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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Zach O'Keefe , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chris Mason , stable@vger.kernel.org Subject: Re: [PATCH] mm/khugepaged: don't map folios that are not uptodate in MADV_COLLAPSE Date: Thu, 5 Nov 2026 17:08:15 -0800 Message-ID: <20261106010815.96125-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261105-set_huge_pmd_uptodate-v1-1-a78d8a1b7117@kernel.org> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: x3g3nakko9qjpjzowezbnejangaanpbh X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E335340009 X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793927304-593556 X-HE-Meta: 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 fAmP58Wf ObMohH2OPg1LuBiWqcJyYAJLrjeRHrHlurf+UwSAG/M6J51WAmC4tO2yYpl89wXMAOyFN22m6uACrRSgjdTncpzsYBGcQnRY3I5J0BX4ohs2RI27M8MvcMmK27+b55L8jnOd0nhbnM2lW5EJdHvdjYpT1GpFPVouyWvkgwj/GOUW1Km8OaQViycB9dxyYnhgyikIjbIX4b6BkrfKIqawXFCpHJ+CpZyflOiF2gAc8q0AICrWoruc9sOOJA0Y20UFzD/r9QltaLYiAXgJzy9cTAhIQXg== 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 Thu, 05 Nov 2026 19:16:44 +0100 "David Hildenbrand (Arm)" wrote: > madvise(MADV_COLLAPSE) can map PMD-sized pagecache folios that are not > uptodate. For example, shmem fallocate() can put such folios into the > page cache. > > collapse_file() already refuses to proceed with folios that are not > uptodate. Let's just do the same in try_collapse_pte_mapped_thp() and skip > such folios, leaving handling to the page faults. > > Note that collapse_file() effectively clears shmem folios through > shmem_get_folio(); let's keep this fix simple and simply let the page > fault path deal with that. Makes sense to me. > > Fixes: 34488399fa08 ("mm/madvise: add file and shmem support to MADV_COLLAPSE") > Reported-by: Chris Mason > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: SJ Park Thanks, SJ [...]