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