From: Shakeel Butt <shakeel.butt@linux.dev>
Date: Fri, 4 Apr 2025 01:39:05 +0000 (-0700)
Subject: memcg: remove root memcg check from refill_stock
X-Git-Tag: v6.16-rc1~92^2~249
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=e56fa8f5e108676393a363201819a094b0991b3c;p=linux-block.git

memcg: remove root memcg check from refill_stock

refill_stock can not be called with root memcg, so there is no need to
check it.  Instead add a warning if root is ever passed to it.

Link: https://lkml.kernel.org/r/20250404013913.1663035-1-shakeel.butt@linux.dev
Link: https://lkml.kernel.org/r/20250404013913.1663035-2-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b16b5b807d7c..ae1e953cead7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1893,13 +1893,13 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
 	unsigned long flags;
 
+	VM_WARN_ON_ONCE(mem_cgroup_is_root(memcg));
+
 	if (!local_trylock_irqsave(&memcg_stock.stock_lock, flags)) {
 		/*
 		 * In case of unlikely failure to lock percpu stock_lock
 		 * uncharge memcg directly.
 		 */
-		if (mem_cgroup_is_root(memcg))
-			return;
 		page_counter_uncharge(&memcg->memory, nr_pages);
 		if (do_memsw_account())
 			page_counter_uncharge(&memcg->memsw, nr_pages);