cache.h

  1/* SPDX-License-Identifier: GPL-2.0-only */
  2/*
  3 * include/linux/sunrpc/cache.h
  4 *
  5 * Generic code for various authentication-related caches
  6 * used by sunrpc clients and servers.
  7 *
  8 * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
  9 */
 10
 11#ifndef _LINUX_SUNRPC_CACHE_H_
 12#define _LINUX_SUNRPC_CACHE_H_
 13
 14#include <linux/kref.h>
 15#include <linux/slab.h>
 16#include <linux/atomic.h>
 17#include <linux/kstrtox.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 existence
 38 * in the hash table.
 39 * We only expire entries when refcount is zero.
 40 * Existence 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 */
 47struct cache_head {
 48	struct hlist_node	cache_list;
 49	time64_t	expiry_time;	/* After time expiry_time, don't use
 50					 * the data */
 51	time64_t	last_refresh;   /* If CACHE_PENDING, this is when upcall was
 52					 * sent, else this is when update was
 53					 * received, though it is alway set to
 54					 * be *after* ->flush_time.
 55					 */
 56	struct kref	ref;
 57	unsigned long	flags;
 58};
 59
 60/* cache_head.flags */
 61enum {
 62	CACHE_VALID,		/* Entry contains valid data */
 63	CACHE_NEGATIVE,		/* Negative entry - there is no match for the key */
 64	CACHE_PENDING,		/* An upcall has been sent but no reply received yet*/
 65	CACHE_CLEANED,		/* Entry has been cleaned from cache */
 66};
 67
 68#define	CACHE_NEW_EXPIRY 120	/* keep new things pending confirmation for 120 seconds */
 69
 70struct cache_detail {
 71	struct module *		owner;
 72	int			hash_size;
 73	struct hlist_head *	hash_table;
 74	spinlock_t		hash_lock;
 75
 76	char			*name;
 77	void			(*cache_put)(struct kref *);
 78
 79	int			(*cache_upcall)(struct cache_detail *,
 80						struct cache_head *);
 81
 82	void			(*cache_request)(struct cache_detail *cd,
 83						 struct cache_head *ch,
 84						 char **bpp, int *blen);
 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	void			(*flush)(void);
 97	int			(*match)(struct cache_head *orig, struct cache_head *new);
 98	void			(*init)(struct cache_head *orig, struct cache_head *new);
 99	void			(*update)(struct cache_head *orig, struct cache_head *new);
100
101	/* fields below this comment are for internal use
102	 * and should not be touched by cache owners
103	 */
104	time64_t		flush_time;		/* flush all cache items with
105							 * last_refresh at or earlier
106							 * than this.  last_refresh
107							 * is never set at or earlier
108							 * than this.
109							 */
110	struct list_head	others;
111	time64_t		nextcheck;
112	int			entries;
113
114	/* fields for communication over channel */
115	struct list_head	queue;
116
117	atomic_t		writers;		/* how many time is /channel open */
118	time64_t		last_close;		/* if no writers, when did last close */
119	time64_t		last_warn;		/* when we last warned about no writers */
120
121	union {
122		struct proc_dir_entry	*procfs;
123		struct dentry		*pipefs;
124	};
125	struct net		*net;
126};
127
128/* this must be embedded in any request structure that
129 * identifies an object that will want a callback on
130 * a cache fill
131 */
132struct cache_req {
133	struct cache_deferred_req *(*defer)(struct cache_req *req);
134	unsigned long	thread_wait;	/* How long (jiffies) we can block the
135					 * current thread to wait for updates.
136					 */
137};
138
139/* this must be embedded in a deferred_request that is being
140 * delayed awaiting cache-fill
141 */
142struct cache_deferred_req {
143	struct hlist_node	hash;	/* on hash chain */
144	struct list_head	recent; /* on fifo */
145	struct cache_head	*item;  /* cache item we wait on */
146	void			*owner; /* we might need to discard all defered requests
147					 * owned by someone */
148	void			(*revisit)(struct cache_deferred_req *req,
149					   int too_many);
150};
151
152/*
153 * timestamps kept in the cache are expressed in seconds
154 * since boot.  This is the best for measuring differences in
155 * real time.
156 * This reimplemnts ktime_get_boottime_seconds() in a slightly
157 * faster but less accurate way. When we end up converting
158 * back to wallclock (CLOCK_REALTIME), that error often
159 * cancels out during the reverse operation.
160 */
161static inline time64_t seconds_since_boot(void)
162{
163	struct timespec64 boot;
164	getboottime64(&boot);
165	return ktime_get_real_seconds() - boot.tv_sec;
166}
167
168static inline time64_t convert_to_wallclock(time64_t sinceboot)
169{
170	struct timespec64 boot;
171	getboottime64(&boot);
172	return boot.tv_sec + sinceboot;
173}
174
175extern const struct file_operations cache_file_operations_pipefs;
176extern const struct file_operations content_file_operations_pipefs;
177extern const struct file_operations cache_flush_operations_pipefs;
178
179extern struct cache_head *
180sunrpc_cache_lookup_rcu(struct cache_detail *detail,
181			struct cache_head *key, int hash);
182extern struct cache_head *
183sunrpc_cache_update(struct cache_detail *detail,
184		    struct cache_head *new, struct cache_head *old, int hash);
185
186extern int
187sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h);
188extern int
189sunrpc_cache_pipe_upcall_timeout(struct cache_detail *detail,
190				 struct cache_head *h);
191
192
193extern void cache_clean_deferred(void *owner);
194
195static inline struct cache_head  *cache_get(struct cache_head *h)
196{
197	kref_get(&h->ref);
198	return h;
199}
200
201static inline struct cache_head  *cache_get_rcu(struct cache_head *h)
202{
203	if (kref_get_unless_zero(&h->ref))
204		return h;
205	return NULL;
206}
207
208static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
209{
210	if (kref_read(&h->ref) <= 2 &&
211	    h->expiry_time < cd->nextcheck)
212		cd->nextcheck = h->expiry_time;
213	kref_put(&h->ref, cd->cache_put);
214}
215
216static inline bool cache_is_expired(struct cache_detail *detail, struct cache_head *h)
217{
218	if (h->expiry_time < seconds_since_boot())
219		return true;
220	if (!test_bit(CACHE_VALID, &h->flags))
221		return false;
222	return detail->flush_time >= h->last_refresh;
223}
224
225extern int cache_check_rcu(struct cache_detail *detail,
226		       struct cache_head *h, struct cache_req *rqstp);
227extern int cache_check(struct cache_detail *detail,
228		       struct cache_head *h, struct cache_req *rqstp);
229extern void cache_flush(void);
230extern void cache_purge(struct cache_detail *detail);
231#define NEVER (0x7FFFFFFF)
232extern void __init cache_initialize(void);
233extern int cache_register_net(struct cache_detail *cd, struct net *net);
234extern void cache_unregister_net(struct cache_detail *cd, struct net *net);
235
236extern struct cache_detail *cache_create_net(const struct cache_detail *tmpl, struct net *net);
237extern void cache_destroy_net(struct cache_detail *cd, struct net *net);
238
239extern void sunrpc_init_cache_detail(struct cache_detail *cd);
240extern void sunrpc_destroy_cache_detail(struct cache_detail *cd);
241extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
242					umode_t, struct cache_detail *);
243extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
244extern void sunrpc_cache_unhash(struct cache_detail *, struct cache_head *);
245
246/* Must store cache_detail in seq_file->private if using next three functions */
247extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
248extern void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos);
249extern void cache_seq_stop_rcu(struct seq_file *file, void *p);
250
251extern void qword_add(char **bpp, int *lp, char *str);
252extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
253extern int qword_get(char **bpp, char *dest, int bufsize);
254
255static inline int get_int(char **bpp, int *anint)
256{
257	char buf[50];
258	char *ep;
259	int rv;
260	int len = qword_get(bpp, buf, sizeof(buf));
261
262	if (len < 0)
263		return -EINVAL;
264	if (len == 0)
265		return -ENOENT;
266
267	rv = simple_strtol(buf, &ep, 0);
268	if (*ep)
269		return -EINVAL;
270
271	*anint = rv;
272	return 0;
273}
274
275static inline int get_uint(char **bpp, unsigned int *anint)
276{
277	char buf[50];
278	int len = qword_get(bpp, buf, sizeof(buf));
279
280	if (len < 0)
281		return -EINVAL;
282	if (len == 0)
283		return -ENOENT;
284
285	if (kstrtouint(buf, 0, anint))
286		return -EINVAL;
287
288	return 0;
289}
290
291static inline int get_time(char **bpp, time64_t *time)
292{
293	char buf[50];
294	long long ll;
295	int len = qword_get(bpp, buf, sizeof(buf));
296
297	if (len < 0)
298		return -EINVAL;
299	if (len == 0)
300		return -ENOENT;
301
302	if (kstrtoll(buf, 0, &ll))
303		return -EINVAL;
304
305	*time = ll;
306	return 0;
307}
308
309static inline int get_expiry(char **bpp, time64_t *rvp)
310{
311	int error;
312	struct timespec64 boot;
313
314	error = get_time(bpp, rvp);
315	if (error)
316		return error;
317
318	getboottime64(&boot);
319	(*rvp) -= boot.tv_sec;
320	return 0;
321}
322
323#endif /*  _LINUX_SUNRPC_CACHE_H_ */