Messages in this thread | | | Date | Tue, 08 Aug 2017 08:02:49 +0000 | From | David R <> | Subject | Re: [MD] Crash with 4.12+ kernel and high disk load -- bisected to 4ad23a976413: MD: use per-cpu counter for writes_pending |
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I will apply this to my home server this evening (BST) and set off a check. Will have results tomorrow.
Thanks for the fix!
David
Quoting NeilBrown <neilb@suse.com>:
> 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
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