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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
47/*
48 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
49 * adjusting internal fragmentation. It also determines the number of
50 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
51 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
52 * in the beginning of an allocated page are occupied by z3fold header, so
53 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
54 * which shows the max number of free chunks in z3fold page, also there will
55 * be 63, or 62, respectively, freelists per pool.
56 */
57#define NCHUNKS_ORDER 6
58
59#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
60#define CHUNK_SIZE (1 << CHUNK_SHIFT)
61#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
62#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
63#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
64#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
65
66#define BUDDY_MASK (0x3)
67#define BUDDY_SHIFT 2
68#define SLOTS_ALIGN (0x40)
69
70/*****************
71 * Structures
72*****************/
73struct z3fold_pool;
74struct z3fold_ops {
75 int (*evict)(struct z3fold_pool *pool, unsigned long handle);
76};
77
78enum buddy {
79 HEADLESS = 0,
80 FIRST,
81 MIDDLE,
82 LAST,
83 BUDDIES_MAX = LAST
84};
85
86struct z3fold_buddy_slots {
87 /*
88 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
89 * be enough slots to hold all possible variants
90 */
91 unsigned long slot[BUDDY_MASK + 1];
92 unsigned long pool; /* back link + flags */
93};
94#define HANDLE_FLAG_MASK (0x03)
95
96/*
97 * struct z3fold_header - z3fold page metadata occupying first chunks of each
98 * z3fold page, except for HEADLESS pages
99 * @buddy: links the z3fold page into the relevant list in the
100 * pool
101 * @page_lock: per-page lock
102 * @refcount: reference count for the z3fold page
103 * @work: work_struct for page layout optimization
104 * @slots: pointer to the structure holding buddy slots
105 * @pool: pointer to the containing pool
106 * @cpu: CPU which this page "belongs" to
107 * @first_chunks: the size of the first buddy in chunks, 0 if free
108 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
109 * @last_chunks: the size of the last buddy in chunks, 0 if free
110 * @first_num: the starting number (for the first handle)
111 * @mapped_count: the number of objects currently mapped
112 */
113struct z3fold_header {
114 struct list_head buddy;
115 spinlock_t page_lock;
116 struct kref refcount;
117 struct work_struct work;
118 struct z3fold_buddy_slots *slots;
119 struct z3fold_pool *pool;
120 short cpu;
121 unsigned short first_chunks;
122 unsigned short middle_chunks;
123 unsigned short last_chunks;
124 unsigned short start_middle;
125 unsigned short first_num:2;
126 unsigned short mapped_count:2;
127};
128
129/**
130 * struct z3fold_pool - stores metadata for each z3fold pool
131 * @name: pool name
132 * @lock: protects pool unbuddied/lru lists
133 * @stale_lock: protects pool stale page list
134 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
135 * buddies; the list each z3fold page is added to depends on
136 * the size of its free region.
137 * @lru: list tracking the z3fold pages in LRU order by most recently
138 * added buddy.
139 * @stale: list of pages marked for freeing
140 * @pages_nr: number of z3fold pages in the pool.
141 * @c_handle: cache for z3fold_buddy_slots allocation
142 * @ops: pointer to a structure of user defined operations specified at
143 * pool creation time.
144 * @compact_wq: workqueue for page layout background optimization
145 * @release_wq: workqueue for safe page release
146 * @work: work_struct for safe page release
147 * @inode: inode for z3fold pseudo filesystem
148 *
149 * This structure is allocated at pool creation time and maintains metadata
150 * pertaining to a particular z3fold pool.
151 */
152struct z3fold_pool {
153 const char *name;
154 spinlock_t lock;
155 spinlock_t stale_lock;
156 struct list_head *unbuddied;
157 struct list_head lru;
158 struct list_head stale;
159 atomic64_t pages_nr;
160 struct kmem_cache *c_handle;
161 const struct z3fold_ops *ops;
162 struct zpool *zpool;
163 const struct zpool_ops *zpool_ops;
164 struct workqueue_struct *compact_wq;
165 struct workqueue_struct *release_wq;
166 struct work_struct work;
167 struct inode *inode;
168};
169
170/*
171 * Internal z3fold page flags
172 */
173enum z3fold_page_flags {
174 PAGE_HEADLESS = 0,
175 MIDDLE_CHUNK_MAPPED,
176 NEEDS_COMPACTING,
177 PAGE_STALE,
178 PAGE_CLAIMED, /* by either reclaim or free */
179};
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 void compact_page_work(struct work_struct *w);
195
196static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
197 gfp_t gfp)
198{
199 struct z3fold_buddy_slots *slots;
200
201 slots = kmem_cache_alloc(pool->c_handle,
202 (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
203
204 if (slots) {
205 memset(slots->slot, 0, sizeof(slots->slot));
206 slots->pool = (unsigned long)pool;
207 }
208
209 return slots;
210}
211
212static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
213{
214 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
215}
216
217static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
218{
219 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
220}
221
222static inline void free_handle(unsigned long handle)
223{
224 struct z3fold_buddy_slots *slots;
225 int i;
226 bool is_free;
227
228 if (handle & (1 << PAGE_HEADLESS))
229 return;
230
231 WARN_ON(*(unsigned long *)handle == 0);
232 *(unsigned long *)handle = 0;
233 slots = handle_to_slots(handle);
234 is_free = true;
235 for (i = 0; i <= BUDDY_MASK; i++) {
236 if (slots->slot[i]) {
237 is_free = false;
238 break;
239 }
240 }
241
242 if (is_free) {
243 struct z3fold_pool *pool = slots_to_pool(slots);
244
245 kmem_cache_free(pool->c_handle, slots);
246 }
247}
248
249static int z3fold_init_fs_context(struct fs_context *fc)
250{
251 return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
252}
253
254static struct file_system_type z3fold_fs = {
255 .name = "z3fold",
256 .init_fs_context = z3fold_init_fs_context,
257 .kill_sb = kill_anon_super,
258};
259
260static struct vfsmount *z3fold_mnt;
261static int z3fold_mount(void)
262{
263 int ret = 0;
264
265 z3fold_mnt = kern_mount(&z3fold_fs);
266 if (IS_ERR(z3fold_mnt))
267 ret = PTR_ERR(z3fold_mnt);
268
269 return ret;
270}
271
272static void z3fold_unmount(void)
273{
274 kern_unmount(z3fold_mnt);
275}
276
277static const struct address_space_operations z3fold_aops;
278static int z3fold_register_migration(struct z3fold_pool *pool)
279{
280 pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
281 if (IS_ERR(pool->inode)) {
282 pool->inode = NULL;
283 return 1;
284 }
285
286 pool->inode->i_mapping->private_data = pool;
287 pool->inode->i_mapping->a_ops = &z3fold_aops;
288 return 0;
289}
290
291static void z3fold_unregister_migration(struct z3fold_pool *pool)
292{
293 if (pool->inode)
294 iput(pool->inode);
295 }
296
297/* Initializes the z3fold header of a newly allocated z3fold page */
298static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
299 struct z3fold_pool *pool, gfp_t gfp)
300{
301 struct z3fold_header *zhdr = page_address(page);
302 struct z3fold_buddy_slots *slots;
303
304 INIT_LIST_HEAD(&page->lru);
305 clear_bit(PAGE_HEADLESS, &page->private);
306 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
307 clear_bit(NEEDS_COMPACTING, &page->private);
308 clear_bit(PAGE_STALE, &page->private);
309 clear_bit(PAGE_CLAIMED, &page->private);
310 if (headless)
311 return zhdr;
312
313 slots = alloc_slots(pool, gfp);
314 if (!slots)
315 return NULL;
316
317 spin_lock_init(&zhdr->page_lock);
318 kref_init(&zhdr->refcount);
319 zhdr->first_chunks = 0;
320 zhdr->middle_chunks = 0;
321 zhdr->last_chunks = 0;
322 zhdr->first_num = 0;
323 zhdr->start_middle = 0;
324 zhdr->cpu = -1;
325 zhdr->slots = slots;
326 zhdr->pool = pool;
327 INIT_LIST_HEAD(&zhdr->buddy);
328 INIT_WORK(&zhdr->work, compact_page_work);
329 return zhdr;
330}
331
332/* Resets the struct page fields and frees the page */
333static void free_z3fold_page(struct page *page, bool headless)
334{
335 if (!headless) {
336 lock_page(page);
337 __ClearPageMovable(page);
338 unlock_page(page);
339 }
340 ClearPagePrivate(page);
341 __free_page(page);
342}
343
344/* Lock a z3fold page */
345static inline void z3fold_page_lock(struct z3fold_header *zhdr)
346{
347 spin_lock(&zhdr->page_lock);
348}
349
350/* Try to lock a z3fold page */
351static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
352{
353 return spin_trylock(&zhdr->page_lock);
354}
355
356/* Unlock a z3fold page */
357static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
358{
359 spin_unlock(&zhdr->page_lock);
360}
361
362/* Helper function to build the index */
363static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
364{
365 return (bud + zhdr->first_num) & BUDDY_MASK;
366}
367
368/*
369 * Encodes the handle of a particular buddy within a z3fold page
370 * Pool lock should be held as this function accesses first_num
371 */
372static unsigned long __encode_handle(struct z3fold_header *zhdr,
373 struct z3fold_buddy_slots *slots,
374 enum buddy bud)
375{
376 unsigned long h = (unsigned long)zhdr;
377 int idx = 0;
378
379 /*
380 * For a headless page, its handle is its pointer with the extra
381 * PAGE_HEADLESS bit set
382 */
383 if (bud == HEADLESS)
384 return h | (1 << PAGE_HEADLESS);
385
386 /* otherwise, return pointer to encoded handle */
387 idx = __idx(zhdr, bud);
388 h += idx;
389 if (bud == LAST)
390 h |= (zhdr->last_chunks << BUDDY_SHIFT);
391
392 slots->slot[idx] = h;
393 return (unsigned long)&slots->slot[idx];
394}
395
396static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
397{
398 return __encode_handle(zhdr, zhdr->slots, bud);
399}
400
401/* Returns the z3fold page where a given handle is stored */
402static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
403{
404 unsigned long addr = h;
405
406 if (!(addr & (1 << PAGE_HEADLESS)))
407 addr = *(unsigned long *)h;
408
409 return (struct z3fold_header *)(addr & PAGE_MASK);
410}
411
412/* only for LAST bud, returns zero otherwise */
413static unsigned short handle_to_chunks(unsigned long handle)
414{
415 unsigned long addr = *(unsigned long *)handle;
416
417 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
418}
419
420/*
421 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
422 * but that doesn't matter. because the masking will result in the
423 * correct buddy number.
424 */
425static enum buddy handle_to_buddy(unsigned long handle)
426{
427 struct z3fold_header *zhdr;
428 unsigned long addr;
429
430 WARN_ON(handle & (1 << PAGE_HEADLESS));
431 addr = *(unsigned long *)handle;
432 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
433 return (addr - zhdr->first_num) & BUDDY_MASK;
434}
435
436static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
437{
438 return zhdr->pool;
439}
440
441static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
442{
443 struct page *page = virt_to_page(zhdr);
444 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
445
446 WARN_ON(!list_empty(&zhdr->buddy));
447 set_bit(PAGE_STALE, &page->private);
448 clear_bit(NEEDS_COMPACTING, &page->private);
449 spin_lock(&pool->lock);
450 if (!list_empty(&page->lru))
451 list_del_init(&page->lru);
452 spin_unlock(&pool->lock);
453 if (locked)
454 z3fold_page_unlock(zhdr);
455 spin_lock(&pool->stale_lock);
456 list_add(&zhdr->buddy, &pool->stale);
457 queue_work(pool->release_wq, &pool->work);
458 spin_unlock(&pool->stale_lock);
459}
460
461static void __attribute__((__unused__))
462 release_z3fold_page(struct kref *ref)
463{
464 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
465 refcount);
466 __release_z3fold_page(zhdr, false);
467}
468
469static void release_z3fold_page_locked(struct kref *ref)
470{
471 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
472 refcount);
473 WARN_ON(z3fold_page_trylock(zhdr));
474 __release_z3fold_page(zhdr, true);
475}
476
477static void release_z3fold_page_locked_list(struct kref *ref)
478{
479 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
480 refcount);
481 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
482 spin_lock(&pool->lock);
483 list_del_init(&zhdr->buddy);
484 spin_unlock(&pool->lock);
485
486 WARN_ON(z3fold_page_trylock(zhdr));
487 __release_z3fold_page(zhdr, true);
488}
489
490static void free_pages_work(struct work_struct *w)
491{
492 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
493
494 spin_lock(&pool->stale_lock);
495 while (!list_empty(&pool->stale)) {
496 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
497 struct z3fold_header, buddy);
498 struct page *page = virt_to_page(zhdr);
499
500 list_del(&zhdr->buddy);
501 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
502 continue;
503 spin_unlock(&pool->stale_lock);
504 cancel_work_sync(&zhdr->work);
505 free_z3fold_page(page, false);
506 cond_resched();
507 spin_lock(&pool->stale_lock);
508 }
509 spin_unlock(&pool->stale_lock);
510}
511
512/*
513 * Returns the number of free chunks in a z3fold page.
514 * NB: can't be used with HEADLESS pages.
515 */
516static int num_free_chunks(struct z3fold_header *zhdr)
517{
518 int nfree;
519 /*
520 * If there is a middle object, pick up the bigger free space
521 * either before or after it. Otherwise just subtract the number
522 * of chunks occupied by the first and the last objects.
523 */
524 if (zhdr->middle_chunks != 0) {
525 int nfree_before = zhdr->first_chunks ?
526 0 : zhdr->start_middle - ZHDR_CHUNKS;
527 int nfree_after = zhdr->last_chunks ?
528 0 : TOTAL_CHUNKS -
529 (zhdr->start_middle + zhdr->middle_chunks);
530 nfree = max(nfree_before, nfree_after);
531 } else
532 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
533 return nfree;
534}
535
536/* Add to the appropriate unbuddied list */
537static inline void add_to_unbuddied(struct z3fold_pool *pool,
538 struct z3fold_header *zhdr)
539{
540 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
541 zhdr->middle_chunks == 0) {
542 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
543
544 int freechunks = num_free_chunks(zhdr);
545 spin_lock(&pool->lock);
546 list_add(&zhdr->buddy, &unbuddied[freechunks]);
547 spin_unlock(&pool->lock);
548 zhdr->cpu = smp_processor_id();
549 put_cpu_ptr(pool->unbuddied);
550 }
551}
552
553static inline void *mchunk_memmove(struct z3fold_header *zhdr,
554 unsigned short dst_chunk)
555{
556 void *beg = zhdr;
557 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
558 beg + (zhdr->start_middle << CHUNK_SHIFT),
559 zhdr->middle_chunks << CHUNK_SHIFT);
560}
561
562#define BIG_CHUNK_GAP 3
563/* Has to be called with lock held */
564static int z3fold_compact_page(struct z3fold_header *zhdr)
565{
566 struct page *page = virt_to_page(zhdr);
567
568 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
569 return 0; /* can't move middle chunk, it's used */
570
571 if (unlikely(PageIsolated(page)))
572 return 0;
573
574 if (zhdr->middle_chunks == 0)
575 return 0; /* nothing to compact */
576
577 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
578 /* move to the beginning */
579 mchunk_memmove(zhdr, ZHDR_CHUNKS);
580 zhdr->first_chunks = zhdr->middle_chunks;
581 zhdr->middle_chunks = 0;
582 zhdr->start_middle = 0;
583 zhdr->first_num++;
584 return 1;
585 }
586
587 /*
588 * moving data is expensive, so let's only do that if
589 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
590 */
591 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
592 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
593 BIG_CHUNK_GAP) {
594 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
595 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
596 return 1;
597 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
598 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
599 + zhdr->middle_chunks) >=
600 BIG_CHUNK_GAP) {
601 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
602 zhdr->middle_chunks;
603 mchunk_memmove(zhdr, new_start);
604 zhdr->start_middle = new_start;
605 return 1;
606 }
607
608 return 0;
609}
610
611static void do_compact_page(struct z3fold_header *zhdr, bool locked)
612{
613 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
614 struct page *page;
615
616 page = virt_to_page(zhdr);
617 if (locked)
618 WARN_ON(z3fold_page_trylock(zhdr));
619 else
620 z3fold_page_lock(zhdr);
621 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
622 z3fold_page_unlock(zhdr);
623 return;
624 }
625 spin_lock(&pool->lock);
626 list_del_init(&zhdr->buddy);
627 spin_unlock(&pool->lock);
628
629 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
630 atomic64_dec(&pool->pages_nr);
631 return;
632 }
633
634 if (unlikely(PageIsolated(page) ||
635 test_bit(PAGE_CLAIMED, &page->private) ||
636 test_bit(PAGE_STALE, &page->private))) {
637 z3fold_page_unlock(zhdr);
638 return;
639 }
640
641 z3fold_compact_page(zhdr);
642 add_to_unbuddied(pool, zhdr);
643 z3fold_page_unlock(zhdr);
644}
645
646static void compact_page_work(struct work_struct *w)
647{
648 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
649 work);
650
651 do_compact_page(zhdr, false);
652}
653
654/* returns _locked_ z3fold page header or NULL */
655static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
656 size_t size, bool can_sleep)
657{
658 struct z3fold_header *zhdr = NULL;
659 struct page *page;
660 struct list_head *unbuddied;
661 int chunks = size_to_chunks(size), i;
662
663lookup:
664 /* First, try to find an unbuddied z3fold page. */
665 unbuddied = get_cpu_ptr(pool->unbuddied);
666 for_each_unbuddied_list(i, chunks) {
667 struct list_head *l = &unbuddied[i];
668
669 zhdr = list_first_entry_or_null(READ_ONCE(l),
670 struct z3fold_header, buddy);
671
672 if (!zhdr)
673 continue;
674
675 /* Re-check under lock. */
676 spin_lock(&pool->lock);
677 l = &unbuddied[i];
678 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
679 struct z3fold_header, buddy)) ||
680 !z3fold_page_trylock(zhdr)) {
681 spin_unlock(&pool->lock);
682 zhdr = NULL;
683 put_cpu_ptr(pool->unbuddied);
684 if (can_sleep)
685 cond_resched();
686 goto lookup;
687 }
688 list_del_init(&zhdr->buddy);
689 zhdr->cpu = -1;
690 spin_unlock(&pool->lock);
691
692 page = virt_to_page(zhdr);
693 if (test_bit(NEEDS_COMPACTING, &page->private)) {
694 z3fold_page_unlock(zhdr);
695 zhdr = NULL;
696 put_cpu_ptr(pool->unbuddied);
697 if (can_sleep)
698 cond_resched();
699 goto lookup;
700 }
701
702 /*
703 * this page could not be removed from its unbuddied
704 * list while pool lock was held, and then we've taken
705 * page lock so kref_put could not be called before
706 * we got here, so it's safe to just call kref_get()
707 */
708 kref_get(&zhdr->refcount);
709 break;
710 }
711 put_cpu_ptr(pool->unbuddied);
712
713 if (!zhdr) {
714 int cpu;
715
716 /* look for _exact_ match on other cpus' lists */
717 for_each_online_cpu(cpu) {
718 struct list_head *l;
719
720 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
721 spin_lock(&pool->lock);
722 l = &unbuddied[chunks];
723
724 zhdr = list_first_entry_or_null(READ_ONCE(l),
725 struct z3fold_header, buddy);
726
727 if (!zhdr || !z3fold_page_trylock(zhdr)) {
728 spin_unlock(&pool->lock);
729 zhdr = NULL;
730 continue;
731 }
732 list_del_init(&zhdr->buddy);
733 zhdr->cpu = -1;
734 spin_unlock(&pool->lock);
735
736 page = virt_to_page(zhdr);
737 if (test_bit(NEEDS_COMPACTING, &page->private)) {
738 z3fold_page_unlock(zhdr);
739 zhdr = NULL;
740 if (can_sleep)
741 cond_resched();
742 continue;
743 }
744 kref_get(&zhdr->refcount);
745 break;
746 }
747 }
748
749 return zhdr;
750}
751
752/*
753 * API Functions
754 */
755
756/**
757 * z3fold_create_pool() - create a new z3fold pool
758 * @name: pool name
759 * @gfp: gfp flags when allocating the z3fold pool structure
760 * @ops: user-defined operations for the z3fold pool
761 *
762 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
763 * failed.
764 */
765static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
766 const struct z3fold_ops *ops)
767{
768 struct z3fold_pool *pool = NULL;
769 int i, cpu;
770
771 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
772 if (!pool)
773 goto out;
774 pool->c_handle = kmem_cache_create("z3fold_handle",
775 sizeof(struct z3fold_buddy_slots),
776 SLOTS_ALIGN, 0, NULL);
777 if (!pool->c_handle)
778 goto out_c;
779 spin_lock_init(&pool->lock);
780 spin_lock_init(&pool->stale_lock);
781 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
782 if (!pool->unbuddied)
783 goto out_pool;
784 for_each_possible_cpu(cpu) {
785 struct list_head *unbuddied =
786 per_cpu_ptr(pool->unbuddied, cpu);
787 for_each_unbuddied_list(i, 0)
788 INIT_LIST_HEAD(&unbuddied[i]);
789 }
790 INIT_LIST_HEAD(&pool->lru);
791 INIT_LIST_HEAD(&pool->stale);
792 atomic64_set(&pool->pages_nr, 0);
793 pool->name = name;
794 pool->compact_wq = create_singlethread_workqueue(pool->name);
795 if (!pool->compact_wq)
796 goto out_unbuddied;
797 pool->release_wq = create_singlethread_workqueue(pool->name);
798 if (!pool->release_wq)
799 goto out_wq;
800 if (z3fold_register_migration(pool))
801 goto out_rwq;
802 INIT_WORK(&pool->work, free_pages_work);
803 pool->ops = ops;
804 return pool;
805
806out_rwq:
807 destroy_workqueue(pool->release_wq);
808out_wq:
809 destroy_workqueue(pool->compact_wq);
810out_unbuddied:
811 free_percpu(pool->unbuddied);
812out_pool:
813 kmem_cache_destroy(pool->c_handle);
814out_c:
815 kfree(pool);
816out:
817 return NULL;
818}
819
820/**
821 * z3fold_destroy_pool() - destroys an existing z3fold pool
822 * @pool: the z3fold pool to be destroyed
823 *
824 * The pool should be emptied before this function is called.
825 */
826static void z3fold_destroy_pool(struct z3fold_pool *pool)
827{
828 kmem_cache_destroy(pool->c_handle);
829
830 /*
831 * We need to destroy pool->compact_wq before pool->release_wq,
832 * as any pending work on pool->compact_wq will call
833 * queue_work(pool->release_wq, &pool->work).
834 *
835 * There are still outstanding pages until both workqueues are drained,
836 * so we cannot unregister migration until then.
837 */
838
839 destroy_workqueue(pool->compact_wq);
840 destroy_workqueue(pool->release_wq);
841 z3fold_unregister_migration(pool);
842 kfree(pool);
843}
844
845/**
846 * z3fold_alloc() - allocates a region of a given size
847 * @pool: z3fold pool from which to allocate
848 * @size: size in bytes of the desired allocation
849 * @gfp: gfp flags used if the pool needs to grow
850 * @handle: handle of the new allocation
851 *
852 * This function will attempt to find a free region in the pool large enough to
853 * satisfy the allocation request. A search of the unbuddied lists is
854 * performed first. If no suitable free region is found, then a new page is
855 * allocated and added to the pool to satisfy the request.
856 *
857 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
858 * as z3fold pool pages.
859 *
860 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
861 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
862 * a new page.
863 */
864static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
865 unsigned long *handle)
866{
867 int chunks = size_to_chunks(size);
868 struct z3fold_header *zhdr = NULL;
869 struct page *page = NULL;
870 enum buddy bud;
871 bool can_sleep = gfpflags_allow_blocking(gfp);
872
873 if (!size)
874 return -EINVAL;
875
876 if (size > PAGE_SIZE)
877 return -ENOSPC;
878
879 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
880 bud = HEADLESS;
881 else {
882retry:
883 zhdr = __z3fold_alloc(pool, size, can_sleep);
884 if (zhdr) {
885 if (zhdr->first_chunks == 0) {
886 if (zhdr->middle_chunks != 0 &&
887 chunks >= zhdr->start_middle)
888 bud = LAST;
889 else
890 bud = FIRST;
891 } else if (zhdr->last_chunks == 0)
892 bud = LAST;
893 else if (zhdr->middle_chunks == 0)
894 bud = MIDDLE;
895 else {
896 if (kref_put(&zhdr->refcount,
897 release_z3fold_page_locked))
898 atomic64_dec(&pool->pages_nr);
899 else
900 z3fold_page_unlock(zhdr);
901 pr_err("No free chunks in unbuddied\n");
902 WARN_ON(1);
903 goto retry;
904 }
905 page = virt_to_page(zhdr);
906 goto found;
907 }
908 bud = FIRST;
909 }
910
911 page = NULL;
912 if (can_sleep) {
913 spin_lock(&pool->stale_lock);
914 zhdr = list_first_entry_or_null(&pool->stale,
915 struct z3fold_header, buddy);
916 /*
917 * Before allocating a page, let's see if we can take one from
918 * the stale pages list. cancel_work_sync() can sleep so we
919 * limit this case to the contexts where we can sleep
920 */
921 if (zhdr) {
922 list_del(&zhdr->buddy);
923 spin_unlock(&pool->stale_lock);
924 cancel_work_sync(&zhdr->work);
925 page = virt_to_page(zhdr);
926 } else {
927 spin_unlock(&pool->stale_lock);
928 }
929 }
930 if (!page)
931 page = alloc_page(gfp);
932
933 if (!page)
934 return -ENOMEM;
935
936 zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
937 if (!zhdr) {
938 __free_page(page);
939 return -ENOMEM;
940 }
941 atomic64_inc(&pool->pages_nr);
942
943 if (bud == HEADLESS) {
944 set_bit(PAGE_HEADLESS, &page->private);
945 goto headless;
946 }
947 if (can_sleep) {
948 lock_page(page);
949 __SetPageMovable(page, pool->inode->i_mapping);
950 unlock_page(page);
951 } else {
952 if (trylock_page(page)) {
953 __SetPageMovable(page, pool->inode->i_mapping);
954 unlock_page(page);
955 }
956 }
957 z3fold_page_lock(zhdr);
958
959found:
960 if (bud == FIRST)
961 zhdr->first_chunks = chunks;
962 else if (bud == LAST)
963 zhdr->last_chunks = chunks;
964 else {
965 zhdr->middle_chunks = chunks;
966 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
967 }
968 add_to_unbuddied(pool, zhdr);
969
970headless:
971 spin_lock(&pool->lock);
972 /* Add/move z3fold page to beginning of LRU */
973 if (!list_empty(&page->lru))
974 list_del(&page->lru);
975
976 list_add(&page->lru, &pool->lru);
977
978 *handle = encode_handle(zhdr, bud);
979 spin_unlock(&pool->lock);
980 if (bud != HEADLESS)
981 z3fold_page_unlock(zhdr);
982
983 return 0;
984}
985
986/**
987 * z3fold_free() - frees the allocation associated with the given handle
988 * @pool: pool in which the allocation resided
989 * @handle: handle associated with the allocation returned by z3fold_alloc()
990 *
991 * In the case that the z3fold page in which the allocation resides is under
992 * reclaim, as indicated by the PG_reclaim flag being set, this function
993 * only sets the first|last_chunks to 0. The page is actually freed
994 * once both buddies are evicted (see z3fold_reclaim_page() below).
995 */
996static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
997{
998 struct z3fold_header *zhdr;
999 struct page *page;
1000 enum buddy bud;
1001 bool page_claimed;
1002
1003 zhdr = handle_to_z3fold_header(handle);
1004 page = virt_to_page(zhdr);
1005 page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1006
1007 if (test_bit(PAGE_HEADLESS, &page->private)) {
1008 /* if a headless page is under reclaim, just leave.
1009 * NB: we use test_and_set_bit for a reason: if the bit
1010 * has not been set before, we release this page
1011 * immediately so we don't care about its value any more.
1012 */
1013 if (!page_claimed) {
1014 spin_lock(&pool->lock);
1015 list_del(&page->lru);
1016 spin_unlock(&pool->lock);
1017 free_z3fold_page(page, true);
1018 atomic64_dec(&pool->pages_nr);
1019 }
1020 return;
1021 }
1022
1023 /* Non-headless case */
1024 z3fold_page_lock(zhdr);
1025 bud = handle_to_buddy(handle);
1026
1027 switch (bud) {
1028 case FIRST:
1029 zhdr->first_chunks = 0;
1030 break;
1031 case MIDDLE:
1032 zhdr->middle_chunks = 0;
1033 break;
1034 case LAST:
1035 zhdr->last_chunks = 0;
1036 break;
1037 default:
1038 pr_err("%s: unknown bud %d\n", __func__, bud);
1039 WARN_ON(1);
1040 z3fold_page_unlock(zhdr);
1041 return;
1042 }
1043
1044 free_handle(handle);
1045 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1046 atomic64_dec(&pool->pages_nr);
1047 return;
1048 }
1049 if (page_claimed) {
1050 /* the page has not been claimed by us */
1051 z3fold_page_unlock(zhdr);
1052 return;
1053 }
1054 if (unlikely(PageIsolated(page)) ||
1055 test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1056 z3fold_page_unlock(zhdr);
1057 clear_bit(PAGE_CLAIMED, &page->private);
1058 return;
1059 }
1060 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1061 spin_lock(&pool->lock);
1062 list_del_init(&zhdr->buddy);
1063 spin_unlock(&pool->lock);
1064 zhdr->cpu = -1;
1065 kref_get(&zhdr->refcount);
1066 do_compact_page(zhdr, true);
1067 clear_bit(PAGE_CLAIMED, &page->private);
1068 return;
1069 }
1070 kref_get(&zhdr->refcount);
1071 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1072 clear_bit(PAGE_CLAIMED, &page->private);
1073 z3fold_page_unlock(zhdr);
1074}
1075
1076/**
1077 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1078 * @pool: pool from which a page will attempt to be evicted
1079 * @retries: number of pages on the LRU list for which eviction will
1080 * be attempted before failing
1081 *
1082 * z3fold reclaim is different from normal system reclaim in that it is done
1083 * from the bottom, up. This is because only the bottom layer, z3fold, has
1084 * information on how the allocations are organized within each z3fold page.
1085 * This has the potential to create interesting locking situations between
1086 * z3fold and the user, however.
1087 *
1088 * To avoid these, this is how z3fold_reclaim_page() should be called:
1089 *
1090 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1091 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1092 * call the user-defined eviction handler with the pool and handle as
1093 * arguments.
1094 *
1095 * If the handle can not be evicted, the eviction handler should return
1096 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1097 * appropriate list and try the next z3fold page on the LRU up to
1098 * a user defined number of retries.
1099 *
1100 * If the handle is successfully evicted, the eviction handler should
1101 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1102 * contains logic to delay freeing the page if the page is under reclaim,
1103 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1104 *
1105 * If all buddies in the z3fold page are successfully evicted, then the
1106 * z3fold page can be freed.
1107 *
1108 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1109 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1110 * the retry limit was hit.
1111 */
1112static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1113{
1114 int i, ret = 0;
1115 struct z3fold_header *zhdr = NULL;
1116 struct page *page = NULL;
1117 struct list_head *pos;
1118 struct z3fold_buddy_slots slots;
1119 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1120
1121 spin_lock(&pool->lock);
1122 if (!pool->ops || !pool->ops->evict || retries == 0) {
1123 spin_unlock(&pool->lock);
1124 return -EINVAL;
1125 }
1126 for (i = 0; i < retries; i++) {
1127 if (list_empty(&pool->lru)) {
1128 spin_unlock(&pool->lock);
1129 return -EINVAL;
1130 }
1131 list_for_each_prev(pos, &pool->lru) {
1132 page = list_entry(pos, struct page, lru);
1133
1134 /* this bit could have been set by free, in which case
1135 * we pass over to the next page in the pool.
1136 */
1137 if (test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1138 page = NULL;
1139 continue;
1140 }
1141
1142 if (unlikely(PageIsolated(page))) {
1143 clear_bit(PAGE_CLAIMED, &page->private);
1144 page = NULL;
1145 continue;
1146 }
1147 zhdr = page_address(page);
1148 if (test_bit(PAGE_HEADLESS, &page->private))
1149 break;
1150
1151 if (!z3fold_page_trylock(zhdr)) {
1152 clear_bit(PAGE_CLAIMED, &page->private);
1153 zhdr = NULL;
1154 continue; /* can't evict at this point */
1155 }
1156 kref_get(&zhdr->refcount);
1157 list_del_init(&zhdr->buddy);
1158 zhdr->cpu = -1;
1159 break;
1160 }
1161
1162 if (!zhdr)
1163 break;
1164
1165 list_del_init(&page->lru);
1166 spin_unlock(&pool->lock);
1167
1168 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1169 /*
1170 * We need encode the handles before unlocking, and
1171 * use our local slots structure because z3fold_free
1172 * can zero out zhdr->slots and we can't do much
1173 * about that
1174 */
1175 first_handle = 0;
1176 last_handle = 0;
1177 middle_handle = 0;
1178 if (zhdr->first_chunks)
1179 first_handle = __encode_handle(zhdr, &slots,
1180 FIRST);
1181 if (zhdr->middle_chunks)
1182 middle_handle = __encode_handle(zhdr, &slots,
1183 MIDDLE);
1184 if (zhdr->last_chunks)
1185 last_handle = __encode_handle(zhdr, &slots,
1186 LAST);
1187 /*
1188 * it's safe to unlock here because we hold a
1189 * reference to this page
1190 */
1191 z3fold_page_unlock(zhdr);
1192 } else {
1193 first_handle = __encode_handle(zhdr, &slots, HEADLESS);
1194 last_handle = middle_handle = 0;
1195 }
1196
1197 /* Issue the eviction callback(s) */
1198 if (middle_handle) {
1199 ret = pool->ops->evict(pool, middle_handle);
1200 if (ret)
1201 goto next;
1202 }
1203 if (first_handle) {
1204 ret = pool->ops->evict(pool, first_handle);
1205 if (ret)
1206 goto next;
1207 }
1208 if (last_handle) {
1209 ret = pool->ops->evict(pool, last_handle);
1210 if (ret)
1211 goto next;
1212 }
1213next:
1214 if (test_bit(PAGE_HEADLESS, &page->private)) {
1215 if (ret == 0) {
1216 free_z3fold_page(page, true);
1217 atomic64_dec(&pool->pages_nr);
1218 return 0;
1219 }
1220 spin_lock(&pool->lock);
1221 list_add(&page->lru, &pool->lru);
1222 spin_unlock(&pool->lock);
1223 clear_bit(PAGE_CLAIMED, &page->private);
1224 } else {
1225 z3fold_page_lock(zhdr);
1226 if (kref_put(&zhdr->refcount,
1227 release_z3fold_page_locked)) {
1228 atomic64_dec(&pool->pages_nr);
1229 return 0;
1230 }
1231 /*
1232 * if we are here, the page is still not completely
1233 * free. Take the global pool lock then to be able
1234 * to add it back to the lru list
1235 */
1236 spin_lock(&pool->lock);
1237 list_add(&page->lru, &pool->lru);
1238 spin_unlock(&pool->lock);
1239 z3fold_page_unlock(zhdr);
1240 clear_bit(PAGE_CLAIMED, &page->private);
1241 }
1242
1243 /* We started off locked to we need to lock the pool back */
1244 spin_lock(&pool->lock);
1245 }
1246 spin_unlock(&pool->lock);
1247 return -EAGAIN;
1248}
1249
1250/**
1251 * z3fold_map() - maps the allocation associated with the given handle
1252 * @pool: pool in which the allocation resides
1253 * @handle: handle associated with the allocation to be mapped
1254 *
1255 * Extracts the buddy number from handle and constructs the pointer to the
1256 * correct starting chunk within the page.
1257 *
1258 * Returns: a pointer to the mapped allocation
1259 */
1260static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1261{
1262 struct z3fold_header *zhdr;
1263 struct page *page;
1264 void *addr;
1265 enum buddy buddy;
1266
1267 zhdr = handle_to_z3fold_header(handle);
1268 addr = zhdr;
1269 page = virt_to_page(zhdr);
1270
1271 if (test_bit(PAGE_HEADLESS, &page->private))
1272 goto out;
1273
1274 z3fold_page_lock(zhdr);
1275 buddy = handle_to_buddy(handle);
1276 switch (buddy) {
1277 case FIRST:
1278 addr += ZHDR_SIZE_ALIGNED;
1279 break;
1280 case MIDDLE:
1281 addr += zhdr->start_middle << CHUNK_SHIFT;
1282 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1283 break;
1284 case LAST:
1285 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1286 break;
1287 default:
1288 pr_err("unknown buddy id %d\n", buddy);
1289 WARN_ON(1);
1290 addr = NULL;
1291 break;
1292 }
1293
1294 if (addr)
1295 zhdr->mapped_count++;
1296 z3fold_page_unlock(zhdr);
1297out:
1298 return addr;
1299}
1300
1301/**
1302 * z3fold_unmap() - unmaps the allocation associated with the given handle
1303 * @pool: pool in which the allocation resides
1304 * @handle: handle associated with the allocation to be unmapped
1305 */
1306static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1307{
1308 struct z3fold_header *zhdr;
1309 struct page *page;
1310 enum buddy buddy;
1311
1312 zhdr = handle_to_z3fold_header(handle);
1313 page = virt_to_page(zhdr);
1314
1315 if (test_bit(PAGE_HEADLESS, &page->private))
1316 return;
1317
1318 z3fold_page_lock(zhdr);
1319 buddy = handle_to_buddy(handle);
1320 if (buddy == MIDDLE)
1321 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1322 zhdr->mapped_count--;
1323 z3fold_page_unlock(zhdr);
1324}
1325
1326/**
1327 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1328 * @pool: pool whose size is being queried
1329 *
1330 * Returns: size in pages of the given pool.
1331 */
1332static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1333{
1334 return atomic64_read(&pool->pages_nr);
1335}
1336
1337static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1338{
1339 struct z3fold_header *zhdr;
1340 struct z3fold_pool *pool;
1341
1342 VM_BUG_ON_PAGE(!PageMovable(page), page);
1343 VM_BUG_ON_PAGE(PageIsolated(page), page);
1344
1345 if (test_bit(PAGE_HEADLESS, &page->private) ||
1346 test_bit(PAGE_CLAIMED, &page->private))
1347 return false;
1348
1349 zhdr = page_address(page);
1350 z3fold_page_lock(zhdr);
1351 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1352 test_bit(PAGE_STALE, &page->private))
1353 goto out;
1354
1355 pool = zhdr_to_pool(zhdr);
1356
1357 if (zhdr->mapped_count == 0) {
1358 kref_get(&zhdr->refcount);
1359 if (!list_empty(&zhdr->buddy))
1360 list_del_init(&zhdr->buddy);
1361 spin_lock(&pool->lock);
1362 if (!list_empty(&page->lru))
1363 list_del(&page->lru);
1364 spin_unlock(&pool->lock);
1365 z3fold_page_unlock(zhdr);
1366 return true;
1367 }
1368out:
1369 z3fold_page_unlock(zhdr);
1370 return false;
1371}
1372
1373static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1374 struct page *page, enum migrate_mode mode)
1375{
1376 struct z3fold_header *zhdr, *new_zhdr;
1377 struct z3fold_pool *pool;
1378 struct address_space *new_mapping;
1379
1380 VM_BUG_ON_PAGE(!PageMovable(page), page);
1381 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1382 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1383
1384 zhdr = page_address(page);
1385 pool = zhdr_to_pool(zhdr);
1386
1387 if (!z3fold_page_trylock(zhdr)) {
1388 return -EAGAIN;
1389 }
1390 if (zhdr->mapped_count != 0) {
1391 z3fold_page_unlock(zhdr);
1392 return -EBUSY;
1393 }
1394 if (work_pending(&zhdr->work)) {
1395 z3fold_page_unlock(zhdr);
1396 return -EAGAIN;
1397 }
1398 new_zhdr = page_address(newpage);
1399 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1400 newpage->private = page->private;
1401 page->private = 0;
1402 z3fold_page_unlock(zhdr);
1403 spin_lock_init(&new_zhdr->page_lock);
1404 INIT_WORK(&new_zhdr->work, compact_page_work);
1405 /*
1406 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1407 * so we only have to reinitialize it.
1408 */
1409 INIT_LIST_HEAD(&new_zhdr->buddy);
1410 new_mapping = page_mapping(page);
1411 __ClearPageMovable(page);
1412 ClearPagePrivate(page);
1413
1414 get_page(newpage);
1415 z3fold_page_lock(new_zhdr);
1416 if (new_zhdr->first_chunks)
1417 encode_handle(new_zhdr, FIRST);
1418 if (new_zhdr->last_chunks)
1419 encode_handle(new_zhdr, LAST);
1420 if (new_zhdr->middle_chunks)
1421 encode_handle(new_zhdr, MIDDLE);
1422 set_bit(NEEDS_COMPACTING, &newpage->private);
1423 new_zhdr->cpu = smp_processor_id();
1424 spin_lock(&pool->lock);
1425 list_add(&newpage->lru, &pool->lru);
1426 spin_unlock(&pool->lock);
1427 __SetPageMovable(newpage, new_mapping);
1428 z3fold_page_unlock(new_zhdr);
1429
1430 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1431
1432 page_mapcount_reset(page);
1433 put_page(page);
1434 return 0;
1435}
1436
1437static void z3fold_page_putback(struct page *page)
1438{
1439 struct z3fold_header *zhdr;
1440 struct z3fold_pool *pool;
1441
1442 zhdr = page_address(page);
1443 pool = zhdr_to_pool(zhdr);
1444
1445 z3fold_page_lock(zhdr);
1446 if (!list_empty(&zhdr->buddy))
1447 list_del_init(&zhdr->buddy);
1448 INIT_LIST_HEAD(&page->lru);
1449 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1450 atomic64_dec(&pool->pages_nr);
1451 return;
1452 }
1453 spin_lock(&pool->lock);
1454 list_add(&page->lru, &pool->lru);
1455 spin_unlock(&pool->lock);
1456 z3fold_page_unlock(zhdr);
1457}
1458
1459static const struct address_space_operations z3fold_aops = {
1460 .isolate_page = z3fold_page_isolate,
1461 .migratepage = z3fold_page_migrate,
1462 .putback_page = z3fold_page_putback,
1463};
1464
1465/*****************
1466 * zpool
1467 ****************/
1468
1469static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1470{
1471 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1472 return pool->zpool_ops->evict(pool->zpool, handle);
1473 else
1474 return -ENOENT;
1475}
1476
1477static const struct z3fold_ops z3fold_zpool_ops = {
1478 .evict = z3fold_zpool_evict
1479};
1480
1481static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1482 const struct zpool_ops *zpool_ops,
1483 struct zpool *zpool)
1484{
1485 struct z3fold_pool *pool;
1486
1487 pool = z3fold_create_pool(name, gfp,
1488 zpool_ops ? &z3fold_zpool_ops : NULL);
1489 if (pool) {
1490 pool->zpool = zpool;
1491 pool->zpool_ops = zpool_ops;
1492 }
1493 return pool;
1494}
1495
1496static void z3fold_zpool_destroy(void *pool)
1497{
1498 z3fold_destroy_pool(pool);
1499}
1500
1501static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1502 unsigned long *handle)
1503{
1504 return z3fold_alloc(pool, size, gfp, handle);
1505}
1506static void z3fold_zpool_free(void *pool, unsigned long handle)
1507{
1508 z3fold_free(pool, handle);
1509}
1510
1511static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1512 unsigned int *reclaimed)
1513{
1514 unsigned int total = 0;
1515 int ret = -EINVAL;
1516
1517 while (total < pages) {
1518 ret = z3fold_reclaim_page(pool, 8);
1519 if (ret < 0)
1520 break;
1521 total++;
1522 }
1523
1524 if (reclaimed)
1525 *reclaimed = total;
1526
1527 return ret;
1528}
1529
1530static void *z3fold_zpool_map(void *pool, unsigned long handle,
1531 enum zpool_mapmode mm)
1532{
1533 return z3fold_map(pool, handle);
1534}
1535static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1536{
1537 z3fold_unmap(pool, handle);
1538}
1539
1540static u64 z3fold_zpool_total_size(void *pool)
1541{
1542 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1543}
1544
1545static struct zpool_driver z3fold_zpool_driver = {
1546 .type = "z3fold",
1547 .owner = THIS_MODULE,
1548 .create = z3fold_zpool_create,
1549 .destroy = z3fold_zpool_destroy,
1550 .malloc = z3fold_zpool_malloc,
1551 .free = z3fold_zpool_free,
1552 .shrink = z3fold_zpool_shrink,
1553 .map = z3fold_zpool_map,
1554 .unmap = z3fold_zpool_unmap,
1555 .total_size = z3fold_zpool_total_size,
1556};
1557
1558MODULE_ALIAS("zpool-z3fold");
1559
1560static int __init init_z3fold(void)
1561{
1562 int ret;
1563
1564 /* Make sure the z3fold header is not larger than the page size */
1565 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1566 ret = z3fold_mount();
1567 if (ret)
1568 return ret;
1569
1570 zpool_register_driver(&z3fold_zpool_driver);
1571
1572 return 0;
1573}
1574
1575static void __exit exit_z3fold(void)
1576{
1577 z3fold_unmount();
1578 zpool_unregister_driver(&z3fold_zpool_driver);
1579}
1580
1581module_init(init_z3fold);
1582module_exit(exit_z3fold);
1583
1584MODULE_LICENSE("GPL");
1585MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1586MODULE_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");