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//kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_BTRFS) += btrfs.o
  23
  24//config:
  25//config:config FEATURE_VOLUMEID_BTRFS
  26//config:       bool "btrfs filesystem"
  27//config:       default y
  28//config:       depends on VOLUMEID
  29//config:       help
  30//config:         TODO
  31//config:
  32
  33#include "volume_id_internal.h"
  34
  35#define BTRFS_UUID_SIZE 16
  36#define BTRFS_LABEL_SIZE 256
  37#define BTRFS_CSUM_SIZE 32
  38#define BTRFS_FSID_SIZE 16
  39
  40#define BTRFS_MAGIC "_BHRfS_M"
  41
  42struct btrfs_dev_item {
  43        uint64_t devid;
  44        uint64_t total_bytes;
  45        uint64_t bytes_used;
  46        uint32_t io_align;
  47        uint32_t io_width;
  48        uint32_t sector_size;
  49        uint64_t type;
  50        uint64_t generation;
  51        uint64_t start_offset;
  52        uint32_t dev_group;
  53        uint8_t seek_speed;
  54        uint8_t bandwidth;
  55        uint8_t uuid[BTRFS_UUID_SIZE];
  56        uint8_t fsid[BTRFS_UUID_SIZE];
  57} PACKED;
  58
  59struct btrfs_super_block {
  60        uint8_t csum[BTRFS_CSUM_SIZE];
  61        uint8_t fsid[BTRFS_FSID_SIZE];  // UUID
  62        uint64_t bytenr;
  63        uint64_t flags;
  64        uint8_t magic[8];
  65        uint64_t generation;
  66        uint64_t root;
  67        uint64_t chunk_root;
  68        uint64_t log_root;
  69        uint64_t log_root_transid;
  70        uint64_t total_bytes;
  71        uint64_t bytes_used;
  72        uint64_t root_dir_objectid;
  73        uint64_t num_devices;
  74        uint32_t sectorsize;
  75        uint32_t nodesize;
  76        uint32_t leafsize;
  77        uint32_t stripesize;
  78        uint32_t sys_chunk_array_size;
  79        uint64_t chunk_root_generation;
  80        uint64_t compat_flags;
  81        uint64_t compat_ro_flags;
  82        uint64_t incompat_flags;
  83        uint16_t csum_type;
  84        uint8_t root_level;
  85        uint8_t chunk_root_level;
  86        uint8_t log_root_level;
  87        struct btrfs_dev_item dev_item;
  88        uint8_t label[BTRFS_LABEL_SIZE];        // LABEL
  89        // ...
  90} PACKED;
  91
  92int FAST_FUNC volume_id_probe_btrfs(struct volume_id *id /*,uint64_t off*/)
  93{
  94        // btrfs has superblocks at 64K, 64M and 256G
  95        // minimum btrfs size is 256M
  96        // so we never step out the device if we analyze
  97        // the first and the second superblocks
  98        struct btrfs_super_block *sb;
  99        unsigned off = 64;
 100
 101        while (off < 64*1024*1024) {
 102                off *= 1024;
 103                dbg("btrfs: probing at offset 0x%x", off);
 104
 105                sb = volume_id_get_buffer(id, off, sizeof(*sb));
 106                if (sb == NULL)
 107                        return -1;
 108
 109                if (memcmp(sb->magic, BTRFS_MAGIC, 8) != 0)
 110                        return -1;
 111        }
 112
 113        // N.B.: btrfs natively supports 256 (>VOLUME_ID_LABEL_SIZE) size labels
 114        volume_id_set_label_string(id, sb->label, VOLUME_ID_LABEL_SIZE);
 115        volume_id_set_uuid(id, sb->fsid, UUID_DCE);
 116        IF_FEATURE_BLKID_TYPE(id->type = "btrfs";)
 117
 118        return 0;
 119}
 120