[PATCH v3 5/8] tls: Suppress spurious saved_data_ready on all receive paths

[Chuck Lever <cel@kernel.org>]

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

Each record release via tls_strp_msg_done() triggers
tls_strp_check_rcv(), which calls tls_rx_msg_ready() and
fires saved_data_ready(). During a multi-record receive,
the first N-1 wakeups are pure overhead: the caller is
already running and will pick up subsequent records on
the next loop iteration. The same waste occurs on the
recvmsg and splice_read paths.

Replace tls_strp_msg_done() with tls_strp_msg_release() in
all three receive paths (read_sock, recvmsg, splice_read),
deferring the tls_strp_check_rcv() call to each path's
exit point. Factor tls_rx_msg_ready() out of
tls_strp_read_sock() so that parsing a record no longer
fires the callback directly, and introduce
tls_strp_check_rcv_quiet() for use in tls_rx_rec_wait(),
which parses queued data without notifying.

With no remaining callers, tls_strp_msg_done() and its
wrapper tls_rx_rec_done() are removed.

Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/tls/tls.h      |  2 +-
 net/tls/tls_strp.c | 27 +++++++++++++++++++--------
 net/tls/tls_sw.c   | 21 ++++++++++++++-------
 3 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/net/tls/tls.h b/net/tls/tls.h
index a97f1acef31d..0ab3b83c3724 100644
--- a/net/tls/tls.h
+++ b/net/tls/tls.h
@@ -193,8 +193,8 @@ int tls_strp_init(struct tls_strparser *strp, struct sock *sk);
 void tls_strp_data_ready(struct tls_strparser *strp);
 
 void tls_strp_check_rcv(struct tls_strparser *strp);
+void tls_strp_check_rcv_quiet(struct tls_strparser *strp);
 void tls_strp_msg_release(struct tls_strparser *strp);
-void tls_strp_msg_done(struct tls_strparser *strp);
 
 int tls_rx_msg_size(struct tls_strparser *strp, struct sk_buff *skb);
 void tls_rx_msg_ready(struct tls_strparser *strp);
diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c
index a7648ebde162..6cf274380da2 100644
--- a/net/tls/tls_strp.c
+++ b/net/tls/tls_strp.c
@@ -368,7 +368,6 @@ static int tls_strp_copyin(read_descriptor_t *desc, struct sk_buff *in_skb,
 		desc->count = 0;
 
 		WRITE_ONCE(strp->msg_ready, 1);
-		tls_rx_msg_ready(strp);
 	}
 
 	return ret;
@@ -539,11 +538,27 @@ static int tls_strp_read_sock(struct tls_strparser *strp)
 		return tls_strp_read_copy(strp, false);
 
 	WRITE_ONCE(strp->msg_ready, 1);
-	tls_rx_msg_ready(strp);
 
 	return 0;
 }
 
+/**
+ * tls_strp_check_rcv_quiet - parse without consumer notification
+ * @strp: TLS stream parser instance
+ *
+ * Parse queued data without firing the consumer notification. A subsequent
+ * tls_strp_check_rcv() is required before the socket lock is released;
+ * otherwise queued data stalls until the next tls_strp_data_ready() event.
+ */
+void tls_strp_check_rcv_quiet(struct tls_strparser *strp)
+{
+	if (unlikely(strp->stopped) || strp->msg_ready)
+		return;
+
+	if (tls_strp_read_sock(strp) == -ENOMEM)
+		queue_work(tls_strp_wq, &strp->work);
+}
+
 void tls_strp_check_rcv(struct tls_strparser *strp)
 {
 	if (unlikely(strp->stopped) || strp->msg_ready)
@@ -551,6 +566,8 @@ void tls_strp_check_rcv(struct tls_strparser *strp)
 
 	if (tls_strp_read_sock(strp) == -ENOMEM)
 		queue_work(tls_strp_wq, &strp->work);
+	else if (strp->msg_ready)
+		tls_rx_msg_ready(strp);
 }
 
 /* Lower sock lock held */
@@ -603,12 +620,6 @@ void tls_strp_msg_release(struct tls_strparser *strp)
 	memset(&strp->stm, 0, sizeof(strp->stm));
 }
 
-void tls_strp_msg_done(struct tls_strparser *strp)
-{
-	tls_strp_msg_release(strp);
-	tls_strp_check_rcv(strp);
-}
-
 void tls_strp_stop(struct tls_strparser *strp)
 {
 	strp->stopped = 1;
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index e5d0447cbba6..43d37b0e6d59 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1384,7 +1384,10 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
 			return ret;
 
 		if (!skb_queue_empty(&sk->sk_receive_queue)) {
-			tls_strp_check_rcv(&ctx->strp);
+			/* tls_strp_check_rcv() is called at each receive
+			 * path's exit before the socket lock is released.
+			 */
+			tls_strp_check_rcv_quiet(&ctx->strp);
 			if (tls_strp_msg_ready(ctx))
 				break;
 		}
@@ -1876,9 +1879,9 @@ static int tls_record_content_type(struct msghdr *msg, struct tls_msg *tlm,
 	return 1;
 }
 
-static void tls_rx_rec_done(struct tls_sw_context_rx *ctx)
+static void tls_rx_rec_release(struct tls_sw_context_rx *ctx)
 {
-	tls_strp_msg_done(&ctx->strp);
+	tls_strp_msg_release(&ctx->strp);
 }
 
 /* This function traverses the rx_list in tls receive context to copies the
@@ -2159,7 +2162,7 @@ int tls_sw_recvmsg(struct sock *sk,
 		err = tls_record_content_type(msg, tls_msg(darg.skb), &control);
 		if (err <= 0) {
 			DEBUG_NET_WARN_ON_ONCE(darg.zc);
-			tls_rx_rec_done(ctx);
+			tls_rx_rec_release(ctx);
 put_on_rx_list_err:
 			__skb_queue_tail(&ctx->rx_list, darg.skb);
 			goto recv_end;
@@ -2173,7 +2176,8 @@ int tls_sw_recvmsg(struct sock *sk,
 		/* TLS 1.3 may have updated the length by more than overhead */
 		rxm = strp_msg(darg.skb);
 		chunk = rxm->full_len;
-		tls_rx_rec_done(ctx);
+		tls_rx_rec_release(ctx);
+		tls_strp_check_rcv_quiet(&ctx->strp);
 
 		if (!darg.zc) {
 			bool partially_consumed = chunk > len;
@@ -2267,6 +2271,7 @@ int tls_sw_recvmsg(struct sock *sk,
 	copied += decrypted;
 
 end:
+	tls_strp_check_rcv(&ctx->strp);
 	tls_rx_reader_unlock(sk, ctx);
 	if (psock)
 		sk_psock_put(sk, psock);
@@ -2307,7 +2312,7 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 		if (err < 0)
 			goto splice_read_end;
 
-		tls_rx_rec_done(ctx);
+		tls_rx_rec_release(ctx);
 		skb = darg.skb;
 	}
 
@@ -2334,6 +2339,7 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 	consume_skb(skb);
 
 splice_read_end:
+	tls_strp_check_rcv(&ctx->strp);
 	tls_rx_reader_unlock(sk, ctx);
 	return copied ? : err;
 
@@ -2399,7 +2405,7 @@ int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc,
 			tlm = tls_msg(skb);
 			decrypted += rxm->full_len;
 
-			tls_rx_rec_done(ctx);
+			tls_rx_rec_release(ctx);
 		}
 
 		/* read_sock does not support reading control messages */
@@ -2429,6 +2435,7 @@ int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc,
 	}
 
 read_sock_end:
+	tls_strp_check_rcv(&ctx->strp);
 	tls_rx_reader_release(sk, ctx);
 	return copied ? : err;
 
-- 
2.52.0