linux-kernel - [PATCH v2] vmscan: fix increasing nr_isolated incurred by putback unevictable pages

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Date:	Tue, 04 Aug 2015 19:40:08 +0900
From:	Jaewon Kim <jaewon31.kim@...sung.com>
To:	akpm@...ux-foundation.org
Cc:	mgorman@...e.de, minchan@...nel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, jaewon31.kim@...il.com,
	Jaewon Kim <jaewon31.kim@...sung.com>
Subject: [PATCH v2] vmscan: fix increasing nr_isolated incurred by putback
 unevictable pages

reclaim_clean_pages_from_list() assumes that shrink_page_list() returns
number of pages removed from the candidate list. But shrink_page_list()
puts back mlocked pages without passing it to caller and without
counting as nr_reclaimed. This incurrs increasing nr_isolated.
To fix this, this patch changes shrink_page_list() to pass unevictable
pages back to caller. Caller will take care those pages.

Signed-off-by: Jaewon Kim <jaewon31.kim@...sung.com>
---
Changes since v1

1/ changed subject from vmscan: reclaim_clean_pages_from_list() must count mlocked pages
2/ changed to return unevictable pages rather than returning the number of unevictable pages

 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5e8eadd..a4b2d07 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1157,7 +1157,7 @@ cull_mlocked:
 		if (PageSwapCache(page))
 			try_to_free_swap(page);
 		unlock_page(page);
-		putback_lru_page(page);
+		list_add(&page->lru, &ret_pages);
 		continue;
 
 activate_locked:
-- 
1.9.1

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