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[209.132.183.28]) by mx.google.com with ESMTPS id e18si898028qkm.85.2019.04.18.13.59.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2019 13:59:16 -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-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 194283082EF1; Thu, 18 Apr 2019 20:59:15 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.236]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E7365600C5; Thu, 18 Apr 2019 20:59:08 +0000 (UTC) Date: Thu, 18 Apr 2019 16:59:07 -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 17/28] userfaultfd: wp: support swap and page migration Message-ID: <20190418205907.GL3288@redhat.com> References: <20190320020642.4000-1-peterx@redhat.com> <20190320020642.4000-18-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190320020642.4000-18-peterx@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Thu, 18 Apr 2019 20:59:15 +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 10:06:31AM +0800, Peter Xu wrote: > For either swap and page migration, we all use the bit 2 of the entry to > identify whether this entry is uffd write-protected. It plays a similar > role as the existing soft dirty bit in swap entries but only for keeping > the uffd-wp tracking for a specific PTE/PMD. > > Something special here is that when we want to recover the uffd-wp bit > from a swap/migration entry to the PTE bit we'll also need to take care > of the _PAGE_RW bit and make sure it's cleared, otherwise even with the > _PAGE_UFFD_WP bit we can't trap it at all. > > Note that this patch removed two lines from "userfaultfd: wp: hook > userfault handler to write protection fault" where we try to remove the > VM_FAULT_WRITE from vmf->flags when uffd-wp is set for the VMA. This > patch will still keep the write flag there. > > Reviewed-by: Mike Rapoport > Signed-off-by: Peter Xu Some missing thing see below. [...] > diff --git a/mm/memory.c b/mm/memory.c > index 6405d56debee..c3d57fa890f2 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -736,6 +736,8 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm, > pte = swp_entry_to_pte(entry); > if (pte_swp_soft_dirty(*src_pte)) > pte = pte_swp_mksoft_dirty(pte); > + if (pte_swp_uffd_wp(*src_pte)) > + pte = pte_swp_mkuffd_wp(pte); > set_pte_at(src_mm, addr, src_pte, pte); > } > } else if (is_device_private_entry(entry)) { You need to handle the is_device_private_entry() as the migration case too. > @@ -2825,6 +2827,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > flush_icache_page(vma, page); > if (pte_swp_soft_dirty(vmf->orig_pte)) > pte = pte_mksoft_dirty(pte); > + if (pte_swp_uffd_wp(vmf->orig_pte)) { > + pte = pte_mkuffd_wp(pte); > + pte = pte_wrprotect(pte); > + } > set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); > arch_do_swap_page(vma->vm_mm, vma, vmf->address, pte, vmf->orig_pte); > vmf->orig_pte = pte; > diff --git a/mm/migrate.c b/mm/migrate.c > index 181f5d2718a9..72cde187d4a1 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -241,6 +241,8 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, > entry = pte_to_swp_entry(*pvmw.pte); > if (is_write_migration_entry(entry)) > pte = maybe_mkwrite(pte, vma); > + else if (pte_swp_uffd_wp(*pvmw.pte)) > + pte = pte_mkuffd_wp(pte); > > if (unlikely(is_zone_device_page(new))) { > if (is_device_private_page(new)) { You need to handle is_device_private_page() case ie mark its swap as uffd_wp > @@ -2301,6 +2303,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > swp_pte = swp_entry_to_pte(entry); > if (pte_soft_dirty(pte)) > swp_pte = pte_swp_mksoft_dirty(swp_pte); > + if (pte_uffd_wp(pte)) > + swp_pte = pte_swp_mkuffd_wp(swp_pte); > set_pte_at(mm, addr, ptep, swp_pte); > > /* > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 855dddb07ff2..96c0f521099d 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -196,6 +196,8 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > newpte = swp_entry_to_pte(entry); > if (pte_swp_soft_dirty(oldpte)) > 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++; Need to handle is_write_device_private_entry() case just below that chunk. Cheers, Jérôme