Bug#1104460: [regression 6.1.y] discard/TRIM through RAID10 blocking

[Antoine Beaupré <anarcat@debian.org>]

On 2025-05-06 08:00:34, Salvatore Bonaccorso wrote:
> Hi Yu,
>
> Thanks for your followups.
>
> On Tue, May 06, 2025 at 09:25:50AM +0800, Yu Kuai wrote:
>> Hi,
>> 
>> 在 2025/05/06 4:59, Antoine Beaupré 写道:
>> > On 2025-05-05 22:36:07, Salvatore Bonaccorso wrote:
>> > > Hi Antoine,
>> > > 
>> > > On Mon, May 05, 2025 at 02:50:32PM -0400, Antoine Beaupré wrote:
>> > > > On 2025-05-05 18:02:37, Salvatore Bonaccorso wrote:
>> > > > > On Mon, May 05, 2025 at 04:00:31PM +0200, Salvatore Bonaccorso wrote:
>> > > > > > Hi Moritz,
>> > > > > > 
>> > > > > > On Mon, May 05, 2025 at 01:47:15PM +0200, Moritz Mühlenhoff wrote:
>> > > > > > > Am Wed, Apr 30, 2025 at 05:55:20PM +0200 schrieb Salvatore Bonaccorso:
>> > > > > > > > Hi
>> > > > > > > > 
>> > > > > > > > We got a regression report in Debian after the update from 6.1.133 to
>> > > > > > > > 6.1.135. Melvin is reporting that discard/trimm trhough a RAID10 array
>> > > > > > > > stalls idefintively. The full report is inlined below and originates
>> > > > > > > > from https://bugs.debian.org/1104460 .
>> > > > > > > 
>> > > > > > > JFTR, we ran into the same problem with a few Wikimedia servers running
>> > > > > > > 6.1.135 and RAID 10: The servers started to lock up once fstrim.service
>> > > > > > > got started. Full oops messages are available at
>> > > > > > > https://phabricator.wikimedia.org/P75746
>> > > > > > 
>> > > > > > Thanks for this aditional datapoints. Assuming you wont be able to
>> > > > > > thest the other stable series where the commit d05af90d6218
>> > > > > > ("md/raid10: fix missing discard IO accounting") went in, might you at
>> > > > > > least be able to test the 6.1.y branch with the commit reverted again
>> > > > > > and manually trigger the issue?
>> > > > > > 
>> > > > > > If needed I can provide a test Debian package of 6.1.135 (or 6.1.137)
>> > > > > > with the patch reverted.
>> > > > > 
>> > > > > So one additional data point as several Debian users were reporting
>> > > > > back beeing affected: One user did upgrade to 6.12.25 (where the
>> > > > > commit was backported as well) and is not able to reproduce the issue
>> > > > > there.
>> > > > 
>> > > > That would be me.
>> > > > 
>> > > > I can reproduce the issue as outlined by Moritz above fairly reliably in
>> > > > 6.1.135 (debian package 6.1.0-34-amd64). The reproducer is simple, on a
>> > > > RAID-10 host:
>> > > > 
>> > > >   1. reboot
>> > > >   2. systemctl start fstrim.service
>> > > > 
>> > > > We're tracking the issue internally in:
>> > > > 
>> > > > https://gitlab.torproject.org/tpo/tpa/team/-/issues/42146
>> > > > 
>> > > > I've managed to workaround the issue by upgrading to the Debian package
>> > > > from testing/unstable (6.12.25), as Salvatore indicated above. There,
>> > > > fstrim doesn't cause any crash and completes successfully. In stable, it
>> > > > just hangs there forever. The kernel doesn't completely panic and the
>> > > > machine is otherwise somewhat still functional: my existing SSH
>> > > > connection keeps working, for example, but new ones fail. And an `apt
>> > > > install` of another kernel hangs forever.
>> > > 
>> > > So likely at least in 6.1.y there are missing pre-requisites causing
>> > > the behaviour.
>> > > 
>> > > If you can test 6.1.135-1 with the commit
>> > > 4a05f7ae33716d996c5ce56478a36a3ede1d76f2 reverted then you can fetch
>> > > built packages at:
>> > > 
>> > > https://people.debian.org/~carnil/tmp/linux/1104460/
>> 
>> Can you also test with 4a05f7ae33716d996c5ce56478a36a3ede1d76f2 not
>> reverted, and also cherry-pick c567c86b90d4715081adfe5eb812141a5b6b4883?
>
> Thank you.
>
> Antoine, Moritz,
> https://people.debian.org/~carnil/tmp/linux/1104460-2/ contains a
> build with 4a05f7ae33716d996c5ce56478a36a3ede1d76f2 *not* reverted and
> with c567c86b90d4715081adfe5eb812141a5b6b4883 cherry-picked, can you
> test this one as well?

I tested this one, and could succesfully run fstrim.service without
problems.

A.

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