[PATCH net] net: gro_cells: Provide lockdep class for gro_cell's bh_lock

One GRO-cell device's NAPI callback can nest into the GRO-cell of
another device if the underlying device is also using GRO-cell.
This is the case for IPsec over vxlan.
These two GRO-cells are separate devices. From lockdep's point of view
it is the same because each device is sharing the same lock class and so
it reports a possible deadlock assuming one device is nesting into
itself.

Provide a lockclass for the bh_lock on for gro-cell device allowing
lockdep to distinguish between individual devices.

Fixes: 25718fdcbdd2 ("net: gro_cells: Use nested-BH locking for gro_cell")
Reported-by: Gal Pressman <redacted>
Closes: https://lore.kernel.org/all/66664116-edb8-48dc-ad72-d5223696dd19@nvidia.com/ (local)
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/net/gro_cells.h | 1 +
 net/core/gro_cells.c    | 1 +
 2 files changed, 2 insertions(+)

diff --git a/include/net/gro_cells.h b/include/net/gro_cells.h
index 596688b67a2a8..2453d0139c205 100644
--- a/include/net/gro_cells.h
+++ b/include/net/gro_cells.h

@@ -10,6 +10,7 @@ struct gro_cell;
 
 struct gro_cells {
 	struct gro_cell __percpu	*cells;
+	struct lock_class_key		cells_bh_key;
 };
 
 int gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb);

diff --git a/net/core/gro_cells.c b/net/core/gro_cells.c
index fd57b845de333..a91fdc47e8096 100644
--- a/net/core/gro_cells.c
+++ b/net/core/gro_cells.c

@@ -88,6 +88,7 @@ int gro_cells_init(struct gro_cells *gcells, struct net_device *dev)
 
 		__skb_queue_head_init(&cell->napi_skbs);
 		local_lock_init(&cell->bh_lock);
+		lockdep_set_class(&cell->bh_lock, &gcells->cells_bh_key);
 
 		set_bit(NAPI_STATE_NO_BUSY_POLL, &cell->napi.state);
 

-- 
2.51.0