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[72.132.29.68]) by smtp.gmail.com with ESMTPSA id f9-20020a056a00228900b004f3ba7d177csm10816506pfe.54.2022.02.27.13.57.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 27 Feb 2022 13:57:45 -0800 (PST) Message-ID: <06469550-a679-145f-b16e-2f1ffc0b07af@kernel.dk> Date: Sun, 27 Feb 2022 14:57:43 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH 2/6] iov_iter: new iov_iter_pin_pages*(), for FOLL_PIN pages Content-Language: en-US To: jhubbard.send.patches@gmail.com, Jan Kara , Christoph Hellwig , Dave Chinner , "Darrick J . Wong" , Theodore Ts'o , Alexander Viro , Miklos Szeredi , Andrew Morton , Chaitanya Kulkarni Cc: linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, LKML , John Hubbard References: <20220227093434.2889464-1-jhubbard@nvidia.com> <20220227093434.2889464-3-jhubbard@nvidia.com> From: Jens Axboe In-Reply-To: <20220227093434.2889464-3-jhubbard@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: bz98s9jxwzedrijb8619htc7nm1brfsz Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel-dk.20210112.gappssmtp.com header.s=20210112 header.b=a+VXPxxt; spf=pass (imf21.hostedemail.com: domain of axboe@kernel.dk designates 209.85.215.178 as permitted sender) smtp.mailfrom=axboe@kernel.dk; dmarc=none X-Rspamd-Queue-Id: ECE821C000E X-HE-Tag: 1645999066-306609 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > +ssize_t iov_iter_pin_pages(struct iov_iter *i, > + struct page **pages, size_t maxsize, unsigned int maxpages, > + size_t *start) > +{ > + size_t len; > + int n, res; > + > + if (maxsize > i->count) > + maxsize = i->count; > + if (!maxsize) > + return 0; > + > + WARN_ON_ONCE(!iter_is_iovec(i)); > + > + if (likely(iter_is_iovec(i))) { > + unsigned int gup_flags = 0; > + unsigned long addr; > + > + if (iov_iter_rw(i) != WRITE) > + gup_flags |= FOLL_WRITE; > + if (i->nofault) > + gup_flags |= FOLL_NOFAULT; > + > + addr = first_iovec_segment(i, &len, start, maxsize, maxpages); > + n = DIV_ROUND_UP(len, PAGE_SIZE); > + res = pin_user_pages_fast(addr, n, gup_flags, pages); > + if (unlikely(res <= 0)) > + return res; > + return (res == n ? len : res * PAGE_SIZE) - *start; Trying to be clever like that just makes the code a lot less readable. I should not have to reason about a return value. Same in the other function. -- Jens Axboe