From: Johannes Weiner <hannes@cmpxchg.org>
Subject: mm/memcg: opencode the inner part of obj_cgroup_uncharge_pages() in drain_obj_stock()

Provide the inner part of refill_stock() as __refill_stock() without
disabling interrupts.  This eases the integration of local_lock_t where
recursive locking must be avoided.  Open code obj_cgroup_uncharge_pages()
in drain_obj_stock() and use __refill_stock().  The caller of
drain_obj_stock() already disables interrupts.

[bigeasy@linutronix.de: patch body around Johannes' diff]
Link: https://lkml.kernel.org/r/20220226204144.1008339-5-bigeasy@linutronix.de
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-opencode-the-inner-part-of-obj_cgroup_uncharge_pages-in-drain_obj_stock
+++ a/mm/memcontrol.c
@@ -2251,12 +2251,9 @@ static void drain_local_stock(struct wor
  * Cache charges(val) to local per_cpu area.
  * This will be consumed by consume_stock() function, later.
  */
-static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
+static void __refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
 	struct memcg_stock_pcp *stock;
-	unsigned long flags;
-
-	local_irq_save(flags);
 
 	stock = this_cpu_ptr(&memcg_stock);
 	if (stock->cached != memcg) { /* reset if necessary */
@@ -2268,7 +2265,14 @@ static void refill_stock(struct mem_cgro
 
 	if (stock->nr_pages > MEMCG_CHARGE_BATCH)
 		drain_stock(stock);
+}
+
+static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
+{
+	unsigned long flags;
 
+	local_irq_save(flags);
+	__refill_stock(memcg, nr_pages);
 	local_irq_restore(flags);
 }
 
@@ -3185,8 +3189,16 @@ static void drain_obj_stock(struct memcg
 		unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT;
 		unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1);
 
-		if (nr_pages)
-			obj_cgroup_uncharge_pages(old, nr_pages);
+		if (nr_pages) {
+			struct mem_cgroup *memcg;
+
+			memcg = get_mem_cgroup_from_objcg(old);
+
+			memcg_account_kmem(memcg, -nr_pages);
+			__refill_stock(memcg, nr_pages);
+
+			css_put(&memcg->css);
+		}
 
 		/*
 		 * The leftover is flushed to the centralized per-memcg value.
_