[PATCH 6/8] nvme: move the NS_DEAD flag to the controller

[Sagi Grimberg]

>>> -
>>> +	if (!test_and_set_bit(NVME_CTRL_NS_DEAD, &ctrl->flags)) {
>>> +		list_for_each_entry(ns, &ctrl->namespaces, list)
>>> +			nvme_set_queue_dying(ns);
>>> +	}
>>
>> Looking at it now, I'm not sure I understand the need for this flag. It
>> seems to make nvme_kill_queues reentrant safe, but the admin queue
>> unquiesce can still end up unbalanced under reentrance?
>>
>> How is this not broken today (or ever since quiesce/unquiesce started
>> accounting)? Maybe I lost some context on the exact subtlety of how
>> nvme-pci uses this interface...
> 
> Yes, this also looks weird and I had a TODO list entry for myself
> to look into what is going on here.  The whole interaction
> with nvme_remove_namespaces is pretty weird to start with, and then
> the code in PCIe is even more weird.  But to feel confident to
> touch this I'd need real hot removal testing, for which I don't
> have a good rig right now.

Lets for start move the bit check up in the function and reverse
the polarity to return if it is set. Unless someone can make sense
of why this is OK.