Messages in this thread | | | Date | Tue, 9 Sep 2014 10:19:45 +0900 | From | Tejun Heo <> | Subject | Re: WARNING in block layer triggered in 3.17-rc3 |
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Hello,
On Mon, Sep 08, 2014 at 01:42:44PM -0400, Alan Stern wrote: > > This looks like a nasty hack. In theory the QUEUE_FLAG_INIT_DONE should > > be unset on blk_unregister_queue() to match the teardown; it's only > > accident it isn't. del_gendisk() in sd_remove() is supposed to tear a > > lot of queue stuff down. > > It's not clear what the operative assumptions are. The comment in > blk_register_queue() implies that bypass is active only because it was > set up that way when the queue was created. The fact that > blk_unregister_queue() doesn't call blk_queue_bypass_start() seems to > support this view -- although it could also be a simple oversight. > > Hopefully Tejun can clear this iup.
Maintaining the initial bypass till queue registration is an optimization because shutting down a fully functional queue is a costly operation and there are drivers which set and destroy queues repeatedly while probing, so, yeah, it's really a special case for when the queue is being registered for the first time.
> > Your hack seems to indicate that this doesn't work on the add->del->add > > transtion of a gendisk. > > Indeed, it does not work.
As such, the change you suggested makes perfect sense to me. Why wouldn't it work?
Thanks.
-- tejun
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