From patchwork Thu Apr 8 23:43:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12192623 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-21.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A941C43460 for ; Thu, 8 Apr 2021 23:43:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 76E7961182 for ; Thu, 8 Apr 2021 23:43:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232958AbhDHXnp (ORCPT ); Thu, 8 Apr 2021 19:43:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60564 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232426AbhDHXno (ORCPT ); Thu, 8 Apr 2021 19:43:44 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87852C061761 for ; Thu, 8 Apr 2021 16:43:32 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id k199so846264ybf.0 for ; Thu, 08 Apr 2021 16:43:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=MMnSfhCYkJZSRWP1+VLEqWOrqNUR73/DviRG9AOZLYg=; b=LhtDACmTgYbILTXL6/+EJFHaBuo+F2p051TBe72ztRCJ/XuVlbOpF83dWSLIbhG0oQ GGmcsOgA+kZKXmwoFtXhjQTwzOcRfi4NmApAdGqItqYY3p++w2Lc8PEkxLQzNAHVFDRZ Zu62dFCr11fqBsLN9jtEqkEX/RBHZ8OSUys346b0rqnQVvQx3YGb+p8dbGTrpgW5sqRO /MPBCQgKAKarc4pQ62sMIrf20lQE6Cy0CZdxWXfuPVVA6KjaILStlTn/OyHIq59gQsLh 3X6pANiICUh8jPl3ZM0H6y/ZyR9wuYc/YpF7zeWO9c5muLoNzZfoallNAUjAx4LUS3x4 ReYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=MMnSfhCYkJZSRWP1+VLEqWOrqNUR73/DviRG9AOZLYg=; b=YWKTIgZHMs81tkFUPBK6jdvBWe/hmkmDJ1Jfltm4emv0trCniSm/frR11rv3WeKUiS rBIlV63vCNUyc5PIUCKmvmPcA85i1zF7wUgTyfB4E+J2gC6gWYlejAqOaBn7NvM4W2Vw ufhwNQVwmtrcbnHPkM5C3QORhNWhprWBXwI3YV3ampo+bTlPQaheGpYyrbOrFLjRHWpP xdizjH5Ra3glCHlxcJcrSAcyopUEbOO0lSPuVaxwg7yD7gFRCEQHIkcMCg1efzmCg9rC U3X6UmgBlqMorG1BdDPHka5AJZJse+RdiMn/tUfzxiVbPaUqRKGb4jKz7iZv4KVYuV50 W8ww== X-Gm-Message-State: AOAM5325HgyxTrz9KtOtRTRkNuduSDQf12aMZF3LK21y/Pt3bn0KOIEB uu3DgwfRpRsWfS8UZiHNbJEdMH4Qe4YpOAjW4FfF X-Google-Smtp-Source: ABdhPJzkp9CEYUxHFGCgud8buw3fO/a/mBZ0krmDrBQMygLKQty7cBNK28FOPd8XyjX019sQC1OyXtn3hc4fzeu703AT X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:3d06:d00f:a626:675a]) (user=axelrasmussen job=sendgmr) by 2002:a25:adc2:: with SMTP id d2mr16351457ybe.334.1617925411786; Thu, 08 Apr 2021 16:43:31 -0700 (PDT) Date: Thu, 8 Apr 2021 16:43:18 -0700 Message-Id: <20210408234327.624367-1-axelrasmussen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.31.1.295.g9ea45b61b8-goog Subject: [PATCH 0/9] userfaultfd: add minor fault handling for shmem From: Axel Rasmussen To: Alexander Viro , Andrea Arcangeli , Andrew Morton , Daniel Colascione , Hugh Dickins , Jerome Glisse , Joe Perches , Lokesh Gidra , Mike Kravetz , Mike Rapoport , Peter Xu , Shaohua Li , Shuah Khan , Stephen Rothwell , Wang Qing Cc: linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Axel Rasmussen , Brian Geffon , "Dr . David Alan Gilbert" , Mina Almasry , Oliver Upton Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Base ==== Since the original series [1] was merged into Andrew's tree, some issues were noticed. Up to this point, we had been working on fixing what's in Andrew's tree [2], but at this point we've changed direction enough that a lot of the fix's delta is undoing what was done in the original series, thereby making it hard to review. As suggested by Hugh Dickins and Peter Xu, this series takes a step back. It can be considered a v3 of the original series [1] - it combines those patches with the fixes, reordered / broken up to allow for easier review. The idea is that it will apply cleanly to akpm's tree, *replacing* the following patches (i.e., drop these first, and then apply this series): userfaultfd-support-minor-fault-handling-for-shmem.patch userfaultfd-support-minor-fault-handling-for-shmem-fix.patch userfaultfd-support-minor-fault-handling-for-shmem-fix-2.patch userfaultfd-support-minor-fault-handling-for-shmem-fix-3.patch userfaultfd-support-minor-fault-handling-for-shmem-fix-4.patch userfaultfd-selftests-use-memfd_create-for-shmem-test-type.patch userfaultfd-selftests-create-alias-mappings-in-the-shmem-test.patch userfaultfd-selftests-reinitialize-test-context-in-each-test.patch userfaultfd-selftests-exercise-minor-fault-handling-shmem-support.patch Changelog ========= Changes since the most recent fixup patch [2]: - Squash the fixes ([2]) in with the original series ([1]). This makes reviewing easier, as we no longer have to sift through deltas undoing what we had done before. [Hugh, Peter] - Modify shmem_mcopy_atomic_pte() to use the new mcopy_atomic_install_ptes() helper, reducing code duplication. [Hugh] - Properly trigger handle_userfault() in the shmem_swapin_page() case. [Hugh] - Use shmem_getpage() instead of find_lock_page() to lookup the existing page in for continue. This properly deals with swapped-out pages. [Hugh] - Unconditionally pte_mkdirty() for anon memory (as before). [Peter] - Don't include userfaultfd_k.h in either hugetlb.h or shmem_fs.h. [Hugh] - Add comment for UFFD_FEATURE_MINOR_SHMEM (to match _HUGETLBFS). [Hugh] - Fix some small cleanup issues (parens, reworded conditionals, reduced plumbing of some parameters, simplify labels/gotos, ...). [Hugh, Peter] Overview ======== See the series which added minor faults for hugetlbfs [3] for a detailed overview of minor fault handling in general. This series adds the same support for shmem-backed areas. This series is structured as follows: - Commits 1 and 2 are cleanups. - Commits 3 and 4 implement the new feature (minor fault handling for shmem). - Commits 5, 6, 7, 8 update the userfaultfd selftest to exercise the feature. - Commit 9 is one final cleanup, modifying an existing code path to re-use a new helper we've introduced. We rely on the selftest to show that this change doesn't break anything. Use Case ======== In some cases it is useful to have VM memory backed by tmpfs instead of hugetlbfs. So, this feature will be used to support the same VM live migration use case described in my original series. Additionally, Android folks (Lokesh Gidra ) hope to optimize the Android Runtime garbage collector using this feature: "The plan is to use userfaultfd for concurrently compacting the heap. With this feature, the heap can be shared-mapped at another location where the GC-thread(s) could continue the compaction operation without the need to invoke userfault ioctl(UFFDIO_COPY) each time. OTOH, if and when Java threads get faults on the heap, UFFDIO_CONTINUE can be used to resume execution. Furthermore, this feature enables updating references in the 'non-moving' portion of the heap efficiently. Without this feature, uneccessary page copying (ioctl(UFFDIO_COPY)) would be required." [1] https://lore.kernel.org/patchwork/cover/1388144/ [2] https://lore.kernel.org/patchwork/patch/1408161/ [3] https://lore.kernel.org/linux-fsdevel/20210301222728.176417-1-axelrasmussen@google.com/T/#t Axel Rasmussen (9): userfaultfd/hugetlbfs: avoid including userfaultfd_k.h in hugetlb.h userfaultfd/shmem: combine shmem_{mcopy_atomic,mfill_zeropage}_pte userfaultfd/shmem: support minor fault registration for shmem userfaultfd/shmem: support UFFDIO_CONTINUE for shmem userfaultfd/selftests: use memfd_create for shmem test type userfaultfd/selftests: create alias mappings in the shmem test userfaultfd/selftests: reinitialize test context in each test userfaultfd/selftests: exercise minor fault handling shmem support userfaultfd/shmem: modify shmem_mcopy_atomic_pte to use install_ptes fs/userfaultfd.c | 6 +- include/linux/hugetlb.h | 5 +- include/linux/shmem_fs.h | 15 +- include/linux/userfaultfd_k.h | 5 + include/uapi/linux/userfaultfd.h | 7 +- mm/hugetlb.c | 1 + mm/memory.c | 8 +- mm/shmem.c | 122 ++++------ mm/userfaultfd.c | 183 ++++++++++----- tools/testing/selftests/vm/userfaultfd.c | 280 +++++++++++++++-------- 10 files changed, 387 insertions(+), 245 deletions(-) --- 2.31.1.295.g9ea45b61b8-goog