Commit 7d6fa31a authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
Browse files

mm/damon/sysfs-schemes: add timeout for update_schemes_tried_regions 

If a scheme is set to not applied to any monitoring target region for any
reasons including the target access pattern, quota, filters, or
watermarks, writing 'update_schemes_tried_regions' to 'state' DAMON sysfs
file can indefinitely hang.  Fix the case by implementing a timeout for
the operation.  The time limit is two apply intervals of each scheme.

Link: https://lkml.kernel.org/r/20231124213840.39157-1-sj@kernel.org


Fixes: 4d4e41b6 ("mm/damon/sysfs-schemes: do not update tried regions more than one DAMON snapshot")
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 854f2764

mm/damon/sysfs-schemes.c

+43 −6
Original line number Diff line number Diff line
@@ -139,6 +139,13 @@ static const struct kobj_type damon_sysfs_scheme_region_ktype = { 
 * 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.

 */
@@ -154,6 +161,7 @@ struct damon_sysfs_scheme_regions { 
	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 *
@@ -1854,7 +1862,9 @@ static int damon_sysfs_after_sampling(struct damon_ctx *ctx) 
	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)

				DAMOS_TRIED_REGIONS_UPD_STARTED ||

				time_after(jiffies,

					sysfs_regions->upd_timeout_jiffies))

			sysfs_regions->upd_status =

				DAMOS_TRIED_REGIONS_UPD_FINISHED;

	}
@@ -1885,14 +1895,41 @@ 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_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_schemes->schemes_arr[i]->tried_regions->upd_status =

			DAMOS_TRIED_REGIONS_UPD_IDLE;

	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.sample_interval);

	}

}



/* Called from damon_sysfs_cmd_request_callback under damon_sysfs_lock */
@@ -1902,7 +1939,7 @@ int damon_sysfs_schemes_update_regions_start( 
{

	damon_sysfs_schemes_clear_regions(sysfs_schemes, ctx);

	damon_sysfs_schemes_for_damos_callback = sysfs_schemes;

	damos_tried_regions_init_upd_status(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;

	ctx->callback.after_sampling = damon_sysfs_after_sampling;