netpoll: Warn if more packets are processed than are budgeted

There is already a warning for this case in the normal netpoll path,
but put a copy here in case how netpoll calls the poll functions
causes a differenet result.

netpoll will shortly call the napi poll routine with a budget 0 to
avoid any rx packets being processed.  As nothing does that today
we may encounter drivers that have problems so a netpoll specific
warning seems desirable.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/netpoll.c

@@ -158,6 +158,7 @@ static int poll_one_napi(struct napi_struct *napi, int budget)
 	set_bit(NAPI_STATE_NPSVC, &napi->state);
 
 	work = napi->poll(napi, budget);
+	WARN_ONCE(work > budget, "%pF exceeded budget in poll\n", napi->poll);
 	trace_napi_poll(napi);
 
 	clear_bit(NAPI_STATE_NPSVC, &napi->state);