2 * volume_id - reads filesystem label and uuid
4 * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
5 * Copyright (C) 2009 Vladimir Dronnikov <dronnikov@gmail.com>
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.
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.
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
22 //kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_BTRFS) += btrfs.o
25 //config:config FEATURE_VOLUMEID_BTRFS
26 //config: bool "btrfs filesystem"
28 //config: depends on VOLUMEID
33 #include "volume_id_internal.h"
35 #define BTRFS_UUID_SIZE 16
36 #define BTRFS_LABEL_SIZE 256
37 #define BTRFS_CSUM_SIZE 32
38 #define BTRFS_FSID_SIZE 16
40 #define BTRFS_MAGIC "_BHRfS_M"
42 struct btrfs_dev_item {
51 uint64_t start_offset;
55 uint8_t uuid[BTRFS_UUID_SIZE];
56 uint8_t fsid[BTRFS_UUID_SIZE];
59 struct btrfs_super_block {
60 uint8_t csum[BTRFS_CSUM_SIZE];
61 uint8_t fsid[BTRFS_FSID_SIZE]; // UUID
69 uint64_t log_root_transid;
72 uint64_t root_dir_objectid;
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;
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
92 int FAST_FUNC volume_id_probe_btrfs(struct volume_id *id /*,uint64_t off*/)
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;
101 while (off < 64*1024*1024) {
103 dbg("btrfs: probing at offset 0x%x", off);
105 sb = volume_id_get_buffer(id, off, sizeof(*sb));
109 if (memcmp(sb->magic, BTRFS_MAGIC, 8) != 0)
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";)