mm: vmscan.c: fix OOM on swap stress test

I found a regression on mm-unstable during my swap stress test, using
tmpfs to compile linux.  The test OOM very soon after the make spawns many
cc processes.

It bisects down to this change: 33dfe9204f29b415bbc0abb1a50642d1ba94f5e9
(mm/gup: clear the LRU flag of a page before adding to LRU batch)

Yu Zhao propose the fix: "I think this is one of the potential side
effects -- Huge mentioned earlier about isolate_lru_folios():"

I test that with it the swap stress test no longer OOM.

Link: https://lore.kernel.org/r/CAOUHufYi9h0kz5uW3LHHS3ZrVwEq-kKp8S6N-MZUmErNAXoXmw@mail.gmail.com/
Link: https://lkml.kernel.org/r/20240905-lru-flag-v2-1-8a2d9046c594@kernel.org
Fixes: 33dfe9204f29 ("mm/gup: clear the LRU flag of a page before adding to LRU batch")
Signed-off-by: Chris Li <chrisl@kernel.org>
Suggested-by: Yu Zhao <yuzhao@google.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Closes: https://lore.kernel.org/all/CAF8kJuNP5iTj2p07QgHSGOJsiUfYpJ2f4R1Q5-3BN9JiD9W_KA@mail.gmail.com/
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd489c1af22893a866d79f068e1bb6ba92908e70..a8d61a8b68944d4d8072541e12ed73f8739a4d87 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4300,7 +4300,7 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_c
        }
 
        /* ineligible */
-       if (zone > sc->reclaim_idx) {
+       if (!folio_test_lru(folio) || zone > sc->reclaim_idx) {
                gen = folio_inc_gen(lruvec, folio, false);
                list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]);
                return true;