[PATCH mm-unstable v2 1/2] mm/vmscan: fix missing NR_ISOLATED counter update in MGLRU reclaim path

[Hui Zhu]

From: Hui Zhu <zhuhui@xxxxxxxxxx>

MGLRU evict_folios() isolates folios from the LRU without updating
the NR_ISOLATED_ANON/FILE counters, unlike the legacy
shrink_inactive_list() path. This causes compaction's
too_many_isolated() check to under-count isolated pages when MGLRU
reclaim is active.

Add NR_ISOLATED counter updates in evict_folios(): increment after
isolate_folios() and decrement after all retry passes complete, using
the existing nr_isolated which holds the original isolated count.

Signed-off-by: Hui Zhu <zhuhui@xxxxxxxxxx>
---
 mm/vmscan.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c1404a59523d..fdc45d7d8fba 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4892,6 +4892,9 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 	scanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness,
 				 &list, &isolated, &type, &type_scanned);
 	nr_isolated = isolated;
+	if (nr_isolated)
+		__mod_node_page_state(pgdat, NR_ISOLATED_ANON + type,
+				      nr_isolated);
 
 	/* Scanning may have emptied the oldest gen, flush it */
 	if (scanned)
@@ -4954,6 +4957,10 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
 		goto retry;
 	}
 
+	if (nr_isolated)
+		mod_node_page_state(pgdat, NR_ISOLATED_ANON + type,
+				    -nr_isolated);
+
 	if (nr_isolated > total_reclaimed)
 		mod_lruvec_state(lruvec, PGROTATE_ANON + type,
 				 nr_isolated - total_reclaimed);
-- 
2.53.0