[RFC PATCH 4/9] mm/damon/sysfs: use damon_call() for update_schemes_stats

[SeongJae Park <sj@xxxxxxxxxx>]

DAMON sysfs interface uses damon_callback with its own synchronization
facility to handle update_schemes_stats kdamond command.  But
damon_call() can support the use case without the additional
synchronizations.  Convert the code to use damon_call() instead.

Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 mm/damon/sysfs.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 8cb940d21fbe..d30d659c794e 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1214,19 +1214,19 @@ static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
 
 /*
  * damon_sysfs_upd_schemes_stats() - Update schemes stats sysfs files.
- * @kdamond:	The kobject wrapper that associated to the kdamond thread.
+ * @data:	The kobject wrapper that associated to the kdamond thread.
  *
  * This function reads the schemes stats 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.
+ * worker thread,to safely access the DAMON contexts-internal data.  Caller
+ * should also ensure holding ``damon_syfs_lock``, and ->damon_ctx of @data is
+ * not NULL but a valid pointer, to safely access DAMON sysfs variables.
  */
-static int damon_sysfs_upd_schemes_stats(struct damon_sysfs_kdamond *kdamond)
+static int damon_sysfs_upd_schemes_stats(void *data)
 {
+	struct damon_sysfs_kdamond *kdamond = data;
 	struct damon_ctx *ctx = kdamond->damon_ctx;
 
-	if (!ctx)
-		return -EINVAL;
 	damon_sysfs_schemes_update_stats(
 			kdamond->contexts->contexts_arr[0]->schemes, ctx);
 	return 0;
@@ -1371,9 +1371,6 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c, bool active,
 	if (!kdamond || kdamond->damon_ctx != c)
 		goto out;
 	switch (damon_sysfs_cmd_request.cmd) {
-	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS:
-		err = damon_sysfs_upd_schemes_stats(kdamond);
-		break;
 	case DAMON_SYSFS_CMD_COMMIT:
 		if (!after_aggregation)
 			goto out;
@@ -1511,6 +1508,18 @@ static int damon_sysfs_turn_damon_off(struct damon_sysfs_kdamond *kdamond)
 	 */
 }
 
+static int damon_sysfs_damon_call(int (*fn)(void *data),
+		struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_call_control call_control = {};
+
+	if (!kdamond->damon_ctx)
+		return -EINVAL;
+	call_control.fn = fn;
+	call_control.data = kdamond;
+	return damon_call(kdamond->damon_ctx, &call_control);
+}
+
 /*
  * damon_sysfs_handle_cmd() - Handle a command for a specific kdamond.
  * @cmd:	The command to handle.
@@ -1529,12 +1538,14 @@ static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd,
 {
 	bool need_wait = true;
 
-	/* Handle commands that doesn't access DAMON context-internal data */
 	switch (cmd) {
 	case DAMON_SYSFS_CMD_ON:
 		return damon_sysfs_turn_damon_on(kdamond);
 	case DAMON_SYSFS_CMD_OFF:
 		return damon_sysfs_turn_damon_off(kdamond);
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS:
+		return damon_sysfs_damon_call(
+				damon_sysfs_upd_schemes_stats, kdamond);
 	case DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS:
 		return damon_sysfs_schemes_clear_regions(
 			kdamond->contexts->contexts_arr[0]->schemes);
-- 
2.39.5