[PATCH 2/5] mm/damon/sysfs: Implement a command to only commit scheme dests

[Bijan Tabatabai <bijan311@gmail.com>]

From: Bijan Tabatabai <bijantabatab@micron.com>

To update DAMOS migration dests, users need to write "commit" to the
"state" file of kdamond, which will recommit all of the damon parameters.
This patch implements another state file input command,
"commit_scheme_dests," that only commits the DAMOS migration dests.

This provides two benefits:
1) It is slightly more efficient
2) When the "commit" command is sent to the state file,
   ctx->next_{aggregation/ops_update}_sis are reset. If a user sends the
   "commit" command frequently (relative to the aggregation and
   ops_update periods) to update the migration dests, the aggregation and
   ops_update events will be prevented from triggering. Having a
   separate command side steps this problem.

Signed-off-by: Bijan Tabatabai <bijantabatab@micron.com>
---
 mm/damon/sysfs-common.h  |  3 +++
 mm/damon/sysfs-schemes.c | 35 ++++++++++++++++++++++++++++++++---
 mm/damon/sysfs.c         | 27 +++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/mm/damon/sysfs-common.h b/mm/damon/sysfs-common.h
index 2099adee11d0..3189b2bda079 100644
--- a/mm/damon/sysfs-common.h
+++ b/mm/damon/sysfs-common.h
@@ -59,3 +59,6 @@ int 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);
+
+int damos_sysfs_set_schemes_dests(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 d355f6c42a98..d30c8b6575c2 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -2445,10 +2445,9 @@ void damos_sysfs_update_effective_quotas(
 	}
 }
 
-static int damos_sysfs_add_migrate_dest(struct damos *scheme,
+static int damos_sysfs_add_migrate_dest(struct damos_migrate_dests *dests,
 		struct damos_sysfs_dests *sysfs_dests)
 {
-	struct damos_migrate_dests *dests = &scheme->migrate_dests;
 	int i;
 
 	dests->node_id_arr = kmalloc_array(sysfs_dests->nr,
@@ -2468,6 +2467,35 @@ static int damos_sysfs_add_migrate_dest(struct damos *scheme,
 	return 0;
 }
 
+int damos_sysfs_set_schemes_dests(struct damon_sysfs_schemes *sysfs_schemes,
+		struct damon_ctx *ctx)
+{
+	struct damos *scheme;
+	int i = 0;
+
+	damon_for_each_scheme(scheme, ctx) {
+		struct damos_sysfs_dests *sysfs_dests;
+		struct damos_migrate_dests dests = {};
+		int err;
+
+		/* user could have removed the scheme sysfs dir */
+		if (i >= sysfs_schemes->nr)
+			break;
+
+		sysfs_dests = sysfs_schemes->schemes_arr[i]->dests;
+		err = damos_sysfs_add_migrate_dest(&dests, sysfs_dests);
+		if (err) {
+			damos_destroy_dests(&dests);
+			return err;
+		}
+
+		damos_destroy_dests(&scheme->migrate_dests);
+		scheme->migrate_dests = dests;
+	}
+
+	return 0;
+}
+
 static struct damos *damon_sysfs_mk_scheme(
 		struct damon_sysfs_scheme *sysfs_scheme)
 {
@@ -2530,7 +2558,8 @@ static struct damos *damon_sysfs_mk_scheme(
 		damon_destroy_scheme(scheme);
 		return NULL;
 	}
-	err = damos_sysfs_add_migrate_dest(scheme, sysfs_scheme->dests);
+	err = damos_sysfs_add_migrate_dest(&scheme->migrate_dests,
+		sysfs_scheme->dests);
 	if (err) {
 		damon_destroy_scheme(scheme);
 		return NULL;
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 1af6aff35d84..c2b036abb25b 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1188,6 +1188,11 @@ enum damon_sysfs_cmd {
 	 * to DAMON.
 	 */
 	DAMON_SYSFS_CMD_COMMIT_SCHEMES_QUOTA_GOALS,
+	/*
+	 * @DAMON_SYSFS_CMD_COMMIT_SCHEMES_DESTS: Commit the scheme dests to
+	 * DAMON.
+	 */
+	DAMON_SYSFS_CMD_COMMIT_SCHEMES_DESTS,
 	/*
 	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS: Update scheme stats sysfs
 	 * files.
@@ -1230,6 +1235,7 @@ static const char * const damon_sysfs_cmd_strs[] = {
 	"off",
 	"commit",
 	"commit_schemes_quota_goals",
+	"commit_schemes_dests",
 	"update_schemes_stats",
 	"update_schemes_tried_bytes",
 	"update_schemes_tried_regions",
@@ -1478,6 +1484,23 @@ static int damon_sysfs_commit_schemes_quota_goals(void *data)
 	return damos_sysfs_set_quota_scores(sysfs_ctx->schemes, ctx);
 }
 
+static int damon_sysfs_commit_schemes_dests(void *data)
+{
+	struct damon_sysfs_kdamond *sysfs_kdamond = data;
+	struct damon_ctx *ctx;
+	struct damon_sysfs_context *sysfs_ctx;
+
+	if (!damon_sysfs_kdamond_running(sysfs_kdamond))
+		return -EINVAL;
+	/* TODO: Support multiple contexts per kdamond */
+	if (sysfs_kdamond->contexts->nr != 1)
+		return -EINVAL;
+
+	ctx = sysfs_kdamond->damon_ctx;
+	sysfs_ctx = sysfs_kdamond->contexts->contexts_arr[0];
+	return damos_sysfs_set_schemes_dests(sysfs_ctx->schemes, ctx);
+}
+
 /*
  * damon_sysfs_upd_schemes_effective_quotas() - Update schemes effective quotas
  * sysfs files.
@@ -1644,6 +1667,10 @@ static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd,
 		return damon_sysfs_damon_call(
 				damon_sysfs_commit_schemes_quota_goals,
 				kdamond);
+	case DAMON_SYSFS_CMD_COMMIT_SCHEMES_DESTS:
+		return damon_sysfs_damon_call(
+				damon_sysfs_commit_schemes_dests,
+				kdamond);
 	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS:
 		return damon_sysfs_damon_call(
 				damon_sysfs_upd_schemes_stats, kdamond);
-- 
2.43.5