[PATCH bpf v2] xdp: Handle device unregister for devmap_hash map type

["Toke Høiland-Jørgensen" <toke@redhat.com>]

It seems I forgot to add handling of devmap_hash type maps to the device
unregister hook for devmaps. This omission causes devices to not be
properly released, which causes hangs.

Fix this by adding the missing handler.

Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
v2:
  - Grab the update lock while walking the map and removing entries.

 kernel/bpf/devmap.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index d27f3b60ff6d..a0a1153da5ae 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -719,6 +719,38 @@ const struct bpf_map_ops dev_map_hash_ops = {
 	.map_check_btf = map_check_no_btf,
 };
 
+static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
+				       struct net_device *netdev)
+{
+	unsigned long flags;
+	int i;
+
+	spin_lock_irqsave(&dtab->index_lock, flags);
+	for (i = 0; i < dtab->n_buckets; i++) {
+		struct bpf_dtab_netdev *dev, *odev;
+		struct hlist_head *head;
+
+		head = dev_map_index_hash(dtab, i);
+		dev = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
+				       struct bpf_dtab_netdev,
+				       index_hlist);
+
+		while (dev) {
+			odev = (netdev == dev->dev) ? dev : NULL;
+			dev = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&dev->index_hlist)),
+					       struct bpf_dtab_netdev,
+					       index_hlist);
+
+			if (odev) {
+				hlist_del_rcu(&odev->index_hlist);
+				call_rcu(&odev->rcu,
+					 __dev_map_entry_free);
+			}
+		}
+	}
+	spin_unlock_irqrestore(&dtab->index_lock, flags);
+}
+
 static int dev_map_notification(struct notifier_block *notifier,
 				ulong event, void *ptr)
 {
@@ -735,6 +767,11 @@ static int dev_map_notification(struct notifier_block *notifier,
 		 */
 		rcu_read_lock();
 		list_for_each_entry_rcu(dtab, &dev_map_list, list) {
+			if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
+				dev_map_hash_remove_netdev(dtab, netdev);
+				continue;
+			}
+
 			for (i = 0; i < dtab->map.max_entries; i++) {
 				struct bpf_dtab_netdev *dev, *odev;
 
-- 
2.23.0