[RFC PATCH 07/10] memcg: use __mod_memcg_state in drain_obj_stock

[Shakeel Butt <shakeel.butt@linux.dev>]

For non-PREEMPT_RT kernels, drain_obj_stock() is always called with irq
disabled, so we can use __mod_memcg_state() instead of
mod_memcg_state(). For PREEMPT_RT, we need to add memcg_stats_[un]lock
in __mod_memcg_state().

Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
---
 mm/memcontrol.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3c4de384b5a0..dfe9c2eb7816 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -707,10 +707,12 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx,
 	if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
 		return;
 
+	memcg_stats_lock();
 	__this_cpu_add(memcg->vmstats_percpu->state[i], val);
 	val = memcg_state_val_in_pages(idx, val);
 	memcg_rstat_updated(memcg, val);
 	trace_mod_memcg_state(memcg, idx, val);
+	memcg_stats_unlock();
 }
 
 #ifdef CONFIG_MEMCG_V1
@@ -2845,7 +2847,7 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock)
 
 			memcg = get_mem_cgroup_from_objcg(old);
 
-			mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages);
+			__mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages);
 			memcg1_account_kmem(memcg, -nr_pages);
 			if (!mem_cgroup_is_root(memcg))
 				memcg_uncharge(memcg, nr_pages);
-- 
2.47.1