1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * z3fold.c
   4 *
   5 * Author: Vitaly Wool <vitaly.wool@konsulko.com>
   6 * Copyright (C) 2016, Sony Mobile Communications Inc.
   7 *
   8 * This implementation is based on zbud written by Seth Jennings.
   9 *
  10 * z3fold is an special purpose allocator for storing compressed pages. It
  11 * can store up to three compressed pages per page which improves the
  12 * compression ratio of zbud while retaining its main concepts (e. g. always
  13 * storing an integral number of objects per page) and simplicity.
  14 * It still has simple and deterministic reclaim properties that make it
  15 * preferable to a higher density approach (with no requirement on integral
  16 * number of object per page) when reclaim is used.
  17 *
  18 * As in zbud, pages are divided into "chunks".  The size of the chunks is
  19 * fixed at compile time and is determined by NCHUNKS_ORDER below.
  20 *
  21 * z3fold doesn't export any API and is meant to be used via zpool API.
  22 */
  23
  24#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  25
  26#include <linux/atomic.h>
  27#include <linux/sched.h>
  28#include <linux/cpumask.h>
  29#include <linux/list.h>
  30#include <linux/mm.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/preempt.h>
  38#include <linux/workqueue.h>
  39#include <linux/slab.h>
  40#include <linux/spinlock.h>
  41#include <linux/zpool.h>
  42#include <linux/kmemleak.h>
  43
  44/*
  45 * NCHUNKS_ORDER determines the internal allocation granularity, effectively
  46 * adjusting internal fragmentation.  It also determines the number of
  47 * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
  48 * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
  49 * in the beginning of an allocated page are occupied by z3fold header, so
  50 * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
  51 * which shows the max number of free chunks in z3fold page, also there will
  52 * be 63, or 62, respectively, freelists per pool.
  53 */
  54#define NCHUNKS_ORDER	6
  55
  56#define CHUNK_SHIFT	(PAGE_SHIFT - NCHUNKS_ORDER)
  57#define CHUNK_SIZE	(1 << CHUNK_SHIFT)
  58#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
  59#define ZHDR_CHUNKS	(ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
  60#define TOTAL_CHUNKS	(PAGE_SIZE >> CHUNK_SHIFT)
  61#define NCHUNKS		(TOTAL_CHUNKS - ZHDR_CHUNKS)
  62
  63#define BUDDY_MASK	(0x3)
  64#define BUDDY_SHIFT	2
  65#define SLOTS_ALIGN	(0x40)
  66
  67/*****************
  68 * Structures
  69*****************/
  70struct z3fold_pool;
 
 
 
  71
  72enum buddy {
  73	HEADLESS = 0,
  74	FIRST,
  75	MIDDLE,
  76	LAST,
  77	BUDDIES_MAX = LAST
  78};
  79
  80struct z3fold_buddy_slots {
  81	/*
  82	 * we are using BUDDY_MASK in handle_to_buddy etc. so there should
  83	 * be enough slots to hold all possible variants
  84	 */
  85	unsigned long slot[BUDDY_MASK + 1];
  86	unsigned long pool; /* back link */
  87	rwlock_t lock;
  88};
  89#define HANDLE_FLAG_MASK	(0x03)
  90
  91/*
  92 * struct z3fold_header - z3fold page metadata occupying first chunks of each
  93 *			z3fold page, except for HEADLESS pages
  94 * @buddy:		links the z3fold page into the relevant list in the
  95 *			pool
  96 * @page_lock:		per-page lock
  97 * @refcount:		reference count for the z3fold page
  98 * @work:		work_struct for page layout optimization
  99 * @slots:		pointer to the structure holding buddy slots
 100 * @pool:		pointer to the containing pool
 101 * @cpu:		CPU which this page "belongs" to
 102 * @first_chunks:	the size of the first buddy in chunks, 0 if free
 103 * @middle_chunks:	the size of the middle buddy in chunks, 0 if free
 104 * @last_chunks:	the size of the last buddy in chunks, 0 if free
 105 * @first_num:		the starting number (for the first handle)
 106 * @mapped_count:	the number of objects currently mapped
 107 */
 108struct z3fold_header {
 109	struct list_head buddy;
 110	spinlock_t page_lock;
 111	struct kref refcount;
 112	struct work_struct work;
 113	struct z3fold_buddy_slots *slots;
 114	struct z3fold_pool *pool;
 115	short cpu;
 116	unsigned short first_chunks;
 117	unsigned short middle_chunks;
 118	unsigned short last_chunks;
 119	unsigned short start_middle;
 120	unsigned short first_num:2;
 121	unsigned short mapped_count:2;
 122	unsigned short foreign_handles:2;
 123};
 124
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 125/**
 126 * struct z3fold_pool - stores metadata for each z3fold pool
 127 * @name:	pool name
 128 * @lock:	protects pool unbuddied/lru lists
 129 * @stale_lock:	protects pool stale page list
 130 * @unbuddied:	per-cpu array of lists tracking z3fold pages that contain 2-
 131 *		buddies; the list each z3fold page is added to depends on
 132 *		the size of its free region.
 133 * @lru:	list tracking the z3fold pages in LRU order by most recently
 134 *		added buddy.
 135 * @stale:	list of pages marked for freeing
 136 * @pages_nr:	number of z3fold pages in the pool.
 137 * @c_handle:	cache for z3fold_buddy_slots allocation
 138 * @zpool:	zpool driver
 139 * @zpool_ops:	zpool operations structure with an evict callback
 140 * @compact_wq:	workqueue for page layout background optimization
 141 * @release_wq:	workqueue for safe page release
 142 * @work:	work_struct for safe page release
 143 *
 144 * This structure is allocated at pool creation time and maintains metadata
 145 * pertaining to a particular z3fold pool.
 146 */
 147struct z3fold_pool {
 148	const char *name;
 149	spinlock_t lock;
 150	spinlock_t stale_lock;
 151	struct list_head *unbuddied;
 152	struct list_head lru;
 153	struct list_head stale;
 154	atomic64_t pages_nr;
 155	struct kmem_cache *c_handle;
 156	struct zpool *zpool;
 157	const struct zpool_ops *zpool_ops;
 158	struct workqueue_struct *compact_wq;
 159	struct workqueue_struct *release_wq;
 160	struct work_struct work;
 161};
 162
 163/*
 164 * Internal z3fold page flags
 165 */
 166enum z3fold_page_flags {
 167	PAGE_HEADLESS = 0,
 168	MIDDLE_CHUNK_MAPPED,
 169	NEEDS_COMPACTING,
 170	PAGE_STALE,
 171	PAGE_CLAIMED, /* by either reclaim or free */
 172	PAGE_MIGRATED, /* page is migrated and soon to be released */
 173};
 174
 175/*
 176 * handle flags, go under HANDLE_FLAG_MASK
 177 */
 178enum z3fold_handle_flags {
 179	HANDLES_NOFREE = 0,
 180};
 181
 182/*
 183 * Forward declarations
 184 */
 185static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
 186static void compact_page_work(struct work_struct *w);
 187
 188/*****************
 189 * Helpers
 190*****************/
 191
 192/* Converts an allocation size in bytes to size in z3fold chunks */
 193static int size_to_chunks(size_t size)
 194{
 195	return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
 196}
 197
 198#define for_each_unbuddied_list(_iter, _begin) \
 199	for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
 200
 201static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
 202							gfp_t gfp)
 203{
 204	struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
 205							     gfp);
 206
 207	if (slots) {
 208		/* It will be freed separately in free_handle(). */
 209		kmemleak_not_leak(slots);
 210		slots->pool = (unsigned long)pool;
 211		rwlock_init(&slots->lock);
 212	}
 213
 214	return slots;
 215}
 216
 217static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
 218{
 219	return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
 220}
 221
 222static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 223{
 224	return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 225}
 226
 227/* Lock a z3fold page */
 228static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 229{
 230	spin_lock(&zhdr->page_lock);
 231}
 232
 233/* Try to lock a z3fold page */
 234static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 235{
 236	return spin_trylock(&zhdr->page_lock);
 237}
 238
 239/* Unlock a z3fold page */
 240static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
 241{
 242	spin_unlock(&zhdr->page_lock);
 243}
 244
 245/* return locked z3fold page if it's not headless */
 246static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
 247{
 248	struct z3fold_buddy_slots *slots;
 249	struct z3fold_header *zhdr;
 250	int locked = 0;
 251
 252	if (!(handle & (1 << PAGE_HEADLESS))) {
 253		slots = handle_to_slots(handle);
 254		do {
 255			unsigned long addr;
 256
 257			read_lock(&slots->lock);
 258			addr = *(unsigned long *)handle;
 259			zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 260			locked = z3fold_page_trylock(zhdr);
 261			read_unlock(&slots->lock);
 262			if (locked) {
 263				struct page *page = virt_to_page(zhdr);
 264
 265				if (!test_bit(PAGE_MIGRATED, &page->private))
 266					break;
 267				z3fold_page_unlock(zhdr);
 268			}
 269			cpu_relax();
 270		} while (true);
 271	} else {
 272		zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
 273	}
 274
 275	return zhdr;
 276}
 277
 278static inline void put_z3fold_header(struct z3fold_header *zhdr)
 279{
 280	struct page *page = virt_to_page(zhdr);
 281
 282	if (!test_bit(PAGE_HEADLESS, &page->private))
 283		z3fold_page_unlock(zhdr);
 284}
 285
 286static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
 287{
 288	struct z3fold_buddy_slots *slots;
 289	int i;
 290	bool is_free;
 291
 292	if (WARN_ON(*(unsigned long *)handle == 0))
 293		return;
 294
 295	slots = handle_to_slots(handle);
 296	write_lock(&slots->lock);
 297	*(unsigned long *)handle = 0;
 298
 299	if (test_bit(HANDLES_NOFREE, &slots->pool)) {
 300		write_unlock(&slots->lock);
 301		return; /* simple case, nothing else to do */
 302	}
 303
 304	if (zhdr->slots != slots)
 305		zhdr->foreign_handles--;
 306
 307	is_free = true;
 308	for (i = 0; i <= BUDDY_MASK; i++) {
 309		if (slots->slot[i]) {
 310			is_free = false;
 311			break;
 312		}
 313	}
 314	write_unlock(&slots->lock);
 315
 316	if (is_free) {
 317		struct z3fold_pool *pool = slots_to_pool(slots);
 318
 319		if (zhdr->slots == slots)
 320			zhdr->slots = NULL;
 321		kmem_cache_free(pool->c_handle, slots);
 322	}
 323}
 324
 325/* Initializes the z3fold header of a newly allocated z3fold page */
 326static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
 327					struct z3fold_pool *pool, gfp_t gfp)
 328{
 329	struct z3fold_header *zhdr = page_address(page);
 330	struct z3fold_buddy_slots *slots;
 331
 332	INIT_LIST_HEAD(&page->lru);
 333	clear_bit(PAGE_HEADLESS, &page->private);
 334	clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
 335	clear_bit(NEEDS_COMPACTING, &page->private);
 336	clear_bit(PAGE_STALE, &page->private);
 337	clear_bit(PAGE_CLAIMED, &page->private);
 338	clear_bit(PAGE_MIGRATED, &page->private);
 339	if (headless)
 340		return zhdr;
 341
 342	slots = alloc_slots(pool, gfp);
 343	if (!slots)
 344		return NULL;
 345
 346	memset(zhdr, 0, sizeof(*zhdr));
 347	spin_lock_init(&zhdr->page_lock);
 348	kref_init(&zhdr->refcount);
 
 
 
 
 
 349	zhdr->cpu = -1;
 350	zhdr->slots = slots;
 351	zhdr->pool = pool;
 352	INIT_LIST_HEAD(&zhdr->buddy);
 353	INIT_WORK(&zhdr->work, compact_page_work);
 354	return zhdr;
 355}
 356
 357/* Resets the struct page fields and frees the page */
 358static void free_z3fold_page(struct page *page, bool headless)
 359{
 360	if (!headless) {
 361		lock_page(page);
 362		__ClearPageMovable(page);
 363		unlock_page(page);
 364	}
 365	__free_page(page);
 366}
 367
 368/* Helper function to build the index */
 369static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 
 
 
 
 
 
 370{
 371	return (bud + zhdr->first_num) & BUDDY_MASK;
 
 
 
 
 
 
 372}
 373
 374/*
 375 * Encodes the handle of a particular buddy within a z3fold page
 376 * Pool lock should be held as this function accesses first_num
 377 */
 378static unsigned long __encode_handle(struct z3fold_header *zhdr,
 379				struct z3fold_buddy_slots *slots,
 380				enum buddy bud)
 381{
 382	unsigned long h = (unsigned long)zhdr;
 383	int idx = 0;
 384
 385	/*
 386	 * For a headless page, its handle is its pointer with the extra
 387	 * PAGE_HEADLESS bit set
 388	 */
 389	if (bud == HEADLESS)
 390		return h | (1 << PAGE_HEADLESS);
 391
 392	/* otherwise, return pointer to encoded handle */
 393	idx = __idx(zhdr, bud);
 394	h += idx;
 395	if (bud == LAST)
 396		h |= (zhdr->last_chunks << BUDDY_SHIFT);
 397
 398	write_lock(&slots->lock);
 399	slots->slot[idx] = h;
 400	write_unlock(&slots->lock);
 401	return (unsigned long)&slots->slot[idx];
 402}
 403
 404static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 405{
 406	return __encode_handle(zhdr, zhdr->slots, bud);
 
 
 
 
 
 407}
 408
 409/* only for LAST bud, returns zero otherwise */
 410static unsigned short handle_to_chunks(unsigned long handle)
 411{
 412	struct z3fold_buddy_slots *slots = handle_to_slots(handle);
 413	unsigned long addr;
 414
 415	read_lock(&slots->lock);
 416	addr = *(unsigned long *)handle;
 417	read_unlock(&slots->lock);
 418	return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 419}
 420
 421/*
 422 * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
 423 *  but that doesn't matter. because the masking will result in the
 424 *  correct buddy number.
 425 */
 426static enum buddy handle_to_buddy(unsigned long handle)
 427{
 428	struct z3fold_header *zhdr;
 429	struct z3fold_buddy_slots *slots = handle_to_slots(handle);
 430	unsigned long addr;
 431
 432	read_lock(&slots->lock);
 433	WARN_ON(handle & (1 << PAGE_HEADLESS));
 434	addr = *(unsigned long *)handle;
 435	read_unlock(&slots->lock);
 436	zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 437	return (addr - zhdr->first_num) & BUDDY_MASK;
 438}
 439
 440static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
 441{
 442	return zhdr->pool;
 443}
 444
 445static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 446{
 447	struct page *page = virt_to_page(zhdr);
 448	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 449
 450	WARN_ON(!list_empty(&zhdr->buddy));
 451	set_bit(PAGE_STALE, &page->private);
 452	clear_bit(NEEDS_COMPACTING, &page->private);
 453	spin_lock(&pool->lock);
 454	if (!list_empty(&page->lru))
 455		list_del_init(&page->lru);
 456	spin_unlock(&pool->lock);
 457
 458	if (locked)
 459		z3fold_page_unlock(zhdr);
 460
 461	spin_lock(&pool->stale_lock);
 462	list_add(&zhdr->buddy, &pool->stale);
 463	queue_work(pool->release_wq, &pool->work);
 464	spin_unlock(&pool->stale_lock);
 
 465
 466	atomic64_dec(&pool->pages_nr);
 
 
 
 
 
 467}
 468
 469static void release_z3fold_page_locked(struct kref *ref)
 470{
 471	struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 472						refcount);
 473	WARN_ON(z3fold_page_trylock(zhdr));
 474	__release_z3fold_page(zhdr, true);
 475}
 476
 477static void release_z3fold_page_locked_list(struct kref *ref)
 478{
 479	struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 480					       refcount);
 481	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 482
 483	spin_lock(&pool->lock);
 484	list_del_init(&zhdr->buddy);
 485	spin_unlock(&pool->lock);
 486
 487	WARN_ON(z3fold_page_trylock(zhdr));
 488	__release_z3fold_page(zhdr, true);
 489}
 490
 491static void free_pages_work(struct work_struct *w)
 492{
 493	struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
 494
 495	spin_lock(&pool->stale_lock);
 496	while (!list_empty(&pool->stale)) {
 497		struct z3fold_header *zhdr = list_first_entry(&pool->stale,
 498						struct z3fold_header, buddy);
 499		struct page *page = virt_to_page(zhdr);
 500
 501		list_del(&zhdr->buddy);
 502		if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
 503			continue;
 504		spin_unlock(&pool->stale_lock);
 505		cancel_work_sync(&zhdr->work);
 506		free_z3fold_page(page, false);
 507		cond_resched();
 508		spin_lock(&pool->stale_lock);
 509	}
 510	spin_unlock(&pool->stale_lock);
 511}
 512
 513/*
 514 * Returns the number of free chunks in a z3fold page.
 515 * NB: can't be used with HEADLESS pages.
 516 */
 517static int num_free_chunks(struct z3fold_header *zhdr)
 518{
 519	int nfree;
 520	/*
 521	 * If there is a middle object, pick up the bigger free space
 522	 * either before or after it. Otherwise just subtract the number
 523	 * of chunks occupied by the first and the last objects.
 524	 */
 525	if (zhdr->middle_chunks != 0) {
 526		int nfree_before = zhdr->first_chunks ?
 527			0 : zhdr->start_middle - ZHDR_CHUNKS;
 528		int nfree_after = zhdr->last_chunks ?
 529			0 : TOTAL_CHUNKS -
 530				(zhdr->start_middle + zhdr->middle_chunks);
 531		nfree = max(nfree_before, nfree_after);
 532	} else
 533		nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 534	return nfree;
 535}
 536
 537/* Add to the appropriate unbuddied list */
 538static inline void add_to_unbuddied(struct z3fold_pool *pool,
 539				struct z3fold_header *zhdr)
 540{
 541	if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
 542			zhdr->middle_chunks == 0) {
 543		struct list_head *unbuddied;
 544		int freechunks = num_free_chunks(zhdr);
 545
 546		migrate_disable();
 547		unbuddied = this_cpu_ptr(pool->unbuddied);
 548		spin_lock(&pool->lock);
 549		list_add(&zhdr->buddy, &unbuddied[freechunks]);
 550		spin_unlock(&pool->lock);
 551		zhdr->cpu = smp_processor_id();
 552		migrate_enable();
 553	}
 554}
 555
 556static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
 557{
 558	enum buddy bud = HEADLESS;
 559
 560	if (zhdr->middle_chunks) {
 561		if (!zhdr->first_chunks &&
 562		    chunks <= zhdr->start_middle - ZHDR_CHUNKS)
 563			bud = FIRST;
 564		else if (!zhdr->last_chunks)
 565			bud = LAST;
 566	} else {
 567		if (!zhdr->first_chunks)
 568			bud = FIRST;
 569		else if (!zhdr->last_chunks)
 570			bud = LAST;
 571		else
 572			bud = MIDDLE;
 573	}
 574
 575	return bud;
 576}
 577
 578static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 579				unsigned short dst_chunk)
 580{
 581	void *beg = zhdr;
 582	return memmove(beg + (dst_chunk << CHUNK_SHIFT),
 583		       beg + (zhdr->start_middle << CHUNK_SHIFT),
 584		       zhdr->middle_chunks << CHUNK_SHIFT);
 585}
 586
 587static inline bool buddy_single(struct z3fold_header *zhdr)
 588{
 589	return !((zhdr->first_chunks && zhdr->middle_chunks) ||
 590			(zhdr->first_chunks && zhdr->last_chunks) ||
 591			(zhdr->middle_chunks && zhdr->last_chunks));
 592}
 593
 594static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
 595{
 596	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 597	void *p = zhdr;
 598	unsigned long old_handle = 0;
 599	size_t sz = 0;
 600	struct z3fold_header *new_zhdr = NULL;
 601	int first_idx = __idx(zhdr, FIRST);
 602	int middle_idx = __idx(zhdr, MIDDLE);
 603	int last_idx = __idx(zhdr, LAST);
 604	unsigned short *moved_chunks = NULL;
 605
 606	/*
 607	 * No need to protect slots here -- all the slots are "local" and
 608	 * the page lock is already taken
 609	 */
 610	if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
 611		p += ZHDR_SIZE_ALIGNED;
 612		sz = zhdr->first_chunks << CHUNK_SHIFT;
 613		old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
 614		moved_chunks = &zhdr->first_chunks;
 615	} else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
 616		p += zhdr->start_middle << CHUNK_SHIFT;
 617		sz = zhdr->middle_chunks << CHUNK_SHIFT;
 618		old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
 619		moved_chunks = &zhdr->middle_chunks;
 620	} else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
 621		p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
 622		sz = zhdr->last_chunks << CHUNK_SHIFT;
 623		old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
 624		moved_chunks = &zhdr->last_chunks;
 625	}
 626
 627	if (sz > 0) {
 628		enum buddy new_bud = HEADLESS;
 629		short chunks = size_to_chunks(sz);
 630		void *q;
 631
 632		new_zhdr = __z3fold_alloc(pool, sz, false);
 633		if (!new_zhdr)
 634			return NULL;
 635
 636		if (WARN_ON(new_zhdr == zhdr))
 637			goto out_fail;
 638
 639		new_bud = get_free_buddy(new_zhdr, chunks);
 640		q = new_zhdr;
 641		switch (new_bud) {
 642		case FIRST:
 643			new_zhdr->first_chunks = chunks;
 644			q += ZHDR_SIZE_ALIGNED;
 645			break;
 646		case MIDDLE:
 647			new_zhdr->middle_chunks = chunks;
 648			new_zhdr->start_middle =
 649				new_zhdr->first_chunks + ZHDR_CHUNKS;
 650			q += new_zhdr->start_middle << CHUNK_SHIFT;
 651			break;
 652		case LAST:
 653			new_zhdr->last_chunks = chunks;
 654			q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
 655			break;
 656		default:
 657			goto out_fail;
 658		}
 659		new_zhdr->foreign_handles++;
 660		memcpy(q, p, sz);
 661		write_lock(&zhdr->slots->lock);
 662		*(unsigned long *)old_handle = (unsigned long)new_zhdr +
 663			__idx(new_zhdr, new_bud);
 664		if (new_bud == LAST)
 665			*(unsigned long *)old_handle |=
 666					(new_zhdr->last_chunks << BUDDY_SHIFT);
 667		write_unlock(&zhdr->slots->lock);
 668		add_to_unbuddied(pool, new_zhdr);
 669		z3fold_page_unlock(new_zhdr);
 670
 671		*moved_chunks = 0;
 672	}
 673
 674	return new_zhdr;
 675
 676out_fail:
 677	if (new_zhdr && !kref_put(&new_zhdr->refcount, release_z3fold_page_locked)) {
 678		add_to_unbuddied(pool, new_zhdr);
 679		z3fold_page_unlock(new_zhdr);
 680	}
 681	return NULL;
 682
 683}
 684
 685#define BIG_CHUNK_GAP	3
 686/* Has to be called with lock held */
 687static int z3fold_compact_page(struct z3fold_header *zhdr)
 688{
 689	struct page *page = virt_to_page(zhdr);
 690
 691	if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
 692		return 0; /* can't move middle chunk, it's used */
 693
 694	if (unlikely(PageIsolated(page)))
 695		return 0;
 696
 697	if (zhdr->middle_chunks == 0)
 698		return 0; /* nothing to compact */
 699
 700	if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 701		/* move to the beginning */
 702		mchunk_memmove(zhdr, ZHDR_CHUNKS);
 703		zhdr->first_chunks = zhdr->middle_chunks;
 704		zhdr->middle_chunks = 0;
 705		zhdr->start_middle = 0;
 706		zhdr->first_num++;
 707		return 1;
 708	}
 709
 710	/*
 711	 * moving data is expensive, so let's only do that if
 712	 * there's substantial gain (at least BIG_CHUNK_GAP chunks)
 713	 */
 714	if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
 715	    zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
 716			BIG_CHUNK_GAP) {
 717		mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
 718		zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 719		return 1;
 720	} else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
 721		   TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
 722					+ zhdr->middle_chunks) >=
 723			BIG_CHUNK_GAP) {
 724		unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
 725			zhdr->middle_chunks;
 726		mchunk_memmove(zhdr, new_start);
 727		zhdr->start_middle = new_start;
 728		return 1;
 729	}
 730
 731	return 0;
 732}
 733
 734static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 735{
 736	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 737	struct page *page;
 
 
 738
 739	page = virt_to_page(zhdr);
 740	if (locked)
 741		WARN_ON(z3fold_page_trylock(zhdr));
 742	else
 743		z3fold_page_lock(zhdr);
 744	if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
 745		z3fold_page_unlock(zhdr);
 746		return;
 747	}
 748	spin_lock(&pool->lock);
 749	list_del_init(&zhdr->buddy);
 750	spin_unlock(&pool->lock);
 751
 752	if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
 753		return;
 754
 755	if (test_bit(PAGE_STALE, &page->private) ||
 756	    test_and_set_bit(PAGE_CLAIMED, &page->private)) {
 757		z3fold_page_unlock(zhdr);
 758		return;
 759	}
 760
 761	if (!zhdr->foreign_handles && buddy_single(zhdr) &&
 762	    zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
 763		if (!kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 764			clear_bit(PAGE_CLAIMED, &page->private);
 765			z3fold_page_unlock(zhdr);
 766		}
 767		return;
 768	}
 769
 770	z3fold_compact_page(zhdr);
 771	add_to_unbuddied(pool, zhdr);
 772	clear_bit(PAGE_CLAIMED, &page->private);
 
 
 
 
 
 
 
 
 
 
 773	z3fold_page_unlock(zhdr);
 774}
 775
 776static void compact_page_work(struct work_struct *w)
 777{
 778	struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
 779						work);
 780
 781	do_compact_page(zhdr, false);
 782}
 783
 784/* returns _locked_ z3fold page header or NULL */
 785static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
 786						size_t size, bool can_sleep)
 787{
 788	struct z3fold_header *zhdr = NULL;
 789	struct page *page;
 790	struct list_head *unbuddied;
 791	int chunks = size_to_chunks(size), i;
 792
 793lookup:
 794	migrate_disable();
 795	/* First, try to find an unbuddied z3fold page. */
 796	unbuddied = this_cpu_ptr(pool->unbuddied);
 797	for_each_unbuddied_list(i, chunks) {
 798		struct list_head *l = &unbuddied[i];
 799
 800		zhdr = list_first_entry_or_null(READ_ONCE(l),
 801					struct z3fold_header, buddy);
 802
 803		if (!zhdr)
 804			continue;
 805
 806		/* Re-check under lock. */
 807		spin_lock(&pool->lock);
 808		if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
 809						struct z3fold_header, buddy)) ||
 810		    !z3fold_page_trylock(zhdr)) {
 811			spin_unlock(&pool->lock);
 812			zhdr = NULL;
 813			migrate_enable();
 814			if (can_sleep)
 815				cond_resched();
 816			goto lookup;
 817		}
 818		list_del_init(&zhdr->buddy);
 819		zhdr->cpu = -1;
 820		spin_unlock(&pool->lock);
 821
 822		page = virt_to_page(zhdr);
 823		if (test_bit(NEEDS_COMPACTING, &page->private) ||
 824		    test_bit(PAGE_CLAIMED, &page->private)) {
 825			z3fold_page_unlock(zhdr);
 826			zhdr = NULL;
 827			migrate_enable();
 828			if (can_sleep)
 829				cond_resched();
 830			goto lookup;
 831		}
 832
 833		/*
 834		 * this page could not be removed from its unbuddied
 835		 * list while pool lock was held, and then we've taken
 836		 * page lock so kref_put could not be called before
 837		 * we got here, so it's safe to just call kref_get()
 838		 */
 839		kref_get(&zhdr->refcount);
 840		break;
 841	}
 842	migrate_enable();
 843
 844	if (!zhdr) {
 845		int cpu;
 846
 847		/* look for _exact_ match on other cpus' lists */
 848		for_each_online_cpu(cpu) {
 849			struct list_head *l;
 850
 851			unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
 852			spin_lock(&pool->lock);
 853			l = &unbuddied[chunks];
 854
 855			zhdr = list_first_entry_or_null(READ_ONCE(l),
 856						struct z3fold_header, buddy);
 857
 858			if (!zhdr || !z3fold_page_trylock(zhdr)) {
 859				spin_unlock(&pool->lock);
 860				zhdr = NULL;
 861				continue;
 862			}
 863			list_del_init(&zhdr->buddy);
 864			zhdr->cpu = -1;
 865			spin_unlock(&pool->lock);
 866
 867			page = virt_to_page(zhdr);
 868			if (test_bit(NEEDS_COMPACTING, &page->private) ||
 869			    test_bit(PAGE_CLAIMED, &page->private)) {
 870				z3fold_page_unlock(zhdr);
 871				zhdr = NULL;
 872				if (can_sleep)
 873					cond_resched();
 874				continue;
 875			}
 876			kref_get(&zhdr->refcount);
 877			break;
 878		}
 879	}
 880
 881	if (zhdr && !zhdr->slots) {
 882		zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
 883		if (!zhdr->slots)
 884			goto out_fail;
 885	}
 886	return zhdr;
 887
 888out_fail:
 889	if (!kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 890		add_to_unbuddied(pool, zhdr);
 891		z3fold_page_unlock(zhdr);
 892	}
 893	return NULL;
 894}
 895
 896/*
 897 * API Functions
 898 */
 899
 900/**
 901 * z3fold_create_pool() - create a new z3fold pool
 902 * @name:	pool name
 903 * @gfp:	gfp flags when allocating the z3fold pool structure
 
 904 *
 905 * Return: pointer to the new z3fold pool or NULL if the metadata allocation
 906 * failed.
 907 */
 908static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp)
 
 909{
 910	struct z3fold_pool *pool = NULL;
 911	int i, cpu;
 912
 913	pool = kzalloc(sizeof(struct z3fold_pool), gfp);
 914	if (!pool)
 915		goto out;
 916	pool->c_handle = kmem_cache_create("z3fold_handle",
 917				sizeof(struct z3fold_buddy_slots),
 918				SLOTS_ALIGN, 0, NULL);
 919	if (!pool->c_handle)
 920		goto out_c;
 921	spin_lock_init(&pool->lock);
 922	spin_lock_init(&pool->stale_lock);
 923	pool->unbuddied = __alloc_percpu(sizeof(struct list_head) * NCHUNKS,
 924					 __alignof__(struct list_head));
 925	if (!pool->unbuddied)
 926		goto out_pool;
 927	for_each_possible_cpu(cpu) {
 928		struct list_head *unbuddied =
 929				per_cpu_ptr(pool->unbuddied, cpu);
 930		for_each_unbuddied_list(i, 0)
 931			INIT_LIST_HEAD(&unbuddied[i]);
 932	}
 933	INIT_LIST_HEAD(&pool->lru);
 934	INIT_LIST_HEAD(&pool->stale);
 935	atomic64_set(&pool->pages_nr, 0);
 936	pool->name = name;
 937	pool->compact_wq = create_singlethread_workqueue(pool->name);
 938	if (!pool->compact_wq)
 939		goto out_unbuddied;
 940	pool->release_wq = create_singlethread_workqueue(pool->name);
 941	if (!pool->release_wq)
 942		goto out_wq;
 943	INIT_WORK(&pool->work, free_pages_work);
 
 944	return pool;
 945
 946out_wq:
 947	destroy_workqueue(pool->compact_wq);
 948out_unbuddied:
 949	free_percpu(pool->unbuddied);
 950out_pool:
 951	kmem_cache_destroy(pool->c_handle);
 952out_c:
 953	kfree(pool);
 954out:
 955	return NULL;
 956}
 957
 958/**
 959 * z3fold_destroy_pool() - destroys an existing z3fold pool
 960 * @pool:	the z3fold pool to be destroyed
 961 *
 962 * The pool should be emptied before this function is called.
 963 */
 964static void z3fold_destroy_pool(struct z3fold_pool *pool)
 965{
 966	kmem_cache_destroy(pool->c_handle);
 967
 968	/*
 969	 * We need to destroy pool->compact_wq before pool->release_wq,
 970	 * as any pending work on pool->compact_wq will call
 971	 * queue_work(pool->release_wq, &pool->work).
 972	 *
 973	 * There are still outstanding pages until both workqueues are drained,
 974	 * so we cannot unregister migration until then.
 975	 */
 976
 977	destroy_workqueue(pool->compact_wq);
 978	destroy_workqueue(pool->release_wq);
 979	free_percpu(pool->unbuddied);
 980	kfree(pool);
 981}
 982
 983static const struct movable_operations z3fold_mops;
 984
 985/**
 986 * z3fold_alloc() - allocates a region of a given size
 987 * @pool:	z3fold pool from which to allocate
 988 * @size:	size in bytes of the desired allocation
 989 * @gfp:	gfp flags used if the pool needs to grow
 990 * @handle:	handle of the new allocation
 991 *
 992 * This function will attempt to find a free region in the pool large enough to
 993 * satisfy the allocation request.  A search of the unbuddied lists is
 994 * performed first. If no suitable free region is found, then a new page is
 995 * allocated and added to the pool to satisfy the request.
 996 *
 
 
 
 997 * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
 998 * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
 999 * a new page.
1000 */
1001static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
1002			unsigned long *handle)
1003{
1004	int chunks = size_to_chunks(size);
1005	struct z3fold_header *zhdr = NULL;
1006	struct page *page = NULL;
1007	enum buddy bud;
1008	bool can_sleep = gfpflags_allow_blocking(gfp);
1009
1010	if (!size || (gfp & __GFP_HIGHMEM))
1011		return -EINVAL;
1012
1013	if (size > PAGE_SIZE)
1014		return -ENOSPC;
1015
1016	if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
1017		bud = HEADLESS;
1018	else {
1019retry:
1020		zhdr = __z3fold_alloc(pool, size, can_sleep);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1021		if (zhdr) {
1022			bud = get_free_buddy(zhdr, chunks);
1023			if (bud == HEADLESS) {
1024				if (!kref_put(&zhdr->refcount,
 
 
 
 
 
 
 
 
 
1025					     release_z3fold_page_locked))
 
 
1026					z3fold_page_unlock(zhdr);
1027				pr_err("No free chunks in unbuddied\n");
1028				WARN_ON(1);
1029				goto retry;
1030			}
1031			page = virt_to_page(zhdr);
1032			goto found;
1033		}
1034		bud = FIRST;
1035	}
1036
1037	page = alloc_page(gfp);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1038	if (!page)
1039		return -ENOMEM;
1040
1041	zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
1042	if (!zhdr) {
1043		__free_page(page);
1044		return -ENOMEM;
1045	}
1046	atomic64_inc(&pool->pages_nr);
 
1047
1048	if (bud == HEADLESS) {
1049		set_bit(PAGE_HEADLESS, &page->private);
1050		goto headless;
1051	}
1052	if (can_sleep) {
1053		lock_page(page);
1054		__SetPageMovable(page, &z3fold_mops);
1055		unlock_page(page);
1056	} else {
1057		WARN_ON(!trylock_page(page));
1058		__SetPageMovable(page, &z3fold_mops);
1059		unlock_page(page);
1060	}
1061	z3fold_page_lock(zhdr);
1062
1063found:
1064	if (bud == FIRST)
1065		zhdr->first_chunks = chunks;
1066	else if (bud == LAST)
1067		zhdr->last_chunks = chunks;
1068	else {
1069		zhdr->middle_chunks = chunks;
1070		zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
1071	}
1072	add_to_unbuddied(pool, zhdr);
 
 
 
 
 
 
 
 
 
 
 
 
1073
1074headless:
1075	spin_lock(&pool->lock);
1076	/* Add/move z3fold page to beginning of LRU */
1077	if (!list_empty(&page->lru))
1078		list_del(&page->lru);
1079
1080	list_add(&page->lru, &pool->lru);
1081
1082	*handle = encode_handle(zhdr, bud);
1083	spin_unlock(&pool->lock);
1084	if (bud != HEADLESS)
1085		z3fold_page_unlock(zhdr);
1086
1087	return 0;
1088}
1089
1090/**
1091 * z3fold_free() - frees the allocation associated with the given handle
1092 * @pool:	pool in which the allocation resided
1093 * @handle:	handle associated with the allocation returned by z3fold_alloc()
1094 *
1095 * In the case that the z3fold page in which the allocation resides is under
1096 * reclaim, as indicated by the PAGE_CLAIMED flag being set, this function
1097 * only sets the first|middle|last_chunks to 0.  The page is actually freed
1098 * once all buddies are evicted (see z3fold_reclaim_page() below).
1099 */
1100static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
1101{
1102	struct z3fold_header *zhdr;
1103	struct page *page;
1104	enum buddy bud;
1105	bool page_claimed;
1106
1107	zhdr = get_z3fold_header(handle);
1108	page = virt_to_page(zhdr);
1109	page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
1110
1111	if (test_bit(PAGE_HEADLESS, &page->private)) {
1112		/* if a headless page is under reclaim, just leave.
1113		 * NB: we use test_and_set_bit for a reason: if the bit
1114		 * has not been set before, we release this page
1115		 * immediately so we don't care about its value any more.
1116		 */
1117		if (!page_claimed) {
1118			spin_lock(&pool->lock);
1119			list_del(&page->lru);
1120			spin_unlock(&pool->lock);
1121			put_z3fold_header(zhdr);
1122			free_z3fold_page(page, true);
1123			atomic64_dec(&pool->pages_nr);
 
 
 
 
 
 
 
 
 
 
1124		}
1125		return;
1126	}
1127
1128	/* Non-headless case */
1129	bud = handle_to_buddy(handle);
1130
1131	switch (bud) {
1132	case FIRST:
1133		zhdr->first_chunks = 0;
1134		break;
1135	case MIDDLE:
1136		zhdr->middle_chunks = 0;
1137		break;
1138	case LAST:
1139		zhdr->last_chunks = 0;
1140		break;
1141	default:
1142		pr_err("%s: unknown bud %d\n", __func__, bud);
1143		WARN_ON(1);
1144		put_z3fold_header(zhdr);
1145		return;
1146	}
1147
1148	if (!page_claimed)
1149		free_handle(handle, zhdr);
1150	if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list))
1151		return;
1152	if (page_claimed) {
1153		/* the page has not been claimed by us */
1154		put_z3fold_header(zhdr);
1155		return;
1156	}
1157	if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1158		clear_bit(PAGE_CLAIMED, &page->private);
1159		put_z3fold_header(zhdr);
1160		return;
1161	}
1162	if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
 
 
 
1163		zhdr->cpu = -1;
1164		kref_get(&zhdr->refcount);
1165		clear_bit(PAGE_CLAIMED, &page->private);
1166		do_compact_page(zhdr, true);
1167		return;
1168	}
1169	kref_get(&zhdr->refcount);
1170	clear_bit(PAGE_CLAIMED, &page->private);
1171	queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1172	put_z3fold_header(zhdr);
1173}
1174
1175/**
1176 * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1177 * @pool:	pool from which a page will attempt to be evicted
1178 * @retries:	number of pages on the LRU list for which eviction will
1179 *		be attempted before failing
1180 *
1181 * z3fold reclaim is different from normal system reclaim in that it is done
1182 * from the bottom, up. This is because only the bottom layer, z3fold, has
1183 * information on how the allocations are organized within each z3fold page.
1184 * This has the potential to create interesting locking situations between
1185 * z3fold and the user, however.
1186 *
1187 * To avoid these, this is how z3fold_reclaim_page() should be called:
1188 *
1189 * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1190 * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1191 * call the user-defined eviction handler with the pool and handle as
1192 * arguments.
1193 *
1194 * If the handle can not be evicted, the eviction handler should return
1195 * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1196 * appropriate list and try the next z3fold page on the LRU up to
1197 * a user defined number of retries.
1198 *
1199 * If the handle is successfully evicted, the eviction handler should
1200 * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1201 * contains logic to delay freeing the page if the page is under reclaim,
1202 * as indicated by the setting of the PG_reclaim flag on the underlying page.
1203 *
1204 * If all buddies in the z3fold page are successfully evicted, then the
1205 * z3fold page can be freed.
1206 *
1207 * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1208 * no pages to evict or an eviction handler is not registered, -EAGAIN if
1209 * the retry limit was hit.
1210 */
1211static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1212{
1213	int i, ret = -1;
1214	struct z3fold_header *zhdr = NULL;
1215	struct page *page = NULL;
1216	struct list_head *pos;
1217	unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1218	struct z3fold_buddy_slots slots __attribute__((aligned(SLOTS_ALIGN)));
1219
1220	rwlock_init(&slots.lock);
1221	slots.pool = (unsigned long)pool | (1 << HANDLES_NOFREE);
1222
1223	spin_lock(&pool->lock);
 
 
 
 
1224	for (i = 0; i < retries; i++) {
1225		if (list_empty(&pool->lru)) {
1226			spin_unlock(&pool->lock);
1227			return -EINVAL;
1228		}
1229		list_for_each_prev(pos, &pool->lru) {
1230			page = list_entry(pos, struct page, lru);
1231
1232			zhdr = page_address(page);
1233			if (test_bit(PAGE_HEADLESS, &page->private)) {
1234				/*
1235				 * For non-headless pages, we wait to do this
1236				 * until we have the page lock to avoid racing
1237				 * with __z3fold_alloc(). Headless pages don't
1238				 * have a lock (and __z3fold_alloc() will never
1239				 * see them), but we still need to test and set
1240				 * PAGE_CLAIMED to avoid racing with
1241				 * z3fold_free(), so just do it now before
1242				 * leaving the loop.
1243				 */
1244				if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1245					continue;
1246
1247				break;
1248			}
1249
1250			if (!z3fold_page_trylock(zhdr)) {
1251				zhdr = NULL;
1252				continue; /* can't evict at this point */
1253			}
1254
1255			/* test_and_set_bit is of course atomic, but we still
1256			 * need to do it under page lock, otherwise checking
1257			 * that bit in __z3fold_alloc wouldn't make sense
1258			 */
1259			if (zhdr->foreign_handles ||
1260			    test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1261				z3fold_page_unlock(zhdr);
1262				zhdr = NULL;
1263				continue; /* can't evict such page */
1264			}
1265			list_del_init(&zhdr->buddy);
1266			zhdr->cpu = -1;
1267			/* See comment in __z3fold_alloc. */
1268			kref_get(&zhdr->refcount);
1269			break;
1270		}
1271
1272		if (!zhdr)
1273			break;
1274
1275		list_del_init(&page->lru);
1276		spin_unlock(&pool->lock);
1277
1278		if (!test_bit(PAGE_HEADLESS, &page->private)) {
1279			/*
1280			 * We need encode the handles before unlocking, and
1281			 * use our local slots structure because z3fold_free
1282			 * can zero out zhdr->slots and we can't do much
1283			 * about that
1284			 */
1285			first_handle = 0;
1286			last_handle = 0;
1287			middle_handle = 0;
1288			memset(slots.slot, 0, sizeof(slots.slot));
1289			if (zhdr->first_chunks)
1290				first_handle = __encode_handle(zhdr, &slots,
1291								FIRST);
1292			if (zhdr->middle_chunks)
1293				middle_handle = __encode_handle(zhdr, &slots,
1294								MIDDLE);
1295			if (zhdr->last_chunks)
1296				last_handle = __encode_handle(zhdr, &slots,
1297								LAST);
1298			/*
1299			 * it's safe to unlock here because we hold a
1300			 * reference to this page
1301			 */
1302			z3fold_page_unlock(zhdr);
1303		} else {
1304			first_handle = encode_handle(zhdr, HEADLESS);
1305			last_handle = middle_handle = 0;
1306		}
 
1307		/* Issue the eviction callback(s) */
1308		if (middle_handle) {
1309			ret = pool->zpool_ops->evict(pool->zpool, middle_handle);
1310			if (ret)
1311				goto next;
1312		}
1313		if (first_handle) {
1314			ret = pool->zpool_ops->evict(pool->zpool, first_handle);
1315			if (ret)
1316				goto next;
1317		}
1318		if (last_handle) {
1319			ret = pool->zpool_ops->evict(pool->zpool, last_handle);
1320			if (ret)
1321				goto next;
1322		}
1323next:
1324		if (test_bit(PAGE_HEADLESS, &page->private)) {
1325			if (ret == 0) {
1326				free_z3fold_page(page, true);
1327				atomic64_dec(&pool->pages_nr);
1328				return 0;
1329			}
1330			spin_lock(&pool->lock);
1331			list_add(&page->lru, &pool->lru);
1332			spin_unlock(&pool->lock);
1333			clear_bit(PAGE_CLAIMED, &page->private);
1334		} else {
1335			struct z3fold_buddy_slots *slots = zhdr->slots;
1336			z3fold_page_lock(zhdr);
 
1337			if (kref_put(&zhdr->refcount,
1338					release_z3fold_page_locked)) {
1339				kmem_cache_free(pool->c_handle, slots);
1340				return 0;
1341			}
1342			/*
1343			 * if we are here, the page is still not completely
1344			 * free. Take the global pool lock then to be able
1345			 * to add it back to the lru list
1346			 */
1347			spin_lock(&pool->lock);
1348			list_add(&page->lru, &pool->lru);
1349			spin_unlock(&pool->lock);
1350			if (list_empty(&zhdr->buddy))
1351				add_to_unbuddied(pool, zhdr);
1352			clear_bit(PAGE_CLAIMED, &page->private);
1353			z3fold_page_unlock(zhdr);
1354		}
1355
1356		/* We started off locked to we need to lock the pool back */
1357		spin_lock(&pool->lock);
1358	}
1359	spin_unlock(&pool->lock);
1360	return -EAGAIN;
1361}
1362
1363/**
1364 * z3fold_map() - maps the allocation associated with the given handle
1365 * @pool:	pool in which the allocation resides
1366 * @handle:	handle associated with the allocation to be mapped
1367 *
1368 * Extracts the buddy number from handle and constructs the pointer to the
1369 * correct starting chunk within the page.
1370 *
1371 * Returns: a pointer to the mapped allocation
1372 */
1373static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1374{
1375	struct z3fold_header *zhdr;
1376	struct page *page;
1377	void *addr;
1378	enum buddy buddy;
1379
1380	zhdr = get_z3fold_header(handle);
1381	addr = zhdr;
1382	page = virt_to_page(zhdr);
1383
1384	if (test_bit(PAGE_HEADLESS, &page->private))
1385		goto out;
1386
 
1387	buddy = handle_to_buddy(handle);
1388	switch (buddy) {
1389	case FIRST:
1390		addr += ZHDR_SIZE_ALIGNED;
1391		break;
1392	case MIDDLE:
1393		addr += zhdr->start_middle << CHUNK_SHIFT;
1394		set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1395		break;
1396	case LAST:
1397		addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1398		break;
1399	default:
1400		pr_err("unknown buddy id %d\n", buddy);
1401		WARN_ON(1);
1402		addr = NULL;
1403		break;
1404	}
1405
1406	if (addr)
1407		zhdr->mapped_count++;
1408out:
1409	put_z3fold_header(zhdr);
1410	return addr;
1411}
1412
1413/**
1414 * z3fold_unmap() - unmaps the allocation associated with the given handle
1415 * @pool:	pool in which the allocation resides
1416 * @handle:	handle associated with the allocation to be unmapped
1417 */
1418static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1419{
1420	struct z3fold_header *zhdr;
1421	struct page *page;
1422	enum buddy buddy;
1423
1424	zhdr = get_z3fold_header(handle);
1425	page = virt_to_page(zhdr);
1426
1427	if (test_bit(PAGE_HEADLESS, &page->private))
1428		return;
1429
 
1430	buddy = handle_to_buddy(handle);
1431	if (buddy == MIDDLE)
1432		clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1433	zhdr->mapped_count--;
1434	put_z3fold_header(zhdr);
1435}
1436
1437/**
1438 * z3fold_get_pool_size() - gets the z3fold pool size in pages
1439 * @pool:	pool whose size is being queried
1440 *
1441 * Returns: size in pages of the given pool.
1442 */
1443static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1444{
1445	return atomic64_read(&pool->pages_nr);
1446}
1447
1448static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1449{
1450	struct z3fold_header *zhdr;
1451	struct z3fold_pool *pool;
1452
1453	VM_BUG_ON_PAGE(!PageMovable(page), page);
1454	VM_BUG_ON_PAGE(PageIsolated(page), page);
1455
1456	if (test_bit(PAGE_HEADLESS, &page->private))
1457		return false;
1458
1459	zhdr = page_address(page);
1460	z3fold_page_lock(zhdr);
1461	if (test_bit(NEEDS_COMPACTING, &page->private) ||
1462	    test_bit(PAGE_STALE, &page->private))
1463		goto out;
1464
1465	if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
1466		goto out;
1467
1468	if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1469		goto out;
1470	pool = zhdr_to_pool(zhdr);
1471	spin_lock(&pool->lock);
1472	if (!list_empty(&zhdr->buddy))
1473		list_del_init(&zhdr->buddy);
1474	if (!list_empty(&page->lru))
1475		list_del_init(&page->lru);
1476	spin_unlock(&pool->lock);
1477
1478	kref_get(&zhdr->refcount);
1479	z3fold_page_unlock(zhdr);
1480	return true;
1481
1482out:
1483	z3fold_page_unlock(zhdr);
1484	return false;
1485}
1486
1487static int z3fold_page_migrate(struct page *newpage, struct page *page,
1488		enum migrate_mode mode)
1489{
1490	struct z3fold_header *zhdr, *new_zhdr;
1491	struct z3fold_pool *pool;
1492
1493	VM_BUG_ON_PAGE(!PageMovable(page), page);
1494	VM_BUG_ON_PAGE(!PageIsolated(page), page);
1495	VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
1496	VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1497
1498	zhdr = page_address(page);
1499	pool = zhdr_to_pool(zhdr);
1500
1501	if (!z3fold_page_trylock(zhdr))
1502		return -EAGAIN;
1503	if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
1504		clear_bit(PAGE_CLAIMED, &page->private);
1505		z3fold_page_unlock(zhdr);
1506		return -EBUSY;
1507	}
1508	if (work_pending(&zhdr->work)) {
1509		z3fold_page_unlock(zhdr);
1510		return -EAGAIN;
1511	}
1512	new_zhdr = page_address(newpage);
1513	memcpy(new_zhdr, zhdr, PAGE_SIZE);
1514	newpage->private = page->private;
1515	set_bit(PAGE_MIGRATED, &page->private);
1516	z3fold_page_unlock(zhdr);
1517	spin_lock_init(&new_zhdr->page_lock);
1518	INIT_WORK(&new_zhdr->work, compact_page_work);
1519	/*
1520	 * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1521	 * so we only have to reinitialize it.
1522	 */
1523	INIT_LIST_HEAD(&new_zhdr->buddy);
1524	__ClearPageMovable(page);
1525
1526	get_page(newpage);
1527	z3fold_page_lock(new_zhdr);
1528	if (new_zhdr->first_chunks)
1529		encode_handle(new_zhdr, FIRST);
1530	if (new_zhdr->last_chunks)
1531		encode_handle(new_zhdr, LAST);
1532	if (new_zhdr->middle_chunks)
1533		encode_handle(new_zhdr, MIDDLE);
1534	set_bit(NEEDS_COMPACTING, &newpage->private);
1535	new_zhdr->cpu = smp_processor_id();
1536	spin_lock(&pool->lock);
1537	list_add(&newpage->lru, &pool->lru);
1538	spin_unlock(&pool->lock);
1539	__SetPageMovable(newpage, &z3fold_mops);
1540	z3fold_page_unlock(new_zhdr);
1541
1542	queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1543
1544	/* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */
1545	page->private = 0;
1546	put_page(page);
1547	return 0;
1548}
1549
1550static void z3fold_page_putback(struct page *page)
1551{
1552	struct z3fold_header *zhdr;
1553	struct z3fold_pool *pool;
1554
1555	zhdr = page_address(page);
1556	pool = zhdr_to_pool(zhdr);
1557
1558	z3fold_page_lock(zhdr);
1559	if (!list_empty(&zhdr->buddy))
1560		list_del_init(&zhdr->buddy);
1561	INIT_LIST_HEAD(&page->lru);
1562	if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
1563		return;
1564	spin_lock(&pool->lock);
1565	list_add(&page->lru, &pool->lru);
1566	spin_unlock(&pool->lock);
1567	if (list_empty(&zhdr->buddy))
1568		add_to_unbuddied(pool, zhdr);
1569	clear_bit(PAGE_CLAIMED, &page->private);
1570	z3fold_page_unlock(zhdr);
1571}
1572
1573static const struct movable_operations z3fold_mops = {
1574	.isolate_page = z3fold_page_isolate,
1575	.migrate_page = z3fold_page_migrate,
1576	.putback_page = z3fold_page_putback,
1577};
1578
1579/*****************
1580 * zpool
1581 ****************/
1582
1583static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1584			       const struct zpool_ops *zpool_ops,
1585			       struct zpool *zpool)
1586{
1587	struct z3fold_pool *pool;
1588
1589	pool = z3fold_create_pool(name, gfp);
 
1590	if (pool) {
1591		pool->zpool = zpool;
1592		pool->zpool_ops = zpool_ops;
1593	}
1594	return pool;
1595}
1596
1597static void z3fold_zpool_destroy(void *pool)
1598{
1599	z3fold_destroy_pool(pool);
1600}
1601
1602static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1603			unsigned long *handle)
1604{
1605	return z3fold_alloc(pool, size, gfp, handle);
1606}
1607static void z3fold_zpool_free(void *pool, unsigned long handle)
1608{
1609	z3fold_free(pool, handle);
1610}
1611
1612static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1613			unsigned int *reclaimed)
1614{
1615	unsigned int total = 0;
1616	int ret = -EINVAL;
1617
1618	while (total < pages) {
1619		ret = z3fold_reclaim_page(pool, 8);
1620		if (ret < 0)
1621			break;
1622		total++;
1623	}
1624
1625	if (reclaimed)
1626		*reclaimed = total;
1627
1628	return ret;
1629}
1630
1631static void *z3fold_zpool_map(void *pool, unsigned long handle,
1632			enum zpool_mapmode mm)
1633{
1634	return z3fold_map(pool, handle);
1635}
1636static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1637{
1638	z3fold_unmap(pool, handle);
1639}
1640
1641static u64 z3fold_zpool_total_size(void *pool)
1642{
1643	return z3fold_get_pool_size(pool) * PAGE_SIZE;
1644}
1645
1646static struct zpool_driver z3fold_zpool_driver = {
1647	.type =		"z3fold",
1648	.sleep_mapped = true,
1649	.owner =	THIS_MODULE,
1650	.create =	z3fold_zpool_create,
1651	.destroy =	z3fold_zpool_destroy,
1652	.malloc =	z3fold_zpool_malloc,
1653	.free =		z3fold_zpool_free,
1654	.shrink =	z3fold_zpool_shrink,
1655	.map =		z3fold_zpool_map,
1656	.unmap =	z3fold_zpool_unmap,
1657	.total_size =	z3fold_zpool_total_size,
1658};
1659
1660MODULE_ALIAS("zpool-z3fold");
1661
1662static int __init init_z3fold(void)
1663{
1664	/*
1665	 * Make sure the z3fold header is not larger than the page size and
1666	 * there has remaining spaces for its buddy.
1667	 */
1668	BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
1669	zpool_register_driver(&z3fold_zpool_driver);
1670
1671	return 0;
1672}
1673
1674static void __exit exit_z3fold(void)
1675{
1676	zpool_unregister_driver(&z3fold_zpool_driver);
1677}
1678
1679module_init(init_z3fold);
1680module_exit(exit_z3fold);
1681
1682MODULE_LICENSE("GPL");
1683MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1684MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");