Loading...
1/*
2 * z3fold.c
3 *
4 * Author: Vitaly Wool <vitaly.wool@konsulko.com>
5 * Copyright (C) 2016, Sony Mobile Communications Inc.
6 *
7 * This implementation is based on zbud written by Seth Jennings.
8 *
9 * z3fold is an special purpose allocator for storing compressed pages. It
10 * can store up to three compressed pages per page which improves the
11 * compression ratio of zbud while retaining its main concepts (e. g. always
12 * storing an integral number of objects per page) and simplicity.
13 * It still has simple and deterministic reclaim properties that make it
14 * preferable to a higher density approach (with no requirement on integral
15 * number of object per page) when reclaim is used.
16 *
17 * As in zbud, pages are divided into "chunks". The size of the chunks is
18 * fixed at compile time and is determined by NCHUNKS_ORDER below.
19 *
20 * z3fold doesn't export any API and is meant to be used via zpool API.
21 */
22
23#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24
25#include <linux/atomic.h>
26#include <linux/list.h>
27#include <linux/mm.h>
28#include <linux/module.h>
29#include <linux/preempt.h>
30#include <linux/slab.h>
31#include <linux/spinlock.h>
32#include <linux/zpool.h>
33
34/*****************
35 * Structures
36*****************/
37/*
38 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
39 * adjusting internal fragmentation. It also determines the number of
40 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
41 * allocation granularity will be in chunks of size PAGE_SIZE/64. As one chunk
42 * in allocated page is occupied by z3fold header, NCHUNKS will be calculated
43 * to 63 which shows the max number of free chunks in z3fold page, also there
44 * will be 63 freelists per pool.
45 */
46#define NCHUNKS_ORDER 6
47
48#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
49#define CHUNK_SIZE (1 << CHUNK_SHIFT)
50#define ZHDR_SIZE_ALIGNED CHUNK_SIZE
51#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
52
53#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1)
54
55struct z3fold_pool;
56struct z3fold_ops {
57 int (*evict)(struct z3fold_pool *pool, unsigned long handle);
58};
59
60/**
61 * struct z3fold_pool - stores metadata for each z3fold pool
62 * @lock: protects all pool fields and first|last_chunk fields of any
63 * z3fold page in the pool
64 * @unbuddied: array of lists tracking z3fold pages that contain 2- buddies;
65 * the lists each z3fold page is added to depends on the size of
66 * its free region.
67 * @buddied: list tracking the z3fold pages that contain 3 buddies;
68 * these z3fold pages are full
69 * @lru: list tracking the z3fold pages in LRU order by most recently
70 * added buddy.
71 * @pages_nr: number of z3fold pages in the pool.
72 * @ops: pointer to a structure of user defined operations specified at
73 * pool creation time.
74 *
75 * This structure is allocated at pool creation time and maintains metadata
76 * pertaining to a particular z3fold pool.
77 */
78struct z3fold_pool {
79 spinlock_t lock;
80 struct list_head unbuddied[NCHUNKS];
81 struct list_head buddied;
82 struct list_head lru;
83 u64 pages_nr;
84 const struct z3fold_ops *ops;
85 struct zpool *zpool;
86 const struct zpool_ops *zpool_ops;
87};
88
89enum buddy {
90 HEADLESS = 0,
91 FIRST,
92 MIDDLE,
93 LAST,
94 BUDDIES_MAX
95};
96
97/*
98 * struct z3fold_header - z3fold page metadata occupying the first chunk of each
99 * z3fold page, except for HEADLESS pages
100 * @buddy: links the z3fold page into the relevant list in the pool
101 * @first_chunks: the size of the first buddy in chunks, 0 if free
102 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
103 * @last_chunks: the size of the last buddy in chunks, 0 if free
104 * @first_num: the starting number (for the first handle)
105 */
106struct z3fold_header {
107 struct list_head buddy;
108 unsigned short first_chunks;
109 unsigned short middle_chunks;
110 unsigned short last_chunks;
111 unsigned short start_middle;
112 unsigned short first_num:NCHUNKS_ORDER;
113};
114
115/*
116 * Internal z3fold page flags
117 */
118enum z3fold_page_flags {
119 UNDER_RECLAIM = 0,
120 PAGE_HEADLESS,
121 MIDDLE_CHUNK_MAPPED,
122};
123
124/*****************
125 * Helpers
126*****************/
127
128/* Converts an allocation size in bytes to size in z3fold chunks */
129static int size_to_chunks(size_t size)
130{
131 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
132}
133
134#define for_each_unbuddied_list(_iter, _begin) \
135 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
136
137/* Initializes the z3fold header of a newly allocated z3fold page */
138static struct z3fold_header *init_z3fold_page(struct page *page)
139{
140 struct z3fold_header *zhdr = page_address(page);
141
142 INIT_LIST_HEAD(&page->lru);
143 clear_bit(UNDER_RECLAIM, &page->private);
144 clear_bit(PAGE_HEADLESS, &page->private);
145 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
146
147 zhdr->first_chunks = 0;
148 zhdr->middle_chunks = 0;
149 zhdr->last_chunks = 0;
150 zhdr->first_num = 0;
151 zhdr->start_middle = 0;
152 INIT_LIST_HEAD(&zhdr->buddy);
153 return zhdr;
154}
155
156/* Resets the struct page fields and frees the page */
157static void free_z3fold_page(struct z3fold_header *zhdr)
158{
159 __free_page(virt_to_page(zhdr));
160}
161
162/*
163 * Encodes the handle of a particular buddy within a z3fold page
164 * Pool lock should be held as this function accesses first_num
165 */
166static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
167{
168 unsigned long handle;
169
170 handle = (unsigned long)zhdr;
171 if (bud != HEADLESS)
172 handle += (bud + zhdr->first_num) & BUDDY_MASK;
173 return handle;
174}
175
176/* Returns the z3fold page where a given handle is stored */
177static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
178{
179 return (struct z3fold_header *)(handle & PAGE_MASK);
180}
181
182/* Returns buddy number */
183static enum buddy handle_to_buddy(unsigned long handle)
184{
185 struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
186 return (handle - zhdr->first_num) & BUDDY_MASK;
187}
188
189/*
190 * Returns the number of free chunks in a z3fold page.
191 * NB: can't be used with HEADLESS pages.
192 */
193static int num_free_chunks(struct z3fold_header *zhdr)
194{
195 int nfree;
196 /*
197 * If there is a middle object, pick up the bigger free space
198 * either before or after it. Otherwise just subtract the number
199 * of chunks occupied by the first and the last objects.
200 */
201 if (zhdr->middle_chunks != 0) {
202 int nfree_before = zhdr->first_chunks ?
203 0 : zhdr->start_middle - 1;
204 int nfree_after = zhdr->last_chunks ?
205 0 : NCHUNKS - zhdr->start_middle - zhdr->middle_chunks;
206 nfree = max(nfree_before, nfree_after);
207 } else
208 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
209 return nfree;
210}
211
212/*****************
213 * API Functions
214*****************/
215/**
216 * z3fold_create_pool() - create a new z3fold pool
217 * @gfp: gfp flags when allocating the z3fold pool structure
218 * @ops: user-defined operations for the z3fold pool
219 *
220 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
221 * failed.
222 */
223static struct z3fold_pool *z3fold_create_pool(gfp_t gfp,
224 const struct z3fold_ops *ops)
225{
226 struct z3fold_pool *pool;
227 int i;
228
229 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
230 if (!pool)
231 return NULL;
232 spin_lock_init(&pool->lock);
233 for_each_unbuddied_list(i, 0)
234 INIT_LIST_HEAD(&pool->unbuddied[i]);
235 INIT_LIST_HEAD(&pool->buddied);
236 INIT_LIST_HEAD(&pool->lru);
237 pool->pages_nr = 0;
238 pool->ops = ops;
239 return pool;
240}
241
242/**
243 * z3fold_destroy_pool() - destroys an existing z3fold pool
244 * @pool: the z3fold pool to be destroyed
245 *
246 * The pool should be emptied before this function is called.
247 */
248static void z3fold_destroy_pool(struct z3fold_pool *pool)
249{
250 kfree(pool);
251}
252
253/* Has to be called with lock held */
254static int z3fold_compact_page(struct z3fold_header *zhdr)
255{
256 struct page *page = virt_to_page(zhdr);
257 void *beg = zhdr;
258
259
260 if (!test_bit(MIDDLE_CHUNK_MAPPED, &page->private) &&
261 zhdr->middle_chunks != 0 &&
262 zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
263 memmove(beg + ZHDR_SIZE_ALIGNED,
264 beg + (zhdr->start_middle << CHUNK_SHIFT),
265 zhdr->middle_chunks << CHUNK_SHIFT);
266 zhdr->first_chunks = zhdr->middle_chunks;
267 zhdr->middle_chunks = 0;
268 zhdr->start_middle = 0;
269 zhdr->first_num++;
270 return 1;
271 }
272 return 0;
273}
274
275/**
276 * z3fold_alloc() - allocates a region of a given size
277 * @pool: z3fold pool from which to allocate
278 * @size: size in bytes of the desired allocation
279 * @gfp: gfp flags used if the pool needs to grow
280 * @handle: handle of the new allocation
281 *
282 * This function will attempt to find a free region in the pool large enough to
283 * satisfy the allocation request. A search of the unbuddied lists is
284 * performed first. If no suitable free region is found, then a new page is
285 * allocated and added to the pool to satisfy the request.
286 *
287 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
288 * as z3fold pool pages.
289 *
290 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
291 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
292 * a new page.
293 */
294static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
295 unsigned long *handle)
296{
297 int chunks = 0, i, freechunks;
298 struct z3fold_header *zhdr = NULL;
299 enum buddy bud;
300 struct page *page;
301
302 if (!size || (gfp & __GFP_HIGHMEM))
303 return -EINVAL;
304
305 if (size > PAGE_SIZE)
306 return -ENOSPC;
307
308 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
309 bud = HEADLESS;
310 else {
311 chunks = size_to_chunks(size);
312 spin_lock(&pool->lock);
313
314 /* First, try to find an unbuddied z3fold page. */
315 zhdr = NULL;
316 for_each_unbuddied_list(i, chunks) {
317 if (!list_empty(&pool->unbuddied[i])) {
318 zhdr = list_first_entry(&pool->unbuddied[i],
319 struct z3fold_header, buddy);
320 page = virt_to_page(zhdr);
321 if (zhdr->first_chunks == 0) {
322 if (zhdr->middle_chunks != 0 &&
323 chunks >= zhdr->start_middle)
324 bud = LAST;
325 else
326 bud = FIRST;
327 } else if (zhdr->last_chunks == 0)
328 bud = LAST;
329 else if (zhdr->middle_chunks == 0)
330 bud = MIDDLE;
331 else {
332 pr_err("No free chunks in unbuddied\n");
333 WARN_ON(1);
334 continue;
335 }
336 list_del(&zhdr->buddy);
337 goto found;
338 }
339 }
340 bud = FIRST;
341 spin_unlock(&pool->lock);
342 }
343
344 /* Couldn't find unbuddied z3fold page, create new one */
345 page = alloc_page(gfp);
346 if (!page)
347 return -ENOMEM;
348 spin_lock(&pool->lock);
349 pool->pages_nr++;
350 zhdr = init_z3fold_page(page);
351
352 if (bud == HEADLESS) {
353 set_bit(PAGE_HEADLESS, &page->private);
354 goto headless;
355 }
356
357found:
358 if (bud == FIRST)
359 zhdr->first_chunks = chunks;
360 else if (bud == LAST)
361 zhdr->last_chunks = chunks;
362 else {
363 zhdr->middle_chunks = chunks;
364 zhdr->start_middle = zhdr->first_chunks + 1;
365 }
366
367 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
368 zhdr->middle_chunks == 0) {
369 /* Add to unbuddied list */
370 freechunks = num_free_chunks(zhdr);
371 list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
372 } else {
373 /* Add to buddied list */
374 list_add(&zhdr->buddy, &pool->buddied);
375 }
376
377headless:
378 /* Add/move z3fold page to beginning of LRU */
379 if (!list_empty(&page->lru))
380 list_del(&page->lru);
381
382 list_add(&page->lru, &pool->lru);
383
384 *handle = encode_handle(zhdr, bud);
385 spin_unlock(&pool->lock);
386
387 return 0;
388}
389
390/**
391 * z3fold_free() - frees the allocation associated with the given handle
392 * @pool: pool in which the allocation resided
393 * @handle: handle associated with the allocation returned by z3fold_alloc()
394 *
395 * In the case that the z3fold page in which the allocation resides is under
396 * reclaim, as indicated by the PG_reclaim flag being set, this function
397 * only sets the first|last_chunks to 0. The page is actually freed
398 * once both buddies are evicted (see z3fold_reclaim_page() below).
399 */
400static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
401{
402 struct z3fold_header *zhdr;
403 int freechunks;
404 struct page *page;
405 enum buddy bud;
406
407 spin_lock(&pool->lock);
408 zhdr = handle_to_z3fold_header(handle);
409 page = virt_to_page(zhdr);
410
411 if (test_bit(PAGE_HEADLESS, &page->private)) {
412 /* HEADLESS page stored */
413 bud = HEADLESS;
414 } else {
415 bud = handle_to_buddy(handle);
416
417 switch (bud) {
418 case FIRST:
419 zhdr->first_chunks = 0;
420 break;
421 case MIDDLE:
422 zhdr->middle_chunks = 0;
423 zhdr->start_middle = 0;
424 break;
425 case LAST:
426 zhdr->last_chunks = 0;
427 break;
428 default:
429 pr_err("%s: unknown bud %d\n", __func__, bud);
430 WARN_ON(1);
431 spin_unlock(&pool->lock);
432 return;
433 }
434 }
435
436 if (test_bit(UNDER_RECLAIM, &page->private)) {
437 /* z3fold page is under reclaim, reclaim will free */
438 spin_unlock(&pool->lock);
439 return;
440 }
441
442 if (bud != HEADLESS) {
443 /* Remove from existing buddy list */
444 list_del(&zhdr->buddy);
445 }
446
447 if (bud == HEADLESS ||
448 (zhdr->first_chunks == 0 && zhdr->middle_chunks == 0 &&
449 zhdr->last_chunks == 0)) {
450 /* z3fold page is empty, free */
451 list_del(&page->lru);
452 clear_bit(PAGE_HEADLESS, &page->private);
453 free_z3fold_page(zhdr);
454 pool->pages_nr--;
455 } else {
456 z3fold_compact_page(zhdr);
457 /* Add to the unbuddied list */
458 freechunks = num_free_chunks(zhdr);
459 list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
460 }
461
462 spin_unlock(&pool->lock);
463}
464
465/**
466 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
467 * @pool: pool from which a page will attempt to be evicted
468 * @retires: number of pages on the LRU list for which eviction will
469 * be attempted before failing
470 *
471 * z3fold reclaim is different from normal system reclaim in that it is done
472 * from the bottom, up. This is because only the bottom layer, z3fold, has
473 * information on how the allocations are organized within each z3fold page.
474 * This has the potential to create interesting locking situations between
475 * z3fold and the user, however.
476 *
477 * To avoid these, this is how z3fold_reclaim_page() should be called:
478
479 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
480 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
481 * call the user-defined eviction handler with the pool and handle as
482 * arguments.
483 *
484 * If the handle can not be evicted, the eviction handler should return
485 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
486 * appropriate list and try the next z3fold page on the LRU up to
487 * a user defined number of retries.
488 *
489 * If the handle is successfully evicted, the eviction handler should
490 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
491 * contains logic to delay freeing the page if the page is under reclaim,
492 * as indicated by the setting of the PG_reclaim flag on the underlying page.
493 *
494 * If all buddies in the z3fold page are successfully evicted, then the
495 * z3fold page can be freed.
496 *
497 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
498 * no pages to evict or an eviction handler is not registered, -EAGAIN if
499 * the retry limit was hit.
500 */
501static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
502{
503 int i, ret = 0, freechunks;
504 struct z3fold_header *zhdr;
505 struct page *page;
506 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
507
508 spin_lock(&pool->lock);
509 if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) ||
510 retries == 0) {
511 spin_unlock(&pool->lock);
512 return -EINVAL;
513 }
514 for (i = 0; i < retries; i++) {
515 page = list_last_entry(&pool->lru, struct page, lru);
516 list_del(&page->lru);
517
518 /* Protect z3fold page against free */
519 set_bit(UNDER_RECLAIM, &page->private);
520 zhdr = page_address(page);
521 if (!test_bit(PAGE_HEADLESS, &page->private)) {
522 list_del(&zhdr->buddy);
523 /*
524 * We need encode the handles before unlocking, since
525 * we can race with free that will set
526 * (first|last)_chunks to 0
527 */
528 first_handle = 0;
529 last_handle = 0;
530 middle_handle = 0;
531 if (zhdr->first_chunks)
532 first_handle = encode_handle(zhdr, FIRST);
533 if (zhdr->middle_chunks)
534 middle_handle = encode_handle(zhdr, MIDDLE);
535 if (zhdr->last_chunks)
536 last_handle = encode_handle(zhdr, LAST);
537 } else {
538 first_handle = encode_handle(zhdr, HEADLESS);
539 last_handle = middle_handle = 0;
540 }
541
542 spin_unlock(&pool->lock);
543
544 /* Issue the eviction callback(s) */
545 if (middle_handle) {
546 ret = pool->ops->evict(pool, middle_handle);
547 if (ret)
548 goto next;
549 }
550 if (first_handle) {
551 ret = pool->ops->evict(pool, first_handle);
552 if (ret)
553 goto next;
554 }
555 if (last_handle) {
556 ret = pool->ops->evict(pool, last_handle);
557 if (ret)
558 goto next;
559 }
560next:
561 spin_lock(&pool->lock);
562 clear_bit(UNDER_RECLAIM, &page->private);
563 if ((test_bit(PAGE_HEADLESS, &page->private) && ret == 0) ||
564 (zhdr->first_chunks == 0 && zhdr->last_chunks == 0 &&
565 zhdr->middle_chunks == 0)) {
566 /*
567 * All buddies are now free, free the z3fold page and
568 * return success.
569 */
570 clear_bit(PAGE_HEADLESS, &page->private);
571 free_z3fold_page(zhdr);
572 pool->pages_nr--;
573 spin_unlock(&pool->lock);
574 return 0;
575 } else if (!test_bit(PAGE_HEADLESS, &page->private)) {
576 if (zhdr->first_chunks != 0 &&
577 zhdr->last_chunks != 0 &&
578 zhdr->middle_chunks != 0) {
579 /* Full, add to buddied list */
580 list_add(&zhdr->buddy, &pool->buddied);
581 } else {
582 z3fold_compact_page(zhdr);
583 /* add to unbuddied list */
584 freechunks = num_free_chunks(zhdr);
585 list_add(&zhdr->buddy,
586 &pool->unbuddied[freechunks]);
587 }
588 }
589
590 /* add to beginning of LRU */
591 list_add(&page->lru, &pool->lru);
592 }
593 spin_unlock(&pool->lock);
594 return -EAGAIN;
595}
596
597/**
598 * z3fold_map() - maps the allocation associated with the given handle
599 * @pool: pool in which the allocation resides
600 * @handle: handle associated with the allocation to be mapped
601 *
602 * Extracts the buddy number from handle and constructs the pointer to the
603 * correct starting chunk within the page.
604 *
605 * Returns: a pointer to the mapped allocation
606 */
607static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
608{
609 struct z3fold_header *zhdr;
610 struct page *page;
611 void *addr;
612 enum buddy buddy;
613
614 spin_lock(&pool->lock);
615 zhdr = handle_to_z3fold_header(handle);
616 addr = zhdr;
617 page = virt_to_page(zhdr);
618
619 if (test_bit(PAGE_HEADLESS, &page->private))
620 goto out;
621
622 buddy = handle_to_buddy(handle);
623 switch (buddy) {
624 case FIRST:
625 addr += ZHDR_SIZE_ALIGNED;
626 break;
627 case MIDDLE:
628 addr += zhdr->start_middle << CHUNK_SHIFT;
629 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
630 break;
631 case LAST:
632 addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
633 break;
634 default:
635 pr_err("unknown buddy id %d\n", buddy);
636 WARN_ON(1);
637 addr = NULL;
638 break;
639 }
640out:
641 spin_unlock(&pool->lock);
642 return addr;
643}
644
645/**
646 * z3fold_unmap() - unmaps the allocation associated with the given handle
647 * @pool: pool in which the allocation resides
648 * @handle: handle associated with the allocation to be unmapped
649 */
650static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
651{
652 struct z3fold_header *zhdr;
653 struct page *page;
654 enum buddy buddy;
655
656 spin_lock(&pool->lock);
657 zhdr = handle_to_z3fold_header(handle);
658 page = virt_to_page(zhdr);
659
660 if (test_bit(PAGE_HEADLESS, &page->private)) {
661 spin_unlock(&pool->lock);
662 return;
663 }
664
665 buddy = handle_to_buddy(handle);
666 if (buddy == MIDDLE)
667 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
668 spin_unlock(&pool->lock);
669}
670
671/**
672 * z3fold_get_pool_size() - gets the z3fold pool size in pages
673 * @pool: pool whose size is being queried
674 *
675 * Returns: size in pages of the given pool. The pool lock need not be
676 * taken to access pages_nr.
677 */
678static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
679{
680 return pool->pages_nr;
681}
682
683/*****************
684 * zpool
685 ****************/
686
687static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
688{
689 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
690 return pool->zpool_ops->evict(pool->zpool, handle);
691 else
692 return -ENOENT;
693}
694
695static const struct z3fold_ops z3fold_zpool_ops = {
696 .evict = z3fold_zpool_evict
697};
698
699static void *z3fold_zpool_create(const char *name, gfp_t gfp,
700 const struct zpool_ops *zpool_ops,
701 struct zpool *zpool)
702{
703 struct z3fold_pool *pool;
704
705 pool = z3fold_create_pool(gfp, zpool_ops ? &z3fold_zpool_ops : NULL);
706 if (pool) {
707 pool->zpool = zpool;
708 pool->zpool_ops = zpool_ops;
709 }
710 return pool;
711}
712
713static void z3fold_zpool_destroy(void *pool)
714{
715 z3fold_destroy_pool(pool);
716}
717
718static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
719 unsigned long *handle)
720{
721 return z3fold_alloc(pool, size, gfp, handle);
722}
723static void z3fold_zpool_free(void *pool, unsigned long handle)
724{
725 z3fold_free(pool, handle);
726}
727
728static int z3fold_zpool_shrink(void *pool, unsigned int pages,
729 unsigned int *reclaimed)
730{
731 unsigned int total = 0;
732 int ret = -EINVAL;
733
734 while (total < pages) {
735 ret = z3fold_reclaim_page(pool, 8);
736 if (ret < 0)
737 break;
738 total++;
739 }
740
741 if (reclaimed)
742 *reclaimed = total;
743
744 return ret;
745}
746
747static void *z3fold_zpool_map(void *pool, unsigned long handle,
748 enum zpool_mapmode mm)
749{
750 return z3fold_map(pool, handle);
751}
752static void z3fold_zpool_unmap(void *pool, unsigned long handle)
753{
754 z3fold_unmap(pool, handle);
755}
756
757static u64 z3fold_zpool_total_size(void *pool)
758{
759 return z3fold_get_pool_size(pool) * PAGE_SIZE;
760}
761
762static struct zpool_driver z3fold_zpool_driver = {
763 .type = "z3fold",
764 .owner = THIS_MODULE,
765 .create = z3fold_zpool_create,
766 .destroy = z3fold_zpool_destroy,
767 .malloc = z3fold_zpool_malloc,
768 .free = z3fold_zpool_free,
769 .shrink = z3fold_zpool_shrink,
770 .map = z3fold_zpool_map,
771 .unmap = z3fold_zpool_unmap,
772 .total_size = z3fold_zpool_total_size,
773};
774
775MODULE_ALIAS("zpool-z3fold");
776
777static int __init init_z3fold(void)
778{
779 /* Make sure the z3fold header will fit in one chunk */
780 BUILD_BUG_ON(sizeof(struct z3fold_header) > ZHDR_SIZE_ALIGNED);
781 zpool_register_driver(&z3fold_zpool_driver);
782
783 return 0;
784}
785
786static void __exit exit_z3fold(void)
787{
788 zpool_unregister_driver(&z3fold_zpool_driver);
789}
790
791module_init(init_z3fold);
792module_exit(exit_z3fold);
793
794MODULE_LICENSE("GPL");
795MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
796MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");
1// SPDX-License-Identifier: GPL-2.0-only
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>
27#include <linux/sched.h>
28#include <linux/cpumask.h>
29#include <linux/list.h>
30#include <linux/mm.h>
31#include <linux/module.h>
32#include <linux/page-flags.h>
33#include <linux/migrate.h>
34#include <linux/node.h>
35#include <linux/compaction.h>
36#include <linux/percpu.h>
37#include <linux/preempt.h>
38#include <linux/workqueue.h>
39#include <linux/slab.h>
40#include <linux/spinlock.h>
41#include <linux/zpool.h>
42#include <linux/kmemleak.h>
43
44/*
45 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
46 * adjusting internal fragmentation. It also determines the number of
47 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
48 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
49 * in the beginning of an allocated page are occupied by z3fold header, so
50 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
51 * which shows the max number of free chunks in z3fold page, also there will
52 * be 63, or 62, respectively, freelists per pool.
53 */
54#define NCHUNKS_ORDER 6
55
56#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
57#define CHUNK_SIZE (1 << CHUNK_SHIFT)
58#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
59#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
60#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
61#define NCHUNKS (TOTAL_CHUNKS - ZHDR_CHUNKS)
62
63#define BUDDY_MASK (0x3)
64#define BUDDY_SHIFT 2
65#define SLOTS_ALIGN (0x40)
66
67/*****************
68 * Structures
69*****************/
70struct z3fold_pool;
71
72enum buddy {
73 HEADLESS = 0,
74 FIRST,
75 MIDDLE,
76 LAST,
77 BUDDIES_MAX = LAST
78};
79
80struct z3fold_buddy_slots {
81 /*
82 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
83 * be enough slots to hold all possible variants
84 */
85 unsigned long slot[BUDDY_MASK + 1];
86 unsigned long pool; /* back link */
87 rwlock_t lock;
88};
89#define HANDLE_FLAG_MASK (0x03)
90
91/*
92 * struct z3fold_header - z3fold page metadata occupying first chunks of each
93 * z3fold page, except for HEADLESS pages
94 * @buddy: links the z3fold page into the relevant list in the
95 * pool
96 * @page_lock: per-page lock
97 * @refcount: reference count for the z3fold page
98 * @work: work_struct for page layout optimization
99 * @slots: pointer to the structure holding buddy slots
100 * @pool: pointer to the containing pool
101 * @cpu: CPU which this page "belongs" to
102 * @first_chunks: the size of the first buddy in chunks, 0 if free
103 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
104 * @last_chunks: the size of the last buddy in chunks, 0 if free
105 * @first_num: the starting number (for the first handle)
106 * @mapped_count: the number of objects currently mapped
107 */
108struct z3fold_header {
109 struct list_head buddy;
110 spinlock_t page_lock;
111 struct kref refcount;
112 struct work_struct work;
113 struct z3fold_buddy_slots *slots;
114 struct z3fold_pool *pool;
115 short cpu;
116 unsigned short first_chunks;
117 unsigned short middle_chunks;
118 unsigned short last_chunks;
119 unsigned short start_middle;
120 unsigned short first_num:2;
121 unsigned short mapped_count:2;
122 unsigned short foreign_handles:2;
123};
124
125/**
126 * struct z3fold_pool - stores metadata for each z3fold pool
127 * @name: pool name
128 * @lock: protects pool unbuddied/lru lists
129 * @stale_lock: protects pool stale page list
130 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
131 * buddies; the list each z3fold page is added to depends on
132 * the size of its free region.
133 * @lru: list tracking the z3fold pages in LRU order by most recently
134 * added buddy.
135 * @stale: list of pages marked for freeing
136 * @pages_nr: number of z3fold pages in the pool.
137 * @c_handle: cache for z3fold_buddy_slots allocation
138 * @zpool: zpool driver
139 * @zpool_ops: zpool operations structure with an evict callback
140 * @compact_wq: workqueue for page layout background optimization
141 * @release_wq: workqueue for safe page release
142 * @work: work_struct for safe page release
143 *
144 * This structure is allocated at pool creation time and maintains metadata
145 * pertaining to a particular z3fold pool.
146 */
147struct z3fold_pool {
148 const char *name;
149 spinlock_t lock;
150 spinlock_t stale_lock;
151 struct list_head *unbuddied;
152 struct list_head lru;
153 struct list_head stale;
154 atomic64_t pages_nr;
155 struct kmem_cache *c_handle;
156 struct zpool *zpool;
157 const struct zpool_ops *zpool_ops;
158 struct workqueue_struct *compact_wq;
159 struct workqueue_struct *release_wq;
160 struct work_struct work;
161};
162
163/*
164 * Internal z3fold page flags
165 */
166enum z3fold_page_flags {
167 PAGE_HEADLESS = 0,
168 MIDDLE_CHUNK_MAPPED,
169 NEEDS_COMPACTING,
170 PAGE_STALE,
171 PAGE_CLAIMED, /* by either reclaim or free */
172 PAGE_MIGRATED, /* page is migrated and soon to be released */
173};
174
175/*
176 * handle flags, go under HANDLE_FLAG_MASK
177 */
178enum z3fold_handle_flags {
179 HANDLES_NOFREE = 0,
180};
181
182/*
183 * Forward declarations
184 */
185static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
186static void compact_page_work(struct work_struct *w);
187
188/*****************
189 * Helpers
190*****************/
191
192/* Converts an allocation size in bytes to size in z3fold chunks */
193static int size_to_chunks(size_t size)
194{
195 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
196}
197
198#define for_each_unbuddied_list(_iter, _begin) \
199 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
200
201static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
202 gfp_t gfp)
203{
204 struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
205 gfp);
206
207 if (slots) {
208 /* It will be freed separately in free_handle(). */
209 kmemleak_not_leak(slots);
210 slots->pool = (unsigned long)pool;
211 rwlock_init(&slots->lock);
212 }
213
214 return slots;
215}
216
217static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
218{
219 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
220}
221
222static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
223{
224 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
225}
226
227/* Lock a z3fold page */
228static inline void z3fold_page_lock(struct z3fold_header *zhdr)
229{
230 spin_lock(&zhdr->page_lock);
231}
232
233/* Try to lock a z3fold page */
234static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
235{
236 return spin_trylock(&zhdr->page_lock);
237}
238
239/* Unlock a z3fold page */
240static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
241{
242 spin_unlock(&zhdr->page_lock);
243}
244
245/* return locked z3fold page if it's not headless */
246static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
247{
248 struct z3fold_buddy_slots *slots;
249 struct z3fold_header *zhdr;
250 int locked = 0;
251
252 if (!(handle & (1 << PAGE_HEADLESS))) {
253 slots = handle_to_slots(handle);
254 do {
255 unsigned long addr;
256
257 read_lock(&slots->lock);
258 addr = *(unsigned long *)handle;
259 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
260 locked = z3fold_page_trylock(zhdr);
261 read_unlock(&slots->lock);
262 if (locked) {
263 struct page *page = virt_to_page(zhdr);
264
265 if (!test_bit(PAGE_MIGRATED, &page->private))
266 break;
267 z3fold_page_unlock(zhdr);
268 }
269 cpu_relax();
270 } while (true);
271 } else {
272 zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
273 }
274
275 return zhdr;
276}
277
278static inline void put_z3fold_header(struct z3fold_header *zhdr)
279{
280 struct page *page = virt_to_page(zhdr);
281
282 if (!test_bit(PAGE_HEADLESS, &page->private))
283 z3fold_page_unlock(zhdr);
284}
285
286static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
287{
288 struct z3fold_buddy_slots *slots;
289 int i;
290 bool is_free;
291
292 if (WARN_ON(*(unsigned long *)handle == 0))
293 return;
294
295 slots = handle_to_slots(handle);
296 write_lock(&slots->lock);
297 *(unsigned long *)handle = 0;
298
299 if (test_bit(HANDLES_NOFREE, &slots->pool)) {
300 write_unlock(&slots->lock);
301 return; /* simple case, nothing else to do */
302 }
303
304 if (zhdr->slots != slots)
305 zhdr->foreign_handles--;
306
307 is_free = true;
308 for (i = 0; i <= BUDDY_MASK; i++) {
309 if (slots->slot[i]) {
310 is_free = false;
311 break;
312 }
313 }
314 write_unlock(&slots->lock);
315
316 if (is_free) {
317 struct z3fold_pool *pool = slots_to_pool(slots);
318
319 if (zhdr->slots == slots)
320 zhdr->slots = NULL;
321 kmem_cache_free(pool->c_handle, slots);
322 }
323}
324
325/* Initializes the z3fold header of a newly allocated z3fold page */
326static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
327 struct z3fold_pool *pool, gfp_t gfp)
328{
329 struct z3fold_header *zhdr = page_address(page);
330 struct z3fold_buddy_slots *slots;
331
332 INIT_LIST_HEAD(&page->lru);
333 clear_bit(PAGE_HEADLESS, &page->private);
334 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
335 clear_bit(NEEDS_COMPACTING, &page->private);
336 clear_bit(PAGE_STALE, &page->private);
337 clear_bit(PAGE_CLAIMED, &page->private);
338 clear_bit(PAGE_MIGRATED, &page->private);
339 if (headless)
340 return zhdr;
341
342 slots = alloc_slots(pool, gfp);
343 if (!slots)
344 return NULL;
345
346 memset(zhdr, 0, sizeof(*zhdr));
347 spin_lock_init(&zhdr->page_lock);
348 kref_init(&zhdr->refcount);
349 zhdr->cpu = -1;
350 zhdr->slots = slots;
351 zhdr->pool = pool;
352 INIT_LIST_HEAD(&zhdr->buddy);
353 INIT_WORK(&zhdr->work, compact_page_work);
354 return zhdr;
355}
356
357/* Resets the struct page fields and frees the page */
358static void free_z3fold_page(struct page *page, bool headless)
359{
360 if (!headless) {
361 lock_page(page);
362 __ClearPageMovable(page);
363 unlock_page(page);
364 }
365 __free_page(page);
366}
367
368/* Helper function to build the index */
369static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
370{
371 return (bud + zhdr->first_num) & BUDDY_MASK;
372}
373
374/*
375 * Encodes the handle of a particular buddy within a z3fold page
376 * Pool lock should be held as this function accesses first_num
377 */
378static unsigned long __encode_handle(struct z3fold_header *zhdr,
379 struct z3fold_buddy_slots *slots,
380 enum buddy bud)
381{
382 unsigned long h = (unsigned long)zhdr;
383 int idx = 0;
384
385 /*
386 * For a headless page, its handle is its pointer with the extra
387 * PAGE_HEADLESS bit set
388 */
389 if (bud == HEADLESS)
390 return h | (1 << PAGE_HEADLESS);
391
392 /* otherwise, return pointer to encoded handle */
393 idx = __idx(zhdr, bud);
394 h += idx;
395 if (bud == LAST)
396 h |= (zhdr->last_chunks << BUDDY_SHIFT);
397
398 write_lock(&slots->lock);
399 slots->slot[idx] = h;
400 write_unlock(&slots->lock);
401 return (unsigned long)&slots->slot[idx];
402}
403
404static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
405{
406 return __encode_handle(zhdr, zhdr->slots, bud);
407}
408
409/* only for LAST bud, returns zero otherwise */
410static unsigned short handle_to_chunks(unsigned long handle)
411{
412 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
413 unsigned long addr;
414
415 read_lock(&slots->lock);
416 addr = *(unsigned long *)handle;
417 read_unlock(&slots->lock);
418 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
419}
420
421/*
422 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
423 * but that doesn't matter. because the masking will result in the
424 * correct buddy number.
425 */
426static enum buddy handle_to_buddy(unsigned long handle)
427{
428 struct z3fold_header *zhdr;
429 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
430 unsigned long addr;
431
432 read_lock(&slots->lock);
433 WARN_ON(handle & (1 << PAGE_HEADLESS));
434 addr = *(unsigned long *)handle;
435 read_unlock(&slots->lock);
436 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
437 return (addr - zhdr->first_num) & BUDDY_MASK;
438}
439
440static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
441{
442 return zhdr->pool;
443}
444
445static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
446{
447 struct page *page = virt_to_page(zhdr);
448 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
449
450 WARN_ON(!list_empty(&zhdr->buddy));
451 set_bit(PAGE_STALE, &page->private);
452 clear_bit(NEEDS_COMPACTING, &page->private);
453 spin_lock(&pool->lock);
454 if (!list_empty(&page->lru))
455 list_del_init(&page->lru);
456 spin_unlock(&pool->lock);
457
458 if (locked)
459 z3fold_page_unlock(zhdr);
460
461 spin_lock(&pool->stale_lock);
462 list_add(&zhdr->buddy, &pool->stale);
463 queue_work(pool->release_wq, &pool->work);
464 spin_unlock(&pool->stale_lock);
465
466 atomic64_dec(&pool->pages_nr);
467}
468
469static void release_z3fold_page_locked(struct kref *ref)
470{
471 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
472 refcount);
473 WARN_ON(z3fold_page_trylock(zhdr));
474 __release_z3fold_page(zhdr, true);
475}
476
477static void release_z3fold_page_locked_list(struct kref *ref)
478{
479 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
480 refcount);
481 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
482
483 spin_lock(&pool->lock);
484 list_del_init(&zhdr->buddy);
485 spin_unlock(&pool->lock);
486
487 WARN_ON(z3fold_page_trylock(zhdr));
488 __release_z3fold_page(zhdr, true);
489}
490
491static void free_pages_work(struct work_struct *w)
492{
493 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
494
495 spin_lock(&pool->stale_lock);
496 while (!list_empty(&pool->stale)) {
497 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
498 struct z3fold_header, buddy);
499 struct page *page = virt_to_page(zhdr);
500
501 list_del(&zhdr->buddy);
502 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
503 continue;
504 spin_unlock(&pool->stale_lock);
505 cancel_work_sync(&zhdr->work);
506 free_z3fold_page(page, false);
507 cond_resched();
508 spin_lock(&pool->stale_lock);
509 }
510 spin_unlock(&pool->stale_lock);
511}
512
513/*
514 * Returns the number of free chunks in a z3fold page.
515 * NB: can't be used with HEADLESS pages.
516 */
517static int num_free_chunks(struct z3fold_header *zhdr)
518{
519 int nfree;
520 /*
521 * If there is a middle object, pick up the bigger free space
522 * either before or after it. Otherwise just subtract the number
523 * of chunks occupied by the first and the last objects.
524 */
525 if (zhdr->middle_chunks != 0) {
526 int nfree_before = zhdr->first_chunks ?
527 0 : zhdr->start_middle - ZHDR_CHUNKS;
528 int nfree_after = zhdr->last_chunks ?
529 0 : TOTAL_CHUNKS -
530 (zhdr->start_middle + zhdr->middle_chunks);
531 nfree = max(nfree_before, nfree_after);
532 } else
533 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
534 return nfree;
535}
536
537/* Add to the appropriate unbuddied list */
538static inline void add_to_unbuddied(struct z3fold_pool *pool,
539 struct z3fold_header *zhdr)
540{
541 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
542 zhdr->middle_chunks == 0) {
543 struct list_head *unbuddied;
544 int freechunks = num_free_chunks(zhdr);
545
546 migrate_disable();
547 unbuddied = this_cpu_ptr(pool->unbuddied);
548 spin_lock(&pool->lock);
549 list_add(&zhdr->buddy, &unbuddied[freechunks]);
550 spin_unlock(&pool->lock);
551 zhdr->cpu = smp_processor_id();
552 migrate_enable();
553 }
554}
555
556static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
557{
558 enum buddy bud = HEADLESS;
559
560 if (zhdr->middle_chunks) {
561 if (!zhdr->first_chunks &&
562 chunks <= zhdr->start_middle - ZHDR_CHUNKS)
563 bud = FIRST;
564 else if (!zhdr->last_chunks)
565 bud = LAST;
566 } else {
567 if (!zhdr->first_chunks)
568 bud = FIRST;
569 else if (!zhdr->last_chunks)
570 bud = LAST;
571 else
572 bud = MIDDLE;
573 }
574
575 return bud;
576}
577
578static inline void *mchunk_memmove(struct z3fold_header *zhdr,
579 unsigned short dst_chunk)
580{
581 void *beg = zhdr;
582 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
583 beg + (zhdr->start_middle << CHUNK_SHIFT),
584 zhdr->middle_chunks << CHUNK_SHIFT);
585}
586
587static inline bool buddy_single(struct z3fold_header *zhdr)
588{
589 return !((zhdr->first_chunks && zhdr->middle_chunks) ||
590 (zhdr->first_chunks && zhdr->last_chunks) ||
591 (zhdr->middle_chunks && zhdr->last_chunks));
592}
593
594static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
595{
596 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
597 void *p = zhdr;
598 unsigned long old_handle = 0;
599 size_t sz = 0;
600 struct z3fold_header *new_zhdr = NULL;
601 int first_idx = __idx(zhdr, FIRST);
602 int middle_idx = __idx(zhdr, MIDDLE);
603 int last_idx = __idx(zhdr, LAST);
604 unsigned short *moved_chunks = NULL;
605
606 /*
607 * No need to protect slots here -- all the slots are "local" and
608 * the page lock is already taken
609 */
610 if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
611 p += ZHDR_SIZE_ALIGNED;
612 sz = zhdr->first_chunks << CHUNK_SHIFT;
613 old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
614 moved_chunks = &zhdr->first_chunks;
615 } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
616 p += zhdr->start_middle << CHUNK_SHIFT;
617 sz = zhdr->middle_chunks << CHUNK_SHIFT;
618 old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
619 moved_chunks = &zhdr->middle_chunks;
620 } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
621 p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
622 sz = zhdr->last_chunks << CHUNK_SHIFT;
623 old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
624 moved_chunks = &zhdr->last_chunks;
625 }
626
627 if (sz > 0) {
628 enum buddy new_bud = HEADLESS;
629 short chunks = size_to_chunks(sz);
630 void *q;
631
632 new_zhdr = __z3fold_alloc(pool, sz, false);
633 if (!new_zhdr)
634 return NULL;
635
636 if (WARN_ON(new_zhdr == zhdr))
637 goto out_fail;
638
639 new_bud = get_free_buddy(new_zhdr, chunks);
640 q = new_zhdr;
641 switch (new_bud) {
642 case FIRST:
643 new_zhdr->first_chunks = chunks;
644 q += ZHDR_SIZE_ALIGNED;
645 break;
646 case MIDDLE:
647 new_zhdr->middle_chunks = chunks;
648 new_zhdr->start_middle =
649 new_zhdr->first_chunks + ZHDR_CHUNKS;
650 q += new_zhdr->start_middle << CHUNK_SHIFT;
651 break;
652 case LAST:
653 new_zhdr->last_chunks = chunks;
654 q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
655 break;
656 default:
657 goto out_fail;
658 }
659 new_zhdr->foreign_handles++;
660 memcpy(q, p, sz);
661 write_lock(&zhdr->slots->lock);
662 *(unsigned long *)old_handle = (unsigned long)new_zhdr +
663 __idx(new_zhdr, new_bud);
664 if (new_bud == LAST)
665 *(unsigned long *)old_handle |=
666 (new_zhdr->last_chunks << BUDDY_SHIFT);
667 write_unlock(&zhdr->slots->lock);
668 add_to_unbuddied(pool, new_zhdr);
669 z3fold_page_unlock(new_zhdr);
670
671 *moved_chunks = 0;
672 }
673
674 return new_zhdr;
675
676out_fail:
677 if (new_zhdr && !kref_put(&new_zhdr->refcount, release_z3fold_page_locked)) {
678 add_to_unbuddied(pool, new_zhdr);
679 z3fold_page_unlock(new_zhdr);
680 }
681 return NULL;
682
683}
684
685#define BIG_CHUNK_GAP 3
686/* Has to be called with lock held */
687static int z3fold_compact_page(struct z3fold_header *zhdr)
688{
689 struct page *page = virt_to_page(zhdr);
690
691 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
692 return 0; /* can't move middle chunk, it's used */
693
694 if (unlikely(PageIsolated(page)))
695 return 0;
696
697 if (zhdr->middle_chunks == 0)
698 return 0; /* nothing to compact */
699
700 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
701 /* move to the beginning */
702 mchunk_memmove(zhdr, ZHDR_CHUNKS);
703 zhdr->first_chunks = zhdr->middle_chunks;
704 zhdr->middle_chunks = 0;
705 zhdr->start_middle = 0;
706 zhdr->first_num++;
707 return 1;
708 }
709
710 /*
711 * moving data is expensive, so let's only do that if
712 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
713 */
714 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
715 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
716 BIG_CHUNK_GAP) {
717 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
718 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
719 return 1;
720 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
721 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
722 + zhdr->middle_chunks) >=
723 BIG_CHUNK_GAP) {
724 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
725 zhdr->middle_chunks;
726 mchunk_memmove(zhdr, new_start);
727 zhdr->start_middle = new_start;
728 return 1;
729 }
730
731 return 0;
732}
733
734static void do_compact_page(struct z3fold_header *zhdr, bool locked)
735{
736 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
737 struct page *page;
738
739 page = virt_to_page(zhdr);
740 if (locked)
741 WARN_ON(z3fold_page_trylock(zhdr));
742 else
743 z3fold_page_lock(zhdr);
744 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
745 z3fold_page_unlock(zhdr);
746 return;
747 }
748 spin_lock(&pool->lock);
749 list_del_init(&zhdr->buddy);
750 spin_unlock(&pool->lock);
751
752 if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
753 return;
754
755 if (test_bit(PAGE_STALE, &page->private) ||
756 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
757 z3fold_page_unlock(zhdr);
758 return;
759 }
760
761 if (!zhdr->foreign_handles && buddy_single(zhdr) &&
762 zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
763 if (!kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
764 clear_bit(PAGE_CLAIMED, &page->private);
765 z3fold_page_unlock(zhdr);
766 }
767 return;
768 }
769
770 z3fold_compact_page(zhdr);
771 add_to_unbuddied(pool, zhdr);
772 clear_bit(PAGE_CLAIMED, &page->private);
773 z3fold_page_unlock(zhdr);
774}
775
776static void compact_page_work(struct work_struct *w)
777{
778 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
779 work);
780
781 do_compact_page(zhdr, false);
782}
783
784/* returns _locked_ z3fold page header or NULL */
785static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
786 size_t size, bool can_sleep)
787{
788 struct z3fold_header *zhdr = NULL;
789 struct page *page;
790 struct list_head *unbuddied;
791 int chunks = size_to_chunks(size), i;
792
793lookup:
794 migrate_disable();
795 /* First, try to find an unbuddied z3fold page. */
796 unbuddied = this_cpu_ptr(pool->unbuddied);
797 for_each_unbuddied_list(i, chunks) {
798 struct list_head *l = &unbuddied[i];
799
800 zhdr = list_first_entry_or_null(READ_ONCE(l),
801 struct z3fold_header, buddy);
802
803 if (!zhdr)
804 continue;
805
806 /* Re-check under lock. */
807 spin_lock(&pool->lock);
808 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
809 struct z3fold_header, buddy)) ||
810 !z3fold_page_trylock(zhdr)) {
811 spin_unlock(&pool->lock);
812 zhdr = NULL;
813 migrate_enable();
814 if (can_sleep)
815 cond_resched();
816 goto lookup;
817 }
818 list_del_init(&zhdr->buddy);
819 zhdr->cpu = -1;
820 spin_unlock(&pool->lock);
821
822 page = virt_to_page(zhdr);
823 if (test_bit(NEEDS_COMPACTING, &page->private) ||
824 test_bit(PAGE_CLAIMED, &page->private)) {
825 z3fold_page_unlock(zhdr);
826 zhdr = NULL;
827 migrate_enable();
828 if (can_sleep)
829 cond_resched();
830 goto lookup;
831 }
832
833 /*
834 * this page could not be removed from its unbuddied
835 * list while pool lock was held, and then we've taken
836 * page lock so kref_put could not be called before
837 * we got here, so it's safe to just call kref_get()
838 */
839 kref_get(&zhdr->refcount);
840 break;
841 }
842 migrate_enable();
843
844 if (!zhdr) {
845 int cpu;
846
847 /* look for _exact_ match on other cpus' lists */
848 for_each_online_cpu(cpu) {
849 struct list_head *l;
850
851 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
852 spin_lock(&pool->lock);
853 l = &unbuddied[chunks];
854
855 zhdr = list_first_entry_or_null(READ_ONCE(l),
856 struct z3fold_header, buddy);
857
858 if (!zhdr || !z3fold_page_trylock(zhdr)) {
859 spin_unlock(&pool->lock);
860 zhdr = NULL;
861 continue;
862 }
863 list_del_init(&zhdr->buddy);
864 zhdr->cpu = -1;
865 spin_unlock(&pool->lock);
866
867 page = virt_to_page(zhdr);
868 if (test_bit(NEEDS_COMPACTING, &page->private) ||
869 test_bit(PAGE_CLAIMED, &page->private)) {
870 z3fold_page_unlock(zhdr);
871 zhdr = NULL;
872 if (can_sleep)
873 cond_resched();
874 continue;
875 }
876 kref_get(&zhdr->refcount);
877 break;
878 }
879 }
880
881 if (zhdr && !zhdr->slots) {
882 zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
883 if (!zhdr->slots)
884 goto out_fail;
885 }
886 return zhdr;
887
888out_fail:
889 if (!kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
890 add_to_unbuddied(pool, zhdr);
891 z3fold_page_unlock(zhdr);
892 }
893 return NULL;
894}
895
896/*
897 * API Functions
898 */
899
900/**
901 * z3fold_create_pool() - create a new z3fold pool
902 * @name: pool name
903 * @gfp: gfp flags when allocating the z3fold pool structure
904 *
905 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
906 * failed.
907 */
908static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp)
909{
910 struct z3fold_pool *pool = NULL;
911 int i, cpu;
912
913 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
914 if (!pool)
915 goto out;
916 pool->c_handle = kmem_cache_create("z3fold_handle",
917 sizeof(struct z3fold_buddy_slots),
918 SLOTS_ALIGN, 0, NULL);
919 if (!pool->c_handle)
920 goto out_c;
921 spin_lock_init(&pool->lock);
922 spin_lock_init(&pool->stale_lock);
923 pool->unbuddied = __alloc_percpu(sizeof(struct list_head) * NCHUNKS,
924 __alignof__(struct list_head));
925 if (!pool->unbuddied)
926 goto out_pool;
927 for_each_possible_cpu(cpu) {
928 struct list_head *unbuddied =
929 per_cpu_ptr(pool->unbuddied, cpu);
930 for_each_unbuddied_list(i, 0)
931 INIT_LIST_HEAD(&unbuddied[i]);
932 }
933 INIT_LIST_HEAD(&pool->lru);
934 INIT_LIST_HEAD(&pool->stale);
935 atomic64_set(&pool->pages_nr, 0);
936 pool->name = name;
937 pool->compact_wq = create_singlethread_workqueue(pool->name);
938 if (!pool->compact_wq)
939 goto out_unbuddied;
940 pool->release_wq = create_singlethread_workqueue(pool->name);
941 if (!pool->release_wq)
942 goto out_wq;
943 INIT_WORK(&pool->work, free_pages_work);
944 return pool;
945
946out_wq:
947 destroy_workqueue(pool->compact_wq);
948out_unbuddied:
949 free_percpu(pool->unbuddied);
950out_pool:
951 kmem_cache_destroy(pool->c_handle);
952out_c:
953 kfree(pool);
954out:
955 return NULL;
956}
957
958/**
959 * z3fold_destroy_pool() - destroys an existing z3fold pool
960 * @pool: the z3fold pool to be destroyed
961 *
962 * The pool should be emptied before this function is called.
963 */
964static void z3fold_destroy_pool(struct z3fold_pool *pool)
965{
966 kmem_cache_destroy(pool->c_handle);
967
968 /*
969 * We need to destroy pool->compact_wq before pool->release_wq,
970 * as any pending work on pool->compact_wq will call
971 * queue_work(pool->release_wq, &pool->work).
972 *
973 * There are still outstanding pages until both workqueues are drained,
974 * so we cannot unregister migration until then.
975 */
976
977 destroy_workqueue(pool->compact_wq);
978 destroy_workqueue(pool->release_wq);
979 free_percpu(pool->unbuddied);
980 kfree(pool);
981}
982
983static const struct movable_operations z3fold_mops;
984
985/**
986 * z3fold_alloc() - allocates a region of a given size
987 * @pool: z3fold pool from which to allocate
988 * @size: size in bytes of the desired allocation
989 * @gfp: gfp flags used if the pool needs to grow
990 * @handle: handle of the new allocation
991 *
992 * This function will attempt to find a free region in the pool large enough to
993 * satisfy the allocation request. A search of the unbuddied lists is
994 * performed first. If no suitable free region is found, then a new page is
995 * allocated and added to the pool to satisfy the request.
996 *
997 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
998 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
999 * a new page.
1000 */
1001static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1002 unsigned long *handle)
1003{
1004 int chunks = size_to_chunks(size);
1005 struct z3fold_header *zhdr = NULL;
1006 struct page *page = NULL;
1007 enum buddy bud;
1008 bool can_sleep = gfpflags_allow_blocking(gfp);
1009
1010 if (!size || (gfp & __GFP_HIGHMEM))
1011 return -EINVAL;
1012
1013 if (size > PAGE_SIZE)
1014 return -ENOSPC;
1015
1016 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1017 bud = HEADLESS;
1018 else {
1019retry:
1020 zhdr = __z3fold_alloc(pool, size, can_sleep);
1021 if (zhdr) {
1022 bud = get_free_buddy(zhdr, chunks);
1023 if (bud == HEADLESS) {
1024 if (!kref_put(&zhdr->refcount,
1025 release_z3fold_page_locked))
1026 z3fold_page_unlock(zhdr);
1027 pr_err("No free chunks in unbuddied\n");
1028 WARN_ON(1);
1029 goto retry;
1030 }
1031 page = virt_to_page(zhdr);
1032 goto found;
1033 }
1034 bud = FIRST;
1035 }
1036
1037 page = alloc_page(gfp);
1038 if (!page)
1039 return -ENOMEM;
1040
1041 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
1042 if (!zhdr) {
1043 __free_page(page);
1044 return -ENOMEM;
1045 }
1046 atomic64_inc(&pool->pages_nr);
1047
1048 if (bud == HEADLESS) {
1049 set_bit(PAGE_HEADLESS, &page->private);
1050 goto headless;
1051 }
1052 if (can_sleep) {
1053 lock_page(page);
1054 __SetPageMovable(page, &z3fold_mops);
1055 unlock_page(page);
1056 } else {
1057 WARN_ON(!trylock_page(page));
1058 __SetPageMovable(page, &z3fold_mops);
1059 unlock_page(page);
1060 }
1061 z3fold_page_lock(zhdr);
1062
1063found:
1064 if (bud == FIRST)
1065 zhdr->first_chunks = chunks;
1066 else if (bud == LAST)
1067 zhdr->last_chunks = chunks;
1068 else {
1069 zhdr->middle_chunks = chunks;
1070 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
1071 }
1072 add_to_unbuddied(pool, zhdr);
1073
1074headless:
1075 spin_lock(&pool->lock);
1076 /* Add/move z3fold page to beginning of LRU */
1077 if (!list_empty(&page->lru))
1078 list_del(&page->lru);
1079
1080 list_add(&page->lru, &pool->lru);
1081
1082 *handle = encode_handle(zhdr, bud);
1083 spin_unlock(&pool->lock);
1084 if (bud != HEADLESS)
1085 z3fold_page_unlock(zhdr);
1086
1087 return 0;
1088}
1089
1090/**
1091 * z3fold_free() - frees the allocation associated with the given handle
1092 * @pool: pool in which the allocation resided
1093 * @handle: handle associated with the allocation returned by z3fold_alloc()
1094 *
1095 * In the case that the z3fold page in which the allocation resides is under
1096 * reclaim, as indicated by the PAGE_CLAIMED flag being set, this function
1097 * only sets the first|middle|last_chunks to 0. The page is actually freed
1098 * once all buddies are evicted (see z3fold_reclaim_page() below).
1099 */
1100static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1101{
1102 struct z3fold_header *zhdr;
1103 struct page *page;
1104 enum buddy bud;
1105 bool page_claimed;
1106
1107 zhdr = get_z3fold_header(handle);
1108 page = virt_to_page(zhdr);
1109 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1110
1111 if (test_bit(PAGE_HEADLESS, &page->private)) {
1112 /* if a headless page is under reclaim, just leave.
1113 * NB: we use test_and_set_bit for a reason: if the bit
1114 * has not been set before, we release this page
1115 * immediately so we don't care about its value any more.
1116 */
1117 if (!page_claimed) {
1118 spin_lock(&pool->lock);
1119 list_del(&page->lru);
1120 spin_unlock(&pool->lock);
1121 put_z3fold_header(zhdr);
1122 free_z3fold_page(page, true);
1123 atomic64_dec(&pool->pages_nr);
1124 }
1125 return;
1126 }
1127
1128 /* Non-headless case */
1129 bud = handle_to_buddy(handle);
1130
1131 switch (bud) {
1132 case FIRST:
1133 zhdr->first_chunks = 0;
1134 break;
1135 case MIDDLE:
1136 zhdr->middle_chunks = 0;
1137 break;
1138 case LAST:
1139 zhdr->last_chunks = 0;
1140 break;
1141 default:
1142 pr_err("%s: unknown bud %d\n", __func__, bud);
1143 WARN_ON(1);
1144 put_z3fold_header(zhdr);
1145 return;
1146 }
1147
1148 if (!page_claimed)
1149 free_handle(handle, zhdr);
1150 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list))
1151 return;
1152 if (page_claimed) {
1153 /* the page has not been claimed by us */
1154 put_z3fold_header(zhdr);
1155 return;
1156 }
1157 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1158 clear_bit(PAGE_CLAIMED, &page->private);
1159 put_z3fold_header(zhdr);
1160 return;
1161 }
1162 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1163 zhdr->cpu = -1;
1164 kref_get(&zhdr->refcount);
1165 clear_bit(PAGE_CLAIMED, &page->private);
1166 do_compact_page(zhdr, true);
1167 return;
1168 }
1169 kref_get(&zhdr->refcount);
1170 clear_bit(PAGE_CLAIMED, &page->private);
1171 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1172 put_z3fold_header(zhdr);
1173}
1174
1175/**
1176 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1177 * @pool: pool from which a page will attempt to be evicted
1178 * @retries: number of pages on the LRU list for which eviction will
1179 * be attempted before failing
1180 *
1181 * z3fold reclaim is different from normal system reclaim in that it is done
1182 * from the bottom, up. This is because only the bottom layer, z3fold, has
1183 * information on how the allocations are organized within each z3fold page.
1184 * This has the potential to create interesting locking situations between
1185 * z3fold and the user, however.
1186 *
1187 * To avoid these, this is how z3fold_reclaim_page() should be called:
1188 *
1189 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1190 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1191 * call the user-defined eviction handler with the pool and handle as
1192 * arguments.
1193 *
1194 * If the handle can not be evicted, the eviction handler should return
1195 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1196 * appropriate list and try the next z3fold page on the LRU up to
1197 * a user defined number of retries.
1198 *
1199 * If the handle is successfully evicted, the eviction handler should
1200 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1201 * contains logic to delay freeing the page if the page is under reclaim,
1202 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1203 *
1204 * If all buddies in the z3fold page are successfully evicted, then the
1205 * z3fold page can be freed.
1206 *
1207 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1208 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1209 * the retry limit was hit.
1210 */
1211static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1212{
1213 int i, ret = -1;
1214 struct z3fold_header *zhdr = NULL;
1215 struct page *page = NULL;
1216 struct list_head *pos;
1217 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1218 struct z3fold_buddy_slots slots __attribute__((aligned(SLOTS_ALIGN)));
1219
1220 rwlock_init(&slots.lock);
1221 slots.pool = (unsigned long)pool | (1 << HANDLES_NOFREE);
1222
1223 spin_lock(&pool->lock);
1224 for (i = 0; i < retries; i++) {
1225 if (list_empty(&pool->lru)) {
1226 spin_unlock(&pool->lock);
1227 return -EINVAL;
1228 }
1229 list_for_each_prev(pos, &pool->lru) {
1230 page = list_entry(pos, struct page, lru);
1231
1232 zhdr = page_address(page);
1233 if (test_bit(PAGE_HEADLESS, &page->private)) {
1234 /*
1235 * For non-headless pages, we wait to do this
1236 * until we have the page lock to avoid racing
1237 * with __z3fold_alloc(). Headless pages don't
1238 * have a lock (and __z3fold_alloc() will never
1239 * see them), but we still need to test and set
1240 * PAGE_CLAIMED to avoid racing with
1241 * z3fold_free(), so just do it now before
1242 * leaving the loop.
1243 */
1244 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1245 continue;
1246
1247 break;
1248 }
1249
1250 if (!z3fold_page_trylock(zhdr)) {
1251 zhdr = NULL;
1252 continue; /* can't evict at this point */
1253 }
1254
1255 /* test_and_set_bit is of course atomic, but we still
1256 * need to do it under page lock, otherwise checking
1257 * that bit in __z3fold_alloc wouldn't make sense
1258 */
1259 if (zhdr->foreign_handles ||
1260 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1261 z3fold_page_unlock(zhdr);
1262 zhdr = NULL;
1263 continue; /* can't evict such page */
1264 }
1265 list_del_init(&zhdr->buddy);
1266 zhdr->cpu = -1;
1267 /* See comment in __z3fold_alloc. */
1268 kref_get(&zhdr->refcount);
1269 break;
1270 }
1271
1272 if (!zhdr)
1273 break;
1274
1275 list_del_init(&page->lru);
1276 spin_unlock(&pool->lock);
1277
1278 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1279 /*
1280 * We need encode the handles before unlocking, and
1281 * use our local slots structure because z3fold_free
1282 * can zero out zhdr->slots and we can't do much
1283 * about that
1284 */
1285 first_handle = 0;
1286 last_handle = 0;
1287 middle_handle = 0;
1288 memset(slots.slot, 0, sizeof(slots.slot));
1289 if (zhdr->first_chunks)
1290 first_handle = __encode_handle(zhdr, &slots,
1291 FIRST);
1292 if (zhdr->middle_chunks)
1293 middle_handle = __encode_handle(zhdr, &slots,
1294 MIDDLE);
1295 if (zhdr->last_chunks)
1296 last_handle = __encode_handle(zhdr, &slots,
1297 LAST);
1298 /*
1299 * it's safe to unlock here because we hold a
1300 * reference to this page
1301 */
1302 z3fold_page_unlock(zhdr);
1303 } else {
1304 first_handle = encode_handle(zhdr, HEADLESS);
1305 last_handle = middle_handle = 0;
1306 }
1307 /* Issue the eviction callback(s) */
1308 if (middle_handle) {
1309 ret = pool->zpool_ops->evict(pool->zpool, middle_handle);
1310 if (ret)
1311 goto next;
1312 }
1313 if (first_handle) {
1314 ret = pool->zpool_ops->evict(pool->zpool, first_handle);
1315 if (ret)
1316 goto next;
1317 }
1318 if (last_handle) {
1319 ret = pool->zpool_ops->evict(pool->zpool, last_handle);
1320 if (ret)
1321 goto next;
1322 }
1323next:
1324 if (test_bit(PAGE_HEADLESS, &page->private)) {
1325 if (ret == 0) {
1326 free_z3fold_page(page, true);
1327 atomic64_dec(&pool->pages_nr);
1328 return 0;
1329 }
1330 spin_lock(&pool->lock);
1331 list_add(&page->lru, &pool->lru);
1332 spin_unlock(&pool->lock);
1333 clear_bit(PAGE_CLAIMED, &page->private);
1334 } else {
1335 struct z3fold_buddy_slots *slots = zhdr->slots;
1336 z3fold_page_lock(zhdr);
1337 if (kref_put(&zhdr->refcount,
1338 release_z3fold_page_locked)) {
1339 kmem_cache_free(pool->c_handle, slots);
1340 return 0;
1341 }
1342 /*
1343 * if we are here, the page is still not completely
1344 * free. Take the global pool lock then to be able
1345 * to add it back to the lru list
1346 */
1347 spin_lock(&pool->lock);
1348 list_add(&page->lru, &pool->lru);
1349 spin_unlock(&pool->lock);
1350 if (list_empty(&zhdr->buddy))
1351 add_to_unbuddied(pool, zhdr);
1352 clear_bit(PAGE_CLAIMED, &page->private);
1353 z3fold_page_unlock(zhdr);
1354 }
1355
1356 /* We started off locked to we need to lock the pool back */
1357 spin_lock(&pool->lock);
1358 }
1359 spin_unlock(&pool->lock);
1360 return -EAGAIN;
1361}
1362
1363/**
1364 * z3fold_map() - maps the allocation associated with the given handle
1365 * @pool: pool in which the allocation resides
1366 * @handle: handle associated with the allocation to be mapped
1367 *
1368 * Extracts the buddy number from handle and constructs the pointer to the
1369 * correct starting chunk within the page.
1370 *
1371 * Returns: a pointer to the mapped allocation
1372 */
1373static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1374{
1375 struct z3fold_header *zhdr;
1376 struct page *page;
1377 void *addr;
1378 enum buddy buddy;
1379
1380 zhdr = get_z3fold_header(handle);
1381 addr = zhdr;
1382 page = virt_to_page(zhdr);
1383
1384 if (test_bit(PAGE_HEADLESS, &page->private))
1385 goto out;
1386
1387 buddy = handle_to_buddy(handle);
1388 switch (buddy) {
1389 case FIRST:
1390 addr += ZHDR_SIZE_ALIGNED;
1391 break;
1392 case MIDDLE:
1393 addr += zhdr->start_middle << CHUNK_SHIFT;
1394 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1395 break;
1396 case LAST:
1397 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1398 break;
1399 default:
1400 pr_err("unknown buddy id %d\n", buddy);
1401 WARN_ON(1);
1402 addr = NULL;
1403 break;
1404 }
1405
1406 if (addr)
1407 zhdr->mapped_count++;
1408out:
1409 put_z3fold_header(zhdr);
1410 return addr;
1411}
1412
1413/**
1414 * z3fold_unmap() - unmaps the allocation associated with the given handle
1415 * @pool: pool in which the allocation resides
1416 * @handle: handle associated with the allocation to be unmapped
1417 */
1418static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1419{
1420 struct z3fold_header *zhdr;
1421 struct page *page;
1422 enum buddy buddy;
1423
1424 zhdr = get_z3fold_header(handle);
1425 page = virt_to_page(zhdr);
1426
1427 if (test_bit(PAGE_HEADLESS, &page->private))
1428 return;
1429
1430 buddy = handle_to_buddy(handle);
1431 if (buddy == MIDDLE)
1432 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1433 zhdr->mapped_count--;
1434 put_z3fold_header(zhdr);
1435}
1436
1437/**
1438 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1439 * @pool: pool whose size is being queried
1440 *
1441 * Returns: size in pages of the given pool.
1442 */
1443static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1444{
1445 return atomic64_read(&pool->pages_nr);
1446}
1447
1448static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1449{
1450 struct z3fold_header *zhdr;
1451 struct z3fold_pool *pool;
1452
1453 VM_BUG_ON_PAGE(!PageMovable(page), page);
1454 VM_BUG_ON_PAGE(PageIsolated(page), page);
1455
1456 if (test_bit(PAGE_HEADLESS, &page->private))
1457 return false;
1458
1459 zhdr = page_address(page);
1460 z3fold_page_lock(zhdr);
1461 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1462 test_bit(PAGE_STALE, &page->private))
1463 goto out;
1464
1465 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1466 goto out;
1467
1468 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1469 goto out;
1470 pool = zhdr_to_pool(zhdr);
1471 spin_lock(&pool->lock);
1472 if (!list_empty(&zhdr->buddy))
1473 list_del_init(&zhdr->buddy);
1474 if (!list_empty(&page->lru))
1475 list_del_init(&page->lru);
1476 spin_unlock(&pool->lock);
1477
1478 kref_get(&zhdr->refcount);
1479 z3fold_page_unlock(zhdr);
1480 return true;
1481
1482out:
1483 z3fold_page_unlock(zhdr);
1484 return false;
1485}
1486
1487static int z3fold_page_migrate(struct page *newpage, struct page *page,
1488 enum migrate_mode mode)
1489{
1490 struct z3fold_header *zhdr, *new_zhdr;
1491 struct z3fold_pool *pool;
1492
1493 VM_BUG_ON_PAGE(!PageMovable(page), page);
1494 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1495 VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
1496 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1497
1498 zhdr = page_address(page);
1499 pool = zhdr_to_pool(zhdr);
1500
1501 if (!z3fold_page_trylock(zhdr))
1502 return -EAGAIN;
1503 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1504 clear_bit(PAGE_CLAIMED, &page->private);
1505 z3fold_page_unlock(zhdr);
1506 return -EBUSY;
1507 }
1508 if (work_pending(&zhdr->work)) {
1509 z3fold_page_unlock(zhdr);
1510 return -EAGAIN;
1511 }
1512 new_zhdr = page_address(newpage);
1513 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1514 newpage->private = page->private;
1515 set_bit(PAGE_MIGRATED, &page->private);
1516 z3fold_page_unlock(zhdr);
1517 spin_lock_init(&new_zhdr->page_lock);
1518 INIT_WORK(&new_zhdr->work, compact_page_work);
1519 /*
1520 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1521 * so we only have to reinitialize it.
1522 */
1523 INIT_LIST_HEAD(&new_zhdr->buddy);
1524 __ClearPageMovable(page);
1525
1526 get_page(newpage);
1527 z3fold_page_lock(new_zhdr);
1528 if (new_zhdr->first_chunks)
1529 encode_handle(new_zhdr, FIRST);
1530 if (new_zhdr->last_chunks)
1531 encode_handle(new_zhdr, LAST);
1532 if (new_zhdr->middle_chunks)
1533 encode_handle(new_zhdr, MIDDLE);
1534 set_bit(NEEDS_COMPACTING, &newpage->private);
1535 new_zhdr->cpu = smp_processor_id();
1536 spin_lock(&pool->lock);
1537 list_add(&newpage->lru, &pool->lru);
1538 spin_unlock(&pool->lock);
1539 __SetPageMovable(newpage, &z3fold_mops);
1540 z3fold_page_unlock(new_zhdr);
1541
1542 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1543
1544 /* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */
1545 page->private = 0;
1546 put_page(page);
1547 return 0;
1548}
1549
1550static void z3fold_page_putback(struct page *page)
1551{
1552 struct z3fold_header *zhdr;
1553 struct z3fold_pool *pool;
1554
1555 zhdr = page_address(page);
1556 pool = zhdr_to_pool(zhdr);
1557
1558 z3fold_page_lock(zhdr);
1559 if (!list_empty(&zhdr->buddy))
1560 list_del_init(&zhdr->buddy);
1561 INIT_LIST_HEAD(&page->lru);
1562 if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
1563 return;
1564 spin_lock(&pool->lock);
1565 list_add(&page->lru, &pool->lru);
1566 spin_unlock(&pool->lock);
1567 if (list_empty(&zhdr->buddy))
1568 add_to_unbuddied(pool, zhdr);
1569 clear_bit(PAGE_CLAIMED, &page->private);
1570 z3fold_page_unlock(zhdr);
1571}
1572
1573static const struct movable_operations z3fold_mops = {
1574 .isolate_page = z3fold_page_isolate,
1575 .migrate_page = z3fold_page_migrate,
1576 .putback_page = z3fold_page_putback,
1577};
1578
1579/*****************
1580 * zpool
1581 ****************/
1582
1583static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1584 const struct zpool_ops *zpool_ops,
1585 struct zpool *zpool)
1586{
1587 struct z3fold_pool *pool;
1588
1589 pool = z3fold_create_pool(name, gfp);
1590 if (pool) {
1591 pool->zpool = zpool;
1592 pool->zpool_ops = zpool_ops;
1593 }
1594 return pool;
1595}
1596
1597static void z3fold_zpool_destroy(void *pool)
1598{
1599 z3fold_destroy_pool(pool);
1600}
1601
1602static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1603 unsigned long *handle)
1604{
1605 return z3fold_alloc(pool, size, gfp, handle);
1606}
1607static void z3fold_zpool_free(void *pool, unsigned long handle)
1608{
1609 z3fold_free(pool, handle);
1610}
1611
1612static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1613 unsigned int *reclaimed)
1614{
1615 unsigned int total = 0;
1616 int ret = -EINVAL;
1617
1618 while (total < pages) {
1619 ret = z3fold_reclaim_page(pool, 8);
1620 if (ret < 0)
1621 break;
1622 total++;
1623 }
1624
1625 if (reclaimed)
1626 *reclaimed = total;
1627
1628 return ret;
1629}
1630
1631static void *z3fold_zpool_map(void *pool, unsigned long handle,
1632 enum zpool_mapmode mm)
1633{
1634 return z3fold_map(pool, handle);
1635}
1636static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1637{
1638 z3fold_unmap(pool, handle);
1639}
1640
1641static u64 z3fold_zpool_total_size(void *pool)
1642{
1643 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1644}
1645
1646static struct zpool_driver z3fold_zpool_driver = {
1647 .type = "z3fold",
1648 .sleep_mapped = true,
1649 .owner = THIS_MODULE,
1650 .create = z3fold_zpool_create,
1651 .destroy = z3fold_zpool_destroy,
1652 .malloc = z3fold_zpool_malloc,
1653 .free = z3fold_zpool_free,
1654 .shrink = z3fold_zpool_shrink,
1655 .map = z3fold_zpool_map,
1656 .unmap = z3fold_zpool_unmap,
1657 .total_size = z3fold_zpool_total_size,
1658};
1659
1660MODULE_ALIAS("zpool-z3fold");
1661
1662static int __init init_z3fold(void)
1663{
1664 /*
1665 * Make sure the z3fold header is not larger than the page size and
1666 * there has remaining spaces for its buddy.
1667 */
1668 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
1669 zpool_register_driver(&z3fold_zpool_driver);
1670
1671 return 0;
1672}
1673
1674static void __exit exit_z3fold(void)
1675{
1676 zpool_unregister_driver(&z3fold_zpool_driver);
1677}
1678
1679module_init(init_z3fold);
1680module_exit(exit_z3fold);
1681
1682MODULE_LICENSE("GPL");
1683MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1684MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");