path: root/net/sunrpc/svc_xprt.c

/*
 * linux/net/sunrpc/svc_xprt.c
 *
 * Author: Tom Tucker <tom@opengridcomputing.com>
 */

#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/errno.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <net/sock.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/svc_xprt.h>
#include <linux/sunrpc/svcsock.h>

#define RPCDBG_FACILITY	RPCDBG_SVCXPRT

static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt);
static int svc_deferred_recv(struct svc_rqst *rqstp);
static struct cache_deferred_req *svc_defer(struct cache_req *req);
static void svc_age_temp_xprts(unsigned long closure);

/* apparently the "standard" is that clients close
 * idle connections after 5 minutes, servers after
 * 6 minutes
 *   http://www.connectathon.org/talks96/nfstcp.pdf
 */
static int svc_conn_age_period = 6*60;

/* List of registered transport classes */
static DEFINE_SPINLOCK(svc_xprt_class_lock);
static LIST_HEAD(svc_xprt_class_list);

/* SMP locking strategy:
 *
 *	svc_pool->sp_lock protects most of the fields of that pool.
 *	svc_serv->sv_lock protects sv_tempsocks, sv_permsocks, sv_tmpcnt.
 *	when both need to be taken (rare), svc_serv->sv_lock is first.
 *	BKL protects svc_serv->sv_nrthread.
 *	svc_sock->sk_lock protects the svc_sock->sk_deferred list
 *             and the ->sk_info_authunix cache.
 *
 *	The XPT_BUSY bit in xprt->xpt_flags prevents a transport being
 *	enqueued multiply. During normal transport processing this bit
 *	is set by svc_xprt_enqueue and cleared by svc_xprt_received.
 *	Providers should not manipulate this bit directly.
 *
 *	Some flags can be set to certain values at any time
 *	providing that certain rules are followed:
 *
 *	XPT_CONN, XPT_DATA:
 *		- Can be set or cleared at any time.
 *		- After a set, svc_xprt_enqueue must be called to enqueue
 *		  the transport for processing.
 *		- After a clear, the transport must be read/accepted.
 *		  If this succeeds, it must be set again.
 *	XPT_CLOSE:
 *		- Can set at any time. It is never cleared.
 *      XPT_DEAD:
 *		- Can only be set while XPT_BUSY is held which ensures
 *		  that no other thread will be using the transport or will
 *		  try to set XPT_DEAD.
 */

int svc_reg_xprt_class(struct svc_xprt_class *xcl)
{
	struct svc_xprt_class *cl;
	int res = -EEXIST;

	dprintk("svc: Adding svc transport class '%s'\n", xcl->xcl_name);

	INIT_LIST_HEAD(&xcl->xcl_list);
	spin_lock(&svc_xprt_class_lock);
	/* Make sure there isn't already a class with the same name */
	list_for_each_entry(cl, &svc_xprt_class_list, xcl_list) {
		if (strcmp(xcl->xcl_name, cl->xcl_name) == 0)
			goto out;
	}
	list_add_tail(&xcl->xcl_list, &svc_xprt_class_list);
	res = 0;
out:
	spin_unlock(&svc_xprt_class_lock);
	return res;
}
EXPORT_SYMBOL_GPL(svc_reg_xprt_class);

void svc_unreg_xprt_class(struct svc_xprt_class *xcl)
{
	dprintk("svc: Removing svc transport class '%s'\n", xcl->xcl_name);
	spin_lock(&svc_xprt_class_lock);
	list_del_init(&xcl->xcl_list);
	spin_unlock(&svc_xprt_class_lock);
}
EXPORT_SYMBOL_GPL(svc_unreg_xprt_class);

/*
 * Format the transport list for printing
 */
int svc_print_xprts(char *buf, int maxlen)
{
	struct list_head *le;
	char tmpstr[80];
	int len = 0;
	buf[0] = '\0';

	spin_lock(&svc_xprt_class_lock);
	list_for_each(le, &svc_xprt_class_list) {
		int slen;
		struct svc_xprt_class *xcl =
			list_entry(le, struct svc_xprt_class, xcl_list);

		sprintf(tmpstr, "%s %d\n", xcl->xcl_name, xcl->xcl_max_payload);
		slen = strlen(tmpstr);
		if (len + slen > maxlen)
			break