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