nvme-multipath: prepare for "queue-depth" iopolicy

This patch prepares for the introduction of a new iopolicy by breaking up
the nvme_find_path() code path into sub-routines.

Signed-off-by: John Meneghini <jmeneghi@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: johnmeneghini

drivers/nvme/host/multipath.c

@@ -291,10 +291,15 @@ static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
 	return list_first_or_null_rcu(&head->list, struct nvme_ns, siblings);
 }
 
-static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
-		int node, struct nvme_ns *old)
+static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head)
 {
 	struct nvme_ns *ns, *found = NULL;
+	int node = numa_node_id();
+	struct nvme_ns *old = srcu_dereference(head->current_path[node],
+					       &head->srcu);
+
+	if (unlikely(!old))
+		return __nvme_find_path(head, node);
 
 	if (list_is_singular(&head->list)) {
 		if (nvme_path_is_disabled(old))
@@ -340,22 +345,26 @@ static inline bool nvme_path_is_optimized(struct nvme_ns *ns)
 		ns->ana_state == NVME_ANA_OPTIMIZED;
 }
 
-inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
+static struct nvme_ns *nvme_numa_path(struct nvme_ns_head *head)
 {
 	int node = numa_node_id();
 	struct nvme_ns *ns;
 
 	ns = srcu_dereference(head->current_path[node], &head->srcu);
 	if (unlikely(!ns))
 		return __nvme_find_path(head, node);
-
-	if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_RR)
-		return nvme_round_robin_path(head, node, ns);
 	if (unlikely(!nvme_path_is_optimized(ns)))
 		return __nvme_find_path(head, node);
 	return ns;
 }
 
+inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
+{
+	if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_RR)
+		return nvme_round_robin_path(head);
+	return nvme_numa_path(head);
+}
+
 static bool nvme_available_path(struct nvme_ns_head *head)
 {
 	struct nvme_ns *ns;