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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 25 Feb 2019 21:09:41 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x1PL9eS955574598 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 25 Feb 2019 21:09:40 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C98D8AE04D; Mon, 25 Feb 2019 21:09:40 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DDF0AAE045; Mon, 25 Feb 2019 21:09:37 +0000 (GMT) Received: from rapoport-lnx (unknown [9.148.204.243]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 25 Feb 2019 21:09:37 +0000 (GMT) Date: Mon, 25 Feb 2019 23:09:35 +0200 From: Mike Rapoport To: Peter Xu 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" Subject: Re: [PATCH v2 23/26] userfaultfd: wp: don't wake up when doing write protect 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/1.5.24 (2015-08-30) X-TM-AS-GCONF: 00 x-cbid: 19022521-0020-0000-0000-0000031B210C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19022521-0021-0000-0000-0000216C83A3 Message-Id: <20190225210934.GE10454@rapoport-lnx> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-02-25_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=761 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902250151 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 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 > --- > 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; This actually means the opposite of the commit message text ;-) Is any dependency of _WP and _DONTWAKE needed at all? > 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) { > range.start = uffdio_wp.range.start; > range.len = uffdio_wp.range.len; > wake_userfault(ctx, &range); > -- > 2.17.1 > -- Sincerely yours, Mike.