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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*****************/
40struct z3fold_pool;
41struct z3fold_ops {
42 int (*evict)(struct z3fold_pool *pool, unsigned long handle);
43};
44
45enum 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 */
68struct 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 */
124struct 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 */
143enum z3fold_page_flags {
144 PAGE_HEADLESS = 0,
145 MIDDLE_CHUNK_MAPPED,
146 NEEDS_COMPACTING,
147 PAGE_STALE,
148 UNDER_RECLAIM
149};
150
151/*****************
152 * Helpers
153*****************/
154
155/* Converts an allocation size in bytes to size in z3fold chunks */
156static int size_to_chunks(size_t size)
157{
158 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
159}
160
161#define for_each_unbuddied_list(_iter, _begin) \
162 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
163
164static void compact_page_work(struct work_struct *w);
165
166/* Initializes the z3fold header of a newly allocated z3fold page */
167static struct z3fold_header *init_z3fold_page(struct page *page,
168 struct z3fold_pool *pool)
169{
170 struct z3fold_header *zhdr = page_address(page);
171
172 INIT_LIST_HEAD(&page->lru);
173 clear_bit(PAGE_HEADLESS, &page->private);
174 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
175 clear_bit(NEEDS_COMPACTING, &page->private);
176 clear_bit(PAGE_STALE, &page->private);
177 clear_bit(UNDER_RECLAIM, &page->private);
178
179 spin_lock_init(&zhdr->page_lock);
180 kref_init(&zhdr->refcount);
181 zhdr->first_chunks = 0;
182 zhdr->middle_chunks = 0;
183 zhdr->last_chunks = 0;
184 zhdr->first_num = 0;
185 zhdr->start_middle = 0;
186 zhdr->cpu = -1;
187 zhdr->pool = pool;
188 INIT_LIST_HEAD(&zhdr->buddy);
189 INIT_WORK(&zhdr->work, compact_page_work);
190 return zhdr;
191}
192
193/* Resets the struct page fields and frees the page */
194static void free_z3fold_page(struct page *page)
195{
196 __free_page(page);
197}
198
199/* Lock a z3fold page */
200static inline void z3fold_page_lock(struct z3fold_header *zhdr)
201{
202 spin_lock(&zhdr->page_lock);
203}
204
205/* Try to lock a z3fold page */
206static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
207{
208 return spin_trylock(&zhdr->page_lock);
209}
210
211/* Unlock a z3fold page */
212static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
213{
214 spin_unlock(&zhdr->page_lock);
215}
216
217/*
218 * Encodes the handle of a particular buddy within a z3fold page
219 * Pool lock should be held as this function accesses first_num
220 */
221static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
222{
223 unsigned long handle;
224
225 handle = (unsigned long)zhdr;
226 if (bud != HEADLESS)
227 handle += (bud + zhdr->first_num) & BUDDY_MASK;
228 return handle;
229}
230
231/* Returns the z3fold page where a given handle is stored */
232static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
233{
234 return (struct z3fold_header *)(handle & PAGE_MASK);
235}
236
237/*
238 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
239 * but that doesn't matter. because the masking will result in the
240 * correct buddy number.
241 */
242static enum buddy handle_to_buddy(unsigned long handle)
243{
244 struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
245 return (handle - zhdr->first_num) & BUDDY_MASK;
246}
247
248static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
249{
250 struct page *page = virt_to_page(zhdr);
251 struct z3fold_pool *pool = zhdr->pool;
252
253 WARN_ON(!list_empty(&zhdr->buddy));
254 set_bit(PAGE_STALE, &page->private);
255 clear_bit(NEEDS_COMPACTING, &page->private);
256 spin_lock(&pool->lock);
257 if (!list_empty(&page->lru))
258 list_del(&page->lru);
259 spin_unlock(&pool->lock);
260 if (locked)
261 z3fold_page_unlock(zhdr);
262 spin_lock(&pool->stale_lock);
263 list_add(&zhdr->buddy, &pool->stale);
264 queue_work(pool->release_wq, &pool->work);
265 spin_unlock(&pool->stale_lock);
266}
267
268static void __attribute__((__unused__))
269 release_z3fold_page(struct kref *ref)
270{
271 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
272 refcount);
273 __release_z3fold_page(zhdr, false);
274}
275
276static void release_z3fold_page_locked(struct kref *ref)
277{
278 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
279 refcount);
280 WARN_ON(z3fold_page_trylock(zhdr));
281 __release_z3fold_page(zhdr, true);
282}
283
284static void release_z3fold_page_locked_list(struct kref *ref)
285{
286 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
287 refcount);
288 spin_lock(&zhdr->pool->lock);
289 list_del_init(&zhdr->buddy);
290 spin_unlock(&zhdr->pool->lock);
291
292 WARN_ON(z3fold_page_trylock(zhdr));
293 __release_z3fold_page(zhdr, true);
294}
295
296static void free_pages_work(struct work_struct *w)
297{
298 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
299
300 spin_lock(&pool->stale_lock);
301 while (!list_empty(&pool->stale)) {
302 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
303 struct z3fold_header, buddy);
304 struct page *page = virt_to_page(zhdr);
305
306 list_del(&zhdr->buddy);
307 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
308 continue;
309 spin_unlock(&pool->stale_lock);
310 cancel_work_sync(&zhdr->work);
311 free_z3fold_page(page);
312 cond_resched();
313 spin_lock(&pool->stale_lock);
314 }
315 spin_unlock(&pool->stale_lock);
316}
317
318/*
319 * Returns the number of free chunks in a z3fold page.
320 * NB: can't be used with HEADLESS pages.
321 */
322static int num_free_chunks(struct z3fold_header *zhdr)
323{
324 int nfree;
325 /*
326 * If there is a middle object, pick up the bigger free space
327 * either before or after it. Otherwise just subtract the number
328 * of chunks occupied by the first and the last objects.
329 */
330 if (zhdr->middle_chunks != 0) {
331 int nfree_before = zhdr->first_chunks ?
332 0 : zhdr->start_middle - ZHDR_CHUNKS;
333 int nfree_after = zhdr->last_chunks ?
334 0 : TOTAL_CHUNKS -
335 (zhdr->start_middle + zhdr->middle_chunks);
336 nfree = max(nfree_before, nfree_after);
337 } else
338 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
339 return nfree;
340}
341
342static inline void *mchunk_memmove(struct z3fold_header *zhdr,
343 unsigned short dst_chunk)
344{
345 void *beg = zhdr;
346 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
347 beg + (zhdr->start_middle << CHUNK_SHIFT),
348 zhdr->middle_chunks << CHUNK_SHIFT);
349}
350
351#define BIG_CHUNK_GAP 3
352/* Has to be called with lock held */
353static int z3fold_compact_page(struct z3fold_header *zhdr)
354{
355 struct page *page = virt_to_page(zhdr);
356
357 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
358 return 0; /* can't move middle chunk, it's used */
359
360 if (zhdr->middle_chunks == 0)
361 return 0; /* nothing to compact */
362
363 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
364 /* move to the beginning */
365 mchunk_memmove(zhdr, ZHDR_CHUNKS);
366 zhdr->first_chunks = zhdr->middle_chunks;
367 zhdr->middle_chunks = 0;
368 zhdr->start_middle = 0;
369 zhdr->first_num++;
370 return 1;
371 }
372
373 /*
374 * moving data is expensive, so let's only do that if
375 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
376 */
377 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
378 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
379 BIG_CHUNK_GAP) {
380 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
381 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
382 return 1;
383 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
384 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
385 + zhdr->middle_chunks) >=
386 BIG_CHUNK_GAP) {
387 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
388 zhdr->middle_chunks;
389 mchunk_memmove(zhdr, new_start);
390 zhdr->start_middle = new_start;
391 return 1;
392 }
393
394 return 0;
395}
396
397static void do_compact_page(struct z3fold_header *zhdr, bool locked)
398{
399 struct z3fold_pool *pool = zhdr->pool;
400 struct page *page;
401 struct list_head *unbuddied;
402 int fchunks;
403
404 page = virt_to_page(zhdr);
405 if (locked)
406 WARN_ON(z3fold_page_trylock(zhdr));
407 else
408 z3fold_page_lock(zhdr);
409 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
410 z3fold_page_unlock(zhdr);
411 return;
412 }
413 spin_lock(&pool->lock);
414 list_del_init(&zhdr->buddy);
415 spin_unlock(&pool->lock);
416
417 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
418 atomic64_dec(&pool->pages_nr);
419 return;
420 }
421
422 z3fold_compact_page(zhdr);
423 unbuddied = get_cpu_ptr(pool->unbuddied);
424 fchunks = num_free_chunks(zhdr);
425 if (fchunks < NCHUNKS &&
426 (!zhdr->first_chunks || !zhdr->middle_chunks ||
427 !zhdr->last_chunks)) {
428 /* the page's not completely free and it's unbuddied */
429 spin_lock(&pool->lock);
430 list_add(&zhdr->buddy, &unbuddied[fchunks]);
431 spin_unlock(&pool->lock);
432 zhdr->cpu = smp_processor_id();
433 }
434 put_cpu_ptr(pool->unbuddied);
435 z3fold_page_unlock(zhdr);
436}
437
438static void compact_page_work(struct work_struct *w)
439{
440 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
441 work);
442
443 do_compact_page(zhdr, false);
444}
445
446
447/*
448 * API Functions
449 */
450
451/**
452 * z3fold_create_pool() - create a new z3fold pool
453 * @name: pool name
454 * @gfp: gfp flags when allocating the z3fold pool structure
455 * @ops: user-defined operations for the z3fold pool
456 *
457 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
458 * failed.
459 */
460static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
461 const struct z3fold_ops *ops)
462{
463 struct z3fold_pool *pool = NULL;
464 int i, cpu;
465
466 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
467 if (!pool)
468 goto out;
469 spin_lock_init(&pool->lock);
470 spin_lock_init(&pool->stale_lock);
471 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
472 if (!pool->unbuddied)
473 goto out_pool;
474 for_each_possible_cpu(cpu) {
475 struct list_head *unbuddied =
476 per_cpu_ptr(pool->unbuddied, cpu);
477 for_each_unbuddied_list(i, 0)
478 INIT_LIST_HEAD(&unbuddied[i]);
479 }
480 INIT_LIST_HEAD(&pool->lru);
481 INIT_LIST_HEAD(&pool->stale);
482 atomic64_set(&pool->pages_nr, 0);
483 pool->name = name;
484 pool->compact_wq = create_singlethread_workqueue(pool->name);
485 if (!pool->compact_wq)
486 goto out_unbuddied;
487 pool->release_wq = create_singlethread_workqueue(pool->name);
488 if (!pool->release_wq)
489 goto out_wq;
490 INIT_WORK(&pool->work, free_pages_work);
491 pool->ops = ops;
492 return pool;
493
494out_wq:
495 destroy_workqueue(pool->compact_wq);
496out_unbuddied:
497 free_percpu(pool->unbuddied);
498out_pool:
499 kfree(pool);
500out:
501 return NULL;
502}
503
504/**
505 * z3fold_destroy_pool() - destroys an existing z3fold pool
506 * @pool: the z3fold pool to be destroyed
507 *
508 * The pool should be emptied before this function is called.
509 */
510static void z3fold_destroy_pool(struct z3fold_pool *pool)
511{
512 destroy_workqueue(pool->release_wq);
513 destroy_workqueue(pool->compact_wq);
514 kfree(pool);
515}
516
517/**
518 * z3fold_alloc() - allocates a region of a given size
519 * @pool: z3fold pool from which to allocate
520 * @size: size in bytes of the desired allocation
521 * @gfp: gfp flags used if the pool needs to grow
522 * @handle: handle of the new allocation
523 *
524 * This function will attempt to find a free region in the pool large enough to
525 * satisfy the allocation request. A search of the unbuddied lists is
526 * performed first. If no suitable free region is found, then a new page is
527 * allocated and added to the pool to satisfy the request.
528 *
529 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
530 * as z3fold pool pages.
531 *
532 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
533 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
534 * a new page.
535 */
536static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
537 unsigned long *handle)
538{
539 int chunks = 0, i, freechunks;
540 struct z3fold_header *zhdr = NULL;
541 struct page *page = NULL;
542 enum buddy bud;
543 bool can_sleep = gfpflags_allow_blocking(gfp);
544
545 if (!size || (gfp & __GFP_HIGHMEM))
546 return -EINVAL;
547
548 if (size > PAGE_SIZE)
549 return -ENOSPC;
550
551 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
552 bud = HEADLESS;
553 else {
554 struct list_head *unbuddied;
555 chunks = size_to_chunks(size);
556
557lookup:
558 /* First, try to find an unbuddied z3fold page. */
559 unbuddied = get_cpu_ptr(pool->unbuddied);
560 for_each_unbuddied_list(i, chunks) {
561 struct list_head *l = &unbuddied[i];
562
563 zhdr = list_first_entry_or_null(READ_ONCE(l),
564 struct z3fold_header, buddy);
565
566 if (!zhdr)
567 continue;
568
569 /* Re-check under lock. */
570 spin_lock(&pool->lock);
571 l = &unbuddied[i];
572 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
573 struct z3fold_header, buddy)) ||
574 !z3fold_page_trylock(zhdr)) {
575 spin_unlock(&pool->lock);
576 put_cpu_ptr(pool->unbuddied);
577 goto lookup;
578 }
579 list_del_init(&zhdr->buddy);
580 zhdr->cpu = -1;
581 spin_unlock(&pool->lock);
582
583 page = virt_to_page(zhdr);
584 if (test_bit(NEEDS_COMPACTING, &page->private)) {
585 z3fold_page_unlock(zhdr);
586 zhdr = NULL;
587 put_cpu_ptr(pool->unbuddied);
588 if (can_sleep)
589 cond_resched();
590 goto lookup;
591 }
592
593 /*
594 * this page could not be removed from its unbuddied
595 * list while pool lock was held, and then we've taken
596 * page lock so kref_put could not be called before
597 * we got here, so it's safe to just call kref_get()
598 */
599 kref_get(&zhdr->refcount);
600 break;
601 }
602 put_cpu_ptr(pool->unbuddied);
603
604 if (zhdr) {
605 if (zhdr->first_chunks == 0) {
606 if (zhdr->middle_chunks != 0 &&
607 chunks >= zhdr->start_middle)
608 bud = LAST;
609 else
610 bud = FIRST;
611 } else if (zhdr->last_chunks == 0)
612 bud = LAST;
613 else if (zhdr->middle_chunks == 0)
614 bud = MIDDLE;
615 else {
616 if (kref_put(&zhdr->refcount,
617 release_z3fold_page_locked))
618 atomic64_dec(&pool->pages_nr);
619 else
620 z3fold_page_unlock(zhdr);
621 pr_err("No free chunks in unbuddied\n");
622 WARN_ON(1);
623 goto lookup;
624 }
625 goto found;
626 }
627 bud = FIRST;
628 }
629
630 page = NULL;
631 if (can_sleep) {
632 spin_lock(&pool->stale_lock);
633 zhdr = list_first_entry_or_null(&pool->stale,
634 struct z3fold_header, buddy);
635 /*
636 * Before allocating a page, let's see if we can take one from
637 * the stale pages list. cancel_work_sync() can sleep so we
638 * limit this case to the contexts where we can sleep
639 */
640 if (zhdr) {
641 list_del(&zhdr->buddy);
642 spin_unlock(&pool->stale_lock);
643 cancel_work_sync(&zhdr->work);
644 page = virt_to_page(zhdr);
645 } else {
646 spin_unlock(&pool->stale_lock);
647 }
648 }
649 if (!page)
650 page = alloc_page(gfp);
651
652 if (!page)
653 return -ENOMEM;
654
655 atomic64_inc(&pool->pages_nr);
656 zhdr = init_z3fold_page(page, pool);
657
658 if (bud == HEADLESS) {
659 set_bit(PAGE_HEADLESS, &page->private);
660 goto headless;
661 }
662 z3fold_page_lock(zhdr);
663
664found:
665 if (bud == FIRST)
666 zhdr->first_chunks = chunks;
667 else if (bud == LAST)
668 zhdr->last_chunks = chunks;
669 else {
670 zhdr->middle_chunks = chunks;
671 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
672 }
673
674 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
675 zhdr->middle_chunks == 0) {
676 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
677
678 /* Add to unbuddied list */
679 freechunks = num_free_chunks(zhdr);
680 spin_lock(&pool->lock);
681 list_add(&zhdr->buddy, &unbuddied[freechunks]);
682 spin_unlock(&pool->lock);
683 zhdr->cpu = smp_processor_id();
684 put_cpu_ptr(pool->unbuddied);
685 }
686
687headless:
688 spin_lock(&pool->lock);
689 /* Add/move z3fold page to beginning of LRU */
690 if (!list_empty(&page->lru))
691 list_del(&page->lru);
692
693 list_add(&page->lru, &pool->lru);
694
695 *handle = encode_handle(zhdr, bud);
696 spin_unlock(&pool->lock);
697 if (bud != HEADLESS)
698 z3fold_page_unlock(zhdr);
699
700 return 0;
701}
702
703/**
704 * z3fold_free() - frees the allocation associated with the given handle
705 * @pool: pool in which the allocation resided
706 * @handle: handle associated with the allocation returned by z3fold_alloc()
707 *
708 * In the case that the z3fold page in which the allocation resides is under
709 * reclaim, as indicated by the PG_reclaim flag being set, this function
710 * only sets the first|last_chunks to 0. The page is actually freed
711 * once both buddies are evicted (see z3fold_reclaim_page() below).
712 */
713static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
714{
715 struct z3fold_header *zhdr;
716 struct page *page;
717 enum buddy bud;
718
719 zhdr = handle_to_z3fold_header(handle);
720 page = virt_to_page(zhdr);
721
722 if (test_bit(PAGE_HEADLESS, &page->private)) {
723 /* HEADLESS page stored */
724 bud = HEADLESS;
725 } else {
726 z3fold_page_lock(zhdr);
727 bud = handle_to_buddy(handle);
728
729 switch (bud) {
730 case FIRST:
731 zhdr->first_chunks = 0;
732 break;
733 case MIDDLE:
734 zhdr->middle_chunks = 0;
735 zhdr->start_middle = 0;
736 break;
737 case LAST:
738 zhdr->last_chunks = 0;
739 break;
740 default:
741 pr_err("%s: unknown bud %d\n", __func__, bud);
742 WARN_ON(1);
743 z3fold_page_unlock(zhdr);
744 return;
745 }
746 }
747
748 if (bud == HEADLESS) {
749 spin_lock(&pool->lock);
750 list_del(&page->lru);
751 spin_unlock(&pool->lock);
752 free_z3fold_page(page);
753 atomic64_dec(&pool->pages_nr);
754 return;
755 }
756
757 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
758 atomic64_dec(&pool->pages_nr);
759 return;
760 }
761 if (test_bit(UNDER_RECLAIM, &page->private)) {
762 z3fold_page_unlock(zhdr);
763 return;
764 }
765 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
766 z3fold_page_unlock(zhdr);
767 return;
768 }
769 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
770 spin_lock(&pool->lock);
771 list_del_init(&zhdr->buddy);
772 spin_unlock(&pool->lock);
773 zhdr->cpu = -1;
774 kref_get(&zhdr->refcount);
775 do_compact_page(zhdr, true);
776 return;
777 }
778 kref_get(&zhdr->refcount);
779 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
780 z3fold_page_unlock(zhdr);
781}
782
783/**
784 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
785 * @pool: pool from which a page will attempt to be evicted
786 * @retries: number of pages on the LRU list for which eviction will
787 * be attempted before failing
788 *
789 * z3fold reclaim is different from normal system reclaim in that it is done
790 * from the bottom, up. This is because only the bottom layer, z3fold, has
791 * information on how the allocations are organized within each z3fold page.
792 * This has the potential to create interesting locking situations between
793 * z3fold and the user, however.
794 *
795 * To avoid these, this is how z3fold_reclaim_page() should be called:
796 *
797 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
798 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
799 * call the user-defined eviction handler with the pool and handle as
800 * arguments.
801 *
802 * If the handle can not be evicted, the eviction handler should return
803 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
804 * appropriate list and try the next z3fold page on the LRU up to
805 * a user defined number of retries.
806 *
807 * If the handle is successfully evicted, the eviction handler should
808 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
809 * contains logic to delay freeing the page if the page is under reclaim,
810 * as indicated by the setting of the PG_reclaim flag on the underlying page.
811 *
812 * If all buddies in the z3fold page are successfully evicted, then the
813 * z3fold page can be freed.
814 *
815 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
816 * no pages to evict or an eviction handler is not registered, -EAGAIN if
817 * the retry limit was hit.
818 */
819static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
820{
821 int i, ret = 0;
822 struct z3fold_header *zhdr = NULL;
823 struct page *page = NULL;
824 struct list_head *pos;
825 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
826
827 spin_lock(&pool->lock);
828 if (!pool->ops || !pool->ops->evict || retries == 0) {
829 spin_unlock(&pool->lock);
830 return -EINVAL;
831 }
832 for (i = 0; i < retries; i++) {
833 if (list_empty(&pool->lru)) {
834 spin_unlock(&pool->lock);
835 return -EINVAL;
836 }
837 list_for_each_prev(pos, &pool->lru) {
838 page = list_entry(pos, struct page, lru);
839 if (test_bit(PAGE_HEADLESS, &page->private))
840 /* candidate found */
841 break;
842
843 zhdr = page_address(page);
844 if (!z3fold_page_trylock(zhdr))
845 continue; /* can't evict at this point */
846 kref_get(&zhdr->refcount);
847 list_del_init(&zhdr->buddy);
848 zhdr->cpu = -1;
849 set_bit(UNDER_RECLAIM, &page->private);
850 break;
851 }
852
853 list_del_init(&page->lru);
854 spin_unlock(&pool->lock);
855
856 if (!test_bit(PAGE_HEADLESS, &page->private)) {
857 /*
858 * We need encode the handles before unlocking, since
859 * we can race with free that will set
860 * (first|last)_chunks to 0
861 */
862 first_handle = 0;
863 last_handle = 0;
864 middle_handle = 0;
865 if (zhdr->first_chunks)
866 first_handle = encode_handle(zhdr, FIRST);
867 if (zhdr->middle_chunks)
868 middle_handle = encode_handle(zhdr, MIDDLE);
869 if (zhdr->last_chunks)
870 last_handle = encode_handle(zhdr, LAST);
871 /*
872 * it's safe to unlock here because we hold a
873 * reference to this page
874 */
875 z3fold_page_unlock(zhdr);
876 } else {
877 first_handle = encode_handle(zhdr, HEADLESS);
878 last_handle = middle_handle = 0;
879 }
880
881 /* Issue the eviction callback(s) */
882 if (middle_handle) {
883 ret = pool->ops->evict(pool, middle_handle);
884 if (ret)
885 goto next;
886 }
887 if (first_handle) {
888 ret = pool->ops->evict(pool, first_handle);
889 if (ret)
890 goto next;
891 }
892 if (last_handle) {
893 ret = pool->ops->evict(pool, last_handle);
894 if (ret)
895 goto next;
896 }
897next:
898 if (test_bit(PAGE_HEADLESS, &page->private)) {
899 if (ret == 0) {
900 free_z3fold_page(page);
901 return 0;
902 }
903 spin_lock(&pool->lock);
904 list_add(&page->lru, &pool->lru);
905 spin_unlock(&pool->lock);
906 } else {
907 z3fold_page_lock(zhdr);
908 clear_bit(UNDER_RECLAIM, &page->private);
909 if (kref_put(&zhdr->refcount,
910 release_z3fold_page_locked)) {
911 atomic64_dec(&pool->pages_nr);
912 return 0;
913 }
914 /*
915 * if we are here, the page is still not completely
916 * free. Take the global pool lock then to be able
917 * to add it back to the lru list
918 */
919 spin_lock(&pool->lock);
920 list_add(&page->lru, &pool->lru);
921 spin_unlock(&pool->lock);
922 z3fold_page_unlock(zhdr);
923 }
924
925 /* We started off locked to we need to lock the pool back */
926 spin_lock(&pool->lock);
927 }
928 spin_unlock(&pool->lock);
929 return -EAGAIN;
930}
931
932/**
933 * z3fold_map() - maps the allocation associated with the given handle
934 * @pool: pool in which the allocation resides
935 * @handle: handle associated with the allocation to be mapped
936 *
937 * Extracts the buddy number from handle and constructs the pointer to the
938 * correct starting chunk within the page.
939 *
940 * Returns: a pointer to the mapped allocation
941 */
942static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
943{
944 struct z3fold_header *zhdr;
945 struct page *page;
946 void *addr;
947 enum buddy buddy;
948
949 zhdr = handle_to_z3fold_header(handle);
950 addr = zhdr;
951 page = virt_to_page(zhdr);
952
953 if (test_bit(PAGE_HEADLESS, &page->private))
954 goto out;
955
956 z3fold_page_lock(zhdr);
957 buddy = handle_to_buddy(handle);
958 switch (buddy) {
959 case FIRST:
960 addr += ZHDR_SIZE_ALIGNED;
961 break;
962 case MIDDLE:
963 addr += zhdr->start_middle << CHUNK_SHIFT;
964 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
965 break;
966 case LAST:
967 addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
968 break;
969 default:
970 pr_err("unknown buddy id %d\n", buddy);
971 WARN_ON(1);
972 addr = NULL;
973 break;
974 }
975
976 z3fold_page_unlock(zhdr);
977out:
978 return addr;
979}
980
981/**
982 * z3fold_unmap() - unmaps the allocation associated with the given handle
983 * @pool: pool in which the allocation resides
984 * @handle: handle associated with the allocation to be unmapped
985 */
986static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
987{
988 struct z3fold_header *zhdr;
989 struct page *page;
990 enum buddy buddy;
991
992 zhdr = handle_to_z3fold_header(handle);
993 page = virt_to_page(zhdr);
994
995 if (test_bit(PAGE_HEADLESS, &page->private))
996 return;
997
998 z3fold_page_lock(zhdr);
999 buddy = handle_to_buddy(handle);
1000 if (buddy == MIDDLE)
1001 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1002 z3fold_page_unlock(zhdr);
1003}
1004
1005/**
1006 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1007 * @pool: pool whose size is being queried
1008 *
1009 * Returns: size in pages of the given pool.
1010 */
1011static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1012{
1013 return atomic64_read(&pool->pages_nr);
1014}
1015
1016/*****************
1017 * zpool
1018 ****************/
1019
1020static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1021{
1022 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1023 return pool->zpool_ops->evict(pool->zpool, handle);
1024 else
1025 return -ENOENT;
1026}
1027
1028static const struct z3fold_ops z3fold_zpool_ops = {
1029 .evict = z3fold_zpool_evict
1030};
1031
1032static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1033 const struct zpool_ops *zpool_ops,
1034 struct zpool *zpool)
1035{
1036 struct z3fold_pool *pool;
1037
1038 pool = z3fold_create_pool(name, gfp,
1039 zpool_ops ? &z3fold_zpool_ops : NULL);
1040 if (pool) {
1041 pool->zpool = zpool;
1042 pool->zpool_ops = zpool_ops;
1043 }
1044 return pool;
1045}
1046
1047static void z3fold_zpool_destroy(void *pool)
1048{
1049 z3fold_destroy_pool(pool);
1050}
1051
1052static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1053 unsigned long *handle)
1054{
1055 return z3fold_alloc(pool, size, gfp, handle);
1056}
1057static void z3fold_zpool_free(void *pool, unsigned long handle)
1058{
1059 z3fold_free(pool, handle);
1060}
1061
1062static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1063 unsigned int *reclaimed)
1064{
1065 unsigned int total = 0;
1066 int ret = -EINVAL;
1067
1068 while (total < pages) {
1069 ret = z3fold_reclaim_page(pool, 8);
1070 if (ret < 0)
1071 break;
1072 total++;
1073 }
1074
1075 if (reclaimed)
1076 *reclaimed = total;
1077
1078 return ret;
1079}
1080
1081static void *z3fold_zpool_map(void *pool, unsigned long handle,
1082 enum zpool_mapmode mm)
1083{
1084 return z3fold_map(pool, handle);
1085}
1086static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1087{
1088 z3fold_unmap(pool, handle);
1089}
1090
1091static u64 z3fold_zpool_total_size(void *pool)
1092{
1093 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1094}
1095
1096static struct zpool_driver z3fold_zpool_driver = {
1097 .type = "z3fold",
1098 .owner = THIS_MODULE,
1099 .create = z3fold_zpool_create,
1100 .destroy = z3fold_zpool_destroy,
1101 .malloc = z3fold_zpool_malloc,
1102 .free = z3fold_zpool_free,
1103 .shrink = z3fold_zpool_shrink,
1104 .map = z3fold_zpool_map,
1105 .unmap = z3fold_zpool_unmap,
1106 .total_size = z3fold_zpool_total_size,
1107};
1108
1109MODULE_ALIAS("zpool-z3fold");
1110
1111static int __init init_z3fold(void)
1112{
1113 /* Make sure the z3fold header is not larger than the page size */
1114 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1115 zpool_register_driver(&z3fold_zpool_driver);
1116
1117 return 0;
1118}
1119
1120static void __exit exit_z3fold(void)
1121{
1122 zpool_unregister_driver(&z3fold_zpool_driver);
1123}
1124
1125module_init(init_z3fold);
1126module_exit(exit_z3fold);
1127
1128MODULE_LICENSE("GPL");
1129MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1130MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");