# Re: \[PATCH\] mmap.2: Add description of MAP\_SHARED\_VALIDATE and MAP\_SYNC

- From: Jan Kara \<hidden\>
- Date: 2018-04-12 14:22:14 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2018/04/135165
- Thread: https://ratatoskr.run/linux-fsdevel/2017/11/129246/t.md

```text
Hello Michael!

On Thu 12-04-18 15:00:49, 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.

Thanks!

> > +.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.

Yes, the first is correct.

								Honza
-- 
Jan Kara [ref]
SUSE Labs, CR
```