[PATCH 1/2] nvme: multipath: round-robin: fix logic for non-optimized paths

[mwilck at suse.com]

From: Martin Wilck <mwilck at suse.com>

Handle the special case where we have exactly one optimized path,
which we should keep using in this case. Also, use the next
non-optimized path, not the last one.

Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 drivers/nvme/host/multipath.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 74bad4e3d377..2c575b783d3e 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -224,13 +224,8 @@ static struct nvme_ns *nvme_next_ns(struct nvme_ns_head *head,
 static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
 		int node, struct nvme_ns *old)
 {
-	struct nvme_ns *ns, *found, *fallback = NULL;
+	struct nvme_ns *ns, *found = NULL;
 
-	if (list_is_singular(&head->list)) {
-		if (nvme_path_is_disabled(old))
-			return NULL;
-		return old;
-	}
 
 	for (ns = nvme_next_ns(head, old);
 	     ns != old;
@@ -242,13 +237,19 @@ static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
 			found = ns;
 			goto out;
 		}
-		if (ns->ana_state == NVME_ANA_NONOPTIMIZED)
-			fallback = ns;
+		if (!found && ns->ana_state == NVME_ANA_NONOPTIMIZED)
+			found = ns;
 	}
 
-	if (!fallback)
+	/* Fall back to old if it's better than the others */
+	if (!nvme_path_is_disabled(old) &&
+	    (old->ana_state == NVME_ANA_OPTIMIZED ||
+	     (!found && old->ana_state == NVME_ANA_NONOPTIMIZED)))
+		found = old;
+
+	if (!found)
 		return NULL;
-	found = fallback;
+
 out:
 	rcu_assign_pointer(head->current_path[node], found);
 	return found;
-- 
2.26.2