Subject: [PATCH 01/34] gro_cells: mark napi struct as not busy poll candidates

From: Eric Dumazet <[email-masked]>
Date: Mon, 14 Nov 2016 16:28:42 -0800

[ Upstream commit e88a2766143a27bfe6704b4493b214de4094cf29 ]

Rolf Neugebauer reported very long delays at netns dismantle.

Eric W. Biederman was kind enough to look at this problem
and noticed synchronize_net() occurring from netif_napi_del() that was
added in linux-4.5

Busy polling makes no sense for tunnels NAPI.
If busy poll is used for sessions over tunnels, the poller will need to
poll the physical device queue anyway.

netif_tx_napi_add() could be used here, but function name is misleading,
and renaming it is not stable material, so set NAPI_STATE_NO_BUSY_POLL
bit directly.

This will avoid inserting gro_cells napi structures in napi_hash[]
and avoid the problematic synchronize_net() (per possible cpu) that
Rolf reported.

Fixes: 93d05d4a320c ("net: provide generic busy polling to all NAPI drivers")
Signed-off-by: Eric Dumazet <[email-masked]>
Reported-by: Rolf Neugebauer <[email-masked]>
Reported-by: Eric W. Biederman <[email-masked]>
Acked-by: Cong Wang <[email-masked]>
Tested-by: Rolf Neugebauer <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 include/net/gro_cells.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/net/gro_cells.h b/include/net/gro_cells.h
index d15214d..2a1abbf 100644
--- a/include/net/gro_cells.h
+++ b/include/net/gro_cells.h
@@ -68,6 +68,9 @@ static inline int gro_cells_init(struct gro_cells *gcells, struct net_device *de
 		struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);
 
 		__skb_queue_head_init(&cell->napi_skbs);
+
+		set_bit(NAPI_STATE_NO_BUSY_POLL, &cell->napi.state);
+
 		netif_napi_add(dev, &cell->napi, gro_cell_poll, 64);
 		napi_enable(&cell->napi);
 	}
-- 
2.7.4