nvmet: fix nvme status code when namespace is disabled

If the user disabled a nvmet namespace, it is removed from the subsystem
namespaces list. When nvmet processes a command directed to an nsid that
was disabled, it cannot differentiate between a nsid that is disabled
vs. a non-existent namespace, and resorts to return NVME_SC_INVALID_NS
with the dnr bit set.

This translates to a non-retryable status for the host, which translates
to a user error. We should expect disabled namespaces to not cause an
I/O error in a multipath environment.

Address this by searching a configfs item for the namespace nvmet failed
to find, and if we found one, conclude that the namespace is disabled
(perhaps temporarily). Return NVME_SC_INTERNAL_PATH_ERROR in this case
and keep DNR bit cleared.

Reported-by: Jirong Feng <[email protected]>
Tested-by: Jirong Feng <[email protected]>
Signed-off-by: Sagi Grimberg <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Signed-off-by: Keith Busch <[email protected]>

Author: sagigrimberg

drivers/nvme/target/configfs.c

@@ -754,6 +754,19 @@ static struct configfs_attribute *nvmet_ns_attrs[] = {
 	NULL,
 };
 
+bool nvmet_subsys_nsid_exists(struct nvmet_subsys *subsys, u32 nsid)
+{
+	struct config_item *ns_item;
+	char name[4] = {};
+
+	if (sprintf(name, "%u", nsid) <= 0)
+		return false;
+	mutex_lock(&subsys->namespaces_group.cg_subsys->su_mutex);
+	ns_item = config_group_find_item(&subsys->namespaces_group, name);
+	mutex_unlock(&subsys->namespaces_group.cg_subsys->su_mutex);
+	return ns_item != NULL;
+}
+
 static void nvmet_ns_release(struct config_item *item)
 {
 	struct nvmet_ns *ns = to_nvmet_ns(item);

drivers/nvme/target/core.c

@@ -437,10 +437,13 @@ void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl)
 u16 nvmet_req_find_ns(struct nvmet_req *req)
 {
 	u32 nsid = le32_to_cpu(req->cmd->common.nsid);
+	struct nvmet_subsys *subsys = nvmet_req_subsys(req);
 
-	req->ns = xa_load(&nvmet_req_subsys(req)->namespaces, nsid);
+	req->ns = xa_load(&subsys->namespaces, nsid);
 	if (unlikely(!req->ns)) {
 		req->error_loc = offsetof(struct nvme_common_command, nsid);
+		if (nvmet_subsys_nsid_exists(subsys, nsid))
+			return NVME_SC_INTERNAL_PATH_ERROR;
 		return NVME_SC_INVALID_NS | NVME_SC_DNR;
 	}
 

drivers/nvme/target/nvmet.h

@@ -543,6 +543,7 @@ void nvmet_subsys_disc_changed(struct nvmet_subsys *subsys,
 		struct nvmet_host *host);
 void nvmet_add_async_event(struct nvmet_ctrl *ctrl, u8 event_type,
 		u8 event_info, u8 log_page);
+bool nvmet_subsys_nsid_exists(struct nvmet_subsys *subsys, u32 nsid);
 
 #define NVMET_MIN_QUEUE_SIZE	16
 #define NVMET_MAX_QUEUE_SIZE	1024