From: Martin Wilck <mwilck@suse.com>
Date: Thu, 6 Aug 2020 15:19:31 +0200
Subject: nvme: multipath: round-robin: fix single non-optimized path case
Patch-mainline: 5.9-rc3
Git-commit: 93eb0381e13d249a18ed4aae203291ff977e7ffb
References: bsc#1172108

If there's only one usable, non-optimized path, nvme_round_robin_path()
returns NULL, which is wrong. Fix it by falling back to "old", like in
the single optimized path case. Also, if the active path isn't changed,
there's no need to re-assign the pointer.

Fixes: 3f6e3246db0e ("nvme-multipath: fix logic for non-optimized paths")
Signed-off-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Martin George <marting@netapp.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/multipath.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 3ded54d2c9c6..a64dfff0d0ce 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -255,12 +255,17 @@ static struct nvme_ns *nvme_round_robin_path(struct nvme_ns_head *head,
 			fallback = ns;
 	}
 
-	/* No optimized path found, re-check the current path */
+	/*
+	 * The loop above skips the current path for round-robin semantics.
+	 * Fall back to the current path if either:
+	 *  - no other optimized path found and current is optimized,
+	 *  - no other usable path found and current is usable.
+	 */
 	if (!nvme_path_is_disabled(old) &&
-	    old->ana_state == NVME_ANA_OPTIMIZED) {
-		found = old;
-		goto out;
-	}
+	    (old->ana_state == NVME_ANA_OPTIMIZED ||
+	     (!fallback && old->ana_state == NVME_ANA_NONOPTIMIZED)))
+		return old;
+
 	if (!fallback)
 		return NULL;
 	found = fallback;