[PATCH] lockdep: avoid lockdep warning in md

md_open takes ->reconfig_mutex which causes lockdep to complain.  This
(normally) doesn't have deadlock potential as the possible conflict is with a
reconfig_mutex in a different device.

I say "normally" because if a loop were created in the array->member hierarchy
a deadlock could happen.  However that causes bigger problems than a deadlock
and should be fixed independently.

So we flag the lock in md_open as a nested lock.  This requires defining
mutex_lock_interruptible_nested.

Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index d2bcb410e3ab..3ce7a5d81d81 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4423,7 +4423,7 @@ static int md_open(struct inode *inode, struct file *file)
         mddev_t *mddev = inode->i_bdev->bd_disk->private_data;
         int err;
 
-        if ((err = mddev_lock(mddev)))
+        if ((err = mutex_lock_interruptible_nested(&mddev->reconfig_mutex, 1)))
                 goto out;
 
         err = 0;