memcg: fix swap accounting

This patch fixes mis-accounting of swap usage in memcg.

In the current implementation, memcg's swap account is uncharged only when
swap is completely freed.  But there are several cases where swap cannot
be freed cleanly.  For handling that, this patch changes that memcg
uncharges swap account when swap has no references other than cache.

By this, memcg's swap entry accounting can be fully synchronous with the
application's behavior.

This patch also changes memcg's hooks for swap-out.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index dca9b9999aeb..c88b36665f79 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -319,10 +319,11 @@ static inline void disable_swap_token(void)
 }
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
-extern void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent);
+extern void
+mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout);
 #else
 static inline void
-mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
+mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 {
 }
 #endif