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Message-Id: <20180627155950.21153-1-ubraun@linux.ibm.com>
Date: Wed, 27 Jun 2018 17:59:50 +0200
From: Ursula Braun <ubraun@...ux.ibm.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, linux-s390@...r.kernel.org,
schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
raspl@...ux.ibm.com, ubraun@...ux.ibm.com,
xiyou.wangcong@...il.com, eric.dumazet@...il.com
Subject: [PATCH net 1/1] net/smc: rebuild nonblocking connect
The recent poll change may lead to stalls for non-blocking connecting
SMC sockets, since sock_poll_wait is no longer performed on the
internal CLC socket, but on the outer SMC socket. kernel_connect() on
the internal CLC socket returns with -EINPROGRESS, but the wake up
logic does not work in all cases. If the internal CLC socket is still
in state TCP_SYN_SENT when polled, sock_poll_wait() from sock_poll()
does not sleep. It is supposed to sleep till the state of the internal
CLC socket switches to TCP_ESTABLISHED.
This problem triggered a redesign of the SMC nonblocking connect logic.
This patch introduces a connect worker covering all connect steps
followed by a wake up of socket waiters. It allows to get rid of all
delays and locks in smc_poll().
Fixes: c0129a061442 ("smc: convert to ->poll_mask")
Signed-off-by: Ursula Braun <ubraun@...ux.ibm.com>
---
net/smc/af_smc.c | 91 +++++++++++++++++++++++++++++++++++++++-----------------
net/smc/smc.h | 8 +++++
2 files changed, 71 insertions(+), 28 deletions(-)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index da7f02edcd37..4d1d4ddb2f49 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -45,6 +45,7 @@ static DEFINE_MUTEX(smc_create_lgr_pending); /* serialize link group
*/
static void smc_tcp_listen_work(struct work_struct *);
+static void smc_connect_work(struct work_struct *);
static void smc_set_keepalive(struct sock *sk, int val)
{
@@ -122,6 +123,12 @@ static int smc_release(struct socket *sock)
goto out;
smc = smc_sk(sk);
+
+ /* cleanup for a dangling non-blocking connect */
+ flush_work(&smc->connect_work);
+ kfree(smc->connect_info);
+ smc->connect_info = NULL;
+
if (sk->sk_state == SMC_LISTEN)
/* smc_close_non_accepted() is called and acquires
* sock lock for child sockets again
@@ -186,6 +193,7 @@ static struct sock *smc_sock_alloc(struct net *net, struct socket *sock,
sk->sk_protocol = protocol;
smc = smc_sk(sk);
INIT_WORK(&smc->tcp_listen_work, smc_tcp_listen_work);
+ INIT_WORK(&smc->connect_work, smc_connect_work);
INIT_DELAYED_WORK(&smc->conn.tx_work, smc_tx_work);
INIT_LIST_HEAD(&smc->accept_q);
spin_lock_init(&smc->accept_q_lock);
@@ -576,6 +584,35 @@ static int __smc_connect(struct smc_sock *smc)
return 0;
}
+static void smc_connect_work(struct work_struct *work)
+{
+ struct smc_sock *smc = container_of(work, struct smc_sock,
+ connect_work);
+ int rc;
+
+ lock_sock(&smc->sk);
+ rc = kernel_connect(smc->clcsock, &smc->connect_info->addr,
+ smc->connect_info->alen, smc->connect_info->flags);
+ if (smc->clcsock->sk->sk_err) {
+ smc->sk.sk_err = smc->clcsock->sk->sk_err;
+ goto out;
+ }
+ if (rc < 0) {
+ smc->sk.sk_err = -rc;
+ goto out;
+ }
+
+ rc = __smc_connect(smc);
+ if (rc < 0)
+ smc->sk.sk_err = -rc;
+
+out:
+ smc->sk.sk_state_change(&smc->sk);
+ kfree(smc->connect_info);
+ smc->connect_info = NULL;
+ release_sock(&smc->sk);
+}
+
static int smc_connect(struct socket *sock, struct sockaddr *addr,
int alen, int flags)
{
@@ -605,15 +642,32 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
smc_copy_sock_settings_to_clc(smc);
tcp_sk(smc->clcsock->sk)->syn_smc = 1;
- rc = kernel_connect(smc->clcsock, addr, alen, flags);
- if (rc)
- goto out;
+ if (flags & O_NONBLOCK) {
+ if (smc->connect_info) {
+ rc = -EALREADY;
+ goto out;
+ }
+ smc->connect_info = kzalloc(alen + 2 * sizeof(int), GFP_KERNEL);
+ if (!smc->connect_info) {
+ rc = -ENOMEM;
+ goto out;
+ }
+ smc->connect_info->alen = alen;
+ smc->connect_info->flags = flags ^ O_NONBLOCK;
+ memcpy(&smc->connect_info->addr, addr, alen);
+ schedule_work(&smc->connect_work);
+ rc = -EINPROGRESS;
+ } else {
+ rc = kernel_connect(smc->clcsock, addr, alen, flags);
+ if (rc)
+ goto out;
- rc = __smc_connect(smc);
- if (rc < 0)
- goto out;
- else
- rc = 0; /* success cases including fallback */
+ rc = __smc_connect(smc);
+ if (rc < 0)
+ goto out;
+ else
+ rc = 0; /* success cases including fallback */
+ }
out:
release_sock(sk);
@@ -1278,34 +1332,17 @@ static __poll_t smc_poll_mask(struct socket *sock, __poll_t events)
struct sock *sk = sock->sk;
__poll_t mask = 0;
struct smc_sock *smc;
- int rc;
if (!sk)
return EPOLLNVAL;
smc = smc_sk(sock->sk);
- sock_hold(sk);
- lock_sock(sk);
if ((sk->sk_state == SMC_INIT) || smc->use_fallback) {
/* delegate to CLC child sock */
- release_sock(sk);
mask = smc->clcsock->ops->poll_mask(smc->clcsock, events);
- lock_sock(sk);
sk->sk_err = smc->clcsock->sk->sk_err;
- if (sk->sk_err) {
+ if (sk->sk_err)
mask |= EPOLLERR;
- } else {
- /* if non-blocking connect finished ... */
- if (sk->sk_state == SMC_INIT &&
- mask & EPOLLOUT &&
- smc->clcsock->sk->sk_state != TCP_CLOSE) {
- rc = __smc_connect(smc);
- if (rc < 0)
- mask |= EPOLLERR;
- /* success cases including fallback */
- mask |= EPOLLOUT | EPOLLWRNORM;
- }
- }
} else {
if (sk->sk_err)
mask |= EPOLLERR;
@@ -1334,8 +1371,6 @@ static __poll_t smc_poll_mask(struct socket *sock, __poll_t events)
mask |= EPOLLPRI;
}
- release_sock(sk);
- sock_put(sk);
return mask;
}
diff --git a/net/smc/smc.h b/net/smc/smc.h
index 51ae1f10d81a..d7ca26570482 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -187,11 +187,19 @@ struct smc_connection {
struct work_struct close_work; /* peer sent some closing */
};
+struct smc_connect_info {
+ int flags;
+ int alen;
+ struct sockaddr addr;
+};
+
struct smc_sock { /* smc sock container */
struct sock sk;
struct socket *clcsock; /* internal tcp socket */
struct smc_connection conn; /* smc connection */
struct smc_sock *listen_smc; /* listen parent */
+ struct smc_connect_info *connect_info; /* connect address & flags */
+ struct work_struct connect_work; /* handle non-blocking connect*/
struct work_struct tcp_listen_work;/* handle tcp socket accepts */
struct work_struct smc_listen_work;/* prepare new accept socket */
struct list_head accept_q; /* sockets to be accepted */
--
2.16.4
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