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From: Muchun Song <muchun.song@linux.dev>
To: bingfangguo@tencent.com
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Chinner <david@fromorbit.com>, Qi Zheng <qi.zheng@linux.dev>,
	Kairui Song <kasong@tencent.com>, Barry Song <baohua@kernel.org>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
	David Hildenbrand <david@kernel.org>,
	Lorenzo Stoakes <ljs@kernel.org>, Bingfang Guo <bfguo@icloud.com>,
	cgroups@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] memcg: keep swap charging under RCU protection
Date: Fri, 18 Sep 2026 20:07:59 +0800	[thread overview]
Message-ID: <CEA43253-5A6F-46EF-A7CF-645D5EC95E05@linux.dev> (raw)
In-Reply-To: <20260918-bingfangguo-memcgid-rework-v1-1-5bbf3220d88f@tencent.com>



> On Sep 18, 2026, at 17:18, Bingfang Guo via B4 Relay <devnull+bingfangguo.tencent.com@kernel.org> wrote:
> 
> From: Bingfang Guo <bingfangguo@tencent.com>
> 
> This is a preparatory work for unbinding memcgid from memcg. No
> functional change.
> 
> The swap charging path currently drops its RCU read lock after acquiring
> a private ID reference. This is safe because the ID reference pins the
> memcg's CSS.
> 
> Moving private ID references to objcgs will remove that lifetime
> guarantee. Keep the RCU read lock held while accessing the memcg for
> counter charging, statistics and failure handling. (This matches what
> __memcg1_swapout() already does.).
> 
> Save the private ID before dropping the RCU read lock, and use the saved
> value when recording the swap entry. The swap cluster locking remains
> outside the RCU read-side critical section.
> 
> Signed-off-by: Bingfang Guo <bingfangguo@tencent.com>

Acked-by: Muchun Song <muchun.song@linux.dev>

Thanks.


  reply	other threads:[~2026-09-18 12:08 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-18  9:18 [PATCH 0/4] memcg: move memcgid refcount to objcg to unpin dying memcgs Bingfang Guo via B4 Relay
2026-09-18  9:18 ` [PATCH 1/4] memcg: keep swap charging under RCU protection Bingfang Guo via B4 Relay
2026-09-18 12:07   ` Muchun Song [this message]
2026-09-18 16:46   ` Shakeel Butt
2026-09-18 17:51     ` Bingfang Guo
2026-09-18  9:18 ` [PATCH 2/4] memcg: base swap charge accounting on memcgid root status Bingfang Guo via B4 Relay
2026-09-19  2:56   ` Muchun Song
2026-09-18  9:18 ` [PATCH 3/4] memcg: manipulate memcg private ID references by ID Bingfang Guo via B4 Relay
2026-09-18 18:14   ` Shakeel Butt
2026-09-18 18:46     ` Bingfang Guo
2026-09-18 20:24       ` Shakeel Butt
2026-09-19  3:06   ` Muchun Song
2026-09-18  9:18 ` [PATCH 4/4] memcg: move memcg private ID refcount to objcg Bingfang Guo via B4 Relay
2026-09-18 18:19   ` Shakeel Butt
2026-09-18 19:14     ` Bingfang Guo
2026-09-19  3:32   ` Muchun Song

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