Re: [PATCH] nvme-tcp: Use __dev_get_by_name instead dev_get_by_name for OPT_HOST_IFACE

quoted

dev_get_by_name() finds network device by name but it also increases
reference count.
Increasing the ref count,
If nvme-tcp queue is present and the network device driver is removed
before nvme_tcp, we will face the following continuous log:
   "kernel:unregister_netdevice: waiting for <eth> to become
   free. Usage count = 2"
And rmmod further halts. Similar case arises during reboot/shutdown
with nvme-tcp queue present and both never completes.

As a fix we will use __dev_get_by_name() which find network device by
name without increasing any reference counter.

And when you remove it without the refcount we'll now have a stale
kernel pointer?

The netdev is not actually needed, its to make sure that it exist as
reference in the host_iface afaict (the netdev is never referenced
afterwards), and I'm pretty sure there was a matching put somewhere in
the former versions of this patch.

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