block: move sync_blockdev from __blkdev_put to blkdev_put

Do the early unlocked syncing even earlier to move more code out of
the recursive path.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210525061301.2242282-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/block_dev.c

@@ -1552,16 +1552,6 @@ static void __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part)
 	struct gendisk *disk = bdev->bd_disk;
 	struct block_device *victim = NULL;
 
-	/*
-	 * Sync early if it looks like we're the last one.  If someone else
-	 * opens the block device between now and the decrement of bd_openers
-	 * then we did a sync that we didn't need to, but that's not the end
-	 * of the world and we want to avoid long (could be several minute)
-	 * syncs while holding the mutex.
-	 */
-	if (bdev->bd_openers == 1)
-		sync_blockdev(bdev);
-
 	mutex_lock_nested(&bdev->bd_mutex, for_part);
 	if (for_part)
 		bdev->bd_part_count--;
@@ -1588,6 +1578,16 @@ void blkdev_put(struct block_device *bdev, fmode_t mode)
 {
 	struct gendisk *disk = bdev->bd_disk;
 
+	/*
+	 * Sync early if it looks like we're the last one.  If someone else
+	 * opens the block device between now and the decrement of bd_openers
+	 * then we did a sync that we didn't need to, but that's not the end
+	 * of the world and we want to avoid long (could be several minute)
+	 * syncs while holding the mutex.
+	 */
+	if (bdev->bd_openers == 1)
+		sync_blockdev(bdev);
+
 	mutex_lock(&bdev->bd_mutex);
 
 	if (mode & FMODE_EXCL) {