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Wed, 13 Nov 2019 12:08:17 +1100 (AEDT) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate14.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 12 Nov 2019 17:08:11 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 12 Nov 2019 17:08:08 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 12 Nov 2019 17:08:08 -0800 Received: from MacBook-Pro-10.local (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 13 Nov 2019 01:08:07 +0000 Subject: Re: [PATCH v3 08/23] vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM To: Dan Williams , Jason Gunthorpe References: <20191112000700.3455038-1-jhubbard@nvidia.com> <20191112000700.3455038-9-jhubbard@nvidia.com> <20191112204338.GE5584@ziepe.ca> <0db36e86-b779-01af-77e7-469af2a2e19c@nvidia.com> <20191112234250.GA19615@ziepe.ca> From: John Hubbard X-Nvconfidentiality: public Message-ID: <28355eb0-4ee5-3418-b430-59302d15b478@nvidia.com> Date: Tue, 12 Nov 2019 17:08:07 -0800 User-Agent: Mozilla/5.0 (Macintosh; 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Miller" , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11/12/19 4:58 PM, Dan Williams wrote: ... >>> It's not redundant relative to upstream which does not do anything the >>> FOLL_LONGTERM in the gup-slow path... but I have not looked at patches >>> 1-7 to see if something there made it redundant. >> >> Oh, the hunk John had below for get_user_pages_remote() also needs to >> call __gup_longterm_locked() when FOLL_LONGTERM is specified, then >> that calls check_dax_vmas() which duplicates the vma_is_fsdax() check >> above. > > Oh true, good eye. It is redundant if it does additionally call > __gup_longterm_locked(), and it needs to do that otherwises it undoes > the CMA migration magic that Aneesh added. > OK. So just to be clear, I'll be removing this from the patch: /* * The lifetime of a vaddr_get_pfn() page pin is * userspace-controlled. In the fs-dax case this could * lead to indefinite stalls in filesystem operations. * Disallow attempts to pin fs-dax pages via this * interface. */ if (ret > 0 && vma_is_fsdax(vmas[0])) { ret = -EOPNOTSUPP; put_page(page[0]); } (and the declaration of "vmas", as well). thanks, -- John Hubbard NVIDIA