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([2620:10d:c092:600::1:6e9b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45e6a135f0csm17325957f8f.27.2026.05.18.02.24.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 May 2026 02:24:40 -0700 (PDT) Message-ID: <4b2f74e9-3225-47f6-85fe-911720030e35@gmail.com> Date: Mon, 18 May 2026 10:24:35 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/10] iov_iter: add iterator type for dmabuf maps To: David Laight Cc: Jens Axboe , Keith Busch , Christoph Hellwig , Sagi Grimberg , Alexander Viro , Christian Brauner , Andrew Morton , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , 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 References: <20a233d2f35274817aa643cc0fe113707eb47e72.1777475843.git.asml.silence@gmail.com> <20260513110557.705bdeed@pumpkin> <20260513142909.03ae6c2b@pumpkin> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20260513142909.03ae6c2b@pumpkin> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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? >> This could be fixed by either making iter_type a bitmask (with one bit set) Not going to do that. It was specifically converted from bitmask before, and the check optimisations like this were voiced back than. >> 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)) ... -- Pavel Begunkov