From: Dominik Brodowski <linux@dominikbrodowski.net>
To: NeilBrown <neilb@suse.com>
Cc: Shaohua Li <shli@fb.com>, David R <david@unsolicited.net>,
linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
tj@kernel.org
Subject: Re: [MD] Crash with 4.12+ kernel and high disk load -- bisected to 4ad23a976413: MD: use per-cpu counter for writes_pending
Date: Tue, 8 Aug 2017 09:36:14 +0200 [thread overview]
Message-ID: <20170808073614.GA21316@light.dominikbrodowski.net> (raw)
In-Reply-To: <87k22esfuf.fsf@notabene.neil.brown.name>
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On Tue, Aug 08, 2017 at 05:01:28PM +1000, NeilBrown wrote:
> On Mon, Aug 07 2017, Dominik Brodowski wrote:
>
> > Neil, Shaohua,
> >
> > following up on David R's bug message: I have observed something similar
> > on v4.12.[345] and v4.13-rc4, but not on v4.11. This is a RAID1 (on bare
> > metal partitions, /dev/sdaX and /dev/sdbY linked together). In case it
> > matters: Further upwards are cryptsetup, a DM volume group, then logical
> > volumes, and then filesystems (ext4, but also happened with xfs).
> >
> > In a tedious bisect (the bug wasn't as quickly reproducible as I would like,
> > but happened when I repeatedly created large lvs and filled them with some
> > content, while compiling kernels in parallel), I was able to track this
> > down to:
> >
> >
> > commit 4ad23a976413aa57fe5ba7a25953dc35ccca5b71
> > Author: NeilBrown <neilb@suse.com>
> > Date: Wed Mar 15 14:05:14 2017 +1100
> >
> > MD: use per-cpu counter for writes_pending
> >
> > The 'writes_pending' counter is used to determine when the
> > array is stable so that it can be marked in the superblock
> > as "Clean". Consequently it needs to be updated frequently
> > but only checked for zero occasionally. Recent changes to
> > raid5 cause the count to be updated even more often - once
> > per 4K rather than once per bio. This provided
> > justification for making the updates more efficient.
> >
> > ...
>
> Thanks for the report... and for bisecting and for re-sending...
>
> I believe I have found the problem, and have sent a patch separately.
>
> If mddev->safemode == 1 and mddev->in_sync != 0, md_check_recovery()
> causes the thread that calls it to spin.
> Prior to the patch you found, that couldn't happen. Now it can,
> so it needs to be handled more carefully.
>
> While I was examining the code, I found another bug - so that is a win!
>
> Thanks,
> NeilBrown
Nice catch. Thanks! Will give it (both patches at once) a try on the test
system immediately.
Thanks,
Dominik
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next prev parent reply other threads:[~2017-08-08 7:36 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <ee7921d2-d3ff-2381-1f05-2c07b8001d08@unsolicited.net>
2017-08-06 17:37 ` RESEND: Crash with 4.12.4 kernel and high disk load (monthly RAID 6 check) David R
2017-08-07 11:20 ` [MD] Crash with 4.12+ kernel and high disk load -- bisected to 4ad23a976413: MD: use per-cpu counter for writes_pending Dominik Brodowski
2017-08-08 4:51 ` Shaohua Li
2017-08-08 6:55 ` David R
2017-08-08 7:01 ` David R
2017-08-08 7:04 ` NeilBrown
2017-08-08 7:10 ` Dominik Brodowski
2017-08-08 7:01 ` NeilBrown
2017-08-08 7:36 ` Dominik Brodowski [this message]
2017-08-08 9:06 ` Dominik Brodowski
2017-08-09 6:28 ` David R
2017-08-08 8:02 ` David R
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