DAMOS_QUOTA_NODE_MEM_{USED,FREE}_BP DAMOS quota goal metrics require the
node id parameter.  However, there is no DAMON user ABI for setting it.
Implement a DAMON sysfs file for that with name 'nid', under the quota
goal directory.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 98108f082178..7681ed293b62 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -936,6 +936,7 @@ struct damos_sysfs_quota_goal {
 	enum damos_quota_goal_metric metric;
 	unsigned long target_value;
 	unsigned long current_value;
+	int nid;
 };
 
 /* This should match with enum damos_action */
@@ -1016,6 +1017,28 @@ static ssize_t current_value_store(struct kobject *kobj,
 	return err ? err : count;
 }
 
+static ssize_t nid_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);
+
+	/* todo: return error if the goal is not using nid */
+
+	return sysfs_emit(buf, "%d\n", goal->nid);
+}
+
+static ssize_t nid_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);
+	int err = kstrtoint(buf, 0, &goal->nid);
+
+	/* feed callback should check existence of this file and read value */
+	return err ? err : count;
+}
+
 static void damos_sysfs_quota_goal_release(struct kobject *kobj)
 {
 	/* or, notify this release to the feed callback */
@@ -1031,10 +1054,14 @@ static struct kobj_attribute damos_sysfs_quota_goal_target_value_attr =
 static struct kobj_attribute damos_sysfs_quota_goal_current_value_attr =
 		__ATTR_RW_MODE(current_value, 0600);
 
+static struct kobj_attribute damos_sysfs_quota_goal_nid_attr =
+		__ATTR_RW_MODE(nid, 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,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damos_sysfs_quota_goal);
-- 
2.39.5