Subject: [net-next 11/15] net/mlx5e: CT, Avoid false lock depenency warning

From: Saeed Mahameed <[email-masked]>
Date: Thu, 7 Jan 2021 21:30:50 -0800

From: Roi Dayan <[email-masked]>

To avoid false lock dependency warning set the ct_entries_ht lock
class different than the lock class of the ht being used when deleting
last flow from a group and then deleting a group, we get into del_sw_flow_group()
which call rhashtable_destroy on fg->ftes_hash which will take ht->mutex but
it's different than the ht->mutex here.

======================================================
WARNING: possible circular locking dependency detected
5.10.0-rc2+ #8 Tainted: G           O
------------------------------------------------------
revalidator23/24009 is trying to acquire lock:
ffff888128d83828 (&node->lock){++++}-{3:3}, at: mlx5_del_flow_rules+0x83/0x7a0 [mlx5_core]

but task is already holding lock:
ffff8881081ef518 (&ht->mutex){+.+.}-{3:3}, at: rhashtable_free_and_destroy+0x37/0x720

which lock already depends on the new lock.

Fixes: 9808dd0a2aee ("net/mlx5e: CT: Use rhashtable's ct entries instead of a separate list")
Signed-off-by: Roi Dayan <[email-masked]>
Reviewed-by: Paul Blakey <[email-masked]>
Signed-off-by: Saeed Mahameed <[email-masked]>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
index 9a189c06ab56..510eab3204d4 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c
@@ -1555,6 +1555,14 @@ tc_ct_cleanup_trk_new_rules(struct mlx5_ct_ft *ft)
 	mlx5_modify_header_dealloc(priv->mdev, ft->trk_new_rules.modify_hdr);
 }
 
+/* To avoid false lock dependency warning set the ct_entries_ht lock
+ * class different than the lock class of the ht being used when deleting
+ * last flow from a group and then deleting a group, we get into del_sw_flow_group()
+ * which call rhashtable_destroy on fg->ftes_hash which will take ht->mutex but
+ * it's different than the ht->mutex here.
+ */
+static struct lock_class_key ct_entries_ht_lock_key;
+
 static struct mlx5_ct_ft *
 mlx5_tc_ct_add_ft_cb(struct mlx5_tc_ct_priv *ct_priv, u16 zone,
 		     struct nf_flowtable *nf_ft)
@@ -1595,6 +1603,8 @@ mlx5_tc_ct_add_ft_cb(struct mlx5_tc_ct_priv *ct_priv, u16 zone,
 	if (err)
 		goto err_init;
 
+	lockdep_set_class(&ft->ct_entries_ht.mutex, &ct_entries_ht_lock_key);
+
 	err = rhashtable_insert_fast(&ct_priv->zone_ht, &ft->node,
 				     zone_params);
 	if (err)
-- 
2.26.2