path: root/net/sunrpc/cache.c

/*
 * net/sunrpc/cache.c
 *
 * Generic code for various authentication-related caches
 * used by sunrpc clients and servers.
 *
 * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
 *
 * Released under terms in GPL version 2.  See COPYING.
 *
 */

#include <linux/types.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/ctype.h>
#include <asm/uaccess.h>
#include <linux/poll.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/net.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <asm/ioctls.h>
#include <linux/sunrpc/types.h>
#include <linux/sunrpc/cache.h>
#include <linux/sunrpc/stats.h>

#define	 RPCDBG_FACILITY RPCDBG_CACHE

static void cache_defer_req(struct cache_req *req, struct cache_head *item);
static void cache_revisit_request(struct cache_head *item);

void cache_init(struct cache_head *h)
{
	time_t now = get_seconds();
	h->next = NULL;
	h->flags = 0;
	atomic_set(&h->refcnt, 1);
	h->expiry_time = now + CACHE_NEW_EXPIRY;
	h->last_refresh = now;
}


static int cache_make_upcall(struct cache_detail *detail, struct cache_head *h);
/*
 * This is the generic cache management routine for all
 * the authentication caches.
 * It checks the currency of a cache item and will (later)
 * initiate an upcall to fill it if needed.
 *
 *
 * Returns 0 if the cache_head can be used, or cache_puts it and returns
 * -EAGAIN if upcall is pending,
 * -ENOENT if cache entry was negative
 */
int cache_check(struct cache_detail *detail,
		    struct cache_head *h, struct cache_req *rqstp)
{
	int rv;
	long refresh_age, age;

	/* First decide return status as best we can */
	if (!test_bit(CACHE_VALID, &h->flags) ||
	    h->expiry_time < get_seconds())
		rv = -EAGAIN;
	else if (detail->flush_time > h->last_refresh)
		rv = -EAGAIN;
	else {
		/* entry is valid */
		if (test_bit(CACHE_NEGATIVE, &h->flags))
			rv = -ENOENT;
		else rv = 0;
	}

	/* now see if we want to start an upcall */
	refresh_age = (h->expiry_time - h->last_refresh);
	age = get_seconds() - h->last_refresh;

	if (rqstp == NULL) {
		if (rv == -EAGAIN)
			rv = -ENOENT;
	} else if (rv == -EAGAIN || age > refresh_age/2) {
		dprintk("Want update, refage=%ld, age=%ld\n", refresh_age, age);
		if (!test_and_set_bit(CACHE_PENDING, &h->flags)) {
			switch (cache_make_upcall(detail, h)) {
			case -EINVAL:
				clear_bit(CACHE_PENDING, &h->flags);
				if (rv == -EAGAIN) {
					set_bit(CACHE_NEGATIVE, &h->flags);
					cache_fresh(detail, h, get_seconds()+CACHE_NEW_EXPIRY);
					rv = -ENOENT;
				}
				break;

			case -EAGAIN:
				clear_bit(CACHE_PENDING, &h->flags);
				cache_revis