mm/damon/core: let goal specified with only target and current values

DAMOS quota auto-tuning feature let users to set the goal by providing a
function for getting the current score of the tuned quota.  It allows
flexible goal setup, but only simple user-set quota is currently being
used.  As a result, the only user of the DAMOS quota auto-tuning is using
a silly void pointer casting based score value passing function.  Simplify
the interface and the user code by letting user directly set the target
and the current value.

Link: https://lkml.kernel.org/r/20240219194431.159606-12-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/damon.h

@@ -128,19 +128,18 @@ enum damos_action {
 
 /**
  * struct damos_quota_goal - DAMOS scheme quota auto-tuning goal.
- * @get_score:		Function for getting current score of the goal.
- * @get_score_arg:	Parameter for @get_score
+ * @target_value:	Target value to achieve with the tuning.
+ * @current_value:	Current value that achieving with the tuning.
  * @list:		List head for siblings.
  *
- * Data structure for getting the current score of the quota tuning goal.
- * Calling @get_score with @get_score_arg as the parameter should return the
- * current score.  Then the score is entered to DAMON's internal feedback loop
- * mechanism to get the auto-tuned quota.  The goal of the tuning is getting
- * the feedback score value of 10,000.
+ * Data structure for getting the current score of the quota tuning goal.  The
+ * score is calculated by how close @current_value and @target_value are.  Then
+ * the score is entered to DAMON's internal feedback loop mechanism to get the
+ * auto-tuned quota.
  */
 struct damos_quota_goal {
-	unsigned long (*get_score)(void *arg);
-	void *get_score_arg;
+	unsigned long target_value;
+	unsigned long current_value;
 	struct list_head list;
 };
 
@@ -690,7 +689,7 @@ void damos_add_filter(struct damos *s, struct damos_filter *f);
 void damos_destroy_filter(struct damos_filter *f);
 
 struct damos_quota_goal *damos_new_quota_goal(
-		unsigned long (*get_score)(void *), void *get_score_arg);
+		unsigned long target_value, unsigned long current_value);
 void damos_add_quota_goal(struct damos_quota *q, struct damos_quota_goal *g);
 void damos_destroy_quota_goal(struct damos_quota_goal *goal);
 

mm/damon/core.c

@@ -300,15 +300,15 @@ void damos_destroy_filter(struct damos_filter *f)
 }
 
 struct damos_quota_goal *damos_new_quota_goal(
-		unsigned long (*get_score)(void *), void *get_score_arg)
+		unsigned long target_value, unsigned long current_value)
 {
 	struct damos_quota_goal *goal;
 
 	goal = kmalloc(sizeof(*goal), GFP_KERNEL);
 	if (!goal)
 		return NULL;
-	goal->get_score = get_score;
-	goal->get_score_arg = get_score_arg;
+	goal->target_value = target_value;
+	goal->current_value = current_value;
 	INIT_LIST_HEAD(&goal->list);
 	return goal;
 }
@@ -1132,7 +1132,8 @@ static unsigned long damos_quota_score(struct damos_quota *quota)
 
 	damos_for_each_quota_goal(goal, quota)
 		highest_score = max(highest_score,
-				goal->get_score(goal->get_score_arg));
+				goal->current_value * 10000 /
+				goal->target_value);
 
 	return highest_score;
 }

mm/damon/sysfs-schemes.c

@@ -1882,11 +1882,6 @@ static int damon_sysfs_set_scheme_filters(struct damos *scheme,
 	return 0;
 }
 
-static unsigned long damos_sysfs_get_quota_score(void *arg)
-{
-	return (unsigned long)arg;
-}
-
 static int damos_sysfs_set_quota_score(
 		struct damos_sysfs_quota_goals *sysfs_goals,
 		struct damos_quota *quota)
@@ -1904,9 +1899,8 @@ static int damos_sysfs_set_quota_score(
 		if (!sysfs_goal->target_value)
 			continue;
 
-		goal = damos_new_quota_goal(damos_sysfs_get_quota_score,
-				(void *)(sysfs_goal->current_value * 10000 /
-				sysfs_goal->target_value));
+		goal = damos_new_quota_goal(sysfs_goal->target_value,
+				sysfs_goal->current_value);
 		if (!goal)
 			return -ENOMEM;
 		damos_add_quota_goal(quota, goal);