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Tue, 13 Aug 2024 09:08:35 -0700 (PDT) Received: from ziepe.ca ([128.77.69.90]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a4c7e11130sm352658285a.125.2024.08.13.09.08.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Aug 2024 09:08:34 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1sdu18-008Iyi-0q; Tue, 13 Aug 2024 13:05:02 -0300 Date: Tue, 13 Aug 2024 13:05:02 -0300 From: Jason Gunthorpe To: Christoph Hellwig Cc: Martin Oliveira , linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Artemy Kovalyov , Greg Kroah-Hartman , Leon Romanovsky , Logan Gunthorpe , Michael Guralnik , Mike Marciniszyn , Shiraz Saleem , Tejun Heo , John Hubbard , Dan Williams , David Sloan Subject: Re: [PATCH v5 3/4] mm/gup: allow FOLL_LONGTERM & FOLL_PCI_P2PDMA Message-ID: <20240813160502.GH1985367@ziepe.ca> References: <20240808183340.483468-1-martin.oliveira@eideticom.com> <20240808183340.483468-4-martin.oliveira@eideticom.com> <20240812231249.GG1985367@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: k3659pa1nmfb5ouwimbqtpthqqosywpn X-Rspamd-Queue-Id: DF13E40025 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1723565316-114640 X-HE-Meta: U2FsdGVkX19cKjaVmiJAVjJT5hHnJojpMaPme1vPoke9eb2oWDva5NKr14HomF2ruhHzLuQ+a2xOeHPzsiHGmD50ZoGqfyFc1z4WI+Fl7SSXt/U0pF9zBMr3uBouoa/qV6dF+dHK/+F5T0HFLum5Tj2/HhLln971+9Cgb0uNcwu+DmutdluUwq8ICOah/JKriYbYgo3Zj35DAan8EOH7O1g9iSdionDFtu+glPXO26VDwBBsdQj9ed2miIo55mrwBBrXD0+pThcznxqjb4PWjf+4K5396CvxMPEHyaRF2OewVTi6Wb8ee3oeF8ZH/2eNYFelorlFVCz+Z+idPi2Zr2hk5aZbxotFABrHZwc/cHNhXoM9kao7CKDp7uUP6VnXq15dEfofI4bEcbqqkrC46DweZwodLZDhBUSB458/WjNROFWTS1KC2x0Uu0iFEz/4bETIe2dBBRG/3Hhoi081/LCgsERWZUk6k5ZV0iwWpkgU+sQBbv1E7ocUiKVM35L4TNhgalIYtK8YRXLkffqqhTkFh4EBFrVshmarFPu5GCtuYhC0xdksWAYuFSwe5Iy2Oi630v0nJIWhnPBP/xzhCt7G/JFKY1DpWdup6YdvdNpUNcsPbBFBJaYhTsOCbQxspNPC7/cC0GIsriZ2zg2y7NNzBgCZhQ7UR0zHv13XpDRAPdMKmZ+iKTQURnmj7TLYn8aphnxR0wV17aIJlCpampxxeetWGHE4pYE6l6nAbGgo1XSYA96rrQ9/H5WA3qi7Ku+18k+q/e8W66AtimJAySIRt28duDkp66yI6vzArXSM8p4AHTc1XN+F6kgPWtGhSgCZqVG7wIVjfua9I3AWMvlXmRiTc2vaU6s9fIWPMq3g+RQ2s+Kf4/lRWgkw0QD3XLK/ZlCGQ5MVWxx2EXFFW3wSmVEpVx3PFdX2UKmT7Ygh6ecAMboBXkzxTaq5we33BJYOpnKx/rplug9kiRG 7YXaURxa OTrNNQx5XiVMbaj7No//yflPlUZfh9k8chsfO54JhueSTO5S1Lm7V+lTbY79FvDAR502St7ZS1jjuqL0jSLZmO+BpZK846u3mSFie0Ptgpi869o/D/xrA1U0CqhUbp/FrD4huO8uaWTklVXzuz9hjIx2DJnxS9Az6RdLbl96/kSmha/iNeQL+dK8GR37fSHOFZvkiDi1yIFNZzZlHtnoJa0fGYWythQfLbBZoh+j5k4uG3Bl56bgD3t1SxZ0KPCMH6wgYJJ0QpIT83xyWFKUJICKAYAbXPyozcxqyU+SC5Z4byHz4pxgHc8Z3KA== 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: List-Subscribe: List-Unsubscribe: On Mon, Aug 12, 2024 at 10:41:20PM -0700, Christoph Hellwig wrote: > On Mon, Aug 12, 2024 at 08:12:49PM -0300, Jason Gunthorpe wrote: > > > This is unfortunately not really minor unless we have a well documented > > > way to force this :( > > > > It is not that different from blocking driver unbind while FDs are > > open which a lot of places do in various ways? > > Where do we block driver unbind with an open resource? I keep seeing it in different subsystems, safe driver unbind is really hard. :\ eg I think VFIO has some waits in it > The whole concept is that open resources will pin the in-memory > object (and modulo for a modular driver), but never an unbind or > hardware unplug, of which unbind really just is a simulation. Yes, ideally, but not every part of the kernel hits that ideal in my experience. It is alot of work and some places don't have any good solutions, like here. Jason