[PATCH net] igb: fix netpoll exit with traffic

[Jesse Brandeburg]

Oleksandr brought a bug report where netpoll causes trace messages in
the log on igb.

[22038.710800] ------------[ cut here ]------------
[22038.710801] igb_poll+0x0/0x1440 [igb] exceeded budget in poll
[22038.710802] WARNING: CPU: 12 PID: 40362 at net/core/netpoll.c:155 netpoll_poll_dev+0x18a/0x1a0

After some discussion and debug from the list, it was deemed that the
right thing to do is initialize the clean_complete variable to false
when the "netpoll mode" of passing a zero budget is used.

This logic should be sane and not risky because the only time budget
should be zero on entry is netpoll.  Change includes a small refactor
of local variable assignments to clean up the look.

Fixes: 16eb8815c235 ("igb: Refactor clean_rx_irq to reduce overhead and improve performance")
Reported-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Suggested-by: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>
---

Compile tested ONLY, but functionally it should be exactly the same for
all cases except when budget is zero on entry, which will hopefully fix
the bug.
---
 drivers/net/ethernet/intel/igb/igb_main.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 0cd37ad81b4e..b0a9bed14071 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -7991,12 +7991,16 @@ static void igb_ring_irq_enable(struct igb_q_vector *q_vector)
  **/
 static int igb_poll(struct napi_struct *napi, int budget)
 {
-	struct igb_q_vector *q_vector = container_of(napi,
-						     struct igb_q_vector,
-						     napi);
-	bool clean_complete = true;
+	struct igb_q_vector *q_vector;
+	bool clean_complete;
 	int work_done = 0;
 
+	/* if budget is zero, we have a special case for netconsole, so
+	 * make sure to set clean_complete to false in that case.
+	 */
+	clean_complete = !!budget;
+
+	q_vector = container_of(napi, struct igb_q_vector, napi);
 #ifdef CONFIG_IGB_DCA
 	if (q_vector->adapter->flags & IGB_FLAG_DCA_ENABLED)
 		igb_update_dca(q_vector);
-- 
2.30.2