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 #include "volume_id_internal.h"
24 #define BTRFS_UUID_SIZE 16
25 #define BTRFS_LABEL_SIZE 256
26 #define BTRFS_CSUM_SIZE 32
27 #define BTRFS_FSID_SIZE 16
29 #define BTRFS_MAGIC "_BHRfS_M"
31 struct btrfs_dev_item {
40 uint64_t start_offset;
44 uint8_t uuid[BTRFS_UUID_SIZE];
45 uint8_t fsid[BTRFS_UUID_SIZE];
48 struct btrfs_super_block {
49 uint8_t csum[BTRFS_CSUM_SIZE];
50 uint8_t fsid[BTRFS_FSID_SIZE]; // UUID
58 uint64_t log_root_transid;
61 uint64_t root_dir_objectid;
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;
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
81 int FAST_FUNC volume_id_probe_btrfs(struct volume_id *id /*,uint64_t off*/)
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;
90 while (off < 64*1024*1024) {
92 dbg("btrfs: probing at offset 0x%x", off);
94 sb = volume_id_get_buffer(id, off, sizeof(*sb));
98 if (memcmp(sb->magic, BTRFS_MAGIC, 8) != 0)
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);