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Received: from willy by casper.infradead.org with local (Exim 4.100.1 #2 (Red Hat Linux)) id 1xK5xh-00000007f3f-0XlY; Fri, 23 Oct 2026 03:28:57 +0000 Date: Fri, 23 Oct 2026 04:28:56 +0100 From: Matthew Wilcox To: Yafang Shao Cc: akpm@linux-foundation.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, "Huang, Ying" Subject: Re: [PATCH] mm/migrate: snapshot the source nid before the misplaced migration Message-ID: References: <20261023023226.29783-1-laoar.shao@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261023023226.29783-1-laoar.shao@gmail.com> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7E42A8000C X-Stat-Signature: d83ionyuhfzk5ibgq5nixbwr7gpfxepk X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792726143-417041 X-HE-Meta: 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 4LO/wWOj 9tWQUYHb1okVtURiV6/clVJMgy1XPlLK+59OWsYpX5BSNRFwKe5cmDghbSvLr16aRQynGA7b4L4Az4nglK24VsbtHRKW4npU2r5lOqA9HPY8ITcZ29gC4wLc/wojjipucKJOsRZYCXZxLLvbu/9x2N9rlcqNUnXgqmzn2iL9Cffl9wvyczpjZAVChIQfnOnSAmepjbNUCODn+pMNl29iznr+gQECYQm0+bp9gaN+L5nKj8sl1UXKScBrxWMH5xr6rXcUwVabudV9uB6yfsoiXB6q5vIdKNhgYvwnGEYWHIqDPcxG3430C1ewWRiVURnrQasiQOInDg1NOMML8KxSQuZ2vq4BumogwDPRk Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Fri, Oct 23, 2026 at 10:32:26AM +0800, Yafang Shao wrote: > A successful migration frees the source folio, so the folio_nid() read > in the promotion counter update can pick up a reallocated page's nid. > Snapshot the nid before the migration, next to the memcg snapshot the > function already takes. I don't understand how a node ID can change even after the folio has been freed. I don't think this patch is wrong, but I don't think there's actually a bug here that's being fixed.