From 1b43501d688d60964462151159f72cac1266c273 Mon Sep 17 00:00:00 2001 From: SJ Park Date: Mon, 29 Jun 2026 21:07:57 -0700 Subject: [PATCH] mm/damon/core: handle unreset nr_accesses in damon_nr_accesses_mvsum() damon_set_attrs() works like reverting aggregations that were made so far for this aggregation window. If this is the end of the aggregation, however, kdamond_fn() will do the operations at the end of the aggregation interval, using cached timestamps. For such operations that rely on damon_region->nr_accesses, damon_update_monitoring_results() doesn't reset the nr_accesses if it is called at the end of the aggregation window. damon_nr_accesses_mvsum() works with fresh timestamps, though. The nr_accesses that are not reset in this case can make the logic to unnecessarily count nr_accesses, resulting in returning higher-than-expected pseudo moving sum nr_accesses. No code is using damon_nr_accesses_mvsum() yet, so this is not causing a real problem. Following commits will add usage of the function, though. For safe usages, calculate the pseudo moving sum without nr_accesses if the remaining window is full. Link: https://lore.kernel.org/20260630040812.149729-5-sj@kernel.org Signed-off-by: SJ Park Cc: Brendan Higgins Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Shuah Khan Cc: Steven Rostedt Signed-off-by: Andrew Morton --- mm/damon/core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index e6f0f7a6752d..fcd7347e48e3 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -266,6 +266,9 @@ unsigned int damon_nr_accesses_mvsum(struct damon_region *r, ctx->passed_sample_intervals; left_window_bp = mult_frac(left_window, 10000, window_len); + if (left_window_bp == 10000) + return r->last_nr_accesses; + return damon_mvsum(r->nr_accesses, r->last_nr_accesses, left_window_bp); }