linux-kernel - [PATCH v3 1/6] mm/vmscan: add a comment about MADV_FREE pages check in folio_check_dirty

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Date:   Mon, 25 Apr 2022 19:12:27 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <ying.huang@...el.com>, <iamjoonsoo.kim@....com>, <hch@....de>,
        <osalvador@...e.de>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH v3 1/6] mm/vmscan: add a comment about MADV_FREE pages check in folio_check_dirty_writeback

The MADV_FREE pages check in folio_check_dirty_writeback is a bit hard to
follow. Add a comment to make the code clear.

Suggested-by: Huang, Ying <ying.huang@...el.com>
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Oscar Salvador <osalvador@...e.de>
---
 mm/vmscan.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 99a572f01cb4..913eb565140c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1438,7 +1438,10 @@ static void folio_check_dirty_writeback(struct folio *folio,
 
 	/*
 	 * Anonymous pages are not handled by flushers and must be written
-	 * from reclaim context. Do not stall reclaim based on them
+	 * from reclaim context. Do not stall reclaim based on them.
+	 * MADV_FREE anonymous pages are put into inactive file list too.
+	 * They could be mistakenly treated as file lru. So further anon
+	 * test is needed.
 	 */
 	if (!folio_is_file_lru(folio) ||
 	    (folio_test_anon(folio) && !folio_test_swapbacked(folio))) {
-- 
2.23.0