Re: [PATCH] io_uring: take page references for NOMMU pbuf_ring mmaps

Greg Kroah-Hartman
2026-04-21T13:55:40Z

On Tue, Apr 21, 2026 at 07:50:32AM -0600, Jens Axboe wrote:
> On 4/21/26 7:46 AM, Greg Kroah-Hartman wrote:
> > Note, I have no way of testing this, I'm only forwarding this on because
> > I got the bug report and was able to generate something that "seems"
>
> AI bug report I presume? Because I can't imagine anyone ever attempted
> to run this.

Yes, I got a bunch of "non-mmu" bug reports, which is a bit odd but I
guess you can do that with qemu these days? I should dig into that,
maybe that way I can test this and get a reproducer for you. If not,
let's just bin the thing.

> > correct, but it might be a total load of crap here, my knowledge of the
> > vm layer is very low so take this for where it is coming from (i.e. a
> > non-deterministic pattern matching system.)
> >
> > I do have another patch that just disables io_uring for !MMU systems, if
> > you want that instead? Or is this feature something that !MMU devices
> > actually care about?
>
> I mean, who really cares about !MMU in the first place, we should just
> kill that off with a passion.
>
> Let me take a closer look at this and bounce it past some vm people, my
> nommu knowledge is close to zero as it's never been relevant in my
> professional life time. Which is saying something...

Let me try to get a reproducer going first, let's not waste any more
human time on this just yet, sorry for sending this out without that
done first...

thanks,

greg k-h