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From: Muchun Song In-Reply-To: <20260807142406.443516-1-shakeel.butt@linux.dev> Date: Sat, 8 Aug 2026 09:35:36 +0800 Cc: Andrew Morton , Michal Hocko , Johannes Weiner , Roman Gushchin , Qi Zheng , Meta kernel team , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Karl Erik Hofseth , stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <9B30927B-4154-4FA4-B62E-425F6EC4FA89@linux.dev> References: <20260807142406.443516-1-shakeel.butt@linux.dev> To: Shakeel Butt X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 4F22840004 X-Stat-Signature: wuz1ddehsoowm6og11wqe19mm7x8idfu X-Rspam-User: X-HE-Tag: 1786152974-20330 X-HE-Meta: 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 dvr1bspV M8Q01XqqzOZA98d23ScsuM6nJXLjU2VAT5us5SXZL8D+kk6TiojmQx3Zgx3GjFCcmmntMiDRXTsHnssIg2V+rRx4Ez0Ypk827KHxEAeWgxK79+TGfd73/XXILwduwEZk4XxaNZ8Cj1aKtxbL3ZUsE9OkBZHBA2lJ/WGHqszSrHpPCY7QDOsE394l31Ppiqe+lTGymrg0WXS4LnYRnHQYjt/EH/6VOBTmLlbMHdO8JIyByggPSqnIKCt8JNyMBQrRZPwB+qg8nPMzEUhcvGOpBEyCSVcUtDejPlpR0HzFD+WJ8vQuHbmOJvS5LWe7iwlE49TBdcPNtRtj3f0ANt2tdmo6Bud7IJfSEqnD1yx1fS682XdAdQWdokJT40BjdQmZsgNVJ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Aug 7, 2026, at 22:24, Shakeel Butt wrote: >=20 > memcg_reparent_objcgs() has an inherent assumption that a folio's = objcg > is the objcg of the folio's node. Folio migration across nodes breaks > that assumption: the new folio simply inherits the old folio's objcg > while living on a different node. >=20 > Once the assumption is broken, the reparenting of the folio's objcg = and > the reparenting of the folio's LRU list are no longer atomic. > memcg_reparent_objcgs() handles one node per iteration and drops all = the > locks in between, so the objcg gets reparented in the iteration for = the > objcg's node while the LRU list gets spliced in the iteration for the > folio's node. Any LRU operation on that folio in between resolves its > lruvec through the objcg, and thus takes the lru_lock of the wrong > memcg, not the lru_lock of the list the folio is actually on. >=20 > Fix this by selecting the objcg by folio_nid() at charge time, and by > re-deriving it for the destination node in mem_cgroup_migrate() and > mem_cgroup_replace_folio(). >=20 > Reported-by: Karl Erik Hofseth > Closes: https://lore.kernel.org/all/anMmd1ADrDVwMO6v@work/ > Fixes: f1cf8d2f36dc ("mm: memcontrol: eliminate the problem of dying = memory cgroup for LRU folios") > Cc: stable@vger.kernel.org > Co-developed-by: Johannes Weiner > Signed-off-by: Johannes Weiner > Signed-off-by: Shakeel Butt Acked-by: Muchun Song Thanks.