From 49ea7eb65e7c5060807fb9312b1ad4c3eab82e2c Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@suse.de>
Date: Mon, 31 Oct 2011 17:07:59 -0700
Subject: [PATCH] mm: vmscan: immediately reclaim end-of-LRU dirty pages when
 writeback completes

When direct reclaim encounters a dirty page, it gets recycled around the
LRU for another cycle.  This patch marks the page PageReclaim similar to
deactivate_page() so that the page gets reclaimed almost immediately after
the page gets cleaned.  This is to avoid reclaiming clean pages that are
younger than a dirty page encountered at the end of the LRU that might
have been something like a use-once page.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Johannes Weiner <jweiner@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/mmzone.h |  2 +-
 mm/vmscan.c            | 10 +++++++++-
 mm/vmstat.c            |  2 +-
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 2c41b2c1943b..188cb2ffe8db 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -100,7 +100,7 @@ enum zone_stat_item {
 	NR_UNSTABLE_NFS,	/* NFS unstable pages */
 	NR_BOUNCE,
 	NR_VMSCAN_WRITE,
-	NR_VMSCAN_WRITE_SKIP,
+	NR_VMSCAN_IMMEDIATE,	/* Prioritise for reclaim when writeback ends */
 	NR_WRITEBACK_TEMP,	/* Writeback using temporary buffers */
 	NR_ISOLATED_ANON,	/* Temporary isolated pages from anon lru */
 	NR_ISOLATED_FILE,	/* Temporary isolated pages from file lru */
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7b0573f33a27..a297603d35bc 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -866,7 +866,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			 */
 			if (page_is_file_cache(page) &&
 					(!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
-				inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
+				/*
+				 * Immediately reclaim when written back.
+				 * Similar in principal to deactivate_page()
+				 * except we already have the page isolated
+				 * and know it's dirty
+				 */
+				inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
+				SetPageReclaim(page);
+
 				goto keep_locked;
 			}
 
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 210bd8ff3a6e..56e529a40517 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -702,7 +702,7 @@ const char * const vmstat_text[] = {
 	"nr_unstable",
 	"nr_bounce",
 	"nr_vmscan_write",
-	"nr_vmscan_write_skip",
+	"nr_vmscan_immediate_reclaim",
 	"nr_writeback_temp",
 	"nr_isolated_anon",
 	"nr_isolated_file",