LXR linux/include/linux/sunrpc/cache.h

   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        struct net              *net;
 121};
 122
 123
 124/* this must be embedded in any request structure that
 125 * identifies an object that will want a callback on
 126 * a cache fill
 127 */
 128struct cache_req {
 129        struct cache_deferred_req *(*defer)(struct cache_req *req);
 130        int thread_wait;  /* How long (jiffies) we can block the
 131                           * current thread to wait for updates.
 132                           */
 133};
 134/* this must be embedded in a deferred_request that is being
 135 * delayed awaiting cache-fill
 136 */
 137struct cache_deferred_req {
 138        struct hlist_node       hash;   /* on hash chain */
 139        struct list_head        recent; /* on fifo */
 140        struct cache_head       *item;  /* cache item we wait on */
 141        void                    *owner; /* we might need to discard all defered requests
 142                                         * owned by someone */
 143        void                    (*revisit)(struct cache_deferred_req *req,
 144                                           int too_many);
 145};
 146
 147
 148extern const struct file_operations cache_file_operations_pipefs;
 149extern const struct file_operations content_file_operations_pipefs;
 150extern const struct file_operations cache_flush_operations_pipefs;
 151
 152extern struct cache_head *
 153sunrpc_cache_lookup(struct cache_detail *detail,
 154                    struct cache_head *key, int hash);
 155extern struct cache_head *
 156sunrpc_cache_update(struct cache_detail *detail,
 157                    struct cache_head *new, struct cache_head *old, int hash);
 158
 159extern int
 160sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
 161                void (*cache_request)(struct cache_detail *,
 162                                      struct cache_head *,
 163                                      char **,
 164                                      int *));
 165
 166
 167extern void cache_clean_deferred(void *owner);
 168
 169static inline struct cache_head  *cache_get(struct cache_head *h)
 170{
 171        kref_get(&h->ref);
 172        return h;
 173}
 174
 175
 176static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 177{
 178        if (atomic_read(&h->ref.refcount) <= 2 &&
 179            h->expiry_time < cd->nextcheck)
 180                cd->nextcheck = h->expiry_time;
 181        kref_put(&h->ref, cd->cache_put);
 182}
 183
 184static inline int cache_valid(struct cache_head *h)
 185{
 186        /* If an item has been unhashed pending removal when
 187         * the refcount drops to 0, the expiry_time will be
 188         * set to 0.  We don't want to consider such items
 189         * valid in this context even though CACHE_VALID is
 190         * set.
 191         */
 192        return (h->expiry_time != 0 && test_bit(CACHE_VALID, &h->flags));
 193}
 194
 195extern int cache_check(struct cache_detail *detail,
 196                       struct cache_head *h, struct cache_req *rqstp);
 197extern void cache_flush(void);
 198extern void cache_purge(struct cache_detail *detail);
 199#define NEVER (0x7FFFFFFF)
 200extern void __init cache_initialize(void);
 201extern int cache_register_net(struct cache_detail *cd, struct net *net);
 202extern void cache_unregister_net(struct cache_detail *cd, struct net *net);
 203
 204extern struct cache_detail *cache_create_net(struct cache_detail *tmpl, struct net *net);
 205extern void cache_destroy_net(struct cache_detail *cd, struct net *net);
 206
 207extern void sunrpc_init_cache_detail(struct cache_detail *cd);
 208extern void sunrpc_destroy_cache_detail(struct cache_detail *cd);
 209extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
 210                                        umode_t, struct cache_detail *);
 211extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
 212
 213extern void qword_add(char **bpp, int *lp, char *str);
 214extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 215extern int qword_get(char **bpp, char *dest, int bufsize);
 216
 217static inline int get_int(char **bpp, int *anint)
 218{
 219        char buf[50];
 220        char *ep;
 221        int rv;
 222        int len = qword_get(bpp, buf, 50);
 223        if (len < 0) return -EINVAL;
 224        if (len ==0) return -ENOENT;
 225        rv = simple_strtol(buf, &ep, 0);
 226        if (*ep) return -EINVAL;
 227        *anint = rv;
 228        return 0;
 229}
 230
 231/*
 232 * timestamps kept in the cache are expressed in seconds
 233 * since boot.  This is the best for measuring differences in
 234 * real time.
 235 */
 236static inline time_t seconds_since_boot(void)
 237{
 238        struct timespec boot;
 239        getboottime(&boot);
 240        return get_seconds() - boot.tv_sec;
 241}
 242
 243static inline time_t convert_to_wallclock(time_t sinceboot)
 244{
 245        struct timespec boot;
 246        getboottime(&boot);
 247        return boot.tv_sec + sinceboot;
 248}
 249
 250static inline time_t get_expiry(char **bpp)
 251{
 252        int rv;
 253        struct timespec boot;
 254
 255        if (get_int(bpp, &rv))
 256                return 0;
 257        if (rv < 0)
 258                return 0;
 259        getboottime(&boot);
 260        return rv - boot.tv_sec;
 261}
 262
 263#endif /*  _LINUX_SUNRPC_CACHE_H_ */
 264