memcg: handle swap caches

SwapCache support for memory resource controller (memcg)

Before mem+swap controller, memcg itself should handle SwapCache in proper
way.  This is cut-out from it.

In current memcg, SwapCache is just leaked and the user can create tons of
SwapCache.  This is a leak of account and should be handled.

SwapCache accounting is done as following.

  charge (anon)
	- charged when it's mapped.
	  (because of readahead, charge at add_to_swap_cache() is not sane)
  uncharge (anon)
	- uncharged when it's dropped from swapcache and fully unmapped.
	  means it's not uncharged at unmap.
	  Note: delete from swap cache at swap-in is done after rmap information
	        is established.
  charge (shmem)
	- charged at swap-in. this prevents charge at add_to_page_cache().

  uncharge (shmem)
	- uncharged when it's dropped from swapcache and not on shmem's
	  radix-tree.

  at migration, check against 'old page' is modified to handle shmem.

Comparing to the old version discussed (and caused troubles), we have
advantages of
  - PCG_USED bit.
  - simple migrating handling.

So, situation is much easier than several months ago, maybe.

[hugh@veritas.com: memcg: handle swap caches build fix]
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 91dee50..f8f3907 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -333,6 +333,22 @@ static inline void disable_swap_token(void)
 	put_swap_token(swap_token_mm);
 }
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+extern int mem_cgroup_cache_charge_swapin(struct page *page,
+				struct mm_struct *mm, gfp_t mask, bool locked);
+extern void mem_cgroup_uncharge_swapcache(struct page *page);
+#else
+static inline
+int mem_cgroup_cache_charge_swapin(struct page *page,
+				struct mm_struct *mm, gfp_t mask, bool locked)
+{
+	return 0;
+}
+static inline void mem_cgroup_uncharge_swapcache(struct page *page)
+{
+}
+#endif
+
 #else /* CONFIG_SWAP */
 
 #define nr_swap_pages				0L
@@ -409,6 +425,12 @@ static inline swp_entry_t get_swap_page(void)
 #define has_swap_token(x) 0
 #define disable_swap_token() do { } while(0)
 
+static inline int mem_cgroup_cache_charge_swapin(struct page *page,
+			struct mm_struct *mm, gfp_t mask, bool locked)
+{
+	return 0;
+}
+
 #endif /* CONFIG_SWAP */
 #endif /* __KERNEL__*/
 #endif /* _LINUX_SWAP_H */