Series comparison

-[PATCH v4 0/3] Enhance sysfs handling for memory hotplug in weighted interleave
+[PATCH v7 0/3] Enhance sysfs handling for memory hotplug in weighted interleave
 ...
 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
+- Memory Leaks: Improper `kobject` teardown 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
-. [PATCH 1/3] Fix memory leaks in weighted interleave sysfs
+. [PATCH 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs
    - Ensures proper cleanup of `kobject` allocations.
-   - Replaces unnecessary `kfree()` calls with `kobject_put()`, preventing
+   - Adds `kobject_del()` before `kobject_put()` to clean up sysfs state correctly.
-     memory leaks and improving system stability.
+   - Prevents memory/resource leaks and improves teardown behavior.
-. [PATCH 2/3] Enable dynamic updates for weighted interleave sysfs
+. [PATCH 2/3] mm/mempolicy: Prepare weighted interleave sysfs for memory hotplug
-   - Restructures sysfs handling to allow runtime updates.
+   - Refactors static sysfs layout into a new `sysfs_wi_group` structure.
-   - The sysfs attributes are now globally accessible, enabling external
+   - Makes per-node sysfs attributes accessible to external modules.
-     modules to manage interleave settings dynamically.
+   - Lays groundwork for future hotplug support by enabling runtime modification.
-. [PATCH 3/3] Support memory hotplug in weighted interleave
+. [PATCH 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
-   - Modifies sysfs creation logic to restrict entries to nodes that are
+   - Dynamically adds/removes sysfs entries when nodes are online/offline.
-     online and have memory, excluding unusable nodes.
+   - Limits sysfs creation to nodes with memory, avoiding unusable node entries.
-   - Introduces a memory hotplug mechanism to dynamically add and remove
+   - Hooks into memory hotplug notifier for runtime updates.
      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 ++++++++++++++++++++++++++++++++-----------------
+ mm/mempolicy.c | 193 +++++++++++++++++++++++++++++++------------------
-file changed, 127 insertions(+), 68 deletions(-)
+file changed, 124 insertions(+), 69 deletions(-)
-base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557
+base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
 --
 .34.1

-[PATCH v4 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs
+[PATCH v7 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
+calls with proper `kobject_del()` and `kobject_put()` sequences,
-memory leaks.
+ensuring correct teardown and preventing memory leaks.
-By correctly using `kobject_put()`, the release function now
+By explicitly calling `kobject_del()` before `kobject_put()`,
-properly deallocates memory without causing resource leaks,
+the release function is now invoked safely, and internal sysfs
-thereby improving system stability.
+state is correctly cleaned up. This guarantees that the memory
 associated with the kobject is fully released and avoids
 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 +++++++++++++++++++++++++-------------------------
+ mm/mempolicy.c | 66 ++++++++++++++++++++++++--------------------------
-file changed, 31 insertions(+), 30 deletions(-)
+file changed, 32 insertions(+), 34 deletions(-)
 diff --git a/mm/mempolicy.c b/mm/mempolicy.c
 index XXXXXXX..XXXXXXX 100644
 --- a/mm/mempolicy.c
 +++ b/mm/mempolicy.c
 ...
  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)
++    if (!wi_kobj) {
++        kfree(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) {
+-    if (err) {
 -        kfree(wi_kobj);
 -        return err;
-+        kobject_put(wi_kobj);
+-    }
-+        goto err_out;
++    if (err)
-     }
++        goto err_put_kobj;
      for_each_node_state(nid, N_POSSIBLE) {
-@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
+         err = add_weight_node(nid, wi_kobj);
-             break;
+         if (err) {
              pr_err("failed to add sysfs [node%d]\n", nid);
 -            break;
 +            goto err_del_kobj;
          }
      }
 -    if (err)
-+    if (err) {
+-        kobject_put(wi_kobj);
          kobject_put(wi_kobj);
 +        goto err_out;
 +    }
 +
      return 0;
 +
-+node_out:
++err_del_kobj:
-+    kfree(node_attrs);
++    kobject_del(wi_kobj);
-+err_out:
++err_put_kobj:
 +    kobject_put(wi_kobj);
 +    return err;
  }
  static void mempolicy_kobj_release(struct kobject *kobj)
 @@ -XXX,XX +XXX,XX @@ static void mempolicy_kobj_release(struct kobject *kobj)
 ...
      err = kobject_init_and_add(mempolicy_kobj, &mempolicy_ktype, mm_kobj,
                     "mempolicy");
      if (err)
 -        goto node_out;
-+        goto err_out;
++        goto err_put_kobj;
      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;
++        goto err_del_kobj;
 +
 +    return 0;
 -    return err;
 -node_out:
 -    kfree(node_attrs);
 -mempol_out:
 -    kfree(mempolicy_kobj);
- err_out:
+-err_out:
 -    pr_err("failed to add mempolicy kobject to the system\n");
++    return 0;
++
++err_del_kobj:
++    kobject_del(mempolicy_kobj);
++err_put_kobj:
 +    kobject_put(mempolicy_kobj);
      return err;
  }
 --
 .34.1

-[PATCH v4 2/3] mm/mempolicy: Support dynamic sysfs updates for weighted interleave
+[PATCH v7 2/3] mm/mempolicy: Prepare weighted interleave sysfs for memory hotplug
 Previously, the weighted interleave sysfs structure was statically
-managed, preventing dynamic updates when nodes were added or removed.
+managed during initialization. This prevented new nodes from being
 recognized when memory hotplug events occurred, limiting the ability
 to update or extend sysfs entries dynamically at runtime.
-This patch restructures the weighted interleave sysfs to support
+To address this, this patch refactors the sysfs infrastructure and
-dynamic insertion and deletion. The sysfs that was part of
+encapsulates it within a new structure, `sysfs_wi_group`, which holds
-the 'weighted_interleave_group' is now globally accessible,
+both the kobject and an array of node attribute pointers.
 allowing external access to that sysfs.
-With this change, sysfs management for weighted interleave is
+By allocating this group structure globally, the per-node sysfs
-more flexible, supporting hotplug events and runtime updates
+attributes can be managed beyond initialization time, enabling
-more effectively.
+external modules to insert or remove node entries in response to
 events such as memory hotplug or node online/offline transitions.
 Instead of allocating all per-node sysfs attributes at once, the
 initialization path now uses the existing sysfs_wi_node_add() and
 sysfs_wi_node_delete() helpers. This refactoring makes it possible
 to modularly manage per-node sysfs entries and ensures the
 infrastructure is ready for runtime extension.
 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 ++++++++++++++++++++++----------------------------
+ mm/mempolicy.c | 61 ++++++++++++++++++++++++--------------------------
-file changed, 31 insertions(+), 40 deletions(-)
+file changed, 29 insertions(+), 32 deletions(-)
 diff --git a/mm/mempolicy.c b/mm/mempolicy.c
 index XXXXXXX..XXXXXXX 100644
 --- a/mm/mempolicy.c
 +++ b/mm/mempolicy.c
 ...
 -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)
++static void sysfs_wi_node_delete(int nid)
  {
 -    if (!node_attr)
 +    if (!wi_group->nattrs[nid])
          return;
 -    sysfs_remove_file(parent, &node_attr->kobj_attr.attr);
 ...
 +    int nid;
 -    kfree(node_attrs);
 -    kfree(wi_kobj);
 +    for (nid = 0; nid < nr_node_ids; nid++)
-+        sysfs_wi_node_release(nid);
++        sysfs_wi_node_delete(nid);
 +    kfree(wi_group);
  }
  static const struct kobj_type wi_ktype = {
 @@ -XXX,XX +XXX,XX @@ static const struct kobj_type wi_ktype = {
 ...
 +    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)
++static int __init 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) +         \
++    wi_group = kzalloc(struct_size(wi_group, nattrs, nr_node_ids),
-+               nr_node_ids * sizeof(struct iw_node_attr *),    \
++               GFP_KERNEL);
 +               GFP_KERNEL);
 +    if (!wi_group)
          return -ENOMEM;
 -    wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
 -    if (!wi_kobj) {
--        err = -ENOMEM;
+-        kfree(node_attrs);
--        goto node_out;
+-        return -ENOMEM;
 -    }
 -
 -    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) {
+     if (err)
--        kobject_put(wi_kobj);
+         goto err_put_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_del_kobj;
-+            goto err_out;
+@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
          }
      }
 -    if (err) {
 -        kobject_put(wi_kobj);
 -        goto err_out;
 -    }
      return 0;
--node_out:
+ err_del_kobj:
--    kfree(node_attrs);
+-    kobject_del(wi_kobj);
- err_out:
++    kobject_del(&wi_group->wi_kobj);
  err_put_kobj:
 -    kobject_put(wi_kobj);
 +    kobject_put(&wi_group->wi_kobj);
      return err;
  }
 --
 .34.1

-[PATCH v4 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
+[PATCH v7 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
 ...
 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>
+Reviewed-by: Oscar Salvador <osalvador@suse.de>
 ---
- mm/mempolicy.c | 113 +++++++++++++++++++++++++++++++++++++++----------
+ mm/mempolicy.c | 106 ++++++++++++++++++++++++++++++++++++++-----------
-file changed, 90 insertions(+), 23 deletions(-)
+file changed, 83 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
 ...
      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)
+ static void sysfs_wi_node_delete(int nid)
  {
 -    if (!wi_group->nattrs[nid])
 +    struct iw_node_attr *attr;
 +
 +    if (nid < 0 || nid >= nr_node_ids)
 ...
 +    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;
 +}
 ...
 +    int err;
 +    struct memory_notify *arg = data;
 +    int nid = arg->status_change_nid;
 +
 +    if (nid < 0)
-+        goto notifier_end;
++        return NOTIFY_OK;
 +
 +    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;
 +            }
 +        }
 +        break;
 +    case MEM_OFFLINE:
-+        if (!node_state(nid, N_MEMORY))
++        sysfs_wi_node_delete(nid);
 +            sysfs_wi_node_release(nid);
 +        break;
 +    }
 +
-+notifier_end:
 +    return NOTIFY_OK;
  }
- static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
+ static int __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
-@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
+@@ -XXX,XX +XXX,XX @@ static int __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
-                GFP_KERNEL);
+                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;
+         goto err_put_kobj;
 -    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)
+@@ -XXX,XX +XXX,XX @@ static int __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
          }
      }
 +    hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
      return 0;
- err_out:
+ err_del_kobj:
 --
 .34.1

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

Previously, sysfs entries for weighted interleave were managed statically
at initialization. This led to several issues:
- Memory Leaks: Improper `kobject` teardown 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] mm/mempolicy: Fix memory leaks in weighted interleave sysfs
   - Ensures proper cleanup of `kobject` allocations.
   - Adds `kobject_del()` before `kobject_put()` to clean up sysfs state correctly.
   - Prevents memory/resource leaks and improves teardown behavior.

2. [PATCH 2/3] mm/mempolicy: Prepare weighted interleave sysfs for memory hotplug
   - Refactors static sysfs layout into a new `sysfs_wi_group` structure.
   - Makes per-node sysfs attributes accessible to external modules.
   - Lays groundwork for future hotplug support by enabling runtime modification.

3. [PATCH 3/3] mm/mempolicy: Support memory hotplug in weighted interleave
   - Dynamically adds/removes sysfs entries when nodes are online/offline.
   - Limits sysfs creation to nodes with memory, avoiding unusable node entries.
   - Hooks into memory hotplug notifier for runtime updates.

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

mm/mempolicy.c | 193 +++++++++++++++++++++++++++++++------------------
 1 file changed, 124 insertions(+), 69 deletions(-)

base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
-- 
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 proper `kobject_del()` and `kobject_put()` sequences,
ensuring correct teardown and preventing memory leaks.

By explicitly calling `kobject_del()` before `kobject_put()`,
the release function is now invoked safely, and internal sysfs
state is correctly cleaned up. This guarantees that the memory
associated with the kobject is fully released and avoids
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 | 66 ++++++++++++++++++++++++--------------------------
 1 file changed, 32 insertions(+), 34 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;
 
+	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)
+	if (!wi_kobj) {
+		kfree(node_attrs);
 		return -ENOMEM;
+	}
 
 	err = kobject_init_and_add(wi_kobj, &wi_ktype, root_kobj,
 				   "weighted_interleave");
-	if (err) {
-		kfree(wi_kobj);
-		return err;
-	}
+	if (err)
+		goto err_put_kobj;
 
 	for_each_node_state(nid, N_POSSIBLE) {
 		err = add_weight_node(nid, wi_kobj);
 		if (err) {
 			pr_err("failed to add sysfs [node%d]\n", nid);
-			break;
+			goto err_del_kobj;
 		}
 	}
-	if (err)
-		kobject_put(wi_kobj);
+
 	return 0;
+
+err_del_kobj:
+	kobject_del(wi_kobj);
+err_put_kobj:
+	kobject_put(wi_kobj);
+	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_put_kobj;
 
 	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_del_kobj;
 
-	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");
+	return 0;
+
+err_del_kobj:
+	kobject_del(mempolicy_kobj);
+err_put_kobj:
+	kobject_put(mempolicy_kobj);
 	return err;
 }
 
-- 
2.34.1

Previously, the weighted interleave sysfs structure was statically
managed during initialization. This prevented new nodes from being
recognized when memory hotplug events occurred, limiting the ability
to update or extend sysfs entries dynamically at runtime.

To address this, this patch refactors the sysfs infrastructure and
encapsulates it within a new structure, `sysfs_wi_group`, which holds
both the kobject and an array of node attribute pointers.

By allocating this group structure globally, the per-node sysfs
attributes can be managed beyond initialization time, enabling
external modules to insert or remove node entries in response to
events such as memory hotplug or node online/offline transitions.

Instead of allocating all per-node sysfs attributes at once, the
initialization path now uses the existing sysfs_wi_node_add() and
sysfs_wi_node_delete() helpers. This refactoring makes it possible
to modularly manage per-node sysfs entries and ensures the
infrastructure is ready for runtime extension.

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, 29 insertions(+), 32 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_delete(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_delete(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 __init 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(struct_size(wi_group, nattrs, nr_node_ids),
+			   GFP_KERNEL);
+	if (!wi_group)
 		return -ENOMEM;
 
-	wi_kobj = kzalloc(sizeof(struct kobject), GFP_KERNEL);
-	if (!wi_kobj) {
-		kfree(node_attrs);
-		return -ENOMEM;
-	}
-
-	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)
 		goto err_put_kobj;
 
 	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);
 			goto err_del_kobj;
@@ -XXX,XX +XXX,XX @@ static int add_weighted_interleave_group(struct kobject *root_kobj)
 	return 0;
 
 err_del_kobj:
-	kobject_del(wi_kobj);
+	kobject_del(&wi_group->wi_kobj);
 err_put_kobj:
-	kobject_put(wi_kobj);
+	kobject_put(&wi_group->wi_kobj);
 	return err;
 }
 
-- 
2.34.1

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>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
---
 mm/mempolicy.c | 106 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 83 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_delete(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)
+		return NOTIFY_OK;
+
+	switch(action) {
+	case MEM_ONLINE:
+		err = sysfs_wi_node_add(nid);
+		if (err)
+			pr_err("failed to add sysfs [node%d]\n", nid);
+		break;
+	case MEM_OFFLINE:
+		sysfs_wi_node_delete(nid);
+		break;
+	}
+
+	return NOTIFY_OK;
 }
 
 static int __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
@@ -XXX,XX +XXX,XX @@ static int __init 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_put_kobj;
 
-	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 __init add_weighted_interleave_group(struct kobject *mempolicy_kobj)
 		}
 	}
 
+	hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
 	return 0;
 
 err_del_kobj:
-- 
2.34.1