mm: memcontrol: report slab usage in cgroup2 memory.stat

Show how much memory is used for storing reclaimable and unreclaimable
in-kernel data structures allocated from slab caches.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4302660..3ad64bf 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5106,6 +5106,9 @@
 		   (u64)stat[MEM_CGROUP_STAT_RSS] * PAGE_SIZE);
 	seq_printf(m, "file %llu\n",
 		   (u64)stat[MEM_CGROUP_STAT_CACHE] * PAGE_SIZE);
+	seq_printf(m, "slab %llu\n",
+		   (u64)(stat[MEMCG_SLAB_RECLAIMABLE] +
+			 stat[MEMCG_SLAB_UNRECLAIMABLE]) * PAGE_SIZE);
 	seq_printf(m, "sock %llu\n",
 		   (u64)stat[MEMCG_SOCK] * PAGE_SIZE);
 
@@ -5126,6 +5129,11 @@
 			   mem_cgroup_lru_names[i], (u64)val * PAGE_SIZE);
 	}
 
+	seq_printf(m, "slab_reclaimable %llu\n",
+		   (u64)stat[MEMCG_SLAB_RECLAIMABLE] * PAGE_SIZE);
+	seq_printf(m, "slab_unreclaimable %llu\n",
+		   (u64)stat[MEMCG_SLAB_UNRECLAIMABLE] * PAGE_SIZE);
+
 	/* Accumulated memory events */
 
 	seq_printf(m, "pgfault %lu\n",