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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/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 ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
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 + flags */
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 * @compact_wq: workqueue for page layout background optimization
148 * @release_wq: workqueue for safe page release
149 * @work: work_struct for safe page release
150 * @inode: inode for z3fold pseudo filesystem
151 *
152 * This structure is allocated at pool creation time and maintains metadata
153 * pertaining to a particular z3fold pool.
154 */
155struct z3fold_pool {
156 const char *name;
157 spinlock_t lock;
158 spinlock_t stale_lock;
159 struct list_head *unbuddied;
160 struct list_head lru;
161 struct list_head stale;
162 atomic64_t pages_nr;
163 struct kmem_cache *c_handle;
164 const struct z3fold_ops *ops;
165 struct zpool *zpool;
166 const struct zpool_ops *zpool_ops;
167 struct workqueue_struct *compact_wq;
168 struct workqueue_struct *release_wq;
169 struct work_struct work;
170 struct inode *inode;
171};
172
173/*
174 * Internal z3fold page flags
175 */
176enum z3fold_page_flags {
177 PAGE_HEADLESS = 0,
178 MIDDLE_CHUNK_MAPPED,
179 NEEDS_COMPACTING,
180 PAGE_STALE,
181 PAGE_CLAIMED, /* by either reclaim or free */
182};
183
184/*
185 * handle flags, go under HANDLE_FLAG_MASK
186 */
187enum z3fold_handle_flags {
188 HANDLES_ORPHANED = 0,
189};
190
191/*
192 * Forward declarations
193 */
194static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
195static void compact_page_work(struct work_struct *w);
196
197/*****************
198 * Helpers
199*****************/
200
201/* Converts an allocation size in bytes to size in z3fold chunks */
202static int size_to_chunks(size_t size)
203{
204 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
205}
206
207#define for_each_unbuddied_list(_iter, _begin) \
208 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
209
210static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
211 gfp_t gfp)
212{
213 struct z3fold_buddy_slots *slots;
214
215 slots = kmem_cache_alloc(pool->c_handle,
216 (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
217
218 if (slots) {
219 /* It will be freed separately in free_handle(). */
220 kmemleak_not_leak(slots);
221 memset(slots->slot, 0, sizeof(slots->slot));
222 slots->pool = (unsigned long)pool;
223 rwlock_init(&slots->lock);
224 }
225
226 return slots;
227}
228
229static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
230{
231 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
232}
233
234static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
235{
236 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
237}
238
239/* Lock a z3fold page */
240static inline void z3fold_page_lock(struct z3fold_header *zhdr)
241{
242 spin_lock(&zhdr->page_lock);
243}
244
245/* Try to lock a z3fold page */
246static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
247{
248 return spin_trylock(&zhdr->page_lock);
249}
250
251/* Unlock a z3fold page */
252static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
253{
254 spin_unlock(&zhdr->page_lock);
255}
256
257
258static inline struct z3fold_header *__get_z3fold_header(unsigned long handle,
259 bool lock)
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 if (lock)
274 locked = z3fold_page_trylock(zhdr);
275 read_unlock(&slots->lock);
276 if (locked)
277 break;
278 cpu_relax();
279 } while (lock);
280 } else {
281 zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
282 }
283
284 return zhdr;
285}
286
287/* Returns the z3fold page where a given handle is stored */
288static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
289{
290 return __get_z3fold_header(h, false);
291}
292
293/* return locked z3fold page if it's not headless */
294static inline struct z3fold_header *get_z3fold_header(unsigned long h)
295{
296 return __get_z3fold_header(h, true);
297}
298
299static inline void put_z3fold_header(struct z3fold_header *zhdr)
300{
301 struct page *page = virt_to_page(zhdr);
302
303 if (!test_bit(PAGE_HEADLESS, &page->private))
304 z3fold_page_unlock(zhdr);
305}
306
307static inline void free_handle(unsigned long handle)
308{
309 struct z3fold_buddy_slots *slots;
310 struct z3fold_header *zhdr;
311 int i;
312 bool is_free;
313
314 if (handle & (1 << PAGE_HEADLESS))
315 return;
316
317 if (WARN_ON(*(unsigned long *)handle == 0))
318 return;
319
320 zhdr = handle_to_z3fold_header(handle);
321 slots = handle_to_slots(handle);
322 write_lock(&slots->lock);
323 *(unsigned long *)handle = 0;
324 if (zhdr->slots == slots) {
325 write_unlock(&slots->lock);
326 return; /* simple case, nothing else to do */
327 }
328
329 /* we are freeing a foreign handle if we are here */
330 zhdr->foreign_handles--;
331 is_free = true;
332 if (!test_bit(HANDLES_ORPHANED, &slots->pool)) {
333 write_unlock(&slots->lock);
334 return;
335 }
336 for (i = 0; i <= BUDDY_MASK; i++) {
337 if (slots->slot[i]) {
338 is_free = false;
339 break;
340 }
341 }
342 write_unlock(&slots->lock);
343
344 if (is_free) {
345 struct z3fold_pool *pool = slots_to_pool(slots);
346
347 kmem_cache_free(pool->c_handle, slots);
348 }
349}
350
351static int z3fold_init_fs_context(struct fs_context *fc)
352{
353 return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
354}
355
356static struct file_system_type z3fold_fs = {
357 .name = "z3fold",
358 .init_fs_context = z3fold_init_fs_context,
359 .kill_sb = kill_anon_super,
360};
361
362static struct vfsmount *z3fold_mnt;
363static int z3fold_mount(void)
364{
365 int ret = 0;
366
367 z3fold_mnt = kern_mount(&z3fold_fs);
368 if (IS_ERR(z3fold_mnt))
369 ret = PTR_ERR(z3fold_mnt);
370
371 return ret;
372}
373
374static void z3fold_unmount(void)
375{
376 kern_unmount(z3fold_mnt);
377}
378
379static const struct address_space_operations z3fold_aops;
380static int z3fold_register_migration(struct z3fold_pool *pool)
381{
382 pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
383 if (IS_ERR(pool->inode)) {
384 pool->inode = NULL;
385 return 1;
386 }
387
388 pool->inode->i_mapping->private_data = pool;
389 pool->inode->i_mapping->a_ops = &z3fold_aops;
390 return 0;
391}
392
393static void z3fold_unregister_migration(struct z3fold_pool *pool)
394{
395 if (pool->inode)
396 iput(pool->inode);
397 }
398
399/* Initializes the z3fold header of a newly allocated z3fold page */
400static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
401 struct z3fold_pool *pool, gfp_t gfp)
402{
403 struct z3fold_header *zhdr = page_address(page);
404 struct z3fold_buddy_slots *slots;
405
406 INIT_LIST_HEAD(&page->lru);
407 clear_bit(PAGE_HEADLESS, &page->private);
408 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
409 clear_bit(NEEDS_COMPACTING, &page->private);
410 clear_bit(PAGE_STALE, &page->private);
411 clear_bit(PAGE_CLAIMED, &page->private);
412 if (headless)
413 return zhdr;
414
415 slots = alloc_slots(pool, gfp);
416 if (!slots)
417 return NULL;
418
419 spin_lock_init(&zhdr->page_lock);
420 kref_init(&zhdr->refcount);
421 zhdr->first_chunks = 0;
422 zhdr->middle_chunks = 0;
423 zhdr->last_chunks = 0;
424 zhdr->first_num = 0;
425 zhdr->start_middle = 0;
426 zhdr->cpu = -1;
427 zhdr->foreign_handles = 0;
428 zhdr->mapped_count = 0;
429 zhdr->slots = slots;
430 zhdr->pool = pool;
431 INIT_LIST_HEAD(&zhdr->buddy);
432 INIT_WORK(&zhdr->work, compact_page_work);
433 return zhdr;
434}
435
436/* Resets the struct page fields and frees the page */
437static void free_z3fold_page(struct page *page, bool headless)
438{
439 if (!headless) {
440 lock_page(page);
441 __ClearPageMovable(page);
442 unlock_page(page);
443 }
444 ClearPagePrivate(page);
445 __free_page(page);
446}
447
448/* Helper function to build the index */
449static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
450{
451 return (bud + zhdr->first_num) & BUDDY_MASK;
452}
453
454/*
455 * Encodes the handle of a particular buddy within a z3fold page
456 * Pool lock should be held as this function accesses first_num
457 */
458static unsigned long __encode_handle(struct z3fold_header *zhdr,
459 struct z3fold_buddy_slots *slots,
460 enum buddy bud)
461{
462 unsigned long h = (unsigned long)zhdr;
463 int idx = 0;
464
465 /*
466 * For a headless page, its handle is its pointer with the extra
467 * PAGE_HEADLESS bit set
468 */
469 if (bud == HEADLESS)
470 return h | (1 << PAGE_HEADLESS);
471
472 /* otherwise, return pointer to encoded handle */
473 idx = __idx(zhdr, bud);
474 h += idx;
475 if (bud == LAST)
476 h |= (zhdr->last_chunks << BUDDY_SHIFT);
477
478 write_lock(&slots->lock);
479 slots->slot[idx] = h;
480 write_unlock(&slots->lock);
481 return (unsigned long)&slots->slot[idx];
482}
483
484static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
485{
486 return __encode_handle(zhdr, zhdr->slots, bud);
487}
488
489/* only for LAST bud, returns zero otherwise */
490static unsigned short handle_to_chunks(unsigned long handle)
491{
492 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
493 unsigned long addr;
494
495 read_lock(&slots->lock);
496 addr = *(unsigned long *)handle;
497 read_unlock(&slots->lock);
498 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
499}
500
501/*
502 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
503 * but that doesn't matter. because the masking will result in the
504 * correct buddy number.
505 */
506static enum buddy handle_to_buddy(unsigned long handle)
507{
508 struct z3fold_header *zhdr;
509 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
510 unsigned long addr;
511
512 read_lock(&slots->lock);
513 WARN_ON(handle & (1 << PAGE_HEADLESS));
514 addr = *(unsigned long *)handle;
515 read_unlock(&slots->lock);
516 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
517 return (addr - zhdr->first_num) & BUDDY_MASK;
518}
519
520static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
521{
522 return zhdr->pool;
523}
524
525static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
526{
527 struct page *page = virt_to_page(zhdr);
528 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
529 bool is_free = true;
530 int i;
531
532 WARN_ON(!list_empty(&zhdr->buddy));
533 set_bit(PAGE_STALE, &page->private);
534 clear_bit(NEEDS_COMPACTING, &page->private);
535 spin_lock(&pool->lock);
536 if (!list_empty(&page->lru))
537 list_del_init(&page->lru);
538 spin_unlock(&pool->lock);
539
540 /* If there are no foreign handles, free the handles array */
541 read_lock(&zhdr->slots->lock);
542 for (i = 0; i <= BUDDY_MASK; i++) {
543 if (zhdr->slots->slot[i]) {
544 is_free = false;
545 break;
546 }
547 }
548 if (!is_free)
549 set_bit(HANDLES_ORPHANED, &zhdr->slots->pool);
550 read_unlock(&zhdr->slots->lock);
551
552 if (is_free)
553 kmem_cache_free(pool->c_handle, zhdr->slots);
554
555 if (locked)
556 z3fold_page_unlock(zhdr);
557
558 spin_lock(&pool->stale_lock);
559 list_add(&zhdr->buddy, &pool->stale);
560 queue_work(pool->release_wq, &pool->work);
561 spin_unlock(&pool->stale_lock);
562}
563
564static void __attribute__((__unused__))
565 release_z3fold_page(struct kref *ref)
566{
567 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
568 refcount);
569 __release_z3fold_page(zhdr, false);
570}
571
572static void release_z3fold_page_locked(struct kref *ref)
573{
574 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
575 refcount);
576 WARN_ON(z3fold_page_trylock(zhdr));
577 __release_z3fold_page(zhdr, true);
578}
579
580static void release_z3fold_page_locked_list(struct kref *ref)
581{
582 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
583 refcount);
584 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
585
586 spin_lock(&pool->lock);
587 list_del_init(&zhdr->buddy);
588 spin_unlock(&pool->lock);
589
590 WARN_ON(z3fold_page_trylock(zhdr));
591 __release_z3fold_page(zhdr, true);
592}
593
594static void free_pages_work(struct work_struct *w)
595{
596 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
597
598 spin_lock(&pool->stale_lock);
599 while (!list_empty(&pool->stale)) {
600 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
601 struct z3fold_header, buddy);
602 struct page *page = virt_to_page(zhdr);
603
604 list_del(&zhdr->buddy);
605 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
606 continue;
607 spin_unlock(&pool->stale_lock);
608 cancel_work_sync(&zhdr->work);
609 free_z3fold_page(page, false);
610 cond_resched();
611 spin_lock(&pool->stale_lock);
612 }
613 spin_unlock(&pool->stale_lock);
614}
615
616/*
617 * Returns the number of free chunks in a z3fold page.
618 * NB: can't be used with HEADLESS pages.
619 */
620static int num_free_chunks(struct z3fold_header *zhdr)
621{
622 int nfree;
623 /*
624 * If there is a middle object, pick up the bigger free space
625 * either before or after it. Otherwise just subtract the number
626 * of chunks occupied by the first and the last objects.
627 */
628 if (zhdr->middle_chunks != 0) {
629 int nfree_before = zhdr->first_chunks ?
630 0 : zhdr->start_middle - ZHDR_CHUNKS;
631 int nfree_after = zhdr->last_chunks ?
632 0 : TOTAL_CHUNKS -
633 (zhdr->start_middle + zhdr->middle_chunks);
634 nfree = max(nfree_before, nfree_after);
635 } else
636 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
637 return nfree;
638}
639
640/* Add to the appropriate unbuddied list */
641static inline void add_to_unbuddied(struct z3fold_pool *pool,
642 struct z3fold_header *zhdr)
643{
644 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
645 zhdr->middle_chunks == 0) {
646 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
647
648 int freechunks = num_free_chunks(zhdr);
649 spin_lock(&pool->lock);
650 list_add(&zhdr->buddy, &unbuddied[freechunks]);
651 spin_unlock(&pool->lock);
652 zhdr->cpu = smp_processor_id();
653 put_cpu_ptr(pool->unbuddied);
654 }
655}
656
657static inline void *mchunk_memmove(struct z3fold_header *zhdr,
658 unsigned short dst_chunk)
659{
660 void *beg = zhdr;
661 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
662 beg + (zhdr->start_middle << CHUNK_SHIFT),
663 zhdr->middle_chunks << CHUNK_SHIFT);
664}
665
666static inline bool buddy_single(struct z3fold_header *zhdr)
667{
668 return !((zhdr->first_chunks && zhdr->middle_chunks) ||
669 (zhdr->first_chunks && zhdr->last_chunks) ||
670 (zhdr->middle_chunks && zhdr->last_chunks));
671}
672
673static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
674{
675 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
676 void *p = zhdr;
677 unsigned long old_handle = 0;
678 size_t sz = 0;
679 struct z3fold_header *new_zhdr = NULL;
680 int first_idx = __idx(zhdr, FIRST);
681 int middle_idx = __idx(zhdr, MIDDLE);
682 int last_idx = __idx(zhdr, LAST);
683 unsigned short *moved_chunks = NULL;
684
685 /*
686 * No need to protect slots here -- all the slots are "local" and
687 * the page lock is already taken
688 */
689 if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
690 p += ZHDR_SIZE_ALIGNED;
691 sz = zhdr->first_chunks << CHUNK_SHIFT;
692 old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
693 moved_chunks = &zhdr->first_chunks;
694 } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
695 p += zhdr->start_middle << CHUNK_SHIFT;
696 sz = zhdr->middle_chunks << CHUNK_SHIFT;
697 old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
698 moved_chunks = &zhdr->middle_chunks;
699 } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
700 p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
701 sz = zhdr->last_chunks << CHUNK_SHIFT;
702 old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
703 moved_chunks = &zhdr->last_chunks;
704 }
705
706 if (sz > 0) {
707 enum buddy new_bud = HEADLESS;
708 short chunks = size_to_chunks(sz);
709 void *q;
710
711 new_zhdr = __z3fold_alloc(pool, sz, false);
712 if (!new_zhdr)
713 return NULL;
714
715 if (WARN_ON(new_zhdr == zhdr))
716 goto out_fail;
717
718 if (new_zhdr->first_chunks == 0) {
719 if (new_zhdr->middle_chunks != 0 &&
720 chunks >= new_zhdr->start_middle) {
721 new_bud = LAST;
722 } else {
723 new_bud = FIRST;
724 }
725 } else if (new_zhdr->last_chunks == 0) {
726 new_bud = LAST;
727 } else if (new_zhdr->middle_chunks == 0) {
728 new_bud = MIDDLE;
729 }
730 q = new_zhdr;
731 switch (new_bud) {
732 case FIRST:
733 new_zhdr->first_chunks = chunks;
734 q += ZHDR_SIZE_ALIGNED;
735 break;
736 case MIDDLE:
737 new_zhdr->middle_chunks = chunks;
738 new_zhdr->start_middle =
739 new_zhdr->first_chunks + ZHDR_CHUNKS;
740 q += new_zhdr->start_middle << CHUNK_SHIFT;
741 break;
742 case LAST:
743 new_zhdr->last_chunks = chunks;
744 q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
745 break;
746 default:
747 goto out_fail;
748 }
749 new_zhdr->foreign_handles++;
750 memcpy(q, p, sz);
751 write_lock(&zhdr->slots->lock);
752 *(unsigned long *)old_handle = (unsigned long)new_zhdr +
753 __idx(new_zhdr, new_bud);
754 if (new_bud == LAST)
755 *(unsigned long *)old_handle |=
756 (new_zhdr->last_chunks << BUDDY_SHIFT);
757 write_unlock(&zhdr->slots->lock);
758 add_to_unbuddied(pool, new_zhdr);
759 z3fold_page_unlock(new_zhdr);
760
761 *moved_chunks = 0;
762 }
763
764 return new_zhdr;
765
766out_fail:
767 if (new_zhdr) {
768 if (kref_put(&new_zhdr->refcount, release_z3fold_page_locked))
769 atomic64_dec(&pool->pages_nr);
770 else {
771 add_to_unbuddied(pool, new_zhdr);
772 z3fold_page_unlock(new_zhdr);
773 }
774 }
775 return NULL;
776
777}
778
779#define BIG_CHUNK_GAP 3
780/* Has to be called with lock held */
781static int z3fold_compact_page(struct z3fold_header *zhdr)
782{
783 struct page *page = virt_to_page(zhdr);
784
785 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
786 return 0; /* can't move middle chunk, it's used */
787
788 if (unlikely(PageIsolated(page)))
789 return 0;
790
791 if (zhdr->middle_chunks == 0)
792 return 0; /* nothing to compact */
793
794 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
795 /* move to the beginning */
796 mchunk_memmove(zhdr, ZHDR_CHUNKS);
797 zhdr->first_chunks = zhdr->middle_chunks;
798 zhdr->middle_chunks = 0;
799 zhdr->start_middle = 0;
800 zhdr->first_num++;
801 return 1;
802 }
803
804 /*
805 * moving data is expensive, so let's only do that if
806 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
807 */
808 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
809 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
810 BIG_CHUNK_GAP) {
811 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
812 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
813 return 1;
814 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
815 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
816 + zhdr->middle_chunks) >=
817 BIG_CHUNK_GAP) {
818 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
819 zhdr->middle_chunks;
820 mchunk_memmove(zhdr, new_start);
821 zhdr->start_middle = new_start;
822 return 1;
823 }
824
825 return 0;
826}
827
828static void do_compact_page(struct z3fold_header *zhdr, bool locked)
829{
830 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
831 struct page *page;
832
833 page = virt_to_page(zhdr);
834 if (locked)
835 WARN_ON(z3fold_page_trylock(zhdr));
836 else
837 z3fold_page_lock(zhdr);
838 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
839 z3fold_page_unlock(zhdr);
840 return;
841 }
842 spin_lock(&pool->lock);
843 list_del_init(&zhdr->buddy);
844 spin_unlock(&pool->lock);
845
846 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
847 atomic64_dec(&pool->pages_nr);
848 return;
849 }
850
851 if (unlikely(PageIsolated(page) ||
852 test_bit(PAGE_CLAIMED, &page->private) ||
853 test_bit(PAGE_STALE, &page->private))) {
854 z3fold_page_unlock(zhdr);
855 return;
856 }
857
858 if (!zhdr->foreign_handles && buddy_single(zhdr) &&
859 zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
860 if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
861 atomic64_dec(&pool->pages_nr);
862 else
863 z3fold_page_unlock(zhdr);
864 return;
865 }
866
867 z3fold_compact_page(zhdr);
868 add_to_unbuddied(pool, zhdr);
869 z3fold_page_unlock(zhdr);
870}
871
872static void compact_page_work(struct work_struct *w)
873{
874 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
875 work);
876
877 do_compact_page(zhdr, false);
878}
879
880/* returns _locked_ z3fold page header or NULL */
881static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
882 size_t size, bool can_sleep)
883{
884 struct z3fold_header *zhdr = NULL;
885 struct page *page;
886 struct list_head *unbuddied;
887 int chunks = size_to_chunks(size), i;
888
889lookup:
890 /* First, try to find an unbuddied z3fold page. */
891 unbuddied = get_cpu_ptr(pool->unbuddied);
892 for_each_unbuddied_list(i, chunks) {
893 struct list_head *l = &unbuddied[i];
894
895 zhdr = list_first_entry_or_null(READ_ONCE(l),
896 struct z3fold_header, buddy);
897
898 if (!zhdr)
899 continue;
900
901 /* Re-check under lock. */
902 spin_lock(&pool->lock);
903 l = &unbuddied[i];
904 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
905 struct z3fold_header, buddy)) ||
906 !z3fold_page_trylock(zhdr)) {
907 spin_unlock(&pool->lock);
908 zhdr = NULL;
909 put_cpu_ptr(pool->unbuddied);
910 if (can_sleep)
911 cond_resched();
912 goto lookup;
913 }
914 list_del_init(&zhdr->buddy);
915 zhdr->cpu = -1;
916 spin_unlock(&pool->lock);
917
918 page = virt_to_page(zhdr);
919 if (test_bit(NEEDS_COMPACTING, &page->private) ||
920 test_bit(PAGE_CLAIMED, &page->private)) {
921 z3fold_page_unlock(zhdr);
922 zhdr = NULL;
923 put_cpu_ptr(pool->unbuddied);
924 if (can_sleep)
925 cond_resched();
926 goto lookup;
927 }
928
929 /*
930 * this page could not be removed from its unbuddied
931 * list while pool lock was held, and then we've taken
932 * page lock so kref_put could not be called before
933 * we got here, so it's safe to just call kref_get()
934 */
935 kref_get(&zhdr->refcount);
936 break;
937 }
938 put_cpu_ptr(pool->unbuddied);
939
940 if (!zhdr) {
941 int cpu;
942
943 /* look for _exact_ match on other cpus' lists */
944 for_each_online_cpu(cpu) {
945 struct list_head *l;
946
947 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
948 spin_lock(&pool->lock);
949 l = &unbuddied[chunks];
950
951 zhdr = list_first_entry_or_null(READ_ONCE(l),
952 struct z3fold_header, buddy);
953
954 if (!zhdr || !z3fold_page_trylock(zhdr)) {
955 spin_unlock(&pool->lock);
956 zhdr = NULL;
957 continue;
958 }
959 list_del_init(&zhdr->buddy);
960 zhdr->cpu = -1;
961 spin_unlock(&pool->lock);
962
963 page = virt_to_page(zhdr);
964 if (test_bit(NEEDS_COMPACTING, &page->private) ||
965 test_bit(PAGE_CLAIMED, &page->private)) {
966 z3fold_page_unlock(zhdr);
967 zhdr = NULL;
968 if (can_sleep)
969 cond_resched();
970 continue;
971 }
972 kref_get(&zhdr->refcount);
973 break;
974 }
975 }
976
977 return zhdr;
978}
979
980/*
981 * API Functions
982 */
983
984/**
985 * z3fold_create_pool() - create a new z3fold pool
986 * @name: pool name
987 * @gfp: gfp flags when allocating the z3fold pool structure
988 * @ops: user-defined operations for the z3fold pool
989 *
990 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
991 * failed.
992 */
993static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
994 const struct z3fold_ops *ops)
995{
996 struct z3fold_pool *pool = NULL;
997 int i, cpu;
998
999 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
1000 if (!pool)
1001 goto out;
1002 pool->c_handle = kmem_cache_create("z3fold_handle",
1003 sizeof(struct z3fold_buddy_slots),
1004 SLOTS_ALIGN, 0, NULL);
1005 if (!pool->c_handle)
1006 goto out_c;
1007 spin_lock_init(&pool->lock);
1008 spin_lock_init(&pool->stale_lock);
1009 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
1010 if (!pool->unbuddied)
1011 goto out_pool;
1012 for_each_possible_cpu(cpu) {
1013 struct list_head *unbuddied =
1014 per_cpu_ptr(pool->unbuddied, cpu);
1015 for_each_unbuddied_list(i, 0)
1016 INIT_LIST_HEAD(&unbuddied[i]);
1017 }
1018 INIT_LIST_HEAD(&pool->lru);
1019 INIT_LIST_HEAD(&pool->stale);
1020 atomic64_set(&pool->pages_nr, 0);
1021 pool->name = name;
1022 pool->compact_wq = create_singlethread_workqueue(pool->name);
1023 if (!pool->compact_wq)
1024 goto out_unbuddied;
1025 pool->release_wq = create_singlethread_workqueue(pool->name);
1026 if (!pool->release_wq)
1027 goto out_wq;
1028 if (z3fold_register_migration(pool))
1029 goto out_rwq;
1030 INIT_WORK(&pool->work, free_pages_work);
1031 pool->ops = ops;
1032 return pool;
1033
1034out_rwq:
1035 destroy_workqueue(pool->release_wq);
1036out_wq:
1037 destroy_workqueue(pool->compact_wq);
1038out_unbuddied:
1039 free_percpu(pool->unbuddied);
1040out_pool:
1041 kmem_cache_destroy(pool->c_handle);
1042out_c:
1043 kfree(pool);
1044out:
1045 return NULL;
1046}
1047
1048/**
1049 * z3fold_destroy_pool() - destroys an existing z3fold pool
1050 * @pool: the z3fold pool to be destroyed
1051 *
1052 * The pool should be emptied before this function is called.
1053 */
1054static void z3fold_destroy_pool(struct z3fold_pool *pool)
1055{
1056 kmem_cache_destroy(pool->c_handle);
1057
1058 /*
1059 * We need to destroy pool->compact_wq before pool->release_wq,
1060 * as any pending work on pool->compact_wq will call
1061 * queue_work(pool->release_wq, &pool->work).
1062 *
1063 * There are still outstanding pages until both workqueues are drained,
1064 * so we cannot unregister migration until then.
1065 */
1066
1067 destroy_workqueue(pool->compact_wq);
1068 destroy_workqueue(pool->release_wq);
1069 z3fold_unregister_migration(pool);
1070 kfree(pool);
1071}
1072
1073/**
1074 * z3fold_alloc() - allocates a region of a given size
1075 * @pool: z3fold pool from which to allocate
1076 * @size: size in bytes of the desired allocation
1077 * @gfp: gfp flags used if the pool needs to grow
1078 * @handle: handle of the new allocation
1079 *
1080 * This function will attempt to find a free region in the pool large enough to
1081 * satisfy the allocation request. A search of the unbuddied lists is
1082 * performed first. If no suitable free region is found, then a new page is
1083 * allocated and added to the pool to satisfy the request.
1084 *
1085 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
1086 * as z3fold pool pages.
1087 *
1088 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
1089 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
1090 * a new page.
1091 */
1092static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1093 unsigned long *handle)
1094{
1095 int chunks = size_to_chunks(size);
1096 struct z3fold_header *zhdr = NULL;
1097 struct page *page = NULL;
1098 enum buddy bud;
1099 bool can_sleep = gfpflags_allow_blocking(gfp);
1100
1101 if (!size)
1102 return -EINVAL;
1103
1104 if (size > PAGE_SIZE)
1105 return -ENOSPC;
1106
1107 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1108 bud = HEADLESS;
1109 else {
1110retry:
1111 zhdr = __z3fold_alloc(pool, size, can_sleep);
1112 if (zhdr) {
1113 if (zhdr->first_chunks == 0) {
1114 if (zhdr->middle_chunks != 0 &&
1115 chunks >= zhdr->start_middle)
1116 bud = LAST;
1117 else
1118 bud = FIRST;
1119 } else if (zhdr->last_chunks == 0)
1120 bud = LAST;
1121 else if (zhdr->middle_chunks == 0)
1122 bud = MIDDLE;
1123 else {
1124 if (kref_put(&zhdr->refcount,
1125 release_z3fold_page_locked))
1126 atomic64_dec(&pool->pages_nr);
1127 else
1128 z3fold_page_unlock(zhdr);
1129 pr_err("No free chunks in unbuddied\n");
1130 WARN_ON(1);
1131 goto retry;
1132 }
1133 page = virt_to_page(zhdr);
1134 goto found;
1135 }
1136 bud = FIRST;
1137 }
1138
1139 page = NULL;
1140 if (can_sleep) {
1141 spin_lock(&pool->stale_lock);
1142 zhdr = list_first_entry_or_null(&pool->stale,
1143 struct z3fold_header, buddy);
1144 /*
1145 * Before allocating a page, let's see if we can take one from
1146 * the stale pages list. cancel_work_sync() can sleep so we
1147 * limit this case to the contexts where we can sleep
1148 */
1149 if (zhdr) {
1150 list_del(&zhdr->buddy);
1151 spin_unlock(&pool->stale_lock);
1152 cancel_work_sync(&zhdr->work);
1153 page = virt_to_page(zhdr);
1154 } else {
1155 spin_unlock(&pool->stale_lock);
1156 }
1157 }
1158 if (!page)
1159 page = alloc_page(gfp);
1160
1161 if (!page)
1162 return -ENOMEM;
1163
1164 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
1165 if (!zhdr) {
1166 __free_page(page);
1167 return -ENOMEM;
1168 }
1169 atomic64_inc(&pool->pages_nr);
1170
1171 if (bud == HEADLESS) {
1172 set_bit(PAGE_HEADLESS, &page->private);
1173 goto headless;
1174 }
1175 if (can_sleep) {
1176 lock_page(page);
1177 __SetPageMovable(page, pool->inode->i_mapping);
1178 unlock_page(page);
1179 } else {
1180 if (trylock_page(page)) {
1181 __SetPageMovable(page, pool->inode->i_mapping);
1182 unlock_page(page);
1183 }
1184 }
1185 z3fold_page_lock(zhdr);
1186
1187found:
1188 if (bud == FIRST)
1189 zhdr->first_chunks = chunks;
1190 else if (bud == LAST)
1191 zhdr->last_chunks = chunks;
1192 else {
1193 zhdr->middle_chunks = chunks;
1194 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
1195 }
1196 add_to_unbuddied(pool, zhdr);
1197
1198headless:
1199 spin_lock(&pool->lock);
1200 /* Add/move z3fold page to beginning of LRU */
1201 if (!list_empty(&page->lru))
1202 list_del(&page->lru);
1203
1204 list_add(&page->lru, &pool->lru);
1205
1206 *handle = encode_handle(zhdr, bud);
1207 spin_unlock(&pool->lock);
1208 if (bud != HEADLESS)
1209 z3fold_page_unlock(zhdr);
1210
1211 return 0;
1212}
1213
1214/**
1215 * z3fold_free() - frees the allocation associated with the given handle
1216 * @pool: pool in which the allocation resided
1217 * @handle: handle associated with the allocation returned by z3fold_alloc()
1218 *
1219 * In the case that the z3fold page in which the allocation resides is under
1220 * reclaim, as indicated by the PG_reclaim flag being set, this function
1221 * only sets the first|last_chunks to 0. The page is actually freed
1222 * once both buddies are evicted (see z3fold_reclaim_page() below).
1223 */
1224static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1225{
1226 struct z3fold_header *zhdr;
1227 struct page *page;
1228 enum buddy bud;
1229 bool page_claimed;
1230
1231 zhdr = get_z3fold_header(handle);
1232 page = virt_to_page(zhdr);
1233 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1234
1235 if (test_bit(PAGE_HEADLESS, &page->private)) {
1236 /* if a headless page is under reclaim, just leave.
1237 * NB: we use test_and_set_bit for a reason: if the bit
1238 * has not been set before, we release this page
1239 * immediately so we don't care about its value any more.
1240 */
1241 if (!page_claimed) {
1242 spin_lock(&pool->lock);
1243 list_del(&page->lru);
1244 spin_unlock(&pool->lock);
1245 put_z3fold_header(zhdr);
1246 free_z3fold_page(page, true);
1247 atomic64_dec(&pool->pages_nr);
1248 }
1249 return;
1250 }
1251
1252 /* Non-headless case */
1253 bud = handle_to_buddy(handle);
1254
1255 switch (bud) {
1256 case FIRST:
1257 zhdr->first_chunks = 0;
1258 break;
1259 case MIDDLE:
1260 zhdr->middle_chunks = 0;
1261 break;
1262 case LAST:
1263 zhdr->last_chunks = 0;
1264 break;
1265 default:
1266 pr_err("%s: unknown bud %d\n", __func__, bud);
1267 WARN_ON(1);
1268 put_z3fold_header(zhdr);
1269 clear_bit(PAGE_CLAIMED, &page->private);
1270 return;
1271 }
1272
1273 if (!page_claimed)
1274 free_handle(handle);
1275 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1276 atomic64_dec(&pool->pages_nr);
1277 return;
1278 }
1279 if (page_claimed) {
1280 /* the page has not been claimed by us */
1281 z3fold_page_unlock(zhdr);
1282 return;
1283 }
1284 if (unlikely(PageIsolated(page)) ||
1285 test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1286 put_z3fold_header(zhdr);
1287 clear_bit(PAGE_CLAIMED, &page->private);
1288 return;
1289 }
1290 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1291 spin_lock(&pool->lock);
1292 list_del_init(&zhdr->buddy);
1293 spin_unlock(&pool->lock);
1294 zhdr->cpu = -1;
1295 kref_get(&zhdr->refcount);
1296 clear_bit(PAGE_CLAIMED, &page->private);
1297 do_compact_page(zhdr, true);
1298 return;
1299 }
1300 kref_get(&zhdr->refcount);
1301 clear_bit(PAGE_CLAIMED, &page->private);
1302 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1303 put_z3fold_header(zhdr);
1304}
1305
1306/**
1307 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1308 * @pool: pool from which a page will attempt to be evicted
1309 * @retries: number of pages on the LRU list for which eviction will
1310 * be attempted before failing
1311 *
1312 * z3fold reclaim is different from normal system reclaim in that it is done
1313 * from the bottom, up. This is because only the bottom layer, z3fold, has
1314 * information on how the allocations are organized within each z3fold page.
1315 * This has the potential to create interesting locking situations between
1316 * z3fold and the user, however.
1317 *
1318 * To avoid these, this is how z3fold_reclaim_page() should be called:
1319 *
1320 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1321 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1322 * call the user-defined eviction handler with the pool and handle as
1323 * arguments.
1324 *
1325 * If the handle can not be evicted, the eviction handler should return
1326 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1327 * appropriate list and try the next z3fold page on the LRU up to
1328 * a user defined number of retries.
1329 *
1330 * If the handle is successfully evicted, the eviction handler should
1331 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1332 * contains logic to delay freeing the page if the page is under reclaim,
1333 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1334 *
1335 * If all buddies in the z3fold page are successfully evicted, then the
1336 * z3fold page can be freed.
1337 *
1338 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1339 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1340 * the retry limit was hit.
1341 */
1342static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1343{
1344 int i, ret = -1;
1345 struct z3fold_header *zhdr = NULL;
1346 struct page *page = NULL;
1347 struct list_head *pos;
1348 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1349
1350 spin_lock(&pool->lock);
1351 if (!pool->ops || !pool->ops->evict || retries == 0) {
1352 spin_unlock(&pool->lock);
1353 return -EINVAL;
1354 }
1355 for (i = 0; i < retries; i++) {
1356 if (list_empty(&pool->lru)) {
1357 spin_unlock(&pool->lock);
1358 return -EINVAL;
1359 }
1360 list_for_each_prev(pos, &pool->lru) {
1361 page = list_entry(pos, struct page, lru);
1362
1363 /* this bit could have been set by free, in which case
1364 * we pass over to the next page in the pool.
1365 */
1366 if (test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1367 page = NULL;
1368 continue;
1369 }
1370
1371 if (unlikely(PageIsolated(page))) {
1372 clear_bit(PAGE_CLAIMED, &page->private);
1373 page = NULL;
1374 continue;
1375 }
1376 zhdr = page_address(page);
1377 if (test_bit(PAGE_HEADLESS, &page->private))
1378 break;
1379
1380 if (!z3fold_page_trylock(zhdr)) {
1381 clear_bit(PAGE_CLAIMED, &page->private);
1382 zhdr = NULL;
1383 continue; /* can't evict at this point */
1384 }
1385 if (zhdr->foreign_handles) {
1386 clear_bit(PAGE_CLAIMED, &page->private);
1387 z3fold_page_unlock(zhdr);
1388 zhdr = NULL;
1389 continue; /* can't evict such page */
1390 }
1391 kref_get(&zhdr->refcount);
1392 list_del_init(&zhdr->buddy);
1393 zhdr->cpu = -1;
1394 break;
1395 }
1396
1397 if (!zhdr)
1398 break;
1399
1400 list_del_init(&page->lru);
1401 spin_unlock(&pool->lock);
1402
1403 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1404 /*
1405 * We need encode the handles before unlocking, and
1406 * use our local slots structure because z3fold_free
1407 * can zero out zhdr->slots and we can't do much
1408 * about that
1409 */
1410 first_handle = 0;
1411 last_handle = 0;
1412 middle_handle = 0;
1413 if (zhdr->first_chunks)
1414 first_handle = encode_handle(zhdr, FIRST);
1415 if (zhdr->middle_chunks)
1416 middle_handle = encode_handle(zhdr, MIDDLE);
1417 if (zhdr->last_chunks)
1418 last_handle = encode_handle(zhdr, LAST);
1419 /*
1420 * it's safe to unlock here because we hold a
1421 * reference to this page
1422 */
1423 z3fold_page_unlock(zhdr);
1424 } else {
1425 first_handle = encode_handle(zhdr, HEADLESS);
1426 last_handle = middle_handle = 0;
1427 }
1428 /* Issue the eviction callback(s) */
1429 if (middle_handle) {
1430 ret = pool->ops->evict(pool, middle_handle);
1431 if (ret)
1432 goto next;
1433 free_handle(middle_handle);
1434 }
1435 if (first_handle) {
1436 ret = pool->ops->evict(pool, first_handle);
1437 if (ret)
1438 goto next;
1439 free_handle(first_handle);
1440 }
1441 if (last_handle) {
1442 ret = pool->ops->evict(pool, last_handle);
1443 if (ret)
1444 goto next;
1445 free_handle(last_handle);
1446 }
1447next:
1448 if (test_bit(PAGE_HEADLESS, &page->private)) {
1449 if (ret == 0) {
1450 free_z3fold_page(page, true);
1451 atomic64_dec(&pool->pages_nr);
1452 return 0;
1453 }
1454 spin_lock(&pool->lock);
1455 list_add(&page->lru, &pool->lru);
1456 spin_unlock(&pool->lock);
1457 clear_bit(PAGE_CLAIMED, &page->private);
1458 } else {
1459 z3fold_page_lock(zhdr);
1460 if (kref_put(&zhdr->refcount,
1461 release_z3fold_page_locked)) {
1462 atomic64_dec(&pool->pages_nr);
1463 return 0;
1464 }
1465 /*
1466 * if we are here, the page is still not completely
1467 * free. Take the global pool lock then to be able
1468 * to add it back to the lru list
1469 */
1470 spin_lock(&pool->lock);
1471 list_add(&page->lru, &pool->lru);
1472 spin_unlock(&pool->lock);
1473 z3fold_page_unlock(zhdr);
1474 clear_bit(PAGE_CLAIMED, &page->private);
1475 }
1476
1477 /* We started off locked to we need to lock the pool back */
1478 spin_lock(&pool->lock);
1479 }
1480 spin_unlock(&pool->lock);
1481 return -EAGAIN;
1482}
1483
1484/**
1485 * z3fold_map() - maps the allocation associated with the given handle
1486 * @pool: pool in which the allocation resides
1487 * @handle: handle associated with the allocation to be mapped
1488 *
1489 * Extracts the buddy number from handle and constructs the pointer to the
1490 * correct starting chunk within the page.
1491 *
1492 * Returns: a pointer to the mapped allocation
1493 */
1494static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1495{
1496 struct z3fold_header *zhdr;
1497 struct page *page;
1498 void *addr;
1499 enum buddy buddy;
1500
1501 zhdr = get_z3fold_header(handle);
1502 addr = zhdr;
1503 page = virt_to_page(zhdr);
1504
1505 if (test_bit(PAGE_HEADLESS, &page->private))
1506 goto out;
1507
1508 buddy = handle_to_buddy(handle);
1509 switch (buddy) {
1510 case FIRST:
1511 addr += ZHDR_SIZE_ALIGNED;
1512 break;
1513 case MIDDLE:
1514 addr += zhdr->start_middle << CHUNK_SHIFT;
1515 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1516 break;
1517 case LAST:
1518 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1519 break;
1520 default:
1521 pr_err("unknown buddy id %d\n", buddy);
1522 WARN_ON(1);
1523 addr = NULL;
1524 break;
1525 }
1526
1527 if (addr)
1528 zhdr->mapped_count++;
1529out:
1530 put_z3fold_header(zhdr);
1531 return addr;
1532}
1533
1534/**
1535 * z3fold_unmap() - unmaps the allocation associated with the given handle
1536 * @pool: pool in which the allocation resides
1537 * @handle: handle associated with the allocation to be unmapped
1538 */
1539static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1540{
1541 struct z3fold_header *zhdr;
1542 struct page *page;
1543 enum buddy buddy;
1544
1545 zhdr = get_z3fold_header(handle);
1546 page = virt_to_page(zhdr);
1547
1548 if (test_bit(PAGE_HEADLESS, &page->private))
1549 return;
1550
1551 buddy = handle_to_buddy(handle);
1552 if (buddy == MIDDLE)
1553 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1554 zhdr->mapped_count--;
1555 put_z3fold_header(zhdr);
1556}
1557
1558/**
1559 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1560 * @pool: pool whose size is being queried
1561 *
1562 * Returns: size in pages of the given pool.
1563 */
1564static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1565{
1566 return atomic64_read(&pool->pages_nr);
1567}
1568
1569static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1570{
1571 struct z3fold_header *zhdr;
1572 struct z3fold_pool *pool;
1573
1574 VM_BUG_ON_PAGE(!PageMovable(page), page);
1575 VM_BUG_ON_PAGE(PageIsolated(page), page);
1576
1577 if (test_bit(PAGE_HEADLESS, &page->private) ||
1578 test_bit(PAGE_CLAIMED, &page->private))
1579 return false;
1580
1581 zhdr = page_address(page);
1582 z3fold_page_lock(zhdr);
1583 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1584 test_bit(PAGE_STALE, &page->private))
1585 goto out;
1586
1587 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1588 goto out;
1589
1590 pool = zhdr_to_pool(zhdr);
1591 spin_lock(&pool->lock);
1592 if (!list_empty(&zhdr->buddy))
1593 list_del_init(&zhdr->buddy);
1594 if (!list_empty(&page->lru))
1595 list_del_init(&page->lru);
1596 spin_unlock(&pool->lock);
1597
1598 kref_get(&zhdr->refcount);
1599 z3fold_page_unlock(zhdr);
1600 return true;
1601
1602out:
1603 z3fold_page_unlock(zhdr);
1604 return false;
1605}
1606
1607static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1608 struct page *page, enum migrate_mode mode)
1609{
1610 struct z3fold_header *zhdr, *new_zhdr;
1611 struct z3fold_pool *pool;
1612 struct address_space *new_mapping;
1613
1614 VM_BUG_ON_PAGE(!PageMovable(page), page);
1615 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1616 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1617
1618 zhdr = page_address(page);
1619 pool = zhdr_to_pool(zhdr);
1620
1621 if (!z3fold_page_trylock(zhdr)) {
1622 return -EAGAIN;
1623 }
1624 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1625 z3fold_page_unlock(zhdr);
1626 return -EBUSY;
1627 }
1628 if (work_pending(&zhdr->work)) {
1629 z3fold_page_unlock(zhdr);
1630 return -EAGAIN;
1631 }
1632 new_zhdr = page_address(newpage);
1633 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1634 newpage->private = page->private;
1635 page->private = 0;
1636 z3fold_page_unlock(zhdr);
1637 spin_lock_init(&new_zhdr->page_lock);
1638 INIT_WORK(&new_zhdr->work, compact_page_work);
1639 /*
1640 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1641 * so we only have to reinitialize it.
1642 */
1643 INIT_LIST_HEAD(&new_zhdr->buddy);
1644 new_mapping = page_mapping(page);
1645 __ClearPageMovable(page);
1646 ClearPagePrivate(page);
1647
1648 get_page(newpage);
1649 z3fold_page_lock(new_zhdr);
1650 if (new_zhdr->first_chunks)
1651 encode_handle(new_zhdr, FIRST);
1652 if (new_zhdr->last_chunks)
1653 encode_handle(new_zhdr, LAST);
1654 if (new_zhdr->middle_chunks)
1655 encode_handle(new_zhdr, MIDDLE);
1656 set_bit(NEEDS_COMPACTING, &newpage->private);
1657 new_zhdr->cpu = smp_processor_id();
1658 spin_lock(&pool->lock);
1659 list_add(&newpage->lru, &pool->lru);
1660 spin_unlock(&pool->lock);
1661 __SetPageMovable(newpage, new_mapping);
1662 z3fold_page_unlock(new_zhdr);
1663
1664 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1665
1666 page_mapcount_reset(page);
1667 put_page(page);
1668 return 0;
1669}
1670
1671static void z3fold_page_putback(struct page *page)
1672{
1673 struct z3fold_header *zhdr;
1674 struct z3fold_pool *pool;
1675
1676 zhdr = page_address(page);
1677 pool = zhdr_to_pool(zhdr);
1678
1679 z3fold_page_lock(zhdr);
1680 if (!list_empty(&zhdr->buddy))
1681 list_del_init(&zhdr->buddy);
1682 INIT_LIST_HEAD(&page->lru);
1683 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1684 atomic64_dec(&pool->pages_nr);
1685 return;
1686 }
1687 spin_lock(&pool->lock);
1688 list_add(&page->lru, &pool->lru);
1689 spin_unlock(&pool->lock);
1690 z3fold_page_unlock(zhdr);
1691}
1692
1693static const struct address_space_operations z3fold_aops = {
1694 .isolate_page = z3fold_page_isolate,
1695 .migratepage = z3fold_page_migrate,
1696 .putback_page = z3fold_page_putback,
1697};
1698
1699/*****************
1700 * zpool
1701 ****************/
1702
1703static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1704{
1705 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1706 return pool->zpool_ops->evict(pool->zpool, handle);
1707 else
1708 return -ENOENT;
1709}
1710
1711static const struct z3fold_ops z3fold_zpool_ops = {
1712 .evict = z3fold_zpool_evict
1713};
1714
1715static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1716 const struct zpool_ops *zpool_ops,
1717 struct zpool *zpool)
1718{
1719 struct z3fold_pool *pool;
1720
1721 pool = z3fold_create_pool(name, gfp,
1722 zpool_ops ? &z3fold_zpool_ops : NULL);
1723 if (pool) {
1724 pool->zpool = zpool;
1725 pool->zpool_ops = zpool_ops;
1726 }
1727 return pool;
1728}
1729
1730static void z3fold_zpool_destroy(void *pool)
1731{
1732 z3fold_destroy_pool(pool);
1733}
1734
1735static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1736 unsigned long *handle)
1737{
1738 return z3fold_alloc(pool, size, gfp, handle);
1739}
1740static void z3fold_zpool_free(void *pool, unsigned long handle)
1741{
1742 z3fold_free(pool, handle);
1743}
1744
1745static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1746 unsigned int *reclaimed)
1747{
1748 unsigned int total = 0;
1749 int ret = -EINVAL;
1750
1751 while (total < pages) {
1752 ret = z3fold_reclaim_page(pool, 8);
1753 if (ret < 0)
1754 break;
1755 total++;
1756 }
1757
1758 if (reclaimed)
1759 *reclaimed = total;
1760
1761 return ret;
1762}
1763
1764static void *z3fold_zpool_map(void *pool, unsigned long handle,
1765 enum zpool_mapmode mm)
1766{
1767 return z3fold_map(pool, handle);
1768}
1769static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1770{
1771 z3fold_unmap(pool, handle);
1772}
1773
1774static u64 z3fold_zpool_total_size(void *pool)
1775{
1776 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1777}
1778
1779static struct zpool_driver z3fold_zpool_driver = {
1780 .type = "z3fold",
1781 .owner = THIS_MODULE,
1782 .create = z3fold_zpool_create,
1783 .destroy = z3fold_zpool_destroy,
1784 .malloc = z3fold_zpool_malloc,
1785 .free = z3fold_zpool_free,
1786 .shrink = z3fold_zpool_shrink,
1787 .map = z3fold_zpool_map,
1788 .unmap = z3fold_zpool_unmap,
1789 .total_size = z3fold_zpool_total_size,
1790};
1791
1792MODULE_ALIAS("zpool-z3fold");
1793
1794static int __init init_z3fold(void)
1795{
1796 int ret;
1797
1798 /* Make sure the z3fold header is not larger than the page size */
1799 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1800 ret = z3fold_mount();
1801 if (ret)
1802 return ret;
1803
1804 zpool_register_driver(&z3fold_zpool_driver);
1805
1806 return 0;
1807}
1808
1809static void __exit exit_z3fold(void)
1810{
1811 z3fold_unmount();
1812 zpool_unregister_driver(&z3fold_zpool_driver);
1813}
1814
1815module_init(init_z3fold);
1816module_exit(exit_z3fold);
1817
1818MODULE_LICENSE("GPL");
1819MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1820MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * z3fold.c
4 *
5 * Author: Vitaly Wool <vitaly.wool@konsulko.com>
6 * Copyright (C) 2016, Sony Mobile Communications Inc.
7 *
8 * This implementation is based on zbud written by Seth Jennings.
9 *
10 * z3fold is an special purpose allocator for storing compressed pages. It
11 * can store up to three compressed pages per page which improves the
12 * compression ratio of zbud while retaining its main concepts (e. g. always
13 * storing an integral number of objects per page) and simplicity.
14 * It still has simple and deterministic reclaim properties that make it
15 * preferable to a higher density approach (with no requirement on integral
16 * number of object per page) when reclaim is used.
17 *
18 * As in zbud, pages are divided into "chunks". The size of the chunks is
19 * fixed at compile time and is determined by NCHUNKS_ORDER below.
20 *
21 * z3fold doesn't export any API and is meant to be used via zpool API.
22 */
23
24#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
25
26#include <linux/atomic.h>
27#include <linux/sched.h>
28#include <linux/cpumask.h>
29#include <linux/list.h>
30#include <linux/mm.h>
31#include <linux/module.h>
32#include <linux/page-flags.h>
33#include <linux/migrate.h>
34#include <linux/node.h>
35#include <linux/compaction.h>
36#include <linux/percpu.h>
37#include <linux/preempt.h>
38#include <linux/workqueue.h>
39#include <linux/slab.h>
40#include <linux/spinlock.h>
41#include <linux/zpool.h>
42#include <linux/kmemleak.h>
43
44/*
45 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
46 * adjusting internal fragmentation. It also determines the number of
47 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
48 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
49 * in the beginning of an allocated page are occupied by z3fold header, so
50 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
51 * which shows the max number of free chunks in z3fold page, also there will
52 * be 63, or 62, respectively, freelists per pool.
53 */
54#define NCHUNKS_ORDER 6
55
56#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
57#define CHUNK_SIZE (1 << CHUNK_SHIFT)
58#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
59#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
60#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
61#define NCHUNKS (TOTAL_CHUNKS - ZHDR_CHUNKS)
62
63#define BUDDY_MASK (0x3)
64#define BUDDY_SHIFT 2
65#define SLOTS_ALIGN (0x40)
66
67/*****************
68 * Structures
69*****************/
70struct z3fold_pool;
71
72enum buddy {
73 HEADLESS = 0,
74 FIRST,
75 MIDDLE,
76 LAST,
77 BUDDIES_MAX = LAST
78};
79
80struct z3fold_buddy_slots {
81 /*
82 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
83 * be enough slots to hold all possible variants
84 */
85 unsigned long slot[BUDDY_MASK + 1];
86 unsigned long pool; /* back link */
87 rwlock_t lock;
88};
89#define HANDLE_FLAG_MASK (0x03)
90
91/*
92 * struct z3fold_header - z3fold page metadata occupying first chunks of each
93 * z3fold page, except for HEADLESS pages
94 * @buddy: links the z3fold page into the relevant list in the
95 * pool
96 * @page_lock: per-page lock
97 * @refcount: reference count for the z3fold page
98 * @work: work_struct for page layout optimization
99 * @slots: pointer to the structure holding buddy slots
100 * @pool: pointer to the containing pool
101 * @cpu: CPU which this page "belongs" to
102 * @first_chunks: the size of the first buddy in chunks, 0 if free
103 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
104 * @last_chunks: the size of the last buddy in chunks, 0 if free
105 * @first_num: the starting number (for the first handle)
106 * @mapped_count: the number of objects currently mapped
107 */
108struct z3fold_header {
109 struct list_head buddy;
110 spinlock_t page_lock;
111 struct kref refcount;
112 struct work_struct work;
113 struct z3fold_buddy_slots *slots;
114 struct z3fold_pool *pool;
115 short cpu;
116 unsigned short first_chunks;
117 unsigned short middle_chunks;
118 unsigned short last_chunks;
119 unsigned short start_middle;
120 unsigned short first_num:2;
121 unsigned short mapped_count:2;
122 unsigned short foreign_handles:2;
123};
124
125/**
126 * struct z3fold_pool - stores metadata for each z3fold pool
127 * @name: pool name
128 * @lock: protects pool unbuddied 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 __percpu *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 * Zhdr->page_lock should be held as this function accesses first_num
369 * if bud != HEADLESS.
370 */
371static unsigned long __encode_handle(struct z3fold_header *zhdr,
372 struct z3fold_buddy_slots *slots,
373 enum buddy bud)
374{
375 unsigned long h = (unsigned long)zhdr;
376 int idx = 0;
377
378 /*
379 * For a headless page, its handle is its pointer with the extra
380 * PAGE_HEADLESS bit set
381 */
382 if (bud == HEADLESS)
383 return h | (1 << PAGE_HEADLESS);
384
385 /* otherwise, return pointer to encoded handle */
386 idx = __idx(zhdr, bud);
387 h += idx;
388 if (bud == LAST)
389 h |= (zhdr->last_chunks << BUDDY_SHIFT);
390
391 write_lock(&slots->lock);
392 slots->slot[idx] = h;
393 write_unlock(&slots->lock);
394 return (unsigned long)&slots->slot[idx];
395}
396
397static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
398{
399 return __encode_handle(zhdr, zhdr->slots, bud);
400}
401
402/* only for LAST bud, returns zero otherwise */
403static unsigned short handle_to_chunks(unsigned long handle)
404{
405 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
406 unsigned long addr;
407
408 read_lock(&slots->lock);
409 addr = *(unsigned long *)handle;
410 read_unlock(&slots->lock);
411 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
412}
413
414/*
415 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
416 * but that doesn't matter. because the masking will result in the
417 * correct buddy number.
418 */
419static enum buddy handle_to_buddy(unsigned long handle)
420{
421 struct z3fold_header *zhdr;
422 struct z3fold_buddy_slots *slots = handle_to_slots(handle);
423 unsigned long addr;
424
425 read_lock(&slots->lock);
426 WARN_ON(handle & (1 << PAGE_HEADLESS));
427 addr = *(unsigned long *)handle;
428 read_unlock(&slots->lock);
429 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
430 return (addr - zhdr->first_num) & BUDDY_MASK;
431}
432
433static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
434{
435 return zhdr->pool;
436}
437
438static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
439{
440 struct page *page = virt_to_page(zhdr);
441 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
442
443 WARN_ON(!list_empty(&zhdr->buddy));
444 set_bit(PAGE_STALE, &page->private);
445 clear_bit(NEEDS_COMPACTING, &page->private);
446 spin_lock(&pool->lock);
447 spin_unlock(&pool->lock);
448
449 if (locked)
450 z3fold_page_unlock(zhdr);
451
452 spin_lock(&pool->stale_lock);
453 list_add(&zhdr->buddy, &pool->stale);
454 queue_work(pool->release_wq, &pool->work);
455 spin_unlock(&pool->stale_lock);
456
457 atomic64_dec(&pool->pages_nr);
458}
459
460static void release_z3fold_page_locked(struct kref *ref)
461{
462 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
463 refcount);
464 WARN_ON(z3fold_page_trylock(zhdr));
465 __release_z3fold_page(zhdr, true);
466}
467
468static void release_z3fold_page_locked_list(struct kref *ref)
469{
470 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
471 refcount);
472 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
473
474 spin_lock(&pool->lock);
475 list_del_init(&zhdr->buddy);
476 spin_unlock(&pool->lock);
477
478 WARN_ON(z3fold_page_trylock(zhdr));
479 __release_z3fold_page(zhdr, true);
480}
481
482static inline int put_z3fold_locked(struct z3fold_header *zhdr)
483{
484 return kref_put(&zhdr->refcount, release_z3fold_page_locked);
485}
486
487static inline int put_z3fold_locked_list(struct z3fold_header *zhdr)
488{
489 return kref_put(&zhdr->refcount, release_z3fold_page_locked_list);
490}
491
492static void free_pages_work(struct work_struct *w)
493{
494 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
495
496 spin_lock(&pool->stale_lock);
497 while (!list_empty(&pool->stale)) {
498 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
499 struct z3fold_header, buddy);
500 struct page *page = virt_to_page(zhdr);
501
502 list_del(&zhdr->buddy);
503 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
504 continue;
505 spin_unlock(&pool->stale_lock);
506 cancel_work_sync(&zhdr->work);
507 free_z3fold_page(page, false);
508 cond_resched();
509 spin_lock(&pool->stale_lock);
510 }
511 spin_unlock(&pool->stale_lock);
512}
513
514/*
515 * Returns the number of free chunks in a z3fold page.
516 * NB: can't be used with HEADLESS pages.
517 */
518static int num_free_chunks(struct z3fold_header *zhdr)
519{
520 int nfree;
521 /*
522 * If there is a middle object, pick up the bigger free space
523 * either before or after it. Otherwise just subtract the number
524 * of chunks occupied by the first and the last objects.
525 */
526 if (zhdr->middle_chunks != 0) {
527 int nfree_before = zhdr->first_chunks ?
528 0 : zhdr->start_middle - ZHDR_CHUNKS;
529 int nfree_after = zhdr->last_chunks ?
530 0 : TOTAL_CHUNKS -
531 (zhdr->start_middle + zhdr->middle_chunks);
532 nfree = max(nfree_before, nfree_after);
533 } else
534 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
535 return nfree;
536}
537
538/* Add to the appropriate unbuddied list */
539static inline void add_to_unbuddied(struct z3fold_pool *pool,
540 struct z3fold_header *zhdr)
541{
542 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
543 zhdr->middle_chunks == 0) {
544 struct list_head *unbuddied;
545 int freechunks = num_free_chunks(zhdr);
546
547 migrate_disable();
548 unbuddied = this_cpu_ptr(pool->unbuddied);
549 spin_lock(&pool->lock);
550 list_add(&zhdr->buddy, &unbuddied[freechunks]);
551 spin_unlock(&pool->lock);
552 zhdr->cpu = smp_processor_id();
553 migrate_enable();
554 }
555}
556
557static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
558{
559 enum buddy bud = HEADLESS;
560
561 if (zhdr->middle_chunks) {
562 if (!zhdr->first_chunks &&
563 chunks <= zhdr->start_middle - ZHDR_CHUNKS)
564 bud = FIRST;
565 else if (!zhdr->last_chunks)
566 bud = LAST;
567 } else {
568 if (!zhdr->first_chunks)
569 bud = FIRST;
570 else if (!zhdr->last_chunks)
571 bud = LAST;
572 else
573 bud = MIDDLE;
574 }
575
576 return bud;
577}
578
579static inline void *mchunk_memmove(struct z3fold_header *zhdr,
580 unsigned short dst_chunk)
581{
582 void *beg = zhdr;
583 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
584 beg + (zhdr->start_middle << CHUNK_SHIFT),
585 zhdr->middle_chunks << CHUNK_SHIFT);
586}
587
588static inline bool buddy_single(struct z3fold_header *zhdr)
589{
590 return !((zhdr->first_chunks && zhdr->middle_chunks) ||
591 (zhdr->first_chunks && zhdr->last_chunks) ||
592 (zhdr->middle_chunks && zhdr->last_chunks));
593}
594
595static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
596{
597 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
598 void *p = zhdr;
599 unsigned long old_handle = 0;
600 size_t sz = 0;
601 struct z3fold_header *new_zhdr = NULL;
602 int first_idx = __idx(zhdr, FIRST);
603 int middle_idx = __idx(zhdr, MIDDLE);
604 int last_idx = __idx(zhdr, LAST);
605 unsigned short *moved_chunks = NULL;
606
607 /*
608 * No need to protect slots here -- all the slots are "local" and
609 * the page lock is already taken
610 */
611 if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
612 p += ZHDR_SIZE_ALIGNED;
613 sz = zhdr->first_chunks << CHUNK_SHIFT;
614 old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
615 moved_chunks = &zhdr->first_chunks;
616 } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
617 p += zhdr->start_middle << CHUNK_SHIFT;
618 sz = zhdr->middle_chunks << CHUNK_SHIFT;
619 old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
620 moved_chunks = &zhdr->middle_chunks;
621 } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
622 p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
623 sz = zhdr->last_chunks << CHUNK_SHIFT;
624 old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
625 moved_chunks = &zhdr->last_chunks;
626 }
627
628 if (sz > 0) {
629 enum buddy new_bud = HEADLESS;
630 short chunks = size_to_chunks(sz);
631 void *q;
632
633 new_zhdr = __z3fold_alloc(pool, sz, false);
634 if (!new_zhdr)
635 return NULL;
636
637 if (WARN_ON(new_zhdr == zhdr))
638 goto out_fail;
639
640 new_bud = get_free_buddy(new_zhdr, chunks);
641 q = new_zhdr;
642 switch (new_bud) {
643 case FIRST:
644 new_zhdr->first_chunks = chunks;
645 q += ZHDR_SIZE_ALIGNED;
646 break;
647 case MIDDLE:
648 new_zhdr->middle_chunks = chunks;
649 new_zhdr->start_middle =
650 new_zhdr->first_chunks + ZHDR_CHUNKS;
651 q += new_zhdr->start_middle << CHUNK_SHIFT;
652 break;
653 case LAST:
654 new_zhdr->last_chunks = chunks;
655 q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
656 break;
657 default:
658 goto out_fail;
659 }
660 new_zhdr->foreign_handles++;
661 memcpy(q, p, sz);
662 write_lock(&zhdr->slots->lock);
663 *(unsigned long *)old_handle = (unsigned long)new_zhdr +
664 __idx(new_zhdr, new_bud);
665 if (new_bud == LAST)
666 *(unsigned long *)old_handle |=
667 (new_zhdr->last_chunks << BUDDY_SHIFT);
668 write_unlock(&zhdr->slots->lock);
669 add_to_unbuddied(pool, new_zhdr);
670 z3fold_page_unlock(new_zhdr);
671
672 *moved_chunks = 0;
673 }
674
675 return new_zhdr;
676
677out_fail:
678 if (new_zhdr && !put_z3fold_locked(new_zhdr)) {
679 add_to_unbuddied(pool, new_zhdr);
680 z3fold_page_unlock(new_zhdr);
681 }
682 return NULL;
683
684}
685
686#define BIG_CHUNK_GAP 3
687/* Has to be called with lock held */
688static int z3fold_compact_page(struct z3fold_header *zhdr)
689{
690 struct page *page = virt_to_page(zhdr);
691
692 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
693 return 0; /* can't move middle chunk, it's used */
694
695 if (unlikely(PageIsolated(page)))
696 return 0;
697
698 if (zhdr->middle_chunks == 0)
699 return 0; /* nothing to compact */
700
701 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
702 /* move to the beginning */
703 mchunk_memmove(zhdr, ZHDR_CHUNKS);
704 zhdr->first_chunks = zhdr->middle_chunks;
705 zhdr->middle_chunks = 0;
706 zhdr->start_middle = 0;
707 zhdr->first_num++;
708 return 1;
709 }
710
711 /*
712 * moving data is expensive, so let's only do that if
713 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
714 */
715 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
716 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
717 BIG_CHUNK_GAP) {
718 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
719 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
720 return 1;
721 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
722 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
723 + zhdr->middle_chunks) >=
724 BIG_CHUNK_GAP) {
725 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
726 zhdr->middle_chunks;
727 mchunk_memmove(zhdr, new_start);
728 zhdr->start_middle = new_start;
729 return 1;
730 }
731
732 return 0;
733}
734
735static void do_compact_page(struct z3fold_header *zhdr, bool locked)
736{
737 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
738 struct page *page;
739
740 page = virt_to_page(zhdr);
741 if (locked)
742 WARN_ON(z3fold_page_trylock(zhdr));
743 else
744 z3fold_page_lock(zhdr);
745 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
746 z3fold_page_unlock(zhdr);
747 return;
748 }
749 spin_lock(&pool->lock);
750 list_del_init(&zhdr->buddy);
751 spin_unlock(&pool->lock);
752
753 if (put_z3fold_locked(zhdr))
754 return;
755
756 if (test_bit(PAGE_STALE, &page->private) ||
757 test_and_set_bit(PAGE_CLAIMED, &page->private)) {
758 z3fold_page_unlock(zhdr);
759 return;
760 }
761
762 if (!zhdr->foreign_handles && buddy_single(zhdr) &&
763 zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
764 if (!put_z3fold_locked(zhdr)) {
765 clear_bit(PAGE_CLAIMED, &page->private);
766 z3fold_page_unlock(zhdr);
767 }
768 return;
769 }
770
771 z3fold_compact_page(zhdr);
772 add_to_unbuddied(pool, zhdr);
773 clear_bit(PAGE_CLAIMED, &page->private);
774 z3fold_page_unlock(zhdr);
775}
776
777static void compact_page_work(struct work_struct *w)
778{
779 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
780 work);
781
782 do_compact_page(zhdr, false);
783}
784
785/* returns _locked_ z3fold page header or NULL */
786static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
787 size_t size, bool can_sleep)
788{
789 struct z3fold_header *zhdr = NULL;
790 struct page *page;
791 struct list_head *unbuddied;
792 int chunks = size_to_chunks(size), i;
793
794lookup:
795 migrate_disable();
796 /* First, try to find an unbuddied z3fold page. */
797 unbuddied = this_cpu_ptr(pool->unbuddied);
798 for_each_unbuddied_list(i, chunks) {
799 struct list_head *l = &unbuddied[i];
800
801 zhdr = list_first_entry_or_null(READ_ONCE(l),
802 struct z3fold_header, buddy);
803
804 if (!zhdr)
805 continue;
806
807 /* Re-check under lock. */
808 spin_lock(&pool->lock);
809 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
810 struct z3fold_header, buddy)) ||
811 !z3fold_page_trylock(zhdr)) {
812 spin_unlock(&pool->lock);
813 zhdr = NULL;
814 migrate_enable();
815 if (can_sleep)
816 cond_resched();
817 goto lookup;
818 }
819 list_del_init(&zhdr->buddy);
820 zhdr->cpu = -1;
821 spin_unlock(&pool->lock);
822
823 page = virt_to_page(zhdr);
824 if (test_bit(NEEDS_COMPACTING, &page->private) ||
825 test_bit(PAGE_CLAIMED, &page->private)) {
826 z3fold_page_unlock(zhdr);
827 zhdr = NULL;
828 migrate_enable();
829 if (can_sleep)
830 cond_resched();
831 goto lookup;
832 }
833
834 /*
835 * this page could not be removed from its unbuddied
836 * list while pool lock was held, and then we've taken
837 * page lock so kref_put could not be called before
838 * we got here, so it's safe to just call kref_get()
839 */
840 kref_get(&zhdr->refcount);
841 break;
842 }
843 migrate_enable();
844
845 if (!zhdr) {
846 int cpu;
847
848 /* look for _exact_ match on other cpus' lists */
849 for_each_online_cpu(cpu) {
850 struct list_head *l;
851
852 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
853 spin_lock(&pool->lock);
854 l = &unbuddied[chunks];
855
856 zhdr = list_first_entry_or_null(READ_ONCE(l),
857 struct z3fold_header, buddy);
858
859 if (!zhdr || !z3fold_page_trylock(zhdr)) {
860 spin_unlock(&pool->lock);
861 zhdr = NULL;
862 continue;
863 }
864 list_del_init(&zhdr->buddy);
865 zhdr->cpu = -1;
866 spin_unlock(&pool->lock);
867
868 page = virt_to_page(zhdr);
869 if (test_bit(NEEDS_COMPACTING, &page->private) ||
870 test_bit(PAGE_CLAIMED, &page->private)) {
871 z3fold_page_unlock(zhdr);
872 zhdr = NULL;
873 if (can_sleep)
874 cond_resched();
875 continue;
876 }
877 kref_get(&zhdr->refcount);
878 break;
879 }
880 }
881
882 if (zhdr && !zhdr->slots) {
883 zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
884 if (!zhdr->slots)
885 goto out_fail;
886 }
887 return zhdr;
888
889out_fail:
890 if (!put_z3fold_locked(zhdr)) {
891 add_to_unbuddied(pool, zhdr);
892 z3fold_page_unlock(zhdr);
893 }
894 return NULL;
895}
896
897/*
898 * API Functions
899 */
900
901/**
902 * z3fold_create_pool() - create a new z3fold pool
903 * @name: pool name
904 * @gfp: gfp flags when allocating the z3fold pool structure
905 *
906 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
907 * failed.
908 */
909static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp)
910{
911 struct z3fold_pool *pool = NULL;
912 int i, cpu;
913
914 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
915 if (!pool)
916 goto out;
917 pool->c_handle = kmem_cache_create("z3fold_handle",
918 sizeof(struct z3fold_buddy_slots),
919 SLOTS_ALIGN, 0, NULL);
920 if (!pool->c_handle)
921 goto out_c;
922 spin_lock_init(&pool->lock);
923 spin_lock_init(&pool->stale_lock);
924 pool->unbuddied = __alloc_percpu(sizeof(struct list_head) * NCHUNKS,
925 __alignof__(struct list_head));
926 if (!pool->unbuddied)
927 goto out_pool;
928 for_each_possible_cpu(cpu) {
929 struct list_head *unbuddied =
930 per_cpu_ptr(pool->unbuddied, cpu);
931 for_each_unbuddied_list(i, 0)
932 INIT_LIST_HEAD(&unbuddied[i]);
933 }
934 INIT_LIST_HEAD(&pool->stale);
935 atomic64_set(&pool->pages_nr, 0);
936 pool->name = name;
937 pool->compact_wq = create_singlethread_workqueue(pool->name);
938 if (!pool->compact_wq)
939 goto out_unbuddied;
940 pool->release_wq = create_singlethread_workqueue(pool->name);
941 if (!pool->release_wq)
942 goto out_wq;
943 INIT_WORK(&pool->work, free_pages_work);
944 return pool;
945
946out_wq:
947 destroy_workqueue(pool->compact_wq);
948out_unbuddied:
949 free_percpu(pool->unbuddied);
950out_pool:
951 kmem_cache_destroy(pool->c_handle);
952out_c:
953 kfree(pool);
954out:
955 return NULL;
956}
957
958/**
959 * z3fold_destroy_pool() - destroys an existing z3fold pool
960 * @pool: the z3fold pool to be destroyed
961 *
962 * The pool should be emptied before this function is called.
963 */
964static void z3fold_destroy_pool(struct z3fold_pool *pool)
965{
966 kmem_cache_destroy(pool->c_handle);
967
968 /*
969 * We need to destroy pool->compact_wq before pool->release_wq,
970 * as any pending work on pool->compact_wq will call
971 * queue_work(pool->release_wq, &pool->work).
972 *
973 * There are still outstanding pages until both workqueues are drained,
974 * so we cannot unregister migration until then.
975 */
976
977 destroy_workqueue(pool->compact_wq);
978 destroy_workqueue(pool->release_wq);
979 free_percpu(pool->unbuddied);
980 kfree(pool);
981}
982
983static const struct movable_operations z3fold_mops;
984
985/**
986 * z3fold_alloc() - allocates a region of a given size
987 * @pool: z3fold pool from which to allocate
988 * @size: size in bytes of the desired allocation
989 * @gfp: gfp flags used if the pool needs to grow
990 * @handle: handle of the new allocation
991 *
992 * This function will attempt to find a free region in the pool large enough to
993 * satisfy the allocation request. A search of the unbuddied lists is
994 * performed first. If no suitable free region is found, then a new page is
995 * allocated and added to the pool to satisfy the request.
996 *
997 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
998 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
999 * a new page.
1000 */
1001static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1002 unsigned long *handle)
1003{
1004 int chunks = size_to_chunks(size);
1005 struct z3fold_header *zhdr = NULL;
1006 struct page *page = NULL;
1007 enum buddy bud;
1008 bool can_sleep = gfpflags_allow_blocking(gfp);
1009
1010 if (!size || (gfp & __GFP_HIGHMEM))
1011 return -EINVAL;
1012
1013 if (size > PAGE_SIZE)
1014 return -ENOSPC;
1015
1016 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1017 bud = HEADLESS;
1018 else {
1019retry:
1020 zhdr = __z3fold_alloc(pool, size, can_sleep);
1021 if (zhdr) {
1022 bud = get_free_buddy(zhdr, chunks);
1023 if (bud == HEADLESS) {
1024 if (!put_z3fold_locked(zhdr))
1025 z3fold_page_unlock(zhdr);
1026 pr_err("No free chunks in unbuddied\n");
1027 WARN_ON(1);
1028 goto retry;
1029 }
1030 page = virt_to_page(zhdr);
1031 goto found;
1032 }
1033 bud = FIRST;
1034 }
1035
1036 page = alloc_page(gfp);
1037 if (!page)
1038 return -ENOMEM;
1039
1040 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
1041 if (!zhdr) {
1042 __free_page(page);
1043 return -ENOMEM;
1044 }
1045 atomic64_inc(&pool->pages_nr);
1046
1047 if (bud == HEADLESS) {
1048 set_bit(PAGE_HEADLESS, &page->private);
1049 goto headless;
1050 }
1051 if (can_sleep) {
1052 lock_page(page);
1053 __SetPageMovable(page, &z3fold_mops);
1054 unlock_page(page);
1055 } else {
1056 WARN_ON(!trylock_page(page));
1057 __SetPageMovable(page, &z3fold_mops);
1058 unlock_page(page);
1059 }
1060 z3fold_page_lock(zhdr);
1061
1062found:
1063 if (bud == FIRST)
1064 zhdr->first_chunks = chunks;
1065 else if (bud == LAST)
1066 zhdr->last_chunks = chunks;
1067 else {
1068 zhdr->middle_chunks = chunks;
1069 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
1070 }
1071 add_to_unbuddied(pool, zhdr);
1072
1073headless:
1074 spin_lock(&pool->lock);
1075 *handle = encode_handle(zhdr, bud);
1076 spin_unlock(&pool->lock);
1077 if (bud != HEADLESS)
1078 z3fold_page_unlock(zhdr);
1079
1080 return 0;
1081}
1082
1083/**
1084 * z3fold_free() - frees the allocation associated with the given handle
1085 * @pool: pool in which the allocation resided
1086 * @handle: handle associated with the allocation returned by z3fold_alloc()
1087 *
1088 * In the case that the z3fold page in which the allocation resides is under
1089 * reclaim, as indicated by the PAGE_CLAIMED flag being set, this function
1090 * only sets the first|middle|last_chunks to 0. The page is actually freed
1091 * once all buddies are evicted (see z3fold_reclaim_page() below).
1092 */
1093static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1094{
1095 struct z3fold_header *zhdr;
1096 struct page *page;
1097 enum buddy bud;
1098 bool page_claimed;
1099
1100 zhdr = get_z3fold_header(handle);
1101 page = virt_to_page(zhdr);
1102 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1103
1104 if (test_bit(PAGE_HEADLESS, &page->private)) {
1105 /* if a headless page is under reclaim, just leave.
1106 * NB: we use test_and_set_bit for a reason: if the bit
1107 * has not been set before, we release this page
1108 * immediately so we don't care about its value any more.
1109 */
1110 if (!page_claimed) {
1111 put_z3fold_header(zhdr);
1112 free_z3fold_page(page, true);
1113 atomic64_dec(&pool->pages_nr);
1114 }
1115 return;
1116 }
1117
1118 /* Non-headless case */
1119 bud = handle_to_buddy(handle);
1120
1121 switch (bud) {
1122 case FIRST:
1123 zhdr->first_chunks = 0;
1124 break;
1125 case MIDDLE:
1126 zhdr->middle_chunks = 0;
1127 break;
1128 case LAST:
1129 zhdr->last_chunks = 0;
1130 break;
1131 default:
1132 pr_err("%s: unknown bud %d\n", __func__, bud);
1133 WARN_ON(1);
1134 put_z3fold_header(zhdr);
1135 return;
1136 }
1137
1138 if (!page_claimed)
1139 free_handle(handle, zhdr);
1140 if (put_z3fold_locked_list(zhdr))
1141 return;
1142 if (page_claimed) {
1143 /* the page has not been claimed by us */
1144 put_z3fold_header(zhdr);
1145 return;
1146 }
1147 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1148 clear_bit(PAGE_CLAIMED, &page->private);
1149 put_z3fold_header(zhdr);
1150 return;
1151 }
1152 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1153 zhdr->cpu = -1;
1154 kref_get(&zhdr->refcount);
1155 clear_bit(PAGE_CLAIMED, &page->private);
1156 do_compact_page(zhdr, true);
1157 return;
1158 }
1159 kref_get(&zhdr->refcount);
1160 clear_bit(PAGE_CLAIMED, &page->private);
1161 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1162 put_z3fold_header(zhdr);
1163}
1164
1165/**
1166 * z3fold_map() - maps the allocation associated with the given handle
1167 * @pool: pool in which the allocation resides
1168 * @handle: handle associated with the allocation to be mapped
1169 *
1170 * Extracts the buddy number from handle and constructs the pointer to the
1171 * correct starting chunk within the page.
1172 *
1173 * Returns: a pointer to the mapped allocation
1174 */
1175static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1176{
1177 struct z3fold_header *zhdr;
1178 struct page *page;
1179 void *addr;
1180 enum buddy buddy;
1181
1182 zhdr = get_z3fold_header(handle);
1183 addr = zhdr;
1184 page = virt_to_page(zhdr);
1185
1186 if (test_bit(PAGE_HEADLESS, &page->private))
1187 goto out;
1188
1189 buddy = handle_to_buddy(handle);
1190 switch (buddy) {
1191 case FIRST:
1192 addr += ZHDR_SIZE_ALIGNED;
1193 break;
1194 case MIDDLE:
1195 addr += zhdr->start_middle << CHUNK_SHIFT;
1196 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1197 break;
1198 case LAST:
1199 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1200 break;
1201 default:
1202 pr_err("unknown buddy id %d\n", buddy);
1203 WARN_ON(1);
1204 addr = NULL;
1205 break;
1206 }
1207
1208 if (addr)
1209 zhdr->mapped_count++;
1210out:
1211 put_z3fold_header(zhdr);
1212 return addr;
1213}
1214
1215/**
1216 * z3fold_unmap() - unmaps the allocation associated with the given handle
1217 * @pool: pool in which the allocation resides
1218 * @handle: handle associated with the allocation to be unmapped
1219 */
1220static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1221{
1222 struct z3fold_header *zhdr;
1223 struct page *page;
1224 enum buddy buddy;
1225
1226 zhdr = get_z3fold_header(handle);
1227 page = virt_to_page(zhdr);
1228
1229 if (test_bit(PAGE_HEADLESS, &page->private))
1230 return;
1231
1232 buddy = handle_to_buddy(handle);
1233 if (buddy == MIDDLE)
1234 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1235 zhdr->mapped_count--;
1236 put_z3fold_header(zhdr);
1237}
1238
1239/**
1240 * z3fold_get_pool_pages() - gets the z3fold pool size in pages
1241 * @pool: pool whose size is being queried
1242 *
1243 * Returns: size in pages of the given pool.
1244 */
1245static u64 z3fold_get_pool_pages(struct z3fold_pool *pool)
1246{
1247 return atomic64_read(&pool->pages_nr);
1248}
1249
1250static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1251{
1252 struct z3fold_header *zhdr;
1253 struct z3fold_pool *pool;
1254
1255 VM_BUG_ON_PAGE(PageIsolated(page), page);
1256
1257 if (test_bit(PAGE_HEADLESS, &page->private))
1258 return false;
1259
1260 zhdr = page_address(page);
1261 z3fold_page_lock(zhdr);
1262 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1263 test_bit(PAGE_STALE, &page->private))
1264 goto out;
1265
1266 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1267 goto out;
1268
1269 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1270 goto out;
1271 pool = zhdr_to_pool(zhdr);
1272 spin_lock(&pool->lock);
1273 if (!list_empty(&zhdr->buddy))
1274 list_del_init(&zhdr->buddy);
1275 spin_unlock(&pool->lock);
1276
1277 kref_get(&zhdr->refcount);
1278 z3fold_page_unlock(zhdr);
1279 return true;
1280
1281out:
1282 z3fold_page_unlock(zhdr);
1283 return false;
1284}
1285
1286static int z3fold_page_migrate(struct page *newpage, struct page *page,
1287 enum migrate_mode mode)
1288{
1289 struct z3fold_header *zhdr, *new_zhdr;
1290 struct z3fold_pool *pool;
1291
1292 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1293 VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
1294 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1295
1296 zhdr = page_address(page);
1297 pool = zhdr_to_pool(zhdr);
1298
1299 if (!z3fold_page_trylock(zhdr))
1300 return -EAGAIN;
1301 if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1302 clear_bit(PAGE_CLAIMED, &page->private);
1303 z3fold_page_unlock(zhdr);
1304 return -EBUSY;
1305 }
1306 if (work_pending(&zhdr->work)) {
1307 z3fold_page_unlock(zhdr);
1308 return -EAGAIN;
1309 }
1310 new_zhdr = page_address(newpage);
1311 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1312 newpage->private = page->private;
1313 set_bit(PAGE_MIGRATED, &page->private);
1314 z3fold_page_unlock(zhdr);
1315 spin_lock_init(&new_zhdr->page_lock);
1316 INIT_WORK(&new_zhdr->work, compact_page_work);
1317 /*
1318 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1319 * so we only have to reinitialize it.
1320 */
1321 INIT_LIST_HEAD(&new_zhdr->buddy);
1322 __ClearPageMovable(page);
1323
1324 get_page(newpage);
1325 z3fold_page_lock(new_zhdr);
1326 if (new_zhdr->first_chunks)
1327 encode_handle(new_zhdr, FIRST);
1328 if (new_zhdr->last_chunks)
1329 encode_handle(new_zhdr, LAST);
1330 if (new_zhdr->middle_chunks)
1331 encode_handle(new_zhdr, MIDDLE);
1332 set_bit(NEEDS_COMPACTING, &newpage->private);
1333 new_zhdr->cpu = smp_processor_id();
1334 __SetPageMovable(newpage, &z3fold_mops);
1335 z3fold_page_unlock(new_zhdr);
1336
1337 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1338
1339 /* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */
1340 page->private = 0;
1341 put_page(page);
1342 return 0;
1343}
1344
1345static void z3fold_page_putback(struct page *page)
1346{
1347 struct z3fold_header *zhdr;
1348 struct z3fold_pool *pool;
1349
1350 zhdr = page_address(page);
1351 pool = zhdr_to_pool(zhdr);
1352
1353 z3fold_page_lock(zhdr);
1354 if (!list_empty(&zhdr->buddy))
1355 list_del_init(&zhdr->buddy);
1356 INIT_LIST_HEAD(&page->lru);
1357 if (put_z3fold_locked(zhdr))
1358 return;
1359 if (list_empty(&zhdr->buddy))
1360 add_to_unbuddied(pool, zhdr);
1361 clear_bit(PAGE_CLAIMED, &page->private);
1362 z3fold_page_unlock(zhdr);
1363}
1364
1365static const struct movable_operations z3fold_mops = {
1366 .isolate_page = z3fold_page_isolate,
1367 .migrate_page = z3fold_page_migrate,
1368 .putback_page = z3fold_page_putback,
1369};
1370
1371/*****************
1372 * zpool
1373 ****************/
1374
1375static void *z3fold_zpool_create(const char *name, gfp_t gfp)
1376{
1377 return z3fold_create_pool(name, gfp);
1378}
1379
1380static void z3fold_zpool_destroy(void *pool)
1381{
1382 z3fold_destroy_pool(pool);
1383}
1384
1385static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1386 unsigned long *handle)
1387{
1388 return z3fold_alloc(pool, size, gfp, handle);
1389}
1390static void z3fold_zpool_free(void *pool, unsigned long handle)
1391{
1392 z3fold_free(pool, handle);
1393}
1394
1395static void *z3fold_zpool_map(void *pool, unsigned long handle,
1396 enum zpool_mapmode mm)
1397{
1398 return z3fold_map(pool, handle);
1399}
1400static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1401{
1402 z3fold_unmap(pool, handle);
1403}
1404
1405static u64 z3fold_zpool_total_pages(void *pool)
1406{
1407 return z3fold_get_pool_pages(pool);
1408}
1409
1410static struct zpool_driver z3fold_zpool_driver = {
1411 .type = "z3fold",
1412 .sleep_mapped = true,
1413 .owner = THIS_MODULE,
1414 .create = z3fold_zpool_create,
1415 .destroy = z3fold_zpool_destroy,
1416 .malloc = z3fold_zpool_malloc,
1417 .free = z3fold_zpool_free,
1418 .map = z3fold_zpool_map,
1419 .unmap = z3fold_zpool_unmap,
1420 .total_pages = z3fold_zpool_total_pages,
1421};
1422
1423MODULE_ALIAS("zpool-z3fold");
1424
1425static int __init init_z3fold(void)
1426{
1427 /*
1428 * Make sure the z3fold header is not larger than the page size and
1429 * there has remaining spaces for its buddy.
1430 */
1431 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
1432 zpool_register_driver(&z3fold_zpool_driver);
1433
1434 return 0;
1435}
1436
1437static void __exit exit_z3fold(void)
1438{
1439 zpool_unregister_driver(&z3fold_zpool_driver);
1440}
1441
1442module_init(init_z3fold);
1443module_exit(exit_z3fold);
1444
1445MODULE_LICENSE("GPL");
1446MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1447MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");