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[209.85.221.174]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-53b2bdb84f5sm3949164e0c.13.2025.08.21.13.24.45 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Aug 2025 13:24:45 -0700 (PDT) Received: by mail-vk1-f174.google.com with SMTP id 71dfb90a1353d-53b1718837dso603898e0c.0 for ; Thu, 21 Aug 2025 13:24:45 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXs+Yotzt647gjmm4JKJmg+fxE4BMSibYPsK0zrdOSlmCk0BSctlu8P8l7DbCbrbNE89eVw22a/vIzGfPCbqGQ=@vger.kernel.org X-Received: by 2002:a05:6122:1ad2:b0:53c:896e:2870 with SMTP id 71dfb90a1353d-53c8a40b923mr212315e0c.12.1755807884664; Thu, 21 Aug 2025 13:24:44 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250821200701.1329277-1-david@redhat.com> <20250821200701.1329277-32-david@redhat.com> In-Reply-To: <20250821200701.1329277-32-david@redhat.com> From: Linus Torvalds Date: Thu, 21 Aug 2025 16:24:23 -0400 X-Gmail-Original-Message-ID: X-Gm-Features: Ac12FXxaZhwn04a0gbwY6rjh9UGLxnRlGOG0Jy0WjRbVAG0UxLDqNy0Wydj0GQk Message-ID: Subject: Re: [PATCH RFC 31/35] crypto: remove nth_page() usage within SG entry To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Herbert Xu , "David S. Miller" , Alexander Potapenko , Andrew Morton , Brendan Jackman , Christoph Lameter , Dennis Zhou , Dmitry Vyukov , dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, iommu@lists.linux.dev, io-uring@vger.kernel.org, Jason Gunthorpe , Jens Axboe , Johannes Weiner , John Hubbard , kasan-dev@googlegroups.com, kvm@vger.kernel.org, "Liam R. Howlett" , linux-arm-kernel@axis.com, linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-ide@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mmc@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, Lorenzo Stoakes , Marco Elver , Marek Szyprowski , Michal Hocko , Mike Rapoport , Muchun Song , netdev@vger.kernel.org, Oscar Salvador , Peter Xu , Robin Murphy , Suren Baghdasaryan , Tejun Heo , virtualization@lists.linux.dev, Vlastimil Babka , wireguard@lists.zx2c4.com, x86@kernel.org, Zi Yan Content-Type: text/plain; charset="UTF-8" On Thu, 21 Aug 2025 at 16:08, David Hildenbrand wrote: > > - page = nth_page(page, offset >> PAGE_SHIFT); > + page += offset / PAGE_SIZE; Please keep the " >> PAGE_SHIFT" form. Is "offset" unsigned? Yes it is, But I had to look at the source code to make sure, because it wasn't locally obvious from the patch. And I'd rather we keep a pattern that is "safe", in that it doesn't generate strange code if the value might be a 's64' (eg loff_t) on 32-bit architectures. Because doing a 64-bit shift on x86-32 is like three cycles. Doing a 64-bit signed division by a simple constant is something like ten strange instructions even if the end result is only 32-bit. And again - not the case *here*, but just a general "let's keep to one pattern", and the shift pattern is simply the better choice. Linus