From patchwork Sat Feb 1 03:40:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Hubbard X-Patchwork-Id: 11360919 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 89B03139A for ; Sat, 1 Feb 2020 03:41:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5E238207FD for ; Sat, 1 Feb 2020 03:41:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="rgUsJVjr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727077AbgBADl3 (ORCPT ); Fri, 31 Jan 2020 22:41:29 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:4444 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727035AbgBADkh (ORCPT ); Fri, 31 Jan 2020 22:40:37 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Fri, 31 Jan 2020 19:39:40 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Fri, 31 Jan 2020 19:40:34 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Fri, 31 Jan 2020 19:40:34 -0800 Received: from HQMAIL107.nvidia.com (172.20.187.13) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Sat, 1 Feb 2020 03:40:33 +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; Sat, 1 Feb 2020 03:40:33 +0000 Received: from blueforge.nvidia.com (Not Verified[10.110.48.28]) by rnnvemgw01.nvidia.com with Trustwave SEG (v7,5,8,10121) id ; Fri, 31 Jan 2020 19:40:33 -0800 From: John Hubbard To: Andrew Morton CC: Al Viro , Christoph Hellwig , Dan Williams , Dave Chinner , Ira Weiny , Jan Kara , Jason Gunthorpe , Jonathan Corbet , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , "Kirill A . Shutemov" , Michal Hocko , Mike Kravetz , Shuah Khan , Vlastimil Babka , Matthew Wilcox , , , , , , LKML , John Hubbard Subject: [PATCH v3 00/12] mm/gup: track FOLL_PIN pages Date: Fri, 31 Jan 2020 19:40:17 -0800 Message-ID: <20200201034029.4063170-1-jhubbard@nvidia.com> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 X-NVConfidentiality: public DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1580528381; bh=PVjdhcWaJdJZJP6YMEesi4FW/EBC/lWrMURT82TytPs=; h=X-PGP-Universal:From:To:CC:Subject:Date:Message-ID:X-Mailer: MIME-Version:X-NVConfidentiality:Content-Type: Content-Transfer-Encoding; b=rgUsJVjrMtF/vDQ9D6u7i/0jWNgq1QgB9vY6QI5zxOn0DrWTp8CRHWzeekJj8yxgN SyF4PMu4YShgVsbHZOg3nwe7j5dIX/q5+5Ey3yISV+1nqSXqrMBnfueby8qIsiAOvc KdQ5dXLYcNByywkRlLqsim0w5EdAwsUaJf41Gzahn6iQ20V5v39zD76cEt0ro50Akx d6NqgdH5PYqQFZNLTdlc9SZtjbV30GeMV3Tu0ZhSe9mK2GZ5kAPLy4+c8AgQsYkuF3 jm0InwaQ5rz1fw3tqyAMEklG/n2XVcDsgBRk4JI16MULBFHuu+PgtKNv7JoAp02bMs D+HrOKQpLlQew== Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org Matthew, I've merged in your dump_page() ideas, and also factored things out into a new __dump_tail_page() routine, in order to save a few indentation levels, mainly. Kirill, thanks for your review comments. I've applied them, and I think splitting this up as you recommended really makes it a lot better, and easier to spot problems. ============================================================ Changes since v2: * Rebased onto linux.git, because the akpm tree for 5.6 has been merged. * Split the tracking patch into even more patches, as requested. * Merged Matthew Wilcox's dump_page() changes into mine, as part of the first patch. * Renamed: page_dma_pinned() --> page_maybe_dma_pinned(), in response to Kirill Shutemov's review. * Moved a WARN to the top of a routine, and fixed a typo in the commit description of patch #7, also as suggested by Kirill. ============================================================ Changes since v1: * Split the tracking patch into 6 smaller patches * Rebased onto today's linux-next/akpm (there weren't any conflicts). * Fixed an "unsigned int" vs. "int" problem in gup_benchmark, reported by Nathan Chancellor. (I don't see it in my local builds, probably because they use gcc, but an LLVM test found the mismatch.) * Fixed a huge page pincount problem (add/subtract vs. increment/decrement), spotted by Jan Kara. ============================================================ There is a reasonable case to be made for merging two of the patches (patches 4 and 5), given that patch 4 provides tracking that has upper limits on the number of pins that can be done with huge pages. Let me know if anyone wants those merged, but unless there is some weird chance of someone grabbing patch 4 and not patch 5, I don't really see the need. Meanwhile, it's easier to review in this form. Also, patch 3 has been revived. Earlier reviewers asked for it to be merged into the tracking patch (one cannot please everyone, heh), but now it's back out on it's own. This activates tracking of FOLL_PIN pages. This is in support of fixing the get_user_pages()+DMA problem described in [1]-[4]. It is based on today's (Jan 28) linux-next (branch: akpm), commit 280e9cb00b41 ("drivers/media/platform/sti/delta/delta-ipc.c: fix read buffer overflow") There is a git repo and branch, for convenience in reviewing: git@github.com:johnhubbard/linux.git track_user_pages_v2_linux-next_akpm_28Jan2020 FOLL_PIN support is (so far) in mmotm and linux-next. However, the patch to use FOLL_PIN to track pages was *not* submitted, because Leon saw an RDMA test suite failure that involved (I think) page refcount overflows when huge pages were used. This patch definitively solves that kind of overflow problem, by adding an exact pincount, for compound pages (of order > 1), in the 3rd struct page of a compound page. If available, that form of pincounting is used, instead of the GUP_PIN_COUNTING_BIAS approach. Thanks again to Jan Kara for that idea. Here's the last reviewed version of the tracking patch (v11): https://lore.kernel.org/r/20191216222537.491123-1-jhubbard@nvidia.com Jan Kara had provided a reviewed-by tag for that, but I've had to remove it (again) here, due to having changed the patch "a little bit", in order to add the feature described above. Other interesting changes: * dump_page(): added one, or two new things to report for compound pages: head refcount (for all compound pages), and map_pincount (for compound pages of order > 1). * Documentation/core-api/pin_user_pages.rst: removed the "TODO" for the huge page refcount upper limit problems, and added notes about how it works now. Also added a note about the dump_page() enhancements. * Added some comments in gup.c and mm.h, to explain that there are two ways to count pinned pages: exact (for compound pages of order > 1) and fuzzy (GUP_PIN_COUNTING_BIAS: for all other pages). ============================================================ General notes about the tracking patch: This is a prerequisite to solving the problem of proper interactions between file-backed pages, and [R]DMA activities, as discussed in [1], [2], [3], [4] and in a remarkable number of email threads since about 2017. :) 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) unpin_user_page() ============================================================ Next steps: * Convert more subsystems from get_user_pages() to pin_user_pages(). * Work with Ira and others to connect this all up with file system leases. [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/ [4] LWN kernel index: get_user_pages() https://lwn.net/Kernel/Index/#Memory_management-get_user_pages John Hubbard (12): mm: dump_page(): better diagnostics for compound pages mm/gup: split get_user_pages_remote() into two routines mm/gup: pass a flags arg to __gup_device_* functions mm: introduce page_ref_sub_return() mm/gup: pass gup flags to two more routines mm/gup: require FOLL_GET for get_user_pages_fast() mm/gup: track FOLL_PIN pages mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages mm: dump_page(): better diagnostics for huge pinned pages mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting mm/gup_benchmark: support pin_user_pages() and related calls selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage Documentation/core-api/pin_user_pages.rst | 53 +-- include/linux/mm.h | 108 ++++- include/linux/mm_types.h | 7 +- include/linux/mmzone.h | 2 + include/linux/page_ref.h | 10 + mm/debug.c | 60 ++- mm/gup.c | 459 ++++++++++++++++----- mm/gup_benchmark.c | 71 +++- mm/huge_memory.c | 29 +- mm/hugetlb.c | 44 +- mm/page_alloc.c | 2 + mm/rmap.c | 6 + mm/vmstat.c | 2 + tools/testing/selftests/vm/gup_benchmark.c | 15 +- tools/testing/selftests/vm/run_vmtests | 22 + 15 files changed, 715 insertions(+), 175 deletions(-)