mm/damon/sysfs-schemes: implement path file under quota goal directory

Add a DAMOS sysfs file for specifying the cgroup of the interest for
DAMOS_QUOTA_NODE_MEMCG_USED_BP.

Link: https://lkml.kernel.org/r/20251017212706.183502-5-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 36 insertions, 2 deletions

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 6536f16006c9..2c440a2b80e6 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -999,6 +999,7 @@ struct damos_sysfs_quota_goal {
 	unsigned long target_value;
 	unsigned long current_value;
 	int nid;
+	char *path;
 };
 
 static struct damos_sysfs_quota_goal *damos_sysfs_quota_goal_alloc(void)
@@ -1128,10 +1129,39 @@ static ssize_t nid_store(struct kobject *kobj,
 	return err ? err : count;
 }
 
+static ssize_t path_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damos_sysfs_quota_goal *goal = container_of(kobj,
+			struct damos_sysfs_quota_goal, kobj);
+
+	return sysfs_emit(buf, "%s\n", goal->path ? goal->path : "");
+}
+
+static ssize_t path_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damos_sysfs_quota_goal *goal = container_of(kobj,
+			struct damos_sysfs_quota_goal, kobj);
+	char *path = kmalloc_array(size_add(count, 1), sizeof(*path),
+				   GFP_KERNEL);
+
+	if (!path)
+		return -ENOMEM;
+
+	strscpy(path, buf, count + 1);
+	kfree(goal->path);
+	goal->path = path;
+	return count;
+}
+
 static void damos_sysfs_quota_goal_release(struct kobject *kobj)
 {
-	/* or, notify this release to the feed callback */
-	kfree(container_of(kobj, struct damos_sysfs_quota_goal, kobj));
+	struct damos_sysfs_quota_goal *goal = container_of(kobj,
+			struct damos_sysfs_quota_goal, kobj);
+
+	kfree(goal->path);
+	kfree(goal);
 }
 
 static struct kobj_attribute damos_sysfs_quota_goal_target_metric_attr =
@@ -1146,11 +1176,15 @@ static struct kobj_attribute damos_sysfs_quota_goal_current_value_attr =
 static struct kobj_attribute damos_sysfs_quota_goal_nid_attr =
 		__ATTR_RW_MODE(nid, 0600);
 
+static struct kobj_attribute damos_sysfs_quota_goal_path_attr =
+		__ATTR_RW_MODE(path, 0600);
+
 static struct attribute *damos_sysfs_quota_goal_attrs[] = {
 	&damos_sysfs_quota_goal_target_metric_attr.attr,
 	&damos_sysfs_quota_goal_target_value_attr.attr,
 	&damos_sysfs_quota_goal_current_value_attr.attr,
 	&damos_sysfs_quota_goal_nid_attr.attr,
+	&damos_sysfs_quota_goal_path_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damos_sysfs_quota_goal);