Re: [PATCH v4 2/3] mm: introduce MAP_VALIDATE a mechanism for adding new mmap flags

[Jan Kara]

On Sun 17-09-17 19:39:45, Christoph Hellwig wrote:
> On Sat, Sep 16, 2017 at 08:44:14PM -0700, Dan Williams wrote:
> > So it wasn't all that easy, and Linus declined to take it. I think we
> > should add a new ->mmap_validate() file operation and save the
> > tree-wide cleanup until later.
> 
> Note that we already have a mmap_capabilities callout for nommu,
> I wonder if we could generalize that.

So if I understood Dan right, Linus refused to merge the patch which adds
'flags' argument to ->mmap callback. That is actually logically independent
change from validating flags passed to mmap(2) syscall. Dan did it just to
save himself from adding a VMA flag for MAP_DIRECT.

For validating flags passed to mmap(2), I agree we could use
->mmap_capabilities() instead of mmap_supported_mask Dan has added. But I
don't have a strong opinion there.

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR