linux-kernel - [RFC PATCH v1 3/4] mm: Fix demotion-only scanning anon pages

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Date:   Tue, 22 Nov 2022 12:38:47 -0800
From:   Mina Almasry <almasrymina@...gle.com>
To:     Huang Ying <ying.huang@...el.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Yosry Ahmed <yosryahmed@...gle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>, weixugc@...gle.com,
        shakeelb@...gle.com, gthelen@...gle.com, fvdl@...gle.com,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Mina Almasry <almasrymina@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org
Subject: [RFC PATCH v1 3/4] mm: Fix demotion-only scanning anon pages

This is likely a missed change from commit a2a36488a61c ("mm/vmscan: Consider
anonymous pages without swap"). Current logic is if !may_swap _or_
!can_reclaim_anon_pages() then we don't scan anon memory.

This should be an 'and'. We would like to scan anon memory if we may swap
or if we can_reclaim_anon_pages().

Fixes: commit a2a36488a61c ("mm/vmscan: Consider anonymous pages without swap")

Signed-off-by: Mina Almasry <almasrymina@...gle.com>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8c1f5416d789..d7e509b3f07f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2931,7 +2931,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 	enum lru_list lru;

 	/* If we have no swap space, do not bother scanning anon folios. */
-	if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
+	if (!sc->may_swap && !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
 		scan_balance = SCAN_FILE;
 		goto out;
 	}
--
2.38.1.584.g0f3c55d4c2-goog