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Commit 24ac3a08 authored by Ursula Braun's avatar Ursula Braun Committed by David S. Miller
Browse files

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: c0129a06 ("smc: convert to ->poll_mask")
Signed-off-by: default avatarUrsula Braun <ubraun@linux.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 15ecbe94

net/smc/af_smc.c

+63 −28
Original line number Diff line number Diff line
@@ -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)

{
@@ -605,6 +642,22 @@ 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;

	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;
@@ -614,6 +667,7 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr, 
			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) {

			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)

		if (sk->sk_err)

			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;

}

net/smc/smc.h

+8 −0
Original line number Diff line number Diff line
@@ -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 */