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From:   Miaohe Lin <linmiaohe@huawei.com>
To:     <akpm@linux-foundation.org>
CC:     <ying.huang@intel.com>, <songmuchun@bytedance.com>,
        <hch@infradead.org>, <willy@infradead.org>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, <linmiaohe@huawei.com>
Subject: [PATCH v2 1/9] mm/vmscan: add a comment about MADV_FREE pages check in folio_check_dirty_writeback
Date:   Sat, 9 Apr 2022 17:34:52 +0800
Message-ID: <20220409093500.10329-2-linmiaohe@huawei.com>
In-Reply-To: <20220409093500.10329-1-linmiaohe@huawei.com>
References: <20220409093500.10329-1-linmiaohe@huawei.com>
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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@intel.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/vmscan.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c77d5052f230..4a76be47bed1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1436,6 +1436,9 @@ 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
+	 * 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