[PATCH 003 of 4] Use mutex_lock_nested for bd_mutex to avoid lockdep warning.

[NeilBrown <neilb@suse.de>]

Now that the nesting in blkdev_{get,put} is simpler, adding
mutex_lock_nested is trivial.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./fs/block_dev.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff .prev/fs/block_dev.c ./fs/block_dev.c
--- .prev/fs/block_dev.c	2006-10-11 15:38:31.000000000 +1000
+++ ./fs/block_dev.c	2006-10-11 15:41:55.000000000 +1000
@@ -909,7 +909,7 @@ static int do_open(struct block_device *
 	}
 	owner = disk->fops->owner;
 
-	mutex_lock(&bdev->bd_mutex);
+	mutex_lock_nested(&bdev->bd_mutex, for_part);
 	if (!bdev->bd_openers) {
 		bdev->bd_disk = disk;
 		bdev->bd_contains = bdev;
@@ -1049,7 +1049,7 @@ static int __blkdev_put(struct block_dev
 	struct gendisk *disk = bdev->bd_disk;
 	struct block_device *victim = NULL;
 
-	mutex_lock(&bdev->bd_mutex);
+	mutex_lock_nested(&bdev->bd_mutex, for_part);
 	lock_kernel();
 	if (for_part)
 		bdev->bd_part_count--;