[PATCH 3/3] mm/page_owner: add NUMA node filter

[Zhen Ni <zhen.ni@easystack.cn>]

Add NUMA node filtering functionality to page_owner to allow
filtering pages by specific NUMA node.

The filter allows users to focus on pages from a specific NUMA node,
which is useful for NUMA-aware memory allocation analysis and debugging.
Setting nid to -1 disables filtering (default behavior).

Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
---
 mm/page_owner.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 214b58eef3d8..ebc29f3f516d 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -726,6 +726,13 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 		if (unlikely(!page_ext))
 			continue;
 
+		if (READ_ONCE(owner_filter.nid) >= 0) {
+			int nid = page_to_nid(page);
+
+			if (nid != READ_ONCE(owner_filter.nid))
+				goto ext_put_continue;
+		}
+
 		/*
 		 * Some pages could be missed by concurrent allocation or free,
 		 * because we don't hold the zone lock.
@@ -987,6 +994,24 @@ static int page_owner_threshold_set(void *data, u64 val)
 DEFINE_SIMPLE_ATTRIBUTE(page_owner_threshold_fops, &page_owner_threshold_get,
 			&page_owner_threshold_set, "%llu");
 
+static int page_owner_nid_filter_get(void *data, u64 *val)
+{
+	*val = READ_ONCE(owner_filter.nid);
+	return 0;
+}
+
+static int page_owner_nid_filter_set(void *data, u64 val)
+{
+	if (val >= MAX_NUMNODES && val != (u64)-1)
+		return -EINVAL;
+	WRITE_ONCE(owner_filter.nid, val);
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(page_owner_nid_filter_fops,
+			&page_owner_nid_filter_get,
+			&page_owner_nid_filter_set, "%lld");
+
 static int page_owner_compact_get(void *data, u64 *val)
 {
 	*val = READ_ONCE(owner_filter.compact);
@@ -1018,6 +1043,8 @@ static int __init pageowner_init(void)
 	debugfs_create_file("page_owner", 0400, NULL, NULL, &page_owner_fops);
 
 	filter_dir = debugfs_create_dir("page_owner_filter", NULL);
+	debugfs_create_file("nid", 0600, filter_dir, NULL,
+			    &page_owner_nid_filter_fops);
 	debugfs_create_file("compact", 0600, filter_dir, NULL,
 			    &page_owner_compact_fops);
 
-- 
2.20.1