From patchwork Thu Apr 15 18:47:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12205921 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=ham 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 B84A9C433ED for ; Thu, 15 Apr 2021 18:47:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 878DF610CE for ; Thu, 15 Apr 2021 18:47:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234635AbhDOSsA (ORCPT ); Thu, 15 Apr 2021 14:48:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234086AbhDOSsA (ORCPT ); Thu, 15 Apr 2021 14:48:00 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D77CFC06175F for ; Thu, 15 Apr 2021 11:47:36 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id v2so3432407ybc.17 for ; Thu, 15 Apr 2021 11:47:36 -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=HOv3LI0amuLnu16Azoij1WiD0ahUGLpZta25xI8mbb4=; b=K+sh8JarhAxis1EkzesQd7EqJyIE6gNyonS8n+ov71E2StwoJ8B2pEj16zjFHpwi1E 6ZAXgOWIG7qs+YTeFn5TiDMqbmrPXVBrmzi2XdQAiFUbT8uHoz5txjNNWW8uyU3J8lus On8DVQ2eOOh4iDqFWQAbUMCGlvMVGNByIOkjFT7OrsMo31nByw19h2IPOnHfowP614H0 56XU7arD5SCK6pNUkw+NXtNCVLWfltQxlouDjl4qsSmZLXSNNbfUSW5CVOq7Cr6YVHh9 XyMXJcn6JsBiQzG3cSNimz3DHSZ0uRHsh+jAsxeSvzJSp8ycAdNi5eVAogPRcnD46KBD sdqQ== 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=HOv3LI0amuLnu16Azoij1WiD0ahUGLpZta25xI8mbb4=; b=g+Brn0LbDyNktbLNvhdG/fqc7BkGMnGKcY1yCx2DegJnlqZHBM4EcepZB4vUOl9dOW 4Dsdstl1fVpXak7WlNAmVJzAwPX97uWHwtwtrSWiF+W3n9SuL02DXotZVTXrvu5iKNnZ 59vP9vUhRNV7RxlGVQcgDFjNLpNGuAXrSmInvzA3iRG+RRQu44Ovvpg2vryVHtSzSl5V lIMiAZVtUmAF3p73903QnVBscLRt4ZPCg7YJOACBG/Ene2TOPhFFlE3XEaX7BKdqF67/ cQAFLZ7XmeudNzkO68dwUnK5HGKiQ3IFOe4FsaBgM8KgWbHXrXaiG6qgRVMcIAQySCrC TSCg== X-Gm-Message-State: AOAM533VAeVDGJ6se7aep8Wh9qvclUEANkpMLFz0vERmvLH1J56800HM s7GC8d/Lok5adhJMBh5S9MgY1XUohcH59a6s/HGI X-Google-Smtp-Source: ABdhPJzoNSXv2urXx3peba3eorPfVQfJb4ZTqrlOnBXFac83aVKjuHsYFDHRRJKeqOVJqqs2DLnDqHPXoPg6+QsjU4Ji X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:21b1:6e5c:b371:7e3]) (user=axelrasmussen job=sendgmr) by 2002:a25:cc05:: with SMTP id l5mr6554359ybf.520.1618512455879; Thu, 15 Apr 2021 11:47:35 -0700 (PDT) Date: Thu, 15 Apr 2021 11:47:22 -0700 Message-Id: <20210415184732.3410521-1-axelrasmussen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.31.1.368.gbe11c130af-goog Subject: [PATCH v3 00/10] userfaultfd: add minor fault handling for shmem From: Axel Rasmussen To: Alexander Viro , Andrea Arcangeli , Andrew Morton , 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-kselftest@vger.kernel.org Base ==== This series is based on (and therefore should apply cleanly to) the tag "v5.12-rc7-mmots-2021-04-11-20-49", additionally with Peter's selftest cleanup series applied first: https://lore.kernel.org/patchwork/cover/1412450/ Changelog ========= v2->v3: - Picked up {Reviewed,Acked}-by's. - Reorder commits: introduce CONTINUE before MINOR registration. [Hugh, Peter] - Don't try to {unlock,put}_page an xarray value in shmem_getpage_gfp. [Hugh] - Move enum mcopy_atomic_mode forward declare out of CONFIG_HUGETLB_PAGE. [Hugh] - Keep mistakenly removed UFFD_USER_MODE_ONLY in selftest. [Peter] - Cleanup context management in self test (make clear implicit, remove unneeded return values now that we have err()). [Peter] - Correct dst_pte argument to dst_pmd in shmem_mcopy_atomic_pte macro. [Hugh] - Mention the new shmem support feature in documentation. [Hugh] v1->v2: - Pick up Reviewed-by's. - Don't swapin page when a minor fault occurs. Notice that it needs to be swapped in, and just immediately fire the minor fault. Let a future CONTINUE deal with swapping in the page. [Peter] - Clarify comment about i_size checks in mm/userfaultfd.c. [Peter] - Only forward declare once (out of #ifdef) in hugetlb.h. [Peter] Changes since [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 (10): userfaultfd/hugetlbfs: avoid including userfaultfd_k.h in hugetlb.h userfaultfd/shmem: combine shmem_{mcopy_atomic,mfill_zeropage}_pte userfaultfd/shmem: support UFFDIO_CONTINUE for shmem userfaultfd/shmem: support minor fault registration 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 userfaultfd: update documentation to mention shmem minor faults Documentation/admin-guide/mm/userfaultfd.rst | 3 +- fs/userfaultfd.c | 6 +- include/linux/hugetlb.h | 4 +- include/linux/shmem_fs.h | 17 +- include/linux/userfaultfd_k.h | 5 + include/uapi/linux/userfaultfd.h | 7 +- mm/hugetlb.c | 1 + mm/memory.c | 8 +- mm/shmem.c | 114 +++----- mm/userfaultfd.c | 183 +++++++++---- tools/testing/selftests/vm/userfaultfd.c | 274 ++++++++++++------- 11 files changed, 371 insertions(+), 251 deletions(-) --- 2.31.1.368.gbe11c130af-goog