On Tue, Oct 31, 2017 at 08:34:50PM +0800, Hou Tao wrote:
> Hi Eryu,
>
> Thanks for your detailed review.
>
> On 2017/10/31 14:46, Eryu Guan wrote:
> > On Thu, Oct 26, 2017 at 03:37:52PM +0800, Hou Tao wrote:
> >> When the first writeback and the retried writeback of dquota buffer get
> >> the same IO error, XFS will let xfsaild to restart the writeback and
> >> xfs_qm_dqflush_done() will not be invoked. xfsaild will try to re-push
> >> the quota log item in AIL, the push will return early everytime after
> >> checking xfs_dqflock_nowait(), and xfsaild will try to push it again.
> >>
> >> IOWs, AIL will never be empty, and the umount process will wait for the
> >> drain of AIL, so the umount process hangs.
> >>
> >> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
> >
> > Sorry for the late review. Is there a specific patch or patchset fixed
> > this bug? I tested on v4.14-rc2 kernel and for-next branch on Darrick's
> > tree, test survivied multiple runs on both kernels.
> The problem has not been fixed yet, and Carlos Maiolino is working on the it [1].
> The pass of the test case is out of my expectation. I had tried it on v4.14-rc6,
> and the test case hangs on umount.
>
> Have you applied the first patch "[PATCH 1/2] dmflakey: support multiple dm targets
> for a dm-flakey device" during the test ? If you have applied it, could you show me
> the full result file of the test case, namely results/xfs/999.full ?
Yes, I applied both of your patches before testing. Test host is a kvm
guest with 4 vcpus and 8G mem running v4.14-rc2 kernel. Below is the
xfs/999.full
me: flakey-test
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 0
Major, minor: 252, 0
Number of targets: 1
flakey-test: 0 31457280 linear 253:6 0
MOUNT_OPTIONS = -o usrquota
User quota on /mnt/testarea/scratch (/dev/mapper/flakey-test)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
fsgqa 0 500 0 00 [------]
User quota on /mnt/testarea/scratch (/dev/mapper/flakey-test)
Inodes
User ID Used Soft Hard Warn/Grace
---------- ---------------------------------
root 3 0 0 00 [------]
fsgqa 0 400 0 00 [------]
Name: flakey-test
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 252, 0
Number of targets: 3
flakey-test: 0 16777256 flakey 253:6 0 0 1 1 error_writes
flakey-test: 16777256 20480 linear 253:6 16777256
flakey-test: 16797736 14659544 flakey 253:6 16797736 0 1 1 error_writes
[snip]
> >> +
> >> +# inject write IO error
> >> +FLAKEY_TABLE=$(_make_xfs_scratch_flakey_table)
> >> +_load_flakey_table $FLAKEY_ALLOW_WRITES
> >
> > Set FLAKEY_TABLE_DROP here and call _load_flakey_table with
> > $FLAKEY_DROP_WRITES
>
> No. We need to use the customized table instead of FLAKEY_TABLE_DROP,
> because we need to let the write return IO error instead of being droppped
> silently and we need to ensure the write of the log will succeed.
I mean something like:
FLAKEY_TABLE_DROP=$(_make_xfs_scratch_flakey_table)
_load_flakey_table $FLAKEY_DROP_WRITES
This basically does the same work as your code, but loading a different
table var. _load_flakey_table selects FLAKEY_TABLE when first argument
is $FLAKEY_ALLOW_WRITES, and selects FLAKEY_TABLE_DROP when the argument
is $FLAKEY_DROP_WRITES. And because you're going to error/drop writes,
it's weired to load table with $FLAKEY_ALLOW_WRITES.
Thanks,
Eryu
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