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[209.132.183.28]) by mx.google.com with ESMTPS id i16si1418067qtr.138.2019.04.18.14.01.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2019 14:01:56 -0700 (PDT) Received-SPF: pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 997CE301EA86; Thu, 18 Apr 2019 21:01:55 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.236]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D402060BFC; Thu, 18 Apr 2019 21:01:49 +0000 (UTC) Date: Thu, 18 Apr 2019 17:01:48 -0400 From: Jerome Glisse To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Hugh Dickins , Maya Gokhale , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Shaohua Li , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Marty McFadden , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" Subject: Re: [PATCH v3 25/28] userfaultfd: wp: fixup swap entries in change_pte_range Message-ID: <20190418210147.GM3288@redhat.com> References: <20190320020642.4000-1-peterx@redhat.com> <20190320020642.4000-26-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320020642.4000-26-peterx@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Thu, 18 Apr 2019 21:01:55 +0000 (UTC) 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: On Wed, Mar 20, 2019 at 10:06:39AM +0800, Peter Xu wrote: > In change_pte_range() we do nothing for uffd if the PTE is a swap > entry. That can lead to data mismatch if the page that we are going > to write protect is swapped out when sending the UFFDIO_WRITEPROTECT. > This patch applies/removes the uffd-wp bit even for the swap entries. > > Signed-off-by: Peter Xu This one seems to address some of the comments i made on patch 17 not all thought. Maybe squash them together ? > --- > > I kept this patch a standalone one majorly to make review easier. The > patch can be considered as standalone or to squash into the patch > "userfaultfd: wp: support swap and page migration". > --- > mm/mprotect.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 96c0f521099d..a23e03053787 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -183,11 +183,11 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > } > ptep_modify_prot_commit(mm, addr, pte, ptent); > pages++; > - } else if (IS_ENABLED(CONFIG_MIGRATION)) { > + } else if (is_swap_pte(oldpte)) { > swp_entry_t entry = pte_to_swp_entry(oldpte); > + pte_t newpte; > > if (is_write_migration_entry(entry)) { > - pte_t newpte; > /* > * A protection check is difficult so > * just be safe and disable write > @@ -198,22 +198,24 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > newpte = pte_swp_mksoft_dirty(newpte); > if (pte_swp_uffd_wp(oldpte)) > newpte = pte_swp_mkuffd_wp(newpte); > - set_pte_at(mm, addr, pte, newpte); > - > - pages++; > - } > - > - if (is_write_device_private_entry(entry)) { > - pte_t newpte; > - > + } else if (is_write_device_private_entry(entry)) { > /* > * We do not preserve soft-dirtiness. See > * copy_one_pte() for explanation. > */ > make_device_private_entry_read(&entry); > newpte = swp_entry_to_pte(entry); > - set_pte_at(mm, addr, pte, newpte); > + } else { > + newpte = oldpte; > + } > > + if (uffd_wp) > + newpte = pte_swp_mkuffd_wp(newpte); > + else if (uffd_wp_resolve) > + newpte = pte_swp_clear_uffd_wp(newpte); > + > + if (!pte_same(oldpte, newpte)) { > + set_pte_at(mm, addr, pte, newpte); > pages++; > } > } > -- > 2.17.1 >