[PATCH RFC] driver core: ensure a device has valid node id in device_add()

[Yunsheng Lin]

Currently a device does not belong to any of the numa nodes
(dev->numa_node is NUMA_NO_NODE) when the FW does not provide
the node id and the device has not no parent device.

According to discussion in [1]:
Even if a device's numa node is not set by fw, the device
really does belong to a node.

This patch sets the device node to node 0 in device_add() if
the fw has not specified the node id and it either has no
parent device, or the parent device also does not have a valid
node id.

There may be explicit handling out there relying on NUMA_NO_NODE,
like in nvme_probe().

[1] https://lkml.org/lkml/2019/9/2/466

Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
---
 drivers/base/core.c  | 17 ++++++++++++++---
 include/linux/numa.h |  2 ++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 1669d41..466b8ff 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2107,9 +2107,20 @@ int device_add(struct device *dev)
 	if (kobj)
 		dev->kobj.parent = kobj;
 
-	/* use parent numa_node */
-	if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
-		set_dev_node(dev, dev_to_node(parent));
+	/* use parent numa_node or default node 0 */
+	if (!numa_node_valid(dev_to_node(dev))) {
+		int nid = parent ? dev_to_node(parent) : NUMA_NO_NODE;
+
+		if (numa_node_valid(nid)) {
+			set_dev_node(dev, nid);
+		} else {
+			if (nr_node_ids > 1U)
+				pr_err("device: '%s': has invalid NUMA node(%d)\n",
+				       dev_name(dev), dev_to_node(dev));
+
+			set_dev_node(dev, 0);
+		}
+	}
 
 	/* first, register with generic layer. */
 	/* we require the name to be set before, and pass NULL */
diff --git a/include/linux/numa.h b/include/linux/numa.h
index 110b0e5..eccc757 100644
--- a/include/linux/numa.h
+++ b/include/linux/numa.h
@@ -13,4 +13,6 @@
 
 #define	NUMA_NO_NODE	(-1)
 
+#define numa_node_valid(node)	((unsigned int)(node) < nr_node_ids)
+
 #endif /* _LINUX_NUMA_H */
-- 
2.8.1