[PATCH 0/4] nvme patches for 6.3

[Keith Busch]

On Fri, Feb 10, 2023 at 03:34:09PM +0100, Niklas Schnelle wrote:
> Hi Christoph, Hi Keith,
> 
> It looks like this series causes crashes on s390x.
> With current linux-next-20230210 and a Samsung PM173X I get the
> below[0] crash. Reverting patches 1-3 makes the NVMe work again. I
> tried reverting just patch 3 and 2/3 but this results in crashes as
> well and as far as I can see patches 2/3 depend on each other. Not
> entirely sure what's going on but patch 3 mentions padding to the cache
> line size and our 256 byte cache lines are definitely unusual. I didn't
> see any obvious place where this would break things though. I did debug
> that in the crashing nvme_unmap_data() iod->nr_allocations is -1 and
> iod->use_sgl is true which is weird since it looks to me like iod-
> >nr_allocations should only be -1 if sg_list couldn't be allocated from
> the pool.

Thanks for the notice.

I think the driver must have received a request with multiple physical
segments, but the dma mapping collapsed it to 1. In that case, the driver won't
use the "simple" sgl, but we don't allocate a descriptor either, so we need to
account for that. I'll send a fix shortly.