linux-kernel - Re: [PATCH] ocfs2: fix circular locking dependency in ocfs2_acquire

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Message-Id: <20260105173711.b33d85c7f72544876c8dcfd3@linux-foundation.org>
Date: Mon, 5 Jan 2026 17:37:11 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Szymon Wilczek <swilczek.lx@...il.com>
Cc: ocfs2-devel@...ts.linux.dev, mark@...heh.com, jlbec@...lplan.org,
 joseph.qi@...ux.alibaba.com, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com,
 syzbot+51244a05705883616c95@...kaller.appspotmail.com
Subject: Re: [PATCH] ocfs2: fix circular locking dependency in
 ocfs2_acquire_dquot

On Sat, 27 Dec 2025 18:42:51 +0100 Szymon Wilczek <swilczek.lx@...il.com> wrote:

> Move ocfs2_extend_no_holes() to execute before ocfs2_lock_global_qf() to
> fix a circular locking dependency reported by syzbot.
> 
> The issue occurs because ocfs2_extend_no_holes() internally calls
> ocfs2_extend_allocation() which starts a transaction (acquiring
> sb_start_intwrite). When called while holding the global quota file
> lock, this conflicts with mount-time operations that acquire
> sb_internal first, creating the following circular dependency:
> 
>   sb_internal -> ocfs2_sysfile_lock_key -> ocfs2_quota_ip_alloc_sem_key
> 
> By moving the quota file extension before acquiring the global quota
> file lock, we ensure that any internal transactions complete before
> quota locks are held, breaking the circular dependency.

Thanks.  This might have escaped reviewer attention due to the holiday
season.  I'll add it to mm.git's mm-nonmm-unstable branch for runtime
testing while we await review (please!).