simplify gendisk and request_queue allocation for bio based drivers

[Christoph Hellwig]

On Wed, May 26, 2021 at 12:41:37AM +0200, Ulf Hansson wrote:
> On Fri, 21 May 2021 at 07:51, Christoph Hellwig <hch at lst.de> wrote:
> >
> > Hi all,
> >
> > this series is the first part of cleaning up lifetimes and allocation of
> > the gendisk and request_queue structure.  It adds a new interface to
> > allocate the disk and queue together for bio based drivers, and a helper
> > for cleanup/free them when a driver is unloaded or a device is removed.
> 
> May I ask what else you have in the pipe for the next steps?
> 
> The reason why I ask is that I am looking into some issues related to
> lifecycle problems of gendisk/mmc, typically triggered at SD/MMC card
> removal.

In the short run not much more than superficial cleanups.  Eventually
I want bio based drivers to not require a separate request_queue, leaving
that purely as a data structure for blk-mq based drivers.  But it will
take a while until we get there, so it should not block any fixes.

For hot unplug handling it might be worth to take a look at nvme, as it
is tested a lot for that case.