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;             /* it no readers, when did last close */
 101 };
 102
 103
 104 /* this must be embedded in any request structure that
 105  * identifies an object that will want a callback on
 106  * a cache fill
 107  */
 108 struct cache_req {
 109         struct cache_deferred_req *(*defer)(struct cache_req *req);
 110 };
 111 /* this must be embedded in a deferred_request that is being
 112  * delayed awaiting cache-fill
 113  */
 114 struct cache_deferred_req {
 115         struct list_head        hash;   /* on hash chain */
 116         struct list_head        recent; /* on fifo */
 117         struct cache_head       *item;  /* cache item we wait on */
 118         time_t                  recv_time;
 119         void                    *owner; /* we might need to discard all defered requests
 120                                          * owned by someone */
 121         void                    (*revisit)(struct cache_deferred_req *req,
 122                                            int too_many);
 123 };
 124
 125 /*
 126  * just like a template in C++, this macro does cache lookup
 127  * for us.
 128  * The function is passed some sort of HANDLE from which a cache_detail
 129  * structure can be determined (via SETUP, DETAIL), a template
 130  * cache entry (type RTN*), and a "set" flag.  Using the HASHFN and the
 131  * TEST, the function will try to find a matching cache entry in the cache.
 132  * If "set" == 0 :
 133  *    If an entry is found, it is returned
 134  *    If no entry is found, a new non-VALID entry is created.
 135  * If "set" == 1 :
 136  *    If no entry is found a new one is inserted with data from "template"
 137  *    If a non-CACHE_VALID entry is found, it is updated from template using UPDATE
 138  *    If a CACHE_VALID entry is found, a new entry is swapped in with data
 139  *       from "template"
 140  * If set == 2, we UPDATE, but don't swap. i.e. update in place
 141  *
 142  * If the passed handle has the CACHE_NEGATIVE flag set, then UPDATE is not
 143  * run but insteead CACHE_NEGATIVE is set in any new item.
 144
 145  *  In any case, the new entry is returned with a reference count.
 146  *
 147  *
 148  * RTN is a struct type for a cache entry
 149  * MEMBER is the member of the cache which is cache_head, which must be first
 150  * FNAME is the name for the function
 151  * ARGS are arguments to function and must contain RTN *item, int set.  May
 152  *   also contain something to be usedby SETUP or DETAIL to find cache_detail.
 153  * SETUP  locates the cache detail and makes it available as...
 154  * DETAIL identifies the cache detail, possibly set up by SETUP
 155  * HASHFN returns a hash value of the cache entry "item"
 156  * TEST  tests if "tmp" matches "item"
 157  * INIT copies key information from "item" to "new"
 158  * UPDATE copies content information from "item" to "tmp"
 159  * INPLACE is true if updates can happen inplace rather than allocating a new structure
 160  */
 161 #define DefineCacheLookup(RTN,MEMBER,FNAME,ARGS,SETUP,DETAIL,HASHFN,TEST,INIT,UPDATE,INPLACE)   \
 162 RTN *FNAME ARGS                                                                         \
 163 {                                                                                       \
 164         RTN *tmp, *new=NULL;                                                            \
 165         struct cache_head **hp, **head;                                                 \
 166         SETUP;                                                                          \
 167  retry:                                                                                 \
 168         head = &(DETAIL)->hash_table[HASHFN];                                           \
 169         if (set||new) write_lock(&(DETAIL)->hash_lock);                                 \
 170         else read_lock(&(DETAIL)->hash_lock);                                           \
 171         for(hp=head; *hp != NULL; hp = &tmp->MEMBER.next) {                             \
 172                 tmp = container_of(*hp, RTN, MEMBER);                                   \
 173                 if (TEST) { /* found a match */                                         \
 174                                                                                         \
 175                         if (set && !INPLACE && test_bit(CACHE_VALID, &tmp->MEMBER.flags) && !new) \
 176                                 break;                                                  \
 177                                                                                         \
 178                         cache_get(&tmp->MEMBER);                                        \
 179                         if (set) {                                                      \
 180                                 if (!INPLACE && test_bit(CACHE_VALID, &tmp->MEMBER.flags))\
 181                                 { /* need to swap in new */                             \
 182                                         RTN *t2;                                        \
 183                                                                                         \
 184                                         new->MEMBER.next = tmp->MEMBER.next;            \
 185                                         *hp = &new->MEMBER;                             \
 186                                         tmp->MEMBER.next = NULL;                        \
 187                                         set_bit(CACHE_HASHED, &new->MEMBER.flags);      \
 188                                         clear_bit(CACHE_HASHED, &tmp->MEMBER.flags);    \
 189                                         t2 = tmp; tmp = new; new = t2;                  \
 190                                 }                                                       \
 191                                 if (test_bit(CACHE_NEGATIVE,  &item->MEMBER.flags))     \
 192                                          set_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);   \
 193                                 else {UPDATE;}                                          \
 194                         }                                                               \
 195                         if (set||new) write_unlock(&(DETAIL)->hash_lock);               \
 196                         else read_unlock(&(DETAIL)->hash_lock);                         \
 197                         if (set)                                                        \
 198                                 cache_fresh(DETAIL, &tmp->MEMBER, item->MEMBER.expiry_time); \
 199                         if (set && !INPLACE && new) cache_fresh(DETAIL, &new->MEMBER, 0);       \
 200                         if (new) (DETAIL)->cache_put(&new->MEMBER, DETAIL);             \
 201                         return tmp;                                                     \
 202                 }                                                                       \
 203         }                                                                               \
 204         /* Didn't find anything */                                                      \
 205         if (new) {                                                                      \
 206                 new->MEMBER.next = *head;                                               \
 207                 *head = &new->MEMBER;                                                   \
 208                 (DETAIL)->entries ++;                                                   \
 209                 set_bit(CACHE_HASHED, &new->MEMBER.flags);                              \
 210                 if (set) {                                                              \
 211                         tmp = new;                                                      \
 212                         if (test_bit(CACHE_NEGATIVE, &item->MEMBER.flags))              \
 213                                 set_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);            \
 214                         else {UPDATE;}                                                  \
 215                 }                                                                       \
 216         }                                                                               \
 217         if (set||new) write_unlock(&(DETAIL)->hash_lock);                               \
 218         else read_unlock(&(DETAIL)->hash_lock);                                         \
 219         if (new && set)                                                                 \
 220                 cache_fresh(DETAIL, &new->MEMBER, item->MEMBER.expiry_time);            \
 221         if (new)                                                                        \
 222                 return new;                                                             \
 223         new = kmalloc(sizeof(*new), GFP_KERNEL);                                        \
 224         if (new) {                                                                      \
 225                 cache_init(&new->MEMBER);                                               \
 226                 cache_get(&new->MEMBER);                                                \
 227                 INIT;                                                                   \
 228                 tmp = new;                                                              \
 229                 goto retry;                                                             \
 230         }                                                                               \
 231         return NULL;                                                                    \
 232 }
 233
 234 #define DefineSimpleCacheLookup(STRUCT,INPLACE) \
 235         DefineCacheLookup(struct STRUCT, h, STRUCT##_lookup, (struct STRUCT *item, int set), /*no setup */,     \
 236                           & STRUCT##_cache, STRUCT##_hash(item), STRUCT##_match(item, tmp),\
 237                           STRUCT##_init(new, item), STRUCT##_update(tmp, item),INPLACE)
 238
 239 #define cache_for_each(pos, detail, index, member)                                              \
 240         for (({read_lock(&(detail)->hash_lock); index = (detail)->hash_size;}) ;                \
 241              ({if (index==0)read_unlock(&(detail)->hash_lock); index--;});                      \
 242                 )                                                                               \
 243                 for (pos = container_of((detail)->hash_table[index], typeof(*pos), member);     \
 244                      &pos->member;                                                              \
 245                      pos = container_of(pos->member.next, typeof(*pos), member))
 246
 247
 248
 249 extern void cache_defer_req(struct cache_req *req, struct cache_head *item);
 250 extern void cache_revisit_request(struct cache_head *item);
 251 extern void cache_clean_deferred(void *owner);
 252
 253 static inline struct cache_head  *cache_get(struct cache_head *h)
 254 {
 255         atomic_inc(&h->refcnt);
 256         return h;
 257 }
 258
 259
 260 static inline int cache_put(struct cache_head *h, struct cache_detail *cd)
 261 {
 262         atomic_dec(&h->refcnt);
 263         if (!atomic_read(&h->refcnt) &&
 264             h->expiry_time < cd->nextcheck)
 265                 cd->nextcheck = h->expiry_time;
 266         if (!test_bit(CACHE_HASHED, &h->flags) &&
 267             !atomic_read(&h->refcnt))
 268                 return 1;
 269
 270         return 0;
 271 }
 272
 273 extern void cache_init(struct cache_head *h);
 274 extern void cache_fresh(struct cache_detail *detail,
 275                         struct cache_head *head, time_t expiry);
 276 extern int cache_check(struct cache_detail *detail,
 277                        struct cache_head *h, struct cache_req *rqstp);
 278 extern int cache_clean(void);
 279 extern void cache_flush(void);
 280 extern void cache_purge(struct cache_detail *detail);
 281 #define NEVER (0x7FFFFFFF)
 282 extern void cache_register(struct cache_detail *cd);
 283 extern int cache_unregister(struct cache_detail *cd);
 284 extern struct cache_detail *cache_find(char *name);
 285 extern void cache_drop(struct cache_detail *detail);
 286
 287 extern void qword_add(char **bpp, int *lp, char *str);
 288 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 289 extern int qword_get(char **bpp, char *dest, int bufsize);
 290
 291 static inline int get_int(char **bpp, int *anint)
 292 {
 293         char buf[50];
 294         char *ep;
 295         int rv;
 296         int len = qword_get(bpp, buf, 50);
 297         if (len < 0) return -EINVAL;
 298         if (len ==0) return -ENOENT;
 299         rv = simple_strtol(buf, &ep, 0);
 300         if (*ep) return -EINVAL;
 301         *anint = rv;
 302         return 0;
 303 }
 304
 305 static inline time_t get_expiry(char **bpp)
 306 {
 307         int rv;
 308         if (get_int(bpp, &rv))
 309                 return 0;
 310         if (rv < 0)
 311                 return 0;
 312         return rv;
 313 }
 314
 315 #endif /*  _LINUX_SUNRPC_CACHE_H_ */