loop: don't grab a reference to the block device

The whole device block device won't be removed while the disk is still
alive, so don't bother to grab a reference to it.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJosef Bacik <josef@toxicpanda.com>
Reviewed-by: NMing Lei <ming.lei@rehat.com>
Reviewed-by: NChaitanya Kulkarni <ckulkarnilinux@gmail.com>
Link: https://lore.kernel.org/r/20210722075402.983367-8-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1304,10 +1304,6 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	if (partscan)
 		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
 
-	/* Grab the block_device to prevent its destruction after we
-	 * put /dev/loopXX inode. Later in __loop_clr_fd() we bdput(bdev).
-	 */
-	bdgrab(bdev);
 	loop_global_unlock(lo, is_loop);
 	if (partscan)
 		loop_reread_partitions(lo);
@@ -1398,7 +1394,6 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
 	blk_queue_physical_block_size(lo->lo_queue, 512);
 	blk_queue_io_min(lo->lo_queue, 512);
 	if (bdev) {
-		bdput(bdev);
 		invalidate_bdev(bdev);
 		bdev->bd_inode->i_mapping->wb_err = 0;
 	}