netdev - [net PATCH] net/smc: make sure EPOLLOUT is raised

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Message-Id: <1566239761-30252-1-git-send-email-jbaron@akamai.com>
Date:   Mon, 19 Aug 2019 14:36:01 -0400
From:   Jason Baron <jbaron@...mai.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Karsten Graul <kgraul@...ux.ibm.com>
Subject: [net PATCH] net/smc: make sure EPOLLOUT is raised

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>
---
 net/smc/smc_tx.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index f0de323..6c8f09c 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -76,13 +76,11 @@ static int smc_tx_wait(struct smc_sock *smc, int flags)
 	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);
@@ -97,8 +95,8 @@ static int smc_tx_wait(struct smc_sock *smc, int flags)
 			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;
 		}
-- 
2.7.4