Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf
[linux-2.6-microblaze.git] / mm / z3fold.c
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 *****************/
73 struct z3fold_pool;
74 struct z3fold_ops {
75         int (*evict)(struct z3fold_pool *pool, unsigned long handle);
76 };
77
78 enum buddy {
79         HEADLESS = 0,
80         FIRST,
81         MIDDLE,
82         LAST,
83         BUDDIES_MAX = LAST
84 };
85
86 struct 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  */
113 struct 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  */
152 struct 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  */
173 enum 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 */
186 static 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
194 static void compact_page_work(struct work_struct *w);
195
196 static 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
212 static 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
217 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
218 {
219         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
220 }
221
222 static 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
249 static int z3fold_init_fs_context(struct fs_context *fc)
250 {
251         return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
252 }
253
254 static 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
260 static struct vfsmount *z3fold_mnt;
261 static 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
272 static void z3fold_unmount(void)
273 {
274         kern_unmount(z3fold_mnt);
275 }
276
277 static const struct address_space_operations z3fold_aops;
278 static 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
291 static 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 */
298 static 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 */
333 static 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 */
345 static 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 */
351 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
352 {
353         return spin_trylock(&zhdr->page_lock);
354 }
355
356 /* Unlock a z3fold page */
357 static 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 */
363 static 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  */
372 static 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
396 static 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 */
402 static 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 */
413 static 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  */
425 static 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
436 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
437 {
438         return zhdr->pool;
439 }
440
441 static 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
461 static 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
469 static 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
477 static 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
490 static 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  */
516 static 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 */
537 static 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
553 static 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 */
564 static 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
611 static 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
646 static 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 */
655 static 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
663 lookup:
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  */
765 static 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
806 out_rwq:
807         destroy_workqueue(pool->release_wq);
808 out_wq:
809         destroy_workqueue(pool->compact_wq);
810 out_unbuddied:
811         free_percpu(pool->unbuddied);
812 out_pool:
813         kmem_cache_destroy(pool->c_handle);
814 out_c:
815         kfree(pool);
816 out:
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  */
826 static 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  */
864 static 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 {
882 retry:
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
959 found:
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
970 headless:
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  */
996 static 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  */
1112 static 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                 }
1213 next:
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  */
1260 static 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);
1297 out:
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  */
1306 static 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  */
1332 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1333 {
1334         return atomic64_read(&pool->pages_nr);
1335 }
1336
1337 static 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         }
1368 out:
1369         z3fold_page_unlock(zhdr);
1370         return false;
1371 }
1372
1373 static 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
1437 static 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
1459 static 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
1469 static 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
1477 static const struct z3fold_ops z3fold_zpool_ops = {
1478         .evict =        z3fold_zpool_evict
1479 };
1480
1481 static 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
1496 static void z3fold_zpool_destroy(void *pool)
1497 {
1498         z3fold_destroy_pool(pool);
1499 }
1500
1501 static 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 }
1506 static void z3fold_zpool_free(void *pool, unsigned long handle)
1507 {
1508         z3fold_free(pool, handle);
1509 }
1510
1511 static 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
1530 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1531                         enum zpool_mapmode mm)
1532 {
1533         return z3fold_map(pool, handle);
1534 }
1535 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1536 {
1537         z3fold_unmap(pool, handle);
1538 }
1539
1540 static u64 z3fold_zpool_total_size(void *pool)
1541 {
1542         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1543 }
1544
1545 static 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
1558 MODULE_ALIAS("zpool-z3fold");
1559
1560 static 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
1575 static void __exit exit_z3fold(void)
1576 {
1577         z3fold_unmount();
1578         zpool_unregister_driver(&z3fold_zpool_driver);
1579 }
1580
1581 module_init(init_z3fold);
1582 module_exit(exit_z3fold);
1583
1584 MODULE_LICENSE("GPL");
1585 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1586 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");