Re: [PATCHv6 11/11] iomap: add support for dma aligned direct-io

Keith Busch
2022-06-23T18:51:24Z

On Thu, Jun 23, 2022 at 02:29:13PM -0400, Eric Farman wrote:
> On Fri, 2022-06-10 at 12:58 -0700, Keith Busch wrote:
> > From: Keith Busch <kbusch@kernel.org>
> >
> > Use the address alignment requirements from the block_device for
> > direct
> > io instead of requiring addresses be aligned to the block size.
>
> Hi Keith,
>
> Our s390 PV guests recently started failing to boot from a -next host,
> and git blame brought me here.
>
> As near as I have been able to tell, we start tripping up on this code
> from patch 9 [1] that gets invoked with this patch:
>
> > for (k = 0; k < i->nr_segs; k++, skip = 0) {
> > size_t len = i->iov[k].iov_len - skip;
> >
> > if (len > size)
> > len = size;
> > if (len & len_mask)
> > return false;
>
> The iovec we're failing on has two segments, one with a len of x200
> (and base of x...000) and another with a len of xe00 (and a base of
> x...200), while len_mask is of course xfff.
>
> So before I go any further on what we might have broken, do you happen
> to have any suggestions what might be going on here, or something I
> should try?

Thanks for the notice, sorry for the trouble. This check wasn't intended to
have any difference from the previous code with respect to the vector lengths.

Could you tell me if you're accessing this through the block device direct-io,
or through iomap filesystem?