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 not measured in refcount but rather in
  41  * CACHE_HASHED flag.
  42  */
  43
  44 /* Every cache item has a common header that is used
  45  * for expiring and refreshing entries.
  46  *
  47  */
  48 struct 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         atomic_t        refcnt;
  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 #define CACHE_HASHED    3       /* Entry is in a hash table */
  61
  62 #define CACHE_NEW_EXPIRY 120    /* keep new things pending confirmation for 120 seconds */
  63
  64 struct cache_detail {
  65         int                     hash_size;
  66         struct cache_head **    hash_table;
  67         rwlock_t                hash_lock;
  68
  69         atomic_t                inuse; /* active user-space update or lookup */
  70
  71         char                    *name;
  72         void                    (*cache_put)(struct cache_head *,
  73                                              struct cache_detail*);
  74
  75         void                    (*cache_request)(struct cache_detail *cd,
  76                                                  struct cache_head *h,
  77                                                  char **bpp, int *blen);
  78         int                     (*cache_parse)(struct cache_detail *,
  79                                                char *buf, int len);
  80
  81         int                     (*cache_show)(struct seq_file *m,
  82                                               struct cache_detail *cd,
  83                                               struct cache_head *h);
  84
  85         /* fields below this comment are for internal use
  86          * and should not be touched by cache owners
  87          */
  88         time_t                  flush_time;             /* flush all cache items with last_refresh
  89                                                          * earlier than this */
  90         struct list_head        others;
  91         time_t                  nextcheck;
  92         int                     entries;
  93
  94         /* fields for communication over channel */
  95         struct list_head        queue;
  96         struct proc_dir_entry   *proc_ent;
  97         struct proc_dir_entry   *flush_ent, *channel_ent, *content_ent;
  98
  99         atomic_t                readers;                /* how many time is /chennel open */
 100         time_t                  last_close;             /* if no readers, when did last close */
 101         time_t                  last_warn;              /* when we last warned about no readers */
 102         void                    (*warn_no_listener)(struct cache_detail *cd);
 103 };
 104
 105
 106 /* this must be embedded in any request structure that
 107  * identifies an object that will want a callback on
 108  * a cache fill
 109  */
 110 struct cache_req {
 111         struct cache_deferred_req *(*defer)(struct cache_req *req);
 112 };
 113 /* this must be embedded in a deferred_request that is being
 114  * delayed awaiting cache-fill
 115  */
 116 struct cache_deferred_req {
 117         struct list_head        hash;   /* on hash chain */
 118         struct list_head        recent; /* on fifo */
 119         struct cache_head       *item;  /* cache item we wait on */
 120         time_t                  recv_time;
 121         void                    *owner; /* we might need to discard all defered requests
 122                                          * owned by someone */
 123         void                    (*revisit)(struct cache_deferred_req *req,
 124                                            int too_many);
 125 };
 126
 127 /*
 128  * just like a template in C++, this macro does cache lookup
 129  * for us.
 130  * The function is passed some sort of HANDLE from which a cache_detail
 131  * structure can be determined (via SETUP, DETAIL), a template
 132  * cache entry (type RTN*), and a "set" flag.  Using the HASHFN and the
 133  * TEST, the function will try to find a matching cache entry in the cache.
 134  * If "set" == 0 :
 135  *    If an entry is found, it is returned
 136  *    If no entry is found, a new non-VALID entry is created.
 137  * If "set" == 1 and INPLACE == 0 :
 138  *    If no entry is found a new one is inserted with data from "template"
 139  *    If a non-CACHE_VALID entry is found, it is updated from template using UPDATE
 140  *    If a CACHE_VALID entry is found, a new entry is swapped in with data
 141  *       from "template"
 142  * If set == 1, and INPLACE == 1 :
 143  *    As above, except that if a CACHE_VALID entry is found, we UPDATE in place
 144  *       instead of swapping in a new entry.
 145  *
 146  * If the passed handle has the CACHE_NEGATIVE flag set, then UPDATE is not
 147  * run but insteead CACHE_NEGATIVE is set in any new item.
 148
 149  *  In any case, the new entry is returned with a reference count.
 150  *
 151  *
 152  * RTN is a struct type for a cache entry
 153  * MEMBER is the member of the cache which is cache_head, which must be first
 154  * FNAME is the name for the function
 155  * ARGS are arguments to function and must contain RTN *item, int set.  May
 156  *   also contain something to be usedby SETUP or DETAIL to find cache_detail.
 157  * SETUP  locates the cache detail and makes it available as...
 158  * DETAIL identifies the cache detail, possibly set up by SETUP
 159  * HASHFN returns a hash value of the cache entry "item"
 160  * TEST  tests if "tmp" matches "item"
 161  * INIT copies key information from "item" to "new"
 162  * UPDATE copies content information from "item" to "tmp"
 163  * INPLACE is true if updates can happen inplace rather than allocating a new structure
 164  */
 165 #define DefineCacheLookup(RTN,MEMBER,FNAME,ARGS,SETUP,DETAIL,HASHFN,TEST,INIT,UPDATE,INPLACE)   \
 166 RTN *FNAME ARGS                                                                         \
 167 {                                                                                       \
 168         RTN *tmp, *new=NULL;                                                            \
 169         struct cache_head **hp, **head;                                                 \
 170         SETUP;                                                                          \
 171         head = &(DETAIL)->hash_table[HASHFN];                                           \
 172  retry:                                                                                 \
 173         if (set||new) write_lock(&(DETAIL)->hash_lock);                                 \
 174         else read_lock(&(DETAIL)->hash_lock);                                           \
 175         for(hp=head; *hp != NULL; hp = &tmp->MEMBER.next) {                             \
 176                 tmp = container_of(*hp, RTN, MEMBER);                                   \
 177                 if (TEST) { /* found a match */                                         \
 178                                                                                         \
 179                         if (set && !INPLACE && test_bit(CACHE_VALID, &tmp->MEMBER.flags) && !new) \
 180                                 break;                                                  \
 181                                                                                         \
 182                         if (new)                                                        \
 183                                 {INIT;}                                                 \
 184                         cache_get(&tmp->MEMBER);                                        \
 185                         if (set) {                                                      \
 186                                 if (!INPLACE && test_bit(CACHE_VALID, &tmp->MEMBER.flags))\
 187                                 { /* need to swap in new */                             \
 188                                         RTN *t2;                                        \
 189                                                                                         \
 190                                         new->MEMBER.next = tmp->MEMBER.next;            \
 191                                         *hp = &new->MEMBER;                             \
 192                                         tmp->MEMBER.next = NULL;                        \
 193                                         set_bit(CACHE_HASHED, &new->MEMBER.flags);      \
 194                                         clear_bit(CACHE_HASHED, &tmp->MEMBER.flags);    \
 195                                         t2 = tmp; tmp = new; new = t2;                  \
 196                                 }                                                       \
 197                                 if (test_bit(CACHE_NEGATIVE,  &item->MEMBER.flags))     \
 198                                         set_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);    \
 199                                 else {                                                  \
 200                                         UPDATE;                                         \
 201                                         clear_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);  \
 202                                 }                                                       \
 203                         }                                                               \
 204                         if (set||new) write_unlock(&(DETAIL)->hash_lock);               \
 205                         else read_unlock(&(DETAIL)->hash_lock);                         \
 206                         if (set)                                                        \
 207                                 cache_fresh(DETAIL, &tmp->MEMBER, item->MEMBER.expiry_time); \
 208                         if (set && !INPLACE && new) cache_fresh(DETAIL, &new->MEMBER, 0);       \
 209                         if (new) (DETAIL)->cache_put(&new->MEMBER, DETAIL);             \
 210                         return tmp;                                                     \
 211                 }                                                                       \
 212         }                                                                               \
 213         /* Didn't find anything */                                                      \
 214         if (new) {                                                                      \
 215                 INIT;                                                                   \
 216                 new->MEMBER.next = *head;                                               \
 217                 *head = &new->MEMBER;                                                   \
 218                 (DETAIL)->entries ++;                                                   \
 219                 set_bit(CACHE_HASHED, &new->MEMBER.flags);                              \
 220                 if (set) {                                                              \
 221                         tmp = new;                                                      \
 222                         if (test_bit(CACHE_NEGATIVE, &item->MEMBER.flags))              \
 223                                 set_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);            \
 224                         else {UPDATE;}                                                  \
 225                 }                                                                       \
 226         }                                                                               \
 227         if (set||new) write_unlock(&(DETAIL)->hash_lock);                               \
 228         else read_unlock(&(DETAIL)->hash_lock);                                         \
 229         if (new && set)                                                                 \
 230                 cache_fresh(DETAIL, &new->MEMBER, item->MEMBER.expiry_time);            \
 231         if (new)                                                                        \
 232                 return new;                                                             \
 233         new = kmalloc(sizeof(*new), GFP_KERNEL);                                        \
 234         if (new) {                                                                      \
 235                 cache_init(&new->MEMBER);                                               \
 236                 cache_get(&new->MEMBER);                                                \
 237                 goto retry;                                                             \
 238         }                                                                               \
 239         return NULL;                                                                    \
 240 }
 241
 242 #define DefineSimpleCacheLookup(STRUCT,INPLACE) \
 243         DefineCacheLookup(struct STRUCT, h, STRUCT##_lookup, (struct STRUCT *item, int set), /*no setup */,     \
 244                           & STRUCT##_cache, STRUCT##_hash(item), STRUCT##_match(item, tmp),\
 245                           STRUCT##_init(new, item), STRUCT##_update(tmp, item),INPLACE)
 246
 247 #define cache_for_each(pos, detail, index, member)                                              \
 248         for (({read_lock(&(detail)->hash_lock); index = (detail)->hash_size;}) ;                \
 249              ({if (index==0)read_unlock(&(detail)->hash_lock); index--;});                      \
 250                 )                                                                               \
 251                 for (pos = container_of((detail)->hash_table[index], typeof(*pos), member);     \
 252                      &pos->member;                                                              \
 253                      pos = container_of(pos->member.next, typeof(*pos), member))
 254
 255
 256
 257 extern void cache_defer_req(struct cache_req *req, struct cache_head *item);
 258 extern void cache_revisit_request(struct cache_head *item);
 259 extern void cache_clean_deferred(void *owner);
 260
 261 static inline struct cache_head  *cache_get(struct cache_head *h)
 262 {
 263         atomic_inc(&h->refcnt);
 264         return h;
 265 }
 266
 267
 268 static inline int cache_put(struct cache_head *h, struct cache_detail *cd)
 269 {
 270         atomic_dec(&h->refcnt);
 271         if (!atomic_read(&h->refcnt) &&
 272             h->expiry_time < cd->nextcheck)
 273                 cd->nextcheck = h->expiry_time;
 274         if (!test_bit(CACHE_HASHED, &h->flags) &&
 275             !atomic_read(&h->refcnt))
 276                 return 1;
 277
 278         return 0;
 279 }
 280
 281 extern void cache_init(struct cache_head *h);
 282 extern void cache_fresh(struct cache_detail *detail,
 283                         struct cache_head *head, time_t expiry);
 284 extern int cache_check(struct cache_detail *detail,
 285                        struct cache_head *h, struct cache_req *rqstp);
 286 extern int cache_clean(void);
 287 extern void cache_flush(void);
 288 extern void cache_purge(struct cache_detail *detail);
 289 #define NEVER (0x7FFFFFFF)
 290 extern void cache_register(struct cache_detail *cd);
 291 extern int cache_unregister(struct cache_detail *cd);
 292 extern struct cache_detail *cache_find(char *name);
 293 extern void cache_drop(struct cache_detail *detail);
 294
 295 extern void qword_add(char **bpp, int *lp, char *str);
 296 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 297 extern int qword_get(char **bpp, char *dest, int bufsize);
 298
 299 static inline int get_int(char **bpp, int *anint)
 300 {
 301         char buf[50];
 302         char *ep;
 303         int rv;
 304         int len = qword_get(bpp, buf, 50);
 305         if (len < 0) return -EINVAL;
 306         if (len ==0) return -ENOENT;
 307         rv = simple_strtol(buf, &ep, 0);
 308         if (*ep) return -EINVAL;
 309         *anint = rv;
 310         return 0;
 311 }
 312
 313 static inline time_t get_expiry(char **bpp)
 314 {
 315         int rv;
 316         if (get_int(bpp, &rv))
 317                 return 0;
 318         if (rv < 0)
 319                 return 0;
 320         return rv;
 321 }
 322
 323 #endif /*  _LINUX_SUNRPC_CACHE_H_ */