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09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
9a001fc1 VW |
2 | /* |
3 | * z3fold.c | |
4 | * | |
5 | * Author: Vitaly Wool <vitaly.wool@konsulko.com> | |
6 | * Copyright (C) 2016, Sony Mobile Communications Inc. | |
7 | * | |
8 | * This implementation is based on zbud written by Seth Jennings. | |
9 | * | |
10 | * z3fold is an special purpose allocator for storing compressed pages. It | |
11 | * can store up to three compressed pages per page which improves the | |
12 | * compression ratio of zbud while retaining its main concepts (e. g. always | |
13 | * storing an integral number of objects per page) and simplicity. | |
14 | * It still has simple and deterministic reclaim properties that make it | |
15 | * preferable to a higher density approach (with no requirement on integral | |
16 | * number of object per page) when reclaim is used. | |
17 | * | |
18 | * As in zbud, pages are divided into "chunks". The size of the chunks is | |
19 | * fixed at compile time and is determined by NCHUNKS_ORDER below. | |
20 | * | |
21 | * z3fold doesn't export any API and is meant to be used via zpool API. | |
22 | */ | |
23 | ||
24 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
25 | ||
26 | #include <linux/atomic.h> | |
d30561c5 | 27 | #include <linux/sched.h> |
1f862989 VW |
28 | #include <linux/cpumask.h> |
29 | #include <linux/dcache.h> | |
9a001fc1 VW |
30 | #include <linux/list.h> |
31 | #include <linux/mm.h> | |
32 | #include <linux/module.h> | |
1f862989 VW |
33 | #include <linux/page-flags.h> |
34 | #include <linux/migrate.h> | |
35 | #include <linux/node.h> | |
36 | #include <linux/compaction.h> | |
d30561c5 | 37 | #include <linux/percpu.h> |
1f862989 VW |
38 | #include <linux/mount.h> |
39 | #include <linux/fs.h> | |
9a001fc1 | 40 | #include <linux/preempt.h> |
d30561c5 | 41 | #include <linux/workqueue.h> |
9a001fc1 VW |
42 | #include <linux/slab.h> |
43 | #include <linux/spinlock.h> | |
44 | #include <linux/zpool.h> | |
45 | ||
7c2b8baa VW |
46 | /* |
47 | * NCHUNKS_ORDER determines the internal allocation granularity, effectively | |
48 | * adjusting internal fragmentation. It also determines the number of | |
49 | * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the | |
50 | * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks | |
51 | * in the beginning of an allocated page are occupied by z3fold header, so | |
52 | * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y), | |
53 | * which shows the max number of free chunks in z3fold page, also there will | |
54 | * be 63, or 62, respectively, freelists per pool. | |
55 | */ | |
56 | #define NCHUNKS_ORDER 6 | |
57 | ||
58 | #define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER) | |
59 | #define CHUNK_SIZE (1 << CHUNK_SHIFT) | |
60 | #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE) | |
61 | #define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT) | |
62 | #define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT) | |
63 | #define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT) | |
64 | ||
65 | #define BUDDY_MASK (0x3) | |
66 | #define BUDDY_SHIFT 2 | |
67 | #define SLOTS_ALIGN (0x40) | |
68 | ||
9a001fc1 VW |
69 | /***************** |
70 | * Structures | |
71 | *****************/ | |
ede93213 VW |
72 | struct z3fold_pool; |
73 | struct z3fold_ops { | |
74 | int (*evict)(struct z3fold_pool *pool, unsigned long handle); | |
75 | }; | |
76 | ||
77 | enum buddy { | |
78 | HEADLESS = 0, | |
79 | FIRST, | |
80 | MIDDLE, | |
81 | LAST, | |
7c2b8baa VW |
82 | BUDDIES_MAX = LAST |
83 | }; | |
84 | ||
85 | struct z3fold_buddy_slots { | |
86 | /* | |
87 | * we are using BUDDY_MASK in handle_to_buddy etc. so there should | |
88 | * be enough slots to hold all possible variants | |
89 | */ | |
90 | unsigned long slot[BUDDY_MASK + 1]; | |
91 | unsigned long pool; /* back link + flags */ | |
ede93213 | 92 | }; |
7c2b8baa | 93 | #define HANDLE_FLAG_MASK (0x03) |
ede93213 VW |
94 | |
95 | /* | |
d30561c5 | 96 | * struct z3fold_header - z3fold page metadata occupying first chunks of each |
ede93213 | 97 | * z3fold page, except for HEADLESS pages |
d30561c5 VW |
98 | * @buddy: links the z3fold page into the relevant list in the |
99 | * pool | |
2f1e5e4d | 100 | * @page_lock: per-page lock |
d30561c5 VW |
101 | * @refcount: reference count for the z3fold page |
102 | * @work: work_struct for page layout optimization | |
7c2b8baa | 103 | * @slots: pointer to the structure holding buddy slots |
bb9a374d | 104 | * @pool: pointer to the containing pool |
d30561c5 | 105 | * @cpu: CPU which this page "belongs" to |
ede93213 VW |
106 | * @first_chunks: the size of the first buddy in chunks, 0 if free |
107 | * @middle_chunks: the size of the middle buddy in chunks, 0 if free | |
108 | * @last_chunks: the size of the last buddy in chunks, 0 if free | |
109 | * @first_num: the starting number (for the first handle) | |
1f862989 | 110 | * @mapped_count: the number of objects currently mapped |
ede93213 VW |
111 | */ |
112 | struct z3fold_header { | |
113 | struct list_head buddy; | |
2f1e5e4d | 114 | spinlock_t page_lock; |
5a27aa82 | 115 | struct kref refcount; |
d30561c5 | 116 | struct work_struct work; |
7c2b8baa | 117 | struct z3fold_buddy_slots *slots; |
bb9a374d | 118 | struct z3fold_pool *pool; |
d30561c5 | 119 | short cpu; |
ede93213 VW |
120 | unsigned short first_chunks; |
121 | unsigned short middle_chunks; | |
122 | unsigned short last_chunks; | |
123 | unsigned short start_middle; | |
124 | unsigned short first_num:2; | |
1f862989 | 125 | unsigned short mapped_count:2; |
ede93213 VW |
126 | }; |
127 | ||
9a001fc1 VW |
128 | /** |
129 | * struct z3fold_pool - stores metadata for each z3fold pool | |
d30561c5 VW |
130 | * @name: pool name |
131 | * @lock: protects pool unbuddied/lru lists | |
132 | * @stale_lock: protects pool stale page list | |
133 | * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2- | |
134 | * buddies; the list each z3fold page is added to depends on | |
135 | * the size of its free region. | |
9a001fc1 VW |
136 | * @lru: list tracking the z3fold pages in LRU order by most recently |
137 | * added buddy. | |
d30561c5 | 138 | * @stale: list of pages marked for freeing |
9a001fc1 | 139 | * @pages_nr: number of z3fold pages in the pool. |
7c2b8baa | 140 | * @c_handle: cache for z3fold_buddy_slots allocation |
9a001fc1 VW |
141 | * @ops: pointer to a structure of user defined operations specified at |
142 | * pool creation time. | |
d30561c5 VW |
143 | * @compact_wq: workqueue for page layout background optimization |
144 | * @release_wq: workqueue for safe page release | |
145 | * @work: work_struct for safe page release | |
1f862989 | 146 | * @inode: inode for z3fold pseudo filesystem |
9a001fc1 VW |
147 | * |
148 | * This structure is allocated at pool creation time and maintains metadata | |
149 | * pertaining to a particular z3fold pool. | |
150 | */ | |
151 | struct z3fold_pool { | |
d30561c5 | 152 | const char *name; |
9a001fc1 | 153 | spinlock_t lock; |
d30561c5 VW |
154 | spinlock_t stale_lock; |
155 | struct list_head *unbuddied; | |
9a001fc1 | 156 | struct list_head lru; |
d30561c5 | 157 | struct list_head stale; |
12d59ae6 | 158 | atomic64_t pages_nr; |
7c2b8baa | 159 | struct kmem_cache *c_handle; |
9a001fc1 VW |
160 | const struct z3fold_ops *ops; |
161 | struct zpool *zpool; | |
162 | const struct zpool_ops *zpool_ops; | |
d30561c5 VW |
163 | struct workqueue_struct *compact_wq; |
164 | struct workqueue_struct *release_wq; | |
165 | struct work_struct work; | |
1f862989 | 166 | struct inode *inode; |
9a001fc1 VW |
167 | }; |
168 | ||
9a001fc1 VW |
169 | /* |
170 | * Internal z3fold page flags | |
171 | */ | |
172 | enum z3fold_page_flags { | |
5a27aa82 | 173 | PAGE_HEADLESS = 0, |
9a001fc1 | 174 | MIDDLE_CHUNK_MAPPED, |
d30561c5 | 175 | NEEDS_COMPACTING, |
6098d7e1 | 176 | PAGE_STALE, |
ca0246bb | 177 | PAGE_CLAIMED, /* by either reclaim or free */ |
9a001fc1 VW |
178 | }; |
179 | ||
180 | /***************** | |
181 | * Helpers | |
182 | *****************/ | |
183 | ||
184 | /* Converts an allocation size in bytes to size in z3fold chunks */ | |
185 | static int size_to_chunks(size_t size) | |
186 | { | |
187 | return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT; | |
188 | } | |
189 | ||
190 | #define for_each_unbuddied_list(_iter, _begin) \ | |
191 | for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++) | |
192 | ||
d30561c5 VW |
193 | static void compact_page_work(struct work_struct *w); |
194 | ||
bb9f6f63 VW |
195 | static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool, |
196 | gfp_t gfp) | |
7c2b8baa VW |
197 | { |
198 | struct z3fold_buddy_slots *slots = kmem_cache_alloc(pool->c_handle, | |
bb9f6f63 | 199 | gfp); |
7c2b8baa VW |
200 | |
201 | if (slots) { | |
202 | memset(slots->slot, 0, sizeof(slots->slot)); | |
203 | slots->pool = (unsigned long)pool; | |
204 | } | |
205 | ||
206 | return slots; | |
207 | } | |
208 | ||
209 | static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s) | |
210 | { | |
211 | return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK); | |
212 | } | |
213 | ||
214 | static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle) | |
215 | { | |
216 | return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1)); | |
217 | } | |
218 | ||
219 | static inline void free_handle(unsigned long handle) | |
220 | { | |
221 | struct z3fold_buddy_slots *slots; | |
222 | int i; | |
223 | bool is_free; | |
224 | ||
225 | if (handle & (1 << PAGE_HEADLESS)) | |
226 | return; | |
227 | ||
228 | WARN_ON(*(unsigned long *)handle == 0); | |
229 | *(unsigned long *)handle = 0; | |
230 | slots = handle_to_slots(handle); | |
231 | is_free = true; | |
232 | for (i = 0; i <= BUDDY_MASK; i++) { | |
233 | if (slots->slot[i]) { | |
234 | is_free = false; | |
235 | break; | |
236 | } | |
237 | } | |
238 | ||
239 | if (is_free) { | |
240 | struct z3fold_pool *pool = slots_to_pool(slots); | |
241 | ||
242 | kmem_cache_free(pool->c_handle, slots); | |
243 | } | |
244 | } | |
245 | ||
1f862989 VW |
246 | static struct dentry *z3fold_do_mount(struct file_system_type *fs_type, |
247 | int flags, const char *dev_name, void *data) | |
248 | { | |
249 | static const struct dentry_operations ops = { | |
250 | .d_dname = simple_dname, | |
251 | }; | |
252 | ||
253 | return mount_pseudo(fs_type, "z3fold:", NULL, &ops, 0x33); | |
254 | } | |
255 | ||
256 | static struct file_system_type z3fold_fs = { | |
257 | .name = "z3fold", | |
258 | .mount = z3fold_do_mount, | |
259 | .kill_sb = kill_anon_super, | |
260 | }; | |
261 | ||
262 | static struct vfsmount *z3fold_mnt; | |
263 | static int z3fold_mount(void) | |
264 | { | |
265 | int ret = 0; | |
266 | ||
267 | z3fold_mnt = kern_mount(&z3fold_fs); | |
268 | if (IS_ERR(z3fold_mnt)) | |
269 | ret = PTR_ERR(z3fold_mnt); | |
270 | ||
271 | return ret; | |
272 | } | |
273 | ||
274 | static void z3fold_unmount(void) | |
275 | { | |
276 | kern_unmount(z3fold_mnt); | |
277 | } | |
278 | ||
279 | static const struct address_space_operations z3fold_aops; | |
280 | static int z3fold_register_migration(struct z3fold_pool *pool) | |
281 | { | |
282 | pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb); | |
283 | if (IS_ERR(pool->inode)) { | |
284 | pool->inode = NULL; | |
285 | return 1; | |
286 | } | |
287 | ||
288 | pool->inode->i_mapping->private_data = pool; | |
289 | pool->inode->i_mapping->a_ops = &z3fold_aops; | |
290 | return 0; | |
291 | } | |
292 | ||
293 | static void z3fold_unregister_migration(struct z3fold_pool *pool) | |
294 | { | |
295 | if (pool->inode) | |
296 | iput(pool->inode); | |
297 | } | |
298 | ||
9a001fc1 | 299 | /* Initializes the z3fold header of a newly allocated z3fold page */ |
d30561c5 | 300 | static struct z3fold_header *init_z3fold_page(struct page *page, |
bb9f6f63 | 301 | struct z3fold_pool *pool, gfp_t gfp) |
9a001fc1 VW |
302 | { |
303 | struct z3fold_header *zhdr = page_address(page); | |
bb9f6f63 | 304 | struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp); |
7c2b8baa VW |
305 | |
306 | if (!slots) | |
307 | return NULL; | |
9a001fc1 VW |
308 | |
309 | INIT_LIST_HEAD(&page->lru); | |
9a001fc1 VW |
310 | clear_bit(PAGE_HEADLESS, &page->private); |
311 | clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); | |
d30561c5 VW |
312 | clear_bit(NEEDS_COMPACTING, &page->private); |
313 | clear_bit(PAGE_STALE, &page->private); | |
ca0246bb | 314 | clear_bit(PAGE_CLAIMED, &page->private); |
9a001fc1 | 315 | |
2f1e5e4d | 316 | spin_lock_init(&zhdr->page_lock); |
5a27aa82 | 317 | kref_init(&zhdr->refcount); |
9a001fc1 VW |
318 | zhdr->first_chunks = 0; |
319 | zhdr->middle_chunks = 0; | |
320 | zhdr->last_chunks = 0; | |
321 | zhdr->first_num = 0; | |
322 | zhdr->start_middle = 0; | |
d30561c5 | 323 | zhdr->cpu = -1; |
7c2b8baa | 324 | zhdr->slots = slots; |
bb9a374d | 325 | zhdr->pool = pool; |
9a001fc1 | 326 | INIT_LIST_HEAD(&zhdr->buddy); |
d30561c5 | 327 | INIT_WORK(&zhdr->work, compact_page_work); |
9a001fc1 VW |
328 | return zhdr; |
329 | } | |
330 | ||
331 | /* Resets the struct page fields and frees the page */ | |
1f862989 | 332 | static void free_z3fold_page(struct page *page, bool headless) |
9a001fc1 | 333 | { |
1f862989 VW |
334 | if (!headless) { |
335 | lock_page(page); | |
336 | __ClearPageMovable(page); | |
337 | unlock_page(page); | |
338 | } | |
339 | ClearPagePrivate(page); | |
5a27aa82 VW |
340 | __free_page(page); |
341 | } | |
342 | ||
2f1e5e4d VW |
343 | /* Lock a z3fold page */ |
344 | static inline void z3fold_page_lock(struct z3fold_header *zhdr) | |
345 | { | |
346 | spin_lock(&zhdr->page_lock); | |
347 | } | |
348 | ||
76e32a2a VW |
349 | /* Try to lock a z3fold page */ |
350 | static inline int z3fold_page_trylock(struct z3fold_header *zhdr) | |
351 | { | |
352 | return spin_trylock(&zhdr->page_lock); | |
353 | } | |
354 | ||
2f1e5e4d VW |
355 | /* Unlock a z3fold page */ |
356 | static inline void z3fold_page_unlock(struct z3fold_header *zhdr) | |
357 | { | |
358 | spin_unlock(&zhdr->page_lock); | |
359 | } | |
360 | ||
7c2b8baa VW |
361 | /* Helper function to build the index */ |
362 | static inline int __idx(struct z3fold_header *zhdr, enum buddy bud) | |
363 | { | |
364 | return (bud + zhdr->first_num) & BUDDY_MASK; | |
365 | } | |
366 | ||
9a001fc1 VW |
367 | /* |
368 | * Encodes the handle of a particular buddy within a z3fold page | |
369 | * Pool lock should be held as this function accesses first_num | |
370 | */ | |
371 | static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud) | |
372 | { | |
7c2b8baa VW |
373 | struct z3fold_buddy_slots *slots; |
374 | unsigned long h = (unsigned long)zhdr; | |
375 | int idx = 0; | |
9a001fc1 | 376 | |
7c2b8baa VW |
377 | /* |
378 | * For a headless page, its handle is its pointer with the extra | |
379 | * PAGE_HEADLESS bit set | |
380 | */ | |
381 | if (bud == HEADLESS) | |
382 | return h | (1 << PAGE_HEADLESS); | |
383 | ||
384 | /* otherwise, return pointer to encoded handle */ | |
385 | idx = __idx(zhdr, bud); | |
386 | h += idx; | |
387 | if (bud == LAST) | |
388 | h |= (zhdr->last_chunks << BUDDY_SHIFT); | |
389 | ||
390 | slots = zhdr->slots; | |
391 | slots->slot[idx] = h; | |
392 | return (unsigned long)&slots->slot[idx]; | |
9a001fc1 VW |
393 | } |
394 | ||
395 | /* Returns the z3fold page where a given handle is stored */ | |
1f862989 | 396 | static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h) |
9a001fc1 | 397 | { |
1f862989 | 398 | unsigned long addr = h; |
7c2b8baa VW |
399 | |
400 | if (!(addr & (1 << PAGE_HEADLESS))) | |
1f862989 | 401 | addr = *(unsigned long *)h; |
7c2b8baa VW |
402 | |
403 | return (struct z3fold_header *)(addr & PAGE_MASK); | |
9a001fc1 VW |
404 | } |
405 | ||
ca0246bb VW |
406 | /* only for LAST bud, returns zero otherwise */ |
407 | static unsigned short handle_to_chunks(unsigned long handle) | |
408 | { | |
7c2b8baa VW |
409 | unsigned long addr = *(unsigned long *)handle; |
410 | ||
411 | return (addr & ~PAGE_MASK) >> BUDDY_SHIFT; | |
ca0246bb VW |
412 | } |
413 | ||
f201ebd8 | 414 | /* |
415 | * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle | |
416 | * but that doesn't matter. because the masking will result in the | |
417 | * correct buddy number. | |
418 | */ | |
9a001fc1 VW |
419 | static enum buddy handle_to_buddy(unsigned long handle) |
420 | { | |
7c2b8baa VW |
421 | struct z3fold_header *zhdr; |
422 | unsigned long addr; | |
423 | ||
424 | WARN_ON(handle & (1 << PAGE_HEADLESS)); | |
425 | addr = *(unsigned long *)handle; | |
426 | zhdr = (struct z3fold_header *)(addr & PAGE_MASK); | |
427 | return (addr - zhdr->first_num) & BUDDY_MASK; | |
9a001fc1 VW |
428 | } |
429 | ||
9050cce1 VW |
430 | static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr) |
431 | { | |
bb9a374d | 432 | return zhdr->pool; |
9050cce1 VW |
433 | } |
434 | ||
d30561c5 VW |
435 | static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked) |
436 | { | |
437 | struct page *page = virt_to_page(zhdr); | |
9050cce1 | 438 | struct z3fold_pool *pool = zhdr_to_pool(zhdr); |
d30561c5 VW |
439 | |
440 | WARN_ON(!list_empty(&zhdr->buddy)); | |
441 | set_bit(PAGE_STALE, &page->private); | |
35529357 | 442 | clear_bit(NEEDS_COMPACTING, &page->private); |
d30561c5 VW |
443 | spin_lock(&pool->lock); |
444 | if (!list_empty(&page->lru)) | |
1f862989 | 445 | list_del_init(&page->lru); |
d30561c5 VW |
446 | spin_unlock(&pool->lock); |
447 | if (locked) | |
448 | z3fold_page_unlock(zhdr); | |
449 | spin_lock(&pool->stale_lock); | |
450 | list_add(&zhdr->buddy, &pool->stale); | |
451 | queue_work(pool->release_wq, &pool->work); | |
452 | spin_unlock(&pool->stale_lock); | |
453 | } | |
454 | ||
455 | static void __attribute__((__unused__)) | |
456 | release_z3fold_page(struct kref *ref) | |
457 | { | |
458 | struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, | |
459 | refcount); | |
460 | __release_z3fold_page(zhdr, false); | |
461 | } | |
462 | ||
463 | static void release_z3fold_page_locked(struct kref *ref) | |
464 | { | |
465 | struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, | |
466 | refcount); | |
467 | WARN_ON(z3fold_page_trylock(zhdr)); | |
468 | __release_z3fold_page(zhdr, true); | |
469 | } | |
470 | ||
471 | static void release_z3fold_page_locked_list(struct kref *ref) | |
472 | { | |
473 | struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, | |
474 | refcount); | |
9050cce1 VW |
475 | struct z3fold_pool *pool = zhdr_to_pool(zhdr); |
476 | spin_lock(&pool->lock); | |
d30561c5 | 477 | list_del_init(&zhdr->buddy); |
9050cce1 | 478 | spin_unlock(&pool->lock); |
d30561c5 VW |
479 | |
480 | WARN_ON(z3fold_page_trylock(zhdr)); | |
481 | __release_z3fold_page(zhdr, true); | |
482 | } | |
483 | ||
484 | static void free_pages_work(struct work_struct *w) | |
485 | { | |
486 | struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work); | |
487 | ||
488 | spin_lock(&pool->stale_lock); | |
489 | while (!list_empty(&pool->stale)) { | |
490 | struct z3fold_header *zhdr = list_first_entry(&pool->stale, | |
491 | struct z3fold_header, buddy); | |
492 | struct page *page = virt_to_page(zhdr); | |
493 | ||
494 | list_del(&zhdr->buddy); | |
495 | if (WARN_ON(!test_bit(PAGE_STALE, &page->private))) | |
496 | continue; | |
d30561c5 VW |
497 | spin_unlock(&pool->stale_lock); |
498 | cancel_work_sync(&zhdr->work); | |
1f862989 | 499 | free_z3fold_page(page, false); |
d30561c5 VW |
500 | cond_resched(); |
501 | spin_lock(&pool->stale_lock); | |
502 | } | |
503 | spin_unlock(&pool->stale_lock); | |
504 | } | |
505 | ||
9a001fc1 VW |
506 | /* |
507 | * Returns the number of free chunks in a z3fold page. | |
508 | * NB: can't be used with HEADLESS pages. | |
509 | */ | |
510 | static int num_free_chunks(struct z3fold_header *zhdr) | |
511 | { | |
512 | int nfree; | |
513 | /* | |
514 | * If there is a middle object, pick up the bigger free space | |
515 | * either before or after it. Otherwise just subtract the number | |
516 | * of chunks occupied by the first and the last objects. | |
517 | */ | |
518 | if (zhdr->middle_chunks != 0) { | |
519 | int nfree_before = zhdr->first_chunks ? | |
ede93213 | 520 | 0 : zhdr->start_middle - ZHDR_CHUNKS; |
9a001fc1 | 521 | int nfree_after = zhdr->last_chunks ? |
ede93213 VW |
522 | 0 : TOTAL_CHUNKS - |
523 | (zhdr->start_middle + zhdr->middle_chunks); | |
9a001fc1 VW |
524 | nfree = max(nfree_before, nfree_after); |
525 | } else | |
526 | nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks; | |
527 | return nfree; | |
528 | } | |
529 | ||
9050cce1 VW |
530 | /* Add to the appropriate unbuddied list */ |
531 | static inline void add_to_unbuddied(struct z3fold_pool *pool, | |
532 | struct z3fold_header *zhdr) | |
533 | { | |
534 | if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 || | |
535 | zhdr->middle_chunks == 0) { | |
536 | struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied); | |
537 | ||
538 | int freechunks = num_free_chunks(zhdr); | |
539 | spin_lock(&pool->lock); | |
540 | list_add(&zhdr->buddy, &unbuddied[freechunks]); | |
541 | spin_unlock(&pool->lock); | |
542 | zhdr->cpu = smp_processor_id(); | |
543 | put_cpu_ptr(pool->unbuddied); | |
544 | } | |
545 | } | |
546 | ||
ede93213 VW |
547 | static inline void *mchunk_memmove(struct z3fold_header *zhdr, |
548 | unsigned short dst_chunk) | |
549 | { | |
550 | void *beg = zhdr; | |
551 | return memmove(beg + (dst_chunk << CHUNK_SHIFT), | |
552 | beg + (zhdr->start_middle << CHUNK_SHIFT), | |
553 | zhdr->middle_chunks << CHUNK_SHIFT); | |
554 | } | |
555 | ||
1b096e5a | 556 | #define BIG_CHUNK_GAP 3 |
9a001fc1 VW |
557 | /* Has to be called with lock held */ |
558 | static int z3fold_compact_page(struct z3fold_header *zhdr) | |
559 | { | |
560 | struct page *page = virt_to_page(zhdr); | |
9a001fc1 | 561 | |
ede93213 VW |
562 | if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private)) |
563 | return 0; /* can't move middle chunk, it's used */ | |
9a001fc1 | 564 | |
1f862989 VW |
565 | if (unlikely(PageIsolated(page))) |
566 | return 0; | |
567 | ||
ede93213 VW |
568 | if (zhdr->middle_chunks == 0) |
569 | return 0; /* nothing to compact */ | |
570 | ||
571 | if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { | |
572 | /* move to the beginning */ | |
573 | mchunk_memmove(zhdr, ZHDR_CHUNKS); | |
9a001fc1 VW |
574 | zhdr->first_chunks = zhdr->middle_chunks; |
575 | zhdr->middle_chunks = 0; | |
576 | zhdr->start_middle = 0; | |
577 | zhdr->first_num++; | |
1b096e5a | 578 | return 1; |
9a001fc1 | 579 | } |
1b096e5a VW |
580 | |
581 | /* | |
582 | * moving data is expensive, so let's only do that if | |
583 | * there's substantial gain (at least BIG_CHUNK_GAP chunks) | |
584 | */ | |
585 | if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 && | |
586 | zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >= | |
587 | BIG_CHUNK_GAP) { | |
588 | mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS); | |
589 | zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; | |
590 | return 1; | |
591 | } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 && | |
592 | TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle | |
593 | + zhdr->middle_chunks) >= | |
594 | BIG_CHUNK_GAP) { | |
595 | unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks - | |
596 | zhdr->middle_chunks; | |
597 | mchunk_memmove(zhdr, new_start); | |
598 | zhdr->start_middle = new_start; | |
599 | return 1; | |
600 | } | |
601 | ||
602 | return 0; | |
9a001fc1 VW |
603 | } |
604 | ||
d30561c5 VW |
605 | static void do_compact_page(struct z3fold_header *zhdr, bool locked) |
606 | { | |
9050cce1 | 607 | struct z3fold_pool *pool = zhdr_to_pool(zhdr); |
d30561c5 | 608 | struct page *page; |
d30561c5 VW |
609 | |
610 | page = virt_to_page(zhdr); | |
611 | if (locked) | |
612 | WARN_ON(z3fold_page_trylock(zhdr)); | |
613 | else | |
614 | z3fold_page_lock(zhdr); | |
5d03a661 | 615 | if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) { |
d30561c5 VW |
616 | z3fold_page_unlock(zhdr); |
617 | return; | |
618 | } | |
619 | spin_lock(&pool->lock); | |
620 | list_del_init(&zhdr->buddy); | |
621 | spin_unlock(&pool->lock); | |
622 | ||
5d03a661 VW |
623 | if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { |
624 | atomic64_dec(&pool->pages_nr); | |
625 | return; | |
626 | } | |
627 | ||
1f862989 VW |
628 | if (unlikely(PageIsolated(page) || |
629 | test_bit(PAGE_STALE, &page->private))) { | |
630 | z3fold_page_unlock(zhdr); | |
631 | return; | |
632 | } | |
633 | ||
d30561c5 | 634 | z3fold_compact_page(zhdr); |
9050cce1 | 635 | add_to_unbuddied(pool, zhdr); |
d30561c5 VW |
636 | z3fold_page_unlock(zhdr); |
637 | } | |
638 | ||
639 | static void compact_page_work(struct work_struct *w) | |
640 | { | |
641 | struct z3fold_header *zhdr = container_of(w, struct z3fold_header, | |
642 | work); | |
643 | ||
644 | do_compact_page(zhdr, false); | |
645 | } | |
646 | ||
9050cce1 VW |
647 | /* returns _locked_ z3fold page header or NULL */ |
648 | static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool, | |
649 | size_t size, bool can_sleep) | |
650 | { | |
651 | struct z3fold_header *zhdr = NULL; | |
652 | struct page *page; | |
653 | struct list_head *unbuddied; | |
654 | int chunks = size_to_chunks(size), i; | |
655 | ||
656 | lookup: | |
657 | /* First, try to find an unbuddied z3fold page. */ | |
658 | unbuddied = get_cpu_ptr(pool->unbuddied); | |
659 | for_each_unbuddied_list(i, chunks) { | |
660 | struct list_head *l = &unbuddied[i]; | |
661 | ||
662 | zhdr = list_first_entry_or_null(READ_ONCE(l), | |
663 | struct z3fold_header, buddy); | |
664 | ||
665 | if (!zhdr) | |
666 | continue; | |
667 | ||
668 | /* Re-check under lock. */ | |
669 | spin_lock(&pool->lock); | |
670 | l = &unbuddied[i]; | |
671 | if (unlikely(zhdr != list_first_entry(READ_ONCE(l), | |
672 | struct z3fold_header, buddy)) || | |
673 | !z3fold_page_trylock(zhdr)) { | |
674 | spin_unlock(&pool->lock); | |
675 | zhdr = NULL; | |
676 | put_cpu_ptr(pool->unbuddied); | |
677 | if (can_sleep) | |
678 | cond_resched(); | |
679 | goto lookup; | |
680 | } | |
681 | list_del_init(&zhdr->buddy); | |
682 | zhdr->cpu = -1; | |
683 | spin_unlock(&pool->lock); | |
684 | ||
685 | page = virt_to_page(zhdr); | |
686 | if (test_bit(NEEDS_COMPACTING, &page->private)) { | |
687 | z3fold_page_unlock(zhdr); | |
688 | zhdr = NULL; | |
689 | put_cpu_ptr(pool->unbuddied); | |
690 | if (can_sleep) | |
691 | cond_resched(); | |
692 | goto lookup; | |
693 | } | |
694 | ||
695 | /* | |
696 | * this page could not be removed from its unbuddied | |
697 | * list while pool lock was held, and then we've taken | |
698 | * page lock so kref_put could not be called before | |
699 | * we got here, so it's safe to just call kref_get() | |
700 | */ | |
701 | kref_get(&zhdr->refcount); | |
702 | break; | |
703 | } | |
704 | put_cpu_ptr(pool->unbuddied); | |
705 | ||
351618b2 VW |
706 | if (!zhdr) { |
707 | int cpu; | |
708 | ||
709 | /* look for _exact_ match on other cpus' lists */ | |
710 | for_each_online_cpu(cpu) { | |
711 | struct list_head *l; | |
712 | ||
713 | unbuddied = per_cpu_ptr(pool->unbuddied, cpu); | |
714 | spin_lock(&pool->lock); | |
715 | l = &unbuddied[chunks]; | |
716 | ||
717 | zhdr = list_first_entry_or_null(READ_ONCE(l), | |
718 | struct z3fold_header, buddy); | |
719 | ||
720 | if (!zhdr || !z3fold_page_trylock(zhdr)) { | |
721 | spin_unlock(&pool->lock); | |
722 | zhdr = NULL; | |
723 | continue; | |
724 | } | |
725 | list_del_init(&zhdr->buddy); | |
726 | zhdr->cpu = -1; | |
727 | spin_unlock(&pool->lock); | |
728 | ||
729 | page = virt_to_page(zhdr); | |
730 | if (test_bit(NEEDS_COMPACTING, &page->private)) { | |
731 | z3fold_page_unlock(zhdr); | |
732 | zhdr = NULL; | |
733 | if (can_sleep) | |
734 | cond_resched(); | |
735 | continue; | |
736 | } | |
737 | kref_get(&zhdr->refcount); | |
738 | break; | |
739 | } | |
740 | } | |
741 | ||
9050cce1 VW |
742 | return zhdr; |
743 | } | |
d30561c5 VW |
744 | |
745 | /* | |
746 | * API Functions | |
747 | */ | |
748 | ||
749 | /** | |
750 | * z3fold_create_pool() - create a new z3fold pool | |
751 | * @name: pool name | |
752 | * @gfp: gfp flags when allocating the z3fold pool structure | |
753 | * @ops: user-defined operations for the z3fold pool | |
754 | * | |
755 | * Return: pointer to the new z3fold pool or NULL if the metadata allocation | |
756 | * failed. | |
757 | */ | |
758 | static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, | |
759 | const struct z3fold_ops *ops) | |
760 | { | |
761 | struct z3fold_pool *pool = NULL; | |
762 | int i, cpu; | |
763 | ||
764 | pool = kzalloc(sizeof(struct z3fold_pool), gfp); | |
765 | if (!pool) | |
766 | goto out; | |
7c2b8baa VW |
767 | pool->c_handle = kmem_cache_create("z3fold_handle", |
768 | sizeof(struct z3fold_buddy_slots), | |
769 | SLOTS_ALIGN, 0, NULL); | |
770 | if (!pool->c_handle) | |
771 | goto out_c; | |
d30561c5 VW |
772 | spin_lock_init(&pool->lock); |
773 | spin_lock_init(&pool->stale_lock); | |
774 | pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2); | |
1ec6995d XW |
775 | if (!pool->unbuddied) |
776 | goto out_pool; | |
d30561c5 VW |
777 | for_each_possible_cpu(cpu) { |
778 | struct list_head *unbuddied = | |
779 | per_cpu_ptr(pool->unbuddied, cpu); | |
780 | for_each_unbuddied_list(i, 0) | |
781 | INIT_LIST_HEAD(&unbuddied[i]); | |
782 | } | |
783 | INIT_LIST_HEAD(&pool->lru); | |
784 | INIT_LIST_HEAD(&pool->stale); | |
785 | atomic64_set(&pool->pages_nr, 0); | |
786 | pool->name = name; | |
787 | pool->compact_wq = create_singlethread_workqueue(pool->name); | |
788 | if (!pool->compact_wq) | |
1ec6995d | 789 | goto out_unbuddied; |
d30561c5 VW |
790 | pool->release_wq = create_singlethread_workqueue(pool->name); |
791 | if (!pool->release_wq) | |
792 | goto out_wq; | |
1f862989 VW |
793 | if (z3fold_register_migration(pool)) |
794 | goto out_rwq; | |
d30561c5 VW |
795 | INIT_WORK(&pool->work, free_pages_work); |
796 | pool->ops = ops; | |
797 | return pool; | |
798 | ||
1f862989 VW |
799 | out_rwq: |
800 | destroy_workqueue(pool->release_wq); | |
d30561c5 VW |
801 | out_wq: |
802 | destroy_workqueue(pool->compact_wq); | |
1ec6995d XW |
803 | out_unbuddied: |
804 | free_percpu(pool->unbuddied); | |
805 | out_pool: | |
7c2b8baa VW |
806 | kmem_cache_destroy(pool->c_handle); |
807 | out_c: | |
d30561c5 | 808 | kfree(pool); |
1ec6995d | 809 | out: |
d30561c5 VW |
810 | return NULL; |
811 | } | |
812 | ||
813 | /** | |
814 | * z3fold_destroy_pool() - destroys an existing z3fold pool | |
815 | * @pool: the z3fold pool to be destroyed | |
816 | * | |
817 | * The pool should be emptied before this function is called. | |
818 | */ | |
819 | static void z3fold_destroy_pool(struct z3fold_pool *pool) | |
820 | { | |
7c2b8baa | 821 | kmem_cache_destroy(pool->c_handle); |
1f862989 | 822 | z3fold_unregister_migration(pool); |
d30561c5 VW |
823 | destroy_workqueue(pool->release_wq); |
824 | destroy_workqueue(pool->compact_wq); | |
825 | kfree(pool); | |
826 | } | |
827 | ||
9a001fc1 VW |
828 | /** |
829 | * z3fold_alloc() - allocates a region of a given size | |
830 | * @pool: z3fold pool from which to allocate | |
831 | * @size: size in bytes of the desired allocation | |
832 | * @gfp: gfp flags used if the pool needs to grow | |
833 | * @handle: handle of the new allocation | |
834 | * | |
835 | * This function will attempt to find a free region in the pool large enough to | |
836 | * satisfy the allocation request. A search of the unbuddied lists is | |
837 | * performed first. If no suitable free region is found, then a new page is | |
838 | * allocated and added to the pool to satisfy the request. | |
839 | * | |
840 | * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used | |
841 | * as z3fold pool pages. | |
842 | * | |
843 | * Return: 0 if success and handle is set, otherwise -EINVAL if the size or | |
844 | * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate | |
845 | * a new page. | |
846 | */ | |
847 | static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, | |
848 | unsigned long *handle) | |
849 | { | |
9050cce1 | 850 | int chunks = size_to_chunks(size); |
9a001fc1 | 851 | struct z3fold_header *zhdr = NULL; |
d30561c5 | 852 | struct page *page = NULL; |
9a001fc1 | 853 | enum buddy bud; |
8a97ea54 | 854 | bool can_sleep = gfpflags_allow_blocking(gfp); |
9a001fc1 VW |
855 | |
856 | if (!size || (gfp & __GFP_HIGHMEM)) | |
857 | return -EINVAL; | |
858 | ||
859 | if (size > PAGE_SIZE) | |
860 | return -ENOSPC; | |
861 | ||
862 | if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) | |
863 | bud = HEADLESS; | |
864 | else { | |
9050cce1 VW |
865 | retry: |
866 | zhdr = __z3fold_alloc(pool, size, can_sleep); | |
d30561c5 | 867 | if (zhdr) { |
2f1e5e4d VW |
868 | if (zhdr->first_chunks == 0) { |
869 | if (zhdr->middle_chunks != 0 && | |
870 | chunks >= zhdr->start_middle) | |
9a001fc1 | 871 | bud = LAST; |
2f1e5e4d VW |
872 | else |
873 | bud = FIRST; | |
874 | } else if (zhdr->last_chunks == 0) | |
875 | bud = LAST; | |
876 | else if (zhdr->middle_chunks == 0) | |
877 | bud = MIDDLE; | |
878 | else { | |
5a27aa82 | 879 | if (kref_put(&zhdr->refcount, |
d30561c5 | 880 | release_z3fold_page_locked)) |
5a27aa82 | 881 | atomic64_dec(&pool->pages_nr); |
d30561c5 VW |
882 | else |
883 | z3fold_page_unlock(zhdr); | |
2f1e5e4d VW |
884 | pr_err("No free chunks in unbuddied\n"); |
885 | WARN_ON(1); | |
9050cce1 | 886 | goto retry; |
9a001fc1 | 887 | } |
9050cce1 | 888 | page = virt_to_page(zhdr); |
2f1e5e4d | 889 | goto found; |
9a001fc1 VW |
890 | } |
891 | bud = FIRST; | |
9a001fc1 VW |
892 | } |
893 | ||
5c9bab59 VW |
894 | page = NULL; |
895 | if (can_sleep) { | |
896 | spin_lock(&pool->stale_lock); | |
897 | zhdr = list_first_entry_or_null(&pool->stale, | |
898 | struct z3fold_header, buddy); | |
899 | /* | |
900 | * Before allocating a page, let's see if we can take one from | |
901 | * the stale pages list. cancel_work_sync() can sleep so we | |
902 | * limit this case to the contexts where we can sleep | |
903 | */ | |
904 | if (zhdr) { | |
905 | list_del(&zhdr->buddy); | |
906 | spin_unlock(&pool->stale_lock); | |
d30561c5 | 907 | cancel_work_sync(&zhdr->work); |
5c9bab59 VW |
908 | page = virt_to_page(zhdr); |
909 | } else { | |
910 | spin_unlock(&pool->stale_lock); | |
911 | } | |
d30561c5 | 912 | } |
5c9bab59 VW |
913 | if (!page) |
914 | page = alloc_page(gfp); | |
d30561c5 | 915 | |
9a001fc1 VW |
916 | if (!page) |
917 | return -ENOMEM; | |
2f1e5e4d | 918 | |
bb9f6f63 | 919 | zhdr = init_z3fold_page(page, pool, gfp); |
9050cce1 VW |
920 | if (!zhdr) { |
921 | __free_page(page); | |
922 | return -ENOMEM; | |
923 | } | |
924 | atomic64_inc(&pool->pages_nr); | |
9a001fc1 VW |
925 | |
926 | if (bud == HEADLESS) { | |
927 | set_bit(PAGE_HEADLESS, &page->private); | |
928 | goto headless; | |
929 | } | |
810481a2 HB |
930 | if (can_sleep) { |
931 | lock_page(page); | |
932 | __SetPageMovable(page, pool->inode->i_mapping); | |
933 | unlock_page(page); | |
934 | } else { | |
935 | if (trylock_page(page)) { | |
936 | __SetPageMovable(page, pool->inode->i_mapping); | |
937 | unlock_page(page); | |
938 | } | |
939 | } | |
2f1e5e4d | 940 | z3fold_page_lock(zhdr); |
9a001fc1 VW |
941 | |
942 | found: | |
943 | if (bud == FIRST) | |
944 | zhdr->first_chunks = chunks; | |
945 | else if (bud == LAST) | |
946 | zhdr->last_chunks = chunks; | |
947 | else { | |
948 | zhdr->middle_chunks = chunks; | |
ede93213 | 949 | zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; |
9a001fc1 | 950 | } |
9050cce1 | 951 | add_to_unbuddied(pool, zhdr); |
9a001fc1 VW |
952 | |
953 | headless: | |
d30561c5 | 954 | spin_lock(&pool->lock); |
9a001fc1 VW |
955 | /* Add/move z3fold page to beginning of LRU */ |
956 | if (!list_empty(&page->lru)) | |
957 | list_del(&page->lru); | |
958 | ||
959 | list_add(&page->lru, &pool->lru); | |
960 | ||
961 | *handle = encode_handle(zhdr, bud); | |
962 | spin_unlock(&pool->lock); | |
2f1e5e4d VW |
963 | if (bud != HEADLESS) |
964 | z3fold_page_unlock(zhdr); | |
9a001fc1 VW |
965 | |
966 | return 0; | |
967 | } | |
968 | ||
969 | /** | |
970 | * z3fold_free() - frees the allocation associated with the given handle | |
971 | * @pool: pool in which the allocation resided | |
972 | * @handle: handle associated with the allocation returned by z3fold_alloc() | |
973 | * | |
974 | * In the case that the z3fold page in which the allocation resides is under | |
975 | * reclaim, as indicated by the PG_reclaim flag being set, this function | |
976 | * only sets the first|last_chunks to 0. The page is actually freed | |
977 | * once both buddies are evicted (see z3fold_reclaim_page() below). | |
978 | */ | |
979 | static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) | |
980 | { | |
981 | struct z3fold_header *zhdr; | |
9a001fc1 VW |
982 | struct page *page; |
983 | enum buddy bud; | |
984 | ||
9a001fc1 VW |
985 | zhdr = handle_to_z3fold_header(handle); |
986 | page = virt_to_page(zhdr); | |
987 | ||
988 | if (test_bit(PAGE_HEADLESS, &page->private)) { | |
ca0246bb VW |
989 | /* if a headless page is under reclaim, just leave. |
990 | * NB: we use test_and_set_bit for a reason: if the bit | |
991 | * has not been set before, we release this page | |
992 | * immediately so we don't care about its value any more. | |
993 | */ | |
994 | if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) { | |
995 | spin_lock(&pool->lock); | |
996 | list_del(&page->lru); | |
997 | spin_unlock(&pool->lock); | |
1f862989 | 998 | free_z3fold_page(page, true); |
ca0246bb | 999 | atomic64_dec(&pool->pages_nr); |
9a001fc1 | 1000 | } |
ca0246bb | 1001 | return; |
9a001fc1 VW |
1002 | } |
1003 | ||
ca0246bb VW |
1004 | /* Non-headless case */ |
1005 | z3fold_page_lock(zhdr); | |
1006 | bud = handle_to_buddy(handle); | |
1007 | ||
1008 | switch (bud) { | |
1009 | case FIRST: | |
1010 | zhdr->first_chunks = 0; | |
1011 | break; | |
1012 | case MIDDLE: | |
1013 | zhdr->middle_chunks = 0; | |
1014 | break; | |
1015 | case LAST: | |
1016 | zhdr->last_chunks = 0; | |
1017 | break; | |
1018 | default: | |
1019 | pr_err("%s: unknown bud %d\n", __func__, bud); | |
1020 | WARN_ON(1); | |
1021 | z3fold_page_unlock(zhdr); | |
d30561c5 VW |
1022 | return; |
1023 | } | |
1024 | ||
7c2b8baa | 1025 | free_handle(handle); |
d30561c5 VW |
1026 | if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) { |
1027 | atomic64_dec(&pool->pages_nr); | |
1028 | return; | |
1029 | } | |
ca0246bb | 1030 | if (test_bit(PAGE_CLAIMED, &page->private)) { |
6098d7e1 VW |
1031 | z3fold_page_unlock(zhdr); |
1032 | return; | |
1033 | } | |
1f862989 VW |
1034 | if (unlikely(PageIsolated(page)) || |
1035 | test_and_set_bit(NEEDS_COMPACTING, &page->private)) { | |
5a27aa82 | 1036 | z3fold_page_unlock(zhdr); |
d30561c5 VW |
1037 | return; |
1038 | } | |
1039 | if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { | |
2f1e5e4d | 1040 | spin_lock(&pool->lock); |
d30561c5 | 1041 | list_del_init(&zhdr->buddy); |
2f1e5e4d | 1042 | spin_unlock(&pool->lock); |
d30561c5 | 1043 | zhdr->cpu = -1; |
5d03a661 | 1044 | kref_get(&zhdr->refcount); |
d30561c5 VW |
1045 | do_compact_page(zhdr, true); |
1046 | return; | |
9a001fc1 | 1047 | } |
5d03a661 | 1048 | kref_get(&zhdr->refcount); |
d30561c5 VW |
1049 | queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work); |
1050 | z3fold_page_unlock(zhdr); | |
9a001fc1 VW |
1051 | } |
1052 | ||
1053 | /** | |
1054 | * z3fold_reclaim_page() - evicts allocations from a pool page and frees it | |
1055 | * @pool: pool from which a page will attempt to be evicted | |
f144c390 | 1056 | * @retries: number of pages on the LRU list for which eviction will |
9a001fc1 VW |
1057 | * be attempted before failing |
1058 | * | |
1059 | * z3fold reclaim is different from normal system reclaim in that it is done | |
1060 | * from the bottom, up. This is because only the bottom layer, z3fold, has | |
1061 | * information on how the allocations are organized within each z3fold page. | |
1062 | * This has the potential to create interesting locking situations between | |
1063 | * z3fold and the user, however. | |
1064 | * | |
1065 | * To avoid these, this is how z3fold_reclaim_page() should be called: | |
f144c390 | 1066 | * |
9a001fc1 VW |
1067 | * The user detects a page should be reclaimed and calls z3fold_reclaim_page(). |
1068 | * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and | |
1069 | * call the user-defined eviction handler with the pool and handle as | |
1070 | * arguments. | |
1071 | * | |
1072 | * If the handle can not be evicted, the eviction handler should return | |
1073 | * non-zero. z3fold_reclaim_page() will add the z3fold page back to the | |
1074 | * appropriate list and try the next z3fold page on the LRU up to | |
1075 | * a user defined number of retries. | |
1076 | * | |
1077 | * If the handle is successfully evicted, the eviction handler should | |
1078 | * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free() | |
1079 | * contains logic to delay freeing the page if the page is under reclaim, | |
1080 | * as indicated by the setting of the PG_reclaim flag on the underlying page. | |
1081 | * | |
1082 | * If all buddies in the z3fold page are successfully evicted, then the | |
1083 | * z3fold page can be freed. | |
1084 | * | |
1085 | * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are | |
1086 | * no pages to evict or an eviction handler is not registered, -EAGAIN if | |
1087 | * the retry limit was hit. | |
1088 | */ | |
1089 | static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) | |
1090 | { | |
d30561c5 VW |
1091 | int i, ret = 0; |
1092 | struct z3fold_header *zhdr = NULL; | |
1093 | struct page *page = NULL; | |
1094 | struct list_head *pos; | |
9a001fc1 VW |
1095 | unsigned long first_handle = 0, middle_handle = 0, last_handle = 0; |
1096 | ||
1097 | spin_lock(&pool->lock); | |
2f1e5e4d | 1098 | if (!pool->ops || !pool->ops->evict || retries == 0) { |
9a001fc1 VW |
1099 | spin_unlock(&pool->lock); |
1100 | return -EINVAL; | |
1101 | } | |
1102 | for (i = 0; i < retries; i++) { | |
2f1e5e4d VW |
1103 | if (list_empty(&pool->lru)) { |
1104 | spin_unlock(&pool->lock); | |
1105 | return -EINVAL; | |
1106 | } | |
d30561c5 VW |
1107 | list_for_each_prev(pos, &pool->lru) { |
1108 | page = list_entry(pos, struct page, lru); | |
ca0246bb VW |
1109 | |
1110 | /* this bit could have been set by free, in which case | |
1111 | * we pass over to the next page in the pool. | |
1112 | */ | |
1113 | if (test_and_set_bit(PAGE_CLAIMED, &page->private)) | |
1114 | continue; | |
1115 | ||
1f862989 VW |
1116 | if (unlikely(PageIsolated(page))) |
1117 | continue; | |
d30561c5 | 1118 | if (test_bit(PAGE_HEADLESS, &page->private)) |
d30561c5 VW |
1119 | break; |
1120 | ||
1f862989 | 1121 | zhdr = page_address(page); |
ca0246bb VW |
1122 | if (!z3fold_page_trylock(zhdr)) { |
1123 | zhdr = NULL; | |
d30561c5 | 1124 | continue; /* can't evict at this point */ |
ca0246bb | 1125 | } |
d30561c5 VW |
1126 | kref_get(&zhdr->refcount); |
1127 | list_del_init(&zhdr->buddy); | |
1128 | zhdr->cpu = -1; | |
6098d7e1 | 1129 | break; |
d30561c5 VW |
1130 | } |
1131 | ||
ca0246bb VW |
1132 | if (!zhdr) |
1133 | break; | |
1134 | ||
5a27aa82 | 1135 | list_del_init(&page->lru); |
d30561c5 | 1136 | spin_unlock(&pool->lock); |
9a001fc1 | 1137 | |
9a001fc1 | 1138 | if (!test_bit(PAGE_HEADLESS, &page->private)) { |
9a001fc1 VW |
1139 | /* |
1140 | * We need encode the handles before unlocking, since | |
1141 | * we can race with free that will set | |
1142 | * (first|last)_chunks to 0 | |
1143 | */ | |
1144 | first_handle = 0; | |
1145 | last_handle = 0; | |
1146 | middle_handle = 0; | |
1147 | if (zhdr->first_chunks) | |
1148 | first_handle = encode_handle(zhdr, FIRST); | |
1149 | if (zhdr->middle_chunks) | |
1150 | middle_handle = encode_handle(zhdr, MIDDLE); | |
1151 | if (zhdr->last_chunks) | |
1152 | last_handle = encode_handle(zhdr, LAST); | |
d30561c5 VW |
1153 | /* |
1154 | * it's safe to unlock here because we hold a | |
1155 | * reference to this page | |
1156 | */ | |
2f1e5e4d | 1157 | z3fold_page_unlock(zhdr); |
9a001fc1 VW |
1158 | } else { |
1159 | first_handle = encode_handle(zhdr, HEADLESS); | |
1160 | last_handle = middle_handle = 0; | |
1161 | } | |
1162 | ||
9a001fc1 VW |
1163 | /* Issue the eviction callback(s) */ |
1164 | if (middle_handle) { | |
1165 | ret = pool->ops->evict(pool, middle_handle); | |
1166 | if (ret) | |
1167 | goto next; | |
1168 | } | |
1169 | if (first_handle) { | |
1170 | ret = pool->ops->evict(pool, first_handle); | |
1171 | if (ret) | |
1172 | goto next; | |
1173 | } | |
1174 | if (last_handle) { | |
1175 | ret = pool->ops->evict(pool, last_handle); | |
1176 | if (ret) | |
1177 | goto next; | |
1178 | } | |
1179 | next: | |
5a27aa82 VW |
1180 | if (test_bit(PAGE_HEADLESS, &page->private)) { |
1181 | if (ret == 0) { | |
1f862989 | 1182 | free_z3fold_page(page, true); |
ca0246bb | 1183 | atomic64_dec(&pool->pages_nr); |
5a27aa82 | 1184 | return 0; |
5a27aa82 | 1185 | } |
6098d7e1 VW |
1186 | spin_lock(&pool->lock); |
1187 | list_add(&page->lru, &pool->lru); | |
1188 | spin_unlock(&pool->lock); | |
1189 | } else { | |
1190 | z3fold_page_lock(zhdr); | |
ca0246bb | 1191 | clear_bit(PAGE_CLAIMED, &page->private); |
6098d7e1 VW |
1192 | if (kref_put(&zhdr->refcount, |
1193 | release_z3fold_page_locked)) { | |
1194 | atomic64_dec(&pool->pages_nr); | |
1195 | return 0; | |
1196 | } | |
1197 | /* | |
1198 | * if we are here, the page is still not completely | |
1199 | * free. Take the global pool lock then to be able | |
1200 | * to add it back to the lru list | |
1201 | */ | |
1202 | spin_lock(&pool->lock); | |
1203 | list_add(&page->lru, &pool->lru); | |
d5567c9d | 1204 | spin_unlock(&pool->lock); |
6098d7e1 | 1205 | z3fold_page_unlock(zhdr); |
5a27aa82 | 1206 | } |
2f1e5e4d | 1207 | |
6098d7e1 VW |
1208 | /* We started off locked to we need to lock the pool back */ |
1209 | spin_lock(&pool->lock); | |
9a001fc1 VW |
1210 | } |
1211 | spin_unlock(&pool->lock); | |
1212 | return -EAGAIN; | |
1213 | } | |
1214 | ||
1215 | /** | |
1216 | * z3fold_map() - maps the allocation associated with the given handle | |
1217 | * @pool: pool in which the allocation resides | |
1218 | * @handle: handle associated with the allocation to be mapped | |
1219 | * | |
1220 | * Extracts the buddy number from handle and constructs the pointer to the | |
1221 | * correct starting chunk within the page. | |
1222 | * | |
1223 | * Returns: a pointer to the mapped allocation | |
1224 | */ | |
1225 | static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle) | |
1226 | { | |
1227 | struct z3fold_header *zhdr; | |
1228 | struct page *page; | |
1229 | void *addr; | |
1230 | enum buddy buddy; | |
1231 | ||
9a001fc1 VW |
1232 | zhdr = handle_to_z3fold_header(handle); |
1233 | addr = zhdr; | |
1234 | page = virt_to_page(zhdr); | |
1235 | ||
1236 | if (test_bit(PAGE_HEADLESS, &page->private)) | |
1237 | goto out; | |
1238 | ||
2f1e5e4d | 1239 | z3fold_page_lock(zhdr); |
9a001fc1 VW |
1240 | buddy = handle_to_buddy(handle); |
1241 | switch (buddy) { | |
1242 | case FIRST: | |
1243 | addr += ZHDR_SIZE_ALIGNED; | |
1244 | break; | |
1245 | case MIDDLE: | |
1246 | addr += zhdr->start_middle << CHUNK_SHIFT; | |
1247 | set_bit(MIDDLE_CHUNK_MAPPED, &page->private); | |
1248 | break; | |
1249 | case LAST: | |
ca0246bb | 1250 | addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT); |
9a001fc1 VW |
1251 | break; |
1252 | default: | |
1253 | pr_err("unknown buddy id %d\n", buddy); | |
1254 | WARN_ON(1); | |
1255 | addr = NULL; | |
1256 | break; | |
1257 | } | |
2f1e5e4d | 1258 | |
1f862989 VW |
1259 | if (addr) |
1260 | zhdr->mapped_count++; | |
2f1e5e4d | 1261 | z3fold_page_unlock(zhdr); |
9a001fc1 | 1262 | out: |
9a001fc1 VW |
1263 | return addr; |
1264 | } | |
1265 | ||
1266 | /** | |
1267 | * z3fold_unmap() - unmaps the allocation associated with the given handle | |
1268 | * @pool: pool in which the allocation resides | |
1269 | * @handle: handle associated with the allocation to be unmapped | |
1270 | */ | |
1271 | static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle) | |
1272 | { | |
1273 | struct z3fold_header *zhdr; | |
1274 | struct page *page; | |
1275 | enum buddy buddy; | |
1276 | ||
9a001fc1 VW |
1277 | zhdr = handle_to_z3fold_header(handle); |
1278 | page = virt_to_page(zhdr); | |
1279 | ||
2f1e5e4d | 1280 | if (test_bit(PAGE_HEADLESS, &page->private)) |
9a001fc1 | 1281 | return; |
9a001fc1 | 1282 | |
2f1e5e4d | 1283 | z3fold_page_lock(zhdr); |
9a001fc1 VW |
1284 | buddy = handle_to_buddy(handle); |
1285 | if (buddy == MIDDLE) | |
1286 | clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); | |
1f862989 | 1287 | zhdr->mapped_count--; |
2f1e5e4d | 1288 | z3fold_page_unlock(zhdr); |
9a001fc1 VW |
1289 | } |
1290 | ||
1291 | /** | |
1292 | * z3fold_get_pool_size() - gets the z3fold pool size in pages | |
1293 | * @pool: pool whose size is being queried | |
1294 | * | |
12d59ae6 | 1295 | * Returns: size in pages of the given pool. |
9a001fc1 VW |
1296 | */ |
1297 | static u64 z3fold_get_pool_size(struct z3fold_pool *pool) | |
1298 | { | |
12d59ae6 | 1299 | return atomic64_read(&pool->pages_nr); |
9a001fc1 VW |
1300 | } |
1301 | ||
1f862989 VW |
1302 | static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode) |
1303 | { | |
1304 | struct z3fold_header *zhdr; | |
1305 | struct z3fold_pool *pool; | |
1306 | ||
1307 | VM_BUG_ON_PAGE(!PageMovable(page), page); | |
1308 | VM_BUG_ON_PAGE(PageIsolated(page), page); | |
1309 | ||
1310 | if (test_bit(PAGE_HEADLESS, &page->private)) | |
1311 | return false; | |
1312 | ||
1313 | zhdr = page_address(page); | |
1314 | z3fold_page_lock(zhdr); | |
1315 | if (test_bit(NEEDS_COMPACTING, &page->private) || | |
1316 | test_bit(PAGE_STALE, &page->private)) | |
1317 | goto out; | |
1318 | ||
1319 | pool = zhdr_to_pool(zhdr); | |
1320 | ||
1321 | if (zhdr->mapped_count == 0) { | |
1322 | kref_get(&zhdr->refcount); | |
1323 | if (!list_empty(&zhdr->buddy)) | |
1324 | list_del_init(&zhdr->buddy); | |
1325 | spin_lock(&pool->lock); | |
1326 | if (!list_empty(&page->lru)) | |
1327 | list_del(&page->lru); | |
1328 | spin_unlock(&pool->lock); | |
1329 | z3fold_page_unlock(zhdr); | |
1330 | return true; | |
1331 | } | |
1332 | out: | |
1333 | z3fold_page_unlock(zhdr); | |
1334 | return false; | |
1335 | } | |
1336 | ||
1337 | static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage, | |
1338 | struct page *page, enum migrate_mode mode) | |
1339 | { | |
1340 | struct z3fold_header *zhdr, *new_zhdr; | |
1341 | struct z3fold_pool *pool; | |
1342 | struct address_space *new_mapping; | |
1343 | ||
1344 | VM_BUG_ON_PAGE(!PageMovable(page), page); | |
1345 | VM_BUG_ON_PAGE(!PageIsolated(page), page); | |
810481a2 | 1346 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
1f862989 VW |
1347 | |
1348 | zhdr = page_address(page); | |
1349 | pool = zhdr_to_pool(zhdr); | |
1350 | ||
1351 | if (!trylock_page(page)) | |
1352 | return -EAGAIN; | |
1353 | ||
1354 | if (!z3fold_page_trylock(zhdr)) { | |
1355 | unlock_page(page); | |
1356 | return -EAGAIN; | |
1357 | } | |
1358 | if (zhdr->mapped_count != 0) { | |
1359 | z3fold_page_unlock(zhdr); | |
1360 | unlock_page(page); | |
1361 | return -EBUSY; | |
1362 | } | |
1363 | new_zhdr = page_address(newpage); | |
1364 | memcpy(new_zhdr, zhdr, PAGE_SIZE); | |
1365 | newpage->private = page->private; | |
1366 | page->private = 0; | |
1367 | z3fold_page_unlock(zhdr); | |
1368 | spin_lock_init(&new_zhdr->page_lock); | |
1369 | new_mapping = page_mapping(page); | |
1370 | __ClearPageMovable(page); | |
1371 | ClearPagePrivate(page); | |
1372 | ||
1373 | get_page(newpage); | |
1374 | z3fold_page_lock(new_zhdr); | |
1375 | if (new_zhdr->first_chunks) | |
1376 | encode_handle(new_zhdr, FIRST); | |
1377 | if (new_zhdr->last_chunks) | |
1378 | encode_handle(new_zhdr, LAST); | |
1379 | if (new_zhdr->middle_chunks) | |
1380 | encode_handle(new_zhdr, MIDDLE); | |
1381 | set_bit(NEEDS_COMPACTING, &newpage->private); | |
1382 | new_zhdr->cpu = smp_processor_id(); | |
1383 | spin_lock(&pool->lock); | |
1384 | list_add(&newpage->lru, &pool->lru); | |
1385 | spin_unlock(&pool->lock); | |
1386 | __SetPageMovable(newpage, new_mapping); | |
1387 | z3fold_page_unlock(new_zhdr); | |
1388 | ||
1389 | queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work); | |
1390 | ||
1391 | page_mapcount_reset(page); | |
1392 | unlock_page(page); | |
1393 | put_page(page); | |
1394 | return 0; | |
1395 | } | |
1396 | ||
1397 | static void z3fold_page_putback(struct page *page) | |
1398 | { | |
1399 | struct z3fold_header *zhdr; | |
1400 | struct z3fold_pool *pool; | |
1401 | ||
1402 | zhdr = page_address(page); | |
1403 | pool = zhdr_to_pool(zhdr); | |
1404 | ||
1405 | z3fold_page_lock(zhdr); | |
1406 | if (!list_empty(&zhdr->buddy)) | |
1407 | list_del_init(&zhdr->buddy); | |
1408 | INIT_LIST_HEAD(&page->lru); | |
1409 | if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { | |
1410 | atomic64_dec(&pool->pages_nr); | |
1411 | return; | |
1412 | } | |
1413 | spin_lock(&pool->lock); | |
1414 | list_add(&page->lru, &pool->lru); | |
1415 | spin_unlock(&pool->lock); | |
1416 | z3fold_page_unlock(zhdr); | |
1417 | } | |
1418 | ||
1419 | static const struct address_space_operations z3fold_aops = { | |
1420 | .isolate_page = z3fold_page_isolate, | |
1421 | .migratepage = z3fold_page_migrate, | |
1422 | .putback_page = z3fold_page_putback, | |
1423 | }; | |
1424 | ||
9a001fc1 VW |
1425 | /***************** |
1426 | * zpool | |
1427 | ****************/ | |
1428 | ||
1429 | static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle) | |
1430 | { | |
1431 | if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict) | |
1432 | return pool->zpool_ops->evict(pool->zpool, handle); | |
1433 | else | |
1434 | return -ENOENT; | |
1435 | } | |
1436 | ||
1437 | static const struct z3fold_ops z3fold_zpool_ops = { | |
1438 | .evict = z3fold_zpool_evict | |
1439 | }; | |
1440 | ||
1441 | static void *z3fold_zpool_create(const char *name, gfp_t gfp, | |
1442 | const struct zpool_ops *zpool_ops, | |
1443 | struct zpool *zpool) | |
1444 | { | |
1445 | struct z3fold_pool *pool; | |
1446 | ||
d30561c5 VW |
1447 | pool = z3fold_create_pool(name, gfp, |
1448 | zpool_ops ? &z3fold_zpool_ops : NULL); | |
9a001fc1 VW |
1449 | if (pool) { |
1450 | pool->zpool = zpool; | |
1451 | pool->zpool_ops = zpool_ops; | |
1452 | } | |
1453 | return pool; | |
1454 | } | |
1455 | ||
1456 | static void z3fold_zpool_destroy(void *pool) | |
1457 | { | |
1458 | z3fold_destroy_pool(pool); | |
1459 | } | |
1460 | ||
1461 | static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp, | |
1462 | unsigned long *handle) | |
1463 | { | |
1464 | return z3fold_alloc(pool, size, gfp, handle); | |
1465 | } | |
1466 | static void z3fold_zpool_free(void *pool, unsigned long handle) | |
1467 | { | |
1468 | z3fold_free(pool, handle); | |
1469 | } | |
1470 | ||
1471 | static int z3fold_zpool_shrink(void *pool, unsigned int pages, | |
1472 | unsigned int *reclaimed) | |
1473 | { | |
1474 | unsigned int total = 0; | |
1475 | int ret = -EINVAL; | |
1476 | ||
1477 | while (total < pages) { | |
1478 | ret = z3fold_reclaim_page(pool, 8); | |
1479 | if (ret < 0) | |
1480 | break; | |
1481 | total++; | |
1482 | } | |
1483 | ||
1484 | if (reclaimed) | |
1485 | *reclaimed = total; | |
1486 | ||
1487 | return ret; | |
1488 | } | |
1489 | ||
1490 | static void *z3fold_zpool_map(void *pool, unsigned long handle, | |
1491 | enum zpool_mapmode mm) | |
1492 | { | |
1493 | return z3fold_map(pool, handle); | |
1494 | } | |
1495 | static void z3fold_zpool_unmap(void *pool, unsigned long handle) | |
1496 | { | |
1497 | z3fold_unmap(pool, handle); | |
1498 | } | |
1499 | ||
1500 | static u64 z3fold_zpool_total_size(void *pool) | |
1501 | { | |
1502 | return z3fold_get_pool_size(pool) * PAGE_SIZE; | |
1503 | } | |
1504 | ||
1505 | static struct zpool_driver z3fold_zpool_driver = { | |
1506 | .type = "z3fold", | |
1507 | .owner = THIS_MODULE, | |
1508 | .create = z3fold_zpool_create, | |
1509 | .destroy = z3fold_zpool_destroy, | |
1510 | .malloc = z3fold_zpool_malloc, | |
1511 | .free = z3fold_zpool_free, | |
1512 | .shrink = z3fold_zpool_shrink, | |
1513 | .map = z3fold_zpool_map, | |
1514 | .unmap = z3fold_zpool_unmap, | |
1515 | .total_size = z3fold_zpool_total_size, | |
1516 | }; | |
1517 | ||
1518 | MODULE_ALIAS("zpool-z3fold"); | |
1519 | ||
1520 | static int __init init_z3fold(void) | |
1521 | { | |
1f862989 VW |
1522 | int ret; |
1523 | ||
ede93213 VW |
1524 | /* Make sure the z3fold header is not larger than the page size */ |
1525 | BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE); | |
1f862989 VW |
1526 | ret = z3fold_mount(); |
1527 | if (ret) | |
1528 | return ret; | |
1529 | ||
9a001fc1 VW |
1530 | zpool_register_driver(&z3fold_zpool_driver); |
1531 | ||
1532 | return 0; | |
1533 | } | |
1534 | ||
1535 | static void __exit exit_z3fold(void) | |
1536 | { | |
1f862989 | 1537 | z3fold_unmount(); |
9a001fc1 VW |
1538 | zpool_unregister_driver(&z3fold_zpool_driver); |
1539 | } | |
1540 | ||
1541 | module_init(init_z3fold); | |
1542 | module_exit(exit_z3fold); | |
1543 | ||
1544 | MODULE_LICENSE("GPL"); | |
1545 | MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>"); | |
1546 | MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages"); |