From patchwork Tue Apr 20 22:07:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12215109 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 553F4C43470 for ; Tue, 20 Apr 2021 22:08:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1831F61409 for ; Tue, 20 Apr 2021 22:08:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234223AbhDTWIm (ORCPT ); Tue, 20 Apr 2021 18:08:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40318 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233992AbhDTWIm (ORCPT ); Tue, 20 Apr 2021 18:08:42 -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 8D95DC06138B for ; Tue, 20 Apr 2021 15:08:08 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id c1-20020a5b0bc10000b02904e7c6399b20so13434326ybr.12 for ; Tue, 20 Apr 2021 15:08:08 -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=zAYOQTHDl7Hr610dsK09yuxxlc7K/Nigz20czYyiBnI=; b=nxHlMRG6xCo+tdbSt/DTkcKAZZBqLMadWvmrfDHX4EbsVJf81n7VGbGKAtF1vLkWy5 A31Ygp5SbdGW3PMjfoRVCul1Z7zDoHgyn3ig/H/IfzjqPx5O1PeFtKVv+CPw8eZH5lTE 6/r+q9ymnkNtJapuiwVngCmO5bGW1ohp+Nck68N1VQg+Y0jsTPBQLcsh6DT7pmyPTtCO tPvL7o2jtcrToUO0Zf9DbQVCnefwGEpU3TcUXzuAryN0LJRS325IZkK2F9w8pqVKfIdL DuiMWSgb8zB9hze142Neij/M3Q4Z5ndfzSfve6AZMyk+aZXe6dFG6QTZQ9B88zz/8RhW Qkhg== 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=zAYOQTHDl7Hr610dsK09yuxxlc7K/Nigz20czYyiBnI=; b=YGIcxr4KHei8N861BN8KPtcLjtMqw1fa0b2o4xEb6iu8U1sGJROaF16By/H86QLJwe xUX3DjQNRecqRFmw3gPyTCgR5xp9qTxbCJSXJqxA7mIHdW7lze20FS3WPa72cGR5BA7x HK5dTmcGpOIsyony+SnQ2ynLtmNYrl4CPnSXG7tCkaivi47nVpYGPfq/HoRpelholyvy HbF5Eg6H+HthASDNNRF/EfWWmTAD+3PGe1Hd2otgvJOilUKAdNFIi8UWSRZkJ15YVPPG zdfK3DGAaWznKrIZ2hJkXYXWGMBRSeR7AyQXtJ/arWCbVziXb7yFBiJHSog2Lf6RsPHH 0YYQ== X-Gm-Message-State: AOAM533ML18rv0TW0x/tDswSl68hhuXCPDIC2tdfBTBXMPCw5nLVXtD7 SBZ1fDSy+PJkt9dlqTm9d4lst9V3rqtfASNUDLeG X-Google-Smtp-Source: ABdhPJwFxbvCWWUeInxSNeVWIGUEol/eHNsU6mnuuHMbcINmvyJlNOwRmQ6AsnNH4Fg5MB0vBNGBmCgAJWgyQCSfuPPX X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:c40e:ee2c:2ab8:257a]) (user=axelrasmussen job=sendgmr) by 2002:a25:fc0a:: with SMTP id v10mr28267957ybd.71.1618956487689; Tue, 20 Apr 2021 15:08:07 -0700 (PDT) Date: Tue, 20 Apr 2021 15:07:54 -0700 Message-Id: <20210420220804.486803-1-axelrasmussen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.31.1.368.gbe11c130af-goog Subject: [PATCH v4 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-fsdevel@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 ========= v3->v4: - Fix handling of the shmem private mcopy case. Previously, I had (incorrectly) assumed that !vma_is_anonymous() was equivalent to "the page will be in the page cache". But, in this case we have an optimization where we allocate a new *anonymous* page. So, use a new "bool page_in_cache" instead, which checks if page->mapping is set. Correct several places with this new check. [Hugh] - Fix calling mm_counter() before page_add_..._rmap(). [Hugh] - When modifying shmem_mcopy_atomic_pte() to use the new install_pte() helper, just use lru_cache_add_inactive_or_unevictable(), no need to branch and maybe use lru_cache_add(). [Hugh] - De-pluralize mcopy_atomic_install_pte(s). [Hugh] - Make "writable" a bool, and initialize consistently. [Hugh] 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. - Commit 10 is a small documentation update to reflect the new changes. 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_pte() 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 | 115 +++----- mm/userfaultfd.c | 175 ++++++++---- tools/testing/selftests/vm/userfaultfd.c | 274 ++++++++++++------- 11 files changed, 364 insertions(+), 251 deletions(-) --- 2.31.1.368.gbe11c130af-goog