[PATCH 10/10] mm/damon/sysfs: remove unused code for schemes tried regions update

SeongJae Park
2025-01-03T17:44:22Z

DAMON sysfs interface was using damon_callback with its own complicated
synchronization logics to update DAMOS scheme applied regions
directories and files. But it is replaced to use damos_walk(), and the
additional synchronization logics are no more being used. Remove those.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
mm/damon/sysfs-common.h | 10 --
mm/damon/sysfs-schemes.c | 204 ---------------------------------------
mm/damon/sysfs.c | 70 +-------------
3 files changed, 2 insertions(+), 282 deletions(-)

diff --git a/mm/damon/sysfs-common.h b/mm/damon/sysfs-common.h
index 81f1c845118f..b3f63bc658b7 100644
--- a/mm/damon/sysfs-common.h
+++ b/mm/damon/sysfs-common.h
@@ -45,16 +45,6 @@ void damon_sysfs_schemes_update_stats(
struct damon_sysfs_schemes *sysfs_schemes,
struct damon_ctx *ctx);

-int damon_sysfs_schemes_update_regions_start(
- struct damon_sysfs_schemes *sysfs_schemes,
- struct damon_ctx *ctx, bool total_bytes_only);
-
-void damos_sysfs_mark_finished_regions_updates(struct damon_ctx *ctx);
-
-bool damos_sysfs_regions_upd_done(void);
-
-int damon_sysfs_schemes_update_regions_stop(struct damon_ctx *ctx);
-
void damos_sysfs_populate_region_dir(struct damon_sysfs_schemes *sysfs_schemes,
struct damon_ctx *ctx, struct damon_target *t,
struct damon_region *r, struct damos *s,
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 1d8ad637051a..5c4490b97258 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -114,55 +114,11 @@ static const struct kobj_type damon_sysfs_scheme_region_ktype = {
* scheme regions directory
*/

-/*
- * enum damos_sysfs_regions_upd_status - Represent DAMOS tried regions update
- * status
- * @DAMOS_TRIED_REGIONS_UPD_IDLE: Waiting for next request.
- * @DAMOS_TRIED_REGIONS_UPD_STARTED: Update started.
- * @DAMOS_TRIED_REGIONS_UPD_FINISHED: Update finished.
- *
- * Each DAMON-based operation scheme (&struct damos) has its own apply
- * interval, and we need to expose the scheme tried regions based on only
- * single snapshot. For this, we keep the tried regions update status for each
- * scheme. The status becomes 'idle' at the beginning.
- *
- * 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()
- * callback.
- *
- * Then, the first followup ->before_damos_apply() callback
- * (damon_sysfs_before_damos_apply()) sets the status 'started'. The first
- * ->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,
- * ->before_damos_apply() will not be called back. Until the situation is
- * changed, the update will not be finished. To avoid this,
- * damon_sysfs_after_sampling() set the status as 'finished' if more than two
- * apply intervals of the scheme is passed while the state is 'idle'.
- *
- * Finally, the tried regions request handling finisher function
- * (damon_sysfs_schemes_update_regions_stop()) unregisters the callbacks.
- */
-enum damos_sysfs_regions_upd_status {
- DAMOS_TRIED_REGIONS_UPD_IDLE,
- DAMOS_TRIED_REGIONS_UPD_STARTED,
- DAMOS_TRIED_REGIONS_UPD_FINISHED,
-};
-
struct damon_sysfs_scheme_regions {
struct kobject kobj;
struct list_head regions_list;
int nr_regions;
unsigned long total_bytes;
- enum damos_sysfs_regions_upd_status upd_status;
- unsigned long upd_timeout_jiffies;
};

static struct damon_sysfs_scheme_regions *
@@ -178,7 +134,6 @@ damon_sysfs_scheme_regions_alloc(void)
INIT_LIST_HEAD(&regions->regions_list);
regions->nr_regions = 0;
regions->total_bytes = 0;
- regions->upd_status = DAMOS_TRIED_REGIONS_UPD_IDLE;
return regions;
}

@@ -2126,63 +2081,6 @@ void damon_sysfs_schemes_update_stats(
}
}

-/*
- * damon_sysfs_schemes that need to update its schemes regions dir. Protected
- * by damon_sysfs_lock
- */
-static struct damon_sysfs_schemes *damon_sysfs_schemes_for_damos_callback;
-static int damon_sysfs_schemes_region_idx;
-static bool damos_regions_upd_total_bytes_only;
-
-/*
- * DAMON callback that called before damos apply. While this callback is
- * registered, damon_sysfs_lock should be held to ensure the regions
- * directories exist.
- */
-static int damon_sysfs_before_damos_apply(struct damon_ctx *ctx,
- struct damon_target *t, struct damon_region *r,
- struct damos *s)
-{
- struct damos *scheme;
- struct damon_sysfs_scheme_regions *sysfs_regions;
- struct damon_sysfs_scheme_region *region;
- struct damon_sysfs_schemes *sysfs_schemes =
- damon_sysfs_schemes_for_damos_callback;
- int schemes_idx = 0;
-
- damon_for_each_scheme(scheme, ctx) {
- if (scheme == s)
- break;
- schemes_idx++;
- }
-
- /* user could have removed the scheme sysfs dir */
- if (schemes_idx >= sysfs_schemes->nr)
- return 0;
-
- sysfs_regions = sysfs_schemes->schemes_arr[schemes_idx]->tried_regions;
- if (sysfs_regions->upd_status == DAMOS_TRIED_REGIONS_UPD_FINISHED)
- return 0;
- if (sysfs_regions->upd_status == DAMOS_TRIED_REGIONS_UPD_IDLE)
- sysfs_regions->upd_status = DAMOS_TRIED_REGIONS_UPD_STARTED;
- sysfs_regions->total_bytes += r->ar.end - r->ar.start;
- if (damos_regions_upd_total_bytes_only)
- return 0;
-
- region = damon_sysfs_scheme_region_alloc(r);
- if (!region)
- return 0;
- list_add_tail(&region->list, &sysfs_regions->regions_list);
- sysfs_regions->nr_regions++;
- if (kobject_init_and_add(&region->kobj,
- &damon_sysfs_scheme_region_ktype,
- &sysfs_regions->kobj, "%d",
- damon_sysfs_schemes_region_idx++)) {
- kobject_put(&region->kobj);
- }
- return 0;
-}
-
/**
* damos_sysfs_populate_region_dir() - Populate a schemes tried region dir.
* @sysfs_schemes: Schemes directory to populate regions directory.
@@ -2231,29 +2129,6 @@ void damos_sysfs_populate_region_dir(struct damon_sysfs_schemes *sysfs_schemes,
}
}

-/*
- * DAMON callback that called after each accesses sampling. While this
- * callback is registered, damon_sysfs_lock should be held to ensure the
- * regions directories exist.
- */
-void damos_sysfs_mark_finished_regions_updates(struct damon_ctx *ctx)
-{
- struct damon_sysfs_schemes *sysfs_schemes =
- damon_sysfs_schemes_for_damos_callback;
- struct damon_sysfs_scheme_regions *sysfs_regions;
- int i;
-
- for (i = 0; i < sysfs_schemes->nr; i++) {
- sysfs_regions = sysfs_schemes->schemes_arr[i]->tried_regions;
- if (sysfs_regions->upd_status ==
- DAMOS_TRIED_REGIONS_UPD_STARTED ||
- time_after(jiffies,
- sysfs_regions->upd_timeout_jiffies))
- sysfs_regions->upd_status =
- DAMOS_TRIED_REGIONS_UPD_FINISHED;
- }
-}
-
/* Called from damon_sysfs_cmd_request_callback under damon_sysfs_lock */
int damon_sysfs_schemes_clear_regions(
struct damon_sysfs_schemes *sysfs_schemes)
@@ -2270,82 +2145,3 @@ int damon_sysfs_schemes_clear_regions(
}
return 0;
}
-
-static struct damos *damos_sysfs_nth_scheme(int n, struct damon_ctx *ctx)
-{
- struct damos *scheme;
- int i = 0;
-
- damon_for_each_scheme(scheme, ctx) {
- if (i == n)
- return scheme;
- i++;
- }
- return NULL;
-}
-
-static void damos_tried_regions_init_upd_status(
- struct damon_sysfs_schemes *sysfs_schemes,
- struct damon_ctx *ctx)
-{
- int i;
- struct damos *scheme;
- struct damon_sysfs_scheme_regions *sysfs_regions;
-
- for (i = 0; i < sysfs_schemes->nr; i++) {
- sysfs_regions = sysfs_schemes->schemes_arr[i]->tried_regions;
- scheme = damos_sysfs_nth_scheme(i, ctx);
- if (!scheme) {
- sysfs_regions->upd_status =
- DAMOS_TRIED_REGIONS_UPD_FINISHED;
- continue;
- }
- sysfs_regions->upd_status = DAMOS_TRIED_REGIONS_UPD_IDLE;
- sysfs_regions->upd_timeout_jiffies = jiffies +
- 2 * usecs_to_jiffies(scheme->apply_interval_us ?
- scheme->apply_interval_us :
- ctx->attrs.aggr_interval);
- }
-}
-
-/* Called while damon_sysfs_lock is hold */
-int damon_sysfs_schemes_update_regions_start(
- struct damon_sysfs_schemes *sysfs_schemes,
- struct damon_ctx *ctx, bool total_bytes_only)
-{
- damon_sysfs_schemes_clear_regions(sysfs_schemes);
- damon_sysfs_schemes_for_damos_callback = sysfs_schemes;
- 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;
- return 0;
-}
-
-bool damos_sysfs_regions_upd_done(void)
-{
- struct damon_sysfs_schemes *sysfs_schemes =
- damon_sysfs_schemes_for_damos_callback;
- struct damon_sysfs_scheme_regions *sysfs_regions;
- int i;
-
- for (i = 0; i < sysfs_schemes->nr; i++) {
- sysfs_regions = sysfs_schemes->schemes_arr[i]->tried_regions;
- if (sysfs_regions->upd_status !=
- DAMOS_TRIED_REGIONS_UPD_FINISHED)
- return false;
- }
- return true;
-}
-
-/*
- * Called from damon_sysfs_cmd_request_callback under damon_sysfs_lock. Caller
- * should unlock damon_sysfs_lock which held before
- * damon_sysfs_schemes_update_regions_start()
- */
-int damon_sysfs_schemes_update_regions_stop(struct damon_ctx *ctx)
-{
- damon_sysfs_schemes_for_damos_callback = NULL;
- ctx->callback.before_damos_apply = NULL;
- damon_sysfs_schemes_region_idx = 0;
- return 0;
-}
diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 4ba44a314f2e..cf8fb5a963d6 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1181,25 +1181,9 @@ static int damon_sysfs_add_targets(struct damon_ctx *ctx,
return 0;
}

-static bool damon_sysfs_schemes_regions_updating;
-
static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
{
struct damon_target *t, *next;
- struct damon_sysfs_kdamond *kdamond;
- enum damon_sysfs_cmd cmd;
-
- /* damon_sysfs_schemes_update_regions_stop() might not yet called */
- kdamond = damon_sysfs_cmd_request.kdamond;
- cmd = damon_sysfs_cmd_request.cmd;
- if (kdamond && ctx == kdamond->damon_ctx &&
- (cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS ||
- cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES) &&
- damon_sysfs_schemes_regions_updating) {
- damon_sysfs_schemes_update_regions_stop(ctx);
- damon_sysfs_schemes_regions_updating = false;
- mutex_unlock(&damon_sysfs_lock);
- }

if (!damon_target_has_pid(ctx))
return;
@@ -1232,28 +1216,6 @@ static int damon_sysfs_upd_schemes_stats(void *data)
return 0;
}

-static int damon_sysfs_upd_schemes_regions_start(
- struct damon_sysfs_kdamond *kdamond, bool total_bytes_only)
-{
- struct damon_ctx *ctx = kdamond->damon_ctx;
-
- if (!ctx)
- return -EINVAL;
- return damon_sysfs_schemes_update_regions_start(
- kdamond->contexts->contexts_arr[0]->schemes, ctx,
- total_bytes_only);
-}
-
-static int damon_sysfs_upd_schemes_regions_stop(
- struct damon_sysfs_kdamond *kdamond)
-{
- struct damon_ctx *ctx = kdamond->damon_ctx;
-
- if (!ctx)
- return -EINVAL;
- return damon_sysfs_schemes_update_regions_stop(ctx);
-}
-
static inline bool damon_sysfs_kdamond_running(
struct damon_sysfs_kdamond *kdamond)
{
@@ -1358,12 +1320,10 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c, bool active,
bool after_aggregation)
{
struct damon_sysfs_kdamond *kdamond;
- bool total_bytes_only = false;
int err = 0;

/* avoid deadlock due to concurrent state_store('off') */
- if (!damon_sysfs_schemes_regions_updating &&
- !mutex_trylock(&damon_sysfs_lock))
+ if (!mutex_trylock(&damon_sysfs_lock))
return 0;
kdamond = damon_sysfs_cmd_request.kdamond;
if (!kdamond || kdamond->damon_ctx != c)
@@ -1374,39 +1334,13 @@ static int damon_sysfs_cmd_request_callback(struct damon_ctx *c, bool active,
goto out;
err = damon_sysfs_commit_input(kdamond);
break;
- case DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES:
- total_bytes_only = true;
- fallthrough;
- case DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS:
- if (!damon_sysfs_schemes_regions_updating) {
- err = damon_sysfs_upd_schemes_regions_start(kdamond,
- total_bytes_only);
- if (!err) {
- damon_sysfs_schemes_regions_updating = true;
- goto keep_lock_out;
- }
- } else {
- damos_sysfs_mark_finished_regions_updates(c);
- /*
- * Continue regions updating if DAMON is till
- * active and the update for all schemes is not
- * finished.
- */
- if (active && !damos_sysfs_regions_upd_done())
- goto keep_lock_out;
- err = damon_sysfs_upd_schemes_regions_stop(kdamond);
- damon_sysfs_schemes_regions_updating = false;
- }
- break;
default:
break;
}
/* Mark the request as invalid now. */
damon_sysfs_cmd_request.kdamond = NULL;
out:
- if (!damon_sysfs_schemes_regions_updating)
- mutex_unlock(&damon_sysfs_lock);
-keep_lock_out:
+ mutex_unlock(&damon_sysfs_lock);
return err;
}

--
2.39.5