[PATCH 7.1 197/271] mm/damon: adjust isolated pages stat for DAMOS_MIGRATE_{HOT,COLD}

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: SJ Park <[email protected]>

commit 1ec0e6b6f7321feb769f50d2f094a0aa6c2eda63 upstream.

Callers of migrate_pages() should adjust NR_MIGRATED_{ANON,FILE} for
isolations and putback of the folios.  That for migration succeeded folios
is done by migrate_pages(), in migrate_folio_done().  That for MR_DEMOTION
reason is an exception though.

DAMOS_MIGRATE_{HOT,COLD} call migrate_pages() but mistakenly not doing the
stat adjustment.  As a result, use of DAMOS_MIGRATE_{HOT,COLD} could
corrupt the stat.  It could confuse too_many_isolated(), make compaction
and reclaim to behave in unexpected ways.  The stat corruption can be
reproduced and confirmed using DAMON user-space tool [1] on NUMA systems,
like below.

    $ numactl --hardware
    available: 2 nodes (0-1)
    [...]
    $ sudo ./damo start --damos_action migrate_hot 1
    $ sudo cat /proc/sys/vm/stat_refresh
    $ sudo dmesg
    [...]
    [   80.215554] vmstat_refresh: nr_isolated_anon -5578
    [   80.216842] vmstat_refresh: nr_isolated_file -34400

This issue was discovered [2] by Sashiko.

Link: https://lore.kernel.org/[email protected]
Link: https://github.com/damonitor/damo [1]
Link: https://lore.kernel.org/[email protected] [2]
Fixes: b51820ebea65 ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion")
Signed-off-by: SJ Park <[email protected]>
Cc: Honggyu Kim <[email protected]>
Cc: Hyeongtak Ji <[email protected]>
Cc: <[email protected]> # 6.11.x
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 mm/damon/ops-common.c |    4 ++++
 mm/damon/paddr.c      |    2 ++
 mm/damon/vaddr.c      |    3 ++-
 3 files changed, 8 insertions(+), 1 deletion(-)

--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -374,6 +374,8 @@ keep:
 	while (!list_empty(folio_list)) {
 		folio = lru_to_folio(folio_list);
 		list_del(&folio->lru);
+		node_stat_sub_folio(folio, NR_ISOLATED_ANON +
+				folio_is_file_lru(folio));
 		folio_putback_lru(folio);
 	}
 
@@ -396,6 +398,8 @@ unsigned long damon_migrate_pages(struct
 			struct folio *folio = lru_to_folio(folio_list);
 
 			list_del(&folio->lru);
+			node_stat_sub_folio(folio, NR_ISOLATED_ANON +
+					folio_is_file_lru(folio));
 			folio_putback_lru(folio);
 		}
 		return nr_migrated;
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -277,6 +277,8 @@ static unsigned long damon_pa_migrate(st
 
 		if (!folio_isolate_lru(folio))
 			goto put_folio;
+		node_stat_add_folio(folio, NR_ISOLATED_ANON +
+				folio_is_file_lru(folio));
 		list_add(&folio->lru, &folio_list);
 put_folio:
 		addr += folio_size(folio);
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -627,7 +627,8 @@ static void damos_va_migrate_dests_add(s
 isolate:
 	if (!folio_isolate_lru(folio))
 		return;
-
+	node_stat_add_folio(folio, NR_ISOLATED_ANON +
+			folio_is_file_lru(folio));
 	list_add(&folio->lru, &migration_lists[i]);
 }