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Mon, 26 Oct 2026 13:59:39 -0400 (EDT) Date: Mon, 26 Oct 2026 17:59:38 +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: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 31595140005 X-Stat-Signature: 76gnet4pmcro7h44kmd8tceg1zkgqk19 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: 1793037583-88559 X-HE-Meta: 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 wCkisC35 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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 06:08:15PM +0100, David Hildenbrand (Arm) wrote: > On 10/26/26 17:36, Kiryl Shutsemau wrote: > > 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. > > I decided to split because it's a slightly different error mode (failing to > discard vs. endless loop) and tackles two different commits. Fair enough. Acked-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov