nvme: fix inconsistent RCU list manipulation in nvme_ns_add_to_ctrl_list()

When inserting a namespace into the controller's namespace list, the
function uses list_add_rcu() when the namespace is inserted in the middle
of the list, but falls back to a regular list_add() when adding at the
head of the list.

This inconsistency could lead to race conditions during concurrent
access, as users might observe a partially updated list. Fix this by
consistently using list_add_rcu() in both code paths to ensure proper
RCU protection throughout the entire function.

Fixes: be647e2 ("nvme: use srcu for iterating namespace list")
Signed-off-by: Zheng Qixing <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>

Author: Zheng Qixing

drivers/nvme/host/core.c

@@ -4077,7 +4077,7 @@ static void nvme_ns_add_to_ctrl_list(struct nvme_ns *ns)
 			return;
 		}
 	}
-	list_add(&ns->list, &ns->ctrl->namespaces);
+	list_add_rcu(&ns->list, &ns->ctrl->namespaces);
 }
 
 static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info)