[RFC PATCH] nvme: prevent hang on surprise removal of NVMe disk

[Christoph Hellwig]

On Tue, Feb 15, 2022 at 07:22:40AM -0800, Keith Busch wrote:
> I can't actually tell if not checking the DYING flag check was
> intentional or not, since the comments in blk_queue_start_drain() say
> otherwise.
> 
> Christoph, do you know the intention here? Should __bio_queue_enter()
> check the queue DYING flag, or do you prefer drivers explicity set the
> disk state like this? It looks to me the queue flags should be checked
> since that's already tied to the freeze wait_queue_head_t.

It was intentional but maybe not fully thought out.  Do you remember why
we're doing the manual setting of the dying flag instead of just calling
del_gendisk early on in nvme?  Because calling del_gendisk is supposed
to be all that a tree needs to do.