linux-kernel - Re: [syzbot] [kernfs?] possible deadlock in kernfs_fop

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Date: Fri, 5 Apr 2024 08:51:35 +0200
From: Christoph Hellwig <hch@....de>
To: Amir Goldstein <amir73il@...il.com>
Cc: Al Viro <viro@...iv.linux.org.uk>,
	syzbot <syzbot+9a5b0ced8b1bfb238b56@...kaller.appspotmail.com>,
	gregkh@...uxfoundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
	tj@...nel.org, valesini@...dex-team.ru,
	Christoph Hellwig <hch@....de>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Miklos Szeredi <miklos@...redi.hu>
Subject: Re: [syzbot] [kernfs?] possible deadlock in kernfs_fop_llseek

On Thu, Apr 04, 2024 at 12:33:40PM +0300, Amir Goldstein wrote:
> I don't follow what you are saying.
> Which code is in non-starter violation?
> kernfs for calling lookup_bdev() with internal of->mutex held?

That is a huge problem, and has been causing endless annoying lockdep
chains in the block layer for us.  If we have some way to kill this
the whole block layer would benefit.