linux-kernel - Re: [PATCH] scsi: target: Fix recursive locking in __configfs_open

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Message-ID: <6927d0f7-5bf5-4035-b1c2-50f3edae4b7f@acm.org>
Date: Wed, 21 Jan 2026 09:59:49 -0800
From: Bart Van Assche <bvanassche@....org>
To: Prithvi <activprithvi@...il.com>
Cc: martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
 target-devel@...r.kernel.org, linux-kernel@...r.kernel.org, hch@....de,
 jlbec@...lplan.org, linux-fsdevel@...r.kernel.org,
 linux-kernel-mentees@...ts.linux.dev, skhan@...uxfoundation.org,
 david.hunter.linux@...il.com, khalid@...nel.org,
 syzbot+f6e8174215573a84b797@...kaller.appspotmail.com, stable@...r.kernel.org
Subject: Re: [PATCH] scsi: target: Fix recursive locking in
 __configfs_open_file()

On 1/21/26 9:51 AM, Prithvi wrote:
> I tried using lockdep_register_key() and lockdep_unregister_key() for the
> frag_sem lock, however it stil gives the possible recursive locking
> warning. Here is the patch and the bug report from its test:
> 
> https://lore.kernel.org/all/6767d8ea.050a0220.226966.0021.GAE@google.com/T/#m3203ceddf3423b7116ba9225d182771608f93a6f
> 
> Would using down_read_nested() and subclasses be a better option here?
> 
> I also checked out some documentation regarding it and learnt that to use
> the _nested() form, the hierarchy among the locks should be mapped
> accurately; however, IIUC, there isn't any hierarchy between the locks in
> this case, is this right?
> 
> Apologies if I am missing something obvious here, and thanks for your
> time and guidance.

This is unexpected. Please ask help from someone who is familiar with 
VFS internals. I'm not familiar with these internals.

Thanks,

Bart.