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 = kcalloc(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 void 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 	seq_printf(seq, "\t%s: used:%u/%u hits:%lu misses:%lu starving:%lu locked:%lu changed:%lu\n",
251 		   lc->name, lc->used, lc->nr_elements,
252 		   lc->hits, lc->misses, lc->starving, lc->locked, lc->changed);
253 }
254 
lc_hash_slot(struct lru_cache * lc,unsigned int enr)255 static struct hlist_head *lc_hash_slot(struct lru_cache *lc, unsigned int enr)
256 {
257 	return  lc->lc_slot + (enr % lc->nr_elements);
258 }
259 
260 
__lc_find(struct lru_cache * lc,unsigned int enr,bool include_changing)261 static struct lc_element *__lc_find(struct lru_cache *lc, unsigned int enr,
262 		bool include_changing)
263 {
264 	struct lc_element *e;
265 
266 	BUG_ON(!lc);
267 	BUG_ON(!lc->nr_elements);
268 	hlist_for_each_entry(e, lc_hash_slot(lc, enr), colision) {
269 		/* "about to be changed" elements, pending transaction commit,
270 		 * are hashed by their "new number". "Normal" elements have
271 		 * lc_number == lc_new_number. */
272 		if (e->lc_new_number != enr)
273 			continue;
274 		if (e->lc_new_number == e->lc_number || include_changing)
275 			return e;
276 		break;
277 	}
278 	return NULL;
279 }
280 
281 /**
282  * lc_find - find element by label, if present in the hash table
283  * @lc: The lru_cache object
284  * @enr: element number
285  *
286  * Returns the pointer to an element, if the element with the requested
287  * "label" or element number is present in the hash table,
288  * or NULL if not found. Does not change the refcnt.
289  * Ignores elements that are "about to be used", i.e. not yet in the active
290  * set, but still pending transaction commit.
291  */
lc_find(struct lru_cache * lc,unsigned int enr)292 struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr)
293 {
294 	return __lc_find(lc, enr, 0);
295 }
296 
297 /**
298  * lc_is_used - find element by label
299  * @lc: The lru_cache object
300  * @enr: element number
301  *
302  * Returns true, if the element with the requested "label" or element number is
303  * present in the hash table, and is used (refcnt > 0).
304  * Also finds elements that are not _currently_ used but only "about to be
305  * used", i.e. on the "to_be_changed" list, pending transaction commit.
306  */
lc_is_used(struct lru_cache * lc,unsigned int enr)307 bool lc_is_used(struct lru_cache *lc, unsigned int enr)
308 {
309 	struct lc_element *e = __lc_find(lc, enr, 1);
310 	return e && e->refcnt;
311 }
312 
313 /**
314  * lc_del - removes an element from the cache
315  * @lc: The lru_cache object
316  * @e: The element to remove
317  *
318  * @e must be unused (refcnt == 0). Moves @e from "lru" to "free" list,
319  * sets @e->enr to %LC_FREE.
320  */
lc_del(struct lru_cache * lc,struct lc_element * e)321 void lc_del(struct lru_cache *lc, struct lc_element *e)
322 {
323 	PARANOIA_ENTRY();
324 	PARANOIA_LC_ELEMENT(lc, e);
325 	BUG_ON(e->refcnt);
326 
327 	e->lc_number = e->lc_new_number = LC_FREE;
328 	hlist_del_init(&e->colision);
329 	list_move(&e->list, &lc->free);
330 	RETURN();
331 }
332 
lc_prepare_for_change(struct lru_cache * lc,unsigned new_number)333 static struct lc_element *lc_prepare_for_change(struct lru_cache *lc, unsigned new_number)
334 {
335 	struct list_head *n;
336 	struct lc_element *e;
337 
338 	if (!list_empty(&lc->free))
339 		n = lc->free.next;
340 	else if (!list_empty(&lc->lru))
341 		n = lc->lru.prev;
342 	else
343 		return NULL;
344 
345 	e = list_entry(n, struct lc_element, list);
346 	PARANOIA_LC_ELEMENT(lc, e);
347 
348 	e->lc_new_number = new_number;
349 	if (!hlist_unhashed(&e->colision))
350 		__hlist_del(&e->colision);
351 	hlist_add_head(&e->colision, lc_hash_slot(lc, new_number));
352 	list_move(&e->list, &lc->to_be_changed);
353 
354 	return e;
355 }
356 
lc_unused_element_available(struct lru_cache * lc)357 static int lc_unused_element_available(struct lru_cache *lc)
358 {
359 	if (!list_empty(&lc->free))
360 		return 1; /* something on the free list */
361 	if (!list_empty(&lc->lru))
362 		return 1;  /* something to evict */
363 
364 	return 0;
365 }
366 
367 /* used as internal flags to __lc_get */
368 enum {
369 	LC_GET_MAY_CHANGE = 1,
370 	LC_GET_MAY_USE_UNCOMMITTED = 2,
371 };
372 
__lc_get(struct lru_cache * lc,unsigned int enr,unsigned int flags)373 static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsigned int flags)
374 {
375 	struct lc_element *e;
376 
377 	PARANOIA_ENTRY();
378 	if (lc->flags & LC_STARVING) {
379 		++lc->starving;
380 		RETURN(NULL);
381 	}
382 
383 	e = __lc_find(lc, enr, 1);
384 	/* if lc_new_number != lc_number,
385 	 * this enr is currently being pulled in already,
386 	 * and will be available once the pending transaction
387 	 * has been committed. */
388 	if (e) {
389 		if (e->lc_new_number != e->lc_number) {
390 			/* It has been found above, but on the "to_be_changed"
391 			 * list, not yet committed.  Don't pull it in twice,
392 			 * wait for the transaction, then try again...
393 			 */
394 			if (!(flags & LC_GET_MAY_USE_UNCOMMITTED))
395 				RETURN(NULL);
396 			/* ... unless the caller is aware of the implications,
397 			 * probably preparing a cumulative transaction. */
398 			++e->refcnt;
399 			++lc->hits;
400 			RETURN(e);
401 		}
402 		/* else: lc_new_number == lc_number; a real hit. */
403 		++lc->hits;
404 		if (e->refcnt++ == 0)
405 			lc->used++;
406 		list_move(&e->list, &lc->in_use); /* Not evictable... */
407 		RETURN(e);
408 	}
409 	/* e == NULL */
410 
411 	++lc->misses;
412 	if (!(flags & LC_GET_MAY_CHANGE))
413 		RETURN(NULL);
414 
415 	/* To avoid races with lc_try_lock(), first, mark us dirty
416 	 * (using test_and_set_bit, as it implies memory barriers), ... */
417 	test_and_set_bit(__LC_DIRTY, &lc->flags);
418 
419 	/* ... only then check if it is locked anyways. If lc_unlock clears
420 	 * the dirty bit again, that's not a problem, we will come here again.
421 	 */
422 	if (test_bit(__LC_LOCKED, &lc->flags)) {
423 		++lc->locked;
424 		RETURN(NULL);
425 	}
426 
427 	/* In case there is nothing available and we can not kick out
428 	 * the LRU element, we have to wait ...
429 	 */
430 	if (!lc_unused_element_available(lc)) {
431 		__set_bit(__LC_STARVING, &lc->flags);
432 		RETURN(NULL);
433 	}
434 
435 	/* It was not present in the active set.  We are going to recycle an
436 	 * unused (or even "free") element, but we won't accumulate more than
437 	 * max_pending_changes changes.  */
438 	if (lc->pending_changes >= lc->max_pending_changes)
439 		RETURN(NULL);
440 
441 	e = lc_prepare_for_change(lc, enr);
442 	BUG_ON(!e);
443 
444 	clear_bit(__LC_STARVING, &lc->flags);
445 	BUG_ON(++e->refcnt != 1);
446 	lc->used++;
447 	lc->pending_changes++;
448 
449 	RETURN(e);
450 }
451 
452 /**
453  * lc_get - get element by label, maybe change the active set
454  * @lc: the lru cache to operate on
455  * @enr: the label to look up
456  *
457  * Finds an element in the cache, increases its usage count,
458  * "touches" and returns it.
459  *
460  * In case the requested number is not present, it needs to be added to the
461  * cache. Therefore it is possible that an other element becomes evicted from
462  * the cache. In either case, the user is notified so he is able to e.g. keep
463  * a persistent log of the cache changes, and therefore the objects in use.
464  *
465  * Return values:
466  *  NULL
467  *     The cache was marked %LC_STARVING,
468  *     or the requested label was not in the active set
469  *     and a changing transaction is still pending (@lc was marked %LC_DIRTY).
470  *     Or no unused or free element could be recycled (@lc will be marked as
471  *     %LC_STARVING, blocking further lc_get() operations).
472  *
473  *  pointer to the element with the REQUESTED element number.
474  *     In this case, it can be used right away
475  *
476  *  pointer to an UNUSED element with some different element number,
477  *          where that different number may also be %LC_FREE.
478  *
479  *          In this case, the cache is marked %LC_DIRTY,
480  *          so lc_try_lock() will no longer succeed.
481  *          The returned element pointer is moved to the "to_be_changed" list,
482  *          and registered with the new element number on the hash collision chains,
483  *          so it is possible to pick it up from lc_is_used().
484  *          Up to "max_pending_changes" (see lc_create()) can be accumulated.
485  *          The user now should do whatever housekeeping is necessary,
486  *          typically serialize on lc_try_lock_for_transaction(), then call
487  *          lc_committed(lc) and lc_unlock(), to finish the change.
488  *
489  * NOTE: The user needs to check the lc_number on EACH use, so he recognizes
490  *       any cache set change.
491  */
lc_get(struct lru_cache * lc,unsigned int enr)492 struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr)
493 {
494 	return __lc_get(lc, enr, LC_GET_MAY_CHANGE);
495 }
496 
497 /**
498  * lc_get_cumulative - like lc_get; also finds to-be-changed elements
499  * @lc: the lru cache to operate on
500  * @enr: the label to look up
501  *
502  * Unlike lc_get this also returns the element for @enr, if it is belonging to
503  * a pending transaction, so the return values are like for lc_get(),
504  * plus:
505  *
506  * pointer to an element already on the "to_be_changed" list.
507  * 	In this case, the cache was already marked %LC_DIRTY.
508  *
509  * Caller needs to make sure that the pending transaction is completed,
510  * before proceeding to actually use this element.
511  */
lc_get_cumulative(struct lru_cache * lc,unsigned int enr)512 struct lc_element *lc_get_cumulative(struct lru_cache *lc, unsigned int enr)
513 {
514 	return __lc_get(lc, enr, LC_GET_MAY_CHANGE|LC_GET_MAY_USE_UNCOMMITTED);
515 }
516 
517 /**
518  * lc_try_get - get element by label, if present; do not change the active set
519  * @lc: the lru cache to operate on
520  * @enr: the label to look up
521  *
522  * Finds an element in the cache, increases its usage count,
523  * "touches" and returns it.
524  *
525  * Return values:
526  *  NULL
527  *     The cache was marked %LC_STARVING,
528  *     or the requested label was not in the active set
529  *
530  *  pointer to the element with the REQUESTED element number.
531  *     In this case, it can be used right away
532  */
lc_try_get(struct lru_cache * lc,unsigned int enr)533 struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr)
534 {
535 	return __lc_get(lc, enr, 0);
536 }
537 
538 /**
539  * lc_committed - tell @lc that pending changes have been recorded
540  * @lc: the lru cache to operate on
541  *
542  * User is expected to serialize on explicit lc_try_lock_for_transaction()
543  * before the transaction is started, and later needs to lc_unlock() explicitly
544  * as well.
545  */
lc_committed(struct lru_cache * lc)546 void lc_committed(struct lru_cache *lc)
547 {
548 	struct lc_element *e, *tmp;
549 
550 	PARANOIA_ENTRY();
551 	list_for_each_entry_safe(e, tmp, &lc->to_be_changed, list) {
552 		/* count number of changes, not number of transactions */
553 		++lc->changed;
554 		e->lc_number = e->lc_new_number;
555 		list_move(&e->list, &lc->in_use);
556 	}
557 	lc->pending_changes = 0;
558 	RETURN();
559 }
560 
561 
562 /**
563  * lc_put - give up refcnt of @e
564  * @lc: the lru cache to operate on
565  * @e: the element to put
566  *
567  * If refcnt reaches zero, the element is moved to the lru list,
568  * and a %LC_STARVING (if set) is cleared.
569  * Returns the new (post-decrement) refcnt.
570  */
lc_put(struct lru_cache * lc,struct lc_element * e)571 unsigned int lc_put(struct lru_cache *lc, struct lc_element *e)
572 {
573 	PARANOIA_ENTRY();
574 	PARANOIA_LC_ELEMENT(lc, e);
575 	BUG_ON(e->refcnt == 0);
576 	BUG_ON(e->lc_number != e->lc_new_number);
577 	if (--e->refcnt == 0) {
578 		/* move it to the front of LRU. */
579 		list_move(&e->list, &lc->lru);
580 		lc->used--;
581 		clear_bit_unlock(__LC_STARVING, &lc->flags);
582 	}
583 	RETURN(e->refcnt);
584 }
585 
586 /**
587  * lc_element_by_index
588  * @lc: the lru cache to operate on
589  * @i: the index of the element to return
590  */
lc_element_by_index(struct lru_cache * lc,unsigned i)591 struct lc_element *lc_element_by_index(struct lru_cache *lc, unsigned i)
592 {
593 	BUG_ON(i >= lc->nr_elements);
594 	BUG_ON(lc->lc_element[i] == NULL);
595 	BUG_ON(lc->lc_element[i]->lc_index != i);
596 	return lc->lc_element[i];
597 }
598 
599 /**
600  * lc_index_of
601  * @lc: the lru cache to operate on
602  * @e: the element to query for its index position in lc->element
603  */
lc_index_of(struct lru_cache * lc,struct lc_element * e)604 unsigned int lc_index_of(struct lru_cache *lc, struct lc_element *e)
605 {
606 	PARANOIA_LC_ELEMENT(lc, e);
607 	return e->lc_index;
608 }
609 
610 /**
611  * lc_set - associate index with label
612  * @lc: the lru cache to operate on
613  * @enr: the label to set
614  * @index: the element index to associate label with.
615  *
616  * Used to initialize the active set to some previously recorded state.
617  */
lc_set(struct lru_cache * lc,unsigned int enr,int index)618 void lc_set(struct lru_cache *lc, unsigned int enr, int index)
619 {
620 	struct lc_element *e;
621 	struct list_head *lh;
622 
623 	if (index < 0 || index >= lc->nr_elements)
624 		return;
625 
626 	e = lc_element_by_index(lc, index);
627 	BUG_ON(e->lc_number != e->lc_new_number);
628 	BUG_ON(e->refcnt != 0);
629 
630 	e->lc_number = e->lc_new_number = enr;
631 	hlist_del_init(&e->colision);
632 	if (enr == LC_FREE)
633 		lh = &lc->free;
634 	else {
635 		hlist_add_head(&e->colision, lc_hash_slot(lc, enr));
636 		lh = &lc->lru;
637 	}
638 	list_move(&e->list, lh);
639 }
640 
641 /**
642  * lc_dump - Dump a complete LRU cache to seq in textual form.
643  * @lc: the lru cache to operate on
644  * @seq: the &struct seq_file pointer to seq_printf into
645  * @utext: user supplied additional "heading" or other info
646  * @detail: function pointer the user may provide to dump further details
647  * of the object the lc_element is embedded in. May be NULL.
648  * Note: a leading space ' ' and trailing newline '\n' is implied.
649  */
lc_seq_dump_details(struct seq_file * seq,struct lru_cache * lc,char * utext,void (* detail)(struct seq_file *,struct lc_element *))650 void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char *utext,
651 	     void (*detail) (struct seq_file *, struct lc_element *))
652 {
653 	unsigned int nr_elements = lc->nr_elements;
654 	struct lc_element *e;
655 	int i;
656 
657 	seq_printf(seq, "\tnn: lc_number (new nr) refcnt %s\n ", utext);
658 	for (i = 0; i < nr_elements; i++) {
659 		e = lc_element_by_index(lc, i);
660 		if (e->lc_number != e->lc_new_number)
661 			seq_printf(seq, "\t%5d: %6d %8d %6d ",
662 				i, e->lc_number, e->lc_new_number, e->refcnt);
663 		else
664 			seq_printf(seq, "\t%5d: %6d %-8s %6d ",
665 				i, e->lc_number, "-\"-", e->refcnt);
666 		if (detail)
667 			detail(seq, e);
668 		seq_putc(seq, '\n');
669 	}
670 }
671 
672 EXPORT_SYMBOL(lc_create);
673 EXPORT_SYMBOL(lc_reset);
674 EXPORT_SYMBOL(lc_destroy);
675 EXPORT_SYMBOL(lc_set);
676 EXPORT_SYMBOL(lc_del);
677 EXPORT_SYMBOL(lc_try_get);
678 EXPORT_SYMBOL(lc_find);
679 EXPORT_SYMBOL(lc_get);
680 EXPORT_SYMBOL(lc_put);
681 EXPORT_SYMBOL(lc_committed);
682 EXPORT_SYMBOL(lc_element_by_index);
683 EXPORT_SYMBOL(lc_index_of);
684 EXPORT_SYMBOL(lc_seq_printf_stats);
685 EXPORT_SYMBOL(lc_seq_dump_details);
686 EXPORT_SYMBOL(lc_try_lock);
687 EXPORT_SYMBOL(lc_is_used);
688 EXPORT_SYMBOL(lc_get_cumulative);
689