nvme: factor out nvme_ns_open and nvme_ns_release helpers

These will be reused for the per-namespace character devices.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Reviewed-by: NJavier González <javier.gonz@samsung.com>
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

drivers/nvme/host/core.c

@@ -1483,9 +1483,8 @@ void nvme_put_ns_from_disk(struct nvme_ns_head *head, int idx)
 		srcu_read_unlock(&head->srcu, idx);
 }
 
-static int nvme_open(struct block_device *bdev, fmode_t mode)
+static int nvme_ns_open(struct nvme_ns *ns)
 {
-	struct nvme_ns *ns = bdev->bd_disk->private_data;
 
 	/* should never be called due to GENHD_FL_HIDDEN */
 	if (WARN_ON_ONCE(nvme_ns_head_multipath(ns->head)))
@@ -1503,14 +1502,23 @@ static int nvme_open(struct block_device *bdev, fmode_t mode)
 	return -ENXIO;
 }
 
-static void nvme_release(struct gendisk *disk, fmode_t mode)
+static void nvme_ns_release(struct nvme_ns *ns)
 {
-	struct nvme_ns *ns = disk->private_data;
 
 	module_put(ns->ctrl->ops->module);
 	nvme_put_ns(ns);
 }
 
+static int nvme_open(struct block_device *bdev, fmode_t mode)
+{
+	return nvme_ns_open(bdev->bd_disk->private_data);
+}
+
+static void nvme_release(struct gendisk *disk, fmode_t mode)
+{
+	nvme_ns_release(disk->private_data);
+}
+
 int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo)
 {
 	/* some standard values */