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Received: from 30.74.144.191(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XDcwS4h_1793085971 cluster:ay36) by smtp.aliyun-inc.com; Tue, 27 Oct 2026 15:26:12 +0800 Message-ID: Date: Tue, 27 Oct 2026 15:26:10 +0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 10/16] mm/shmem: discard whole new large folios on fallocate rollback To: "David Hildenbrand (Arm)" , Andrew Morton , Gregory Price , Zi Yan , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-10-703206d5fa0c@kernel.org> From: Baolin Wang In-Reply-To: <20261026-fixes_shmem-v1-10-703206d5fa0c@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9819AC0002 X-Stat-Signature: 3q816fn66jywzouodqihgjb6mebz53b7 X-Rspam-User: X-Spam-Status: No, score=-19.8 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, UNPARSEABLE_RELAY,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793085977-922327 X-HE-Meta: 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 c0Ar4hmi fuYhKFDQKXBcUUTSlySRCg2Ifdjdb+5fdylwUBLC3qqI6O4VkNDVUe0n8emKvRC+r6rc2VVLpvwJh/R4Xwp8qRin6/sZSb+uOe1ynGnL9TCT+BuO9j3VTBcCDFEMNm4RuJ8DhDBovdjdRwptjBxPIfX/EqtXcTfC03bcHf4r+v3ROAZaHK2if2uRsQKjd7aJhUvqVBKy5nwApZ4JpFUsa7EA5UK5tryFiTYCKUCg3RpodvJ9cpARtOj46AKuRmZbcMVEaYZH+4JTAg15fyEFuo5vFnOVhvn6Va9KbzhHN6kxXPZmhtRLp+kWGZFN+xMJA2KXXbZAaun/0oe+WZZmcdphEGTV7cqagYv9HhebHRAxsGrOD4rdperYx6/7I0czVwpVuiBfK6ehZMk3GFNvWpptaLboFHN71ObePhtE4jyjrNAI= 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 10/26/26 5:40 PM, David Hildenbrand (Arm) wrote: > When undoing a failed fallocate(), shmem_undo_range() must discard each > newly allocated folio. Its second scan instead passes large > folios to truncate_inode_partial_folio(), which does not necessarily > discard the entire large folio, but instead tries splitting it to > discard only the requested range. > > For example, with huge=always, a failed allocation starting at offset > 4 KiB can leave page 0 allocated in an otherwise empty file. > > Discard the whole folio when unfalloc is set. Note that we enter this > path only for folios that are not uptodate, and can consequently be > dropped without losing any data. > > Fixes: 55ac8bbe358b ("mm/shmem: fix race in shmem_undo_range w/THP") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) > --- Good catch. LGTM. Reviewed-by: Baolin Wang