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

[Hannes Reinecke]

On 01/10/2018 09:32 AM, Christoph Hellwig wrote:
> 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..
> 
We're getting an additional 'change' event once the tables are loaded
and setup properly. That's not a problem, and in fact the DASD driver
has the very same issue/feature/design.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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