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);

static void cache_init(struct cache_head *h)
{
	time_t now = get_seconds();
	h->next = NULL;
	h->flags = 0;
	kref_init(&h->ref);
	h->expiry_time = now + CACHE_NEW_EXPIRY;
	h->last_refresh = now;
}

struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
				       struct cache_head *key, int hash)
{
	struct cache_head **head,  **hp;
	struct cache_head *new = NULL;

	head = &detail->hash_table[hash];

	read_lock(&detail->hash_lock);

	for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
		struct cache_head *tmp = *hp;
		if (detail->match(tmp, key)) {
			cache_get(tmp);
			read_unlock(&detail->hash_lock);
			return tmp;
		}
	}
	read_unlock(&detail->hash_lock);
	/* Didn't find anything, insert an empty entry */

	new = detail->alloc();
	if (!new)
		return NULL;
	cache_init(new);

	write_lock(&detail->hash_lock);

	/* check if entry appeared while we slept */
	for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
		struct cache_head *tmp = *hp;
		if (detail->match(tmp, key)) {
			cache_get(tmp);
			write_unlock(&detail->hash_lock);
			cache_put(new, detail);
			return tmp;
		}
	}
	detail->init(new, key);
	new->next = *head;
	*head = new;
	detail->entries++;
	cache_get(new);
	write_unlock(&detail->hash_lock);

	return new;
}
EXPORT_SYMBOL(sunrpc_cache_lookup);


static void queue_loose(struct cache_detail *detail, struct cache_head *ch);

static int cache_fresh_locked(struct cache_head *head, time_t expiry)
{
	head->expiry_time = expiry;
	head->last_refresh = get_seconds();
	return !test_and_set_bit(CACHE_VALID, &head->flags);
}

static void cache_fresh_unlocked(struct cache_head *head,
			struct cache_detail *detail, int new)
{
	if (new)
		cache_revisit_request(head);
	if (test_and_clear_bit(CACHE_PENDING, &head->flags)) {
		cache_revisit_request(head);
		queue_loose(detail, head);
	}
}

struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
				       struct cache_head *new, struct cache_head *old, int hash)
{
	/* The 'old' entry is to be replaced by 'new'.
	 * If 'old' is not VALID, we update it directly,
	 * otherwise we need to replace it
	 */
	struct cache_head **head;
	struct cache_head *tmp;
	int is_new;

	if (!test_bit(CACHE_VALID, &old->flags)) {
		write_lock(&detail->hash_lock);
		if (!test_bit(CACHE_VALID, &old->flags)) {
			if (test_bit(CACHE_NEGATIVE, &new->flags))
				set_bit(CACHE_NEGATIVE, &old->flags);
			else
				detail->update(old, new);
			is_new = cache_fresh_locked(old, new->expiry_time);
			write_unlock(&detail->hash_lock);
			cache_fresh_unlocked(old, detail, is_new);
			return old;
		}
		write_unlock(&detail->hash_lock);
	}
	/* We need to insert a new entry */
	tmp = detail->alloc();
	if (!tmp) {
		cache_put(old, detail);
		return NULL;
	}
	cache_init(tmp);
	detail->init(tmp, old);
	head = &detail->hash_table[hash];

	write_lock(&detail->hash_lock);
	if (test_bit(CACHE_NEGATIVE, &new->flags))
		set_bit(CACHE_NEGATIVE, &tmp->flags);
	else
		detail->update(tmp, new);
	tmp->next = *head;
	*head = t