[PATCH] PCI: sysfs: Suppress FW_BUG warning when NUMA node already matches

[lirongqing <lirongqing@baidu.com>]

From: Li RongQing <lirongqing@baidu.com>

The numa_node sysfs interface allows users to manually override a PCI
device's NUMA node assignment. Currently, every write triggers a
FW_BUG warning and taints the kernel, even when writing the same value
that is already set.

Fix by comparing the new value against the existing dev->numa_node.
Only emit the warning and update the node when they differ. Writing
the same value becomes a harmless no-op.

Signed-off-by: Li RongQing <lirongqing@baidu.com>
---
 drivers/pci/pci-sysfs.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 16eaaf7..9f52410 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -378,11 +378,13 @@ static ssize_t numa_node_store(struct device *dev,
 	if (node != NUMA_NO_NODE && !node_online(node))
 		return -EINVAL;
 
-	add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
-	pci_alert(pdev, FW_BUG "Overriding NUMA node to %d.  Contact your vendor for updates.",
-		  node);
+	if (node != dev->numa_node) {
+		add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+		pci_alert(pdev, FW_BUG "Overriding NUMA node to %d.  Contact your vendor for updates.",
+			  node);
+		dev->numa_node = node;
+	}
 
-	dev->numa_node = node;
 	return count;
 }
 
-- 
2.9.4