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_pipefs {
  68         struct dentry *dir;
  69 };
  70
  71 struct 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  */
 126 struct 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  */
 132 struct 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
 143 extern const struct file_operations cache_file_operations_pipefs;
 144 extern const struct file_operations content_file_operations_pipefs;
 145 extern const struct file_operations cache_flush_operations_pipefs;
 146
 147 extern struct cache_head *
 148 sunrpc_cache_lookup(struct cache_detail *detail,
 149                     struct cache_head *key, int hash);
 150 extern struct cache_head *
 151 sunrpc_cache_update(struct cache_detail *detail,
 152                     struct cache_head *new, struct cache_head *old, int hash);
 153
 154 extern int
 155 sunrpc_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
 162 extern void cache_clean_deferred(void *owner);
 163
 164 static inline struct cache_head  *cache_get(struct cache_head *h)
 165 {
 166         kref_get(&h->ref);
 167         return h;
 168 }
 169
 170
 171 static 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
 179 static 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
 190 extern int cache_check(struct cache_detail *detail,
 191                        struct cache_head *h, struct cache_req *rqstp);
 192 extern void cache_flush(void);
 193 extern void cache_purge(struct cache_detail *detail);
 194 #define NEVER (0x7FFFFFFF)
 195 extern int cache_register(struct cache_detail *cd);
 196 extern void cache_unregister(struct cache_detail *cd);
 197
 198 extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
 199                                         mode_t, struct cache_detail *);
 200 extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
 201
 202 extern void qword_add(char **bpp, int *lp, char *str);
 203 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 204 extern int qword_get(char **bpp, char *dest, int bufsize);
 205
 206 static 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
 220 static 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_ */