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dkim=pass header.d=Nvidia.com header.s=selector2 header.b="GXbe1Yw/"; spf=none (imf31.hostedemail.com: domain of jhubbard@nvidia.com has no SPF policy when checking 40.107.94.41) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com X-HE-Tag: 1646018986-890227 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 2/27/22 14:15, Al Viro wrote: > On Sun, Feb 27, 2022 at 01:34:31AM -0800, jhubbard.send.patches@gmail.com wrote: >> From: John Hubbard >> >> Upcoming changes to Direct IO will change it from acquiring pages via >> get_user_pages_fast(), to calling pin_user_pages_fast() instead. >> >> Place a few assertions at key points, that the pages are IOVEC (user >> pages), to enforce the assumptions that there are no kernel or pipe or >> other odd variations being passed. > > Umm... And what should happen when O_DIRECT file gets passed to splice()? OK, right, this is not going to work as-is. Any of the remaining iov_iter_get_pages*() callers that do direct IO (vmsplice, ceph, ...) will end up calling bio_release_pages(), which is now unconditionally calling unpin_user_pages(). So this is just completely broken. And so, once again, I'm back to, "must convert the whole pile of iov_iter_get_page*() callers at once". Back to the drawing board. thanks, -- John Hubbard NVIDIA