Decouple DAMOS sysfs interface from damos_quota_goal_metric.  For this,
define and use new sysfs-schemes internal data structure that maps the
user-space keywords and damos_quota_goal_metric, instead of having
the implicit and unflexible array index rule.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 55 ++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 14 deletions(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 30ae7518ffbf..3747dc6678f2 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -941,27 +941,51 @@ struct damos_sysfs_quota_goal {
 	int nid;
 };
 
-/* This should match with enum damos_quota_goal_metric */
-static const char * const damos_sysfs_quota_goal_metric_strs[] = {
-	"user_input",
-	"some_mem_psi_us",
-	"node_mem_used_bp",
-	"node_mem_free_bp",
-};
-
 static struct damos_sysfs_quota_goal *damos_sysfs_quota_goal_alloc(void)
 {
 	return kzalloc(sizeof(struct damos_sysfs_quota_goal), GFP_KERNEL);
 }
 
+struct damos_sysfs_qgoal_metric_name {
+	enum damos_quota_goal_metric metric;
+	char *name;
+};
+
+static
+struct damos_sysfs_qgoal_metric_name damos_sysfs_qgoal_metric_names[] = {
+	{
+		.metric = DAMOS_QUOTA_USER_INPUT,
+		.name = "user_input",
+	},
+	{
+		.metric = DAMOS_QUOTA_SOME_MEM_PSI_US,
+		.name = "some_mem_psi_us",
+	},
+	{
+		.metric = DAMOS_QUOTA_NODE_MEM_USED_BP,
+		.name = "node_mem_used_bp",
+	},
+	{
+		.metric = DAMOS_QUOTA_NODE_MEM_FREE_BP,
+		.name = "node_mem_free_bp",
+	},
+};
+
 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);
+	int i;
 
-	return sysfs_emit(buf, "%s\n",
-			damos_sysfs_quota_goal_metric_strs[goal->metric]);
+	for (i = 0; i < ARRAY_SIZE(damos_sysfs_qgoal_metric_names); i++) {
+		struct damos_sysfs_qgoal_metric_name *metric_name;
+
+		metric_name = &damos_sysfs_qgoal_metric_names[i];
+		if (metric_name->metric == goal->metric)
+			return sysfs_emit(buf, "%s\n", metric_name->name);
+	}
+	return -EINVAL;
 }
 
 static ssize_t target_metric_store(struct kobject *kobj,
@@ -969,11 +993,14 @@ static ssize_t target_metric_store(struct kobject *kobj,
 {
 	struct damos_sysfs_quota_goal *goal = container_of(kobj,
 			struct damos_sysfs_quota_goal, kobj);
-	enum damos_quota_goal_metric m;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(damos_sysfs_qgoal_metric_names); i++) {
+		struct damos_sysfs_qgoal_metric_name *metric_name;
 
-	for (m = 0; m < NR_DAMOS_QUOTA_GOAL_METRICS; m++) {
-		if (sysfs_streq(buf, damos_sysfs_quota_goal_metric_strs[m])) {
-			goal->metric = m;
+		metric_name = &damos_sysfs_qgoal_metric_names[i];
+		if (sysfs_streq(buf, metric_name->name)) {
+			goal->metric = metric_name->metric;
 			return count;
 		}
 	}
-- 
2.39.5