nvme: open code nvme_{get,put}_ns_from_disk in nvme_ns_head_ioctl

nvme_ns_head_ioctl is always used on multipath nodes, no need to
deal with the de-multiplexers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/ioctl.c

@@ -387,14 +387,15 @@ static int nvme_ns_head_ctrl_ioctl(struct nvme_ns *ns, unsigned int cmd,
 int nvme_ns_head_ioctl(struct block_device *bdev, fmode_t mode,
 		unsigned int cmd, unsigned long arg)
 {
-	struct nvme_ns_head *head = NULL;
+	struct nvme_ns_head *head = bdev->bd_disk->private_data;
 	void __user *argp = (void __user *)arg;
 	struct nvme_ns *ns;
-	int srcu_idx, ret;
+	int srcu_idx, ret = -EWOULDBLOCK;
 
-	ns = nvme_get_ns_from_disk(bdev->bd_disk, &head, &srcu_idx);
-	if (unlikely(!ns))
-		return -EWOULDBLOCK;
+	srcu_idx = srcu_read_lock(&head->srcu);
+	ns = nvme_find_path(head);
+	if (!ns)
+		goto out_unlock;
 
 	/*
 	 * Handle ioctls that apply to the controller instead of the namespace
@@ -402,12 +403,11 @@ int nvme_ns_head_ioctl(struct block_device *bdev, fmode_t mode,
 	 * deadlock when deleting namespaces using the passthrough interface.
 	 */
 	if (is_ctrl_ioctl(cmd))
-		ret = nvme_ns_head_ctrl_ioctl(ns, cmd, argp, head, srcu_idx);
-	else {
-		ret = nvme_ns_ioctl(ns, cmd, argp);
-		nvme_put_ns_from_disk(head, srcu_idx);
-	}
+		return nvme_ns_head_ctrl_ioctl(ns, cmd, argp, head, srcu_idx);
 
+	ret = nvme_ns_ioctl(ns, cmd, argp);
+out_unlock:
+	srcu_read_unlock(&head->srcu, srcu_idx);
 	return ret;
 }