mm/hmm: add new helper to hotplug CDM memory region
[linux-2.6-microblaze.git] / mm / z3fold.c
1 /*
2  * z3fold.c
3  *
4  * Author: Vitaly Wool <vitaly.wool@konsulko.com>
5  * Copyright (C) 2016, Sony Mobile Communications Inc.
6  *
7  * This implementation is based on zbud written by Seth Jennings.
8  *
9  * z3fold is an special purpose allocator for storing compressed pages. It
10  * can store up to three compressed pages per page which improves the
11  * compression ratio of zbud while retaining its main concepts (e. g. always
12  * storing an integral number of objects per page) and simplicity.
13  * It still has simple and deterministic reclaim properties that make it
14  * preferable to a higher density approach (with no requirement on integral
15  * number of object per page) when reclaim is used.
16  *
17  * As in zbud, pages are divided into "chunks".  The size of the chunks is
18  * fixed at compile time and is determined by NCHUNKS_ORDER below.
19  *
20  * z3fold doesn't export any API and is meant to be used via zpool API.
21  */
22
23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
24
25 #include <linux/atomic.h>
26 #include <linux/sched.h>
27 #include <linux/list.h>
28 #include <linux/mm.h>
29 #include <linux/module.h>
30 #include <linux/percpu.h>
31 #include <linux/preempt.h>
32 #include <linux/workqueue.h>
33 #include <linux/slab.h>
34 #include <linux/spinlock.h>
35 #include <linux/zpool.h>
36
37 /*****************
38  * Structures
39 *****************/
40 struct z3fold_pool;
41 struct z3fold_ops {
42         int (*evict)(struct z3fold_pool *pool, unsigned long handle);
43 };
44
45 enum buddy {
46         HEADLESS = 0,
47         FIRST,
48         MIDDLE,
49         LAST,
50         BUDDIES_MAX
51 };
52
53 /*
54  * struct z3fold_header - z3fold page metadata occupying first chunks of each
55  *                      z3fold page, except for HEADLESS pages
56  * @buddy:              links the z3fold page into the relevant list in the
57  *                      pool
58  * @page_lock:          per-page lock
59  * @refcount:           reference count for the z3fold page
60  * @work:               work_struct for page layout optimization
61  * @pool:               pointer to the pool which this page belongs to
62  * @cpu:                CPU which this page "belongs" to
63  * @first_chunks:       the size of the first buddy in chunks, 0 if free
64  * @middle_chunks:      the size of the middle buddy in chunks, 0 if free
65  * @last_chunks:        the size of the last buddy in chunks, 0 if free
66  * @first_num:          the starting number (for the first handle)
67  */
68 struct z3fold_header {
69         struct list_head buddy;
70         spinlock_t page_lock;
71         struct kref refcount;
72         struct work_struct work;
73         struct z3fold_pool *pool;
74         short cpu;
75         unsigned short first_chunks;
76         unsigned short middle_chunks;
77         unsigned short last_chunks;
78         unsigned short start_middle;
79         unsigned short first_num:2;
80 };
81
82 /*
83  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
84  * adjusting internal fragmentation.  It also determines the number of
85  * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
86  * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
87  * in the beginning of an allocated page are occupied by z3fold header, so
88  * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
89  * which shows the max number of free chunks in z3fold page, also there will
90  * be 63, or 62, respectively, freelists per pool.
91  */
92 #define NCHUNKS_ORDER   6
93
94 #define CHUNK_SHIFT     (PAGE_SHIFT - NCHUNKS_ORDER)
95 #define CHUNK_SIZE      (1 << CHUNK_SHIFT)
96 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
97 #define ZHDR_CHUNKS     (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
98 #define TOTAL_CHUNKS    (PAGE_SIZE >> CHUNK_SHIFT)
99 #define NCHUNKS         ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
100
101 #define BUDDY_MASK      (0x3)
102
103 /**
104  * struct z3fold_pool - stores metadata for each z3fold pool
105  * @name:       pool name
106  * @lock:       protects pool unbuddied/lru lists
107  * @stale_lock: protects pool stale page list
108  * @unbuddied:  per-cpu array of lists tracking z3fold pages that contain 2-
109  *              buddies; the list each z3fold page is added to depends on
110  *              the size of its free region.
111  * @lru:        list tracking the z3fold pages in LRU order by most recently
112  *              added buddy.
113  * @stale:      list of pages marked for freeing
114  * @pages_nr:   number of z3fold pages in the pool.
115  * @ops:        pointer to a structure of user defined operations specified at
116  *              pool creation time.
117  * @compact_wq: workqueue for page layout background optimization
118  * @release_wq: workqueue for safe page release
119  * @work:       work_struct for safe page release
120  *
121  * This structure is allocated at pool creation time and maintains metadata
122  * pertaining to a particular z3fold pool.
123  */
124 struct z3fold_pool {
125         const char *name;
126         spinlock_t lock;
127         spinlock_t stale_lock;
128         struct list_head *unbuddied;
129         struct list_head lru;
130         struct list_head stale;
131         atomic64_t pages_nr;
132         const struct z3fold_ops *ops;
133         struct zpool *zpool;
134         const struct zpool_ops *zpool_ops;
135         struct workqueue_struct *compact_wq;
136         struct workqueue_struct *release_wq;
137         struct work_struct work;
138 };
139
140 /*
141  * Internal z3fold page flags
142  */
143 enum z3fold_page_flags {
144         PAGE_HEADLESS = 0,
145         MIDDLE_CHUNK_MAPPED,
146         NEEDS_COMPACTING,
147         PAGE_STALE
148 };
149
150 /*****************
151  * Helpers
152 *****************/
153
154 /* Converts an allocation size in bytes to size in z3fold chunks */
155 static int size_to_chunks(size_t size)
156 {
157         return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
158 }
159
160 #define for_each_unbuddied_list(_iter, _begin) \
161         for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
162
163 static void compact_page_work(struct work_struct *w);
164
165 /* Initializes the z3fold header of a newly allocated z3fold page */
166 static struct z3fold_header *init_z3fold_page(struct page *page,
167                                         struct z3fold_pool *pool)
168 {
169         struct z3fold_header *zhdr = page_address(page);
170
171         INIT_LIST_HEAD(&page->lru);
172         clear_bit(PAGE_HEADLESS, &page->private);
173         clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
174         clear_bit(NEEDS_COMPACTING, &page->private);
175         clear_bit(PAGE_STALE, &page->private);
176
177         spin_lock_init(&zhdr->page_lock);
178         kref_init(&zhdr->refcount);
179         zhdr->first_chunks = 0;
180         zhdr->middle_chunks = 0;
181         zhdr->last_chunks = 0;
182         zhdr->first_num = 0;
183         zhdr->start_middle = 0;
184         zhdr->cpu = -1;
185         zhdr->pool = pool;
186         INIT_LIST_HEAD(&zhdr->buddy);
187         INIT_WORK(&zhdr->work, compact_page_work);
188         return zhdr;
189 }
190
191 /* Resets the struct page fields and frees the page */
192 static void free_z3fold_page(struct page *page)
193 {
194         __free_page(page);
195 }
196
197 /* Lock a z3fold page */
198 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
199 {
200         spin_lock(&zhdr->page_lock);
201 }
202
203 /* Try to lock a z3fold page */
204 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
205 {
206         return spin_trylock(&zhdr->page_lock);
207 }
208
209 /* Unlock a z3fold page */
210 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
211 {
212         spin_unlock(&zhdr->page_lock);
213 }
214
215 /*
216  * Encodes the handle of a particular buddy within a z3fold page
217  * Pool lock should be held as this function accesses first_num
218  */
219 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
220 {
221         unsigned long handle;
222
223         handle = (unsigned long)zhdr;
224         if (bud != HEADLESS)
225                 handle += (bud + zhdr->first_num) & BUDDY_MASK;
226         return handle;
227 }
228
229 /* Returns the z3fold page where a given handle is stored */
230 static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
231 {
232         return (struct z3fold_header *)(handle & PAGE_MASK);
233 }
234
235 /*
236  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
237  *  but that doesn't matter. because the masking will result in the
238  *  correct buddy number.
239  */
240 static enum buddy handle_to_buddy(unsigned long handle)
241 {
242         struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
243         return (handle - zhdr->first_num) & BUDDY_MASK;
244 }
245
246 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
247 {
248         struct page *page = virt_to_page(zhdr);
249         struct z3fold_pool *pool = zhdr->pool;
250
251         WARN_ON(!list_empty(&zhdr->buddy));
252         set_bit(PAGE_STALE, &page->private);
253         spin_lock(&pool->lock);
254         if (!list_empty(&page->lru))
255                 list_del(&page->lru);
256         spin_unlock(&pool->lock);
257         if (locked)
258                 z3fold_page_unlock(zhdr);
259         spin_lock(&pool->stale_lock);
260         list_add(&zhdr->buddy, &pool->stale);
261         queue_work(pool->release_wq, &pool->work);
262         spin_unlock(&pool->stale_lock);
263 }
264
265 static void __attribute__((__unused__))
266                         release_z3fold_page(struct kref *ref)
267 {
268         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
269                                                 refcount);
270         __release_z3fold_page(zhdr, false);
271 }
272
273 static void release_z3fold_page_locked(struct kref *ref)
274 {
275         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
276                                                 refcount);
277         WARN_ON(z3fold_page_trylock(zhdr));
278         __release_z3fold_page(zhdr, true);
279 }
280
281 static void release_z3fold_page_locked_list(struct kref *ref)
282 {
283         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
284                                                refcount);
285         spin_lock(&zhdr->pool->lock);
286         list_del_init(&zhdr->buddy);
287         spin_unlock(&zhdr->pool->lock);
288
289         WARN_ON(z3fold_page_trylock(zhdr));
290         __release_z3fold_page(zhdr, true);
291 }
292
293 static void free_pages_work(struct work_struct *w)
294 {
295         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
296
297         spin_lock(&pool->stale_lock);
298         while (!list_empty(&pool->stale)) {
299                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
300                                                 struct z3fold_header, buddy);
301                 struct page *page = virt_to_page(zhdr);
302
303                 list_del(&zhdr->buddy);
304                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
305                         continue;
306                 clear_bit(NEEDS_COMPACTING, &page->private);
307                 spin_unlock(&pool->stale_lock);
308                 cancel_work_sync(&zhdr->work);
309                 free_z3fold_page(page);
310                 cond_resched();
311                 spin_lock(&pool->stale_lock);
312         }
313         spin_unlock(&pool->stale_lock);
314 }
315
316 /*
317  * Returns the number of free chunks in a z3fold page.
318  * NB: can't be used with HEADLESS pages.
319  */
320 static int num_free_chunks(struct z3fold_header *zhdr)
321 {
322         int nfree;
323         /*
324          * If there is a middle object, pick up the bigger free space
325          * either before or after it. Otherwise just subtract the number
326          * of chunks occupied by the first and the last objects.
327          */
328         if (zhdr->middle_chunks != 0) {
329                 int nfree_before = zhdr->first_chunks ?
330                         0 : zhdr->start_middle - ZHDR_CHUNKS;
331                 int nfree_after = zhdr->last_chunks ?
332                         0 : TOTAL_CHUNKS -
333                                 (zhdr->start_middle + zhdr->middle_chunks);
334                 nfree = max(nfree_before, nfree_after);
335         } else
336                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
337         return nfree;
338 }
339
340 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
341                                 unsigned short dst_chunk)
342 {
343         void *beg = zhdr;
344         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
345                        beg + (zhdr->start_middle << CHUNK_SHIFT),
346                        zhdr->middle_chunks << CHUNK_SHIFT);
347 }
348
349 #define BIG_CHUNK_GAP   3
350 /* Has to be called with lock held */
351 static int z3fold_compact_page(struct z3fold_header *zhdr)
352 {
353         struct page *page = virt_to_page(zhdr);
354
355         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
356                 return 0; /* can't move middle chunk, it's used */
357
358         if (zhdr->middle_chunks == 0)
359                 return 0; /* nothing to compact */
360
361         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
362                 /* move to the beginning */
363                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
364                 zhdr->first_chunks = zhdr->middle_chunks;
365                 zhdr->middle_chunks = 0;
366                 zhdr->start_middle = 0;
367                 zhdr->first_num++;
368                 return 1;
369         }
370
371         /*
372          * moving data is expensive, so let's only do that if
373          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
374          */
375         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
376             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
377                         BIG_CHUNK_GAP) {
378                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
379                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
380                 return 1;
381         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
382                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
383                                         + zhdr->middle_chunks) >=
384                         BIG_CHUNK_GAP) {
385                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
386                         zhdr->middle_chunks;
387                 mchunk_memmove(zhdr, new_start);
388                 zhdr->start_middle = new_start;
389                 return 1;
390         }
391
392         return 0;
393 }
394
395 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
396 {
397         struct z3fold_pool *pool = zhdr->pool;
398         struct page *page;
399         struct list_head *unbuddied;
400         int fchunks;
401
402         page = virt_to_page(zhdr);
403         if (locked)
404                 WARN_ON(z3fold_page_trylock(zhdr));
405         else
406                 z3fold_page_lock(zhdr);
407         if (test_bit(PAGE_STALE, &page->private) ||
408             !test_and_clear_bit(NEEDS_COMPACTING, &page->private)) {
409                 z3fold_page_unlock(zhdr);
410                 return;
411         }
412         spin_lock(&pool->lock);
413         list_del_init(&zhdr->buddy);
414         spin_unlock(&pool->lock);
415
416         z3fold_compact_page(zhdr);
417         unbuddied = get_cpu_ptr(pool->unbuddied);
418         fchunks = num_free_chunks(zhdr);
419         if (fchunks < NCHUNKS &&
420             (!zhdr->first_chunks || !zhdr->middle_chunks ||
421                         !zhdr->last_chunks)) {
422                 /* the page's not completely free and it's unbuddied */
423                 spin_lock(&pool->lock);
424                 list_add(&zhdr->buddy, &unbuddied[fchunks]);
425                 spin_unlock(&pool->lock);
426                 zhdr->cpu = smp_processor_id();
427         }
428         put_cpu_ptr(pool->unbuddied);
429         z3fold_page_unlock(zhdr);
430 }
431
432 static void compact_page_work(struct work_struct *w)
433 {
434         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
435                                                 work);
436
437         do_compact_page(zhdr, false);
438 }
439
440
441 /*
442  * API Functions
443  */
444
445 /**
446  * z3fold_create_pool() - create a new z3fold pool
447  * @name:       pool name
448  * @gfp:        gfp flags when allocating the z3fold pool structure
449  * @ops:        user-defined operations for the z3fold pool
450  *
451  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
452  * failed.
453  */
454 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
455                 const struct z3fold_ops *ops)
456 {
457         struct z3fold_pool *pool = NULL;
458         int i, cpu;
459
460         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
461         if (!pool)
462                 goto out;
463         spin_lock_init(&pool->lock);
464         spin_lock_init(&pool->stale_lock);
465         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
466         for_each_possible_cpu(cpu) {
467                 struct list_head *unbuddied =
468                                 per_cpu_ptr(pool->unbuddied, cpu);
469                 for_each_unbuddied_list(i, 0)
470                         INIT_LIST_HEAD(&unbuddied[i]);
471         }
472         INIT_LIST_HEAD(&pool->lru);
473         INIT_LIST_HEAD(&pool->stale);
474         atomic64_set(&pool->pages_nr, 0);
475         pool->name = name;
476         pool->compact_wq = create_singlethread_workqueue(pool->name);
477         if (!pool->compact_wq)
478                 goto out;
479         pool->release_wq = create_singlethread_workqueue(pool->name);
480         if (!pool->release_wq)
481                 goto out_wq;
482         INIT_WORK(&pool->work, free_pages_work);
483         pool->ops = ops;
484         return pool;
485
486 out_wq:
487         destroy_workqueue(pool->compact_wq);
488 out:
489         kfree(pool);
490         return NULL;
491 }
492
493 /**
494  * z3fold_destroy_pool() - destroys an existing z3fold pool
495  * @pool:       the z3fold pool to be destroyed
496  *
497  * The pool should be emptied before this function is called.
498  */
499 static void z3fold_destroy_pool(struct z3fold_pool *pool)
500 {
501         destroy_workqueue(pool->release_wq);
502         destroy_workqueue(pool->compact_wq);
503         kfree(pool);
504 }
505
506 /**
507  * z3fold_alloc() - allocates a region of a given size
508  * @pool:       z3fold pool from which to allocate
509  * @size:       size in bytes of the desired allocation
510  * @gfp:        gfp flags used if the pool needs to grow
511  * @handle:     handle of the new allocation
512  *
513  * This function will attempt to find a free region in the pool large enough to
514  * satisfy the allocation request.  A search of the unbuddied lists is
515  * performed first. If no suitable free region is found, then a new page is
516  * allocated and added to the pool to satisfy the request.
517  *
518  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
519  * as z3fold pool pages.
520  *
521  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
522  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
523  * a new page.
524  */
525 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
526                         unsigned long *handle)
527 {
528         int chunks = 0, i, freechunks;
529         struct z3fold_header *zhdr = NULL;
530         struct page *page = NULL;
531         enum buddy bud;
532         bool can_sleep = (gfp & __GFP_RECLAIM) == __GFP_RECLAIM;
533
534         if (!size || (gfp & __GFP_HIGHMEM))
535                 return -EINVAL;
536
537         if (size > PAGE_SIZE)
538                 return -ENOSPC;
539
540         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
541                 bud = HEADLESS;
542         else {
543                 struct list_head *unbuddied;
544                 chunks = size_to_chunks(size);
545
546 lookup:
547                 /* First, try to find an unbuddied z3fold page. */
548                 unbuddied = get_cpu_ptr(pool->unbuddied);
549                 for_each_unbuddied_list(i, chunks) {
550                         struct list_head *l = &unbuddied[i];
551
552                         zhdr = list_first_entry_or_null(READ_ONCE(l),
553                                                 struct z3fold_header, buddy);
554
555                         if (!zhdr)
556                                 continue;
557
558                         /* Re-check under lock. */
559                         spin_lock(&pool->lock);
560                         l = &unbuddied[i];
561                         if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
562                                         struct z3fold_header, buddy)) ||
563                             !z3fold_page_trylock(zhdr)) {
564                                 spin_unlock(&pool->lock);
565                                 put_cpu_ptr(pool->unbuddied);
566                                 goto lookup;
567                         }
568                         list_del_init(&zhdr->buddy);
569                         zhdr->cpu = -1;
570                         spin_unlock(&pool->lock);
571
572                         page = virt_to_page(zhdr);
573                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
574                                 z3fold_page_unlock(zhdr);
575                                 zhdr = NULL;
576                                 put_cpu_ptr(pool->unbuddied);
577                                 if (can_sleep)
578                                         cond_resched();
579                                 goto lookup;
580                         }
581
582                         /*
583                          * this page could not be removed from its unbuddied
584                          * list while pool lock was held, and then we've taken
585                          * page lock so kref_put could not be called before
586                          * we got here, so it's safe to just call kref_get()
587                          */
588                         kref_get(&zhdr->refcount);
589                         break;
590                 }
591                 put_cpu_ptr(pool->unbuddied);
592
593                 if (zhdr) {
594                         if (zhdr->first_chunks == 0) {
595                                 if (zhdr->middle_chunks != 0 &&
596                                     chunks >= zhdr->start_middle)
597                                         bud = LAST;
598                                 else
599                                         bud = FIRST;
600                         } else if (zhdr->last_chunks == 0)
601                                 bud = LAST;
602                         else if (zhdr->middle_chunks == 0)
603                                 bud = MIDDLE;
604                         else {
605                                 if (kref_put(&zhdr->refcount,
606                                              release_z3fold_page_locked))
607                                         atomic64_dec(&pool->pages_nr);
608                                 else
609                                         z3fold_page_unlock(zhdr);
610                                 pr_err("No free chunks in unbuddied\n");
611                                 WARN_ON(1);
612                                 goto lookup;
613                         }
614                         goto found;
615                 }
616                 bud = FIRST;
617         }
618
619         spin_lock(&pool->stale_lock);
620         zhdr = list_first_entry_or_null(&pool->stale,
621                                         struct z3fold_header, buddy);
622         /*
623          * Before allocating a page, let's see if we can take one from the
624          * stale pages list. cancel_work_sync() can sleep so we must make
625          * sure it won't be called in case we're in atomic context.
626          */
627         if (zhdr && (can_sleep || !work_pending(&zhdr->work) ||
628             !unlikely(work_busy(&zhdr->work)))) {
629                 list_del(&zhdr->buddy);
630                 clear_bit(NEEDS_COMPACTING, &page->private);
631                 spin_unlock(&pool->stale_lock);
632                 if (can_sleep)
633                         cancel_work_sync(&zhdr->work);
634                 page = virt_to_page(zhdr);
635         } else {
636                 spin_unlock(&pool->stale_lock);
637                 page = alloc_page(gfp);
638         }
639
640         if (!page)
641                 return -ENOMEM;
642
643         atomic64_inc(&pool->pages_nr);
644         zhdr = init_z3fold_page(page, pool);
645
646         if (bud == HEADLESS) {
647                 set_bit(PAGE_HEADLESS, &page->private);
648                 goto headless;
649         }
650         z3fold_page_lock(zhdr);
651
652 found:
653         if (bud == FIRST)
654                 zhdr->first_chunks = chunks;
655         else if (bud == LAST)
656                 zhdr->last_chunks = chunks;
657         else {
658                 zhdr->middle_chunks = chunks;
659                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
660         }
661
662         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
663                         zhdr->middle_chunks == 0) {
664                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
665
666                 /* Add to unbuddied list */
667                 freechunks = num_free_chunks(zhdr);
668                 spin_lock(&pool->lock);
669                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
670                 spin_unlock(&pool->lock);
671                 zhdr->cpu = smp_processor_id();
672                 put_cpu_ptr(pool->unbuddied);
673         }
674
675 headless:
676         spin_lock(&pool->lock);
677         /* Add/move z3fold page to beginning of LRU */
678         if (!list_empty(&page->lru))
679                 list_del(&page->lru);
680
681         list_add(&page->lru, &pool->lru);
682
683         *handle = encode_handle(zhdr, bud);
684         spin_unlock(&pool->lock);
685         if (bud != HEADLESS)
686                 z3fold_page_unlock(zhdr);
687
688         return 0;
689 }
690
691 /**
692  * z3fold_free() - frees the allocation associated with the given handle
693  * @pool:       pool in which the allocation resided
694  * @handle:     handle associated with the allocation returned by z3fold_alloc()
695  *
696  * In the case that the z3fold page in which the allocation resides is under
697  * reclaim, as indicated by the PG_reclaim flag being set, this function
698  * only sets the first|last_chunks to 0.  The page is actually freed
699  * once both buddies are evicted (see z3fold_reclaim_page() below).
700  */
701 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
702 {
703         struct z3fold_header *zhdr;
704         struct page *page;
705         enum buddy bud;
706
707         zhdr = handle_to_z3fold_header(handle);
708         page = virt_to_page(zhdr);
709
710         if (test_bit(PAGE_HEADLESS, &page->private)) {
711                 /* HEADLESS page stored */
712                 bud = HEADLESS;
713         } else {
714                 z3fold_page_lock(zhdr);
715                 bud = handle_to_buddy(handle);
716
717                 switch (bud) {
718                 case FIRST:
719                         zhdr->first_chunks = 0;
720                         break;
721                 case MIDDLE:
722                         zhdr->middle_chunks = 0;
723                         zhdr->start_middle = 0;
724                         break;
725                 case LAST:
726                         zhdr->last_chunks = 0;
727                         break;
728                 default:
729                         pr_err("%s: unknown bud %d\n", __func__, bud);
730                         WARN_ON(1);
731                         z3fold_page_unlock(zhdr);
732                         return;
733                 }
734         }
735
736         if (bud == HEADLESS) {
737                 spin_lock(&pool->lock);
738                 list_del(&page->lru);
739                 spin_unlock(&pool->lock);
740                 free_z3fold_page(page);
741                 atomic64_dec(&pool->pages_nr);
742                 return;
743         }
744
745         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
746                 atomic64_dec(&pool->pages_nr);
747                 return;
748         }
749         if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
750                 z3fold_page_unlock(zhdr);
751                 return;
752         }
753         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
754                 spin_lock(&pool->lock);
755                 list_del_init(&zhdr->buddy);
756                 spin_unlock(&pool->lock);
757                 zhdr->cpu = -1;
758                 do_compact_page(zhdr, true);
759                 return;
760         }
761         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
762         z3fold_page_unlock(zhdr);
763 }
764
765 /**
766  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
767  * @pool:       pool from which a page will attempt to be evicted
768  * @retires:    number of pages on the LRU list for which eviction will
769  *              be attempted before failing
770  *
771  * z3fold reclaim is different from normal system reclaim in that it is done
772  * from the bottom, up. This is because only the bottom layer, z3fold, has
773  * information on how the allocations are organized within each z3fold page.
774  * This has the potential to create interesting locking situations between
775  * z3fold and the user, however.
776  *
777  * To avoid these, this is how z3fold_reclaim_page() should be called:
778
779  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
780  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
781  * call the user-defined eviction handler with the pool and handle as
782  * arguments.
783  *
784  * If the handle can not be evicted, the eviction handler should return
785  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
786  * appropriate list and try the next z3fold page on the LRU up to
787  * a user defined number of retries.
788  *
789  * If the handle is successfully evicted, the eviction handler should
790  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
791  * contains logic to delay freeing the page if the page is under reclaim,
792  * as indicated by the setting of the PG_reclaim flag on the underlying page.
793  *
794  * If all buddies in the z3fold page are successfully evicted, then the
795  * z3fold page can be freed.
796  *
797  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
798  * no pages to evict or an eviction handler is not registered, -EAGAIN if
799  * the retry limit was hit.
800  */
801 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
802 {
803         int i, ret = 0;
804         struct z3fold_header *zhdr = NULL;
805         struct page *page = NULL;
806         struct list_head *pos;
807         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
808
809         spin_lock(&pool->lock);
810         if (!pool->ops || !pool->ops->evict || retries == 0) {
811                 spin_unlock(&pool->lock);
812                 return -EINVAL;
813         }
814         for (i = 0; i < retries; i++) {
815                 if (list_empty(&pool->lru)) {
816                         spin_unlock(&pool->lock);
817                         return -EINVAL;
818                 }
819                 list_for_each_prev(pos, &pool->lru) {
820                         page = list_entry(pos, struct page, lru);
821                         if (test_bit(PAGE_HEADLESS, &page->private))
822                                 /* candidate found */
823                                 break;
824
825                         zhdr = page_address(page);
826                         if (!z3fold_page_trylock(zhdr))
827                                 continue; /* can't evict at this point */
828                         kref_get(&zhdr->refcount);
829                         list_del_init(&zhdr->buddy);
830                         zhdr->cpu = -1;
831                 }
832
833                 list_del_init(&page->lru);
834                 spin_unlock(&pool->lock);
835
836                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
837                         /*
838                          * We need encode the handles before unlocking, since
839                          * we can race with free that will set
840                          * (first|last)_chunks to 0
841                          */
842                         first_handle = 0;
843                         last_handle = 0;
844                         middle_handle = 0;
845                         if (zhdr->first_chunks)
846                                 first_handle = encode_handle(zhdr, FIRST);
847                         if (zhdr->middle_chunks)
848                                 middle_handle = encode_handle(zhdr, MIDDLE);
849                         if (zhdr->last_chunks)
850                                 last_handle = encode_handle(zhdr, LAST);
851                         /*
852                          * it's safe to unlock here because we hold a
853                          * reference to this page
854                          */
855                         z3fold_page_unlock(zhdr);
856                 } else {
857                         first_handle = encode_handle(zhdr, HEADLESS);
858                         last_handle = middle_handle = 0;
859                 }
860
861                 /* Issue the eviction callback(s) */
862                 if (middle_handle) {
863                         ret = pool->ops->evict(pool, middle_handle);
864                         if (ret)
865                                 goto next;
866                 }
867                 if (first_handle) {
868                         ret = pool->ops->evict(pool, first_handle);
869                         if (ret)
870                                 goto next;
871                 }
872                 if (last_handle) {
873                         ret = pool->ops->evict(pool, last_handle);
874                         if (ret)
875                                 goto next;
876                 }
877 next:
878                 if (test_bit(PAGE_HEADLESS, &page->private)) {
879                         if (ret == 0) {
880                                 free_z3fold_page(page);
881                                 return 0;
882                         }
883                 } else if (kref_put(&zhdr->refcount, release_z3fold_page)) {
884                         atomic64_dec(&pool->pages_nr);
885                         return 0;
886                 }
887                 spin_lock(&pool->lock);
888
889                 /*
890                  * Add to the beginning of LRU.
891                  * Pool lock has to be kept here to ensure the page has
892                  * not already been released
893                  */
894                 list_add(&page->lru, &pool->lru);
895         }
896         spin_unlock(&pool->lock);
897         return -EAGAIN;
898 }
899
900 /**
901  * z3fold_map() - maps the allocation associated with the given handle
902  * @pool:       pool in which the allocation resides
903  * @handle:     handle associated with the allocation to be mapped
904  *
905  * Extracts the buddy number from handle and constructs the pointer to the
906  * correct starting chunk within the page.
907  *
908  * Returns: a pointer to the mapped allocation
909  */
910 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
911 {
912         struct z3fold_header *zhdr;
913         struct page *page;
914         void *addr;
915         enum buddy buddy;
916
917         zhdr = handle_to_z3fold_header(handle);
918         addr = zhdr;
919         page = virt_to_page(zhdr);
920
921         if (test_bit(PAGE_HEADLESS, &page->private))
922                 goto out;
923
924         z3fold_page_lock(zhdr);
925         buddy = handle_to_buddy(handle);
926         switch (buddy) {
927         case FIRST:
928                 addr += ZHDR_SIZE_ALIGNED;
929                 break;
930         case MIDDLE:
931                 addr += zhdr->start_middle << CHUNK_SHIFT;
932                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
933                 break;
934         case LAST:
935                 addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
936                 break;
937         default:
938                 pr_err("unknown buddy id %d\n", buddy);
939                 WARN_ON(1);
940                 addr = NULL;
941                 break;
942         }
943
944         z3fold_page_unlock(zhdr);
945 out:
946         return addr;
947 }
948
949 /**
950  * z3fold_unmap() - unmaps the allocation associated with the given handle
951  * @pool:       pool in which the allocation resides
952  * @handle:     handle associated with the allocation to be unmapped
953  */
954 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
955 {
956         struct z3fold_header *zhdr;
957         struct page *page;
958         enum buddy buddy;
959
960         zhdr = handle_to_z3fold_header(handle);
961         page = virt_to_page(zhdr);
962
963         if (test_bit(PAGE_HEADLESS, &page->private))
964                 return;
965
966         z3fold_page_lock(zhdr);
967         buddy = handle_to_buddy(handle);
968         if (buddy == MIDDLE)
969                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
970         z3fold_page_unlock(zhdr);
971 }
972
973 /**
974  * z3fold_get_pool_size() - gets the z3fold pool size in pages
975  * @pool:       pool whose size is being queried
976  *
977  * Returns: size in pages of the given pool.
978  */
979 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
980 {
981         return atomic64_read(&pool->pages_nr);
982 }
983
984 /*****************
985  * zpool
986  ****************/
987
988 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
989 {
990         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
991                 return pool->zpool_ops->evict(pool->zpool, handle);
992         else
993                 return -ENOENT;
994 }
995
996 static const struct z3fold_ops z3fold_zpool_ops = {
997         .evict =        z3fold_zpool_evict
998 };
999
1000 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1001                                const struct zpool_ops *zpool_ops,
1002                                struct zpool *zpool)
1003 {
1004         struct z3fold_pool *pool;
1005
1006         pool = z3fold_create_pool(name, gfp,
1007                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1008         if (pool) {
1009                 pool->zpool = zpool;
1010                 pool->zpool_ops = zpool_ops;
1011         }
1012         return pool;
1013 }
1014
1015 static void z3fold_zpool_destroy(void *pool)
1016 {
1017         z3fold_destroy_pool(pool);
1018 }
1019
1020 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1021                         unsigned long *handle)
1022 {
1023         return z3fold_alloc(pool, size, gfp, handle);
1024 }
1025 static void z3fold_zpool_free(void *pool, unsigned long handle)
1026 {
1027         z3fold_free(pool, handle);
1028 }
1029
1030 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1031                         unsigned int *reclaimed)
1032 {
1033         unsigned int total = 0;
1034         int ret = -EINVAL;
1035
1036         while (total < pages) {
1037                 ret = z3fold_reclaim_page(pool, 8);
1038                 if (ret < 0)
1039                         break;
1040                 total++;
1041         }
1042
1043         if (reclaimed)
1044                 *reclaimed = total;
1045
1046         return ret;
1047 }
1048
1049 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1050                         enum zpool_mapmode mm)
1051 {
1052         return z3fold_map(pool, handle);
1053 }
1054 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1055 {
1056         z3fold_unmap(pool, handle);
1057 }
1058
1059 static u64 z3fold_zpool_total_size(void *pool)
1060 {
1061         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1062 }
1063
1064 static struct zpool_driver z3fold_zpool_driver = {
1065         .type =         "z3fold",
1066         .owner =        THIS_MODULE,
1067         .create =       z3fold_zpool_create,
1068         .destroy =      z3fold_zpool_destroy,
1069         .malloc =       z3fold_zpool_malloc,
1070         .free =         z3fold_zpool_free,
1071         .shrink =       z3fold_zpool_shrink,
1072         .map =          z3fold_zpool_map,
1073         .unmap =        z3fold_zpool_unmap,
1074         .total_size =   z3fold_zpool_total_size,
1075 };
1076
1077 MODULE_ALIAS("zpool-z3fold");
1078
1079 static int __init init_z3fold(void)
1080 {
1081         /* Make sure the z3fold header is not larger than the page size */
1082         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1083         zpool_register_driver(&z3fold_zpool_driver);
1084
1085         return 0;
1086 }
1087
1088 static void __exit exit_z3fold(void)
1089 {
1090         zpool_unregister_driver(&z3fold_zpool_driver);
1091 }
1092
1093 module_init(init_z3fold);
1094 module_exit(exit_z3fold);
1095
1096 MODULE_LICENSE("GPL");
1097 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1098 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");