mm, memcg: rename ambiguously named memory.stat counters and functions

I spent literally an hour trying to work out why an earlier version of
my memory.events aggregation code doesn't work properly, only to find
out I was calling memcg->events instead of memcg->memory_events, which
is fairly confusing.

This naming seems in need of reworking, so make it harder to do the
wrong thing by using vmevents instead of events, which makes it more
clear that these are vm counters rather than memcg-specific counters.

There are also a few other inconsistent names in both the percpu and
aggregated structs, so these are all cleaned up to be more coherent and
easy to understand.

This commit contains code cleanup only: there are no logic changes.

[akpm@linux-foundation.org: fix it for preceding changes]
Link: http://lkml.kernel.org/r/20190208224319.GA23801@chrisdown.nameSigned-off-by: Chris Down <chris@chrisdown.name>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -94,8 +94,8 @@ enum mem_cgroup_events_target {
 	MEM_CGROUP_NTARGETS,
 };
 
-struct mem_cgroup_stat_cpu {
-	long count[MEMCG_NR_STAT];
+struct memcg_vmstats_percpu {
+	long stat[MEMCG_NR_STAT];
 	unsigned long events[NR_VM_EVENT_ITEMS];
 	unsigned long nr_page_events;
 	unsigned long targets[MEM_CGROUP_NTARGETS];
@@ -274,12 +274,12 @@ struct mem_cgroup {
 	struct task_struct	*move_lock_task;
 
 	/* memory.stat */
-	struct mem_cgroup_stat_cpu __percpu *stat_cpu;
+	struct memcg_vmstats_percpu __percpu *vmstats_percpu;
 
 	MEMCG_PADDING(_pad2_);
 
-	atomic_long_t		stat[MEMCG_NR_STAT];
-	atomic_long_t		events[NR_VM_EVENT_ITEMS];
+	atomic_long_t		vmstats[MEMCG_NR_STAT];
+	atomic_long_t		vmevents[NR_VM_EVENT_ITEMS];
 	atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS];
 
 	unsigned long		socket_pressure;
@@ -557,7 +557,7 @@ void unlock_page_memcg(struct page *page);
 static inline unsigned long memcg_page_state(struct mem_cgroup *memcg,
 					     int idx)
 {
-	long x = atomic_long_read(&memcg->stat[idx]);
+	long x = atomic_long_read(&memcg->vmstats[idx]);
 #ifdef CONFIG_SMP
 	if (x < 0)
 		x = 0;
@@ -574,12 +574,12 @@ static inline void __mod_memcg_state(struct mem_cgroup *memcg,
 	if (mem_cgroup_disabled())
 		return;
 
-	x = val + __this_cpu_read(memcg->stat_cpu->count[idx]);
+	x = val + __this_cpu_read(memcg->vmstats_percpu->stat[idx]);
 	if (unlikely(abs(x) > MEMCG_CHARGE_BATCH)) {
-		atomic_long_add(x, &memcg->stat[idx]);
+		atomic_long_add(x, &memcg->vmstats[idx]);
 		x = 0;
 	}
-	__this_cpu_write(memcg->stat_cpu->count[idx], x);
+	__this_cpu_write(memcg->vmstats_percpu->stat[idx], x);
 }
 
 /* idx can be of type enum memcg_stat_item or node_stat_item */
@@ -717,12 +717,12 @@ static inline void __count_memcg_events(struct mem_cgroup *memcg,
 	if (mem_cgroup_disabled())
 		return;
 
-	x = count + __this_cpu_read(memcg->stat_cpu->events[idx]);
+	x = count + __this_cpu_read(memcg->vmstats_percpu->events[idx]);
 	if (unlikely(x > MEMCG_CHARGE_BATCH)) {
-		atomic_long_add(x, &memcg->events[idx]);
+		atomic_long_add(x, &memcg->vmevents[idx]);
 		x = 0;
 	}
-	__this_cpu_write(memcg->stat_cpu->events[idx], x);
+	__this_cpu_write(memcg->vmstats_percpu->events[idx], x);
 }
 
 static inline void count_memcg_events(struct mem_cgroup *memcg,