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

[Mikulas Patocka]

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;
 }