loop: use blk_mq_alloc_disk and blk_cleanup_disk

Use blk_mq_alloc_disk and blk_cleanup_disk to simplify the gendisk and
request_queue allocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-19-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -2117,12 +2117,12 @@ static int loop_add(struct loop_device **l, int i)
 	if (err)
 		goto out_free_idr;
 
-	lo->lo_queue = blk_mq_init_queue(&lo->tag_set);
-	if (IS_ERR(lo->lo_queue)) {
-		err = PTR_ERR(lo->lo_queue);
+	disk = lo->lo_disk = blk_mq_alloc_disk(&lo->tag_set, lo);
+	if (IS_ERR(disk)) {
+		err = PTR_ERR(disk);
 		goto out_cleanup_tags;
 	}
-	lo->lo_queue->queuedata = lo;
+	lo->lo_queue = lo->lo_disk->queue;
 
 	blk_queue_max_hw_sectors(lo->lo_queue, BLK_DEF_MAX_SECTORS);
 
@@ -2134,11 +2134,6 @@ static int loop_add(struct loop_device **l, int i)
 	 */
 	blk_queue_flag_set(QUEUE_FLAG_NOMERGES, lo->lo_queue);
 
-	err = -ENOMEM;
-	disk = lo->lo_disk = alloc_disk(1 << part_shift);
-	if (!disk)
-		goto out_free_queue;
-
 	/*
 	 * Disable partition scanning by default. The in-kernel partition
 	 * scanning can be requested individually per-device during its
@@ -2166,6 +2161,7 @@ static int loop_add(struct loop_device **l, int i)
 	spin_lock_init(&lo->lo_lock);
 	disk->major		= LOOP_MAJOR;
 	disk->first_minor	= i << part_shift;
+	disk->minors		= 1 << part_shift;
 	disk->fops		= &lo_fops;
 	disk->private_data	= lo;
 	disk->queue		= lo->lo_queue;
@@ -2174,8 +2170,6 @@ static int loop_add(struct loop_device **l, int i)
 	*l = lo;
 	return lo->lo_number;
 
-out_free_queue:
-	blk_cleanup_queue(lo->lo_queue);
 out_cleanup_tags:
 	blk_mq_free_tag_set(&lo->tag_set);
 out_free_idr:
@@ -2189,9 +2183,8 @@ static int loop_add(struct loop_device **l, int i)
 static void loop_remove(struct loop_device *lo)
 {
 	del_gendisk(lo->lo_disk);
-	blk_cleanup_queue(lo->lo_queue);
 	blk_mq_free_tag_set(&lo->tag_set);
-	put_disk(lo->lo_disk);
+	blk_cleanup_disk(lo->lo_disk);
 	mutex_destroy(&lo->lo_mutex);
 	kfree(lo);
 }