[PATCH] lockdep: annotate blkdev nesting

Teach special (recursive) locking code to the lock validator.

Effects on non-lockdep kernels:

- the introduction of the following function variants:

  extern struct block_device *open_partition_by_devnum(dev_t, unsigned);

  extern int blkdev_put_partition(struct block_device *);

  static int
  blkdev_get_whole(struct block_device *bdev, mode_t mode, unsigned flags);

 which on non-lockdep are the same as open_by_devnum(), blkdev_put()
 and blkdev_get().

- a subclass parameter to do_open(). [unused on non-lockdep]

- a subclass parameter to __blkdev_put(), which is a new internal
  function for the main blkdev_put*() functions. [parameter unused
  on non-lockdep kernels, except for two sanity check WARN_ON()s]

these functions carry no semantical difference - they only express
object dependencies towards the lockdep subsystem.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/md.c

@@ -1404,7 +1404,7 @@ static int lock_rdev(mdk_rdev_t *rdev, dev_t dev)
 	struct block_device *bdev;
 	char b[BDEVNAME_SIZE];
 
-	bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE);
+	bdev = open_partition_by_devnum(dev, FMODE_READ|FMODE_WRITE);
 	if (IS_ERR(bdev)) {
 		printk(KERN_ERR "md: could not open %s.\n",
 			__bdevname(dev, b));
@@ -1414,7 +1414,7 @@ static int lock_rdev(mdk_rdev_t *rdev, dev_t dev)
 	if (err) {
 		printk(KERN_ERR "md: could not bd_claim %s.\n",
 			bdevname(bdev, b));
-		blkdev_put(bdev);
+		blkdev_put_partition(bdev);
 		return err;
 	}
 	rdev->bdev = bdev;
@@ -1428,7 +1428,7 @@ static void unlock_rdev(mdk_rdev_t *rdev)
 	if (!bdev)
 		MD_BUG();
 	bd_release(bdev);
-	blkdev_put(bdev);
+	blkdev_put_partition(bdev);
 }
 
 void md_autodetect_dev(dev_t dev);