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c6ae4c04 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
b411b363 PR |
2 | /* |
3 | lru_cache.c | |
4 | ||
5 | This file is part of DRBD by Philipp Reisner and Lars Ellenberg. | |
6 | ||
7 | Copyright (C) 2003-2008, LINBIT Information Technologies GmbH. | |
8 | Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>. | |
9 | Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>. | |
10 | ||
b411b363 PR |
11 | |
12 | */ | |
13 | ||
14 | #include <linux/module.h> | |
15 | #include <linux/bitops.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/string.h> /* for memset */ | |
18 | #include <linux/seq_file.h> /* for seq_printf */ | |
19 | #include <linux/lru_cache.h> | |
20 | ||
21 | MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, " | |
22 | "Lars Ellenberg <lars@linbit.com>"); | |
23 | MODULE_DESCRIPTION("lru_cache - Track sets of hot objects"); | |
24 | MODULE_LICENSE("GPL"); | |
25 | ||
26 | /* this is developers aid only. | |
27 | * it catches concurrent access (lack of locking on the users part) */ | |
28 | #define PARANOIA_ENTRY() do { \ | |
29 | BUG_ON(!lc); \ | |
30 | BUG_ON(!lc->nr_elements); \ | |
31 | BUG_ON(test_and_set_bit(__LC_PARANOIA, &lc->flags)); \ | |
32 | } while (0) | |
33 | ||
34 | #define RETURN(x...) do { \ | |
4738fa16 LE |
35 | clear_bit_unlock(__LC_PARANOIA, &lc->flags); \ |
36 | return x ; } while (0) | |
b411b363 PR |
37 | |
38 | /* BUG() if e is not one of the elements tracked by lc */ | |
39 | #define PARANOIA_LC_ELEMENT(lc, e) do { \ | |
40 | struct lru_cache *lc_ = (lc); \ | |
41 | struct lc_element *e_ = (e); \ | |
42 | unsigned i = e_->lc_index; \ | |
43 | BUG_ON(i >= lc_->nr_elements); \ | |
44 | BUG_ON(lc_->lc_element[i] != e_); } while (0) | |
45 | ||
46a15bc3 LE |
46 | |
47 | /* We need to atomically | |
48 | * - try to grab the lock (set LC_LOCKED) | |
49 | * - only if there is no pending transaction | |
50 | * (neither LC_DIRTY nor LC_STARVING is set) | |
51 | * Because of PARANOIA_ENTRY() above abusing lc->flags as well, | |
52 | * it is not sufficient to just say | |
53 | * return 0 == cmpxchg(&lc->flags, 0, LC_LOCKED); | |
54 | */ | |
55 | int lc_try_lock(struct lru_cache *lc) | |
56 | { | |
57 | unsigned long val; | |
58 | do { | |
59 | val = cmpxchg(&lc->flags, 0, LC_LOCKED); | |
60 | } while (unlikely (val == LC_PARANOIA)); | |
61 | /* Spin until no-one is inside a PARANOIA_ENTRY()/RETURN() section. */ | |
62 | return 0 == val; | |
63 | #if 0 | |
64 | /* Alternative approach, spin in case someone enters or leaves a | |
65 | * PARANOIA_ENTRY()/RETURN() section. */ | |
66 | unsigned long old, new, val; | |
67 | do { | |
68 | old = lc->flags & LC_PARANOIA; | |
69 | new = old | LC_LOCKED; | |
70 | val = cmpxchg(&lc->flags, old, new); | |
71 | } while (unlikely (val == (old ^ LC_PARANOIA))); | |
72 | return old == val; | |
73 | #endif | |
74 | } | |
75 | ||
b411b363 PR |
76 | /** |
77 | * lc_create - prepares to track objects in an active set | |
78 | * @name: descriptive name only used in lc_seq_printf_stats and lc_seq_dump_details | |
c95c2d32 | 79 | * @cache: cache root pointer |
46a15bc3 | 80 | * @max_pending_changes: maximum changes to accumulate until a transaction is required |
b411b363 PR |
81 | * @e_count: number of elements allowed to be active simultaneously |
82 | * @e_size: size of the tracked objects | |
83 | * @e_off: offset to the &struct lc_element member in a tracked object | |
84 | * | |
85 | * Returns a pointer to a newly initialized struct lru_cache on success, | |
86 | * or NULL on (allocation) failure. | |
87 | */ | |
88 | struct lru_cache *lc_create(const char *name, struct kmem_cache *cache, | |
46a15bc3 | 89 | unsigned max_pending_changes, |
b411b363 PR |
90 | unsigned e_count, size_t e_size, size_t e_off) |
91 | { | |
92 | struct hlist_head *slot = NULL; | |
93 | struct lc_element **element = NULL; | |
94 | struct lru_cache *lc; | |
95 | struct lc_element *e; | |
96 | unsigned cache_obj_size = kmem_cache_size(cache); | |
97 | unsigned i; | |
98 | ||
99 | WARN_ON(cache_obj_size < e_size); | |
100 | if (cache_obj_size < e_size) | |
101 | return NULL; | |
102 | ||
103 | /* e_count too big; would probably fail the allocation below anyways. | |
104 | * for typical use cases, e_count should be few thousand at most. */ | |
105 | if (e_count > LC_MAX_ACTIVE) | |
106 | return NULL; | |
107 | ||
a08aa355 | 108 | slot = kcalloc(e_count, sizeof(struct hlist_head), GFP_KERNEL); |
b411b363 PR |
109 | if (!slot) |
110 | goto out_fail; | |
6396bb22 | 111 | element = kcalloc(e_count, sizeof(struct lc_element *), GFP_KERNEL); |
b411b363 PR |
112 | if (!element) |
113 | goto out_fail; | |
114 | ||
115 | lc = kzalloc(sizeof(*lc), GFP_KERNEL); | |
116 | if (!lc) | |
117 | goto out_fail; | |
118 | ||
119 | INIT_LIST_HEAD(&lc->in_use); | |
120 | INIT_LIST_HEAD(&lc->lru); | |
121 | INIT_LIST_HEAD(&lc->free); | |
46a15bc3 | 122 | INIT_LIST_HEAD(&lc->to_be_changed); |
b411b363 PR |
123 | |
124 | lc->name = name; | |
125 | lc->element_size = e_size; | |
126 | lc->element_off = e_off; | |
127 | lc->nr_elements = e_count; | |
46a15bc3 | 128 | lc->max_pending_changes = max_pending_changes; |
b411b363 PR |
129 | lc->lc_cache = cache; |
130 | lc->lc_element = element; | |
131 | lc->lc_slot = slot; | |
132 | ||
133 | /* preallocate all objects */ | |
134 | for (i = 0; i < e_count; i++) { | |
135 | void *p = kmem_cache_alloc(cache, GFP_KERNEL); | |
136 | if (!p) | |
137 | break; | |
138 | memset(p, 0, lc->element_size); | |
139 | e = p + e_off; | |
140 | e->lc_index = i; | |
141 | e->lc_number = LC_FREE; | |
46a15bc3 | 142 | e->lc_new_number = LC_FREE; |
b411b363 PR |
143 | list_add(&e->list, &lc->free); |
144 | element[i] = e; | |
145 | } | |
146 | if (i == e_count) | |
147 | return lc; | |
148 | ||
149 | /* else: could not allocate all elements, give up */ | |
150 | for (i--; i; i--) { | |
151 | void *p = element[i]; | |
152 | kmem_cache_free(cache, p - e_off); | |
153 | } | |
154 | kfree(lc); | |
155 | out_fail: | |
156 | kfree(element); | |
157 | kfree(slot); | |
158 | return NULL; | |
159 | } | |
160 | ||
8ce953aa | 161 | static void lc_free_by_index(struct lru_cache *lc, unsigned i) |
b411b363 PR |
162 | { |
163 | void *p = lc->lc_element[i]; | |
164 | WARN_ON(!p); | |
165 | if (p) { | |
166 | p -= lc->element_off; | |
167 | kmem_cache_free(lc->lc_cache, p); | |
168 | } | |
169 | } | |
170 | ||
171 | /** | |
172 | * lc_destroy - frees memory allocated by lc_create() | |
173 | * @lc: the lru cache to destroy | |
174 | */ | |
175 | void lc_destroy(struct lru_cache *lc) | |
176 | { | |
177 | unsigned i; | |
178 | if (!lc) | |
179 | return; | |
180 | for (i = 0; i < lc->nr_elements; i++) | |
181 | lc_free_by_index(lc, i); | |
182 | kfree(lc->lc_element); | |
183 | kfree(lc->lc_slot); | |
184 | kfree(lc); | |
185 | } | |
186 | ||
187 | /** | |
188 | * lc_reset - does a full reset for @lc and the hash table slots. | |
189 | * @lc: the lru cache to operate on | |
190 | * | |
191 | * It is roughly the equivalent of re-allocating a fresh lru_cache object, | |
192 | * basically a short cut to lc_destroy(lc); lc = lc_create(...); | |
193 | */ | |
194 | void lc_reset(struct lru_cache *lc) | |
195 | { | |
196 | unsigned i; | |
197 | ||
198 | INIT_LIST_HEAD(&lc->in_use); | |
199 | INIT_LIST_HEAD(&lc->lru); | |
200 | INIT_LIST_HEAD(&lc->free); | |
46a15bc3 | 201 | INIT_LIST_HEAD(&lc->to_be_changed); |
b411b363 PR |
202 | lc->used = 0; |
203 | lc->hits = 0; | |
204 | lc->misses = 0; | |
205 | lc->starving = 0; | |
46a15bc3 | 206 | lc->locked = 0; |
b411b363 | 207 | lc->changed = 0; |
46a15bc3 | 208 | lc->pending_changes = 0; |
b411b363 | 209 | lc->flags = 0; |
b411b363 PR |
210 | memset(lc->lc_slot, 0, sizeof(struct hlist_head) * lc->nr_elements); |
211 | ||
212 | for (i = 0; i < lc->nr_elements; i++) { | |
213 | struct lc_element *e = lc->lc_element[i]; | |
214 | void *p = e; | |
215 | p -= lc->element_off; | |
216 | memset(p, 0, lc->element_size); | |
217 | /* re-init it */ | |
218 | e->lc_index = i; | |
219 | e->lc_number = LC_FREE; | |
46a15bc3 | 220 | e->lc_new_number = LC_FREE; |
b411b363 PR |
221 | list_add(&e->list, &lc->free); |
222 | } | |
223 | } | |
224 | ||
225 | /** | |
226 | * lc_seq_printf_stats - print stats about @lc into @seq | |
227 | * @seq: the seq_file to print into | |
228 | * @lc: the lru cache to print statistics of | |
229 | */ | |
bb649b34 | 230 | void lc_seq_printf_stats(struct seq_file *seq, struct lru_cache *lc) |
b411b363 PR |
231 | { |
232 | /* NOTE: | |
233 | * total calls to lc_get are | |
234 | * (starving + hits + misses) | |
46a15bc3 | 235 | * misses include "locked" count (update from an other thread in |
b411b363 PR |
236 | * progress) and "changed", when this in fact lead to an successful |
237 | * update of the cache. | |
238 | */ | |
d50f8f8d JP |
239 | seq_printf(seq, "\t%s: used:%u/%u hits:%lu misses:%lu starving:%lu locked:%lu changed:%lu\n", |
240 | lc->name, lc->used, lc->nr_elements, | |
241 | lc->hits, lc->misses, lc->starving, lc->locked, lc->changed); | |
b411b363 PR |
242 | } |
243 | ||
244 | static struct hlist_head *lc_hash_slot(struct lru_cache *lc, unsigned int enr) | |
245 | { | |
246 | return lc->lc_slot + (enr % lc->nr_elements); | |
247 | } | |
248 | ||
249 | ||
46a15bc3 LE |
250 | static struct lc_element *__lc_find(struct lru_cache *lc, unsigned int enr, |
251 | bool include_changing) | |
b411b363 | 252 | { |
b411b363 PR |
253 | struct lc_element *e; |
254 | ||
255 | BUG_ON(!lc); | |
256 | BUG_ON(!lc->nr_elements); | |
b67bfe0d | 257 | hlist_for_each_entry(e, lc_hash_slot(lc, enr), colision) { |
46a15bc3 LE |
258 | /* "about to be changed" elements, pending transaction commit, |
259 | * are hashed by their "new number". "Normal" elements have | |
260 | * lc_number == lc_new_number. */ | |
261 | if (e->lc_new_number != enr) | |
262 | continue; | |
263 | if (e->lc_new_number == e->lc_number || include_changing) | |
b411b363 | 264 | return e; |
46a15bc3 | 265 | break; |
b411b363 PR |
266 | } |
267 | return NULL; | |
268 | } | |
269 | ||
46a15bc3 LE |
270 | /** |
271 | * lc_find - find element by label, if present in the hash table | |
272 | * @lc: The lru_cache object | |
273 | * @enr: element number | |
274 | * | |
275 | * Returns the pointer to an element, if the element with the requested | |
276 | * "label" or element number is present in the hash table, | |
277 | * or NULL if not found. Does not change the refcnt. | |
278 | * Ignores elements that are "about to be used", i.e. not yet in the active | |
279 | * set, but still pending transaction commit. | |
280 | */ | |
281 | struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr) | |
b411b363 | 282 | { |
46a15bc3 LE |
283 | return __lc_find(lc, enr, 0); |
284 | } | |
b411b363 | 285 | |
46a15bc3 LE |
286 | /** |
287 | * lc_is_used - find element by label | |
288 | * @lc: The lru_cache object | |
289 | * @enr: element number | |
290 | * | |
291 | * Returns true, if the element with the requested "label" or element number is | |
292 | * present in the hash table, and is used (refcnt > 0). | |
293 | * Also finds elements that are not _currently_ used but only "about to be | |
294 | * used", i.e. on the "to_be_changed" list, pending transaction commit. | |
295 | */ | |
296 | bool lc_is_used(struct lru_cache *lc, unsigned int enr) | |
297 | { | |
298 | struct lc_element *e = __lc_find(lc, enr, 1); | |
299 | return e && e->refcnt; | |
b411b363 PR |
300 | } |
301 | ||
302 | /** | |
303 | * lc_del - removes an element from the cache | |
304 | * @lc: The lru_cache object | |
305 | * @e: The element to remove | |
306 | * | |
307 | * @e must be unused (refcnt == 0). Moves @e from "lru" to "free" list, | |
308 | * sets @e->enr to %LC_FREE. | |
309 | */ | |
310 | void lc_del(struct lru_cache *lc, struct lc_element *e) | |
311 | { | |
312 | PARANOIA_ENTRY(); | |
313 | PARANOIA_LC_ELEMENT(lc, e); | |
314 | BUG_ON(e->refcnt); | |
315 | ||
46a15bc3 | 316 | e->lc_number = e->lc_new_number = LC_FREE; |
b411b363 PR |
317 | hlist_del_init(&e->colision); |
318 | list_move(&e->list, &lc->free); | |
319 | RETURN(); | |
320 | } | |
321 | ||
46a15bc3 | 322 | static struct lc_element *lc_prepare_for_change(struct lru_cache *lc, unsigned new_number) |
b411b363 PR |
323 | { |
324 | struct list_head *n; | |
46a15bc3 LE |
325 | struct lc_element *e; |
326 | ||
327 | if (!list_empty(&lc->free)) | |
328 | n = lc->free.next; | |
329 | else if (!list_empty(&lc->lru)) | |
330 | n = lc->lru.prev; | |
331 | else | |
332 | return NULL; | |
333 | ||
334 | e = list_entry(n, struct lc_element, list); | |
335 | PARANOIA_LC_ELEMENT(lc, e); | |
b411b363 | 336 | |
46a15bc3 LE |
337 | e->lc_new_number = new_number; |
338 | if (!hlist_unhashed(&e->colision)) | |
339 | __hlist_del(&e->colision); | |
340 | hlist_add_head(&e->colision, lc_hash_slot(lc, new_number)); | |
341 | list_move(&e->list, &lc->to_be_changed); | |
b411b363 | 342 | |
46a15bc3 | 343 | return e; |
b411b363 PR |
344 | } |
345 | ||
346 | static int lc_unused_element_available(struct lru_cache *lc) | |
347 | { | |
348 | if (!list_empty(&lc->free)) | |
349 | return 1; /* something on the free list */ | |
350 | if (!list_empty(&lc->lru)) | |
351 | return 1; /* something to evict */ | |
352 | ||
353 | return 0; | |
354 | } | |
355 | ||
cbe5e610 LE |
356 | /* used as internal flags to __lc_get */ |
357 | enum { | |
358 | LC_GET_MAY_CHANGE = 1, | |
359 | LC_GET_MAY_USE_UNCOMMITTED = 2, | |
360 | }; | |
361 | ||
362 | static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsigned int flags) | |
b411b363 PR |
363 | { |
364 | struct lc_element *e; | |
365 | ||
366 | PARANOIA_ENTRY(); | |
367 | if (lc->flags & LC_STARVING) { | |
368 | ++lc->starving; | |
369 | RETURN(NULL); | |
370 | } | |
371 | ||
46a15bc3 LE |
372 | e = __lc_find(lc, enr, 1); |
373 | /* if lc_new_number != lc_number, | |
374 | * this enr is currently being pulled in already, | |
375 | * and will be available once the pending transaction | |
376 | * has been committed. */ | |
cbe5e610 LE |
377 | if (e) { |
378 | if (e->lc_new_number != e->lc_number) { | |
379 | /* It has been found above, but on the "to_be_changed" | |
380 | * list, not yet committed. Don't pull it in twice, | |
381 | * wait for the transaction, then try again... | |
382 | */ | |
383 | if (!(flags & LC_GET_MAY_USE_UNCOMMITTED)) | |
384 | RETURN(NULL); | |
385 | /* ... unless the caller is aware of the implications, | |
386 | * probably preparing a cumulative transaction. */ | |
387 | ++e->refcnt; | |
388 | ++lc->hits; | |
389 | RETURN(e); | |
390 | } | |
391 | /* else: lc_new_number == lc_number; a real hit. */ | |
b411b363 PR |
392 | ++lc->hits; |
393 | if (e->refcnt++ == 0) | |
394 | lc->used++; | |
395 | list_move(&e->list, &lc->in_use); /* Not evictable... */ | |
396 | RETURN(e); | |
397 | } | |
cbe5e610 | 398 | /* e == NULL */ |
b411b363 PR |
399 | |
400 | ++lc->misses; | |
cbe5e610 | 401 | if (!(flags & LC_GET_MAY_CHANGE)) |
46a15bc3 LE |
402 | RETURN(NULL); |
403 | ||
404 | /* To avoid races with lc_try_lock(), first, mark us dirty | |
405 | * (using test_and_set_bit, as it implies memory barriers), ... */ | |
406 | test_and_set_bit(__LC_DIRTY, &lc->flags); | |
407 | ||
408 | /* ... only then check if it is locked anyways. If lc_unlock clears | |
409 | * the dirty bit again, that's not a problem, we will come here again. | |
410 | */ | |
411 | if (test_bit(__LC_LOCKED, &lc->flags)) { | |
412 | ++lc->locked; | |
413 | RETURN(NULL); | |
414 | } | |
415 | ||
b411b363 PR |
416 | /* In case there is nothing available and we can not kick out |
417 | * the LRU element, we have to wait ... | |
418 | */ | |
419 | if (!lc_unused_element_available(lc)) { | |
420 | __set_bit(__LC_STARVING, &lc->flags); | |
421 | RETURN(NULL); | |
422 | } | |
423 | ||
46a15bc3 LE |
424 | /* It was not present in the active set. We are going to recycle an |
425 | * unused (or even "free") element, but we won't accumulate more than | |
426 | * max_pending_changes changes. */ | |
427 | if (lc->pending_changes >= lc->max_pending_changes) | |
b411b363 | 428 | RETURN(NULL); |
b411b363 | 429 | |
46a15bc3 | 430 | e = lc_prepare_for_change(lc, enr); |
b411b363 PR |
431 | BUG_ON(!e); |
432 | ||
433 | clear_bit(__LC_STARVING, &lc->flags); | |
434 | BUG_ON(++e->refcnt != 1); | |
435 | lc->used++; | |
46a15bc3 | 436 | lc->pending_changes++; |
b411b363 PR |
437 | |
438 | RETURN(e); | |
439 | } | |
440 | ||
a9efc748 LE |
441 | /** |
442 | * lc_get - get element by label, maybe change the active set | |
443 | * @lc: the lru cache to operate on | |
444 | * @enr: the label to look up | |
445 | * | |
446 | * Finds an element in the cache, increases its usage count, | |
447 | * "touches" and returns it. | |
448 | * | |
449 | * In case the requested number is not present, it needs to be added to the | |
450 | * cache. Therefore it is possible that an other element becomes evicted from | |
451 | * the cache. In either case, the user is notified so he is able to e.g. keep | |
452 | * a persistent log of the cache changes, and therefore the objects in use. | |
453 | * | |
454 | * Return values: | |
455 | * NULL | |
456 | * The cache was marked %LC_STARVING, | |
457 | * or the requested label was not in the active set | |
458 | * and a changing transaction is still pending (@lc was marked %LC_DIRTY). | |
459 | * Or no unused or free element could be recycled (@lc will be marked as | |
460 | * %LC_STARVING, blocking further lc_get() operations). | |
461 | * | |
462 | * pointer to the element with the REQUESTED element number. | |
463 | * In this case, it can be used right away | |
464 | * | |
465 | * pointer to an UNUSED element with some different element number, | |
466 | * where that different number may also be %LC_FREE. | |
467 | * | |
46a15bc3 LE |
468 | * In this case, the cache is marked %LC_DIRTY, |
469 | * so lc_try_lock() will no longer succeed. | |
470 | * The returned element pointer is moved to the "to_be_changed" list, | |
471 | * and registered with the new element number on the hash collision chains, | |
472 | * so it is possible to pick it up from lc_is_used(). | |
473 | * Up to "max_pending_changes" (see lc_create()) can be accumulated. | |
474 | * The user now should do whatever housekeeping is necessary, | |
475 | * typically serialize on lc_try_lock_for_transaction(), then call | |
476 | * lc_committed(lc) and lc_unlock(), to finish the change. | |
a9efc748 LE |
477 | * |
478 | * NOTE: The user needs to check the lc_number on EACH use, so he recognizes | |
479 | * any cache set change. | |
b411b363 | 480 | */ |
a9efc748 | 481 | struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr) |
b411b363 | 482 | { |
cbe5e610 LE |
483 | return __lc_get(lc, enr, LC_GET_MAY_CHANGE); |
484 | } | |
485 | ||
486 | /** | |
487 | * lc_get_cumulative - like lc_get; also finds to-be-changed elements | |
488 | * @lc: the lru cache to operate on | |
489 | * @enr: the label to look up | |
490 | * | |
491 | * Unlike lc_get this also returns the element for @enr, if it is belonging to | |
492 | * a pending transaction, so the return values are like for lc_get(), | |
493 | * plus: | |
494 | * | |
495 | * pointer to an element already on the "to_be_changed" list. | |
496 | * In this case, the cache was already marked %LC_DIRTY. | |
497 | * | |
498 | * Caller needs to make sure that the pending transaction is completed, | |
499 | * before proceeding to actually use this element. | |
500 | */ | |
501 | struct lc_element *lc_get_cumulative(struct lru_cache *lc, unsigned int enr) | |
502 | { | |
503 | return __lc_get(lc, enr, LC_GET_MAY_CHANGE|LC_GET_MAY_USE_UNCOMMITTED); | |
a9efc748 | 504 | } |
b411b363 | 505 | |
a9efc748 LE |
506 | /** |
507 | * lc_try_get - get element by label, if present; do not change the active set | |
508 | * @lc: the lru cache to operate on | |
509 | * @enr: the label to look up | |
510 | * | |
511 | * Finds an element in the cache, increases its usage count, | |
512 | * "touches" and returns it. | |
513 | * | |
514 | * Return values: | |
515 | * NULL | |
516 | * The cache was marked %LC_STARVING, | |
517 | * or the requested label was not in the active set | |
518 | * | |
519 | * pointer to the element with the REQUESTED element number. | |
520 | * In this case, it can be used right away | |
521 | */ | |
522 | struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr) | |
523 | { | |
524 | return __lc_get(lc, enr, 0); | |
b411b363 PR |
525 | } |
526 | ||
527 | /** | |
46a15bc3 | 528 | * lc_committed - tell @lc that pending changes have been recorded |
b411b363 | 529 | * @lc: the lru cache to operate on |
46a15bc3 LE |
530 | * |
531 | * User is expected to serialize on explicit lc_try_lock_for_transaction() | |
532 | * before the transaction is started, and later needs to lc_unlock() explicitly | |
533 | * as well. | |
b411b363 | 534 | */ |
46a15bc3 | 535 | void lc_committed(struct lru_cache *lc) |
b411b363 | 536 | { |
46a15bc3 LE |
537 | struct lc_element *e, *tmp; |
538 | ||
b411b363 | 539 | PARANOIA_ENTRY(); |
46a15bc3 LE |
540 | list_for_each_entry_safe(e, tmp, &lc->to_be_changed, list) { |
541 | /* count number of changes, not number of transactions */ | |
542 | ++lc->changed; | |
543 | e->lc_number = e->lc_new_number; | |
544 | list_move(&e->list, &lc->in_use); | |
545 | } | |
546 | lc->pending_changes = 0; | |
b411b363 PR |
547 | RETURN(); |
548 | } | |
549 | ||
550 | ||
551 | /** | |
552 | * lc_put - give up refcnt of @e | |
553 | * @lc: the lru cache to operate on | |
554 | * @e: the element to put | |
555 | * | |
556 | * If refcnt reaches zero, the element is moved to the lru list, | |
557 | * and a %LC_STARVING (if set) is cleared. | |
558 | * Returns the new (post-decrement) refcnt. | |
559 | */ | |
560 | unsigned int lc_put(struct lru_cache *lc, struct lc_element *e) | |
561 | { | |
562 | PARANOIA_ENTRY(); | |
563 | PARANOIA_LC_ELEMENT(lc, e); | |
564 | BUG_ON(e->refcnt == 0); | |
46a15bc3 | 565 | BUG_ON(e->lc_number != e->lc_new_number); |
b411b363 PR |
566 | if (--e->refcnt == 0) { |
567 | /* move it to the front of LRU. */ | |
568 | list_move(&e->list, &lc->lru); | |
569 | lc->used--; | |
4738fa16 | 570 | clear_bit_unlock(__LC_STARVING, &lc->flags); |
b411b363 PR |
571 | } |
572 | RETURN(e->refcnt); | |
573 | } | |
574 | ||
575 | /** | |
576 | * lc_element_by_index | |
577 | * @lc: the lru cache to operate on | |
578 | * @i: the index of the element to return | |
579 | */ | |
580 | struct lc_element *lc_element_by_index(struct lru_cache *lc, unsigned i) | |
581 | { | |
582 | BUG_ON(i >= lc->nr_elements); | |
583 | BUG_ON(lc->lc_element[i] == NULL); | |
584 | BUG_ON(lc->lc_element[i]->lc_index != i); | |
585 | return lc->lc_element[i]; | |
586 | } | |
587 | ||
588 | /** | |
589 | * lc_index_of | |
590 | * @lc: the lru cache to operate on | |
591 | * @e: the element to query for its index position in lc->element | |
592 | */ | |
593 | unsigned int lc_index_of(struct lru_cache *lc, struct lc_element *e) | |
594 | { | |
595 | PARANOIA_LC_ELEMENT(lc, e); | |
596 | return e->lc_index; | |
597 | } | |
598 | ||
599 | /** | |
600 | * lc_set - associate index with label | |
601 | * @lc: the lru cache to operate on | |
602 | * @enr: the label to set | |
603 | * @index: the element index to associate label with. | |
604 | * | |
605 | * Used to initialize the active set to some previously recorded state. | |
606 | */ | |
607 | void lc_set(struct lru_cache *lc, unsigned int enr, int index) | |
608 | { | |
609 | struct lc_element *e; | |
46a15bc3 | 610 | struct list_head *lh; |
b411b363 PR |
611 | |
612 | if (index < 0 || index >= lc->nr_elements) | |
613 | return; | |
614 | ||
615 | e = lc_element_by_index(lc, index); | |
46a15bc3 LE |
616 | BUG_ON(e->lc_number != e->lc_new_number); |
617 | BUG_ON(e->refcnt != 0); | |
b411b363 | 618 | |
46a15bc3 | 619 | e->lc_number = e->lc_new_number = enr; |
b411b363 | 620 | hlist_del_init(&e->colision); |
46a15bc3 LE |
621 | if (enr == LC_FREE) |
622 | lh = &lc->free; | |
623 | else { | |
624 | hlist_add_head(&e->colision, lc_hash_slot(lc, enr)); | |
625 | lh = &lc->lru; | |
626 | } | |
627 | list_move(&e->list, lh); | |
b411b363 PR |
628 | } |
629 | ||
630 | /** | |
c95c2d32 | 631 | * lc_seq_dump_details - Dump a complete LRU cache to seq in textual form. |
b411b363 PR |
632 | * @lc: the lru cache to operate on |
633 | * @seq: the &struct seq_file pointer to seq_printf into | |
54e6fc38 | 634 | * @utext: user supplied additional "heading" or other info |
b411b363 | 635 | * @detail: function pointer the user may provide to dump further details |
54e6fc38 LE |
636 | * of the object the lc_element is embedded in. May be NULL. |
637 | * Note: a leading space ' ' and trailing newline '\n' is implied. | |
b411b363 PR |
638 | */ |
639 | void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char *utext, | |
640 | void (*detail) (struct seq_file *, struct lc_element *)) | |
641 | { | |
642 | unsigned int nr_elements = lc->nr_elements; | |
643 | struct lc_element *e; | |
644 | int i; | |
645 | ||
54e6fc38 | 646 | seq_printf(seq, "\tnn: lc_number (new nr) refcnt %s\n ", utext); |
b411b363 PR |
647 | for (i = 0; i < nr_elements; i++) { |
648 | e = lc_element_by_index(lc, i); | |
54e6fc38 LE |
649 | if (e->lc_number != e->lc_new_number) |
650 | seq_printf(seq, "\t%5d: %6d %8d %6d ", | |
651 | i, e->lc_number, e->lc_new_number, e->refcnt); | |
652 | else | |
653 | seq_printf(seq, "\t%5d: %6d %-8s %6d ", | |
654 | i, e->lc_number, "-\"-", e->refcnt); | |
655 | if (detail) | |
b411b363 | 656 | detail(seq, e); |
54e6fc38 | 657 | seq_putc(seq, '\n'); |
b411b363 PR |
658 | } |
659 | } | |
660 | ||
661 | EXPORT_SYMBOL(lc_create); | |
662 | EXPORT_SYMBOL(lc_reset); | |
663 | EXPORT_SYMBOL(lc_destroy); | |
664 | EXPORT_SYMBOL(lc_set); | |
665 | EXPORT_SYMBOL(lc_del); | |
666 | EXPORT_SYMBOL(lc_try_get); | |
667 | EXPORT_SYMBOL(lc_find); | |
668 | EXPORT_SYMBOL(lc_get); | |
669 | EXPORT_SYMBOL(lc_put); | |
46a15bc3 | 670 | EXPORT_SYMBOL(lc_committed); |
b411b363 PR |
671 | EXPORT_SYMBOL(lc_element_by_index); |
672 | EXPORT_SYMBOL(lc_index_of); | |
673 | EXPORT_SYMBOL(lc_seq_printf_stats); | |
674 | EXPORT_SYMBOL(lc_seq_dump_details); | |
46a15bc3 LE |
675 | EXPORT_SYMBOL(lc_try_lock); |
676 | EXPORT_SYMBOL(lc_is_used); | |
cbe5e610 | 677 | EXPORT_SYMBOL(lc_get_cumulative); |