Add a new DAMON sysfs interface file, namely 'goal_tuner' under the
DAMOS quotas directory.  It is connected to the damos_quota->goal_tuner
field.  Users can therefore select their favorite goal-based quotas
tuning algorithm by writing the name of the tuner to the file.  Reading
the file returns the name of the currently selected tuner.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 58 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 3a0782e576fab..5186966dafb35 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1488,6 +1488,7 @@ struct damon_sysfs_quotas {
 	unsigned long sz;
 	unsigned long reset_interval_ms;
 	unsigned long effective_sz;	/* Effective size quota in bytes */
+	enum damos_quota_goal_tuner goal_tuner;
 };
 
 static struct damon_sysfs_quotas *damon_sysfs_quotas_alloc(void)
@@ -1610,6 +1611,58 @@ static ssize_t effective_bytes_show(struct kobject *kobj,
 	return sysfs_emit(buf, "%lu\n", quotas->effective_sz);
 }
 
+struct damos_sysfs_qgoal_tuner_name {
+	enum damos_quota_goal_tuner tuner;
+	char *name;
+};
+
+static struct damos_sysfs_qgoal_tuner_name damos_sysfs_qgoal_tuner_names[] = {
+	{
+		.tuner = DAMOS_QUOTA_GOAL_TUNER_CONSIST,
+		.name = "consist",
+	},
+	{
+		.tuner = DAMOS_QUOTA_GOAL_TUNER_TEMPORAL,
+		.name = "temporal",
+	},
+};
+
+static ssize_t goal_tuner_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_quotas *quotas = container_of(kobj,
+			struct damon_sysfs_quotas, kobj);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(damos_sysfs_qgoal_tuner_names); i++) {
+		struct damos_sysfs_qgoal_tuner_name *tuner_name;
+
+		tuner_name = &damos_sysfs_qgoal_tuner_names[i];
+		if (tuner_name->tuner == quotas->goal_tuner)
+			return sysfs_emit(buf, "%s\n", tuner_name->name);
+	}
+	return -EINVAL;
+}
+
+static ssize_t goal_tuner_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_quotas *quotas = container_of(kobj,
+			struct damon_sysfs_quotas, kobj);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(damos_sysfs_qgoal_tuner_names); i++) {
+		struct damos_sysfs_qgoal_tuner_name *tuner_name;
+
+		tuner_name = &damos_sysfs_qgoal_tuner_names[i];
+		if (sysfs_streq(buf, tuner_name->name)) {
+			quotas->goal_tuner = tuner_name->tuner;
+			return count;
+		}
+	}
+	return -EINVAL;
+}
+
 static void damon_sysfs_quotas_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_quotas, kobj));
@@ -1627,11 +1680,15 @@ static struct kobj_attribute damon_sysfs_quotas_reset_interval_ms_attr =
 static struct kobj_attribute damon_sysfs_quotas_effective_bytes_attr =
 		__ATTR_RO_MODE(effective_bytes, 0400);
 
+static struct kobj_attribute damon_sysfs_quotas_goal_tuner_attr =
+		__ATTR_RW_MODE(goal_tuner, 0600);
+
 static struct attribute *damon_sysfs_quotas_attrs[] = {
 	&damon_sysfs_quotas_ms_attr.attr,
 	&damon_sysfs_quotas_sz_attr.attr,
 	&damon_sysfs_quotas_reset_interval_ms_attr.attr,
 	&damon_sysfs_quotas_effective_bytes_attr.attr,
+	&damon_sysfs_quotas_goal_tuner_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_quotas);
@@ -2718,6 +2775,7 @@ static struct damos *damon_sysfs_mk_scheme(
 		.weight_sz = sysfs_weights->sz,
 		.weight_nr_accesses = sysfs_weights->nr_accesses,
 		.weight_age = sysfs_weights->age,
+		.goal_tuner = sysfs_quotas->goal_tuner,
 	};
 	struct damos_watermarks wmarks = {
 		.metric = sysfs_wmarks->metric,
-- 
2.47.3