At time of damon_reset_aggregated(), aggregation of the interval should
be completed, and hence nr_accesses and nr_accesses_bp should match.  I
found a few bugs caused it to be broken in the past, from online
parameters update and complicated nr_accesses handling changes.  Add a
sanity check for that under CONFIG_DAMON_DEBUG_SANITY.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/core.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index be2300cf3aeae..e8c44541754f7 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1666,6 +1666,23 @@ static void damon_warn_fix_nr_accesses_corruption(struct damon_region *r)
 	r->nr_accesses_bp = r->nr_accesses * 10000;
 }
 
+#ifdef CONFIG_DAMON_DEBUG_SANITY
+static void damon_verify_reset_aggregated(struct damon_region *r,
+		struct damon_ctx *c)
+{
+	WARN_ONCE(r->nr_accesses_bp != r->last_nr_accesses * 10000,
+			"nr_accesses_bp %u last_nr_accesses %u sis %lu %lu\n",
+			r->nr_accesses_bp, r->last_nr_accesses,
+			c->passed_sample_intervals, c->next_aggregation_sis);
+}
+#else
+static void damon_verify_reset_aggregated(struct damon_region *r,
+		struct damon_ctx *c)
+{
+}
+#endif
+
+
 /*
  * Reset the aggregated monitoring results ('nr_accesses' of each region).
  */
@@ -1682,6 +1699,7 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 			damon_warn_fix_nr_accesses_corruption(r);
 			r->last_nr_accesses = r->nr_accesses;
 			r->nr_accesses = 0;
+			damon_verify_reset_aggregated(r, c);
 		}
 		ti++;
 	}
-- 
2.47.3