Series comparison

-[PATCH v4 0/3] Enhance sysfs handling for memory hotplug in weighted interleave
+[PATCH v5 0/3] Enhance sysfs handling for memory hotplug in weighted interleave
 ...
      preventing stale or redundant entries from persisting.
 These patches have been tested under CXL-based memory configurations,
 including hotplug scenarios, to ensure proper behavior and stability.
- mm/mempolicy.c | 195 ++++++++++++++++++++++++++++++++-----------------
+ mm/mempolicy.c | 192 +++++++++++++++++++++++++++++++------------------
-file changed, 127 insertions(+), 68 deletions(-)
+file changed, 124 insertions(+), 68 deletions(-)
 base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557
 --
 .34.1

-[PATCH v4 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs
+[PATCH v5 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs
 Memory leaks occurred when removing sysfs attributes for weighted
 interleave. Improper kobject deallocation led to unreleased memory
 when initialization failed or when nodes were removed.
 This patch resolves the issue by replacing unnecessary `kfree()`
 calls with `kobject_put()`, ensuring proper cleanup and preventing
 memory leaks.
 By correctly using `kobject_put()`, the release function now
 properly deallocates memory without causing resource leaks,
 thereby improving system stability.
 Fixes: dce41f5ae253 ("mm/mempolicy: implement the sysfs-based weighted_interleave interface")
 Signed-off-by: Rakie Kim <rakie.kim@sk.com>
 Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
 Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
 Reviewed-by: Gregory Price <gourry@gourry.net>
 ---
  mm/mempolicy.c | 61 +++++++++++++++++++++++++-------------------------
 file changed, 31 insertions(+), 30 deletions(-)
 diff --git a/mm/mempolicy.c b/mm/mempolicy.c
 index XXXXXXX..XXXXXXX 100644
 --- a/mm/mempolicy.c
 +++ b/mm/mempolicy.c
 @@ -XXX,XX +XXX,XX @@ static void sysfs_wi_release(struct kobject *wi_kobj)
      for (i = 0; i < nr_node_ids; i++)
          sysfs_wi_node_release(node_attrs[i], wi_kobj);
 -    kobject_put(wi_kobj);
 +
 +    kfree(node_attrs);
 +    kfree(wi_kobj);
  }
  static const struct kobj_type wi_ktype = {
 @@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
      struct kobject *wi_kobj;
      int nid, err;
 -    wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
 -    if (!wi_kobj)
 +    node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
 +                 GFP_KERNEL);
 +    if (!node_attrs)
          return -ENOMEM;
 +    wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
 +    if (!wi_kobj) {
 +        err = -ENOMEM;
 +        goto node_out;
 +    }
 +
      err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
                     "weighted_interleave");
      if (err) {
 -        kfree(wi_kobj);
 -        return err;
 +        kobject_put(wi_kobj);
 +        goto err_out;
      }
      for_each_node_state(nid, N_POSSIBLE) {
 @@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
              break;
          }
      }
 -    if (err)
 +    if (err) {
          kobject_put(wi_kobj);
 +        goto err_out;
 +    }
 +
      return 0;
 +
 +node_out:
 +    kfree(node_attrs);
 +err_out:
 +    return err;
  }
  static void mempolicy_kobj_release(struct kobject *kobj)
 @@ -XXX,XX +XXX,XX @@ static void mempolicy_kobj_release(struct kobject *kobj)
      mutex_unlock(&iw_table_lock);
      synchronize_rcu();
      kfree(old);
 -    kfree(node_attrs);
      kfree(kobj);
  }
 @@ -XXX,XX +XXX,XX @@ static int __init mempolicy_sysfs_init(void)
      static struct kobject *mempolicy_kobj;
      mempolicy_kobj = kzalloc(sizeof(*mempolicy_kobj), GFP_KERNEL);
 -    if (!mempolicy_kobj) {
 -        err = -ENOMEM;
 -        goto err_out;
 -    }
 -
 -    node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
 -                 GFP_KERNEL);
 -    if (!node_attrs) {
 -        err = -ENOMEM;
 -        goto mempol_out;
 -    }
 +    if (!mempolicy_kobj)
 +        return -ENOMEM;
      err = kobject_init_and_add(mempolicy_kobj, &mempolicy_ktype, mm_kobj,
                     "mempolicy");
      if (err)
 -        goto node_out;
 +        goto err_out;
      err = add_weighted_interleave_group(mempolicy_kobj);
 -    if (err) {
 -        pr_err("mempolicy sysfs structure failed to initialize\n");
 -        kobject_put(mempolicy_kobj);
 -        return err;
 -    }
 +    if (err)
 +        goto err_out;
 +
 +    return 0;
 -    return err;
 -node_out:
 -    kfree(node_attrs);
 -mempol_out:
 -    kfree(mempolicy_kobj);
  err_out:
 -    pr_err("failed to add mempolicy kobject to the system\n");
 +    kobject_put(mempolicy_kobj);
      return err;
  }
 --
 .34.1

-[PATCH v4 2/3] mm/mempolicy: Support dynamic sysfs updates for weighted interleave
+[PATCH v5 2/3] mm/mempolicy: Support dynamic sysfs updates for weighted interleave
 Previously, the weighted interleave sysfs structure was statically
 managed, preventing dynamic updates when nodes were added or removed.
 This patch restructures the weighted interleave sysfs to support
 dynamic insertion and deletion. The sysfs that was part of
 the 'weighted_interleave_group' is now globally accessible,
 allowing external access to that sysfs.
 With this change, sysfs management for weighted interleave is
 more flexible, supporting hotplug events and runtime updates
 more effectively.
 Signed-off-by: Rakie Kim <rakie.kim@sk.com>
 Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
 Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
 Reviewed-by: Gregory Price <gourry@gourry.net>
 ---
  mm/mempolicy.c | 71 ++++++++++++++++++++++----------------------------
 file changed, 31 insertions(+), 40 deletions(-)
 diff --git a/mm/mempolicy.c b/mm/mempolicy.c
 index XXXXXXX..XXXXXXX 100644
 --- a/mm/mempolicy.c
 +++ b/mm/mempolicy.c
 @@ -XXX,XX +XXX,XX @@ struct iw_node_attr {
      int nid;
  };
 +struct sysfs_wi_group {
 +    struct kobject wi_kobj;
 +    struct iw_node_attr *nattrs[];
 +};
 +
 +static struct sysfs_wi_group *wi_group;
 +
  static ssize_t node_show(struct kobject *kobj, struct kobj_attribute *attr,
               char *buf)
  {
 @@ -XXX,XX +XXX,XX @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
      return count;
  }
 -static struct iw_node_attr **node_attrs;
 -
 -static void sysfs_wi_node_release(struct iw_node_attr *node_attr,
 -                  struct kobject *parent)
 +static void sysfs_wi_node_release(int nid)
  {
 -    if (!node_attr)
 +    if (!wi_group->nattrs[nid])
          return;
 -    sysfs_remove_file(parent, &node_attr->kobj_attr.attr);
 -    kfree(node_attr->kobj_attr.attr.name);
 -    kfree(node_attr);
 +
 +    sysfs_remove_file(&wi_group->wi_kobj,
 +              &wi_group->nattrs[nid]->kobj_attr.attr);
 +    kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
 +    kfree(wi_group->nattrs[nid]);
  }
  static void sysfs_wi_release(struct kobject *wi_kobj)
  {
 -    int i;
 -
 -    for (i = 0; i < nr_node_ids; i++)
 -        sysfs_wi_node_release(node_attrs[i], wi_kobj);
 +    int nid;
 -    kfree(node_attrs);
 -    kfree(wi_kobj);
 +    for (nid = 0; nid < nr_node_ids; nid++)
 +        sysfs_wi_node_release(nid);
 +    kfree(wi_group);
  }
  static const struct kobj_type wi_ktype = {
 @@ -XXX,XX +XXX,XX @@ static const struct kobj_type wi_ktype = {
      .release = sysfs_wi_release,
  };
 -static int add_weight_node(int nid, struct kobject *wi_kobj)
 +static int sysfs_wi_node_add(int nid)
  {
      struct iw_node_attr *node_attr;
      char *name;
 @@ -XXX,XX +XXX,XX @@ static int add_weight_node(int nid, struct kobject *wi_kobj)
      node_attr->kobj_attr.store = node_store;
      node_attr->nid = nid;
 -    if (sysfs_create_file(wi_kobj, &node_attr->kobj_attr.attr)) {
 +    if (sysfs_create_file(&wi_group->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;
      }
 -    node_attrs[nid] = node_attr;
 +    wi_group->nattrs[nid] = node_attr;
      return 0;
  }
 -static int add_weighted_interleave_group(struct kobject *root_kobj)
 +static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
  {
 -    struct kobject *wi_kobj;
      int nid, err;
 -    node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
 -                 GFP_KERNEL);
 -    if (!node_attrs)
 +    wi_group = kzalloc(sizeof(struct sysfs_wi_group) +         \
 +               nr_node_ids * sizeof(struct iw_node_attr *),    \
 +               GFP_KERNEL);
 +    if (!wi_group)
          return -ENOMEM;
 -    wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
 -    if (!wi_kobj) {
 -        err = -ENOMEM;
 -        goto node_out;
 -    }
 -
 -    err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
 +    err = kobject_init_and_add(&wi_group->wi_kobj, &wi_ktype, mempolicy_kobj,
                     "weighted_interleave");
 -    if (err) {
 -        kobject_put(wi_kobj);
 +    if (err)
          goto err_out;
 -    }
      for_each_node_state(nid, N_POSSIBLE) {
 -        err = add_weight_node(nid, wi_kobj);
 +        err = sysfs_wi_node_add(nid);
          if (err) {
              pr_err("failed to add sysfs [node%d]\n", nid);
 -            break;
 +            goto err_out;
          }
      }
 -    if (err) {
 -        kobject_put(wi_kobj);
 -        goto err_out;
 -    }
      return 0;
 -node_out:
 -    kfree(node_attrs);
  err_out:
 +    kobject_put(&wi_group->wi_kobj);
      return err;
  }
 --
 .34.1

-[PATCH v4 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
+[PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
 ...
 Signed-off-by: Rakie Kim <rakie.kim@sk.com>
 Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
 Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
 ---
- mm/mempolicy.c | 113 +++++++++++++++++++++++++++++++++++++++----------
+ mm/mempolicy.c | 110 ++++++++++++++++++++++++++++++++++++++-----------
-file changed, 90 insertions(+), 23 deletions(-)
+file changed, 87 insertions(+), 23 deletions(-)
 diff --git a/mm/mempolicy.c b/mm/mempolicy.c
 index XXXXXXX..XXXXXXX 100644
 --- a/mm/mempolicy.c
 +++ b/mm/mempolicy.c
 ...
 +    attr = wi_group->nattrs[nid];
 +    if (!attr) {
 +        mutex_unlock(&wi_group->kobj_lock);
          return;
 +    }
++
++    wi_group->nattrs[nid] = NULL;
++    mutex_unlock(&wi_group->kobj_lock);
 -    sysfs_remove_file(&wi_group->wi_kobj,
 -              &wi_group->nattrs[nid]->kobj_attr.attr);
 -    kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
 -    kfree(wi_group->nattrs[nid]);
-+    wi_group->nattrs[nid] = NULL;
-+    mutex_unlock(&wi_group->kobj_lock);
-+
 +    sysfs_remove_file(&wi_group->wi_kobj, &attr->kobj_attr.attr);
 +    kfree(attr->kobj_attr.attr.name);
 +    kfree(attr);
  }
 ...
 +        pr_info("Node [%d] already exists\n", nid);
 +        kfree(new_attr);
 +        kfree(name);
 +        return 0;
 +    }
++    wi_group->nattrs[nid] = new_attr;
 -    if (sysfs_create_file(&wi_group->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;
-+    wi_group->nattrs[nid] = new_attr;
-+    mutex_unlock(&wi_group->kobj_lock);
-+
 +    sysfs_attr_init(&wi_group->nattrs[nid]->kobj_attr.attr);
 +    wi_group->nattrs[nid]->kobj_attr.attr.name = name;
 +    wi_group->nattrs[nid]->kobj_attr.attr.mode = 0644;
 +    wi_group->nattrs[nid]->kobj_attr.show = node_show;
 +    wi_group->nattrs[nid]->kobj_attr.store = node_store;
 ...
 +        kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
 +        kfree(wi_group->nattrs[nid]);
 +        wi_group->nattrs[nid] = NULL;
 +        pr_err("Failed to add attribute to weighted_interleave: %d\n", ret);
      }
++    mutex_unlock(&wi_group->kobj_lock);
 -    wi_group->nattrs[nid] = node_attr;
 -    return 0;
 +    return ret;
 +}
 ...
 +    if (nid < 0)
 +        goto notifier_end;
 +
 +    switch(action) {
 +    case MEM_ONLINE:
-+        if (node_state(nid, N_MEMORY)) {
++        err = sysfs_wi_node_add(nid);
-+            err = sysfs_wi_node_add(nid);
++        if (err) {
-+            if (err) {
++            pr_err("failed to add sysfs [node%d]\n", nid);
-+                pr_err("failed to add sysfs [node%d]\n", nid);
++            return NOTIFY_BAD;
 +                return NOTIFY_BAD;
 +            }
 +        }
 +        break;
 +    case MEM_OFFLINE:
 +        if (!node_state(nid, N_MEMORY))
 +            sysfs_wi_node_release(nid);
 ...

The following patch series enhances the weighted interleave policy in the
memory management subsystem by improving sysfs handling, fixing memory leaks,
and introducing dynamic sysfs updates for memory hotplug support.

### Background
The weighted interleave policy distributes memory allocations across multiple
NUMA nodes based on their performance weight, thereby optimizing memory
bandwidth utilization. The weight values are configured through sysfs.

Previously, sysfs entries for weighted interleave were managed statically
at initialization. This led to several issues:
- Memory Leaks: Improper `kobject` deallocation caused memory leaks
  when initialization failed or when nodes were removed.
- Lack of Dynamic Updates: Sysfs attributes were created only during
  initialization, preventing nodes added at runtime from being recognized.
- Handling of Unusable Nodes: Sysfs entries were generated for all
  possible nodes (`N_POSSIBLE`), including memoryless or unavailable nodes,
  leading to sysfs entries for unusable nodes and potential
  misconfigurations.

### Patch Overview
1. [PATCH 1/3] Fix memory leaks in weighted interleave sysfs
   - Ensures proper cleanup of `kobject` allocations.
   - Replaces unnecessary `kfree()` calls with `kobject_put()`, preventing
     memory leaks and improving system stability.

2. [PATCH 2/3] Enable dynamic updates for weighted interleave sysfs
   - Restructures sysfs handling to allow runtime updates.
   - The sysfs attributes are now globally accessible, enabling external
     modules to manage interleave settings dynamically.

3. [PATCH 3/3] Support memory hotplug in weighted interleave
   - Modifies sysfs creation logic to restrict entries to nodes that are
     online and have memory, excluding unusable nodes.
   - Introduces a memory hotplug mechanism to dynamically add and remove
     sysfs attributes when nodes transition into or out of the `N_MEMORY` set.
   - Ensures that sysfs attributes are properly removed when nodes go offline,
     preventing stale or redundant entries from persisting.

These patches have been tested under CXL-based memory configurations,
including hotplug scenarios, to ensure proper behavior and stability.

mm/mempolicy.c | 195 ++++++++++++++++++++++++++++++++-----------------
 1 file changed, 127 insertions(+), 68 deletions(-)

base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557
-- 
2.34.1

Memory leaks occurred when removing sysfs attributes for weighted
interleave. Improper kobject deallocation led to unreleased memory
when initialization failed or when nodes were removed.

This patch resolves the issue by replacing unnecessary `kfree()`
calls with `kobject_put()`, ensuring proper cleanup and preventing
memory leaks.

By correctly using `kobject_put()`, the release function now
properly deallocates memory without causing resource leaks,
thereby improving system stability.

Fixes: dce41f5ae253 ("mm/mempolicy: implement the sysfs-based weighted_interleave interface")
Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
---
 mm/mempolicy.c | 61 +++++++++++++++++++++++++-------------------------
 1 file changed, 31 insertions(+), 30 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index XXXXXXX..XXXXXXX 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -XXX,XX +XXX,XX @@ static void sysfs_wi_release(struct kobject *wi_kobj)
 
 	for (i = 0; i < nr_node_ids; i++)
 		sysfs_wi_node_release(node_attrs[i], wi_kobj);
-	kobject_put(wi_kobj);
+
+	kfree(node_attrs);
+	kfree(wi_kobj);
 }
 
 static const struct kobj_type wi_ktype = {
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
 	struct kobject *wi_kobj;
 	int nid, err;
 
-	wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
-	if (!wi_kobj)
+	node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
+			     GFP_KERNEL);
+	if (!node_attrs)
 		return -ENOMEM;
 
+	wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
+	if (!wi_kobj) {
+		err = -ENOMEM;
+		goto node_out;
+	}
+
 	err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
 				   "weighted_interleave");
 	if (err) {
-		kfree(wi_kobj);
-		return err;
+		kobject_put(wi_kobj);
+		goto err_out;
 	}
 
 	for_each_node_state(nid, N_POSSIBLE) {
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
 			break;
 		}
 	}
-	if (err)
+	if (err) {
 		kobject_put(wi_kobj);
+		goto err_out;
+	}
+
 	return 0;
+
+node_out:
+	kfree(node_attrs);
+err_out:
+	return err;
 }
 
 static void mempolicy_kobj_release(struct kobject *kobj)
@@ -XXX,XX +XXX,XX @@ static void mempolicy_kobj_release(struct kobject *kobj)
 	mutex_unlock(&iw_table_lock);
 	synchronize_rcu();
 	kfree(old);
-	kfree(node_attrs);
 	kfree(kobj);
 }
 
@@ -XXX,XX +XXX,XX @@ static int __init mempolicy_sysfs_init(void)
 	static struct kobject *mempolicy_kobj;
 
 	mempolicy_kobj = kzalloc(sizeof(*mempolicy_kobj), GFP_KERNEL);
-	if (!mempolicy_kobj) {
-		err = -ENOMEM;
-		goto err_out;
-	}
-
-	node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
-			     GFP_KERNEL);
-	if (!node_attrs) {
-		err = -ENOMEM;
-		goto mempol_out;
-	}
+	if (!mempolicy_kobj)
+		return -ENOMEM;
 
 	err = kobject_init_and_add(mempolicy_kobj, &mempolicy_ktype, mm_kobj,
 				   "mempolicy");
 	if (err)
-		goto node_out;
+		goto err_out;
 
 	err = add_weighted_interleave_group(mempolicy_kobj);
-	if (err) {
-		pr_err("mempolicy sysfs structure failed to initialize\n");
-		kobject_put(mempolicy_kobj);
-		return err;
-	}
+	if (err)
+		goto err_out;
+
+	return 0;
 
-	return err;
-node_out:
-	kfree(node_attrs);
-mempol_out:
-	kfree(mempolicy_kobj);
 err_out:
-	pr_err("failed to add mempolicy kobject to the system\n");
+	kobject_put(mempolicy_kobj);
 	return err;
 }
 
-- 
2.34.1

Previously, the weighted interleave sysfs structure was statically
managed, preventing dynamic updates when nodes were added or removed.

This patch restructures the weighted interleave sysfs to support
dynamic insertion and deletion. The sysfs that was part of
the 'weighted_interleave_group' is now globally accessible,
allowing external access to that sysfs.

With this change, sysfs management for weighted interleave is
more flexible, supporting hotplug events and runtime updates
more effectively.

Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
---
 mm/mempolicy.c | 71 ++++++++++++++++++++++----------------------------
 1 file changed, 31 insertions(+), 40 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index XXXXXXX..XXXXXXX 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -XXX,XX +XXX,XX @@ struct iw_node_attr {
 	int nid;
 };
 
+struct sysfs_wi_group {
+	struct kobject wi_kobj;
+	struct iw_node_attr *nattrs[];
+};
+
+static struct sysfs_wi_group *wi_group;
+
 static ssize_t node_show(struct kobject *kobj, struct kobj_attribute *attr,
 			 char *buf)
 {
@@ -XXX,XX +XXX,XX @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
 	return count;
 }
 
-static struct iw_node_attr **node_attrs;
-
-static void sysfs_wi_node_release(struct iw_node_attr *node_attr,
-				  struct kobject *parent)
+static void sysfs_wi_node_release(int nid)
 {
-	if (!node_attr)
+	if (!wi_group->nattrs[nid])
 		return;
-	sysfs_remove_file(parent, &node_attr->kobj_attr.attr);
-	kfree(node_attr->kobj_attr.attr.name);
-	kfree(node_attr);
+
+	sysfs_remove_file(&wi_group->wi_kobj,
+			  &wi_group->nattrs[nid]->kobj_attr.attr);
+	kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
+	kfree(wi_group->nattrs[nid]);
 }
 
 static void sysfs_wi_release(struct kobject *wi_kobj)
 {
-	int i;
-
-	for (i = 0; i < nr_node_ids; i++)
-		sysfs_wi_node_release(node_attrs[i], wi_kobj);
+	int nid;
 
-	kfree(node_attrs);
-	kfree(wi_kobj);
+	for (nid = 0; nid < nr_node_ids; nid++)
+		sysfs_wi_node_release(nid);
+	kfree(wi_group);
 }
 
 static const struct kobj_type wi_ktype = {
@@ -XXX,XX +XXX,XX @@ static const struct kobj_type wi_ktype = {
 	.release = sysfs_wi_release,
 };
 
-static int add_weight_node(int nid, struct kobject *wi_kobj)
+static int sysfs_wi_node_add(int nid)
 {
 	struct iw_node_attr *node_attr;
 	char *name;
@@ -XXX,XX +XXX,XX @@ static int add_weight_node(int nid, struct kobject *wi_kobj)
 	node_attr->kobj_attr.store = node_store;
 	node_attr->nid = nid;
 
-	if (sysfs_create_file(wi_kobj, &node_attr->kobj_attr.attr)) {
+	if (sysfs_create_file(&wi_group->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;
 	}
 
-	node_attrs[nid] = node_attr;
+	wi_group->nattrs[nid] = node_attr;
 	return 0;
 }
 
-static int add_weighted_interleave_group(struct kobject *root_kobj)
+static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 {
-	struct kobject *wi_kobj;
 	int nid, err;
 
-	node_attrs = kcalloc(nr_node_ids, sizeof(struct iw_node_attr *),
-			     GFP_KERNEL);
-	if (!node_attrs)
+	wi_group = kzalloc(sizeof(struct sysfs_wi_group) + 		\
+		       nr_node_ids * sizeof(struct iw_node_attr *),	\
+		       GFP_KERNEL);
+	if (!wi_group)
 		return -ENOMEM;
 
-	wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
-	if (!wi_kobj) {
-		err = -ENOMEM;
-		goto node_out;
-	}
-
-	err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
+	err = kobject_init_and_add(&wi_group->wi_kobj, &wi_ktype, mempolicy_kobj,
 				   "weighted_interleave");
-	if (err) {
-		kobject_put(wi_kobj);
+	if (err)
 		goto err_out;
-	}
 
 	for_each_node_state(nid, N_POSSIBLE) {
-		err = add_weight_node(nid, wi_kobj);
+		err = sysfs_wi_node_add(nid);
 		if (err) {
 			pr_err("failed to add sysfs [node%d]\n", nid);
-			break;
+			goto err_out;
 		}
 	}
-	if (err) {
-		kobject_put(wi_kobj);
-		goto err_out;
-	}
 
 	return 0;
 
-node_out:
-	kfree(node_attrs);
 err_out:
+	kobject_put(&wi_group->wi_kobj);
 	return err;
 }
 
-- 
2.34.1

The weighted interleave policy distributes page allocations across multiple
NUMA nodes based on their performance weight, thereby improving memory
bandwidth utilization. The weight values for each node are configured
through sysfs.

Previously, sysfs entries for configuring weighted interleave were created
for all possible nodes (N_POSSIBLE) at initialization, including nodes that
might not have memory. However, not all nodes in N_POSSIBLE are usable at
runtime, as some may remain memoryless or offline.
This led to sysfs entries being created for unusable nodes, causing
potential misconfiguration issues.

To address this issue, this patch modifies the sysfs creation logic to:
1) Limit sysfs entries to nodes that are online and have memory, avoiding
   the creation of sysfs entries for nodes that cannot be used.
2) Support memory hotplug by dynamically adding and removing sysfs entries
   based on whether a node transitions into or out of the N_MEMORY state.

Additionally, the patch ensures that sysfs attributes are properly managed
when nodes go offline, preventing stale or redundant entries from persisting
in the system.

By making these changes, the weighted interleave policy now manages its
sysfs entries more efficiently, ensuring that only relevant nodes are
considered for interleaving, and dynamically adapting to memory hotplug
events.

Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
---
 mm/mempolicy.c | 113 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 90 insertions(+), 23 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index XXXXXXX..XXXXXXX 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -XXX,XX +XXX,XX @@
 #include <asm/tlbflush.h>
 #include <asm/tlb.h>
 #include <linux/uaccess.h>
+#include <linux/memory.h>
 
 #include "internal.h"
 
@@ -XXX,XX +XXX,XX @@ struct iw_node_attr {
 
 struct sysfs_wi_group {
 	struct kobject wi_kobj;
+	struct mutex kobj_lock;
 	struct iw_node_attr *nattrs[];
 };
 
@@ -XXX,XX +XXX,XX @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 static void sysfs_wi_node_release(int nid)
 {
-	if (!wi_group->nattrs[nid])
+	struct iw_node_attr *attr;
+
+	if (nid < 0 || nid >= nr_node_ids)
+		return;
+
+	mutex_lock(&wi_group->kobj_lock);
+	attr = wi_group->nattrs[nid];
+	if (!attr) {
+		mutex_unlock(&wi_group->kobj_lock);
 		return;
+	}
 
-	sysfs_remove_file(&wi_group->wi_kobj,
-			  &wi_group->nattrs[nid]->kobj_attr.attr);
-	kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
-	kfree(wi_group->nattrs[nid]);
+	wi_group->nattrs[nid] = NULL;
+	mutex_unlock(&wi_group->kobj_lock);
+
+	sysfs_remove_file(&wi_group->wi_kobj, &attr->kobj_attr.attr);
+	kfree(attr->kobj_attr.attr.name);
+	kfree(attr);
 }
 
 static void sysfs_wi_release(struct kobject *wi_kobj)
@@ -XXX,XX +XXX,XX @@ 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;
+	struct iw_node_attr *new_attr = NULL;
 
-	node_attr = kzalloc(sizeof(*node_attr), GFP_KERNEL);
-	if (!node_attr)
+	if (nid < 0 || nid >= nr_node_ids) {
+		pr_err("Invalid node id: %d\n", nid);
+		return -EINVAL;
+	}
+
+	new_attr = kzalloc(sizeof(struct iw_node_attr), GFP_KERNEL);
+	if (!new_attr)
 		return -ENOMEM;
 
 	name = kasprintf(GFP_KERNEL, "node%d", nid);
 	if (!name) {
-		kfree(node_attr);
+		kfree(new_attr);
 		return -ENOMEM;
 	}
 
-	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;
+	mutex_lock(&wi_group->kobj_lock);
+	if (wi_group->nattrs[nid]) {
+		mutex_unlock(&wi_group->kobj_lock);
+		pr_info("Node [%d] already exists\n", nid);
+		kfree(new_attr);
+		kfree(name);
+		return 0;
+	}
 
-	if (sysfs_create_file(&wi_group->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;
+	wi_group->nattrs[nid] = new_attr;
+	mutex_unlock(&wi_group->kobj_lock);
+
+	sysfs_attr_init(&wi_group->nattrs[nid]->kobj_attr.attr);
+	wi_group->nattrs[nid]->kobj_attr.attr.name = name;
+	wi_group->nattrs[nid]->kobj_attr.attr.mode = 0644;
+	wi_group->nattrs[nid]->kobj_attr.show = node_show;
+	wi_group->nattrs[nid]->kobj_attr.store = node_store;
+	wi_group->nattrs[nid]->nid = nid;
+
+	ret = sysfs_create_file(&wi_group->wi_kobj,
+				&wi_group->nattrs[nid]->kobj_attr.attr);
+	if (ret) {
+		kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
+		kfree(wi_group->nattrs[nid]);
+		wi_group->nattrs[nid] = NULL;
+		pr_err("Failed to add attribute to weighted_interleave: %d\n", ret);
 	}
 
-	wi_group->nattrs[nid] = node_attr;
-	return 0;
+	return ret;
+}
+
+static int wi_node_notifier(struct notifier_block *nb,
+			       unsigned long action, void *data)
+{
+	int err;
+	struct memory_notify *arg = data;
+	int nid = arg->status_change_nid;
+
+	if (nid < 0)
+		goto notifier_end;
+
+	switch(action) {
+	case MEM_ONLINE:
+		if (node_state(nid, N_MEMORY)) {
+			err = sysfs_wi_node_add(nid);
+			if (err) {
+				pr_err("failed to add sysfs [node%d]\n", nid);
+				return NOTIFY_BAD;
+			}
+		}
+		break;
+	case MEM_OFFLINE:
+		if (!node_state(nid, N_MEMORY))
+			sysfs_wi_node_release(nid);
+		break;
+	}
+
+notifier_end:
+	return NOTIFY_OK;
 }
 
 static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 		       GFP_KERNEL);
 	if (!wi_group)
 		return -ENOMEM;
+	mutex_init(&wi_group->kobj_lock);
 
 	err = kobject_init_and_add(&wi_group->wi_kobj, &wi_ktype, mempolicy_kobj,
 				   "weighted_interleave");
 	if (err)
 		goto err_out;
 
-	for_each_node_state(nid, N_POSSIBLE) {
+	for_each_online_node(nid) {
+		if (!node_state(nid, N_MEMORY))
+			continue;
+
 		err = sysfs_wi_node_add(nid);
 		if (err) {
 			pr_err("failed to add sysfs [node%d]\n", nid);
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 		}
 	}
 
+	hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
 	return 0;
 
 err_out:
-- 
2.34.1

These patches have been tested under CXL-based memory configurations,
including hotplug scenarios, to ensure proper behavior and stability.

mm/mempolicy.c | 192 +++++++++++++++++++++++++++++++------------------
 1 file changed, 124 insertions(+), 68 deletions(-)

base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557
-- 
2.34.1

Memory leaks occurred when removing sysfs attributes for weighted
interleave. Improper kobject deallocation led to unreleased memory
when initialization failed or when nodes were removed.

This patch resolves the issue by replacing unnecessary `kfree()`
calls with `kobject_put()`, ensuring proper cleanup and preventing
memory leaks.

By correctly using `kobject_put()`, the release function now
properly deallocates memory without causing resource leaks,
thereby improving system stability.

Previously, the weighted interleave sysfs structure was statically
managed, preventing dynamic updates when nodes were added or removed.

With this change, sysfs management for weighted interleave is
more flexible, supporting hotplug events and runtime updates
more effectively.

Additionally, the patch ensures that sysfs attributes are properly managed
when nodes go offline, preventing stale or redundant entries from persisting
in the system.

Signed-off-by: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: Yunjeong Mun <yunjeong.mun@sk.com>
---
 mm/mempolicy.c | 110 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 87 insertions(+), 23 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index XXXXXXX..XXXXXXX 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -XXX,XX +XXX,XX @@
 #include <asm/tlbflush.h>
 #include <asm/tlb.h>
 #include <linux/uaccess.h>
+#include <linux/memory.h>
 
 #include "internal.h"
 
@@ -XXX,XX +XXX,XX @@ struct iw_node_attr {
 
 struct sysfs_wi_group {
 	struct kobject wi_kobj;
+	struct mutex kobj_lock;
 	struct iw_node_attr *nattrs[];
 };
 
@@ -XXX,XX +XXX,XX @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 static void sysfs_wi_node_release(int nid)
 {
-	if (!wi_group->nattrs[nid])
+	struct iw_node_attr *attr;
+
+	if (nid < 0 || nid >= nr_node_ids)
+		return;
+
+	mutex_lock(&wi_group->kobj_lock);
+	attr = wi_group->nattrs[nid];
+	if (!attr) {
+		mutex_unlock(&wi_group->kobj_lock);
 		return;
+	}
+
+	wi_group->nattrs[nid] = NULL;
+	mutex_unlock(&wi_group->kobj_lock);
 
-	sysfs_remove_file(&wi_group->wi_kobj,
-			  &wi_group->nattrs[nid]->kobj_attr.attr);
-	kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
-	kfree(wi_group->nattrs[nid]);
+	sysfs_remove_file(&wi_group->wi_kobj, &attr->kobj_attr.attr);
+	kfree(attr->kobj_attr.attr.name);
+	kfree(attr);
 }
 
 static void sysfs_wi_release(struct kobject *wi_kobj)
@@ -XXX,XX +XXX,XX @@ 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;
+	struct iw_node_attr *new_attr = NULL;
 
-	node_attr = kzalloc(sizeof(*node_attr), GFP_KERNEL);
-	if (!node_attr)
+	if (nid < 0 || nid >= nr_node_ids) {
+		pr_err("Invalid node id: %d\n", nid);
+		return -EINVAL;
+	}
+
+	new_attr = kzalloc(sizeof(struct iw_node_attr), GFP_KERNEL);
+	if (!new_attr)
 		return -ENOMEM;
 
 	name = kasprintf(GFP_KERNEL, "node%d", nid);
 	if (!name) {
-		kfree(node_attr);
+		kfree(new_attr);
 		return -ENOMEM;
 	}
 
-	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;
+	mutex_lock(&wi_group->kobj_lock);
+	if (wi_group->nattrs[nid]) {
+		mutex_unlock(&wi_group->kobj_lock);
+		pr_info("Node [%d] already exists\n", nid);
+		kfree(new_attr);
+		kfree(name);
+		return 0;
+	}
+	wi_group->nattrs[nid] = new_attr;
 
-	if (sysfs_create_file(&wi_group->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;
+	sysfs_attr_init(&wi_group->nattrs[nid]->kobj_attr.attr);
+	wi_group->nattrs[nid]->kobj_attr.attr.name = name;
+	wi_group->nattrs[nid]->kobj_attr.attr.mode = 0644;
+	wi_group->nattrs[nid]->kobj_attr.show = node_show;
+	wi_group->nattrs[nid]->kobj_attr.store = node_store;
+	wi_group->nattrs[nid]->nid = nid;
+
+	ret = sysfs_create_file(&wi_group->wi_kobj,
+				&wi_group->nattrs[nid]->kobj_attr.attr);
+	if (ret) {
+		kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
+		kfree(wi_group->nattrs[nid]);
+		wi_group->nattrs[nid] = NULL;
+		pr_err("Failed to add attribute to weighted_interleave: %d\n", ret);
 	}
+	mutex_unlock(&wi_group->kobj_lock);
 
-	wi_group->nattrs[nid] = node_attr;
-	return 0;
+	return ret;
+}
+
+static int wi_node_notifier(struct notifier_block *nb,
+			       unsigned long action, void *data)
+{
+	int err;
+	struct memory_notify *arg = data;
+	int nid = arg->status_change_nid;
+
+	if (nid < 0)
+		goto notifier_end;
+
+	switch(action) {
+	case MEM_ONLINE:
+		err = sysfs_wi_node_add(nid);
+		if (err) {
+			pr_err("failed to add sysfs [node%d]\n", nid);
+			return NOTIFY_BAD;
+		}
+		break;
+	case MEM_OFFLINE:
+		if (!node_state(nid, N_MEMORY))
+			sysfs_wi_node_release(nid);
+		break;
+	}
+
+notifier_end:
+	return NOTIFY_OK;
 }
 
 static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 		       GFP_KERNEL);
 	if (!wi_group)
 		return -ENOMEM;
+	mutex_init(&wi_group->kobj_lock);
 
 	err = kobject_init_and_add(&wi_group->wi_kobj, &wi_ktype, mempolicy_kobj,
 				   "weighted_interleave");
 	if (err)
 		goto err_out;
 
-	for_each_node_state(nid, N_POSSIBLE) {
+	for_each_online_node(nid) {
+		if (!node_state(nid, N_MEMORY))
+			continue;
+
 		err = sysfs_wi_node_add(nid);
 		if (err) {
 			pr_err("failed to add sysfs [node%d]\n", nid);
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 		}
 	}
 
+	hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
 	return 0;
 
 err_out:
-- 
2.34.1