alinux: mm, memcg: account throttle over memory.high for memcg direct reclaim

to #26424368

Commit 6202ab24 ("mm, memcg: throttle
allocators when failing reclaim over memory.high") introduces explicit
throttling when reclaim is failing to keep memcg size contained at the
memory.high setting.

Just account this latency on memcg direct reclaim latency histogram.
Signed-off-by: NXu Yu <xuyu@linux.alibaba.com>
Reviewed-by: NXunlei Pang <xlpang@linux.alibaba.com>
Reviewed-by: NYang Shi <yang.shi@linux.alibaba.com>

mm/memcontrol.c

@@ -2463,8 +2463,6 @@ void mem_cgroup_handle_over_high(void)
 	memcg = get_mem_cgroup_from_mm(current->mm);
 	start = ktime_get_ns();
 	reclaim_high(memcg, nr_pages, GFP_KERNEL);
-	memcg_lat_stat_update(MEM_LAT_MEMCG_DIRECT_RECLAIM,
-			      (ktime_get_ns() - start));
 	current->memcg_nr_pages_over_high = 0;
 
 	/*
@@ -2533,6 +2531,8 @@ void mem_cgroup_handle_over_high(void)
 	psi_memstall_leave(&pflags);
 
 out:
+	memcg_lat_stat_update(MEM_LAT_MEMCG_DIRECT_RECLAIM,
+			      (ktime_get_ns() - start));
 	css_put(&memcg->css);
 }