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 BE3CFC43381 for ; Thu, 21 Feb 2019 18:37:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 98DC42081B for ; Thu, 21 Feb 2019 18:37:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726626AbfBUShE (ORCPT ); Thu, 21 Feb 2019 13:37:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40342 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725845AbfBUShE (ORCPT ); Thu, 21 Feb 2019 13:37:04 -0500 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 3E3DF3086275; Thu, 21 Feb 2019 18:37:03 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.236]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EA0B460139; Thu, 21 Feb 2019 18:36:55 +0000 (UTC) Date: Thu, 21 Feb 2019 13:36:54 -0500 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 , Marty McFadden , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" Subject: Re: [PATCH v2 23/26] userfaultfd: wp: don't wake up when doing write protect Message-ID: <20190221183653.GV2813@redhat.com> References: <20190212025632.28946-1-peterx@redhat.com> <20190212025632.28946-24-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190212025632.28946-24-peterx@redhat.com> User-Agent: Mutt/1.10.0 (2018-05-17) 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 [10.5.110.49]); Thu, 21 Feb 2019 18:37:03 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 12, 2019 at 10:56:29AM +0800, Peter Xu wrote: > It does not make sense to try to wake up any waiting thread when we're > write-protecting a memory region. Only wake up when resolving a write > protected page fault. > > Signed-off-by: Peter Xu I am bit confuse here, see below. > --- > fs/userfaultfd.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index 81962d62520c..f1f61a0278c2 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1771,6 +1771,7 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, > struct uffdio_writeprotect uffdio_wp; > struct uffdio_writeprotect __user *user_uffdio_wp; > struct userfaultfd_wake_range range; > + bool mode_wp, mode_dontwake; > > if (READ_ONCE(ctx->mmap_changing)) > return -EAGAIN; > @@ -1789,18 +1790,20 @@ static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, > if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | > UFFDIO_WRITEPROTECT_MODE_WP)) > return -EINVAL; > - if ((uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP) && > - (uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) > + > + mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; > + mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; > + > + if (mode_wp && mode_dontwake) > return -EINVAL; I am confuse by the logic here. DONTWAKE means do not wake any waiting thread right ? So if the patch header it seems to me the logic should be: if (mode_wp && !mode_dontwake) return -EINVAL; At very least this part does seems to mean the opposite of what the commit message says. > > ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, > - uffdio_wp.range.len, uffdio_wp.mode & > - UFFDIO_WRITEPROTECT_MODE_WP, > + uffdio_wp.range.len, mode_wp, > &ctx->mmap_changing); > if (ret) > return ret; > > - if (!(uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE)) { > + if (!mode_wp && !mode_dontwake) { This part match the commit message :) > range.start = uffdio_wp.range.start; > range.len = uffdio_wp.range.len; > wake_userfault(ctx, &range);