z2ram: 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/20210602065345.355274-31-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/z2ram.c

@@ -323,27 +323,20 @@ static const struct blk_mq_ops z2_mq_ops = {
 
 static int z2ram_register_disk(int minor)
 {
-	struct request_queue *q;
 	struct gendisk *disk;
 
-	disk = alloc_disk(1);
-	if (!disk)
-		return -ENOMEM;
-
-	q = blk_mq_init_queue(&tag_set);
-	if (IS_ERR(q)) {
-		put_disk(disk);
-		return PTR_ERR(q);
-	}
+	disk = blk_mq_alloc_disk(&tag_set, NULL);
+	if (IS_ERR(disk))
+		return PTR_ERR(disk);
 
 	disk->major = Z2RAM_MAJOR;
 	disk->first_minor = minor;
+	disk->minors = 1;
 	disk->fops = &z2_fops;
 	if (minor)
 		sprintf(disk->disk_name, "z2ram%d", minor);
 	else
 		sprintf(disk->disk_name, "z2ram");
-	disk->queue = q;
 
 	z2ram_gendisk[minor] = disk;
 	add_disk(disk);