[PATCH bpf] skmsg: schedule psock work if the cached skb exists on the psock

[Liu Jian <liujian56@huawei.com>]

In sk_psock_backlog function, for ingress direction skb, if no new data
packet arrives after the skb is cached, the cached skb does not have a
chance to be added to the receive queue of psock. As a result, the cached
skb cannot be received by the upper-layer application.

Fix this by reschedule the psock work to dispose the cached skb in
sk_msg_recvmsg function.

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Liu Jian <liujian56@huawei.com>
---
 net/core/skmsg.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 188f8558d27d..ca70525621c7 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -434,8 +434,10 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 			if (copied + copy > len)
 				copy = len - copied;
 			copy = copy_page_to_iter(page, sge->offset, copy, iter);
-			if (!copy)
-				return copied ? copied : -EFAULT;
+			if (!copy) {
+				copied = copied ? copied : -EFAULT;
+				goto out;
+			}
 
 			copied += copy;
 			if (likely(!peek)) {
@@ -455,7 +457,7 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 				 * didn't copy the entire length lets just break.
 				 */
 				if (copy != sge->length)
-					return copied;
+					goto out;
 				sk_msg_iter_var_next(i);
 			}
 
@@ -477,7 +479,9 @@ int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 		}
 		msg_rx = sk_psock_peek_msg(psock);
 	}
-
+out:
+	if (psock->work_state.skb && copied > 0)
+		schedule_work(&psock->work);
 	return copied;
 }
 EXPORT_SYMBOL_GPL(sk_msg_recvmsg);
-- 
2.17.1