On 2018/06/27 17:10, Qu Wenruo wrote:
>
>
> 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.
Yes, this is what I see after running btrfs/114 (/dev/sdh1 is scratch dev):
$ sudo btrfs check -Q /dev/sdh1
Checking filesystem on /dev/sdh1
UUID: d07f6028-0ae7-40d4-ac45-01a4505ddcfb
Print quota groups for /dev/sdh1
UUID: d07f6028-0ae7-40d4-ac45-01a4505ddcfb
Counts for qgroup id: 0/5 are different
our: referenced 170999808 referenced compressed 170999808
disk: referenced 16384 referenced compressed 16384
diff: referenced 170983424 referenced compressed 170983424
our: exclusive 170999808 exclusive compressed 170999808
disk: exclusive 16384 exclusive compressed 16384
diff: exclusive 170983424 exclusive compressed 170983424
$ sudo btrfs inspect-internal dump-tree -t quota /dev/sdh1
btrfs-progs v4.17
quota tree key (QUOTA_TREE ROOT_ITEM 0)
leaf 213958656 items 3 free space 16096 generation 9 owner QUOTA_TREE
leaf 213958656 flags 0x1(WRITTEN) backref revision 1
fs uuid d07f6028-0ae7-40d4-ac45-01a4505ddcfb
chunk uuid 78d753d0-eeb7-4c3e-b825-b6c2c5de5c7a
item 0 key (0 QGROUP_STATUS 0) itemoff 16251 itemsize 32
version 1 generation 9 flags ON scan 30572545
item 1 key (0 QGROUP_INFO 0/5) itemoff 16211 itemsize 40
generation 7
referenced 16384 referenced_compressed 16384
exclusive 16384 exclusive_compressed 16384
item 2 key (0 QGROUP_LIMIT 0/5) itemoff 16171 itemsize 40
flags 0
max_referenced 0 max_exclusive 0
rsv_referenced 0 rsv_exclusive 0
total bytes 26843545600
bytes used 171769856
uuid d07f6028-0ae7-40d4-ac45-01a4505ddcfb
And if I mount+rescan again:
$ sudo mount /dev/sdh1 /mnt
$ sudo btrfs quota rescan -w /mnt
$ sudo umount /mnt
$ sudo btrfs check -Q /dev/sdh1
Checking filesystem on /dev/sdh1
UUID: d07f6028-0ae7-40d4-ac45-01a4505ddcfb
Print quota groups for /dev/sdh1
UUID: d07f6028-0ae7-40d4-ac45-01a4505ddcfb
Counts for qgroup id: 0/5
our: referenced 170999808 referenced compressed 170999808
disk: referenced 170999808 referenced compressed 170999808
our: exclusive 170999808 exclusive compressed 170999808
disk: exclusive 170999808 exclusive compressed 170999808
$ sudo btrfs inspect-internal dump-tree -t quota /dev/sdh1
btrfs-progs v4.17
quota tree key (QUOTA_TREE ROOT_ITEM 0)
leaf 31309824 items 3 free space 16096 generation 13 owner QUOTA_TREE
leaf 31309824 flags 0x1(WRITTEN) backref revision 1
fs uuid d07f6028-0ae7-40d4-ac45-01a4505ddcfb
chunk uuid 78d753d0-eeb7-4c3e-b825-b6c2c5de5c7a
item 0 key (0 QGROUP_STATUS 0) itemoff 16251 itemsize 32
version 1 generation 13 flags ON scan 213827585
item 1 key (0 QGROUP_INFO 0/5) itemoff 16211 itemsize 40
generation 11
referenced 170999808 referenced_compressed 170999808
exclusive 170999808 exclusive_compressed 170999808
item 2 key (0 QGROUP_LIMIT 0/5) itemoff 16171 itemsize 40
flags 0
max_referenced 0 max_exclusive 0
rsv_referenced 0 rsv_exclusive 0
total bytes 26843545600
bytes used 171769856
uuid d07f6028-0ae7-40d4-ac45-01a4505ddcfb
>
> 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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>
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