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

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 41 ++++++++++++++++++++++++++++++----------
 1 file changed, 31 insertions(+), 10 deletions(-)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 117d27544173..3d42d24bb33a 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -785,10 +785,21 @@ static struct damon_sysfs_watermarks *damon_sysfs_watermarks_alloc(
 	return watermarks;
 }
 
-/* Should match with enum damos_wmark_metric */
-static const char * const damon_sysfs_wmark_metric_strs[] = {
-	"none",
-	"free_mem_rate",
+struct damos_sysfs_wmark_metric_name {
+	enum damos_wmark_metric metric;
+	char *name;
+};
+
+static const struct damos_sysfs_wmark_metric_name
+damos_sysfs_wmark_metric_names[] = {
+	{
+		.metric = DAMOS_WMARK_NONE,
+		.name = "none",
+	},
+	{
+		.metric = DAMOS_WMARK_FREE_MEM_RATE,
+		.name = "free_mem_rate",
+	},
 };
 
 static ssize_t metric_show(struct kobject *kobj, struct kobj_attribute *attr,
@@ -796,9 +807,16 @@ static ssize_t metric_show(struct kobject *kobj, struct kobj_attribute *attr,
 {
 	struct damon_sysfs_watermarks *watermarks = container_of(kobj,
 			struct damon_sysfs_watermarks, kobj);
+	int i;
 
-	return sysfs_emit(buf, "%s\n",
-			damon_sysfs_wmark_metric_strs[watermarks->metric]);
+	for (i = 0; i < ARRAY_SIZE(damos_sysfs_wmark_metric_names); i++) {
+		const struct damos_sysfs_wmark_metric_name *metric_name;
+
+		metric_name = &damos_sysfs_wmark_metric_names[i];
+		if (metric_name->metric == watermarks->metric)
+			return sysfs_emit(buf, "%s\n", metric_name->name);
+	}
+	return -EINVAL;
 }
 
 static ssize_t metric_store(struct kobject *kobj, struct kobj_attribute *attr,
@@ -806,11 +824,14 @@ static ssize_t metric_store(struct kobject *kobj, struct kobj_attribute *attr,
 {
 	struct damon_sysfs_watermarks *watermarks = container_of(kobj,
 			struct damon_sysfs_watermarks, kobj);
-	enum damos_wmark_metric metric;
+	int i;
 
-	for (metric = 0; metric < NR_DAMOS_WMARK_METRICS; metric++) {
-		if (sysfs_streq(buf, damon_sysfs_wmark_metric_strs[metric])) {
-			watermarks->metric = metric;
+	for (i = 0; i < ARRAY_SIZE(damos_sysfs_wmark_metric_names); i++) {
+		const struct damos_sysfs_wmark_metric_name *metric_name;
+
+		metric_name = &damos_sysfs_wmark_metric_names[i];
+		if (sysfs_streq(buf, metric_name->name)) {
+			watermarks->metric = metric_name->metric;
 			return count;
 		}
 	}
-- 
2.39.5