mm/damon/core: copy nr_accesses when splitting region

commit 1f3730f upstream.

Regions split function ('damon_split_region_at()') is called at the
beginning of an aggregation interval, and when DAMOS applying the actions
and charging quota.  Because 'nr_accesses' fields of all regions are reset
at the beginning of each aggregation interval, and DAMOS was applying the
action at the end of each aggregation interval, there was no need to copy
the 'nr_accesses' field to the split-out region.

However, commit 42f994b ("mm/damon/core: implement scheme-specific
apply interval") made DAMOS applies action on its own timing interval.
Hence, 'nr_accesses' should also copied to split-out regions, but the
commit didn't.  Fix it by copying it.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 42f994b ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: SeongJae Park <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

mm/damon/core.c

@@ -1215,6 +1215,7 @@ static void damon_split_region_at(struct damon_target *t,
 
 	new->age = r->age;
 	new->last_nr_accesses = r->last_nr_accesses;
+	new->nr_accesses = r->nr_accesses;
 
 	damon_insert_region(new, r, damon_next_region(r), t);
 }