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_procfs {
  63         struct proc_dir_entry   *proc_ent;
  64         struct proc_dir_entry   *flush_ent, *channel_ent, *content_ent;
  65 };
  66
  67 struct cache_detail {
  68         struct module *         owner;
  69         int                     hash_size;
  70         struct cache_head **    hash_table;
  71         rwlock_t                hash_lock;
  72
  73         atomic_t                inuse; /* active user-space update or lookup */
  74
  75         char                    *name;
  76         void                    (*cache_put)(struct kref *);
  77
  78         int                     (*cache_upcall)(struct cache_detail *,
  79                                                 struct cache_head *);
  80
  81         int                     (*cache_parse)(struct cache_detail *,
  82                                                char *buf, int len);
  83
  84         int                     (*cache_show)(struct seq_file *m,
  85                                               struct cache_detail *cd,
  86                                               struct cache_head *h);
  87         void                    (*warn_no_listener)(struct cache_detail *cd,
  88                                               int has_died);
  89
  90         struct cache_head *     (*alloc)(void);
  91         int                     (*match)(struct cache_head *orig, struct cache_head *new);
  92         void                    (*init)(struct cache_head *orig, struct cache_head *new);
  93         void                    (*update)(struct cache_head *orig, struct cache_head *new);
  94
  95         /* fields below this comment are for internal use
  96          * and should not be touched by cache owners
  97          */
  98         time_t                  flush_time;             /* flush all cache items with last_refresh
  99                                                          * earlier than this */
 100         struct list_head        others;
 101         time_t                  nextcheck;
 102         int                     entries;
 103
 104         /* fields for communication over channel */
 105         struct list_head        queue;
 106
 107         atomic_t                readers;                /* how many time is /chennel open */
 108         time_t                  last_close;             /* if no readers, when did last close */
 109         time_t                  last_warn;              /* when we last warned about no readers */
 110
 111         union {
 112                 struct cache_detail_procfs procfs;
 113         } u;
 114 };
 115
 116
 117 /* this must be embedded in any request structure that
 118  * identifies an object that will want a callback on
 119  * a cache fill
 120  */
 121 struct cache_req {
 122         struct cache_deferred_req *(*defer)(struct cache_req *req);
 123 };
 124 /* this must be embedded in a deferred_request that is being
 125  * delayed awaiting cache-fill
 126  */
 127 struct cache_deferred_req {
 128         struct list_head        hash;   /* on hash chain */
 129         struct list_head        recent; /* on fifo */
 130         struct cache_head       *item;  /* cache item we wait on */
 131         void                    *owner; /* we might need to discard all defered requests
 132                                          * owned by someone */
 133         void                    (*revisit)(struct cache_deferred_req *req,
 134                                            int too_many);
 135 };
 136
 137
 138 extern struct cache_head *
 139 sunrpc_cache_lookup(struct cache_detail *detail,
 140                     struct cache_head *key, int hash);
 141 extern struct cache_head *
 142 sunrpc_cache_update(struct cache_detail *detail,
 143                     struct cache_head *new, struct cache_head *old, int hash);
 144
 145 extern int
 146 sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
 147                 void (*cache_request)(struct cache_detail *,
 148                                       struct cache_head *,
 149                                       char **,
 150                                       int *));
 151
 152
 153 extern void cache_clean_deferred(void *owner);
 154
 155 static inline struct cache_head  *cache_get(struct cache_head *h)
 156 {
 157         kref_get(&h->ref);
 158         return h;
 159 }
 160
 161
 162 static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 163 {
 164         if (atomic_read(&h->ref.refcount) <= 2 &&
 165             h->expiry_time < cd->nextcheck)
 166                 cd->nextcheck = h->expiry_time;
 167         kref_put(&h->ref, cd->cache_put);
 168 }
 169
 170 static inline int cache_valid(struct cache_head *h)
 171 {
 172         /* If an item has been unhashed pending removal when
 173          * the refcount drops to 0, the expiry_time will be
 174          * set to 0.  We don't want to consider such items
 175          * valid in this context even though CACHE_VALID is
 176          * set.
 177          */
 178         return (h->expiry_time != 0 && test_bit(CACHE_VALID, &h->flags));
 179 }
 180
 181 extern int cache_check(struct cache_detail *detail,
 182                        struct cache_head *h, struct cache_req *rqstp);
 183 extern void cache_flush(void);
 184 extern void cache_purge(struct cache_detail *detail);
 185 #define NEVER (0x7FFFFFFF)
 186 extern int cache_register(struct cache_detail *cd);
 187 extern void cache_unregister(struct cache_detail *cd);
 188
 189 extern void qword_add(char **bpp, int *lp, char *str);
 190 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 191 extern int qword_get(char **bpp, char *dest, int bufsize);
 192
 193 static inline int get_int(char **bpp, int *anint)
 194 {
 195         char buf[50];
 196         char *ep;
 197         int rv;
 198         int len = qword_get(bpp, buf, 50);
 199         if (len < 0) return -EINVAL;
 200         if (len ==0) return -ENOENT;
 201         rv = simple_strtol(buf, &ep, 0);
 202         if (*ep) return -EINVAL;
 203         *anint = rv;
 204         return 0;
 205 }
 206
 207 static inline time_t get_expiry(char **bpp)
 208 {
 209         int rv;
 210         if (get_int(bpp, &rv))
 211                 return 0;
 212         if (rv < 0)
 213                 return 0;
 214         return rv;
 215 }
 216
 217 #endif /*  _LINUX_SUNRPC_CACHE_H_ */