linux-kernel - [PATCH 4.19 36/93] net/smc: make sure EPOLLOUT is raised

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Date:   Wed,  4 Sep 2019 19:53:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jason Baron <jbaron@...mai.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.19 36/93] net/smc: make sure EPOLLOUT is raised

From: Jason Baron <jbaron@...mai.com>

[ Upstream commit 4651d1802f7063e4d8c0bcad957f46ece0c04024 ]

Currently, we are only explicitly setting SOCK_NOSPACE on a write timeout
for non-blocking sockets. Epoll() edge-trigger mode relies on SOCK_NOSPACE
being set when -EAGAIN is returned to ensure that EPOLLOUT is raised.
Expand the setting of SOCK_NOSPACE to non-blocking sockets as well that can
use SO_SNDTIMEO to adjust their write timeout. This mirrors the behavior
that Eric Dumazet introduced for tcp sockets.

Signed-off-by: Jason Baron <jbaron@...mai.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Ursula Braun <ubraun@...ux.ibm.com>
Cc: Karsten Graul <kgraul@...ux.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/smc/smc_tx.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -75,13 +75,11 @@ static int smc_tx_wait(struct smc_sock *
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 	struct smc_connection *conn = &smc->conn;
 	struct sock *sk = &smc->sk;
-	bool noblock;
 	long timeo;
 	int rc = 0;
 
 	/* similar to sk_stream_wait_memory */
 	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
-	noblock = timeo ? false : true;
 	add_wait_queue(sk_sleep(sk), &wait);
 	while (1) {
 		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
@@ -96,8 +94,8 @@ static int smc_tx_wait(struct smc_sock *
 			break;
 		}
 		if (!timeo) {
-			if (noblock)
-				set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+			/* ensure EPOLLOUT is subsequently generated */
+			set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 			rc = -EAGAIN;
 			break;
 		}