memcg: show swap usage in stat file

We now count MEM_CGROUP_STAT_SWAPOUT, so we can show swap usage.  It would
be useful for users to show swap usage in memory.stat file, because they
don't need calculate memsw.usage - res.usage to know swap usage.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -2676,6 +2676,7 @@ enum {
 	MCS_MAPPED_FILE,
 	MCS_PGPGIN,
 	MCS_PGPGOUT,
+	MCS_SWAP,
 	MCS_INACTIVE_ANON,
 	MCS_ACTIVE_ANON,
 	MCS_INACTIVE_FILE,
@@ -2697,6 +2698,7 @@ struct {
 	{"mapped_file", "total_mapped_file"},
 	{"pgpgin", "total_pgpgin"},
 	{"pgpgout", "total_pgpgout"},
+	{"swap", "total_swap"},
 	{"inactive_anon", "total_inactive_anon"},
 	{"active_anon", "total_active_anon"},
 	{"inactive_file", "total_inactive_file"},
@@ -2721,6 +2723,10 @@ static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
 	s->stat[MCS_PGPGIN] += val;
 	val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_PGPGOUT_COUNT);
 	s->stat[MCS_PGPGOUT] += val;
+	if (do_swap_account) {
+		val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_SWAPOUT);
+		s->stat[MCS_SWAP] += val * PAGE_SIZE;
+	}
 
 	/* per zone stat */
 	val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
@@ -2752,8 +2758,11 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
 	memset(&mystat, 0, sizeof(mystat));
 	mem_cgroup_get_local_stat(mem_cont, &mystat);
 
-	for (i = 0; i < NR_MCS_STAT; i++)
+	for (i = 0; i < NR_MCS_STAT; i++) {
+		if (i == MCS_SWAP && !do_swap_account)
+			continue;
 		cb->fill(cb, memcg_stat_strings[i].local_name, mystat.stat[i]);
+	}
 
 	/* Hierarchical information */
 	{
@@ -2766,9 +2775,11 @@ static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
 
 	memset(&mystat, 0, sizeof(mystat));
 	mem_cgroup_get_total_stat(mem_cont, &mystat);
-	for (i = 0; i < NR_MCS_STAT; i++)
+	for (i = 0; i < NR_MCS_STAT; i++) {
+		if (i == MCS_SWAP && !do_swap_account)
+			continue;
 		cb->fill(cb, memcg_stat_strings[i].total_name, mystat.stat[i]);
-
+	}
 
 #ifdef CONFIG_DEBUG_VM
 	cb->fill(cb, "inactive_ratio", calc_inactive_ratio(mem_cont, NULL));