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Thu, 12 Nov 2026 09:28:03 -0500 (EST) Date: Thu, 12 Nov 2026 14:28:02 +0000 From: Kiryl Shutsemau To: sashiko-reviews@lists.linux.dev Cc: Andrew Morton , Linus Torvalds , David Hildenbrand , Matthew Wilcox , Vlastimil Babka , Lorenzo Stoakes , Jan Kara , Hugh Dickins , Christian Brauner , Alexander Viro , Harry Yoo , Miklos Szeredi , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kairui Song , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , "Paul E. McKenney" , Pedro Falcato , Luis Chamberlain , Ilya Gladyshev , Jaegeuk Kim , linux-mm@kvack.org, kernel-team@meta.com Subject: Re: [RFC PATCH v2 07/18] mm: free the pages waiting for a grace period before isolation fails Message-ID: References: <20261104130118.2507513-1-kas@kernel.org> <20261104130118.2507513-8-kas@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A8AFBC000F X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Stat-Signature: mo9dnhzktusceytqxie5ixn7ysj4gqy5 X-HE-Tag: 1794493696-724878 X-HE-Meta: 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 NLnwJ3re ojiq5AmNVHcOcGz51wSOoXRAP3OWSU5a07y1/CEFP0xekDA7gmHCogXR9bh8E8MLxxZgwHPuRmdxno2fqovCbMAK6qnZKr4/+xIYmlBPG2xa79+HyH979Fx+M8LI7DDv85ugUPmMf4LK3BLhBMRj7+SuYQ3lM7juf4sfoAIbwRUC65k1qTKnjbWHq7CDQXqbBWFMXPptrS6VL7QBBSJ2b42DocpFiwwpxb53a2uWf0Z1OhjG5jAlX3ZNAlrPbEVWT508ZxgZksU2jhT/6vYya46/D/NV0HfTcC2Vfs4UoEqgHIatSap20WC/YFRe2qgDN9ucXmFRsAjhN9ek+5isVNCLfP7eD0RgbuyrJjzkK7fbK3YNJdxTcEI2RtQ== 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 Thu, Nov 05, 2026 at 01:03:37PM +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider: > - [Medium] mm: premature NR_FREE_RCU_PAGES decrement in rcu_free_pages() skips sync Only the zone's last batch can make zone_rcu_free_waiting() read 0 while a work is still freeing it, and the pages reach the buddy lists right after. alloc_contig_range() fails as it does on a transient page reference, and offline_pages() takes one more pass. I don't think the window is worth closing. > - [Medium] mm: stale outer_start in alloc_contig_frozen_range_noprof() after RCU free merge The first case is real. In v3 alloc_contig_range() finds outer_start again and re-checks whenever the check fails, not only when pages are waiting. The second case is a free racing with isolate_freepages_range(), which can happen without this series too. > - [Medium] mm: page_is_unmovable() treats freed compound PG_rcu_free folios as unmovable Valid. In v3 the flag stays set until the grace period ends, and page_is_unmovable() counts a large folio with PG_rcu_free and no references as movable. -- Kiryl Shutsemau / Kirill A. Shutemov