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Sat, 19 Sep 2026 03:07:12 +0000 X-Mizu-Trace-ID: 17c77f7b96f6f559 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.700.51.1.1\)) Subject: Re: [PATCH 3/4] memcg: manipulate memcg private ID references by ID From: Muchun Song In-Reply-To: <20260918-bingfangguo-memcgid-rework-v1-3-5bbf3220d88f@tencent.com> Date: Sat, 19 Sep 2026 11:06:49 +0800 Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Andrew Morton , Dave Chinner , Qi Zheng , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , David Hildenbrand , Lorenzo Stoakes , Bingfang Guo , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <90F1D900-0756-4A33-AEB9-5554D646DA57@linux.dev> References: <20260918-bingfangguo-memcgid-rework-v1-0-5bbf3220d88f@tencent.com> <20260918-bingfangguo-memcgid-rework-v1-3-5bbf3220d88f@tencent.com> To: bingfangguo@tencent.com X-Mailer: Apple Mail (2.3864.700.51.1.1) X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C815F40002 X-Stat-Signature: zat6yfgjfhingg85369t4h4e5kky84be X-HE-Tag: 1789787233-370040 X-HE-Meta: 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 h4/UXEda 5GGTCUAx83tqIiHCIIBhRN5URGEwujMCFy+UbJv6sooWLTngJeyKMiTF0Jd3VPnfH8K3zPMSFHHuIWSXfTGbDlswV912TWM5lw9LsJhdd7yxWXDxjRPqPzg9NvHINoffEHg0wvO7Oh3z2OQ+LIY20jsoQ1ye917uHJj8smjX1K2KizsfaXECKkZ3uOTjj49oaJXvZK/MjDY30QbUlClCc5mxnTn1BEADazLWJXvcIpQ0xEAdHsQm8aLqZdWuLe8ltm86ZOSw1IL9QIFmG/0kV6UyCmA79ALUBdpnLAerHjbRrVDl3h8+WfSvHCA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Sep 18, 2026, at 17:18, Bingfang Guo via B4 Relay = wrote: >=20 > From: Bingfang Guo >=20 > This is a preparatory work for moving memcgid from memcg to objcg. >=20 > Swap entries retain a private ID rather than a memcg pointer. Once > private ID references are moved to objcgs, the ID can also outlive the > memcg to which it was originally assigned. So it's better to make the > get and put functions accept the ID itself instead of the memcg. >=20 > Rename mem_cgroup_private_id_get_online() to > mem_cgroup_private_id_get(), and make it return the ID only. If the > memcg is already dying, the dying memcg will still be used for = charging > and stats accounting in v2 swap charging path. But they are = hierarchical > and will be reparented after offlining so it doesn't matter. >=20 > Make mem_cgroup_private_id_put() take the ID and resolve the reference > holder internally. Convert swap uncharge and charge rollback to = release > the reference using that ID. This introduces an extra xarray lookup = for > now, which will be removed in the final patch. >=20 > Separate the online-state reference release into > mem_cgroup_private_id_kill(). The offline path already has the memcg > pointer and can call the underlying put helper directly. >=20 > Signed-off-by: Bingfang Guo With Shakeel's suggestion. Acked-by: Muchun Song