mm: memcg: group swapped-out statistics counter logically

The counter of currently swapped out pages in a memcg (hierarchy) is
sitting amidst ever-increasing event counters.  Move this item to the
other counters that reflect current state rather than history.

This technically breaks the kernel ABI, but hopefully nobody relies on the
order of items in memory.stat.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -4043,9 +4043,9 @@ enum {
 	MCS_CACHE,
 	MCS_RSS,
 	MCS_FILE_MAPPED,
+	MCS_SWAP,
 	MCS_PGPGIN,
 	MCS_PGPGOUT,
-	MCS_SWAP,
 	MCS_PGFAULT,
 	MCS_PGMAJFAULT,
 	MCS_INACTIVE_ANON,
@@ -4064,9 +4064,9 @@ static const char *memcg_stat_strings[NR_MCS_STAT] = {
 	"cache",
 	"rss",
 	"mapped_file",
+	"swap",
 	"pgpgin",
 	"pgpgout",
-	"swap",
 	"pgfault",
 	"pgmajfault",
 	"inactive_anon",