linux-kernel - [PATCH] acpi, numa: fix pxm to online numa node associations

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Date:   Thu, 15 Mar 2018 20:08:37 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     linux-nvdimm@...ts.01.org
Cc:     stable@...r.kernel.org, Toshi Kani <toshi.kani@...com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] acpi, numa: fix pxm to online numa node associations

Commit 99759869faf1 "acpi: Add acpi_map_pxm_to_online_node()" added
support for mapping a given proximity to its nearest, by SLIT distance,
online node. However, it sometimes returns unexpected results due to the
fact that it switches from comparing the PXM node to the last node that
was closer than the current max.

    for_each_online_node(n) {
            dist = node_distance(node, n);
            if (dist < min_dist) {
                    min_dist = dist;
                    node = n;	<---- from this point we're using the
				      wrong node for node_distance()


Fixes: 99759869faf1 ("acpi: Add acpi_map_pxm_to_online_node()")
Cc: <stable@...r.kernel.org>
Cc: Toshi Kani <toshi.kani@...com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
Rafael, I can take this through the nvdimm tree with your ack. I have a
few other nvdimm fixes pending for 4.16.

 drivers/acpi/numa.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
index 8ccaae3550d2..85167603b9c9 100644
--- a/drivers/acpi/numa.c
+++ b/drivers/acpi/numa.c
@@ -103,25 +103,27 @@ int acpi_map_pxm_to_node(int pxm)
  */
 int acpi_map_pxm_to_online_node(int pxm)
 {
-	int node, n, dist, min_dist;
+	int node, min_node;
 
 	node = acpi_map_pxm_to_node(pxm);
 
 	if (node == NUMA_NO_NODE)
 		node = 0;
 
+	min_node = node;
 	if (!node_online(node)) {
-		min_dist = INT_MAX;
+		int min_dist = INT_MAX, dist, n;
+
 		for_each_online_node(n) {
 			dist = node_distance(node, n);
 			if (dist < min_dist) {
 				min_dist = dist;
-				node = n;
+				min_node = n;
 			}
 		}
 	}
 
-	return node;
+	return min_node;
 }
 EXPORT_SYMBOL(acpi_map_pxm_to_online_node);