On Tue 24-10-17 15:10:07, Ross Zwisler wrote: > On Tue, Oct 24, 2017 at 05:24:15PM +0200, Jan Kara wrote: > > Signed-off-by: Jan Kara <jack@xxxxxxx> > > This looks unchanged since the previous version? Ah, thanks for checking. I forgot to commit modifications. Attached is really updated patch. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
>From 59eeec2998ed9b3840aab951f213148cb1d053a5 Mon Sep 17 00:00:00 2001 From: Jan Kara <jack@xxxxxxx> Date: Thu, 19 Oct 2017 14:44:55 +0200 Subject: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC Signed-off-by: Jan Kara <jack@xxxxxxx> --- man2/mmap.2 | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/man2/mmap.2 b/man2/mmap.2 index 47c3148653be..b38ee6809327 100644 --- a/man2/mmap.2 +++ b/man2/mmap.2 @@ -125,6 +125,21 @@ are carried through to the underlying file. to the underlying file requires the use of .BR msync (2).) .TP +.BR MAP_SHARED_VALIDATE " (since Linux 4.15)" +The same as +.B MAP_SHARED +except that +.B MAP_SHARED +mappings ignore unknown flags in +.IR flags . +In contrast when creating mapping of +.B MAP_SHARED_VALIDATE +mapping type, the kernel verifies all passed flags are known and fails the +mapping with +.BR EOPNOTSUPP +otherwise. This mapping type is also required to be able to use some mapping +flags. +.TP .B MAP_PRIVATE Create a private copy-on-write mapping. Updates to the mapping are not visible to other processes @@ -134,7 +149,10 @@ It is unspecified whether changes made to the file after the .BR mmap () call are visible in the mapped region. .PP -Both of these flags are described in POSIX.1-2001 and POSIX.1-2008. +.B MAP_SHARED +and +.B MAP_PRIVATE +are described in POSIX.1-2001 and POSIX.1-2008. .PP In addition, zero or more of the following values can be ORed in .IR flags : @@ -352,6 +370,21 @@ option. Because of the security implications, that option is normally enabled only on embedded devices (i.e., devices where one has complete control of the contents of user memory). +.TP +.BR MAP_SYNC " (since Linux 4.15)" +This flags is available only with +.B MAP_SHARED_VALIDATE +mapping type. Mappings of +.B MAP_SHARED +type will silently ignore this flag. +This flag is supported only for files supporting DAX (direct mapping of persistent +memory). For other files, creating mapping with this flag results in +.B EOPNOTSUPP +error. Shared file mappings with this flag provide the guarantee that while +some memory is writeably mapped in the address space of the process, it will +be visible in the same file at the same offset even after the system crashes or +is rebooted. This allows users of such mappings to make data modifications +persistent in a more efficient way using appropriate CPU instructions. .PP Of the above flags, only .B MAP_FIXED -- 2.12.3
