Re: [PATCH v6 01/26] fuse: Fix dax truncate/punch_hole fault path

Stefan Hajnoczi
2025-02-06T18:11:08Z

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On Thu, Feb 06, 2025 at 03:59:03PM +0100, Albert Esteve wrote:
> Hi!
>
> On Thu, Feb 6, 2025 at 3:30 PM Stefan Hajnoczi <stefanha@redhat.com> wrote:
> >
> > On Thu, Feb 06, 2025 at 08:37:07AM -0500, Vivek Goyal wrote:
> > > And then there are challenges at QEMU level. virtiofsd needs additional
> > > vhost-user commands to implement DAX and these never went upstream in
> > > QEMU. I hope these challenges are sorted at some point of time.
> >
> > Albert Esteve has been working on QEMU support:
> > https://lore.kernel.org/qemu-devel/20240912145335.129447-1-aesteve@redhat.com/
> >
> > He has a viable solution. I think the remaining issue is how to best
> > structure the memory regions. The reason for slow progress is not
> > because it can't be done, it's probably just because this is a
> > background task.
>
> It is partially that, indeed. But what has me blocked for now on posting the
> next version is that I was reworking a bit the MMAP strategy.
> Following David comments, I am relying more on RAMBlocks and
> subregions for mmaps. But this turned out more difficult than anticipated.
>
> I hope I can make it work this month and then post the next version.
> If there are no major blockers/reworks, further iterations on the
> patch shall go smoother.
>
> I have a separate patch for the vhost-user spec which could
> iterate faster, if that'd help.

Let's see if anyone needs the vhost-user spec extension now. Otherwise
it seems fine to merge it together with the implementation of that spec.

Stefan

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