On Thu, Apr 12, 2018 at 03:00:49PM +0200, Michael Kerrisk (man-pages) wrote: > Hello Jan, > > I have applied your patch, and tweaked the text a little, and pushed > the result to the git repo. > > On 1 November 2017 at 16:36, Jan Kara <jack@xxxxxxx> wrote: > > Reviewed-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > > Signed-off-by: Jan Kara <jack@xxxxxxx> > > I have a question below. > > > --- > > 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. > > It feels like there's a word missing/unclear wording in the previous > line, before "using". Without that word, the sentence feels a bit > ambiguous. > > Should it be: > > persistent in a more efficient way *through the use of* appropriate > CPU instructions. > > or: > > persistent in a more efficient way *than using* appropriate CPU instructions. > > ? > > Is suspect the first is correct, but need to check. You're right, the first one is correct.
