The patch titled
Subject: mm/damon/sysfs-schemes: add timeout for update_schemes_tried_regions
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-sysfs-schemes-add-timeout-for-update_schemes_tried_regions.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-sysfs-schemes-add-timeout-for-update_schemes_tried_regions.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: mm/damon/sysfs-schemes: add timeout for update_schemes_tried_regions
Date: Fri, 24 Nov 2023 21:38:40 +0000
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@xxxxxxxxxx
Fixes: 4d4e41b68299 ("mm/damon/sysfs-schemes: do not update tried regions more than one DAMON snapshot")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/sysfs-schemes.c | 49 ++++++++++++++++++++++++++++++++-----
1 file changed, 43 insertions(+), 6 deletions(-)
--- a/mm/damon/sysfs-schemes.c~mm-damon-sysfs-schemes-add-timeout-for-update_schemes_tried_regions
+++ a/mm/damon/sysfs-schemes.c
@@ -139,6 +139,13 @@ static const struct kobj_type damon_sysf
* 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(st
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_s
{
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;
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-core-copy-nr_accesses-when-splitting-region.patch
mm-damon-sysfs-schemes-add-timeout-for-update_schemes_tried_regions.patch
mm-damon-core-test-test-damon_split_region_ats-access-rate-copying.patch
