[RFC] mm:do recheck for freeable page in reclaim path

From: "Wang, Yalin" <Yalin.Wang@sonymobile.com>
To: "'Minchan Kim'" <minchan@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Michal Hocko <mhocko@suse.cz>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
	Shaohua Li <shli@kernel.org>
Subject: [RFC] mm:do recheck for freeable page in reclaim path
Date: Wed, 11 Mar 2015 17:47:28 +0800	[thread overview]
Message-ID: <35FD53F367049845BC99AC72306C23D10458D6173C0C@CNBJMBX05.corpusers.net> (raw)
In-Reply-To: <1426036838-18154-3-git-send-email-minchan@kernel.org>

In reclaim path, if encounter a freeable page,
the try_to_unmap may fail, because the page's pte is
dirty, we can recheck this page as normal non-freeable page,
this means we can swap out this page into swap partition.

Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
---
 mm/vmscan.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 260c413..9930850 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1000,6 +1000,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			}
 		}
 
+recheck:
 		if (!force_reclaim)
 			references = page_check_references(page, sc,
 							&freeable);
@@ -1045,6 +1046,10 @@ unmap:
 			switch (try_to_unmap(page,
 				freeable ? TTU_FREE : ttu_flags)) {
 			case SWAP_FAIL:
+				if (freeable) {
+					freeable = false;
+					goto recheck;
+				}
 				goto activate_locked;
 			case SWAP_AGAIN:
 				goto keep_locked;
-- 
2.2.2
