From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S642774AbdEAFnw (ORCPT ); Mon, 1 May 2017 01:43:52 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:51901 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S642672AbdEAFng (ORCPT ); Mon, 1 May 2017 01:43:36 -0400 From: Mike Rapoport To: "Michael Kerrisk (man-pages)" Cc: Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-man@vger.kernel.org, Mike Rapoport Subject: [PATCH man-pages 3/5] ioctl_userfaultfd.2: add BUGS section Date: Mon, 1 May 2017 08:43:17 +0300 X-Mailer: git-send-email 1.9.1 In-Reply-To: <1493617399-20897-1-git-send-email-rppt@linux.vnet.ibm.com> References: <1493617399-20897-1-git-send-email-rppt@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17050105-0020-0000-0000-000003574B1C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17050105-0021-0000-0000-000041833F39 Message-Id: <1493617399-20897-4-git-send-email-rppt@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-05-01_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1705010035 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The features handshake is not quite convenient. Elaborate about it in the BUGS section. Signed-off-by: Mike Rapoport --- man2/ioctl_userfaultfd.2 | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index e12b9de..50316de 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -650,6 +650,15 @@ operations are Linux-specific. .SH EXAMPLE See .BR userfaultfd (2). +.SH BUGS +In order to detect available userfault features and +enable certain subset of those features +the usefault file descriptor must be closed after the first +.BR UFFDIO_API +operation that queries features availability and re-opened before +the second +.BR UFFDIO_API +call that actually enables the desired features. .SH SEE ALSO .BR ioctl (2), .BR mmap (2), -- 1.9.1