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  */
  47 struct 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
  62 struct cache_detail {
  63         struct module *         owner;
  64         int                     hash_size;
  65         struct cache_head **    hash_table;
  66         rwlock_t                hash_lock;
  67
  68         atomic_t                inuse; /* active user-space update or lookup */
  69
  70         char                    *name;
  71         void                    (*cache_put)(struct kref *);
  72
  73         void                    (*cache_request)(struct cache_detail *cd,
  74                                                  struct cache_head *h,
  75                                                  char **bpp, int *blen);
  76         int                     (*cache_parse)(struct cache_detail *,
  77                                                char *buf, int len);
  78
  79         int                     (*cache_show)(struct seq_file *m,
  80                                               struct cache_detail *cd,
  81                                               struct cache_head *h);
  82
  83         struct cache_head *     (*alloc)(void);
  84         int                     (*match)(struct cache_head *orig, struct cache_head *new);
  85         void                    (*init)(struct cache_head *orig, struct cache_head *new);
  86         void                    (*update)(struct cache_head *orig, struct cache_head *new);
  87
  88         /* fields below this comment are for internal use
  89          * and should not be touched by cache owners
  90          */
  91         time_t                  flush_time;             /* flush all cache items with last_refresh
  92                                                          * earlier than this */
  93         struct list_head        others;
  94         time_t                  nextcheck;
  95         int                     entries;
  96
  97         /* fields for communication over channel */
  98         struct list_head        queue;
  99         struct proc_dir_entry   *proc_ent;
 100         struct proc_dir_entry   *flush_ent, *channel_ent, *content_ent;
 101
 102         atomic_t                readers;                /* how many time is /chennel open */
 103         time_t                  last_close;             /* if no readers, when did last close */
 104         time_t                  last_warn;              /* when we last warned about no readers */
 105         void                    (*warn_no_listener)(struct cache_detail *cd);
 106 };
 107
 108
 109 /* this must be embedded in any request structure that
 110  * identifies an object that will want a callback on
 111  * a cache fill
 112  */
 113 struct cache_req {
 114         struct cache_deferred_req *(*defer)(struct cache_req *req);
 115 };
 116 /* this must be embedded in a deferred_request that is being
 117  * delayed awaiting cache-fill
 118  */
 119 struct cache_deferred_req {
 120         struct list_head        hash;   /* on hash chain */
 121         struct list_head        recent; /* on fifo */
 122         struct cache_head       *item;  /* cache item we wait on */
 123         void                    *owner; /* we might need to discard all defered requests
 124                                          * owned by someone */
 125         void                    (*revisit)(struct cache_deferred_req *req,
 126                                            int too_many);
 127 };
 128
 129
 130 extern struct cache_head *
 131 sunrpc_cache_lookup(struct cache_detail *detail,
 132                     struct cache_head *key, int hash);
 133 extern struct cache_head *
 134 sunrpc_cache_update(struct cache_detail *detail,
 135                     struct cache_head *new, struct cache_head *old, int hash);
 136
 137
 138 extern void cache_clean_deferred(void *owner);
 139
 140 static inline struct cache_head  *cache_get(struct cache_head *h)
 141 {
 142         kref_get(&h->ref);
 143         return h;
 144 }
 145
 146
 147 static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 148 {
 149         if (atomic_read(&h->ref.refcount) <= 2 &&
 150             h->expiry_time < cd->nextcheck)
 151                 cd->nextcheck = h->expiry_time;
 152         kref_put(&h->ref, cd->cache_put);
 153 }
 154
 155 static inline int cache_valid(struct cache_head *h)
 156 {
 157         /* If an item has been unhashed pending removal when
 158          * the refcount drops to 0, the expiry_time will be
 159          * set to 0.  We don't want to consider such items
 160          * valid in this context even though CACHE_VALID is
 161          * set.
 162          */
 163         return (h->expiry_time != 0 && test_bit(CACHE_VALID, &h->flags));
 164 }
 165
 166 extern int cache_check(struct cache_detail *detail,
 167                        struct cache_head *h, struct cache_req *rqstp);
 168 extern void cache_flush(void);
 169 extern void cache_purge(struct cache_detail *detail);
 170 #define NEVER (0x7FFFFFFF)
 171 extern int cache_register(struct cache_detail *cd);
 172 extern void cache_unregister(struct cache_detail *cd);
 173
 174 extern void qword_add(char **bpp, int *lp, char *str);
 175 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 176 extern int qword_get(char **bpp, char *dest, int bufsize);
 177
 178 static inline int get_int(char **bpp, int *anint)
 179 {
 180         char buf[50];
 181         char *ep;
 182         int rv;
 183         int len = qword_get(bpp, buf, 50);
 184         if (len < 0) return -EINVAL;
 185         if (len ==0) return -ENOENT;
 186         rv = simple_strtol(buf, &ep, 0);
 187         if (*ep) return -EINVAL;
 188         *anint = rv;
 189         return 0;
 190 }
 191
 192 static inline time_t get_expiry(char **bpp)
 193 {
 194         int rv;
 195         if (get_int(bpp, &rv))
 196                 return 0;
 197         if (rv < 0)
 198                 return 0;
 199         return rv;
 200 }
 201
 202 #endif /*  _LINUX_SUNRPC_CACHE_H_ */