Re: [PATCH 5/8] iomap: only set iocb->private for polled bio

Jens Axboe
2023-07-21T15:38:14Z

On 7/21/23 9:35?AM, Darrick J. Wong wrote:
> On Thu, Jul 20, 2023 at 12:13:07PM -0600, Jens Axboe wrote:
>> iocb->private is only used for polled IO, where the completer will
>> find the bio to poll through that field.
>>
>> Assign it when we're submitting a polled bio, and get rid of the
>> dio->poll_bio indirection.
>
> IIRC, the only time iomap actually honors HIPRI requests from the iocb
> is if the entire write can be satisfied with a single bio -- no zeroing
> around, no dirty file metadata, no writes past EOF, no unwritten blocks,
> etc. Right?
>
> There was only ever going to be one assign to dio->submit.poll_bio,
> which means the WRITE_ONCE isn't going to overwrite some non-NULL value.
> Correct?
>
> All this does is remove the indirection like you said.
>
> If the answers are {yes, yes} then I understand the HIPRI mechanism
> enough to say

Correct, yes to both. For multi bio or not a straight overwrite, iomap
disables polling.

> Reviewed-by: Darrick J. Wong <djwong@kernel.org>

Thanks!

--
Jens Axboe