This is a note to let you know that I've just added the patch titled bpf, sockmap: On receive programs try to fast track SK_PASS ingress to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bpf-sockmap-on-receive-programs-try-to-fast-track-sk.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit b574b088aa19b0d5c99f15f224f2160b646eb8c4 Author: John Fastabend <john.fastabend@xxxxxxxxx> Date: Fri Oct 9 11:36:37 2020 -0700 bpf, sockmap: On receive programs try to fast track SK_PASS ingress [ Upstream commit 9ecbfb06a078c4911fb444203e8e41d93d22f886 ] When we receive an skb and the ingress skb verdict program returns SK_PASS we currently set the ingress flag and put it on the workqueue so it can be turned into a sk_msg and put on the sk_msg ingress queue. Then finally telling userspace with data_ready hook. Here we observe that if the workqueue is empty then we can try to convert into a sk_msg type and call data_ready directly without bouncing through a workqueue. Its a common pattern to have a recv verdict program for visibility that always returns SK_PASS. In this case unless there is an ENOMEM error or we overrun the socket we can avoid the workqueue completely only using it when we fall back to error cases caused by memory pressure. By doing this we eliminate another case where data may be dropped if errors occur on memory limits in workqueue. Fixes: 51199405f9672 ("bpf: skb_verdict, support SK_PASS on RX BPF path") Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Link: https://lore.kernel.org/bpf/160226859704.5692.12929678876744977669.stgit@john-Precision-5820-Tower Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/core/skmsg.c b/net/core/skmsg.c index 605c48df7eb68..4fad59ee3df0b 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -767,6 +767,7 @@ static void sk_psock_verdict_apply(struct sk_psock *psock, { struct tcp_skb_cb *tcp; struct sock *sk_other; + int err = -EIO; switch (verdict) { case __SK_PASS: @@ -778,8 +779,20 @@ static void sk_psock_verdict_apply(struct sk_psock *psock, tcp = TCP_SKB_CB(skb); tcp->bpf.flags |= BPF_F_INGRESS; - skb_queue_tail(&psock->ingress_skb, skb); - schedule_work(&psock->work); + + /* If the queue is empty then we can submit directly + * into the msg queue. If its not empty we have to + * queue work otherwise we may get OOO data. Otherwise, + * if sk_psock_skb_ingress errors will be handled by + * retrying later from workqueue. + */ + if (skb_queue_empty(&psock->ingress_skb)) { + err = sk_psock_skb_ingress(psock, skb); + } + if (err < 0) { + skb_queue_tail(&psock->ingress_skb, skb); + schedule_work(&psock->work); + } break; case __SK_REDIRECT: sk_psock_skb_redirect(skb);