From d87f377e4eefcb136b96f235a64c5dd0c0af706b Mon Sep 17 00:00:00 2001
From: Michael Kerrisk <mtk.manpages@gmail.com>
Date: Fri, 21 Apr 2017 09:06:09 +0200
Subject: [PATCH] ioctl_userfaultfd.2: Explain concept of "compatible" mapping
 for UFFDIO_REGISTER

Reported-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
---
 man2/ioctl_userfaultfd.2 | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2
index 4ea10db65..5539bb6f8 100644
--- a/man2/ioctl_userfaultfd.2
+++ b/man2/ioctl_userfaultfd.2
@@ -163,6 +163,12 @@ field was not zero.
 .SS UFFDIO_REGISTER
 (Since Linux 4.3.)
 Register a memory address range with the userfaultfd object.
+The pages in the range must be "compatible".
+In the current implementation,
+.\" According to Mike Rapoport, this will change in Linux 4.11.
+only private anonymous ranges are compatible for registering with
+.BR UFFDIO_REGISTER .
+
 The
 .I argp
 argument is a pointer to a