Signed-off-by: Jan Kara <[email protected]>
---
man2/mmap.2 | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/man2/mmap.2 b/man2/mmap.2
index 47c3148653be..598ff0c64f7f 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
+.B MAP_SHARED_VALIDATE
+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
@@ -352,6 +367,21 @@ 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
On Thu, Oct 19, 2017 at 02:58:17PM +0200, Jan Kara wrote:
> Signed-off-by: Jan Kara <[email protected]>
> ---
> man2/mmap.2 | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index 47c3148653be..598ff0c64f7f 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
> +.B MAP_SHARED_VALIDATE
> +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
Some small nits:
I think you should maybe include a "(since Linux 4.15)" type note after the
MAP_SHARED_VALIDATE header. You also need to update the following line:
Both of these flags are described in POSIX.1-2001 and POSIX.1-2008.
Which used to refer to MAP_SYNC and MAP_PRIVATE.
On Fri 20-10-17 15:47:53, Ross Zwisler wrote:
> On Thu, Oct 19, 2017 at 02:58:17PM +0200, Jan Kara wrote:
> > Signed-off-by: Jan Kara <[email protected]>
> > ---
> > man2/mmap.2 | 30 ++++++++++++++++++++++++++++++
> > 1 file changed, 30 insertions(+)
> >
> > diff --git a/man2/mmap.2 b/man2/mmap.2
> > index 47c3148653be..598ff0c64f7f 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
> > +.B MAP_SHARED_VALIDATE
> > +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
>
> Some small nits:
>
> I think you should maybe include a "(since Linux 4.15)" type note after the
> MAP_SHARED_VALIDATE header. You also need to update the following line:
>
> Both of these flags are described in POSIX.1-2001 and POSIX.1-2008.
>
> Which used to refer to MAP_SYNC and MAP_PRIVATE.
Thanks, I've fixed these.
Honza
--
Jan Kara <jack-IBi9RG/[email protected]>
SUSE Labs, CR
On Tue, Oct 24, 2017 at 03:27:13PM +0200, Jan Kara wrote:
> On Fri 20-10-17 15:47:53, Ross Zwisler wrote:
> > On Thu, Oct 19, 2017 at 02:58:17PM +0200, Jan Kara wrote:
> > > Signed-off-by: Jan Kara <[email protected]>
> > > ---
> > > man2/mmap.2 | 30 ++++++++++++++++++++++++++++++
> > > 1 file changed, 30 insertions(+)
> > >
> > > diff --git a/man2/mmap.2 b/man2/mmap.2
> > > index 47c3148653be..598ff0c64f7f 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
> > > +.B MAP_SHARED_VALIDATE
> > > +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
> >
> > Some small nits:
> >
> > I think you should maybe include a "(since Linux 4.15)" type note after the
> > MAP_SHARED_VALIDATE header. You also need to update the following line:
> >
> > Both of these flags are described in POSIX.1-2001 and POSIX.1-2008.
> >
> > Which used to refer to MAP_SYNC and MAP_PRIVATE.
>
> Thanks, I've fixed these.
Cool, you can add my:
Reviewed-by: Ross Zwisler <ross.zwisler-VuQAYsv1563Yd54FQh9/[email protected]>