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Mon, 26 Oct 2026 12:30:11 -0400 (EDT) Date: Mon, 26 Oct 2026 16:30:10 +0000 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Gregory Price , Zi Yan , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , Baolin Wang , Lukas Czerner , Carlos Maiolino , Christian Brauner , Jan Kara , Daniel Verkamp , Jeff Xu , Muchun Song , Oscar Salvador , David Stevens , "Matthew Wilcox (Oracle)" , William Kucharski , Chris Li , Kairui Song , Nhat Pham , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org Subject: Re: [PATCH 07/16] mm/shmem: avoid moving the truncation start backwards Message-ID: References: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-7-703206d5fa0c@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261026-fixes_shmem-v1-7-703206d5fa0c@kernel.org> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 885A9160005 X-Stat-Signature: 6xusk1nh8yo5b3jqjb33pmtstqehy37d X-Rspam-User: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793032217-604470 X-HE-Meta: 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 B7TpYKRo 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 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 Mon, Oct 26, 2026 at 10:40:40AM +0100, David Hildenbrand (Arm) wrote: > From: Chris Mason > > A nonuniform folio split can fail with -ENOMEM after splitting off some > smaller folios. shmem_undo_range() then sets start to the end of the > original folio, which may now lie before the truncation boundary. > > The final scan can consequently discard data below the new EOF, or > keep retrying a large folio whose split point lies outside it. > > Keep start at least at its original value when skipping a folio after > a failed split. The part in the truncated range has already been zeroed. > > Fix generated by an LLM and sent by Chris Mason in private. > > Fixes: 7460b470a131f ("mm/truncate: use folio_split() in truncate operation") > Cc: stable@vger.kernel.org > Signed-off-by: Chris Mason > [ david: split fixes, simplify descriptions, adjust comments ] > Signed-off-by: David Hildenbrand (Arm) Acked-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov