memcg: export memory cgroup's swappiness with mem_cgroup_swappiness()

Each memory cgroup has a 'swappiness' value which can be accessed by
get_swappiness(memcg).  The major user is try_to_free_mem_cgroup_pages()
and swappiness is passed by argument.  It's propagated by scan_control.

get_swappiness() is a static function but some planned updates will need
to get swappiness from files other than memcontrol.c This patch exports
get_swappiness() as mem_cgroup_swappiness().  With this, we can remove the
argument of swapiness from try_to_free...  and drop swappiness from
scan_control.  only memcg uses it.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Ying Han <yinghan@google.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index a273468f8285..44558b600ee3 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -252,11 +252,9 @@ static inline void lru_cache_add_file(struct page *page)
 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 					gfp_t gfp_mask, nodemask_t *mask);
 extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
-						  gfp_t gfp_mask, bool noswap,
-						  unsigned int swappiness);
+						  gfp_t gfp_mask, bool noswap);
 extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
 						gfp_t gfp_mask, bool noswap,
-						unsigned int swappiness,
 						struct zone *zone,
 						unsigned long *nr_scanned);
 extern int __isolate_lru_page(struct page *page, int mode, int file);
@@ -299,7 +297,14 @@ static inline void scan_unevictable_unregister_node(struct node *node)
 
 extern int kswapd_run(int nid);
 extern void kswapd_stop(int nid);
-
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+extern int mem_cgroup_swappiness(struct mem_cgroup *mem);
+#else
+static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
+{
+	return vm_swappiness;
+}
+#endif
 #ifdef CONFIG_SWAP
 /* linux/mm/page_io.c */
 extern int swap_readpage(struct page *);