Re: [PATCH v1] mm/gup: disallow FOLL_FORCE|FOLL_WRITE on hugetlb mappings

[David Hildenbrand]

On 31.10.22 23:13, Mike Kravetz wrote:
> On 10/31/22 13:14, Jason Gunthorpe wrote:
> > On Mon, Oct 31, 2022 at 04:25:24PM +0100, David Hildenbrand wrote:
> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > > Cc: Peter Xu <peterx@xxxxxxxxxx>
> > > Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> > > Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > > Reported-by: syzbot+f0b97304ef90f0d0b1dc@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> > > ---
> > >
> > > I assume this has been broken at least since 2014, when mm/gup.c came to
> > > life. I failed to come up with a suitable Fixes tag quickly.
> >
> > I'm worried this would break RDMA over hugetlbfs maps - which is a
> > real thing people do.
>
> Yes, it is a real thing.  Unfortunately, I do not know exactly how it is used.
>
> > MikeK do you have test cases?
>
> Sorry, I do not have any test cases.
>
> I can ask one of our product groups about their usage.  But, that would
> certainly not be a comprehensive view.

With

https://lkml.kernel.org/r/20221116102659.70287-1-david@xxxxxxxxxx

on it's way, the RDMA concern should be gone, hopefully.

@Andrew, can you queue this one? Thanks.

--
Thanks,

David / dhildenb