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1 /*
2    lru_cache.c
3 
4    This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
5 
6    Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
7    Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
8    Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
9 
10    drbd is free software; you can redistribute it and/or modify
11    it under the terms of the GNU General Public License as published by
12    the Free Software Foundation; either version 2, or (at your option)
13    any later version.
14 
15    drbd is distributed in the hope that it will be useful,
16    but WITHOUT ANY WARRANTY; without even the implied warranty of
17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18    GNU General Public License for more details.
19 
20    You should have received a copy of the GNU General Public License
21    along with drbd; see the file COPYING.  If not, write to
22    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
23 
24  */
25 
26 #include <linux/module.h>
27 #include <linux/bitops.h>
28 #include <linux/slab.h>
29 #include <linux/string.h> /* for memset */
30 #include <linux/seq_file.h> /* for seq_printf */
31 #include <linux/lru_cache.h>
32 
33 MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
34 	      "Lars Ellenberg <lars@linbit.com>");
35 MODULE_DESCRIPTION("lru_cache - Track sets of hot objects");
36 MODULE_LICENSE("GPL");
37 
38 /* this is developers aid only.
39  * it catches concurrent access (lack of locking on the users part) */
40 #define PARANOIA_ENTRY() do {		\
41 	BUG_ON(!lc);			\
42 	BUG_ON(!lc->nr_elements);	\
43 	BUG_ON(test_and_set_bit(__LC_PARANOIA, &lc->flags)); \
44 } while (0)
45 
46 #define RETURN(x...)     do { \
47 	clear_bit_unlock(__LC_PARANOIA, &lc->flags); \
48 	return x ; } while (0)
49 
50 /* BUG() if e is not one of the elements tracked by lc */
51 #define PARANOIA_LC_ELEMENT(lc, e) do {	\
52 	struct lru_cache *lc_ = (lc);	\
53 	struct lc_element *e_ = (e);	\
54 	unsigned i = e_->lc_index;	\
55 	BUG_ON(i >= lc_->nr_elements);	\
56 	BUG_ON(lc_->lc_element[i] != e_); } while (0)
57 
58 
59 /* We need to atomically
60  *  - try to grab the lock (set LC_LOCKED)
61  *  - only if there is no pending transaction
62  *    (neither LC_DIRTY nor LC_STARVING is set)
63  * Because of PARANOIA_ENTRY() above abusing lc->flags as well,
64  * it is not sufficient to just say
65  *	return 0 == cmpxchg(&lc->flags, 0, LC_LOCKED);
66  */
lc_try_lock(struct lru_cache * lc)67 int lc_try_lock(struct lru_cache *lc)
68 {
69 	unsigned long val;
70 	do {
71 		val = cmpxchg(&lc->flags, 0, LC_LOCKED);
72 	} while (unlikely (val == LC_PARANOIA));
73 	/* Spin until no-one is inside a PARANOIA_ENTRY()/RETURN() section. */
74 	return 0 == val;
75 #if 0
76 	/* Alternative approach, spin in case someone enters or leaves a
77 	 * PARANOIA_ENTRY()/RETURN() section. */
78 	unsigned long old, new, val;
79 	do {
80 		old = lc->flags & LC_PARANOIA;
81 		new = old | LC_LOCKED;
82 		val = cmpxchg(&lc->flags, old, new);
83 	} while (unlikely (val == (old ^ LC_PARANOIA)));
84 	return old == val;
85 #endif
86 }
87 
88 /**
89  * lc_create - prepares to track objects in an active set
90  * @name: descriptive name only used in lc_seq_printf_stats and lc_seq_dump_details
91  * @max_pending_changes: maximum changes to accumulate until a transaction is required
92  * @e_count: number of elements allowed to be active simultaneously
93  * @e_size: size of the tracked objects
94  * @e_off: offset to the &struct lc_element member in a tracked object
95  *
96  * Returns a pointer to a newly initialized struct lru_cache on success,
97  * or NULL on (allocation) failure.
98  */
lc_create(const char * name,struct kmem_cache * cache,unsigned max_pending_changes,unsigned e_count,size_t e_size,size_t e_off)99 struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
100 		unsigned max_pending_changes,
101 		unsigned e_count, size_t e_size, size_t e_off)
102 {
103 	struct hlist_head *slot = NULL;
104 	struct lc_element **element = NULL;
105 	struct lru_cache *lc;
106 	struct lc_element *e;
107 	unsigned cache_obj_size = kmem_cache_size(cache);
108 	unsigned i;
109 
110 	WARN_ON(cache_obj_size < e_size);
111 	if (cache_obj_size < e_size)
112 		return NULL;
113 
114 	/* e_count too big; would probably fail the allocation below anyways.
115 	 * for typical use cases, e_count should be few thousand at most. */
116 	if (e_count > LC_MAX_ACTIVE)
117 		return NULL;
118 
119 	slot = kcalloc(e_count, sizeof(struct hlist_head), GFP_KERNEL);
120 	if (!slot)
121 		goto out_fail;
122 	element = kzalloc(e_count * sizeof(struct lc_element *), GFP_KERNEL);
123 	if (!element)
124 		goto out_fail;
125 
126 	lc = kzalloc(sizeof(*lc), GFP_KERNEL);
127 	if (!lc)
128 		goto out_fail;
129 
130 	INIT_LIST_HEAD(&lc->in_use);
131 	INIT_LIST_HEAD(&lc->lru);
132 	INIT_LIST_HEAD(&lc->free);
133 	INIT_LIST_HEAD(&lc->to_be_changed);
134 
135 	lc->name = name;
136 	lc->element_size = e_size;
137 	lc->element_off = e_off;
138 	lc->nr_elements = e_count;
139 	lc->max_pending_changes = max_pending_changes;
140 	lc->lc_cache = cache;
141 	lc->lc_element = element;
142 	lc->lc_slot = slot;
143 
144 	/* preallocate all objects */
145 	for (i = 0; i < e_count; i++) {
146 		void *p = kmem_cache_alloc(cache, GFP_KERNEL);
147 		if (!p)
148 			break;
149 		memset(p, 0, lc->element_size);
150 		e = p + e_off;
151 		e->lc_index = i;
152 		e->lc_number = LC_FREE;
153 		e->lc_new_number = LC_FREE;
154 		list_add(&e->list, &lc->free);
155 		element[i] = e;
156 	}
157 	if (i == e_count)
158 		return lc;
159 
160 	/* else: could not allocate all elements, give up */
161 	for (i--; i; i--) {
162 		void *p = element[i];
163 		kmem_cache_free(cache, p - e_off);
164 	}
165 	kfree(lc);
166 out_fail:
167 	kfree(element);
168 	kfree(slot);
169 	return NULL;
170 }
171 
lc_free_by_index(struct lru_cache * lc,unsigned i)172 static void lc_free_by_index(struct lru_cache *lc, unsigned i)
173 {
174 	void *p = lc->lc_element[i];
175 	WARN_ON(!p);
176 	if (p) {
177 		p -= lc->element_off;
178 		kmem_cache_free(lc->lc_cache, p);
179 	}
180 }
181 
182 /**
183  * lc_destroy - frees memory allocated by lc_create()
184  * @lc: the lru cache to destroy
185  */
lc_destroy(struct lru_cache * lc)186 void lc_destroy(struct lru_cache *lc)
187 {
188 	unsigned i;
189 	if (!lc)
190 		return;
191 	for (i = 0; i < lc->nr_elements; i++)
192 		lc_free_by_index(lc, i);
193 	kfree(lc->lc_element);
194 	kfree(lc->lc_slot);
195 	kfree(lc);
196 }
197 
198 /**
199  * lc_reset - does a full reset for @lc and the hash table slots.
200  * @lc: the lru cache to operate on
201  *
202  * It is roughly the equivalent of re-allocating a fresh lru_cache object,
203  * basically a short cut to lc_destroy(lc); lc = lc_create(...);
204  */
lc_reset(struct lru_cache * lc)205 void lc_reset(struct lru_cache *lc)
206 {
207 	unsigned i;
208 
209 	INIT_LIST_HEAD(&lc->in_use);
210 	INIT_LIST_HEAD(&lc->lru);
211 	INIT_LIST_HEAD(&lc->free);
212 	INIT_LIST_HEAD(&lc->to_be_changed);
213 	lc->used = 0;
214 	lc->hits = 0;
215 	lc->misses = 0;
216 	lc->starving = 0;
217 	lc->locked = 0;
218 	lc->changed = 0;
219 	lc->pending_changes = 0;
220 	lc->flags = 0;
221 	memset(lc->lc_slot, 0, sizeof(struct hlist_head) * lc->nr_elements);
222 
223 	for (i = 0; i < lc->nr_elements; i++) {
224 		struct lc_element *e = lc->lc_element[i];
225 		void *p = e;
226 		p -= lc->element_off;
227 		memset(p, 0, lc->element_size);
228 		/* re-init it */
229 		e->lc_index = i;
230 		e->lc_number = LC_FREE;
231 		e->lc_new_number = LC_FREE;
232 		list_add(&e->list, &lc->free);
233 	}
234 }
235 
236 /**
237  * lc_seq_printf_stats - print stats about @lc into @seq
238  * @seq: the seq_file to print into
239  * @lc: the lru cache to print statistics of
240  */
lc_seq_printf_stats(struct seq_file * seq,struct lru_cache * lc)241 size_t lc_seq_printf_stats(struct seq_file *seq, struct lru_cache *lc)
242 {
243 	/* NOTE:
244 	 * total calls to lc_get are
245 	 * (starving + hits + misses)
246 	 * misses include "locked" count (update from an other thread in
247 	 * progress) and "changed", when this in fact lead to an successful
248 	 * update of the cache.
249 	 */
250 	return seq_printf(seq, "\t%s: used:%u/%u "
251 		"hits:%lu misses:%lu starving:%lu locked:%lu changed:%lu\n",
252 		lc->name, lc->used, lc->nr_elements,
253 		lc->hits, lc->misses, lc->starving, lc->locked, lc->changed);
254 }
255 
lc_hash_slot(struct lru_cache * lc,unsigned int enr)256 static struct hlist_head *lc_hash_slot(struct lru_cache *lc, unsigned int enr)
257 {
258 	return  lc->lc_slot + (enr % lc->nr_elements);
259 }
260 
261 
__lc_find(struct lru_cache * lc,unsigned int enr,bool include_changing)262 static struct lc_element *__lc_find(struct lru_cache *lc, unsigned int enr,
263 		bool include_changing)
264 {
265 	struct lc_element *e;
266 
267 	BUG_ON(!lc);
268 	BUG_ON(!lc->nr_elements);
269 	hlist_for_each_entry(e, lc_hash_slot(lc, enr), colision) {
270 		/* "about to be changed" elements, pending transaction commit,
271 		 * are hashed by their "new number". "Normal" elements have
272 		 * lc_number == lc_new_number. */
273 		if (e->lc_new_number != enr)
274 			continue;
275 		if (e->lc_new_number == e->lc_number || include_changing)
276 			return e;
277 		break;
278 	}
279 	return NULL;
280 }
281 
282 /**
283  * lc_find - find element by label, if present in the hash table
284  * @lc: The lru_cache object
285  * @enr: element number
286  *
287  * Returns the pointer to an element, if the element with the requested
288  * "label" or element number is present in the hash table,
289  * or NULL if not found. Does not change the refcnt.
290  * Ignores elements that are "about to be used", i.e. not yet in the active
291  * set, but still pending transaction commit.
292  */
lc_find(struct lru_cache * lc,unsigned int enr)293 struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr)
294 {
295 	return __lc_find(lc, enr, 0);
296 }
297 
298 /**
299  * lc_is_used - find element by label
300  * @lc: The lru_cache object
301  * @enr: element number
302  *
303  * Returns true, if the element with the requested "label" or element number is
304  * present in the hash table, and is used (refcnt > 0).
305  * Also finds elements that are not _currently_ used but only "about to be
306  * used", i.e. on the "to_be_changed" list, pending transaction commit.
307  */
lc_is_used(struct lru_cache * lc,unsigned int enr)308 bool lc_is_used(struct lru_cache *lc, unsigned int enr)
309 {
310 	struct lc_element *e = __lc_find(lc, enr, 1);
311 	return e && e->refcnt;
312 }
313 
314 /**
315  * lc_del - removes an element from the cache
316  * @lc: The lru_cache object
317  * @e: The element to remove
318  *
319  * @e must be unused (refcnt == 0). Moves @e from "lru" to "free" list,
320  * sets @e->enr to %LC_FREE.
321  */
lc_del(struct lru_cache * lc,struct lc_element * e)322 void lc_del(struct lru_cache *lc, struct lc_element *e)
323 {
324 	PARANOIA_ENTRY();
325 	PARANOIA_LC_ELEMENT(lc, e);
326 	BUG_ON(e->refcnt);
327 
328 	e->lc_number = e->lc_new_number = LC_FREE;
329 	hlist_del_init(&e->colision);
330 	list_move(&e->list, &lc->free);
331 	RETURN();
332 }
333 
lc_prepare_for_change(struct lru_cache * lc,unsigned new_number)334 static struct lc_element *lc_prepare_for_change(struct lru_cache *lc, unsigned new_number)
335 {
336 	struct list_head *n;
337 	struct lc_element *e;
338 
339 	if (!list_empty(&lc->free))
340 		n = lc->free.next;
341 	else if (!list_empty(&lc->lru))
342 		n = lc->lru.prev;
343 	else
344 		return NULL;
345 
346 	e = list_entry(n, struct lc_element, list);
347 	PARANOIA_LC_ELEMENT(lc, e);
348 
349 	e->lc_new_number = new_number;
350 	if (!hlist_unhashed(&e->colision))
351 		__hlist_del(&e->colision);
352 	hlist_add_head(&e->colision, lc_hash_slot(lc, new_number));
353 	list_move(&e->list, &lc->to_be_changed);
354 
355 	return e;
356 }
357 
lc_unused_element_available(struct lru_cache * lc)358 static int lc_unused_element_available(struct lru_cache *lc)
359 {
360 	if (!list_empty(&lc->free))
361 		return 1; /* something on the free list */
362 	if (!list_empty(&lc->lru))
363 		return 1;  /* something to evict */
364 
365 	return 0;
366 }
367 
368 /* used as internal flags to __lc_get */
369 enum {
370 	LC_GET_MAY_CHANGE = 1,
371 	LC_GET_MAY_USE_UNCOMMITTED = 2,
372 };
373 
__lc_get(struct lru_cache * lc,unsigned int enr,unsigned int flags)374 static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsigned int flags)
375 {
376 	struct lc_element *e;
377 
378 	PARANOIA_ENTRY();
379 	if (lc->flags & LC_STARVING) {
380 		++lc->starving;
381 		RETURN(NULL);
382 	}
383 
384 	e = __lc_find(lc, enr, 1);
385 	/* if lc_new_number != lc_number,
386 	 * this enr is currently being pulled in already,
387 	 * and will be available once the pending transaction
388 	 * has been committed. */
389 	if (e) {
390 		if (e->lc_new_number != e->lc_number) {
391 			/* It has been found above, but on the "to_be_changed"
392 			 * list, not yet committed.  Don't pull it in twice,
393 			 * wait for the transaction, then try again...
394 			 */
395 			if (!(flags & LC_GET_MAY_USE_UNCOMMITTED))
396 				RETURN(NULL);
397 			/* ... unless the caller is aware of the implications,
398 			 * probably preparing a cumulative transaction. */
399 			++e->refcnt;
400 			++lc->hits;
401 			RETURN(e);
402 		}
403 		/* else: lc_new_number == lc_number; a real hit. */
404 		++lc->hits;
405 		if (e->refcnt++ == 0)
406 			lc->used++;
407 		list_move(&e->list, &lc->in_use); /* Not evictable... */
408 		RETURN(e);
409 	}
410 	/* e == NULL */
411 
412 	++lc->misses;
413 	if (!(flags & LC_GET_MAY_CHANGE))
414 		RETURN(NULL);
415 
416 	/* To avoid races with lc_try_lock(), first, mark us dirty
417 	 * (using test_and_set_bit, as it implies memory barriers), ... */
418 	test_and_set_bit(__LC_DIRTY, &lc->flags);
419 
420 	/* ... only then check if it is locked anyways. If lc_unlock clears
421 	 * the dirty bit again, that's not a problem, we will come here again.
422 	 */
423 	if (test_bit(__LC_LOCKED, &lc->flags)) {
424 		++lc->locked;
425 		RETURN(NULL);
426 	}
427 
428 	/* In case there is nothing available and we can not kick out
429 	 * the LRU element, we have to wait ...
430 	 */
431 	if (!lc_unused_element_available(lc)) {
432 		__set_bit(__LC_STARVING, &lc->flags);
433 		RETURN(NULL);
434 	}
435 
436 	/* It was not present in the active set.  We are going to recycle an
437 	 * unused (or even "free") element, but we won't accumulate more than
438 	 * max_pending_changes changes.  */
439 	if (lc->pending_changes >= lc->max_pending_changes)
440 		RETURN(NULL);
441 
442 	e = lc_prepare_for_change(lc, enr);
443 	BUG_ON(!e);
444 
445 	clear_bit(__LC_STARVING, &lc->flags);
446 	BUG_ON(++e->refcnt != 1);
447 	lc->used++;
448 	lc->pending_changes++;
449 
450 	RETURN(e);
451 }
452 
453 /**
454  * lc_get - get element by label, maybe change the active set
455  * @lc: the lru cache to operate on
456  * @enr: the label to look up
457  *
458  * Finds an element in the cache, increases its usage count,
459  * "touches" and returns it.
460  *
461  * In case the requested number is not present, it needs to be added to the
462  * cache. Therefore it is possible that an other element becomes evicted from
463  * the cache. In either case, the user is notified so he is able to e.g. keep
464  * a persistent log of the cache changes, and therefore the objects in use.
465  *
466  * Return values:
467  *  NULL
468  *     The cache was marked %LC_STARVING,
469  *     or the requested label was not in the active set
470  *     and a changing transaction is still pending (@lc was marked %LC_DIRTY).
471  *     Or no unused or free element could be recycled (@lc will be marked as
472  *     %LC_STARVING, blocking further lc_get() operations).
473  *
474  *  pointer to the element with the REQUESTED element number.
475  *     In this case, it can be used right away
476  *
477  *  pointer to an UNUSED element with some different element number,
478  *          where that different number may also be %LC_FREE.
479  *
480  *          In this case, the cache is marked %LC_DIRTY,
481  *          so lc_try_lock() will no longer succeed.
482  *          The returned element pointer is moved to the "to_be_changed" list,
483  *          and registered with the new element number on the hash collision chains,
484  *          so it is possible to pick it up from lc_is_used().
485  *          Up to "max_pending_changes" (see lc_create()) can be accumulated.
486  *          The user now should do whatever housekeeping is necessary,
487  *          typically serialize on lc_try_lock_for_transaction(), then call
488  *          lc_committed(lc) and lc_unlock(), to finish the change.
489  *
490  * NOTE: The user needs to check the lc_number on EACH use, so he recognizes
491  *       any cache set change.
492  */
lc_get(struct lru_cache * lc,unsigned int enr)493 struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr)
494 {
495 	return __lc_get(lc, enr, LC_GET_MAY_CHANGE);
496 }
497 
498 /**
499  * lc_get_cumulative - like lc_get; also finds to-be-changed elements
500  * @lc: the lru cache to operate on
501  * @enr: the label to look up
502  *
503  * Unlike lc_get this also returns the element for @enr, if it is belonging to
504  * a pending transaction, so the return values are like for lc_get(),
505  * plus:
506  *
507  * pointer to an element already on the "to_be_changed" list.
508  * 	In this case, the cache was already marked %LC_DIRTY.
509  *
510  * Caller needs to make sure that the pending transaction is completed,
511  * before proceeding to actually use this element.
512  */
lc_get_cumulative(struct lru_cache * lc,unsigned int enr)513 struct lc_element *lc_get_cumulative(struct lru_cache *lc, unsigned int enr)
514 {
515 	return __lc_get(lc, enr, LC_GET_MAY_CHANGE|LC_GET_MAY_USE_UNCOMMITTED);
516 }
517 
518 /**
519  * lc_try_get - get element by label, if present; do not change the active set
520  * @lc: the lru cache to operate on
521  * @enr: the label to look up
522  *
523  * Finds an element in the cache, increases its usage count,
524  * "touches" and returns it.
525  *
526  * Return values:
527  *  NULL
528  *     The cache was marked %LC_STARVING,
529  *     or the requested label was not in the active set
530  *
531  *  pointer to the element with the REQUESTED element number.
532  *     In this case, it can be used right away
533  */
lc_try_get(struct lru_cache * lc,unsigned int enr)534 struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr)
535 {
536 	return __lc_get(lc, enr, 0);
537 }
538 
539 /**
540  * lc_committed - tell @lc that pending changes have been recorded
541  * @lc: the lru cache to operate on
542  *
543  * User is expected to serialize on explicit lc_try_lock_for_transaction()
544  * before the transaction is started, and later needs to lc_unlock() explicitly
545  * as well.
546  */
lc_committed(struct lru_cache * lc)547 void lc_committed(struct lru_cache *lc)
548 {
549 	struct lc_element *e, *tmp;
550 
551 	PARANOIA_ENTRY();
552 	list_for_each_entry_safe(e, tmp, &lc->to_be_changed, list) {
553 		/* count number of changes, not number of transactions */
554 		++lc->changed;
555 		e->lc_number = e->lc_new_number;
556 		list_move(&e->list, &lc->in_use);
557 	}
558 	lc->pending_changes = 0;
559 	RETURN();
560 }
561 
562 
563 /**
564  * lc_put - give up refcnt of @e
565  * @lc: the lru cache to operate on
566  * @e: the element to put
567  *
568  * If refcnt reaches zero, the element is moved to the lru list,
569  * and a %LC_STARVING (if set) is cleared.
570  * Returns the new (post-decrement) refcnt.
571  */
lc_put(struct lru_cache * lc,struct lc_element * e)572 unsigned int lc_put(struct lru_cache *lc, struct lc_element *e)
573 {
574 	PARANOIA_ENTRY();
575 	PARANOIA_LC_ELEMENT(lc, e);
576 	BUG_ON(e->refcnt == 0);
577 	BUG_ON(e->lc_number != e->lc_new_number);
578 	if (--e->refcnt == 0) {
579 		/* move it to the front of LRU. */
580 		list_move(&e->list, &lc->lru);
581 		lc->used--;
582 		clear_bit_unlock(__LC_STARVING, &lc->flags);
583 	}
584 	RETURN(e->refcnt);
585 }
586 
587 /**
588  * lc_element_by_index
589  * @lc: the lru cache to operate on
590  * @i: the index of the element to return
591  */
lc_element_by_index(struct lru_cache * lc,unsigned i)592 struct lc_element *lc_element_by_index(struct lru_cache *lc, unsigned i)
593 {
594 	BUG_ON(i >= lc->nr_elements);
595 	BUG_ON(lc->lc_element[i] == NULL);
596 	BUG_ON(lc->lc_element[i]->lc_index != i);
597 	return lc->lc_element[i];
598 }
599 
600 /**
601  * lc_index_of
602  * @lc: the lru cache to operate on
603  * @e: the element to query for its index position in lc->element
604  */
lc_index_of(struct lru_cache * lc,struct lc_element * e)605 unsigned int lc_index_of(struct lru_cache *lc, struct lc_element *e)
606 {
607 	PARANOIA_LC_ELEMENT(lc, e);
608 	return e->lc_index;
609 }
610 
611 /**
612  * lc_set - associate index with label
613  * @lc: the lru cache to operate on
614  * @enr: the label to set
615  * @index: the element index to associate label with.
616  *
617  * Used to initialize the active set to some previously recorded state.
618  */
lc_set(struct lru_cache * lc,unsigned int enr,int index)619 void lc_set(struct lru_cache *lc, unsigned int enr, int index)
620 {
621 	struct lc_element *e;
622 	struct list_head *lh;
623 
624 	if (index < 0 || index >= lc->nr_elements)
625 		return;
626 
627 	e = lc_element_by_index(lc, index);
628 	BUG_ON(e->lc_number != e->lc_new_number);
629 	BUG_ON(e->refcnt != 0);
630 
631 	e->lc_number = e->lc_new_number = enr;
632 	hlist_del_init(&e->colision);
633 	if (enr == LC_FREE)
634 		lh = &lc->free;
635 	else {
636 		hlist_add_head(&e->colision, lc_hash_slot(lc, enr));
637 		lh = &lc->lru;
638 	}
639 	list_move(&e->list, lh);
640 }
641 
642 /**
643  * lc_dump - Dump a complete LRU cache to seq in textual form.
644  * @lc: the lru cache to operate on
645  * @seq: the &struct seq_file pointer to seq_printf into
646  * @utext: user supplied additional "heading" or other info
647  * @detail: function pointer the user may provide to dump further details
648  * of the object the lc_element is embedded in. May be NULL.
649  * Note: a leading space ' ' and trailing newline '\n' is implied.
650  */
lc_seq_dump_details(struct seq_file * seq,struct lru_cache * lc,char * utext,void (* detail)(struct seq_file *,struct lc_element *))651 void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char *utext,
652 	     void (*detail) (struct seq_file *, struct lc_element *))
653 {
654 	unsigned int nr_elements = lc->nr_elements;
655 	struct lc_element *e;
656 	int i;
657 
658 	seq_printf(seq, "\tnn: lc_number (new nr) refcnt %s\n ", utext);
659 	for (i = 0; i < nr_elements; i++) {
660 		e = lc_element_by_index(lc, i);
661 		if (e->lc_number != e->lc_new_number)
662 			seq_printf(seq, "\t%5d: %6d %8d %6d ",
663 				i, e->lc_number, e->lc_new_number, e->refcnt);
664 		else
665 			seq_printf(seq, "\t%5d: %6d %-8s %6d ",
666 				i, e->lc_number, "-\"-", e->refcnt);
667 		if (detail)
668 			detail(seq, e);
669 		seq_putc(seq, '\n');
670 	}
671 }
672 
673 EXPORT_SYMBOL(lc_create);
674 EXPORT_SYMBOL(lc_reset);
675 EXPORT_SYMBOL(lc_destroy);
676 EXPORT_SYMBOL(lc_set);
677 EXPORT_SYMBOL(lc_del);
678 EXPORT_SYMBOL(lc_try_get);
679 EXPORT_SYMBOL(lc_find);
680 EXPORT_SYMBOL(lc_get);
681 EXPORT_SYMBOL(lc_put);
682 EXPORT_SYMBOL(lc_committed);
683 EXPORT_SYMBOL(lc_element_by_index);
684 EXPORT_SYMBOL(lc_index_of);
685 EXPORT_SYMBOL(lc_seq_printf_stats);
686 EXPORT_SYMBOL(lc_seq_dump_details);
687 EXPORT_SYMBOL(lc_try_lock);
688 EXPORT_SYMBOL(lc_is_used);
689 EXPORT_SYMBOL(lc_get_cumulative);
690