[dm-devel] [PATCH V5 05/12] block: add new field into 'struct bvec_iter'

[Ming Lei]

On Mon, Apr 12, 2021 at 10:26:53AM +0100, Christoph Hellwig wrote:
> I don't like where this is going.
> 
> I think the model of storing the polling cookie in the bio is useful,
> but:
> 
>  (1) I think having this in the iter is a mess.  Can you measure if
>      just marking bvec_iter __packed will generate much worse code
>      at all anymore?  If not we can just move this into the bio

Just test with packed 'struct bvec_iter' by running io_uring/libaio over
nvme/null_blk with different bs size, not see obvious difference
compared with unpacked bvec_iter.

So will switch to packed bvec_iter in next version.

>      If it really generates much worse code I think you need to pick
>      a different name as  as that i really confusing vs the bio field
>      of the same name that is used entirely differenly.  Similarly
>      the bio_get_private_data and bio_set_private_data helpers are
>      entirely misnamed, as the names suggest they deal with the
>      bi_private field in struct bio.  I actually suspect not having
>      these helpers would be much preferable

OK, how about naming it as .bi_poll_data?


Thanks,
Ming