From patchwork Wed Feb 10 21:21:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12081767 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,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 EA6EBC433DB for ; Wed, 10 Feb 2021 21:24:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7B2364EDA for ; Wed, 10 Feb 2021 21:24:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233627AbhBJVYA (ORCPT ); Wed, 10 Feb 2021 16:24:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233466AbhBJVXC (ORCPT ); Wed, 10 Feb 2021 16:23:02 -0500 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A980C0617A7 for ; Wed, 10 Feb 2021 13:22:15 -0800 (PST) Received: by mail-qk1-x74a.google.com with SMTP id 124so2748599qkg.6 for ; Wed, 10 Feb 2021 13:22:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=GZiDGzBZc6CdQco6utSqJxvMDhSmOX0vGMrGoDVipFA=; b=CSNZplzMVyec7GHEIAFJ1eRCsQNhOq/fj6tcy3OeZYMxVQ0KVyYmb0dTEK7zKHFTGS yebuUuuasp9KvEVUdZL5opsPRGziEruE1yuW80GOuHJd8OTK/AQMO0URaaXVNWOY9yE4 XwdwtnodywYIMXJ5E9ykKtwlxvJbCfYQpihPabgZwv1gJm/69Elh2UqDmzr/MRnIhC89 RrBQfdi3VBH3neG0sO+qFV+9OgWaH109CixY6+ca6R1+eIxQFqRkHSIbkvO6G12QDnrZ EclOhkjUfZdpL44LIIw/9EUTZdEtY13TGdzOUzevn0BlDx3rM1E1JbTX41JR1mf0SBsE zYoQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=GZiDGzBZc6CdQco6utSqJxvMDhSmOX0vGMrGoDVipFA=; b=mMn6J2nVh29Ct052rcaohoi4Oo+JvdI47xIiwLC4EhB7cCBF4lIh2TBlWqPPSpvKQs xpGeUbshYk1/igCG0pfZLVAYnINvawLzDY35mbrpDHocSMkx/ixp6mUopoE9P9yswqNA z7jreAQjmsC1I6QTiuJIsZGrIEbedtaU+8eyxN0PxdID2gJeZJkAnh5ZXAtylQiDJpAW be7ob8KDXcOVOMxF/mmymEAMRxqL/5FjuF6ID1yzghsuYzlewR3Pd9fdSK7OiF1yNqfr XsV799LVv/B+qKfE6A9ivurswTyL0rdxwx16PmIUvY2ArNYVG/8hf/i/OSS++wv13mKP yF3Q== X-Gm-Message-State: AOAM5306SzkrUuLRBVhKHMnIq8oVS+9L9iHydcVFy4I6nOgpYpqM9McC +9fsZCWLxhZE2ZeIoALoQHHw+D+a+y2b/6dkCg/Z X-Google-Smtp-Source: ABdhPJyeUvHSePNxBk4zXDwQilv7B/ls1YQ+N4EzdaCrrLILHIqkJGtRKVUfnXXG71oYRXMNeelVp+MO89+DHWJBPIcN Sender: "axelrasmussen via sendgmr" X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:94ee:de01:168:9f20]) (user=axelrasmussen job=sendgmr) by 2002:a0c:fec3:: with SMTP id z3mr4869971qvs.52.1612992134367; Wed, 10 Feb 2021 13:22:14 -0800 (PST) Date: Wed, 10 Feb 2021 13:21:54 -0800 In-Reply-To: <20210210212200.1097784-1-axelrasmussen@google.com> Message-Id: <20210210212200.1097784-5-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210210212200.1097784-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.30.0.478.g8a0d178c01-goog Subject: [PATCH v5 04/10] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp From: Axel Rasmussen To: Alexander Viro , Alexey Dobriyan , Andrea Arcangeli , Andrew Morton , Anshuman Khandual , Catalin Marinas , Chinwen Chang , Huang Ying , Ingo Molnar , Jann Horn , Jerome Glisse , Lokesh Gidra , "Matthew Wilcox (Oracle)" , Michael Ellerman , " =?utf-8?q?Michal_Koutn=C3=BD?= " , Michel Lespinasse , Mike Kravetz , Mike Rapoport , Nicholas Piggin , Peter Xu , Shaohua Li , Shawn Anastasio , Steven Rostedt , Steven Price , Vlastimil Babka Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Adam Ruprecht , Axel Rasmussen , Cannon Matthews , "Dr . David Alan Gilbert" , David Rientjes , Mina Almasry , Oliver Upton Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Peter Xu Huge pmd sharing for hugetlbfs is racy with userfaultfd-wp because userfaultfd-wp is always based on pgtable entries, so they cannot be shared. Walk the hugetlb range and unshare all such mappings if there is, right before UFFDIO_REGISTER will succeed and return to userspace. This will pair with want_pmd_share() in hugetlb code so that huge pmd sharing is completely disabled for userfaultfd-wp registered range. Signed-off-by: Peter Xu Signed-off-by: Axel Rasmussen --- fs/userfaultfd.c | 48 ++++++++++++++++++++++++++++++++++++ include/linux/mmu_notifier.h | 1 + 2 files changed, 49 insertions(+) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 0be8cdd4425a..1f4a34b1a1e7 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -1191,6 +1192,50 @@ static ssize_t userfaultfd_read(struct file *file, char __user *buf, } } +/* + * This function will unconditionally remove all the shared pmd pgtable entries + * within the specific vma for a hugetlbfs memory range. + */ +static void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) +{ +#ifdef CONFIG_HUGETLB_PAGE + struct hstate *h = hstate_vma(vma); + unsigned long sz = huge_page_size(h); + struct mm_struct *mm = vma->vm_mm; + struct mmu_notifier_range range; + unsigned long address; + spinlock_t *ptl; + pte_t *ptep; + + if (!(vma->vm_flags & VM_MAYSHARE)) + return; + + /* + * No need to call adjust_range_if_pmd_sharing_possible(), because + * we're going to operate on the whole vma + */ + mmu_notifier_range_init(&range, MMU_NOTIFY_HUGETLB_UNSHARE, + 0, vma, mm, vma->vm_start, vma->vm_end); + mmu_notifier_invalidate_range_start(&range); + i_mmap_lock_write(vma->vm_file->f_mapping); + for (address = vma->vm_start; address < vma->vm_end; address += sz) { + ptep = huge_pte_offset(mm, address, sz); + if (!ptep) + continue; + ptl = huge_pte_lock(h, mm, ptep); + huge_pmd_unshare(mm, vma, &address, ptep); + spin_unlock(ptl); + } + flush_hugetlb_tlb_range(vma, vma->vm_start, vma->vm_end); + i_mmap_unlock_write(vma->vm_file->f_mapping); + /* + * No need to call mmu_notifier_invalidate_range(), see + * Documentation/vm/mmu_notifier.rst. + */ + mmu_notifier_invalidate_range_end(&range); +#endif +} + static void __wake_userfault(struct userfaultfd_ctx *ctx, struct userfaultfd_wake_range *range) { @@ -1449,6 +1494,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, vma->vm_flags = new_flags; vma->vm_userfaultfd_ctx.ctx = ctx; + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) + hugetlb_unshare_all_pmds(vma); + skip: prev = vma; start = vma->vm_end; diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index b8200782dede..ff50c8528113 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -51,6 +51,7 @@ enum mmu_notifier_event { MMU_NOTIFY_SOFT_DIRTY, MMU_NOTIFY_RELEASE, MMU_NOTIFY_MIGRATE, + MMU_NOTIFY_HUGETLB_UNSHARE, }; #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)