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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4549120ec0asm40068578f8f.17.2026.05.13.06.29.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 06:29:11 -0700 (PDT) Date: Wed, 13 May 2026 14:29:09 +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: <20260513142909.03ae6c2b@pumpkin> In-Reply-To: <20260513110557.705bdeed@pumpkin> References: <20a233d2f35274817aa643cc0fe113707eb47e72.1777475843.git.asml.silence@gmail.com> <20260513110557.705bdeed@pumpkin> 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-20260513_062914_014853_39591041 X-CRM114-Status: GOOD ( 15.16 ) 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 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? > This could be fixed by either making iter_type a bitmask (with one bit set) > 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) int foo(void *); int f(struct iov_iter *i) { return ITER_IS_ONE_OF(i, UBUF, KVEC) ? foo(i) : 0; } See https://godbolt.org/z/sMz93zah1 Pasting ITER_ on the front ensures the values are constants of the right type. OTOH it makes it harder to search for uses of each type. You could paste _ITER_ on the front, elsewhere define _ITER_ITER_UVEC to be ITER_UVEC (etc), and require the caller use the full name. -- David