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From:   Roman Gushchin <roman.gushchin@linux.dev>
To:     linux-mm@kvack.org
Cc:     linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Dennis Zhou <dennis@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>
Subject: [PATCH rfc 5/5] percpu: scoped objcg protection
Date:   Wed, 27 Sep 2023 08:08:32 -0700
Message-ID: <20230927150832.335132-6-roman.gushchin@linux.dev>
In-Reply-To: <20230927150832.335132-1-roman.gushchin@linux.dev>
References: <20230927150832.335132-1-roman.gushchin@linux.dev>
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Precedence: bulk

Similar to slab and kmem, switch to a scope-based protection of the
objcg pointer to avoid.

Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
---
 mm/percpu.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index a7665de8485f..f53ba692d67a 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1628,14 +1628,12 @@ static bool pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp,
 	if (!memcg_kmem_online() || !(gfp & __GFP_ACCOUNT))
 		return true;
 
-	objcg = get_obj_cgroup_from_current();
+	objcg = current_obj_cgroup();
 	if (!objcg)
 		return true;
 
-	if (obj_cgroup_charge(objcg, gfp, pcpu_obj_full_size(size))) {
-		obj_cgroup_put(objcg);
+	if (obj_cgroup_charge(objcg, gfp, pcpu_obj_full_size(size)))
 		return false;
-	}
 
 	*objcgp = objcg;
 	return true;
@@ -1649,6 +1647,7 @@ static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,
 		return;
 
 	if (likely(chunk && chunk->obj_cgroups)) {
+		obj_cgroup_get(objcg);
 		chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = objcg;
 
 		rcu_read_lock();
@@ -1657,7 +1656,6 @@ static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,
 		rcu_read_unlock();
 	} else {
 		obj_cgroup_uncharge(objcg, pcpu_obj_full_size(size));
-		obj_cgroup_put(objcg);
 	}
 }
 
-- 
2.42.0