cache.h

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/*
 * include/linux/sunrpc/cache.h
 *
 * Generic code for various authentication-related caches
 * used by sunrpc clients and servers.
 *
 * Copyright (C) 2002 Neil Brown <[email protected]>
 *
 * 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_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 *);

    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);
};


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,
        void (*cache_request)(struct cache_detail *,
                      struct cache_head *,
                      char **,
                      int *));


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 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];
    int len = qword_get(bpp, buf, sizeof(buf));

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

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

    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;
}

/*
 * 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;
}

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

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

#endif /*  _LINUX_SUNRPC_CACHE_H_ */