Re: [GIT PULL] Block updates for 6.9-rc1

Jens Axboe
2024-03-12T01:17:25Z

On 3/11/24 7:09 PM, Christoph Hellwig wrote:
> On Mon, Mar 11, 2024 at 08:28:50PM -0400, Mike Snitzer wrote:
>> All for Jens being made to suffer with dm-crypt but I think we need a
>> proper root cause of what is happening for you and Johannes ;)
>
> I'm going to try to stay out of the cranking, but I think the reason is
> that the limits stacking inherits the max_segment_size, nvme has weird
> rules for them due their odd PRPs, and dm-crypt set it's own
> max_segment_size to split out each page. The regression here is
> that we now actually verify that conflict.
>
> So this happens only for dm-crypt on nvme. The fix is probably
> to not inherit low-level limits like max_segment_size, but I need
> to think about it a bit more and come up with an automated test case
> using say nvme-loop.

That does seem like the most plausible explanation, I'm just puzzled why
nobody hit it before it landed in Linus's tree. I know linux-next isn't
THAT well runtime tested, but still. That aside, obviously the usual
test cases should've hit it. Unless that was all on non-nvme storage,
which is of course possible.

> So for now the revert is the right thing.

Yup

--
Jens Axboe