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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: 4d4e41b682 ("mm/damon/sysfs-schemes: do not update tried regions more than one DAMON snapshot")
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2023-11-24 21:38:40 +00:00 committed by Andrew Morton
parent 854f2764b5
commit 7d6fa31a2f
1 changed files with 43 additions and 6 deletions
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49
mm/damon/sysfs-schemes.c
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@ -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;