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

[Christoph Hellwig]

So, I think in th short run setting GD_DEAD is the right thing as a
non-invasive fix, but I'd rather do it in blk_set_queue_dying to also
cover the other drivers with a similar pattern.  blk_set_queue_dying
is never used for cases where q->disk isn't valid so that should be
fine.

In the long run I think we just need to remove the fsync_bdev in
del_gendisk or at least make it conditional.