mm/memcg: mem_cgroup_per_node is already set to 0 on allocation

kzalloc_node() would set data to 0, so it's not necessary to set it
again.

Link: https://lkml.kernel.org/r/20220201004643.8391-1-richard.weiyang@gmail.comSigned-off-by: NWei Yang <richard.weiyang@gmail.com>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NRoman Gushchin <guro@fb.com>
Reviewed-by: NMike Rapoport <rppt@linux.ibm.com>
Reviewed-by: NShakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -5105,8 +5105,6 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 	}
 
 	lruvec_init(&pn->lruvec);
-	pn->usage_in_excess = 0;
-	pn->on_tree = false;
 	pn->memcg = memcg;
 
 	memcg->nodeinfo[node] = pn;