mm/damon/sysfs: add a file for efficiently get total size of DAMOS tried regions

index 50cf89dcd898..6d3462eb31f2 100644
@@ -117,6 +117,7 @@ struct damon_sysfs_scheme_regions {
 	struct kobject kobj;
 	struct list_head regions_list;
 	int nr_regions;
+	unsigned long total_bytes;
 };
 
 static struct damon_sysfs_scheme_regions *

@@ -128,9 +129,19 @@ damon_sysfs_scheme_regions_alloc(void)
 	regions->kobj = (struct kobject){};
 	INIT_LIST_HEAD(&regions->regions_list);
 	regions->nr_regions = 0;
+	regions->total_bytes = 0;
 	return regions;
 }
 
+static ssize_t total_bytes_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_scheme_regions *regions = container_of(kobj,
+			struct damon_sysfs_scheme_regions, kobj);
+
+	return sysfs_emit(buf, "%lu\n", regions->total_bytes);
+}
+
 static void damon_sysfs_scheme_regions_rm_dirs(
 		struct damon_sysfs_scheme_regions *regions)
 {

@@ -148,7 +159,11 @@ static void damon_sysfs_scheme_regions_release(struct kobject *kobj)
 	kfree(container_of(kobj, struct damon_sysfs_scheme_regions, kobj));
 }
 
+static struct kobj_attribute damon_sysfs_scheme_regions_total_bytes_attr =
+		__ATTR_RO_MODE(total_bytes, 0400);
+
 static struct attribute *damon_sysfs_scheme_regions_attrs[] = {
+	&damon_sysfs_scheme_regions_total_bytes_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_scheme_regions);

@@ -1648,6 +1663,7 @@ static int damon_sysfs_before_damos_apply(struct damon_ctx *ctx,
 		return 0;
 
 	sysfs_regions = sysfs_schemes->schemes_arr[schemes_idx]->tried_regions;
+	sysfs_regions->total_bytes += r->ar.end - r->ar.start;
 	region = damon_sysfs_scheme_region_alloc(r);
 	list_add_tail(&region->list, &sysfs_regions->regions_list);
 	sysfs_regions->nr_regions++;

@@ -1678,6 +1694,7 @@ int damon_sysfs_schemes_clear_regions(
 		sysfs_scheme = sysfs_schemes->schemes_arr[schemes_idx++];
 		damon_sysfs_scheme_regions_rm_dirs(
 				sysfs_scheme->tried_regions);
+		sysfs_scheme->tried_regions->total_bytes = 0;
 	}
 	return 0;
 }

index db677eba78fd..fd482a0639b4 100644
@@ -47,7 +47,7 @@ void damon_sysfs_schemes_update_stats(
 
 int damon_sysfs_schemes_update_regions_start(
 		struct damon_sysfs_schemes *sysfs_schemes,
-		struct damon_ctx *ctx);
+		struct damon_ctx *ctx, bool total_bytes_only);
 
 int damon_sysfs_schemes_update_regions_stop(struct damon_ctx *ctx);
 

index 6d3462eb31f2..9a015079f3a4 100644
@@ -1635,6 +1635,7 @@ void damon_sysfs_schemes_update_stats(
  */
 static struct damon_sysfs_schemes *damon_sysfs_schemes_for_damos_callback;
 static int damon_sysfs_schemes_region_idx;
+static bool damos_regions_upd_total_bytes_only;
 
 /*
  * DAMON callback that called before damos apply.  While this callback is

@@ -1664,6 +1665,9 @@ static int damon_sysfs_before_damos_apply(struct damon_ctx *ctx,
 
 	sysfs_regions = sysfs_schemes->schemes_arr[schemes_idx]->tried_regions;
 	sysfs_regions->total_bytes += r->ar.end - r->ar.start;
+	if (damos_regions_upd_total_bytes_only)
+		return 0;
+
 	region = damon_sysfs_scheme_region_alloc(r);
 	list_add_tail(&region->list, &sysfs_regions->regions_list);
 	sysfs_regions->nr_regions++;

@@ -1702,10 +1706,11 @@ int damon_sysfs_schemes_clear_regions(
 /* Called from damon_sysfs_cmd_request_callback under damon_sysfs_lock */
 int damon_sysfs_schemes_update_regions_start(
 		struct damon_sysfs_schemes *sysfs_schemes,
-		struct damon_ctx *ctx)
+		struct damon_ctx *ctx, bool total_bytes_only)
 {
 	damon_sysfs_schemes_clear_regions(sysfs_schemes, ctx);
 	damon_sysfs_schemes_for_damos_callback = sysfs_schemes;
+	damos_regions_upd_total_bytes_only = total_bytes_only;
 	ctx->callback.before_damos_apply = damon_sysfs_before_damos_apply;
 	return 0;
 }

index 533d06052c09..808a8efe0523 100644
@@ -999,6 +999,11 @@ enum damon_sysfs_cmd {
 	 * files.
 	 */
 	DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES: Update
+	 * tried_regions/total_bytes sysfs files for each scheme.
+	 */
+	DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES,
 	/*
 	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS: Update schemes tried
 	 * regions

@@ -1021,6 +1026,7 @@ static const char * const damon_sysfs_cmd_strs[] = {
 	"off",
 	"commit",
 	"update_schemes_stats",
+	"update_schemes_tried_bytes",
 	"update_schemes_tried_regions",
 	"clear_schemes_tried_regions",
 };

@@ -1206,12 +1212,14 @@ static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
 {
 	struct damon_target *t, *next;
 	struct damon_sysfs_kdamond *kdamond;
+	enum damon_sysfs_cmd cmd;
 
 	/* damon_sysfs_schemes_update_regions_stop() might not yet called */
 	kdamond = damon_sysfs_cmd_request.kdamond;
-	if (kdamond && damon_sysfs_cmd_request.cmd ==
-			DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS &&
-			ctx == kdamond->damon_ctx) {
+	cmd = damon_sysfs_cmd_request.cmd;
+	if (kdamond && ctx == kdamond->damon_ctx &&
+			(cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS ||
+			 cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES)) {
 		damon_sysfs_schemes_update_regions_stop(ctx);
 		mutex_unlock(&damon_sysfs_lock);
 	}

@@ -1248,14 +1256,15 @@ static int damon_sysfs_upd_schemes_stats(struct damon_sysfs_kdamond *kdamond)
 }
 
 static int damon_sysfs_upd_schemes_regions_start(
-		struct damon_sysfs_kdamond *kdamond)
+		struct damon_sysfs_kdamond *kdamond, bool total_bytes_only)
 {
 	struct damon_ctx *ctx = kdamond->damon_ctx;
 
 	if (!ctx)
 		return -EINVAL;
 	return damon_sysfs_schemes_update_regions_start(
-			kdamond->contexts->contexts_arr[0]->schemes, ctx);
+			kdamond->contexts->contexts_arr[0]->schemes, ctx,
+			total_bytes_only);
 }
 
 static int damon_sysfs_upd_schemes_regions_stop(

@@ -1332,6 +1341,7 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c)
 {
 	struct damon_sysfs_kdamond *kdamond;
 	static bool damon_sysfs_schemes_regions_updating;
+	bool total_bytes_only = false;
 	int err = 0;
 
 	/* avoid deadlock due to concurrent state_store('off') */

@@ -1348,9 +1358,13 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c)
 	case DAMON_SYSFS_CMD_COMMIT:
 		err = damon_sysfs_commit_input(kdamond);
 		break;
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES:
+		total_bytes_only = true;
+		fallthrough;
 	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS:
 		if (!damon_sysfs_schemes_regions_updating) {
-			err = damon_sysfs_upd_schemes_regions_start(kdamond);
+			err = damon_sysfs_upd_schemes_regions_start(kdamond,
+					total_bytes_only);
 			if (!err) {
 				damon_sysfs_schemes_regions_updating = true;
 				goto keep_lock_out;