From c070da23913f66b7c08340a137622ba2f2203616 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Fri, 6 Mar 2026 07:29:09 -0800 Subject: [PATCH] mm/damon/core: add damon_merge_regions_of() debug_sanity check damon_merge_regions_of() should be called only after aggregation is finished and therefore each region's nr_accesses and nr_accesses_bp match. There were bugs that broke the assumption, during development of online DAMON parameter updates and monitoring results handling changes. Add a sanity check for that under CONFIG_DAMON_DEBUG_SANITY. Link: https://lkml.kernel.org/r/20260306152914.86303-7-sj@kernel.org Signed-off-by: SeongJae Park Cc: Brendan Higgins Cc: David Gow Cc: Shuah Khan Signed-off-by: Andrew Morton --- mm/damon/core.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index 0fa694aff617..3f55dfcb54e4 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2507,6 +2507,20 @@ static void damon_merge_two_regions(struct damon_target *t, damon_destroy_region(r, t); } +#ifdef CONFIG_DAMON_DEBUG_SANITY +static void damon_verify_merge_regions_of(struct damon_region *r) +{ + WARN_ONCE(r->nr_accesses != r->nr_accesses_bp / 10000, + "nr_accesses (%u) != nr_accesses_bp (%u)\n", + r->nr_accesses, r->nr_accesses_bp); +} +#else +static void damon_verify_merge_regions_of(struct damon_region *r) +{ +} +#endif + + /* * Merge adjacent regions having similar access frequencies * @@ -2520,6 +2534,7 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres, struct damon_region *r, *prev = NULL, *next; damon_for_each_region_safe(r, next, t) { + damon_verify_merge_regions_of(r); if (abs(r->nr_accesses - r->last_nr_accesses) > thres) r->age = 0; else if ((r->nr_accesses == 0) != (r->last_nr_accesses == 0))