loop: Use invalidate_disk() helper to invalidate gendisk

Use invalidate_disk() helper to simplify the code for gendisk
invalidation.
Signed-off-by: NXie Yongji <xieyongji@bytedance.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210922123711.187-3-xieyongji@bytedance.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1395,11 +1395,7 @@ static int __loop_clr_fd(struct loop_device *lo, bool release)
 	blk_queue_logical_block_size(lo->lo_queue, 512);
 	blk_queue_physical_block_size(lo->lo_queue, 512);
 	blk_queue_io_min(lo->lo_queue, 512);
-	if (bdev) {
-		invalidate_bdev(bdev);
-		bdev->bd_inode->i_mapping->wb_err = 0;
-	}
-	set_capacity(lo->lo_disk, 0);
+	invalidate_disk(lo->lo_disk);
 	loop_sysfs_exit(lo);
 	if (bdev) {
 		/* let user-space know about this change */