[PATCH v2] nvme: find numa distance only if controller has valid numa id

[Chaitanya Kulkarni]

On 4/15/24 07:22, Nilay Shroff wrote:
> On 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).
>
> Link: https://lore.kernel.org/all/20240413090614.678353-1-nilay@linux.ibm.com/
> Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
> ---
> Changes from v1:
> 	Formatting cleanups (Christoph)
>
>   drivers/nvme/host/multipath.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index 5397fb428b24..08e598c87b08 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -247,7 +247,8 @@ static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
>   		if (nvme_path_is_disabled(ns))
>   			continue;
>   
> -		if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
> +		if (ns->ctrl->numa_node != NUMA_NO_NODE &&
> +				READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)

unless something is wrong when I apply this patch, above line should be
kept under 80 char ?

something like following totally untested :-

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 5397fb428b24..d16e976ae1a4 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -247,7 +247,8 @@ static struct nvme_ns *__nvme_find_path(struct 
nvme_ns_head *head, int node)
                 if (nvme_path_is_disabled(ns))
                         continue;

-               if (READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
+               if (ns->ctrl->numa_node != NUMA_NO_NODE &&
+                   READ_ONCE(head->subsys->iopolicy) == NVME_IOPOLICY_NUMA)
                         distance = node_distance(node, 
ns->ctrl->numa_node);
                 else
                         distance = LOCAL_DISTANCE;

-ck