[RFC][PATCH 3/8] memcg: swapcache handling retry

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

Now swapcache is not accounted. (because it had some troubles.)

This is retrying account swap cache, based on remove-refcnt patch.

This does.
 * When a page is swap-cache,  mem_cgroup_uncharge_page() will *not*
   uncharge page even if page->mapcount == 0.
 * When a page is removed from swap-cache, mem_cgroup_uncharge_page()
   is called again.
 * A swapcache page is newly charged only when it's mapped.

Changelog:
 - adjusted to 2.6.25-mm1.

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

---
 mm/migrate.c    |    3 ++-
 mm/swap_state.c |    1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

Index: mm-2.6.25-mm1/mm/migrate.c
===================================================================
--- mm-2.6.25-mm1.orig/mm/migrate.c
+++ mm-2.6.25-mm1/mm/migrate.c
@@ -359,7 +359,8 @@ static int migrate_page_move_mapping(str
 	write_unlock_irq(&mapping->tree_lock);
 	if (!PageSwapCache(newpage)) {
 		mem_cgroup_uncharge_cache_page(page);
-	}
+	} else
+		mem_cgroup_uncharge_page(page);
 
 	return 0;
 }
Index: mm-2.6.25-mm1/mm/swap_state.c
===================================================================
--- mm-2.6.25-mm1.orig/mm/swap_state.c
+++ mm-2.6.25-mm1/mm/swap_state.c
@@ -110,6 +110,7 @@ void __delete_from_swap_cache(struct pag
 	total_swapcache_pages--;
 	__dec_zone_page_state(page, NR_FILE_PAGES);
 	INC_CACHE_INFO(del_total);
+	mem_cgroup_uncharge_page(page);
 }
 
 /**
Index: mm-2.6.25-mm1/mm/memcontrol.c
===================================================================
--- mm-2.6.25-mm1.orig/mm/memcontrol.c
+++ mm-2.6.25-mm1/mm/memcontrol.c
@@ -675,7 +675,8 @@ void __mem_cgroup_uncharge_common(struct
 
 	if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
 	    && ((pc->flags & PAGE_CGROUP_FLAG_CACHE)
-		|| page_mapped(page)))
+		|| page_mapped(page)
+		|| PageSwapCache(page)))
 		goto unlock;
 
 	mz = page_cgroup_zoneinfo(pc);

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