[Patch v4 5/8] suppress "Device nodeX does not have a release() function" warning

[Wen Congyang]

From: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>

When calling unregister_node(), the function shows following message at
device_release().

"Device 'node2' does not have a release() function, it is broken and must
be fixed."

The reason is node's device struct does not have a release() function.

So the patch registers node_device_release() to the device's release()
function for suppressing the warning message. Additionally, the patch adds
memset() to initialize a node struct into register_node(). Because the node
struct is part of node_devices[] array and it cannot be freed by
node_device_release(). So if system reuses the node struct, it has a garbage.

CC: David Rientjes <rientjes@xxxxxxxxxx>
CC: Jiang Liu <liuj97@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
---
 drivers/base/node.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 28216ce..4282e82 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -252,6 +252,24 @@ static inline void hugetlb_register_node(struct node *node) {}
 static inline void hugetlb_unregister_node(struct node *node) {}
 #endif
 
+static void node_device_release(struct device *dev)
+{
+	struct node *node = to_node(dev);
+
+#if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HUGETLBFS)
+	/*
+	 * We schedule the work only when a memory section is
+	 * onlined/offlined on this node. When we come here,
+	 * all the memory on this node has been offlined,
+	 * so we won't enqueue new work to this work.
+	 *
+	 * The work is using node->node_work, so we should
+	 * flush work before freeing the memory.
+	 */
+	flush_work(&node->node_work);
+#endif
+	kfree(node);
+}
 
 /*
  * register_node - Setup a sysfs device for a node.
@@ -265,6 +283,7 @@ int register_node(struct node *node, int num, struct node *parent)
 
 	node->dev.id = num;
 	node->dev.bus = &node_subsys;
+	node->dev.release = node_device_release;
 	error = device_register(&node->dev);
 
 	if (!error){
@@ -586,7 +605,6 @@ int register_one_node(int nid)
 void unregister_one_node(int nid)
 {
 	unregister_node(node_devices[nid]);
-	kfree(node_devices[nid]);
 	node_devices[nid] = NULL;
 }
 
-- 
1.8.0

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