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. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
