From: Miaohe Lin <linmiaohe@huawei.com>
Date: Wed, 8 Jun 2022 14:14:32 +0000 (+0800)
Subject: mm/vmscan: don't try to reclaim freed folios
X-Git-Tag: maple_v12_fixes~115
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=be25e67e3aeb11e164c92c39563f8a0b32472a21;p=users%2Fjedix%2Flinux-maple.git

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 I/O.

Link: https://lkml.kernel.org/r/20220608141432.23258-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 97ac6c6c026d..cd2201ba6d7c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1610,13 +1610,19 @@ retry:
 		folio = lru_to_folio(page_list);
 		list_del(&folio->lru);
 
+		nr_pages = folio_nr_pages(folio);
+
+		if (folio_ref_count(folio) == 1 &&
+		    folio_ref_freeze(folio, 1)) {
+			/* folio was freed from under us. So we are done. */
+			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;