From mboxrd@z Thu Jan 1 00:00:00 1970 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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 1E754C43381 for ; Tue, 26 Feb 2019 06:06:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DF848213A2 for ; Tue, 26 Feb 2019 06:06:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726465AbfBZGGn (ORCPT ); Tue, 26 Feb 2019 01:06:43 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35784 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725908AbfBZGGn (ORCPT ); Tue, 26 Feb 2019 01:06:43 -0500 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 71E6A3082163; Tue, 26 Feb 2019 06:06:42 +0000 (UTC) Received: from xz-x1 (dhcp-14-116.nay.redhat.com [10.66.14.116]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 462E460BE7; Tue, 26 Feb 2019 06:06:30 +0000 (UTC) Date: Tue, 26 Feb 2019 14:06:27 +0800 From: Peter Xu To: Mike Rapoport Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Hugh Dickins , Maya Gokhale , Jerome Glisse , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Shaohua Li , Marty McFadden , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" , Rik van Riel Subject: Re: [PATCH v2 20/26] userfaultfd: wp: support write protection for userfault vma range Message-ID: <20190226060627.GG13653@xz-x1> References: <20190212025632.28946-1-peterx@redhat.com> <20190212025632.28946-21-peterx@redhat.com> <20190225205233.GC10454@rapoport-lnx> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190225205233.GC10454@rapoport-lnx> User-Agent: Mutt/1.10.1 (2018-07-13) 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]); Tue, 26 Feb 2019 06:06:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 25, 2019 at 10:52:34PM +0200, Mike Rapoport wrote: > On Tue, Feb 12, 2019 at 10:56:26AM +0800, Peter Xu wrote: > > From: Shaohua Li > > > > Add API to enable/disable writeprotect a vma range. Unlike mprotect, > > this doesn't split/merge vmas. > > > > Cc: Andrea Arcangeli > > Cc: Rik van Riel > > Cc: Kirill A. Shutemov > > Cc: Mel Gorman > > Cc: Hugh Dickins > > Cc: Johannes Weiner > > Signed-off-by: Shaohua Li > > Signed-off-by: Andrea Arcangeli > > [peterx: > > - use the helper to find VMA; > > - return -ENOENT if not found to match mcopy case; > > - use the new MM_CP_UFFD_WP* flags for change_protection > > - check against mmap_changing for failures] > > Signed-off-by: Peter Xu > > --- > > include/linux/userfaultfd_k.h | 3 ++ > > mm/userfaultfd.c | 54 +++++++++++++++++++++++++++++++++++ > > 2 files changed, 57 insertions(+) > > > > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > > index 765ce884cec0..8f6e6ed544fb 100644 > > --- a/include/linux/userfaultfd_k.h > > +++ b/include/linux/userfaultfd_k.h > > @@ -39,6 +39,9 @@ extern ssize_t mfill_zeropage(struct mm_struct *dst_mm, > > unsigned long dst_start, > > unsigned long len, > > bool *mmap_changing); > > +extern int mwriteprotect_range(struct mm_struct *dst_mm, > > + unsigned long start, unsigned long len, > > + bool enable_wp, bool *mmap_changing); > > > > /* mm helpers */ > > static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > > index fefa81c301b7..529d180bb4d7 100644 > > --- a/mm/userfaultfd.c > > +++ b/mm/userfaultfd.c > > @@ -639,3 +639,57 @@ ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, > > { > > return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing, 0); > > } > > + > > +int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, > > + unsigned long len, bool enable_wp, bool *mmap_changing) > > +{ > > + struct vm_area_struct *dst_vma; > > + pgprot_t newprot; > > + int err; > > + > > + /* > > + * Sanitize the command parameters: > > + */ > > + BUG_ON(start & ~PAGE_MASK); > > + BUG_ON(len & ~PAGE_MASK); > > + > > + /* Does the address range wrap, or is the span zero-sized? */ > > + BUG_ON(start + len <= start); > > I'd replace these BUG_ON()s with > > if (WARN_ON()) > return -EINVAL; I believe BUG_ON() is used because these parameters should have been checked in userfaultfd_writeprotect() already by the common validate_range() even before calling mwriteprotect_range(). So I'm fine with the WARN_ON() approach but I'd slightly prefer to simply keep the patch as is to keep Jerome's r-b if you won't disagree. :) Thanks, -- Peter Xu