/*
* include/linux/sunrpc/cache.h
*
* 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.
*
*/
#ifndef _LINUX_SUNRPC_CACHE_H_
#define _LINUX_SUNRPC_CACHE_H_
#include <linux/slab.h>
#include <asm/atomic.h>
#include <linux/proc_fs.h>
/*
* Each cache requires:
* - A 'struct cache_detail' which contains information specific to the cache
* for common code to use.
* - An item structure that must contain a "struct cache_head"
* - A lookup function defined using DefineCacheLookup
* - A 'put' function that can release a cache item. It will only
* be called after cache_put has succeed, so there are guarantee
* to be no references.
* - A function to calculate a hash of an item's key.
*
* as well as assorted code fragments (e.g. compare keys) and numbers
* (e.g. hash size, goal_age, etc).
*
* Each cache must be registered so that it can be cleaned regularly.
* When the cache is unregistered, it is flushed completely.
*
* Entries have a ref count and a 'hashed' flag which counts the existance
* in the hash table.
* We only expire entries when refcount is zero.
* Existance in the cache is counted the refcount.
*/
/* Every cache item has a common header that is used
* for expiring and refreshing entries.
*
*/
struct cache_head {
struct cache_head * next;
time_t expiry_time; /* After time time, don't use the data */
time_t last_refresh; /* If CACHE_PENDING, this is when upcall
* was sent, else this is when update was received
*/
struct kref ref;
unsigned long flags;
};
#define CACHE_VALID 0 /* Entry contains valid data */
#define CACHE_NEGATIVE 1 /* Negative entry - there is no match for the key */
#define CACHE_PENDING 2 /* An upcall has been sent but no reply received yet*/
#define CACHE_NEW_EXPIRY 120 /* keep new things pending confirmation for 120 seconds */
struct cache_detail {
struct module * owner;
int hash_size;
struct cache_head ** hash_table;
rwlock_t hash_lock;
atomic_t inuse; /* active user-space update or lookup */
char *name;
void (*cache_put)(struct kref *);
void (*cache_request)(struct cache_detail *cd,
struct cache_head *h,
char **bpp, int *blen);
int (*cache_parse)(struct cache_detail *,
char *buf, int len);
int (*cache_show)(struct seq_file *m,
struct cache_detail *cd,
struct cache_head *h);
struct cache_head * (*alloc)(void);
int (*match)(struct cache_head *orig, struct cache_head *new);
void (*init)(struct cache_head *orig, struct cache_head *new);
void (*update)(struct cache_head *orig, struct cache_head *new);
/* fields below this comment are for internal use
* and should not be touched by cache owners
*/
time_t flush_time; /* flush all cache items with last_refresh
* earlier than this */
struct list_head others;
time_t nextcheck;
int entries;
/* fields for communication over channel */
struct list_head queue;
struct proc_dir_entry *proc_ent;
struct proc_dir_entry *flush_ent, *channel_ent, *content_ent;
atomic_t readers; /* how many time is /chennel open */
time_t last_close; /* if no readers, when did last close */
time_t last_warn; /* when we last warned about no readers */
void (*warn_no_listener)(struct cache_detail *cd);
};
/* this must be embedded in any request structure that
* identifies an object that will want a callback on
* a cache fill
*/
struct cache_req {
struct cache_deferred_req *(*defer)(struct cache_req *req);
};
/* this must be embedded in a deferred_request that is being
* delayed awaiting cache-fill
*/
struct cache_deferred_req {
struct list_head hash; /* on hash chain */
struct list_head recent; /* on fifo */
struct cache_head *item; /* cache item we wait on */
void *owner; /* we might need to discard all defered requests
* owned by someone */
void (*revisit)(struct cache_deferred_req *req,
int too_many);
};
extern struct cache_head *
sunrpc_cache_lookup(struct cache_detail *detail,
struct cache_head *key, int hash);
extern struct cache_head *
sunrpc_cache_update(struct cache_detail *detail,
struct cache_head *new, struct cache_head *old, int hash);
extern void cache_clean_deferred(void *owner);
static inline struct cache_head *cache_get(struct cache_head *h)
{
kref_get(&h->ref);
return h;
}
static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
{
if (atomic_read(&h->ref.refcount) <= 2 &&
h->expiry_time < cd->nextcheck)
cd->nextcheck = h->expiry_time;
kref_put(&h->ref, cd->cache_put);
}
static inline int cache_valid(struct cache_head *h)
{
/* If an item has been unhashed pending removal when
* the refcount drops to 0, the expiry_time will be
* set to 0. We don't want to consider such items
* valid in this context even though CACHE_VALID is
* set.
*/
return (h->expiry_time != 0 && test_bit(CACHE_VALID, &h->flags));
}
extern int cache_check(struct cache_detail *detail,
struct cache_head *h, struct cache_req *rqstp);
extern void cache_flush(void);
extern void cache_purge(struct cache_detail *detail);
#define NEVER (0x7FFFFFFF)
extern int cache_register(struct cache_detail *cd);
extern void cache_unregister(struct cache_detail *cd);
extern void qword_add(char **bpp, int *lp, char *str);
extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
extern int qword_get(char **bpp, char *dest, int bufsize);
static inline int get_int(char **bpp, int *anint)
{
char buf[50];
char *ep;
int rv;
int len = qword_get(bpp, buf, 50);
if (len < 0) return -EINVAL;
if (len ==0) return -ENOENT;
rv = simple_strtol(buf, &ep, 0);
if (*ep) return -EINVAL;
*anint = rv;
return 0;
}
static inline time_t get_expiry(char **bpp)
{
int rv;
if (get_int(bpp, &rv))
return 0;
if (rv < 0)
return 0;
return rv;
}
#endif /* _LINUX_SUNRPC_CACHE_H_ */
