[RFC PATCH 16/18] mm/damon/sysfs-schemes: implement DAMOS tried regions clear command

[SeongJae Park <sj@kernel.org>]

When there are huge number of DAMON regions that specific scheme actions
are tried to be applied, directories and files under 'tried_regions'
scheme directory could waste some memory.  Add another special input
keyword for 'state' file of each kdamond sysfs directory that can be
used for cleanup of the 'tried_regions' sub-directories.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-common.h  |  4 ++++
 mm/damon/sysfs-schemes.c | 17 +++++++++++++++++
 mm/damon/sysfs.c         | 18 ++++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/mm/damon/sysfs-common.h b/mm/damon/sysfs-common.h
index 634a6e7fca78..604a6cbc3ede 100644
--- a/mm/damon/sysfs-common.h
+++ b/mm/damon/sysfs-common.h
@@ -50,3 +50,7 @@ int damon_sysfs_schemes_update_regions_start(
 		struct damon_ctx *ctx);
 
 int damon_sysfs_schemes_update_regions_stop(struct damon_ctx *ctx);
+
+int damon_sysfs_schemes_clear_regions(
+		struct damon_sysfs_schemes *sysfs_schemes,
+		struct damon_ctx *ctx);
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 2cea58e49d8d..223de1d06740 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1262,3 +1262,20 @@ int damon_sysfs_schemes_update_regions_stop(struct damon_ctx *ctx)
 	damon_sysfs_schemes_region_idx = 0;
 	return 0;
 }
+
+int damon_sysfs_schemes_clear_regions(
+		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_scheme *sysfs_scheme;
+
+		sysfs_scheme = sysfs_schemes->schemes_arr[schemes_idx++];
+		damon_sysfs_scheme_regions_rm_dirs(
+				sysfs_scheme->tried_regions);
+	}
+	return 0;
+}
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 6d26ae6052b6..acc16473f6fd 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1001,6 +1001,9 @@ enum damon_sysfs_cmd {
 	DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS,
 	/* @DAMON_SYSFS_CMD_UPDATE_SCHEMES_REGIONS: Update scheme regions */
 	DAMON_SYSFS_CMD_UPDATE_SCHEMES_REGIONS,
+	/* @DAMON_SYSFS_CMD_CLEAR_SCHEMES_REGIONS: Clear scheme regions */
+	DAMON_SYSFS_CMD_CLEAR_SCHEMES_REGIONS,
+
 	/*
 	 * @NR_DAMON_SYSFS_CMDS: Total number of DAMON sysfs commands.
 	 */
@@ -1014,6 +1017,7 @@ static const char * const damon_sysfs_cmd_strs[] = {
 	"commit",
 	"update_schemes_stats",
 	"update_schemes_regions",
+	"clear_schemes_regions",
 };
 
 /*
@@ -1259,6 +1263,17 @@ static int damon_sysfs_upd_schemes_regions_stop(
 	return damon_sysfs_schemes_update_regions_stop(ctx);
 }
 
+static int damon_sysfs_clear_schemes_regions(
+		struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	return damon_sysfs_schemes_clear_regions(
+			kdamond->contexts->contexts_arr[0]->schemes, ctx);
+}
+
 static inline bool damon_sysfs_kdamond_running(
 		struct damon_sysfs_kdamond *kdamond)
 {
@@ -1340,6 +1355,9 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c)
 			damon_sysfs_schemes_regions_updating = false;
 		}
 		break;
+	case DAMON_SYSFS_CMD_CLEAR_SCHEMES_REGIONS:
+		err = damon_sysfs_clear_schemes_regions(kdamond);
+		break;
 	default:
 		break;
 	}
-- 
2.25.1