mm/damon: improve readability, clarity and test coverage

index bbb190b474015..836353c4ab9aa 100644
@@ -400,7 +400,6 @@ struct damos_stat {
  * @DAMOS_FILTER_TYPE_ADDR:	Address range.
  * @DAMOS_FILTER_TYPE_TARGET:	Data Access Monitoring target.
  * @DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:	probe_hits weighted sum range.
- * @NR_DAMOS_FILTER_TYPES:	Number of filter types.
  *
  * All types except &DAMOS_FILTER_TYPE_ADDR, &DAMOS_FILTER_TYPE_TARGET and
  * &DAMOS_FILTER_TYPE_PROBE_HITS_WSUM are handled by the underlying &struct

@@ -422,7 +421,6 @@ enum damos_filter_type {
 	DAMOS_FILTER_TYPE_ADDR,
 	DAMOS_FILTER_TYPE_TARGET,
 	DAMOS_FILTER_TYPE_PROBE_HITS_WSUM,
-	NR_DAMOS_FILTER_TYPES,
 };
 
 /**

index 707fdc82de3a5..0299729e79ed9 100644
@@ -2927,10 +2927,7 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 	if (score >= goal * 2)
 		return min_input;
 
-	if (over_achieving)
-		score_goal_diff = score - goal;
-	else
-		score_goal_diff = goal - score;
+	score_goal_diff = abs_diff(score, goal);
 
 	if (last_input < ULONG_MAX / score_goal_diff)
 		compensation = last_input * score_goal_diff / goal;

index 0299729e79ed9..7bbbd44379301 100644
@@ -2928,11 +2928,7 @@ static unsigned long damon_feed_loop_next_input(unsigned long last_input,
 		return min_input;
 
 	score_goal_diff = abs_diff(score, goal);
-
-	if (last_input < ULONG_MAX / score_goal_diff)
-		compensation = last_input * score_goal_diff / goal;
-	else
-		compensation = last_input / goal * score_goal_diff;
+	compensation = mult_frac(last_input, score_goal_diff, goal);
 
 	if (over_achieving)
 		return max(last_input - compensation, min_input);

index 7bbbd44379301..9120a1b707b24 100644
@@ -939,6 +939,7 @@ struct damon_ctx *damon_new_ctx(void)
 	INIT_LIST_HEAD(&ctx->schemes);
 
 	ctx->call_controls_obsolete = true;
+	ctx->walk_control_obsolete = true;
 	prandom_seed_state(&ctx->rnd_state, get_random_u64());
 
 	return ctx;

@@ -2308,10 +2309,6 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)
  * passed at least one &damos->apply_interval_us, kdamond marks the request as
  * completed so that damos_walk() can wakeup and return.
  *
- * Note that this function should be called only after damon_start() with the
- * @ctx has succeeded.  Otherwise, this function could fall into an indefinite
- * wait.
- *
  * Return: 0 on success, negative error code otherwise.
  */
 int damos_walk(struct damon_ctx *ctx, struct damos_walk_control *control)

index 9120a1b707b24..4687b909d42c9 100644
@@ -2258,6 +2258,9 @@ int damon_kdamond_pid(struct damon_ctx *ctx)
  *
  * When this function is failed, the @ctx is guaranteed to be stopped.
  *
+ * This function should not be called in parallel to damon_start() for the
+ * @ctx.  In the case, this function could indefinitely hang.
+ *
  * Return: 0 on success, negative error code otherwise.
  */
 int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)

index 5abfabaa339e0..2cfdc356b4157 100644
@@ -163,8 +163,7 @@ static bool damon_pa_filter_match(struct damon_filter *filter,
 	return matched == filter->matching;
 }
 
-static bool damon_pa_filter_pass(phys_addr_t pa, struct folio *folio,
-		struct damon_probe *p)
+static bool damon_pa_filter_pass(struct folio *folio, struct damon_probe *p)
 {
 	struct damon_filter *f;
 	bool pass = true;

@@ -200,7 +199,7 @@ static unsigned int damon_pa_apply_probes(struct damon_ctx *ctx,
 					ctx->addr_unit);
 			folio = damon_get_folio(PHYS_PFN(pa));
 			damon_for_each_probe(p, ctx) {
-				if (damon_pa_filter_pass(pa, folio, p))
+				if (damon_pa_filter_pass(folio, p))
 					r->probe_hits[i]++;
 				i++;
 			}

index 82c542afaa60e..1244cfeae5e70 100644
@@ -835,6 +835,9 @@ static void damos_test_commit_quota_goal_for(struct kunit *test,
 		KUNIT_EXPECT_EQ(test, dst->nid, src->nid);
 		KUNIT_EXPECT_EQ(test, dst->memcg_id, src->memcg_id);
 		break;
+	case DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP:
+		KUNIT_EXPECT_EQ(test, dst->nid, src->nid);
+		break;
 	default:
 		break;
 	}

@@ -898,6 +901,13 @@ static void damos_test_commit_quota_goal(struct kunit *test)
 			.current_value = 345,
 			.last_psi_total = 567,
 			});
+	damos_test_commit_quota_goal_for(test, &dst,
+			&(struct damos_quota_goal){
+			.metric = DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP,
+			.target_value = 12,
+			.current_value = 345,
+			.nid = 6,
+			});
 }
 
 static void damos_test_commit_quota_goals_for(struct kunit *test,

index 1244cfeae5e70..df84d9cc7d204 100644
@@ -1166,6 +1166,10 @@ static void damos_test_commit_filter_for(struct kunit *test,
 		KUNIT_EXPECT_EQ(test, dst->sz_range.min, src->sz_range.min);
 		KUNIT_EXPECT_EQ(test, dst->sz_range.max, src->sz_range.max);
 		break;
+	case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM:
+		KUNIT_EXPECT_EQ(test, dst->range_min, src->range_min);
+		KUNIT_EXPECT_EQ(test, dst->range_max, src->range_max);
+		break;
 	default:
 		break;
 	}

@@ -1239,6 +1243,22 @@ static void damos_test_commit_filter(struct kunit *test)
 			.allow = true,
 			.target_idx = 6,
 			}, false);
+	damos_test_commit_filter_for(test, &dst,
+			&(struct damos_filter){
+			.type = DAMOS_FILTER_TYPE_PROBE_HITS_WSUM,
+			.matching = false,
+			.allow = true,
+			.range_min = 12,
+			.range_max = 34,
+			}, false);
+	damos_test_commit_filter_for(test, &dst,
+			&(struct damos_filter){
+			.type = DAMOS_FILTER_TYPE_PROBE_HITS_WSUM,
+			.matching = false,
+			.allow = true,
+			.range_min = 34,
+			.range_max = 12,
+			}, true);
 }
 
 static void damos_test_help_initailize_scheme(struct damos *scheme)