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Philipp Reisnerb411b362009-09-25 16:07:19 -07001/*
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
33MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
34 "Lars Ellenberg <lars@linbit.com>");
35MODULE_DESCRIPTION("lru_cache - Track sets of hot objects");
36MODULE_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 { \
Lars Ellenberg4738fa12011-02-21 13:20:55 +010047 clear_bit_unlock(__LC_PARANOIA, &lc->flags); \
48 return x ; } while (0)
Philipp Reisnerb411b362009-09-25 16:07:19 -070049
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
Lars Ellenberg46a15bc2011-02-21 13:21:01 +010058
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 */
67int 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
Philipp Reisnerb411b362009-09-25 16:07:19 -070088/**
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
Lars Ellenberg46a15bc2011-02-21 13:21:01 +010091 * @max_pending_changes: maximum changes to accumulate until a transaction is required
Philipp Reisnerb411b362009-09-25 16:07:19 -070092 * @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 */
99struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100100 unsigned max_pending_changes,
Philipp Reisnerb411b362009-09-25 16:07:19 -0700101 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
Ilia Mirkina08aa352011-05-24 17:13:30 -0700119 slot = kcalloc(e_count, sizeof(struct hlist_head), GFP_KERNEL);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700120 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);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100133 INIT_LIST_HEAD(&lc->to_be_changed);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700134
135 lc->name = name;
136 lc->element_size = e_size;
137 lc->element_off = e_off;
138 lc->nr_elements = e_count;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100139 lc->max_pending_changes = max_pending_changes;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700140 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;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100153 e->lc_new_number = LC_FREE;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700154 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);
166out_fail:
167 kfree(element);
168 kfree(slot);
169 return NULL;
170}
171
172void 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 */
186void 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 */
205void 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);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100212 INIT_LIST_HEAD(&lc->to_be_changed);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700213 lc->used = 0;
214 lc->hits = 0;
215 lc->misses = 0;
216 lc->starving = 0;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100217 lc->locked = 0;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700218 lc->changed = 0;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100219 lc->pending_changes = 0;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700220 lc->flags = 0;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700221 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;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100231 e->lc_new_number = LC_FREE;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700232 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 */
241size_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)
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100246 * misses include "locked" count (update from an other thread in
Philipp Reisnerb411b362009-09-25 16:07:19 -0700247 * 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 "
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100251 "hits:%lu misses:%lu starving:%lu locked:%lu changed:%lu\n",
Philipp Reisnerb411b362009-09-25 16:07:19 -0700252 lc->name, lc->used, lc->nr_elements,
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100253 lc->hits, lc->misses, lc->starving, lc->locked, lc->changed);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700254}
255
256static 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
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100262static struct lc_element *__lc_find(struct lru_cache *lc, unsigned int enr,
263 bool include_changing)
264{
265 struct hlist_node *n;
266 struct lc_element *e;
267
268 BUG_ON(!lc);
269 BUG_ON(!lc->nr_elements);
270 hlist_for_each_entry(e, n, lc_hash_slot(lc, enr), colision) {
271 /* "about to be changed" elements, pending transaction commit,
272 * are hashed by their "new number". "Normal" elements have
273 * lc_number == lc_new_number. */
274 if (e->lc_new_number != enr)
275 continue;
276 if (e->lc_new_number == e->lc_number || include_changing)
277 return e;
278 break;
279 }
280 return NULL;
281}
282
Philipp Reisnerb411b362009-09-25 16:07:19 -0700283/**
284 * lc_find - find element by label, if present in the hash table
285 * @lc: The lru_cache object
286 * @enr: element number
287 *
288 * Returns the pointer to an element, if the element with the requested
289 * "label" or element number is present in the hash table,
290 * or NULL if not found. Does not change the refcnt.
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100291 * Ignores elements that are "about to be used", i.e. not yet in the active
292 * set, but still pending transaction commit.
Philipp Reisnerb411b362009-09-25 16:07:19 -0700293 */
294struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr)
295{
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100296 return __lc_find(lc, enr, 0);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700297}
298
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100299/**
300 * lc_is_used - find element by label
301 * @lc: The lru_cache object
302 * @enr: element number
303 *
304 * Returns true, if the element with the requested "label" or element number is
305 * present in the hash table, and is used (refcnt > 0).
306 * Also finds elements that are not _currently_ used but only "about to be
307 * used", i.e. on the "to_be_changed" list, pending transaction commit.
308 */
309bool lc_is_used(struct lru_cache *lc, unsigned int enr)
Philipp Reisnerb411b362009-09-25 16:07:19 -0700310{
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100311 struct lc_element *e = __lc_find(lc, enr, 1);
312 return e && e->refcnt;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700313}
314
315/**
316 * lc_del - removes an element from the cache
317 * @lc: The lru_cache object
318 * @e: The element to remove
319 *
320 * @e must be unused (refcnt == 0). Moves @e from "lru" to "free" list,
321 * sets @e->enr to %LC_FREE.
322 */
323void lc_del(struct lru_cache *lc, struct lc_element *e)
324{
325 PARANOIA_ENTRY();
326 PARANOIA_LC_ELEMENT(lc, e);
327 BUG_ON(e->refcnt);
328
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100329 e->lc_number = e->lc_new_number = LC_FREE;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700330 hlist_del_init(&e->colision);
331 list_move(&e->list, &lc->free);
332 RETURN();
333}
334
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100335static struct lc_element *lc_prepare_for_change(struct lru_cache *lc, unsigned new_number)
Philipp Reisnerb411b362009-09-25 16:07:19 -0700336{
337 struct list_head *n;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100338 struct lc_element *e;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700339
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100340 if (!list_empty(&lc->free))
341 n = lc->free.next;
342 else if (!list_empty(&lc->lru))
343 n = lc->lru.prev;
344 else
345 return NULL;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700346
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100347 e = list_entry(n, struct lc_element, list);
348 PARANOIA_LC_ELEMENT(lc, e);
349
350 e->lc_new_number = new_number;
351 if (!hlist_unhashed(&e->colision))
352 __hlist_del(&e->colision);
353 hlist_add_head(&e->colision, lc_hash_slot(lc, new_number));
354 list_move(&e->list, &lc->to_be_changed);
355
356 return e;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700357}
358
359static int lc_unused_element_available(struct lru_cache *lc)
360{
361 if (!list_empty(&lc->free))
362 return 1; /* something on the free list */
363 if (!list_empty(&lc->lru))
364 return 1; /* something to evict */
365
366 return 0;
367}
368
Lars Ellenberga9efc742011-02-21 13:20:58 +0100369static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, bool may_change)
370{
371 struct lc_element *e;
372
373 PARANOIA_ENTRY();
374 if (lc->flags & LC_STARVING) {
375 ++lc->starving;
376 RETURN(NULL);
377 }
378
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100379 e = __lc_find(lc, enr, 1);
380 /* if lc_new_number != lc_number,
381 * this enr is currently being pulled in already,
382 * and will be available once the pending transaction
383 * has been committed. */
384 if (e && e->lc_new_number == e->lc_number) {
Lars Ellenberga9efc742011-02-21 13:20:58 +0100385 ++lc->hits;
386 if (e->refcnt++ == 0)
387 lc->used++;
388 list_move(&e->list, &lc->in_use); /* Not evictable... */
389 RETURN(e);
390 }
391
392 ++lc->misses;
393 if (!may_change)
394 RETURN(NULL);
395
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100396 /* It has been found above, but on the "to_be_changed" list, not yet
397 * committed. Don't pull it in twice, wait for the transaction, then
398 * try again */
399 if (e)
400 RETURN(NULL);
401
402 /* To avoid races with lc_try_lock(), first, mark us dirty
403 * (using test_and_set_bit, as it implies memory barriers), ... */
404 test_and_set_bit(__LC_DIRTY, &lc->flags);
405
406 /* ... only then check if it is locked anyways. If lc_unlock clears
407 * the dirty bit again, that's not a problem, we will come here again.
408 */
409 if (test_bit(__LC_LOCKED, &lc->flags)) {
410 ++lc->locked;
411 RETURN(NULL);
412 }
413
Lars Ellenberga9efc742011-02-21 13:20:58 +0100414 /* In case there is nothing available and we can not kick out
415 * the LRU element, we have to wait ...
416 */
417 if (!lc_unused_element_available(lc)) {
418 __set_bit(__LC_STARVING, &lc->flags);
419 RETURN(NULL);
420 }
421
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100422 /* It was not present in the active set. We are going to recycle an
423 * unused (or even "free") element, but we won't accumulate more than
424 * max_pending_changes changes. */
425 if (lc->pending_changes >= lc->max_pending_changes)
Lars Ellenberga9efc742011-02-21 13:20:58 +0100426 RETURN(NULL);
Lars Ellenberga9efc742011-02-21 13:20:58 +0100427
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100428 e = lc_prepare_for_change(lc, enr);
Lars Ellenberga9efc742011-02-21 13:20:58 +0100429 BUG_ON(!e);
430
431 clear_bit(__LC_STARVING, &lc->flags);
432 BUG_ON(++e->refcnt != 1);
433 lc->used++;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100434 lc->pending_changes++;
Lars Ellenberga9efc742011-02-21 13:20:58 +0100435
436 RETURN(e);
437}
Philipp Reisnerb411b362009-09-25 16:07:19 -0700438
439/**
440 * lc_get - get element by label, maybe change the active set
441 * @lc: the lru cache to operate on
442 * @enr: the label to look up
443 *
444 * Finds an element in the cache, increases its usage count,
445 * "touches" and returns it.
446 *
447 * In case the requested number is not present, it needs to be added to the
448 * cache. Therefore it is possible that an other element becomes evicted from
449 * the cache. In either case, the user is notified so he is able to e.g. keep
450 * a persistent log of the cache changes, and therefore the objects in use.
451 *
452 * Return values:
453 * NULL
454 * The cache was marked %LC_STARVING,
455 * or the requested label was not in the active set
456 * and a changing transaction is still pending (@lc was marked %LC_DIRTY).
457 * Or no unused or free element could be recycled (@lc will be marked as
458 * %LC_STARVING, blocking further lc_get() operations).
459 *
460 * pointer to the element with the REQUESTED element number.
461 * In this case, it can be used right away
462 *
463 * pointer to an UNUSED element with some different element number,
464 * where that different number may also be %LC_FREE.
465 *
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100466 * In this case, the cache is marked %LC_DIRTY,
467 * so lc_try_lock() will no longer succeed.
468 * The returned element pointer is moved to the "to_be_changed" list,
469 * and registered with the new element number on the hash collision chains,
470 * so it is possible to pick it up from lc_is_used().
471 * Up to "max_pending_changes" (see lc_create()) can be accumulated.
472 * The user now should do whatever housekeeping is necessary,
473 * typically serialize on lc_try_lock_for_transaction(), then call
474 * lc_committed(lc) and lc_unlock(), to finish the change.
Philipp Reisnerb411b362009-09-25 16:07:19 -0700475 *
476 * NOTE: The user needs to check the lc_number on EACH use, so he recognizes
477 * any cache set change.
478 */
479struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr)
480{
Lars Ellenberga9efc742011-02-21 13:20:58 +0100481 return __lc_get(lc, enr, 1);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700482}
483
Lars Ellenberga9efc742011-02-21 13:20:58 +0100484/**
485 * lc_try_get - get element by label, if present; do not change the active set
486 * @lc: the lru cache to operate on
487 * @enr: the label to look up
488 *
489 * Finds an element in the cache, increases its usage count,
490 * "touches" and returns it.
491 *
492 * Return values:
493 * NULL
494 * The cache was marked %LC_STARVING,
495 * or the requested label was not in the active set
496 *
497 * pointer to the element with the REQUESTED element number.
498 * In this case, it can be used right away
Philipp Reisnerb411b362009-09-25 16:07:19 -0700499 */
500struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr)
501{
Lars Ellenberga9efc742011-02-21 13:20:58 +0100502 return __lc_get(lc, enr, 0);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700503}
504
505/**
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100506 * lc_committed - tell @lc that pending changes have been recorded
Philipp Reisnerb411b362009-09-25 16:07:19 -0700507 * @lc: the lru cache to operate on
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100508 *
509 * User is expected to serialize on explicit lc_try_lock_for_transaction()
510 * before the transaction is started, and later needs to lc_unlock() explicitly
511 * as well.
Philipp Reisnerb411b362009-09-25 16:07:19 -0700512 */
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100513void lc_committed(struct lru_cache *lc)
Philipp Reisnerb411b362009-09-25 16:07:19 -0700514{
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100515 struct lc_element *e, *tmp;
516
Philipp Reisnerb411b362009-09-25 16:07:19 -0700517 PARANOIA_ENTRY();
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100518 list_for_each_entry_safe(e, tmp, &lc->to_be_changed, list) {
519 /* count number of changes, not number of transactions */
520 ++lc->changed;
521 e->lc_number = e->lc_new_number;
522 list_move(&e->list, &lc->in_use);
523 }
524 lc->pending_changes = 0;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700525 RETURN();
526}
527
528
529/**
530 * lc_put - give up refcnt of @e
531 * @lc: the lru cache to operate on
532 * @e: the element to put
533 *
534 * If refcnt reaches zero, the element is moved to the lru list,
535 * and a %LC_STARVING (if set) is cleared.
536 * Returns the new (post-decrement) refcnt.
537 */
538unsigned int lc_put(struct lru_cache *lc, struct lc_element *e)
539{
540 PARANOIA_ENTRY();
541 PARANOIA_LC_ELEMENT(lc, e);
542 BUG_ON(e->refcnt == 0);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100543 BUG_ON(e->lc_number != e->lc_new_number);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700544 if (--e->refcnt == 0) {
545 /* move it to the front of LRU. */
546 list_move(&e->list, &lc->lru);
547 lc->used--;
Lars Ellenberg4738fa12011-02-21 13:20:55 +0100548 clear_bit_unlock(__LC_STARVING, &lc->flags);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700549 }
550 RETURN(e->refcnt);
551}
552
553/**
554 * lc_element_by_index
555 * @lc: the lru cache to operate on
556 * @i: the index of the element to return
557 */
558struct lc_element *lc_element_by_index(struct lru_cache *lc, unsigned i)
559{
560 BUG_ON(i >= lc->nr_elements);
561 BUG_ON(lc->lc_element[i] == NULL);
562 BUG_ON(lc->lc_element[i]->lc_index != i);
563 return lc->lc_element[i];
564}
565
566/**
567 * lc_index_of
568 * @lc: the lru cache to operate on
569 * @e: the element to query for its index position in lc->element
570 */
571unsigned int lc_index_of(struct lru_cache *lc, struct lc_element *e)
572{
573 PARANOIA_LC_ELEMENT(lc, e);
574 return e->lc_index;
575}
576
577/**
578 * lc_set - associate index with label
579 * @lc: the lru cache to operate on
580 * @enr: the label to set
581 * @index: the element index to associate label with.
582 *
583 * Used to initialize the active set to some previously recorded state.
584 */
585void lc_set(struct lru_cache *lc, unsigned int enr, int index)
586{
587 struct lc_element *e;
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100588 struct list_head *lh;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700589
590 if (index < 0 || index >= lc->nr_elements)
591 return;
592
593 e = lc_element_by_index(lc, index);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100594 BUG_ON(e->lc_number != e->lc_new_number);
595 BUG_ON(e->refcnt != 0);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700596
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100597 e->lc_number = e->lc_new_number = enr;
Philipp Reisnerb411b362009-09-25 16:07:19 -0700598 hlist_del_init(&e->colision);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100599 if (enr == LC_FREE)
600 lh = &lc->free;
601 else {
602 hlist_add_head(&e->colision, lc_hash_slot(lc, enr));
603 lh = &lc->lru;
604 }
605 list_move(&e->list, lh);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700606}
607
608/**
609 * lc_dump - Dump a complete LRU cache to seq in textual form.
610 * @lc: the lru cache to operate on
611 * @seq: the &struct seq_file pointer to seq_printf into
612 * @utext: user supplied "heading" or other info
613 * @detail: function pointer the user may provide to dump further details
614 * of the object the lc_element is embedded in.
615 */
616void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char *utext,
617 void (*detail) (struct seq_file *, struct lc_element *))
618{
619 unsigned int nr_elements = lc->nr_elements;
620 struct lc_element *e;
621 int i;
622
623 seq_printf(seq, "\tnn: lc_number refcnt %s\n ", utext);
624 for (i = 0; i < nr_elements; i++) {
625 e = lc_element_by_index(lc, i);
626 if (e->lc_number == LC_FREE) {
627 seq_printf(seq, "\t%2d: FREE\n", i);
628 } else {
629 seq_printf(seq, "\t%2d: %4u %4u ", i,
630 e->lc_number, e->refcnt);
631 detail(seq, e);
632 }
633 }
634}
635
636EXPORT_SYMBOL(lc_create);
637EXPORT_SYMBOL(lc_reset);
638EXPORT_SYMBOL(lc_destroy);
639EXPORT_SYMBOL(lc_set);
640EXPORT_SYMBOL(lc_del);
641EXPORT_SYMBOL(lc_try_get);
642EXPORT_SYMBOL(lc_find);
643EXPORT_SYMBOL(lc_get);
644EXPORT_SYMBOL(lc_put);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100645EXPORT_SYMBOL(lc_committed);
Philipp Reisnerb411b362009-09-25 16:07:19 -0700646EXPORT_SYMBOL(lc_element_by_index);
647EXPORT_SYMBOL(lc_index_of);
648EXPORT_SYMBOL(lc_seq_printf_stats);
649EXPORT_SYMBOL(lc_seq_dump_details);
Lars Ellenberg46a15bc2011-02-21 13:21:01 +0100650EXPORT_SYMBOL(lc_try_lock);
651EXPORT_SYMBOL(lc_is_used);