Re: [PATCH 01/19] mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags

On Tue, Oct 17, 2017 at 01:50:47PM +0200, Jan Kara wrote:

OK, I can do that. But I had just realized that if MAP_DIRECT isn't going
to end up using mmap(2) interface but something else (and I'm not sure
where discussions on this matter ended), we don't need flags argument for
->mmap at all. MAP_SYNC uses a VMA flag anyway and thus it is fine with the
current ->mmap interface. We still need some opt-in mechanism for
MAP_SHARED_VALIDATE though (probably supported mmap flags as Dan had in one
version of his patch). Thoughts on which way to go for now?

Yes, I'd much prefer the mmap_flags in file_operations.  The other
option would be a new FMODE_* flag which is what Al did for various
other optional features, but I generally thing that is a confusing
interface.