[PATCH net-next v8 5/5] tls: Flush backlog before waiting for a new record

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

While lock_sock is held, incoming TCP segments land on
sk->sk_backlog rather than sk->sk_receive_queue.
tls_rx_rec_wait() inspects only sk_receive_queue, so
backlog data remains invisible. For non-blocking callers
(read_sock, and recvmsg or splice_read with MSG_DONTWAIT)
this causes a spurious -EAGAIN. For blocking callers it
forces an unnecessary sleep/wakeup cycle.

Flush the backlog inside tls_rx_rec_wait() before checking
sk_receive_queue so the strparser can parse newly-arrived
segments immediately. On the next loop iteration
tls_read_flush_backlog() may redundantly flush, but this
path is cold and the cost is negligible.

Suggested-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/tls/tls_sw.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index a16f2954d393..0f365cc944a7 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1382,6 +1382,8 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
 		if (ret < 0)
 			return ret;
 
+		if (sk_flush_backlog(sk))
+			released = true;
 		if (!skb_queue_empty(&sk->sk_receive_queue)) {
 			/* Defer notification to the exit point;
 			 * this thread will consume the record

-- 
2.53.0