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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 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 * @stale: list of pages marked for freeing
134 * @pages_nr: number of z3fold pages in the pool.
135 * @c_handle: cache for z3fold_buddy_slots allocation
136 * @compact_wq: workqueue for page layout background optimization
137 * @release_wq: workqueue for safe page release
138 * @work: work_struct for safe page release
139 *
140 * This structure is allocated at pool creation time and maintains metadata
141 * pertaining to a particular z3fold pool.
142 */
143struct z3fold_pool {
144 const char *name;
145 spinlock_t lock;
146 spinlock_t stale_lock;
147 struct list_head *unbuddied;
148 struct list_head stale;
149 atomic64_t pages_nr;
150 struct kmem_cache *c_handle;
151 struct workqueue_struct *compact_wq;
152 struct workqueue_struct *release_wq;
153 struct work_struct work;
154};
155
156/*
157 * Internal z3fold page flags
158 */
159enum z3fold_page_flags {
160 PAGE_HEADLESS = 0,
161 MIDDLE_CHUNK_MAPPED,
162 NEEDS_COMPACTING,
163 PAGE_STALE,
164 PAGE_CLAIMED, /* by either reclaim or free */
165 PAGE_MIGRATED, /* page is migrated and soon to be released */
166};
167
168/*
169 * handle flags, go under HANDLE_FLAG_MASK
170 */
171enum z3fold_handle_flags {
172 HANDLES_NOFREE = 0,
173};
174
175/*
176 * Forward declarations
177 */
178static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
179static void compact_page_work(struct work_struct *w);
180
181/*****************
182 * Helpers
183*****************/
184
185/* Converts an allocation size in bytes to size in z3fold chunks */
186static int size_to_chunks(size_t size)
187{
188 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
189}
190
191#define for_each_unbuddied_list(_iter, _begin) \
192 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
193
194static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
195 gfp_t gfp)
196{
197 struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
198 gfp);
199
200 if (slots) {
201 /* It will be freed separately in free_handle(). */
202 kmemleak_not_leak(slots);
203 slots->pool = (unsigned long)pool;
204 rwlock_init(&slots->lock);
205 }
206
207 return slots;
208}
209
210static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
211{
212 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
213}
214
215static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
216{
217 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
218}
219
220/* Lock a z3fold page */
221static inline void z3fold_page_lock(struct z3fold_header *zhdr)
222{
223 spin_lock(&zhdr->page_lock);
224}
225
226/* Try to lock a z3fold page */
227static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
228{
229 return spin_trylock(&zhdr->page_lock);
230}
231
232/* Unlock a z3fold page */
233static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
234{
235 spin_unlock(&zhdr->page_lock);
236}
237
238/* return locked z3fold page if it's not headless */
239static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
240{
241 struct z3fold_buddy_slots *slots;
242 struct z3fold_header *zhdr;
243 int locked = 0;
244
245 if (!(handle & (1 << PAGE_HEADLESS))) {
246 slots = handle_to_slots(handle);
247 do {
248 unsigned long addr;
249
250 read_lock(&slots->lock);
251 addr = *(unsigned long *)handle;
252 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
253 locked = z3fold_page_trylock(zhdr);
254 read_unlock(&slots->lock);
255 if (locked) {
256 struct page *page = virt_to_page(zhdr);
257
258 if (!test_bit(PAGE_MIGRATED, &page->private))
259 break;
260 z3fold_page_unlock(zhdr);
261 }
262 cpu_relax();
263 } while (true);
264 } else {
265 zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
266 }
267
268 return zhdr;
269}
270
271static inline void put_z3fold_header(struct z3fold_header *zhdr)
272{
273 struct page *page = virt_to_page(zhdr);
274
275 if (!test_bit(PAGE_HEADLESS, &page->private))
276 z3fold_page_unlock(zhdr);
277}
278
279static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
280{
281 struct z3fold_buddy_slots *slots;
282 int i;
283 bool is_free;
284
285 if (WARN_ON(*(unsigned long *)handle == 0))
286 return;
287
288 slots = handle_to_slots(handle);
289 write_lock(&slots->lock);
290 *(unsigned long *)handle = 0;
291
292 if (test_bit(HANDLES_NOFREE, &slots->pool)) {
293 write_unlock(&slots->lock);
294 return; /* simple case, nothing else to do */
295 }
296
297 if (zhdr->slots != slots)
298 zhdr->foreign_handles--;
299
300 is_free = true;
301 for (i = 0; i <= BUDDY_MASK; i++) {
302 if (slots->slot[i]) {
303 is_free = false;
304 break;
305 }
306 }
307 write_unlock(&slots->lock);
308
309 if (is_free) {
310 struct z3fold_pool *pool = slots_to_pool(slots);
311
312 if (zhdr->slots == slots)
313 zhdr->slots = NULL;
314 kmem_cache_free(pool->c_handle, slots);
315 }
316}
317
318/* Initializes the z3fold header of a newly allocated z3fold page */
319static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
320 struct z3fold_pool *pool, gfp_t gfp)
321{
322 struct z3fold_header *zhdr = page_address(page);
323 struct z3fold_buddy_slots *slots;
324
325 clear_bit(PAGE_HEADLESS, &page->private);
326 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
327 clear_bit(NEEDS_COMPACTING, &page->private);
328 clear_bit(PAGE_STALE, &page->private);
329 clear_bit(PAGE_CLAIMED, &page->private);
330 clear_bit(PAGE_MIGRATED, &page->private);
331 if (headless)
332 return zhdr;
333
334 slots = alloc_slots(pool, gfp);
335 if (!slots)
336 return NULL;
337
338 memset(zhdr, 0, sizeof(*zhdr));
339 spin_lock_init(&zhdr->page_lock);
340 kref_init(&zhdr->refcount);
341 zhdr->cpu = -1;
342 zhdr->slots = slots;
343 zhdr->pool = pool;
344 INIT_LIST_HEAD(&zhdr->buddy);
345 INIT_WORK(&zhdr->work, compact_page_work);
346 return zhdr;
347}
348
349/* Resets the struct page fields and frees the page */
350static void free_z3fold_page(struct page *page, bool headless)
351{
352 if (!headless) {
353 lock_page(page);
354 __ClearPageMovable(page);
355 unlock_page(page);
356 }
357 __free_page(page);
358}
359
360/* Helper function to build the index */
361static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
362{
363 return (bud + zhdr->first_num) & BUDDY_MASK;
364}
365
366/*
367 * Encodes the handle of a particular buddy within a z3fold page
368 * Pool lock should be held as this function accesses first_num
369 */
370static unsigned long __encode_handle(struct z3fold_header *zhdr,
371 struct z3fold_buddy_slots *slots,
372 enum buddy bud)
373{
374 unsigned long h = (unsigned long)zhdr;
375 int idx = 0;
376
377 /*
378 * For a headless page, its handle is its pointer with the extra
379 * PAGE_HEADLESS bit set
380 */
381 if (bud == HEADLESS)
382 return h | (1 << PAGE_HEADLESS);
383
384 /* otherwise, return pointer to encoded handle */
385 idx = __idx(zhdr, bud);
386 h += idx;
387 if (bud == LAST)
388 h |= (zhdr->last_chunks << BUDDY_SHIFT);
389
390 write_lock(&slots->lock);
391 slots->slot[idx] = h;
392 write_unlock(&slots->lock);
393 return (unsigned long)&slots->slot[idx];
394}
395
396static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
397{
398 return __encode_handle(zhdr, zhdr->slots, bud);
399}
400
401/* only for LAST bud, returns zero otherwise */
402static unsigned short handle_to_chunks(unsigned long handle)
403{
404 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
405 unsigned long addr;
406
407 read_lock(&slots->lock);
408 addr = *(unsigned long *)handle;
409 read_unlock(&slots->lock);
410 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
411}
412
413/*
414 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
415 * but that doesn't matter. because the masking will result in the
416 * correct buddy number.
417 */
418static enum buddy handle_to_buddy(unsigned long handle)
419{
420 struct z3fold_header *zhdr;
421 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
422 unsigned long addr;
423
424 read_lock(&slots->lock);
425 WARN_ON(handle & (1 << PAGE_HEADLESS));
426 addr = *(unsigned long *)handle;
427 read_unlock(&slots->lock);
428 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
429 return (addr - zhdr->first_num) & BUDDY_MASK;
430}
431
432static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
433{
434 return zhdr->pool;
435}
436
437static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
438{
439 struct page *page = virt_to_page(zhdr);
440 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
441
442 WARN_ON(!list_empty(&zhdr->buddy));
443 set_bit(PAGE_STALE, &page->private);
444 clear_bit(NEEDS_COMPACTING, &page->private);
445 spin_lock(&pool->lock);
446 spin_unlock(&pool->lock);
447
448 if (locked)
449 z3fold_page_unlock(zhdr);
450
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 atomic64_dec(&pool->pages_nr);
457}
458
459static void release_z3fold_page_locked(struct kref *ref)
460{
461 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
462 refcount);
463 WARN_ON(z3fold_page_trylock(zhdr));
464 __release_z3fold_page(zhdr, true);
465}
466
467static void release_z3fold_page_locked_list(struct kref *ref)
468{
469 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
470 refcount);
471 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
472
473 spin_lock(&pool->lock);
474 list_del_init(&zhdr->buddy);
475 spin_unlock(&pool->lock);
476
477 WARN_ON(z3fold_page_trylock(zhdr));
478 __release_z3fold_page(zhdr, true);
479}
480
481static inline int put_z3fold_locked(struct z3fold_header *zhdr)
482{
483 return kref_put(&zhdr->refcount, release_z3fold_page_locked);
484}
485
486static inline int put_z3fold_locked_list(struct z3fold_header *zhdr)
487{
488 return kref_put(&zhdr->refcount, release_z3fold_page_locked_list);
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 && !put_z3fold_locked(new_zhdr)) {
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 (put_z3fold_locked(zhdr))
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 (!put_z3fold_locked(zhdr)) {
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 (!put_z3fold_locked(zhdr)) {
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->stale);
934 atomic64_set(&pool->pages_nr, 0);
935 pool->name = name;
936 pool->compact_wq = create_singlethread_workqueue(pool->name);
937 if (!pool->compact_wq)
938 goto out_unbuddied;
939 pool->release_wq = create_singlethread_workqueue(pool->name);
940 if (!pool->release_wq)
941 goto out_wq;
942 INIT_WORK(&pool->work, free_pages_work);
943 return pool;
944
945out_wq:
946 destroy_workqueue(pool->compact_wq);
947out_unbuddied:
948 free_percpu(pool->unbuddied);
949out_pool:
950 kmem_cache_destroy(pool->c_handle);
951out_c:
952 kfree(pool);
953out:
954 return NULL;
955}
956
957/**
958 * z3fold_destroy_pool() - destroys an existing z3fold pool
959 * @pool: the z3fold pool to be destroyed
960 *
961 * The pool should be emptied before this function is called.
962 */
963static void z3fold_destroy_pool(struct z3fold_pool *pool)
964{
965 kmem_cache_destroy(pool->c_handle);
966
967 /*
968 * We need to destroy pool->compact_wq before pool->release_wq,
969 * as any pending work on pool->compact_wq will call
970 * queue_work(pool->release_wq, &pool->work).
971 *
972 * There are still outstanding pages until both workqueues are drained,
973 * so we cannot unregister migration until then.
974 */
975
976 destroy_workqueue(pool->compact_wq);
977 destroy_workqueue(pool->release_wq);
978 free_percpu(pool->unbuddied);
979 kfree(pool);
980}
981
982static const struct movable_operations z3fold_mops;
983
984/**
985 * z3fold_alloc() - allocates a region of a given size
986 * @pool: z3fold pool from which to allocate
987 * @size: size in bytes of the desired allocation
988 * @gfp: gfp flags used if the pool needs to grow
989 * @handle: handle of the new allocation
990 *
991 * This function will attempt to find a free region in the pool large enough to
992 * satisfy the allocation request. A search of the unbuddied lists is
993 * performed first. If no suitable free region is found, then a new page is
994 * allocated and added to the pool to satisfy the request.
995 *
996 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
997 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
998 * a new page.
999 */
1000static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1001 unsigned long *handle)
1002{
1003 int chunks = size_to_chunks(size);
1004 struct z3fold_header *zhdr = NULL;
1005 struct page *page = NULL;
1006 enum buddy bud;
1007 bool can_sleep = gfpflags_allow_blocking(gfp);
1008
1009 if (!size || (gfp & __GFP_HIGHMEM))
1010 return -EINVAL;
1011
1012 if (size > PAGE_SIZE)
1013 return -ENOSPC;
1014
1015 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1016 bud = HEADLESS;
1017 else {
1018retry:
1019 zhdr = __z3fold_alloc(pool, size, can_sleep);
1020 if (zhdr) {
1021 bud = get_free_buddy(zhdr, chunks);
1022 if (bud == HEADLESS) {
1023 if (!put_z3fold_locked(zhdr))
1024 z3fold_page_unlock(zhdr);
1025 pr_err("No free chunks in unbuddied\n");
1026 WARN_ON(1);
1027 goto retry;
1028 }
1029 page = virt_to_page(zhdr);
1030 goto found;
1031 }
1032 bud = FIRST;
1033 }
1034
1035 page = alloc_page(gfp);
1036 if (!page)
1037 return -ENOMEM;
1038
1039 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
1040 if (!zhdr) {
1041 __free_page(page);
1042 return -ENOMEM;
1043 }
1044 atomic64_inc(&pool->pages_nr);
1045
1046 if (bud == HEADLESS) {
1047 set_bit(PAGE_HEADLESS, &page->private);
1048 goto headless;
1049 }
1050 if (can_sleep) {
1051 lock_page(page);
1052 __SetPageMovable(page, &z3fold_mops);
1053 unlock_page(page);
1054 } else {
1055 WARN_ON(!trylock_page(page));
1056 __SetPageMovable(page, &z3fold_mops);
1057 unlock_page(page);
1058 }
1059 z3fold_page_lock(zhdr);
1060
1061found:
1062 if (bud == FIRST)
1063 zhdr->first_chunks = chunks;
1064 else if (bud == LAST)
1065 zhdr->last_chunks = chunks;
1066 else {
1067 zhdr->middle_chunks = chunks;
1068 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
1069 }
1070 add_to_unbuddied(pool, zhdr);
1071
1072headless:
1073 spin_lock(&pool->lock);
1074 *handle = encode_handle(zhdr, bud);
1075 spin_unlock(&pool->lock);
1076 if (bud != HEADLESS)
1077 z3fold_page_unlock(zhdr);
1078
1079 return 0;
1080}
1081
1082/**
1083 * z3fold_free() - frees the allocation associated with the given handle
1084 * @pool: pool in which the allocation resided
1085 * @handle: handle associated with the allocation returned by z3fold_alloc()
1086 *
1087 * In the case that the z3fold page in which the allocation resides is under
1088 * reclaim, as indicated by the PAGE_CLAIMED flag being set, this function
1089 * only sets the first|middle|last_chunks to 0. The page is actually freed
1090 * once all buddies are evicted (see z3fold_reclaim_page() below).
1091 */
1092static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1093{
1094 struct z3fold_header *zhdr;
1095 struct page *page;
1096 enum buddy bud;
1097 bool page_claimed;
1098
1099 zhdr = get_z3fold_header(handle);
1100 page = virt_to_page(zhdr);
1101 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1102
1103 if (test_bit(PAGE_HEADLESS, &page->private)) {
1104 /* if a headless page is under reclaim, just leave.
1105 * NB: we use test_and_set_bit for a reason: if the bit
1106 * has not been set before, we release this page
1107 * immediately so we don't care about its value any more.
1108 */
1109 if (!page_claimed) {
1110 put_z3fold_header(zhdr);
1111 free_z3fold_page(page, true);
1112 atomic64_dec(&pool->pages_nr);
1113 }
1114 return;
1115 }
1116
1117 /* Non-headless case */
1118 bud = handle_to_buddy(handle);
1119
1120 switch (bud) {
1121 case FIRST:
1122 zhdr->first_chunks = 0;
1123 break;
1124 case MIDDLE:
1125 zhdr->middle_chunks = 0;
1126 break;
1127 case LAST:
1128 zhdr->last_chunks = 0;
1129 break;
1130 default:
1131 pr_err("%s: unknown bud %d\n", __func__, bud);
1132 WARN_ON(1);
1133 put_z3fold_header(zhdr);
1134 return;
1135 }
1136
1137 if (!page_claimed)
1138 free_handle(handle, zhdr);
1139 if (put_z3fold_locked_list(zhdr))
1140 return;
1141 if (page_claimed) {
1142 /* the page has not been claimed by us */
1143 put_z3fold_header(zhdr);
1144 return;
1145 }
1146 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1147 clear_bit(PAGE_CLAIMED, &page->private);
1148 put_z3fold_header(zhdr);
1149 return;
1150 }
1151 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1152 zhdr->cpu = -1;
1153 kref_get(&zhdr->refcount);
1154 clear_bit(PAGE_CLAIMED, &page->private);
1155 do_compact_page(zhdr, true);
1156 return;
1157 }
1158 kref_get(&zhdr->refcount);
1159 clear_bit(PAGE_CLAIMED, &page->private);
1160 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1161 put_z3fold_header(zhdr);
1162}
1163
1164/**
1165 * z3fold_map() - maps the allocation associated with the given handle
1166 * @pool: pool in which the allocation resides
1167 * @handle: handle associated with the allocation to be mapped
1168 *
1169 * Extracts the buddy number from handle and constructs the pointer to the
1170 * correct starting chunk within the page.
1171 *
1172 * Returns: a pointer to the mapped allocation
1173 */
1174static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1175{
1176 struct z3fold_header *zhdr;
1177 struct page *page;
1178 void *addr;
1179 enum buddy buddy;
1180
1181 zhdr = get_z3fold_header(handle);
1182 addr = zhdr;
1183 page = virt_to_page(zhdr);
1184
1185 if (test_bit(PAGE_HEADLESS, &page->private))
1186 goto out;
1187
1188 buddy = handle_to_buddy(handle);
1189 switch (buddy) {
1190 case FIRST:
1191 addr += ZHDR_SIZE_ALIGNED;
1192 break;
1193 case MIDDLE:
1194 addr += zhdr->start_middle << CHUNK_SHIFT;
1195 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1196 break;
1197 case LAST:
1198 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1199 break;
1200 default:
1201 pr_err("unknown buddy id %d\n", buddy);
1202 WARN_ON(1);
1203 addr = NULL;
1204 break;
1205 }
1206
1207 if (addr)
1208 zhdr->mapped_count++;
1209out:
1210 put_z3fold_header(zhdr);
1211 return addr;
1212}
1213
1214/**
1215 * z3fold_unmap() - unmaps the allocation associated with the given handle
1216 * @pool: pool in which the allocation resides
1217 * @handle: handle associated with the allocation to be unmapped
1218 */
1219static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1220{
1221 struct z3fold_header *zhdr;
1222 struct page *page;
1223 enum buddy buddy;
1224
1225 zhdr = get_z3fold_header(handle);
1226 page = virt_to_page(zhdr);
1227
1228 if (test_bit(PAGE_HEADLESS, &page->private))
1229 return;
1230
1231 buddy = handle_to_buddy(handle);
1232 if (buddy == MIDDLE)
1233 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1234 zhdr->mapped_count--;
1235 put_z3fold_header(zhdr);
1236}
1237
1238/**
1239 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1240 * @pool: pool whose size is being queried
1241 *
1242 * Returns: size in pages of the given pool.
1243 */
1244static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1245{
1246 return atomic64_read(&pool->pages_nr);
1247}
1248
1249static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1250{
1251 struct z3fold_header *zhdr;
1252 struct z3fold_pool *pool;
1253
1254 VM_BUG_ON_PAGE(PageIsolated(page), page);
1255
1256 if (test_bit(PAGE_HEADLESS, &page->private))
1257 return false;
1258
1259 zhdr = page_address(page);
1260 z3fold_page_lock(zhdr);
1261 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1262 test_bit(PAGE_STALE, &page->private))
1263 goto out;
1264
1265 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1266 goto out;
1267
1268 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1269 goto out;
1270 pool = zhdr_to_pool(zhdr);
1271 spin_lock(&pool->lock);
1272 if (!list_empty(&zhdr->buddy))
1273 list_del_init(&zhdr->buddy);
1274 spin_unlock(&pool->lock);
1275
1276 kref_get(&zhdr->refcount);
1277 z3fold_page_unlock(zhdr);
1278 return true;
1279
1280out:
1281 z3fold_page_unlock(zhdr);
1282 return false;
1283}
1284
1285static int z3fold_page_migrate(struct page *newpage, struct page *page,
1286 enum migrate_mode mode)
1287{
1288 struct z3fold_header *zhdr, *new_zhdr;
1289 struct z3fold_pool *pool;
1290
1291 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1292 VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
1293 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1294
1295 zhdr = page_address(page);
1296 pool = zhdr_to_pool(zhdr);
1297
1298 if (!z3fold_page_trylock(zhdr))
1299 return -EAGAIN;
1300 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1301 clear_bit(PAGE_CLAIMED, &page->private);
1302 z3fold_page_unlock(zhdr);
1303 return -EBUSY;
1304 }
1305 if (work_pending(&zhdr->work)) {
1306 z3fold_page_unlock(zhdr);
1307 return -EAGAIN;
1308 }
1309 new_zhdr = page_address(newpage);
1310 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1311 newpage->private = page->private;
1312 set_bit(PAGE_MIGRATED, &page->private);
1313 z3fold_page_unlock(zhdr);
1314 spin_lock_init(&new_zhdr->page_lock);
1315 INIT_WORK(&new_zhdr->work, compact_page_work);
1316 /*
1317 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1318 * so we only have to reinitialize it.
1319 */
1320 INIT_LIST_HEAD(&new_zhdr->buddy);
1321 __ClearPageMovable(page);
1322
1323 get_page(newpage);
1324 z3fold_page_lock(new_zhdr);
1325 if (new_zhdr->first_chunks)
1326 encode_handle(new_zhdr, FIRST);
1327 if (new_zhdr->last_chunks)
1328 encode_handle(new_zhdr, LAST);
1329 if (new_zhdr->middle_chunks)
1330 encode_handle(new_zhdr, MIDDLE);
1331 set_bit(NEEDS_COMPACTING, &newpage->private);
1332 new_zhdr->cpu = smp_processor_id();
1333 __SetPageMovable(newpage, &z3fold_mops);
1334 z3fold_page_unlock(new_zhdr);
1335
1336 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1337
1338 /* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */
1339 page->private = 0;
1340 put_page(page);
1341 return 0;
1342}
1343
1344static void z3fold_page_putback(struct page *page)
1345{
1346 struct z3fold_header *zhdr;
1347 struct z3fold_pool *pool;
1348
1349 zhdr = page_address(page);
1350 pool = zhdr_to_pool(zhdr);
1351
1352 z3fold_page_lock(zhdr);
1353 if (!list_empty(&zhdr->buddy))
1354 list_del_init(&zhdr->buddy);
1355 INIT_LIST_HEAD(&page->lru);
1356 if (put_z3fold_locked(zhdr))
1357 return;
1358 if (list_empty(&zhdr->buddy))
1359 add_to_unbuddied(pool, zhdr);
1360 clear_bit(PAGE_CLAIMED, &page->private);
1361 z3fold_page_unlock(zhdr);
1362}
1363
1364static const struct movable_operations z3fold_mops = {
1365 .isolate_page = z3fold_page_isolate,
1366 .migrate_page = z3fold_page_migrate,
1367 .putback_page = z3fold_page_putback,
1368};
1369
1370/*****************
1371 * zpool
1372 ****************/
1373
1374static void *z3fold_zpool_create(const char *name, gfp_t gfp)
1375{
1376 return z3fold_create_pool(name, gfp);
1377}
1378
1379static void z3fold_zpool_destroy(void *pool)
1380{
1381 z3fold_destroy_pool(pool);
1382}
1383
1384static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1385 unsigned long *handle)
1386{
1387 return z3fold_alloc(pool, size, gfp, handle);
1388}
1389static void z3fold_zpool_free(void *pool, unsigned long handle)
1390{
1391 z3fold_free(pool, handle);
1392}
1393
1394static void *z3fold_zpool_map(void *pool, unsigned long handle,
1395 enum zpool_mapmode mm)
1396{
1397 return z3fold_map(pool, handle);
1398}
1399static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1400{
1401 z3fold_unmap(pool, handle);
1402}
1403
1404static u64 z3fold_zpool_total_size(void *pool)
1405{
1406 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1407}
1408
1409static struct zpool_driver z3fold_zpool_driver = {
1410 .type = "z3fold",
1411 .sleep_mapped = true,
1412 .owner = THIS_MODULE,
1413 .create = z3fold_zpool_create,
1414 .destroy = z3fold_zpool_destroy,
1415 .malloc = z3fold_zpool_malloc,
1416 .free = z3fold_zpool_free,
1417 .map = z3fold_zpool_map,
1418 .unmap = z3fold_zpool_unmap,
1419 .total_size = z3fold_zpool_total_size,
1420};
1421
1422MODULE_ALIAS("zpool-z3fold");
1423
1424static int __init init_z3fold(void)
1425{
1426 /*
1427 * Make sure the z3fold header is not larger than the page size and
1428 * there has remaining spaces for its buddy.
1429 */
1430 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
1431 zpool_register_driver(&z3fold_zpool_driver);
1432
1433 return 0;
1434}
1435
1436static void __exit exit_z3fold(void)
1437{
1438 zpool_unregister_driver(&z3fold_zpool_driver);
1439}
1440
1441module_init(init_z3fold);
1442module_exit(exit_z3fold);
1443
1444MODULE_LICENSE("GPL");
1445MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1446MODULE_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/mount.h>
38#include <linux/pseudo_fs.h>
39#include <linux/fs.h>
40#include <linux/preempt.h>
41#include <linux/workqueue.h>
42#include <linux/slab.h>
43#include <linux/spinlock.h>
44#include <linux/zpool.h>
45#include <linux/magic.h>
46#include <linux/kmemleak.h>
47
48/*
49 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
50 * adjusting internal fragmentation. It also determines the number of
51 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
52 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
53 * in the beginning of an allocated page are occupied by z3fold header, so
54 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
55 * which shows the max number of free chunks in z3fold page, also there will
56 * be 63, or 62, respectively, freelists per pool.
57 */
58#define NCHUNKS_ORDER 6
59
60#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
61#define CHUNK_SIZE (1 << CHUNK_SHIFT)
62#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
63#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
64#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
65#define NCHUNKS (TOTAL_CHUNKS - ZHDR_CHUNKS)
66
67#define BUDDY_MASK (0x3)
68#define BUDDY_SHIFT 2
69#define SLOTS_ALIGN (0x40)
70
71/*****************
72 * Structures
73*****************/
74struct z3fold_pool;
75struct z3fold_ops {
76 int (*evict)(struct z3fold_pool *pool, unsigned long handle);
77};
78
79enum buddy {
80 HEADLESS = 0,
81 FIRST,
82 MIDDLE,
83 LAST,
84 BUDDIES_MAX = LAST
85};
86
87struct z3fold_buddy_slots {
88 /*
89 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
90 * be enough slots to hold all possible variants
91 */
92 unsigned long slot[BUDDY_MASK + 1];
93 unsigned long pool; /* back link */
94 rwlock_t lock;
95};
96#define HANDLE_FLAG_MASK (0x03)
97
98/*
99 * struct z3fold_header - z3fold page metadata occupying first chunks of each
100 * z3fold page, except for HEADLESS pages
101 * @buddy: links the z3fold page into the relevant list in the
102 * pool
103 * @page_lock: per-page lock
104 * @refcount: reference count for the z3fold page
105 * @work: work_struct for page layout optimization
106 * @slots: pointer to the structure holding buddy slots
107 * @pool: pointer to the containing pool
108 * @cpu: CPU which this page "belongs" to
109 * @first_chunks: the size of the first buddy in chunks, 0 if free
110 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
111 * @last_chunks: the size of the last buddy in chunks, 0 if free
112 * @first_num: the starting number (for the first handle)
113 * @mapped_count: the number of objects currently mapped
114 */
115struct z3fold_header {
116 struct list_head buddy;
117 spinlock_t page_lock;
118 struct kref refcount;
119 struct work_struct work;
120 struct z3fold_buddy_slots *slots;
121 struct z3fold_pool *pool;
122 short cpu;
123 unsigned short first_chunks;
124 unsigned short middle_chunks;
125 unsigned short last_chunks;
126 unsigned short start_middle;
127 unsigned short first_num:2;
128 unsigned short mapped_count:2;
129 unsigned short foreign_handles:2;
130};
131
132/**
133 * struct z3fold_pool - stores metadata for each z3fold pool
134 * @name: pool name
135 * @lock: protects pool unbuddied/lru lists
136 * @stale_lock: protects pool stale page list
137 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
138 * buddies; the list each z3fold page is added to depends on
139 * the size of its free region.
140 * @lru: list tracking the z3fold pages in LRU order by most recently
141 * added buddy.
142 * @stale: list of pages marked for freeing
143 * @pages_nr: number of z3fold pages in the pool.
144 * @c_handle: cache for z3fold_buddy_slots allocation
145 * @ops: pointer to a structure of user defined operations specified at
146 * pool creation time.
147 * @zpool: zpool driver
148 * @zpool_ops: zpool operations structure with an evict callback
149 * @compact_wq: workqueue for page layout background optimization
150 * @release_wq: workqueue for safe page release
151 * @work: work_struct for safe page release
152 * @inode: inode for z3fold pseudo filesystem
153 *
154 * This structure is allocated at pool creation time and maintains metadata
155 * pertaining to a particular z3fold pool.
156 */
157struct z3fold_pool {
158 const char *name;
159 spinlock_t lock;
160 spinlock_t stale_lock;
161 struct list_head *unbuddied;
162 struct list_head lru;
163 struct list_head stale;
164 atomic64_t pages_nr;
165 struct kmem_cache *c_handle;
166 const struct z3fold_ops *ops;
167 struct zpool *zpool;
168 const struct zpool_ops *zpool_ops;
169 struct workqueue_struct *compact_wq;
170 struct workqueue_struct *release_wq;
171 struct work_struct work;
172 struct inode *inode;
173};
174
175/*
176 * Internal z3fold page flags
177 */
178enum z3fold_page_flags {
179 PAGE_HEADLESS = 0,
180 MIDDLE_CHUNK_MAPPED,
181 NEEDS_COMPACTING,
182 PAGE_STALE,
183 PAGE_CLAIMED, /* by either reclaim or free */
184};
185
186/*
187 * handle flags, go under HANDLE_FLAG_MASK
188 */
189enum z3fold_handle_flags {
190 HANDLES_NOFREE = 0,
191};
192
193/*
194 * Forward declarations
195 */
196static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
197static void compact_page_work(struct work_struct *w);
198
199/*****************
200 * Helpers
201*****************/
202
203/* Converts an allocation size in bytes to size in z3fold chunks */
204static int size_to_chunks(size_t size)
205{
206 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
207}
208
209#define for_each_unbuddied_list(_iter, _begin) \
210 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
211
212static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
213 gfp_t gfp)
214{
215 struct z3fold_buddy_slots *slots;
216
217 slots = kmem_cache_zalloc(pool->c_handle,
218 (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
219
220 if (slots) {
221 /* It will be freed separately in free_handle(). */
222 kmemleak_not_leak(slots);
223 slots->pool = (unsigned long)pool;
224 rwlock_init(&slots->lock);
225 }
226
227 return slots;
228}
229
230static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
231{
232 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
233}
234
235static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
236{
237 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
238}
239
240/* Lock a z3fold page */
241static inline void z3fold_page_lock(struct z3fold_header *zhdr)
242{
243 spin_lock(&zhdr->page_lock);
244}
245
246/* Try to lock a z3fold page */
247static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
248{
249 return spin_trylock(&zhdr->page_lock);
250}
251
252/* Unlock a z3fold page */
253static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
254{
255 spin_unlock(&zhdr->page_lock);
256}
257
258/* return locked z3fold page if it's not headless */
259static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
260{
261 struct z3fold_buddy_slots *slots;
262 struct z3fold_header *zhdr;
263 int locked = 0;
264
265 if (!(handle & (1 << PAGE_HEADLESS))) {
266 slots = handle_to_slots(handle);
267 do {
268 unsigned long addr;
269
270 read_lock(&slots->lock);
271 addr = *(unsigned long *)handle;
272 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
273 locked = z3fold_page_trylock(zhdr);
274 read_unlock(&slots->lock);
275 if (locked)
276 break;
277 cpu_relax();
278 } while (true);
279 } else {
280 zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
281 }
282
283 return zhdr;
284}
285
286static inline void put_z3fold_header(struct z3fold_header *zhdr)
287{
288 struct page *page = virt_to_page(zhdr);
289
290 if (!test_bit(PAGE_HEADLESS, &page->private))
291 z3fold_page_unlock(zhdr);
292}
293
294static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
295{
296 struct z3fold_buddy_slots *slots;
297 int i;
298 bool is_free;
299
300 if (handle & (1 << PAGE_HEADLESS))
301 return;
302
303 if (WARN_ON(*(unsigned long *)handle == 0))
304 return;
305
306 slots = handle_to_slots(handle);
307 write_lock(&slots->lock);
308 *(unsigned long *)handle = 0;
309
310 if (test_bit(HANDLES_NOFREE, &slots->pool)) {
311 write_unlock(&slots->lock);
312 return; /* simple case, nothing else to do */
313 }
314
315 if (zhdr->slots != slots)
316 zhdr->foreign_handles--;
317
318 is_free = true;
319 for (i = 0; i <= BUDDY_MASK; i++) {
320 if (slots->slot[i]) {
321 is_free = false;
322 break;
323 }
324 }
325 write_unlock(&slots->lock);
326
327 if (is_free) {
328 struct z3fold_pool *pool = slots_to_pool(slots);
329
330 if (zhdr->slots == slots)
331 zhdr->slots = NULL;
332 kmem_cache_free(pool->c_handle, slots);
333 }
334}
335
336static int z3fold_init_fs_context(struct fs_context *fc)
337{
338 return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
339}
340
341static struct file_system_type z3fold_fs = {
342 .name = "z3fold",
343 .init_fs_context = z3fold_init_fs_context,
344 .kill_sb = kill_anon_super,
345};
346
347static struct vfsmount *z3fold_mnt;
348static int z3fold_mount(void)
349{
350 int ret = 0;
351
352 z3fold_mnt = kern_mount(&z3fold_fs);
353 if (IS_ERR(z3fold_mnt))
354 ret = PTR_ERR(z3fold_mnt);
355
356 return ret;
357}
358
359static void z3fold_unmount(void)
360{
361 kern_unmount(z3fold_mnt);
362}
363
364static const struct address_space_operations z3fold_aops;
365static int z3fold_register_migration(struct z3fold_pool *pool)
366{
367 pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
368 if (IS_ERR(pool->inode)) {
369 pool->inode = NULL;
370 return 1;
371 }
372
373 pool->inode->i_mapping->private_data = pool;
374 pool->inode->i_mapping->a_ops = &z3fold_aops;
375 return 0;
376}
377
378static void z3fold_unregister_migration(struct z3fold_pool *pool)
379{
380 if (pool->inode)
381 iput(pool->inode);
382}
383
384/* Initializes the z3fold header of a newly allocated z3fold page */
385static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
386 struct z3fold_pool *pool, gfp_t gfp)
387{
388 struct z3fold_header *zhdr = page_address(page);
389 struct z3fold_buddy_slots *slots;
390
391 INIT_LIST_HEAD(&page->lru);
392 clear_bit(PAGE_HEADLESS, &page->private);
393 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
394 clear_bit(NEEDS_COMPACTING, &page->private);
395 clear_bit(PAGE_STALE, &page->private);
396 clear_bit(PAGE_CLAIMED, &page->private);
397 if (headless)
398 return zhdr;
399
400 slots = alloc_slots(pool, gfp);
401 if (!slots)
402 return NULL;
403
404 memset(zhdr, 0, sizeof(*zhdr));
405 spin_lock_init(&zhdr->page_lock);
406 kref_init(&zhdr->refcount);
407 zhdr->cpu = -1;
408 zhdr->slots = slots;
409 zhdr->pool = pool;
410 INIT_LIST_HEAD(&zhdr->buddy);
411 INIT_WORK(&zhdr->work, compact_page_work);
412 return zhdr;
413}
414
415/* Resets the struct page fields and frees the page */
416static void free_z3fold_page(struct page *page, bool headless)
417{
418 if (!headless) {
419 lock_page(page);
420 __ClearPageMovable(page);
421 unlock_page(page);
422 }
423 ClearPagePrivate(page);
424 __free_page(page);
425}
426
427/* Helper function to build the index */
428static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
429{
430 return (bud + zhdr->first_num) & BUDDY_MASK;
431}
432
433/*
434 * Encodes the handle of a particular buddy within a z3fold page
435 * Pool lock should be held as this function accesses first_num
436 */
437static unsigned long __encode_handle(struct z3fold_header *zhdr,
438 struct z3fold_buddy_slots *slots,
439 enum buddy bud)
440{
441 unsigned long h = (unsigned long)zhdr;
442 int idx = 0;
443
444 /*
445 * For a headless page, its handle is its pointer with the extra
446 * PAGE_HEADLESS bit set
447 */
448 if (bud == HEADLESS)
449 return h | (1 << PAGE_HEADLESS);
450
451 /* otherwise, return pointer to encoded handle */
452 idx = __idx(zhdr, bud);
453 h += idx;
454 if (bud == LAST)
455 h |= (zhdr->last_chunks << BUDDY_SHIFT);
456
457 write_lock(&slots->lock);
458 slots->slot[idx] = h;
459 write_unlock(&slots->lock);
460 return (unsigned long)&slots->slot[idx];
461}
462
463static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
464{
465 return __encode_handle(zhdr, zhdr->slots, bud);
466}
467
468/* only for LAST bud, returns zero otherwise */
469static unsigned short handle_to_chunks(unsigned long handle)
470{
471 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
472 unsigned long addr;
473
474 read_lock(&slots->lock);
475 addr = *(unsigned long *)handle;
476 read_unlock(&slots->lock);
477 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
478}
479
480/*
481 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
482 * but that doesn't matter. because the masking will result in the
483 * correct buddy number.
484 */
485static enum buddy handle_to_buddy(unsigned long handle)
486{
487 struct z3fold_header *zhdr;
488 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
489 unsigned long addr;
490
491 read_lock(&slots->lock);
492 WARN_ON(handle & (1 << PAGE_HEADLESS));
493 addr = *(unsigned long *)handle;
494 read_unlock(&slots->lock);
495 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
496 return (addr - zhdr->first_num) & BUDDY_MASK;
497}
498
499static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
500{
501 return zhdr->pool;
502}
503
504static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
505{
506 struct page *page = virt_to_page(zhdr);
507 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
508
509 WARN_ON(!list_empty(&zhdr->buddy));
510 set_bit(PAGE_STALE, &page->private);
511 clear_bit(NEEDS_COMPACTING, &page->private);
512 spin_lock(&pool->lock);
513 if (!list_empty(&page->lru))
514 list_del_init(&page->lru);
515 spin_unlock(&pool->lock);
516
517 if (locked)
518 z3fold_page_unlock(zhdr);
519
520 spin_lock(&pool->stale_lock);
521 list_add(&zhdr->buddy, &pool->stale);
522 queue_work(pool->release_wq, &pool->work);
523 spin_unlock(&pool->stale_lock);
524}
525
526static void release_z3fold_page(struct kref *ref)
527{
528 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
529 refcount);
530 __release_z3fold_page(zhdr, false);
531}
532
533static void release_z3fold_page_locked(struct kref *ref)
534{
535 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
536 refcount);
537 WARN_ON(z3fold_page_trylock(zhdr));
538 __release_z3fold_page(zhdr, true);
539}
540
541static void release_z3fold_page_locked_list(struct kref *ref)
542{
543 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
544 refcount);
545 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
546
547 spin_lock(&pool->lock);
548 list_del_init(&zhdr->buddy);
549 spin_unlock(&pool->lock);
550
551 WARN_ON(z3fold_page_trylock(zhdr));
552 __release_z3fold_page(zhdr, true);
553}
554
555static void free_pages_work(struct work_struct *w)
556{
557 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
558
559 spin_lock(&pool->stale_lock);
560 while (!list_empty(&pool->stale)) {
561 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
562 struct z3fold_header, buddy);
563 struct page *page = virt_to_page(zhdr);
564
565 list_del(&zhdr->buddy);
566 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
567 continue;
568 spin_unlock(&pool->stale_lock);
569 cancel_work_sync(&zhdr->work);
570 free_z3fold_page(page, false);
571 cond_resched();
572 spin_lock(&pool->stale_lock);
573 }
574 spin_unlock(&pool->stale_lock);
575}
576
577/*
578 * Returns the number of free chunks in a z3fold page.
579 * NB: can't be used with HEADLESS pages.
580 */
581static int num_free_chunks(struct z3fold_header *zhdr)
582{
583 int nfree;
584 /*
585 * If there is a middle object, pick up the bigger free space
586 * either before or after it. Otherwise just subtract the number
587 * of chunks occupied by the first and the last objects.
588 */
589 if (zhdr->middle_chunks != 0) {
590 int nfree_before = zhdr->first_chunks ?
591 0 : zhdr->start_middle - ZHDR_CHUNKS;
592 int nfree_after = zhdr->last_chunks ?
593 0 : TOTAL_CHUNKS -
594 (zhdr->start_middle + zhdr->middle_chunks);
595 nfree = max(nfree_before, nfree_after);
596 } else
597 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
598 return nfree;
599}
600
601/* Add to the appropriate unbuddied list */
602static inline void add_to_unbuddied(struct z3fold_pool *pool,
603 struct z3fold_header *zhdr)
604{
605 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
606 zhdr->middle_chunks == 0) {
607 struct list_head *unbuddied;
608 int freechunks = num_free_chunks(zhdr);
609
610 migrate_disable();
611 unbuddied = this_cpu_ptr(pool->unbuddied);
612 spin_lock(&pool->lock);
613 list_add(&zhdr->buddy, &unbuddied[freechunks]);
614 spin_unlock(&pool->lock);
615 zhdr->cpu = smp_processor_id();
616 migrate_enable();
617 }
618}
619
620static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
621{
622 enum buddy bud = HEADLESS;
623
624 if (zhdr->middle_chunks) {
625 if (!zhdr->first_chunks &&
626 chunks <= zhdr->start_middle - ZHDR_CHUNKS)
627 bud = FIRST;
628 else if (!zhdr->last_chunks)
629 bud = LAST;
630 } else {
631 if (!zhdr->first_chunks)
632 bud = FIRST;
633 else if (!zhdr->last_chunks)
634 bud = LAST;
635 else
636 bud = MIDDLE;
637 }
638
639 return bud;
640}
641
642static inline void *mchunk_memmove(struct z3fold_header *zhdr,
643 unsigned short dst_chunk)
644{
645 void *beg = zhdr;
646 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
647 beg + (zhdr->start_middle << CHUNK_SHIFT),
648 zhdr->middle_chunks << CHUNK_SHIFT);
649}
650
651static inline bool buddy_single(struct z3fold_header *zhdr)
652{
653 return !((zhdr->first_chunks && zhdr->middle_chunks) ||
654 (zhdr->first_chunks && zhdr->last_chunks) ||
655 (zhdr->middle_chunks && zhdr->last_chunks));
656}
657
658static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
659{
660 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
661 void *p = zhdr;
662 unsigned long old_handle = 0;
663 size_t sz = 0;
664 struct z3fold_header *new_zhdr = NULL;
665 int first_idx = __idx(zhdr, FIRST);
666 int middle_idx = __idx(zhdr, MIDDLE);
667 int last_idx = __idx(zhdr, LAST);
668 unsigned short *moved_chunks = NULL;
669
670 /*
671 * No need to protect slots here -- all the slots are "local" and
672 * the page lock is already taken
673 */
674 if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
675 p += ZHDR_SIZE_ALIGNED;
676 sz = zhdr->first_chunks << CHUNK_SHIFT;
677 old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
678 moved_chunks = &zhdr->first_chunks;
679 } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
680 p += zhdr->start_middle << CHUNK_SHIFT;
681 sz = zhdr->middle_chunks << CHUNK_SHIFT;
682 old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
683 moved_chunks = &zhdr->middle_chunks;
684 } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
685 p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
686 sz = zhdr->last_chunks << CHUNK_SHIFT;
687 old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
688 moved_chunks = &zhdr->last_chunks;
689 }
690
691 if (sz > 0) {
692 enum buddy new_bud = HEADLESS;
693 short chunks = size_to_chunks(sz);
694 void *q;
695
696 new_zhdr = __z3fold_alloc(pool, sz, false);
697 if (!new_zhdr)
698 return NULL;
699
700 if (WARN_ON(new_zhdr == zhdr))
701 goto out_fail;
702
703 new_bud = get_free_buddy(new_zhdr, chunks);
704 q = new_zhdr;
705 switch (new_bud) {
706 case FIRST:
707 new_zhdr->first_chunks = chunks;
708 q += ZHDR_SIZE_ALIGNED;
709 break;
710 case MIDDLE:
711 new_zhdr->middle_chunks = chunks;
712 new_zhdr->start_middle =
713 new_zhdr->first_chunks + ZHDR_CHUNKS;
714 q += new_zhdr->start_middle << CHUNK_SHIFT;
715 break;
716 case LAST:
717 new_zhdr->last_chunks = chunks;
718 q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
719 break;
720 default:
721 goto out_fail;
722 }
723 new_zhdr->foreign_handles++;
724 memcpy(q, p, sz);
725 write_lock(&zhdr->slots->lock);
726 *(unsigned long *)old_handle = (unsigned long)new_zhdr +
727 __idx(new_zhdr, new_bud);
728 if (new_bud == LAST)
729 *(unsigned long *)old_handle |=
730 (new_zhdr->last_chunks << BUDDY_SHIFT);
731 write_unlock(&zhdr->slots->lock);
732 add_to_unbuddied(pool, new_zhdr);
733 z3fold_page_unlock(new_zhdr);
734
735 *moved_chunks = 0;
736 }
737
738 return new_zhdr;
739
740out_fail:
741 if (new_zhdr) {
742 if (kref_put(&new_zhdr->refcount, release_z3fold_page_locked))
743 atomic64_dec(&pool->pages_nr);
744 else {
745 add_to_unbuddied(pool, new_zhdr);
746 z3fold_page_unlock(new_zhdr);
747 }
748 }
749 return NULL;
750
751}
752
753#define BIG_CHUNK_GAP 3
754/* Has to be called with lock held */
755static int z3fold_compact_page(struct z3fold_header *zhdr)
756{
757 struct page *page = virt_to_page(zhdr);
758
759 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
760 return 0; /* can't move middle chunk, it's used */
761
762 if (unlikely(PageIsolated(page)))
763 return 0;
764
765 if (zhdr->middle_chunks == 0)
766 return 0; /* nothing to compact */
767
768 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
769 /* move to the beginning */
770 mchunk_memmove(zhdr, ZHDR_CHUNKS);
771 zhdr->first_chunks = zhdr->middle_chunks;
772 zhdr->middle_chunks = 0;
773 zhdr->start_middle = 0;
774 zhdr->first_num++;
775 return 1;
776 }
777
778 /*
779 * moving data is expensive, so let's only do that if
780 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
781 */
782 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
783 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
784 BIG_CHUNK_GAP) {
785 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
786 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
787 return 1;
788 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
789 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
790 + zhdr->middle_chunks) >=
791 BIG_CHUNK_GAP) {
792 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
793 zhdr->middle_chunks;
794 mchunk_memmove(zhdr, new_start);
795 zhdr->start_middle = new_start;
796 return 1;
797 }
798
799 return 0;
800}
801
802static void do_compact_page(struct z3fold_header *zhdr, bool locked)
803{
804 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
805 struct page *page;
806
807 page = virt_to_page(zhdr);
808 if (locked)
809 WARN_ON(z3fold_page_trylock(zhdr));
810 else
811 z3fold_page_lock(zhdr);
812 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
813 z3fold_page_unlock(zhdr);
814 return;
815 }
816 spin_lock(&pool->lock);
817 list_del_init(&zhdr->buddy);
818 spin_unlock(&pool->lock);
819
820 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
821 atomic64_dec(&pool->pages_nr);
822 return;
823 }
824
825 if (test_bit(PAGE_STALE, &page->private) ||
826 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
827 z3fold_page_unlock(zhdr);
828 return;
829 }
830
831 if (!zhdr->foreign_handles && buddy_single(zhdr) &&
832 zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
833 if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
834 atomic64_dec(&pool->pages_nr);
835 else {
836 clear_bit(PAGE_CLAIMED, &page->private);
837 z3fold_page_unlock(zhdr);
838 }
839 return;
840 }
841
842 z3fold_compact_page(zhdr);
843 add_to_unbuddied(pool, zhdr);
844 clear_bit(PAGE_CLAIMED, &page->private);
845 z3fold_page_unlock(zhdr);
846}
847
848static void compact_page_work(struct work_struct *w)
849{
850 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
851 work);
852
853 do_compact_page(zhdr, false);
854}
855
856/* returns _locked_ z3fold page header or NULL */
857static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
858 size_t size, bool can_sleep)
859{
860 struct z3fold_header *zhdr = NULL;
861 struct page *page;
862 struct list_head *unbuddied;
863 int chunks = size_to_chunks(size), i;
864
865lookup:
866 migrate_disable();
867 /* First, try to find an unbuddied z3fold page. */
868 unbuddied = this_cpu_ptr(pool->unbuddied);
869 for_each_unbuddied_list(i, chunks) {
870 struct list_head *l = &unbuddied[i];
871
872 zhdr = list_first_entry_or_null(READ_ONCE(l),
873 struct z3fold_header, buddy);
874
875 if (!zhdr)
876 continue;
877
878 /* Re-check under lock. */
879 spin_lock(&pool->lock);
880 l = &unbuddied[i];
881 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
882 struct z3fold_header, buddy)) ||
883 !z3fold_page_trylock(zhdr)) {
884 spin_unlock(&pool->lock);
885 zhdr = NULL;
886 migrate_enable();
887 if (can_sleep)
888 cond_resched();
889 goto lookup;
890 }
891 list_del_init(&zhdr->buddy);
892 zhdr->cpu = -1;
893 spin_unlock(&pool->lock);
894
895 page = virt_to_page(zhdr);
896 if (test_bit(NEEDS_COMPACTING, &page->private) ||
897 test_bit(PAGE_CLAIMED, &page->private)) {
898 z3fold_page_unlock(zhdr);
899 zhdr = NULL;
900 migrate_enable();
901 if (can_sleep)
902 cond_resched();
903 goto lookup;
904 }
905
906 /*
907 * this page could not be removed from its unbuddied
908 * list while pool lock was held, and then we've taken
909 * page lock so kref_put could not be called before
910 * we got here, so it's safe to just call kref_get()
911 */
912 kref_get(&zhdr->refcount);
913 break;
914 }
915 migrate_enable();
916
917 if (!zhdr) {
918 int cpu;
919
920 /* look for _exact_ match on other cpus' lists */
921 for_each_online_cpu(cpu) {
922 struct list_head *l;
923
924 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
925 spin_lock(&pool->lock);
926 l = &unbuddied[chunks];
927
928 zhdr = list_first_entry_or_null(READ_ONCE(l),
929 struct z3fold_header, buddy);
930
931 if (!zhdr || !z3fold_page_trylock(zhdr)) {
932 spin_unlock(&pool->lock);
933 zhdr = NULL;
934 continue;
935 }
936 list_del_init(&zhdr->buddy);
937 zhdr->cpu = -1;
938 spin_unlock(&pool->lock);
939
940 page = virt_to_page(zhdr);
941 if (test_bit(NEEDS_COMPACTING, &page->private) ||
942 test_bit(PAGE_CLAIMED, &page->private)) {
943 z3fold_page_unlock(zhdr);
944 zhdr = NULL;
945 if (can_sleep)
946 cond_resched();
947 continue;
948 }
949 kref_get(&zhdr->refcount);
950 break;
951 }
952 }
953
954 if (zhdr && !zhdr->slots)
955 zhdr->slots = alloc_slots(pool,
956 can_sleep ? GFP_NOIO : GFP_ATOMIC);
957 return zhdr;
958}
959
960/*
961 * API Functions
962 */
963
964/**
965 * z3fold_create_pool() - create a new z3fold pool
966 * @name: pool name
967 * @gfp: gfp flags when allocating the z3fold pool structure
968 * @ops: user-defined operations for the z3fold pool
969 *
970 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
971 * failed.
972 */
973static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
974 const struct z3fold_ops *ops)
975{
976 struct z3fold_pool *pool = NULL;
977 int i, cpu;
978
979 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
980 if (!pool)
981 goto out;
982 pool->c_handle = kmem_cache_create("z3fold_handle",
983 sizeof(struct z3fold_buddy_slots),
984 SLOTS_ALIGN, 0, NULL);
985 if (!pool->c_handle)
986 goto out_c;
987 spin_lock_init(&pool->lock);
988 spin_lock_init(&pool->stale_lock);
989 pool->unbuddied = __alloc_percpu(sizeof(struct list_head) * NCHUNKS,
990 __alignof__(struct list_head));
991 if (!pool->unbuddied)
992 goto out_pool;
993 for_each_possible_cpu(cpu) {
994 struct list_head *unbuddied =
995 per_cpu_ptr(pool->unbuddied, cpu);
996 for_each_unbuddied_list(i, 0)
997 INIT_LIST_HEAD(&unbuddied[i]);
998 }
999 INIT_LIST_HEAD(&pool->lru);
1000 INIT_LIST_HEAD(&pool->stale);
1001 atomic64_set(&pool->pages_nr, 0);
1002 pool->name = name;
1003 pool->compact_wq = create_singlethread_workqueue(pool->name);
1004 if (!pool->compact_wq)
1005 goto out_unbuddied;
1006 pool->release_wq = create_singlethread_workqueue(pool->name);
1007 if (!pool->release_wq)
1008 goto out_wq;
1009 if (z3fold_register_migration(pool))
1010 goto out_rwq;
1011 INIT_WORK(&pool->work, free_pages_work);
1012 pool->ops = ops;
1013 return pool;
1014
1015out_rwq:
1016 destroy_workqueue(pool->release_wq);
1017out_wq:
1018 destroy_workqueue(pool->compact_wq);
1019out_unbuddied:
1020 free_percpu(pool->unbuddied);
1021out_pool:
1022 kmem_cache_destroy(pool->c_handle);
1023out_c:
1024 kfree(pool);
1025out:
1026 return NULL;
1027}
1028
1029/**
1030 * z3fold_destroy_pool() - destroys an existing z3fold pool
1031 * @pool: the z3fold pool to be destroyed
1032 *
1033 * The pool should be emptied before this function is called.
1034 */
1035static void z3fold_destroy_pool(struct z3fold_pool *pool)
1036{
1037 kmem_cache_destroy(pool->c_handle);
1038
1039 /*
1040 * We need to destroy pool->compact_wq before pool->release_wq,
1041 * as any pending work on pool->compact_wq will call
1042 * queue_work(pool->release_wq, &pool->work).
1043 *
1044 * There are still outstanding pages until both workqueues are drained,
1045 * so we cannot unregister migration until then.
1046 */
1047
1048 destroy_workqueue(pool->compact_wq);
1049 destroy_workqueue(pool->release_wq);
1050 z3fold_unregister_migration(pool);
1051 free_percpu(pool->unbuddied);
1052 kfree(pool);
1053}
1054
1055/**
1056 * z3fold_alloc() - allocates a region of a given size
1057 * @pool: z3fold pool from which to allocate
1058 * @size: size in bytes of the desired allocation
1059 * @gfp: gfp flags used if the pool needs to grow
1060 * @handle: handle of the new allocation
1061 *
1062 * This function will attempt to find a free region in the pool large enough to
1063 * satisfy the allocation request. A search of the unbuddied lists is
1064 * performed first. If no suitable free region is found, then a new page is
1065 * allocated and added to the pool to satisfy the request.
1066 *
1067 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
1068 * as z3fold pool pages.
1069 *
1070 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
1071 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
1072 * a new page.
1073 */
1074static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1075 unsigned long *handle)
1076{
1077 int chunks = size_to_chunks(size);
1078 struct z3fold_header *zhdr = NULL;
1079 struct page *page = NULL;
1080 enum buddy bud;
1081 bool can_sleep = gfpflags_allow_blocking(gfp);
1082
1083 if (!size)
1084 return -EINVAL;
1085
1086 if (size > PAGE_SIZE)
1087 return -ENOSPC;
1088
1089 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1090 bud = HEADLESS;
1091 else {
1092retry:
1093 zhdr = __z3fold_alloc(pool, size, can_sleep);
1094 if (zhdr) {
1095 bud = get_free_buddy(zhdr, chunks);
1096 if (bud == HEADLESS) {
1097 if (kref_put(&zhdr->refcount,
1098 release_z3fold_page_locked))
1099 atomic64_dec(&pool->pages_nr);
1100 else
1101 z3fold_page_unlock(zhdr);
1102 pr_err("No free chunks in unbuddied\n");
1103 WARN_ON(1);
1104 goto retry;
1105 }
1106 page = virt_to_page(zhdr);
1107 goto found;
1108 }
1109 bud = FIRST;
1110 }
1111
1112 page = NULL;
1113 if (can_sleep) {
1114 spin_lock(&pool->stale_lock);
1115 zhdr = list_first_entry_or_null(&pool->stale,
1116 struct z3fold_header, buddy);
1117 /*
1118 * Before allocating a page, let's see if we can take one from
1119 * the stale pages list. cancel_work_sync() can sleep so we
1120 * limit this case to the contexts where we can sleep
1121 */
1122 if (zhdr) {
1123 list_del(&zhdr->buddy);
1124 spin_unlock(&pool->stale_lock);
1125 cancel_work_sync(&zhdr->work);
1126 page = virt_to_page(zhdr);
1127 } else {
1128 spin_unlock(&pool->stale_lock);
1129 }
1130 }
1131 if (!page)
1132 page = alloc_page(gfp);
1133
1134 if (!page)
1135 return -ENOMEM;
1136
1137 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
1138 if (!zhdr) {
1139 __free_page(page);
1140 return -ENOMEM;
1141 }
1142 atomic64_inc(&pool->pages_nr);
1143
1144 if (bud == HEADLESS) {
1145 set_bit(PAGE_HEADLESS, &page->private);
1146 goto headless;
1147 }
1148 if (can_sleep) {
1149 lock_page(page);
1150 __SetPageMovable(page, pool->inode->i_mapping);
1151 unlock_page(page);
1152 } else {
1153 if (trylock_page(page)) {
1154 __SetPageMovable(page, pool->inode->i_mapping);
1155 unlock_page(page);
1156 }
1157 }
1158 z3fold_page_lock(zhdr);
1159
1160found:
1161 if (bud == FIRST)
1162 zhdr->first_chunks = chunks;
1163 else if (bud == LAST)
1164 zhdr->last_chunks = chunks;
1165 else {
1166 zhdr->middle_chunks = chunks;
1167 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
1168 }
1169 add_to_unbuddied(pool, zhdr);
1170
1171headless:
1172 spin_lock(&pool->lock);
1173 /* Add/move z3fold page to beginning of LRU */
1174 if (!list_empty(&page->lru))
1175 list_del(&page->lru);
1176
1177 list_add(&page->lru, &pool->lru);
1178
1179 *handle = encode_handle(zhdr, bud);
1180 spin_unlock(&pool->lock);
1181 if (bud != HEADLESS)
1182 z3fold_page_unlock(zhdr);
1183
1184 return 0;
1185}
1186
1187/**
1188 * z3fold_free() - frees the allocation associated with the given handle
1189 * @pool: pool in which the allocation resided
1190 * @handle: handle associated with the allocation returned by z3fold_alloc()
1191 *
1192 * In the case that the z3fold page in which the allocation resides is under
1193 * reclaim, as indicated by the PG_reclaim flag being set, this function
1194 * only sets the first|last_chunks to 0. The page is actually freed
1195 * once both buddies are evicted (see z3fold_reclaim_page() below).
1196 */
1197static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1198{
1199 struct z3fold_header *zhdr;
1200 struct page *page;
1201 enum buddy bud;
1202 bool page_claimed;
1203
1204 zhdr = get_z3fold_header(handle);
1205 page = virt_to_page(zhdr);
1206 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1207
1208 if (test_bit(PAGE_HEADLESS, &page->private)) {
1209 /* if a headless page is under reclaim, just leave.
1210 * NB: we use test_and_set_bit for a reason: if the bit
1211 * has not been set before, we release this page
1212 * immediately so we don't care about its value any more.
1213 */
1214 if (!page_claimed) {
1215 spin_lock(&pool->lock);
1216 list_del(&page->lru);
1217 spin_unlock(&pool->lock);
1218 put_z3fold_header(zhdr);
1219 free_z3fold_page(page, true);
1220 atomic64_dec(&pool->pages_nr);
1221 }
1222 return;
1223 }
1224
1225 /* Non-headless case */
1226 bud = handle_to_buddy(handle);
1227
1228 switch (bud) {
1229 case FIRST:
1230 zhdr->first_chunks = 0;
1231 break;
1232 case MIDDLE:
1233 zhdr->middle_chunks = 0;
1234 break;
1235 case LAST:
1236 zhdr->last_chunks = 0;
1237 break;
1238 default:
1239 pr_err("%s: unknown bud %d\n", __func__, bud);
1240 WARN_ON(1);
1241 put_z3fold_header(zhdr);
1242 return;
1243 }
1244
1245 if (!page_claimed)
1246 free_handle(handle, zhdr);
1247 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1248 atomic64_dec(&pool->pages_nr);
1249 return;
1250 }
1251 if (page_claimed) {
1252 /* the page has not been claimed by us */
1253 z3fold_page_unlock(zhdr);
1254 return;
1255 }
1256 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1257 put_z3fold_header(zhdr);
1258 clear_bit(PAGE_CLAIMED, &page->private);
1259 return;
1260 }
1261 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1262 spin_lock(&pool->lock);
1263 list_del_init(&zhdr->buddy);
1264 spin_unlock(&pool->lock);
1265 zhdr->cpu = -1;
1266 kref_get(&zhdr->refcount);
1267 clear_bit(PAGE_CLAIMED, &page->private);
1268 do_compact_page(zhdr, true);
1269 return;
1270 }
1271 kref_get(&zhdr->refcount);
1272 clear_bit(PAGE_CLAIMED, &page->private);
1273 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1274 put_z3fold_header(zhdr);
1275}
1276
1277/**
1278 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1279 * @pool: pool from which a page will attempt to be evicted
1280 * @retries: number of pages on the LRU list for which eviction will
1281 * be attempted before failing
1282 *
1283 * z3fold reclaim is different from normal system reclaim in that it is done
1284 * from the bottom, up. This is because only the bottom layer, z3fold, has
1285 * information on how the allocations are organized within each z3fold page.
1286 * This has the potential to create interesting locking situations between
1287 * z3fold and the user, however.
1288 *
1289 * To avoid these, this is how z3fold_reclaim_page() should be called:
1290 *
1291 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1292 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1293 * call the user-defined eviction handler with the pool and handle as
1294 * arguments.
1295 *
1296 * If the handle can not be evicted, the eviction handler should return
1297 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1298 * appropriate list and try the next z3fold page on the LRU up to
1299 * a user defined number of retries.
1300 *
1301 * If the handle is successfully evicted, the eviction handler should
1302 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1303 * contains logic to delay freeing the page if the page is under reclaim,
1304 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1305 *
1306 * If all buddies in the z3fold page are successfully evicted, then the
1307 * z3fold page can be freed.
1308 *
1309 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1310 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1311 * the retry limit was hit.
1312 */
1313static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1314{
1315 int i, ret = -1;
1316 struct z3fold_header *zhdr = NULL;
1317 struct page *page = NULL;
1318 struct list_head *pos;
1319 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1320 struct z3fold_buddy_slots slots __attribute__((aligned(SLOTS_ALIGN)));
1321
1322 rwlock_init(&slots.lock);
1323 slots.pool = (unsigned long)pool | (1 << HANDLES_NOFREE);
1324
1325 spin_lock(&pool->lock);
1326 if (!pool->ops || !pool->ops->evict || retries == 0) {
1327 spin_unlock(&pool->lock);
1328 return -EINVAL;
1329 }
1330 for (i = 0; i < retries; i++) {
1331 if (list_empty(&pool->lru)) {
1332 spin_unlock(&pool->lock);
1333 return -EINVAL;
1334 }
1335 list_for_each_prev(pos, &pool->lru) {
1336 page = list_entry(pos, struct page, lru);
1337
1338 zhdr = page_address(page);
1339 if (test_bit(PAGE_HEADLESS, &page->private)) {
1340 /*
1341 * For non-headless pages, we wait to do this
1342 * until we have the page lock to avoid racing
1343 * with __z3fold_alloc(). Headless pages don't
1344 * have a lock (and __z3fold_alloc() will never
1345 * see them), but we still need to test and set
1346 * PAGE_CLAIMED to avoid racing with
1347 * z3fold_free(), so just do it now before
1348 * leaving the loop.
1349 */
1350 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1351 continue;
1352
1353 break;
1354 }
1355
1356 if (kref_get_unless_zero(&zhdr->refcount) == 0) {
1357 zhdr = NULL;
1358 break;
1359 }
1360 if (!z3fold_page_trylock(zhdr)) {
1361 if (kref_put(&zhdr->refcount,
1362 release_z3fold_page))
1363 atomic64_dec(&pool->pages_nr);
1364 zhdr = NULL;
1365 continue; /* can't evict at this point */
1366 }
1367
1368 /* test_and_set_bit is of course atomic, but we still
1369 * need to do it under page lock, otherwise checking
1370 * that bit in __z3fold_alloc wouldn't make sense
1371 */
1372 if (zhdr->foreign_handles ||
1373 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1374 if (kref_put(&zhdr->refcount,
1375 release_z3fold_page_locked))
1376 atomic64_dec(&pool->pages_nr);
1377 else
1378 z3fold_page_unlock(zhdr);
1379 zhdr = NULL;
1380 continue; /* can't evict such page */
1381 }
1382 list_del_init(&zhdr->buddy);
1383 zhdr->cpu = -1;
1384 break;
1385 }
1386
1387 if (!zhdr)
1388 break;
1389
1390 list_del_init(&page->lru);
1391 spin_unlock(&pool->lock);
1392
1393 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1394 /*
1395 * We need encode the handles before unlocking, and
1396 * use our local slots structure because z3fold_free
1397 * can zero out zhdr->slots and we can't do much
1398 * about that
1399 */
1400 first_handle = 0;
1401 last_handle = 0;
1402 middle_handle = 0;
1403 memset(slots.slot, 0, sizeof(slots.slot));
1404 if (zhdr->first_chunks)
1405 first_handle = __encode_handle(zhdr, &slots,
1406 FIRST);
1407 if (zhdr->middle_chunks)
1408 middle_handle = __encode_handle(zhdr, &slots,
1409 MIDDLE);
1410 if (zhdr->last_chunks)
1411 last_handle = __encode_handle(zhdr, &slots,
1412 LAST);
1413 /*
1414 * it's safe to unlock here because we hold a
1415 * reference to this page
1416 */
1417 z3fold_page_unlock(zhdr);
1418 } else {
1419 first_handle = encode_handle(zhdr, HEADLESS);
1420 last_handle = middle_handle = 0;
1421 }
1422 /* Issue the eviction callback(s) */
1423 if (middle_handle) {
1424 ret = pool->ops->evict(pool, middle_handle);
1425 if (ret)
1426 goto next;
1427 }
1428 if (first_handle) {
1429 ret = pool->ops->evict(pool, first_handle);
1430 if (ret)
1431 goto next;
1432 }
1433 if (last_handle) {
1434 ret = pool->ops->evict(pool, last_handle);
1435 if (ret)
1436 goto next;
1437 }
1438next:
1439 if (test_bit(PAGE_HEADLESS, &page->private)) {
1440 if (ret == 0) {
1441 free_z3fold_page(page, true);
1442 atomic64_dec(&pool->pages_nr);
1443 return 0;
1444 }
1445 spin_lock(&pool->lock);
1446 list_add(&page->lru, &pool->lru);
1447 spin_unlock(&pool->lock);
1448 clear_bit(PAGE_CLAIMED, &page->private);
1449 } else {
1450 struct z3fold_buddy_slots *slots = zhdr->slots;
1451 z3fold_page_lock(zhdr);
1452 if (kref_put(&zhdr->refcount,
1453 release_z3fold_page_locked)) {
1454 kmem_cache_free(pool->c_handle, slots);
1455 atomic64_dec(&pool->pages_nr);
1456 return 0;
1457 }
1458 /*
1459 * if we are here, the page is still not completely
1460 * free. Take the global pool lock then to be able
1461 * to add it back to the lru list
1462 */
1463 spin_lock(&pool->lock);
1464 list_add(&page->lru, &pool->lru);
1465 spin_unlock(&pool->lock);
1466 z3fold_page_unlock(zhdr);
1467 clear_bit(PAGE_CLAIMED, &page->private);
1468 }
1469
1470 /* We started off locked to we need to lock the pool back */
1471 spin_lock(&pool->lock);
1472 }
1473 spin_unlock(&pool->lock);
1474 return -EAGAIN;
1475}
1476
1477/**
1478 * z3fold_map() - maps the allocation associated with the given handle
1479 * @pool: pool in which the allocation resides
1480 * @handle: handle associated with the allocation to be mapped
1481 *
1482 * Extracts the buddy number from handle and constructs the pointer to the
1483 * correct starting chunk within the page.
1484 *
1485 * Returns: a pointer to the mapped allocation
1486 */
1487static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1488{
1489 struct z3fold_header *zhdr;
1490 struct page *page;
1491 void *addr;
1492 enum buddy buddy;
1493
1494 zhdr = get_z3fold_header(handle);
1495 addr = zhdr;
1496 page = virt_to_page(zhdr);
1497
1498 if (test_bit(PAGE_HEADLESS, &page->private))
1499 goto out;
1500
1501 buddy = handle_to_buddy(handle);
1502 switch (buddy) {
1503 case FIRST:
1504 addr += ZHDR_SIZE_ALIGNED;
1505 break;
1506 case MIDDLE:
1507 addr += zhdr->start_middle << CHUNK_SHIFT;
1508 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1509 break;
1510 case LAST:
1511 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1512 break;
1513 default:
1514 pr_err("unknown buddy id %d\n", buddy);
1515 WARN_ON(1);
1516 addr = NULL;
1517 break;
1518 }
1519
1520 if (addr)
1521 zhdr->mapped_count++;
1522out:
1523 put_z3fold_header(zhdr);
1524 return addr;
1525}
1526
1527/**
1528 * z3fold_unmap() - unmaps the allocation associated with the given handle
1529 * @pool: pool in which the allocation resides
1530 * @handle: handle associated with the allocation to be unmapped
1531 */
1532static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1533{
1534 struct z3fold_header *zhdr;
1535 struct page *page;
1536 enum buddy buddy;
1537
1538 zhdr = get_z3fold_header(handle);
1539 page = virt_to_page(zhdr);
1540
1541 if (test_bit(PAGE_HEADLESS, &page->private))
1542 return;
1543
1544 buddy = handle_to_buddy(handle);
1545 if (buddy == MIDDLE)
1546 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1547 zhdr->mapped_count--;
1548 put_z3fold_header(zhdr);
1549}
1550
1551/**
1552 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1553 * @pool: pool whose size is being queried
1554 *
1555 * Returns: size in pages of the given pool.
1556 */
1557static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1558{
1559 return atomic64_read(&pool->pages_nr);
1560}
1561
1562static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1563{
1564 struct z3fold_header *zhdr;
1565 struct z3fold_pool *pool;
1566
1567 VM_BUG_ON_PAGE(!PageMovable(page), page);
1568 VM_BUG_ON_PAGE(PageIsolated(page), page);
1569
1570 if (test_bit(PAGE_HEADLESS, &page->private))
1571 return false;
1572
1573 zhdr = page_address(page);
1574 z3fold_page_lock(zhdr);
1575 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1576 test_bit(PAGE_STALE, &page->private))
1577 goto out;
1578
1579 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1580 goto out;
1581
1582 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1583 goto out;
1584 pool = zhdr_to_pool(zhdr);
1585 spin_lock(&pool->lock);
1586 if (!list_empty(&zhdr->buddy))
1587 list_del_init(&zhdr->buddy);
1588 if (!list_empty(&page->lru))
1589 list_del_init(&page->lru);
1590 spin_unlock(&pool->lock);
1591
1592 kref_get(&zhdr->refcount);
1593 z3fold_page_unlock(zhdr);
1594 return true;
1595
1596out:
1597 z3fold_page_unlock(zhdr);
1598 return false;
1599}
1600
1601static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1602 struct page *page, enum migrate_mode mode)
1603{
1604 struct z3fold_header *zhdr, *new_zhdr;
1605 struct z3fold_pool *pool;
1606 struct address_space *new_mapping;
1607
1608 VM_BUG_ON_PAGE(!PageMovable(page), page);
1609 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1610 VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
1611 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1612
1613 zhdr = page_address(page);
1614 pool = zhdr_to_pool(zhdr);
1615
1616 if (!z3fold_page_trylock(zhdr))
1617 return -EAGAIN;
1618 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1619 z3fold_page_unlock(zhdr);
1620 clear_bit(PAGE_CLAIMED, &page->private);
1621 return -EBUSY;
1622 }
1623 if (work_pending(&zhdr->work)) {
1624 z3fold_page_unlock(zhdr);
1625 return -EAGAIN;
1626 }
1627 new_zhdr = page_address(newpage);
1628 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1629 newpage->private = page->private;
1630 page->private = 0;
1631 z3fold_page_unlock(zhdr);
1632 spin_lock_init(&new_zhdr->page_lock);
1633 INIT_WORK(&new_zhdr->work, compact_page_work);
1634 /*
1635 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1636 * so we only have to reinitialize it.
1637 */
1638 INIT_LIST_HEAD(&new_zhdr->buddy);
1639 new_mapping = page_mapping(page);
1640 __ClearPageMovable(page);
1641 ClearPagePrivate(page);
1642
1643 get_page(newpage);
1644 z3fold_page_lock(new_zhdr);
1645 if (new_zhdr->first_chunks)
1646 encode_handle(new_zhdr, FIRST);
1647 if (new_zhdr->last_chunks)
1648 encode_handle(new_zhdr, LAST);
1649 if (new_zhdr->middle_chunks)
1650 encode_handle(new_zhdr, MIDDLE);
1651 set_bit(NEEDS_COMPACTING, &newpage->private);
1652 new_zhdr->cpu = smp_processor_id();
1653 spin_lock(&pool->lock);
1654 list_add(&newpage->lru, &pool->lru);
1655 spin_unlock(&pool->lock);
1656 __SetPageMovable(newpage, new_mapping);
1657 z3fold_page_unlock(new_zhdr);
1658
1659 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1660
1661 page_mapcount_reset(page);
1662 clear_bit(PAGE_CLAIMED, &page->private);
1663 put_page(page);
1664 return 0;
1665}
1666
1667static void z3fold_page_putback(struct page *page)
1668{
1669 struct z3fold_header *zhdr;
1670 struct z3fold_pool *pool;
1671
1672 zhdr = page_address(page);
1673 pool = zhdr_to_pool(zhdr);
1674
1675 z3fold_page_lock(zhdr);
1676 if (!list_empty(&zhdr->buddy))
1677 list_del_init(&zhdr->buddy);
1678 INIT_LIST_HEAD(&page->lru);
1679 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1680 atomic64_dec(&pool->pages_nr);
1681 return;
1682 }
1683 spin_lock(&pool->lock);
1684 list_add(&page->lru, &pool->lru);
1685 spin_unlock(&pool->lock);
1686 clear_bit(PAGE_CLAIMED, &page->private);
1687 z3fold_page_unlock(zhdr);
1688}
1689
1690static const struct address_space_operations z3fold_aops = {
1691 .isolate_page = z3fold_page_isolate,
1692 .migratepage = z3fold_page_migrate,
1693 .putback_page = z3fold_page_putback,
1694};
1695
1696/*****************
1697 * zpool
1698 ****************/
1699
1700static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1701{
1702 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1703 return pool->zpool_ops->evict(pool->zpool, handle);
1704 else
1705 return -ENOENT;
1706}
1707
1708static const struct z3fold_ops z3fold_zpool_ops = {
1709 .evict = z3fold_zpool_evict
1710};
1711
1712static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1713 const struct zpool_ops *zpool_ops,
1714 struct zpool *zpool)
1715{
1716 struct z3fold_pool *pool;
1717
1718 pool = z3fold_create_pool(name, gfp,
1719 zpool_ops ? &z3fold_zpool_ops : NULL);
1720 if (pool) {
1721 pool->zpool = zpool;
1722 pool->zpool_ops = zpool_ops;
1723 }
1724 return pool;
1725}
1726
1727static void z3fold_zpool_destroy(void *pool)
1728{
1729 z3fold_destroy_pool(pool);
1730}
1731
1732static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1733 unsigned long *handle)
1734{
1735 return z3fold_alloc(pool, size, gfp, handle);
1736}
1737static void z3fold_zpool_free(void *pool, unsigned long handle)
1738{
1739 z3fold_free(pool, handle);
1740}
1741
1742static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1743 unsigned int *reclaimed)
1744{
1745 unsigned int total = 0;
1746 int ret = -EINVAL;
1747
1748 while (total < pages) {
1749 ret = z3fold_reclaim_page(pool, 8);
1750 if (ret < 0)
1751 break;
1752 total++;
1753 }
1754
1755 if (reclaimed)
1756 *reclaimed = total;
1757
1758 return ret;
1759}
1760
1761static void *z3fold_zpool_map(void *pool, unsigned long handle,
1762 enum zpool_mapmode mm)
1763{
1764 return z3fold_map(pool, handle);
1765}
1766static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1767{
1768 z3fold_unmap(pool, handle);
1769}
1770
1771static u64 z3fold_zpool_total_size(void *pool)
1772{
1773 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1774}
1775
1776static struct zpool_driver z3fold_zpool_driver = {
1777 .type = "z3fold",
1778 .sleep_mapped = true,
1779 .owner = THIS_MODULE,
1780 .create = z3fold_zpool_create,
1781 .destroy = z3fold_zpool_destroy,
1782 .malloc = z3fold_zpool_malloc,
1783 .free = z3fold_zpool_free,
1784 .shrink = z3fold_zpool_shrink,
1785 .map = z3fold_zpool_map,
1786 .unmap = z3fold_zpool_unmap,
1787 .total_size = z3fold_zpool_total_size,
1788};
1789
1790MODULE_ALIAS("zpool-z3fold");
1791
1792static int __init init_z3fold(void)
1793{
1794 int ret;
1795
1796 /*
1797 * Make sure the z3fold header is not larger than the page size and
1798 * there has remaining spaces for its buddy.
1799 */
1800 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
1801 ret = z3fold_mount();
1802 if (ret)
1803 return ret;
1804
1805 zpool_register_driver(&z3fold_zpool_driver);
1806
1807 return 0;
1808}
1809
1810static void __exit exit_z3fold(void)
1811{
1812 z3fold_unmount();
1813 zpool_unregister_driver(&z3fold_zpool_driver);
1814}
1815
1816module_init(init_z3fold);
1817module_exit(exit_z3fold);
1818
1819MODULE_LICENSE("GPL");
1820MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1821MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");