linux-kernel - Re: [PATCH] mm: fix hugetlb page unmap count balance issue

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Date:   Wed, 7 Jun 2023 14:16:55 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Gerd Hoffmann <kraxel@...hat.com>,
        Junxiao Chang <junxiao.chang@...el.com>,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        jmarchan@...hat.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, muchun.song@...ux.dev,
        Vivek Kasireddy <vivek.kasireddy@...el.com>,
        Dongwon Kim <dongwon.kim@...el.com>,
        James Houghton <jthoughton@...gle.com>,
        dri-devel@...ts.freedesktop.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] mm: fix hugetlb page unmap count balance issue

On 06/07/23 14:00, Andrew Morton wrote:
> On Wed, 7 Jun 2023 13:53:10 -0700 Mike Kravetz <mike.kravetz@...cle.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@...ts.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?

I can put together a patch to do that.

-- 
Mike Kravetz