| Message ID | 20171024152415.22864-19-jack@suse.cz |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC | expand |
On Tue, Oct 24, 2017 at 05:24:15PM +0200, Jan Kara wrote: > Signed-off-by: Jan Kara <jack@suse.cz> This looks unchanged since the previous version? > --- > 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 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@suse.cz> > > This looks unchanged since the previous version? Ah, thanks for checking. I forgot to commit modifications. Attached is really updated patch. Honza
On Thu, Oct 26, 2017 at 03:24:02PM +0200, Jan Kara wrote: > 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@suse.cz> > > > > 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@suse.com> > SUSE Labs, CR > From 59eeec2998ed9b3840aab951f213148cb1d053a5 Mon Sep 17 00:00:00 2001 > From: Jan Kara <jack@suse.cz> > 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@suse.cz> Looks good, you can add: Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
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
Signed-off-by: Jan Kara <jack@suse.cz> --- man2/mmap.2 | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)