On 2018年06月26日 14:00, Misono Tomohiro wrote:
> Hello Nikolay,
>
> I noticed that commit 5d23515be669 ("btrfs: Move qgroup rescan
> on quota enable to btrfs_quota_enable") in 4.17 sometimes causes
> to fail correctly rescanning quota when quota is enabled.
>
> Simple reproducer:
>
> $ mkfs.btrfs -f $DEV
> $ mount $DEV /mnt
> $ dd if=/dev/urandom of=/mnt/file bs=1000 count=1000
> $ btrfs quota enbale /mnt
> $ umount /mnt
> $ btrfs check $DEV
> ...
> checking quota groups
> Counts for qgroup id: 0/5 are different
> our: referenced 1019904 referenced compressed 1019904
> disk: referenced 16384 referenced compressed 16384
> diff: referenced 1003520 referenced compressed 1003520
> our: exclusive 1019904 exclusive compressed 1019904
> disk: exclusive 16384 exclusive compressed 16384
> diff: exclusive 1003520 exclusive compressed 1003520
> found 1413120 bytes used, error(s) found
> ...
>
> This can be also observed in btrfs/114. (Note that progs < 4.17
> returns error code 0 even if quota is not consistency and therefore
> test will incorrectly pass.)
BTW, would you please try to dump the quota tree for such mismatch case?
It could be a btrfs-progs bug which it should skip quota checking if it
found the quota status item has RESCAN flag.
Thanks,
Qu
>
> My observation is that this commit changed to call initial quota rescan
> when quota is enabeld instead of first comit transaction after enabling
> quota, and therefore if there is something not commited at that time,
> their usage will not be accounted.
>
> Actually this can be simply fixed by calling "btrfs rescan" again or
> calling "btrfs fi sync" before "btrfs quota enable".
>
> I think the commit itself makes the code much easier to read, so it may
> be better to fix the problem in progs (i.e. calling sync before quota enable).
>
> Do you have any thoughts?
>
> Thanks,
> Tomohiro Misono
>
>
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