Re: [PATCH V6 00/12] block: support bio based io polling

Ming Lei
2021-05-17T07:15:17Z

Hi JeffleXu,

On Mon, May 17, 2021 at 02:16:39PM +0800, JeffleXu wrote:
> Hi all,
>
> What's the latest progress of this bio-based polling feature?
>
> I've noticed that hch has also sent a patch set on this [1]. But as far
> as I know, hch's patch set only refactors the interface of polling in
> the block layer. It indeed helps bio-based polling for some kind of
> bio-based driver, but for DM/MD where one bio could be mapped to several
> split bios, more work is obviously needed, just like Lei Ming's
> io_context related code in this patch set.
>
> hch may have better idea, after all [1] is just a preparation patch set.

Yeah, we have to rebase V6 against Christoph's patchset anyway.

Looks there is at least two approaches left for us:

1) keep the generic approach in V6, just rebase after Christoph's patch
is finalized

2) support io polling simply in bio driver, since bio->bi_cookie is
assigned for underlying bio, and it shouldn't be very difficult to
support that in DM/MD. I have been thinking of it a while, but not
coding it yet. BTW, all underlying bios can be linked to DM
bio->bi_next, and we can add one new callback of .io_poll for polling
DM/MD's bio.

Thanks,
Ming