Re: Regression: NVMe: kernel BUG at lib/sg_pool.c:103!

Christoph Hellwig
2019-02-21T13:37:03Z

On Thu, Feb 21, 2019 at 01:29:57AM +0000, Chaitanya Kulkarni wrote:
> Hi Martin,
>
> I don't mind going though that route, here are some points about
> benefits of not using REQ_SPECIAL_PAYLOAD for write-zeroes :-
>
> 1. We are using RQF_SPECIAL_PAYLOAD for only discard commands and not for
> write-zeroes because it does not have any payload. Using this in the code will
> trigger more code changes to handle in the completion path.

Yes. And that is the big difference to SCSI where REQ_OP_WRITE_ZEROES
turns into a WRITE SAME command that has a payload. So for SCSI
RQF_SPECIAL_PAYLOAD for REQ_OP_WRITE_ZEROES makes a lot of sense, for
NVMe it does not.