This is a note to let you know that I've just added the patch titled
dm snapshot: workaround for a false positive lockdep warning
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-snapshot-workaround-for-a-false-positive-lockdep-warning.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5ea330a75bd86b2b2a01d7b85c516983238306fb Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Wed, 18 Sep 2013 19:14:22 -0400
Subject: dm snapshot: workaround for a false positive lockdep warning
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
commit 5ea330a75bd86b2b2a01d7b85c516983238306fb upstream.
The kernel reports a lockdep warning if a snapshot is invalidated because
it runs out of space.
The lockdep warning was triggered by commit 0976dfc1d0cd80a4e9dfaf87bd87
("workqueue: Catch more locking problems with flush_work()") in v3.5.
The warning is false positive. The real cause for the warning is that
the lockdep engine treats different instances of md->lock as a single
lock.
This patch is a workaround - we use flush_workqueue instead of flush_work.
This code path is not performance sensitive (it is called only on
initialization or invalidation), thus it doesn't matter that we flush the
whole workqueue.
The real fix for the problem would be to teach the lockdep engine to treat
different instances of md->lock as separate locks.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Acked-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-snap-persistent.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -251,7 +251,7 @@ static int chunk_io(struct pstore *ps, v
*/
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;
}
Patches currently in stable-queue which might be from mpatocka@xxxxxxxxxx are
queue-3.0/dm-snapshot-fix-performance-degradation-due-to-small-hash-size.patch
queue-3.0/dm-snapshot-workaround-for-a-false-positive-lockdep-warning.patch
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