Subject: Re: [BUG] fs: ocfs2: possible ABBA deadlock in
 ocfs2_dio_end_io_write() and ocfs2_move_extents()
To:     Joseph Qi <joseph.qi@linux.alibaba.com>, mark@fasheh.com,
        jlbec@evilplan.org
Cc:     ocfs2-devel@oss.oracle.com,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <8ae1bb9c-3e58-c8b6-8823-3d2ea8b241e2@gmail.com>
 <bd6dfb63-6d3d-c8f6-f401-8bdd5334afed@linux.alibaba.com>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <093db193-baf8-b2c1-5667-7ded591a8437@gmail.com>
Date:   Tue, 14 Dec 2021 15:19:42 +0800
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On 2021/12/14 15:08, Joseph Qi wrote:
> Hi,
>
> Thanks for the report. But I don't think this is a possible deadlock in
> practice. Please see my comments below.
>
> On 12/10/21 4:38 PM, Jia-Ju Bai wrote:
>> Hello,
>>
>> My static analysis tool reports a possible ABBA deadlock in the ocfs2 module in Linux 5.10:
>>
>> ocfs2_dio_end_io_write()
>>    down_write(&oi->ip_alloc_sem); --> Line 2322 (Lock A)
>>    ocfs2_del_inode_from_orphan()
>>      inode_lock(orphan_dir_inode);  --> Line 2701 (Lock B)
> Just as the variable name indicates, it is orphan dir inode, which is a
> system file (something hidden inside the filesystem) and not visible for
> end user.
>
>> ocfs2_move_extents()
>>    inode_lock(inode); --> Line 916 (Lock B)
> This is called from a ioctl from user, it a normal file inode.

Okay, thanks for the explanation :)


Best wishes,
Jia-Ju Bai