[PATCH v5 0/3] Enhance sysfs handling for memory hotplug in weighted interleave

[PATCH v5 0/3] Enhance sysfs handling for memory hotplug in weighted interleave

[Rakie Kim]

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 | 192 +++++++++++++++++++++++++++++++------------------
 1 file changed, 124 insertions(+), 68 deletions(-)


base-commit: 38fec10eb60d687e30c8c6b5420d86e8149f7557
-- 
2.34.1

[PATCH v5 1/3] mm/mempolicy: Fix memory leaks in weighted interleave sysfs

[Rakie Kim]

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 bbaadbeeb291..5950d5d5b85e 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -3448,7 +3448,9 @@ 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 = {
@@ -3494,15 +3496,22 @@ 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) {
@@ -3512,9 +3521,17 @@ 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)
@@ -3528,7 +3545,6 @@ static void mempolicy_kobj_release(struct kobject *kobj)
 	mutex_unlock(&iw_table_lock);
 	synchronize_rcu();
 	kfree(old);
-	kfree(node_attrs);
 	kfree(kobj);
 }
 
@@ -3542,37 +3558,22 @@ 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

[PATCH v5 2/3] mm/mempolicy: Support dynamic sysfs updates for weighted interleave

[Rakie Kim]

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 5950d5d5b85e..3092a792bd28 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -3388,6 +3388,13 @@ 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)
 {
@@ -3430,27 +3437,24 @@ 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 = {
@@ -3458,7 +3462,7 @@ 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;
@@ -3480,57 +3484,44 @@ 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

[PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Rakie Kim]

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 | 110 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 87 insertions(+), 23 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 3092a792bd28..ea4f3f3f2cdd 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -113,6 +113,7 @@
 #include <asm/tlbflush.h>
 #include <asm/tlb.h>
 #include <linux/uaccess.h>
+#include <linux/memory.h>
 
 #include "internal.h"
 
@@ -3390,6 +3391,7 @@ struct iw_node_attr {
 
 struct sysfs_wi_group {
 	struct kobject wi_kobj;
+	struct mutex kobj_lock;
 	struct iw_node_attr *nattrs[];
 };
 
@@ -3439,13 +3441,24 @@ 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)
@@ -3464,35 +3477,81 @@ 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)
@@ -3504,13 +3563,17 @@ 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);
@@ -3518,6 +3581,7 @@ 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

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Honggyu Kim]

Hi Rakie,

This is to fix the following broken status.
https://lore.kernel.org/linux-mm/b8ac8654-92bd-4c08-a3fc-e28a7be5e0e6@sk.com

So we must add the following tag for this patch.
Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for 
weighted interleaving")


Hi Gregory,

This patch is already in Andrew's tree. Is the current version okay for you?


Hi Andrew,

I'm not sure if this is going to the final version but could you please add this
patch to stable with Cc: <stable@vger.kernel.org>?
We might need to bring the whole series to avoid conflicts to stable tree.

Thanks,
Honggyu

On 4/2/2025 10:49 AM, Rakie Kim wrote:
> 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 | 110 ++++++++++++++++++++++++++++++++++++++-----------
>   1 file changed, 87 insertions(+), 23 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 3092a792bd28..ea4f3f3f2cdd 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -113,6 +113,7 @@
>   #include <asm/tlbflush.h>
>   #include <asm/tlb.h>
>   #include <linux/uaccess.h>
> +#include <linux/memory.h>
>   
>   #include "internal.h"
>   
> @@ -3390,6 +3391,7 @@ struct iw_node_attr {
>   
>   struct sysfs_wi_group {
>   	struct kobject wi_kobj;
> +	struct mutex kobj_lock;
>   	struct iw_node_attr *nattrs[];
>   };
>   
> @@ -3439,13 +3441,24 @@ 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)
> @@ -3464,35 +3477,81 @@ 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)
> @@ -3504,13 +3563,17 @@ 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);
> @@ -3518,6 +3581,7 @@ static int add_weighted_interleave_group(struct kobject *mempolicy_kobj)
>   		}
>   	}
>   
> +	hotplug_memory_notifier(wi_node_notifier, DEFAULT_CALLBACK_PRI);
>   	return 0;
>   
>   err_out:

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Andrew Morton]

On Wed, 2 Apr 2025 13:18:51 +0900 Honggyu Kim <honggyu.kim@sk.com> wrote:

> This is to fix the following broken status.
> https://lore.kernel.org/linux-mm/b8ac8654-92bd-4c08-a3fc-e28a7be5e0e6@sk.com
> 
> So we must add the following tag for this patch.
> Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for 
> weighted interleaving")
> 
> 
> Hi Gregory,
> 
> This patch is already in Andrew's tree. Is the current version okay for you?
> 
> 
> Hi Andrew,
> 
> I'm not sure if this is going to the final version but could you please add this
> patch to stable with Cc: <stable@vger.kernel.org>?
> We might need to bring the whole series to avoid conflicts to stable tree.

This is all rather confused.

Do we need to backport all three patches into -stable?  If so, all three
should have Fixes:.  Preferably they all have the same Fixes: so we
aren't backporting untested patch combinations.

I presently have:

Subject: mm/mempolicy: fix memory leaks in weighted interleave sysfs
Fixes: dce41f5ae253 ("mm/mempolicy: implement the sysfs-based weighted_interleave interface")
Cc: <stable@vger.kernel.org>

Subject: mm/mempolicy: support dynamic sysfs updates for weighted interleave
Cc: <stable@vger.kernel.org>

Subject: mm/mempolicy: support memory hotplug in weighted interleave
Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving")
Cc: <stable@vger.kernel.org>


[2/3] doesn't look like a fix.

Perhaps the whole thing should be redone: a two-patch bugfix series,
each with a Fixes: and a cc:stable and feature patch with neither a
Fixes: nor a cc:stable.

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Gregory Price]

On Tue, Apr 01, 2025 at 09:34:39PM -0700, Andrew Morton wrote:
> > I'm not sure if this is going to the final version but could you please add this
> > patch to stable with Cc: <stable@vger.kernel.org>?
> > We might need to bring the whole series to avoid conflicts to stable tree.
> 
> This is all rather confused.
> 
> Do we need to backport all three patches into -stable?  If so, all three
> should have Fixes:.  Preferably they all have the same Fixes: so we
> aren't backporting untested patch combinations.
>

I'd just as soon leave the entire thing out of stable backports.

Only the first patch actually fixes a bug (very small memory leak
during system tear down, so it's not even a critical bug). This could
be added to stable.

Patches 2 and 3 aren't fixes, they're desired behavioral changes
to the feature. An interface being confusing doesn't mean it's broken.

~Gregory

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Gregory Price]

On Wed, Apr 02, 2025 at 01:15:48AM -0400, Gregory Price wrote:
> On Tue, Apr 01, 2025 at 09:34:39PM -0700, Andrew Morton wrote:
> > 
> > Do we need to backport all three patches into -stable?  If so, all three
> > should have Fixes:.  Preferably they all have the same Fixes: so we
> > aren't backporting untested patch combinations.
> >
> 
> Patches 2 and 3 aren't fixes, they're desired behavioral changes
> to the feature. An interface being confusing doesn't mean it's broken.
>

Just some added clarity:

The behavioral change in sysfs change goes from N_POSSIBLE nodes always
being exposed - to sysfs entries coming and going as nodes transition
between having memory and not having memory.

I can see the argument for wanting this backported as a fix to ensure
userspace software is consistent across LTS.

So for backporting: all or nothing - and all the fixes tags should be
the same.

~Gregory

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Honggyu Kim]

Hi Gregory,

On 4/2/2025 2:15 PM, Gregory Price wrote:
> On Tue, Apr 01, 2025 at 09:34:39PM -0700, Andrew Morton wrote:
>>> I'm not sure if this is going to the final version but could you please add this
>>> patch to stable with Cc: <stable@vger.kernel.org>?
>>> We might need to bring the whole series to avoid conflicts to stable tree.
>>
>> This is all rather confused.
>>
>> Do we need to backport all three patches into -stable?  If so, all three
>> should have Fixes:.  Preferably they all have the same Fixes: so we
>> aren't backporting untested patch combinations.
>>
> 
> I'd just as soon leave the entire thing out of stable backports.
> 
> Only the first patch actually fixes a bug (very small memory leak
> during system tear down, so it's not even a critical bug). This could
> be added to stable.
> 
> Patches 2 and 3 aren't fixes, they're desired behavioral changes
> to the feature. An interface being confusing doesn't mean it's broken.

I think those are fixes but I also agree that this is behavioral changes as
well.  So I'm fine leaving these out of stable backports.


Hi Andrew,

I won't ask changes so please keep the current status as is.  Sorry for making
confusion.

Thanks,
Honggyu

> 
> ~Gregory

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Oscar Salvador]

On Wed, Apr 02, 2025 at 10:49:04AM +0900, Rakie Kim wrote:
> 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>

Sorry to jump at v5, and maybe this was already discussed but:

> +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);

This check is not needed.

If status_change_nid is different than NUMA_NO_NODE, it means that the memory
state of the numa node was effectively changed.
So doing:
 
  case MEM_OFFLINE:
          sysfs_wi_node_release(nid)
 
is enough.

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Gregory Price]

On Wed, Apr 02, 2025 at 11:51:17AM +0200, Oscar Salvador wrote:
> > +	case MEM_OFFLINE:
> > +		if (!node_state(nid, N_MEMORY))
> > +			sysfs_wi_node_release(nid);
> 
> This check is not needed.
> 
> If status_change_nid is different than NUMA_NO_NODE, it means that the memory
> state of the numa node was effectively changed.
> So doing:
>  
>   case MEM_OFFLINE:
>           sysfs_wi_node_release(nid)
>  
> is enough.

offline_pages will call this callback unconditionally any time it's
called (and succeeds).  If 2 dax devices online into the same node, it's
possible to offline one chunk of blocks without offlining the other
chunks of blocks - which is why we did the additional check.

~Gregory

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Oscar Salvador]

On Wed, Apr 02, 2025 at 10:14:42AM -0400, Gregory Price wrote:
> On Wed, Apr 02, 2025 at 11:51:17AM +0200, Oscar Salvador wrote:
> > > +	case MEM_OFFLINE:
> > > +		if (!node_state(nid, N_MEMORY))
> > > +			sysfs_wi_node_release(nid);
> > 
> > This check is not needed.
> > 
> > If status_change_nid is different than NUMA_NO_NODE, it means that the memory
> > state of the numa node was effectively changed.
> > So doing:
> >  
> >   case MEM_OFFLINE:
> >           sysfs_wi_node_release(nid)
> >  
> > is enough.
> 
> offline_pages will call this callback unconditionally any time it's
> called (and succeeds).  If 2 dax devices online into the same node, it's

Yes, this callback will be called whenever {online,offline}_pages succeeds, but
status_change_nid will be != NUMA_NO_NODE IFF the node state changes.
And you already have the check

 if (nid < 0)
    goto out

at the beginning, which means that all {offline,online}_pages operation that
do not carry a numa node state change will be filtered out there.

Makes sense, or am I missing something?

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Gregory Price]

On Wed, Apr 02, 2025 at 05:41:57PM +0200, Oscar Salvador wrote:
> 
> Yes, this callback will be called whenever {online,offline}_pages succeeds, but
> status_change_nid will be != NUMA_NO_NODE IFF the node state changes.
> And you already have the check
> 
>  if (nid < 0)
>     goto out
> 
> at the beginning, which means that all {offline,online}_pages operation that
> do not carry a numa node state change will be filtered out there.
> 
> Makes sense, or am I missing something?
>

Ah, you're quite right.  That was difficult to see on the surface, so
the check in fact superfluous.  No need for an extra version, can just
add a patch to squash and drop it.

~Gregory

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Rakie Kim]

On Wed, 2 Apr 2025 12:36:24 -0400 Gregory Price <gourry@gourry.net> wrote:
> On Wed, Apr 02, 2025 at 05:41:57PM +0200, Oscar Salvador wrote:
> > 
> > Yes, this callback will be called whenever {online,offline}_pages succeeds, but
> > status_change_nid will be != NUMA_NO_NODE IFF the node state changes.
> > And you already have the check
> > 
> >  if (nid < 0)
> >     goto out
> > 
> > at the beginning, which means that all {offline,online}_pages operation that
> > do not carry a numa node state change will be filtered out there.
> > 
> > Makes sense, or am I missing something?
> >
> 
> Ah, you're quite right.  That was difficult to see on the surface, so
> the check in fact superfluous.  No need for an extra version, can just
> add a patch to squash and drop it.
> 
> ~Gregory

To Gregory and Oscar

As Oscar correctly pointed out, the check for
'if (!node_state(nid, N_MEMORY))' is unnecessary and should be removed.

Additionally, there are other suggestions from Dan Williams that should
be applied as well:
Link: https://lore.kernel.org/lkml/67ed66ef7c070_9dac294e0@dwillia2-xfh.jf.intel.com.notmuch/

I will incorporate all of these improvements and submit a new version (v6).

Rakie

Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

[Rakie Kim]

On Thu,  3 Apr 2025 13:26:14 +0900 Rakie Kim <rakie.kim@sk.com> wrote:
> On Wed, 2 Apr 2025 12:36:24 -0400 Gregory Price <gourry@gourry.net> wrote:
> > On Wed, Apr 02, 2025 at 05:41:57PM +0200, Oscar Salvador wrote:
> > > 
> > > Yes, this callback will be called whenever {online,offline}_pages succeeds, but
> > > status_change_nid will be != NUMA_NO_NODE IFF the node state changes.
> > > And you already have the check
> > > 
> > >  if (nid < 0)
> > >     goto out
> > > 
> > > at the beginning, which means that all {offline,online}_pages operation that
> > > do not carry a numa node state change will be filtered out there.
> > > 
> > > Makes sense, or am I missing something?
> > >
> > 
> > Ah, you're quite right.  That was difficult to see on the surface, so
> > the check in fact superfluous.  No need for an extra version, can just
> > add a patch to squash and drop it.
> > 
> > ~Gregory
> 
> To Gregory and Oscar
> 
> As Oscar correctly pointed out, the check for
> 'if (!node_state(nid, N_MEMORY))' is unnecessary and should be removed.
> 
> Additionally, there are other suggestions from Dan Williams that should
> be applied as well:
> Link: https://lore.kernel.org/lkml/67ed66ef7c070_9dac294e0@dwillia2-xfh.jf.intel.com.notmuch/
> 
> I will incorporate all of these improvements and submit a new version (v6).
> 
> Rakie

To Andrew

I sincerely apologize for the inconvenience. It appears that this commit
still requires additional corrections. I would appreciate it if you could
drop the changes you merged into -mm, mm-new branch yesterday.

<1>
The patch titled
     Subject: mm/mempolicy: fix memory leaks in weighted interleave sysfs has been added to the -mm mm-new branch.  Its filename is
     mm-mempolicy-fix-memory-leaks-in-weighted-interleave-sysfs.patch
This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-fix-memory-leaks-in-weighted-interleave-sysfs.patch
<2>
The patch titled
     Subject: mm/mempolicy: support dynamic sysfs updates for weighted interleave has been added to the -mm mm-new branch.  Its filename is
     mm-mempolicy-support-dynamic-sysfs-updates-for-weighted-interleave.patch
This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-support-dynamic-sysfs-updates-for-weighted-interleave.patch
<3>
The patch titled
     Subject: mm/mempolicy: support memory hotplug in weighted interleave has been added to the -mm mm-new branch.  Its filename is
     mm-mempolicy-support-memory-hotplug-in-weighted-interleave.patch
This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mempolicy-support-memory-hotplug-in-weighted-interleave.patch

Rakie