BACKPORT: mm/damon/core: copy nr_accesses when splitting region

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 42f994b714 ("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.

Bug: 254441685
Link: https://lkml.kernel.org/r/20231119171529.66863-1-sj@kernel.org
Fixes: 42f994b714 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 1f3730fd9e)
[Lee: Trivial surrounding diff related conflict]
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I3cea444ee39471b982b337cb4d2854afa311c3ed

mm/damon/core.c

@@ -1208,6 +1208,7 @@ 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);
 }