From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) by kanga.kvack.org (Postfix) with ESMTP id 301958E0001 for ; Mon, 21 Jan 2019 02:59:49 -0500 (EST) Received: by mail-qk1-f197.google.com with SMTP id w28so18271338qkj.22 for ; Sun, 20 Jan 2019 23:59:49 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id b16si11661148qtp.115.2019.01.20.23.59.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 20 Jan 2019 23:59:48 -0800 (PST) From: Peter Xu Subject: [PATCH RFC 17/24] userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork Date: Mon, 21 Jan 2019 15:57:15 +0800 Message-Id: <20190121075722.7945-18-peterx@redhat.com> In-Reply-To: <20190121075722.7945-1-peterx@redhat.com> References: <20190121075722.7945-1-peterx@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hugh Dickins , Maya Gokhale , Jerome Glisse , Johannes Weiner , peterx@redhat.com, Martin Cracauer , Denis Plotnikov , Shaohua Li , Andrea Arcangeli , Pavel Emelyanov , Mike Kravetz , Marty McFadden , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" UFFD_EVENT_FORK support for uffd-wp should be already there, except that we should clean the uffd-wp bit if uffd fork event is not enabled. Detect that to avoid _PAGE_UFFD_WP being set even if the VMA is not being tracked by VM_UFFD_WP. Do this for both small PTEs and huge PMDs. Signed-off-by: Peter Xu --- mm/huge_memory.c | 8 ++++++++ mm/memory.c | 8 ++++++++ 2 files changed, 16 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 169795c8e56c..2a3ec62e83b6 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -928,6 +928,14 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, ret = -EAGAIN; pmd = *src_pmd; + /* + * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA + * does not have the VM_UFFD_WP, which means that the uffd + * fork event is not enabled. + */ + if (!(vma->vm_flags & VM_UFFD_WP)) + pmd = pmd_clear_uffd_wp(pmd); + #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION if (unlikely(is_swap_pmd(pmd))) { swp_entry_t entry = pmd_to_swp_entry(pmd); diff --git a/mm/memory.c b/mm/memory.c index a3de13b728f4..f5497752d2a3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -788,6 +788,14 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte = pte_mkclean(pte); pte = pte_mkold(pte); + /* + * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA + * does not have the VM_UFFD_WP, which means that the uffd + * fork event is not enabled. + */ + if (!(vm_flags & VM_UFFD_WP)) + pte = pte_clear_uffd_wp(pte); + page = vm_normal_page(vma, addr, pte); if (page) { get_page(page); -- 2.17.1