[PATCH v2 4/4] mm/mempolicy: Fix duplicate node addition in sysfs for weighted interleave

[Rakie Kim <rakie.kim@sk.com>]

Sysfs attributes for interleave control were registered both at initialization
and when new nodes were detected via hotplug, leading to potential duplicates.

This patch ensures that each node is registered only once, preventing conflicts
and redundant sysfs entries.

Signed-off-by: Rakie Kim <rakie.kim@sk.com>
---
 mm/mempolicy.c | 66 +++++++++++++++++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 20 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 71aff1276d4d..5f20521036ec 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -3391,6 +3391,7 @@ struct iw_node_attr {
 
 struct iw_node_group {
 	struct kobject *wi_kobj;
+	struct mutex kobj_lock;
 	struct iw_node_attr **nattrs;
 };
 
@@ -3440,12 +3441,17 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 static void sysfs_wi_node_release(int nid)
 {
-	if (!ngrp->nattrs[nid])
+	mutex_lock(&ngrp->kobj_lock);
+	if (!ngrp->nattrs[nid]) {
+		mutex_unlock(&ngrp->kobj_lock);
 		return;
+	}
 
 	sysfs_remove_file(ngrp->wi_kobj, &ngrp->nattrs[nid]->kobj_attr.attr);
 	kfree(ngrp->nattrs[nid]->kobj_attr.attr.name);
 	kfree(ngrp->nattrs[nid]);
+	ngrp->nattrs[nid] = NULL;
+	mutex_unlock(&ngrp->kobj_lock);
 }
 
 static void sysfs_wi_release(struct kobject *wi_kobj)
@@ -3464,35 +3470,54 @@ static const struct kobj_type wi_ktype = {
 
 static int sysfs_wi_node_add(int nid)
 {
-	struct iw_node_attr *node_attr;
+	int ret = 0;
 	char *name;
 
-	node_attr = kzalloc(sizeof(*node_attr), GFP_KERNEL);
-	if (!node_attr)
-		return -ENOMEM;
+	if (nid < 0 || nid >= nr_node_ids) {
+		pr_err("Invalid node id: %d\n", nid);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ngrp->kobj_lock);
+	if (!ngrp->nattrs[nid]) {
+		ngrp->nattrs[nid] = kzalloc(sizeof(struct iw_node_attr), GFP_KERNEL);
+	} else {
+		mutex_unlock(&ngrp->kobj_lock);
+		pr_info("Node [%d] is already existed\n", nid);
+		goto out;
+	}
+	mutex_unlock(&ngrp->kobj_lock);
+
+	if (!ngrp->nattrs[nid]) {
+		ret = -ENOMEM;
+		goto out;
+	}
 
 	name = kasprintf(GFP_KERNEL, "node%d", nid);
 	if (!name) {
-		kfree(node_attr);
-		return -ENOMEM;
+		kfree(ngrp->nattrs[nid]);
+		ret = -ENOMEM;
+		goto out;
 	}
 
-	sysfs_attr_init(&node_attr->kobj_attr.attr);
-	node_attr->kobj_attr.attr.name = name;
-	node_attr->kobj_attr.attr.mode = 0644;
-	node_attr->kobj_attr.show = node_show;
-	node_attr->kobj_attr.store = node_store;
-	node_attr->nid = nid;
+	sysfs_attr_init(&ngrp->nattrs[nid]->kobj_attr.attr);
+	ngrp->nattrs[nid]->kobj_attr.attr.name = name;
+	ngrp->nattrs[nid]->kobj_attr.attr.mode = 0644;
+	ngrp->nattrs[nid]->kobj_attr.show = node_show;
+	ngrp->nattrs[nid]->kobj_attr.store = node_store;
+	ngrp->nattrs[nid]->nid = nid;
 
-	if (sysfs_create_file(ngrp->wi_kobj, &node_attr->kobj_attr.attr)) {
-		kfree(node_attr->kobj_attr.attr.name);
-		kfree(node_attr);
-		pr_err("failed to add attribute to weighted_interleave\n");
-		return -ENOMEM;
+	ret = sysfs_create_file(ngrp->wi_kobj, &ngrp->nattrs[nid]->kobj_attr.attr);
+	if (ret) {
+		kfree(ngrp->nattrs[nid]->kobj_attr.attr.name);
+		kfree(ngrp->nattrs[nid]);
+		pr_err("failed to add attribute to weighted_interleave: %d\n", ret);
+		goto out;
 	}
 
-	ngrp->nattrs[nid] = node_attr;
-	return 0;
+out:
+	return ret;
 }
 
 static int wi_node_notifier(struct notifier_block *nb,
@@ -3588,6 +3613,7 @@ static int __init mempolicy_sysfs_init(void)
 		err = -ENOMEM;
 		goto err_out;
 	}
+	mutex_init(&ngrp->kobj_lock);
 
 	ngrp->nattrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
 			       GFP_KERNEL);
-- 
2.34.1