z2ram: use separate gendisk for the different modes

Use separate gendisks (which share a tag_set) for the different operating
modes instead of redirecting the gendisk lookup using a probe callback.
This avoids potential problems with aliased block_device instances and
will eventually allow for removing the blk_register_region framework.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/z2ram.c

@@ -63,7 +63,7 @@ static int current_device = -1;
 
 static DEFINE_SPINLOCK(z2ram_lock);
 
-static struct gendisk *z2ram_gendisk;
+static struct gendisk *z2ram_gendisk[Z2MINOR_COUNT];
 
 static blk_status_t z2_queue_rq(struct blk_mq_hw_ctx *hctx,
 				const struct blk_mq_queue_data *bd)
@@ -283,7 +283,7 @@ static int z2_open(struct block_device *bdev, fmode_t mode)
 
 		current_device = device;
 		z2ram_size <<= Z2RAM_CHUNKSHIFT;
-		set_capacity(z2ram_gendisk, z2ram_size >> 9);
+		set_capacity(z2ram_gendisk[device], z2ram_size >> 9);
 	}
 
 	mutex_unlock(&z2ram_mutex);
@@ -315,71 +315,87 @@ static const struct block_device_operations z2_fops = {
 	.release = z2_release,
 };
 
-static struct kobject *z2_find(dev_t dev, int *part, void *data)
-{
-	*part = 0;
-	return get_disk_and_module(z2ram_gendisk);
-}
-
-static struct request_queue *z2_queue;
 static struct blk_mq_tag_set tag_set;
 
 static const struct blk_mq_ops z2_mq_ops = {
 	.queue_rq = z2_queue_rq,
 };
 
+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->major = Z2RAM_MAJOR;
+	disk->first_minor = minor;
+	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);
+	return 0;
+}
+
 static int __init z2_init(void)
 {
-	int ret;
+	int ret, i;
 
 	if (!MACH_IS_AMIGA)
 		return -ENODEV;
 
-	ret = -EBUSY;
 	if (register_blkdev(Z2RAM_MAJOR, DEVICE_NAME))
-		goto err;
-
-	ret = -ENOMEM;
-	z2ram_gendisk = alloc_disk(1);
-	if (!z2ram_gendisk)
-		goto out_disk;
-
-	z2_queue = blk_mq_init_sq_queue(&tag_set, &z2_mq_ops, 16,
-					BLK_MQ_F_SHOULD_MERGE);
-	if (IS_ERR(z2_queue)) {
-		ret = PTR_ERR(z2_queue);
-		z2_queue = NULL;
-		goto out_queue;
+		return -EBUSY;
+
+	tag_set.ops = &z2_mq_ops;
+	tag_set.nr_hw_queues = 1;
+	tag_set.nr_maps = 1;
+	tag_set.queue_depth = 16;
+	tag_set.numa_node = NUMA_NO_NODE;
+	tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
+	ret = blk_mq_alloc_tag_set(&tag_set);
+	if (ret)
+		goto out_unregister_blkdev;
+
+	for (i = 0; i < Z2MINOR_COUNT; i++) {
+		ret = z2ram_register_disk(i);
+		if (ret && i == 0)
+			goto out_free_tagset;
 	}
 
-	z2ram_gendisk->major = Z2RAM_MAJOR;
-	z2ram_gendisk->first_minor = 0;
-	z2ram_gendisk->fops = &z2_fops;
-	sprintf(z2ram_gendisk->disk_name, "z2ram");
-
-	z2ram_gendisk->queue = z2_queue;
-	add_disk(z2ram_gendisk);
-	blk_register_region(MKDEV(Z2RAM_MAJOR, 0), Z2MINOR_COUNT, THIS_MODULE,
-			    z2_find, NULL, NULL);
-
 	return 0;
 
-out_queue:
-	put_disk(z2ram_gendisk);
-out_disk:
+out_free_tagset:
+	blk_mq_free_tag_set(&tag_set);
+out_unregister_blkdev:
 	unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
-err:
 	return ret;
 }
 
 static void __exit z2_exit(void)
 {
 	int i, j;
-	blk_unregister_region(MKDEV(Z2RAM_MAJOR, 0), Z2MINOR_COUNT);
+
 	unregister_blkdev(Z2RAM_MAJOR, DEVICE_NAME);
-	del_gendisk(z2ram_gendisk);
-	put_disk(z2ram_gendisk);
-	blk_cleanup_queue(z2_queue);
+
+	for (i = 0; i < Z2MINOR_COUNT; i++) {
+		del_gendisk(z2ram_gendisk[i]);
+		blk_cleanup_queue(z2ram_gendisk[i]->queue);
+		put_disk(z2ram_gendisk[i]);
+	}
 	blk_mq_free_tag_set(&tag_set);
 
 	if (current_device != -1) {