[PATCH V2 05/13] block: only account passthrough IO from userspace

[Christoph Hellwig]

On Tue, Jan 25, 2022 at 05:09:42PM +0800, Ming Lei wrote:
> Follows another simple way by accounting all request with bio attached,
> except for requests with kernel buffer.

> -	else if (rq->q->disk)
> +	else if (rq->q->disk && rq->bio)
>  		rq->part = rq->q->disk->part0;

Most passthrough requests will have a bio, so you'll still use e.g.
the sd gendisk for sg request here.

I think the right way would be to just remove this branch entirely.
This means we only account bios with a block_device, which implies
they have a gendisk.