btrfs-find-root.c

   1 /*
   2  * Copyright (C) 2011 Red Hat.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #define _XOPEN_SOURCE 500
  20 #define _GNU_SOURCE 1
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <fcntl.h>
  25 #include <sys/stat.h>
  26 #include <zlib.h>
  27 #include "kerncompat.h"
  28 #include "ctree.h"
  29 #include "disk-io.h"
  30 #include "print-tree.h"
  31 #include "transaction.h"
  32 #include "list.h"
  33 #include "version.h"
  34 #include "volumes.h"
  35 #include "utils.h"
  36 #include "crc32c.h"
  37
  38 static u16 csum_size = 0;
  39 static u64 search_objectid = BTRFS_ROOT_TREE_OBJECTID;
  40
  41 static void usage()
  42 {
  43         fprintf(stderr, "Usage: find-roots [-o search_objectid] <device>\n");
  44 }
  45
  46 int csum_block(void *buf, u32 len)
  47 {
  48         char *result;
  49         u32 crc = ~(u32)0;
  50         int ret = 0;
  51
  52         result = malloc(csum_size * sizeof(char));
  53         if (!result) {
  54                 fprintf(stderr, "No memory\n");
  55                 return 1;
  56         }
  57
  58         len -= BTRFS_CSUM_SIZE;
  59         crc = crc32c(crc, buf + BTRFS_CSUM_SIZE, len);
  60         btrfs_csum_final(crc, result);
  61
  62         if (memcmp(buf, result, csum_size))
  63                 ret = 1;
  64         free(result);
  65         return ret;
  66 }
  67
  68 static struct btrfs_root *open_ctree_broken(int fd, const char *device)
  69 {
  70         struct btrfs_fs_info *fs_info;
  71         struct btrfs_super_block *disk_super;
  72         struct btrfs_fs_devices *fs_devices = NULL;
  73         struct extent_buffer *eb;
  74         int ret;
  75
  76         fs_info = btrfs_new_fs_info(0, BTRFS_SUPER_INFO_OFFSET);
  77         if (!fs_info) {
  78                 fprintf(stderr, "Failed to allocate memory for fs_info\n");
  79                 return NULL;
  80         }
  81
  82         ret = btrfs_scan_fs_devices(fd, device, &fs_devices);
  83         if (ret)
  84                 goto out;
  85
  86         fs_info->fs_devices = fs_devices;
  87
  88         ret = btrfs_open_devices(fs_devices, O_RDONLY);
  89         if (ret)
  90                 goto out_devices;
  91
  92         disk_super = fs_info->super_copy;
  93         ret = btrfs_read_dev_super(fs_devices->latest_bdev,
  94                                    disk_super, fs_info->super_bytenr);
  95         if (ret) {
  96                 printk("No valid btrfs found\n");
  97                 goto out_devices;
  98         }
  99
 100         memcpy(fs_info->fsid, &disk_super->fsid, BTRFS_FSID_SIZE);
 101
 102         ret = btrfs_check_fs_compatibility(disk_super, 0);
 103         if (ret)
 104                 goto out_devices;
 105
 106         ret = btrfs_setup_chunk_tree_and_device_map(fs_info);
 107         if (ret)
 108                 goto out_chunk;
 109
 110         eb = fs_info->chunk_root->node;
 111         read_extent_buffer(eb, fs_info->chunk_tree_uuid,
 112                            (unsigned long)btrfs_header_chunk_tree_uuid(eb),
 113                            BTRFS_UUID_SIZE);
 114
 115         return fs_info->chunk_root;
 116 out_chunk:
 117         free_extent_buffer(fs_info->chunk_root->node);
 118         btrfs_cleanup_all_caches(fs_info);
 119 out_devices:
 120         btrfs_close_devices(fs_info->fs_devices);
 121 out:
 122         btrfs_free_fs_info(fs_info);
 123         return NULL;
 124 }
 125
 126 static int search_iobuf(struct btrfs_root *root, void *iobuf,
 127                         size_t iobuf_size, off_t offset)
 128 {
 129         u64 gen = btrfs_super_generation(root->fs_info->super_copy);
 130         u64 objectid = search_objectid;
 131         u32 size = btrfs_super_nodesize(root->fs_info->super_copy);
 132         u8 level = root->fs_info->super_copy->root_level;
 133         size_t block_off = 0;
 134
 135         while (block_off < iobuf_size) {
 136                 void *block = iobuf + block_off;
 137                 struct btrfs_header *header = block;
 138                 u64 h_byte, h_level, h_gen, h_owner;
 139
 140 //              printf("searching %Lu\n", offset + block_off);
 141                 h_byte = le64_to_cpu(header->bytenr);
 142                 h_owner = le64_to_cpu(header->owner);
 143                 h_level = header->level;
 144                 h_gen = le64_to_cpu(header->generation);
 145
 146                 if (h_owner != objectid)
 147                         goto next;
 148                 if (h_byte != (offset + block_off))
 149                         goto next;
 150                 if (h_level != level)
 151                         goto next;
 152                 if (csum_block(block, size)) {
 153                         fprintf(stderr, "Well block %Lu seems good, "
 154                                 "but the csum doesn't match\n",
 155                                 h_byte);
 156                         goto next;
 157                 }
 158                 if (h_gen != gen) {
 159                         fprintf(stderr, "Well block %Lu seems great, "
 160                                 "but generation doesn't match, "
 161                                 "have=%Lu, want=%Lu\n", h_byte, h_gen,
 162                                 gen);
 163                         goto next;
 164                 }
 165                 printf("Found tree root at %Lu\n", h_byte);
 166                 return 0;
 167 next:
 168                 block_off += size;
 169         }
 170
 171         return 1;
 172 }
 173
 174 static int read_physical(struct btrfs_root *root, int fd, u64 offset,
 175                          u64 bytenr, u64 len)
 176 {
 177         char *iobuf = malloc(len);
 178         ssize_t done;
 179         size_t total_read = 0;
 180         int ret = 1;
 181
 182         if (!iobuf) {
 183                 fprintf(stderr, "No memory\n");
 184                 return -1;
 185         }
 186
 187         while (total_read < len) {
 188                 done = pread64(fd, iobuf + total_read, len - total_read,
 189                                bytenr + total_read);
 190                 if (done < 0) {
 191                         fprintf(stderr, "Failed to read: %s\n",
 192                                 strerror(errno));
 193                         ret = -1;
 194                         goto out;
 195                 }
 196                 total_read += done;
 197         }
 198
 199         ret = search_iobuf(root, iobuf, total_read, offset);
 200 out:
 201         free(iobuf);
 202         return ret;
 203 }
 204
 205 static int find_root(struct btrfs_root *root)
 206 {
 207         struct btrfs_multi_bio *multi = NULL;
 208         struct btrfs_device *device;
 209         u64 metadata_offset = 0, metadata_size = 0;
 210         off_t offset = 0;
 211         off_t bytenr;
 212         int fd;
 213         int err;
 214         int ret = 1;
 215
 216         printf("Super think's the tree root is at %Lu, chunk root %Lu\n",
 217                btrfs_super_root(root->fs_info->super_copy),
 218                btrfs_super_chunk_root(root->fs_info->super_copy));
 219
 220         err = btrfs_next_metadata(&root->fs_info->mapping_tree,
 221                                   &metadata_offset, &metadata_size);
 222         if (err)
 223                 return ret;
 224
 225         offset = metadata_offset;
 226         while (1) {
 227                 u64 map_length = 4096;
 228                 u64 type;
 229
 230                 if (offset >
 231                     btrfs_super_total_bytes(root->fs_info->super_copy)) {
 232                         printf("Went past the fs size, exiting");
 233                         break;
 234                 }
 235                 if (offset >= (metadata_offset + metadata_size)) {
 236                         err = btrfs_next_metadata(&root->fs_info->mapping_tree,
 237                                                   &metadata_offset,
 238                                                   &metadata_size);
 239                         if (err) {
 240                                 printf("No more metdata to scan, exiting\n");
 241                                 break;
 242                         }
 243                         offset = metadata_offset;
 244                 }
 245                 err = __btrfs_map_block(&root->fs_info->mapping_tree, READ,
 246                                       offset, &map_length, &type,
 247                                       &multi, 0, NULL);
 248                 if (err) {
 249                         offset += map_length;
 250                         continue;
 251                 }
 252
 253                 if (!(type & BTRFS_BLOCK_GROUP_METADATA)) {
 254                         offset += map_length;
 255                         kfree(multi);
 256                         continue;
 257                 }
 258
 259                 device = multi->stripes[0].dev;
 260                 fd = device->fd;
 261                 bytenr = multi->stripes[0].physical;
 262                 kfree(multi);
 263
 264                 err = read_physical(root, fd, offset, bytenr, map_length);
 265                 if (!err) {
 266                         ret = 0;
 267                         break;
 268                 } else if (err < 0) {
 269                         ret = err;
 270                         break;
 271                 }
 272                 offset += map_length;
 273         }
 274         return ret;
 275 }
 276
 277 int main(int argc, char **argv)
 278 {
 279         struct btrfs_root *root;
 280         int dev_fd;
 281         int opt;
 282         int ret;
 283
 284         while ((opt = getopt(argc, argv, "o:")) != -1) {
 285                 switch(opt) {
 286                         case 'o':
 287                                 errno = 0;
 288                                 search_objectid = (u64)strtoll(optarg, NULL,
 289                                                                10);
 290                                 if (errno) {
 291                                         fprintf(stderr, "Error parsing "
 292                                                 "objectid\n");
 293                                         exit(1);
 294                                 }
 295                                 break;
 296                         default:
 297                                 usage();
 298                                 exit(1);
 299                 }
 300         }
 301
 302         if (optind >= argc) {
 303                 usage();
 304                 exit(1);
 305         }
 306
 307         dev_fd = open(argv[optind], O_RDONLY);
 308         if (dev_fd < 0) {
 309                 fprintf(stderr, "Failed to open device %s\n", argv[optind]);
 310                 exit(1);
 311         }
 312
 313         root = open_ctree_broken(dev_fd, argv[optind]);
 314         close(dev_fd);
 315
 316         if (!root) {
 317                 fprintf(stderr, "Open ctree failed\n");
 318                 exit(1);
 319         }
 320
 321         csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 322         ret = find_root(root);
 323         close_ctree(root);
 324         return ret;
 325 }