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Fri, 06 Nov 2026 01:50:37 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-492d3d60e78sm2755152f8f.1.2026.11.06.01.50.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Nov 2026 01:50:37 -0800 (PST) Message-ID: <6662ae76-c8dc-4bc5-9730-bf9f537ca9cb@gmail.com> Date: Fri, 6 Nov 2026 10:50:34 +0100 X-Mailing-List: iommu@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] mm: limit pagecache folio refcount when splicing into pipes To: "David Hildenbrand (Arm)" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Jan Kara , 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 , Hugh Dickins , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Jason Gunthorpe , Kevin Tian , "Joerg Roedel (AMD)" , Robin Murphy , Steve Sistare , John Hubbard Cc: 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-v1-0-70b9c655da3e@kernel.org> <20261105-refcount_overflow_stable-v1-2-70b9c655da3e@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261105-refcount_overflow_stable-v1-2-70b9c655da3e@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/5/26 2:10 PM, 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. > > 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) LGTM: Reviewed-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a