[PATCH 3/3] man/mremap.2: don't unmap the overlapping VMA(s)

[Piotr Kwapulinski]

mremap.2 man page update for MREAP_DONTUNMAP flag of mremap.

Signed-off-by: Piotr Kwapulinski <kwapulinski.piotr@xxxxxxxxx>
---
It should be considered to be merged only in case the patch
"[PATCH 2/3] mm/mremap.c: don't unmap the overlapping VMA(s)"
is merged.
---
 man2/mremap.2 | 50 +++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/man2/mremap.2 b/man2/mremap.2
index e4998a4..978d509 100644
--- a/man2/mremap.2
+++ b/man2/mremap.2
@@ -27,7 +27,7 @@
 .\"            Update for Linux 1.3.87 and later
 .\" 2005-10-11 mtk: Added NOTES for MREMAP_FIXED; revised EINVAL text.
 .\"
-.TH MREMAP 2 2015-12-05 "Linux" "Linux Programmer's Manual"
+.TH MREMAP 2 2016-04-02 "Linux" "Linux Programmer's Manual"
 .SH NAME
 mremap \- remap a virtual memory address
 .SH SYNOPSIS
@@ -104,7 +104,9 @@ accepts a fifth argument,
 .IR "void\ *new_address" ,
 which specifies a page-aligned address to which the mapping must
 be moved.
-Any previous mapping at the address range specified by
+If
+.B MREMAP_DONTUNMAP
+is not set then any previous mapping at the address range specified by
 .I new_address
 and
 .I new_size
@@ -114,6 +116,30 @@ If
 is specified, then
 .B MREMAP_MAYMOVE
 must also be specified.
+.TP
+.BR MREMAP_DONTUNMAP " (since Linux 4.6)"
+This flag is similar to
+.B MAP_DONTUNMAP
+flag of
+.BR mmap (2).
+If this flag and
+.B MREMAP_FIXED
+are set and the memory region specified by
+.I new_address
+and
+.I new_size
+overlaps pages of any existing mapping(s), then the
+.BR mremap ()
+will fail with
+.BR ENOMEM .
+No existing mapping(s) will be discarded. If
+.B MREMAP_DONTUNMAP
+is specified, then
+.B MREMAP_FIXED
+must also be specified.
+
+Note: currently, this flag is not implemented in the glibc wrapper.
+Use the numerical value 4, if you want to use it.
 .PP
 If the memory segment specified by
 .I old_address
@@ -156,8 +182,9 @@ page aligned; a value other than
 .B MREMAP_MAYMOVE
 or
 .B MREMAP_FIXED
-was specified in
-.IR flags ;
+or
+.B MREMAP_DONTUNMAP
+was specified in \fIflags\fP;
 .I new_size
 was zero;
 .I new_size
@@ -175,13 +202,26 @@ and
 or
 .B MREMAP_FIXED
 was specified without also specifying
-.BR MREMAP_MAYMOVE .
+.BR MREMAP_MAYMOVE ;
+or
+.B MREMAP_DONTUNMAP
+was specified without also specifying
+.BR MREMAP_FIXED .
 .TP
 .B ENOMEM
 The memory area cannot be expanded at the current virtual address, and the
 .B MREMAP_MAYMOVE
 flag is not set in \fIflags\fP.
 Or, there is not enough (virtual) memory available.
+Or, both the
+.B MREMAP_FIXED
+and
+.B MREMAP_DONTUNMAP
+flags are set and the memory region specified by
+.I new_address
+and
+.I new_size
+overlaps pages of any existing mapping(s).
 .SH CONFORMING TO
 This call is Linux-specific, and should not be used in programs
 intended to be portable.
-- 
2.7.4