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| author | Qu Wenruo <wqu@suse.com> | 2026-04-07 19:03:59 +0930 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2026-05-26 18:46:47 +0200 |
| commit | c2b47cf3923e6e55ecdecbe19d49ebd2991e6060 (patch) | |
| tree | 784c84205313fa7cb974f06cc27e70442c9d6262 /fs | |
| parent | 7395eb2df57f3229032a01083af72259db90cb3f (diff) | |
| download | linux-next-history-c2b47cf3923e6e55ecdecbe19d49ebd2991e6060.tar.gz | |
btrfs: remove the dev stats item when removing a device
[MINOR BUG]
The following script will cause DEV_STATS item to be left after the
corresponding device is removed:
# mkfs.btrfs -f $dev1
# mount $dev1 $mnt
# btrfs dev add $dev2 $mnt
# umount $mnt
## Without real errors, only at mount time btrfs will update
## dev->dev_stats_ccnt, thus we need a mount cycle to create the
## DEV_STATS item for the new device.
# mount $dev1 $mnt
# touch $mnt/foobar
# sync
# btrfs dev remove $dev2 $mnt
# umount $mnt
This will result the DEV_STATS item for devid 2 still left in device
tree:
device tree key (DEV_TREE ROOT_ITEM 0)
leaf 31064064 items 7 free space 15788 generation 18 owner DEV_TREE
leaf 31064064 flags 0x1(WRITTEN) backref revision 1
fs uuid 4bd853ed-f6ef-45fd-bbf1-1c3a2d9987cb
chunk uuid b496eab1-ec23-46b5-81c1-2f1b3503ca07
item 0 key (DEV_STATS PERSISTENT_ITEM 1) itemoff 16243 itemsize 40
persistent item objectid DEV_STATS offset 1
device stats
write_errs 0 read_errs 0 flush_errs 0 corruption_errs 0 generation 0
item 1 key (DEV_STATS PERSISTENT_ITEM 2) itemoff 16203 itemsize 40
persistent item objectid DEV_STATS offset 2
device stats
write_errs 0 read_errs 0 flush_errs 0 corruption_errs 0 generation 0
This is not a huge problem, but if the existing DEV_STATS contains
errors, and a new device is added into the fs taking the old devid, then
after a mount cycle, the new device will suddenly inherit old errors
which can give false alerts.
[CAUSE]
Btrfs never has the ability to delete DEV_STATS items.
It either create a new one through update_dev_stat_item(), or read an
existing one through btrfs_device_init_dev_stats().
However update_dev_stat_item() is only called lazily, if a new device is
created and no new update to dev stats, then it will skip the update of
the on-disk item.
So if the old DEV_STATS item exists and a new device is added, and no
errors during the remaining operations, the old DEV_STATS will not be
updated.
Then at the next mount cycle, btrfs_device_init_dev_stats() is called at
mount time, which will read out the old records, causing false alerts to
the newly added device.
[FIX]
Manually remove the DEV_STATS item during btrfs_rm_device().
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/volumes.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index bfbb63cf14f55..5733b964ab7e5 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2397,6 +2397,12 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, return ret; } + ret = btrfs_remove_dev_stat_item(trans, device->devid); + if (unlikely(ret)) { + btrfs_abort_transaction(trans, ret); + btrfs_end_transaction(trans); + return ret; + } clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state); btrfs_scrub_cancel_dev(device); |