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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id p64sm554108pfi.56.2019.02.13.15.11.10 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Feb 2019 15:11:10 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1gu3gM-0001M9-5y; Wed, 13 Feb 2019 16:11:10 -0700 Date: Wed, 13 Feb 2019 16:11:10 -0700 From: Jason Gunthorpe To: ira.weiny@intel.com Cc: linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, kvm@vger.kernel.org, linux-fpga@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-scsi@vger.kernel.org, devel@driverdev.osuosl.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-fbdev@vger.kernel.org, xen-devel@lists.xenproject.org, devel@lists.orangefs.org, linux-mm@kvack.org, ceph-devel@vger.kernel.org, rds-devel@oss.oracle.com, John Hubbard , David Hildenbrand , Cornelia Huck , Yoshinori Sato , Rich Felker , "David S. Miller" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Joerg Roedel , Wu Hao , Alan Tull , Moritz Fischer , David Airlie , Daniel Vetter , Dennis Dalessandro , Christian Benvenuti , Mauro Carvalho Chehab , Matt Porter , Alexandre Bounine , Kai =?utf-8?B?TcOka2lzYXJh?= , "James E.J. Bottomley" , "Martin K. Petersen" , Rob Springer , Todd Poynor , Ben Chan , Jens Wiklander , Alex Williamson , "Michael S. Tsirkin" , Jason Wang , Bartlomiej Zolnierkiewicz , Stefano Stabellini , Martin Brandenburg , Peter Zijlstra , Alexander Viro , Andrew Morton , Michal Hocko , "Kirill A. Shutemov" Subject: Re: [PATCH V2 3/7] mm/gup: Change GUP fast to use flags rather than a write 'bool' Message-ID: <20190213231110.GD24692@ziepe.ca> References: <20190211201643.7599-1-ira.weiny@intel.com> <20190213230455.5605-1-ira.weiny@intel.com> <20190213230455.5605-4-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190213230455.5605-4-ira.weiny@intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) 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: On Wed, Feb 13, 2019 at 03:04:51PM -0800, ira.weiny@intel.com wrote: > From: Ira Weiny > > To facilitate additional options to get_user_pages_fast() change the > singular write parameter to be gup_flags. So now we have: long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, struct page **pages, unsigned int gup_flags); and int get_user_pages_fast(unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages) Does this make any sense? At least the arguments should be in the same order, I think. Also this comment: /* * get_user_pages_unlocked() is suitable to replace the form: * * down_read(&mm->mmap_sem); * get_user_pages(tsk, mm, ..., pages, NULL); * up_read(&mm->mmap_sem); * * with: * * get_user_pages_unlocked(tsk, mm, ..., pages); * * It is functionally equivalent to get_user_pages_fast so * get_user_pages_fast should be used instead if specific gup_flags * (e.g. FOLL_FORCE) are not required. */ Needs some attention as the recommendation is now nonsense. Honestly a proper explanation of why two functions exist would be great at this point :) Jason