From 7d6fa31a2fd7072376b3c8be66bf8527b2c8208c Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Fri, 24 Nov 2023 21:38:40 +0000 Subject: 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: 4d4e41b68299 ("mm/damon/sysfs-schemes: do not update tried regions more than one DAMON snapshot") Signed-off-by: SeongJae Park Signed-off-by: Andrew Morton --- mm/damon/sysfs-schemes.c | 49 ++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 43 insertions(+), 6 deletions(-) (limited to 'mm') diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c index be667236b8e6..fe0fe2562000 100644 --- a/mm/damon/sysfs-schemes.c +++ b/mm/damon/sysfs-schemes.c @@ -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; -- cgit