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Mon, 26 Oct 2026 12:37:01 -0400 (EDT) Date: Mon, 26 Oct 2026 16:36:59 +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 08/16] mm/shmem: stop retrying folios that cannot be split Message-ID: References: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-8-703206d5fa0c@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-v1-8-703206d5fa0c@kernel.org> X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E1FA0180002 X-Stat-Signature: cqjabpcmky97hn7gt6rm3doaut4ihqaa 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: 1793032625-513406 X-HE-Meta: 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 s1SGymjK 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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 10:40:41AM +0100, David Hildenbrand (Arm) wrote: > From: Chris Mason > > A fault or collapse can insert a large folio crossing EOF after > shmem_undo_range() has handled the boundary folios. If splitting that > folio fails, truncate_inode_partial_folio() retains it when it is dirty. > The final scan then repeatedly finds it because it restarts from an > unchanged start. > > Truncation keeps the inode lock and ignores fatal signals while looping. > A concurrent unlink() can then block other directory operations while > holding the directory lock and waiting for the file's lock. > > Advance start past the retained folio, whose truncated part has already > been zeroed. Do not move start backwards if the failed split has shrunk > the folio. > > Fix generated by an LLM and sent by Chris Mason in private. > > Fixes: 55ac8bbe358b ("mm/shmem: fix race in shmem_undo_range w/THP") > Cc: stable@vger.kernel.org > Signed-off-by: Chris Mason > [ david: split fixes, simplify descriptions, adjust comments ] > Signed-off-by: David Hildenbrand (Arm) Any reason, this should not be in the same patch as 07/16? It is the same failure mode in the same function. -- Kiryl Shutsemau / Kirill A. Shutemov