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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fe4c90b27sm255713955e9.8.2026.05.18.03.40.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 03:40:12 -0700 (PDT) Date: Mon, 18 May 2026 11:40:10 +0100 From: David Laight To: Pavel Begunkov Cc: Jens Axboe , Keith Busch , Christoph Hellwig , Sagi Grimberg , Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , Christian =?UTF-8?B?S8O2bmln?= , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Nitesh Shetty , Kanchan Joshi , Anuj Gupta , Tushar Gohad , William Power , Phil Cayton , Jason Gunthorpe Subject: Re: [PATCH v3 02/10] iov_iter: add iterator type for dmabuf maps Message-ID: <20260518114010.6e1f7391@pumpkin> In-Reply-To: <4b2f74e9-3225-47f6-85fe-911720030e35@gmail.com> References: <20a233d2f35274817aa643cc0fe113707eb47e72.1777475843.git.asml.silence@gmail.com> <20260513110557.705bdeed@pumpkin> <20260513142909.03ae6c2b@pumpkin> <4b2f74e9-3225-47f6-85fe-911720030e35@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260518_114014_681346_FFE0AB56 X-CRM114-Status: GOOD ( 18.49 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Mon, 18 May 2026 10:24:35 +0100 Pavel Begunkov wrote: > On 5/13/26 14:29, David Laight wrote: > > On Wed, 13 May 2026 11:05:57 +0100 > > David Laight wrote: > > > > ... > >>> @@ -575,7 +575,8 @@ void iov_iter_advance(struct iov_iter *i, size_t size) > >>> { > >>> if (unlikely(i->count < size)) > >>> size = i->count; > >>> - if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) { > >>> + if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i)) || > >>> + unlikely(iov_iter_is_dmabuf_map(i))) { > >> > >> > >> Doesn't the extra check add more code to all the non-ubuf cases? ... > >> or writing an iter_is_one_of(i, ITER_xxx, ITER_yyy) define that uses > >> '(1 << i->iter_type) & ((1 << ITER_xxx) | ...)' > > > > This seems to DTRT: > > > > #define _ITER_IS_ONE_OF(iter, t1, t2, t3, t4, t5, t6, t7, t8, ...) \ > > ((1u << (iter)->iter_type) & ((1u << ITER_##t1) | (1u << ITER_##t2) | \ > > (1u << ITER_##t3) | (1u << ITER_##t4) | (1u << ITER_##t5) | \ > > (1u << ITER_##t6) | (1u << ITER_##t7) | (1u << ITER_##t8))) > > #define ITER_IS_ONE_OF(iter, t, ...) \ > > _ITER_IS_ONE_OF(iter, t, ## __VA_ARGS__, t, t, t, t, t, t, t) > > We definitely don't want that, using them directly would've been > much cleaner. > > if (get_type_mask(i) & (TYPE1 | TYPE2)) ... You need to shift all the TYPEn as well. The above condition would become: if (likely(ITER_IS_ONE_OF(i, UBUF, XARRAY, DMABUF_MAP))) { which reads reasonable well. Without the token pasting it becomes: if (likely(ITER_IS_ONE_OF(i, ITER_UBUF, ITER_XARRAY, ITER_DMABUF_MAP))) { and the line starts getting long. Although that version probably needs a check that the mask is constant. -- David >