linux/include/linux/sunrpc/cache.h
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   1/*
   2 * include/linux/sunrpc/cache.h
   3 *
   4 * Generic code for various authentication-related caches
   5 * used by sunrpc clients and servers.
   6 *
   7 * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
   8 *
   9 * Released under terms in GPL version 2.  See COPYING.
  10 *
  11 */
  12
  13#ifndef _LINUX_SUNRPC_CACHE_H_
  14#define _LINUX_SUNRPC_CACHE_H_
  15
  16#include <linux/kref.h>
  17#include <linux/slab.h>
  18#include <linux/atomic.h>
  19#include <linux/proc_fs.h>
  20
  21/*
  22 * Each cache requires:
  23 *  - A 'struct cache_detail' which contains information specific to the cache
  24 *    for common code to use.
  25 *  - An item structure that must contain a "struct cache_head"
  26 *  - A lookup function defined using DefineCacheLookup
  27 *  - A 'put' function that can release a cache item. It will only
  28 *    be called after cache_put has succeed, so there are guarantee
  29 *    to be no references.
  30 *  - A function to calculate a hash of an item's key.
  31 *
  32 * as well as assorted code fragments (e.g. compare keys) and numbers
  33 * (e.g. hash size, goal_age, etc).
  34 *
  35 * Each cache must be registered so that it can be cleaned regularly.
  36 * When the cache is unregistered, it is flushed completely.
  37 *
  38 * Entries have a ref count and a 'hashed' flag which counts the existence
  39 * in the hash table.
  40 * We only expire entries when refcount is zero.
  41 * Existence in the cache is counted  the refcount.
  42 */
  43
  44/* Every cache item has a common header that is used
  45 * for expiring and refreshing entries.
  46 * 
  47 */
  48struct cache_head {
  49        struct cache_head * next;
  50        time_t          expiry_time;    /* After time time, don't use the data */
  51        time_t          last_refresh;   /* If CACHE_PENDING, this is when upcall 
  52                                         * was sent, else this is when update was received
  53                                         */
  54        struct kref     ref;
  55        unsigned long   flags;
  56};
  57#define CACHE_VALID     0       /* Entry contains valid data */
  58#define CACHE_NEGATIVE  1       /* Negative entry - there is no match for the key */
  59#define CACHE_PENDING   2       /* An upcall has been sent but no reply received yet*/
  60
  61#define CACHE_NEW_EXPIRY 120    /* keep new things pending confirmation for 120 seconds */
  62
  63struct cache_detail_procfs {
  64        struct proc_dir_entry   *proc_ent;
  65        struct proc_dir_entry   *flush_ent, *channel_ent, *content_ent;
  66};
  67
  68struct cache_detail_pipefs {
  69        struct dentry *dir;
  70};
  71
  72struct cache_detail {
  73        struct module *         owner;
  74        int                     hash_size;
  75        struct cache_head **    hash_table;
  76        rwlock_t                hash_lock;
  77
  78        atomic_t                inuse; /* active user-space update or lookup */
  79
  80        char                    *name;
  81        void                    (*cache_put)(struct kref *);
  82
  83        int                     (*cache_upcall)(struct cache_detail *,
  84                                                struct cache_head *);
  85
  86        int                     (*cache_parse)(struct cache_detail *,
  87                                               char *buf, int len);
  88
  89        int                     (*cache_show)(struct seq_file *m,
  90                                              struct cache_detail *cd,
  91                                              struct cache_head *h);
  92        void                    (*warn_no_listener)(struct cache_detail *cd,
  93                                              int has_died);
  94
  95        struct cache_head *     (*alloc)(void);
  96        int                     (*match)(struct cache_head *orig, struct cache_head *new);
  97        void                    (*init)(struct cache_head *orig, struct cache_head *new);
  98        void                    (*update)(struct cache_head *orig, struct cache_head *new);
  99
 100        /* fields below this comment are for internal use
 101         * and should not be touched by cache owners
 102         */
 103        time_t                  flush_time;             /* flush all cache items with last_refresh
 104                                                         * earlier than this */
 105        struct list_head        others;
 106        time_t                  nextcheck;
 107        int                     entries;
 108
 109        /* fields for communication over channel */
 110        struct list_head        queue;
 111
 112        atomic_t                readers;                /* how many time is /chennel open */
 113        time_t                  last_close;             /* if no readers, when did last close */
 114        time_t                  last_warn;              /* when we last warned about no readers */
 115
 116        union {
 117                struct cache_detail_procfs procfs;
 118                struct cache_detail_pipefs pipefs;
 119        } u;
 120};
 121
 122
 123/* this must be embedded in any request structure that
 124 * identifies an object that will want a callback on
 125 * a cache fill
 126 */
 127struct cache_req {
 128        struct cache_deferred_req *(*defer)(struct cache_req *req);
 129        int thread_wait;  /* How long (jiffies) we can block the
 130                           * current thread to wait for updates.
 131                           */
 132};
 133/* this must be embedded in a deferred_request that is being
 134 * delayed awaiting cache-fill
 135 */
 136struct cache_deferred_req {
 137        struct hlist_node       hash;   /* on hash chain */
 138        struct list_head        recent; /* on fifo */
 139        struct cache_head       *item;  /* cache item we wait on */
 140        void                    *owner; /* we might need to discard all defered requests
 141                                         * owned by someone */
 142        void                    (*revisit)(struct cache_deferred_req *req,
 143                                           int too_many);
 144};
 145
 146
 147extern const struct file_operations cache_file_operations_pipefs;
 148extern const struct file_operations content_file_operations_pipefs;
 149extern const struct file_operations cache_flush_operations_pipefs;
 150
 151extern struct cache_head *
 152sunrpc_cache_lookup(struct cache_detail *detail,
 153                    struct cache_head *key, int hash);
 154extern struct cache_head *
 155sunrpc_cache_update(struct cache_detail *detail,
 156                    struct cache_head *new, struct cache_head *old, int hash);
 157
 158extern int
 159sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
 160                void (*cache_request)(struct cache_detail *,
 161                                      struct cache_head *,
 162                                      char **,
 163                                      int *));
 164
 165
 166extern void cache_clean_deferred(void *owner);
 167
 168static inline struct cache_head  *cache_get(struct cache_head *h)
 169{
 170        kref_get(&h->ref);
 171        return h;
 172}
 173
 174
 175static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 176{
 177        if (atomic_read(&h->ref.refcount) <= 2 &&
 178            h->expiry_time < cd->nextcheck)
 179                cd->nextcheck = h->expiry_time;
 180        kref_put(&h->ref, cd->cache_put);
 181}
 182
 183static inline int cache_valid(struct cache_head *h)
 184{
 185        /* If an item has been unhashed pending removal when
 186         * the refcount drops to 0, the expiry_time will be
 187         * set to 0.  We don't want to consider such items
 188         * valid in this context even though CACHE_VALID is
 189         * set.
 190         */
 191        return (h->expiry_time != 0 && test_bit(CACHE_VALID, &h->flags));
 192}
 193
 194extern int cache_check(struct cache_detail *detail,
 195                       struct cache_head *h, struct cache_req *rqstp);
 196extern void cache_flush(void);
 197extern void cache_purge(struct cache_detail *detail);
 198#define NEVER (0x7FFFFFFF)
 199extern void __init cache_initialize(void);
 200extern int cache_register(struct cache_detail *cd);
 201extern int cache_register_net(struct cache_detail *cd, struct net *net);
 202extern void cache_unregister(struct cache_detail *cd);
 203extern void cache_unregister_net(struct cache_detail *cd, struct net *net);
 204
 205extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
 206                                        umode_t, struct cache_detail *);
 207extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
 208
 209extern void qword_add(char **bpp, int *lp, char *str);
 210extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 211extern int qword_get(char **bpp, char *dest, int bufsize);
 212
 213static inline int get_int(char **bpp, int *anint)
 214{
 215        char buf[50];
 216        char *ep;
 217        int rv;
 218        int len = qword_get(bpp, buf, 50);
 219        if (len < 0) return -EINVAL;
 220        if (len ==0) return -ENOENT;
 221        rv = simple_strtol(buf, &ep, 0);
 222        if (*ep) return -EINVAL;
 223        *anint = rv;
 224        return 0;
 225}
 226
 227/*
 228 * timestamps kept in the cache are expressed in seconds
 229 * since boot.  This is the best for measuring differences in
 230 * real time.
 231 */
 232static inline time_t seconds_since_boot(void)
 233{
 234        struct timespec boot;
 235        getboottime(&boot);
 236        return get_seconds() - boot.tv_sec;
 237}
 238
 239static inline time_t convert_to_wallclock(time_t sinceboot)
 240{
 241        struct timespec boot;
 242        getboottime(&boot);
 243        return boot.tv_sec + sinceboot;
 244}
 245
 246static inline time_t get_expiry(char **bpp)
 247{
 248        int rv;
 249        struct timespec boot;
 250
 251        if (get_int(bpp, &rv))
 252                return 0;
 253        if (rv < 0)
 254                return 0;
 255        getboottime(&boot);
 256        return rv - boot.tv_sec;
 257}
 258
 259#endif /*  _LINUX_SUNRPC_CACHE_H_ */
 260