[PATCH 1/2] nvmet-rdma: avoid circular locking dependency on install_queue()

[Sagi Grimberg]

>> According to 777dc82395de ("nvmet-rdma: occasionally flush ongoing
>> controller teardown") this is just for reducing the memory footprint.
>> Wonder if we need to bother, and whether it won't be better to remove
>> the whole thing entirely.
> 
> Well, Sagi added it, so I'll let him chime in on the usefulness.

While I don't like having nvmet arbitrarily replying busy and instead
have lockdep simply just accept that its not a deadlock here, but we can
simply just sidetrack it as proposed I guess.

But Hannes, this is on the other extreme.. Now every connect that nvmet
gets, if there is even a single queue that is disconnecting (global
scope), then the host is denied. Lets give it a sane backlog.
We use rdma_listen backlog of 128, so maybe stick with this magic
number... This way we are busy only if more than 128 queues are tearing
down to prevent the memory footprint from exploding, and hopefully it is
rare enough that the normal host does not see an arbitrary busy
rejection.

Same comment for nvmet-tcp.