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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Jonathan Corbet , Shuah Khan , Randy Dunlap , Peter Xu , Breno Leitao , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gerd Hoffmann , linux-doc@vger.kernel.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Josef Bacik Content-Transfer-Encoding: quoted-printable Message-Id: References: <20261028-fixes_hugetlb-v1-0-a0a033db180f@kernel.org> <20261028-fixes_hugetlb-v1-9-a0a033db180f@kernel.org> To: "David Hildenbrand (Arm)" X-Mailer: Apple Mail (2.3901.200.71.1.16) 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-Rspamd-Server: rspam09 X-Stat-Signature: iz57xso7fdrmwfeseikb1xq1a6y97n9n X-Rspamd-Queue-Id: 3D9ED40003 X-Rspam-User: X-HE-Tag: 1793784283-192642 X-HE-Meta: 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 YxKGPSgh 5mjT+990b6leexnyCFJ428Aa7Eh15tUuHZ+KpuOaHW9BwbQnlgMnS/T02kqBjMbCJzj+5mGMGvArZc7hzDxvwC5PiPad1AzBbdZdDLA30am96Q1TL3wLInckJJsAZUzw9sd7sdfvNlpNvsEVi0DVP4gvA+7L6WkrZuSjOG7wrayaBzVCzcU+2WJPaVePAmXqNWdytaQ+EeRZXHgxjGlRk9V7FQiIDW6gqjldEr2lGCRvVj8h+tbxWgEEQKHs5iK9seBae5YHwGk9DYPRnbXWFXBI5UqcJFPYEZ/l5cCcfIZZ6WUzMZ/My5XIyuUbUptkqAsOQ0YJUdmMyjThcSfyfUpf2tAOwx+D5VwxkyQX/pboNmaqxPpfW0XEjfS+9xJQzQtM6GLgVMNNQP5TrDjIsANRqgBFLclCYIzTjZoVpPhnbeTk= 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 Oct 29, 2026, at 04:13, David Hildenbrand (Arm) = wrote: >=20 > A concurrent fault or PIN request can populate the page cache > after memfd_pin_folios() misses it in the page cache but before > memfd_alloc_folio() takes the fault mutex. The latter still tries to > allocate another folio and can return -ENOMEM even though the = requested > folio is already cached. >=20 > In particular, hugetlb_reserve_pages() finds the existing = reservation-map > entry and reserves nothing. If no global reservations remain, > alloc_hugetlb_folio_reserve() fails even when the pool has free pages, > effectively failing memfd_pin_folios(). >=20 > Recheck the page cache before reserving or allocating. If the folio is > present, drop the lookup reference and return -EEXIST so > memfd_pin_folios() retries its lookup. >=20 > This is probably not worth backporting to stable. >=20 > Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning = memfd folios") > Reported-by: Josef Bacik > Signed-off-by: David Hildenbrand (Arm) Acked-by: Muchun Song Thanks.