mm/damon/sysfs: implement a kdamond command for updating schemes' effective quotas

Implement yet another kdamond 'state' file input command, namely
'update_schemes_effective_quotas'.  If it is written, the
'effective_bytes' files of the kdamond will be updated to provide the
current effective size quota of each scheme in bytes.

Link: https://lkml.kernel.org/r/20240219194431.159606-4-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/damon/sysfs-common.h

@@ -61,3 +61,7 @@ int damon_sysfs_schemes_clear_regions(
 
 void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 		struct damon_ctx *ctx);
+
+void damos_sysfs_update_effective_quotas(
+		struct damon_sysfs_schemes *sysfs_schemes,
+		struct damon_ctx *ctx);

mm/damon/sysfs-schemes.c

@@ -1930,6 +1930,26 @@ void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 	}
 }
 
+void damos_sysfs_update_effective_quotas(
+		struct damon_sysfs_schemes *sysfs_schemes,
+		struct damon_ctx *ctx)
+{
+	struct damos *scheme;
+	int schemes_idx = 0;
+
+	damon_for_each_scheme(scheme, ctx) {
+		struct damon_sysfs_quotas *sysfs_quotas;
+
+		/* user could have removed the scheme sysfs dir */
+		if (schemes_idx >= sysfs_schemes->nr)
+			break;
+
+		sysfs_quotas =
+			sysfs_schemes->schemes_arr[schemes_idx++]->quotas;
+		sysfs_quotas->effective_sz = scheme->quota.esz;
+	}
+}
+
 static struct damos *damon_sysfs_mk_scheme(
 		struct damon_sysfs_scheme *sysfs_scheme)
 {

mm/damon/sysfs.c

@@ -1019,6 +1019,11 @@ enum damon_sysfs_cmd {
 	 * regions
 	 */
 	DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS: Update the
+	 * effective size quota of the scheme in bytes.
+	 */
+	DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS,
 	/*
 	 * @NR_DAMON_SYSFS_CMDS: Total number of DAMON sysfs commands.
 	 */
@@ -1035,6 +1040,7 @@ static const char * const damon_sysfs_cmd_strs[] = {
 	"update_schemes_tried_bytes",
 	"update_schemes_tried_regions",
 	"clear_schemes_tried_regions",
+	"update_schemes_effective_quotas",
 };
 
 /*
@@ -1375,6 +1381,29 @@ static int damon_sysfs_commit_schemes_quota_goals(
 	return 0;
 }
 
+/*
+ * damon_sysfs_upd_schemes_effective_quotas() - Update schemes effective quotas
+ * sysfs files.
+ * @kdamond:	The kobject wrapper that associated to the kdamond thread.
+ *
+ * This function reads the schemes' effective quotas of specific kdamond and
+ * update the related values for sysfs files.  This function should be called
+ * from DAMON callbacks while holding ``damon_syfs_lock``, to safely access the
+ * DAMON contexts-internal data and DAMON sysfs variables.
+ */
+static int damon_sysfs_upd_schemes_effective_quotas(
+		struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	damos_sysfs_update_effective_quotas(
+			kdamond->contexts->contexts_arr[0]->schemes, ctx);
+	return 0;
+}
+
+
 /*
  * damon_sysfs_cmd_request_callback() - DAMON callback for handling requests.
  * @c:		The DAMON context of the callback.
@@ -1437,6 +1466,9 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c, bool active,
 	case DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS:
 		err = damon_sysfs_clear_schemes_regions(kdamond);
 		break;
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_EFFECTIVE_QUOTAS:
+		err = damon_sysfs_upd_schemes_effective_quotas(kdamond);
+		break;
 	default:
 		break;
 	}