[PATCH 1/7] mm/damon/core: use mult_frac()

[SeongJae Park <sj@kernel.org>]

There are multiple places in core code that do open-code rate
calculations.  Use mult_frac(), which is developed for doing that in a
way more safe from overflow and precision loss.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index cd2d7a8e3fe92..4e931f7380477 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -665,7 +665,7 @@ static unsigned int damon_accesses_bp_to_nr_accesses(
 static unsigned int damon_nr_accesses_to_accesses_bp(
 		unsigned int nr_accesses, struct damon_attrs *attrs)
 {
-	return nr_accesses * 10000 / damon_max_nr_accesses(attrs);
+	return mult_frac(nr_accesses, 10000, damon_max_nr_accesses(attrs));
 }
 
 static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_accesses,
@@ -1722,7 +1722,7 @@ static unsigned long damon_get_intervals_score(struct damon_ctx *c)
 	}
 	target_access_events = max_access_events * goal_bp / 10000;
 	target_access_events = target_access_events ? : 1;
-	return access_events * 10000 / target_access_events;
+	return mult_frac(access_events, 10000, target_access_events);
 }
 
 static unsigned long damon_feed_loop_next_input(unsigned long last_input,
@@ -2202,7 +2202,7 @@ static __kernel_ulong_t damos_get_node_mem_bp(
 		numerator = i.totalram - i.freeram;
 	else	/* DAMOS_QUOTA_NODE_MEM_FREE_BP */
 		numerator = i.freeram;
-	return numerator * 10000 / i.totalram;
+	return mult_frac(numerator, 10000, i.totalram);
 }
 
 static unsigned long damos_get_node_memcg_used_bp(
@@ -2235,7 +2235,7 @@ static unsigned long damos_get_node_memcg_used_bp(
 		numerator = used_pages;
 	else	/* DAMOS_QUOTA_NODE_MEMCG_FREE_BP */
 		numerator = i.totalram - used_pages;
-	return numerator * 10000 / i.totalram;
+	return mult_frac(numerator, 10000, i.totalram);
 }
 #else
 static __kernel_ulong_t damos_get_node_mem_bp(
@@ -2265,8 +2265,8 @@ static unsigned int damos_get_in_active_mem_bp(bool active_ratio)
 		global_node_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE);
 	total = active + inactive;
 	if (active_ratio)
-		return active * 10000 / total;
-	return inactive * 10000 / total;
+		return mult_frac(active, 10000, total);
+	return mult_frac(inactive, 10000, total);
 }
 
 static void damos_set_quota_goal_current_value(struct damos_quota_goal *goal)
@@ -2309,8 +2309,8 @@ static unsigned long damos_quota_score(struct damos_quota *quota)
 	damos_for_each_quota_goal(goal, quota) {
 		damos_set_quota_goal_current_value(goal);
 		highest_score = max(highest_score,
-				goal->current_value * 10000 /
-				goal->target_value);
+				mult_frac(goal->current_value, 10000,
+					goal->target_value));
 	}
 
 	return highest_score;
@@ -2340,8 +2340,8 @@ static void damos_set_effective_quota(struct damos_quota *quota)
 
 	if (quota->ms) {
 		if (quota->total_charged_ns)
-			throughput = mult_frac(quota->total_charged_sz, 1000000,
-							quota->total_charged_ns);
+			throughput = mult_frac(quota->total_charged_sz,
+					1000000, quota->total_charged_ns);
 		else
 			throughput = PAGE_SIZE * 1024;
 		esz = min(throughput * quota->ms, esz);
-- 
2.47.3