linux-kernel - Re: Known and unfixed active data loss bug in MM + XFS with large folios since Dec 2021 (any kernel from 6.1 upwards)

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Message-Id: <0A480EBE-9B4D-49CC-9A32-3526F32426E6@flyingcircus.io>
Date: Fri, 11 Oct 2024 11:08:26 +0200
From: Christian Theune <ct@...ingcircus.io>
To: Chris Mason <clm@...a.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
 Dave Chinner <david@...morbit.com>,
 Matthew Wilcox <willy@...radead.org>,
 Jens Axboe <axboe@...nel.dk>,
 linux-mm@...ck.org,
 "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
 linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Daniel Dao <dqminh@...udflare.com>,
 regressions@...ts.linux.dev,
 regressions@...mhuis.info
Subject: Re: Known and unfixed active data loss bug in MM + XFS with large
 folios since Dec 2021 (any kernel from 6.1 upwards)


> On 11. Oct 2024, at 09:27, Christian Theune <ct@...ingcircus.io> wrote:
> 
> I’m going to gather a few more instances during the day and will post them as a batch later.

I’ve received 8 alerts in the last hours and managed to get detailed, repeated walker output from two of them:

- FC-41287.log
- FC-41289.log

The other logs are tracebacks as the kernel reported them but the situation resolved itself faster than I could log in and run the walker script. In FC-41289.log I’m also providing output from `ps auxf` to see what the process tree looks like, maybe that helps, too.

My observations: 

- different entry points from the XFS code: unlink, f(data)sync, truncate
- in none of the cases I caught I could see any real competing traffic (aside from maybe occasional journal writes and very little background noise), all affected machines are staging environments that saw basically no usage during that timeframe

I’m stopping my alerting now as it’s been interrupting me every few minutes and I’m running out of steam sitting around waiting for the alert. ;)

Christian


Download attachment "FC-41281.log" of type "application/octet-stream" (2345 bytes)

Download attachment "FC-41282.log" of type "application/octet-stream" (1781 bytes)

Download attachment "FC-41283.log" of type "application/octet-stream" (1724 bytes)

Download attachment "FC-41285.log" of type "application/octet-stream" (1567 bytes)

Download attachment "FC-41286.log" of type "application/octet-stream" (2237 bytes)

Download attachment "FC-41287.log" of type "application/octet-stream" (5752 bytes)

Download attachment "FC-41288.log" of type "application/octet-stream" (1684 bytes)

Download attachment "FC-41289.log" of type "application/octet-stream" (166376 bytes)



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