nvme: fix the deadlock in nvme_update_formats

nvme_update_formats will invoke nvme_ns_remove under namespaces_mutext.
The will cause deadlock because nvme_ns_remove will also require
the namespaces_mutext. Fix it by getting the ns entries which should
be removed under namespaces_mutext and invoke nvme_ns_remove out of
namespaces_mutext.

Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/core.c

@@ -1117,14 +1117,19 @@ static u32 nvme_passthru_start(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 
 static void nvme_update_formats(struct nvme_ctrl *ctrl)
 {
-	struct nvme_ns *ns;
+	struct nvme_ns *ns, *next;
+	LIST_HEAD(rm_list);
 
 	mutex_lock(&ctrl->namespaces_mutex);
 	list_for_each_entry(ns, &ctrl->namespaces, list) {
-		if (ns->disk && nvme_revalidate_disk(ns->disk))
-			nvme_ns_remove(ns);
+		if (ns->disk && nvme_revalidate_disk(ns->disk)) {
+			list_move_tail(&ns->list, &rm_list);
+		}
 	}
 	mutex_unlock(&ctrl->namespaces_mutex);
+
+	list_for_each_entry_safe(ns, next, &rm_list, list)
+		nvme_ns_remove(ns);
 }
 
 static void nvme_passthru_end(struct nvme_ctrl *ctrl, u32 effects)