Request-based dm and bio-based dm will coexist, since there are
some target drivers which are more fitting to bio-based dm.
dm decides the hook type for a dm device and initializes the queue,
when a table is loaded to the dm device, not device creation time.
Then, request-based dm sets q->request_fn and wants to register
the queue correctly again.
dm-devel mailing list
03-19-2008, 10:09 PM
block: export blk_register_queue
This patch exports blk_register_queue().
blk_register_queue() is called through add_disk().
Request-based dm defers queue allocation/initialization until
a mapping table is loaded, since the way to initialize queue
is different between bio-based mapping and request-based mapping.
So request-based dm needs to call add_disk() and blk_register_queue()