root/include/linux/sunrpc/cache.h

INCLUDED FROM

DEFINITIONS

1. seconds_since_boot
2. convert_to_wallclock
3. cache_get
4. cache_put
5. cache_is_expired
6. get_int
7. get_uint
8. get_time
9. get_expiry

/*
 * 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/kref.h>
#include <linux/slab.h>
#include <linux/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 existence
 * in the hash table.
 * We only expire entries when refcount is zero.
 * Existence 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_CLEANED   3       /* Entry has been cleaned from cache */

#define CACHE_NEW_EXPIRY 120    /* keep new things pending confirmation for 120 seconds */

struct cache_detail_procfs {
        struct proc_dir_entry   *proc_ent;
        struct proc_dir_entry   *flush_ent, *channel_ent, *content_ent;
};

struct cache_detail_pipefs {
        struct dentry *dir;
};

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 *);

        int                     (*cache_upcall)(struct cache_detail *,
                                                struct cache_head *);

        void                    (*cache_request)(struct cache_detail *cd,
                                                 struct cache_head *ch,
                                                 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);
        void                    (*warn_no_listener)(struct cache_detail *cd,
                                              int has_died);

        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;

        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 */

        union {
                struct cache_detail_procfs procfs;
                struct cache_detail_pipefs pipefs;
        } u;
        struct net              *net;
};


/* 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);
        int thread_wait;  /* How long (jiffies) we can block the
                           * current thread to wait for updates.
                           */
};
/* this must be embedded in a deferred_request that is being
 * delayed awaiting cache-fill
 */
struct cache_deferred_req {
        struct hlist_node       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);
};

/*
 * timestamps kept in the cache are expressed in seconds
 * since boot.  This is the best for measuring differences in
 * real time.
 */
static inline time_t seconds_since_boot(void)
{
        struct timespec boot;
        getboottime(&boot);
        return get_seconds() - boot.tv_sec;
}

static inline time_t convert_to_wallclock(time_t sinceboot)
{
        struct timespec boot;
        getboottime(&boot);
        return boot.tv_sec + sinceboot;
}

extern const struct file_operations cache_file_operations_pipefs;
extern const struct file_operations content_file_operations_pipefs;
extern const struct file_operations cache_flush_operations_pipefs;

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 int
sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h);


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_is_expired(struct cache_detail *detail, struct cache_head *h)
{
        return  (h->expiry_time < seconds_since_boot()) ||
                (detail->flush_time > h->last_refresh);
}

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 void __init cache_initialize(void);
extern int cache_register_net(struct cache_detail *cd, struct net *net);
extern void cache_unregister_net(struct cache_detail *cd, struct net *net);

extern struct cache_detail *cache_create_net(struct cache_detail *tmpl, struct net *net);
extern void cache_destroy_net(struct cache_detail *cd, struct net *net);

extern void sunrpc_init_cache_detail(struct cache_detail *cd);
extern void sunrpc_destroy_cache_detail(struct cache_detail *cd);
extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
                                        umode_t, struct cache_detail *);
extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);

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, sizeof(buf));

        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 int get_uint(char **bpp, unsigned int *anint)
{
        char buf[50];
        int len = qword_get(bpp, buf, sizeof(buf));

        if (len < 0)
                return -EINVAL;
        if (len == 0)
                return -ENOENT;

        if (kstrtouint(buf, 0, anint))
                return -EINVAL;

        return 0;
}

static inline int get_time(char **bpp, time_t *time)
{
        char buf[50];
        long long ll;
        int len = qword_get(bpp, buf, sizeof(buf));

        if (len < 0)
                return -EINVAL;
        if (len == 0)
                return -ENOENT;

        if (kstrtoll(buf, 0, &ll))
                return -EINVAL;

        *time = (time_t)ll;
        return 0;
}

static inline time_t get_expiry(char **bpp)
{
        time_t rv;
        struct timespec boot;

        if (get_time(bpp, &rv))
                return 0;
        if (rv < 0)
                return 0;
        getboottime(&boot);
        return rv - boot.tv_sec;
}

#endif /*  _LINUX_SUNRPC_CACHE_H_ */