From patchwork Tue Nov 12 00:06:37 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11238349 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id EC48414E5 for ; Tue, 12 Nov 2019 00:11:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0D5421E6F for ; Tue, 12 Nov 2019 00:11:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="o9SF4xl6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727132AbfKLAHN (ORCPT ); Mon, 11 Nov 2019 19:07:13 -0500 Received: from hqemgate14.nvidia.com ([216.228.121.143]:10605 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726949AbfKLAHN (ORCPT ); Mon, 11 Nov 2019 19:07:13 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate14.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 11 Nov 2019 16:07:06 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 11 Nov 2019 16:07:04 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 11 Nov 2019 16:07:04 -0800 Received: from HQMAIL107.nvidia.com (172.20.187.13) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 12 Nov 2019 00:07:03 +0000 Received: from rnnvemgw01.nvidia.com (10.128.109.123) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3 via Frontend Transport; Tue, 12 Nov 2019 00:07:02 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Mon, 11 Nov 2019 16:07:02 -0800 From: John Hubbard To: Andrew Morton CC: Al Viro , Alex Williamson , Benjamin Herrenschmidt , =?utf-8?b?QmrDtnJuIFQ=?= =?utf-8?b?w7ZwZWw=?= , Christoph Hellwig , Dan Williams , Daniel Vetter , Dave Chinner , David Airlie , "David S . Miller" , Ira Weiny , Jan Kara , Jason Gunthorpe , Jens Axboe , Jonathan Corbet , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Magnus Karlsson , Mauro Carvalho Chehab , Michael Ellerman , Michal Hocko , Mike Kravetz , Paul Mackerras , Shuah Khan , Vlastimil Babka , , , , , , , , , , , , , LKML , John Hubbard Subject: [PATCH v3 00/23] mm/gup: track dma-pinned pages: FOLL_PIN, FOLL_LONGTERM Date: Mon, 11 Nov 2019 16:06:37 -0800 Message-ID: <20191112000700.3455038-1-jhubbard@nvidia.com> X-Mailer: git-send-email 2.24.0 MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1573517227; bh=JNzo7F9Uhd78yzMBde3KTfKR6QFKvOysu7c55VwbHak=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: MIME-Version:X-NVConfidentiality:Content-Type: Content-Transfer-Encoding; b=o9SF4xl64HRgEPHvkHoWRVd6NPoz/55me3p6LoD2kIji1LweghyUDktb6XSAQ3iJ3 cfhFxMryHc9DJrJcCIFZ3iGqYwt2ssscfuhFFw/XpSbJT58EIt8L9y6LerhnrPSHE3 EdEpFQ6NH4d8IOKai6LAR4Axw5mIKHuTnBygTtUlZdZPySg+d0A3Oy0fKaInMWyT9J SvANrkrJ9clhDPNVmeNO+XuHM5bjvqzzMZ/NiVknqIu7c9yXMCGlTlzlbPMzqDPBT5 jrQ55E6H2Wxm3RXAN8Ep0kb7yVwABixc+8zsJQbE9QB8LK08Q0+uUWO2trTbA96gmB /2JmtFtig54FQ== Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi, The cover letter is long, so the more important stuff is first: * Jason, if you or someone could look at the the VFIO cleanup (patch 8) and conversion to FOLL_PIN (patch 18), to make sure it's use of remote and longterm gup matches what we discussed during the review of v2, I'd appreciate it. * Also for Jason and IB: as noted below, in patch 11, I am (too?) boldly converting from put_user_pages() to release_pages(). * Jerome, I am going to take a look at doing your FOLL_GET change idea (some callers should set FOLL_GET) separately, because it blew up "a little bit" in my face. It's definitely a separate--tiny, but risky--project. It also looks more reasonable when applied on top of this series here (and it conflicts a lot), so I'm going to send it as a follow-up. Changes since v2: * Added a patch to convert IB/umem from normal gup, to gup_fast(). This is also posted separately, in order to hopefully get some runtime testing. * Changed the page devmap code to be a little clearer, thanks to Jerome for that. * Split out the page devmap changes into a separate patch (and moved Ira's Signed-off-by to that patch). * Fixed my bug in IB: ODP code does not require pin_user_pages() semantics. Therefore, revert the put_user_page() calls to put_page(), and leave the get_user_pages() call as-is. * As part of the revert, I am proposing here a change directly from put_user_pages(), to release_pages(). I'd feel better if someone agrees that this is the best way. It uses the more efficient release_pages(), instead of put_page() in a loop, and keep the change to just a few character on one line, but OTOH it is not a pure revert. * Loosened the FOLL_LONGTERM restrictions in the __get_user_pages_locked() implementation, and used that in order to fix up a VFIO bug. Thanks to Jason for that idea. * Note the use of release_pages() in IB: is that OK? * Added a few more WARN's and clarifying comments nearby. * Many documentation improvements in various comments. * Moved the new pin_user_pages.rst from Documentation/vm/ to Documentation/core-api/ . * Commit descriptions: added clarifying notes to the three patches (drm/via, fs/io_uring, net/xdp) that already had put_user_page() calls in place. * Collected all pending Reviewed-by and Acked-by tags, from v1 and v2 email threads. * Lot of churn from v2 --> v3, so it's possible that new bugs sneaked in. NOT DONE: separate patchset is required: * __get_user_pages_locked(): stop compensating for buggy callers who failed to set FOLL_GET. Instead, assert that FOLL_GET is set (and fail if it's not). ====================================================================== Original cover letter (edited to fix up the patch description numbers) This applies cleanly to linux-next and mmotm, and also to linux.git if linux-next's commit 20cac10710c9 ("mm/gup_benchmark: fix MAP_HUGETLB case") is first applied there. This provides tracking of dma-pinned pages. This is a prerequisite to solving the larger problem of proper interactions between file-backed pages, and [R]DMA activities, as discussed in [1], [2], [3], and in a remarkable number of email threads since about 2017. :) A new internal gup flag, FOLL_PIN is introduced, and thoroughly documented in the last patch's Documentation/vm/pin_user_pages.rst. I believe that this will provide a good starting point for doing the layout lease work that Ira Weiny has been working on. That's because these new wrapper functions provide a clean, constrained, systematically named set of functionality that, again, is required in order to even know if a page is "dma-pinned". In contrast to earlier approaches, the page tracking can be incrementally applied to the kernel call sites that, until now, have been simply calling get_user_pages() ("gup"). In other words, opt-in by changing from this: get_user_pages() (sets FOLL_GET) put_page() to this: pin_user_pages() (sets FOLL_PIN) put_user_page() Because there are interdependencies with FOLL_LONGTERM, a similar conversion as for FOLL_PIN, was applied. The change was from this: get_user_pages(FOLL_LONGTERM) (also sets FOLL_GET) put_page() to this: pin_longterm_pages() (sets FOLL_PIN | FOLL_LONGTERM) put_user_page() ============================================================ Patch summary: * Patches 1-8: refactoring and preparatory cleanup, independent fixes * Patch 9: introduce pin_user_pages(), FOLL_PIN, but no functional changes yet * Patches 10-15: Convert existing put_user_page() callers, to use the new pin*() * Patch 16: Activate tracking of FOLL_PIN pages. * Patches 17-19: convert FOLL_LONGTERM callers * Patches: 20-22: gup_benchmark and run_vmtests support * Patch 23: enforce FOLL_LONGTERM as a gup-internal (only) flag ============================================================ Testing: * I've done some overall kernel testing (LTP, and a few other goodies), and some directed testing to exercise some of the changes. And as you can see, gup_benchmark is enhanced to exercise this. Basically, I've been able to runtime test the core get_user_pages() and pin_user_pages() and related routines, but not so much on several of the call sites--but those are generally just a couple of lines changed, each. Not much of the kernel is actually using this, which on one hand reduces risk quite a lot. But on the other hand, testing coverage is low. So I'd love it if, in particular, the Infiniband and PowerPC folks could do a smoke test of this series for me. Also, my runtime testing for the call sites so far is very weak: * io_uring: Some directed tests from liburing exercise this, and they pass. * process_vm_access.c: A small directed test passes. * gup_benchmark: the enhanced version hits the new gup.c code, and passes. * infiniband (still only have crude "IB pingpong" working, on a good day: it's not exercising my conversions at runtime...) * VFIO: compiles (I'm vowing to set up a run time test soon, but it's not ready just yet) * powerpc: it compiles... * drm/via: compiles... * goldfish: compiles... * net/xdp: compiles... * media/v4l2: compiles... ============================================================ Next: * Get the block/bio_vec sites converted to use pin_user_pages(). * Work with Ira and Dave Chinner to weave this together with the layout lease stuff. ============================================================ [1] Some slow progress on get_user_pages() (Apr 2, 2019): https://lwn.net/Articles/784574/ [2] DMA and get_user_pages() (LPC: Dec 12, 2018): https://lwn.net/Articles/774411/ [3] The trouble with get_user_pages() (Apr 30, 2018): https://lwn.net/Articles/753027/ John Hubbard (23): mm/gup: pass flags arg to __gup_device_* functions mm/gup: factor out duplicate code from four routines mm/gup: move try_get_compound_head() to top, fix minor issues mm: devmap: refactor 1-based refcounting for ZONE_DEVICE pages goldish_pipe: rename local pin_user_pages() routine IB/umem: use get_user_pages_fast() to pin DMA pages media/v4l2-core: set pages dirty upon releasing DMA buffers vfio, mm: fix get_user_pages_remote() and FOLL_LONGTERM mm/gup: introduce pin_user_pages*() and FOLL_PIN goldish_pipe: convert to pin_user_pages() and put_user_page() IB/{core,hw,umem}: set FOLL_PIN, FOLL_LONGTERM via pin_longterm_pages*() mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote() drm/via: set FOLL_PIN via pin_user_pages_fast() fs/io_uring: set FOLL_PIN via pin_user_pages() net/xdp: set FOLL_PIN via pin_user_pages() mm/gup: track FOLL_PIN pages media/v4l2-core: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion vfio, mm: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion powerpc: book3s64: convert to pin_longterm_pages() and put_user_page() mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1" mm/gup_benchmark: support pin_user_pages() and related calls selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage mm/gup: remove support for gup(FOLL_LONGTERM) Documentation/core-api/index.rst | 1 + Documentation/core-api/pin_user_pages.rst | 218 +++++++ arch/powerpc/mm/book3s64/iommu_api.c | 15 +- drivers/gpu/drm/via/via_dmablit.c | 2 +- drivers/infiniband/core/umem.c | 17 +- drivers/infiniband/core/umem_odp.c | 24 +- drivers/infiniband/hw/hfi1/user_pages.c | 4 +- drivers/infiniband/hw/mthca/mthca_memfree.c | 3 +- drivers/infiniband/hw/qib/qib_user_pages.c | 8 +- drivers/infiniband/hw/qib/qib_user_sdma.c | 2 +- drivers/infiniband/hw/usnic/usnic_uiom.c | 9 +- drivers/infiniband/sw/siw/siw_mem.c | 5 +- drivers/media/v4l2-core/videobuf-dma-sg.c | 10 +- drivers/platform/goldfish/goldfish_pipe.c | 35 +- drivers/vfio/vfio_iommu_type1.c | 35 +- fs/io_uring.c | 5 +- include/linux/mm.h | 164 +++++- include/linux/mmzone.h | 2 + include/linux/page_ref.h | 10 + mm/gup.c | 608 ++++++++++++++++---- mm/gup_benchmark.c | 87 ++- mm/huge_memory.c | 54 +- mm/hugetlb.c | 39 +- mm/memremap.c | 67 +-- mm/process_vm_access.c | 28 +- mm/vmstat.c | 2 + net/xdp/xdp_umem.c | 4 +- tools/testing/selftests/vm/gup_benchmark.c | 34 +- tools/testing/selftests/vm/run_vmtests | 22 + 29 files changed, 1180 insertions(+), 334 deletions(-) create mode 100644 Documentation/core-api/pin_user_pages.rst