Re: [PATCH] dm-snapshot: workaround for a lockdep warning

[Zdenek Kabelac <zkabelac@redhat.com>]

Dne 18.9.2013 17:57, Mikulas Patocka napsal(a):
>
>
> On Wed, 18 Sep 2013, Zdenek Kabelac wrote:
>
>> Dne 18.9.2013 02:08, Mikulas Patocka napsal(a):
>>>
>>>
>>> On Tue, 17 Sep 2013, Mikulas Patocka wrote:
>>>
>>>> BTW. this patch is no longer needed on 3.11 because md->io_lock was
>>>> removed there, so the false lockdep warning doesn't happen.
>>>>
>>>> So we need to get this patch to stable trees 3.5 to 3.10, but not
>>>> upstream. How to push the patch there without pushing it upstream?
>>>>
>>>> Mikulas
>>>
>>> It's more complicated than that - the original Zdenek's report shows that
>>> the false warning happened on kernel "3.11.1-300.fc20.x86_64+debug". But I
>>> am not able to reproduce the bug on 3.11, I only reproduced it on 3.5-3.10
>>> kernels.
>>>
>>> Zdenek, could you reproduce the bug on kernel 3.11?
>>>
>>> Mikulas
>>>
>>
>>
>> Since I do not have clean 3.11 at my hands  - I've reproduced it with my -rc6
>> kernel (few patches based on 8495e9c4a9616c9d19f23182d0536485902259db)
>> With enabled kmemleak=on lockdep.prove_locking=1 lockdep.lock_stat=1.
>
> So - try this patch and tell me if it fixes the problem:
>
> Index: linux-2.6-devel/drivers/md/dm-snap-persistent.c
> ===================================================================
> --- linux-2.6-devel.orig/drivers/md/dm-snap-persistent.c	2013-05-10 18:27:31.132358000 +0200
> +++ linux-2.6-devel/drivers/md/dm-snap-persistent.c	2013-09-17 18:41:39.023940000 +0200
> @@ -256,7 +256,7 @@
>   	 */
>   	INIT_WORK_ONSTACK(&req.work, do_metadata);
>   	queue_work(ps->metadata_wq, &req.work);
> -	flush_work(&req.work);
> +	flush_workqueue(ps->metadata_wq);
>
>   	return req.result;
>   }
>

Yes - this seems to eliminate reported INFO.

Though I'm getting curious why some tests are running much much much slower 
when kmemleak and lockdep is in use.

Zdenek