mm: memcg: remove unnecessary preemption disabling

lock_page_cgroup() disables preemption, remove explicit preemption
disabling for code paths holding this lock.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -921,8 +921,6 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
 					 struct page *page,
 					 bool anon, int nr_pages)
 {
-	preempt_disable();
-
 	/*
 	 * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
 	 * counted as CACHE even if it's on ANON LRU.
@@ -947,8 +945,6 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
 	}
 
 	__this_cpu_add(memcg->stat->nr_page_events, nr_pages);
-
-	preempt_enable();
 }
 
 unsigned long
@@ -3748,17 +3744,14 @@ void mem_cgroup_split_huge_fixup(struct page *head)
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
-static inline
-void mem_cgroup_move_account_page_stat(struct mem_cgroup *from,
+static void mem_cgroup_move_account_page_stat(struct mem_cgroup *from,
 					      struct mem_cgroup *to,
 					      unsigned int nr_pages,
 					      enum mem_cgroup_stat_index idx)
 {
 	/* Update stat data for mem_cgroup */
-	preempt_disable();
 	__this_cpu_sub(from->stat->count[idx], nr_pages);
 	__this_cpu_add(to->stat->count[idx], nr_pages);
-	preempt_enable();
 }
 
 /**