[BUGFIX][RFC][PATCH][only -mm] FIX memory leak in memory cgroup vs. page migration [2/1] additional patch for migrate page/memory cgroup

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

The patch I sent needs following fix, sorry.
Anyway, I'll repost good-version with reflected comments again.

Thanks,
 -Kame
=
fix-page-migration-under-memory-controller patch needs this fix..sorry.

 - We should uncharge page by mem_cgroup_end_migration() only if
   page is not charged by mem_cgroup_prepare_migration().
 - move mem_cgroup_prepare_migration() after goto:

  Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Index: linux-2.6.23-rc8-mm2/mm/memcontrol.c
===================================================================
--- linux-2.6.23-rc8-mm2.orig/mm/memcontrol.c
+++ linux-2.6.23-rc8-mm2/mm/memcontrol.c
@@ -445,7 +445,7 @@ retry:
 	}
 }
 
-void mem_cgroup_prepare_migration(struct page *page)
+int mem_cgroup_prepare_migration(struct page *page)
 {
 	struct page_cgroup *pc;
 	lock_page_cgroup(page);
@@ -453,7 +453,7 @@ void mem_cgroup_prepare_migration(struct
 	if (pc)
 		atomic_inc(&pc->ref_cnt);
 	unlock_page_cgroup(page);
-	return;
+	return (pc != NULL);
 }
 
 void mem_cgroup_end_migration(struct page *page)
Index: linux-2.6.23-rc8-mm2/include/linux/memcontrol.h
===================================================================
--- linux-2.6.23-rc8-mm2.orig/include/linux/memcontrol.h
+++ linux-2.6.23-rc8-mm2/include/linux/memcontrol.h
@@ -47,7 +47,7 @@ extern void mem_cgroup_out_of_memory(str
 extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 					gfp_t gfp_mask);
 /* For handling page migration in proper way */
-extern void mem_cgroup_prepare_migration(struct page *page);
+extern int mem_cgroup_prepare_migration(struct page *page);
 extern void mem_cgroup_end_migration(struct page *page);
 extern void mem_cgroup_page_migration(struct page *newpage, struct page *page);
 
@@ -114,9 +114,9 @@ static inline struct mem_cgroup *mm_cgro
 }
 
 /* For page migration */
-static inline void mem_cgroup_prepare_migration(struct page *page)
+static inline int mem_cgroup_prepare_migration(struct page *page)
 {
-	return;
+	return 0;
 }
 
 static inline void mem_cgroup_end_migration(struct mem_cgroup *cgroup)
Index: linux-2.6.23-rc8-mm2/mm/migrate.c
===================================================================
--- linux-2.6.23-rc8-mm2.orig/mm/migrate.c
+++ linux-2.6.23-rc8-mm2/mm/migrate.c
@@ -620,6 +620,7 @@ static int unmap_and_move(new_page_t get
 	int *result = NULL;
 	struct page *newpage = get_new_page(page, private, &result);
 	int rcu_locked = 0;
+	int charge = 0;
 
 	if (!newpage)
 		return -ENOMEM;
@@ -652,8 +653,6 @@ static int unmap_and_move(new_page_t get
 		rcu_read_lock();
 		rcu_locked = 1;
 	}
-	mem_cgroup_prepare_migration(page);
-
 	/*
 	 * This is a corner case handling.
 	 * When a new swap-cache is read into, it is linked to LRU
@@ -663,6 +662,8 @@ static int unmap_and_move(new_page_t get
 	 */
 	if (!page->mapping)
 		goto rcu_unlock;
+
+	charge = mem_cgroup_prepare_migration(page);
 	/* Establish migration ptes or remove ptes */
 	try_to_unmap(page, 1);
 
@@ -671,8 +672,9 @@ static int unmap_and_move(new_page_t get
 
 	if (rc) {
 		remove_migration_ptes(page, page);
-		mem_cgroup_end_migration(page);
-	} else
+		if (charge)
+			mem_cgroup_end_migration(page);
+	} else if (charge)
 		mem_cgroup_end_migration(newpage);
 
 rcu_unlock:

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