root)
                        rec->is_root = 1;
                if (tmpl->content_checked)
                        rec->content_checked = 1;
                if (tmpl->owner_ref_checked)
                        rec->owner_ref_checked = 1;
                memcpy(&rec->parent_key, &tmpl->parent_key,
                                sizeof(tmpl->parent_key));
                if (tmpl->parent_generation)
                        rec->parent_generation = tmpl->parent_generation;
                if (rec->max_size < tmpl->max_size)
                        rec->max_size = tmpl->max_size;

                /*
                 * A metadata extent can't cross stripe_len boundary, otherwise
                 * kernel scrub won't be able to handle it.
                 * As now stripe_len is fixed to BTRFS_STRIPE_LEN, just check
                 * it.
                 */
                if (tmpl->metadata)
                        rec->crossing_stripes = check_crossing_stripes(
                                        global_info, rec->start,
                                        global_info->nodesize);
                check_extent_type(rec);
                maybe_free_extent_rec(extent_cache, rec);
                return ret;
        }

        ret = add_extent_rec_nolookup(extent_cache, tmpl);

        return ret;
}

static int add_tree_backref(struct cache_tree *extent_cache, u64 bytenr,
                            u64 parent, u64 root, int found_ref)
{
        struct extent_record *rec;
        struct tree_backref *back;
        struct cache_extent *cache;
        int ret;
        bool insert = false;

        cache = lookup_cache_extent(extent_cache, bytenr, 1);
        if (!cache) {
                struct extent_record tmpl;

                memset(&tmpl, 0, sizeof(tmpl));
                tmpl.start = bytenr;
                tmpl.nr = 1;
                tmpl.metadata = 1;
                tmpl.max_size = 1;

                ret = add_extent_rec_nolookup(extent_cache, &tmpl);
                if (ret)
                        return ret;

                /* really a bug in cache_extent implement now */
                cache = lookup_cache_extent(extent_cache, bytenr, 1);
                if (!cache)
                        return -ENOENT;
        }

        rec = container_of(cache, struct extent_record, cache);
        if (rec->start != bytenr) {
                /*
                 * Several cause, from unaligned bytenr to over lapping extents
                 */
                return -EEXIST;
        }

        back = find_tree_backref(rec, parent, root);
        if (!back) {
                back = alloc_tree_backref(rec, parent, root);
                if (!back)
                        return -ENOMEM;
                insert = true;
        }

        if (found_ref) {
                if (back->node.found_ref) {
                        fprintf(stderr, "Extent back ref already exists "
                                "for %llu parent %llu root %llu \n",
                                (unsigned long long)bytenr,
                                (unsigned long long)parent,
                                (unsigned long long)root);
                }
                back->node.found_ref = 1;
        } else {
                if (back->node.found_extent_tree) {
                        fprintf(stderr, "Extent back ref already exists "
                                "for %llu parent %llu root %llu \n",
                                (unsigned long long)bytenr,
                                (unsigned long long)parent,
                                (unsigned long long)root);
                }
                back->node.found_extent_tree = 1;
        }
        if (insert)
                WARN_ON(rb_insert(&rec->backref_tree, &back->node.node,
                        compare_extent_backref));
        check_extent_type(rec);
        maybe_free_extent_rec(extent_cache, rec);
        return 0;
}

static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
                            u64 parent, u64 root, u64 owner, u64 offset,
                            u32 num_refs, int found_ref, u64 max_size)
{
        struct extent_record *rec;
        struct data_backref *back;
        struct cache_extent *cache;
        int ret;
        bool insert = false;

        cache = lookup_cache_extent(extent_cache, bytenr, 1);
        if (!cache) {
                struct extent_record tmpl;

                memset(&tmpl, 0, sizeof(tmpl));
                tmpl.start = bytenr;
                tmpl.nr = 1;
                tmpl.max_size = max_size;

                ret = add_extent_rec_nolookup(extent_cache, &tmpl);
                if (ret)
                        return ret;

                cache = lookup_cache_extent(extent_cache, bytenr, 1);
                if (!cache)
                        abort();
        }

        rec = container_of(cache, struct extent_record, cache);
        if (rec->max_size < max_size)
                rec->max_size = max_size;

        /*
         * If found_ref is set then max_size is the real size and must match the
         * existing refs.  So if we have already found a ref then we need to
         * make sure that this ref matches the existing one, otherwise we need
         * to add a new backref so we can notice that the backrefs don't match
         * and we need to figure out who is telling the truth.  This is to
         * account for that awful fsync bug I introduced where we'd end up with
         * a btrfs_file_extent_item that would have its length include multiple
         * prealloc extents or point inside of a prealloc extent.
         */
        back = find_data_backref(rec, parent, root, owner, offset, found_ref,
                                 bytenr, max_size);
        if (!back) {
                back = alloc_data_backref(rec, parent, root, owner, offset,
                                          max_size);
                BUG_ON(!back);
                insert = true;
        }

        if (found_ref) {
                BUG_ON(num_refs != 1);
                if (back->node.found_ref)
                        BUG_ON(back->bytes != max_size);
                back->node.found_ref = 1;
                back->found_ref += 1;
                if (back->bytes != max_size || back->disk_bytenr != bytenr) {
                        back->bytes = max_size;
                        back->disk_bytenr = bytenr;

                        /* Need to reinsert if not already in the tree */
                        if (!insert) {
                                rb_erase(&back->node.node, &rec->backref_tree);
                                insert = true;
                        }
                }
                rec->refs += 1;
                rec->content_checked = 1;
                rec->owner_ref_checked = 1;
        } else {
                if (back->node.found_extent_tree) {
                        fprintf(stderr, "Extent back ref already exists "
                                "for %llu parent %llu root %llu "
                                "owner %llu offset %llu num_refs %lu\n",
                                (unsigned long long)bytenr,
                                (unsigned long long)parent,
                                (unsigned long long)root,
                                (unsigned long long)owner,
                                (unsigned long long)offset,
                                (unsigned long)num_refs);
                }
                back->num_refs = num_refs;
                back->node.found_extent_tree = 1;
        }
        if (insert)
                WARN_ON(rb_insert(&rec->backref_tree, &back->node.node,
                        compare_extent_backref));

        maybe_free_extent_rec(extent_cache, rec);
        return 0;
}

static int add_pending(struct cache_tree *pending,
                       struct cache_tree *seen, u64 bytenr, u32 size)
{
        int ret;
        ret = add_cache_extent(seen, bytenr, size);
        if (ret)
                return ret;
        add_cache_extent(pending, bytenr, size);
        return 0;
}

static int pick_next_pending(struct cache_tree *pending,
                        struct cache_tree *reada,
                        struct cache_tree *nodes,
                        u64 last, struct block_info *bits, int bits_nr,
                        int *reada_bits)
{
        unsigned long node_start = last;
        struct cache_extent *cache;
        int ret;

        cache = search_cache_extent(reada, 0);
        if (cache) {
                bits[0].start = cache->start;
                bits[0].size = cache->size;
                *reada_bits = 1;
                return 1;
        }
        *reada_bits = 0;
        if (node_start > 32768)
                node_start -= 32768;

        cache = search_cache_extent(nodes, node_start);
        if (!cache)
                cache = search_cache_extent(nodes, 0);

        if (!cache) {
                 cache = search_cache_extent(pending, 0);
                 if (!cache)
                         return 0;
                 ret = 0;
                 do {
                         bits[ret].start = cache->start;
                         bits[ret].size = cache->size;
                         cache = next_cache_extent(cache);
                         ret++;
                 } while (cache && ret < bits_nr);
                 return ret;
        }

        ret = 0;
        do {
                bits[ret].start = cache->start;
                bits[ret].size = cache->size;
                cache = next_cache_extent(cache);
                ret++;
        } while (cache && ret < bits_nr);

        if (bits_nr - ret > 8) {
                u64 lookup = bits[0].start + bits[0].size;
                struct cache_extent *next;
                next = search_cache_extent(pending, lookup);
                while(next) {
                        if (next->start - lookup > 32768)
                                break;
                        bits[ret].start = next->start;
                        bits[ret].size = next->size;
                        lookup = next->start + next->size;
                        ret++;
                        if (ret == bits_nr)
                                break;
                        next = next_cache_extent(next);
                        if (!next)
                                break;
                }
        }
        return ret;
}

static void free_chunk_record(struct cache_extent *cache)
{
        struct chunk_record *rec;

        rec = container_of(cache, struct chunk_record, cache);
        list_del_init(&rec->list);
        list_del_init(&rec->dextents);
        free(rec);
}

void free_chunk_cache_tree(struct cache_tree *chunk_cache)
{
        cache_tree_free_extents(chunk_cache, free_chunk_record);
}

static void free_device_record(struct rb_node *node)
{
        struct device_record *rec;

        rec = container_of(node, struct device_record, node);
        free(rec);
}

FREE_RB_BASED_TREE(device_cache, free_device_record);

int insert_block_group_record(struct block_group_tree *tree,
                              struct block_group_record *bg_rec)
{
        int ret;

        ret = insert_cache_extent(&tree->tree, &bg_rec->cache);
        if (ret)
                return ret;

        list_add_tail(&bg_rec->list, &tree->block_groups);
        return 0;
}

static void free_block_group_record(struct cache_extent *cache)
{
        struct block_group_record *rec;

        rec = container_of(cache, struct block_group_record, cache);
        list_del_init(&rec->list);
        free(rec);
}

void free_block_group_tree(struct block_group_tree *tree)
{
        cache_tree_free_extents(&tree->tree, free_block_group_record);
}

int insert_device_extent_record(struct device_extent_tree *tree,
                                struct device_extent_record *de_rec)
{
        int ret;

        /*
         * Device extent is a bit different from the other extents, because
         * the extents which belong to the different devices may have the
         * same start and size, so we need use the special extent cache
         * search/insert functions.
         */
        ret = insert_cache_extent2(&tree->tree, &de_rec->cache);
        if (ret)
                return ret;

        list_add_tail(&de_rec->chunk_list, &tree->no_chunk_orphans);
        list_add_tail(&de_rec->device_list, &tree->no_device_orphans);
        return 0;
}

static void free_device_extent_record(struct cache_extent *cache)
{
        struct device_extent_record *rec;

        rec = container_of(cache, struct device_extent_record, cache);
        if (!list_empty(&rec->chunk_list))
                list_del_init(&rec->chunk_list);
        if (!list_empty(&rec->device_list))
                list_del_init(&rec->device_list);
        free(rec);
}

void free_device_extent_tree(struct device_extent_tree *tree)
{
        cache_tree_free_extents(&tree->tree, free_device_extent_record);
}

#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
static int process_extent_ref_v0(struct cache_tree *extent_cache,
                                 struct extent_buffer *leaf, int slot)
{
        struct btrfs_extent_ref_v0 *ref0;
        struct btrfs_key key;
        int ret;

        btrfs_item_key_to_cpu(leaf, &key, slot);
        ref0 = btrfs_item_ptr(leaf, slot, struct btrfs_extent_ref_v0);
        if (btrfs_ref_objectid_v0(leaf, ref0) < BTRFS_FIRST_FREE_OBJECTID) {
                ret = add_tree_backref(extent_cache, key.objectid, key.offset,
                                0, 0);
        } else {
                ret = add_data_backref(extent_cache, key.objectid, key.offset,
                                0, 0, 0, btrfs_ref_count_v0(leaf, ref0), 0, 0);
        }
        return ret;
}
#endif

struct chunk_record *btrfs_new_chunk_record(struct extent_buffer *leaf,
                                            struct btrfs_key *key,
                                            int slot)
{
        struct btrfs_chunk *ptr;
        struct chunk_record *rec;
        int num_stripes, i;

        ptr = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
        num_stripes = btrfs_chunk_num_stripes(leaf, ptr);

        rec = calloc(1, btrfs_chunk_record_size(num_stripes));
        if (!rec) {
                fprintf(stderr, "memory allocation failed\n");
                exit(-1);
        }

        INIT_LIST_HEAD(&rec->list);
        INIT_LIST_HEAD(&rec->dextents);
        rec->bg_rec = NULL;

        rec->cache.start = key->offset;
        rec->cache.size = btrfs_chunk_length(leaf, ptr);

        rec->generation = btrfs_header_generation(leaf);

        rec->objectid = key->objectid;
        rec->type = key->type;
        rec->offset = key->offset;

        rec->length = rec->cache.size;
        rec->owner = btrfs_chunk_owner(leaf, ptr);
        rec->stripe_len = btrfs_chunk_stripe_len(leaf, ptr);
        rec->type_flags = btrfs_chunk_type(leaf, ptr);
        rec->io_width = btrfs_chunk_io_width(leaf, ptr);
        rec->io_align = btrfs_chunk_io_align(leaf, ptr);
        rec->sector_size = btrfs_chunk_sector_size(leaf, ptr);
        rec->num_stripes = num_stripes;
        rec->sub_stripes = btrfs_chunk_sub_stripes(leaf, ptr);

        for (i = 0; i < rec->num_stripes; ++i) {
                rec->stripes[i].devid =
                        btrfs_stripe_devid_nr(leaf, ptr, i);
                rec->stripes[i].offset =
                        btrfs_stripe_offset_nr(leaf, ptr, i);
                read_extent_buffer(leaf, rec->stripes[i].dev_uuid,
                                (unsigned long)btrfs_stripe_dev_uuid_nr(ptr, i),
                                BTRFS_UUID_SIZE);
        }

        return rec;
}

static int process_chunk_item(struct cache_tree *chunk_cache,
                              struct btrfs_key *key, struct extent_buffer *eb,
                              int slot)
{
        struct chunk_record *rec;
        struct btrfs_chunk *chunk;
        int ret = 0;

        chunk = btrfs_item_ptr(eb, slot, struct btrfs_chunk);
        /*
         * Do extra check for this chunk item,
         *
         * It's still possible one can craft a leaf with CHUNK_ITEM, with
         * wrong onwer(3) out of chunk tree, to pass both chunk tree check
         * and owner<->key_type check.
         */
        ret = btrfs_check_chunk_valid(global_info, eb, chunk, slot,
                                      key->offset);
        if (ret < 0) {
                error("chunk(%llu, %llu) is not valid, ignore it",
                      key->offset, btrfs_chunk_length(eb, chunk));
                return 0;
        }
        rec = btrfs_new_chunk_record(eb, key, slot);
        ret = insert_cache_extent(chunk_cache, &rec->cache);
        if (ret) {
                fprintf(stderr, "Chunk[%llu, %llu] existed.\n",
                        rec->offset, rec->length);
                free(rec);
        }

        return ret;
}

static int process_device_item(struct rb_root *dev_cache,
                struct btrfs_key *key, struct extent_buffer *eb, int slot)
{
        struct btrfs_dev_item *ptr;
        struct device_record *rec;
        int ret = 0;

        ptr = btrfs_item_ptr(eb,
                slot, struct btrfs_dev_item);

        rec = malloc(sizeof(*rec));
        if (!rec) {
                fprintf(stderr, "memory allocation failed\n");
                return -ENOMEM;
        }

        rec->devid = key->offset;
        rec->generation = btrfs_header_generation(eb);

        rec->objectid = key->objectid;
        rec->type = key->type;
        rec->offset = key->offset;

        rec->devid = btrfs_device_id(eb, ptr);
        rec->total_byte = btrfs_device_total_bytes(eb, ptr);
        rec->byte_used = btrfs_device_bytes_used(eb, ptr);

        ret = rb_insert(dev_cache, &rec->node, device_record_compare);
        if (ret) {
                fprintf(stderr, "Device[%llu] existed.\n", rec->devid);
                free(rec);
        }

        return ret;
}

struct block_group_record *
btrfs_new_block_group_record(struct extent_buffer *leaf, struct btrfs_key *key,
                             int slot)
{
        struct btrfs_block_group_item *ptr;
        struct block_group_record *rec;

        rec = calloc(1, sizeof(*rec));
        if (!rec) {
                fprintf(stderr, "memory allocation failed\n");
                exit(-1);
        }

        rec->cache.start = key->objectid;
        rec->cache.size = key->offset;

        rec->generation = btrfs_header_generation(leaf);

        rec->objectid = key->objectid;
        rec->type = key->type;
        rec->offset = key->offset;

        ptr = btrfs_item_ptr(leaf, slot, struct btrfs_block_group_item);
        rec->flags = btrfs_disk_block_group_flags(leaf, ptr);

        INIT_LIST_HEAD(&rec->list);

        return rec;
}

static int process_block_group_item(struct block_group_tree *block_group_cache,
                                    struct btrfs_key *key,
                                    struct extent_buffer *eb, int slot)
{
        struct block_group_record *rec;
        int ret = 0;

        rec = btrfs_new_block_group_record(eb, key, slot);
        ret = insert_block_group_record(block_group_cache, rec);
        if (ret) {
                fprintf(stderr, "Block Group[%llu, %llu] existed.\n",
                        rec->objectid, rec->offset);
                free(rec);
        }

        return ret;
}

struct device_extent_record *
btrfs_new_device_extent_record(struct extent_buffer *leaf,
                               struct btrfs_key *key, int slot)
{
        struct device_extent_record *rec;
        struct btrfs_dev_extent *ptr;

        rec = calloc(1, sizeof(*rec));
        if (!rec) {
                fprintf(stderr, "memory allocation failed\n");
                exit(-1);
        }

        rec->cache.objectid = key->objectid;
        rec->cache.start = key->offset;

        rec->generation = btrfs_header_generation(leaf);

        rec->objectid = key->objectid;
        rec->type = key->type;
        rec->offset = key->offset;

        ptr = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
        rec->chunk_objecteid =
                btrfs_dev_extent_chunk_objectid(leaf, ptr);
        rec->chunk_offset =
                btrfs_dev_extent_chunk_offset(leaf, ptr);
        rec->length = btrfs_dev_extent_length(leaf, ptr);
        rec->cache.size = rec->length;

        INIT_LIST_HEAD(&rec->chunk_list);
        INIT_LIST_HEAD(&rec->device_list);

        return rec;
}

static int
process_device_extent_item(struct device_extent_tree *dev_extent_cache,
                           struct btrfs_key *key, struct extent_buffer *eb,
                           int slot)
{
        struct device_extent_record *rec;
        int ret;

        rec = btrfs_new_device_extent_record(eb, key, slot);
        ret = insert_device_extent_record(dev_extent_cache, rec);
        if (ret) {
                fprintf(stderr,
                        "Device extent[%llu, %llu, %llu] existed.\n",
                        rec->objectid, rec->offset, rec->length);
                free(rec);
        }

        return ret;
}

static int process_extent_item(struct btrfs_root *root,
                               struct cache_tree *extent_cache,
                               struct extent_buffer *eb, int slot)
{
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_extent_data_ref *dref;
        struct btrfs_shared_data_ref *sref;
        struct btrfs_key key;
        struct extent_record tmpl;
        unsigned long end;
        unsigned long ptr;
        int ret;
        int type;
        u32 item_size = btrfs_item_size_nr(eb, slot);
        u64 refs = 0;
        u64 offset;
        u64 num_bytes;
        int metadata = 0;

        btrfs_item_key_to_cpu(eb, &key, slot);

        if (key.type == BTRFS_METADATA_ITEM_KEY) {
                metadata = 1;
                num_bytes = root->fs_info->nodesize;
        } else {
                num_bytes = key.offset;
        }

        if (!IS_ALIGNED(key.objectid, root->fs_info->sectorsize)) {
                error("ignoring invalid extent, bytenr %llu is not aligned to %u",
                      key.objectid, root->fs_info->sectorsize);
                return -EIO;
        }
        if (item_size < sizeof(*ei)) {
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
                struct btrfs_extent_item_v0 *ei0;
                BUG_ON(item_size != sizeof(*ei0));
                ei0 = btrfs_item_ptr(eb, slot, struct btrfs_extent_item_v0);
                refs = btrfs_extent_refs_v0(eb, ei0);
#else
                BUG();
#endif
                memset(&tmpl, 0, sizeof(tmpl));
                tmpl.start = key.objectid;
                tmpl.nr = num_bytes;
                tmpl.extent_item_refs = refs;
                tmpl.metadata = metadata;
                tmpl.found_rec = 1;
                tmpl.max_size = num_bytes;

                return add_extent_rec(extent_cache, &tmpl);
        }

        ei = btrfs_item_ptr(eb, slot, struct btrfs_extent_item);
        refs = btrfs_extent_refs(eb, ei);
        if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK)
                metadata = 1;
        else
                metadata = 0;
        if (metadata && num_bytes != root->fs_info->nodesize) {
                error("ignore invalid metadata extent, length %llu does not equal to %u",
                      num_bytes, root->fs_info->nodesize);
                return -EIO;
        }
        if (!metadata && !IS_ALIGNED(num_bytes, root->fs_info->sectorsize)) {
                error("ignore invalid data extent, length %llu is not aligned to %u",
                      num_bytes, root->fs_info->sectorsize);
                return -EIO;
        }

        memset(&tmpl, 0, sizeof(tmpl));
        tmpl.start = key.objectid;
        tmpl.nr = num_bytes;
        tmpl.extent_item_refs = refs;
        tmpl.metadata = metadata;
        tmpl.found_rec = 1;
        tmpl.max_size = num_bytes;
        add_extent_rec(extent_cache, &tmpl);

        ptr = (unsigned long)(ei + 1);
        if (btrfs_extent_flags(eb, ei) & BTRFS_EXTENT_FLAG_TREE_BLOCK &&
            key.type == BTRFS_EXTENT_ITEM_KEY)
                ptr += sizeof(struct btrfs_tree_block_info);

        end = (unsigned long)ei + item_size;
        while (ptr < end) {
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(eb, iref);
                offset = btrfs_extent_inline_ref_offset(eb, iref);
                switch (type) {
                case BTRFS_TREE_BLOCK_REF_KEY:
                        ret = add_tree_backref(extent_cache, key.objectid,
                                        0, offset, 0);
                        if (ret < 0)
                                error(
                        "add_tree_backref failed (extent items tree block): %s",
                                      strerror(-ret));
                        break;
                case BTRFS_SHARED_BLOCK_REF_KEY:
                        ret = add_tree_backref(extent_cache, key.objectid,
                                        offset, 0, 0);
                        if (ret < 0)
                                error(
                        "add_tree_backref failed (extent items shared block): %s",
                                      strerror(-ret));
                        break;
                case BTRFS_EXTENT_DATA_REF_KEY:
                        dref = (struct btrfs_extent_data_ref *)(&iref->offset);
                        add_data_backref(extent_cache, key.objectid, 0,
                                        btrfs_extent_data_ref_root(eb, dref),
                                        btrfs_extent_data_ref_objectid(eb,
                                                                       dref),
                                        btrfs_extent_data_ref_offset(eb, dref),
                                        btrfs_extent_data_ref_count(eb, dref),
                                        0, num_bytes);
                        break;
                case BTRFS_SHARED_DATA_REF_KEY:
                        sref = (struct btrfs_shared_data_ref *)(iref + 1);
                        add_data_backref(extent_cache, key.objectid, offset,
                                        0, 0, 0,
                                        btrfs_shared_data_ref_count(eb, sref),
                                        0, num_bytes);
                        break;
                default:
                        fprintf(stderr, "corrupt extent record: key %Lu %u %Lu\n",
                                key.objectid, key.type, num_bytes);
                        goto out;
                }
                ptr += btrfs_extent_inline_ref_size(type);
        }
        WARN_ON(ptr > end);
out:
        return 0;
}

static int check_cache_range(struct btrfs_root *root,
                             struct btrfs_block_group_cache *cache,
                             u64 offset, u64 bytes)
{
        struct btrfs_free_space *entry;
        u64 *logical;
        u64 bytenr;
        int stripe_len;
        int i, nr, ret;

        for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
                bytenr = btrfs_sb_offset(i);
                ret = btrfs_rmap_block(root->fs_info,
                                       cache->key.objectid, bytenr, 0,
                                       &logical, &nr, &stripe_len);
                if (ret)
                        return ret;

                while (nr--) {
                        if (logical[nr] + stripe_len <= offset)
                                continue;
                        if (offset + bytes <= logical[nr])
                                continue;
                        if (logical[nr] == offset) {
                                if (stripe_len >= bytes) {
                                        free(logical);
                                        return 0;
                                }
                                bytes -= stripe_len;
                                offset += stripe_len;
                        } else if (logical[nr] < offset) {
                                if (logical[nr] + stripe_len >=
                                    offset + bytes) {
                                        free(logical);
                                        return 0;
                                }
                                bytes = (offset + bytes) -
                                        (logical[nr] + stripe_len);
                                offset = logical[nr] + stripe_len;
                        } else {
                                /*
                                 * Could be tricky, the super may land in the
                                 * middle of the area we're checking.  First
                                 * check the easiest case, it's at the end.
                                 */
                                if (logical[nr] + stripe_len >=
                                    bytes + offset) {
                                        bytes = logical[nr] - offset;
                                        continue;
                                }

                                /* Check the left side */
                                ret = check_cache_range(root, cache,
                                                        offset,
                                                        logical[nr] - offset);
                                if (ret) {
                                        free(logical);
                                        return ret;
                                }

                                /* Now we continue with the right side */
                                bytes = (offset + bytes) -
                                        (logical[nr] + stripe_len);
                                offset = logical[nr] + stripe_len;
                        }
                }

                free(logical);
        }

        entry = btrfs_find_free_space(cache->free_space_ctl, offset, bytes);
        if (!entry) {
                fprintf(stderr, "There is no free space entry for %Lu-%Lu\n",
                        offset, offset+bytes);
                return -EINVAL;
        }

        if (entry->offset != offset) {
                fprintf(stderr, "Wanted offset %Lu, found %Lu\n", offset,
                        entry->offset);
                return -EINVAL;
        }

        if (entry->bytes != bytes) {
                fprintf(stderr, "Wanted bytes %Lu, found %Lu for off %Lu\n",
                        bytes, entry->bytes, offset);
                return -EINVAL;
        }

        unlink_free_space(cache->free_space_ctl, entry);
        free(entry);
        return 0;
}

static int verify_space_cache(struct btrfs_root *root,
                              struct btrfs_block_group_cache *cache)
{
        struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        u64 last;
        int ret = 0;

        root = root->fs_info->extent_root;

        last = max_t(u64, cache->key.objectid, BTRFS_SUPER_INFO_OFFSET);

        btrfs_init_path(&path);
        key.objectid = last;
        key.offset = 0;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        ret = 0;
        while (1) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        ret = btrfs_next_leaf(root, &path);
                        if (ret < 0)
                                goto out;
                        if (ret > 0) {
                                ret = 0;
                                break;
                        }
                }
                leaf = path.nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.objectid >= cache->key.offset + cache->key.objectid)
                        break;
                if (key.type != BTRFS_EXTENT_ITEM_KEY &&
                    key.type != BTRFS_METADATA_ITEM_KEY) {
                        path.slots[0]++;
                        continue;
                }

                if (last == key.objectid) {
                        if (key.type == BTRFS_EXTENT_ITEM_KEY)
                                last = key.objectid + key.offset;
                        else
                                last = key.objectid + root->fs_info->nodesize;
                        path.slots[0]++;
                        continue;
                }

                ret = check_cache_range(root, cache, last,
                                        key.objectid - last);
                if (ret)
                        break;
                if (key.type == BTRFS_EXTENT_ITEM_KEY)
                        last = key.objectid + key.offset;
                else
                        last = key.objectid + root->fs_info->nodesize;
                path.slots[0]++;
        }

        if (last < cache->key.objectid + cache->key.offset)
                ret = check_cache_range(root, cache, last,
                                        cache->key.objectid +
                                        cache->key.offset - last);

out:
        btrfs_release_path(&path);

        if (!ret &&
            !RB_EMPTY_ROOT(&cache->free_space_ctl->free_space_offset)) {
                fprintf(stderr, "There are still entries left in the space "
                        "cache\n");
                ret = -EINVAL;
        }

        return ret;
}

static int check_space_cache(struct btrfs_root *root)
{
        struct btrfs_block_group_cache *cache;
        u64 start = BTRFS_SUPER_INFO_OFFSET + BTRFS_SUPER_INFO_SIZE;
        int ret;
        int error = 0;

        if (btrfs_super_cache_generation(root->fs_info->super_copy) != -1ULL &&
            btrfs_super_generation(root->fs_info->super_copy) !=
            btrfs_super_cache_generation(root->fs_info->super_copy)) {
                printf("cache and super generation don't match, space cache "
                       "will be invalidated\n");
                return 0;
        }

        if (ctx.progress_enabled) {
                ctx.tp = TASK_FREE_SPACE;
                task_start(ctx.info);
        }

        while (1) {
                cache = btrfs_lookup_first_block_group(root->fs_info, start);
                if (!cache)
                        break;

                start = cache->key.objectid + cache->key.offset;
                if (!cache->free_space_ctl) {
                        if (btrfs_init_free_space_ctl(cache,
                                                root->fs_info->sectorsize)) {
                                ret = -ENOMEM;
                                break;
                        }
                } else {
                        btrfs_remove_free_space_cache(cache);
                }

                if (btrfs_fs_compat_ro(root->fs_info, FREE_SPACE_TREE)) {
                        ret = exclude_super_stripes(root, cache);
                        if (ret) {
                                fprintf(stderr, "could not exclude super stripes: %s\n",
                                        strerror(-ret));
                                error++;
                                continue;
                        }
                        ret = load_free_space_tree(root->fs_info, cache);
                        free_excluded_extents(root, cache);
                        if (ret < 0) {
                                fprintf(stderr, "could not load free space tree: %s\n",
                                        strerror(-ret));
                                error++;
                                continue;
                        }
                        error += ret;
                } else {
                        ret = load_free_space_cache(root->fs_info, cache);
                        if (!ret)
                                continue;
                }

                ret = verify_space_cache(root, cache);
                if (ret) {
                        fprintf(stderr, "cache appears valid but isn't %Lu\n",
                                cache->key.objectid);
                        error++;
                }
        }

        task_stop(ctx.info);

        return error ? -EINVAL : 0;
}

static int check_extent_csums(struct btrfs_root *root, u64 bytenr,
                        u64 num_bytes, unsigned long leaf_offset,
                        struct extent_buffer *eb) {

        struct btrfs_fs_info *fs_info = root->fs_info;
        u64 offset = 0;
        u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
        char *data;
        unsigned long csum_offset;
        u32 csum;
        u32 csum_expected;
        u64 read_len;
        u64 data_checked = 0;
        u64 tmp;
        int ret = 0;
        int mirror;
        int num_copies;

        if (num_bytes % fs_info->sectorsize)
                return -EINVAL;

        data = malloc(num_bytes);
        if (!data)
                return -ENOMEM;

        while (offset < num_bytes) {
                mirror = 0;
again:
                read_len = num_bytes - offset;
                /* read as much space once a time */
                ret = read_extent_data(fs_info, data + offset,
                                bytenr + offset, &read_len, mirror);
                if (ret)
                        goto out;
                data_checked = 0;
                /* verify every 4k data's checksum */
                while (data_checked < read_len) {
                        csum = ~(u32)0;
                        tmp = offset + data_checked;

                        csum = btrfs_csum_data((char *)data + tmp,
                                               csum, fs_info->sectorsize);
                        btrfs_csum_final(csum, (u8 *)&csum);

                        csum_offset = leaf_offset +
                                 tmp / fs_info->sectorsize * csum_size;
                        read_extent_buffer(eb, (char *)&csum_expected,
                                           csum_offset, csum_size);
                        /* try another mirror */
                        if (csum != csum_expected) {
                                fprintf(stderr, "mirror %d bytenr %llu csum %u expected csum %u\n",
                                                mirror, bytenr + tmp,
                                                csum, csum_expected);
                                num_copies = btrfs_num_copies(root->fs_info,
                                                bytenr, num_bytes);
                                if (mirror < num_copies - 1) {
                                        mirror += 1;
                                        goto again;
                                }
                        }
                        data_checked += fs_info->sectorsize;
                }
                offset += read_len;
        }
out:
        free(data);
        return ret;
}

static int check_extent_exists(struct btrfs_root *root, u64 bytenr,
                               u64 num_bytes)
{
        struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        int ret;

        btrfs_init_path(&path);
        key.objectid = bytenr;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = (u64)-1;

again:
        ret = btrfs_search_slot(NULL, root->fs_info->extent_root, &key, &path,
                                0, 0);
        if (ret < 0) {
                fprintf(stderr, "Error looking up extent record %d\n", ret);
                btrfs_release_path(&path);
                return ret;
        } else if (ret) {
                if (path.slots[0] > 0) {
                        path.slots[0]--;
                } else {
                        ret = btrfs_prev_leaf(root, &path);
                        if (ret < 0) {
                                goto out;
                        } else if (ret > 0) {
                                ret = 0;
                                goto out;
                        }
                }
        }

        btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);

        /*
         * Block group items come before extent items if they have the same
         * bytenr, so walk back one more just in case.  Dear future traveller,
         * first congrats on mastering time travel.  Now if it's not too much
         * trouble could you go back to 2006 and tell Chris to make the
         * BLOCK_GROUP_ITEM_KEY (and BTRFS_*_REF_KEY) lower than the
         * EXTENT_ITEM_KEY please?
         */
        while (key.type > BTRFS_EXTENT_ITEM_KEY) {
                if (path.slots[0] > 0) {
                        path.slots[0]--;
                } else {
                        ret = btrfs_prev_leaf(root, &path);
                        if (ret < 0) {
                                goto out;
                        } else if (ret > 0) {
                                ret = 0;
                                goto out;
                        }
                }
                btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
        }

        while (num_bytes) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        ret = btrfs_next_leaf(root, &path);
                        if (ret < 0) {
                                fprintf(stderr, "Error going to next leaf "
                                        "%d\n", ret);
                                btrfs_release_path(&path);
                                return ret;
                        } else if (ret) {
                                break;
                        }
                }
                leaf = path.nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type != BTRFS_EXTENT_ITEM_KEY) {
                        path.slots[0]++;
                        continue;
                }
                if (key.objectid + key.offset < bytenr) {
                        path.slots[0]++;
                        continue;
                }
                if (key.objectid > bytenr + num_bytes)
                        break;

                if (key.objectid == bytenr) {
                        if (key.offset >= num_bytes) {
                                num_bytes = 0;
                                break;
                        }
                        num_bytes -= key.offset;
                        bytenr += key.offset;
                } else if (key.objectid < bytenr) {
                        if (key.objectid + key.offset >= bytenr + num_bytes) {
                                num_bytes = 0;
                                break;
                        }
                        num_bytes = (bytenr + num_bytes) -
                                (key.objectid + key.offset);
                        bytenr = key.objectid + key.offset;
                } else {
                        if (key.objectid + key.offset < bytenr + num_bytes) {
                                u64 new_start = key.objectid + key.offset;
                                u64 new_bytes = bytenr + num_bytes - new_start;

                                /*
                                 * Weird case, the extent is in the middle of
                                 * our range, we'll have to search one side
                                 * and then the other.  Not sure if this happens
                                 * in real life, but no harm in coding it up
                                 * anyway just in case.
                                 */
                                btrfs_release_path(&path);
                                ret = check_extent_exists(root, new_start,
                                                          new_bytes);
                                if (ret) {
                                        fprintf(stderr, "Right section didn't "
                                                "have a record\n");
                                        break;
                                }
                                num_bytes = key.objectid - bytenr;
                                goto again;
                        }
                        num_bytes = key.objectid - bytenr;
                }
                path.slots[0]++;
        }
        ret = 0;

out:
        if (num_bytes && !ret) {
                fprintf(stderr, "There are no extents for csum range "
                        "%Lu-%Lu\n", bytenr, bytenr+num_bytes);
                ret = 1;
        }

        btrfs_release_path(&path);
        return ret;
}

static int check_csums(struct btrfs_root *root)
{
        struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        u64 offset = 0, num_bytes = 0;
        u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
        int errors = 0;
        int ret;
        u64 data_len;
        unsigned long leaf_offset;

        root = root->fs_info->csum_root;
        if (!extent_buffer_uptodate(root->node)) {
                fprintf(stderr, "No valid csum tree found\n");
                return -ENOENT;
        }

        btrfs_init_path(&path);
        key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
        key.type = BTRFS_EXTENT_CSUM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0) {
                fprintf(stderr, "Error searching csum tree %d\n", ret);
                btrfs_release_path(&path);
                return ret;
        }

        if (ret > 0 && path.slots[0])
                path.slots[0]--;
        ret = 0;

        while (1) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        ret = btrfs_next_leaf(root, &path);
                        if (ret < 0) {
                                fprintf(stderr, "Error going to next leaf "
                                        "%d\n", ret);
                                break;
                        }
                        if (ret)
                                break;
                }
                leaf = path.nodes[0];

                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type != BTRFS_EXTENT_CSUM_KEY) {
                        path.slots[0]++;
                        continue;
                }

                data_len = (btrfs_item_size_nr(leaf, path.slots[0]) /
                              csum_size) * root->fs_info->sectorsize;
                if (!check_data_csum)
                        goto skip_csum_check;
                leaf_offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
                ret = check_extent_csums(root, key.offset, data_len,
                                         leaf_offset, leaf);
                if (ret)
                        break;
skip_csum_check:
                if (!num_bytes) {
                        offset = key.offset;
                } else if (key.offset != offset + num_bytes) {
                        ret = check_extent_exists(root, offset, num_bytes);
                        if (ret) {
                                fprintf(stderr, "Csum exists for %Lu-%Lu but "
                                        "there is no extent record\n",
                                        offset, offset+num_bytes);
                                errors++;
                        }
                        offset = key.offset;
                        num_bytes = 0;
                }
                num_bytes += data_len;
                path.slots[0]++;
        }

        btrfs_release_path(&path);
        return errors;
}

static int is_dropped_key(struct btrfs_key *key,
                          struct btrfs_key *drop_key) {
        if (key->objectid < drop_key->objectid)
                return 1;
        else if (key->objectid == drop_key->objectid) {
                if (key->type < drop_key->type)
                        return 1;
                else if (key->type == drop_key->type) {
                        if (key->offset < drop_key->offset)
                                return 1;
                }
        }
        return 0;
}

/*
 * Here are the rules for FULL_BACKREF.
 *
 * 1) If BTRFS_HEADER_FLAG_RELOC is set then we have FULL_BACKREF set.
 * 2) If btrfs_header_owner(buf) no longer points to buf then we have
 *      FULL_BACKREF set.
 * 3) We cowed the block walking down a reloc tree.  This is impossible to tell
 *    if it happened after the relocation occurred since we'll have dropped the
 *    reloc root, so it's entirely possible to have FULL_BACKREF set on buf and
 *    have no real way to know for sure.
 *
 * We process the blocks one root at a time, and we start from the lowest root
 * objectid and go to the highest.  So we can just lookup the owner backref for
 * the record and if we don't find it then we know it doesn't exist and we have
 * a FULL BACKREF.
 *
 * FIXME: if we ever start reclaiming root objectid's then we need to fix this
 * assumption and simply indicate that we _think_ that the FULL BACKREF needs to
 * be set or not and then we can check later once we've gathered all the refs.
 */
static int calc_extent_flag(struct cache_tree *extent_cache,
                           struct extent_buffer *buf,
                           struct root_item_record *ri,
                           u64 *flags)
{
        struct extent_record *rec;
        struct cache_extent *cache;
        struct tree_backref *tback;
        u64 owner = 0;

        cache = lookup_cache_extent(extent_cache, buf->start, 1);
        /* we have added this extent before */
        if (!cache)
                return -ENOENT;

        rec = container_of(cache, struct extent_record, cache);

        /*
         * Except file/reloc tree, we can not have
         * FULL BACKREF MODE
         */
        if (ri->objectid < BTRFS_FIRST_FREE_OBJECTID)
                goto normal;
        /*
         * root node
         */
        if (buf->start == ri->bytenr)
                goto normal;

        if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))
                goto full_backref;

        owner = btrfs_header_owner(buf);
        if (owner == ri->objectid)
                goto normal;

        tback = find_tree_backref(rec, 0, owner);
        if (!tback)
                goto full_backref;
normal:
        *flags = 0;
        if (rec->flag_block_full_backref != FLAG_UNSET &&
            rec->flag_block_full_backref != 0)
                rec->bad_full_backref = 1;
        return 0;
full_backref:
        *flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
        if (rec->flag_block_full_backref != FLAG_UNSET &&
            rec->flag_block_full_backref != 1)
                rec->bad_full_backref = 1;
        return 0;
}

static void report_mismatch_key_root(u8 key_type, u64 rootid)
{
        fprintf(stderr, "Invalid key type(");
        print_key_type(stderr, 0, key_type);
        fprintf(stderr, ") found in root(");
        print_objectid(stderr, rootid, 0);
        fprintf(stderr, ")\n");
}

/*
 * Check if the key is valid with its extent buffer.
 *
 * This is a early check in case invalid key exists in a extent buffer
 * This is not comprehensive yet, but should prevent wrong key/item passed
 * further
 */
static int check_type_with_root(u64 rootid, u8 key_type)
{
        switch (key_type) {
        /* Only valid in chunk tree */
        case BTRFS_DEV_ITEM_KEY:
        case BTRFS_CHUNK_ITEM_KEY:
                if (rootid != BTRFS_CHUNK_TREE_OBJECTID)
                        goto err;
                break;
        /* valid in csum and log tree */
        case BTRFS_CSUM_TREE_OBJECTID:
                if (!(rootid == BTRFS_TREE_LOG_OBJECTID ||
                      is_fstree(rootid)))
                        goto err;
                break;
        case BTRFS_EXTENT_ITEM_KEY:
        case BTRFS_METADATA_ITEM_KEY:
        case BTRFS_BLOCK_GROUP_ITEM_KEY:
                if (rootid != BTRFS_EXTENT_TREE_OBJECTID)
                        goto err;
                break;
        case BTRFS_ROOT_ITEM_KEY:
                if (rootid != BTRFS_ROOT_TREE_OBJECTID)
                        goto err;
                break;
        case BTRFS_DEV_EXTENT_KEY:
                if (rootid != BTRFS_DEV_TREE_OBJECTID)
                        goto err;
                break;
        }
        return 0;
err:
        report_mismatch_key_root(key_type, rootid);
        return -EINVAL;
}

static int run_next_block(struct btrfs_root *root,
                          struct block_info *bits,
                          int bits_nr,
                          u64 *last,
                          struct cache_tree *pending,
                          struct cache_tree *seen,
                          struct cache_tree *reada,
                          struct cache_tree *nodes,
                          struct cache_tree *extent_cache,
                          struct cache_tree *chunk_cache,
                          struct rb_root *dev_cache,
                          struct block_group_tree *block_group_cache,
                          struct device_extent_tree *dev_extent_cache,
                          struct root_item_record *ri)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct extent_buffer *buf;
        struct extent_record *rec = NULL;
        u64 bytenr;
        u32 size;
        u64 parent;
        u64 owner;
        u64 flags;
        u64 ptr;
        u64 gen = 0;
        int ret = 0;
        int i;
        int nritems;
        struct btrfs_key key;
        struct cache_extent *cache;
        int reada_bits;

        nritems = pick_next_pending(pending, reada, nodes, *last, bits,
                                    bits_nr, &reada_bits);
        if (nritems == 0)
                return 1;

        if (!reada_bits) {
                for(i = 0; i < nritems; i++) {
                        ret = add_cache_extent(reada, bits[i].start,
                                               bits[i].size);
                        if (ret == -EEXIST)
                                continue;

                        /* fixme, get the parent transid */
                        readahead_tree_block(fs_info, bits[i].start, 0);
                }
        }
        *last = bits[0].start;
        bytenr = bits[0].start;
        size = bits[0].size;

        cache = lookup_cache_extent(pending, bytenr, size);
        if (cache) {
                remove_cache_extent(pending, cache);
                free(cache);
        }
        cache = lookup_cache_extent(reada, bytenr, size);
        if (cache) {
                remove_cache_extent(reada, cache);
                free(cache);
        }
        cache = lookup_cache_extent(nodes, bytenr, size);
        if (cache) {
                remove_cache_extent(nodes, cache);
                free(cache);
        }
        cache = lookup_cache_extent(extent_cache, bytenr, size);
        if (cache) {
                rec = container_of(cache, struct extent_record, cache);
                gen = rec->parent_generation;
        }

        /* fixme, get the real parent transid */
        buf = read_tree_block(root->fs_info, bytenr, gen);
        if (!extent_buffer_uptodate(buf)) {
                record_bad_block_io(root->fs_info,
                                    extent_cache, bytenr, size);
                goto out;
        }

        nritems = btrfs_header_nritems(buf);

        flags = 0;
        if (!init_extent_tree) {
                ret = btrfs_lookup_extent_info(NULL, root, bytenr,
                                       btrfs_header_level(buf), 1, NULL,
                                       &flags);
                if (ret < 0) {
                        ret = calc_extent_flag(extent_cache, buf, ri, &flags);
                        if (ret < 0) {
                                fprintf(stderr, "Couldn't calc extent flags\n");
                                flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
                        }
                }
        } else {
                flags = 0;
                ret = calc_extent_flag(extent_cache, buf, ri, &flags);
                if (ret < 0) {
                        fprintf(stderr, "Couldn't calc extent flags\n");
                        flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
                }
        }

        if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
                if (ri != NULL &&
                    ri->objectid != BTRFS_TREE_RELOC_OBJECTID &&
                    ri->objectid == btrfs_header_owner(buf)) {
                        /*
                         * Ok we got to this block from it's original owner and
                         * we have FULL_BACKREF set.  Relocation can leave
                         * converted blocks over so this is altogether possible,
                         * however it's not possible if the generation > the
                         * last snapshot, so check for this case.
                         */
                        if (!btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC) &&
                            btrfs_header_generation(buf) > ri->last_snapshot) {
                                flags &= ~BTRFS_BLOCK_FLAG_FULL_BACKREF;
                                rec->bad_full_backref = 1;
                        }
                }
        } else {
                if (ri != NULL &&
                    (ri->objectid == BTRFS_TREE_RELOC_OBJECTID ||
                     btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))) {
                        flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
                        rec->bad_full_backref = 1;
                }
        }

        if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
                rec->flag_block_full_backref = 1;
                parent = bytenr;
                owner = 0;
        } else {
                rec->flag_block_full_backref = 0;
                parent = 0;
                owner = btrfs_header_owner(buf);
        }

        ret = check_block(root, extent_cache, buf, flags);
        if (ret)
                goto out;

        if (btrfs_is_leaf(buf)) {
                btree_space_waste += btrfs_leaf_free_space(root, buf);
                for (i = 0; i < nritems; i++) {
                        struct btrfs_file_extent_item *fi;
                        btrfs_item_key_to_cpu(buf, &key, i);
                        /*
                         * Check key type against the leaf owner.
                         * Could filter quite a lot of early error if
                         * owner is correct
                         */
                        if (check_type_with_root(btrfs_header_owner(buf),
                                                 key.type)) {
                                fprintf(stderr, "ignoring invalid key\n");
                                continue;
                        }
                        if (key.type == BTRFS_EXTENT_ITEM_KEY) {
                                process_extent_item(root, extent_cache, buf,
                                                    i);
                                continue;
                        }
                        if (key.type == BTRFS_METADATA_ITEM_KEY) {
                                process_extent_item(root, extent_cache, buf,
                                                    i);
                                continue;
                        }
                        if (key.type == BTRFS_EXTENT_CSUM_KEY) {
                                total_csum_bytes +=
                                        btrfs_item_size_nr(buf, i);
                                continue;
                        }
                        if (key.type == BTRFS_CHUNK_ITEM_KEY) {
                                process_chunk_item(chunk_cache, &key, buf, i);
                                continue;
                        }
                        if (key.type == BTRFS_DEV_ITEM_KEY) {
                                process_device_item(dev_cache, &key, buf, i);
                                continue;
                        }
                        if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
                                process_block_group_item(block_group_cache,
                                        &key, buf, i);
                                continue;
                        }
                        if (key.type == BTRFS_DEV_EXTENT_KEY) {
                                process_device_extent_item(dev_extent_cache,
                                        &key, buf, i);
                                continue;

                        }
                        if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
#ifdef BTRFS_COMPAT_EXTENT_TREE_V0
                                process_extent_ref_v0(extent_cache, buf, i);
#else
                                BUG();
#endif
                                continue;
                        }

                        if (key.type == BTRFS_TREE_BLOCK_REF_KEY) {
                                ret = add_tree_backref(extent_cache,
                                                key.objectid, 0, key.offset, 0);
                                if (ret < 0)
                                        error(
                                "add_tree_backref failed (leaf tree block): %s",
                                              strerror(-ret));
                                continue;
                        }
                        if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
                                ret = add_tree_backref(extent_cache,
                                                key.objectid, key.offset, 0, 0);
                                if (ret < 0)
                                        error(
                                "add_tree_backref failed (leaf shared block): %s",
                                              strerror(-ret));
                                continue;
                        }
                        if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
                                struct btrfs_extent_data_ref *ref;
                                ref = btrfs_item_ptr(buf, i,
                                                struct btrfs_extent_data_ref);
                                add_data_backref(extent_cache,
                                        key.objectid, 0,
                                        btrfs_extent_data_ref_root(buf, ref),
                                        btrfs_extent_data_ref_objectid(buf,
                                                                       ref),
                                        btrfs_extent_data_ref_offset(buf, ref),
                                        btrfs_extent_data_ref_count(buf, ref),
                                        0, root->fs_info->sectorsize);
                                continue;
                        }
                        if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
                                struct btrfs_shared_data_ref *ref;
                                ref = btrfs_item_ptr(buf, i,
                                                struct btrfs_shared_data_ref);
                                add_data_backref(extent_cache,
                                        key.objectid, key.offset, 0, 0, 0,
                                        btrfs_shared_data_ref_count(buf, ref),
                                        0, root->fs_info->sectorsize);
                                continue;
                        }
                        if (key.type == BTRFS_ORPHAN_ITEM_KEY) {
                                struct bad_item *bad;

                                if (key.objectid == BTRFS_ORPHAN_OBJECTID)
                                        continue;
                                if (!owner)
                                        continue;
                                bad = malloc(sizeof(struct bad_item));
                                if (!bad)
                                        continue;
                                INIT_LIST_HEAD(&bad->list);
                                memcpy(&bad->key, &key,
                                       sizeof(struct btrfs_key));
                                bad->root_id = owner;
                                list_add_tail(&bad->list, &delete_items);
                                continue;
                        }
                        if (key.type != BTRFS_EXTENT_DATA_KEY)
                                continue;
                        fi = btrfs_item_ptr(buf, i,
                                            struct btrfs_file_extent_item);
                        if (btrfs_file_extent_type(buf, fi) ==
                            BTRFS_FILE_EXTENT_INLINE)
                                continue;
                        if (btrfs_file_extent_disk_bytenr(buf, fi) == 0)
                                continue;

                        data_bytes_allocated +=
                                btrfs_file_extent_disk_num_bytes(buf, fi);
                        if (data_bytes_allocated < root->fs_info->sectorsize) {
                                abort();
                        }
                        data_bytes_referenced +=
                                btrfs_file_extent_num_bytes(buf, fi);
                        add_data_backref(extent_cache,
                                btrfs_file_extent_disk_bytenr(buf, fi),
                                parent, owner, key.objectid, key.offset -
                                btrfs_file_extent_offset(buf, fi), 1, 1,
                                btrfs_file_extent_disk_num_bytes(buf, fi));
                }
        } else {
                int level;
                struct btrfs_key first_key;

                first_key.objectid = 0;

                if (nritems > 0)
                        btrfs_item_key_to_cpu(buf, &first_key, 0);
                level = btrfs_header_level(buf);
                for (i = 0; i < nritems; i++) {
                        struct extent_record tmpl;

                        ptr = btrfs_node_blockptr(buf, i);
                        size = root->fs_info->nodesize;
                        btrfs_node_key_to_cpu(buf, &key, i);
                        if (ri != NULL) {
                                if ((level == ri->drop_level)
                                    && is_dropped_key(&key, &ri->drop_key)) {
                                        continue;
                                }
                        }

                        memset(&tmpl, 0, sizeof(tmpl));
                        btrfs_cpu_key_to_disk(&tmpl.parent_key, &key);
                        tmpl.parent_generation = btrfs_node_ptr_generation(buf, i);
                        tmpl.start = ptr;
                        tmpl.nr = size;
                        tmpl.refs = 1;
                        tmpl.metadata = 1;
                        tmpl.max_size = size;
                        ret = add_extent_rec(extent_cache, &tmpl);
                        if (ret < 0)
                                goto out;

                        ret = add_tree_backref(extent_cache, ptr, parent,
                                        owner, 1);
                        if (ret < 0) {
                                error(
                                "add_tree_backref failed (non-leaf block): %s",
                                      strerror(-ret));
                                continue;
                        }

                        if (level > 1) {
                                add_pending(nodes, seen, ptr, size);
                        } else {
                                add_pending(pending, seen, ptr, size);
                        }
                }
                btree_space_waste += (BTRFS_NODEPTRS_PER_BLOCK(root) -
                                      nritems) * sizeof(struct btrfs_key_ptr);
        }
        total_btree_bytes += buf->len;
        if (fs_root_objectid(btrfs_header_owner(buf)))
                total_fs_tree_bytes += buf->len;
        if (btrfs_header_owner(buf) == BTRFS_EXTENT_TREE_OBJECTID)
                total_extent_tree_bytes += buf->len;
out:
        free_extent_buffer(buf);
        return ret;
}

static int add_root_to_pending(struct extent_buffer *buf,
                               struct cache_tree *extent_cache,
                               struct cache_tree *pending,
                               struct cache_tree *seen,
                               struct cache_tree *nodes,
                               u64 objectid)
{
        struct extent_record tmpl;
        int ret;

        if (btrfs_header_level(buf) > 0)
                add_pending(nodes, seen, buf->start, buf->len);
        else
                add_pending(pending, seen, buf->start, buf->len);

        memset(&tmpl, 0, sizeof(tmpl));
        tmpl.start = buf->start;
        tmpl.nr = buf->len;
        tmpl.is_root = 1;
        tmpl.refs = 1;
        tmpl.metadata = 1;
        tmpl.max_size = buf->len;
        add_extent_rec(extent_cache, &tmpl);

        if (objectid == BTRFS_TREE_RELOC_OBJECTID ||
            btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
                ret = add_tree_backref(extent_cache, buf->start, buf->start,
                                0, 1);
        else
                ret = add_tree_backref(extent_cache, buf->start, 0, objectid,
                                1);
        return ret;
}

/* as we fix the tree, we might be deleting blocks that
 * we're tracking for repair.  This hook makes sure we
 * remove any backrefs for blocks as we are fixing them.
 */
static int free_extent_hook(struct btrfs_trans_handle *trans,
                            struct btrfs_root *root,
                            u64 bytenr, u64 num_bytes, u64 parent,
                            u64 root_objectid, u64 owner, u64 offset,
                            int refs_to_drop)
{
        struct extent_record *rec;
        struct cache_extent *cache;
        int is_data;
        struct cache_tree *extent_cache = root->fs_info->fsck_extent_cache;

        is_data = owner >= BTRFS_FIRST_FREE_OBJECTID;
        cache = lookup_cache_extent(extent_cache, bytenr, num_bytes);
        if (!cache)
                return 0;

        rec = container_of(cache, struct extent_record, cache);
        if (is_data) {
                struct data_backref *back;
                back = find_data_backref(rec, parent, root_objectid, owner,
                                         offset, 1, bytenr, num_bytes);
                if (!back)
                        goto out;
                if (back->node.found_ref) {
                        back->found_ref -= refs_to_drop;
                        if (rec->refs)
                                rec->refs -= refs_to_drop;
                }
                if (back->node.found_extent_tree) {
                        back->num_refs -= refs_to_drop;
                        if (rec->extent_item_refs)
                                rec->extent_item_refs -= refs_to_drop;
                }
                if (back->found_ref == 0)
                        back->node.found_ref = 0;
                if (back->num_refs == 0)
                        back->node.found_extent_tree = 0;

                if (!back->node.found_extent_tree && back->node.found_ref) {
                        rb_erase(&back->node.node, &rec->backref_tree);
                        free(back);
                }
        } else {
                struct tree_backref *back;
                back = find_tree_backref(rec, parent, root_objectid);
                if (!back)
                        goto out;
                if (back->node.found_ref) {
                        if (rec->refs)
                                rec->refs--;
                        back->node.found_ref = 0;
                }
                if (back->node.found_extent_tree) {
                        if (rec->extent_item_refs)
                                rec->extent_item_refs--;
                        back->node.found_extent_tree = 0;
                }
                if (!back->node.found_extent_tree && back->node.found_ref) {
                        rb_erase(&back->node.node, &rec->backref_tree);
                        free(back);
                }
        }
        maybe_free_extent_rec(extent_cache, rec);
out:
        return 0;
}

static int delete_extent_records(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_path *path,
                                 u64 bytenr)
{
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct extent_buffer *leaf;
        int ret;
        int slot;


        key.objectid = bytenr;
        key.type = (u8)-1;
        key.offset = (u64)-1;

        while(1) {
                ret = btrfs_search_slot(trans, root->fs_info->extent_root,
                                        &key, path, 0, 1);
                if (ret < 0)
                        break;

                if (ret > 0) {
                        ret = 0;
                        if (path->slots[0] == 0)
                                break;
                        path->slots[0]--;
                }
                ret = 0;

                leaf = path->nodes[0];
                slot = path->slots[0];

                btrfs_item_key_to_cpu(leaf, &found_key, slot);
                if (found_key.objectid != bytenr)
                        break;

                if (found_key.type != BTRFS_EXTENT_ITEM_KEY &&
                    found_key.type != BTRFS_METADATA_ITEM_KEY &&
                    found_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
                    found_key.type != BTRFS_EXTENT_DATA_REF_KEY &&
                    found_key.type != BTRFS_EXTENT_REF_V0_KEY &&
                    found_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
                    found_key.type != BTRFS_SHARED_DATA_REF_KEY) {
                        btrfs_release_path(path);
                        if (found_key.type == 0) {
                                if (found_key.offset == 0)
                                        break;
                                key.offset = found_key.offset - 1;
                                key.type = found_key.type;
                        }
                        key.type = found_key.type - 1;
                        key.offset = (u64)-1;
                        continue;
                }

                fprintf(stderr, "repair deleting extent record: key %Lu %u %Lu\n",
                        found_key.objectid, found_key.type, found_key.offset);

                ret = btrfs_del_item(trans, root->fs_info->extent_root, path);
                if (ret)
                        break;
                btrfs_release_path(path);

                if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
                    found_key.type == BTRFS_METADATA_ITEM_KEY) {
                        u64 bytes = (found_key.type == BTRFS_EXTENT_ITEM_KEY) ?
                                found_key.offset : root->fs_info->nodesize;

                        ret = btrfs_update_block_group(trans, root, bytenr,
                                                       bytes, 0, 0);
                        if (ret)
                                break;
                }
        }

        btrfs_release_path(path);
        return ret;
}

/*
 * for a single backref, this will allocate a new extent
 * and add the backref to it.
 */
static int record_extent(struct btrfs_trans_handle *trans,
                         struct btrfs_fs_info *info,
                         struct btrfs_path *path,
                         struct extent_record *rec,
                         struct extent_backref *back,
                         int allocated, u64 flags)
{
        int ret = 0;
        struct btrfs_root *extent_root = info->extent_root;
        struct extent_buffer *leaf;
        struct btrfs_key ins_key;
        struct btrfs_extent_item *ei;
        struct data_backref *dback;
        struct btrfs_tree_block_info *bi;

        if (!back->is_data)
                rec->max_size = max_t(u64, rec->max_size,
                                    info->nodesize);

        if (!allocated) {
                u32 item_size = sizeof(*ei);

                if (!back->is_data)
                        item_size += sizeof(*bi);

                ins_key.objectid = rec->start;
                ins_key.offset = rec->max_size;
                ins_key.type = BTRFS_EXTENT_ITEM_KEY;

                ret = btrfs_insert_empty_item(trans, extent_root, path,
                                        &ins_key, item_size);
                if (ret)
                        goto fail;

                leaf = path->nodes[0];
                ei = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_extent_item);

                btrfs_set_extent_refs(leaf, ei, 0);
                btrfs_set_extent_generation(leaf, ei, rec->generation);

                if (back->is_data) {
                        btrfs_set_extent_flags(leaf, ei,
                                               BTRFS_EXTENT_FLAG_DATA);
                } else {
                        struct btrfs_disk_key copy_key;;

                        bi = (struct btrfs_tree_block_info *)(ei + 1);
                        memset_extent_buffer(leaf, 0, (unsigned long)bi,
                                             sizeof(*bi));

                        btrfs_set_disk_key_objectid(&copy_key,
                                                    rec->info_objectid);
                        btrfs_set_disk_key_type(&copy_key, 0);
                        btrfs_set_disk_key_offset(&copy_key, 0);

                        btrfs_set_tree_block_level(leaf, bi, rec->info_level);
                        btrfs_set_tree_block_key(leaf, bi, &copy_key);

                        btrfs_set_extent_flags(leaf, ei,
                                               BTRFS_EXTENT_FLAG_TREE_BLOCK | flags);
                }

                btrfs_mark_buffer_dirty(leaf);
                ret = btrfs_update_block_group(trans, extent_root, rec->start,
                                               rec->max_size, 1, 0);
                if (ret)
                        goto fail;
                btrfs_release_path(path);
        }

        if (back->is_data) {
                u64 parent;
                int i;

                dback = to_data_backref(back);
                if (back->full_backref)
                        parent = dback->parent;
                else
                        parent = 0;

                for (i = 0; i < dback->found_ref; i++) {
                        /* if parent != 0, we're doing a full backref
                         * passing BTRFS_FIRST_FREE_OBJECTID as the owner
                         * just makes the backref allocator create a data
                         * backref
                         */
                        ret = btrfs_inc_extent_ref(trans, info->extent_root,
                                                   rec->start, rec->max_size,
                                                   parent,
                                                   dback->root,
                                                   parent ?
                                                   BTRFS_FIRST_FREE_OBJECTID :
                                                   dback->owner,
                                                   dback->offset);
                        if (ret)
                                break;
                }
                fprintf(stderr, "adding new data backref"
                                " on %llu %s %llu owner %llu"
                                " offset %llu found %d\n",
                                (unsigned long long)rec->start,
                                back->full_backref ?
                                "parent" : "root",
                                back->full_backref ?
                                (unsigned long long)parent :
                                (unsigned long long)dback->root,
                                (unsigned long long)dback->owner,
                                (unsigned long long)dback->offset,
                                dback->found_ref);
        } else {
                u64 parent;
                struct tree_backref *tback;

                tback = to_tree_backref(back);
                if (back->full_backref)
                        parent = tback->parent;
                else
                        parent = 0;

                ret = btrfs_inc_extent_ref(trans, info->extent_root,
                                           rec->start, rec->max_size,
                                           parent, tback->root, 0, 0);
                fprintf(stderr, "adding new tree backref on "
                        "start %llu len %llu parent %llu root %llu\n",
                        rec->start, rec->max_size, parent, tback->root);
        }
fail:
        btrfs_release_path(path);
        return ret;
}

static struct extent_entry *find_entry(struct list_head *entries,
                                       u64 bytenr, u64 bytes)
{
        struct extent_entry *entry = NULL;

        list_for_each_entry(entry, entries, list) {
                if (entry->bytenr == bytenr && entry->bytes == bytes)
                        return entry;
        }

        return NULL;
}

static struct extent_entry *find_most_right_entry(struct list_head *entries)
{
        struct extent_entry *entry, *best = NULL, *prev = NULL;

        list_for_each_entry(entry, entries, list) {
                /*
                 * If there are as many broken entries as entries then we know
                 * not to trust this particular entry.
                 */
                if (entry->broken == entry->count)
                        continue;

                /*
                 * Special case, when there are only two entries and 'best' is
                 * the first one
                 */
                if (!prev) {
                        best = entry;
                        prev = entry;
                        continue;
                }

                /*
                 * If our current entry == best then we can't be sure our best
                 * is really the best, so we need to keep searching.
                 */
                if (best && best->count == entry->count) {
                        prev = entry;
                        best = NULL;
                        continue;
                }

                /* Prev == entry, not good enough, have to keep searching */
                if (!prev->broken && prev->count == entry->count)
                        continue;

                if (!best)
                        best = (prev->count > entry->count) ? prev : entry;
                else if (best->count < entry->count)
                        best = entry;
                prev = entry;
        }

        return best;
}

static int repair_ref(struct btrfs_fs_info *info, struct btrfs_path *path,
                      struct data_backref *dback, struct extent_entry *entry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root;
        struct btrfs_file_extent_item *fi;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        u64 bytenr, bytes;
        int ret, err;

        key.objectid = dback->root;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;
        root = btrfs_read_fs_root(info, &key);
        if (IS_ERR(root)) {
                fprintf(stderr, "Couldn't find root for our ref\n");
                return -EINVAL;
        }

        /*
         * The backref points to the original offset of the extent if it was
         * split, so we need to search down to the offset we have and then walk
         * forward until we find the backref we're looking for.
         */
        key.objectid = dback->owner;
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = dback->offset;
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0) {
                fprintf(stderr, "Error looking up ref %d\n", ret);
                return ret;
        }

        while (1) {
                if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret) {
                                fprintf(stderr, "Couldn't find our ref, next\n");
                                return -EINVAL;
                        }
                }
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                if (key.objectid != dback->owner ||
                    key.type != BTRFS_EXTENT_DATA_KEY) {
                        fprintf(stderr, "Couldn't find our ref, search\n");
                        return -EINVAL;
                }
                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);

                if (bytenr == dback->disk_bytenr && bytes == dback->bytes)
                        break;
                path->slots[0]++;
        }

        btrfs_release_path(path);

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        /*
         * Ok we have the key of the file extent we want to fix, now we can cow
         * down to the thing and fix it.
         */
        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
        if (ret < 0) {
                fprintf(stderr, "Error cowing down to ref [%Lu, %u, %Lu]: %d\n",
                        key.objectid, key.type, key.offset, ret);
                goto out;
        }
        if (ret > 0) {
                fprintf(stderr, "Well that's odd, we just found this key "
                        "[%Lu, %u, %Lu]\n", key.objectid, key.type,
                        key.offset);
                ret = -EINVAL;
                goto out;
        }
        leaf = path->nodes[0];
        fi = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);

        if (btrfs_file_extent_compression(leaf, fi) &&
            dback->disk_bytenr != entry->bytenr) {
                fprintf(stderr, "Ref doesn't match the record start and is "
                        "compressed, please take a btrfs-image of this file "
                        "system and send it to a btrfs developer so they can "
                        "complete this functionality for bytenr %Lu\n",
                        dback->disk_bytenr);
                ret = -EINVAL;
                goto out;
        }

        if (dback->node.broken && dback->disk_bytenr != entry->bytenr) {
                btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
        } else if (dback->disk_bytenr > entry->bytenr) {
                u64 off_diff, offset;

                off_diff = dback->disk_bytenr - entry->bytenr;
                offset = btrfs_file_extent_offset(leaf, fi);
                if (dback->disk_bytenr + offset +
                    btrfs_file_extent_num_bytes(leaf, fi) >
                    entry->bytenr + entry->bytes) {
                        fprintf(stderr, "Ref is past the entry end, please "
                                "take a btrfs-image of this file system and "
                                "send it to a btrfs developer, ref %Lu\n",
                                dback->disk_bytenr);
                        ret = -EINVAL;
                        goto out;
                }
                offset += off_diff;
                btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
                btrfs_set_file_extent_offset(leaf, fi, offset);
        } else if (dback->disk_bytenr < entry->bytenr) {
                u64 offset;

                offset = btrfs_file_extent_offset(leaf, fi);
                if (dback->disk_bytenr + offset < entry->bytenr) {
                        fprintf(stderr, "Ref is before the entry start, please"
                                " take a btrfs-image of this file system and "
                                "send it to a btrfs developer, ref %Lu\n",
                                dback->disk_bytenr);
                        ret = -EINVAL;
                        goto out;
                }

                offset += dback->disk_bytenr;
                offset -= entry->bytenr;
                btrfs_set_file_extent_disk_bytenr(leaf, fi, entry->bytenr);
                btrfs_set_file_extent_offset(leaf, fi, offset);
        }

        btrfs_set_file_extent_disk_num_bytes(leaf, fi, entry->bytes);

        /*
         * Chances are if disk_num_bytes were wrong then so is ram_bytes, but
         * only do this if we aren't using compression, otherwise it's a
         * trickier case.
         */
        if (!btrfs_file_extent_compression(leaf, fi))
                btrfs_set_file_extent_ram_bytes(leaf, fi, entry->bytes);
        else
                printf("ram bytes may be wrong?\n");
        btrfs_mark_buffer_dirty(leaf);
out:
        err = btrfs_commit_transaction(trans, root);
        btrfs_release_path(path);
        return ret ? ret : err;
}

static int verify_backrefs(struct btrfs_fs_info *info, struct btrfs_path *path,
                           struct extent_record *rec)
{
        struct extent_backref *back, *tmp;
        struct data_backref *dback;
        struct extent_entry *entry, *best = NULL;
        LIST_HEAD(entries);
        int nr_entries = 0;
        int broken_entries = 0;
        int ret = 0;
        short mismatch = 0;

        /*
         * Metadata is easy and the backrefs should always agree on bytenr and
         * size, if not we've got bigger issues.
         */
        if (rec->metadata)
                return 0;

        rbtree_postorder_for_each_entry_safe(back, tmp,
                                             &rec->backref_tree, node) {
                if (back->full_backref || !back->is_data)
                        continue;

                dback = to_data_backref(back);

                /*
                 * We only pay attention to backrefs that we found a real
                 * backref for.
                 */
                if (dback->found_ref == 0)
                        continue;

                /*
                 * For now we only catch when the bytes don't match, not the
                 * bytenr.  We can easily do this at the same time, but I want
                 * to have a fs image to test on before we just add repair
                 * functionality willy-nilly so we know we won't screw up the
                 * repair.
                 */

                entry = find_entry(&entries, dback->disk_bytenr,
                                   dback->bytes);
                if (!entry) {
                        entry = malloc(sizeof(struct extent_entry));
                        if (!entry) {
                                ret = -ENOMEM;
                                goto out;
                        }
                        memset(entry, 0, sizeof(*entry));
                        entry->bytenr = dback->disk_bytenr;
                        entry->bytes = dback->bytes;
                        list_add_tail(&entry->list, &entries);
                        nr_entries++;
                }

                /*
                 * If we only have on entry we may think the entries agree when
                 * in reality they don't so we have to do some extra checking.
                 */
                if (dback->disk_bytenr != rec->start ||
                    dback->bytes != rec->nr || back->broken)
                        mismatch = 1;

                if (back->broken) {
                        entry->broken++;
                        broken_entries++;
                }

                entry->count++;
        }

        /* Yay all the backrefs agree, carry on good sir */
        if (nr_entries <= 1 && !mismatch)
                goto out;

        fprintf(stderr, "attempting to repair backref discrepency for bytenr "
                "%Lu\n", rec->start);

        /*
         * First we want to see if the backrefs can agree amongst themselves who
         * is right, so figure out which one of the entries has the highest
         * count.
         */
        best = find_most_right_entry(&entries);

        /*
         * Ok so we may have an even split between what the backrefs think, so
         * this is where we use the extent ref to see what it thinks.
         */
        if (!best) {
                entry = find_entry(&entries, rec->start, rec->nr);
                if (!entry && (!broken_entries || !rec->found_rec)) {
                        fprintf(stderr, "Backrefs don't agree with each other "
                                "and extent record doesn't agree with anybody,"
                                " so we can't fix bytenr %Lu bytes %Lu\n",
                                rec->start, rec->nr);
                        ret = -EINVAL;
                        goto out;
                } else if (!entry) {
                        /*
                         * Ok our backrefs were broken, we'll assume this is the
                         * correct value and add an entry for this range.
                         */
                        entry = malloc(sizeof(struct extent_entry));
                        if (!entry) {
                                ret = -ENOMEM;
                                goto out;
                        }
                        memset(entry, 0, sizeof(*entry));
                        entry->bytenr = rec->start;
                        entry->bytes = rec->nr;
                        list_add_tail(&entry->list, &entries);
                        nr_entries++;
                }
                entry->count++;
                best = find_most_right_entry(&entries);
                if (!best) {
                        fprintf(stderr, "Backrefs and extent record evenly "
                                "split on who is right, this is going to "
                                "require user input to fix bytenr %Lu bytes "
                                "%Lu\n", rec->start, rec->nr);
                        ret = -EINVAL;
                        goto out;
                }
        }

        /*
         * I don't think this can happen currently as we'll abort() if we catch
         * this case higher up, but in case somebody removes that we still can't
         * deal with it properly here yet, so just bail out of that's the case.
         */
        if (best->bytenr != rec->start) {
                fprintf(stderr, "Extent start and backref starts don't match, "
                        "please use btrfs-image on this file system and send "
                        "it to a btrfs developer so they can make fsck fix "
                        "this particular case.  bytenr is %Lu, bytes is %Lu\n",
                        rec->start, rec->nr);
                ret = -EINVAL;
                goto out;
        }

        /*
         * Ok great we all agreed on an extent record, let's go find the real
         * references and fix up the ones that don't match.
         */
        rbtree_postorder_for_each_entry_safe(back, tmp,
                                             &rec->backref_tree, node) {
                if (back->full_backref || !back->is_data)
                        continue;

                dback = to_data_backref(back);

                /*
                 * Still ignoring backrefs that don't have a real ref attached
                 * to them.
                 */
                if (dback->found_ref == 0)
                        continue;

                if (dback->bytes == best->bytes &&
                    dback->disk_bytenr == best->bytenr)
                        continue;

                ret = repair_ref(info, path, dback, best);
                if (ret)
                        goto out;
        }

        /*
         * Ok we messed with the actual refs, which means we need to drop our
         * entire cache and go back and rescan.  I know this is a huge pain and
         * adds a lot of extra work, but it's the only way to be safe.  Once all
         * the backrefs agree we may not need to do anything to the extent
         * record itself.
         */
        ret = -EAGAIN;
out:
        while (!list_empty(&entries)) {
                entry = list_entry(entries.next, struct extent_entry, list);
                list_del_init(&entry->list);
                free(entry);
        }
        return ret;
}

static int process_duplicates(struct cache_tree *extent_cache,
                              struct extent_record *rec)
{
        struct extent_record *good, *tmp;
        struct cache_extent *cache;
        int ret;

        /*
         * If we found a extent record for this extent then return, or if we
         * have more than one duplicate we are likely going to need to delete
         * something.
         */
        if (rec->found_rec || rec->num_duplicates > 1)
                return 0;

        /* Shouldn't happen but just in case */
        BUG_ON(!rec->num_duplicates);

        /*
         * So this happens if we end up with a backref that doesn't match the
         * actual extent entry.  So either the backref is bad or the extent
         * entry is bad.  Either way we want to have the extent_record actually
         * reflect what we found in the extent_tree, so we need to take the
         * duplicate out and use that as the extent_record since the only way we
         * get a duplicate is if we find a real life BTRFS_EXTENT_ITEM_KEY.
         */
        remove_cache_extent(extent_cache, &rec->cache);

        good = to_extent_record(rec->dups.next);
        list_del_init(&good->list);
        INIT_LIST_HEAD(&good->backrefs);
        INIT_LIST_HEAD(&good->dups);
        good->cache.start = good->start;
        good->cache.size = good->nr;
        good->content_checked = 0;
        good->owner_ref_checked = 0;
        good->num_duplicates = 0;
        good->refs = rec->refs;
        list_splice_init(&rec->backrefs, &good->backrefs);
        while (1) {
                cache = lookup_cache_extent(extent_cache, good->start,
                                            good->nr);
                if (!cache)
                        break;
                tmp = container_of(cache, struct extent_record, cache);

                /*
                 * If we find another overlapping extent and it's found_rec is
                 * set then it's a duplicate and we need to try and delete
                 * something.
                 */
                if (tmp->found_rec || tmp->num_duplicates > 0) {
                        if (list_empty(&good->list))
                                list_add_tail(&good->list,
                                              &duplicate_extents);
                        good->num_duplicates += tmp->num_duplicates + 1;
                        list_splice_init(&tmp->dups, &good->dups);
                        list_del_init(&tmp->list);
                        list_add_tail(&tmp->list, &good->dups);
                        remove_cache_extent(extent_cache, &tmp->cache);
                        continue;
                }

                /*
                 * Ok we have another non extent item backed extent rec, so lets
                 * just add it to this extent and carry on like we did above.
                 */
                good->refs += tmp->refs;
                list_splice_init(&tmp->backrefs, &good->backrefs);
                remove_cache_extent(extent_cache, &tmp->cache);
                free(tmp);
        }
        ret = insert_cache_extent(extent_cache, &good->cache);
        BUG_ON(ret);
        free(rec);
        return good->num_duplicates ? 0 : 1;
}

static int delete_duplicate_records(struct btrfs_root *root,
                                    struct extent_record *rec)
{
        struct btrfs_trans_handle *trans;
        LIST_HEAD(delete_list);
        struct btrfs_path path;
        struct extent_record *tmp, *good, *n;
        int nr_del = 0;
        int ret = 0, err;
        struct btrfs_key key;

        btrfs_init_path(&path);

        good = rec;
        /* Find the record that covers all of the duplicates. */
        list_for_each_entry(tmp, &rec->dups, list) {
                if (good->start < tmp->start)
                        continue;
                if (good->nr > tmp->nr)
                        continue;

                if (tmp->start + tmp->nr < good->start + good->nr) {
                        fprintf(stderr, "Ok we have overlapping extents that "
                                "aren't completely covered by each other, this "
                                "is going to require more careful thought.  "
                                "The extents are [%Lu-%Lu] and [%Lu-%Lu]\n",
                                tmp->start, tmp->nr, good->start, good->nr);
                        abort();
                }
                good = tmp;
        }

        if (good != rec)
                list_add_tail(&rec->list, &delete_list);

        list_for_each_entry_safe(tmp, n, &rec->dups, list) {
                if (tmp == good)
                        continue;
                list_move_tail(&tmp->list, &delete_list);
        }

        root = root->fs_info->extent_root;
        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out;
        }

        list_for_each_entry(tmp, &delete_list, list) {
                if (tmp->found_rec == 0)
                        continue;
                key.objectid = tmp->start;
                key.type = BTRFS_EXTENT_ITEM_KEY;
                key.offset = tmp->nr;

                /* Shouldn't happen but just in case */
                if (tmp->metadata) {
                        fprintf(stderr, "Well this shouldn't happen, extent "
                                "record overlaps but is metadata? "
                                "[%Lu, %Lu]\n", tmp->start, tmp->nr);
                        abort();
                }

                ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
                if (ret) {
                        if (ret > 0)
                                ret = -EINVAL;
                        break;
                }
                ret = btrfs_del_item(trans, root, &path);
                if (ret)
                        break;
                btrfs_release_path(&path);
                nr_del++;
        }
        err = btrfs_commit_transaction(trans, root);
        if (err && !ret)
                ret = err;
out:
        while (!list_empty(&delete_list)) {
                tmp = to_extent_record(delete_list.next);
                list_del_init(&tmp->list);
                if (tmp == rec)
                        continue;
                free(tmp);
        }

        while (!list_empty(&rec->dups)) {
                tmp = to_extent_record(rec->dups.next);
                list_del_init(&tmp->list);
                free(tmp);
        }

        btrfs_release_path(&path);

        if (!ret && !nr_del)
                rec->num_duplicates = 0;

        return ret ? ret : nr_del;
}

static int find_possible_backrefs(struct btrfs_fs_info *info,
                                  struct btrfs_path *path,
                                  struct cache_tree *extent_cache,
                                  struct extent_record *rec)
{
        struct btrfs_root *root;
        struct extent_backref *back, *tmp;
        struct data_backref *dback;
        struct cache_extent *cache;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        u64 bytenr, bytes;
        int ret;

        rbtree_postorder_for_each_entry_safe(back, tmp,
                                             &rec->backref_tree, node) {
                /* Don't care about full backrefs (poor unloved backrefs) */
                if (back->full_backref || !back->is_data)
                        continue;

                dback = to_data_backref(back);

                /* We found this one, we don't need to do a lookup */
                if (dback->found_ref)
                        continue;

                key.objectid = dback->root;
                key.type = BTRFS_ROOT_ITEM_KEY;
                key.offset = (u64)-1;

                root = btrfs_read_fs_root(info, &key);

                /* No root, definitely a bad ref, skip */
                if (IS_ERR(root) && PTR_ERR(root) == -ENOENT)
                        continue;
                /* Other err, exit */
                if (IS_ERR(root))
                        return PTR_ERR(root);

                key.objectid = dback->owner;
                key.type = BTRFS_EXTENT_DATA_KEY;
                key.offset = dback->offset;
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret) {
                        btrfs_release_path(path);
                        if (ret < 0)
                                return ret;
                        /* Didn't find it, we can carry on */
                        ret = 0;
                        continue;
                }

                fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                    struct btrfs_file_extent_item);
                bytenr = btrfs_file_extent_disk_bytenr(path->nodes[0], fi);
                bytes = btrfs_file_extent_disk_num_bytes(path->nodes[0], fi);
                btrfs_release_path(path);
                cache = lookup_cache_extent(extent_cache, bytenr, 1);
                if (cache) {
                        struct extent_record *tmp;
                        tmp = container_of(cache, struct extent_record, cache);

                        /*
                         * If we found an extent record for the bytenr for this
                         * particular backref then we can't add it to our
                         * current extent record.  We only want to add backrefs
                         * that don't have a corresponding extent item in the
                         * extent tree since they likely belong to this record
                         * and we need to fix it if it doesn't match bytenrs.
                         */
                        if  (tmp->found_rec)
                                continue;
                }

                dback->found_ref += 1;
                dback->disk_bytenr = bytenr;
                dback->bytes = bytes;

                /*
                 * Set this so the verify backref code knows not to trust the
                 * values in this backref.
                 */
                back->broken = 1;
        }

        return 0;
}

/*
 * Record orphan data ref into corresponding root.
 *
 * Return 0 if the extent item contains data ref and recorded.
 * Return 1 if the extent item contains no useful data ref
 *   On that case, it may contains only shared_dataref or metadata backref
 *   or the file extent exists(this should be handled by the extent bytenr
 *   recovery routine)
 * Return <0 if something goes wrong.
 */
static int record_orphan_data_extents(struct btrfs_fs_info *fs_info,
                                      struct extent_record *rec)
{
        struct btrfs_key key;
        struct btrfs_root *dest_root;
        struct extent_backref *back, *tmp;
        struct data_backref *dback;
        struct orphan_data_extent *orphan;
        struct btrfs_path path;
        int recorded_data_ref = 0;
        int ret = 0;

        if (rec->metadata)
                return 1;
        btrfs_init_path(&path);
        rbtree_postorder_for_each_entry_safe(back, tmp,
                                             &rec->backref_tree, node) {
                if (back->full_backref || !back->is_data ||
                    !back->found_extent_tree)
                        continue;
                dback = to_data_backref(back);
                if (dback->found_ref)
                        continue;
                key.objectid = dback->root;
                key.type = BTRFS_ROOT_ITEM_KEY;
                key.offset = (u64)-1;

                dest_root = btrfs_read_fs_root(fs_info, &key);

                /* For non-exist root we just skip it */
                if (IS_ERR(dest_root) || !dest_root)
                        continue;

                key.objectid = dback->owner;
                key.type = BTRFS_EXTENT_DATA_KEY;
                key.offset = dback->offset;

                ret = btrfs_search_slot(NULL, dest_root, &key, &path, 0, 0);
                btrfs_release_path(&path);
                /*
                 * For ret < 0, it's OK since the fs-tree may be corrupted,
                 * we need to record it for inode/file extent rebuild.
                 * For ret > 0, we record it only for file extent rebuild.
                 * For ret == 0, the file extent exists but only bytenr
                 * mismatch, let the original bytenr fix routine to handle,
                 * don't record it.
                 */
                if (ret == 0)
                        continue;
                ret = 0;
                orphan = malloc(sizeof(*orphan));
                if (!orphan) {
                        ret = -ENOMEM;
                        goto out;
                }
                INIT_LIST_HEAD(&orphan->list);
                orphan->root = dback->root;
                orphan->objectid = dback->owner;
                orphan->offset = dback->offset;
                orphan->disk_bytenr = rec->cache.start;
                orphan->disk_len = rec->cache.size;
                list_add(&dest_root->orphan_data_extents, &orphan->list);
                recorded_data_ref = 1;
        }
out:
        btrfs_release_path(&path);
        if (!ret)
                return !recorded_data_ref;
        else
                return ret;
}

/*
 * when an incorrect extent item is found, this will delete
 * all of the existing entries for it and recreate them
 * based on what the tree scan found.
 */
static int fixup_extent_refs(struct btrfs_fs_info *info,
                             struct cache_tree *extent_cache,
                             struct extent_record *rec)
{
        struct btrfs_trans_handle *trans = NULL;
        int ret;
        struct btrfs_path path;
        struct cache_extent *cache;
        struct extent_backref *back, *tmp;
        int allocated = 0;
        u64 flags = 0;

        if (rec->flag_block_full_backref)
                flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;

        btrfs_init_path(&path);
        if (rec->refs != rec->extent_item_refs && !rec->metadata) {
                /*
                 * Sometimes the backrefs themselves are so broken they don't
                 * get attached to any meaningful rec, so first go back and
                 * check any of our backrefs that we couldn't find and throw
                 * them into the list if we find the backref so that
                 * verify_backrefs can figure out what to do.
                 */
                ret = find_possible_backrefs(info, &path, extent_cache, rec);
                if (ret < 0)
                        goto out;
        }

        /* step one, make sure all of the backrefs agree */
        ret = verify_backrefs(info, &path, rec);
        if (ret < 0)
                goto out;

        trans = btrfs_start_transaction(info->extent_root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out;
        }

        /* step two, delete all the existing records */
        ret = delete_extent_records(trans, info->extent_root, &path,
                                    rec->start);

        if (ret < 0)
                goto out;

        /* was this block corrupt?  If so, don't add references to it */
        cache = lookup_cache_extent(info->corrupt_blocks,
                                    rec->start, rec->max_size);
        if (cache) {
                ret = 0;
                goto out;
        }

        /* step three, recreate all the refs we did find */
        rbtree_postorder_for_each_entry_safe(back, tmp,
                                             &rec->backref_tree, node) {
                /*
                 * if we didn't find any references, don't create a
                 * new extent record
                 */
                if (!back->found_ref)
                        continue;

                rec->bad_full_backref = 0;
                ret = record_extent(trans, info, &path, rec, back, allocated, flags);
                allocated = 1;

                if (ret)
                        goto out;
        }
out:
        if (trans) {
                int err = btrfs_commit_transaction(trans, info->extent_root);
                if (!ret)
                        ret = err;
        }

        if (!ret)
                fprintf(stderr, "Repaired extent references for %llu\n",
                                (unsigned long long)rec->start);

        btrfs_release_path(&path);
        return ret;
}

static int fixup_extent_flags(struct btrfs_fs_info *fs_info,
                              struct extent_record *rec)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = fs_info->extent_root;
        struct btrfs_path path;
        struct btrfs_extent_item *ei;
        struct btrfs_key key;
        u64 flags;
        int ret = 0;

        key.objectid = rec->start;
        if (rec->metadata) {
                key.type = BTRFS_METADATA_ITEM_KEY;
                key.offset = rec->info_level;
        } else {
                key.type = BTRFS_EXTENT_ITEM_KEY;
                key.offset = rec->max_size;
        }

        trans = btrfs_start_transaction(root, 0);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_init_path(&path);
        ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
        if (ret < 0) {
                btrfs_release_path(&path);
                btrfs_commit_transaction(trans, root);
                return ret;
        } else if (ret) {
                fprintf(stderr, "Didn't find extent for %llu\n",
                        (unsigned long long)rec->start);
                btrfs_release_path(&path);
                btrfs_commit_transaction(trans, root);
                return -ENOENT;
        }

        ei = btrfs_item_ptr(path.nodes[0], path.slots[0],
                            struct btrfs_extent_item);
        flags = btrfs_extent_flags(path.nodes[0], ei);
        if (rec->flag_block_full_backref) {
                fprintf(stderr, "setting full backref on %llu\n",
                        (unsigned long long)key.objectid);
                flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
        } else {
                fprintf(stderr, "clearing full backref on %llu\n",
                        (unsigned long long)key.objectid);
                flags &= ~BTRFS_BLOCK_FLAG_FULL_BACKREF;
        }
        btrfs_set_extent_flags(path.nodes[0], ei, flags);
        btrfs_mark_buffer_dirty(path.nodes[0]);
        btrfs_release_path(&path);
        ret = btrfs_commit_transaction(trans, root);
        if (!ret)
                fprintf(stderr, "Repaired extent flags for %llu\n",
                                (unsigned long long)rec->start);

        return ret;
}

/* right now we only prune from the extent allocation tree */
static int prune_one_block(struct btrfs_trans_handle *trans,
                           struct btrfs_fs_info *info,
                           struct btrfs_corrupt_block *corrupt)
{
        int ret;
        struct btrfs_path path;
        struct extent_buffer *eb;
        u64 found;
        int slot;
        int nritems;
        int level = corrupt->level + 1;

        btrfs_init_path(&path);
again:
        /* we want to stop at the parent to our busted block */
        path.lowest_level = level;

        ret = btrfs_search_slot(trans, info->extent_root,
                                &corrupt->key, &path, -1, 1);

        if (ret < 0)
                goto out;

        eb = path.nodes[level];
        if (!eb) {
                ret = -ENOENT;
                goto out;
        }

        /*
         * hopefully the search gave us the block we want to prune,
         * lets try that first
         */
        slot = path.slots[level];
        found =  btrfs_node_blockptr(eb, slot);
        if (found == corrupt->cache.start)
                goto del_ptr;

        nritems = btrfs_header_nritems(eb);

        /* the search failed, lets scan this node and hope we find it */
        for (slot = 0; slot < nritems; slot++) {
                found =  btrfs_node_blockptr(eb, slot);
                if (found == corrupt->cache.start)
                        goto del_ptr;
        }
        /*
         * we couldn't find the bad block.  TODO, search all the nodes for pointers
         * to this block
         */
        if (eb == info->extent_root->node) {
                ret = -ENOENT;
                goto out;
        } else {
                level++;
                btrfs_release_path(&path);
                goto again;
        }

del_ptr:
        printk("deleting pointer to block %Lu\n", corrupt->cache.start);
        ret = btrfs_del_ptr(info->extent_root, &path, level, slot);

out:
        btrfs_release_path(&path);
        return ret;
}

static int prune_corrupt_blocks(struct btrfs_fs_info *info)
{
        struct btrfs_trans_handle *trans = NULL;
        struct cache_extent *cache;
        struct btrfs_corrupt_block *corrupt;

        while (1) {
                cache = search_cache_extent(info->corrupt_blocks, 0);
                if (!cache)
                        break;
                if (!trans) {
                        trans = btrfs_start_transaction(info->extent_root, 1);
                        if (IS_ERR(trans))
                                return PTR_ERR(trans);
                }
                corrupt = container_of(cache, struct btrfs_corrupt_block, cache);
                prune_one_block(trans, info, corrupt);
                remove_cache_extent(info->corrupt_blocks, cache);
        }
        if (trans)
                return btrfs_commit_transaction(trans, info->extent_root);
        return 0;
}

static void reset_cached_block_groups(struct btrfs_fs_info *fs_info)
{
        struct btrfs_block_group_cache *cache;
        u64 start, end;
        int ret;

        while (1) {
                ret = find_first_extent_bit(&fs_info->free_space_cache, 0,
                                            &start, &end, EXTENT_DIRTY);
                if (ret)
                        break;
                clear_extent_dirty(&fs_info->free_space_cache, start, end);
        }

        start = 0;
        while (1) {
                cache = btrfs_lookup_first_block_group(fs_info, start);
                if (!cache)
                        break;
                if (cache->cached)
                        cache->cached = 0;
                start = cache->key.objectid + cache->key.offset;
        }
}

static int check_extent_refs(struct btrfs_root *root,
                             struct cache_tree *extent_cache)
{
        struct extent_record *rec;
        struct cache_extent *cache;
        int ret = 0;
        int had_dups = 0;

        if (repair) {
                /*
                 * if we're doing a repair, we have to make sure
                 * we don't allocate from the problem extents.
                 * In the worst case, this will be all the
                 * extents in the FS
                 */
                cache = search_cache_extent(extent_cache, 0);
                while(cache) {
                        rec = container_of(cache, struct extent_record, cache);
                        set_extent_dirty(root->fs_info->excluded_extents,
                                         rec->start,
                                         rec->start + rec->max_size - 1);
                        cache = next_cache_extent(cache);
                }

                /* pin down all the corrupted blocks too */
                cache = search_cache_extent(root->fs_info->corrupt_blocks, 0);
                while(cache) {
                        set_extent_dirty(root->fs_info->excluded_extents,
                                         cache->start,
                                         cache->start + cache->size - 1);
                        cache = next_cache_extent(cache);
                }
                prune_corrupt_blocks(root->fs_info);
                reset_cached_block_groups(root->fs_info);
        }

        reset_cached_block_groups(root->fs_info);

        /*
         * We need to delete any duplicate entries we find first otherwise we
         * could mess up the extent tree when we have backrefs that actually
         * belong to a different extent item and not the weird duplicate one.
         */
        while (repair && !list_empty(&duplicate_extents)) {
                rec = to_extent_record(duplicate_extents.next);
                list_del_init(&rec->list);

                /* Sometimes we can find a backref before we find an actual
                 * extent, so we need to process it a little bit to see if there
                 * truly are multiple EXTENT_ITEM_KEY's for the same range, or
                 * if this is a backref screwup.  If we need to delete stuff
                 * process_duplicates() will return 0, otherwise it will return
                 * 1 and we
                 */
                if (process_duplicates(extent_cache, rec))
                        continue;
                ret = delete_duplicate_records(root, rec);
                if (ret < 0)
                        return ret;
                /*
                 * delete_duplicate_records will return the number of entries
                 * deleted, so if it's greater than 0 then we know we actually
                 * did something and we need to remove.
                 */
                if (ret)
                        had_dups = 1;
        }

        if (had_dups)
                return -EAGAIN;

        while(1) {
                int cur_err = 0;
                int fix = 0;

                cache = search_cache_extent(extent_cache, 0);
                if (!cache)
                        break;
                rec = container_of(cache, struct extent_record, cache);
                if (rec->num_duplicates) {
                        fprintf(stderr, "extent item %llu has multiple extent "
                                "items\n", (unsigned long long)rec->start);
                        cur_err = 1;
                }

                if (rec->refs != rec->extent_item_refs) {
                        fprintf(stderr, "ref mismatch on [%llu %llu] ",
                                (unsigned long long)rec->start,
                                (unsigned long long)rec->nr);
                        fprintf(stderr, "extent item %llu, found %llu\n",
                                (unsigned long long)rec->extent_item_refs,
                                (unsigned long long)rec->refs);
                        ret = record_orphan_data_extents(root->fs_info, rec);
                        if (ret < 0)
                                goto repair_abort;
                        fix = ret;
                        cur_err = 1;
                }
                if (all_backpointers_checked(rec, 1)) {
                        fprintf(stderr, "backpointer mismatch on [%llu %llu]\n",
                                (unsigned long long)rec->start,
                                (unsigned long long)rec->nr);
                        fix = 1;
                        cur_err = 1;
                }
                if (!rec->owner_ref_checked) {
                        fprintf(stderr, "owner ref check failed [%llu %llu]\n",
                                (unsigned long long)rec->start,
                                (unsigned long long)rec->nr);
                        fix = 1;
                        cur_err = 1;
                }

                if (repair && fix) {
                        ret = fixup_extent_refs(root->fs_info, extent_cache, rec);
                        if (ret)
                                goto repair_abort;
                }


                if (rec->bad_full_backref) {
                        fprintf(stderr, "bad full backref, on [%llu]\n",
                                (unsigned long long)rec->start);
                        if (repair) {
                                ret = fixup_extent_flags(root->fs_info, rec);
                                if (ret)
                                        goto repair_abort;
                                fix = 1;
                        }
                        cur_err = 1;
                }
                /*
                 * Although it's not a extent ref's problem, we reuse this
                 * routine for error reporting.
                 * No repair function yet.
                 */
                if (rec->crossing_stripes) {
                        fprintf(stderr,
                                "bad metadata [%llu, %llu) crossing stripe boundary\n",
                                rec->start, rec->start + rec->max_size);
                        cur_err = 1;
                }

                if (rec->wrong_chunk_type) {
                        fprintf(stderr,
                                "bad extent [%llu, %llu), type mismatch with chunk\n",
                                rec->start, rec->start + rec->max_size);
                        cur_err = 1;
                }

                remove_cache_extent(extent_cache, cache);
                free_all_extent_backrefs(rec);
                if (!init_extent_tree && repair && (!cur_err || fix))
                        clear_extent_dirty(root->fs_info->excluded_extents,
                                           rec->start,
                                           rec->start + rec->max_size - 1);
                free(rec);
        }
repair_abort:
        if (repair) {
                if (ret && ret != -EAGAIN) {
                        fprintf(stderr, "failed to repair damaged filesystem, aborting\n");
                        exit(1);
                } else if (!ret) {
                        struct btrfs_trans_handle *trans;

                        root = root->fs_info->extent_root;
                        trans = btrfs_start_transaction(root, 1);
                        if (IS_ERR(trans)) {
                                ret = PTR_ERR(trans);
                                goto repair_abort;
                        }

                        ret = btrfs_fix_block_accounting(trans, root);
                        if (ret)
                                goto repair_abort;
                        ret = btrfs_commit_transaction(trans, root);
                        if (ret)
                                goto repair_abort;
                }
                return ret;
        }
        return 0;
}

u64 calc_stripe_length(u64 type, u64 length, int num_stripes)
{
        u64 stripe_size;

        if (type & BTRFS_BLOCK_GROUP_RAID0) {
                stripe_size = length;
                stripe_size /= num_stripes;
        } else if (type & BTRFS_BLOCK_GROUP_RAID10) {
                stripe_size = length * 2;
                stripe_size /= num_stripes;
        } else if (type & BTRFS_BLOCK_GROUP_RAID5) {
                stripe_size = length;
                stripe_size /= (num_stripes - 1);
        } else if (type & BTRFS_BLOCK_GROUP_RAID6) {
                stripe_size = length;
                stripe_size /= (num_stripes - 2);
        } else {
                stripe_size = length;
        }
        return stripe_size;
}

/*
 * Check the chunk with its block group/dev list ref:
 * Return 0 if all refs seems valid.
 * Return 1 if part of refs seems valid, need later check for rebuild ref
 * like missing block group and needs to search extent tree to rebuild them.
 * Return -1 if essential refs are missing and unable to rebuild.
 */
static int check_chunk_refs(struct chunk_record *chunk_rec,
                            struct block_group_tree *block_group_cache,
                            struct device_extent_tree *dev_extent_cache,
                            int silent)
{
        struct cache_extent *block_group_item;
        struct block_group_record *block_group_rec;
        struct cache_extent *dev_extent_item;
        struct device_extent_record *dev_extent_rec;
        u64 devid;
        u64 offset;
        u64 length;
        int metadump_v2 = 0;
        int i;
        int ret = 0;

        block_group_item = lookup_cache_extent(&block_group_cache->tree,
                                               chunk_rec->offset,
                                               chunk_rec->length);
        if (block_group_item) {
                block_group_rec = container_of(block_group_item,
                                               struct block_group_record,
                                               cache);
                if (chunk_rec->length != block_group_rec->offset ||
                    chunk_rec->offset != block_group_rec->objectid ||
                    (!metadump_v2 &&
                     chunk_rec->type_flags != block_group_rec->flags)) {
                        if (!silent)
                                fprintf(stderr,
                                        "Chunk[%llu, %u, %llu]: length(%llu), offset(%llu), type(%llu) mismatch with block group[%llu, %u, %llu]: offset(%llu), objectid(%llu), flags(%llu)\n",
                                        chunk_rec->objectid,
                                        chunk_rec->type,
                                        chunk_rec->offset,
                                        chunk_rec->length,
                                        chunk_rec->offset,
                                        chunk_rec->type_flags,
                                        block_group_rec->objectid,
                                        block_group_rec->type,
                                        block_group_rec->offset,
                                        block_group_rec->offset,
                                        block_group_rec->objectid,
                                        block_group_rec->flags);
                        ret = -1;
                } else {
                        list_del_init(&block_group_rec->list);
                        chunk_rec->bg_rec = block_group_rec;
                }
        } else {
                if (!silent)
                        fprintf(stderr,
                                "Chunk[%llu, %u, %llu]: length(%llu), offset(%llu), type(%llu) is not found in block group\n",
                                chunk_rec->objectid,
                                chunk_rec->type,
                                chunk_rec->offset,
                                chunk_rec->length,
                                chunk_rec->offset,
                                chunk_rec->type_flags);
                ret = 1;
        }

        if (metadump_v2)
                return ret;

        length = calc_stripe_length(chunk_rec->type_flags, chunk_rec->length,
                                    chunk_rec->num_stripes);
        for (i = 0; i < chunk_rec->num_stripes; ++i) {
                devid = chunk_rec->stripes[i].devid;
                offset = chunk_rec->stripes[i].offset;
                dev_extent_item = lookup_cache_extent2(&dev_extent_cache->tree,
                                                       devid, offset, length);
                if (dev_extent_item) {
                        dev_extent_rec = container_of(dev_extent_item,
                                                struct device_extent_record,
                                                cache);
                        if (dev_extent_rec->objectid != devid ||
                            dev_extent_rec->offset != offset ||
                            dev_extent_rec->chunk_offset != chunk_rec->offset ||
                            dev_extent_rec->length != length) {
                                if (!silent)
                                        fprintf(stderr,
                                                "Chunk[%llu, %u, %llu] stripe[%llu, %llu] dismatch dev extent[%llu, %llu, %llu]\n",
                                                chunk_rec->objectid,
                                                chunk_rec->type,
                                                chunk_rec->offset,
                                                chunk_rec->stripes[i].devid,
                                                chunk_rec->stripes[i].offset,
                                                dev_extent_rec->objectid,
                                                dev_extent_rec->offset,
                                                dev_extent_rec->length);
                                ret = -1;
                        } else {
                                list_move(&dev_extent_rec->chunk_list,
                                          &chunk_rec->dextents);
                        }
                } else {
                        if (!silent)
                                fprintf(stderr,
                                        "Chunk[%llu, %u, %llu] stripe[%llu, %llu] is not found in dev extent\n",
                                        chunk_rec->objectid,
                                        chunk_rec->type,
                                        chunk_rec->offset,
                                        chunk_rec->stripes[i].devid,
                                        chunk_rec->stripes[i].offset);
                        ret = -1;
                }
        }
        return ret;
}

/* check btrfs_chunk -> btrfs_dev_extent / btrfs_block_group_item */
int check_chunks(struct cache_tree *chunk_cache,
                 struct block_group_tree *block_group_cache,
                 struct device_extent_tree *dev_extent_cache,
                 struct list_head *good, struct list_head *bad,
                 struct list_head *rebuild, int silent)
{
        struct cache_extent *chunk_item;
        struct chunk_record *chunk_rec;
        struct block_group_record *bg_rec;
        struct device_extent_record *dext_rec;
        int err;
        int ret = 0;

        chunk_item = first_cache_extent(chunk_cache);
        while (chunk_item) {
                chunk_rec = container_of(chunk_item, struct chunk_record,
                                         cache);
                err = check_chunk_refs(chunk_rec, block_group_cache,
                                       dev_extent_cache, silent);
                if (err < 0)
                        ret = err;
                if (err == 0 && good)
                        list_add_tail(&chunk_rec->list, good);
                if (err > 0 && rebuild)
                        list_add_tail(&chunk_rec->list, rebuild);
                if (err < 0 && bad)
                        list_add_tail(&chunk_rec->list, bad);
                chunk_item = next_cache_extent(chunk_item);
        }

        list_for_each_entry(bg_rec, &block_group_cache->block_groups, list) {
                if (!silent)
                        fprintf(stderr,
                                "Block group[%llu, %llu] (flags = %llu) didn't find the relative chunk.\n",
                                bg_rec->objectid,
                                bg_rec->offset,
                                bg_rec->flags);
                if (!ret)
                        ret = 1;
        }

        list_for_each_entry(dext_rec, &dev_extent_cache->no_chunk_orphans,
                            chunk_list) {
                if (!silent)
                        fprintf(stderr,
                                "Device extent[%llu, %llu, %llu] didn't find the relative chunk.\n",
                                dext_rec->objectid,
                                dext_rec->offset,
                                dext_rec->length);
                if (!ret)
                        ret = 1;
        }
        return ret;
}


static int check_device_used(struct device_record *dev_rec,
                             struct device_extent_tree *dext_cache)
{
        struct cache_extent *cache;
        struct device_extent_record *dev_extent_rec;
        u64 total_byte = 0;

        cache = search_cache_extent2(&dext_cache->tree, dev_rec->devid, 0);
        while (cache) {
                dev_extent_rec = container_of(cache,
                                              struct device_extent_record,
                                              cache);
                if (dev_extent_rec->objectid != dev_rec->devid)
                        break;

                list_del_init(&dev_extent_rec->device_list);
                total_byte += dev_extent_rec->length;
                cache = next_cache_extent(cache);
        }

        if (total_byte != dev_rec->byte_used) {
                fprintf(stderr,
                        "Dev extent's total-byte(%llu) is not equal to byte-used(%llu) in dev[%llu, %u, %llu]\n",
                        total_byte, dev_rec->byte_used, dev_rec->objectid,
                        dev_rec->type, dev_rec->offset);
                return -1;
        } else {
                return 0;
        }
}

/* check btrfs_dev_item -> btrfs_dev_extent */
static int check_devices(struct rb_root *dev_cache,
                         struct device_extent_tree *dev_extent_cache)
{
        struct rb_node *dev_node;
        struct device_record *dev_rec;
        struct device_extent_record *dext_rec;
        int err;
        int ret = 0;

        dev_node = rb_first(dev_cache);
        while (dev_node) {
                dev_rec = container_of(dev_node, struct device_record, node);
                err = check_device_used(dev_rec, dev_extent_cache);
                if (err)
                        ret = err;

                dev_node = rb_next(dev_node);
        }
        list_for_each_entry(dext_rec, &dev_extent_cache->no_device_orphans,
                            device_list) {
                fprintf(stderr,
                        "Device extent[%llu, %llu, %llu] didn't find its device.\n",
                        dext_rec->objectid, dext_rec->offset, dext_rec->length);
                if (!ret)
                        ret = 1;
        }
        return ret;
}

static int add_root_item_to_list(struct list_head *head,
                                  u64 objectid, u64 bytenr, u64 last_snapshot,
                                  u8 level, u8 drop_level,
                                  struct btrfs_key *drop_key)
{

        struct root_item_record *ri_rec;
        ri_rec = malloc(sizeof(*ri_rec));
        if (!ri_rec)
                return -ENOMEM;
        ri_rec->bytenr = bytenr;
        ri_rec->objectid = objectid;
        ri_rec->level = level;
        ri_rec->drop_level = drop_level;
        ri_rec->last_snapshot = last_snapshot;
        if (drop_key)
                memcpy(&ri_rec->drop_key, drop_key, sizeof(*drop_key));
        list_add_tail(&ri_rec->list, head);

        return 0;
}

static void free_root_item_list(struct list_head *list)
{
        struct root_item_record *ri_rec;

        while (!list_empty(list)) {
                ri_rec = list_first_entry(list, struct root_item_record,
                                          list);
                list_del_init(&ri_rec->list);
                free(ri_rec);
        }
}

static int deal_root_from_list(struct list_head *list,
                               struct btrfs_root *root,
                               struct block_info *bits,
                               int bits_nr,
                               struct cache_tree *pending,
                               struct cache_tree *seen,
                               struct cache_tree *reada,
                               struct cache_tree *nodes,
                               struct cache_tree *extent_cache,
                               struct cache_tree *chunk_cache,
                               struct rb_root *dev_cache,
                               struct block_group_tree *block_group_cache,
                               struct device_extent_tree *dev_extent_cache)
{
        int ret = 0;
        u64 last;

        while (!list_empty(list)) {
                struct root_item_record *rec;
                struct extent_buffer *buf;
                rec = list_entry(list->next,
                                 struct root_item_record, list);
                last = 0;
                buf = read_tree_block(root->fs_info, rec->bytenr, 0);
                if (!extent_buffer_uptodate(buf)) {
                        free_extent_buffer(buf);
                        ret = -EIO;
                        break;
                }
                ret = add_root_to_pending(buf, extent_cache, pending,
                                    seen, nodes, rec->objectid);
                if (ret < 0)
                        break;
                /*
                 * To rebuild extent tree, we need deal with snapshot
                 * one by one, otherwise we deal with node firstly which
                 * can maximize readahead.
                 */
                while (1) {
                        ret = run_next_block(root, bits, bits_nr, &last,
                                             pending, seen, reada, nodes,
                                             extent_cache, chunk_cache,
                                             dev_cache, block_group_cache,
                                             dev_extent_cache, rec);
                        if (ret != 0)
                                break;
                }
                free_extent_buffer(buf);
                list_del(&rec->list);
                free(rec);
                if (ret < 0)
                        break;
        }
        while (ret >= 0) {
                ret = run_next_block(root, bits, bits_nr, &last, pending, seen,
                                     reada, nodes, extent_cache, chunk_cache,
                                     dev_cache, block_group_cache,
                                     dev_extent_cache, NULL);
                if (ret != 0) {
                        if (ret > 0)
                                ret = 0;
                        break;
                }
        }
        return ret;
}

static int check_chunks_and_extents(struct btrfs_fs_info *fs_info)
{
        struct rb_root dev_cache;
        struct cache_tree chunk_cache;
        struct block_group_tree block_group_cache;
        struct device_extent_tree dev_extent_cache;
        struct cache_tree extent_cache;
        struct cache_tree seen;
        struct cache_tree pending;
        struct cache_tree reada;
        struct cache_tree nodes;
        struct extent_io_tree excluded_extents;
        struct cache_tree corrupt_blocks;
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_key found_key;
        int ret, err = 0;
        struct block_info *bits;
        int bits_nr;
        struct extent_buffer *leaf;
        int slot;
        struct btrfs_root_item ri;
        struct list_head dropping_trees;
        struct list_head normal_trees;
        struct btrfs_root *root1;
        struct btrfs_root *root;
        u64 objectid;
        u8 level;

        root = fs_info->fs_root;
        dev_cache = RB_ROOT;
        cache_tree_init(&chunk_cache);
        block_group_tree_init(&block_group_cache);
        device_extent_tree_init(&dev_extent_cache);

        cache_tree_init(&extent_cache);
        cache_tree_init(&seen);
        cache_tree_init(&pending);
        cache_tree_init(&nodes);
        cache_tree_init(&reada);
        cache_tree_init(&corrupt_blocks);
        extent_io_tree_init(&excluded_extents);
        INIT_LIST_HEAD(&dropping_trees);
        INIT_LIST_HEAD(&normal_trees);

        if (repair) {
                fs_info->excluded_extents = &excluded_extents;
                fs_info->fsck_extent_cache = &extent_cache;
                fs_info->free_extent_hook = free_extent_hook;
                fs_info->corrupt_blocks = &corrupt_blocks;
        }

        bits_nr = 1024;
        bits = malloc(bits_nr * sizeof(struct block_info));
        if (!bits) {
                perror("malloc");
                exit(1);
        }

        if (ctx.progress_enabled) {
                ctx.tp = TASK_EXTENTS;
                task_start(ctx.info);
        }

again:
        root1 = fs_info->tree_root;
        level = btrfs_header_level(root1->node);
        ret = add_root_item_to_list(&normal_trees, root1->root_key.objectid,
                                    root1->node->start, 0, level, 0, NULL);
        if (ret < 0)
                goto out;
        root1 = fs_info->chunk_root;
        level = btrfs_header_level(root1->node);
        ret = add_root_item_to_list(&normal_trees, root1->root_key.objectid,
                                    root1->node->start, 0, level, 0, NULL);
        if (ret < 0)
                goto out;
        btrfs_init_path(&path);
        key.offset = 0;
        key.objectid = 0;
        key.type = BTRFS_ROOT_ITEM_KEY;
        ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        while(1) {
                leaf = path.nodes[0];
                slot = path.slots[0];
                if (slot >= btrfs_header_nritems(path.nodes[0])) {
                        ret = btrfs_next_leaf(root, &path);
                        if (ret != 0)
                                break;
                        leaf = path.nodes[0];
                        slot = path.slots[0];
                }
                btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);
                if (found_key.type == BTRFS_ROOT_ITEM_KEY) {
                        unsigned long offset;
                        u64 last_snapshot;

                        offset = btrfs_item_ptr_offset(leaf, path.slots[0]);
                        read_extent_buffer(leaf, &ri, offset, sizeof(ri));
                        last_snapshot = btrfs_root_last_snapshot(&ri);
                        if (btrfs_disk_key_objectid(&ri.drop_progress) == 0) {
                                level = btrfs_root_level(&ri);
                                ret = add_root_item_to_list(&normal_trees,
                                                found_key.objectid,
                                                btrfs_root_bytenr(&ri),
                                                last_snapshot, level,
                                                0, NULL);
                                if (ret < 0)
                                        goto out;
                        } else {
                                level = btrfs_root_level(&ri);
                                objectid = found_key.objectid;
                                btrfs_disk_key_to_cpu(&found_key,
                                                      &ri.drop_progress);
                                ret = add_root_item_to_list(&dropping_trees,
                                                objectid,
                                                btrfs_root_bytenr(&ri),
                                                last_snapshot, level,
                                                ri.drop_level, &found_key);
                                if (ret < 0)
                                        goto out;
                        }
                }
                path.slots[0]++;
        }
        btrfs_release_path(&path);

        /*
         * check_block can return -EAGAIN if it fixes something, please keep
         * this in mind when dealing with return values from these functions, if
         * we get -EAGAIN we want to fall through and restart the loop.
         */
        ret = deal_root_from_list(&normal_trees, root, bits, bits_nr, &pending,
                                  &seen, &reada, &nodes, &extent_cache,
                                  &chunk_cache, &dev_cache, &block_group_cache,
                                  &dev_extent_cache);
        if (ret < 0) {
                if (ret == -EAGAIN)
                        goto loop;
                goto out;
        }
        ret = deal_root_from_list(&dropping_trees, root, bits, bits_nr,
                                  &pending, &seen, &reada, &nodes,
                                  &extent_cache, &chunk_cache, &dev_cache,
                                  &block_group_cache, &dev_extent_cache);
        if (ret < 0) {
                if (ret == -EAGAIN)
                        goto loop;
                goto out;
        }

        ret = check_chunks(&chunk_cache, &block_group_cache,
                           &dev_extent_cache, NULL, NULL, NULL, 0);
        if (ret) {
                if (ret == -EAGAIN)
                        goto loop;
                err = ret;
        }

        ret = check_extent_refs(root, &extent_cache);
        if (ret < 0) {
                if (ret == -EAGAIN)
                        goto loop;
                goto out;
        }

        ret = check_devices(&dev_cache, &dev_extent_cache);
        if (ret && err)
                ret = err;

out:
        task_stop(ctx.info);
        if (repair) {
                free_corrupt_blocks_tree(fs_info->corrupt_blocks);
                extent_io_tree_cleanup(&excluded_extents);
                fs_info->fsck_extent_cache = NULL;
                fs_info->free_extent_hook = NULL;
                fs_info->corrupt_blocks = NULL;
                fs_info->excluded_extents = NULL;
        }
        free(bits);
        free_chunk_cache_tree(&chunk_cache);
        free_device_cache_tree(&dev_cache);
        free_block_group_tree(&block_group_cache);
        free_device_extent_tree(&dev_extent_cache);
        free_extent_cache_tree(&seen);
        free_extent_cache_tree(&pending);
        free_extent_cache_tree(&reada);
        free_extent_cache_tree(&nodes);
        free_root_item_list(&normal_trees);
        free_root_item_list(&dropping_trees);
        return ret;
loop:
        free_corrupt_blocks_tree(fs_info->corrupt_blocks);
        free_extent_cache_tree(&seen);
        free_extent_cache_tree(&pending);
        free_extent_cache_tree(&reada);
        free_extent_cache_tree(&nodes);
        free_chunk_cache_tree(&chunk_cache);
        free_block_group_tree(&block_group_cache);
        free_device_cache_tree(&dev_cache);
        free_device_extent_tree(&dev_extent_cache);
        free_extent_record_cache(&extent_cache);
        free_root_item_list(&normal_trees);
        free_root_item_list(&dropping_trees);
        extent_io_tree_cleanup(&excluded_extents);
        goto again;
}

/*
 * Check backrefs of a tree block given by @bytenr or @eb.
 *
 * @root:       the root containing the @bytenr or @eb
 * @eb:         tree block extent buffer, can be NULL
 * @bytenr:     bytenr of the tree block to search
 * @level:      tree level of the tree block
 * @owner:      owner of the tree block
 *
 * Return >0 for any error found and output error message
 * Return 0 for no error found
 */
static int check_tree_block_ref(struct btrfs_root *root,
                                struct extent_buffer *eb, u64 bytenr,
                                int level, u64 owner)
{
        struct btrfs_key key;
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_path path;
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        struct extent_buffer *leaf;
        unsigned long end;
        unsigned long ptr;
        int slot;
        int skinny_level;
        int type;
        u32 nodesize = root->fs_info->nodesize;
        u32 item_size;
        u64 offset;
        int tree_reloc_root = 0;
        int found_ref = 0;
        int err = 0;
        int ret;

        if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
            btrfs_header_bytenr(root->node) == bytenr)
                tree_reloc_root = 1;

        btrfs_init_path(&path);
        key.objectid = bytenr;
        if (btrfs_fs_incompat(root->fs_info, SKINNY_METADATA))
                key.type = BTRFS_METADATA_ITEM_KEY;
        else
                key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = (u64)-1;

        /* Search for the backref in extent tree */
        ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
        if (ret < 0) {
                err |= BACKREF_MISSING;
                goto out;
        }
        ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
        if (ret) {
                err |= BACKREF_MISSING;
                goto out;
        }

        leaf = path.nodes[0];
        slot = path.slots[0];
        btrfs_item_key_to_cpu(leaf, &key, slot);

        ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);

        if (key.type == BTRFS_METADATA_ITEM_KEY) {
                skinny_level = (int)key.offset;
                iref = (struct btrfs_extent_inline_ref *)(ei + 1);
        } else {
                struct btrfs_tree_block_info *info;

                info = (struct btrfs_tree_block_info *)(ei + 1);
                skinny_level = btrfs_tree_block_level(leaf, info);
                iref = (struct btrfs_extent_inline_ref *)(info + 1);
        }

        if (eb) {
                u64 header_gen;
                u64 extent_gen;

                if (!(btrfs_extent_flags(leaf, ei) &
                      BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
                        error(
                "extent[%llu %u] backref type mismatch, missing bit: %llx",
                                key.objectid, nodesize,
                                BTRFS_EXTENT_FLAG_TREE_BLOCK);
                        err = BACKREF_MISMATCH;
                }
                header_gen = btrfs_header_generation(eb);
                extent_gen = btrfs_extent_generation(leaf, ei);
                if (header_gen != extent_gen) {
                        error(
        "extent[%llu %u] backref generation mismatch, wanted: %llu, have: %llu",
                                key.objectid, nodesize, header_gen,
                                extent_gen);
                        err = BACKREF_MISMATCH;
                }
                if (level != skinny_level) {
                        error(
                        "extent[%llu %u] level mismatch, wanted: %u, have: %u",
                                key.objectid, nodesize, level, skinny_level);
                        err = BACKREF_MISMATCH;
                }
                if (!is_fstree(owner) && btrfs_extent_refs(leaf, ei) != 1) {
                        error(
                        "extent[%llu %u] is referred by other roots than %llu",
                                key.objectid, nodesize, root->objectid);
                        err = BACKREF_MISMATCH;
                }
        }

        /*
         * Iterate the extent/metadata item to find the exact backref
         */
        item_size = btrfs_item_size_nr(leaf, slot);
        ptr = (unsigned long)iref;
        end = (unsigned long)ei + item_size;
        while (ptr < end) {
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(leaf, iref);
                offset = btrfs_extent_inline_ref_offset(leaf, iref);

                if (type == BTRFS_TREE_BLOCK_REF_KEY &&
                        (offset == root->objectid || offset == owner)) {
                        found_ref = 1;
                } else if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
                        /*
                         * Backref of tree reloc root points to itself, no need
                         * to check backref any more.
                         */
                        if (tree_reloc_root)
                                found_ref = 1;
                        else
                        /* Check if the backref points to valid referencer */
                                found_ref = !check_tree_block_ref(root, NULL,
                                                offset, level + 1, owner);
                }

                if (found_ref)
                        break;
                ptr += btrfs_extent_inline_ref_size(type);
        }

        /*
         * Inlined extent item doesn't have what we need, check
         * TREE_BLOCK_REF_KEY
         */
        if (!found_ref) {
                btrfs_release_path(&path);
                key.objectid = bytenr;
                key.type = BTRFS_TREE_BLOCK_REF_KEY;
                key.offset = root->objectid;

                ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
                if (!ret)
                        found_ref = 1;
        }
        if (!found_ref)
                err |= BACKREF_MISSING;
out:
        btrfs_release_path(&path);
        if (eb && (err & BACKREF_MISSING))
                error("extent[%llu %u] backref lost (owner: %llu, level: %u)",
                        bytenr, nodesize, owner, level);
        return err;
}

/*
 * Check EXTENT_DATA item, mainly for its dbackref in extent tree
 *
 * Return >0 any error found and output error message
 * Return 0 for no error found
 */
static int check_extent_data_item(struct btrfs_root *root,
                                  struct extent_buffer *eb, int slot)
{
        struct btrfs_file_extent_item *fi;
        struct btrfs_path path;
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_key fi_key;
        struct btrfs_key dbref_key;
        struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_extent_data_ref *dref;
        u64 owner;
        u64 disk_bytenr;
        u64 disk_num_bytes;
        u64 extent_num_bytes;
        u64 extent_flags;
        u32 item_size;
        unsigned long end;
        unsigned long ptr;
        int type;
        u64 ref_root;
        int found_dbackref = 0;
        int err = 0;
        int ret;

        btrfs_item_key_to_cpu(eb, &fi_key, slot);
        fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);

        /* Nothing to check for hole and inline data extents */
        if (btrfs_file_extent_type(eb, fi) == BTRFS_FILE_EXTENT_INLINE ||
            btrfs_file_extent_disk_bytenr(eb, fi) == 0)
                return 0;

        disk_bytenr = btrfs_file_extent_disk_bytenr(eb, fi);
        disk_num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
        extent_num_bytes = btrfs_file_extent_num_bytes(eb, fi);

        /* Check unaligned disk_num_bytes and num_bytes */
        if (!IS_ALIGNED(disk_num_bytes, root->fs_info->sectorsize)) {
                error(
"file extent [%llu, %llu] has unaligned disk num bytes: %llu, should be aligned to %u",
                        fi_key.objectid, fi_key.offset, disk_num_bytes,
                        root->fs_info->sectorsize);
                err |= BYTES_UNALIGNED;
        } else {
                data_bytes_allocated += disk_num_bytes;
        }
        if (!IS_ALIGNED(extent_num_bytes, root->fs_info->sectorsize)) {
                error(
"file extent [%llu, %llu] has unaligned num bytes: %llu, should be aligned to %u",
                        fi_key.objectid, fi_key.offset, extent_num_bytes,
                        root->fs_info->sectorsize);
                err |= BYTES_UNALIGNED;
        } else {
                data_bytes_referenced += extent_num_bytes;
        }
        owner = btrfs_header_owner(eb);

        /* Check the extent item of the file extent in extent tree */
        btrfs_init_path(&path);
        dbref_key.objectid = btrfs_file_extent_disk_bytenr(eb, fi);
        dbref_key.type = BTRFS_EXTENT_ITEM_KEY;
        dbref_key.offset = btrfs_file_extent_disk_num_bytes(eb, fi);

        ret = btrfs_search_slot(NULL, extent_root, &dbref_key, &path, 0, 0);
        if (ret)
                goto out;

        leaf = path.nodes[0];
        slot = path.slots[0];
        ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);

        extent_flags = btrfs_extent_flags(leaf, ei);

        if (!(extent_flags & BTRFS_EXTENT_FLAG_DATA)) {
                error(
                    "extent[%llu %llu] backref type mismatch, wanted bit: %llx",
                    disk_bytenr, disk_num_bytes,
                    BTRFS_EXTENT_FLAG_DATA);
                err |= BACKREF_MISMATCH;
        }

        /* Check data backref inside that extent item */
        item_size = btrfs_item_size_nr(leaf, path.slots[0]);
        iref = (struct btrfs_extent_inline_ref *)(ei + 1);
        ptr = (unsigned long)iref;
        end = (unsigned long)ei + item_size;
        while (ptr < end) {
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(leaf, iref);
                dref = (struct btrfs_extent_data_ref *)(&iref->offset);

                if (type == BTRFS_EXTENT_DATA_REF_KEY) {
                        ref_root = btrfs_extent_data_ref_root(leaf, dref);
                        if (ref_root == owner || ref_root == root->objectid)
                                found_dbackref = 1;
                } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
                        found_dbackref = !check_tree_block_ref(root, NULL,
                                btrfs_extent_inline_ref_offset(leaf, iref),
                                0, owner);
                }

                if (found_dbackref)
                        break;
                ptr += btrfs_extent_inline_ref_size(type);
        }

        if (!found_dbackref) {
                btrfs_release_path(&path);

                /* Didn't find inlined data backref, try EXTENT_DATA_REF_KEY */
                dbref_key.objectid = btrfs_file_extent_disk_bytenr(eb, fi);
                dbref_key.type = BTRFS_EXTENT_DATA_REF_KEY;
                dbref_key.offset = hash_extent_data_ref(root->objectid,
                                fi_key.objectid, fi_key.offset);

                ret = btrfs_search_slot(NULL, root->fs_info->extent_root,
                                        &dbref_key, &path, 0, 0);
                if (!ret) {
                        found_dbackref = 1;
                        goto out;
                }

                btrfs_release_path(&path);

                /*
                 * Neither inlined nor EXTENT_DATA_REF found, try
                 * SHARED_DATA_REF as last chance.
                 */
                dbref_key.objectid = disk_bytenr;
                dbref_key.type = BTRFS_SHARED_DATA_REF_KEY;
                dbref_key.offset = eb->start;

                ret = btrfs_search_slot(NULL, root->fs_info->extent_root,
                                        &dbref_key, &path, 0, 0);
                if (!ret) {
                        found_dbackref = 1;
                        goto out;
                }
        }

out:
        if (!found_dbackref)
                err |= BACKREF_MISSING;
        btrfs_release_path(&path);
        if (err & BACKREF_MISSING) {
                error("data extent[%llu %llu] backref lost",
                      disk_bytenr, disk_num_bytes);
        }
        return err;
}

/*
 * Get real tree block level for the case like shared block
 * Return >= 0 as tree level
 * Return <0 for error
 */
static int query_tree_block_level(struct btrfs_fs_info *fs_info, u64 bytenr)
{
        struct extent_buffer *eb;
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_extent_item *ei;
        u64 flags;
        u64 transid;
        u8 backref_level;
        u8 header_level;
        int ret;

        /* Search extent tree for extent generation and level */
        key.objectid = bytenr;
        key.type = BTRFS_METADATA_ITEM_KEY;
        key.offset = (u64)-1;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, &path, 0, 0);
        if (ret < 0)
                goto release_out;
        ret = btrfs_previous_extent_item(fs_info->extent_root, &path, bytenr);
        if (ret < 0)
                goto release_out;
        if (ret > 0) {
                ret = -ENOENT;
                goto release_out;
        }

        btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
        ei = btrfs_item_ptr(path.nodes[0], path.slots[0],
                            struct btrfs_extent_item);
        flags = btrfs_extent_flags(path.nodes[0], ei);
        if (!(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
                ret = -ENOENT;
                goto release_out;
        }

        /* Get transid for later read_tree_block() check */
        transid = btrfs_extent_generation(path.nodes[0], ei);

        /* Get backref level as one source */
        if (key.type == BTRFS_METADATA_ITEM_KEY) {
                backref_level = key.offset;
        } else {
                struct btrfs_tree_block_info *info;

                info = (struct btrfs_tree_block_info *)(ei + 1);
                backref_level = btrfs_tree_block_level(path.nodes[0], info);
        }
        btrfs_release_path(&path);

        /* Get level from tree block as an alternative source */
        eb = read_tree_block(fs_info, bytenr, transid);
        if (!extent_buffer_uptodate(eb)) {
                free_extent_buffer(eb);
                return -EIO;
        }
        header_level = btrfs_header_level(eb);
        free_extent_buffer(eb);

        if (header_level != backref_level)
                return -EIO;
        return header_level;

release_out:
        btrfs_release_path(&path);
        return ret;
}

/*
 * Check if a tree block backref is valid (points to a valid tree block)
 * if level == -1, level will be resolved
 * Return >0 for any error found and print error message
 */
static int check_tree_block_backref(struct btrfs_fs_info *fs_info, u64 root_id,
                                    u64 bytenr, int level)
{
        struct btrfs_root *root;
        struct btrfs_key key;
        struct btrfs_path path;
        struct extent_buffer *eb;
        struct extent_buffer *node;
        u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
        int err = 0;
        int ret;

        /* Query level for level == -1 special case */
        if (level == -1)
                level = query_tree_block_level(fs_info, bytenr);
        if (level < 0) {
                err |= REFERENCER_MISSING;
                goto out;
        }

        key.objectid = root_id;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;

        root = btrfs_read_fs_root(fs_info, &key);
        if (IS_ERR(root)) {
                err |= REFERENCER_MISSING;
                goto out;
        }

        /* Read out the tree block to get item/node key */
        eb = read_tree_block(fs_info, bytenr, 0);
        if (!extent_buffer_uptodate(eb)) {
                err |= REFERENCER_MISSING;
                free_extent_buffer(eb);
                goto out;
        }

        /* Empty tree, no need to check key */
        if (!btrfs_header_nritems(eb) && !level) {
                free_extent_buffer(eb);
                goto out;
        }

        if (level)
                btrfs_node_key_to_cpu(eb, &key, 0);
        else
                btrfs_item_key_to_cpu(eb, &key, 0);

        free_extent_buffer(eb);

        btrfs_init_path(&path);
        path.lowest_level = level;
        /* Search with the first key, to ensure we can reach it */
        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0) {
                err |= REFERENCER_MISSING;
                goto release_out;
        }

        node = path.nodes[level];
        if (btrfs_header_bytenr(node) != bytenr) {
                error(
        "extent [%llu %d] referencer bytenr mismatch, wanted: %llu, have: %llu",
                        bytenr, nodesize, bytenr,
                        btrfs_header_bytenr(node));
                err |= REFERENCER_MISMATCH;
        }
        if (btrfs_header_level(node) != level) {
                error(
        "extent [%llu %d] referencer level mismatch, wanted: %d, have: %d",
                        bytenr, nodesize, level,
                        btrfs_header_level(node));
                err |= REFERENCER_MISMATCH;
        }

release_out:
        btrfs_release_path(&path);
out:
        if (err & REFERENCER_MISSING) {
                if (level < 0)
                        error("extent [%llu %d] lost referencer (owner: %llu)",
                                bytenr, nodesize, root_id);
                else
                        error(
                "extent [%llu %d] lost referencer (owner: %llu, level: %u)",
                                bytenr, nodesize, root_id, level);
        }

        return err;
}

/*
 * Check if tree block @eb is tree reloc root.
 * Return 0 if it's not or any problem happens
 * Return 1 if it's a tree reloc root
 */
static int is_tree_reloc_root(struct btrfs_fs_info *fs_info,
                                 struct extent_buffer *eb)
{
        struct btrfs_root *tree_reloc_root;
        struct btrfs_key key;
        u64 bytenr = btrfs_header_bytenr(eb);
        u64 owner = btrfs_header_owner(eb);
        int ret = 0;

        key.objectid = BTRFS_TREE_RELOC_OBJECTID;
        key.offset = owner;
        key.type = BTRFS_ROOT_ITEM_KEY;

        tree_reloc_root = btrfs_read_fs_root_no_cache(fs_info, &key);
        if (IS_ERR(tree_reloc_root))
                return 0;

        if (bytenr == btrfs_header_bytenr(tree_reloc_root->node))
                ret = 1;
        btrfs_free_fs_root(tree_reloc_root);
        return ret;
}

/*
 * Check referencer for shared block backref
 * If level == -1, this function will resolve the level.
 */
static int check_shared_block_backref(struct btrfs_fs_info *fs_info,
                                     u64 parent, u64 bytenr, int level)
{
        struct extent_buffer *eb;
        u32 nr;
        int found_parent = 0;
        int i;

        eb = read_tree_block(fs_info, parent, 0);
        if (!extent_buffer_uptodate(eb))
                goto out;

        if (level == -1)
                level = query_tree_block_level(fs_info, bytenr);
        if (level < 0)
                goto out;

        /* It's possible it's a tree reloc root */
        if (parent == bytenr) {
                if (is_tree_reloc_root(fs_info, eb))
                        found_parent = 1;
                goto out;
        }

        if (level + 1 != btrfs_header_level(eb))
                goto out;

        nr = btrfs_header_nritems(eb);
        for (i = 0; i < nr; i++) {
                if (bytenr == btrfs_node_blockptr(eb, i)) {
                        found_parent = 1;
                        break;
                }
        }
out:
        free_extent_buffer(eb);
        if (!found_parent) {
                error(
        "shared extent[%llu %u] lost its parent (parent: %llu, level: %u)",
                        bytenr, fs_info->nodesize, parent, level);
                return REFERENCER_MISSING;
        }
        return 0;
}

/*
 * Check referencer for normal (inlined) data ref
 * If len == 0, it will be resolved by searching in extent tree
 */
static int check_extent_data_backref(struct btrfs_fs_info *fs_info,
                                     u64 root_id, u64 objectid, u64 offset,
                                     u64 bytenr, u64 len, u32 count)
{
        struct btrfs_root *root;
        struct btrfs_root *extent_root = fs_info->extent_root;
        struct btrfs_key key;
        struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        u32 found_count = 0;
        int slot;
        int ret = 0;

        if (!len) {
                key.objectid = bytenr;
                key.type = BTRFS_EXTENT_ITEM_KEY;
                key.offset = (u64)-1;

                btrfs_init_path(&path);
                ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
                if (ret < 0)
                        goto out;
                ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
                if (ret)
                        goto out;
                btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
                if (key.objectid != bytenr ||
                    key.type != BTRFS_EXTENT_ITEM_KEY)
                        goto out;
                len = key.offset;
                btrfs_release_path(&path);
        }
        key.objectid = root_id;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;
        btrfs_init_path(&path);

        root = btrfs_read_fs_root(fs_info, &key);
        if (IS_ERR(root))
                goto out;

        key.objectid = objectid;
        key.type = BTRFS_EXTENT_DATA_KEY;
        /*
         * It can be nasty as data backref offset is
         * file offset - file extent offset, which is smaller or
         * equal to original backref offset.  The only special case is
         * overflow.  So we need to special check and do further search.
         */
        key.offset = offset & (1ULL << 63) ? 0 : offset;

        ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;

        /*
         * Search afterwards to get correct one
         * NOTE: As we must do a comprehensive check on the data backref to
         * make sure the dref count also matches, we must iterate all file
         * extents for that inode.
         */
        while (1) {
                leaf = path.nodes[0];
                slot = path.slots[0];

                if (slot >= btrfs_header_nritems(leaf))
                        goto next;
                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
                        break;
                fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
                /*
                 * Except normal disk bytenr and disk num bytes, we still
                 * need to do extra check on dbackref offset as
                 * dbackref offset = file_offset - file_extent_offset
                 */
                if (btrfs_file_extent_disk_bytenr(leaf, fi) == bytenr &&
                    btrfs_file_extent_disk_num_bytes(leaf, fi) == len &&
                    (u64)(key.offset - btrfs_file_extent_offset(leaf, fi)) ==
                    offset)
                        found_count++;

next:
                ret = btrfs_next_item(root, &path);
                if (ret)
                        break;
        }
out:
        btrfs_release_path(&path);
        if (found_count != count) {
                error(
"extent[%llu, %llu] referencer count mismatch (root: %llu, owner: %llu, offset: %llu) wanted: %u, have: %u",
                        bytenr, len, root_id, objectid, offset, count, found_count);
                return REFERENCER_MISSING;
        }
        return 0;
}

/*
 * Check if the referencer of a shared data backref exists
 */
static int check_shared_data_backref(struct btrfs_fs_info *fs_info,
                                     u64 parent, u64 bytenr)
{
        struct extent_buffer *eb;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        u32 nr;
        int found_parent = 0;
        int i;

        eb = read_tree_block(fs_info, parent, 0);
        if (!extent_buffer_uptodate(eb))
                goto out;

        nr = btrfs_header_nritems(eb);
        for (i = 0; i < nr; i++) {
                btrfs_item_key_to_cpu(eb, &key, i);
                if (key.type != BTRFS_EXTENT_DATA_KEY)
                        continue;

                fi = btrfs_item_ptr(eb, i, struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(eb, fi) == BTRFS_FILE_EXTENT_INLINE)
                        continue;

                if (btrfs_file_extent_disk_bytenr(eb, fi) == bytenr) {
                        found_parent = 1;
                        break;
                }
        }

out:
        free_extent_buffer(eb);
        if (!found_parent) {
                error("shared extent %llu referencer lost (parent: %llu)",
                        bytenr, parent);
                return REFERENCER_MISSING;
        }
        return 0;
}

/*
 * This function will check a given extent item, including its backref and
 * itself (like crossing stripe boundary and type)
 *
 * Since we don't use extent_record anymore, introduce new error bit
 */
static int check_extent_item(struct btrfs_fs_info *fs_info,
                             struct extent_buffer *eb, int slot)
{
        struct btrfs_extent_item *ei;
        struct btrfs_extent_inline_ref *iref;
        struct btrfs_extent_data_ref *dref;
        unsigned long end;
        unsigned long ptr;
        int type;
        u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
        u32 item_size = btrfs_item_size_nr(eb, slot);
        u64 flags;
        u64 offset;
        int metadata = 0;
        int level;
        struct btrfs_key key;
        int ret;
        int err = 0;

        btrfs_item_key_to_cpu(eb, &key, slot);
        if (key.type == BTRFS_EXTENT_ITEM_KEY)
                bytes_used += key.offset;
        else
                bytes_used += nodesize;

        if (item_size < sizeof(*ei)) {
                /*
                 * COMPAT_EXTENT_TREE_V0 case, but it's already a super
                 * old thing when on disk format is still un-determined.
                 * No need to care about it anymore
                 */
                error("unsupported COMPAT_EXTENT_TREE_V0 detected");
                return -ENOTTY;
        }

        ei = btrfs_item_ptr(eb, slot, struct btrfs_extent_item);
        flags = btrfs_extent_flags(eb, ei);

        if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
                metadata = 1;
        if (metadata && check_crossing_stripes(global_info, key.objectid,
                                               eb->len)) {
                error("bad metadata [%llu, %llu) crossing stripe boundary",
                      key.objectid, key.objectid + nodesize);
                err |= CROSSING_STRIPE_BOUNDARY;
        }

        ptr = (unsigned long)(ei + 1);

        if (metadata && key.type == BTRFS_EXTENT_ITEM_KEY) {
                /* Old EXTENT_ITEM metadata */
                struct btrfs_tree_block_info *info;

                info = (struct btrfs_tree_block_info *)ptr;
                level = btrfs_tree_block_level(eb, info);
                ptr += sizeof(struct btrfs_tree_block_info);
        } else {
                /* New METADATA_ITEM */
                level = key.offset;
        }
        end = (unsigned long)ei + item_size;

next:
        /* Reached extent item end normally */
        if (ptr == end)
                goto out;

        /* Beyond extent item end, wrong item size */
        if (ptr > end) {
                err |= ITEM_SIZE_MISMATCH;
                error("extent item at bytenr %llu slot %d has wrong size",
                        eb->start, slot);
                goto out;
        }

        /* Now check every backref in this extent item */
        iref = (struct btrfs_extent_inline_ref *)ptr;
        type = btrfs_extent_inline_ref_type(eb, iref);
        offset = btrfs_extent_inline_ref_offset(eb, iref);
        switch (type) {
        case BTRFS_TREE_BLOCK_REF_KEY:
                ret = check_tree_block_backref(fs_info, offset, key.objectid,
                                               level);
                err |= ret;
                break;
        case BTRFS_SHARED_BLOCK_REF_KEY:
                ret = check_shared_block_backref(fs_info, offset, key.objectid,
                                                 level);
                err |= ret;
                break;
        case BTRFS_EXTENT_DATA_REF_KEY:
                dref = (struct btrfs_extent_data_ref *)(&iref->offset);
                ret = check_extent_data_backref(fs_info,
                                btrfs_extent_data_ref_root(eb, dref),
                                btrfs_extent_data_ref_objectid(eb, dref),
                                btrfs_extent_data_ref_offset(eb, dref),
                                key.objectid, key.offset,
                                btrfs_extent_data_ref_count(eb, dref));
                err |= ret;
                break;
        case BTRFS_SHARED_DATA_REF_KEY:
                ret = check_shared_data_backref(fs_info, offset, key.objectid);
                err |= ret;
                break;
        default:
                error("extent[%llu %d %llu] has unknown ref type: %d",
                        key.objectid, key.type, key.offset, type);
                err |= UNKNOWN_TYPE;
                goto out;
        }

        ptr += btrfs_extent_inline_ref_size(type);
        goto next;

out:
        return err;
}

/*
 * Check if a dev extent item is referred correctly by its chunk
 */
static int check_dev_extent_item(struct btrfs_fs_info *fs_info,
                                 struct extent_buffer *eb, int slot)
{
        struct btrfs_root *chunk_root = fs_info->chunk_root;
        struct btrfs_dev_extent *ptr;
        struct btrfs_path path;
        struct btrfs_key chunk_key;
        struct btrfs_key devext_key;
        struct btrfs_chunk *chunk;
        struct extent_buffer *l;
        int num_stripes;
        u64 length;
        int i;
        int found_chunk = 0;
        int ret;

        btrfs_item_key_to_cpu(eb, &devext_key, slot);
        ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_extent);
        length = btrfs_dev_extent_length(eb, ptr);

        chunk_key.objectid = btrfs_dev_extent_chunk_objectid(eb, ptr);
        chunk_key.type = BTRFS_CHUNK_ITEM_KEY;
        chunk_key.offset = btrfs_dev_extent_chunk_offset(eb, ptr);

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, chunk_root, &chunk_key, &path, 0, 0);
        if (ret)
                goto out;

        l = path.nodes[0];
        chunk = btrfs_item_ptr(l, path.slots[0], struct btrfs_chunk);
        ret = btrfs_check_chunk_valid(fs_info, l, chunk, path.slots[0],
                                      chunk_key.offset);
        if (ret < 0)
                goto out;

        if (btrfs_stripe_length(fs_info, l, chunk) != length)
                goto out;

        num_stripes = btrfs_chunk_num_stripes(l, chunk);
        for (i = 0; i < num_stripes; i++) {
                u64 devid = btrfs_stripe_devid_nr(l, chunk, i);
                u64 offset = btrfs_stripe_offset_nr(l, chunk, i);

                if (devid == devext_key.objectid &&
                    offset == devext_key.offset) {
                        found_chunk = 1;
                        break;
                }
        }
out:
        btrfs_release_path(&path);
        if (!found_chunk) {
                error(
                "device extent[%llu, %llu, %llu] did not find the related chunk",
                        devext_key.objectid, devext_key.offset, length);
                return REFERENCER_MISSING;
        }
        return 0;
}

/*
 * Check if the used space is correct with the dev item
 */
static int check_dev_item(struct btrfs_fs_info *fs_info,
                          struct extent_buffer *eb, int slot)
{
        struct btrfs_root *dev_root = fs_info->dev_root;
        struct btrfs_dev_item *dev_item;
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_dev_extent *ptr;
        u64 dev_id;
        u64 used;
        u64 total = 0;
        int ret;

        dev_item = btrfs_item_ptr(eb, slot, struct btrfs_dev_item);
        dev_id = btrfs_device_id(eb, dev_item);
        used = btrfs_device_bytes_used(eb, dev_item);

        key.objectid = dev_id;
        key.type = BTRFS_DEV_EXTENT_KEY;
        key.offset = 0;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, dev_root, &key, &path, 0, 0);
        if (ret < 0) {
                btrfs_item_key_to_cpu(eb, &key, slot);
                error("cannot find any related dev extent for dev[%llu, %u, %llu]",
                        key.objectid, key.type, key.offset);
                btrfs_release_path(&path);
                return REFERENCER_MISSING;
        }

        /* Iterate dev_extents to calculate the used space of a device */
        while (1) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0]))
                        goto next;

                btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
                if (key.objectid > dev_id)
                        break;
                if (key.type != BTRFS_DEV_EXTENT_KEY || key.objectid != dev_id)
                        goto next;

                ptr = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                     struct btrfs_dev_extent);
                total += btrfs_dev_extent_length(path.nodes[0], ptr);
next:
                ret = btrfs_next_item(dev_root, &path);
                if (ret)
                        break;
        }
        btrfs_release_path(&path);

        if (used != total) {
                btrfs_item_key_to_cpu(eb, &key, slot);
                error(
"Dev extent's total-byte %llu is not equal to bytes-used %llu in dev[%llu, %u, %llu]",
                        total, used, BTRFS_ROOT_TREE_OBJECTID,
                        BTRFS_DEV_EXTENT_KEY, dev_id);
                return ACCOUNTING_MISMATCH;
        }
        return 0;
}

/*
 * Check a block group item with its referener (chunk) and its used space
 * with extent/metadata item
 */
static int check_block_group_item(struct btrfs_fs_info *fs_info,
                                  struct extent_buffer *eb, int slot)
{
        struct btrfs_root *extent_root = fs_info->extent_root;
        struct btrfs_root *chunk_root = fs_info->chunk_root;
        struct btrfs_block_group_item *bi;
        struct btrfs_block_group_item bg_item;
        struct btrfs_path path;
        struct btrfs_key bg_key;
        struct btrfs_key chunk_key;
        struct btrfs_key extent_key;
        struct btrfs_chunk *chunk;
        struct extent_buffer *leaf;
        struct btrfs_extent_item *ei;
        u32 nodesize = btrfs_super_nodesize(fs_info->super_copy);
        u64 flags;
        u64 bg_flags;
        u64 used;
        u64 total = 0;
        int ret;
        int err = 0;

        btrfs_item_key_to_cpu(eb, &bg_key, slot);
        bi = btrfs_item_ptr(eb, slot, struct btrfs_block_group_item);
        read_extent_buffer(eb, &bg_item, (unsigned long)bi, sizeof(bg_item));
        used = btrfs_block_group_used(&bg_item);
        bg_flags = btrfs_block_group_flags(&bg_item);

        chunk_key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
        chunk_key.type = BTRFS_CHUNK_ITEM_KEY;
        chunk_key.offset = bg_key.objectid;

        btrfs_init_path(&path);
        /* Search for the referencer chunk */
        ret = btrfs_search_slot(NULL, chunk_root, &chunk_key, &path, 0, 0);
        if (ret) {
                error(
                "block group[%llu %llu] did not find the related chunk item",
                        bg_key.objectid, bg_key.offset);
                err |= REFERENCER_MISSING;
        } else {
                chunk = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                        struct btrfs_chunk);
                if (btrfs_chunk_length(path.nodes[0], chunk) !=
                                                bg_key.offset) {
                        error(
        "block group[%llu %llu] related chunk item length does not match",
                                bg_key.objectid, bg_key.offset);
                        err |= REFERENCER_MISMATCH;
                }
        }
        btrfs_release_path(&path);

        /* Search from the block group bytenr */
        extent_key.objectid = bg_key.objectid;
        extent_key.type = 0;
        extent_key.offset = 0;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, extent_root, &extent_key, &path, 0, 0);
        if (ret < 0)
                goto out;

        /* Iterate extent tree to account used space */
        while (1) {
                leaf = path.nodes[0];

                /* Search slot can point to the last item beyond leaf nritems */
                if (path.slots[0] >= btrfs_header_nritems(leaf))
                        goto next;

                btrfs_item_key_to_cpu(leaf, &extent_key, path.slots[0]);
                if (extent_key.objectid >= bg_key.objectid + bg_key.offset)
                        break;

                if (extent_key.type != BTRFS_METADATA_ITEM_KEY &&
                    extent_key.type != BTRFS_EXTENT_ITEM_KEY)
                        goto next;
                if (extent_key.objectid < bg_key.objectid)
                        goto next;

                if (extent_key.type == BTRFS_METADATA_ITEM_KEY)
                        total += nodesize;
                else
                        total += extent_key.offset;

                ei = btrfs_item_ptr(leaf, path.slots[0],
                                    struct btrfs_extent_item);
                flags = btrfs_extent_flags(leaf, ei);
                if (flags & BTRFS_EXTENT_FLAG_DATA) {
                        if (!(bg_flags & BTRFS_BLOCK_GROUP_DATA)) {
                                error(
                        "bad extent[%llu, %llu) type mismatch with chunk",
                                        extent_key.objectid,
                                        extent_key.objectid + extent_key.offset);
                                err |= CHUNK_TYPE_MISMATCH;
                        }
                } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
                        if (!(bg_flags & (BTRFS_BLOCK_GROUP_SYSTEM |
                                    BTRFS_BLOCK_GROUP_METADATA))) {
                                error(
                        "bad extent[%llu, %llu) type mismatch with chunk",
                                        extent_key.objectid,
                                        extent_key.objectid + nodesize);
                                err |= CHUNK_TYPE_MISMATCH;
                        }
                }
next:
                ret = btrfs_next_item(extent_root, &path);
                if (ret)
                        break;
        }

out:
        btrfs_release_path(&path);

        if (total != used) {
                error(
                "block group[%llu %llu] used %llu but extent items used %llu",
                        bg_key.objectid, bg_key.offset, used, total);
                err |= ACCOUNTING_MISMATCH;
        }
        return err;
}

/*
 * Check a chunk item.
 * Including checking all referred dev_extents and block group
 */
static int check_chunk_item(struct btrfs_fs_info *fs_info,
                            struct extent_buffer *eb, int slot)
{
        struct btrfs_root *extent_root = fs_info->extent_root;
        struct btrfs_root *dev_root = fs_info->dev_root;
        struct btrfs_path path;
        struct btrfs_key chunk_key;
        struct btrfs_key bg_key;
        struct btrfs_key devext_key;
        struct btrfs_chunk *chunk;
        struct extent_buffer *leaf;
        struct btrfs_block_group_item *bi;
        struct btrfs_block_group_item bg_item;
        struct btrfs_dev_extent *ptr;
        u64 length;
        u64 chunk_end;
        u64 stripe_len;
        u64 type;
        int num_stripes;
        u64 offset;
        u64 objectid;
        int i;
        int ret;
        int err = 0;

        btrfs_item_key_to_cpu(eb, &chunk_key, slot);
        chunk = btrfs_item_ptr(eb, slot, struct btrfs_chunk);
        length = btrfs_chunk_length(eb, chunk);
        chunk_end = chunk_key.offset + length;
        ret = btrfs_check_chunk_valid(fs_info, eb, chunk, slot,
                                      chunk_key.offset);
        if (ret < 0) {
                error("chunk[%llu %llu) is invalid", chunk_key.offset,
                        chunk_end);
                err |= BYTES_UNALIGNED | UNKNOWN_TYPE;
                goto out;
        }
        type = btrfs_chunk_type(eb, chunk);

        bg_key.objectid = chunk_key.offset;
        bg_key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
        bg_key.offset = length;

        btrfs_init_path(&path);
        ret = btrfs_search_slot(NULL, extent_root, &bg_key, &path, 0, 0);
        if (ret) {
                error(
                "chunk[%llu %llu) did not find the related block group item",
                        chunk_key.offset, chunk_end);
                err |= REFERENCER_MISSING;
        } else{
                leaf = path.nodes[0];
                bi = btrfs_item_ptr(leaf, path.slots[0],
                                    struct btrfs_block_group_item);
                read_extent_buffer(leaf, &bg_item, (unsigned long)bi,
                                   sizeof(bg_item));
                if (btrfs_block_group_flags(&bg_item) != type) {
                        error(
"chunk[%llu %llu) related block group item flags mismatch, wanted: %llu, have: %llu",
                                chunk_key.offset, chunk_end, type,
                                btrfs_block_group_flags(&bg_item));
                        err |= REFERENCER_MISSING;
                }
        }

        num_stripes = btrfs_chunk_num_stripes(eb, chunk);
        stripe_len = btrfs_stripe_length(fs_info, eb, chunk);
        for (i = 0; i < num_stripes; i++) {
                btrfs_release_path(&path);
                btrfs_init_path(&path);
                devext_key.objectid = btrfs_stripe_devid_nr(eb, chunk, i);
                devext_key.type = BTRFS_DEV_EXTENT_KEY;
                devext_key.offset = btrfs_stripe_offset_nr(eb, chunk, i);

                ret = btrfs_search_slot(NULL, dev_root, &devext_key, &path,
                                        0, 0);
                if (ret)
                        goto not_match_dev;

                leaf = path.nodes[0];
                ptr = btrfs_item_ptr(leaf, path.slots[0],
                                     struct btrfs_dev_extent);
                objectid = btrfs_dev_extent_chunk_objectid(leaf, ptr);
                offset = btrfs_dev_extent_chunk_offset(leaf, ptr);
                if (objectid != chunk_key.objectid ||
                    offset != chunk_key.offset ||
                    btrfs_dev_extent_length(leaf, ptr) != stripe_len)
                        goto not_match_dev;
                continue;
not_match_dev:
                err |= BACKREF_MISSING;
                error(
                "chunk[%llu %llu) stripe %d did not find the related dev extent",
                        chunk_key.objectid, chunk_end, i);
                continue;
        }
        btrfs_release_path(&path);
out:
        return err;
}

/*
 * Main entry function to check known items and update related accounting info
 */
static int check_leaf_items(struct btrfs_root *root, struct extent_buffer *eb)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_key key;
        int slot = 0;
        int type;
        struct btrfs_extent_data_ref *dref;
        int ret;
        int err = 0;

next:
        btrfs_item_key_to_cpu(eb, &key, slot);
        type = key.type;

        switch (type) {
        case BTRFS_EXTENT_DATA_KEY:
                ret = check_extent_data_item(root, eb, slot);
                err |= ret;
                break;
        case BTRFS_BLOCK_GROUP_ITEM_KEY:
                ret = check_block_group_item(fs_info, eb, slot);
                err |= ret;
                break;
        case BTRFS_DEV_ITEM_KEY:
                ret = check_dev_item(fs_info, eb, slot);
                err |= ret;
                break;
        case BTRFS_CHUNK_ITEM_KEY:
                ret = check_chunk_item(fs_info, eb, slot);
                err |= ret;
                break;
        case BTRFS_DEV_EXTENT_KEY:
                ret = check_dev_extent_item(fs_info, eb, slot);
                err |= ret;
                break;
        case BTRFS_EXTENT_ITEM_KEY:
        case BTRFS_METADATA_ITEM_KEY:
                ret = check_extent_item(fs_info, eb, slot);
                err |= ret;
                break;
        case BTRFS_EXTENT_CSUM_KEY:
                total_csum_bytes += btrfs_item_size_nr(eb, slot);
                break;
        case BTRFS_TREE_BLOCK_REF_KEY:
                ret = check_tree_block_backref(fs_info, key.offset,
                                               key.objectid, -1);
                err |= ret;
                break;
        case BTRFS_EXTENT_DATA_REF_KEY:
                dref = btrfs_item_ptr(eb, slot, struct btrfs_extent_data_ref);
                ret = check_extent_data_backref(fs_info,
                                btrfs_extent_data_ref_root(eb, dref),
                                btrfs_extent_data_ref_objectid(eb, dref),
                                btrfs_extent_data_ref_offset(eb, dref),
                                key.objectid, 0,
                                btrfs_extent_data_ref_count(eb, dref));
                err |= ret;
                break;
        case BTRFS_SHARED_BLOCK_REF_KEY:
                ret = check_shared_block_backref(fs_info, key.offset,
                                                 key.objectid, -1);
                err |= ret;
                break;
        case BTRFS_SHARED_DATA_REF_KEY:
                ret = check_shared_data_backref(fs_info, key.offset,
                                                key.objectid);
                err |= ret;
                break;
        default:
                break;
        }

        if (++slot < btrfs_header_nritems(eb))
                goto next;

        return err;
}

/*
 * Helper function for later fs/subvol tree check.  To determine if a tree
 * block should be checked.
 * This function will ensure only the direct referencer with lowest rootid to
 * check a fs/subvolume tree block.
 *
 * Backref check at extent tree would detect errors like missing subvolume
 * tree, so we can do aggressive check to reduce duplicated checks.
 */
static int should_check(struct btrfs_root *root, struct extent_buffer *eb)
{
        struct btrfs_root *extent_root = root->fs_info->extent_root;
        struct btrfs_key key;
        struct btrfs_path path;
        struct extent_buffer *leaf;
        int slot;
        struct btrfs_extent_item *ei;
        unsigned long ptr;
        unsigned long end;
        int type;
        u32 item_size;
        u64 offset;
        struct btrfs_extent_inline_ref *iref;
        int ret;

        btrfs_init_path(&path);
        key.objectid = btrfs_header_bytenr(eb);
        key.type = BTRFS_METADATA_ITEM_KEY;
        key.offset = (u64)-1;

        /*
         * Any failure in backref resolving means we can't determine
         * whom the tree block belongs to.
         * So in that case, we need to check that tree block
         */
        ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
        if (ret < 0)
                goto need_check;

        ret = btrfs_previous_extent_item(extent_root, &path,
                                         btrfs_header_bytenr(eb));
        if (ret)
                goto need_check;

        leaf = path.nodes[0];
        slot = path.slots[0];
        btrfs_item_key_to_cpu(leaf, &key, slot);
        ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);

        if (key.type == BTRFS_METADATA_ITEM_KEY) {
                iref = (struct btrfs_extent_inline_ref *)(ei + 1);
        } else {
                struct btrfs_tree_block_info *info;

                info = (struct btrfs_tree_block_info *)(ei + 1);
                iref = (struct btrfs_extent_inline_ref *)(info + 1);
        }

        item_size = btrfs_item_size_nr(leaf, slot);
        ptr = (unsigned long)iref;
        end = (unsigned long)ei + item_size;
        while (ptr < end) {
                iref = (struct btrfs_extent_inline_ref *)ptr;
                type = btrfs_extent_inline_ref_type(leaf, iref);
                offset = btrfs_extent_inline_ref_offset(leaf, iref);

                /*
                 * We only check the tree block if current root is
                 * the lowest referencer of it.
                 */
                if (type == BTRFS_TREE_BLOCK_REF_KEY &&
                    offset < root->objectid) {
                        btrfs_release_path(&path);
                        return 0;
                }

                ptr += btrfs_extent_inline_ref_size(type);
        }
        /*
         * Normally we should also check keyed tree block ref, but that may be
         * very time consuming.  Inlined ref should already make us skip a lot
         * of refs now.  So skip search keyed tree block ref.
         */

need_check:
        btrfs_release_path(&path);
        return 1;
}

/*
 * Traversal function for tree block. We will do:
 * 1) Skip shared fs/subvolume tree blocks
 * 2) Update related bytes accounting
 * 3) Pre-order traversal
 */
static int traverse_tree_block(struct btrfs_root *root,
                                struct extent_buffer *node)
{
        struct extent_buffer *eb;
        struct btrfs_key key;
        struct btrfs_key drop_key;
        int level;
        u64 nr;
        int i;
        int err = 0;
        int ret;

        /*
         * Skip shared fs/subvolume tree block, in that case they will
         * be checked by referencer with lowest rootid
         */
        if (is_fstree(root->objectid) && !should_check(root, node))
                return 0;

        /* Update bytes accounting */
        total_btree_bytes += node->len;
        if (fs_root_objectid(btrfs_header_owner(node)))
                total_fs_tree_bytes += node->len;
        if (btrfs_header_owner(node) == BTRFS_EXTENT_TREE_OBJECTID)
                total_extent_tree_bytes += node->len;

        /* pre-order tranversal, check itself first */
        level = btrfs_header_level(node);
        ret = check_tree_block_ref(root, node, btrfs_header_bytenr(node),
                                   btrfs_header_level(node),
                                   btrfs_header_owner(node));
        err |= ret;
        if (err)
                error(
        "check %s failed root %llu bytenr %llu level %d, force continue check",
                        level ? "node":"leaf", root->objectid,
                        btrfs_header_bytenr(node), btrfs_header_level(node));

        if (!level) {
                btree_space_waste += btrfs_leaf_free_space(root, node);
                ret = check_leaf_items(root, node);
                err |= ret;
                return err;
        }

        nr = btrfs_header_nritems(node);
        btrfs_disk_key_to_cpu(&drop_key, &root->root_item.drop_progress);
        btree_space_waste += (BTRFS_NODEPTRS_PER_BLOCK(root) - nr) *
                sizeof(struct btrfs_key_ptr);

        /* Then check all its children */
        for (i = 0; i < nr; i++) {
                u64 blocknr = btrfs_node_blockptr(node, i);

                btrfs_node_key_to_cpu(node, &key, i);
                if (level == root->root_item.drop_level &&
                    is_dropped_key(&key, &drop_key))
                        continue;

                /*
                 * As a btrfs tree has most 8 levels (0..7), so it's quite safe
                 * to call the function itself.
                 */
                eb = read_tree_block(root->fs_info, blocknr, 0);
                if (extent_buffer_uptodate(eb)) {
                        ret = traverse_tree_block(root, eb);
                        err |= ret;
                }
                free_extent_buffer(eb);
        }

        return err;
}

/*
 * Low memory usage version check_chunks_and_extents.
 */
static int check_chunks_and_extents_v2(struct btrfs_fs_info *fs_info)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct btrfs_root *root1;
        struct btrfs_root *root;
        struct btrfs_root *cur_root;
        int err = 0;
        int ret;

        root = fs_info->fs_root;

        root1 = root->fs_info->chunk_root;
        ret = traverse_tree_block(root1, root1->node);
        err |= ret;

        root1 = root->fs_info->tree_root;
        ret = traverse_tree_block(root1, root1->node);
        err |= ret;

        btrfs_init_path(&path);
        key.objectid = BTRFS_EXTENT_TREE_OBJECTID;
        key.offset = 0;
        key.type = BTRFS_ROOT_ITEM_KEY;

        ret = btrfs_search_slot(NULL, root1, &key, &path, 0, 0);
        if (ret) {
                error("cannot find extent treet in tree_root");
                goto out;
        }

        while (1) {
                btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
                if (key.type != BTRFS_ROOT_ITEM_KEY)
                        goto next;
                key.offset = (u64)-1;

                if (key.objectid == BTRFS_TREE_RELOC_OBJECTID)
                        cur_root = btrfs_read_fs_root_no_cache(root->fs_info,
                                        &key);
                else
                        cur_root = btrfs_read_fs_root(root->fs_info, &key);
                if (IS_ERR(cur_root) || !cur_root) {
                        error("failed to read tree: %lld", key.objectid);
                        goto next;
                }

                ret = traverse_tree_block(cur_root, cur_root->node);
                err |= ret;

                if (key.objectid == BTRFS_TREE_RELOC_OBJECTID)
                        btrfs_free_fs_root(cur_root);
next:
                ret = btrfs_next_item(root1, &path);
                if (ret)
                        goto out;
        }

out:
        btrfs_release_path(&path);
        return err;
}

static int do_check_chunks_and_extents(struct btrfs_fs_info *fs_info)
{
        int ret;

        if (!ctx.progress_enabled)
                fprintf(stderr, "checking extents\n");
        if (check_mode == CHECK_MODE_LOWMEM)
                ret = check_chunks_and_extents_v2(fs_info);
        else
                ret = check_chunks_and_extents(fs_info);

        return ret;
}

static int btrfs_fsck_reinit_root(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root, int overwrite)
{
        struct extent_buffer *c;
        struct extent_buffer *old = root->node;
        int level;
        int ret;
        struct btrfs_disk_key disk_key = {0,0,0};

        level = 0;

        if (overwrite) {
                c = old;
                extent_buffer_get(c);
                goto init;
        }
        c = btrfs_alloc_free_block(trans, root,
                                   root->fs_info->nodesize,
                                   root->root_key.objectid,
                                   &disk_key, level, 0, 0);
        if (IS_ERR(c)) {
                c = old;
                extent_buffer_get(c);
                overwrite = 1;
        }
init:
        memset_extent_buffer(c, 0, 0, sizeof(struct btrfs_header));
        btrfs_set_header_level(c, level);
        btrfs_set_header_bytenr(c, c->start);
        btrfs_set_header_generation(c, trans->transid);
        btrfs_set_header_backref_rev(c, BTRFS_MIXED_BACKREF_REV);
        btrfs_set_header_owner(c, root->root_key.objectid);

        write_extent_buffer(c, root->fs_info->fsid,
                            btrfs_header_fsid(), BTRFS_FSID_SIZE);

        write_extent_buffer(c, root->fs_info->chunk_tree_uuid,
                            btrfs_header_chunk_tree_uuid(c),
                            BTRFS_UUID_SIZE);

        btrfs_mark_buffer_dirty(c);
        /*
         * this case can happen in the following case:
         *
         * 1.overwrite previous root.
         *
         * 2.reinit reloc data root, this is because we skip pin
         * down reloc data tree before which means we can allocate
         * same block bytenr here.
         */
        if (old->start == c->start) {
                btrfs_set_root_generation(&root->root_item,
                                          trans->transid);
                root->root_item.level = btrfs_header_level(root->node);
                ret = btrfs_update_root(trans, root->fs_info->tree_root,
                                        &root->root_key, &root->root_item);
                if (ret) {
                        free_extent_buffer(c);
                        return ret;
                }
        }
        free_extent_buffer(old);
        root->node = c;
        add_root_to_dirty_list(root);
        return 0;
}

static int pin_down_tree_blocks(struct btrfs_fs_info *fs_info,
                                struct extent_buffer *eb, int tree_root)
{
        struct extent_buffer *tmp;
        struct btrfs_root_item *ri;
        struct btrfs_key key;
        u64 bytenr;
        int level = btrfs_header_level(eb);
        int nritems;
        int ret;
        int i;

        /*
         * If we have pinned this block before, don't pin it again.
         * This can not only avoid forever loop with broken filesystem
         * but also give us some speedups.
         */
        if (test_range_bit(&fs_info->pinned_extents, eb->start,
                           eb->start + eb->len - 1, EXTENT_DIRTY, 0))
                return 0;

        btrfs_pin_extent(fs_info, eb->start, eb->len);

        nritems = btrfs_header_nritems(eb);
        for (i = 0; i < nritems; i++) {
                if (level == 0) {
                        btrfs_item_key_to_cpu(eb, &key, i);
                        if (key.type != BTRFS_ROOT_ITEM_KEY)
                                continue;
                        /* Skip the extent root and reloc roots */
                        if (key.objectid == BTRFS_EXTENT_TREE_OBJECTID ||
                            key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
                            key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
                                continue;
                        ri = btrfs_item_ptr(eb, i, struct btrfs_root_item);
                        bytenr = btrfs_disk_root_bytenr(eb, ri);

                        /*
                         * If at any point we start needing the real root we
                         * will have to build a stump root for the root we are
                         * in, but for now this doesn't actually use the root so
                         * just pass in extent_root.
                         */
                        tmp = read_tree_block(fs_info, bytenr, 0);
                        if (!extent_buffer_uptodate(tmp)) {
                                fprintf(stderr, "Error reading root block\n");
                                return -EIO;
                        }
                        ret = pin_down_tree_blocks(fs_info, tmp, 0);
                        free_extent_buffer(tmp);
                        if (ret)
                                return ret;
                } else {
                        bytenr = btrfs_node_blockptr(eb, i);

                        /* If we aren't the tree root don't read the block */
                        if (level == 1 && !tree_root) {
                                btrfs_pin_extent(fs_info, bytenr,
                                                fs_info->nodesize);
                                continue;
                        }

                        tmp = read_tree_block(fs_info, bytenr, 0);
                        if (!extent_buffer_uptodate(tmp)) {
                                fprintf(stderr, "Error reading tree block\n");
                                return -EIO;
                        }
                        ret = pin_down_tree_blocks(fs_info, tmp, tree_root);
                        free_extent_buffer(tmp);
                        if (ret)
                                return ret;
                }
        }

        return 0;
}

static int pin_metadata_blocks(struct btrfs_fs_info *fs_info)
{
        int ret;

        ret = pin_down_tree_blocks(fs_info, fs_info->chunk_root->node, 0);
        if (ret)
                return ret;

        return pin_down_tree_blocks(fs_info, fs_info->tree_root->node, 1);
}

static int reset_block_groups(struct btrfs_fs_info *fs_info)
{
        struct btrfs_block_group_cache *cache;
        struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_chunk *chunk;
        struct btrfs_key key;
        int ret;
        u64 start;

        btrfs_init_path(&path);
        key.objectid = 0;
        key.type = BTRFS_CHUNK_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(NULL, fs_info->chunk_root, &key, &path, 0, 0);
        if (ret < 0) {
                btrfs_release_path(&path);
                return ret;
        }

        /*
         * We do this in case the block groups were screwed up and had alloc
         * bits that aren't actually set on the chunks.  This happens with
         * restored images every time and could happen in real life I guess.
         */
        fs_info->avail_data_alloc_bits = 0;
        fs_info->avail_metadata_alloc_bits = 0;
        fs_info->avail_system_alloc_bits = 0;

        /* First we need to create the in-memory block groups */
        while (1) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        ret = btrfs_next_leaf(fs_info->chunk_root, &path);
                        if (ret < 0) {
                                btrfs_release_path(&path);
                                return ret;
                        }
                        if (ret) {
                                ret = 0;
                                break;
                        }
                }
                leaf = path.nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type != BTRFS_CHUNK_ITEM_KEY) {
                        path.slots[0]++;
                        continue;
                }

                chunk = btrfs_item_ptr(leaf, path.slots[0], struct btrfs_chunk);
                btrfs_add_block_group(fs_info, 0,
                                      btrfs_chunk_type(leaf, chunk),
                                      key.objectid, key.offset,
                                      btrfs_chunk_length(leaf, chunk));
                set_extent_dirty(&fs_info->free_space_cache, key.offset,
                                 key.offset + btrfs_chunk_length(leaf, chunk));
                path.slots[0]++;
        }
        start = 0;
        while (1) {
                cache = btrfs_lookup_first_block_group(fs_info, start);
                if (!cache)
                        break;
                cache->cached = 1;
                start = cache->key.objectid + cache->key.offset;
        }

        btrfs_release_path(&path);
        return 0;
}

static int reset_balance(struct btrfs_trans_handle *trans,
                         struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *root = fs_info->tree_root;
        struct btrfs_path path;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        int del_slot, del_nr = 0;
        int ret;
        int found = 0;

        btrfs_init_path(&path);
        key.objectid = BTRFS_BALANCE_OBJECTID;
        key.type = BTRFS_BALANCE_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
        if (ret) {
                if (ret > 0)
                        ret = 0;
                if (!ret)
                        goto reinit_data_reloc;
                else
                        goto out;
        }

        ret = btrfs_del_item(trans, root, &path);
        if (ret)
                goto out;
        btrfs_release_path(&path);

        key.objectid = BTRFS_TREE_RELOC_OBJECTID;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
        if (ret < 0)
                goto out;
        while (1) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        if (!found)
                                break;

                        if (del_nr) {
                                ret = btrfs_del_items(trans, root, &path,
                                                      del_slot, del_nr);
                                del_nr = 0;
                                if (ret)
                                        goto out;
                        }
                        key.offset++;
                        btrfs_release_path(&path);

                        found = 0;
                        ret = btrfs_search_slot(trans, root, &key, &path,
                                                -1, 1);
                        if (ret < 0)
                                goto out;
                        continue;
                }
                found = 1;
                leaf = path.nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.objectid > BTRFS_TREE_RELOC_OBJECTID)
                        break;
                if (key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
                        path.slots[0]++;
                        continue;
                }
                if (!del_nr) {
                        del_slot = path.slots[0];
                        del_nr = 1;
                } else {
                        del_nr++;
                }
                path.slots[0]++;
        }

        if (del_nr) {
                ret = btrfs_del_items(trans, root, &path, del_slot, del_nr);
                if (ret)
                        goto out;
        }
        btrfs_release_path(&path);

reinit_data_reloc:
        key.objectid = BTRFS_DATA_RELOC_TREE_OBJECTID;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;
        root = btrfs_read_fs_root(fs_info, &key);
        if (IS_ERR(root)) {
                fprintf(stderr, "Error reading data reloc tree\n");
                ret = PTR_ERR(root);
                goto out;
        }
        record_root_in_trans(trans, root);
        ret = btrfs_fsck_reinit_root(trans, root, 0);
        if (ret)
                goto out;
        ret = btrfs_make_root_dir(trans, root, BTRFS_FIRST_FREE_OBJECTID);
out:
        btrfs_release_path(&path);
        return ret;
}

static int reinit_extent_tree(struct btrfs_trans_handle *trans,
                              struct btrfs_fs_info *fs_info)
{
        u64 start = 0;
        int ret;

        /*
         * The only reason we don't do this is because right now we're just
         * walking the trees we find and pinning down their bytes, we don't look
         * at any of the leaves.  In order to do mixed groups we'd have to check
         * the leaves of any fs roots and pin down the bytes for any file
         * extents we find.  Not hard but why do it if we don't have to?
         */
        if (btrfs_fs_incompat(fs_info, MIXED_GROUPS)) {
                fprintf(stderr, "We don't support re-initing the extent tree "
                        "for mixed block groups yet, please notify a btrfs "
                        "developer you want to do this so they can add this "
                        "functionality.\n");
                return -EINVAL;
        }

        /*
         * first we need to walk all of the trees except the extent tree and pin
         * down the bytes that are in use so we don't overwrite any existing
         * metadata.
         */
        ret = pin_metadata_blocks(fs_info);
        if (ret) {
                fprintf(stderr, "error pinning down used bytes\n");
                return ret;
        }

        /*
         * Need to drop all the block groups since we're going to recreate all
         * of them again.
         */
        btrfs_free_block_groups(fs_info);
        ret = reset_block_groups(fs_info);
        if (ret) {
                fprintf(stderr, "error resetting the block groups\n");
                return ret;
        }

        /* Ok we can allocate now, reinit the extent root */
        ret = btrfs_fsck_reinit_root(trans, fs_info->extent_root, 0);
        if (ret) {
                fprintf(stderr, "extent root initialization failed\n");
                /*
                 * When the transaction code is updated we should end the
                 * transaction, but for now progs only knows about commit so
                 * just return an error.
                 */
                return ret;
        }

        /*
         * Now we have all the in-memory block groups setup so we can make
         * allocations properly, and the metadata we care about is safe since we
         * pinned all of it above.
         */
        while (1) {
                struct btrfs_block_group_cache *cache;

                cache = btrfs_lookup_first_block_group(fs_info, start);
                if (!cache)
                        break;
                start = cache->key.objectid + cache->key.offset;
                ret = btrfs_insert_item(trans, fs_info->extent_root,
                                        &cache->key, &cache->item,
                                        sizeof(cache->item));
                if (ret) {
                        fprintf(stderr, "Error adding block group\n");
                        return ret;
                }
                btrfs_extent_post_op(trans, fs_info->extent_root);
        }

        ret = reset_balance(trans, fs_info);
        if (ret)
                fprintf(stderr, "error resetting the pending balance\n");

        return ret;
}

static int recow_extent_buffer(struct btrfs_root *root, struct extent_buffer *eb)
{
        struct btrfs_path path;
        struct btrfs_trans_handle *trans;
        struct btrfs_key key;
        int ret;

        printf("Recowing metadata block %llu\n", eb->start);
        key.objectid = btrfs_header_owner(eb);
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;

        root = btrfs_read_fs_root(root->fs_info, &key);
        if (IS_ERR(root)) {
                fprintf(stderr, "Couldn't find owner root %llu\n",
                        key.objectid);
                return PTR_ERR(root);
        }

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_init_path(&path);
        path.lowest_level = btrfs_header_level(eb);
        if (path.lowest_level)
                btrfs_node_key_to_cpu(eb, &key, 0);
        else
                btrfs_item_key_to_cpu(eb, &key, 0);

        ret = btrfs_search_slot(trans, root, &key, &path, 0, 1);
        btrfs_commit_transaction(trans, root);
        btrfs_release_path(&path);
        return ret;
}

static int delete_bad_item(struct btrfs_root *root, struct bad_item *bad)
{
        struct btrfs_path path;
        struct btrfs_trans_handle *trans;
        struct btrfs_key key;
        int ret;

        printf("Deleting bad item [%llu,%u,%llu]\n", bad->key.objectid,
               bad->key.type, bad->key.offset);
        key.objectid = bad->root_id;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = (u64)-1;

        root = btrfs_read_fs_root(root->fs_info, &key);
        if (IS_ERR(root)) {
                fprintf(stderr, "Couldn't find owner root %llu\n",
                        key.objectid);
                return PTR_ERR(root);
        }

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_init_path(&path);
        ret = btrfs_search_slot(trans, root, &bad->key, &path, -1, 1);
        if (ret) {
                if (ret > 0)
                        ret = 0;
                goto out;
        }
        ret = btrfs_del_item(trans, root, &path);
out:
        btrfs_commit_transaction(trans, root);
        btrfs_release_path(&path);
        return ret;
}

static int zero_log_tree(struct btrfs_root *root)
{
        struct btrfs_trans_handle *trans;
        int ret;

        trans = btrfs_start_transaction(root, 1);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                return ret;
        }
        btrfs_set_super_log_root(root->fs_info->super_copy, 0);
        btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);
        ret = btrfs_commit_transaction(trans, root);
        return ret;
}

static int populate_csum(struct btrfs_trans_handle *trans,
                         struct btrfs_root *csum_root, char *buf, u64 start,
                         u64 len)
{
        struct btrfs_fs_info *fs_info = csum_root->fs_info;
        u64 offset = 0;
        u64 sectorsize;
        int ret = 0;

        while (offset < len) {
                sectorsize = fs_info->sectorsize;
                ret = read_extent_data(fs_info, buf, start + offset,
                                       &sectorsize, 0);
                if (ret)
                        break;
                ret = btrfs_csum_file_block(trans, csum_root, start + len,
                                            start + offset, buf, sectorsize);
                if (ret)
                        break;
                offset += sectorsize;
        }
        return ret;
}

static int fill_csum_tree_from_one_fs_root(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *csum_root,
                                      struct btrfs_root *cur_root)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct extent_buffer *node;
        struct btrfs_file_extent_item *fi;
        char *buf = NULL;
        u64 start = 0;
        u64 len = 0;
        int slot = 0;
        int ret = 0;

        buf = malloc(cur_root->fs_info->sectorsize);
        if (!buf)
                return -ENOMEM;

        btrfs_init_path(&path);
        key.objectid = 0;
        key.offset = 0;
        key.type = 0;
        ret = btrfs_search_slot(NULL, cur_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        /* Iterate all regular file extents and fill its csum */
        while (1) {
                btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);

                if (key.type != BTRFS_EXTENT_DATA_KEY)
                        goto next;
                node = path.nodes[0];
                slot = path.slots[0];
                fi = btrfs_item_ptr(node, slot, struct btrfs_file_extent_item);
                if (btrfs_file_extent_type(node, fi) != BTRFS_FILE_EXTENT_REG)
                        goto next;
                start = btrfs_file_extent_disk_bytenr(node, fi);
                len = btrfs_file_extent_disk_num_bytes(node, fi);

                ret = populate_csum(trans, csum_root, buf, start, len);
                if (ret == -EEXIST)
                        ret = 0;
                if (ret < 0)
                        goto out;
next:
                /*
                 * TODO: if next leaf is corrupted, jump to nearest next valid
                 * leaf.
                 */
                ret = btrfs_next_item(cur_root, &path);
                if (ret < 0)
                        goto out;
                if (ret > 0) {
                        ret = 0;
                        goto out;
                }
        }

out:
        btrfs_release_path(&path);
        free(buf);
        return ret;
}

static int fill_csum_tree_from_fs(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *csum_root)
{
        struct btrfs_fs_info *fs_info = csum_root->fs_info;
        struct btrfs_path path;
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_root *cur_root;
        struct extent_buffer *node;
        struct btrfs_key key;
        int slot = 0;
        int ret = 0;

        btrfs_init_path(&path);
        key.objectid = BTRFS_FS_TREE_OBJECTID;
        key.offset = 0;
        key.type = BTRFS_ROOT_ITEM_KEY;
        ret = btrfs_search_slot(NULL, tree_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        if (ret > 0) {
                ret = -ENOENT;
                goto out;
        }

        while (1) {
                node = path.nodes[0];
                slot = path.slots[0];
                btrfs_item_key_to_cpu(node, &key, slot);
                if (key.objectid > BTRFS_LAST_FREE_OBJECTID)
                        goto out;
                if (key.type != BTRFS_ROOT_ITEM_KEY)
                        goto next;
                if (!is_fstree(key.objectid))
                        goto next;
                key.offset = (u64)-1;

                cur_root = btrfs_read_fs_root(fs_info, &key);
                if (IS_ERR(cur_root) || !cur_root) {
                        fprintf(stderr, "Fail to read fs/subvol tree: %lld\n",
                                key.objectid);
                        goto out;
                }
                ret = fill_csum_tree_from_one_fs_root(trans, csum_root,
                                cur_root);
                if (ret < 0)
                        goto out;
next:
                ret = btrfs_next_item(tree_root, &path);
                if (ret > 0) {
                        ret = 0;
                        goto out;
                }
                if (ret < 0)
                        goto out;
        }

out:
        btrfs_release_path(&path);
        return ret;
}

static int fill_csum_tree_from_extent(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *csum_root)
{
        struct btrfs_root *extent_root = csum_root->fs_info->extent_root;
        struct btrfs_path path;
        struct btrfs_extent_item *ei;
        struct extent_buffer *leaf;
        char *buf;
        struct btrfs_key key;
        int ret;

        btrfs_init_path(&path);
        key.objectid = 0;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
        if (ret < 0) {
                btrfs_release_path(&path);
                return ret;
        }

        buf = malloc(csum_root->fs_info->sectorsize);
        if (!buf) {
                btrfs_release_path(&path);
                return -ENOMEM;
        }

        while (1) {
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
                        ret = btrfs_next_leaf(extent_root, &path);
                        if (ret < 0)
                                break;
                        if (ret) {
                                ret = 0;
                                break;
                        }
                }
                leaf = path.nodes[0];

                btrfs_item_key_to_cpu(leaf, &key, path.slots[0]);
                if (key.type != BTRFS_EXTENT_ITEM_KEY) {
                        path.slots[0]++;
                        continue;
                }

                ei = btrfs_item_ptr(leaf, path.slots[0],
                                    struct btrfs_extent_item);
                if (!(btrfs_extent_flags(leaf, ei) &
                      BTRFS_EXTENT_FLAG_DATA)) {
                        path.slots[0]++;
                        continue;
                }

                ret = populate_csum(trans, csum_root, buf, key.objectid,
                                    key.offset);
                if (ret)
                        break;
                path.slots[0]++;
        }

        btrfs_release_path(&path);
        free(buf);
        return ret;
}

/*
 * Recalculate the csum and put it into the csum tree.
 *
 * Extent tree init will wipe out all the extent info, so in that case, we
 * can't depend on extent tree, but use fs tree.  If search_fs_tree is set, we
 * will use fs/subvol trees to init the csum tree.
 */
static int fill_csum_tree(struct btrfs_trans_handle *trans,
                          struct btrfs_root *csum_root,
                          int search_fs_tree)
{
        if (search_fs_tree)
                return fill_csum_tree_from_fs(trans, csum_root);
        else
                return fill_csum_tree_from_extent(trans, csum_root);
}

static void free_roots_info_cache(void)
{
        if (!roots_info_cache)
                return;

        while (!cache_tree_empty(roots_info_cache)) {
                struct cache_extent *entry;
                struct root_item_info *rii;

                entry = first_cache_extent(roots_info_cache);
                if (!entry)
                        break;
                remove_cache_extent(roots_info_cache, entry);
                rii = container_of(entry, struct root_item_info, cache_extent);
                free(rii);
        }

        free(roots_info_cache);
        roots_info_cache = NULL;
}

static int build_roots_info_cache(struct btrfs_fs_info *info)
{
        int ret = 0;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_path path;

        if (!roots_info_cache) {
                roots_info_cache = malloc(sizeof(*roots_info_cache));
                if (!roots_info_cache)
                        return -ENOMEM;
                cache_tree_init(roots_info_cache);
        }

        btrfs_init_path(&path);
        key.objectid = 0;
        key.type = BTRFS_EXTENT_ITEM_KEY;
        key.offset = 0;
        ret = btrfs_search_slot(NULL, info->extent_root, &key, &path, 0, 0);
        if (ret < 0)
                goto out;
        leaf = path.nodes[0];

        while (1) {
                struct btrfs_key found_key;
                struct btrfs_extent_item *ei;
                struct btrfs_extent_inline_ref *iref;
                int slot = path.slots[0];
                int type;
                u64 flags;
                u64 root_id;
                u8 level;
                struct cache_extent *entry;
                struct root_item_info *rii;

                if (slot >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(info->extent_root, &path);
                        if (ret < 0) {
                                break;
                        } else if (ret) {
                                ret = 0;
                                break;
                        }
                        leaf = path.nodes[0];
                        slot = path.slots[0];
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);

                if (found_key.type != BTRFS_EXTENT_ITEM_KEY &&
                    found_key.type != BTRFS_METADATA_ITEM_KEY)
                        goto next;

                ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
                flags = btrfs_extent_flags(leaf, ei);

                if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
                    !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
                        goto next;

                if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
                        iref = (struct btrfs_extent_inline_ref *)(ei + 1);
                        level = found_key.offset;
                } else {
                        struct btrfs_tree_block_info *binfo;

                        binfo = (struct btrfs_tree_block_info *)(ei + 1);
                        iref = (struct btrfs_extent_inline_ref *)(binfo + 1);
                        level = btrfs_tree_block_level(leaf, binfo);
                }

                /*
                 * For a root extent, it must be of the following type and the
                 * first (and only one) iref in the item.
                 */
                type = btrfs_extent_inline_ref_type(leaf, iref);
                if (type != BTRFS_TREE_BLOCK_REF_KEY)
                        goto next;

                root_id = btrfs_extent_inline_ref_offset(leaf, iref);
                entry = lookup_cache_extent(roots_info_cache, root_id, 1);
                if (!entry) {
                        rii = malloc(sizeof(struct root_item_info));
                        if (!rii) {
                                ret = -ENOMEM;
                                goto out;
                        }
                        rii->cache_extent.start = root_id;
                        rii->cache_extent.size = 1;
                        rii->level = (u8)-1;
                        entry = &rii->cache_extent;
                        ret = insert_cache_extent(roots_info_cache, entry);
                        ASSERT(ret == 0);
                } else {
                        rii = container_of(entry, struct root_item_info,
                                           cache_extent);
                }

                ASSERT(rii->cache_extent.start == root_id);
                ASSERT(rii->cache_extent.size == 1);

                if (level > rii->level || rii->level == (u8)-1) {
                        rii->level = level;
                        rii->bytenr = found_key.objectid;
                        rii->gen = btrfs_extent_generation(leaf, ei);
                        rii->node_count = 1;
                } else if (level == rii->level) {
                        rii->node_count++;
                }
next:
                path.slots[0]++;
        }

out:
        btrfs_release_path(&path);

        return ret;
}

static int maybe_repair_root_item(struct btrfs_path *path,
                                  const struct btrfs_key *root_key,
                                  const int read_only_mode)
{
        const u64 root_id = root_key->objectid;
        struct cache_extent *entry;
        struct root_item_info *rii;
        struct btrfs_root_item ri;
        unsigned long offset;

        entry = lookup_cache_extent(roots_info_cache, root_id, 1);
        if (!entry) {
                fprintf(stderr,
                        "Error: could not find extent items for root %llu\n",
                        root_key->objectid);
                return -ENOENT;
        }

        rii = container_of(entry, struct root_item_info, cache_extent);
        ASSERT(rii->cache_extent.start == root_id);
        ASSERT(rii->cache_extent.size == 1);

        if (rii->node_count != 1) {
                fprintf(stderr,
                        "Error: could not find btree root extent for root %llu\n",
                        root_id);
                return -ENOENT;
        }

        offset = btrfs_item_ptr_offset(path->nodes[0], path->slots[0]);
        read_extent_buffer(path->nodes[0], &ri, offset, sizeof(ri));

        if (btrfs_root_bytenr(&ri) != rii->bytenr ||
            btrfs_root_level(&ri) != rii->level ||
            btrfs_root_generation(&ri) != rii->gen) {

                /*
                 * If we're in repair mode but our caller told us to not update
                 * the root item, i.e. just check if it needs to be updated, don't
                 * print this message, since the caller will call us again shortly
                 * for the same root item without read only mode (the caller will
                 * open a transaction first).
                 */
                if (!(read_only_mode && repair))
                        fprintf(stderr,
                                "%sroot item for root %llu,"
                                " current bytenr %llu, current gen %llu, current level %u,"
                                " new bytenr %llu, new gen %llu, new level %u\n",
                                (read_only_mode ? "" : "fixing "),
                                root_id,
                                btrfs_root_bytenr(&ri), btrfs_root_generation(&ri),
                                btrfs_root_level(&ri),
                                rii->bytenr, rii->gen, rii->level);

                if (btrfs_root_generation(&ri) > rii->gen) {
                        fprintf(stderr,
                                "root %llu has a root item with a more recent gen (%llu) compared to the found root node (%llu)\n",
                                root_id, btrfs_root_generation(&ri), rii->gen);
                        return -EINVAL;
                }

                if (!read_only_mode) {
                        btrfs_set_root_bytenr(&ri, rii->bytenr);
                        btrfs_set_root_level(&ri, rii->level);
                        btrfs_set_root_generation(&ri, rii->gen);
                        write_extent_buffer(path->nodes[0], &ri,
                                            offset, sizeof(ri));
                }

                return 1;
        }

        return 0;
}

/*
 * A regression introduced in the 3.17 kernel (more specifically in 3.17-rc2),
 * caused read-only snapshots to be corrupted if they were created at a moment
 * when the source subvolume/snapshot had orphan items. The issue was that the
 * on-disk root items became incorrect, referring to the pre orphan cleanup root
 * node instead of the post orphan cleanup root node.
 * So this function, and its callees, just detects and fixes those cases. Even
 * though the regression was for read-only snapshots, this function applies to
 * any snapshot/subvolume root.
 * This must be run before any other repair code - not doing it so, makes other
 * repair code delete or modify backrefs in the extent tree for example, which
 * will result in an inconsistent fs after repairing the root items.
 */
static int repair_root_items(struct btrfs_fs_info *info)
{
        struct btrfs_path path;
        struct btrfs_key key;
        struct extent_buffer *leaf;
        struct btrfs_trans_handle *trans = NULL;
        int ret = 0;
        int bad_roots = 0;
        int need_trans = 0;

        btrfs_init_path(&path);

        ret = build_roots_info_cache(info);
        if (ret)
                goto out;

        key.objectid = BTRFS_FIRST_FREE_OBJECTID;
        key.type = BTRFS_ROOT_ITEM_KEY;
        key.offset = 0;

again:
        /*
         * Avoid opening and committing transactions if a leaf doesn't have
         * any root items that need to be fixed, so that we avoid rotating
         * backup roots unnecessarily.
         */
        if (need_trans) {
                trans = btrfs_start_transaction(info->tree_root, 1);
                if (IS_ERR(trans)) {
                        ret = PTR_ERR(trans);
                        goto out;
                }
        }

        ret = btrfs_search_slot(trans, info->tree_root, &key, &path,
                                0, trans ? 1 : 0);
        if (ret < 0)
                goto out;
        leaf = path.nodes[0];

        while (1) {
                struct btrfs_key found_key;

                if (path.slots[0] >= btrfs_header_nritems(leaf)) {
                        int no_more_keys = find_next_key(&path, &key);

                        btrfs_release_path(&path);
                        if (trans) {
                                ret = btrfs_commit_transaction(trans,
                                                               info->tree_root);
                                trans = NULL;
                                if (ret < 0)
                                        goto out;
                        }
                        need_trans = 0;
                        if (no_more_keys)
                                break;
                        goto again;
                }

                btrfs_item_key_to_cpu(leaf, &found_key, path.slots[0]);

                if (found_key.type != BTRFS_ROOT_ITEM_KEY)
                        goto next;
                if (found_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
                        goto next;

                ret = maybe_repair_root_item(&path, &found_key, trans ? 0 : 1);
                if (ret < 0)
                        goto out;
                if (ret) {
                        if (!trans && repair) {
                                need_trans = 1;
                                key = found_key;
                                btrfs_release_path(&path);
                                goto again;
                        }
                        bad_roots++;
                }
next:
                path.slots[0]++;
        }
        ret = 0;
out:
        free_roots_info_cache();
        btrfs_release_path(&path);
        if (trans)
                btrfs_commit_transaction(trans, info->tree_root);
        if (ret < 0)
                return ret;

        return bad_roots;
}

static int clear_free_space_cache(struct btrfs_fs_info *fs_info)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_block_group_cache *bg_cache;
        u64 current = 0;
        int ret = 0;

        /* Clear all free space cache inodes and its extent data */
        while (1) {
                bg_cache = btrfs_lookup_first_block_group(fs_info, current);
                if (!bg_cache)
                        break;
                ret = btrfs_clear_free_space_cache(fs_info, bg_cache);
                if (ret < 0)
                        return ret;
                current = bg_cache->key.objectid + bg_cache->key.offset;
        }

        /* Don't forget to set cache_generation to -1 */
        trans = btrfs_start_transaction(fs_info->tree_root, 0);
        if (IS_ERR(trans)) {
                error("failed to update super block cache generation");
                return PTR_ERR(trans);
        }
        btrfs_set_super_cache_generation(fs_info->super_copy, (u64)-1);
        btrfs_commit_transaction(trans, fs_info->tree_root);

        return ret;
}

static int do_clear_free_space_cache(struct btrfs_fs_info *fs_info,
                int clear_version)
{
        int ret = 0;

        if (clear_version == 1) {
                if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                        error(
                "free space cache v2 detected, use --clear-space-cache v2");
                        ret = 1;
                        goto close_out;
                }
                printf("Clearing free space cache\n");
                ret = clear_free_space_cache(fs_info);
                if (ret) {
                        error("failed to clear free space cache");
                        ret = 1;
                } else {
                        printf("Free space cache cleared\n");
                }
        } else if (clear_version == 2) {
                if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
                        printf("no free space cache v2 to clear\n");
                        ret = 0;
                        goto close_out;
                }
                printf("Clear free space cache v2\n");
                ret = btrfs_clear_free_space_tree(fs_info);
                if (ret) {
                        error("failed to clear free space cache v2: %d", ret);
                        ret = 1;
                } else {
                        printf("free space cache v2 cleared\n");
                }
        }
close_out:
        return ret;
}

const char * const cmd_check_usage[] = {
        "btrfs check [options] <device>",
        "Check structural integrity of a filesystem (unmounted).",
        "Check structural integrity of an unmounted filesystem. Verify internal",
        "trees' consistency and item connectivity. In the repair mode try to",
        "fix the problems found. ",
        "WARNING: the repair mode is considered dangerous",
        "",
        "-s|--super <superblock>     use this superblock copy",
        "-b|--backup                 use the first valid backup root copy",
        "--force                     skip mount checks, repair is not possible",
        "--repair                    try to repair the filesystem",
        "--readonly                  run in read-only mode (default)",
        "--init-csum-tree            create a new CRC tree",
        "--init-extent-tree          create a new extent tree",
        "--mode <MODE>               allows choice of memory/IO trade-offs",
        "                            where MODE is one of:",
        "                            original - read inodes and extents to memory (requires",
        "                                       more memory, does less IO)",
        "                            lowmem   - try to use less memory but read blocks again",
        "                                       when needed",
        "--check-data-csum           verify checksums of data blocks",
        "-Q|--qgroup-report          print a report on qgroup consistency",
        "-E|--subvol-extents <subvolid>",
        "                            print subvolume extents and sharing state",
        "-r|--tree-root <bytenr>     use the given bytenr for the tree root",
        "--chunk-root <bytenr>       use the given bytenr for the chunk tree root",
        "-p|--progress               indicate progress",
        "--clear-space-cache v1|v2   clear space cache for v1 or v2",
        NULL
};

int cmd_check(int argc, char **argv)
{
        struct cache_tree root_cache;
        struct btrfs_root *root;
        struct btrfs_fs_info *info;
        u64 bytenr = 0;
        u64 subvolid = 0;
        u64 tree_root_bytenr = 0;
        u64 chunk_root_bytenr = 0;
        char uuidbuf[BTRFS_UUID_UNPARSED_SIZE];
        int ret = 0;
        int err = 0;
        u64 num;
        int init_csum_tree = 0;
        int readonly = 0;
        int clear_space_cache = 0;
        int qgroup_report = 0;
        int qgroups_repaired = 0;
        unsigned ctree_flags = OPEN_CTREE_EXCLUSIVE;
        int force = 0;

        while(1) {
                int c;
                enum { GETOPT_VAL_REPAIR = 257, GETOPT_VAL_INIT_CSUM,
                        GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
                        GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
                        GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE,
                        GETOPT_VAL_FORCE };
                static const struct option long_options[] = {
                        { "super", required_argument, NULL, 's' },
                        { "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
                        { "readonly", no_argument, NULL, GETOPT_VAL_READONLY },
                        { "init-csum-tree", no_argument, NULL,
                                GETOPT_VAL_INIT_CSUM },
                        { "init-extent-tree", no_argument, NULL,
                                GETOPT_VAL_INIT_EXTENT },
                        { "check-data-csum", no_argument, NULL,
                                GETOPT_VAL_CHECK_CSUM },
                        { "backup", no_argument, NULL, 'b' },
                        { "subvol-extents", required_argument, NULL, 'E' },
                        { "qgroup-report", no_argument, NULL, 'Q' },
                        { "tree-root", required_argument, NULL, 'r' },
                        { "chunk-root", required_argument, NULL,
                                GETOPT_VAL_CHUNK_TREE },
                        { "progress", no_argument, NULL, 'p' },
                        { "mode", required_argument, NULL,
                                GETOPT_VAL_MODE },
                        { "clear-space-cache", required_argument, NULL,
                                GETOPT_VAL_CLEAR_SPACE_CACHE},
                        { "force", no_argument, NULL, GETOPT_VAL_FORCE },
                        { NULL, 0, NULL, 0}
                };

                c = getopt_long(argc, argv, "as:br:pEQ", long_options, NULL);
                if (c < 0)
                        break;
                switch(c) {
                        case 'a': /* ignored */ break;
                        case 'b':
                                ctree_flags |= OPEN_CTREE_BACKUP_ROOT;
                                break;
                        case 's':
                                num = arg_strtou64(optarg);
                                if (num >= BTRFS_SUPER_MIRROR_MAX) {
                                        error(
                                        "super mirror should be less than %d",
                                                BTRFS_SUPER_MIRROR_MAX);
                                        exit(1);
                                }
                                bytenr = btrfs_sb_offset(((int)num));
                                printf("using SB copy %llu, bytenr %llu\n", num,
                                       (unsigned long long)bytenr);
                                break;
                        case 'Q':
                                qgroup_report = 1;
                                break;
                        case 'E':
                                subvolid = arg_strtou64(optarg);
                                break;
                        case 'r':
                                tree_root_bytenr = arg_strtou64(optarg);
                                break;
                        case GETOPT_VAL_CHUNK_TREE:
                                chunk_root_bytenr = arg_strtou64(optarg);
                                break;
                        case 'p':
                                ctx.progress_enabled = true;
                                break;
                        case '?':
                        case 'h':
                                usage(cmd_check_usage);
                        case GETOPT_VAL_REPAIR:
                                printf("enabling repair mode\n");
                                repair = 1;
                                ctree_flags |= OPEN_CTREE_WRITES;
                                break;
                        case GETOPT_VAL_READONLY:
                                readonly = 1;
                                break;
                        case GETOPT_VAL_INIT_CSUM:
                                printf("Creating a new CRC tree\n");
                                init_csum_tree = 1;
                                repair = 1;
                                ctree_flags |= OPEN_CTREE_WRITES;
                                break;
                        case GETOPT_VAL_INIT_EXTENT:
                                init_extent_tree = 1;
                                ctree_flags |= (OPEN_CTREE_WRITES |
                                                OPEN_CTREE_NO_BLOCK_GROUPS);
                                repair = 1;
                                break;
                        case GETOPT_VAL_CHECK_CSUM:
                                check_data_csum = 1;
                                break;
                        case GETOPT_VAL_MODE:
                                check_mode = parse_check_mode(optarg);
                                if (check_mode == CHECK_MODE_UNKNOWN) {
                                        error("unknown mode: %s", optarg);
                                        exit(1);
                                }
                                break;
                        case GETOPT_VAL_CLEAR_SPACE_CACHE:
                                if (strcmp(optarg, "v1") == 0) {
                                        clear_space_cache = 1;
                                } else if (strcmp(optarg, "v2") == 0) {
                                        clear_space_cache = 2;
                                        ctree_flags |= OPEN_CTREE_INVALIDATE_FST;
                                } else {
                                        error(
                "invalid argument to --clear-space-cache, must be v1 or v2");
                                        exit(1);
                                }
                                ctree_flags |= OPEN_CTREE_WRITES;
                                break;
                        case GETOPT_VAL_FORCE:
                                force = 1;
                                break;
                }
        }

        if (check_argc_exact(argc - optind, 1))
                usage(cmd_check_usage);

        if (ctx.progress_enabled) {
                ctx.tp = TASK_NOTHING;
                ctx.info = task_init(print_status_check, print_status_return, &ctx);
        }

        /* This check is the only reason for --readonly to exist */
        if (readonly && repair) {
                error("repair options are not compatible with --readonly");
                exit(1);
        }

        /*
         * experimental and dangerous
         */
        if (repair && check_mode == CHECK_MODE_LOWMEM)
                warning("low-memory mode repair support is only partial");

        radix_tree_init();
        cache_tree_init(&root_cache);

        ret = check_mounted(argv[optind]);
        if (!force) {
                if (ret < 0) {
                        error("could not check mount status: %s",
                                        strerror(-ret));
                        err |= !!ret;
                        goto err_out;
                } else if (ret) {
                        error(
"%s is currently mounted, use --force if you really intend to check the filesystem",
                                argv[optind]);
                        ret = -EBUSY;
                        err |= !!ret;
                        goto err_out;
                }
        } else {
                if (repair) {
                        error("repair and --force is not yet supported");
                        ret = 1;
                        err |= !!ret;
                        goto err_out;
                }
                if (ret < 0) {
                        warning(
"cannot check mount status of %s, the filesystem could be mounted, continuing because of --force",
                                argv[optind]);
                } else if (ret) {
                        warning(
                        "filesystem mounted, continuing because of --force");
                }
                /* A block device is mounted in exclusive mode by kernel */
                ctree_flags &= ~OPEN_CTREE_EXCLUSIVE;
        }

        /* only allow partial opening under repair mode */
        if (repair)
                ctree_flags |= OPEN_CTREE_PARTIAL;

        info = open_ctree_fs_info(argv[optind], bytenr, tree_root_bytenr,
                                  chunk_root_bytenr, ctree_flags);
        if (!info) {
                error("cannot open file system");
                ret = -EIO;
                err |= !!ret;
                goto err_out;
        }

        global_info = info;
        root = info->fs_root;
        uuid_unparse(info->super_copy->fsid, uuidbuf);

        printf("Checking filesystem on %s\nUUID: %s\n", argv[optind], uuidbuf);

        /*
         * Check the bare minimum before starting anything else that could rely
         * on it, namely the tree roots, any local consistency checks
         */
        if (!extent_buffer_uptodate(info->tree_root->node) ||
            !extent_buffer_uptodate(info->dev_root->node) ||
            !extent_buffer_uptodate(info->chunk_root->node)) {
                error("critical roots corrupted, unable to check the filesystem");
                err |= !!ret;
                ret = -EIO;
                goto close_out;
        }

        if (clear_space_cache) {
                ret = do_clear_free_space_cache(info, clear_space_cache);
                err |= !!ret;
                goto close_out;
        }

        /*
         * repair mode will force us to commit transaction which
         * will make us fail to load log tree when mounting.
         */
        if (repair && btrfs_super_log_root(info->super_copy)) {
                ret = ask_user("repair mode will force to clear out log tree, are you sure?");
                if (!ret) {
                        ret = 1;
                        err |= !!ret;
                        goto close_out;
                }
                ret = zero_log_tree(root);
                err |= !!ret;
                if (ret) {
                        error("failed to zero log tree: %d", ret);
                        goto close_out;
                }
        }

        if (qgroup_report) {
                printf("Print quota groups for %s\nUUID: %s\n", argv[optind],
                       uuidbuf);
                ret = qgroup_verify_all(info);
                err |= !!ret;
                if (ret == 0)
                        report_qgroups(1);
                goto close_out;
        }
        if (subvolid) {
                printf("Print extent state for subvolume %llu on %s\nUUID: %s\n",
                       subvolid, argv[optind], uuidbuf);
                ret = print_extent_state(info, subvolid);
                err |= !!ret;
                goto close_out;
        }

        if (init_extent_tree || init_csum_tree) {
                struct btrfs_trans_handle *trans;

                trans = btrfs_start_transaction(info->extent_root, 0);
                if (IS_ERR(trans)) {
                        error("error starting transaction");
                        ret = PTR_ERR(trans);
                        err |= !!ret;
                        goto close_out;
                }

                if (init_extent_tree) {
                        printf("Creating a new extent tree\n");
                        ret = reinit_extent_tree(trans, info);
                        err |= !!ret;
                        if (ret)
                                goto close_out;
                }

                if (init_csum_tree) {
                        printf("Reinitialize checksum tree\n");
                        ret = btrfs_fsck_reinit_root(trans, info->csum_root, 0);
                        if (ret) {
                                error("checksum tree initialization failed: %d",
                                                ret);
                                ret = -EIO;
                                err |= !!ret;
                                goto close_out;
                        }

                        ret = fill_csum_tree(trans, info->csum_root,
                                             init_extent_tree);
                        err |= !!ret;
                        if (ret) {
                                error("checksum tree refilling failed: %d", ret);
                                return -EIO;
                        }
                }
                /*
                 * Ok now we commit and run the normal fsck, which will add
                 * extent entries for all of the items it finds.
                 */
                ret = btrfs_commit_transaction(trans, info->extent_root);
                err |= !!ret;
                if (ret)
                        goto close_out;
        }
        if (!extent_buffer_uptodate(info->extent_root->node)) {
                error("critical: extent_root, unable to check the filesystem");
                ret = -EIO;
                err |= !!ret;
                goto close_out;
        }
        if (!extent_buffer_uptodate(info->csum_root->node)) {
                error("critical: csum_root, unable to check the filesystem");
                ret = -EIO;
                err |= !!ret;
                goto close_out;
        }

        ret = do_check_chunks_and_extents(info);
        err |= !!ret;
        if (ret)
                error(
                "errors found in extent allocation tree or chunk allocation");

        ret = repair_root_items(info);
        err |= !!ret;
        if (ret < 0) {
                error("failed to repair root items: %s", strerror(-ret));
                goto close_out;
        }
        if (repair) {
                fprintf(stderr, "Fixed %d roots.\n", ret);
                ret = 0;
        } else if (ret > 0) {
                fprintf(stderr,
                       "Found %d roots with an outdated root item.\n",
                       ret);
                fprintf(stderr,
                        "Please run a filesystem check with the option --repair to fix them.\n");
                ret = 1;
                err |= !!ret;
                goto close_out;
        }

        if (!ctx.progress_enabled) {
                if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
                        fprintf(stderr, "checking free space tree\n");
                else
                        fprintf(stderr, "checking free space cache\n");
        }
        ret = check_space_cache(root);
        err |= !!ret;
        if (ret) {
                if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
                        error("errors found in free space tree");
                else
                        error("errors found in free space cache");
                goto out;
        }

        /*
         * We used to have to have these hole extents in between our real
         * extents so if we don't have this flag set we need to make sure there
         * are no gaps in the file extents for inodes, otherwise we can just
         * ignore it when this happens.
         */
        no_holes = btrfs_fs_incompat(root->fs_info, NO_HOLES);
        ret = do_check_fs_roots(info, &root_cache);
        err |= !!ret;
        if (ret) {
                error("errors found in fs roots");
                goto out;
        }

        fprintf(stderr, "checking csums\n");
        ret = check_csums(root);
        err |= !!ret;
        if (ret) {
                error("errors found in csum tree");
                goto out;
        }

        fprintf(stderr, "checking root refs\n");
        /* For low memory mode, check_fs_roots_v2 handles root refs */
        if (check_mode != CHECK_MODE_LOWMEM) {
                ret = check_root_refs(root, &root_cache);
                err |= !!ret;
                if (ret) {
                        error("errors found in root refs");
                        goto out;
                }
        }

        while (repair && !list_empty(&root->fs_info->recow_ebs)) {
                struct extent_buffer *eb;

                eb = list_first_entry(&root->fs_info->recow_ebs,
                                      struct extent_buffer, recow);
                list_del_init(&eb->recow);
                ret = recow_extent_buffer(root, eb);
                err |= !!ret;
                if (ret) {
                        error("fails to fix transid errors");
                        break;
                }
        }

        while (!list_empty(&delete_items)) {
                struct bad_item *bad;

                bad = list_first_entry(&delete_items, struct bad_item, list);
                list_del_init(&bad->list);
                if (repair) {
                        ret = delete_bad_item(root, bad);
                        err |= !!ret;
                }
                free(bad);
        }

        if (info->quota_enabled) {
                fprintf(stderr, "checking quota groups\n");
                ret = qgroup_verify_all(info);
                err |= !!ret;
                if (ret) {
                        error("failed to check quota groups");
                        goto out;
                }
                report_qgroups(0);
                ret = repair_qgroups(info, &qgroups_repaired);
                err |= !!ret;
                if (err) {
                        error("failed to repair quota groups");
                        goto out;
                }
                ret = 0;
        }

        if (!list_empty(&root->fs_info->recow_ebs)) {
                error("transid errors in file system");
                ret = 1;
                err |= !!ret;
        }
out:
        printf("found %llu bytes used, ",
               (unsigned long long)bytes_used);
        if (err)
                printf("error(s) found\n");
        else
                printf("no error found\n");
        printf("total csum bytes: %llu\n",(unsigned long long)total_csum_bytes);
        printf("total tree bytes: %llu\n",
               (unsigned long long)total_btree_bytes);
        printf("total fs tree bytes: %llu\n",
               (unsigned long long)total_fs_tree_bytes);
        printf("total extent tree bytes: %llu\n",
               (unsigned long long)total_extent_tree_bytes);
        printf("btree space waste bytes: %llu\n",
               (unsigned long long)btree_space_waste);
        printf("file data blocks allocated: %llu\n referenced %llu\n",
                (unsigned long long)data_bytes_allocated,
                (unsigned long long)data_bytes_referenced);

        free_qgroup_counts();
        free_root_recs_tree(&root_cache);
close_out:
        close_ctree(root);
err_out:
        if (ctx.progress_enabled)
                task_deinit(ctx.info);

        return err;
}