linux-kernel - Re: possible deadlock in ovl

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Message-ID: <CAJfpeguBfKB4MGEUkJ=+ZFT9uYJ1DXtCTW9oLrEE0af7XTi=VA@mail.gmail.com>
Date: Wed, 13 Mar 2024 15:47:17 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: Amir Goldstein <amir73il@...il.com>
Cc: Weiß, Simone <Simone.Weiss@...ktrobit.com>, 
	"linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: possible deadlock in ovl_llseek 27c1936af506

On Wed, 13 Mar 2024 at 14:14, Amir Goldstein <amir73il@...il.com> wrote:

> The reason for this report is calling llseek() on lower ovl from
> ovl_copy_up_data() when ovl_copy_up_data() is called with upper
> inode lock and the lower ovl uses the same upper fs.
>
> It looks to me like the possible deadlock should have been solved by commit
> c63e56a4a652 ovl: do not open/llseek lower file with upper sb_writers held
> that moved ovl_copy_up_data() out of the inode_lock() scope.

That commit is in v6.7, so something different must be happening on v6.8-rc1.

Simone, please send a new report for v6.8-rc1 if a lockdep splat can
be reproduced on that kernel.

Thanks,
Miklos