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Sat, 05 Sep 2026 12:18:26 +0000 X-Mizu-Trace-ID: b1c979f2108c0cd3 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 RFC v2 6/6] mm/memcg: filter out reparented memcgs got from memcgid From: Muchun Song In-Reply-To: <20260901-bingfangguo-memcgid-rework-v2-6-8edd7f7a7251@tencent.com> Date: Sat, 5 Sep 2026 20:18:03 +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: <3F681C23-8462-4BA3-B3C6-B7A45A9341DE@linux.dev> References: <20260901-bingfangguo-memcgid-rework-v2-0-8edd7f7a7251@tencent.com> <20260901-bingfangguo-memcgid-rework-v2-6-8edd7f7a7251@tencent.com> To: bingfangguo@tencent.com X-Mailer: Apple Mail (2.3864.700.51.1.1) X-Stat-Signature: jo1e4howfhh8n8usj3g4o3ie6qe55nig X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 27EEE180002 X-Rspam-User: X-HE-Tag: 1788610717-391233 X-HE-Meta: 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 dQhXKyxg 6aITKGtiFrO8WKrtQTd/6aEngfJhlKLOUrH5z3jMoxhvrZDPDd3efuVPPi9pn0oi3AtkkrsbRrM4o0achfiz7MYdYmcSDr2A4uflD10yREWP+PwDwK+xMjF23ub7QleSs+S6ak1JFKlxdymi7Uo65xzWCUUdtN0vB2cSZrLokREHlIlbjeE9boyHIDYTJAhh53vJ+6dFbqp1s6v4n4/19lWuh9lcbmv0Sxp4e0L+P5pdhZZ6ob/NkPqKIuVyksFB3fWbW9KH9bhon105ZALLFGDLN/qy91NHcW9rR++flsgmhBjo2vcOTIP0AauoFePCNkvnJw10L6DAjA3QZBelDhEIR/w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Sep 1, 2026, at 16:58, Bingfang Guo via B4 Relay = wrote: >=20 > From: Bingfang Guo >=20 > mem_cgroup_from_private_id() looks up the objcg that owns the id and > returns the objcg's current memcg. After reparenting, that memcg can > differ from the one the id originally belonged to. >=20 > Callers such as the list lru and workingset refault code expect to get > back exactly the memcg referred to by the memcgid, so check that the > returned memcg still owns the id and return NULL otherwise. In this > case, make list_lru just skip and workingset tests use the root (as = the > comments said in workingset.c:460). >=20 > Signed-off-by: Bingfang Guo We should move this patch earlier to avoid introducing the problem first and then fixing it later. Muchun, Thanks.