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//config:config FEATURE_VOLUMEID_BTRFS
  22//config:       bool "btrfs filesystem"
  23//config:       default y
  24//config:       depends on VOLUMEID
  25
  26//kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_BTRFS) += btrfs.o
  27
  28#include "volume_id_internal.h"
  29
  30#define BTRFS_UUID_SIZE 16
  31#define BTRFS_LABEL_SIZE 256
  32#define BTRFS_CSUM_SIZE 32
  33#define BTRFS_FSID_SIZE 16
  34
  35#define BTRFS_MAGIC "_BHRfS_M"
  36
  37struct btrfs_dev_item {
  38        uint64_t devid;
  39        uint64_t total_bytes;
  40        uint64_t bytes_used;
  41        uint32_t io_align;
  42        uint32_t io_width;
  43        uint32_t sector_size;
  44        uint64_t type;
  45        uint64_t generation;
  46        uint64_t start_offset;
  47        uint32_t dev_group;
  48        uint8_t seek_speed;
  49        uint8_t bandwidth;
  50        uint8_t uuid[BTRFS_UUID_SIZE];
  51        uint8_t fsid[BTRFS_UUID_SIZE];
  52} PACKED;
  53
  54struct btrfs_super_block {
  55        uint8_t csum[BTRFS_CSUM_SIZE];
  56        uint8_t fsid[BTRFS_FSID_SIZE];  // UUID
  57        uint64_t bytenr;
  58        uint64_t flags;
  59        uint8_t magic[8];
  60        uint64_t generation;
  61        uint64_t root;
  62        uint64_t chunk_root;
  63        uint64_t log_root;
  64        uint64_t log_root_transid;
  65        uint64_t total_bytes;
  66        uint64_t bytes_used;
  67        uint64_t root_dir_objectid;
  68        uint64_t num_devices;
  69        uint32_t sectorsize;
  70        uint32_t nodesize;
  71        uint32_t leafsize;
  72        uint32_t stripesize;
  73        uint32_t sys_chunk_array_size;
  74        uint64_t chunk_root_generation;
  75        uint64_t compat_flags;
  76        uint64_t compat_ro_flags;
  77        uint64_t incompat_flags;
  78        uint16_t csum_type;
  79        uint8_t root_level;
  80        uint8_t chunk_root_level;
  81        uint8_t log_root_level;
  82        struct btrfs_dev_item dev_item;
  83        uint8_t label[BTRFS_LABEL_SIZE];        // LABEL
  84        // ...
  85} PACKED;
  86
  87int FAST_FUNC volume_id_probe_btrfs(struct volume_id *id /*,uint64_t off*/)
  88{
  89        // btrfs has superblocks at 64K, 64M and 256G
  90        // minimum btrfs size is 256M
  91        // so we never step out the device if we analyze
  92        // the first and the second superblocks
  93        struct btrfs_super_block *sb;
  94        unsigned off = 64;
  95
  96        while (off < 64*1024*1024) {
  97                off *= 1024;
  98                dbg("btrfs: probing at offset 0x%x", off);
  99
 100                sb = volume_id_get_buffer(id, off, sizeof(*sb));
 101                if (sb == NULL)
 102                        return -1;
 103
 104                if (memcmp(sb->magic, BTRFS_MAGIC, 8) != 0)
 105                        return -1;
 106        }
 107
 108        // N.B.: btrfs natively supports 256 (>VOLUME_ID_LABEL_SIZE) size labels
 109        volume_id_set_label_string(id, sb->label, VOLUME_ID_LABEL_SIZE);
 110        volume_id_set_uuid(id, sb->fsid, UUID_DCE);
 111        IF_FEATURE_BLKID_TYPE(id->type = "btrfs";)
 112
 113        return 0;
 114}
 115