blob: b42322e50f6308f9445fe83380f29973e99864b3
1 | /* |
2 | * zbud.c |
3 | * |
4 | * Copyright (C) 2013, Seth Jennings, IBM |
5 | * |
6 | * Concepts based on zcache internal zbud allocator by Dan Magenheimer. |
7 | * |
8 | * zbud is an special purpose allocator for storing compressed pages. Contrary |
9 | * to what its name may suggest, zbud is not a buddy allocator, but rather an |
10 | * allocator that "buddies" two compressed pages together in a single memory |
11 | * page. |
12 | * |
13 | * While this design limits storage density, it has simple and deterministic |
14 | * reclaim properties that make it preferable to a higher density approach when |
15 | * reclaim will be used. |
16 | * |
17 | * zbud works by storing compressed pages, or "zpages", together in pairs in a |
18 | * single memory page called a "zbud page". The first buddy is "left |
19 | * justified" at the beginning of the zbud page, and the last buddy is "right |
20 | * justified" at the end of the zbud page. The benefit is that if either |
21 | * buddy is freed, the freed buddy space, coalesced with whatever slack space |
22 | * that existed between the buddies, results in the largest possible free region |
23 | * within the zbud page. |
24 | * |
25 | * zbud also provides an attractive lower bound on density. The ratio of zpages |
26 | * to zbud pages can not be less than 1. This ensures that zbud can never "do |
27 | * harm" by using more pages to store zpages than the uncompressed zpages would |
28 | * have used on their own. |
29 | * |
30 | * zbud pages are divided into "chunks". The size of the chunks is fixed at |
31 | * compile time and determined by NCHUNKS_ORDER below. Dividing zbud pages |
32 | * into chunks allows organizing unbuddied zbud pages into a manageable number |
33 | * of unbuddied lists according to the number of free chunks available in the |
34 | * zbud page. |
35 | * |
36 | * The zbud API differs from that of conventional allocators in that the |
37 | * allocation function, zbud_alloc(), returns an opaque handle to the user, |
38 | * not a dereferenceable pointer. The user must map the handle using |
39 | * zbud_map() in order to get a usable pointer by which to access the |
40 | * allocation data and unmap the handle with zbud_unmap() when operations |
41 | * on the allocation data are complete. |
42 | */ |
43 | |
44 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
45 | |
46 | #include <linux/atomic.h> |
47 | #include <linux/list.h> |
48 | #include <linux/mm.h> |
49 | #include <linux/module.h> |
50 | #include <linux/preempt.h> |
51 | #include <linux/slab.h> |
52 | #include <linux/spinlock.h> |
53 | #include <linux/zbud.h> |
54 | #include <linux/zpool.h> |
55 | |
56 | /***************** |
57 | * Structures |
58 | *****************/ |
59 | /* |
60 | * NCHUNKS_ORDER determines the internal allocation granularity, effectively |
61 | * adjusting internal fragmentation. It also determines the number of |
62 | * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the |
63 | * allocation granularity will be in chunks of size PAGE_SIZE/64. As one chunk |
64 | * in allocated page is occupied by zbud header, NCHUNKS will be calculated to |
65 | * 63 which shows the max number of free chunks in zbud page, also there will be |
66 | * 63 freelists per pool. |
67 | */ |
68 | #define NCHUNKS_ORDER 6 |
69 | |
70 | #define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER) |
71 | #define CHUNK_SIZE (1 << CHUNK_SHIFT) |
72 | #define ZHDR_SIZE_ALIGNED CHUNK_SIZE |
73 | #define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT) |
74 | |
75 | /** |
76 | * struct zbud_pool - stores metadata for each zbud pool |
77 | * @lock: protects all pool fields and first|last_chunk fields of any |
78 | * zbud page in the pool |
79 | * @unbuddied: array of lists tracking zbud pages that only contain one buddy; |
80 | * the lists each zbud page is added to depends on the size of |
81 | * its free region. |
82 | * @buddied: list tracking the zbud pages that contain two buddies; |
83 | * these zbud pages are full |
84 | * @lru: list tracking the zbud pages in LRU order by most recently |
85 | * added buddy. |
86 | * @pages_nr: number of zbud pages in the pool. |
87 | * @ops: pointer to a structure of user defined operations specified at |
88 | * pool creation time. |
89 | * |
90 | * This structure is allocated at pool creation time and maintains metadata |
91 | * pertaining to a particular zbud pool. |
92 | */ |
93 | struct zbud_pool { |
94 | spinlock_t lock; |
95 | struct list_head unbuddied[NCHUNKS]; |
96 | struct list_head buddied; |
97 | struct list_head lru; |
98 | u64 pages_nr; |
99 | const struct zbud_ops *ops; |
100 | #ifdef CONFIG_ZPOOL |
101 | struct zpool *zpool; |
102 | const struct zpool_ops *zpool_ops; |
103 | #endif |
104 | }; |
105 | |
106 | /* |
107 | * struct zbud_header - zbud page metadata occupying the first chunk of each |
108 | * zbud page. |
109 | * @buddy: links the zbud page into the unbuddied/buddied lists in the pool |
110 | * @lru: links the zbud page into the lru list in the pool |
111 | * @first_chunks: the size of the first buddy in chunks, 0 if free |
112 | * @last_chunks: the size of the last buddy in chunks, 0 if free |
113 | */ |
114 | struct zbud_header { |
115 | struct list_head buddy; |
116 | struct list_head lru; |
117 | unsigned int first_chunks; |
118 | unsigned int last_chunks; |
119 | bool under_reclaim; |
120 | }; |
121 | |
122 | /***************** |
123 | * zpool |
124 | ****************/ |
125 | |
126 | #ifdef CONFIG_ZPOOL |
127 | |
128 | static int zbud_zpool_evict(struct zbud_pool *pool, unsigned long handle) |
129 | { |
130 | if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict) |
131 | return pool->zpool_ops->evict(pool->zpool, handle); |
132 | else |
133 | return -ENOENT; |
134 | } |
135 | |
136 | static const struct zbud_ops zbud_zpool_ops = { |
137 | .evict = zbud_zpool_evict |
138 | }; |
139 | |
140 | static void *zbud_zpool_create(const char *name, gfp_t gfp, |
141 | const struct zpool_ops *zpool_ops, |
142 | struct zpool *zpool) |
143 | { |
144 | struct zbud_pool *pool; |
145 | |
146 | pool = zbud_create_pool(gfp, zpool_ops ? &zbud_zpool_ops : NULL); |
147 | if (pool) { |
148 | pool->zpool = zpool; |
149 | pool->zpool_ops = zpool_ops; |
150 | } |
151 | return pool; |
152 | } |
153 | |
154 | static void zbud_zpool_destroy(void *pool) |
155 | { |
156 | zbud_destroy_pool(pool); |
157 | } |
158 | |
159 | static int zbud_zpool_malloc(void *pool, size_t size, gfp_t gfp, |
160 | unsigned long *handle) |
161 | { |
162 | return zbud_alloc(pool, size, gfp, handle); |
163 | } |
164 | static void zbud_zpool_free(void *pool, unsigned long handle) |
165 | { |
166 | zbud_free(pool, handle); |
167 | } |
168 | |
169 | static int zbud_zpool_shrink(void *pool, unsigned int pages, |
170 | unsigned int *reclaimed) |
171 | { |
172 | unsigned int total = 0; |
173 | int ret = -EINVAL; |
174 | |
175 | while (total < pages) { |
176 | ret = zbud_reclaim_page(pool, 8); |
177 | if (ret < 0) |
178 | break; |
179 | total++; |
180 | } |
181 | |
182 | if (reclaimed) |
183 | *reclaimed = total; |
184 | |
185 | return ret; |
186 | } |
187 | |
188 | static void *zbud_zpool_map(void *pool, unsigned long handle, |
189 | enum zpool_mapmode mm) |
190 | { |
191 | return zbud_map(pool, handle); |
192 | } |
193 | static void zbud_zpool_unmap(void *pool, unsigned long handle) |
194 | { |
195 | zbud_unmap(pool, handle); |
196 | } |
197 | |
198 | static u64 zbud_zpool_total_size(void *pool) |
199 | { |
200 | return zbud_get_pool_size(pool) * PAGE_SIZE; |
201 | } |
202 | |
203 | static struct zpool_driver zbud_zpool_driver = { |
204 | .type = "zbud", |
205 | .owner = THIS_MODULE, |
206 | .create = zbud_zpool_create, |
207 | .destroy = zbud_zpool_destroy, |
208 | .malloc = zbud_zpool_malloc, |
209 | .free = zbud_zpool_free, |
210 | .shrink = zbud_zpool_shrink, |
211 | .map = zbud_zpool_map, |
212 | .unmap = zbud_zpool_unmap, |
213 | .total_size = zbud_zpool_total_size, |
214 | }; |
215 | |
216 | MODULE_ALIAS("zpool-zbud"); |
217 | #endif /* CONFIG_ZPOOL */ |
218 | |
219 | /***************** |
220 | * Helpers |
221 | *****************/ |
222 | /* Just to make the code easier to read */ |
223 | enum buddy { |
224 | FIRST, |
225 | LAST |
226 | }; |
227 | |
228 | /* Converts an allocation size in bytes to size in zbud chunks */ |
229 | static int size_to_chunks(size_t size) |
230 | { |
231 | return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; |
232 | } |
233 | |
234 | #define for_each_unbuddied_list(_iter, _begin) \ |
235 | for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++) |
236 | |
237 | /* Initializes the zbud header of a newly allocated zbud page */ |
238 | static struct zbud_header *init_zbud_page(struct page *page) |
239 | { |
240 | struct zbud_header *zhdr = page_address(page); |
241 | zhdr->first_chunks = 0; |
242 | zhdr->last_chunks = 0; |
243 | INIT_LIST_HEAD(&zhdr->buddy); |
244 | INIT_LIST_HEAD(&zhdr->lru); |
245 | zhdr->under_reclaim = 0; |
246 | return zhdr; |
247 | } |
248 | |
249 | /* Resets the struct page fields and frees the page */ |
250 | static void free_zbud_page(struct zbud_header *zhdr) |
251 | { |
252 | __free_page(virt_to_page(zhdr)); |
253 | } |
254 | |
255 | /* |
256 | * Encodes the handle of a particular buddy within a zbud page |
257 | * Pool lock should be held as this function accesses first|last_chunks |
258 | */ |
259 | static unsigned long encode_handle(struct zbud_header *zhdr, enum buddy bud) |
260 | { |
261 | unsigned long handle; |
262 | |
263 | /* |
264 | * For now, the encoded handle is actually just the pointer to the data |
265 | * but this might not always be the case. A little information hiding. |
266 | * Add CHUNK_SIZE to the handle if it is the first allocation to jump |
267 | * over the zbud header in the first chunk. |
268 | */ |
269 | handle = (unsigned long)zhdr; |
270 | if (bud == FIRST) |
271 | /* skip over zbud header */ |
272 | handle += ZHDR_SIZE_ALIGNED; |
273 | else /* bud == LAST */ |
274 | handle += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT); |
275 | return handle; |
276 | } |
277 | |
278 | /* Returns the zbud page where a given handle is stored */ |
279 | static struct zbud_header *handle_to_zbud_header(unsigned long handle) |
280 | { |
281 | return (struct zbud_header *)(handle & PAGE_MASK); |
282 | } |
283 | |
284 | /* Returns the number of free chunks in a zbud page */ |
285 | static int num_free_chunks(struct zbud_header *zhdr) |
286 | { |
287 | /* |
288 | * Rather than branch for different situations, just use the fact that |
289 | * free buddies have a length of zero to simplify everything. |
290 | */ |
291 | return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks; |
292 | } |
293 | |
294 | /***************** |
295 | * API Functions |
296 | *****************/ |
297 | /** |
298 | * zbud_create_pool() - create a new zbud pool |
299 | * @gfp: gfp flags when allocating the zbud pool structure |
300 | * @ops: user-defined operations for the zbud pool |
301 | * |
302 | * Return: pointer to the new zbud pool or NULL if the metadata allocation |
303 | * failed. |
304 | */ |
305 | struct zbud_pool *zbud_create_pool(gfp_t gfp, const struct zbud_ops *ops) |
306 | { |
307 | struct zbud_pool *pool; |
308 | int i; |
309 | |
310 | pool = kzalloc(sizeof(struct zbud_pool), gfp); |
311 | if (!pool) |
312 | return NULL; |
313 | spin_lock_init(&pool->lock); |
314 | for_each_unbuddied_list(i, 0) |
315 | INIT_LIST_HEAD(&pool->unbuddied[i]); |
316 | INIT_LIST_HEAD(&pool->buddied); |
317 | INIT_LIST_HEAD(&pool->lru); |
318 | pool->pages_nr = 0; |
319 | pool->ops = ops; |
320 | return pool; |
321 | } |
322 | |
323 | /** |
324 | * zbud_destroy_pool() - destroys an existing zbud pool |
325 | * @pool: the zbud pool to be destroyed |
326 | * |
327 | * The pool should be emptied before this function is called. |
328 | */ |
329 | void zbud_destroy_pool(struct zbud_pool *pool) |
330 | { |
331 | kfree(pool); |
332 | } |
333 | |
334 | /** |
335 | * zbud_alloc() - allocates a region of a given size |
336 | * @pool: zbud pool from which to allocate |
337 | * @size: size in bytes of the desired allocation |
338 | * @gfp: gfp flags used if the pool needs to grow |
339 | * @handle: handle of the new allocation |
340 | * |
341 | * This function will attempt to find a free region in the pool large enough to |
342 | * satisfy the allocation request. A search of the unbuddied lists is |
343 | * performed first. If no suitable free region is found, then a new page is |
344 | * allocated and added to the pool to satisfy the request. |
345 | * |
346 | * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used |
347 | * as zbud pool pages. |
348 | * |
349 | * Return: 0 if success and handle is set, otherwise -EINVAL if the size or |
350 | * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate |
351 | * a new page. |
352 | */ |
353 | int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp, |
354 | unsigned long *handle) |
355 | { |
356 | int chunks, i, freechunks; |
357 | struct zbud_header *zhdr = NULL; |
358 | enum buddy bud; |
359 | struct page *page; |
360 | |
361 | if (!size || (gfp & __GFP_HIGHMEM)) |
362 | return -EINVAL; |
363 | if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) |
364 | return -ENOSPC; |
365 | chunks = size_to_chunks(size); |
366 | spin_lock(&pool->lock); |
367 | |
368 | /* First, try to find an unbuddied zbud page. */ |
369 | zhdr = NULL; |
370 | for_each_unbuddied_list(i, chunks) { |
371 | if (!list_empty(&pool->unbuddied[i])) { |
372 | zhdr = list_first_entry(&pool->unbuddied[i], |
373 | struct zbud_header, buddy); |
374 | list_del(&zhdr->buddy); |
375 | if (zhdr->first_chunks == 0) |
376 | bud = FIRST; |
377 | else |
378 | bud = LAST; |
379 | goto found; |
380 | } |
381 | } |
382 | |
383 | /* Couldn't find unbuddied zbud page, create new one */ |
384 | spin_unlock(&pool->lock); |
385 | page = alloc_page(gfp); |
386 | if (!page) |
387 | return -ENOMEM; |
388 | spin_lock(&pool->lock); |
389 | pool->pages_nr++; |
390 | zhdr = init_zbud_page(page); |
391 | bud = FIRST; |
392 | |
393 | found: |
394 | if (bud == FIRST) |
395 | zhdr->first_chunks = chunks; |
396 | else |
397 | zhdr->last_chunks = chunks; |
398 | |
399 | if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0) { |
400 | /* Add to unbuddied list */ |
401 | freechunks = num_free_chunks(zhdr); |
402 | list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); |
403 | } else { |
404 | /* Add to buddied list */ |
405 | list_add(&zhdr->buddy, &pool->buddied); |
406 | } |
407 | |
408 | /* Add/move zbud page to beginning of LRU */ |
409 | if (!list_empty(&zhdr->lru)) |
410 | list_del(&zhdr->lru); |
411 | list_add(&zhdr->lru, &pool->lru); |
412 | |
413 | *handle = encode_handle(zhdr, bud); |
414 | spin_unlock(&pool->lock); |
415 | |
416 | return 0; |
417 | } |
418 | |
419 | /** |
420 | * zbud_free() - frees the allocation associated with the given handle |
421 | * @pool: pool in which the allocation resided |
422 | * @handle: handle associated with the allocation returned by zbud_alloc() |
423 | * |
424 | * In the case that the zbud page in which the allocation resides is under |
425 | * reclaim, as indicated by the PG_reclaim flag being set, this function |
426 | * only sets the first|last_chunks to 0. The page is actually freed |
427 | * once both buddies are evicted (see zbud_reclaim_page() below). |
428 | */ |
429 | void zbud_free(struct zbud_pool *pool, unsigned long handle) |
430 | { |
431 | struct zbud_header *zhdr; |
432 | int freechunks; |
433 | |
434 | spin_lock(&pool->lock); |
435 | zhdr = handle_to_zbud_header(handle); |
436 | |
437 | /* If first buddy, handle will be page aligned */ |
438 | if ((handle - ZHDR_SIZE_ALIGNED) & ~PAGE_MASK) |
439 | zhdr->last_chunks = 0; |
440 | else |
441 | zhdr->first_chunks = 0; |
442 | |
443 | if (zhdr->under_reclaim) { |
444 | /* zbud page is under reclaim, reclaim will free */ |
445 | spin_unlock(&pool->lock); |
446 | return; |
447 | } |
448 | |
449 | /* Remove from existing buddy list */ |
450 | list_del(&zhdr->buddy); |
451 | |
452 | if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { |
453 | /* zbud page is empty, free */ |
454 | list_del(&zhdr->lru); |
455 | free_zbud_page(zhdr); |
456 | pool->pages_nr--; |
457 | } else { |
458 | /* Add to unbuddied list */ |
459 | freechunks = num_free_chunks(zhdr); |
460 | list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); |
461 | } |
462 | |
463 | spin_unlock(&pool->lock); |
464 | } |
465 | |
466 | /** |
467 | * zbud_reclaim_page() - evicts allocations from a pool page and frees it |
468 | * @pool: pool from which a page will attempt to be evicted |
469 | * @retires: number of pages on the LRU list for which eviction will |
470 | * be attempted before failing |
471 | * |
472 | * zbud reclaim is different from normal system reclaim in that the reclaim is |
473 | * done from the bottom, up. This is because only the bottom layer, zbud, has |
474 | * information on how the allocations are organized within each zbud page. This |
475 | * has the potential to create interesting locking situations between zbud and |
476 | * the user, however. |
477 | * |
478 | * To avoid these, this is how zbud_reclaim_page() should be called: |
479 | |
480 | * The user detects a page should be reclaimed and calls zbud_reclaim_page(). |
481 | * zbud_reclaim_page() will remove a zbud page from the pool LRU list and call |
482 | * the user-defined eviction handler with the pool and handle as arguments. |
483 | * |
484 | * If the handle can not be evicted, the eviction handler should return |
485 | * non-zero. zbud_reclaim_page() will add the zbud page back to the |
486 | * appropriate list and try the next zbud page on the LRU up to |
487 | * a user defined number of retries. |
488 | * |
489 | * If the handle is successfully evicted, the eviction handler should |
490 | * return 0 _and_ should have called zbud_free() on the handle. zbud_free() |
491 | * contains logic to delay freeing the page if the page is under reclaim, |
492 | * as indicated by the setting of the PG_reclaim flag on the underlying page. |
493 | * |
494 | * If all buddies in the zbud page are successfully evicted, then the |
495 | * zbud page can be freed. |
496 | * |
497 | * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are |
498 | * no pages to evict or an eviction handler is not registered, -EAGAIN if |
499 | * the retry limit was hit. |
500 | */ |
501 | int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries) |
502 | { |
503 | int i, ret, freechunks; |
504 | struct zbud_header *zhdr; |
505 | unsigned long first_handle = 0, last_handle = 0; |
506 | |
507 | spin_lock(&pool->lock); |
508 | if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) || |
509 | retries == 0) { |
510 | spin_unlock(&pool->lock); |
511 | return -EINVAL; |
512 | } |
513 | for (i = 0; i < retries; i++) { |
514 | zhdr = list_last_entry(&pool->lru, struct zbud_header, lru); |
515 | list_del(&zhdr->lru); |
516 | list_del(&zhdr->buddy); |
517 | /* Protect zbud page against free */ |
518 | zhdr->under_reclaim = true; |
519 | /* |
520 | * We need encode the handles before unlocking, since we can |
521 | * race with free that will set (first|last)_chunks to 0 |
522 | */ |
523 | first_handle = 0; |
524 | last_handle = 0; |
525 | if (zhdr->first_chunks) |
526 | first_handle = encode_handle(zhdr, FIRST); |
527 | if (zhdr->last_chunks) |
528 | last_handle = encode_handle(zhdr, LAST); |
529 | spin_unlock(&pool->lock); |
530 | |
531 | /* Issue the eviction callback(s) */ |
532 | if (first_handle) { |
533 | ret = pool->ops->evict(pool, first_handle); |
534 | if (ret) |
535 | goto next; |
536 | } |
537 | if (last_handle) { |
538 | ret = pool->ops->evict(pool, last_handle); |
539 | if (ret) |
540 | goto next; |
541 | } |
542 | next: |
543 | spin_lock(&pool->lock); |
544 | zhdr->under_reclaim = false; |
545 | if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { |
546 | /* |
547 | * Both buddies are now free, free the zbud page and |
548 | * return success. |
549 | */ |
550 | free_zbud_page(zhdr); |
551 | pool->pages_nr--; |
552 | spin_unlock(&pool->lock); |
553 | return 0; |
554 | } else if (zhdr->first_chunks == 0 || |
555 | zhdr->last_chunks == 0) { |
556 | /* add to unbuddied list */ |
557 | freechunks = num_free_chunks(zhdr); |
558 | list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); |
559 | } else { |
560 | /* add to buddied list */ |
561 | list_add(&zhdr->buddy, &pool->buddied); |
562 | } |
563 | |
564 | /* add to beginning of LRU */ |
565 | list_add(&zhdr->lru, &pool->lru); |
566 | } |
567 | spin_unlock(&pool->lock); |
568 | return -EAGAIN; |
569 | } |
570 | |
571 | /** |
572 | * zbud_map() - maps the allocation associated with the given handle |
573 | * @pool: pool in which the allocation resides |
574 | * @handle: handle associated with the allocation to be mapped |
575 | * |
576 | * While trivial for zbud, the mapping functions for others allocators |
577 | * implementing this allocation API could have more complex information encoded |
578 | * in the handle and could create temporary mappings to make the data |
579 | * accessible to the user. |
580 | * |
581 | * Returns: a pointer to the mapped allocation |
582 | */ |
583 | void *zbud_map(struct zbud_pool *pool, unsigned long handle) |
584 | { |
585 | return (void *)(handle); |
586 | } |
587 | |
588 | /** |
589 | * zbud_unmap() - maps the allocation associated with the given handle |
590 | * @pool: pool in which the allocation resides |
591 | * @handle: handle associated with the allocation to be unmapped |
592 | */ |
593 | void zbud_unmap(struct zbud_pool *pool, unsigned long handle) |
594 | { |
595 | } |
596 | |
597 | /** |
598 | * zbud_get_pool_size() - gets the zbud pool size in pages |
599 | * @pool: pool whose size is being queried |
600 | * |
601 | * Returns: size in pages of the given pool. The pool lock need not be |
602 | * taken to access pages_nr. |
603 | */ |
604 | u64 zbud_get_pool_size(struct zbud_pool *pool) |
605 | { |
606 | return pool->pages_nr; |
607 | } |
608 | |
609 | static int __init init_zbud(void) |
610 | { |
611 | /* Make sure the zbud header will fit in one chunk */ |
612 | BUILD_BUG_ON(sizeof(struct zbud_header) > ZHDR_SIZE_ALIGNED); |
613 | pr_info("loaded\n"); |
614 | |
615 | #ifdef CONFIG_ZPOOL |
616 | zpool_register_driver(&zbud_zpool_driver); |
617 | #endif |
618 | |
619 | return 0; |
620 | } |
621 | |
622 | static void __exit exit_zbud(void) |
623 | { |
624 | #ifdef CONFIG_ZPOOL |
625 | zpool_unregister_driver(&zbud_zpool_driver); |
626 | #endif |
627 | |
628 | pr_info("unloaded\n"); |
629 | } |
630 | |
631 | module_init(init_zbud); |
632 | module_exit(exit_zbud); |
633 | |
634 | MODULE_LICENSE("GPL"); |
635 | MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>"); |
636 | MODULE_DESCRIPTION("Buddy Allocator for Compressed Pages"); |
637 |