xprt.c

Linux Kernel 2.6.9 for OMAP1710

/*
 *  linux/net/sunrpc/xprt.c
 *
 *  This is a generic RPC call interface supporting congestion avoidance,
 *  and asynchronous calls.
 *
 *  The interface works like this:
 *
 *  -	When a process places a call, it allocates a request slot if
 *	one is available. Otherwise, it sleeps on the backlog queue
 *	(xprt_reserve).
 *  -	Next, the caller puts together the RPC message, stuffs it into
 *	the request struct, and calls xprt_call().
 *  -	xprt_call transmits the message and installs the caller on the
 *	socket's wait list. At the same time, it installs a timer that
 *	is run after the packet's timeout has expired.
 *  -	When a packet arrives, the data_ready handler walks the list of
 *	pending requests for that socket. If a matching XID is found, the
 *	caller is woken up, and the timer removed.
 *  -	When no reply arrives within the timeout interval, the timer is
 *	fired by the kernel and runs xprt_timer(). It either adjusts the
 *	timeout values (minor timeout) or wakes up the caller with a status
 *	of -ETIMEDOUT.
 *  -	When the caller receives a notification from RPC that a reply arrived,
 *	it should release the RPC slot, and process the reply.
 *	If the call timed out, it may choose to retry the operation by
 *	adjusting the initial timeout value, and simply calling rpc_call
 *	again.
 *
 *  Support for async RPC is done through a set of RPC-specific scheduling
 *  primitives that `transparently' work for processes as well as async
 *  tasks that rely on callbacks.
 *
 *  Copyright (C) 1995-1997, Olaf Kirch <[e-mail]>
 *
 *  TCP callback races fixes (C) 1998 Red Hat Software <[e-mail]>
 *  TCP send fixes (C) 1998 Red Hat Software <[e-mail]>
 *  TCP NFS related read + write fixes
 *   (C) 1999 Dave Airlie, University of Limerick, Ireland <[e-mail]>
 *
 *  Rewrite of larges part of the code in order to stabilize TCP stuff.
 *  Fix behaviour when socket buffer is full.
 *   (C) 1999 Trond Myklebust <[e-mail]>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/capability.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/net.h>
#include <linux/mm.h>
#include <linux/udp.h>
#include <linux/tcp.h>
#include <linux/sunrpc/clnt.h>
#include <linux/file.h>
#include <linux/workqueue.h>
#include <linux/random.h>

#include <net/sock.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <net/tcp.h>

/*
 * Local variables
 */

#ifdef RPC_DEBUG
# undef  RPC_DEBUG_DATA
# define RPCDBG_FACILITY	RPCDBG_XPRT
#endif

#define XPRT_MAX_BACKOFF	(8)
#define XPRT_IDLE_TIMEOUT	(5*60*HZ)
#define XPRT_MAX_RESVPORT	(800)

/*
 * Local functions
 */
static void	xprt_request_init(struct rpc_task *, struct rpc_xprt *);
static inline void	do_xprt_reserve(struct rpc_task *);
static void	xprt_disconnect(struct rpc_xprt *);
static void	xprt_connect_status(struct rpc_task *task);
static struct rpc_xprt * xprt_setup(int proto, struct sockaddr_in *ap,
						struct rpc_timeout *to);
static struct socket *xprt_create_socket(struct rpc_xprt *, int, int);
static void	xprt_bind_socket(struct rpc_xprt *, struct socket *);
static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);

#ifdef RPC_DEBUG_DATA
/*
 * Print the buffer contents (first 128 bytes only--just enough for
 * diropres return).
 */
static void
xprt_pktdump(char *msg, u32 *packet, unsigned int count)
{
	u8	*buf = (u8 *) packet;
	int	j;

	dprintk("RPC:      %s\n", msg);
	for (j = 0; j < count && j < 128; j += 4) {
		if (!(j & 31)) {
			if (j)
				dprintk("\n");
			dprintk("0x%04x ", j);
		}
		dprintk("%02x%02x%02x%02x ",
			buf[j], buf[j+1], buf[j+2], buf[j+3]);
	}
	dprintk("\n");
}
#else
static inline void
xprt_pktdump(char *msg, u32 *packet, unsigned int count)
{
	/* NOP */
}
#endif

/*
 * Look up RPC transport given an INET socket
 */
static inline struct rpc_xprt *
xprt_from_sock(struct sock *sk)
{
	return (struct rpc_xprt *) sk->sk_user_data;
}

/*
 * Serialize write access to sockets, in order to prevent different
 * requests from interfering with each other.
 * Also prevents TCP socket connects from colliding with writes.
 */
static int
__xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
	struct rpc_rqst *req = task->tk_rqstp;

	if (test_and_set_bit(XPRT_LOCKED, &xprt->sockstate)) {
		if (task == xprt->snd_task)
			return 1;
		if (task == NULL)
			return 0;
		goto out_sleep;
	}
	if (xprt->nocong || __xprt_get_cong(xprt, task)) {
		xprt->snd_task = task;
		if (req) {
			req->rq_bytes_sent = 0;
			req->rq_ntrans++;
		}
		return 1;
	}
	smp_mb__before_clear_bit();
	clear_bit(XPRT_LOCKED, &xprt->sockstate);
	smp_mb__after_clear_bit();
out_sleep:
	dprintk("RPC: %4d failed to lock socket %p\n", task->tk_pid, xprt);
	task->tk_timeout = 0;
	task->tk_status = -EAGAIN;
	if (req && req->rq_ntrans)
		rpc_sleep_on(&xprt->resend, task, NULL, NULL);
	else
		rpc_sleep_on(&xprt->sending, task, NULL, NULL);
	return 0;
}

static inline int
xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
	int retval;

	spin_lock_bh(&xprt->sock_lock);
	retval = __xprt_lock_write(xprt, task);
	spin_unlock_bh(&xprt->sock_lock);
	return retval;
}


static void
__xprt_lock_write_next(struct rpc_xprt *xprt)
{
	struct rpc_task *task;

	if (test_and_set_bit(XPRT_LOCKED, &xprt->sockstate))
		return;
	if (!xprt->nocong && RPCXPRT_CONGESTED(xprt))
		goto out_unlock;
	task = rpc_wake_up_next(&xprt->resend);
	if (!task) {
		task = rpc_wake_up_next(&xprt->sending);
		if (!task)
			goto out_unlock;
	}
	if (xprt->nocong || __xprt_get_cong(xprt, task)) {
		struct rpc_rqst *req = task->tk_rqstp;
		xprt->snd_task = task;
		if (req) {
			req->rq_bytes_sent = 0;
			req->rq_ntrans++;
		}
		return;
	}
out_unlock:
	smp_mb__before_clear_bit();
	clear_bit(XPRT_LOCKED, &xprt->sockstate);
	smp_mb__after_clear_bit();
}

/*
 * Releases the socket for use by other requests.
 */
static void
__xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
	if (xprt->snd_task == task) {
		xprt->snd_task = NULL;
		smp_mb__before_clear_bit();
		clear_bit(XPRT_LOCKED, &xprt->sockstate);
		smp_mb__after_clear_bit();
		__xprt_lock_write_next(xprt);
	}
}

static inline void
xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)
{
	spin_lock_bh(&xprt->sock_lock);
	__xprt_release_write(xprt, task);
	spin_unlock_bh(&xprt->sock_lock);
}

/*
 * Write data to socket.
 */
static inline int
xprt_sendmsg(struct rpc_xprt *xprt, struct rpc_rqst *req)
{
	struct socket	*sock = xprt->sock;
	struct xdr_buf	*xdr = &req->rq_snd_buf;
	struct sockaddr *addr = NULL;
	int addrlen = 0;
	unsigned int	skip;
	int		result;

	if (!sock)
		return -ENOTCONN;

	xprt_pktdump("packet data:",
				req->rq_svec->iov_base,
				req->rq_svec->iov_len);

	/* For UDP, we need to provide an address */
	if (!xprt->stream) {
		addr = (struct sockaddr *) &xprt->addr;
		addrlen = sizeof(xprt->addr);
	}
	/* Dont repeat bytes */
	skip = req->rq_bytes_sent;

	clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
	result = xdr_sendpages(sock, addr, addrlen, xdr, skip, MSG_DONTWAIT);

	dprintk("RPC:      xprt_sendmsg(%d) = %d\n", xdr->len - skip, result);

	if (result >= 0)
		return result;

	switch (result) {
	case -ECONNREFUSED:
		/* When the server has died, an ICMP port unreachable message
		 * prompts ECONNREFUSED.
		 */
	case -EAGAIN:
		break;
	case -ECONNRESET:
	case -ENOTCONN:
	case -EPIPE:
		/* connection broken */
		if (xprt->stream)
			result = -ENOTCONN;
		break;
	default:
		printk(KERN_NOTICE "RPC: sendmsg returned error %d\n", -result);
	}
	return result;
}

/*
 * Van Jacobson congestion avoidance. Check if the congestion window
 * overflowed. Put the task to sleep if this is the case.
 */
static int
__xprt_get_cong(struct rpc_xprt *xprt, struct rpc_task *task)
{
	struct rpc_rqst *req = task->tk_rqstp;

	if (req->rq_cong)
		return 1;
	dprintk("RPC: %4d xprt_cwnd_limited cong = %ld cwnd = %ld\n",
			task->tk_pid, xprt->cong, xprt->cwnd);
	if (RPCXPRT_CONGESTED(xprt))
		return 0;
	req->rq_cong = 1;
	xprt->cong += RPC_CWNDSCALE;
	return 1;
}

/*
 * Adjust the congestion window, and wake up the next task
 * that has been sleeping due to congestion
 */
static void
__xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
{
	if (!req->rq_cong)
		return;
	req->rq_cong = 0;
	xprt->cong -= RPC_CWNDSCALE;
	__xprt_lock_write_next(xprt);
}

/*
 * Adjust RPC congestion window
 * We use a time-smoothed congestion estimator to avoid heavy oscillation.
 */
static void
xprt_adjust_cwnd(struct rpc_xprt *xprt, int result)
{
	unsigned long	cwnd;

	cwnd = xprt->cwnd;
	if (result >= 0 && cwnd <= xprt->cong) {
		/* The (cwnd >> 1) term makes sure
		 * the result gets rounded properly. */
		cwnd += (RPC_CWNDSCALE * RPC_CWNDSCALE + (cwnd >> 1)) / cwnd;
		if (cwnd > RPC_MAXCWND(xprt))
			cwnd = RPC_MAXCWND(xprt);
		__xprt_lock_write_next(xprt);
	} else if (result == -ETIMEDOUT) {
		cwnd >>= 1;
		if (cwnd < RPC_CWNDSCALE)
			cwnd = RPC_CWNDSCALE;
	}
	dprintk("RPC:      cong %ld, cwnd was %ld, now %ld\n",
			xprt->cong, xprt->cwnd, cwnd);
	xprt->cwnd = cwnd;
}

/*
 * Reset the major timeout value
 */
static void xprt_reset_majortimeo(struct rpc_rqst *req)
{
	struct rpc_timeout *to = &req->rq_xprt->timeout;

	req->rq_majortimeo = req->rq_timeout;
	if (to->to_exponential)
		req->rq_majortimeo <<= to->to_retries;
	else
		req->rq_majortimeo += to->to_increment * to->to_retries;
	if (req->rq_majortimeo > to->to_maxval || req->rq_majortimeo == 0)
		req->rq_majortimeo = to->to_maxval;
	req->rq_majortimeo += jiffies;
}

/*
 * Adjust timeout values etc for next retransmit
 */
int xprt_adjust_timeout(struct rpc_rqst *req)
{
	struct rpc_xprt *xprt = req->rq_xprt;
	struct rpc_timeout *to = &xprt->timeout;
	int status = 0;

	if (time_before(jiffies, req->rq_majortimeo)) {
		if (to->to_exponential)
			req->rq_timeout <<= 1;
		else
			req->rq_timeout += to->to_increment;
		if (to->to_maxval && req->rq_timeout >= to->to_maxval)
			req->rq_timeout = to->to_maxval;
		req->rq_retries++;
		pprintk("RPC: %lu retrans\n", jiffies);
	} else {
		req->rq_timeout = to->to_initval;
		req->rq_retries = 0;
		xprt_reset_majortimeo(req);
		/* Reset the RTT counters == "slow start" */
		spin_lock_bh(&xprt->sock_lock);
		rpc_init_rtt(req->rq_task->tk_client->cl_rtt, to->to_initval);
		spin_unlock_bh(&xprt->sock_lock);
		pprintk("RPC: %lu timeout\n", jiffies);
		status = -ETIMEDOUT;
	}

	if (req->rq_timeout == 0) {
		printk(KERN_WARNING "xprt_adjust_timeout: rq_timeout = 0!\n");
		req->rq_timeout = 5 * HZ;
	}
	return status;
}

/*
 * Close down a transport socket
 */
static void
xprt_close(struct rpc_xprt *xprt)
{
	struct socket	*sock = xprt->sock;
	struct sock	*sk = xprt->inet;

	if (!sk)
		return;

	write_lock_bh(&sk->sk_callback_lock);
	xprt->inet = NULL;
	xprt->sock = NULL;

	sk->sk_user_data    = NULL;
	sk->sk_data_ready   = xprt->old_data_ready;
	sk->sk_state_change = xprt->old_state_change;
	sk->sk_write_space  = xprt->old_write_space;
	write_unlock_bh(&sk->sk_callback_lock);

	sk->sk_no_check	 = 0;

	sock_release(sock);
}

static void
xprt_socket_autoclose(void *args)
{
	struct rpc_xprt *xprt = (struct rpc_xprt *)args;

	xprt_disconnect(xprt);
	xprt_close(xprt);
	xprt_release_write(xprt, NULL);
}

/*
 * Mark a transport as disconnected
 */
static void
xprt_disconnect(struct rpc_xprt *xprt)
{
	dprintk("RPC:      disconnected transport %p\n", xprt);
	spin_lock_bh(&xprt->sock_lock);
	xprt_clear_connected(xprt);
	rpc_wake_up_status(&xprt->pending, -ENOTCONN);
	spin_unlock_bh(&xprt->sock_lock);
}

/*
 * Used to allow disconnection when we've been idle
 */
static void
xprt_init_autodisconnect(unsigned long data)
{
	struct rpc_xprt *xprt = (struct rpc_xprt *)data;

	spin_lock(&xprt->sock_lock);
	if (!list_empty(&xprt->recv) || xprt->shutdown)
		goto out_abort;
	if (test_and_set_bit(XPRT_LOCKED, &xprt->sockstate))
		goto out_abort;
	spin_unlock(&xprt->sock_lock);
	/* Let keventd close the socket */
	if (test_bit(XPRT_CONNECTING, &xprt->sockstate) != 0)
		xprt_release_write(xprt, NULL);
	else
		schedule_work(&xprt->task_cleanup);
	return;
out_abort:
	spin_unlock(&xprt->sock_lock);
}

static void xprt_socket_connect(void *args)
{
	struct rpc_xprt *xprt = (struct rpc_xprt *)args;
	struct socket *sock = xprt->sock;
	int status = -EIO;

	if (xprt->shutdown || xprt->addr.sin_port == 0)
		goto out;

	/*
	 * Start by resetting any existing state
	 */
	xprt_close(xprt);
	sock = xprt_create_socket(xprt, xprt->prot, xprt->resvport);
	if (sock == NULL) {
		/* couldn't create socket or bind to reserved port;
		 * this is likely a permanent error, so cause an abort */
		goto out;
	}
	xprt_bind_socket(xprt, sock);
	xprt_sock_setbufsize(xprt);

	status = 0;
	if (!xprt->stream)
		goto out;

	/*
	 * Tell the socket layer to start connecting...
	 */
	status = sock->ops->connect(sock, (struct sockaddr *) &xprt->addr,
			sizeof(xprt->addr), O_NONBLOCK);
	dprintk("RPC: %p  connect status %d connected %d sock state %d\n",
			xprt, -status, xprt_connected(xprt), sock->sk->sk_state);
	if (status < 0) {
		switch (status) {
			case -EINPROGRESS:
			case -EALREADY:
				goto out_clear;
		}
	}
out:
	if (status < 0)
		rpc_wake_up_status(&xprt->pending, status);
	else
		rpc_wake_up(&xprt->pending);
out_clear:
	smp_mb__before_clear_bit();
	clear_bit(XPRT_CONNECTING, &xprt->sockstate);
	smp_mb__after_clear_bit();
}

/*
 * Attempt to connect a TCP socket.
 *
 */
void xprt_connect(struct rpc_task *task)
{
	struct rpc_xprt	*xprt = task->tk_xprt;

	dprintk("RPC: %4d xprt_connect xprt %p %s connected\n", task->tk_pid,
			xprt, (xprt_connected(xprt) ? "is" : "is not"));

	if (xprt->shutdown) {
		task->tk_status = -EIO;
		return;
	}
	if (!xprt->addr.sin_port) {
		task->tk_status = -EIO;
		return;
	}
	if (!xprt_lock_write(xprt, task))
		return;
	if (xprt_connected(xprt))
		goto out_write;

	if (task->tk_rqstp)
		task->tk_rqstp->rq_bytes_sent = 0;