btrfs: fix check_shared for fiemap ioctl
authorLu Fengqi <lufq.fnst@cn.fujitsu.com>
Mon, 13 Jun 2016 01:36:46 +0000 (09:36 +0800)
committerDavid Sterba <dsterba@suse.com>
Mon, 26 Sep 2016 15:59:49 +0000 (17:59 +0200)
Only in the case of different root_id or different object_id, check_shared
identified extent as the shared. However, If a extent was referred by
different offset of same file, it should also be identified as shared.
In addition, check_shared's loop scale is at least n^3, so if a extent
has too many references, even causes soft hang up.

First, add all delayed_ref to the ref_tree and calculate the unqiue_refs,
if the unique_refs is greater than one, return BACKREF_FOUND_SHARED.
Then individually add the on-disk reference(inline/keyed) to the ref_tree
and calculate the unique_refs of the ref_tree to check if the unique_refs
is greater than one.Because once there are two references to return
SHARED, so the time complexity is close to the constant.

Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/backref.c
fs/btrfs/extent_io.c

index 455a6b2..d9688ad 100644 (file)
@@ -17,6 +17,7 @@
  */
 
 #include <linux/vmalloc.h>
+#include <linux/rbtree.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "backref.h"
@@ -34,6 +35,265 @@ struct extent_inode_elem {
        struct extent_inode_elem *next;
 };
 
+/*
+ * ref_root is used as the root of the ref tree that hold a collection
+ * of unique references.
+ */
+struct ref_root {
+       struct rb_root rb_root;
+
+       /*
+        * The unique_refs represents the number of ref_nodes with a positive
+        * count stored in the tree. Even if a ref_node (the count is greater
+        * than one) is added, the unique_refs will only increase by one.
+        */
+       unsigned int unique_refs;
+};
+
+/* ref_node is used to store a unique reference to the ref tree. */
+struct ref_node {
+       struct rb_node rb_node;
+
+       /* For NORMAL_REF, otherwise all these fields should be set to 0 */
+       u64 root_id;
+       u64 object_id;
+       u64 offset;
+
+       /* For SHARED_REF, otherwise parent field should be set to 0 */
+       u64 parent;
+
+       /* Ref to the ref_mod of btrfs_delayed_ref_node */
+       int ref_mod;
+};
+
+/* Dynamically allocate and initialize a ref_root */
+static struct ref_root *ref_root_alloc(void)
+{
+       struct ref_root *ref_tree;
+
+       ref_tree = kmalloc(sizeof(*ref_tree), GFP_NOFS);
+       if (!ref_tree)
+               return NULL;
+
+       ref_tree->rb_root = RB_ROOT;
+       ref_tree->unique_refs = 0;
+
+       return ref_tree;
+}
+
+/* Free all nodes in the ref tree, and reinit ref_root */
+static void ref_root_fini(struct ref_root *ref_tree)
+{
+       struct ref_node *node;
+       struct rb_node *next;
+
+       while ((next = rb_first(&ref_tree->rb_root)) != NULL) {
+               node = rb_entry(next, struct ref_node, rb_node);
+               rb_erase(next, &ref_tree->rb_root);
+               kfree(node);
+       }
+
+       ref_tree->rb_root = RB_ROOT;
+       ref_tree->unique_refs = 0;
+}
+
+static void ref_root_free(struct ref_root *ref_tree)
+{
+       if (!ref_tree)
+               return;
+
+       ref_root_fini(ref_tree);
+       kfree(ref_tree);
+}
+
+/*
+ * Compare ref_node with (root_id, object_id, offset, parent)
+ *
+ * The function compares two ref_node a and b. It returns an integer less
+ * than, equal to, or greater than zero , respectively, to be less than, to
+ * equal, or be greater than b.
+ */
+static int ref_node_cmp(struct ref_node *a, struct ref_node *b)
+{
+       if (a->root_id < b->root_id)
+               return -1;
+       else if (a->root_id > b->root_id)
+               return 1;
+
+       if (a->object_id < b->object_id)
+               return -1;
+       else if (a->object_id > b->object_id)
+               return 1;
+
+       if (a->offset < b->offset)
+               return -1;
+       else if (a->offset > b->offset)
+               return 1;
+
+       if (a->parent < b->parent)
+               return -1;
+       else if (a->parent > b->parent)
+               return 1;
+
+       return 0;
+}
+
+/*
+ * Search ref_node with (root_id, object_id, offset, parent) in the tree
+ *
+ * if found, the pointer of the ref_node will be returned;
+ * if not found, NULL will be returned and pos will point to the rb_node for
+ * insert, pos_parent will point to pos'parent for insert;
+*/
+static struct ref_node *__ref_tree_search(struct ref_root *ref_tree,
+                                         struct rb_node ***pos,
+                                         struct rb_node **pos_parent,
+                                         u64 root_id, u64 object_id,
+                                         u64 offset, u64 parent)
+{
+       struct ref_node *cur = NULL;
+       struct ref_node entry;
+       int ret;
+
+       entry.root_id = root_id;
+       entry.object_id = object_id;
+       entry.offset = offset;
+       entry.parent = parent;
+
+       *pos = &ref_tree->rb_root.rb_node;
+
+       while (**pos) {
+               *pos_parent = **pos;
+               cur = rb_entry(*pos_parent, struct ref_node, rb_node);
+
+               ret = ref_node_cmp(cur, &entry);
+               if (ret > 0)
+                       *pos = &(**pos)->rb_left;
+               else if (ret < 0)
+                       *pos = &(**pos)->rb_right;
+               else
+                       return cur;
+       }
+
+       return NULL;
+}
+
+/*
+ * Insert a ref_node to the ref tree
+ * @pos used for specifiy the position to insert
+ * @pos_parent for specifiy pos's parent
+ *
+ * success, return 0;
+ * ref_node already exists, return -EEXIST;
+*/
+static int ref_tree_insert(struct ref_root *ref_tree, struct rb_node **pos,
+                          struct rb_node *pos_parent, struct ref_node *ins)
+{
+       struct rb_node **p = NULL;
+       struct rb_node *parent = NULL;
+       struct ref_node *cur = NULL;
+
+       if (!pos) {
+               cur = __ref_tree_search(ref_tree, &p, &parent, ins->root_id,
+                                       ins->object_id, ins->offset,
+                                       ins->parent);
+               if (cur)
+                       return -EEXIST;
+       } else {
+               p = pos;
+               parent = pos_parent;
+       }
+
+       rb_link_node(&ins->rb_node, parent, p);
+       rb_insert_color(&ins->rb_node, &ref_tree->rb_root);
+
+       return 0;
+}
+
+/* Erase and free ref_node, caller should update ref_root->unique_refs */
+static void ref_tree_remove(struct ref_root *ref_tree, struct ref_node *node)
+{
+       rb_erase(&node->rb_node, &ref_tree->rb_root);
+       kfree(node);
+}
+
+/*
+ * Update ref_root->unique_refs
+ *
+ * Call __ref_tree_search
+ *     1. if ref_node doesn't exist, ref_tree_insert this node, and update
+ *     ref_root->unique_refs:
+ *             if ref_node->ref_mod > 0, ref_root->unique_refs++;
+ *             if ref_node->ref_mod < 0, do noting;
+ *
+ *     2. if ref_node is found, then get origin ref_node->ref_mod, and update
+ *     ref_node->ref_mod.
+ *             if ref_node->ref_mod is equal to 0,then call ref_tree_remove
+ *
+ *             according to origin_mod and new_mod, update ref_root->items
+ *             +----------------+--------------+-------------+
+ *             |                |new_count <= 0|new_count > 0|
+ *             +----------------+--------------+-------------+
+ *             |origin_count < 0|       0      |      1      |
+ *             +----------------+--------------+-------------+
+ *             |origin_count > 0|      -1      |      0      |
+ *             +----------------+--------------+-------------+
+ *
+ * In case of allocation failure, -ENOMEM is returned and the ref_tree stays
+ * unaltered.
+ * Success, return 0
+ */
+static int ref_tree_add(struct ref_root *ref_tree, u64 root_id, u64 object_id,
+                       u64 offset, u64 parent, int count)
+{
+       struct ref_node *node = NULL;
+       struct rb_node **pos = NULL;
+       struct rb_node *pos_parent = NULL;
+       int origin_count;
+       int ret;
+
+       if (!count)
+               return 0;
+
+       node = __ref_tree_search(ref_tree, &pos, &pos_parent, root_id,
+                                object_id, offset, parent);
+       if (node == NULL) {
+               node = kmalloc(sizeof(*node), GFP_NOFS);
+               if (!node)
+                       return -ENOMEM;
+
+               node->root_id = root_id;
+               node->object_id = object_id;
+               node->offset = offset;
+               node->parent = parent;
+               node->ref_mod = count;
+
+               ret = ref_tree_insert(ref_tree, pos, pos_parent, node);
+               ASSERT(!ret);
+               if (ret) {
+                       kfree(node);
+                       return ret;
+               }
+
+               ref_tree->unique_refs += node->ref_mod > 0 ? 1 : 0;
+
+               return 0;
+       }
+
+       origin_count = node->ref_mod;
+       node->ref_mod += count;
+
+       if (node->ref_mod > 0)
+               ref_tree->unique_refs += origin_count > 0 ? 0 : 1;
+       else if (node->ref_mod <= 0)
+               ref_tree->unique_refs += origin_count > 0 ? -1 : 0;
+
+       if (!node->ref_mod)
+               ref_tree_remove(ref_tree, node);
+
+       return 0;
+}
+
 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
                                struct btrfs_file_extent_item *fi,
                                u64 extent_item_pos,
@@ -700,6 +960,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
                             struct btrfs_path *path, u64 bytenr,
                             int *info_level, struct list_head *prefs,
+                            struct ref_root *ref_tree,
                             u64 *total_refs, u64 inum)
 {
        int ret = 0;
@@ -767,6 +1028,13 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
                        count = btrfs_shared_data_ref_count(leaf, sdref);
                        ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
                                               bytenr, count, GFP_NOFS);
+                       if (ref_tree) {
+                               if (!ret)
+                                       ret = ref_tree_add(ref_tree, 0, 0, 0,
+                                                          bytenr, count);
+                               if (!ret && ref_tree->unique_refs > 1)
+                                       ret = BACKREF_FOUND_SHARED;
+                       }
                        break;
                }
                case BTRFS_TREE_BLOCK_REF_KEY:
@@ -794,6 +1062,15 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
                        root = btrfs_extent_data_ref_root(leaf, dref);
                        ret = __add_prelim_ref(prefs, root, &key, 0, 0,
                                               bytenr, count, GFP_NOFS);
+                       if (ref_tree) {
+                               if (!ret)
+                                       ret = ref_tree_add(ref_tree, root,
+                                                          key.objectid,
+                                                          key.offset, 0,
+                                                          count);
+                               if (!ret && ref_tree->unique_refs > 1)
+                                       ret = BACKREF_FOUND_SHARED;
+                       }
                        break;
                }
                default:
@@ -812,7 +1089,8 @@ static int __add_inline_refs(struct btrfs_fs_info *fs_info,
  */
 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
                            struct btrfs_path *path, u64 bytenr,
-                           int info_level, struct list_head *prefs, u64 inum)
+                           int info_level, struct list_head *prefs,
+                           struct ref_root *ref_tree, u64 inum)
 {
        struct btrfs_root *extent_root = fs_info->extent_root;
        int ret;
@@ -855,6 +1133,13 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
                        count = btrfs_shared_data_ref_count(leaf, sdref);
                        ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
                                                bytenr, count, GFP_NOFS);
+                       if (ref_tree) {
+                               if (!ret)
+                                       ret = ref_tree_add(ref_tree, 0, 0, 0,
+                                                          bytenr, count);
+                               if (!ret && ref_tree->unique_refs > 1)
+                                       ret = BACKREF_FOUND_SHARED;
+                       }
                        break;
                }
                case BTRFS_TREE_BLOCK_REF_KEY:
@@ -883,6 +1168,15 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
                        root = btrfs_extent_data_ref_root(leaf, dref);
                        ret = __add_prelim_ref(prefs, root, &key, 0, 0,
                                               bytenr, count, GFP_NOFS);
+                       if (ref_tree) {
+                               if (!ret)
+                                       ret = ref_tree_add(ref_tree, root,
+                                                          key.objectid,
+                                                          key.offset, 0,
+                                                          count);
+                               if (!ret && ref_tree->unique_refs > 1)
+                                       ret = BACKREF_FOUND_SHARED;
+                       }
                        break;
                }
                default:
@@ -909,13 +1203,16 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
  * commit root.
  * The special case is for qgroup to search roots in commit_transaction().
  *
+ * If check_shared is set to 1, any extent has more than one ref item, will
+ * be returned BACKREF_FOUND_SHARED immediately.
+ *
  * FIXME some caching might speed things up
  */
 static int find_parent_nodes(struct btrfs_trans_handle *trans,
                             struct btrfs_fs_info *fs_info, u64 bytenr,
                             u64 time_seq, struct ulist *refs,
                             struct ulist *roots, const u64 *extent_item_pos,
-                            u64 root_objectid, u64 inum)
+                            u64 root_objectid, u64 inum, int check_shared)
 {
        struct btrfs_key key;
        struct btrfs_path *path;
@@ -927,6 +1224,7 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
        struct list_head prefs;
        struct __prelim_ref *ref;
        struct extent_inode_elem *eie = NULL;
+       struct ref_root *ref_tree = NULL;
        u64 total_refs = 0;
 
        INIT_LIST_HEAD(&prefs);
@@ -958,6 +1256,18 @@ static int find_parent_nodes(struct btrfs_trans_handle *trans,
 again:
        head = NULL;
 
+       if (check_shared) {
+               if (!ref_tree) {
+                       ref_tree = ref_root_alloc();
+                       if (!ref_tree) {
+                               ret = -ENOMEM;
+                               goto out;
+                       }
+               } else {
+                       ref_root_fini(ref_tree);
+               }
+       }
+
        ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
@@ -1002,6 +1312,36 @@ again:
                } else {
                        spin_unlock(&delayed_refs->lock);
                }
+
+               if (check_shared && !list_empty(&prefs_delayed)) {
+                       /*
+                        * Add all delay_ref to the ref_tree and check if there
+                        * are multiple ref items added.
+                        */
+                       list_for_each_entry(ref, &prefs_delayed, list) {
+                               if (ref->key_for_search.type) {
+                                       ret = ref_tree_add(ref_tree,
+                                               ref->root_id,
+                                               ref->key_for_search.objectid,
+                                               ref->key_for_search.offset,
+                                               0, ref->count);
+                                       if (ret)
+                                               goto out;
+                               } else {
+                                       ret = ref_tree_add(ref_tree, 0, 0, 0,
+                                                    ref->parent, ref->count);
+                                       if (ret)
+                                               goto out;
+                               }
+
+                       }
+
+                       if (ref_tree->unique_refs > 1) {
+                               ret = BACKREF_FOUND_SHARED;
+                               goto out;
+                       }
+
+               }
        }
 
        if (path->slots[0]) {
@@ -1017,11 +1357,13 @@ again:
                     key.type == BTRFS_METADATA_ITEM_KEY)) {
                        ret = __add_inline_refs(fs_info, path, bytenr,
                                                &info_level, &prefs,
-                                               &total_refs, inum);
+                                               ref_tree, &total_refs,
+                                               inum);
                        if (ret)
                                goto out;
                        ret = __add_keyed_refs(fs_info, path, bytenr,
-                                              info_level, &prefs, inum);
+                                              info_level, &prefs,
+                                              ref_tree, inum);
                        if (ret)
                                goto out;
                }
@@ -1106,6 +1448,7 @@ again:
 
 out:
        btrfs_free_path(path);
+       ref_root_free(ref_tree);
        while (!list_empty(&prefs)) {
                ref = list_first_entry(&prefs, struct __prelim_ref, list);
                list_del(&ref->list);
@@ -1159,8 +1502,8 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
        if (!*leafs)
                return -ENOMEM;
 
-       ret = find_parent_nodes(trans, fs_info, bytenr,
-                               time_seq, *leafs, NULL, extent_item_pos, 0, 0);
+       ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
+                               *leafs, NULL, extent_item_pos, 0, 0, 0);
        if (ret < 0 && ret != -ENOENT) {
                free_leaf_list(*leafs);
                return ret;
@@ -1202,8 +1545,8 @@ static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans,
 
        ULIST_ITER_INIT(&uiter);
        while (1) {
-               ret = find_parent_nodes(trans, fs_info, bytenr,
-                                       time_seq, tmp, *roots, NULL, 0, 0);
+               ret = find_parent_nodes(trans, fs_info, bytenr, time_seq,
+                                       tmp, *roots, NULL, 0, 0, 0);
                if (ret < 0 && ret != -ENOENT) {
                        ulist_free(tmp);
                        ulist_free(*roots);
@@ -1273,7 +1616,7 @@ int btrfs_check_shared(struct btrfs_trans_handle *trans,
        ULIST_ITER_INIT(&uiter);
        while (1) {
                ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
-                                       roots, NULL, root_objectid, inum);
+                                       roots, NULL, root_objectid, inum, 1);
                if (ret == BACKREF_FOUND_SHARED) {
                        /* this is the only condition under which we return 1 */
                        ret = 1;
index 44fe66b..8644df8 100644 (file)
@@ -20,6 +20,7 @@
 #include "locking.h"
 #include "rcu-string.h"
 #include "backref.h"
+#include "transaction.h"
 
 static struct kmem_cache *extent_state_cache;
 static struct kmem_cache *extent_buffer_cache;
@@ -4487,21 +4488,36 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                        flags |= (FIEMAP_EXTENT_DELALLOC |
                                  FIEMAP_EXTENT_UNKNOWN);
                } else if (fieinfo->fi_extents_max) {
+                       struct btrfs_trans_handle *trans;
+
                        u64 bytenr = em->block_start -
                                (em->start - em->orig_start);
 
                        disko = em->block_start + offset_in_extent;
 
                        /*
+                        * We need a trans handle to get delayed refs
+                        */
+                       trans = btrfs_join_transaction(root);
+                       /*
+                        * It's OK if we can't start a trans we can still check
+                        * from commit_root
+                        */
+                       if (IS_ERR(trans))
+                               trans = NULL;
+
+                       /*
                         * As btrfs supports shared space, this information
                         * can be exported to userspace tools via
                         * flag FIEMAP_EXTENT_SHARED.  If fi_extents_max == 0
                         * then we're just getting a count and we can skip the
                         * lookup stuff.
                         */
-                       ret = btrfs_check_shared(NULL, root->fs_info,
+                       ret = btrfs_check_shared(trans, root->fs_info,
                                                 root->objectid,
                                                 btrfs_ino(inode), bytenr);
+                       if (trans)
+                               btrfs_end_transaction(trans, root);
                        if (ret < 0)
                                goto out_free;
                        if (ret)