mm/damon/sysfs: handle 'state' file inputs for every sampling interval if possible

DAMON sysfs interface need to access kdamond-touching data for some of
kdamond user commands.  It uses ->after_aggregation() kdamond callback to
safely access the data in the case.  It had to use the aggregation
interval callback because that was the only callback that users can access
complete monitoring results.

Since patch series "mm/damon: provide pseudo-moving sum based access
rate", which starts from commit 78fbfb155d20 ("mm/damon/core: define and
use a dedicated function for region access rate update"), DAMON provides
good-to-use quality moitoring results for every sampling interval.  It
aims to help users who need to quickly retrieve the monitoring results. 
When the aggregation interval is set too long and therefore waiting for
the aggregation interval can degrade user experience, or when the access
pattern is expected to be significantly changed[1] could be such cases.

However, because DAMON sysfs interface is still handling the commands per
aggregation interval, the end user cannot get the benefit.  Update DAMON
sysfs interface to handle kdamond commands for every sampling interval if
applicable.  Specifically, all kdamond data accessing commands except
'commit' command are applicable.

[1] https://lore.kernel.org/r/20240129121316.GA9706@cuiyangpei

Link: https://lkml.kernel.org/r/20240206025158.203097-1-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: xiongping1 <xiongping1@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 9 insertions, 13 deletions

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index ae0f0b314f3a..f6c7f43f06cc 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -127,17 +127,17 @@ static const struct kobj_type damon_sysfs_scheme_region_ktype = {
  *
  * Once the tried regions update request is received, the request handling
  * start function (damon_sysfs_scheme_update_regions_start()) sets the status
- * of all schemes as 'idle' again, and register ->before_damos_apply() and
- * ->after_sampling() callbacks.
+ * of all schemes as 'idle' again, and register ->before_damos_apply()
+ * callback.
  *
  * Then, the first followup ->before_damos_apply() callback
  * (damon_sysfs_before_damos_apply()) sets the status 'started'.  The first
- * ->after_sampling() callback (damon_sysfs_after_sampling()) after the call
- * is called only after the scheme is completely applied
- * to the given snapshot.  Hence the callback knows the situation by showing
- * 'started' status, and sets the status as 'finished'.  Then,
- * damon_sysfs_before_damos_apply() understands the situation by showing the
- * 'finished' status and do nothing.
+ * ->after_sampling() or ->after_aggregation() callback
+ *  (damon_sysfs_cmd_request_callback()) after the call is called only after
+ *  the scheme is completely applied to the given snapshot.  Hence the callback
+ *  knows the situation by showing 'started' status, and sets the status as
+ *  'finished'.  Then, damon_sysfs_before_damos_apply() understands the
+ *  situation by showing the 'finished' status and do nothing.
  *
  * If DAMOS is not applied to any region due to any reasons including the
  * access pattern, the watermarks, the quotas, and the filters,
@@ -2122,7 +2122,7 @@ static int damon_sysfs_before_damos_apply(struct damon_ctx *ctx,
  * callback is registered, damon_sysfs_lock should be held to ensure the
  * regions directories exist.
  */
-static int damon_sysfs_after_sampling(struct damon_ctx *ctx)
+void damos_sysfs_mark_finished_regions_updates(struct damon_ctx *ctx)
 {
 	struct damon_sysfs_schemes *sysfs_schemes =
 		damon_sysfs_schemes_for_damos_callback;
@@ -2138,8 +2138,6 @@ static int damon_sysfs_after_sampling(struct damon_ctx *ctx)
 			sysfs_regions->upd_status =
 				DAMOS_TRIED_REGIONS_UPD_FINISHED;
 	}
-
-	return 0;
 }
 
 /* Called from damon_sysfs_cmd_request_callback under damon_sysfs_lock */
@@ -2212,7 +2210,6 @@ int damon_sysfs_schemes_update_regions_start(
 	damos_tried_regions_init_upd_status(sysfs_schemes, ctx);
 	damos_regions_upd_total_bytes_only = total_bytes_only;
 	ctx->callback.before_damos_apply = damon_sysfs_before_damos_apply;
-	ctx->callback.after_sampling = damon_sysfs_after_sampling;
 	return 0;
 }
 
@@ -2241,7 +2238,6 @@ int damon_sysfs_schemes_update_regions_stop(struct damon_ctx *ctx)
 {
 	damon_sysfs_schemes_for_damos_callback = NULL;
 	ctx->callback.before_damos_apply = NULL;
-	ctx->callback.after_sampling = NULL;
 	damon_sysfs_schemes_region_idx = 0;
 	return 0;
 }