mm/damon/sysfs-schemes: support PSI-based quota auto-tune

Extend DAMON sysfs interface to support the PSI-based quota auto-tuning by
adding a new file, 'target_metric' under the quota goal directory.  Old
users don't get any behavioral changes since the default value of the
metric is 'user input'.

Link: https://lkml.kernel.org/r/20240219194431.159606-15-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs-schemes.c

@@ -826,15 +826,48 @@ static const struct kobj_type damon_sysfs_watermarks_ktype = {
 
 struct damos_sysfs_quota_goal {
 	struct kobject kobj;
+	enum damos_quota_goal_metric metric;
 	unsigned long target_value;
 	unsigned long current_value;
 };
 
+/* This should match with enum damos_action */
+static const char * const damos_sysfs_quota_goal_metric_strs[] = {
+	"user_input",
+	"some_mem_psi_us",
+};
+
 static struct damos_sysfs_quota_goal *damos_sysfs_quota_goal_alloc(void)
 {
 	return kzalloc(sizeof(struct damos_sysfs_quota_goal), GFP_KERNEL);
 }
 
+static ssize_t target_metric_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",
+			damos_sysfs_quota_goal_metric_strs[goal->metric]);
+}
+
+static ssize_t target_metric_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);
+	enum damos_quota_goal_metric m;
+
+	for (m = 0; m < NR_DAMOS_QUOTA_GOAL_METRICS; m++) {
+		if (sysfs_streq(buf, damos_sysfs_quota_goal_metric_strs[m])) {
+			goal->metric = m;
+			return count;
+		}
+	}
+	return -EINVAL;
+}
+
 static ssize_t target_value_show(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
@@ -880,6 +913,9 @@ static void damos_sysfs_quota_goal_release(struct kobject *kobj)
 	kfree(container_of(kobj, struct damos_sysfs_quota_goal, kobj));
 }
 
+static struct kobj_attribute damos_sysfs_quota_goal_target_metric_attr =
+		__ATTR_RW_MODE(target_metric, 0600);
+
 static struct kobj_attribute damos_sysfs_quota_goal_target_value_attr =
 		__ATTR_RW_MODE(target_value, 0600);
 
@@ -887,6 +923,7 @@ static struct kobj_attribute damos_sysfs_quota_goal_current_value_attr =
 		__ATTR_RW_MODE(current_value, 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,
 	NULL,
@@ -1899,11 +1936,12 @@ static int damos_sysfs_set_quota_score(
 		if (!sysfs_goal->target_value)
 			continue;
 
-		goal = damos_new_quota_goal(DAMOS_QUOTA_USER_INPUT,
+		goal = damos_new_quota_goal(sysfs_goal->metric,
 				sysfs_goal->target_value);
 		if (!goal)
 			return -ENOMEM;
-		goal->current_value = sysfs_goal->current_value;
+		if (sysfs_goal->metric == DAMOS_QUOTA_USER_INPUT)
+			goal->current_value = sysfs_goal->current_value;
 		damos_add_quota_goal(quota, goal);
 	}
 	return 0;