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[142.162.115.133]) by smtp.gmail.com with ESMTPSA id h75sm91222qke.130.2021.01.11.08.05.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Jan 2021 08:05:49 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kyzhV-005YPG-0o; Mon, 11 Jan 2021 12:05:49 -0400 Date: Mon, 11 Jan 2021 12:05:49 -0400 From: Jason Gunthorpe To: John Hubbard Cc: Linus Torvalds , Andrea Arcangeli , Andrew Morton , Linux-MM , Linux Kernel Mailing List , Yu Zhao , Andy Lutomirski , Peter Xu , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Peter Zijlstra , Hugh Dickins , "Kirill A. Shutemov" , Matthew Wilcox , Oleg Nesterov , Jann Horn , Kees Cook , Leon Romanovsky , Jan Kara , Kirill Tkhai , Nadav Amit , Jens Axboe Subject: Re: [PATCH 0/1] mm: restore full accuracy in COW page reuse Message-ID: <20210111160549.GN504133@ziepe.ca> References: <20210110004435.26382-1-aarcange@redhat.com> <45806a5a-65c2-67ce-fc92-dc8c2144d766@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45806a5a-65c2-67ce-fc92-dc8c2144d766@nvidia.com> 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 Sun, Jan 10, 2021 at 11:26:57PM -0800, John Hubbard wrote: > So: > > FOLL_PIN: would use DMA_PIN_COUNTING_BIAS to increment page refcount. > These are long term pins for dma. > > FOLL_GET: would use GUP_PIN_COUNTING_BIAS to increment page refcount. > These are not long term pins. Do we have any places yet that care about the long-term-ness? The only place long term would matter is if something is waiting for the page ref count to drop. Jason