[dm-devel] [for-4.16 PATCH v2 2/3] block: cope with gendisk's 'queue' being added later

[Christoph Hellwig]

On Tue, Jan 09, 2018 at 09:41:03PM -0500, Mike Snitzer wrote:
> Since I can remember DM has forced the block layer to allow the
> allocation and initialization of the request_queue to be distinct
> operations.  Reason for this was block/genhd.c:add_disk() has required
> that the request_queue (and associated bdi) be tied to the gendisk
> before add_disk() is called -- because add_disk() also deals with
> exposing the request_queue via blk_register_queue().

Hmm.  I don't even know how that could be safe given that the disk
is live and visible to userspace once added..