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Mon, 09 Nov 2026 01:05:34 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-49596ea51cbsm9541323f8f.27.2026.11.09.01.05.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 09 Nov 2026 01:05:33 -0800 (PST) Message-ID: <8ff83fbf-2ecb-4f9b-ac8f-ee88fece67cb@gmail.com> Date: Mon, 9 Nov 2026 10:05:30 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/5] mm/gup: limit pagecache folio refcount when grabbing references To: "David Hildenbrand (Arm)" , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Jan Kara , Andrew Morton , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Johannes Weiner , Song Liu , Rik van Riel , Miklos Szeredi , Alexander Viro , Christian Brauner , Hugh Dickins , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Arnd Bergmann , Jason Gunthorpe , Kevin Tian , "Joerg Roedel (AMD)" , Robin Murphy , Steve Sistare , John Hubbard , Josef Bacik Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.linux.dev, linux-arch@vger.kernel.org, iommu@lists.linux.dev, stable@vger.kernel.org References: <20261107-refcount_overflow_stable-v2-0-c38f6809b106@kernel.org> <20261107-refcount_overflow_stable-v2-5-c38f6809b106@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261107-refcount_overflow_stable-v2-5-c38f6809b106@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 7nxmh8p63qp65tim8z96wyjxjz9iau7b X-Rspamd-Queue-Id: E450040006 X-Rspam-User: X-Rspamd-Server: rspam11 X-Spam-Status: No, score=-9.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794215135-434511 X-HE-Meta: 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 NV5HWN+y 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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 11/7/26 11:23 PM, David Hildenbrand (Arm) wrote: > Let's add a folio_ref_count_over_limit() check in fast and slow GUP > before acquiring additional references or pins. > > Keep it simple and use the check for all folio types. > > Don't check capabilities with IRQs disabled, as even unaudited capability > checks can take locks. Refuse access to the admin reserve, so GUP-fast will > fail and fall back to GUP-slow if possible. > > Also propagate try_grab_folio() errors when grabbing additional > references in __get_user_pages() and in memfd_pin_folios(), so hitting > the limit returns -ENOMEM instead of -EFAULT and -EINVAL, respectively. nice! > Keep the existing invalid-refcount warnings. > > Fixes: 800d8c63b2e9 ("shmem: add huge pages support") > Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") > Fixes: 793917d997df ("mm/readahead: Add large folio readahead") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a