[PATCH bpf-next v2] bpf/devmap: convert remaining READ_ONCE() to rcu_dereference_check()

There were a couple of READ_ONCE()-invocations left-over by the devmap RCU
conversion. Convert these to rcu_dereference_check() as well to avoid
complaints from sparse.

v2:
 - Use rcu_dereference_check()

Fixes: 782347b6bcad ("xdp: Add proper __rcu annotations to redirect map entries")
Reported-by: kernel test robot <redacted>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Toke Høiland-Jørgensen <redacted>
---
 kernel/bpf/devmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 2f6bd75cd682..e4ebe70cf201 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c

@@ -558,7 +558,8 @@ int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
 
 	if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
 		for (i = 0; i < map->max_entries; i++) {
-			dst = READ_ONCE(dtab->netdev_map[i]);
+			dst = rcu_dereference_check(dtab->netdev_map[i],
+						    rcu_read_lock_bh_held());
 			if (!is_valid_dst(dst, xdp, exclude_ifindex))
 				continue;
 

@@ -654,7 +655,8 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
 
 	if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
 		for (i = 0; i < map->max_entries; i++) {
-			dst = READ_ONCE(dtab->netdev_map[i]);
+			dst = rcu_dereference_check(dtab->netdev_map[i],
+						    rcu_read_lock_bh_held());
 			if (!dst || dst->dev->ifindex == exclude_ifindex)
 				continue;
 

-- 
2.32.0

On Tue, Jun 29, 2021 at 11:39:07AM +0200, Toke Høiland-Jørgensen wrote:

There were a couple of READ_ONCE()-invocations left-over by the devmap RCU
conversion. Convert these to rcu_dereference_check() as well to avoid
complaints from sparse.

v2:
 - Use rcu_dereference_check()

Acked-by: Martin KaFai Lau <redacted>

Hello:

This patch was applied to bpf/bpf.git (refs/heads/master):

On Tue, 29 Jun 2021 11:39:07 +0200 you wrote:

There were a couple of READ_ONCE()-invocations left-over by the devmap RCU
conversion. Convert these to rcu_dereference_check() as well to avoid
complaints from sparse.

v2:
 - Use rcu_dereference_check()

[...]

Here is the summary with links:
  - [bpf-next,v2] bpf/devmap: convert remaining READ_ONCE() to rcu_dereference_check()
    https://git.kernel.org/bpf/bpf/c/0fc4dcc13f09

You are awesome, thank you!
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