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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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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> 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