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

[Sagi Grimberg]

>>> That being said ->make_request basically doesn't care about actual
>>> limits at all, it mostly care about support features (e.g. discard, fua,
>>> etc).  So I think a lot of these limits could porbably be lifted,
>>> but I'd need to add the check to generic_make_request_checks back.
>>
>> Different virt_boundary capabilities will trigger bio splits which
>> can make make_request blocking (due to lack of tags).
> 
> All the bio splitting is done in blk_queue_split, and other things
> related to limits are done even later in blk_mq_make_request when
> building the request.  For normal make_request based stacking drivers
> nothing of this matters, although a few drivers t call blk_queue_split
> manually from their make_request method.

Maybe I misunderstood the change log comment, but didn't it said that
the caller is not allowed to submit a bio that might split?