Re: [PATCH] ocfs2: fix circular locking dependency in reflink

[Joseph Qi]

On 8/1/26 2:21 AM, Andrew Morton wrote:
> On Fri, 31 Jul 2026 19:34:25 +0800 Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> wrote:
> 
>> Lockdep reports a possible deadlock involving ip_alloc_sem,
>> j_trans_barrier, and ip_xattr_sem:
>>
> 
> Cool.
> 
> Sashiko said a couple of things:
> 	https://sashiko.dev/#/patchset/20260731113425.4130293-1-joseph.qi@xxxxxxxxxxxxxxxxx
> 

The issue sashiko has found is real.

After a deep look, I think it can be fixed by breaking j_trans_barrier
-> ip_xattr_sem instread of ip_xattr_sem -> ip_alloc_sem, which is
actually posted by Krystian Kaniewski in thread (I've ACKed):
https://lore.kernel.org/ocfs2-devel/f98ff905-74bf-4017-a673-fd28f30f11d3@xxxxxxxxxxxxxxxxx/T/#t

So please drop this patch and let's keep the existing order for
ip_xattr_sem -> ip_alloc_sem.

Thanks,
Joseph


>> Fix by swapping the lock order in both functions to acquire
>> ip_alloc_sem before ip_xattr_sem, consistent with the rest of the
>> codebase.
>>
>> Fixes: 09bf27a00020 ("ocfs2: Implement ocfs2_reflink.")
>> Fixes: 8b2c0dba5159 ("ocfs2: Call refcount tree remove process properly.")
> 
> Should we backport this into -stable kernels?
>