[PATCH 08/10] block: provide a generic_make_request_fast helper

[Sagi Grimberg]

> This helper allows reinserting a bio into a new queue without much
> overhead, but requires all queue limits to be the same for the upper
> and lower queues, and it does not provide any recursion preventions,
> which requires the caller to not split the bio.

Isn't the same limits constraint too restrictive?

Say I have two paths to the same namespace via two different HBAs, each
with its own virt_boundary capability for example? That would require us
to split failover bio wouldn't it?

> +/*
> + * Fast-path version of generic_make_request.

generic_make_request is also called in the fast-path, maybe reword it
to: "Fast version of generic_make_request"