# \[PATCH bpf-next v2\] bpf/devmap: convert remaining READ\_ONCE() to rcu\_dereference\_check()

- Subsystems: XDP (eXpress Data Path), BPF \[GENERAL\] (Safe Dynamic Programs and Tools), THE REST
- Maintainers: Alexei Starovoitov, Daniel Borkmann, David S. Miller, Jakub Kicinski, Jesper Dangaard Brouer, John Fastabend, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
- Status: LANDED: 1 review, 1 by a maintainer (0fc4dcc13f09 · 2021-07-01 07:28 M Paul E. McKenney)
- Landed in mainline as 0fc4dcc13f09 on 2021-07-01.
- 1 review trailer.
- List: netdev
- 3 messages, 3 authors
- Page: https://ratatoskr.run/netdev/2021/06/7772607/t

## \[PATCH bpf-next v2\] bpf/devmap: convert remaining READ\_ONCE() to rcu\_dereference\_check()

- From: Toke Høiland-Jørgensen \<hidden\>
- Date: 2021-06-29 09:39:27 
- Message: https://ratatoskr.run/netdev/2021/06/7772607.md

```text
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

```

## Re: \[PATCH bpf-next v2\] bpf/devmap: convert remaining READ\_ONCE() to rcu\_dereference\_check()

- From: Martin KaFai Lau \<hidden\>
- Date: 2021-06-30 00:09:09 
- Message: https://ratatoskr.run/netdev/2021/06/7772659.md

```text
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>
```

## Re: \[PATCH bpf-next v2\] bpf/devmap: convert remaining READ\_ONCE() to rcu\_dereference\_check()

- From: patchwork-bot+netdevbpf@kernel.org
- Date: 2021-07-01 07:30:04 
- Message: https://ratatoskr.run/netdev/2021/07/7772684.md

```text
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!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html


```