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Fri, 1 Nov 2019 11:48:41 +1100 (AEDT) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 31 Oct 2019 17:48:43 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 31 Oct 2019 17:48:37 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 31 Oct 2019 17:48:37 -0700 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 1 Nov 2019 00:48:36 +0000 Subject: Re: [PATCH 19/19] Documentation/vm: add pin_user_pages.rst To: Ira Weiny References: <20191030224930.3990755-1-jhubbard@nvidia.com> <20191030224930.3990755-20-jhubbard@nvidia.com> <20191031234922.GM14771@iweiny-DESK2.sc.intel.com> X-Nvconfidentiality: public From: John Hubbard Message-ID: <8f92713c-7df8-9463-93f2-40967eba27b5@nvidia.com> Date: Thu, 31 Oct 2019 17:48:36 -0700 User-Agent: Mozilla/5.0 (X11; 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Miller" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 10/31/19 4:49 PM, Ira Weiny wrote: > On Wed, Oct 30, 2019 at 03:49:30PM -0700, John Hubbard wrote: ... >> +TODO: There is also a special case when the pages are DAX pages: in addition to >> +the above flags, the caller needs something like a layout lease on the >> +associated file. This is yet to be implemented. When it is implemented, it's >> +expected that the lease will be a prerequisite to setting FOLL_LONGTERM. > > For now we probably want to leave this note out until we figure out how this is > going to work. Best to say something like: > > Some pages, such as DAX pages, can't be pinned with longterm pins and will > fail. > OK, I have this wording queued up for the v2 patch: NOTE: Some pages, such as DAX pages, cannot be pinned with longterm pins. That's because DAX pages do not have a separate page cache, and so "pinning" implies locking down file system blocks, which is not (yet) supported in that way. thanks, John Hubbard NVIDIA