mm: memcontrol: add "sock" to cgroup2 memory.stat

Provide statistics on how much of a cgroup's memory footprint is made up
of socket buffers from network connections owned by the group.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -50,6 +50,9 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_WRITEBACK,	/* # of pages under writeback */
 	MEM_CGROUP_STAT_SWAP,		/* # of pages, swapped out */
 	MEM_CGROUP_STAT_NSTATS,
+	/* default hierarchy stats */
+	MEMCG_SOCK,
+	MEMCG_NR_STAT,
 };
 
 struct mem_cgroup_reclaim_cookie {
@@ -87,7 +90,7 @@ enum mem_cgroup_events_target {
 
 #ifdef CONFIG_MEMCG
 struct mem_cgroup_stat_cpu {
-	long count[MEM_CGROUP_STAT_NSTATS];
+	long count[MEMCG_NR_STAT];
 	unsigned long events[MEMCG_NR_EVENTS];
 	unsigned long nr_page_events;
 	unsigned long targets[MEM_CGROUP_NTARGETS];

mm/memcontrol.c

@@ -5128,6 +5128,8 @@ static int memory_stat_show(struct seq_file *m, void *v)
 		   (u64)tree_stat(memcg, MEM_CGROUP_STAT_RSS) * PAGE_SIZE);
 	seq_printf(m, "file %llu\n",
 		   (u64)tree_stat(memcg, MEM_CGROUP_STAT_CACHE) * PAGE_SIZE);
+	seq_printf(m, "sock %llu\n",
+		   (u64)tree_stat(memcg, MEMCG_SOCK) * PAGE_SIZE);
 
 	seq_printf(m, "file_mapped %llu\n",
 		   (u64)tree_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED) *
@@ -5631,6 +5633,8 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
 	if (in_softirq())
 		gfp_mask = GFP_NOWAIT;
 
+	this_cpu_add(memcg->stat->count[MEMCG_SOCK], nr_pages);
+
 	if (try_charge(memcg, gfp_mask, nr_pages) == 0)
 		return true;
 
@@ -5650,6 +5654,8 @@ void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
 		return;
 	}
 
+	this_cpu_sub(memcg->stat->count[MEMCG_SOCK], nr_pages);
+
 	page_counter_uncharge(&memcg->memory, nr_pages);
 	css_put_many(&memcg->css, nr_pages);
 }