linux-kernel - [PATCH] mm/vmscan: don't try to reclaim freed folios

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Message-ID: <20220527080451.48549-1-linmiaohe@huawei.com>
Date:   Fri, 27 May 2022 16:04:51 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm/vmscan: don't try to reclaim freed folios

If folios were freed from under us, there's no need to reclaim them. Skip
these folios to save lots of cpu cycles and avoid possible unnecessary
disk IO.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/vmscan.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f7d9a683e3a7..646dd1efad32 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1556,12 +1556,18 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		folio = lru_to_folio(page_list);
 		list_del(&folio->lru);
 
+		nr_pages = folio_nr_pages(folio);
+		if (folio_ref_count(folio) == 1) {
+			/* folio was freed from under us. So we are done. */
+			WARN_ON(!folio_put_testzero(folio));
+			goto free_it;
+		}
+
 		if (!folio_trylock(folio))
 			goto keep;
 
 		VM_BUG_ON_FOLIO(folio_test_active(folio), folio);
 
-		nr_pages = folio_nr_pages(folio);
 
 		/* Account the number of base pages */
 		sc->nr_scanned += nr_pages;
-- 
2.23.0