From patchwork Wed Jul 14 22:25:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Xu X-Patchwork-Id: 12377981 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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,USER_AGENT_GIT 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 9D377C47E48 for ; Wed, 14 Jul 2021 22:25:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4DE70613D1 for ; Wed, 14 Jul 2021 22:25:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4DE70613D1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9C6566B00D2; Wed, 14 Jul 2021 18:25:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 99D1C6B00D3; Wed, 14 Jul 2021 18:25:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7F0C86B00D4; Wed, 14 Jul 2021 18:25:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0178.hostedemail.com [216.40.44.178]) by kanga.kvack.org (Postfix) with ESMTP id 5A9D66B00D2 for ; Wed, 14 Jul 2021 18:25:23 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 4651918479C79 for ; Wed, 14 Jul 2021 22:25:22 +0000 (UTC) X-FDA: 78362625684.06.9F3C62A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf15.hostedemail.com (Postfix) with ESMTP id DB673D0000B8 for ; Wed, 14 Jul 2021 22:25:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626301521; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5H2OJLKid4CPQSAYIKsaabG8iASKh4992R4GxsoqMUU=; b=LeqpfBzTX8/jBzFX7dXKOmQ3ApS8qa9f5P6cL7nFfGiMDFuTrRcvJR53DVtBilWASn7K+c 9zR3+dlkLrPwwGZ1sXkl4WBgvEYjob8KxKiXRhSEcCZvXWKPXmt6KfW4QjOU/clvQr48vM jcOcw7ly8KY2tOj9N6wHny8fo8HBQDo= Received: from mail-qv1-f71.google.com (mail-qv1-f71.google.com [209.85.219.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-595-7M86jNZEPh6qrSPZpLmtTQ-1; Wed, 14 Jul 2021 18:25:20 -0400 X-MC-Unique: 7M86jNZEPh6qrSPZpLmtTQ-1 Received: by mail-qv1-f71.google.com with SMTP id k12-20020a0cfd6c0000b029020df9543019so2686016qvs.14 for ; Wed, 14 Jul 2021 15:25:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=5H2OJLKid4CPQSAYIKsaabG8iASKh4992R4GxsoqMUU=; b=hvkKacfONi2RrkmuytJR97byPrXmvGa4qzKUtp5KE1MkhhGG7HTvV/UtoNFlKRDOIs y0IT7Yum5N/LXIIiMUAAFC4t3PifM+2PzIabcZ0eYQLdlK+zaS1Oy/KysBGoyslyJa0S tYoC8dGQL0XN/VgSUDOqKOmJjjOly66n9TDUGvluXUb6ddqq2bWsBDyDL8wbkm/Jbhvh lQn0SSMtVSpdogGQUK00tuU9TyNtMFn7+nEMrUZx9CLPlxk7ykpVZt7hi/hTM9J/ADFp 8jz33qByEr7f6snT6QlJ3e05qDjEzGrr3RaLmmMJ53VXTzIHz6hFiTKwYVMEo+adfGnO szWg== X-Gm-Message-State: AOAM533+bqtdHVTQSZD1jvUzRAhQGuWo6t69tCi7U37k8+IsHnlYnxd5 GJlIjHdVvrGTZRws5tAWi3YCQwQbgO3A7Id2EFAgWTTOPX8qphKBbVS+4jvfX0uQwtHJ9k9LCPf GMdxNrGc69prMLA4G//uVv5Fo0MOoAl/6MAUPD5IGJgZdH1LhOANL6Popi/YP X-Received: by 2002:ad4:45c6:: with SMTP id v6mr417661qvt.38.1626301519630; Wed, 14 Jul 2021 15:25:19 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxDsfUj8eHJSSZFsQqs5KUYC+Cg/+WCkNyKzSsO7dLgYBKhrd4DqJafrAOU4DH6gx9z1hUVsA== X-Received: by 2002:ad4:45c6:: with SMTP id v6mr417628qvt.38.1626301519369; Wed, 14 Jul 2021 15:25:19 -0700 (PDT) Received: from localhost.localdomain (bras-base-toroon474qw-grc-65-184-144-111-238.dsl.bell.ca. [184.144.111.238]) by smtp.gmail.com with ESMTPSA id s202sm1671235qke.80.2021.07.14.15.25.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jul 2021 15:25:18 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , Mike Kravetz , Axel Rasmussen , Miaohe Lin , "Kirill A . Shutemov" , Hugh Dickins , Jason Gunthorpe , Alistair Popple , Matthew Wilcox , peterx@redhat.com, Jerome Glisse , Andrea Arcangeli , Mike Rapoport , Nadav Amit , David Hildenbrand Subject: [PATCH v4 21/26] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler Date: Wed, 14 Jul 2021 18:25:15 -0400 Message-Id: <20210714222515.49144-1-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210714222117.47648-1-peterx@redhat.com> References: <20210714222117.47648-1-peterx@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LeqpfBzT; spf=none (imf15.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DB673D0000B8 X-Stat-Signature: mk33haups6rfpekbsiwd1ay7dh9rjg63 X-HE-Tag: 1626301521-310581 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Teach the hugetlb page fault code to understand uffd-wp special pte. For example, when seeing such a pte we need to convert any write fault into a read one (which is fake - we'll retry the write later if so). Meanwhile, for handle_userfault() we'll need to make sure we must wait for the special swap pte too just like a none pte. Note that we also need to teach UFFDIO_COPY about this special pte across the code path so that we can safely install a new page at this special pte as long as we know it's a stall entry. Signed-off-by: Peter Xu --- fs/userfaultfd.c | 5 ++++- mm/hugetlb.c | 26 ++++++++++++++++++++------ mm/userfaultfd.c | 5 ++++- 3 files changed, 28 insertions(+), 8 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index e1c1cbc7bcc8..644df737fbb2 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -245,8 +245,11 @@ static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, /* * Lockless access: we're in a wait_event so it's ok if it * changes under us. + * + * Regarding uffd-wp special case, please refer to comments in + * userfaultfd_must_wait(). */ - if (huge_pte_none(pte)) + if (huge_pte_none(pte) || pte_swp_uffd_wp_special(pte)) ret = true; if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) ret = true; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6a66b598245e..15e5de480cf0 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4786,7 +4786,8 @@ static inline vm_fault_t hugetlb_handle_userfault(struct vm_area_struct *vma, static vm_fault_t hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, struct address_space *mapping, pgoff_t idx, - unsigned long address, pte_t *ptep, unsigned int flags) + unsigned long address, pte_t *ptep, + pte_t old_pte, unsigned int flags) { struct hstate *h = hstate_vma(vma); vm_fault_t ret = VM_FAULT_SIGBUS; @@ -4910,7 +4911,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, ptl = huge_pte_lock(h, mm, ptep); ret = 0; - if (!huge_pte_none(huge_ptep_get(ptep))) + if (!pte_same(huge_ptep_get(ptep), old_pte)) goto backout; if (anon_rmap) { @@ -4920,6 +4921,12 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, page_dup_rmap(page, true); new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE) && (vma->vm_flags & VM_SHARED))); + /* + * If this pte was previously wr-protected, keep it wr-protected even + * if populated. + */ + if (unlikely(pte_swp_uffd_wp_special(old_pte))) + new_pte = huge_pte_wrprotect(huge_pte_mkuffd_wp(new_pte)); set_huge_pte_at(mm, haddr, ptep, new_pte); hugetlb_count_add(pages_per_huge_page(h), mm); @@ -5035,8 +5042,13 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, mutex_lock(&hugetlb_fault_mutex_table[hash]); entry = huge_ptep_get(ptep); - if (huge_pte_none(entry)) { - ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, flags); + /* + * uffd-wp-special should be handled merely the same as pte none + * because it's basically a none pte with a special marker + */ + if (huge_pte_none(entry) || pte_swp_uffd_wp_special(entry)) { + ret = hugetlb_no_page(mm, vma, mapping, idx, address, ptep, + entry, flags); goto out_mutex; } @@ -5170,7 +5182,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr); unsigned long size; int vm_shared = dst_vma->vm_flags & VM_SHARED; - pte_t _dst_pte; + pte_t _dst_pte, cur_pte; spinlock_t *ptl; int ret = -ENOMEM; struct page *page; @@ -5287,8 +5299,10 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, if (idx >= size) goto out_release_unlock; + cur_pte = huge_ptep_get(dst_pte); ret = -EEXIST; - if (!huge_pte_none(huge_ptep_get(dst_pte))) + /* Please refer to shmem_mfill_atomic_pte() for uffd-wp special case */ + if (!huge_pte_none(cur_pte) && !pte_swp_uffd_wp_special(cur_pte)) goto out_release_unlock; if (vm_shared) { diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 7ba721aca1c5..a8038903effd 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -363,6 +363,8 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, } while (src_addr < src_start + len) { + pte_t pteval; + BUG_ON(dst_addr >= dst_start + len); /* @@ -385,8 +387,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, goto out_unlock; } + pteval = huge_ptep_get(dst_pte); if (mode != MCOPY_ATOMIC_CONTINUE && - !huge_pte_none(huge_ptep_get(dst_pte))) { + !huge_pte_none(pteval) && !pte_swp_uffd_wp_special(pteval)) { err = -EEXIST; mutex_unlock(&hugetlb_fault_mutex_table[hash]); i_mmap_unlock_read(mapping);