btrfs.c 2.9 KB

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  1. /*
  2. * volume_id - reads filesystem label and uuid
  3. *
  4. * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
  5. * Copyright (C) 2009 Vladimir Dronnikov <dronnikov@gmail.com>
  6. *
  7. * This library is free software; you can redistribute it and/or
  8. * modify it under the terms of the GNU Lesser General Public
  9. * License as published by the Free Software Foundation; either
  10. * version 2.1 of the License, or (at your option) any later version.
  11. *
  12. * This library is distributed in the hope that it will be useful,
  13. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15. * Lesser General Public License for more details.
  16. *
  17. * You should have received a copy of the GNU Lesser General Public
  18. * License along with this library; if not, write to the Free Software
  19. * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  20. */
  21. #include "volume_id_internal.h"
  22. #define BTRFS_UUID_SIZE 16
  23. #define BTRFS_LABEL_SIZE 256
  24. #define BTRFS_CSUM_SIZE 32
  25. #define BTRFS_FSID_SIZE 16
  26. #define BTRFS_MAGIC "_BHRfS_M"
  27. struct btrfs_dev_item {
  28. uint64_t devid;
  29. uint64_t total_bytes;
  30. uint64_t bytes_used;
  31. uint32_t io_align;
  32. uint32_t io_width;
  33. uint32_t sector_size;
  34. uint64_t type;
  35. uint64_t generation;
  36. uint64_t start_offset;
  37. uint32_t dev_group;
  38. uint8_t seek_speed;
  39. uint8_t bandwidth;
  40. uint8_t uuid[BTRFS_UUID_SIZE];
  41. uint8_t fsid[BTRFS_UUID_SIZE];
  42. } PACKED;
  43. struct btrfs_super_block {
  44. uint8_t csum[BTRFS_CSUM_SIZE];
  45. uint8_t fsid[BTRFS_FSID_SIZE]; // UUID
  46. uint64_t bytenr;
  47. uint64_t flags;
  48. uint8_t magic[8];
  49. uint64_t generation;
  50. uint64_t root;
  51. uint64_t chunk_root;
  52. uint64_t log_root;
  53. uint64_t log_root_transid;
  54. uint64_t total_bytes;
  55. uint64_t bytes_used;
  56. uint64_t root_dir_objectid;
  57. uint64_t num_devices;
  58. uint32_t sectorsize;
  59. uint32_t nodesize;
  60. uint32_t leafsize;
  61. uint32_t stripesize;
  62. uint32_t sys_chunk_array_size;
  63. uint64_t chunk_root_generation;
  64. uint64_t compat_flags;
  65. uint64_t compat_ro_flags;
  66. uint64_t incompat_flags;
  67. uint16_t csum_type;
  68. uint8_t root_level;
  69. uint8_t chunk_root_level;
  70. uint8_t log_root_level;
  71. struct btrfs_dev_item dev_item;
  72. uint8_t label[BTRFS_LABEL_SIZE]; // LABEL
  73. // ...
  74. } PACKED;
  75. int FAST_FUNC volume_id_probe_btrfs(struct volume_id *id /*,uint64_t off*/)
  76. {
  77. // btrfs has superblocks at 64K, 64M and 256G
  78. // minimum btrfs size is 256M
  79. // so we never step out the device if we analyze
  80. // the first and the second superblocks
  81. struct btrfs_super_block *sb;
  82. unsigned off = 64;
  83. while (off < 64*1024*1024) {
  84. off *= 1024;
  85. dbg("btrfs: probing at offset 0x%x", off);
  86. sb = volume_id_get_buffer(id, off, sizeof(*sb));
  87. if (sb == NULL)
  88. return -1;
  89. if (memcmp(sb->magic, BTRFS_MAGIC, 8) != 0)
  90. return -1;
  91. }
  92. // N.B.: btrfs natively supports 256 (>VOLUME_ID_LABEL_SIZE) size labels
  93. volume_id_set_label_string(id, sb->label, VOLUME_ID_LABEL_SIZE);
  94. volume_id_set_uuid(id, sb->fsid, UUID_DCE);
  95. return 0;
  96. }