7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Donggeun Yoo [ Upstream commit 4ff3b4a54a32142497fb44b79d0920aa6ba3393d ] Patch series "mm/damon/core: fix the size charged for a filter-trimmed region", v2. An address range DAMOS filter that partially overlaps a monitoring region splits it, so the scheme action reaches only one side of the boundary. damos_apply_scheme() reads the region size before that split and never re-reads it, so the quota charge and schemes//stats/sz_tried account for the whole original region. Patch 1 re-reads the size after the core filters have run. Patch 2 adds KUnit coverage for what the function charges and reports, for the trimmed cases and for the cases that must not change. This patch (of 2): An address range DAMOS filter that partially overlaps a monitoring region splits the region at the filter boundary, so the scheme action is applied to only one side of it. damos_apply_scheme() reads the region size once on entry, before damos_core_filter_out() performs that split. The quota charge and the statistics update therefore account for the region as it was before the trim. schemes//stats/sz_tried counts memory the filter excluded, which Documentation/mm/damon/design.rst says is not counted as tried, and with quotas/bytes set the excluded part is charged against the budget, throttling the scheme to a fraction of what was configured. User impact is that DAMOS could unexpectedly slowly run, due to over-charged quota. DAMOS stat could also be confusing. No critical events such as crashes or leask happen. Re-read the region size after the core filters have run. Link: https://lore.kernel.org/20260921152443.80132-1-sj@kernel.org Link: https://lore.kernel.org/20260921152443.80132-2-sj@kernel.org Fixes: ab9bda001b68 ("mm/damon/core: introduce address range type damos filter") Signed-off-by: Donggeun Yoo Signed-off-by: SJ Park Signed-off-by: Andrew Morton Reviewed-by: SJ Park Cc: Brendan Higgins Cc: David Gow Cc: Signed-off-by: Sasha Levin --- mm/damon/core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index a4542a49ff80a..4290e2a1c7e8d 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2653,6 +2653,7 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, } if (damos_core_filter_out(c, t, r, s)) return; + sz = damon_sz_region(r); ktime_get_coarse_ts64(&begin); trace_damos_before_apply(cidx, sidx, tidx, r, nr_accesses, damon_nr_regions(t), do_trace); -- 2.53.0