[PATCH] mm: fix hugetlb page unmap count balance issue

[Andrew Morton]

On Wed, 7 Jun 2023 13:53:10 -0700 Mike Kravetz <mike.kravetz at oracle.com> wrote:

> > 
> > BUGs aren't good.  Can we please find a way to push this along?
> > 
> > Have we heard anything from any udmabuf people?
> > 
> 
> I have not heard anything.  When this issue popped up, it took me by surprise.
> 
> udmabuf maintainer (Gerd Hoffmann), the people who added hugetlb support and
> the list where udmabuf was developed (dri-devel at lists.freedesktop.org) have
> been on cc.

Maybe Greg can suggest a way forward.

> My 'gut reaction' would be to remove hugetlb support from udmabuf.  From a
> quick look, if we really want this support then there will need to be some
> API changes.  For example UDMABUF_CREATE should be hugetlb page aligned
> and a multiple of hugetlb page size if using a hugetlb mapping.
> 
> It would be good to know about users of the driver.

So disabling "hugetlb=on" (and adding an explanatory printk) would
suffice for now?