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/kref.h>
  17 #include <linux/slab.h>
  18 #include <linux/atomic.h>
  19 #include <linux/proc_fs.h>
  20
  21 /*
  22  * Each cache requires:
  23  *  - A 'struct cache_detail' which contains information specific to the cache
  24  *    for common code to use.
  25  *  - An item structure that must contain a "struct cache_head"
  26  *  - A lookup function defined using DefineCacheLookup
  27  *  - A 'put' function that can release a cache item. It will only
  28  *    be called after cache_put has succeed, so there are guarantee
  29  *    to be no references.
  30  *  - A function to calculate a hash of an item's key.
  31  *
  32  * as well as assorted code fragments (e.g. compare keys) and numbers
  33  * (e.g. hash size, goal_age, etc).
  34  *
  35  * Each cache must be registered so that it can be cleaned regularly.
  36  * When the cache is unregistered, it is flushed completely.
  37  *
  38  * Entries have a ref count and a 'hashed' flag which counts the existence
  39  * in the hash table.
  40  * We only expire entries when refcount is zero.
  41  * Existence in the cache is counted  the refcount.
  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         struct kref     ref;
  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
  61 #define CACHE_NEW_EXPIRY 120    /* keep new things pending confirmation for 120 seconds */
  62
  63 struct cache_detail_procfs {
  64         struct proc_dir_entry   *proc_ent;
  65         struct proc_dir_entry   *flush_ent, *channel_ent, *content_ent;
  66 };
  67
  68 struct cache_detail_pipefs {
  69         struct dentry *dir;
  70 };
  71
  72 struct cache_detail {
  73         struct module *         owner;
  74         int                     hash_size;
  75         struct cache_head **    hash_table;
  76         rwlock_t                hash_lock;
  77
  78         atomic_t                inuse; /* active user-space update or lookup */
  79
  80         char                    *name;
  81         void                    (*cache_put)(struct kref *);
  82
  83         int                     (*cache_upcall)(struct cache_detail *,
  84                                                 struct cache_head *);
  85
  86         int                     (*cache_parse)(struct cache_detail *,
  87                                                char *buf, int len);
  88
  89         int                     (*cache_show)(struct seq_file *m,
  90                                               struct cache_detail *cd,
  91                                               struct cache_head *h);
  92         void                    (*warn_no_listener)(struct cache_detail *cd,
  93                                               int has_died);
  94
  95         struct cache_head *     (*alloc)(void);
  96         int                     (*match)(struct cache_head *orig, struct cache_head *new);
  97         void                    (*init)(struct cache_head *orig, struct cache_head *new);
  98         void                    (*update)(struct cache_head *orig, struct cache_head *new);
  99
 100         /* fields below this comment are for internal use
 101          * and should not be touched by cache owners
 102          */
 103         time_t                  flush_time;             /* flush all cache items with last_refresh
 104                                                          * earlier than this */
 105         struct list_head        others;
 106         time_t                  nextcheck;
 107         int                     entries;
 108
 109         /* fields for communication over channel */
 110         struct list_head        queue;
 111
 112         atomic_t                readers;                /* how many time is /chennel open */
 113         time_t                  last_close;             /* if no readers, when did last close */
 114         time_t                  last_warn;              /* when we last warned about no readers */
 115
 116         union {
 117                 struct cache_detail_procfs procfs;
 118                 struct cache_detail_pipefs pipefs;
 119         } u;
 120 };
 121
 122
 123 /* this must be embedded in any request structure that
 124  * identifies an object that will want a callback on
 125  * a cache fill
 126  */
 127 struct cache_req {
 128         struct cache_deferred_req *(*defer)(struct cache_req *req);
 129         int thread_wait;  /* How long (jiffies) we can block the
 130                            * current thread to wait for updates.
 131                            */
 132 };
 133 /* this must be embedded in a deferred_request that is being
 134  * delayed awaiting cache-fill
 135  */
 136 struct cache_deferred_req {
 137         struct hlist_node       hash;   /* on hash chain */
 138         struct list_head        recent; /* on fifo */
 139         struct cache_head       *item;  /* cache item we wait on */
 140         void                    *owner; /* we might need to discard all defered requests
 141                                          * owned by someone */
 142         void                    (*revisit)(struct cache_deferred_req *req,
 143                                            int too_many);
 144 };
 145
 146
 147 extern const struct file_operations cache_file_operations_pipefs;
 148 extern const struct file_operations content_file_operations_pipefs;
 149 extern const struct file_operations cache_flush_operations_pipefs;
 150
 151 extern struct cache_head *
 152 sunrpc_cache_lookup(struct cache_detail *detail,
 153                     struct cache_head *key, int hash);
 154 extern struct cache_head *
 155 sunrpc_cache_update(struct cache_detail *detail,
 156                     struct cache_head *new, struct cache_head *old, int hash);
 157
 158 extern int
 159 sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
 160                 void (*cache_request)(struct cache_detail *,
 161                                       struct cache_head *,
 162                                       char **,
 163                                       int *));
 164
 165
 166 extern void cache_clean_deferred(void *owner);
 167
 168 static inline struct cache_head  *cache_get(struct cache_head *h)
 169 {
 170         kref_get(&h->ref);
 171         return h;
 172 }
 173
 174
 175 static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
 176 {
 177         if (atomic_read(&h->ref.refcount) <= 2 &&
 178             h->expiry_time < cd->nextcheck)
 179                 cd->nextcheck = h->expiry_time;
 180         kref_put(&h->ref, cd->cache_put);
 181 }
 182
 183 static inline int cache_valid(struct cache_head *h)
 184 {
 185         /* If an item has been unhashed pending removal when
 186          * the refcount drops to 0, the expiry_time will be
 187          * set to 0.  We don't want to consider such items
 188          * valid in this context even though CACHE_VALID is
 189          * set.
 190          */
 191         return (h->expiry_time != 0 && test_bit(CACHE_VALID, &h->flags));
 192 }
 193
 194 extern int cache_check(struct cache_detail *detail,
 195                        struct cache_head *h, struct cache_req *rqstp);
 196 extern void cache_flush(void);
 197 extern void cache_purge(struct cache_detail *detail);
 198 #define NEVER (0x7FFFFFFF)
 199 extern void __init cache_initialize(void);
 200 extern int cache_register(struct cache_detail *cd);
 201 extern int cache_register_net(struct cache_detail *cd, struct net *net);
 202 extern void cache_unregister(struct cache_detail *cd);
 203 extern void cache_unregister_net(struct cache_detail *cd, struct net *net);
 204
 205 extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
 206                                         umode_t, struct cache_detail *);
 207 extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
 208
 209 extern void qword_add(char **bpp, int *lp, char *str);
 210 extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
 211 extern int qword_get(char **bpp, char *dest, int bufsize);
 212
 213 static inline int get_int(char **bpp, int *anint)
 214 {
 215         char buf[50];
 216         char *ep;
 217         int rv;
 218         int len = qword_get(bpp, buf, 50);
 219         if (len < 0) return -EINVAL;
 220         if (len ==0) return -ENOENT;
 221         rv = simple_strtol(buf, &ep, 0);
 222         if (*ep) return -EINVAL;
 223         *anint = rv;
 224         return 0;
 225 }
 226
 227 /*
 228  * timestamps kept in the cache are expressed in seconds
 229  * since boot.  This is the best for measuring differences in
 230  * real time.
 231  */
 232 static inline time_t seconds_since_boot(void)
 233 {
 234         struct timespec boot;
 235         getboottime(&boot);
 236         return get_seconds() - boot.tv_sec;
 237 }
 238
 239 static inline time_t convert_to_wallclock(time_t sinceboot)
 240 {
 241         struct timespec boot;
 242         getboottime(&boot);
 243         return boot.tv_sec + sinceboot;
 244 }
 245
 246 static inline time_t get_expiry(char **bpp)
 247 {
 248         int rv;
 249         struct timespec boot;
 250
 251         if (get_int(bpp, &rv))
 252                 return 0;
 253         if (rv < 0)
 254                 return 0;
 255         getboottime(&boot);
 256         return rv - boot.tv_sec;
 257 }
 258
 259 #endif /*  _LINUX_SUNRPC_CACHE_H_ */