[PATCH] nvme: find numa distance only if controller has valid numa id

[Nilay Shroff]

On numa aware system where native nvme multipath is configured and 
iopolicy is set to numa but the nvme controller numa node id is 
undefined or -1 (NUMA_NO_NODE) then avoid calculating node distance 
for finding optimal io path. In such case we may access numa distance
table with invalid index and that may potentially refer to incorrect
memory. So this patch ensures that if the nvme controller numa node
id is -1 then instead of calculating node distance for finding optimal
io path, we set the numa node distance of such controller to default 10
(LOCAL_DISTANCE).

Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
 drivers/nvme/host/multipath.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 5397fb428b24..4c73a8038978 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -240,17 +240,19 @@ static bool nvme_path_is_disabled(struct nvme_ns *ns)
 
 static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
 {
-	int found_distance = INT_MAX, fallback_distance = INT_MAX, distance;
+	int found_distance = INT_MAX, fallback_distance = INT_MAX;
 	struct nvme_ns *found = NULL, *fallback = NULL, *ns;
 
 	list_for_each_entry_rcu(ns, &head->list, siblings) {
+		int distance = LOCAL_DISTANCE;
+
 		if (nvme_path_is_disabled(ns))
 			continue;
 
-		if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
-			distance = node_distance(node, ns->ctrl->numa_node);
-		else
-			distance = LOCAL_DISTANCE;
+		if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA) {
+			if (ns->ctrl->numa_node != NUMA_NO_NODE)
+				distance = node_distance(node, ns->ctrl->numa_node);
+		}
 
 		switch (ns->ana_state) {
 		case NVME_ANA_OPTIMIZED:
-- 
2.44.0