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#define BUDDY_SHIFT 2
103
104/**
105 * struct z3fold_pool - stores metadata for each z3fold pool
106 * @name: pool name
107 * @lock: protects pool unbuddied/lru lists
108 * @stale_lock: protects pool stale page list
109 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
110 * buddies; the list each z3fold page is added to depends on
111 * the size of its free region.
112 * @lru: list tracking the z3fold pages in LRU order by most recently
113 * added buddy.
114 * @stale: list of pages marked for freeing
115 * @pages_nr: number of z3fold pages in the pool.
116 * @ops: pointer to a structure of user defined operations specified at
117 * pool creation time.
118 * @compact_wq: workqueue for page layout background optimization
119 * @release_wq: workqueue for safe page release
120 * @work: work_struct for safe page release
121 *
122 * This structure is allocated at pool creation time and maintains metadata
123 * pertaining to a particular z3fold pool.
124 */
125struct z3fold_pool {
126 const char *name;
127 spinlock_t lock;
128 spinlock_t stale_lock;
129 struct list_head *unbuddied;
130 struct list_head lru;
131 struct list_head stale;
132 atomic64_t pages_nr;
133 const struct z3fold_ops *ops;
134 struct zpool *zpool;
135 const struct zpool_ops *zpool_ops;
136 struct workqueue_struct *compact_wq;
137 struct workqueue_struct *release_wq;
138 struct work_struct work;
139};
140
141/*
142 * Internal z3fold page flags
143 */
144enum z3fold_page_flags {
145 PAGE_HEADLESS = 0,
146 MIDDLE_CHUNK_MAPPED,
147 NEEDS_COMPACTING,
148 PAGE_STALE,
149 PAGE_CLAIMED, /* by either reclaim or free */
150};
151
152/*****************
153 * Helpers
154*****************/
155
156/* Converts an allocation size in bytes to size in z3fold chunks */
157static int size_to_chunks(size_t size)
158{
159 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
160}
161
162#define for_each_unbuddied_list(_iter, _begin) \
163 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
164
165static void compact_page_work(struct work_struct *w);
166
167/* Initializes the z3fold header of a newly allocated z3fold page */
168static struct z3fold_header *init_z3fold_page(struct page *page,
169 struct z3fold_pool *pool)
170{
171 struct z3fold_header *zhdr = page_address(page);
172
173 INIT_LIST_HEAD(&page->lru);
174 clear_bit(PAGE_HEADLESS, &page->private);
175 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
176 clear_bit(NEEDS_COMPACTING, &page->private);
177 clear_bit(PAGE_STALE, &page->private);
178 clear_bit(PAGE_CLAIMED, &page->private);
179
180 spin_lock_init(&zhdr->page_lock);
181 kref_init(&zhdr->refcount);
182 zhdr->first_chunks = 0;
183 zhdr->middle_chunks = 0;
184 zhdr->last_chunks = 0;
185 zhdr->first_num = 0;
186 zhdr->start_middle = 0;
187 zhdr->cpu = -1;
188 zhdr->pool = pool;
189 INIT_LIST_HEAD(&zhdr->buddy);
190 INIT_WORK(&zhdr->work, compact_page_work);
191 return zhdr;
192}
193
194/* Resets the struct page fields and frees the page */
195static void free_z3fold_page(struct page *page)
196{
197 __free_page(page);
198}
199
200/* Lock a z3fold page */
201static inline void z3fold_page_lock(struct z3fold_header *zhdr)
202{
203 spin_lock(&zhdr->page_lock);
204}
205
206/* Try to lock a z3fold page */
207static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
208{
209 return spin_trylock(&zhdr->page_lock);
210}
211
212/* Unlock a z3fold page */
213static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
214{
215 spin_unlock(&zhdr->page_lock);
216}
217
218/*
219 * Encodes the handle of a particular buddy within a z3fold page
220 * Pool lock should be held as this function accesses first_num
221 */
222static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
223{
224 unsigned long handle;
225
226 handle = (unsigned long)zhdr;
227 if (bud != HEADLESS) {
228 handle |= (bud + zhdr->first_num) & BUDDY_MASK;
229 if (bud == LAST)
230 handle |= (zhdr->last_chunks << BUDDY_SHIFT);
231 }
232 return handle;
233}
234
235/* Returns the z3fold page where a given handle is stored */
236static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
237{
238 return (struct z3fold_header *)(handle & PAGE_MASK);
239}
240
241/* only for LAST bud, returns zero otherwise */
242static unsigned short handle_to_chunks(unsigned long handle)
243{
244 return (handle & ~PAGE_MASK) >> BUDDY_SHIFT;
245}
246
247/*
248 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
249 * but that doesn't matter. because the masking will result in the
250 * correct buddy number.
251 */
252static enum buddy handle_to_buddy(unsigned long handle)
253{
254 struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
255 return (handle - zhdr->first_num) & BUDDY_MASK;
256}
257
258static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
259{
260 struct page *page = virt_to_page(zhdr);
261 struct z3fold_pool *pool = zhdr->pool;
262
263 WARN_ON(!list_empty(&zhdr->buddy));
264 set_bit(PAGE_STALE, &page->private);
265 clear_bit(NEEDS_COMPACTING, &page->private);
266 spin_lock(&pool->lock);
267 if (!list_empty(&page->lru))
268 list_del(&page->lru);
269 spin_unlock(&pool->lock);
270 if (locked)
271 z3fold_page_unlock(zhdr);
272 spin_lock(&pool->stale_lock);
273 list_add(&zhdr->buddy, &pool->stale);
274 queue_work(pool->release_wq, &pool->work);
275 spin_unlock(&pool->stale_lock);
276}
277
278static void __attribute__((__unused__))
279 release_z3fold_page(struct kref *ref)
280{
281 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
282 refcount);
283 __release_z3fold_page(zhdr, false);
284}
285
286static void release_z3fold_page_locked(struct kref *ref)
287{
288 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
289 refcount);
290 WARN_ON(z3fold_page_trylock(zhdr));
291 __release_z3fold_page(zhdr, true);
292}
293
294static void release_z3fold_page_locked_list(struct kref *ref)
295{
296 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
297 refcount);
298 spin_lock(&zhdr->pool->lock);
299 list_del_init(&zhdr->buddy);
300 spin_unlock(&zhdr->pool->lock);
301
302 WARN_ON(z3fold_page_trylock(zhdr));
303 __release_z3fold_page(zhdr, true);
304}
305
306static void free_pages_work(struct work_struct *w)
307{
308 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
309
310 spin_lock(&pool->stale_lock);
311 while (!list_empty(&pool->stale)) {
312 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
313 struct z3fold_header, buddy);
314 struct page *page = virt_to_page(zhdr);
315
316 list_del(&zhdr->buddy);
317 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
318 continue;
319 spin_unlock(&pool->stale_lock);
320 cancel_work_sync(&zhdr->work);
321 free_z3fold_page(page);
322 cond_resched();
323 spin_lock(&pool->stale_lock);
324 }
325 spin_unlock(&pool->stale_lock);
326}
327
328/*
329 * Returns the number of free chunks in a z3fold page.
330 * NB: can't be used with HEADLESS pages.
331 */
332static int num_free_chunks(struct z3fold_header *zhdr)
333{
334 int nfree;
335 /*
336 * If there is a middle object, pick up the bigger free space
337 * either before or after it. Otherwise just subtract the number
338 * of chunks occupied by the first and the last objects.
339 */
340 if (zhdr->middle_chunks != 0) {
341 int nfree_before = zhdr->first_chunks ?
342 0 : zhdr->start_middle - ZHDR_CHUNKS;
343 int nfree_after = zhdr->last_chunks ?
344 0 : TOTAL_CHUNKS -
345 (zhdr->start_middle + zhdr->middle_chunks);
346 nfree = max(nfree_before, nfree_after);
347 } else
348 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
349 return nfree;
350}
351
352static inline void *mchunk_memmove(struct z3fold_header *zhdr,
353 unsigned short dst_chunk)
354{
355 void *beg = zhdr;
356 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
357 beg + (zhdr->start_middle << CHUNK_SHIFT),
358 zhdr->middle_chunks << CHUNK_SHIFT);
359}
360
361#define BIG_CHUNK_GAP 3
362/* Has to be called with lock held */
363static int z3fold_compact_page(struct z3fold_header *zhdr)
364{
365 struct page *page = virt_to_page(zhdr);
366
367 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
368 return 0; /* can't move middle chunk, it's used */
369
370 if (zhdr->middle_chunks == 0)
371 return 0; /* nothing to compact */
372
373 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
374 /* move to the beginning */
375 mchunk_memmove(zhdr, ZHDR_CHUNKS);
376 zhdr->first_chunks = zhdr->middle_chunks;
377 zhdr->middle_chunks = 0;
378 zhdr->start_middle = 0;
379 zhdr->first_num++;
380 return 1;
381 }
382
383 /*
384 * moving data is expensive, so let's only do that if
385 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
386 */
387 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
388 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
389 BIG_CHUNK_GAP) {
390 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
391 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
392 return 1;
393 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
394 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
395 + zhdr->middle_chunks) >=
396 BIG_CHUNK_GAP) {
397 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
398 zhdr->middle_chunks;
399 mchunk_memmove(zhdr, new_start);
400 zhdr->start_middle = new_start;
401 return 1;
402 }
403
404 return 0;
405}
406
407static void do_compact_page(struct z3fold_header *zhdr, bool locked)
408{
409 struct z3fold_pool *pool = zhdr->pool;
410 struct page *page;
411 struct list_head *unbuddied;
412 int fchunks;
413
414 page = virt_to_page(zhdr);
415 if (locked)
416 WARN_ON(z3fold_page_trylock(zhdr));
417 else
418 z3fold_page_lock(zhdr);
419 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
420 z3fold_page_unlock(zhdr);
421 return;
422 }
423 spin_lock(&pool->lock);
424 list_del_init(&zhdr->buddy);
425 spin_unlock(&pool->lock);
426
427 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
428 atomic64_dec(&pool->pages_nr);
429 return;
430 }
431
432 z3fold_compact_page(zhdr);
433 unbuddied = get_cpu_ptr(pool->unbuddied);
434 fchunks = num_free_chunks(zhdr);
435 if (fchunks < NCHUNKS &&
436 (!zhdr->first_chunks || !zhdr->middle_chunks ||
437 !zhdr->last_chunks)) {
438 /* the page's not completely free and it's unbuddied */
439 spin_lock(&pool->lock);
440 list_add(&zhdr->buddy, &unbuddied[fchunks]);
441 spin_unlock(&pool->lock);
442 zhdr->cpu = smp_processor_id();
443 }
444 put_cpu_ptr(pool->unbuddied);
445 z3fold_page_unlock(zhdr);
446}
447
448static void compact_page_work(struct work_struct *w)
449{
450 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
451 work);
452
453 do_compact_page(zhdr, false);
454}
455
456
457/*
458 * API Functions
459 */
460
461/**
462 * z3fold_create_pool() - create a new z3fold pool
463 * @name: pool name
464 * @gfp: gfp flags when allocating the z3fold pool structure
465 * @ops: user-defined operations for the z3fold pool
466 *
467 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
468 * failed.
469 */
470static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
471 const struct z3fold_ops *ops)
472{
473 struct z3fold_pool *pool = NULL;
474 int i, cpu;
475
476 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
477 if (!pool)
478 goto out;
479 spin_lock_init(&pool->lock);
480 spin_lock_init(&pool->stale_lock);
481 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
482 if (!pool->unbuddied)
483 goto out_pool;
484 for_each_possible_cpu(cpu) {
485 struct list_head *unbuddied =
486 per_cpu_ptr(pool->unbuddied, cpu);
487 for_each_unbuddied_list(i, 0)
488 INIT_LIST_HEAD(&unbuddied[i]);
489 }
490 INIT_LIST_HEAD(&pool->lru);
491 INIT_LIST_HEAD(&pool->stale);
492 atomic64_set(&pool->pages_nr, 0);
493 pool->name = name;
494 pool->compact_wq = create_singlethread_workqueue(pool->name);
495 if (!pool->compact_wq)
496 goto out_unbuddied;
497 pool->release_wq = create_singlethread_workqueue(pool->name);
498 if (!pool->release_wq)
499 goto out_wq;
500 INIT_WORK(&pool->work, free_pages_work);
501 pool->ops = ops;
502 return pool;
503
504out_wq:
505 destroy_workqueue(pool->compact_wq);
506out_unbuddied:
507 free_percpu(pool->unbuddied);
508out_pool:
509 kfree(pool);
510out:
511 return NULL;
512}
513
514/**
515 * z3fold_destroy_pool() - destroys an existing z3fold pool
516 * @pool: the z3fold pool to be destroyed
517 *
518 * The pool should be emptied before this function is called.
519 */
520static void z3fold_destroy_pool(struct z3fold_pool *pool)
521{
522 destroy_workqueue(pool->release_wq);
523 destroy_workqueue(pool->compact_wq);
524 kfree(pool);
525}
526
527/**
528 * z3fold_alloc() - allocates a region of a given size
529 * @pool: z3fold pool from which to allocate
530 * @size: size in bytes of the desired allocation
531 * @gfp: gfp flags used if the pool needs to grow
532 * @handle: handle of the new allocation
533 *
534 * This function will attempt to find a free region in the pool large enough to
535 * satisfy the allocation request. A search of the unbuddied lists is
536 * performed first. If no suitable free region is found, then a new page is
537 * allocated and added to the pool to satisfy the request.
538 *
539 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
540 * as z3fold pool pages.
541 *
542 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
543 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
544 * a new page.
545 */
546static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
547 unsigned long *handle)
548{
549 int chunks = 0, i, freechunks;
550 struct z3fold_header *zhdr = NULL;
551 struct page *page = NULL;
552 enum buddy bud;
553 bool can_sleep = gfpflags_allow_blocking(gfp);
554
555 if (!size || (gfp & __GFP_HIGHMEM))
556 return -EINVAL;
557
558 if (size > PAGE_SIZE)
559 return -ENOSPC;
560
561 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
562 bud = HEADLESS;
563 else {
564 struct list_head *unbuddied;
565 chunks = size_to_chunks(size);
566
567lookup:
568 /* First, try to find an unbuddied z3fold page. */
569 unbuddied = get_cpu_ptr(pool->unbuddied);
570 for_each_unbuddied_list(i, chunks) {
571 struct list_head *l = &unbuddied[i];
572
573 zhdr = list_first_entry_or_null(READ_ONCE(l),
574 struct z3fold_header, buddy);
575
576 if (!zhdr)
577 continue;
578
579 /* Re-check under lock. */
580 spin_lock(&pool->lock);
581 l = &unbuddied[i];
582 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
583 struct z3fold_header, buddy)) ||
584 !z3fold_page_trylock(zhdr)) {
585 spin_unlock(&pool->lock);
586 put_cpu_ptr(pool->unbuddied);
587 goto lookup;
588 }
589 list_del_init(&zhdr->buddy);
590 zhdr->cpu = -1;
591 spin_unlock(&pool->lock);
592
593 page = virt_to_page(zhdr);
594 if (test_bit(NEEDS_COMPACTING, &page->private)) {
595 z3fold_page_unlock(zhdr);
596 zhdr = NULL;
597 put_cpu_ptr(pool->unbuddied);
598 if (can_sleep)
599 cond_resched();
600 goto lookup;
601 }
602
603 /*
604 * this page could not be removed from its unbuddied
605 * list while pool lock was held, and then we've taken
606 * page lock so kref_put could not be called before
607 * we got here, so it's safe to just call kref_get()
608 */
609 kref_get(&zhdr->refcount);
610 break;
611 }
612 put_cpu_ptr(pool->unbuddied);
613
614 if (zhdr) {
615 if (zhdr->first_chunks == 0) {
616 if (zhdr->middle_chunks != 0 &&
617 chunks >= zhdr->start_middle)
618 bud = LAST;
619 else
620 bud = FIRST;
621 } else if (zhdr->last_chunks == 0)
622 bud = LAST;
623 else if (zhdr->middle_chunks == 0)
624 bud = MIDDLE;
625 else {
626 if (kref_put(&zhdr->refcount,
627 release_z3fold_page_locked))
628 atomic64_dec(&pool->pages_nr);
629 else
630 z3fold_page_unlock(zhdr);
631 pr_err("No free chunks in unbuddied\n");
632 WARN_ON(1);
633 goto lookup;
634 }
635 goto found;
636 }
637 bud = FIRST;
638 }
639
640 page = NULL;
641 if (can_sleep) {
642 spin_lock(&pool->stale_lock);
643 zhdr = list_first_entry_or_null(&pool->stale,
644 struct z3fold_header, buddy);
645 /*
646 * Before allocating a page, let's see if we can take one from
647 * the stale pages list. cancel_work_sync() can sleep so we
648 * limit this case to the contexts where we can sleep
649 */
650 if (zhdr) {
651 list_del(&zhdr->buddy);
652 spin_unlock(&pool->stale_lock);
653 cancel_work_sync(&zhdr->work);
654 page = virt_to_page(zhdr);
655 } else {
656 spin_unlock(&pool->stale_lock);
657 }
658 }
659 if (!page)
660 page = alloc_page(gfp);
661
662 if (!page)
663 return -ENOMEM;
664
665 atomic64_inc(&pool->pages_nr);
666 zhdr = init_z3fold_page(page, pool);
667
668 if (bud == HEADLESS) {
669 set_bit(PAGE_HEADLESS, &page->private);
670 goto headless;
671 }
672 z3fold_page_lock(zhdr);
673
674found:
675 if (bud == FIRST)
676 zhdr->first_chunks = chunks;
677 else if (bud == LAST)
678 zhdr->last_chunks = chunks;
679 else {
680 zhdr->middle_chunks = chunks;
681 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
682 }
683
684 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
685 zhdr->middle_chunks == 0) {
686 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
687
688 /* Add to unbuddied list */
689 freechunks = num_free_chunks(zhdr);
690 spin_lock(&pool->lock);
691 list_add(&zhdr->buddy, &unbuddied[freechunks]);
692 spin_unlock(&pool->lock);
693 zhdr->cpu = smp_processor_id();
694 put_cpu_ptr(pool->unbuddied);
695 }
696
697headless:
698 spin_lock(&pool->lock);
699 /* Add/move z3fold page to beginning of LRU */
700 if (!list_empty(&page->lru))
701 list_del(&page->lru);
702
703 list_add(&page->lru, &pool->lru);
704
705 *handle = encode_handle(zhdr, bud);
706 spin_unlock(&pool->lock);
707 if (bud != HEADLESS)
708 z3fold_page_unlock(zhdr);
709
710 return 0;
711}
712
713/**
714 * z3fold_free() - frees the allocation associated with the given handle
715 * @pool: pool in which the allocation resided
716 * @handle: handle associated with the allocation returned by z3fold_alloc()
717 *
718 * In the case that the z3fold page in which the allocation resides is under
719 * reclaim, as indicated by the PG_reclaim flag being set, this function
720 * only sets the first|last_chunks to 0. The page is actually freed
721 * once both buddies are evicted (see z3fold_reclaim_page() below).
722 */
723static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
724{
725 struct z3fold_header *zhdr;
726 struct page *page;
727 enum buddy bud;
728
729 zhdr = handle_to_z3fold_header(handle);
730 page = virt_to_page(zhdr);
731
732 if (test_bit(PAGE_HEADLESS, &page->private)) {
733 /* if a headless page is under reclaim, just leave.
734 * NB: we use test_and_set_bit for a reason: if the bit
735 * has not been set before, we release this page
736 * immediately so we don't care about its value any more.
737 */
738 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
739 spin_lock(&pool->lock);
740 list_del(&page->lru);
741 spin_unlock(&pool->lock);
742 free_z3fold_page(page);
743 atomic64_dec(&pool->pages_nr);
744 }
745 return;
746 }
747
748 /* Non-headless case */
749 z3fold_page_lock(zhdr);
750 bud = handle_to_buddy(handle);
751
752 switch (bud) {
753 case FIRST:
754 zhdr->first_chunks = 0;
755 break;
756 case MIDDLE:
757 zhdr->middle_chunks = 0;
758 break;
759 case LAST:
760 zhdr->last_chunks = 0;
761 break;
762 default:
763 pr_err("%s: unknown bud %d\n", __func__, bud);
764 WARN_ON(1);
765 z3fold_page_unlock(zhdr);
766 return;
767 }
768
769 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
770 atomic64_dec(&pool->pages_nr);
771 return;
772 }
773 if (test_bit(PAGE_CLAIMED, &page->private)) {
774 z3fold_page_unlock(zhdr);
775 return;
776 }
777 if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
778 z3fold_page_unlock(zhdr);
779 return;
780 }
781 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
782 spin_lock(&pool->lock);
783 list_del_init(&zhdr->buddy);
784 spin_unlock(&pool->lock);
785 zhdr->cpu = -1;
786 kref_get(&zhdr->refcount);
787 do_compact_page(zhdr, true);
788 return;
789 }
790 kref_get(&zhdr->refcount);
791 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
792 z3fold_page_unlock(zhdr);
793}
794
795/**
796 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
797 * @pool: pool from which a page will attempt to be evicted
798 * @retries: number of pages on the LRU list for which eviction will
799 * be attempted before failing
800 *
801 * z3fold reclaim is different from normal system reclaim in that it is done
802 * from the bottom, up. This is because only the bottom layer, z3fold, has
803 * information on how the allocations are organized within each z3fold page.
804 * This has the potential to create interesting locking situations between
805 * z3fold and the user, however.
806 *
807 * To avoid these, this is how z3fold_reclaim_page() should be called:
808 *
809 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
810 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
811 * call the user-defined eviction handler with the pool and handle as
812 * arguments.
813 *
814 * If the handle can not be evicted, the eviction handler should return
815 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
816 * appropriate list and try the next z3fold page on the LRU up to
817 * a user defined number of retries.
818 *
819 * If the handle is successfully evicted, the eviction handler should
820 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
821 * contains logic to delay freeing the page if the page is under reclaim,
822 * as indicated by the setting of the PG_reclaim flag on the underlying page.
823 *
824 * If all buddies in the z3fold page are successfully evicted, then the
825 * z3fold page can be freed.
826 *
827 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
828 * no pages to evict or an eviction handler is not registered, -EAGAIN if
829 * the retry limit was hit.
830 */
831static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
832{
833 int i, ret = 0;
834 struct z3fold_header *zhdr = NULL;
835 struct page *page = NULL;
836 struct list_head *pos;
837 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
838
839 spin_lock(&pool->lock);
840 if (!pool->ops || !pool->ops->evict || retries == 0) {
841 spin_unlock(&pool->lock);
842 return -EINVAL;
843 }
844 for (i = 0; i < retries; i++) {
845 if (list_empty(&pool->lru)) {
846 spin_unlock(&pool->lock);
847 return -EINVAL;
848 }
849 list_for_each_prev(pos, &pool->lru) {
850 page = list_entry(pos, struct page, lru);
851
852 /* this bit could have been set by free, in which case
853 * we pass over to the next page in the pool.
854 */
855 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
856 continue;
857
858 zhdr = page_address(page);
859 if (test_bit(PAGE_HEADLESS, &page->private))
860 break;
861
862 if (!z3fold_page_trylock(zhdr)) {
863 zhdr = NULL;
864 continue; /* can't evict at this point */
865 }
866 kref_get(&zhdr->refcount);
867 list_del_init(&zhdr->buddy);
868 zhdr->cpu = -1;
869 break;
870 }
871
872 if (!zhdr)
873 break;
874
875 list_del_init(&page->lru);
876 spin_unlock(&pool->lock);
877
878 if (!test_bit(PAGE_HEADLESS, &page->private)) {
879 /*
880 * We need encode the handles before unlocking, since
881 * we can race with free that will set
882 * (first|last)_chunks to 0
883 */
884 first_handle = 0;
885 last_handle = 0;
886 middle_handle = 0;
887 if (zhdr->first_chunks)
888 first_handle = encode_handle(zhdr, FIRST);
889 if (zhdr->middle_chunks)
890 middle_handle = encode_handle(zhdr, MIDDLE);
891 if (zhdr->last_chunks)
892 last_handle = encode_handle(zhdr, LAST);
893 /*
894 * it's safe to unlock here because we hold a
895 * reference to this page
896 */
897 z3fold_page_unlock(zhdr);
898 } else {
899 first_handle = encode_handle(zhdr, HEADLESS);
900 last_handle = middle_handle = 0;
901 }
902
903 /* Issue the eviction callback(s) */
904 if (middle_handle) {
905 ret = pool->ops->evict(pool, middle_handle);
906 if (ret)
907 goto next;
908 }
909 if (first_handle) {
910 ret = pool->ops->evict(pool, first_handle);
911 if (ret)
912 goto next;
913 }
914 if (last_handle) {
915 ret = pool->ops->evict(pool, last_handle);
916 if (ret)
917 goto next;
918 }
919next:
920 if (test_bit(PAGE_HEADLESS, &page->private)) {
921 if (ret == 0) {
922 free_z3fold_page(page);
923 atomic64_dec(&pool->pages_nr);
924 return 0;
925 }
926 spin_lock(&pool->lock);
927 list_add(&page->lru, &pool->lru);
928 spin_unlock(&pool->lock);
929 } else {
930 z3fold_page_lock(zhdr);
931 clear_bit(PAGE_CLAIMED, &page->private);
932 if (kref_put(&zhdr->refcount,
933 release_z3fold_page_locked)) {
934 atomic64_dec(&pool->pages_nr);
935 return 0;
936 }
937 /*
938 * if we are here, the page is still not completely
939 * free. Take the global pool lock then to be able
940 * to add it back to the lru list
941 */
942 spin_lock(&pool->lock);
943 list_add(&page->lru, &pool->lru);
944 spin_unlock(&pool->lock);
945 z3fold_page_unlock(zhdr);
946 }
947
948 /* We started off locked to we need to lock the pool back */
949 spin_lock(&pool->lock);
950 }
951 spin_unlock(&pool->lock);
952 return -EAGAIN;
953}
954
955/**
956 * z3fold_map() - maps the allocation associated with the given handle
957 * @pool: pool in which the allocation resides
958 * @handle: handle associated with the allocation to be mapped
959 *
960 * Extracts the buddy number from handle and constructs the pointer to the
961 * correct starting chunk within the page.
962 *
963 * Returns: a pointer to the mapped allocation
964 */
965static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
966{
967 struct z3fold_header *zhdr;
968 struct page *page;
969 void *addr;
970 enum buddy buddy;
971
972 zhdr = handle_to_z3fold_header(handle);
973 addr = zhdr;
974 page = virt_to_page(zhdr);
975
976 if (test_bit(PAGE_HEADLESS, &page->private))
977 goto out;
978
979 z3fold_page_lock(zhdr);
980 buddy = handle_to_buddy(handle);
981 switch (buddy) {
982 case FIRST:
983 addr += ZHDR_SIZE_ALIGNED;
984 break;
985 case MIDDLE:
986 addr += zhdr->start_middle << CHUNK_SHIFT;
987 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
988 break;
989 case LAST:
990 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
991 break;
992 default:
993 pr_err("unknown buddy id %d\n", buddy);
994 WARN_ON(1);
995 addr = NULL;
996 break;
997 }
998
999 z3fold_page_unlock(zhdr);
1000out:
1001 return addr;
1002}
1003
1004/**
1005 * z3fold_unmap() - unmaps the allocation associated with the given handle
1006 * @pool: pool in which the allocation resides
1007 * @handle: handle associated with the allocation to be unmapped
1008 */
1009static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1010{
1011 struct z3fold_header *zhdr;
1012 struct page *page;
1013 enum buddy buddy;
1014
1015 zhdr = handle_to_z3fold_header(handle);
1016 page = virt_to_page(zhdr);
1017
1018 if (test_bit(PAGE_HEADLESS, &page->private))
1019 return;
1020
1021 z3fold_page_lock(zhdr);
1022 buddy = handle_to_buddy(handle);
1023 if (buddy == MIDDLE)
1024 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1025 z3fold_page_unlock(zhdr);
1026}
1027
1028/**
1029 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1030 * @pool: pool whose size is being queried
1031 *
1032 * Returns: size in pages of the given pool.
1033 */
1034static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1035{
1036 return atomic64_read(&pool->pages_nr);
1037}
1038
1039/*****************
1040 * zpool
1041 ****************/
1042
1043static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1044{
1045 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1046 return pool->zpool_ops->evict(pool->zpool, handle);
1047 else
1048 return -ENOENT;
1049}
1050
1051static const struct z3fold_ops z3fold_zpool_ops = {
1052 .evict = z3fold_zpool_evict
1053};
1054
1055static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1056 const struct zpool_ops *zpool_ops,
1057 struct zpool *zpool)
1058{
1059 struct z3fold_pool *pool;
1060
1061 pool = z3fold_create_pool(name, gfp,
1062 zpool_ops ? &z3fold_zpool_ops : NULL);
1063 if (pool) {
1064 pool->zpool = zpool;
1065 pool->zpool_ops = zpool_ops;
1066 }
1067 return pool;
1068}
1069
1070static void z3fold_zpool_destroy(void *pool)
1071{
1072 z3fold_destroy_pool(pool);
1073}
1074
1075static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1076 unsigned long *handle)
1077{
1078 return z3fold_alloc(pool, size, gfp, handle);
1079}
1080static void z3fold_zpool_free(void *pool, unsigned long handle)
1081{
1082 z3fold_free(pool, handle);
1083}
1084
1085static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1086 unsigned int *reclaimed)
1087{
1088 unsigned int total = 0;
1089 int ret = -EINVAL;
1090
1091 while (total < pages) {
1092 ret = z3fold_reclaim_page(pool, 8);
1093 if (ret < 0)
1094 break;
1095 total++;
1096 }
1097
1098 if (reclaimed)
1099 *reclaimed = total;
1100
1101 return ret;
1102}
1103
1104static void *z3fold_zpool_map(void *pool, unsigned long handle,
1105 enum zpool_mapmode mm)
1106{
1107 return z3fold_map(pool, handle);
1108}
1109static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1110{
1111 z3fold_unmap(pool, handle);
1112}
1113
1114static u64 z3fold_zpool_total_size(void *pool)
1115{
1116 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1117}
1118
1119static struct zpool_driver z3fold_zpool_driver = {
1120 .type = "z3fold",
1121 .owner = THIS_MODULE,
1122 .create = z3fold_zpool_create,
1123 .destroy = z3fold_zpool_destroy,
1124 .malloc = z3fold_zpool_malloc,
1125 .free = z3fold_zpool_free,
1126 .shrink = z3fold_zpool_shrink,
1127 .map = z3fold_zpool_map,
1128 .unmap = z3fold_zpool_unmap,
1129 .total_size = z3fold_zpool_total_size,
1130};
1131
1132MODULE_ALIAS("zpool-z3fold");
1133
1134static int __init init_z3fold(void)
1135{
1136 /* Make sure the z3fold header is not larger than the page size */
1137 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1138 zpool_register_driver(&z3fold_zpool_driver);
1139
1140 return 0;
1141}
1142
1143static void __exit exit_z3fold(void)
1144{
1145 zpool_unregister_driver(&z3fold_zpool_driver);
1146}
1147
1148module_init(init_z3fold);
1149module_exit(exit_z3fold);
1150
1151MODULE_LICENSE("GPL");
1152MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1153MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");
1154