1 // SPDX-License-Identifier: GPL-2.0-only
5 * Author: Vitaly Wool <vitaly.wool@konsulko.com>
6 * Copyright (C) 2016, Sony Mobile Communications Inc.
8 * This implementation is based on zbud written by Seth Jennings.
10 * z3fold is an special purpose allocator for storing compressed pages. It
11 * can store up to three compressed pages per page which improves the
12 * compression ratio of zbud while retaining its main concepts (e. g. always
13 * storing an integral number of objects per page) and simplicity.
14 * It still has simple and deterministic reclaim properties that make it
15 * preferable to a higher density approach (with no requirement on integral
16 * number of object per page) when reclaim is used.
18 * As in zbud, pages are divided into "chunks". The size of the chunks is
19 * fixed at compile time and is determined by NCHUNKS_ORDER below.
21 * z3fold doesn't export any API and is meant to be used via zpool API.
24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
26 #include <linux/atomic.h>
27 #include <linux/sched.h>
28 #include <linux/cpumask.h>
29 #include <linux/list.h>
31 #include <linux/module.h>
32 #include <linux/page-flags.h>
33 #include <linux/migrate.h>
34 #include <linux/node.h>
35 #include <linux/compaction.h>
36 #include <linux/percpu.h>
37 #include <linux/mount.h>
38 #include <linux/pseudo_fs.h>
40 #include <linux/preempt.h>
41 #include <linux/workqueue.h>
42 #include <linux/slab.h>
43 #include <linux/spinlock.h>
44 #include <linux/zpool.h>
45 #include <linux/magic.h>
48 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
49 * adjusting internal fragmentation. It also determines the number of
50 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
51 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
52 * in the beginning of an allocated page are occupied by z3fold header, so
53 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
54 * which shows the max number of free chunks in z3fold page, also there will
55 * be 63, or 62, respectively, freelists per pool.
57 #define NCHUNKS_ORDER 6
59 #define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
60 #define CHUNK_SIZE (1 << CHUNK_SHIFT)
61 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
62 #define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
63 #define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
64 #define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
66 #define BUDDY_MASK (0x3)
68 #define SLOTS_ALIGN (0x40)
75 int (*evict)(struct z3fold_pool *pool, unsigned long handle);
86 struct z3fold_buddy_slots {
88 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
89 * be enough slots to hold all possible variants
91 unsigned long slot[BUDDY_MASK + 1];
92 unsigned long pool; /* back link + flags */
94 #define HANDLE_FLAG_MASK (0x03)
97 * struct z3fold_header - z3fold page metadata occupying first chunks of each
98 * z3fold page, except for HEADLESS pages
99 * @buddy: links the z3fold page into the relevant list in the
101 * @page_lock: per-page lock
102 * @refcount: reference count for the z3fold page
103 * @work: work_struct for page layout optimization
104 * @slots: pointer to the structure holding buddy slots
105 * @pool: pointer to the containing pool
106 * @cpu: CPU which this page "belongs" to
107 * @first_chunks: the size of the first buddy in chunks, 0 if free
108 * @middle_chunks: the size of the middle buddy in chunks, 0 if free
109 * @last_chunks: the size of the last buddy in chunks, 0 if free
110 * @first_num: the starting number (for the first handle)
111 * @mapped_count: the number of objects currently mapped
113 struct z3fold_header {
114 struct list_head buddy;
115 spinlock_t page_lock;
116 struct kref refcount;
117 struct work_struct work;
118 struct z3fold_buddy_slots *slots;
119 struct z3fold_pool *pool;
121 unsigned short first_chunks;
122 unsigned short middle_chunks;
123 unsigned short last_chunks;
124 unsigned short start_middle;
125 unsigned short first_num:2;
126 unsigned short mapped_count:2;
130 * struct z3fold_pool - stores metadata for each z3fold pool
132 * @lock: protects pool unbuddied/lru lists
133 * @stale_lock: protects pool stale page list
134 * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
135 * buddies; the list each z3fold page is added to depends on
136 * the size of its free region.
137 * @lru: list tracking the z3fold pages in LRU order by most recently
139 * @stale: list of pages marked for freeing
140 * @pages_nr: number of z3fold pages in the pool.
141 * @c_handle: cache for z3fold_buddy_slots allocation
142 * @ops: pointer to a structure of user defined operations specified at
143 * pool creation time.
144 * @compact_wq: workqueue for page layout background optimization
145 * @release_wq: workqueue for safe page release
146 * @work: work_struct for safe page release
147 * @inode: inode for z3fold pseudo filesystem
149 * This structure is allocated at pool creation time and maintains metadata
150 * pertaining to a particular z3fold pool.
155 spinlock_t stale_lock;
156 struct list_head *unbuddied;
157 struct list_head lru;
158 struct list_head stale;
160 struct kmem_cache *c_handle;
161 const struct z3fold_ops *ops;
163 const struct zpool_ops *zpool_ops;
164 struct workqueue_struct *compact_wq;
165 struct workqueue_struct *release_wq;
166 struct work_struct work;
171 * Internal z3fold page flags
173 enum z3fold_page_flags {
178 PAGE_CLAIMED, /* by either reclaim or free */
185 /* Converts an allocation size in bytes to size in z3fold chunks */
186 static int size_to_chunks(size_t size)
188 return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
191 #define for_each_unbuddied_list(_iter, _begin) \
192 for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
194 static void compact_page_work(struct work_struct *w);
196 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
199 struct z3fold_buddy_slots *slots;
201 slots = kmem_cache_alloc(pool->c_handle,
202 (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
205 memset(slots->slot, 0, sizeof(slots->slot));
206 slots->pool = (unsigned long)pool;
212 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
214 return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
217 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
219 return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
222 static inline void free_handle(unsigned long handle)
224 struct z3fold_buddy_slots *slots;
228 if (handle & (1 << PAGE_HEADLESS))
231 WARN_ON(*(unsigned long *)handle == 0);
232 *(unsigned long *)handle = 0;
233 slots = handle_to_slots(handle);
235 for (i = 0; i <= BUDDY_MASK; i++) {
236 if (slots->slot[i]) {
243 struct z3fold_pool *pool = slots_to_pool(slots);
245 kmem_cache_free(pool->c_handle, slots);
249 static int z3fold_init_fs_context(struct fs_context *fc)
251 return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
254 static struct file_system_type z3fold_fs = {
256 .init_fs_context = z3fold_init_fs_context,
257 .kill_sb = kill_anon_super,
260 static struct vfsmount *z3fold_mnt;
261 static int z3fold_mount(void)
265 z3fold_mnt = kern_mount(&z3fold_fs);
266 if (IS_ERR(z3fold_mnt))
267 ret = PTR_ERR(z3fold_mnt);
272 static void z3fold_unmount(void)
274 kern_unmount(z3fold_mnt);
277 static const struct address_space_operations z3fold_aops;
278 static int z3fold_register_migration(struct z3fold_pool *pool)
280 pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
281 if (IS_ERR(pool->inode)) {
286 pool->inode->i_mapping->private_data = pool;
287 pool->inode->i_mapping->a_ops = &z3fold_aops;
291 static void z3fold_unregister_migration(struct z3fold_pool *pool)
297 /* Initializes the z3fold header of a newly allocated z3fold page */
298 static struct z3fold_header *init_z3fold_page(struct page *page,
299 struct z3fold_pool *pool, gfp_t gfp)
301 struct z3fold_header *zhdr = page_address(page);
302 struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp);
307 INIT_LIST_HEAD(&page->lru);
308 clear_bit(PAGE_HEADLESS, &page->private);
309 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
310 clear_bit(NEEDS_COMPACTING, &page->private);
311 clear_bit(PAGE_STALE, &page->private);
312 clear_bit(PAGE_CLAIMED, &page->private);
314 spin_lock_init(&zhdr->page_lock);
315 kref_init(&zhdr->refcount);
316 zhdr->first_chunks = 0;
317 zhdr->middle_chunks = 0;
318 zhdr->last_chunks = 0;
320 zhdr->start_middle = 0;
324 INIT_LIST_HEAD(&zhdr->buddy);
325 INIT_WORK(&zhdr->work, compact_page_work);
329 /* Resets the struct page fields and frees the page */
330 static void free_z3fold_page(struct page *page, bool headless)
334 __ClearPageMovable(page);
337 ClearPagePrivate(page);
341 /* Lock a z3fold page */
342 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
344 spin_lock(&zhdr->page_lock);
347 /* Try to lock a z3fold page */
348 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
350 return spin_trylock(&zhdr->page_lock);
353 /* Unlock a z3fold page */
354 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
356 spin_unlock(&zhdr->page_lock);
359 /* Helper function to build the index */
360 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
362 return (bud + zhdr->first_num) & BUDDY_MASK;
366 * Encodes the handle of a particular buddy within a z3fold page
367 * Pool lock should be held as this function accesses first_num
369 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
371 struct z3fold_buddy_slots *slots;
372 unsigned long h = (unsigned long)zhdr;
376 * For a headless page, its handle is its pointer with the extra
377 * PAGE_HEADLESS bit set
380 return h | (1 << PAGE_HEADLESS);
382 /* otherwise, return pointer to encoded handle */
383 idx = __idx(zhdr, bud);
386 h |= (zhdr->last_chunks << BUDDY_SHIFT);
389 slots->slot[idx] = h;
390 return (unsigned long)&slots->slot[idx];
393 /* Returns the z3fold page where a given handle is stored */
394 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
396 unsigned long addr = h;
398 if (!(addr & (1 << PAGE_HEADLESS)))
399 addr = *(unsigned long *)h;
401 return (struct z3fold_header *)(addr & PAGE_MASK);
404 /* only for LAST bud, returns zero otherwise */
405 static unsigned short handle_to_chunks(unsigned long handle)
407 unsigned long addr = *(unsigned long *)handle;
409 return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
413 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
414 * but that doesn't matter. because the masking will result in the
415 * correct buddy number.
417 static enum buddy handle_to_buddy(unsigned long handle)
419 struct z3fold_header *zhdr;
422 WARN_ON(handle & (1 << PAGE_HEADLESS));
423 addr = *(unsigned long *)handle;
424 zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
425 return (addr - zhdr->first_num) & BUDDY_MASK;
428 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
433 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
435 struct page *page = virt_to_page(zhdr);
436 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
438 WARN_ON(!list_empty(&zhdr->buddy));
439 set_bit(PAGE_STALE, &page->private);
440 clear_bit(NEEDS_COMPACTING, &page->private);
441 spin_lock(&pool->lock);
442 if (!list_empty(&page->lru))
443 list_del_init(&page->lru);
444 spin_unlock(&pool->lock);
446 z3fold_page_unlock(zhdr);
447 spin_lock(&pool->stale_lock);
448 list_add(&zhdr->buddy, &pool->stale);
449 queue_work(pool->release_wq, &pool->work);
450 spin_unlock(&pool->stale_lock);
453 static void __attribute__((__unused__))
454 release_z3fold_page(struct kref *ref)
456 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
458 __release_z3fold_page(zhdr, false);
461 static void release_z3fold_page_locked(struct kref *ref)
463 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
465 WARN_ON(z3fold_page_trylock(zhdr));
466 __release_z3fold_page(zhdr, true);
469 static void release_z3fold_page_locked_list(struct kref *ref)
471 struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
473 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
474 spin_lock(&pool->lock);
475 list_del_init(&zhdr->buddy);
476 spin_unlock(&pool->lock);
478 WARN_ON(z3fold_page_trylock(zhdr));
479 __release_z3fold_page(zhdr, true);
482 static void free_pages_work(struct work_struct *w)
484 struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
486 spin_lock(&pool->stale_lock);
487 while (!list_empty(&pool->stale)) {
488 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
489 struct z3fold_header, buddy);
490 struct page *page = virt_to_page(zhdr);
492 list_del(&zhdr->buddy);
493 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
495 spin_unlock(&pool->stale_lock);
496 cancel_work_sync(&zhdr->work);
497 free_z3fold_page(page, false);
499 spin_lock(&pool->stale_lock);
501 spin_unlock(&pool->stale_lock);
505 * Returns the number of free chunks in a z3fold page.
506 * NB: can't be used with HEADLESS pages.
508 static int num_free_chunks(struct z3fold_header *zhdr)
512 * If there is a middle object, pick up the bigger free space
513 * either before or after it. Otherwise just subtract the number
514 * of chunks occupied by the first and the last objects.
516 if (zhdr->middle_chunks != 0) {
517 int nfree_before = zhdr->first_chunks ?
518 0 : zhdr->start_middle - ZHDR_CHUNKS;
519 int nfree_after = zhdr->last_chunks ?
521 (zhdr->start_middle + zhdr->middle_chunks);
522 nfree = max(nfree_before, nfree_after);
524 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
528 /* Add to the appropriate unbuddied list */
529 static inline void add_to_unbuddied(struct z3fold_pool *pool,
530 struct z3fold_header *zhdr)
532 if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
533 zhdr->middle_chunks == 0) {
534 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
536 int freechunks = num_free_chunks(zhdr);
537 spin_lock(&pool->lock);
538 list_add(&zhdr->buddy, &unbuddied[freechunks]);
539 spin_unlock(&pool->lock);
540 zhdr->cpu = smp_processor_id();
541 put_cpu_ptr(pool->unbuddied);
545 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
546 unsigned short dst_chunk)
549 return memmove(beg + (dst_chunk << CHUNK_SHIFT),
550 beg + (zhdr->start_middle << CHUNK_SHIFT),
551 zhdr->middle_chunks << CHUNK_SHIFT);
554 #define BIG_CHUNK_GAP 3
555 /* Has to be called with lock held */
556 static int z3fold_compact_page(struct z3fold_header *zhdr)
558 struct page *page = virt_to_page(zhdr);
560 if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
561 return 0; /* can't move middle chunk, it's used */
563 if (unlikely(PageIsolated(page)))
566 if (zhdr->middle_chunks == 0)
567 return 0; /* nothing to compact */
569 if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
570 /* move to the beginning */
571 mchunk_memmove(zhdr, ZHDR_CHUNKS);
572 zhdr->first_chunks = zhdr->middle_chunks;
573 zhdr->middle_chunks = 0;
574 zhdr->start_middle = 0;
580 * moving data is expensive, so let's only do that if
581 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
583 if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
584 zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
586 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
587 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
589 } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
590 TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
591 + zhdr->middle_chunks) >=
593 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
595 mchunk_memmove(zhdr, new_start);
596 zhdr->start_middle = new_start;
603 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
605 struct z3fold_pool *pool = zhdr_to_pool(zhdr);
608 page = virt_to_page(zhdr);
610 WARN_ON(z3fold_page_trylock(zhdr));
612 z3fold_page_lock(zhdr);
613 if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
614 z3fold_page_unlock(zhdr);
617 spin_lock(&pool->lock);
618 list_del_init(&zhdr->buddy);
619 spin_unlock(&pool->lock);
621 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
622 atomic64_dec(&pool->pages_nr);
626 if (unlikely(PageIsolated(page) ||
627 test_bit(PAGE_STALE, &page->private))) {
628 z3fold_page_unlock(zhdr);
632 z3fold_compact_page(zhdr);
633 add_to_unbuddied(pool, zhdr);
634 z3fold_page_unlock(zhdr);
637 static void compact_page_work(struct work_struct *w)
639 struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
642 do_compact_page(zhdr, false);
645 /* returns _locked_ z3fold page header or NULL */
646 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
647 size_t size, bool can_sleep)
649 struct z3fold_header *zhdr = NULL;
651 struct list_head *unbuddied;
652 int chunks = size_to_chunks(size), i;
655 /* First, try to find an unbuddied z3fold page. */
656 unbuddied = get_cpu_ptr(pool->unbuddied);
657 for_each_unbuddied_list(i, chunks) {
658 struct list_head *l = &unbuddied[i];
660 zhdr = list_first_entry_or_null(READ_ONCE(l),
661 struct z3fold_header, buddy);
666 /* Re-check under lock. */
667 spin_lock(&pool->lock);
669 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
670 struct z3fold_header, buddy)) ||
671 !z3fold_page_trylock(zhdr)) {
672 spin_unlock(&pool->lock);
674 put_cpu_ptr(pool->unbuddied);
679 list_del_init(&zhdr->buddy);
681 spin_unlock(&pool->lock);
683 page = virt_to_page(zhdr);
684 if (test_bit(NEEDS_COMPACTING, &page->private)) {
685 z3fold_page_unlock(zhdr);
687 put_cpu_ptr(pool->unbuddied);
694 * this page could not be removed from its unbuddied
695 * list while pool lock was held, and then we've taken
696 * page lock so kref_put could not be called before
697 * we got here, so it's safe to just call kref_get()
699 kref_get(&zhdr->refcount);
702 put_cpu_ptr(pool->unbuddied);
707 /* look for _exact_ match on other cpus' lists */
708 for_each_online_cpu(cpu) {
711 unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
712 spin_lock(&pool->lock);
713 l = &unbuddied[chunks];
715 zhdr = list_first_entry_or_null(READ_ONCE(l),
716 struct z3fold_header, buddy);
718 if (!zhdr || !z3fold_page_trylock(zhdr)) {
719 spin_unlock(&pool->lock);
723 list_del_init(&zhdr->buddy);
725 spin_unlock(&pool->lock);
727 page = virt_to_page(zhdr);
728 if (test_bit(NEEDS_COMPACTING, &page->private)) {
729 z3fold_page_unlock(zhdr);
735 kref_get(&zhdr->refcount);
748 * z3fold_create_pool() - create a new z3fold pool
750 * @gfp: gfp flags when allocating the z3fold pool structure
751 * @ops: user-defined operations for the z3fold pool
753 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
756 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
757 const struct z3fold_ops *ops)
759 struct z3fold_pool *pool = NULL;
762 pool = kzalloc(sizeof(struct z3fold_pool), gfp);
765 pool->c_handle = kmem_cache_create("z3fold_handle",
766 sizeof(struct z3fold_buddy_slots),
767 SLOTS_ALIGN, 0, NULL);
770 spin_lock_init(&pool->lock);
771 spin_lock_init(&pool->stale_lock);
772 pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
773 if (!pool->unbuddied)
775 for_each_possible_cpu(cpu) {
776 struct list_head *unbuddied =
777 per_cpu_ptr(pool->unbuddied, cpu);
778 for_each_unbuddied_list(i, 0)
779 INIT_LIST_HEAD(&unbuddied[i]);
781 INIT_LIST_HEAD(&pool->lru);
782 INIT_LIST_HEAD(&pool->stale);
783 atomic64_set(&pool->pages_nr, 0);
785 pool->compact_wq = create_singlethread_workqueue(pool->name);
786 if (!pool->compact_wq)
788 pool->release_wq = create_singlethread_workqueue(pool->name);
789 if (!pool->release_wq)
791 if (z3fold_register_migration(pool))
793 INIT_WORK(&pool->work, free_pages_work);
798 destroy_workqueue(pool->release_wq);
800 destroy_workqueue(pool->compact_wq);
802 free_percpu(pool->unbuddied);
804 kmem_cache_destroy(pool->c_handle);
812 * z3fold_destroy_pool() - destroys an existing z3fold pool
813 * @pool: the z3fold pool to be destroyed
815 * The pool should be emptied before this function is called.
817 static void z3fold_destroy_pool(struct z3fold_pool *pool)
819 kmem_cache_destroy(pool->c_handle);
822 * We need to destroy pool->compact_wq before pool->release_wq,
823 * as any pending work on pool->compact_wq will call
824 * queue_work(pool->release_wq, &pool->work).
826 * There are still outstanding pages until both workqueues are drained,
827 * so we cannot unregister migration until then.
830 destroy_workqueue(pool->compact_wq);
831 destroy_workqueue(pool->release_wq);
832 z3fold_unregister_migration(pool);
837 * z3fold_alloc() - allocates a region of a given size
838 * @pool: z3fold pool from which to allocate
839 * @size: size in bytes of the desired allocation
840 * @gfp: gfp flags used if the pool needs to grow
841 * @handle: handle of the new allocation
843 * This function will attempt to find a free region in the pool large enough to
844 * satisfy the allocation request. A search of the unbuddied lists is
845 * performed first. If no suitable free region is found, then a new page is
846 * allocated and added to the pool to satisfy the request.
848 * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
849 * as z3fold pool pages.
851 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
852 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
855 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
856 unsigned long *handle)
858 int chunks = size_to_chunks(size);
859 struct z3fold_header *zhdr = NULL;
860 struct page *page = NULL;
862 bool can_sleep = gfpflags_allow_blocking(gfp);
867 if (size > PAGE_SIZE)
870 if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
874 zhdr = __z3fold_alloc(pool, size, can_sleep);
876 if (zhdr->first_chunks == 0) {
877 if (zhdr->middle_chunks != 0 &&
878 chunks >= zhdr->start_middle)
882 } else if (zhdr->last_chunks == 0)
884 else if (zhdr->middle_chunks == 0)
887 if (kref_put(&zhdr->refcount,
888 release_z3fold_page_locked))
889 atomic64_dec(&pool->pages_nr);
891 z3fold_page_unlock(zhdr);
892 pr_err("No free chunks in unbuddied\n");
896 page = virt_to_page(zhdr);
904 spin_lock(&pool->stale_lock);
905 zhdr = list_first_entry_or_null(&pool->stale,
906 struct z3fold_header, buddy);
908 * Before allocating a page, let's see if we can take one from
909 * the stale pages list. cancel_work_sync() can sleep so we
910 * limit this case to the contexts where we can sleep
913 list_del(&zhdr->buddy);
914 spin_unlock(&pool->stale_lock);
915 cancel_work_sync(&zhdr->work);
916 page = virt_to_page(zhdr);
918 spin_unlock(&pool->stale_lock);
922 page = alloc_page(gfp);
927 zhdr = init_z3fold_page(page, pool, gfp);
932 atomic64_inc(&pool->pages_nr);
934 if (bud == HEADLESS) {
935 set_bit(PAGE_HEADLESS, &page->private);
940 __SetPageMovable(page, pool->inode->i_mapping);
943 if (trylock_page(page)) {
944 __SetPageMovable(page, pool->inode->i_mapping);
948 z3fold_page_lock(zhdr);
952 zhdr->first_chunks = chunks;
953 else if (bud == LAST)
954 zhdr->last_chunks = chunks;
956 zhdr->middle_chunks = chunks;
957 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
959 add_to_unbuddied(pool, zhdr);
962 spin_lock(&pool->lock);
963 /* Add/move z3fold page to beginning of LRU */
964 if (!list_empty(&page->lru))
965 list_del(&page->lru);
967 list_add(&page->lru, &pool->lru);
969 *handle = encode_handle(zhdr, bud);
970 spin_unlock(&pool->lock);
972 z3fold_page_unlock(zhdr);
978 * z3fold_free() - frees the allocation associated with the given handle
979 * @pool: pool in which the allocation resided
980 * @handle: handle associated with the allocation returned by z3fold_alloc()
982 * In the case that the z3fold page in which the allocation resides is under
983 * reclaim, as indicated by the PG_reclaim flag being set, this function
984 * only sets the first|last_chunks to 0. The page is actually freed
985 * once both buddies are evicted (see z3fold_reclaim_page() below).
987 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
989 struct z3fold_header *zhdr;
993 zhdr = handle_to_z3fold_header(handle);
994 page = virt_to_page(zhdr);
996 if (test_bit(PAGE_HEADLESS, &page->private)) {
997 /* if a headless page is under reclaim, just leave.
998 * NB: we use test_and_set_bit for a reason: if the bit
999 * has not been set before, we release this page
1000 * immediately so we don't care about its value any more.
1002 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1003 spin_lock(&pool->lock);
1004 list_del(&page->lru);
1005 spin_unlock(&pool->lock);
1006 free_z3fold_page(page, true);
1007 atomic64_dec(&pool->pages_nr);
1012 /* Non-headless case */
1013 z3fold_page_lock(zhdr);
1014 bud = handle_to_buddy(handle);
1018 zhdr->first_chunks = 0;
1021 zhdr->middle_chunks = 0;
1024 zhdr->last_chunks = 0;
1027 pr_err("%s: unknown bud %d\n", __func__, bud);
1029 z3fold_page_unlock(zhdr);
1033 free_handle(handle);
1034 if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1035 atomic64_dec(&pool->pages_nr);
1038 if (test_bit(PAGE_CLAIMED, &page->private)) {
1039 z3fold_page_unlock(zhdr);
1042 if (unlikely(PageIsolated(page)) ||
1043 test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1044 z3fold_page_unlock(zhdr);
1047 if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1048 spin_lock(&pool->lock);
1049 list_del_init(&zhdr->buddy);
1050 spin_unlock(&pool->lock);
1052 kref_get(&zhdr->refcount);
1053 do_compact_page(zhdr, true);
1056 kref_get(&zhdr->refcount);
1057 queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1058 z3fold_page_unlock(zhdr);
1062 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1063 * @pool: pool from which a page will attempt to be evicted
1064 * @retries: number of pages on the LRU list for which eviction will
1065 * be attempted before failing
1067 * z3fold reclaim is different from normal system reclaim in that it is done
1068 * from the bottom, up. This is because only the bottom layer, z3fold, has
1069 * information on how the allocations are organized within each z3fold page.
1070 * This has the potential to create interesting locking situations between
1071 * z3fold and the user, however.
1073 * To avoid these, this is how z3fold_reclaim_page() should be called:
1075 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1076 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1077 * call the user-defined eviction handler with the pool and handle as
1080 * If the handle can not be evicted, the eviction handler should return
1081 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1082 * appropriate list and try the next z3fold page on the LRU up to
1083 * a user defined number of retries.
1085 * If the handle is successfully evicted, the eviction handler should
1086 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1087 * contains logic to delay freeing the page if the page is under reclaim,
1088 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1090 * If all buddies in the z3fold page are successfully evicted, then the
1091 * z3fold page can be freed.
1093 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1094 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1095 * the retry limit was hit.
1097 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1100 struct z3fold_header *zhdr = NULL;
1101 struct page *page = NULL;
1102 struct list_head *pos;
1103 unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1105 spin_lock(&pool->lock);
1106 if (!pool->ops || !pool->ops->evict || retries == 0) {
1107 spin_unlock(&pool->lock);
1110 for (i = 0; i < retries; i++) {
1111 if (list_empty(&pool->lru)) {
1112 spin_unlock(&pool->lock);
1115 list_for_each_prev(pos, &pool->lru) {
1116 page = list_entry(pos, struct page, lru);
1118 /* this bit could have been set by free, in which case
1119 * we pass over to the next page in the pool.
1121 if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1124 if (unlikely(PageIsolated(page)))
1126 if (test_bit(PAGE_HEADLESS, &page->private))
1129 zhdr = page_address(page);
1130 if (!z3fold_page_trylock(zhdr)) {
1132 continue; /* can't evict at this point */
1134 kref_get(&zhdr->refcount);
1135 list_del_init(&zhdr->buddy);
1143 list_del_init(&page->lru);
1144 spin_unlock(&pool->lock);
1146 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1148 * We need encode the handles before unlocking, since
1149 * we can race with free that will set
1150 * (first|last)_chunks to 0
1155 if (zhdr->first_chunks)
1156 first_handle = encode_handle(zhdr, FIRST);
1157 if (zhdr->middle_chunks)
1158 middle_handle = encode_handle(zhdr, MIDDLE);
1159 if (zhdr->last_chunks)
1160 last_handle = encode_handle(zhdr, LAST);
1162 * it's safe to unlock here because we hold a
1163 * reference to this page
1165 z3fold_page_unlock(zhdr);
1167 first_handle = encode_handle(zhdr, HEADLESS);
1168 last_handle = middle_handle = 0;
1171 /* Issue the eviction callback(s) */
1172 if (middle_handle) {
1173 ret = pool->ops->evict(pool, middle_handle);
1178 ret = pool->ops->evict(pool, first_handle);
1183 ret = pool->ops->evict(pool, last_handle);
1188 if (test_bit(PAGE_HEADLESS, &page->private)) {
1190 free_z3fold_page(page, true);
1191 atomic64_dec(&pool->pages_nr);
1194 spin_lock(&pool->lock);
1195 list_add(&page->lru, &pool->lru);
1196 spin_unlock(&pool->lock);
1198 z3fold_page_lock(zhdr);
1199 clear_bit(PAGE_CLAIMED, &page->private);
1200 if (kref_put(&zhdr->refcount,
1201 release_z3fold_page_locked)) {
1202 atomic64_dec(&pool->pages_nr);
1206 * if we are here, the page is still not completely
1207 * free. Take the global pool lock then to be able
1208 * to add it back to the lru list
1210 spin_lock(&pool->lock);
1211 list_add(&page->lru, &pool->lru);
1212 spin_unlock(&pool->lock);
1213 z3fold_page_unlock(zhdr);
1216 /* We started off locked to we need to lock the pool back */
1217 spin_lock(&pool->lock);
1219 spin_unlock(&pool->lock);
1224 * z3fold_map() - maps the allocation associated with the given handle
1225 * @pool: pool in which the allocation resides
1226 * @handle: handle associated with the allocation to be mapped
1228 * Extracts the buddy number from handle and constructs the pointer to the
1229 * correct starting chunk within the page.
1231 * Returns: a pointer to the mapped allocation
1233 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1235 struct z3fold_header *zhdr;
1240 zhdr = handle_to_z3fold_header(handle);
1242 page = virt_to_page(zhdr);
1244 if (test_bit(PAGE_HEADLESS, &page->private))
1247 z3fold_page_lock(zhdr);
1248 buddy = handle_to_buddy(handle);
1251 addr += ZHDR_SIZE_ALIGNED;
1254 addr += zhdr->start_middle << CHUNK_SHIFT;
1255 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1258 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1261 pr_err("unknown buddy id %d\n", buddy);
1268 zhdr->mapped_count++;
1269 z3fold_page_unlock(zhdr);
1275 * z3fold_unmap() - unmaps the allocation associated with the given handle
1276 * @pool: pool in which the allocation resides
1277 * @handle: handle associated with the allocation to be unmapped
1279 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1281 struct z3fold_header *zhdr;
1285 zhdr = handle_to_z3fold_header(handle);
1286 page = virt_to_page(zhdr);
1288 if (test_bit(PAGE_HEADLESS, &page->private))
1291 z3fold_page_lock(zhdr);
1292 buddy = handle_to_buddy(handle);
1293 if (buddy == MIDDLE)
1294 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1295 zhdr->mapped_count--;
1296 z3fold_page_unlock(zhdr);
1300 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1301 * @pool: pool whose size is being queried
1303 * Returns: size in pages of the given pool.
1305 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1307 return atomic64_read(&pool->pages_nr);
1310 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1312 struct z3fold_header *zhdr;
1313 struct z3fold_pool *pool;
1315 VM_BUG_ON_PAGE(!PageMovable(page), page);
1316 VM_BUG_ON_PAGE(PageIsolated(page), page);
1318 if (test_bit(PAGE_HEADLESS, &page->private))
1321 zhdr = page_address(page);
1322 z3fold_page_lock(zhdr);
1323 if (test_bit(NEEDS_COMPACTING, &page->private) ||
1324 test_bit(PAGE_STALE, &page->private))
1327 pool = zhdr_to_pool(zhdr);
1329 if (zhdr->mapped_count == 0) {
1330 kref_get(&zhdr->refcount);
1331 if (!list_empty(&zhdr->buddy))
1332 list_del_init(&zhdr->buddy);
1333 spin_lock(&pool->lock);
1334 if (!list_empty(&page->lru))
1335 list_del(&page->lru);
1336 spin_unlock(&pool->lock);
1337 z3fold_page_unlock(zhdr);
1341 z3fold_page_unlock(zhdr);
1345 static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1346 struct page *page, enum migrate_mode mode)
1348 struct z3fold_header *zhdr, *new_zhdr;
1349 struct z3fold_pool *pool;
1350 struct address_space *new_mapping;
1352 VM_BUG_ON_PAGE(!PageMovable(page), page);
1353 VM_BUG_ON_PAGE(!PageIsolated(page), page);
1354 VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1356 zhdr = page_address(page);
1357 pool = zhdr_to_pool(zhdr);
1359 if (!z3fold_page_trylock(zhdr)) {
1362 if (zhdr->mapped_count != 0) {
1363 z3fold_page_unlock(zhdr);
1366 if (work_pending(&zhdr->work)) {
1367 z3fold_page_unlock(zhdr);
1370 new_zhdr = page_address(newpage);
1371 memcpy(new_zhdr, zhdr, PAGE_SIZE);
1372 newpage->private = page->private;
1374 z3fold_page_unlock(zhdr);
1375 spin_lock_init(&new_zhdr->page_lock);
1376 INIT_WORK(&new_zhdr->work, compact_page_work);
1378 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1379 * so we only have to reinitialize it.
1381 INIT_LIST_HEAD(&new_zhdr->buddy);
1382 new_mapping = page_mapping(page);
1383 __ClearPageMovable(page);
1384 ClearPagePrivate(page);
1387 z3fold_page_lock(new_zhdr);
1388 if (new_zhdr->first_chunks)
1389 encode_handle(new_zhdr, FIRST);
1390 if (new_zhdr->last_chunks)
1391 encode_handle(new_zhdr, LAST);
1392 if (new_zhdr->middle_chunks)
1393 encode_handle(new_zhdr, MIDDLE);
1394 set_bit(NEEDS_COMPACTING, &newpage->private);
1395 new_zhdr->cpu = smp_processor_id();
1396 spin_lock(&pool->lock);
1397 list_add(&newpage->lru, &pool->lru);
1398 spin_unlock(&pool->lock);
1399 __SetPageMovable(newpage, new_mapping);
1400 z3fold_page_unlock(new_zhdr);
1402 queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1404 page_mapcount_reset(page);
1409 static void z3fold_page_putback(struct page *page)
1411 struct z3fold_header *zhdr;
1412 struct z3fold_pool *pool;
1414 zhdr = page_address(page);
1415 pool = zhdr_to_pool(zhdr);
1417 z3fold_page_lock(zhdr);
1418 if (!list_empty(&zhdr->buddy))
1419 list_del_init(&zhdr->buddy);
1420 INIT_LIST_HEAD(&page->lru);
1421 if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1422 atomic64_dec(&pool->pages_nr);
1425 spin_lock(&pool->lock);
1426 list_add(&page->lru, &pool->lru);
1427 spin_unlock(&pool->lock);
1428 z3fold_page_unlock(zhdr);
1431 static const struct address_space_operations z3fold_aops = {
1432 .isolate_page = z3fold_page_isolate,
1433 .migratepage = z3fold_page_migrate,
1434 .putback_page = z3fold_page_putback,
1441 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1443 if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1444 return pool->zpool_ops->evict(pool->zpool, handle);
1449 static const struct z3fold_ops z3fold_zpool_ops = {
1450 .evict = z3fold_zpool_evict
1453 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1454 const struct zpool_ops *zpool_ops,
1455 struct zpool *zpool)
1457 struct z3fold_pool *pool;
1459 pool = z3fold_create_pool(name, gfp,
1460 zpool_ops ? &z3fold_zpool_ops : NULL);
1462 pool->zpool = zpool;
1463 pool->zpool_ops = zpool_ops;
1468 static void z3fold_zpool_destroy(void *pool)
1470 z3fold_destroy_pool(pool);
1473 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1474 unsigned long *handle)
1476 return z3fold_alloc(pool, size, gfp, handle);
1478 static void z3fold_zpool_free(void *pool, unsigned long handle)
1480 z3fold_free(pool, handle);
1483 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1484 unsigned int *reclaimed)
1486 unsigned int total = 0;
1489 while (total < pages) {
1490 ret = z3fold_reclaim_page(pool, 8);
1502 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1503 enum zpool_mapmode mm)
1505 return z3fold_map(pool, handle);
1507 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1509 z3fold_unmap(pool, handle);
1512 static u64 z3fold_zpool_total_size(void *pool)
1514 return z3fold_get_pool_size(pool) * PAGE_SIZE;
1517 static struct zpool_driver z3fold_zpool_driver = {
1519 .owner = THIS_MODULE,
1520 .create = z3fold_zpool_create,
1521 .destroy = z3fold_zpool_destroy,
1522 .malloc = z3fold_zpool_malloc,
1523 .free = z3fold_zpool_free,
1524 .shrink = z3fold_zpool_shrink,
1525 .map = z3fold_zpool_map,
1526 .unmap = z3fold_zpool_unmap,
1527 .total_size = z3fold_zpool_total_size,
1530 MODULE_ALIAS("zpool-z3fold");
1532 static int __init init_z3fold(void)
1536 /* Make sure the z3fold header is not larger than the page size */
1537 BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1538 ret = z3fold_mount();
1542 zpool_register_driver(&z3fold_zpool_driver);
1547 static void __exit exit_z3fold(void)
1550 zpool_unregister_driver(&z3fold_zpool_driver);
1553 module_init(init_z3fold);
1554 module_exit(exit_z3fold);
1556 MODULE_LICENSE("GPL");
1557 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1558 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");