linux-kernel - Re: [REGRESSION] 9pfs issues on 6.12-rc1

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Message-ID: <aJmfBTflGvAI6sBs@codewreck.org>
Date: Mon, 11 Aug 2025 16:43:01 +0900
From: Dominique Martinet <asmadeus@...ewreck.org>
To: Arnout Engelen <arnout@...t.net>
Cc: ryan@...fa.xyz, antony.antony@...unet.com, antony@...nome.org,
	brauner@...nel.org, ericvh@...nel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux_oss@...debyte.com, lucho@...kov.net, maximilian@...sch.me,
	netfs@...ts.linux.dev, regressions@...ts.linux.dev,
	sedat.dilek@...il.com, v9fs@...ts.linux.dev,
	Matthew Wilcox <willy@...radead.org>, dhowells@...hat.com
Subject: Re: [REGRESSION] 9pfs issues on 6.12-rc1

asmadeus@...ewreck.org wrote on Mon, Aug 11, 2025 at 09:57:51AM +0900:
> Also I haven't been able to reproduce it with a kernel I built myself/my
> environment, but it reproduces reliably 99% of the times in the nixos
> VM, so we're missing a last piece for a "simple" (non-nix) reproducer,
> but I think it's good enough for me to dig into this;

(okay, I got this to work wedging my kernel into the nixos initrd; this
requires the iov to be built off non-contiguous pages and so having
systemd thrash around was apparently a required step...)

So that wasn't a 9p bug, I'm not sure if I should be happy or not?

I've sent "proper-ish" patches at [1] which most concerned people should
be in Cc; I'm fairly confident this will make the bug go away but any
testing is appreciated, please reply to the patches with a Tested-by if
you have time.

[1] https://lkml.kernel.org/r/20250811-iot_iter_folio-v1-0-d9c223adf93c@codewreck.org


Thank you all again, and sorry I haven't had the time to look further
into this without a clean reproducer, this really shouldn't have taken
that long...
-- 
Dominique Martinet | Asmadeus