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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: c0129a0614 ("smc: convert to ->poll_mask")
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ursula Braun 2018-06-27 17:59:50 +02:00 committed by David S. Miller
parent 15ecbe94a4
commit 24ac3a08e6
2 changed files with 71 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

91
net/smc/af_smc.c
View File

@ -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;
}

8
net/smc/smc.h
View File

@ -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 */