Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
[platform/kernel/linux-rpi.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/dcache.h>
30 #include <linux/list.h>
31 #include <linux/mm.h>
32 #include <linux/module.h>
33 #include <linux/page-flags.h>
34 #include <linux/migrate.h>
35 #include <linux/node.h>
36 #include <linux/compaction.h>
37 #include <linux/percpu.h>
38 #include <linux/mount.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
46 /*
47  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
48  * adjusting internal fragmentation.  It also determines the number of
49  * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
50  * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
51  * in the beginning of an allocated page are occupied by z3fold header, so
52  * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
53  * which shows the max number of free chunks in z3fold page, also there will
54  * be 63, or 62, respectively, freelists per pool.
55  */
56 #define NCHUNKS_ORDER   6
57
58 #define CHUNK_SHIFT     (PAGE_SHIFT - NCHUNKS_ORDER)
59 #define CHUNK_SIZE      (1 << CHUNK_SHIFT)
60 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
61 #define ZHDR_CHUNKS     (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
62 #define TOTAL_CHUNKS    (PAGE_SIZE >> CHUNK_SHIFT)
63 #define NCHUNKS         ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
64
65 #define BUDDY_MASK      (0x3)
66 #define BUDDY_SHIFT     2
67 #define SLOTS_ALIGN     (0x40)
68
69 /*****************
70  * Structures
71 *****************/
72 struct z3fold_pool;
73 struct z3fold_ops {
74         int (*evict)(struct z3fold_pool *pool, unsigned long handle);
75 };
76
77 enum buddy {
78         HEADLESS = 0,
79         FIRST,
80         MIDDLE,
81         LAST,
82         BUDDIES_MAX = LAST
83 };
84
85 struct z3fold_buddy_slots {
86         /*
87          * we are using BUDDY_MASK in handle_to_buddy etc. so there should
88          * be enough slots to hold all possible variants
89          */
90         unsigned long slot[BUDDY_MASK + 1];
91         unsigned long pool; /* back link + flags */
92 };
93 #define HANDLE_FLAG_MASK        (0x03)
94
95 /*
96  * struct z3fold_header - z3fold page metadata occupying first chunks of each
97  *                      z3fold page, except for HEADLESS pages
98  * @buddy:              links the z3fold page into the relevant list in the
99  *                      pool
100  * @page_lock:          per-page lock
101  * @refcount:           reference count for the z3fold page
102  * @work:               work_struct for page layout optimization
103  * @slots:              pointer to the structure holding buddy slots
104  * @cpu:                CPU which this page "belongs" to
105  * @first_chunks:       the size of the first buddy in chunks, 0 if free
106  * @middle_chunks:      the size of the middle buddy in chunks, 0 if free
107  * @last_chunks:        the size of the last buddy in chunks, 0 if free
108  * @first_num:          the starting number (for the first handle)
109  * @mapped_count:       the number of objects currently mapped
110  */
111 struct z3fold_header {
112         struct list_head buddy;
113         spinlock_t page_lock;
114         struct kref refcount;
115         struct work_struct work;
116         struct z3fold_buddy_slots *slots;
117         short cpu;
118         unsigned short first_chunks;
119         unsigned short middle_chunks;
120         unsigned short last_chunks;
121         unsigned short start_middle;
122         unsigned short first_num:2;
123         unsigned short mapped_count:2;
124 };
125
126 /**
127  * struct z3fold_pool - stores metadata for each z3fold pool
128  * @name:       pool name
129  * @lock:       protects pool unbuddied/lru lists
130  * @stale_lock: protects pool stale page list
131  * @unbuddied:  per-cpu array of lists tracking z3fold pages that contain 2-
132  *              buddies; the list each z3fold page is added to depends on
133  *              the size of its free region.
134  * @lru:        list tracking the z3fold pages in LRU order by most recently
135  *              added buddy.
136  * @stale:      list of pages marked for freeing
137  * @pages_nr:   number of z3fold pages in the pool.
138  * @c_handle:   cache for z3fold_buddy_slots allocation
139  * @ops:        pointer to a structure of user defined operations specified at
140  *              pool creation time.
141  * @compact_wq: workqueue for page layout background optimization
142  * @release_wq: workqueue for safe page release
143  * @work:       work_struct for safe page release
144  * @inode:      inode for z3fold pseudo filesystem
145  *
146  * This structure is allocated at pool creation time and maintains metadata
147  * pertaining to a particular z3fold pool.
148  */
149 struct z3fold_pool {
150         const char *name;
151         spinlock_t lock;
152         spinlock_t stale_lock;
153         struct list_head *unbuddied;
154         struct list_head lru;
155         struct list_head stale;
156         atomic64_t pages_nr;
157         struct kmem_cache *c_handle;
158         const struct z3fold_ops *ops;
159         struct zpool *zpool;
160         const struct zpool_ops *zpool_ops;
161         struct workqueue_struct *compact_wq;
162         struct workqueue_struct *release_wq;
163         struct work_struct work;
164         struct inode *inode;
165 };
166
167 /*
168  * Internal z3fold page flags
169  */
170 enum z3fold_page_flags {
171         PAGE_HEADLESS = 0,
172         MIDDLE_CHUNK_MAPPED,
173         NEEDS_COMPACTING,
174         PAGE_STALE,
175         PAGE_CLAIMED, /* by either reclaim or free */
176 };
177
178 /*****************
179  * Helpers
180 *****************/
181
182 /* Converts an allocation size in bytes to size in z3fold chunks */
183 static int size_to_chunks(size_t size)
184 {
185         return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
186 }
187
188 #define for_each_unbuddied_list(_iter, _begin) \
189         for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
190
191 static void compact_page_work(struct work_struct *w);
192
193 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool)
194 {
195         struct z3fold_buddy_slots *slots = kmem_cache_alloc(pool->c_handle,
196                                                         GFP_KERNEL);
197
198         if (slots) {
199                 memset(slots->slot, 0, sizeof(slots->slot));
200                 slots->pool = (unsigned long)pool;
201         }
202
203         return slots;
204 }
205
206 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
207 {
208         return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
209 }
210
211 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
212 {
213         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
214 }
215
216 static inline void free_handle(unsigned long handle)
217 {
218         struct z3fold_buddy_slots *slots;
219         int i;
220         bool is_free;
221
222         if (handle & (1 << PAGE_HEADLESS))
223                 return;
224
225         WARN_ON(*(unsigned long *)handle == 0);
226         *(unsigned long *)handle = 0;
227         slots = handle_to_slots(handle);
228         is_free = true;
229         for (i = 0; i <= BUDDY_MASK; i++) {
230                 if (slots->slot[i]) {
231                         is_free = false;
232                         break;
233                 }
234         }
235
236         if (is_free) {
237                 struct z3fold_pool *pool = slots_to_pool(slots);
238
239                 kmem_cache_free(pool->c_handle, slots);
240         }
241 }
242
243 static struct dentry *z3fold_do_mount(struct file_system_type *fs_type,
244                                 int flags, const char *dev_name, void *data)
245 {
246         static const struct dentry_operations ops = {
247                 .d_dname = simple_dname,
248         };
249
250         return mount_pseudo(fs_type, "z3fold:", NULL, &ops, 0x33);
251 }
252
253 static struct file_system_type z3fold_fs = {
254         .name           = "z3fold",
255         .mount          = z3fold_do_mount,
256         .kill_sb        = kill_anon_super,
257 };
258
259 static struct vfsmount *z3fold_mnt;
260 static int z3fold_mount(void)
261 {
262         int ret = 0;
263
264         z3fold_mnt = kern_mount(&z3fold_fs);
265         if (IS_ERR(z3fold_mnt))
266                 ret = PTR_ERR(z3fold_mnt);
267
268         return ret;
269 }
270
271 static void z3fold_unmount(void)
272 {
273         kern_unmount(z3fold_mnt);
274 }
275
276 static const struct address_space_operations z3fold_aops;
277 static int z3fold_register_migration(struct z3fold_pool *pool)
278 {
279         pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
280         if (IS_ERR(pool->inode)) {
281                 pool->inode = NULL;
282                 return 1;
283         }
284
285         pool->inode->i_mapping->private_data = pool;
286         pool->inode->i_mapping->a_ops = &z3fold_aops;
287         return 0;
288 }
289
290 static void z3fold_unregister_migration(struct z3fold_pool *pool)
291 {
292         if (pool->inode)
293                 iput(pool->inode);
294  }
295
296 /* Initializes the z3fold header of a newly allocated z3fold page */
297 static struct z3fold_header *init_z3fold_page(struct page *page,
298                                         struct z3fold_pool *pool)
299 {
300         struct z3fold_header *zhdr = page_address(page);
301         struct z3fold_buddy_slots *slots = alloc_slots(pool);
302
303         if (!slots)
304                 return NULL;
305
306         INIT_LIST_HEAD(&page->lru);
307         clear_bit(PAGE_HEADLESS, &page->private);
308         clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
309         clear_bit(NEEDS_COMPACTING, &page->private);
310         clear_bit(PAGE_STALE, &page->private);
311         clear_bit(PAGE_CLAIMED, &page->private);
312
313         spin_lock_init(&zhdr->page_lock);
314         kref_init(&zhdr->refcount);
315         zhdr->first_chunks = 0;
316         zhdr->middle_chunks = 0;
317         zhdr->last_chunks = 0;
318         zhdr->first_num = 0;
319         zhdr->start_middle = 0;
320         zhdr->cpu = -1;
321         zhdr->slots = slots;
322         INIT_LIST_HEAD(&zhdr->buddy);
323         INIT_WORK(&zhdr->work, compact_page_work);
324         return zhdr;
325 }
326
327 /* Resets the struct page fields and frees the page */
328 static void free_z3fold_page(struct page *page, bool headless)
329 {
330         if (!headless) {
331                 lock_page(page);
332                 __ClearPageMovable(page);
333                 unlock_page(page);
334         }
335         ClearPagePrivate(page);
336         __free_page(page);
337 }
338
339 /* Lock a z3fold page */
340 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
341 {
342         spin_lock(&zhdr->page_lock);
343 }
344
345 /* Try to lock a z3fold page */
346 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
347 {
348         return spin_trylock(&zhdr->page_lock);
349 }
350
351 /* Unlock a z3fold page */
352 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
353 {
354         spin_unlock(&zhdr->page_lock);
355 }
356
357 /* Helper function to build the index */
358 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
359 {
360         return (bud + zhdr->first_num) & BUDDY_MASK;
361 }
362
363 /*
364  * Encodes the handle of a particular buddy within a z3fold page
365  * Pool lock should be held as this function accesses first_num
366  */
367 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
368 {
369         struct z3fold_buddy_slots *slots;
370         unsigned long h = (unsigned long)zhdr;
371         int idx = 0;
372
373         /*
374          * For a headless page, its handle is its pointer with the extra
375          * PAGE_HEADLESS bit set
376          */
377         if (bud == HEADLESS)
378                 return h | (1 << PAGE_HEADLESS);
379
380         /* otherwise, return pointer to encoded handle */
381         idx = __idx(zhdr, bud);
382         h += idx;
383         if (bud == LAST)
384                 h |= (zhdr->last_chunks << BUDDY_SHIFT);
385
386         slots = zhdr->slots;
387         slots->slot[idx] = h;
388         return (unsigned long)&slots->slot[idx];
389 }
390
391 /* Returns the z3fold page where a given handle is stored */
392 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
393 {
394         unsigned long addr = h;
395
396         if (!(addr & (1 << PAGE_HEADLESS)))
397                 addr = *(unsigned long *)h;
398
399         return (struct z3fold_header *)(addr & PAGE_MASK);
400 }
401
402 /* only for LAST bud, returns zero otherwise */
403 static unsigned short handle_to_chunks(unsigned long handle)
404 {
405         unsigned long addr = *(unsigned long *)handle;
406
407         return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
408 }
409
410 /*
411  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
412  *  but that doesn't matter. because the masking will result in the
413  *  correct buddy number.
414  */
415 static enum buddy handle_to_buddy(unsigned long handle)
416 {
417         struct z3fold_header *zhdr;
418         unsigned long addr;
419
420         WARN_ON(handle & (1 << PAGE_HEADLESS));
421         addr = *(unsigned long *)handle;
422         zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
423         return (addr - zhdr->first_num) & BUDDY_MASK;
424 }
425
426 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
427 {
428         return slots_to_pool(zhdr->slots);
429 }
430
431 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
432 {
433         struct page *page = virt_to_page(zhdr);
434         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
435
436         WARN_ON(!list_empty(&zhdr->buddy));
437         set_bit(PAGE_STALE, &page->private);
438         clear_bit(NEEDS_COMPACTING, &page->private);
439         spin_lock(&pool->lock);
440         if (!list_empty(&page->lru))
441                 list_del_init(&page->lru);
442         spin_unlock(&pool->lock);
443         if (locked)
444                 z3fold_page_unlock(zhdr);
445         spin_lock(&pool->stale_lock);
446         list_add(&zhdr->buddy, &pool->stale);
447         queue_work(pool->release_wq, &pool->work);
448         spin_unlock(&pool->stale_lock);
449 }
450
451 static void __attribute__((__unused__))
452                         release_z3fold_page(struct kref *ref)
453 {
454         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
455                                                 refcount);
456         __release_z3fold_page(zhdr, false);
457 }
458
459 static void release_z3fold_page_locked(struct kref *ref)
460 {
461         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
462                                                 refcount);
463         WARN_ON(z3fold_page_trylock(zhdr));
464         __release_z3fold_page(zhdr, true);
465 }
466
467 static void release_z3fold_page_locked_list(struct kref *ref)
468 {
469         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
470                                                refcount);
471         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
472         spin_lock(&pool->lock);
473         list_del_init(&zhdr->buddy);
474         spin_unlock(&pool->lock);
475
476         WARN_ON(z3fold_page_trylock(zhdr));
477         __release_z3fold_page(zhdr, true);
478 }
479
480 static void free_pages_work(struct work_struct *w)
481 {
482         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
483
484         spin_lock(&pool->stale_lock);
485         while (!list_empty(&pool->stale)) {
486                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
487                                                 struct z3fold_header, buddy);
488                 struct page *page = virt_to_page(zhdr);
489
490                 list_del(&zhdr->buddy);
491                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
492                         continue;
493                 spin_unlock(&pool->stale_lock);
494                 cancel_work_sync(&zhdr->work);
495                 free_z3fold_page(page, false);
496                 cond_resched();
497                 spin_lock(&pool->stale_lock);
498         }
499         spin_unlock(&pool->stale_lock);
500 }
501
502 /*
503  * Returns the number of free chunks in a z3fold page.
504  * NB: can't be used with HEADLESS pages.
505  */
506 static int num_free_chunks(struct z3fold_header *zhdr)
507 {
508         int nfree;
509         /*
510          * If there is a middle object, pick up the bigger free space
511          * either before or after it. Otherwise just subtract the number
512          * of chunks occupied by the first and the last objects.
513          */
514         if (zhdr->middle_chunks != 0) {
515                 int nfree_before = zhdr->first_chunks ?
516                         0 : zhdr->start_middle - ZHDR_CHUNKS;
517                 int nfree_after = zhdr->last_chunks ?
518                         0 : TOTAL_CHUNKS -
519                                 (zhdr->start_middle + zhdr->middle_chunks);
520                 nfree = max(nfree_before, nfree_after);
521         } else
522                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
523         return nfree;
524 }
525
526 /* Add to the appropriate unbuddied list */
527 static inline void add_to_unbuddied(struct z3fold_pool *pool,
528                                 struct z3fold_header *zhdr)
529 {
530         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
531                         zhdr->middle_chunks == 0) {
532                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
533
534                 int freechunks = num_free_chunks(zhdr);
535                 spin_lock(&pool->lock);
536                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
537                 spin_unlock(&pool->lock);
538                 zhdr->cpu = smp_processor_id();
539                 put_cpu_ptr(pool->unbuddied);
540         }
541 }
542
543 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
544                                 unsigned short dst_chunk)
545 {
546         void *beg = zhdr;
547         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
548                        beg + (zhdr->start_middle << CHUNK_SHIFT),
549                        zhdr->middle_chunks << CHUNK_SHIFT);
550 }
551
552 #define BIG_CHUNK_GAP   3
553 /* Has to be called with lock held */
554 static int z3fold_compact_page(struct z3fold_header *zhdr)
555 {
556         struct page *page = virt_to_page(zhdr);
557
558         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
559                 return 0; /* can't move middle chunk, it's used */
560
561         if (unlikely(PageIsolated(page)))
562                 return 0;
563
564         if (zhdr->middle_chunks == 0)
565                 return 0; /* nothing to compact */
566
567         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
568                 /* move to the beginning */
569                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
570                 zhdr->first_chunks = zhdr->middle_chunks;
571                 zhdr->middle_chunks = 0;
572                 zhdr->start_middle = 0;
573                 zhdr->first_num++;
574                 return 1;
575         }
576
577         /*
578          * moving data is expensive, so let's only do that if
579          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
580          */
581         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
582             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
583                         BIG_CHUNK_GAP) {
584                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
585                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
586                 return 1;
587         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
588                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
589                                         + zhdr->middle_chunks) >=
590                         BIG_CHUNK_GAP) {
591                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
592                         zhdr->middle_chunks;
593                 mchunk_memmove(zhdr, new_start);
594                 zhdr->start_middle = new_start;
595                 return 1;
596         }
597
598         return 0;
599 }
600
601 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
602 {
603         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
604         struct page *page;
605
606         page = virt_to_page(zhdr);
607         if (locked)
608                 WARN_ON(z3fold_page_trylock(zhdr));
609         else
610                 z3fold_page_lock(zhdr);
611         if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
612                 z3fold_page_unlock(zhdr);
613                 return;
614         }
615         spin_lock(&pool->lock);
616         list_del_init(&zhdr->buddy);
617         spin_unlock(&pool->lock);
618
619         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
620                 atomic64_dec(&pool->pages_nr);
621                 return;
622         }
623
624         if (unlikely(PageIsolated(page) ||
625                      test_bit(PAGE_STALE, &page->private))) {
626                 z3fold_page_unlock(zhdr);
627                 return;
628         }
629
630         z3fold_compact_page(zhdr);
631         add_to_unbuddied(pool, zhdr);
632         z3fold_page_unlock(zhdr);
633 }
634
635 static void compact_page_work(struct work_struct *w)
636 {
637         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
638                                                 work);
639
640         do_compact_page(zhdr, false);
641 }
642
643 /* returns _locked_ z3fold page header or NULL */
644 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
645                                                 size_t size, bool can_sleep)
646 {
647         struct z3fold_header *zhdr = NULL;
648         struct page *page;
649         struct list_head *unbuddied;
650         int chunks = size_to_chunks(size), i;
651
652 lookup:
653         /* First, try to find an unbuddied z3fold page. */
654         unbuddied = get_cpu_ptr(pool->unbuddied);
655         for_each_unbuddied_list(i, chunks) {
656                 struct list_head *l = &unbuddied[i];
657
658                 zhdr = list_first_entry_or_null(READ_ONCE(l),
659                                         struct z3fold_header, buddy);
660
661                 if (!zhdr)
662                         continue;
663
664                 /* Re-check under lock. */
665                 spin_lock(&pool->lock);
666                 l = &unbuddied[i];
667                 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
668                                                 struct z3fold_header, buddy)) ||
669                     !z3fold_page_trylock(zhdr)) {
670                         spin_unlock(&pool->lock);
671                         zhdr = NULL;
672                         put_cpu_ptr(pool->unbuddied);
673                         if (can_sleep)
674                                 cond_resched();
675                         goto lookup;
676                 }
677                 list_del_init(&zhdr->buddy);
678                 zhdr->cpu = -1;
679                 spin_unlock(&pool->lock);
680
681                 page = virt_to_page(zhdr);
682                 if (test_bit(NEEDS_COMPACTING, &page->private)) {
683                         z3fold_page_unlock(zhdr);
684                         zhdr = NULL;
685                         put_cpu_ptr(pool->unbuddied);
686                         if (can_sleep)
687                                 cond_resched();
688                         goto lookup;
689                 }
690
691                 /*
692                  * this page could not be removed from its unbuddied
693                  * list while pool lock was held, and then we've taken
694                  * page lock so kref_put could not be called before
695                  * we got here, so it's safe to just call kref_get()
696                  */
697                 kref_get(&zhdr->refcount);
698                 break;
699         }
700         put_cpu_ptr(pool->unbuddied);
701
702         if (!zhdr) {
703                 int cpu;
704
705                 /* look for _exact_ match on other cpus' lists */
706                 for_each_online_cpu(cpu) {
707                         struct list_head *l;
708
709                         unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
710                         spin_lock(&pool->lock);
711                         l = &unbuddied[chunks];
712
713                         zhdr = list_first_entry_or_null(READ_ONCE(l),
714                                                 struct z3fold_header, buddy);
715
716                         if (!zhdr || !z3fold_page_trylock(zhdr)) {
717                                 spin_unlock(&pool->lock);
718                                 zhdr = NULL;
719                                 continue;
720                         }
721                         list_del_init(&zhdr->buddy);
722                         zhdr->cpu = -1;
723                         spin_unlock(&pool->lock);
724
725                         page = virt_to_page(zhdr);
726                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
727                                 z3fold_page_unlock(zhdr);
728                                 zhdr = NULL;
729                                 if (can_sleep)
730                                         cond_resched();
731                                 continue;
732                         }
733                         kref_get(&zhdr->refcount);
734                         break;
735                 }
736         }
737
738         return zhdr;
739 }
740
741 /*
742  * API Functions
743  */
744
745 /**
746  * z3fold_create_pool() - create a new z3fold pool
747  * @name:       pool name
748  * @gfp:        gfp flags when allocating the z3fold pool structure
749  * @ops:        user-defined operations for the z3fold pool
750  *
751  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
752  * failed.
753  */
754 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
755                 const struct z3fold_ops *ops)
756 {
757         struct z3fold_pool *pool = NULL;
758         int i, cpu;
759
760         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
761         if (!pool)
762                 goto out;
763         pool->c_handle = kmem_cache_create("z3fold_handle",
764                                 sizeof(struct z3fold_buddy_slots),
765                                 SLOTS_ALIGN, 0, NULL);
766         if (!pool->c_handle)
767                 goto out_c;
768         spin_lock_init(&pool->lock);
769         spin_lock_init(&pool->stale_lock);
770         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
771         if (!pool->unbuddied)
772                 goto out_pool;
773         for_each_possible_cpu(cpu) {
774                 struct list_head *unbuddied =
775                                 per_cpu_ptr(pool->unbuddied, cpu);
776                 for_each_unbuddied_list(i, 0)
777                         INIT_LIST_HEAD(&unbuddied[i]);
778         }
779         INIT_LIST_HEAD(&pool->lru);
780         INIT_LIST_HEAD(&pool->stale);
781         atomic64_set(&pool->pages_nr, 0);
782         pool->name = name;
783         pool->compact_wq = create_singlethread_workqueue(pool->name);
784         if (!pool->compact_wq)
785                 goto out_unbuddied;
786         pool->release_wq = create_singlethread_workqueue(pool->name);
787         if (!pool->release_wq)
788                 goto out_wq;
789         if (z3fold_register_migration(pool))
790                 goto out_rwq;
791         INIT_WORK(&pool->work, free_pages_work);
792         pool->ops = ops;
793         return pool;
794
795 out_rwq:
796         destroy_workqueue(pool->release_wq);
797 out_wq:
798         destroy_workqueue(pool->compact_wq);
799 out_unbuddied:
800         free_percpu(pool->unbuddied);
801 out_pool:
802         kmem_cache_destroy(pool->c_handle);
803 out_c:
804         kfree(pool);
805 out:
806         return NULL;
807 }
808
809 /**
810  * z3fold_destroy_pool() - destroys an existing z3fold pool
811  * @pool:       the z3fold pool to be destroyed
812  *
813  * The pool should be emptied before this function is called.
814  */
815 static void z3fold_destroy_pool(struct z3fold_pool *pool)
816 {
817         kmem_cache_destroy(pool->c_handle);
818         z3fold_unregister_migration(pool);
819         destroy_workqueue(pool->release_wq);
820         destroy_workqueue(pool->compact_wq);
821         kfree(pool);
822 }
823
824 /**
825  * z3fold_alloc() - allocates a region of a given size
826  * @pool:       z3fold pool from which to allocate
827  * @size:       size in bytes of the desired allocation
828  * @gfp:        gfp flags used if the pool needs to grow
829  * @handle:     handle of the new allocation
830  *
831  * This function will attempt to find a free region in the pool large enough to
832  * satisfy the allocation request.  A search of the unbuddied lists is
833  * performed first. If no suitable free region is found, then a new page is
834  * allocated and added to the pool to satisfy the request.
835  *
836  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
837  * as z3fold pool pages.
838  *
839  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
840  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
841  * a new page.
842  */
843 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
844                         unsigned long *handle)
845 {
846         int chunks = size_to_chunks(size);
847         struct z3fold_header *zhdr = NULL;
848         struct page *page = NULL;
849         enum buddy bud;
850         bool can_sleep = gfpflags_allow_blocking(gfp);
851
852         if (!size || (gfp & __GFP_HIGHMEM))
853                 return -EINVAL;
854
855         if (size > PAGE_SIZE)
856                 return -ENOSPC;
857
858         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
859                 bud = HEADLESS;
860         else {
861 retry:
862                 zhdr = __z3fold_alloc(pool, size, can_sleep);
863                 if (zhdr) {
864                         if (zhdr->first_chunks == 0) {
865                                 if (zhdr->middle_chunks != 0 &&
866                                     chunks >= zhdr->start_middle)
867                                         bud = LAST;
868                                 else
869                                         bud = FIRST;
870                         } else if (zhdr->last_chunks == 0)
871                                 bud = LAST;
872                         else if (zhdr->middle_chunks == 0)
873                                 bud = MIDDLE;
874                         else {
875                                 if (kref_put(&zhdr->refcount,
876                                              release_z3fold_page_locked))
877                                         atomic64_dec(&pool->pages_nr);
878                                 else
879                                         z3fold_page_unlock(zhdr);
880                                 pr_err("No free chunks in unbuddied\n");
881                                 WARN_ON(1);
882                                 goto retry;
883                         }
884                         page = virt_to_page(zhdr);
885                         goto found;
886                 }
887                 bud = FIRST;
888         }
889
890         page = NULL;
891         if (can_sleep) {
892                 spin_lock(&pool->stale_lock);
893                 zhdr = list_first_entry_or_null(&pool->stale,
894                                                 struct z3fold_header, buddy);
895                 /*
896                  * Before allocating a page, let's see if we can take one from
897                  * the stale pages list. cancel_work_sync() can sleep so we
898                  * limit this case to the contexts where we can sleep
899                  */
900                 if (zhdr) {
901                         list_del(&zhdr->buddy);
902                         spin_unlock(&pool->stale_lock);
903                         cancel_work_sync(&zhdr->work);
904                         page = virt_to_page(zhdr);
905                 } else {
906                         spin_unlock(&pool->stale_lock);
907                 }
908         }
909         if (!page)
910                 page = alloc_page(gfp);
911
912         if (!page)
913                 return -ENOMEM;
914
915         zhdr = init_z3fold_page(page, pool);
916         if (!zhdr) {
917                 __free_page(page);
918                 return -ENOMEM;
919         }
920         atomic64_inc(&pool->pages_nr);
921
922         if (bud == HEADLESS) {
923                 set_bit(PAGE_HEADLESS, &page->private);
924                 goto headless;
925         }
926         __SetPageMovable(page, pool->inode->i_mapping);
927         z3fold_page_lock(zhdr);
928
929 found:
930         if (bud == FIRST)
931                 zhdr->first_chunks = chunks;
932         else if (bud == LAST)
933                 zhdr->last_chunks = chunks;
934         else {
935                 zhdr->middle_chunks = chunks;
936                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
937         }
938         add_to_unbuddied(pool, zhdr);
939
940 headless:
941         spin_lock(&pool->lock);
942         /* Add/move z3fold page to beginning of LRU */
943         if (!list_empty(&page->lru))
944                 list_del(&page->lru);
945
946         list_add(&page->lru, &pool->lru);
947
948         *handle = encode_handle(zhdr, bud);
949         spin_unlock(&pool->lock);
950         if (bud != HEADLESS)
951                 z3fold_page_unlock(zhdr);
952
953         return 0;
954 }
955
956 /**
957  * z3fold_free() - frees the allocation associated with the given handle
958  * @pool:       pool in which the allocation resided
959  * @handle:     handle associated with the allocation returned by z3fold_alloc()
960  *
961  * In the case that the z3fold page in which the allocation resides is under
962  * reclaim, as indicated by the PG_reclaim flag being set, this function
963  * only sets the first|last_chunks to 0.  The page is actually freed
964  * once both buddies are evicted (see z3fold_reclaim_page() below).
965  */
966 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
967 {
968         struct z3fold_header *zhdr;
969         struct page *page;
970         enum buddy bud;
971
972         zhdr = handle_to_z3fold_header(handle);
973         page = virt_to_page(zhdr);
974
975         if (test_bit(PAGE_HEADLESS, &page->private)) {
976                 /* if a headless page is under reclaim, just leave.
977                  * NB: we use test_and_set_bit for a reason: if the bit
978                  * has not been set before, we release this page
979                  * immediately so we don't care about its value any more.
980                  */
981                 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
982                         spin_lock(&pool->lock);
983                         list_del(&page->lru);
984                         spin_unlock(&pool->lock);
985                         free_z3fold_page(page, true);
986                         atomic64_dec(&pool->pages_nr);
987                 }
988                 return;
989         }
990
991         /* Non-headless case */
992         z3fold_page_lock(zhdr);
993         bud = handle_to_buddy(handle);
994
995         switch (bud) {
996         case FIRST:
997                 zhdr->first_chunks = 0;
998                 break;
999         case MIDDLE:
1000                 zhdr->middle_chunks = 0;
1001                 break;
1002         case LAST:
1003                 zhdr->last_chunks = 0;
1004                 break;
1005         default:
1006                 pr_err("%s: unknown bud %d\n", __func__, bud);
1007                 WARN_ON(1);
1008                 z3fold_page_unlock(zhdr);
1009                 return;
1010         }
1011
1012         free_handle(handle);
1013         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1014                 atomic64_dec(&pool->pages_nr);
1015                 return;
1016         }
1017         if (test_bit(PAGE_CLAIMED, &page->private)) {
1018                 z3fold_page_unlock(zhdr);
1019                 return;
1020         }
1021         if (unlikely(PageIsolated(page)) ||
1022             test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1023                 z3fold_page_unlock(zhdr);
1024                 return;
1025         }
1026         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1027                 spin_lock(&pool->lock);
1028                 list_del_init(&zhdr->buddy);
1029                 spin_unlock(&pool->lock);
1030                 zhdr->cpu = -1;
1031                 kref_get(&zhdr->refcount);
1032                 do_compact_page(zhdr, true);
1033                 return;
1034         }
1035         kref_get(&zhdr->refcount);
1036         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1037         z3fold_page_unlock(zhdr);
1038 }
1039
1040 /**
1041  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1042  * @pool:       pool from which a page will attempt to be evicted
1043  * @retries:    number of pages on the LRU list for which eviction will
1044  *              be attempted before failing
1045  *
1046  * z3fold reclaim is different from normal system reclaim in that it is done
1047  * from the bottom, up. This is because only the bottom layer, z3fold, has
1048  * information on how the allocations are organized within each z3fold page.
1049  * This has the potential to create interesting locking situations between
1050  * z3fold and the user, however.
1051  *
1052  * To avoid these, this is how z3fold_reclaim_page() should be called:
1053  *
1054  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1055  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1056  * call the user-defined eviction handler with the pool and handle as
1057  * arguments.
1058  *
1059  * If the handle can not be evicted, the eviction handler should return
1060  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1061  * appropriate list and try the next z3fold page on the LRU up to
1062  * a user defined number of retries.
1063  *
1064  * If the handle is successfully evicted, the eviction handler should
1065  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1066  * contains logic to delay freeing the page if the page is under reclaim,
1067  * as indicated by the setting of the PG_reclaim flag on the underlying page.
1068  *
1069  * If all buddies in the z3fold page are successfully evicted, then the
1070  * z3fold page can be freed.
1071  *
1072  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1073  * no pages to evict or an eviction handler is not registered, -EAGAIN if
1074  * the retry limit was hit.
1075  */
1076 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1077 {
1078         int i, ret = 0;
1079         struct z3fold_header *zhdr = NULL;
1080         struct page *page = NULL;
1081         struct list_head *pos;
1082         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1083
1084         spin_lock(&pool->lock);
1085         if (!pool->ops || !pool->ops->evict || retries == 0) {
1086                 spin_unlock(&pool->lock);
1087                 return -EINVAL;
1088         }
1089         for (i = 0; i < retries; i++) {
1090                 if (list_empty(&pool->lru)) {
1091                         spin_unlock(&pool->lock);
1092                         return -EINVAL;
1093                 }
1094                 list_for_each_prev(pos, &pool->lru) {
1095                         page = list_entry(pos, struct page, lru);
1096
1097                         /* this bit could have been set by free, in which case
1098                          * we pass over to the next page in the pool.
1099                          */
1100                         if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1101                                 continue;
1102
1103                         if (unlikely(PageIsolated(page)))
1104                                 continue;
1105                         if (test_bit(PAGE_HEADLESS, &page->private))
1106                                 break;
1107
1108                         zhdr = page_address(page);
1109                         if (!z3fold_page_trylock(zhdr)) {
1110                                 zhdr = NULL;
1111                                 continue; /* can't evict at this point */
1112                         }
1113                         kref_get(&zhdr->refcount);
1114                         list_del_init(&zhdr->buddy);
1115                         zhdr->cpu = -1;
1116                         break;
1117                 }
1118
1119                 if (!zhdr)
1120                         break;
1121
1122                 list_del_init(&page->lru);
1123                 spin_unlock(&pool->lock);
1124
1125                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1126                         /*
1127                          * We need encode the handles before unlocking, since
1128                          * we can race with free that will set
1129                          * (first|last)_chunks to 0
1130                          */
1131                         first_handle = 0;
1132                         last_handle = 0;
1133                         middle_handle = 0;
1134                         if (zhdr->first_chunks)
1135                                 first_handle = encode_handle(zhdr, FIRST);
1136                         if (zhdr->middle_chunks)
1137                                 middle_handle = encode_handle(zhdr, MIDDLE);
1138                         if (zhdr->last_chunks)
1139                                 last_handle = encode_handle(zhdr, LAST);
1140                         /*
1141                          * it's safe to unlock here because we hold a
1142                          * reference to this page
1143                          */
1144                         z3fold_page_unlock(zhdr);
1145                 } else {
1146                         first_handle = encode_handle(zhdr, HEADLESS);
1147                         last_handle = middle_handle = 0;
1148                 }
1149
1150                 /* Issue the eviction callback(s) */
1151                 if (middle_handle) {
1152                         ret = pool->ops->evict(pool, middle_handle);
1153                         if (ret)
1154                                 goto next;
1155                 }
1156                 if (first_handle) {
1157                         ret = pool->ops->evict(pool, first_handle);
1158                         if (ret)
1159                                 goto next;
1160                 }
1161                 if (last_handle) {
1162                         ret = pool->ops->evict(pool, last_handle);
1163                         if (ret)
1164                                 goto next;
1165                 }
1166 next:
1167                 if (test_bit(PAGE_HEADLESS, &page->private)) {
1168                         if (ret == 0) {
1169                                 free_z3fold_page(page, true);
1170                                 atomic64_dec(&pool->pages_nr);
1171                                 return 0;
1172                         }
1173                         spin_lock(&pool->lock);
1174                         list_add(&page->lru, &pool->lru);
1175                         spin_unlock(&pool->lock);
1176                 } else {
1177                         z3fold_page_lock(zhdr);
1178                         clear_bit(PAGE_CLAIMED, &page->private);
1179                         if (kref_put(&zhdr->refcount,
1180                                         release_z3fold_page_locked)) {
1181                                 atomic64_dec(&pool->pages_nr);
1182                                 return 0;
1183                         }
1184                         /*
1185                          * if we are here, the page is still not completely
1186                          * free. Take the global pool lock then to be able
1187                          * to add it back to the lru list
1188                          */
1189                         spin_lock(&pool->lock);
1190                         list_add(&page->lru, &pool->lru);
1191                         spin_unlock(&pool->lock);
1192                         z3fold_page_unlock(zhdr);
1193                 }
1194
1195                 /* We started off locked to we need to lock the pool back */
1196                 spin_lock(&pool->lock);
1197         }
1198         spin_unlock(&pool->lock);
1199         return -EAGAIN;
1200 }
1201
1202 /**
1203  * z3fold_map() - maps the allocation associated with the given handle
1204  * @pool:       pool in which the allocation resides
1205  * @handle:     handle associated with the allocation to be mapped
1206  *
1207  * Extracts the buddy number from handle and constructs the pointer to the
1208  * correct starting chunk within the page.
1209  *
1210  * Returns: a pointer to the mapped allocation
1211  */
1212 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1213 {
1214         struct z3fold_header *zhdr;
1215         struct page *page;
1216         void *addr;
1217         enum buddy buddy;
1218
1219         zhdr = handle_to_z3fold_header(handle);
1220         addr = zhdr;
1221         page = virt_to_page(zhdr);
1222
1223         if (test_bit(PAGE_HEADLESS, &page->private))
1224                 goto out;
1225
1226         z3fold_page_lock(zhdr);
1227         buddy = handle_to_buddy(handle);
1228         switch (buddy) {
1229         case FIRST:
1230                 addr += ZHDR_SIZE_ALIGNED;
1231                 break;
1232         case MIDDLE:
1233                 addr += zhdr->start_middle << CHUNK_SHIFT;
1234                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1235                 break;
1236         case LAST:
1237                 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1238                 break;
1239         default:
1240                 pr_err("unknown buddy id %d\n", buddy);
1241                 WARN_ON(1);
1242                 addr = NULL;
1243                 break;
1244         }
1245
1246         if (addr)
1247                 zhdr->mapped_count++;
1248         z3fold_page_unlock(zhdr);
1249 out:
1250         return addr;
1251 }
1252
1253 /**
1254  * z3fold_unmap() - unmaps the allocation associated with the given handle
1255  * @pool:       pool in which the allocation resides
1256  * @handle:     handle associated with the allocation to be unmapped
1257  */
1258 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1259 {
1260         struct z3fold_header *zhdr;
1261         struct page *page;
1262         enum buddy buddy;
1263
1264         zhdr = handle_to_z3fold_header(handle);
1265         page = virt_to_page(zhdr);
1266
1267         if (test_bit(PAGE_HEADLESS, &page->private))
1268                 return;
1269
1270         z3fold_page_lock(zhdr);
1271         buddy = handle_to_buddy(handle);
1272         if (buddy == MIDDLE)
1273                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1274         zhdr->mapped_count--;
1275         z3fold_page_unlock(zhdr);
1276 }
1277
1278 /**
1279  * z3fold_get_pool_size() - gets the z3fold pool size in pages
1280  * @pool:       pool whose size is being queried
1281  *
1282  * Returns: size in pages of the given pool.
1283  */
1284 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1285 {
1286         return atomic64_read(&pool->pages_nr);
1287 }
1288
1289 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1290 {
1291         struct z3fold_header *zhdr;
1292         struct z3fold_pool *pool;
1293
1294         VM_BUG_ON_PAGE(!PageMovable(page), page);
1295         VM_BUG_ON_PAGE(PageIsolated(page), page);
1296
1297         if (test_bit(PAGE_HEADLESS, &page->private))
1298                 return false;
1299
1300         zhdr = page_address(page);
1301         z3fold_page_lock(zhdr);
1302         if (test_bit(NEEDS_COMPACTING, &page->private) ||
1303             test_bit(PAGE_STALE, &page->private))
1304                 goto out;
1305
1306         pool = zhdr_to_pool(zhdr);
1307
1308         if (zhdr->mapped_count == 0) {
1309                 kref_get(&zhdr->refcount);
1310                 if (!list_empty(&zhdr->buddy))
1311                         list_del_init(&zhdr->buddy);
1312                 spin_lock(&pool->lock);
1313                 if (!list_empty(&page->lru))
1314                         list_del(&page->lru);
1315                 spin_unlock(&pool->lock);
1316                 z3fold_page_unlock(zhdr);
1317                 return true;
1318         }
1319 out:
1320         z3fold_page_unlock(zhdr);
1321         return false;
1322 }
1323
1324 static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1325                                struct page *page, enum migrate_mode mode)
1326 {
1327         struct z3fold_header *zhdr, *new_zhdr;
1328         struct z3fold_pool *pool;
1329         struct address_space *new_mapping;
1330
1331         VM_BUG_ON_PAGE(!PageMovable(page), page);
1332         VM_BUG_ON_PAGE(!PageIsolated(page), page);
1333
1334         zhdr = page_address(page);
1335         pool = zhdr_to_pool(zhdr);
1336
1337         if (!trylock_page(page))
1338                 return -EAGAIN;
1339
1340         if (!z3fold_page_trylock(zhdr)) {
1341                 unlock_page(page);
1342                 return -EAGAIN;
1343         }
1344         if (zhdr->mapped_count != 0) {
1345                 z3fold_page_unlock(zhdr);
1346                 unlock_page(page);
1347                 return -EBUSY;
1348         }
1349         new_zhdr = page_address(newpage);
1350         memcpy(new_zhdr, zhdr, PAGE_SIZE);
1351         newpage->private = page->private;
1352         page->private = 0;
1353         z3fold_page_unlock(zhdr);
1354         spin_lock_init(&new_zhdr->page_lock);
1355         new_mapping = page_mapping(page);
1356         __ClearPageMovable(page);
1357         ClearPagePrivate(page);
1358
1359         get_page(newpage);
1360         z3fold_page_lock(new_zhdr);
1361         if (new_zhdr->first_chunks)
1362                 encode_handle(new_zhdr, FIRST);
1363         if (new_zhdr->last_chunks)
1364                 encode_handle(new_zhdr, LAST);
1365         if (new_zhdr->middle_chunks)
1366                 encode_handle(new_zhdr, MIDDLE);
1367         set_bit(NEEDS_COMPACTING, &newpage->private);
1368         new_zhdr->cpu = smp_processor_id();
1369         spin_lock(&pool->lock);
1370         list_add(&newpage->lru, &pool->lru);
1371         spin_unlock(&pool->lock);
1372         __SetPageMovable(newpage, new_mapping);
1373         z3fold_page_unlock(new_zhdr);
1374
1375         queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1376
1377         page_mapcount_reset(page);
1378         unlock_page(page);
1379         put_page(page);
1380         return 0;
1381 }
1382
1383 static void z3fold_page_putback(struct page *page)
1384 {
1385         struct z3fold_header *zhdr;
1386         struct z3fold_pool *pool;
1387
1388         zhdr = page_address(page);
1389         pool = zhdr_to_pool(zhdr);
1390
1391         z3fold_page_lock(zhdr);
1392         if (!list_empty(&zhdr->buddy))
1393                 list_del_init(&zhdr->buddy);
1394         INIT_LIST_HEAD(&page->lru);
1395         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1396                 atomic64_dec(&pool->pages_nr);
1397                 return;
1398         }
1399         spin_lock(&pool->lock);
1400         list_add(&page->lru, &pool->lru);
1401         spin_unlock(&pool->lock);
1402         z3fold_page_unlock(zhdr);
1403 }
1404
1405 static const struct address_space_operations z3fold_aops = {
1406         .isolate_page = z3fold_page_isolate,
1407         .migratepage = z3fold_page_migrate,
1408         .putback_page = z3fold_page_putback,
1409 };
1410
1411 /*****************
1412  * zpool
1413  ****************/
1414
1415 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1416 {
1417         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1418                 return pool->zpool_ops->evict(pool->zpool, handle);
1419         else
1420                 return -ENOENT;
1421 }
1422
1423 static const struct z3fold_ops z3fold_zpool_ops = {
1424         .evict =        z3fold_zpool_evict
1425 };
1426
1427 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1428                                const struct zpool_ops *zpool_ops,
1429                                struct zpool *zpool)
1430 {
1431         struct z3fold_pool *pool;
1432
1433         pool = z3fold_create_pool(name, gfp,
1434                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1435         if (pool) {
1436                 pool->zpool = zpool;
1437                 pool->zpool_ops = zpool_ops;
1438         }
1439         return pool;
1440 }
1441
1442 static void z3fold_zpool_destroy(void *pool)
1443 {
1444         z3fold_destroy_pool(pool);
1445 }
1446
1447 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1448                         unsigned long *handle)
1449 {
1450         return z3fold_alloc(pool, size, gfp, handle);
1451 }
1452 static void z3fold_zpool_free(void *pool, unsigned long handle)
1453 {
1454         z3fold_free(pool, handle);
1455 }
1456
1457 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1458                         unsigned int *reclaimed)
1459 {
1460         unsigned int total = 0;
1461         int ret = -EINVAL;
1462
1463         while (total < pages) {
1464                 ret = z3fold_reclaim_page(pool, 8);
1465                 if (ret < 0)
1466                         break;
1467                 total++;
1468         }
1469
1470         if (reclaimed)
1471                 *reclaimed = total;
1472
1473         return ret;
1474 }
1475
1476 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1477                         enum zpool_mapmode mm)
1478 {
1479         return z3fold_map(pool, handle);
1480 }
1481 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1482 {
1483         z3fold_unmap(pool, handle);
1484 }
1485
1486 static u64 z3fold_zpool_total_size(void *pool)
1487 {
1488         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1489 }
1490
1491 static struct zpool_driver z3fold_zpool_driver = {
1492         .type =         "z3fold",
1493         .owner =        THIS_MODULE,
1494         .create =       z3fold_zpool_create,
1495         .destroy =      z3fold_zpool_destroy,
1496         .malloc =       z3fold_zpool_malloc,
1497         .free =         z3fold_zpool_free,
1498         .shrink =       z3fold_zpool_shrink,
1499         .map =          z3fold_zpool_map,
1500         .unmap =        z3fold_zpool_unmap,
1501         .total_size =   z3fold_zpool_total_size,
1502 };
1503
1504 MODULE_ALIAS("zpool-z3fold");
1505
1506 static int __init init_z3fold(void)
1507 {
1508         int ret;
1509
1510         /* Make sure the z3fold header is not larger than the page size */
1511         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1512         ret = z3fold_mount();
1513         if (ret)
1514                 return ret;
1515
1516         zpool_register_driver(&z3fold_zpool_driver);
1517
1518         return 0;
1519 }
1520
1521 static void __exit exit_z3fold(void)
1522 {
1523         z3fold_unmount();
1524         zpool_unregister_driver(&z3fold_zpool_driver);
1525 }
1526
1527 module_init(init_z3fold);
1528 module_exit(exit_z3fold);
1529
1530 MODULE_LICENSE("GPL");
1531 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1532 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");