On Tue, Jan 26, 2021 at 11:57:48AM +0800, Ming Lei wrote:

quoted

 				*same_page = false;
 				return false;
 			}

So far we don't need bio->bi_disk or bio->bi_bdev(will be changed in
Christoph's patch) during adding page to bio, so there is null ptr
refereance risk.

I've started resurrecting my old plan to always have a valid device
in the bio from allocation time on.  It is pretty invasive, but
probably worth it.  Sending out the first prep series right now, the
actual changes should be ready for an RFC later this week.