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