From f821942c0d34266b4abf966e277c808e11177172 Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@suse.de>
Date: Thu, 12 Jan 2012 17:19:38 -0800
Subject: [PATCH] --- yaml --- r: 284402 b: refs/heads/master c:
 c82449352854ff09e43062246af86bdeb628f0c3 h: refs/heads/master v: v3

---
 [refs]                       |  2 +-
 trunk/include/linux/mmzone.h |  2 ++
 trunk/mm/compaction.c        |  3 +++
 trunk/mm/vmscan.c            | 35 +++++++++++++++++++++++++++++++++--
 4 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index f6ccade21977..93a8560d835e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b969c4ab9f182a6e1b2a0848be349f99714947b0
+refs/heads/master: c82449352854ff09e43062246af86bdeb628f0c3
diff --git a/trunk/include/linux/mmzone.h b/trunk/include/linux/mmzone.h
index 42e544cd4c9f..2038b90ca6e3 100644
--- a/trunk/include/linux/mmzone.h
+++ b/trunk/include/linux/mmzone.h
@@ -177,6 +177,8 @@ struct lruvec {
 #define ISOLATE_CLEAN		((__force isolate_mode_t)0x4)
 /* Isolate unmapped file */
 #define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x8)
+/* Isolate for asynchronous migration */
+#define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x10)
 
 /* LRU Isolation modes. */
 typedef unsigned __bitwise__ isolate_mode_t;
diff --git a/trunk/mm/compaction.c b/trunk/mm/compaction.c
index d31e64becb38..fb291585e1bf 100644
--- a/trunk/mm/compaction.c
+++ b/trunk/mm/compaction.c
@@ -349,6 +349,9 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 			continue;
 		}
 
+		if (!cc->sync)
+			mode |= ISOLATE_ASYNC_MIGRATE;
+
 		/* Try isolate the page */
 		if (__isolate_lru_page(page, mode, 0) != 0)
 			continue;
diff --git a/trunk/mm/vmscan.c b/trunk/mm/vmscan.c
index cb68c53db4ec..efbcab1c8f54 100644
--- a/trunk/mm/vmscan.c
+++ b/trunk/mm/vmscan.c
@@ -1075,8 +1075,39 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
 
 	ret = -EBUSY;
 
-	if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
-		return ret;
+	/*
+	 * To minimise LRU disruption, the caller can indicate that it only
+	 * wants to isolate pages it will be able to operate on without
+	 * blocking - clean pages for the most part.
+	 *
+	 * ISOLATE_CLEAN means that only clean pages should be isolated. This
+	 * is used by reclaim when it is cannot write to backing storage
+	 *
+	 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
+	 * that it is possible to migrate without blocking
+	 */
+	if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
+		/* All the caller can do on PageWriteback is block */
+		if (PageWriteback(page))
+			return ret;
+
+		if (PageDirty(page)) {
+			struct address_space *mapping;
+
+			/* ISOLATE_CLEAN means only clean pages */
+			if (mode & ISOLATE_CLEAN)
+				return ret;
+
+			/*
+			 * Only pages without mappings or that have a
+			 * ->migratepage callback are possible to migrate
+			 * without blocking
+			 */
+			mapping = page_mapping(page);
+			if (mapping && !mapping->a_ops->migratepage)
+				return ret;
+		}
+	}
 
 	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
 		return ret;