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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 | 197 | { |
f1549cb5 HB |
198 | struct z3fold_buddy_slots *slots; |
199 | ||
200 | slots = kmem_cache_alloc(pool->c_handle, | |
201 | (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE))); | |
7c2b8baa VW |
202 | |
203 | if (slots) { | |
204 | memset(slots->slot, 0, sizeof(slots->slot)); | |
205 | slots->pool = (unsigned long)pool; | |
206 | } | |
207 | ||
208 | return slots; | |
209 | } | |
210 | ||
211 | static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s) | |
212 | { | |
213 | return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK); | |
214 | } | |
215 | ||
216 | static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle) | |
217 | { | |
218 | return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1)); | |
219 | } | |
220 | ||
221 | static inline void free_handle(unsigned long handle) | |
222 | { | |
223 | struct z3fold_buddy_slots *slots; | |
224 | int i; | |
225 | bool is_free; | |
226 | ||
227 | if (handle & (1 << PAGE_HEADLESS)) | |
228 | return; | |
229 | ||
230 | WARN_ON(*(unsigned long *)handle == 0); | |
231 | *(unsigned long *)handle = 0; | |
232 | slots = handle_to_slots(handle); | |
233 | is_free = true; | |
234 | for (i = 0; i <= BUDDY_MASK; i++) { | |
235 | if (slots->slot[i]) { | |
236 | is_free = false; | |
237 | break; | |
238 | } | |
239 | } | |
240 | ||
241 | if (is_free) { | |
242 | struct z3fold_pool *pool = slots_to_pool(slots); | |
243 | ||
244 | kmem_cache_free(pool->c_handle, slots); | |
245 | } | |
246 | } | |
247 | ||
1f862989 VW |
248 | static struct dentry *z3fold_do_mount(struct file_system_type *fs_type, |
249 | int flags, const char *dev_name, void *data) | |
250 | { | |
251 | static const struct dentry_operations ops = { | |
252 | .d_dname = simple_dname, | |
253 | }; | |
254 | ||
255 | return mount_pseudo(fs_type, "z3fold:", NULL, &ops, 0x33); | |
256 | } | |
257 | ||
258 | static struct file_system_type z3fold_fs = { | |
259 | .name = "z3fold", | |
260 | .mount = z3fold_do_mount, | |
261 | .kill_sb = kill_anon_super, | |
262 | }; | |
263 | ||
264 | static struct vfsmount *z3fold_mnt; | |
265 | static int z3fold_mount(void) | |
266 | { | |
267 | int ret = 0; | |
268 | ||
269 | z3fold_mnt = kern_mount(&z3fold_fs); | |
270 | if (IS_ERR(z3fold_mnt)) | |
271 | ret = PTR_ERR(z3fold_mnt); | |
272 | ||
273 | return ret; | |
274 | } | |
275 | ||
276 | static void z3fold_unmount(void) | |
277 | { | |
278 | kern_unmount(z3fold_mnt); | |
279 | } | |
280 | ||
281 | static const struct address_space_operations z3fold_aops; | |
282 | static int z3fold_register_migration(struct z3fold_pool *pool) | |
283 | { | |
284 | pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb); | |
285 | if (IS_ERR(pool->inode)) { | |
286 | pool->inode = NULL; | |
287 | return 1; | |
288 | } | |
289 | ||
290 | pool->inode->i_mapping->private_data = pool; | |
291 | pool->inode->i_mapping->a_ops = &z3fold_aops; | |
292 | return 0; | |
293 | } | |
294 | ||
295 | static void z3fold_unregister_migration(struct z3fold_pool *pool) | |
296 | { | |
297 | if (pool->inode) | |
298 | iput(pool->inode); | |
299 | } | |
300 | ||
9a001fc1 | 301 | /* Initializes the z3fold header of a newly allocated z3fold page */ |
d30561c5 | 302 | static struct z3fold_header *init_z3fold_page(struct page *page, |
bb9f6f63 | 303 | struct z3fold_pool *pool, gfp_t gfp) |
9a001fc1 VW |
304 | { |
305 | struct z3fold_header *zhdr = page_address(page); | |
bb9f6f63 | 306 | struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp); |
7c2b8baa VW |
307 | |
308 | if (!slots) | |
309 | return NULL; | |
9a001fc1 VW |
310 | |
311 | INIT_LIST_HEAD(&page->lru); | |
9a001fc1 VW |
312 | clear_bit(PAGE_HEADLESS, &page->private); |
313 | clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); | |
d30561c5 VW |
314 | clear_bit(NEEDS_COMPACTING, &page->private); |
315 | clear_bit(PAGE_STALE, &page->private); | |
ca0246bb | 316 | clear_bit(PAGE_CLAIMED, &page->private); |
9a001fc1 | 317 | |
2f1e5e4d | 318 | spin_lock_init(&zhdr->page_lock); |
5a27aa82 | 319 | kref_init(&zhdr->refcount); |
9a001fc1 VW |
320 | zhdr->first_chunks = 0; |
321 | zhdr->middle_chunks = 0; | |
322 | zhdr->last_chunks = 0; | |
323 | zhdr->first_num = 0; | |
324 | zhdr->start_middle = 0; | |
d30561c5 | 325 | zhdr->cpu = -1; |
7c2b8baa | 326 | zhdr->slots = slots; |
bb9a374d | 327 | zhdr->pool = pool; |
9a001fc1 | 328 | INIT_LIST_HEAD(&zhdr->buddy); |
d30561c5 | 329 | INIT_WORK(&zhdr->work, compact_page_work); |
9a001fc1 VW |
330 | return zhdr; |
331 | } | |
332 | ||
333 | /* Resets the struct page fields and frees the page */ | |
1f862989 | 334 | static void free_z3fold_page(struct page *page, bool headless) |
9a001fc1 | 335 | { |
1f862989 VW |
336 | if (!headless) { |
337 | lock_page(page); | |
338 | __ClearPageMovable(page); | |
339 | unlock_page(page); | |
340 | } | |
341 | ClearPagePrivate(page); | |
5a27aa82 VW |
342 | __free_page(page); |
343 | } | |
344 | ||
2f1e5e4d VW |
345 | /* Lock a z3fold page */ |
346 | static inline void z3fold_page_lock(struct z3fold_header *zhdr) | |
347 | { | |
348 | spin_lock(&zhdr->page_lock); | |
349 | } | |
350 | ||
76e32a2a VW |
351 | /* Try to lock a z3fold page */ |
352 | static inline int z3fold_page_trylock(struct z3fold_header *zhdr) | |
353 | { | |
354 | return spin_trylock(&zhdr->page_lock); | |
355 | } | |
356 | ||
2f1e5e4d VW |
357 | /* Unlock a z3fold page */ |
358 | static inline void z3fold_page_unlock(struct z3fold_header *zhdr) | |
359 | { | |
360 | spin_unlock(&zhdr->page_lock); | |
361 | } | |
362 | ||
7c2b8baa VW |
363 | /* Helper function to build the index */ |
364 | static inline int __idx(struct z3fold_header *zhdr, enum buddy bud) | |
365 | { | |
366 | return (bud + zhdr->first_num) & BUDDY_MASK; | |
367 | } | |
368 | ||
9a001fc1 VW |
369 | /* |
370 | * Encodes the handle of a particular buddy within a z3fold page | |
371 | * Pool lock should be held as this function accesses first_num | |
372 | */ | |
373 | static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud) | |
374 | { | |
7c2b8baa VW |
375 | struct z3fold_buddy_slots *slots; |
376 | unsigned long h = (unsigned long)zhdr; | |
377 | int idx = 0; | |
9a001fc1 | 378 | |
7c2b8baa VW |
379 | /* |
380 | * For a headless page, its handle is its pointer with the extra | |
381 | * PAGE_HEADLESS bit set | |
382 | */ | |
383 | if (bud == HEADLESS) | |
384 | return h | (1 << PAGE_HEADLESS); | |
385 | ||
386 | /* otherwise, return pointer to encoded handle */ | |
387 | idx = __idx(zhdr, bud); | |
388 | h += idx; | |
389 | if (bud == LAST) | |
390 | h |= (zhdr->last_chunks << BUDDY_SHIFT); | |
391 | ||
392 | slots = zhdr->slots; | |
393 | slots->slot[idx] = h; | |
394 | return (unsigned long)&slots->slot[idx]; | |
9a001fc1 VW |
395 | } |
396 | ||
397 | /* Returns the z3fold page where a given handle is stored */ | |
1f862989 | 398 | static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h) |
9a001fc1 | 399 | { |
1f862989 | 400 | unsigned long addr = h; |
7c2b8baa VW |
401 | |
402 | if (!(addr & (1 << PAGE_HEADLESS))) | |
1f862989 | 403 | addr = *(unsigned long *)h; |
7c2b8baa VW |
404 | |
405 | return (struct z3fold_header *)(addr & PAGE_MASK); | |
9a001fc1 VW |
406 | } |
407 | ||
ca0246bb VW |
408 | /* only for LAST bud, returns zero otherwise */ |
409 | static unsigned short handle_to_chunks(unsigned long handle) | |
410 | { | |
7c2b8baa VW |
411 | unsigned long addr = *(unsigned long *)handle; |
412 | ||
413 | return (addr & ~PAGE_MASK) >> BUDDY_SHIFT; | |
ca0246bb VW |
414 | } |
415 | ||
f201ebd8 | 416 | /* |
417 | * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle | |
418 | * but that doesn't matter. because the masking will result in the | |
419 | * correct buddy number. | |
420 | */ | |
9a001fc1 VW |
421 | static enum buddy handle_to_buddy(unsigned long handle) |
422 | { | |
7c2b8baa VW |
423 | struct z3fold_header *zhdr; |
424 | unsigned long addr; | |
425 | ||
426 | WARN_ON(handle & (1 << PAGE_HEADLESS)); | |
427 | addr = *(unsigned long *)handle; | |
428 | zhdr = (struct z3fold_header *)(addr & PAGE_MASK); | |
429 | return (addr - zhdr->first_num) & BUDDY_MASK; | |
9a001fc1 VW |
430 | } |
431 | ||
9050cce1 VW |
432 | static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr) |
433 | { | |
bb9a374d | 434 | return zhdr->pool; |
9050cce1 VW |
435 | } |
436 | ||
d30561c5 VW |
437 | static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked) |
438 | { | |
439 | struct page *page = virt_to_page(zhdr); | |
9050cce1 | 440 | struct z3fold_pool *pool = zhdr_to_pool(zhdr); |
d30561c5 VW |
441 | |
442 | WARN_ON(!list_empty(&zhdr->buddy)); | |
443 | set_bit(PAGE_STALE, &page->private); | |
35529357 | 444 | clear_bit(NEEDS_COMPACTING, &page->private); |
d30561c5 VW |
445 | spin_lock(&pool->lock); |
446 | if (!list_empty(&page->lru)) | |
1f862989 | 447 | list_del_init(&page->lru); |
d30561c5 VW |
448 | spin_unlock(&pool->lock); |
449 | if (locked) | |
450 | z3fold_page_unlock(zhdr); | |
451 | spin_lock(&pool->stale_lock); | |
452 | list_add(&zhdr->buddy, &pool->stale); | |
453 | queue_work(pool->release_wq, &pool->work); | |
454 | spin_unlock(&pool->stale_lock); | |
455 | } | |
456 | ||
457 | static void __attribute__((__unused__)) | |
458 | release_z3fold_page(struct kref *ref) | |
459 | { | |
460 | struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, | |
461 | refcount); | |
462 | __release_z3fold_page(zhdr, false); | |
463 | } | |
464 | ||
465 | static void release_z3fold_page_locked(struct kref *ref) | |
466 | { | |
467 | struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, | |
468 | refcount); | |
469 | WARN_ON(z3fold_page_trylock(zhdr)); | |
470 | __release_z3fold_page(zhdr, true); | |
471 | } | |
472 | ||
473 | static void release_z3fold_page_locked_list(struct kref *ref) | |
474 | { | |
475 | struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, | |
476 | refcount); | |
9050cce1 VW |
477 | struct z3fold_pool *pool = zhdr_to_pool(zhdr); |
478 | spin_lock(&pool->lock); | |
d30561c5 | 479 | list_del_init(&zhdr->buddy); |
9050cce1 | 480 | spin_unlock(&pool->lock); |
d30561c5 VW |
481 | |
482 | WARN_ON(z3fold_page_trylock(zhdr)); | |
483 | __release_z3fold_page(zhdr, true); | |
484 | } | |
485 | ||
486 | static void free_pages_work(struct work_struct *w) | |
487 | { | |
488 | struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work); | |
489 | ||
490 | spin_lock(&pool->stale_lock); | |
491 | while (!list_empty(&pool->stale)) { | |
492 | struct z3fold_header *zhdr = list_first_entry(&pool->stale, | |
493 | struct z3fold_header, buddy); | |
494 | struct page *page = virt_to_page(zhdr); | |
495 | ||
496 | list_del(&zhdr->buddy); | |
497 | if (WARN_ON(!test_bit(PAGE_STALE, &page->private))) | |
498 | continue; | |
d30561c5 VW |
499 | spin_unlock(&pool->stale_lock); |
500 | cancel_work_sync(&zhdr->work); | |
1f862989 | 501 | free_z3fold_page(page, false); |
d30561c5 VW |
502 | cond_resched(); |
503 | spin_lock(&pool->stale_lock); | |
504 | } | |
505 | spin_unlock(&pool->stale_lock); | |
506 | } | |
507 | ||
9a001fc1 VW |
508 | /* |
509 | * Returns the number of free chunks in a z3fold page. | |
510 | * NB: can't be used with HEADLESS pages. | |
511 | */ | |
512 | static int num_free_chunks(struct z3fold_header *zhdr) | |
513 | { | |
514 | int nfree; | |
515 | /* | |
516 | * If there is a middle object, pick up the bigger free space | |
517 | * either before or after it. Otherwise just subtract the number | |
518 | * of chunks occupied by the first and the last objects. | |
519 | */ | |
520 | if (zhdr->middle_chunks != 0) { | |
521 | int nfree_before = zhdr->first_chunks ? | |
ede93213 | 522 | 0 : zhdr->start_middle - ZHDR_CHUNKS; |
9a001fc1 | 523 | int nfree_after = zhdr->last_chunks ? |
ede93213 VW |
524 | 0 : TOTAL_CHUNKS - |
525 | (zhdr->start_middle + zhdr->middle_chunks); | |
9a001fc1 VW |
526 | nfree = max(nfree_before, nfree_after); |
527 | } else | |
528 | nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks; | |
529 | return nfree; | |
530 | } | |
531 | ||
9050cce1 VW |
532 | /* Add to the appropriate unbuddied list */ |
533 | static inline void add_to_unbuddied(struct z3fold_pool *pool, | |
534 | struct z3fold_header *zhdr) | |
535 | { | |
536 | if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 || | |
537 | zhdr->middle_chunks == 0) { | |
538 | struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied); | |
539 | ||
540 | int freechunks = num_free_chunks(zhdr); | |
541 | spin_lock(&pool->lock); | |
542 | list_add(&zhdr->buddy, &unbuddied[freechunks]); | |
543 | spin_unlock(&pool->lock); | |
544 | zhdr->cpu = smp_processor_id(); | |
545 | put_cpu_ptr(pool->unbuddied); | |
546 | } | |
547 | } | |
548 | ||
ede93213 VW |
549 | static inline void *mchunk_memmove(struct z3fold_header *zhdr, |
550 | unsigned short dst_chunk) | |
551 | { | |
552 | void *beg = zhdr; | |
553 | return memmove(beg + (dst_chunk << CHUNK_SHIFT), | |
554 | beg + (zhdr->start_middle << CHUNK_SHIFT), | |
555 | zhdr->middle_chunks << CHUNK_SHIFT); | |
556 | } | |
557 | ||
1b096e5a | 558 | #define BIG_CHUNK_GAP 3 |
9a001fc1 VW |
559 | /* Has to be called with lock held */ |
560 | static int z3fold_compact_page(struct z3fold_header *zhdr) | |
561 | { | |
562 | struct page *page = virt_to_page(zhdr); | |
9a001fc1 | 563 | |
ede93213 VW |
564 | if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private)) |
565 | return 0; /* can't move middle chunk, it's used */ | |
9a001fc1 | 566 | |
1f862989 VW |
567 | if (unlikely(PageIsolated(page))) |
568 | return 0; | |
569 | ||
ede93213 VW |
570 | if (zhdr->middle_chunks == 0) |
571 | return 0; /* nothing to compact */ | |
572 | ||
573 | if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) { | |
574 | /* move to the beginning */ | |
575 | mchunk_memmove(zhdr, ZHDR_CHUNKS); | |
9a001fc1 VW |
576 | zhdr->first_chunks = zhdr->middle_chunks; |
577 | zhdr->middle_chunks = 0; | |
578 | zhdr->start_middle = 0; | |
579 | zhdr->first_num++; | |
1b096e5a | 580 | return 1; |
9a001fc1 | 581 | } |
1b096e5a VW |
582 | |
583 | /* | |
584 | * moving data is expensive, so let's only do that if | |
585 | * there's substantial gain (at least BIG_CHUNK_GAP chunks) | |
586 | */ | |
587 | if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 && | |
588 | zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >= | |
589 | BIG_CHUNK_GAP) { | |
590 | mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS); | |
591 | zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; | |
592 | return 1; | |
593 | } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 && | |
594 | TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle | |
595 | + zhdr->middle_chunks) >= | |
596 | BIG_CHUNK_GAP) { | |
597 | unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks - | |
598 | zhdr->middle_chunks; | |
599 | mchunk_memmove(zhdr, new_start); | |
600 | zhdr->start_middle = new_start; | |
601 | return 1; | |
602 | } | |
603 | ||
604 | return 0; | |
9a001fc1 VW |
605 | } |
606 | ||
d30561c5 VW |
607 | static void do_compact_page(struct z3fold_header *zhdr, bool locked) |
608 | { | |
9050cce1 | 609 | struct z3fold_pool *pool = zhdr_to_pool(zhdr); |
d30561c5 | 610 | struct page *page; |
d30561c5 VW |
611 | |
612 | page = virt_to_page(zhdr); | |
613 | if (locked) | |
614 | WARN_ON(z3fold_page_trylock(zhdr)); | |
615 | else | |
616 | z3fold_page_lock(zhdr); | |
5d03a661 | 617 | if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) { |
d30561c5 VW |
618 | z3fold_page_unlock(zhdr); |
619 | return; | |
620 | } | |
621 | spin_lock(&pool->lock); | |
622 | list_del_init(&zhdr->buddy); | |
623 | spin_unlock(&pool->lock); | |
624 | ||
5d03a661 VW |
625 | if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { |
626 | atomic64_dec(&pool->pages_nr); | |
627 | return; | |
628 | } | |
629 | ||
1f862989 VW |
630 | if (unlikely(PageIsolated(page) || |
631 | test_bit(PAGE_STALE, &page->private))) { | |
632 | z3fold_page_unlock(zhdr); | |
633 | return; | |
634 | } | |
635 | ||
d30561c5 | 636 | z3fold_compact_page(zhdr); |
9050cce1 | 637 | add_to_unbuddied(pool, zhdr); |
d30561c5 VW |
638 | z3fold_page_unlock(zhdr); |
639 | } | |
640 | ||
641 | static void compact_page_work(struct work_struct *w) | |
642 | { | |
643 | struct z3fold_header *zhdr = container_of(w, struct z3fold_header, | |
644 | work); | |
645 | ||
646 | do_compact_page(zhdr, false); | |
647 | } | |
648 | ||
9050cce1 VW |
649 | /* returns _locked_ z3fold page header or NULL */ |
650 | static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool, | |
651 | size_t size, bool can_sleep) | |
652 | { | |
653 | struct z3fold_header *zhdr = NULL; | |
654 | struct page *page; | |
655 | struct list_head *unbuddied; | |
656 | int chunks = size_to_chunks(size), i; | |
657 | ||
658 | lookup: | |
659 | /* First, try to find an unbuddied z3fold page. */ | |
660 | unbuddied = get_cpu_ptr(pool->unbuddied); | |
661 | for_each_unbuddied_list(i, chunks) { | |
662 | struct list_head *l = &unbuddied[i]; | |
663 | ||
664 | zhdr = list_first_entry_or_null(READ_ONCE(l), | |
665 | struct z3fold_header, buddy); | |
666 | ||
667 | if (!zhdr) | |
668 | continue; | |
669 | ||
670 | /* Re-check under lock. */ | |
671 | spin_lock(&pool->lock); | |
672 | l = &unbuddied[i]; | |
673 | if (unlikely(zhdr != list_first_entry(READ_ONCE(l), | |
674 | struct z3fold_header, buddy)) || | |
675 | !z3fold_page_trylock(zhdr)) { | |
676 | spin_unlock(&pool->lock); | |
677 | zhdr = NULL; | |
678 | put_cpu_ptr(pool->unbuddied); | |
679 | if (can_sleep) | |
680 | cond_resched(); | |
681 | goto lookup; | |
682 | } | |
683 | list_del_init(&zhdr->buddy); | |
684 | zhdr->cpu = -1; | |
685 | spin_unlock(&pool->lock); | |
686 | ||
687 | page = virt_to_page(zhdr); | |
688 | if (test_bit(NEEDS_COMPACTING, &page->private)) { | |
689 | z3fold_page_unlock(zhdr); | |
690 | zhdr = NULL; | |
691 | put_cpu_ptr(pool->unbuddied); | |
692 | if (can_sleep) | |
693 | cond_resched(); | |
694 | goto lookup; | |
695 | } | |
696 | ||
697 | /* | |
698 | * this page could not be removed from its unbuddied | |
699 | * list while pool lock was held, and then we've taken | |
700 | * page lock so kref_put could not be called before | |
701 | * we got here, so it's safe to just call kref_get() | |
702 | */ | |
703 | kref_get(&zhdr->refcount); | |
704 | break; | |
705 | } | |
706 | put_cpu_ptr(pool->unbuddied); | |
707 | ||
351618b2 VW |
708 | if (!zhdr) { |
709 | int cpu; | |
710 | ||
711 | /* look for _exact_ match on other cpus' lists */ | |
712 | for_each_online_cpu(cpu) { | |
713 | struct list_head *l; | |
714 | ||
715 | unbuddied = per_cpu_ptr(pool->unbuddied, cpu); | |
716 | spin_lock(&pool->lock); | |
717 | l = &unbuddied[chunks]; | |
718 | ||
719 | zhdr = list_first_entry_or_null(READ_ONCE(l), | |
720 | struct z3fold_header, buddy); | |
721 | ||
722 | if (!zhdr || !z3fold_page_trylock(zhdr)) { | |
723 | spin_unlock(&pool->lock); | |
724 | zhdr = NULL; | |
725 | continue; | |
726 | } | |
727 | list_del_init(&zhdr->buddy); | |
728 | zhdr->cpu = -1; | |
729 | spin_unlock(&pool->lock); | |
730 | ||
731 | page = virt_to_page(zhdr); | |
732 | if (test_bit(NEEDS_COMPACTING, &page->private)) { | |
733 | z3fold_page_unlock(zhdr); | |
734 | zhdr = NULL; | |
735 | if (can_sleep) | |
736 | cond_resched(); | |
737 | continue; | |
738 | } | |
739 | kref_get(&zhdr->refcount); | |
740 | break; | |
741 | } | |
742 | } | |
743 | ||
9050cce1 VW |
744 | return zhdr; |
745 | } | |
d30561c5 VW |
746 | |
747 | /* | |
748 | * API Functions | |
749 | */ | |
750 | ||
751 | /** | |
752 | * z3fold_create_pool() - create a new z3fold pool | |
753 | * @name: pool name | |
754 | * @gfp: gfp flags when allocating the z3fold pool structure | |
755 | * @ops: user-defined operations for the z3fold pool | |
756 | * | |
757 | * Return: pointer to the new z3fold pool or NULL if the metadata allocation | |
758 | * failed. | |
759 | */ | |
760 | static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp, | |
761 | const struct z3fold_ops *ops) | |
762 | { | |
763 | struct z3fold_pool *pool = NULL; | |
764 | int i, cpu; | |
765 | ||
766 | pool = kzalloc(sizeof(struct z3fold_pool), gfp); | |
767 | if (!pool) | |
768 | goto out; | |
7c2b8baa VW |
769 | pool->c_handle = kmem_cache_create("z3fold_handle", |
770 | sizeof(struct z3fold_buddy_slots), | |
771 | SLOTS_ALIGN, 0, NULL); | |
772 | if (!pool->c_handle) | |
773 | goto out_c; | |
d30561c5 VW |
774 | spin_lock_init(&pool->lock); |
775 | spin_lock_init(&pool->stale_lock); | |
776 | pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2); | |
1ec6995d XW |
777 | if (!pool->unbuddied) |
778 | goto out_pool; | |
d30561c5 VW |
779 | for_each_possible_cpu(cpu) { |
780 | struct list_head *unbuddied = | |
781 | per_cpu_ptr(pool->unbuddied, cpu); | |
782 | for_each_unbuddied_list(i, 0) | |
783 | INIT_LIST_HEAD(&unbuddied[i]); | |
784 | } | |
785 | INIT_LIST_HEAD(&pool->lru); | |
786 | INIT_LIST_HEAD(&pool->stale); | |
787 | atomic64_set(&pool->pages_nr, 0); | |
788 | pool->name = name; | |
789 | pool->compact_wq = create_singlethread_workqueue(pool->name); | |
790 | if (!pool->compact_wq) | |
1ec6995d | 791 | goto out_unbuddied; |
d30561c5 VW |
792 | pool->release_wq = create_singlethread_workqueue(pool->name); |
793 | if (!pool->release_wq) | |
794 | goto out_wq; | |
1f862989 VW |
795 | if (z3fold_register_migration(pool)) |
796 | goto out_rwq; | |
d30561c5 VW |
797 | INIT_WORK(&pool->work, free_pages_work); |
798 | pool->ops = ops; | |
799 | return pool; | |
800 | ||
1f862989 VW |
801 | out_rwq: |
802 | destroy_workqueue(pool->release_wq); | |
d30561c5 VW |
803 | out_wq: |
804 | destroy_workqueue(pool->compact_wq); | |
1ec6995d XW |
805 | out_unbuddied: |
806 | free_percpu(pool->unbuddied); | |
807 | out_pool: | |
7c2b8baa VW |
808 | kmem_cache_destroy(pool->c_handle); |
809 | out_c: | |
d30561c5 | 810 | kfree(pool); |
1ec6995d | 811 | out: |
d30561c5 VW |
812 | return NULL; |
813 | } | |
814 | ||
815 | /** | |
816 | * z3fold_destroy_pool() - destroys an existing z3fold pool | |
817 | * @pool: the z3fold pool to be destroyed | |
818 | * | |
819 | * The pool should be emptied before this function is called. | |
820 | */ | |
821 | static void z3fold_destroy_pool(struct z3fold_pool *pool) | |
822 | { | |
7c2b8baa | 823 | kmem_cache_destroy(pool->c_handle); |
1f862989 | 824 | z3fold_unregister_migration(pool); |
d30561c5 VW |
825 | destroy_workqueue(pool->release_wq); |
826 | destroy_workqueue(pool->compact_wq); | |
827 | kfree(pool); | |
828 | } | |
829 | ||
9a001fc1 VW |
830 | /** |
831 | * z3fold_alloc() - allocates a region of a given size | |
832 | * @pool: z3fold pool from which to allocate | |
833 | * @size: size in bytes of the desired allocation | |
834 | * @gfp: gfp flags used if the pool needs to grow | |
835 | * @handle: handle of the new allocation | |
836 | * | |
837 | * This function will attempt to find a free region in the pool large enough to | |
838 | * satisfy the allocation request. A search of the unbuddied lists is | |
839 | * performed first. If no suitable free region is found, then a new page is | |
840 | * allocated and added to the pool to satisfy the request. | |
841 | * | |
842 | * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used | |
843 | * as z3fold pool pages. | |
844 | * | |
845 | * Return: 0 if success and handle is set, otherwise -EINVAL if the size or | |
846 | * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate | |
847 | * a new page. | |
848 | */ | |
849 | static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, | |
850 | unsigned long *handle) | |
851 | { | |
9050cce1 | 852 | int chunks = size_to_chunks(size); |
9a001fc1 | 853 | struct z3fold_header *zhdr = NULL; |
d30561c5 | 854 | struct page *page = NULL; |
9a001fc1 | 855 | enum buddy bud; |
8a97ea54 | 856 | bool can_sleep = gfpflags_allow_blocking(gfp); |
9a001fc1 | 857 | |
f1549cb5 | 858 | if (!size) |
9a001fc1 VW |
859 | return -EINVAL; |
860 | ||
861 | if (size > PAGE_SIZE) | |
862 | return -ENOSPC; | |
863 | ||
864 | if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE) | |
865 | bud = HEADLESS; | |
866 | else { | |
9050cce1 VW |
867 | retry: |
868 | zhdr = __z3fold_alloc(pool, size, can_sleep); | |
d30561c5 | 869 | if (zhdr) { |
2f1e5e4d VW |
870 | if (zhdr->first_chunks == 0) { |
871 | if (zhdr->middle_chunks != 0 && | |
872 | chunks >= zhdr->start_middle) | |
9a001fc1 | 873 | bud = LAST; |
2f1e5e4d VW |
874 | else |
875 | bud = FIRST; | |
876 | } else if (zhdr->last_chunks == 0) | |
877 | bud = LAST; | |
878 | else if (zhdr->middle_chunks == 0) | |
879 | bud = MIDDLE; | |
880 | else { | |
5a27aa82 | 881 | if (kref_put(&zhdr->refcount, |
d30561c5 | 882 | release_z3fold_page_locked)) |
5a27aa82 | 883 | atomic64_dec(&pool->pages_nr); |
d30561c5 VW |
884 | else |
885 | z3fold_page_unlock(zhdr); | |
2f1e5e4d VW |
886 | pr_err("No free chunks in unbuddied\n"); |
887 | WARN_ON(1); | |
9050cce1 | 888 | goto retry; |
9a001fc1 | 889 | } |
9050cce1 | 890 | page = virt_to_page(zhdr); |
2f1e5e4d | 891 | goto found; |
9a001fc1 VW |
892 | } |
893 | bud = FIRST; | |
9a001fc1 VW |
894 | } |
895 | ||
5c9bab59 VW |
896 | page = NULL; |
897 | if (can_sleep) { | |
898 | spin_lock(&pool->stale_lock); | |
899 | zhdr = list_first_entry_or_null(&pool->stale, | |
900 | struct z3fold_header, buddy); | |
901 | /* | |
902 | * Before allocating a page, let's see if we can take one from | |
903 | * the stale pages list. cancel_work_sync() can sleep so we | |
904 | * limit this case to the contexts where we can sleep | |
905 | */ | |
906 | if (zhdr) { | |
907 | list_del(&zhdr->buddy); | |
908 | spin_unlock(&pool->stale_lock); | |
d30561c5 | 909 | cancel_work_sync(&zhdr->work); |
5c9bab59 VW |
910 | page = virt_to_page(zhdr); |
911 | } else { | |
912 | spin_unlock(&pool->stale_lock); | |
913 | } | |
d30561c5 | 914 | } |
5c9bab59 VW |
915 | if (!page) |
916 | page = alloc_page(gfp); | |
d30561c5 | 917 | |
9a001fc1 VW |
918 | if (!page) |
919 | return -ENOMEM; | |
2f1e5e4d | 920 | |
bb9f6f63 | 921 | zhdr = init_z3fold_page(page, pool, gfp); |
9050cce1 VW |
922 | if (!zhdr) { |
923 | __free_page(page); | |
924 | return -ENOMEM; | |
925 | } | |
926 | atomic64_inc(&pool->pages_nr); | |
9a001fc1 VW |
927 | |
928 | if (bud == HEADLESS) { | |
929 | set_bit(PAGE_HEADLESS, &page->private); | |
930 | goto headless; | |
931 | } | |
810481a2 HB |
932 | if (can_sleep) { |
933 | lock_page(page); | |
934 | __SetPageMovable(page, pool->inode->i_mapping); | |
935 | unlock_page(page); | |
936 | } else { | |
937 | if (trylock_page(page)) { | |
938 | __SetPageMovable(page, pool->inode->i_mapping); | |
939 | unlock_page(page); | |
940 | } | |
941 | } | |
2f1e5e4d | 942 | z3fold_page_lock(zhdr); |
9a001fc1 VW |
943 | |
944 | found: | |
945 | if (bud == FIRST) | |
946 | zhdr->first_chunks = chunks; | |
947 | else if (bud == LAST) | |
948 | zhdr->last_chunks = chunks; | |
949 | else { | |
950 | zhdr->middle_chunks = chunks; | |
ede93213 | 951 | zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS; |
9a001fc1 | 952 | } |
9050cce1 | 953 | add_to_unbuddied(pool, zhdr); |
9a001fc1 VW |
954 | |
955 | headless: | |
d30561c5 | 956 | spin_lock(&pool->lock); |
9a001fc1 VW |
957 | /* Add/move z3fold page to beginning of LRU */ |
958 | if (!list_empty(&page->lru)) | |
959 | list_del(&page->lru); | |
960 | ||
961 | list_add(&page->lru, &pool->lru); | |
962 | ||
963 | *handle = encode_handle(zhdr, bud); | |
964 | spin_unlock(&pool->lock); | |
2f1e5e4d VW |
965 | if (bud != HEADLESS) |
966 | z3fold_page_unlock(zhdr); | |
9a001fc1 VW |
967 | |
968 | return 0; | |
969 | } | |
970 | ||
971 | /** | |
972 | * z3fold_free() - frees the allocation associated with the given handle | |
973 | * @pool: pool in which the allocation resided | |
974 | * @handle: handle associated with the allocation returned by z3fold_alloc() | |
975 | * | |
976 | * In the case that the z3fold page in which the allocation resides is under | |
977 | * reclaim, as indicated by the PG_reclaim flag being set, this function | |
978 | * only sets the first|last_chunks to 0. The page is actually freed | |
979 | * once both buddies are evicted (see z3fold_reclaim_page() below). | |
980 | */ | |
981 | static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) | |
982 | { | |
983 | struct z3fold_header *zhdr; | |
9a001fc1 VW |
984 | struct page *page; |
985 | enum buddy bud; | |
986 | ||
9a001fc1 VW |
987 | zhdr = handle_to_z3fold_header(handle); |
988 | page = virt_to_page(zhdr); | |
989 | ||
990 | if (test_bit(PAGE_HEADLESS, &page->private)) { | |
ca0246bb VW |
991 | /* if a headless page is under reclaim, just leave. |
992 | * NB: we use test_and_set_bit for a reason: if the bit | |
993 | * has not been set before, we release this page | |
994 | * immediately so we don't care about its value any more. | |
995 | */ | |
996 | if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) { | |
997 | spin_lock(&pool->lock); | |
998 | list_del(&page->lru); | |
999 | spin_unlock(&pool->lock); | |
1f862989 | 1000 | free_z3fold_page(page, true); |
ca0246bb | 1001 | atomic64_dec(&pool->pages_nr); |
9a001fc1 | 1002 | } |
ca0246bb | 1003 | return; |
9a001fc1 VW |
1004 | } |
1005 | ||
ca0246bb VW |
1006 | /* Non-headless case */ |
1007 | z3fold_page_lock(zhdr); | |
1008 | bud = handle_to_buddy(handle); | |
1009 | ||
1010 | switch (bud) { | |
1011 | case FIRST: | |
1012 | zhdr->first_chunks = 0; | |
1013 | break; | |
1014 | case MIDDLE: | |
1015 | zhdr->middle_chunks = 0; | |
1016 | break; | |
1017 | case LAST: | |
1018 | zhdr->last_chunks = 0; | |
1019 | break; | |
1020 | default: | |
1021 | pr_err("%s: unknown bud %d\n", __func__, bud); | |
1022 | WARN_ON(1); | |
1023 | z3fold_page_unlock(zhdr); | |
d30561c5 VW |
1024 | return; |
1025 | } | |
1026 | ||
7c2b8baa | 1027 | free_handle(handle); |
d30561c5 VW |
1028 | if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) { |
1029 | atomic64_dec(&pool->pages_nr); | |
1030 | return; | |
1031 | } | |
ca0246bb | 1032 | if (test_bit(PAGE_CLAIMED, &page->private)) { |
6098d7e1 VW |
1033 | z3fold_page_unlock(zhdr); |
1034 | return; | |
1035 | } | |
1f862989 VW |
1036 | if (unlikely(PageIsolated(page)) || |
1037 | test_and_set_bit(NEEDS_COMPACTING, &page->private)) { | |
5a27aa82 | 1038 | z3fold_page_unlock(zhdr); |
d30561c5 VW |
1039 | return; |
1040 | } | |
1041 | if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) { | |
2f1e5e4d | 1042 | spin_lock(&pool->lock); |
d30561c5 | 1043 | list_del_init(&zhdr->buddy); |
2f1e5e4d | 1044 | spin_unlock(&pool->lock); |
d30561c5 | 1045 | zhdr->cpu = -1; |
5d03a661 | 1046 | kref_get(&zhdr->refcount); |
d30561c5 VW |
1047 | do_compact_page(zhdr, true); |
1048 | return; | |
9a001fc1 | 1049 | } |
5d03a661 | 1050 | kref_get(&zhdr->refcount); |
d30561c5 VW |
1051 | queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work); |
1052 | z3fold_page_unlock(zhdr); | |
9a001fc1 VW |
1053 | } |
1054 | ||
1055 | /** | |
1056 | * z3fold_reclaim_page() - evicts allocations from a pool page and frees it | |
1057 | * @pool: pool from which a page will attempt to be evicted | |
f144c390 | 1058 | * @retries: number of pages on the LRU list for which eviction will |
9a001fc1 VW |
1059 | * be attempted before failing |
1060 | * | |
1061 | * z3fold reclaim is different from normal system reclaim in that it is done | |
1062 | * from the bottom, up. This is because only the bottom layer, z3fold, has | |
1063 | * information on how the allocations are organized within each z3fold page. | |
1064 | * This has the potential to create interesting locking situations between | |
1065 | * z3fold and the user, however. | |
1066 | * | |
1067 | * To avoid these, this is how z3fold_reclaim_page() should be called: | |
f144c390 | 1068 | * |
9a001fc1 VW |
1069 | * The user detects a page should be reclaimed and calls z3fold_reclaim_page(). |
1070 | * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and | |
1071 | * call the user-defined eviction handler with the pool and handle as | |
1072 | * arguments. | |
1073 | * | |
1074 | * If the handle can not be evicted, the eviction handler should return | |
1075 | * non-zero. z3fold_reclaim_page() will add the z3fold page back to the | |
1076 | * appropriate list and try the next z3fold page on the LRU up to | |
1077 | * a user defined number of retries. | |
1078 | * | |
1079 | * If the handle is successfully evicted, the eviction handler should | |
1080 | * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free() | |
1081 | * contains logic to delay freeing the page if the page is under reclaim, | |
1082 | * as indicated by the setting of the PG_reclaim flag on the underlying page. | |
1083 | * | |
1084 | * If all buddies in the z3fold page are successfully evicted, then the | |
1085 | * z3fold page can be freed. | |
1086 | * | |
1087 | * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are | |
1088 | * no pages to evict or an eviction handler is not registered, -EAGAIN if | |
1089 | * the retry limit was hit. | |
1090 | */ | |
1091 | static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) | |
1092 | { | |
d30561c5 VW |
1093 | int i, ret = 0; |
1094 | struct z3fold_header *zhdr = NULL; | |
1095 | struct page *page = NULL; | |
1096 | struct list_head *pos; | |
9a001fc1 VW |
1097 | unsigned long first_handle = 0, middle_handle = 0, last_handle = 0; |
1098 | ||
1099 | spin_lock(&pool->lock); | |
2f1e5e4d | 1100 | if (!pool->ops || !pool->ops->evict || retries == 0) { |
9a001fc1 VW |
1101 | spin_unlock(&pool->lock); |
1102 | return -EINVAL; | |
1103 | } | |
1104 | for (i = 0; i < retries; i++) { | |
2f1e5e4d VW |
1105 | if (list_empty(&pool->lru)) { |
1106 | spin_unlock(&pool->lock); | |
1107 | return -EINVAL; | |
1108 | } | |
d30561c5 VW |
1109 | list_for_each_prev(pos, &pool->lru) { |
1110 | page = list_entry(pos, struct page, lru); | |
ca0246bb VW |
1111 | |
1112 | /* this bit could have been set by free, in which case | |
1113 | * we pass over to the next page in the pool. | |
1114 | */ | |
1115 | if (test_and_set_bit(PAGE_CLAIMED, &page->private)) | |
1116 | continue; | |
1117 | ||
1f862989 VW |
1118 | if (unlikely(PageIsolated(page))) |
1119 | continue; | |
d30561c5 | 1120 | if (test_bit(PAGE_HEADLESS, &page->private)) |
d30561c5 VW |
1121 | break; |
1122 | ||
1f862989 | 1123 | zhdr = page_address(page); |
ca0246bb VW |
1124 | if (!z3fold_page_trylock(zhdr)) { |
1125 | zhdr = NULL; | |
d30561c5 | 1126 | continue; /* can't evict at this point */ |
ca0246bb | 1127 | } |
d30561c5 VW |
1128 | kref_get(&zhdr->refcount); |
1129 | list_del_init(&zhdr->buddy); | |
1130 | zhdr->cpu = -1; | |
6098d7e1 | 1131 | break; |
d30561c5 VW |
1132 | } |
1133 | ||
ca0246bb VW |
1134 | if (!zhdr) |
1135 | break; | |
1136 | ||
5a27aa82 | 1137 | list_del_init(&page->lru); |
d30561c5 | 1138 | spin_unlock(&pool->lock); |
9a001fc1 | 1139 | |
9a001fc1 | 1140 | if (!test_bit(PAGE_HEADLESS, &page->private)) { |
9a001fc1 VW |
1141 | /* |
1142 | * We need encode the handles before unlocking, since | |
1143 | * we can race with free that will set | |
1144 | * (first|last)_chunks to 0 | |
1145 | */ | |
1146 | first_handle = 0; | |
1147 | last_handle = 0; | |
1148 | middle_handle = 0; | |
1149 | if (zhdr->first_chunks) | |
1150 | first_handle = encode_handle(zhdr, FIRST); | |
1151 | if (zhdr->middle_chunks) | |
1152 | middle_handle = encode_handle(zhdr, MIDDLE); | |
1153 | if (zhdr->last_chunks) | |
1154 | last_handle = encode_handle(zhdr, LAST); | |
d30561c5 VW |
1155 | /* |
1156 | * it's safe to unlock here because we hold a | |
1157 | * reference to this page | |
1158 | */ | |
2f1e5e4d | 1159 | z3fold_page_unlock(zhdr); |
9a001fc1 VW |
1160 | } else { |
1161 | first_handle = encode_handle(zhdr, HEADLESS); | |
1162 | last_handle = middle_handle = 0; | |
1163 | } | |
1164 | ||
9a001fc1 VW |
1165 | /* Issue the eviction callback(s) */ |
1166 | if (middle_handle) { | |
1167 | ret = pool->ops->evict(pool, middle_handle); | |
1168 | if (ret) | |
1169 | goto next; | |
1170 | } | |
1171 | if (first_handle) { | |
1172 | ret = pool->ops->evict(pool, first_handle); | |
1173 | if (ret) | |
1174 | goto next; | |
1175 | } | |
1176 | if (last_handle) { | |
1177 | ret = pool->ops->evict(pool, last_handle); | |
1178 | if (ret) | |
1179 | goto next; | |
1180 | } | |
1181 | next: | |
5a27aa82 VW |
1182 | if (test_bit(PAGE_HEADLESS, &page->private)) { |
1183 | if (ret == 0) { | |
1f862989 | 1184 | free_z3fold_page(page, true); |
ca0246bb | 1185 | atomic64_dec(&pool->pages_nr); |
5a27aa82 | 1186 | return 0; |
5a27aa82 | 1187 | } |
6098d7e1 VW |
1188 | spin_lock(&pool->lock); |
1189 | list_add(&page->lru, &pool->lru); | |
1190 | spin_unlock(&pool->lock); | |
1191 | } else { | |
1192 | z3fold_page_lock(zhdr); | |
ca0246bb | 1193 | clear_bit(PAGE_CLAIMED, &page->private); |
6098d7e1 VW |
1194 | if (kref_put(&zhdr->refcount, |
1195 | release_z3fold_page_locked)) { | |
1196 | atomic64_dec(&pool->pages_nr); | |
1197 | return 0; | |
1198 | } | |
1199 | /* | |
1200 | * if we are here, the page is still not completely | |
1201 | * free. Take the global pool lock then to be able | |
1202 | * to add it back to the lru list | |
1203 | */ | |
1204 | spin_lock(&pool->lock); | |
1205 | list_add(&page->lru, &pool->lru); | |
d5567c9d | 1206 | spin_unlock(&pool->lock); |
6098d7e1 | 1207 | z3fold_page_unlock(zhdr); |
5a27aa82 | 1208 | } |
2f1e5e4d | 1209 | |
6098d7e1 VW |
1210 | /* We started off locked to we need to lock the pool back */ |
1211 | spin_lock(&pool->lock); | |
9a001fc1 VW |
1212 | } |
1213 | spin_unlock(&pool->lock); | |
1214 | return -EAGAIN; | |
1215 | } | |
1216 | ||
1217 | /** | |
1218 | * z3fold_map() - maps the allocation associated with the given handle | |
1219 | * @pool: pool in which the allocation resides | |
1220 | * @handle: handle associated with the allocation to be mapped | |
1221 | * | |
1222 | * Extracts the buddy number from handle and constructs the pointer to the | |
1223 | * correct starting chunk within the page. | |
1224 | * | |
1225 | * Returns: a pointer to the mapped allocation | |
1226 | */ | |
1227 | static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle) | |
1228 | { | |
1229 | struct z3fold_header *zhdr; | |
1230 | struct page *page; | |
1231 | void *addr; | |
1232 | enum buddy buddy; | |
1233 | ||
9a001fc1 VW |
1234 | zhdr = handle_to_z3fold_header(handle); |
1235 | addr = zhdr; | |
1236 | page = virt_to_page(zhdr); | |
1237 | ||
1238 | if (test_bit(PAGE_HEADLESS, &page->private)) | |
1239 | goto out; | |
1240 | ||
2f1e5e4d | 1241 | z3fold_page_lock(zhdr); |
9a001fc1 VW |
1242 | buddy = handle_to_buddy(handle); |
1243 | switch (buddy) { | |
1244 | case FIRST: | |
1245 | addr += ZHDR_SIZE_ALIGNED; | |
1246 | break; | |
1247 | case MIDDLE: | |
1248 | addr += zhdr->start_middle << CHUNK_SHIFT; | |
1249 | set_bit(MIDDLE_CHUNK_MAPPED, &page->private); | |
1250 | break; | |
1251 | case LAST: | |
ca0246bb | 1252 | addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT); |
9a001fc1 VW |
1253 | break; |
1254 | default: | |
1255 | pr_err("unknown buddy id %d\n", buddy); | |
1256 | WARN_ON(1); | |
1257 | addr = NULL; | |
1258 | break; | |
1259 | } | |
2f1e5e4d | 1260 | |
1f862989 VW |
1261 | if (addr) |
1262 | zhdr->mapped_count++; | |
2f1e5e4d | 1263 | z3fold_page_unlock(zhdr); |
9a001fc1 | 1264 | out: |
9a001fc1 VW |
1265 | return addr; |
1266 | } | |
1267 | ||
1268 | /** | |
1269 | * z3fold_unmap() - unmaps the allocation associated with the given handle | |
1270 | * @pool: pool in which the allocation resides | |
1271 | * @handle: handle associated with the allocation to be unmapped | |
1272 | */ | |
1273 | static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle) | |
1274 | { | |
1275 | struct z3fold_header *zhdr; | |
1276 | struct page *page; | |
1277 | enum buddy buddy; | |
1278 | ||
9a001fc1 VW |
1279 | zhdr = handle_to_z3fold_header(handle); |
1280 | page = virt_to_page(zhdr); | |
1281 | ||
2f1e5e4d | 1282 | if (test_bit(PAGE_HEADLESS, &page->private)) |
9a001fc1 | 1283 | return; |
9a001fc1 | 1284 | |
2f1e5e4d | 1285 | z3fold_page_lock(zhdr); |
9a001fc1 VW |
1286 | buddy = handle_to_buddy(handle); |
1287 | if (buddy == MIDDLE) | |
1288 | clear_bit(MIDDLE_CHUNK_MAPPED, &page->private); | |
1f862989 | 1289 | zhdr->mapped_count--; |
2f1e5e4d | 1290 | z3fold_page_unlock(zhdr); |
9a001fc1 VW |
1291 | } |
1292 | ||
1293 | /** | |
1294 | * z3fold_get_pool_size() - gets the z3fold pool size in pages | |
1295 | * @pool: pool whose size is being queried | |
1296 | * | |
12d59ae6 | 1297 | * Returns: size in pages of the given pool. |
9a001fc1 VW |
1298 | */ |
1299 | static u64 z3fold_get_pool_size(struct z3fold_pool *pool) | |
1300 | { | |
12d59ae6 | 1301 | return atomic64_read(&pool->pages_nr); |
9a001fc1 VW |
1302 | } |
1303 | ||
1f862989 VW |
1304 | static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode) |
1305 | { | |
1306 | struct z3fold_header *zhdr; | |
1307 | struct z3fold_pool *pool; | |
1308 | ||
1309 | VM_BUG_ON_PAGE(!PageMovable(page), page); | |
1310 | VM_BUG_ON_PAGE(PageIsolated(page), page); | |
1311 | ||
1312 | if (test_bit(PAGE_HEADLESS, &page->private)) | |
1313 | return false; | |
1314 | ||
1315 | zhdr = page_address(page); | |
1316 | z3fold_page_lock(zhdr); | |
1317 | if (test_bit(NEEDS_COMPACTING, &page->private) || | |
1318 | test_bit(PAGE_STALE, &page->private)) | |
1319 | goto out; | |
1320 | ||
1321 | pool = zhdr_to_pool(zhdr); | |
1322 | ||
1323 | if (zhdr->mapped_count == 0) { | |
1324 | kref_get(&zhdr->refcount); | |
1325 | if (!list_empty(&zhdr->buddy)) | |
1326 | list_del_init(&zhdr->buddy); | |
1327 | spin_lock(&pool->lock); | |
1328 | if (!list_empty(&page->lru)) | |
1329 | list_del(&page->lru); | |
1330 | spin_unlock(&pool->lock); | |
1331 | z3fold_page_unlock(zhdr); | |
1332 | return true; | |
1333 | } | |
1334 | out: | |
1335 | z3fold_page_unlock(zhdr); | |
1336 | return false; | |
1337 | } | |
1338 | ||
1339 | static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage, | |
1340 | struct page *page, enum migrate_mode mode) | |
1341 | { | |
1342 | struct z3fold_header *zhdr, *new_zhdr; | |
1343 | struct z3fold_pool *pool; | |
1344 | struct address_space *new_mapping; | |
1345 | ||
1346 | VM_BUG_ON_PAGE(!PageMovable(page), page); | |
1347 | VM_BUG_ON_PAGE(!PageIsolated(page), page); | |
810481a2 | 1348 | VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); |
1f862989 VW |
1349 | |
1350 | zhdr = page_address(page); | |
1351 | pool = zhdr_to_pool(zhdr); | |
1352 | ||
1f862989 | 1353 | if (!z3fold_page_trylock(zhdr)) { |
1f862989 VW |
1354 | return -EAGAIN; |
1355 | } | |
1356 | if (zhdr->mapped_count != 0) { | |
1357 | z3fold_page_unlock(zhdr); | |
1f862989 VW |
1358 | return -EBUSY; |
1359 | } | |
1360 | new_zhdr = page_address(newpage); | |
1361 | memcpy(new_zhdr, zhdr, PAGE_SIZE); | |
1362 | newpage->private = page->private; | |
1363 | page->private = 0; | |
1364 | z3fold_page_unlock(zhdr); | |
1365 | spin_lock_init(&new_zhdr->page_lock); | |
1366 | new_mapping = page_mapping(page); | |
1367 | __ClearPageMovable(page); | |
1368 | ClearPagePrivate(page); | |
1369 | ||
1370 | get_page(newpage); | |
1371 | z3fold_page_lock(new_zhdr); | |
1372 | if (new_zhdr->first_chunks) | |
1373 | encode_handle(new_zhdr, FIRST); | |
1374 | if (new_zhdr->last_chunks) | |
1375 | encode_handle(new_zhdr, LAST); | |
1376 | if (new_zhdr->middle_chunks) | |
1377 | encode_handle(new_zhdr, MIDDLE); | |
1378 | set_bit(NEEDS_COMPACTING, &newpage->private); | |
1379 | new_zhdr->cpu = smp_processor_id(); | |
1380 | spin_lock(&pool->lock); | |
1381 | list_add(&newpage->lru, &pool->lru); | |
1382 | spin_unlock(&pool->lock); | |
1383 | __SetPageMovable(newpage, new_mapping); | |
1384 | z3fold_page_unlock(new_zhdr); | |
1385 | ||
1386 | queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work); | |
1387 | ||
1388 | page_mapcount_reset(page); | |
1f862989 VW |
1389 | put_page(page); |
1390 | return 0; | |
1391 | } | |
1392 | ||
1393 | static void z3fold_page_putback(struct page *page) | |
1394 | { | |
1395 | struct z3fold_header *zhdr; | |
1396 | struct z3fold_pool *pool; | |
1397 | ||
1398 | zhdr = page_address(page); | |
1399 | pool = zhdr_to_pool(zhdr); | |
1400 | ||
1401 | z3fold_page_lock(zhdr); | |
1402 | if (!list_empty(&zhdr->buddy)) | |
1403 | list_del_init(&zhdr->buddy); | |
1404 | INIT_LIST_HEAD(&page->lru); | |
1405 | if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) { | |
1406 | atomic64_dec(&pool->pages_nr); | |
1407 | return; | |
1408 | } | |
1409 | spin_lock(&pool->lock); | |
1410 | list_add(&page->lru, &pool->lru); | |
1411 | spin_unlock(&pool->lock); | |
1412 | z3fold_page_unlock(zhdr); | |
1413 | } | |
1414 | ||
1415 | static const struct address_space_operations z3fold_aops = { | |
1416 | .isolate_page = z3fold_page_isolate, | |
1417 | .migratepage = z3fold_page_migrate, | |
1418 | .putback_page = z3fold_page_putback, | |
1419 | }; | |
1420 | ||
9a001fc1 VW |
1421 | /***************** |
1422 | * zpool | |
1423 | ****************/ | |
1424 | ||
1425 | static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle) | |
1426 | { | |
1427 | if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict) | |
1428 | return pool->zpool_ops->evict(pool->zpool, handle); | |
1429 | else | |
1430 | return -ENOENT; | |
1431 | } | |
1432 | ||
1433 | static const struct z3fold_ops z3fold_zpool_ops = { | |
1434 | .evict = z3fold_zpool_evict | |
1435 | }; | |
1436 | ||
1437 | static void *z3fold_zpool_create(const char *name, gfp_t gfp, | |
1438 | const struct zpool_ops *zpool_ops, | |
1439 | struct zpool *zpool) | |
1440 | { | |
1441 | struct z3fold_pool *pool; | |
1442 | ||
d30561c5 VW |
1443 | pool = z3fold_create_pool(name, gfp, |
1444 | zpool_ops ? &z3fold_zpool_ops : NULL); | |
9a001fc1 VW |
1445 | if (pool) { |
1446 | pool->zpool = zpool; | |
1447 | pool->zpool_ops = zpool_ops; | |
1448 | } | |
1449 | return pool; | |
1450 | } | |
1451 | ||
1452 | static void z3fold_zpool_destroy(void *pool) | |
1453 | { | |
1454 | z3fold_destroy_pool(pool); | |
1455 | } | |
1456 | ||
1457 | static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp, | |
1458 | unsigned long *handle) | |
1459 | { | |
1460 | return z3fold_alloc(pool, size, gfp, handle); | |
1461 | } | |
1462 | static void z3fold_zpool_free(void *pool, unsigned long handle) | |
1463 | { | |
1464 | z3fold_free(pool, handle); | |
1465 | } | |
1466 | ||
1467 | static int z3fold_zpool_shrink(void *pool, unsigned int pages, | |
1468 | unsigned int *reclaimed) | |
1469 | { | |
1470 | unsigned int total = 0; | |
1471 | int ret = -EINVAL; | |
1472 | ||
1473 | while (total < pages) { | |
1474 | ret = z3fold_reclaim_page(pool, 8); | |
1475 | if (ret < 0) | |
1476 | break; | |
1477 | total++; | |
1478 | } | |
1479 | ||
1480 | if (reclaimed) | |
1481 | *reclaimed = total; | |
1482 | ||
1483 | return ret; | |
1484 | } | |
1485 | ||
1486 | static void *z3fold_zpool_map(void *pool, unsigned long handle, | |
1487 | enum zpool_mapmode mm) | |
1488 | { | |
1489 | return z3fold_map(pool, handle); | |
1490 | } | |
1491 | static void z3fold_zpool_unmap(void *pool, unsigned long handle) | |
1492 | { | |
1493 | z3fold_unmap(pool, handle); | |
1494 | } | |
1495 | ||
1496 | static u64 z3fold_zpool_total_size(void *pool) | |
1497 | { | |
1498 | return z3fold_get_pool_size(pool) * PAGE_SIZE; | |
1499 | } | |
1500 | ||
1501 | static struct zpool_driver z3fold_zpool_driver = { | |
1502 | .type = "z3fold", | |
1503 | .owner = THIS_MODULE, | |
1504 | .create = z3fold_zpool_create, | |
1505 | .destroy = z3fold_zpool_destroy, | |
1506 | .malloc = z3fold_zpool_malloc, | |
1507 | .free = z3fold_zpool_free, | |
1508 | .shrink = z3fold_zpool_shrink, | |
1509 | .map = z3fold_zpool_map, | |
1510 | .unmap = z3fold_zpool_unmap, | |
1511 | .total_size = z3fold_zpool_total_size, | |
1512 | }; | |
1513 | ||
1514 | MODULE_ALIAS("zpool-z3fold"); | |
1515 | ||
1516 | static int __init init_z3fold(void) | |
1517 | { | |
1f862989 VW |
1518 | int ret; |
1519 | ||
ede93213 VW |
1520 | /* Make sure the z3fold header is not larger than the page size */ |
1521 | BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE); | |
1f862989 VW |
1522 | ret = z3fold_mount(); |
1523 | if (ret) | |
1524 | return ret; | |
1525 | ||
9a001fc1 VW |
1526 | zpool_register_driver(&z3fold_zpool_driver); |
1527 | ||
1528 | return 0; | |
1529 | } | |
1530 | ||
1531 | static void __exit exit_z3fold(void) | |
1532 | { | |
1f862989 | 1533 | z3fold_unmount(); |
9a001fc1 VW |
1534 | zpool_unregister_driver(&z3fold_zpool_driver); |
1535 | } | |
1536 | ||
1537 | module_init(init_z3fold); | |
1538 | module_exit(exit_z3fold); | |
1539 | ||
1540 | MODULE_LICENSE("GPL"); | |
1541 | MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>"); | |
1542 | MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages"); |