[patch 3/4] mm: memcontrol: remove unnecessary PCG_MEM memory charge flag

From: Johannes Weiner
Date: Mon Oct 20 2014 - 11:22:57 EST


PCG_MEM is a remnant from an earlier version of 0a31bc97c80c ("mm:
memcontrol: rewrite uncharge API"), used to tell whether migration
cleared a charge while leaving pc->mem_cgroup valid and PCG_USED set.
But in the final version, mem_cgroup_migrate() directly uncharges the
source page, rendering this distinction unnecessary. Remove it.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
include/linux/page_cgroup.h | 1 -
mm/memcontrol.c | 4 +---
2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index da62ee2be28b..97536e685843 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -4,7 +4,6 @@
enum {
/* flags for mem_cgroup */
PCG_USED = 0x01, /* This page is charged to a memcg */
- PCG_MEM = 0x02, /* This page holds a memory charge */
};

struct pglist_data;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9bab35fc3e9e..1d66ac49e702 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2606,7 +2606,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
* have the page locked
*/
pc->mem_cgroup = memcg;
- pc->flags = PCG_USED | PCG_MEM;
+ pc->flags = PCG_USED;

if (lrucare)
unlock_page_lru(page, isolated);
@@ -6177,8 +6177,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
if (!PageCgroupUsed(pc))
return;

- VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM), oldpage);
-
if (lrucare)
lock_page_lru(oldpage, &isolated);

--
2.1.2

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