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t=1794004960; bh=JlbEJ/mAQ5AEryfKs406khz/jZEGvS7oBKVbDoRy+Xo=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=JGMdQPeYWvZkx75geWZtgyTHasxq12eL2mvw130fUowkgQt5u/0QMWgjSwtPkrv9x nAmjmlLC7P72HaNBsSW594Z2aGntB2xZRIbb1q2R8ZtMH3EYlK1ql87XNKKuF6C8g9 YgeHFDQ0cWMuaQUVjBvcVGKQAJpu6mwtlDJ0sGswiWtLGmASIR6/6q4X0dEpOAE2eF iNsdg9qv5vVMyNNORv0rIQQxNkFL+m6shCr1VUsNJuYFfxAv45qwMOjzvRCmv+QD+r SbMFCEmReiNw5AyNldI87KX38Qhwj6dZrU+wBDI8Sqtq/2STIRj0mAqTnzOzfGK3Zx OkxQrVY8oZSWw== Message-ID: <6b8d6030-efe7-47d2-8aa2-3f8fd77ce95c@kernel.org> Date: Fri, 6 Nov 2026 22:57:19 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] mm: limit pagecache folio refcount when splicing into pipes To: Lance Yang Cc: akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, willy@infradead.org, jack@suse.cz, ziy@nvidia.com, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, peterx@redhat.com, hannes@cmpxchg.org, songliubraving@fb.com, riel@surriel.com, hughd@google.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org, jgg@ziepe.ca, kevin.tian@intel.com, joro@8bytes.org, robin.murphy@arm.com, steven.sistare@oracle.com, jhubbard@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, iommu@lists.linux.dev, stable@vger.kernel.org References: <20261105-refcount_overflow_stable-v1-2-70b9c655da3e@kernel.org> <20261106100320.77084-1-lance.yang@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20261106100320.77084-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 69jxpeeo7kmyubqyzip14w7m1au7b7di X-Rspamd-Queue-Id: 5E7C9100005 X-Rspam-User: X-Rspamd-Server: rspam11 X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1794004961-731006 X-HE-Meta: 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 cPg2yVUI 70QTBytauycZbVYXk7FovMBdzKg/VVQYbpSdMWFi6sMycrIDbQRi6jFk5MQJoRCiMFCz/pDJFO9AnL1BIg4kdzkSTCFvFHY1RntPvXsi4lWkzovB3SF+UpTGGcO7AIdVEQnv5MQOeygOa0aPQNsHwUfI4mcqxOoq64SL4k/darWPx804ZrZoQ6epG/L8xhJuAW8gD2Ucj+MznC4WJ6WCBC4MCoxaAHqcAXhCX4OjoV3j9tdDHbzyAwu0FHTz7QStkL7FHdp+MhgL3FWGSPGcoPUHrMI6QNtvyVXt34yGaPYpHWQqr82TEen0DkEW2RKwjBfU1UJ7zdJZ//LkMY6zW5pvHDA== 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 11/6/26 11:03, Lance Yang wrote: > > On Thu, Nov 05, 2026 at 02:10:11PM +0100, David Hildenbrand (Arm) wrote: >> Similar to mapping pagecache folios into page tables, let's reject splicing >> folios into a pipe if the refcount is at it's limit, similar to how we >> handle it during GUP. >> >> This will prevent more cases of possible folio refcount overflows with >> large pagecache folios. >> >> Let's keep it simple and check in the two callers of >> splice_folio_into_pipe(). >> >> Also check in try_get_page() to cover pipe-buffer duplication by tee() >> and partial pipe-to-pipe splicing. > > What about fuse_ref_folio()? Buffered FUSE_WRITE requests can carry > pagecache folios into a pipe through /dev/fuse without going through > splice_folio_into_pipe() or try_get_page() ... Of course it has its own handling ... :) Thanks! I was hoping the number of folio references would be bounded ... I guess one reference per pipe buffer is not the end of the world, but, let's just add it, and fallback to copying. -- Cheers, David