LXR busybox/util-linux/volume

   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
  22#include "volume_id_internal.h"
  23
  24#define BTRFS_UUID_SIZE 16
  25#define BTRFS_LABEL_SIZE 256
  26#define BTRFS_CSUM_SIZE 32
  27#define BTRFS_FSID_SIZE 16
  28
  29#define BTRFS_MAGIC "_BHRfS_M"
  30
  31struct btrfs_dev_item {
  32        uint64_t devid;
  33        uint64_t total_bytes;
  34        uint64_t bytes_used;
  35        uint32_t io_align;
  36        uint32_t io_width;
  37        uint32_t sector_size;
  38        uint64_t type;
  39        uint64_t generation;
  40        uint64_t start_offset;
  41        uint32_t dev_group;
  42        uint8_t seek_speed;
  43        uint8_t bandwidth;
  44        uint8_t uuid[BTRFS_UUID_SIZE];
  45        uint8_t fsid[BTRFS_UUID_SIZE];
  46} PACKED;
  47
  48struct btrfs_super_block {
  49        uint8_t csum[BTRFS_CSUM_SIZE];
  50        uint8_t fsid[BTRFS_FSID_SIZE];  // UUID
  51        uint64_t bytenr;
  52        uint64_t flags;
  53        uint8_t magic[8];
  54        uint64_t generation;
  55        uint64_t root;
  56        uint64_t chunk_root;
  57        uint64_t log_root;
  58        uint64_t log_root_transid;
  59        uint64_t total_bytes;
  60        uint64_t bytes_used;
  61        uint64_t root_dir_objectid;
  62        uint64_t num_devices;
  63        uint32_t sectorsize;
  64        uint32_t nodesize;
  65        uint32_t leafsize;
  66        uint32_t stripesize;
  67        uint32_t sys_chunk_array_size;
  68        uint64_t chunk_root_generation;
  69        uint64_t compat_flags;
  70        uint64_t compat_ro_flags;
  71        uint64_t incompat_flags;
  72        uint16_t csum_type;
  73        uint8_t root_level;
  74        uint8_t chunk_root_level;
  75        uint8_t log_root_level;
  76        struct btrfs_dev_item dev_item;
  77        uint8_t label[BTRFS_LABEL_SIZE];        // LABEL
  78        // ...
  79} PACKED;
  80
  81int FAST_FUNC volume_id_probe_btrfs(struct volume_id *id /*,uint64_t off*/)
  82{
  83        // btrfs has superblocks at 64K, 64M and 256G
  84        // minimum btrfs size is 256M
  85        // so we never step out the device if we analyze
  86        // the first and the second superblocks
  87        struct btrfs_super_block *sb;
  88        unsigned off = 64;
  89
  90        while (off < 64*1024*1024) {
  91                off *= 1024;
  92                dbg("btrfs: probing at offset 0x%x", off);
  93
  94                sb = volume_id_get_buffer(id, off, sizeof(*sb));
  95                if (sb == NULL)
  96                        return -1;
  97
  98                if (memcmp(sb->magic, BTRFS_MAGIC, 8) != 0)
  99                        return -1;
 100        }
 101
 102        // N.B.: btrfs natively supports 256 (>VOLUME_ID_LABEL_SIZE) size labels
 103        volume_id_set_label_string(id, sb->label, VOLUME_ID_LABEL_SIZE);
 104        volume_id_set_uuid(id, sb->fsid, UUID_DCE);
 105
 106        return 0;
 107}
 108