1/*
   2 * zsmalloc memory allocator
   3 *
   4 * Copyright (C) 2011  Nitin Gupta
   5 * Copyright (C) 2012, 2013 Minchan Kim
   6 *
   7 * This code is released using a dual license strategy: BSD/GPL
   8 * You can choose the license that better fits your requirements.
   9 *
  10 * Released under the terms of 3-clause BSD License
  11 * Released under the terms of GNU General Public License Version 2.0
  12 */
  13
  14/*
  15 * Following is how we use various fields and flags of underlying
  16 * struct page(s) to form a zspage.
  17 *
  18 * Usage of struct page fields:
  19 *	page->private: points to zspage
  20 *	page->freelist(index): links together all component pages of a zspage
  21 *		For the huge page, this is always 0, so we use this field
  22 *		to store handle.
  23 *	page->units: first object offset in a subpage of zspage
  24 *
  25 * Usage of struct page flags:
  26 *	PG_private: identifies the first component page
  27 *	PG_owner_priv_1: identifies the huge component page
  28 *
  29 */
  30
  31#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  32
  33#include <linux/module.h>
  34#include <linux/kernel.h>
  35#include <linux/sched.h>
  36#include <linux/magic.h>
  37#include <linux/bitops.h>
  38#include <linux/errno.h>
  39#include <linux/highmem.h>
  40#include <linux/string.h>
  41#include <linux/slab.h>
 
  42#include <asm/tlbflush.h>
  43#include <asm/pgtable.h>
  44#include <linux/cpumask.h>
  45#include <linux/cpu.h>
  46#include <linux/vmalloc.h>
  47#include <linux/preempt.h>
  48#include <linux/spinlock.h>
  49#include <linux/shrinker.h>
  50#include <linux/types.h>
  51#include <linux/debugfs.h>
  52#include <linux/zsmalloc.h>
  53#include <linux/zpool.h>
  54#include <linux/mount.h>
 
  55#include <linux/migrate.h>
 
  56#include <linux/pagemap.h>
  57#include <linux/fs.h>
  58
  59#define ZSPAGE_MAGIC	0x58
  60
  61/*
  62 * This must be power of 2 and greater than of equal to sizeof(link_free).
  63 * These two conditions ensure that any 'struct link_free' itself doesn't
  64 * span more than 1 page which avoids complex case of mapping 2 pages simply
  65 * to restore link_free pointer values.
  66 */
  67#define ZS_ALIGN		8
  68
  69/*
  70 * A single 'zspage' is composed of up to 2^N discontiguous 0-order (single)
  71 * pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N.
  72 */
  73#define ZS_MAX_ZSPAGE_ORDER 2
  74#define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)
  75
  76#define ZS_HANDLE_SIZE (sizeof(unsigned long))
  77
  78/*
  79 * Object location (<PFN>, <obj_idx>) is encoded as
  80 * as single (unsigned long) handle value.
  81 *
  82 * Note that object index <obj_idx> starts from 0.
  83 *
  84 * This is made more complicated by various memory models and PAE.
  85 */
  86
  87#ifndef MAX_POSSIBLE_PHYSMEM_BITS
  88#ifdef MAX_PHYSMEM_BITS
  89#define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS
  90#else
  91/*
  92 * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
  93 * be PAGE_SHIFT
  94 */
  95#define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG
  96#endif
  97#endif
  98
  99#define _PFN_BITS		(MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
 100
 101/*
 102 * Memory for allocating for handle keeps object position by
 103 * encoding <page, obj_idx> and the encoded value has a room
 104 * in least bit(ie, look at obj_to_location).
 105 * We use the bit to synchronize between object access by
 106 * user and migration.
 107 */
 108#define HANDLE_PIN_BIT	0
 109
 110/*
 111 * Head in allocated object should have OBJ_ALLOCATED_TAG
 112 * to identify the object was allocated or not.
 113 * It's okay to add the status bit in the least bit because
 114 * header keeps handle which is 4byte-aligned address so we
 115 * have room for two bit at least.
 116 */
 117#define OBJ_ALLOCATED_TAG 1
 118#define OBJ_TAG_BITS 1
 119#define OBJ_INDEX_BITS	(BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
 120#define OBJ_INDEX_MASK	((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
 121
 122#define FULLNESS_BITS	2
 123#define CLASS_BITS	8
 124#define ISOLATED_BITS	3
 125#define MAGIC_VAL_BITS	8
 126
 127#define MAX(a, b) ((a) >= (b) ? (a) : (b))
 128/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
 129#define ZS_MIN_ALLOC_SIZE \
 130	MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
 131/* each chunk includes extra space to keep handle */
 132#define ZS_MAX_ALLOC_SIZE	PAGE_SIZE
 133
 134/*
 135 * On systems with 4K page size, this gives 255 size classes! There is a
 136 * trader-off here:
 137 *  - Large number of size classes is potentially wasteful as free page are
 138 *    spread across these classes
 139 *  - Small number of size classes causes large internal fragmentation
 140 *  - Probably its better to use specific size classes (empirically
 141 *    determined). NOTE: all those class sizes must be set as multiple of
 142 *    ZS_ALIGN to make sure link_free itself never has to span 2 pages.
 143 *
 144 *  ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
 145 *  (reason above)
 146 */
 147#define ZS_SIZE_CLASS_DELTA	(PAGE_SIZE >> CLASS_BITS)
 148#define ZS_SIZE_CLASSES	(DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
 149				      ZS_SIZE_CLASS_DELTA) + 1)
 150
 151enum fullness_group {
 152	ZS_EMPTY,
 153	ZS_ALMOST_EMPTY,
 154	ZS_ALMOST_FULL,
 155	ZS_FULL,
 156	NR_ZS_FULLNESS,
 157};
 158
 159enum zs_stat_type {
 160	CLASS_EMPTY,
 161	CLASS_ALMOST_EMPTY,
 162	CLASS_ALMOST_FULL,
 163	CLASS_FULL,
 164	OBJ_ALLOCATED,
 165	OBJ_USED,
 166	NR_ZS_STAT_TYPE,
 167};
 168
 169struct zs_size_stat {
 170	unsigned long objs[NR_ZS_STAT_TYPE];
 171};
 172
 173#ifdef CONFIG_ZSMALLOC_STAT
 174static struct dentry *zs_stat_root;
 175#endif
 176
 177#ifdef CONFIG_COMPACTION
 178static struct vfsmount *zsmalloc_mnt;
 179#endif
 180
 181/*
 182 * We assign a page to ZS_ALMOST_EMPTY fullness group when:
 183 *	n <= N / f, where
 184 * n = number of allocated objects
 185 * N = total number of objects zspage can store
 186 * f = fullness_threshold_frac
 187 *
 188 * Similarly, we assign zspage to:
 189 *	ZS_ALMOST_FULL	when n > N / f
 190 *	ZS_EMPTY	when n == 0
 191 *	ZS_FULL		when n == N
 192 *
 193 * (see: fix_fullness_group())
 194 */
 195static const int fullness_threshold_frac = 4;
 196static size_t huge_class_size;
 197
 198struct size_class {
 199	spinlock_t lock;
 200	struct list_head fullness_list[NR_ZS_FULLNESS];
 201	/*
 202	 * Size of objects stored in this class. Must be multiple
 203	 * of ZS_ALIGN.
 204	 */
 205	int size;
 206	int objs_per_zspage;
 207	/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
 208	int pages_per_zspage;
 209
 210	unsigned int index;
 211	struct zs_size_stat stats;
 212};
 213
 214/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
 215static void SetPageHugeObject(struct page *page)
 216{
 217	SetPageOwnerPriv1(page);
 218}
 219
 220static void ClearPageHugeObject(struct page *page)
 221{
 222	ClearPageOwnerPriv1(page);
 223}
 224
 225static int PageHugeObject(struct page *page)
 226{
 227	return PageOwnerPriv1(page);
 228}
 229
 230/*
 231 * Placed within free objects to form a singly linked list.
 232 * For every zspage, zspage->freeobj gives head of this list.
 233 *
 234 * This must be power of 2 and less than or equal to ZS_ALIGN
 235 */
 236struct link_free {
 237	union {
 238		/*
 239		 * Free object index;
 240		 * It's valid for non-allocated object
 241		 */
 242		unsigned long next;
 243		/*
 244		 * Handle of allocated object.
 245		 */
 246		unsigned long handle;
 247	};
 248};
 249
 250struct zs_pool {
 251	const char *name;
 252
 253	struct size_class *size_class[ZS_SIZE_CLASSES];
 254	struct kmem_cache *handle_cachep;
 255	struct kmem_cache *zspage_cachep;
 256
 257	atomic_long_t pages_allocated;
 258
 259	struct zs_pool_stats stats;
 260
 261	/* Compact classes */
 262	struct shrinker shrinker;
 263
 264#ifdef CONFIG_ZSMALLOC_STAT
 265	struct dentry *stat_dentry;
 266#endif
 267#ifdef CONFIG_COMPACTION
 268	struct inode *inode;
 269	struct work_struct free_work;
 
 
 
 
 270#endif
 271};
 272
 273struct zspage {
 274	struct {
 275		unsigned int fullness:FULLNESS_BITS;
 276		unsigned int class:CLASS_BITS + 1;
 277		unsigned int isolated:ISOLATED_BITS;
 278		unsigned int magic:MAGIC_VAL_BITS;
 279	};
 280	unsigned int inuse;
 281	unsigned int freeobj;
 282	struct page *first_page;
 283	struct list_head list; /* fullness list */
 284#ifdef CONFIG_COMPACTION
 285	rwlock_t lock;
 286#endif
 287};
 288
 289struct mapping_area {
 290#ifdef CONFIG_PGTABLE_MAPPING
 291	struct vm_struct *vm; /* vm area for mapping object that span pages */
 292#else
 293	char *vm_buf; /* copy buffer for objects that span pages */
 294#endif
 295	char *vm_addr; /* address of kmap_atomic()'ed pages */
 296	enum zs_mapmode vm_mm; /* mapping mode */
 297};
 298
 299#ifdef CONFIG_COMPACTION
 300static int zs_register_migration(struct zs_pool *pool);
 301static void zs_unregister_migration(struct zs_pool *pool);
 302static void migrate_lock_init(struct zspage *zspage);
 303static void migrate_read_lock(struct zspage *zspage);
 304static void migrate_read_unlock(struct zspage *zspage);
 305static void kick_deferred_free(struct zs_pool *pool);
 306static void init_deferred_free(struct zs_pool *pool);
 307static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
 308#else
 309static int zsmalloc_mount(void) { return 0; }
 310static void zsmalloc_unmount(void) {}
 311static int zs_register_migration(struct zs_pool *pool) { return 0; }
 312static void zs_unregister_migration(struct zs_pool *pool) {}
 313static void migrate_lock_init(struct zspage *zspage) {}
 314static void migrate_read_lock(struct zspage *zspage) {}
 315static void migrate_read_unlock(struct zspage *zspage) {}
 316static void kick_deferred_free(struct zs_pool *pool) {}
 317static void init_deferred_free(struct zs_pool *pool) {}
 318static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
 319#endif
 320
 321static int create_cache(struct zs_pool *pool)
 322{
 323	pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
 324					0, 0, NULL);
 325	if (!pool->handle_cachep)
 326		return 1;
 327
 328	pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
 329					0, 0, NULL);
 330	if (!pool->zspage_cachep) {
 331		kmem_cache_destroy(pool->handle_cachep);
 332		pool->handle_cachep = NULL;
 333		return 1;
 334	}
 335
 336	return 0;
 337}
 338
 339static void destroy_cache(struct zs_pool *pool)
 340{
 341	kmem_cache_destroy(pool->handle_cachep);
 342	kmem_cache_destroy(pool->zspage_cachep);
 343}
 344
 345static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
 346{
 347	return (unsigned long)kmem_cache_alloc(pool->handle_cachep,
 348			gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
 349}
 350
 351static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
 352{
 353	kmem_cache_free(pool->handle_cachep, (void *)handle);
 354}
 355
 356static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
 357{
 358	return kmem_cache_alloc(pool->zspage_cachep,
 359			flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
 360}
 361
 362static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
 363{
 364	kmem_cache_free(pool->zspage_cachep, zspage);
 365}
 366
 367static void record_obj(unsigned long handle, unsigned long obj)
 368{
 369	/*
 370	 * lsb of @obj represents handle lock while other bits
 371	 * represent object value the handle is pointing so
 372	 * updating shouldn't do store tearing.
 373	 */
 374	WRITE_ONCE(*(unsigned long *)handle, obj);
 375}
 376
 377/* zpool driver */
 378
 379#ifdef CONFIG_ZPOOL
 380
 381static void *zs_zpool_create(const char *name, gfp_t gfp,
 382			     const struct zpool_ops *zpool_ops,
 383			     struct zpool *zpool)
 384{
 385	/*
 386	 * Ignore global gfp flags: zs_malloc() may be invoked from
 387	 * different contexts and its caller must provide a valid
 388	 * gfp mask.
 389	 */
 390	return zs_create_pool(name);
 391}
 392
 393static void zs_zpool_destroy(void *pool)
 394{
 395	zs_destroy_pool(pool);
 396}
 397
 398static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
 399			unsigned long *handle)
 400{
 401	*handle = zs_malloc(pool, size, gfp);
 402	return *handle ? 0 : -1;
 403}
 404static void zs_zpool_free(void *pool, unsigned long handle)
 405{
 406	zs_free(pool, handle);
 407}
 408
 409static void *zs_zpool_map(void *pool, unsigned long handle,
 410			enum zpool_mapmode mm)
 411{
 412	enum zs_mapmode zs_mm;
 413
 414	switch (mm) {
 415	case ZPOOL_MM_RO:
 416		zs_mm = ZS_MM_RO;
 417		break;
 418	case ZPOOL_MM_WO:
 419		zs_mm = ZS_MM_WO;
 420		break;
 421	case ZPOOL_MM_RW: /* fallthru */
 422	default:
 423		zs_mm = ZS_MM_RW;
 424		break;
 425	}
 426
 427	return zs_map_object(pool, handle, zs_mm);
 428}
 429static void zs_zpool_unmap(void *pool, unsigned long handle)
 430{
 431	zs_unmap_object(pool, handle);
 432}
 433
 434static u64 zs_zpool_total_size(void *pool)
 435{
 436	return zs_get_total_pages(pool) << PAGE_SHIFT;
 437}
 438
 439static struct zpool_driver zs_zpool_driver = {
 440	.type =		"zsmalloc",
 441	.owner =	THIS_MODULE,
 442	.create =	zs_zpool_create,
 443	.destroy =	zs_zpool_destroy,
 444	.malloc =	zs_zpool_malloc,
 445	.free =		zs_zpool_free,
 446	.map =		zs_zpool_map,
 447	.unmap =	zs_zpool_unmap,
 448	.total_size =	zs_zpool_total_size,
 
 449};
 450
 451MODULE_ALIAS("zpool-zsmalloc");
 452#endif /* CONFIG_ZPOOL */
 453
 454/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
 455static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
 456
 457static bool is_zspage_isolated(struct zspage *zspage)
 458{
 459	return zspage->isolated;
 460}
 461
 462static __maybe_unused int is_first_page(struct page *page)
 463{
 464	return PagePrivate(page);
 465}
 466
 467/* Protected by class->lock */
 468static inline int get_zspage_inuse(struct zspage *zspage)
 469{
 470	return zspage->inuse;
 471}
 472
 473static inline void set_zspage_inuse(struct zspage *zspage, int val)
 474{
 475	zspage->inuse = val;
 476}
 477
 478static inline void mod_zspage_inuse(struct zspage *zspage, int val)
 479{
 480	zspage->inuse += val;
 481}
 482
 483static inline struct page *get_first_page(struct zspage *zspage)
 484{
 485	struct page *first_page = zspage->first_page;
 486
 487	VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
 488	return first_page;
 489}
 490
 491static inline int get_first_obj_offset(struct page *page)
 492{
 493	return page->units;
 494}
 495
 496static inline void set_first_obj_offset(struct page *page, int offset)
 497{
 498	page->units = offset;
 499}
 500
 501static inline unsigned int get_freeobj(struct zspage *zspage)
 502{
 503	return zspage->freeobj;
 504}
 505
 506static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
 507{
 508	zspage->freeobj = obj;
 509}
 510
 511static void get_zspage_mapping(struct zspage *zspage,
 512				unsigned int *class_idx,
 513				enum fullness_group *fullness)
 514{
 515	BUG_ON(zspage->magic != ZSPAGE_MAGIC);
 516
 517	*fullness = zspage->fullness;
 518	*class_idx = zspage->class;
 519}
 520
 521static void set_zspage_mapping(struct zspage *zspage,
 522				unsigned int class_idx,
 523				enum fullness_group fullness)
 524{
 525	zspage->class = class_idx;
 526	zspage->fullness = fullness;
 527}
 528
 529/*
 530 * zsmalloc divides the pool into various size classes where each
 531 * class maintains a list of zspages where each zspage is divided
 532 * into equal sized chunks. Each allocation falls into one of these
 533 * classes depending on its size. This function returns index of the
 534 * size class which has chunk size big enough to hold the give size.
 535 */
 536static int get_size_class_index(int size)
 537{
 538	int idx = 0;
 539
 540	if (likely(size > ZS_MIN_ALLOC_SIZE))
 541		idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
 542				ZS_SIZE_CLASS_DELTA);
 543
 544	return min_t(int, ZS_SIZE_CLASSES - 1, idx);
 545}
 546
 547/* type can be of enum type zs_stat_type or fullness_group */
 548static inline void zs_stat_inc(struct size_class *class,
 549				int type, unsigned long cnt)
 550{
 551	class->stats.objs[type] += cnt;
 552}
 553
 554/* type can be of enum type zs_stat_type or fullness_group */
 555static inline void zs_stat_dec(struct size_class *class,
 556				int type, unsigned long cnt)
 557{
 558	class->stats.objs[type] -= cnt;
 559}
 560
 561/* type can be of enum type zs_stat_type or fullness_group */
 562static inline unsigned long zs_stat_get(struct size_class *class,
 563				int type)
 564{
 565	return class->stats.objs[type];
 566}
 567
 568#ifdef CONFIG_ZSMALLOC_STAT
 569
 570static void __init zs_stat_init(void)
 571{
 572	if (!debugfs_initialized()) {
 573		pr_warn("debugfs not available, stat dir not created\n");
 574		return;
 575	}
 576
 577	zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
 578	if (!zs_stat_root)
 579		pr_warn("debugfs 'zsmalloc' stat dir creation failed\n");
 580}
 581
 582static void __exit zs_stat_exit(void)
 583{
 584	debugfs_remove_recursive(zs_stat_root);
 585}
 586
 587static unsigned long zs_can_compact(struct size_class *class);
 588
 589static int zs_stats_size_show(struct seq_file *s, void *v)
 590{
 591	int i;
 592	struct zs_pool *pool = s->private;
 593	struct size_class *class;
 594	int objs_per_zspage;
 595	unsigned long class_almost_full, class_almost_empty;
 596	unsigned long obj_allocated, obj_used, pages_used, freeable;
 597	unsigned long total_class_almost_full = 0, total_class_almost_empty = 0;
 598	unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
 599	unsigned long total_freeable = 0;
 600
 601	seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n",
 602			"class", "size", "almost_full", "almost_empty",
 603			"obj_allocated", "obj_used", "pages_used",
 604			"pages_per_zspage", "freeable");
 605
 606	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
 607		class = pool->size_class[i];
 608
 609		if (class->index != i)
 610			continue;
 611
 612		spin_lock(&class->lock);
 613		class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL);
 614		class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY);
 615		obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
 616		obj_used = zs_stat_get(class, OBJ_USED);
 617		freeable = zs_can_compact(class);
 618		spin_unlock(&class->lock);
 619
 620		objs_per_zspage = class->objs_per_zspage;
 621		pages_used = obj_allocated / objs_per_zspage *
 622				class->pages_per_zspage;
 623
 624		seq_printf(s, " %5u %5u %11lu %12lu %13lu"
 625				" %10lu %10lu %16d %8lu\n",
 626			i, class->size, class_almost_full, class_almost_empty,
 627			obj_allocated, obj_used, pages_used,
 628			class->pages_per_zspage, freeable);
 629
 630		total_class_almost_full += class_almost_full;
 631		total_class_almost_empty += class_almost_empty;
 632		total_objs += obj_allocated;
 633		total_used_objs += obj_used;
 634		total_pages += pages_used;
 635		total_freeable += freeable;
 636	}
 637
 638	seq_puts(s, "\n");
 639	seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n",
 640			"Total", "", total_class_almost_full,
 641			total_class_almost_empty, total_objs,
 642			total_used_objs, total_pages, "", total_freeable);
 643
 644	return 0;
 645}
 646DEFINE_SHOW_ATTRIBUTE(zs_stats_size);
 647
 648static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 649{
 650	struct dentry *entry;
 651
 652	if (!zs_stat_root) {
 653		pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
 654		return;
 655	}
 656
 657	entry = debugfs_create_dir(name, zs_stat_root);
 658	if (!entry) {
 659		pr_warn("debugfs dir <%s> creation failed\n", name);
 660		return;
 661	}
 662	pool->stat_dentry = entry;
 663
 664	entry = debugfs_create_file("classes", S_IFREG | S_IRUGO,
 665			pool->stat_dentry, pool, &zs_stats_size_fops);
 666	if (!entry) {
 667		pr_warn("%s: debugfs file entry <%s> creation failed\n",
 668				name, "classes");
 669		debugfs_remove_recursive(pool->stat_dentry);
 670		pool->stat_dentry = NULL;
 671	}
 672}
 673
 674static void zs_pool_stat_destroy(struct zs_pool *pool)
 675{
 676	debugfs_remove_recursive(pool->stat_dentry);
 677}
 678
 679#else /* CONFIG_ZSMALLOC_STAT */
 680static void __init zs_stat_init(void)
 681{
 682}
 683
 684static void __exit zs_stat_exit(void)
 685{
 686}
 687
 688static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 689{
 690}
 691
 692static inline void zs_pool_stat_destroy(struct zs_pool *pool)
 693{
 694}
 695#endif
 696
 697
 698/*
 699 * For each size class, zspages are divided into different groups
 700 * depending on how "full" they are. This was done so that we could
 701 * easily find empty or nearly empty zspages when we try to shrink
 702 * the pool (not yet implemented). This function returns fullness
 703 * status of the given page.
 704 */
 705static enum fullness_group get_fullness_group(struct size_class *class,
 706						struct zspage *zspage)
 707{
 708	int inuse, objs_per_zspage;
 709	enum fullness_group fg;
 710
 711	inuse = get_zspage_inuse(zspage);
 712	objs_per_zspage = class->objs_per_zspage;
 713
 714	if (inuse == 0)
 715		fg = ZS_EMPTY;
 716	else if (inuse == objs_per_zspage)
 717		fg = ZS_FULL;
 718	else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
 719		fg = ZS_ALMOST_EMPTY;
 720	else
 721		fg = ZS_ALMOST_FULL;
 722
 723	return fg;
 724}
 725
 726/*
 727 * Each size class maintains various freelists and zspages are assigned
 728 * to one of these freelists based on the number of live objects they
 729 * have. This functions inserts the given zspage into the freelist
 730 * identified by <class, fullness_group>.
 731 */
 732static void insert_zspage(struct size_class *class,
 733				struct zspage *zspage,
 734				enum fullness_group fullness)
 735{
 736	struct zspage *head;
 737
 738	zs_stat_inc(class, fullness, 1);
 739	head = list_first_entry_or_null(&class->fullness_list[fullness],
 740					struct zspage, list);
 741	/*
 742	 * We want to see more ZS_FULL pages and less almost empty/full.
 743	 * Put pages with higher ->inuse first.
 744	 */
 745	if (head) {
 746		if (get_zspage_inuse(zspage) < get_zspage_inuse(head)) {
 747			list_add(&zspage->list, &head->list);
 748			return;
 749		}
 750	}
 751	list_add(&zspage->list, &class->fullness_list[fullness]);
 752}
 753
 754/*
 755 * This function removes the given zspage from the freelist identified
 756 * by <class, fullness_group>.
 757 */
 758static void remove_zspage(struct size_class *class,
 759				struct zspage *zspage,
 760				enum fullness_group fullness)
 761{
 762	VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
 763	VM_BUG_ON(is_zspage_isolated(zspage));
 764
 765	list_del_init(&zspage->list);
 766	zs_stat_dec(class, fullness, 1);
 767}
 768
 769/*
 770 * Each size class maintains zspages in different fullness groups depending
 771 * on the number of live objects they contain. When allocating or freeing
 772 * objects, the fullness status of the page can change, say, from ALMOST_FULL
 773 * to ALMOST_EMPTY when freeing an object. This function checks if such
 774 * a status change has occurred for the given page and accordingly moves the
 775 * page from the freelist of the old fullness group to that of the new
 776 * fullness group.
 777 */
 778static enum fullness_group fix_fullness_group(struct size_class *class,
 779						struct zspage *zspage)
 780{
 781	int class_idx;
 782	enum fullness_group currfg, newfg;
 783
 784	get_zspage_mapping(zspage, &class_idx, &currfg);
 785	newfg = get_fullness_group(class, zspage);
 786	if (newfg == currfg)
 787		goto out;
 788
 789	if (!is_zspage_isolated(zspage)) {
 790		remove_zspage(class, zspage, currfg);
 791		insert_zspage(class, zspage, newfg);
 792	}
 793
 794	set_zspage_mapping(zspage, class_idx, newfg);
 795
 796out:
 797	return newfg;
 798}
 799
 800/*
 801 * We have to decide on how many pages to link together
 802 * to form a zspage for each size class. This is important
 803 * to reduce wastage due to unusable space left at end of
 804 * each zspage which is given as:
 805 *     wastage = Zp % class_size
 806 *     usage = Zp - wastage
 807 * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
 808 *
 809 * For example, for size class of 3/8 * PAGE_SIZE, we should
 810 * link together 3 PAGE_SIZE sized pages to form a zspage
 811 * since then we can perfectly fit in 8 such objects.
 812 */
 813static int get_pages_per_zspage(int class_size)
 814{
 815	int i, max_usedpc = 0;
 816	/* zspage order which gives maximum used size per KB */
 817	int max_usedpc_order = 1;
 818
 819	for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
 820		int zspage_size;
 821		int waste, usedpc;
 822
 823		zspage_size = i * PAGE_SIZE;
 824		waste = zspage_size % class_size;
 825		usedpc = (zspage_size - waste) * 100 / zspage_size;
 826
 827		if (usedpc > max_usedpc) {
 828			max_usedpc = usedpc;
 829			max_usedpc_order = i;
 830		}
 831	}
 832
 833	return max_usedpc_order;
 834}
 835
 836static struct zspage *get_zspage(struct page *page)
 837{
 838	struct zspage *zspage = (struct zspage *)page->private;
 839
 840	BUG_ON(zspage->magic != ZSPAGE_MAGIC);
 841	return zspage;
 842}
 843
 844static struct page *get_next_page(struct page *page)
 845{
 846	if (unlikely(PageHugeObject(page)))
 847		return NULL;
 848
 849	return page->freelist;
 850}
 851
 852/**
 853 * obj_to_location - get (<page>, <obj_idx>) from encoded object value
 854 * @obj: the encoded object value
 855 * @page: page object resides in zspage
 856 * @obj_idx: object index
 857 */
 858static void obj_to_location(unsigned long obj, struct page **page,
 859				unsigned int *obj_idx)
 860{
 861	obj >>= OBJ_TAG_BITS;
 862	*page = pfn_to_page(obj >> OBJ_INDEX_BITS);
 863	*obj_idx = (obj & OBJ_INDEX_MASK);
 864}
 865
 866/**
 867 * location_to_obj - get obj value encoded from (<page>, <obj_idx>)
 868 * @page: page object resides in zspage
 869 * @obj_idx: object index
 870 */
 871static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
 872{
 873	unsigned long obj;
 874
 875	obj = page_to_pfn(page) << OBJ_INDEX_BITS;
 876	obj |= obj_idx & OBJ_INDEX_MASK;
 877	obj <<= OBJ_TAG_BITS;
 878
 879	return obj;
 880}
 881
 882static unsigned long handle_to_obj(unsigned long handle)
 883{
 884	return *(unsigned long *)handle;
 885}
 886
 887static unsigned long obj_to_head(struct page *page, void *obj)
 888{
 889	if (unlikely(PageHugeObject(page))) {
 890		VM_BUG_ON_PAGE(!is_first_page(page), page);
 891		return page->index;
 892	} else
 893		return *(unsigned long *)obj;
 894}
 895
 896static inline int testpin_tag(unsigned long handle)
 897{
 898	return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
 899}
 900
 901static inline int trypin_tag(unsigned long handle)
 902{
 903	return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
 904}
 905
 906static void pin_tag(unsigned long handle)
 907{
 908	bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
 909}
 910
 911static void unpin_tag(unsigned long handle)
 912{
 913	bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
 914}
 915
 916static void reset_page(struct page *page)
 917{
 918	__ClearPageMovable(page);
 919	ClearPagePrivate(page);
 920	set_page_private(page, 0);
 921	page_mapcount_reset(page);
 922	ClearPageHugeObject(page);
 923	page->freelist = NULL;
 924}
 925
 926/*
 927 * To prevent zspage destroy during migration, zspage freeing should
 928 * hold locks of all pages in the zspage.
 929 */
 930void lock_zspage(struct zspage *zspage)
 931{
 932	struct page *page = get_first_page(zspage);
 933
 934	do {
 935		lock_page(page);
 936	} while ((page = get_next_page(page)) != NULL);
 937}
 938
 939int trylock_zspage(struct zspage *zspage)
 940{
 941	struct page *cursor, *fail;
 942
 943	for (cursor = get_first_page(zspage); cursor != NULL; cursor =
 944					get_next_page(cursor)) {
 945		if (!trylock_page(cursor)) {
 946			fail = cursor;
 947			goto unlock;
 948		}
 949	}
 950
 951	return 1;
 952unlock:
 953	for (cursor = get_first_page(zspage); cursor != fail; cursor =
 954					get_next_page(cursor))
 955		unlock_page(cursor);
 956
 957	return 0;
 958}
 959
 960static void __free_zspage(struct zs_pool *pool, struct size_class *class,
 961				struct zspage *zspage)
 962{
 963	struct page *page, *next;
 964	enum fullness_group fg;
 965	unsigned int class_idx;
 966
 967	get_zspage_mapping(zspage, &class_idx, &fg);
 968
 969	assert_spin_locked(&class->lock);
 970
 971	VM_BUG_ON(get_zspage_inuse(zspage));
 972	VM_BUG_ON(fg != ZS_EMPTY);
 973
 974	next = page = get_first_page(zspage);
 975	do {
 976		VM_BUG_ON_PAGE(!PageLocked(page), page);
 977		next = get_next_page(page);
 978		reset_page(page);
 979		unlock_page(page);
 980		dec_zone_page_state(page, NR_ZSPAGES);
 981		put_page(page);
 982		page = next;
 983	} while (page != NULL);
 984
 985	cache_free_zspage(pool, zspage);
 986
 987	zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage);
 988	atomic_long_sub(class->pages_per_zspage,
 989					&pool->pages_allocated);
 990}
 991
 992static void free_zspage(struct zs_pool *pool, struct size_class *class,
 993				struct zspage *zspage)
 994{
 995	VM_BUG_ON(get_zspage_inuse(zspage));
 996	VM_BUG_ON(list_empty(&zspage->list));
 997
 998	if (!trylock_zspage(zspage)) {
 999		kick_deferred_free(pool);
1000		return;
1001	}
1002
1003	remove_zspage(class, zspage, ZS_EMPTY);
1004	__free_zspage(pool, class, zspage);
1005}
1006
1007/* Initialize a newly allocated zspage */
1008static void init_zspage(struct size_class *class, struct zspage *zspage)
1009{
1010	unsigned int freeobj = 1;
1011	unsigned long off = 0;
1012	struct page *page = get_first_page(zspage);
1013
1014	while (page) {
1015		struct page *next_page;
1016		struct link_free *link;
1017		void *vaddr;
1018
1019		set_first_obj_offset(page, off);
1020
1021		vaddr = kmap_atomic(page);
1022		link = (struct link_free *)vaddr + off / sizeof(*link);
1023
1024		while ((off += class->size) < PAGE_SIZE) {
1025			link->next = freeobj++ << OBJ_TAG_BITS;
1026			link += class->size / sizeof(*link);
1027		}
1028
1029		/*
1030		 * We now come to the last (full or partial) object on this
1031		 * page, which must point to the first object on the next
1032		 * page (if present)
1033		 */
1034		next_page = get_next_page(page);
1035		if (next_page) {
1036			link->next = freeobj++ << OBJ_TAG_BITS;
1037		} else {
1038			/*
1039			 * Reset OBJ_TAG_BITS bit to last link to tell
1040			 * whether it's allocated object or not.
1041			 */
1042			link->next = -1UL << OBJ_TAG_BITS;
1043		}
1044		kunmap_atomic(vaddr);
1045		page = next_page;
1046		off %= PAGE_SIZE;
1047	}
1048
1049	set_freeobj(zspage, 0);
1050}
1051
1052static void create_page_chain(struct size_class *class, struct zspage *zspage,
1053				struct page *pages[])
1054{
1055	int i;
1056	struct page *page;
1057	struct page *prev_page = NULL;
1058	int nr_pages = class->pages_per_zspage;
1059
1060	/*
1061	 * Allocate individual pages and link them together as:
1062	 * 1. all pages are linked together using page->freelist
1063	 * 2. each sub-page point to zspage using page->private
1064	 *
1065	 * we set PG_private to identify the first page (i.e. no other sub-page
1066	 * has this flag set).
1067	 */
1068	for (i = 0; i < nr_pages; i++) {
1069		page = pages[i];
1070		set_page_private(page, (unsigned long)zspage);
1071		page->freelist = NULL;
1072		if (i == 0) {
1073			zspage->first_page = page;
1074			SetPagePrivate(page);
1075			if (unlikely(class->objs_per_zspage == 1 &&
1076					class->pages_per_zspage == 1))
1077				SetPageHugeObject(page);
1078		} else {
1079			prev_page->freelist = page;
1080		}
1081		prev_page = page;
1082	}
1083}
1084
1085/*
1086 * Allocate a zspage for the given size class
1087 */
1088static struct zspage *alloc_zspage(struct zs_pool *pool,
1089					struct size_class *class,
1090					gfp_t gfp)
1091{
1092	int i;
1093	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
1094	struct zspage *zspage = cache_alloc_zspage(pool, gfp);
1095
1096	if (!zspage)
1097		return NULL;
1098
1099	memset(zspage, 0, sizeof(struct zspage));
1100	zspage->magic = ZSPAGE_MAGIC;
1101	migrate_lock_init(zspage);
1102
1103	for (i = 0; i < class->pages_per_zspage; i++) {
1104		struct page *page;
1105
1106		page = alloc_page(gfp);
1107		if (!page) {
1108			while (--i >= 0) {
1109				dec_zone_page_state(pages[i], NR_ZSPAGES);
1110				__free_page(pages[i]);
1111			}
1112			cache_free_zspage(pool, zspage);
1113			return NULL;
1114		}
1115
1116		inc_zone_page_state(page, NR_ZSPAGES);
1117		pages[i] = page;
1118	}
1119
1120	create_page_chain(class, zspage, pages);
1121	init_zspage(class, zspage);
1122
1123	return zspage;
1124}
1125
1126static struct zspage *find_get_zspage(struct size_class *class)
1127{
1128	int i;
1129	struct zspage *zspage;
1130
1131	for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) {
1132		zspage = list_first_entry_or_null(&class->fullness_list[i],
1133				struct zspage, list);
1134		if (zspage)
1135			break;
1136	}
1137
1138	return zspage;
1139}
1140
1141#ifdef CONFIG_PGTABLE_MAPPING
1142static inline int __zs_cpu_up(struct mapping_area *area)
1143{
1144	/*
1145	 * Make sure we don't leak memory if a cpu UP notification
1146	 * and zs_init() race and both call zs_cpu_up() on the same cpu
1147	 */
1148	if (area->vm)
1149		return 0;
1150	area->vm = alloc_vm_area(PAGE_SIZE * 2, NULL);
1151	if (!area->vm)
1152		return -ENOMEM;
1153	return 0;
1154}
1155
1156static inline void __zs_cpu_down(struct mapping_area *area)
1157{
1158	if (area->vm)
1159		free_vm_area(area->vm);
1160	area->vm = NULL;
1161}
1162
1163static inline void *__zs_map_object(struct mapping_area *area,
1164				struct page *pages[2], int off, int size)
1165{
1166	BUG_ON(map_vm_area(area->vm, PAGE_KERNEL, pages));
 
 
1167	area->vm_addr = area->vm->addr;
1168	return area->vm_addr + off;
1169}
1170
1171static inline void __zs_unmap_object(struct mapping_area *area,
1172				struct page *pages[2], int off, int size)
1173{
1174	unsigned long addr = (unsigned long)area->vm_addr;
1175
1176	unmap_kernel_range(addr, PAGE_SIZE * 2);
1177}
1178
1179#else /* CONFIG_PGTABLE_MAPPING */
1180
1181static inline int __zs_cpu_up(struct mapping_area *area)
1182{
1183	/*
1184	 * Make sure we don't leak memory if a cpu UP notification
1185	 * and zs_init() race and both call zs_cpu_up() on the same cpu
1186	 */
1187	if (area->vm_buf)
1188		return 0;
1189	area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
1190	if (!area->vm_buf)
1191		return -ENOMEM;
1192	return 0;
1193}
1194
1195static inline void __zs_cpu_down(struct mapping_area *area)
1196{
1197	kfree(area->vm_buf);
1198	area->vm_buf = NULL;
1199}
1200
1201static void *__zs_map_object(struct mapping_area *area,
1202			struct page *pages[2], int off, int size)
1203{
1204	int sizes[2];
1205	void *addr;
1206	char *buf = area->vm_buf;
1207
1208	/* disable page faults to match kmap_atomic() return conditions */
1209	pagefault_disable();
1210
1211	/* no read fastpath */
1212	if (area->vm_mm == ZS_MM_WO)
1213		goto out;
1214
1215	sizes[0] = PAGE_SIZE - off;
1216	sizes[1] = size - sizes[0];
1217
1218	/* copy object to per-cpu buffer */
1219	addr = kmap_atomic(pages[0]);
1220	memcpy(buf, addr + off, sizes[0]);
1221	kunmap_atomic(addr);
1222	addr = kmap_atomic(pages[1]);
1223	memcpy(buf + sizes[0], addr, sizes[1]);
1224	kunmap_atomic(addr);
1225out:
1226	return area->vm_buf;
1227}
1228
1229static void __zs_unmap_object(struct mapping_area *area,
1230			struct page *pages[2], int off, int size)
1231{
1232	int sizes[2];
1233	void *addr;
1234	char *buf;
1235
1236	/* no write fastpath */
1237	if (area->vm_mm == ZS_MM_RO)
1238		goto out;
1239
1240	buf = area->vm_buf;
1241	buf = buf + ZS_HANDLE_SIZE;
1242	size -= ZS_HANDLE_SIZE;
1243	off += ZS_HANDLE_SIZE;
1244
1245	sizes[0] = PAGE_SIZE - off;
1246	sizes[1] = size - sizes[0];
1247
1248	/* copy per-cpu buffer to object */
1249	addr = kmap_atomic(pages[0]);
1250	memcpy(addr + off, buf, sizes[0]);
1251	kunmap_atomic(addr);
1252	addr = kmap_atomic(pages[1]);
1253	memcpy(addr, buf + sizes[0], sizes[1]);
1254	kunmap_atomic(addr);
1255
1256out:
1257	/* enable page faults to match kunmap_atomic() return conditions */
1258	pagefault_enable();
1259}
1260
1261#endif /* CONFIG_PGTABLE_MAPPING */
1262
1263static int zs_cpu_prepare(unsigned int cpu)
1264{
1265	struct mapping_area *area;
1266
1267	area = &per_cpu(zs_map_area, cpu);
1268	return __zs_cpu_up(area);
1269}
1270
1271static int zs_cpu_dead(unsigned int cpu)
1272{
1273	struct mapping_area *area;
1274
1275	area = &per_cpu(zs_map_area, cpu);
1276	__zs_cpu_down(area);
1277	return 0;
1278}
1279
1280static bool can_merge(struct size_class *prev, int pages_per_zspage,
1281					int objs_per_zspage)
1282{
1283	if (prev->pages_per_zspage == pages_per_zspage &&
1284		prev->objs_per_zspage == objs_per_zspage)
1285		return true;
1286
1287	return false;
1288}
1289
1290static bool zspage_full(struct size_class *class, struct zspage *zspage)
1291{
1292	return get_zspage_inuse(zspage) == class->objs_per_zspage;
1293}
1294
1295unsigned long zs_get_total_pages(struct zs_pool *pool)
1296{
1297	return atomic_long_read(&pool->pages_allocated);
1298}
1299EXPORT_SYMBOL_GPL(zs_get_total_pages);
1300
1301/**
1302 * zs_map_object - get address of allocated object from handle.
1303 * @pool: pool from which the object was allocated
1304 * @handle: handle returned from zs_malloc
1305 * @mm: maping mode to use
1306 *
1307 * Before using an object allocated from zs_malloc, it must be mapped using
1308 * this function. When done with the object, it must be unmapped using
1309 * zs_unmap_object.
1310 *
1311 * Only one object can be mapped per cpu at a time. There is no protection
1312 * against nested mappings.
1313 *
1314 * This function returns with preemption and page faults disabled.
1315 */
1316void *zs_map_object(struct zs_pool *pool, unsigned long handle,
1317			enum zs_mapmode mm)
1318{
1319	struct zspage *zspage;
1320	struct page *page;
1321	unsigned long obj, off;
1322	unsigned int obj_idx;
1323
1324	unsigned int class_idx;
1325	enum fullness_group fg;
1326	struct size_class *class;
1327	struct mapping_area *area;
1328	struct page *pages[2];
1329	void *ret;
1330
1331	/*
1332	 * Because we use per-cpu mapping areas shared among the
1333	 * pools/users, we can't allow mapping in interrupt context
1334	 * because it can corrupt another users mappings.
1335	 */
1336	BUG_ON(in_interrupt());
1337
1338	/* From now on, migration cannot move the object */
1339	pin_tag(handle);
1340
1341	obj = handle_to_obj(handle);
1342	obj_to_location(obj, &page, &obj_idx);
1343	zspage = get_zspage(page);
1344
1345	/* migration cannot move any subpage in this zspage */
1346	migrate_read_lock(zspage);
1347
1348	get_zspage_mapping(zspage, &class_idx, &fg);
1349	class = pool->size_class[class_idx];
1350	off = (class->size * obj_idx) & ~PAGE_MASK;
1351
1352	area = &get_cpu_var(zs_map_area);
1353	area->vm_mm = mm;
1354	if (off + class->size <= PAGE_SIZE) {
1355		/* this object is contained entirely within a page */
1356		area->vm_addr = kmap_atomic(page);
1357		ret = area->vm_addr + off;
1358		goto out;
1359	}
1360
1361	/* this object spans two pages */
1362	pages[0] = page;
1363	pages[1] = get_next_page(page);
1364	BUG_ON(!pages[1]);
1365
1366	ret = __zs_map_object(area, pages, off, class->size);
1367out:
1368	if (likely(!PageHugeObject(page)))
1369		ret += ZS_HANDLE_SIZE;
1370
1371	return ret;
1372}
1373EXPORT_SYMBOL_GPL(zs_map_object);
1374
1375void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1376{
1377	struct zspage *zspage;
1378	struct page *page;
1379	unsigned long obj, off;
1380	unsigned int obj_idx;
1381
1382	unsigned int class_idx;
1383	enum fullness_group fg;
1384	struct size_class *class;
1385	struct mapping_area *area;
1386
1387	obj = handle_to_obj(handle);
1388	obj_to_location(obj, &page, &obj_idx);
1389	zspage = get_zspage(page);
1390	get_zspage_mapping(zspage, &class_idx, &fg);
1391	class = pool->size_class[class_idx];
1392	off = (class->size * obj_idx) & ~PAGE_MASK;
1393
1394	area = this_cpu_ptr(&zs_map_area);
1395	if (off + class->size <= PAGE_SIZE)
1396		kunmap_atomic(area->vm_addr);
1397	else {
1398		struct page *pages[2];
1399
1400		pages[0] = page;
1401		pages[1] = get_next_page(page);
1402		BUG_ON(!pages[1]);
1403
1404		__zs_unmap_object(area, pages, off, class->size);
1405	}
1406	put_cpu_var(zs_map_area);
1407
1408	migrate_read_unlock(zspage);
1409	unpin_tag(handle);
1410}
1411EXPORT_SYMBOL_GPL(zs_unmap_object);
1412
1413/**
1414 * zs_huge_class_size() - Returns the size (in bytes) of the first huge
1415 *                        zsmalloc &size_class.
1416 * @pool: zsmalloc pool to use
1417 *
1418 * The function returns the size of the first huge class - any object of equal
1419 * or bigger size will be stored in zspage consisting of a single physical
1420 * page.
1421 *
1422 * Context: Any context.
1423 *
1424 * Return: the size (in bytes) of the first huge zsmalloc &size_class.
1425 */
1426size_t zs_huge_class_size(struct zs_pool *pool)
1427{
1428	return huge_class_size;
1429}
1430EXPORT_SYMBOL_GPL(zs_huge_class_size);
1431
1432static unsigned long obj_malloc(struct size_class *class,
1433				struct zspage *zspage, unsigned long handle)
1434{
1435	int i, nr_page, offset;
1436	unsigned long obj;
1437	struct link_free *link;
1438
1439	struct page *m_page;
1440	unsigned long m_offset;
1441	void *vaddr;
1442
1443	handle |= OBJ_ALLOCATED_TAG;
1444	obj = get_freeobj(zspage);
1445
1446	offset = obj * class->size;
1447	nr_page = offset >> PAGE_SHIFT;
1448	m_offset = offset & ~PAGE_MASK;
1449	m_page = get_first_page(zspage);
1450
1451	for (i = 0; i < nr_page; i++)
1452		m_page = get_next_page(m_page);
1453
1454	vaddr = kmap_atomic(m_page);
1455	link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1456	set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
1457	if (likely(!PageHugeObject(m_page)))
1458		/* record handle in the header of allocated chunk */
1459		link->handle = handle;
1460	else
1461		/* record handle to page->index */
1462		zspage->first_page->index = handle;
1463
1464	kunmap_atomic(vaddr);
1465	mod_zspage_inuse(zspage, 1);
1466	zs_stat_inc(class, OBJ_USED, 1);
1467
1468	obj = location_to_obj(m_page, obj);
1469
1470	return obj;
1471}
1472
1473
1474/**
1475 * zs_malloc - Allocate block of given size from pool.
1476 * @pool: pool to allocate from
1477 * @size: size of block to allocate
1478 * @gfp: gfp flags when allocating object
1479 *
1480 * On success, handle to the allocated object is returned,
1481 * otherwise 0.
1482 * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
1483 */
1484unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
1485{
1486	unsigned long handle, obj;
1487	struct size_class *class;
1488	enum fullness_group newfg;
1489	struct zspage *zspage;
1490
1491	if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
1492		return 0;
1493
1494	handle = cache_alloc_handle(pool, gfp);
1495	if (!handle)
1496		return 0;
1497
1498	/* extra space in chunk to keep the handle */
1499	size += ZS_HANDLE_SIZE;
1500	class = pool->size_class[get_size_class_index(size)];
1501
1502	spin_lock(&class->lock);
1503	zspage = find_get_zspage(class);
1504	if (likely(zspage)) {
1505		obj = obj_malloc(class, zspage, handle);
1506		/* Now move the zspage to another fullness group, if required */
1507		fix_fullness_group(class, zspage);
1508		record_obj(handle, obj);
1509		spin_unlock(&class->lock);
1510
1511		return handle;
1512	}
1513
1514	spin_unlock(&class->lock);
1515
1516	zspage = alloc_zspage(pool, class, gfp);
1517	if (!zspage) {
1518		cache_free_handle(pool, handle);
1519		return 0;
1520	}
1521
1522	spin_lock(&class->lock);
1523	obj = obj_malloc(class, zspage, handle);
1524	newfg = get_fullness_group(class, zspage);
1525	insert_zspage(class, zspage, newfg);
1526	set_zspage_mapping(zspage, class->index, newfg);
1527	record_obj(handle, obj);
1528	atomic_long_add(class->pages_per_zspage,
1529				&pool->pages_allocated);
1530	zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
1531
1532	/* We completely set up zspage so mark them as movable */
1533	SetZsPageMovable(pool, zspage);
1534	spin_unlock(&class->lock);
1535
1536	return handle;
1537}
1538EXPORT_SYMBOL_GPL(zs_malloc);
1539
1540static void obj_free(struct size_class *class, unsigned long obj)
1541{
1542	struct link_free *link;
1543	struct zspage *zspage;
1544	struct page *f_page;
1545	unsigned long f_offset;
1546	unsigned int f_objidx;
1547	void *vaddr;
1548
1549	obj &= ~OBJ_ALLOCATED_TAG;
1550	obj_to_location(obj, &f_page, &f_objidx);
1551	f_offset = (class->size * f_objidx) & ~PAGE_MASK;
1552	zspage = get_zspage(f_page);
1553
1554	vaddr = kmap_atomic(f_page);
1555
1556	/* Insert this object in containing zspage's freelist */
1557	link = (struct link_free *)(vaddr + f_offset);
1558	link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
1559	kunmap_atomic(vaddr);
1560	set_freeobj(zspage, f_objidx);
1561	mod_zspage_inuse(zspage, -1);
1562	zs_stat_dec(class, OBJ_USED, 1);
1563}
1564
1565void zs_free(struct zs_pool *pool, unsigned long handle)
1566{
1567	struct zspage *zspage;
1568	struct page *f_page;
1569	unsigned long obj;
1570	unsigned int f_objidx;
1571	int class_idx;
1572	struct size_class *class;
1573	enum fullness_group fullness;
1574	bool isolated;
1575
1576	if (unlikely(!handle))
1577		return;
1578
1579	pin_tag(handle);
1580	obj = handle_to_obj(handle);
1581	obj_to_location(obj, &f_page, &f_objidx);
1582	zspage = get_zspage(f_page);
1583
1584	migrate_read_lock(zspage);
1585
1586	get_zspage_mapping(zspage, &class_idx, &fullness);
1587	class = pool->size_class[class_idx];
1588
1589	spin_lock(&class->lock);
1590	obj_free(class, obj);
1591	fullness = fix_fullness_group(class, zspage);
1592	if (fullness != ZS_EMPTY) {
1593		migrate_read_unlock(zspage);
1594		goto out;
1595	}
1596
1597	isolated = is_zspage_isolated(zspage);
1598	migrate_read_unlock(zspage);
1599	/* If zspage is isolated, zs_page_putback will free the zspage */
1600	if (likely(!isolated))
1601		free_zspage(pool, class, zspage);
1602out:
1603
1604	spin_unlock(&class->lock);
1605	unpin_tag(handle);
1606	cache_free_handle(pool, handle);
1607}
1608EXPORT_SYMBOL_GPL(zs_free);
1609
1610static void zs_object_copy(struct size_class *class, unsigned long dst,
1611				unsigned long src)
1612{
1613	struct page *s_page, *d_page;
1614	unsigned int s_objidx, d_objidx;
1615	unsigned long s_off, d_off;
1616	void *s_addr, *d_addr;
1617	int s_size, d_size, size;
1618	int written = 0;
1619
1620	s_size = d_size = class->size;
1621
1622	obj_to_location(src, &s_page, &s_objidx);
1623	obj_to_location(dst, &d_page, &d_objidx);
1624
1625	s_off = (class->size * s_objidx) & ~PAGE_MASK;
1626	d_off = (class->size * d_objidx) & ~PAGE_MASK;
1627
1628	if (s_off + class->size > PAGE_SIZE)
1629		s_size = PAGE_SIZE - s_off;
1630
1631	if (d_off + class->size > PAGE_SIZE)
1632		d_size = PAGE_SIZE - d_off;
1633
1634	s_addr = kmap_atomic(s_page);
1635	d_addr = kmap_atomic(d_page);
1636
1637	while (1) {
1638		size = min(s_size, d_size);
1639		memcpy(d_addr + d_off, s_addr + s_off, size);
1640		written += size;
1641
1642		if (written == class->size)
1643			break;
1644
1645		s_off += size;
1646		s_size -= size;
1647		d_off += size;
1648		d_size -= size;
1649
1650		if (s_off >= PAGE_SIZE) {
1651			kunmap_atomic(d_addr);
1652			kunmap_atomic(s_addr);
1653			s_page = get_next_page(s_page);
1654			s_addr = kmap_atomic(s_page);
1655			d_addr = kmap_atomic(d_page);
1656			s_size = class->size - written;
1657			s_off = 0;
1658		}
1659
1660		if (d_off >= PAGE_SIZE) {
1661			kunmap_atomic(d_addr);
1662			d_page = get_next_page(d_page);
1663			d_addr = kmap_atomic(d_page);
1664			d_size = class->size - written;
1665			d_off = 0;
1666		}
1667	}
1668
1669	kunmap_atomic(d_addr);
1670	kunmap_atomic(s_addr);
1671}
1672
1673/*
1674 * Find alloced object in zspage from index object and
1675 * return handle.
1676 */
1677static unsigned long find_alloced_obj(struct size_class *class,
1678					struct page *page, int *obj_idx)
1679{
1680	unsigned long head;
1681	int offset = 0;
1682	int index = *obj_idx;
1683	unsigned long handle = 0;
1684	void *addr = kmap_atomic(page);
1685
1686	offset = get_first_obj_offset(page);
1687	offset += class->size * index;
1688
1689	while (offset < PAGE_SIZE) {
1690		head = obj_to_head(page, addr + offset);
1691		if (head & OBJ_ALLOCATED_TAG) {
1692			handle = head & ~OBJ_ALLOCATED_TAG;
1693			if (trypin_tag(handle))
1694				break;
1695			handle = 0;
1696		}
1697
1698		offset += class->size;
1699		index++;
1700	}
1701
1702	kunmap_atomic(addr);
1703
1704	*obj_idx = index;
1705
1706	return handle;
1707}
1708
1709struct zs_compact_control {
1710	/* Source spage for migration which could be a subpage of zspage */
1711	struct page *s_page;
1712	/* Destination page for migration which should be a first page
1713	 * of zspage. */
1714	struct page *d_page;
1715	 /* Starting object index within @s_page which used for live object
1716	  * in the subpage. */
1717	int obj_idx;
1718};
1719
1720static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
1721				struct zs_compact_control *cc)
1722{
1723	unsigned long used_obj, free_obj;
1724	unsigned long handle;
1725	struct page *s_page = cc->s_page;
1726	struct page *d_page = cc->d_page;
1727	int obj_idx = cc->obj_idx;
1728	int ret = 0;
1729
1730	while (1) {
1731		handle = find_alloced_obj(class, s_page, &obj_idx);
1732		if (!handle) {
1733			s_page = get_next_page(s_page);
1734			if (!s_page)
1735				break;
1736			obj_idx = 0;
1737			continue;
1738		}
1739
1740		/* Stop if there is no more space */
1741		if (zspage_full(class, get_zspage(d_page))) {
1742			unpin_tag(handle);
1743			ret = -ENOMEM;
1744			break;
1745		}
1746
1747		used_obj = handle_to_obj(handle);
1748		free_obj = obj_malloc(class, get_zspage(d_page), handle);
1749		zs_object_copy(class, free_obj, used_obj);
1750		obj_idx++;
1751		/*
1752		 * record_obj updates handle's value to free_obj and it will
1753		 * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
1754		 * breaks synchronization using pin_tag(e,g, zs_free) so
1755		 * let's keep the lock bit.
1756		 */
1757		free_obj |= BIT(HANDLE_PIN_BIT);
1758		record_obj(handle, free_obj);
1759		unpin_tag(handle);
1760		obj_free(class, used_obj);
1761	}
1762
1763	/* Remember last position in this iteration */
1764	cc->s_page = s_page;
1765	cc->obj_idx = obj_idx;
1766
1767	return ret;
1768}
1769
1770static struct zspage *isolate_zspage(struct size_class *class, bool source)
1771{
1772	int i;
1773	struct zspage *zspage;
1774	enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL};
1775
1776	if (!source) {
1777		fg[0] = ZS_ALMOST_FULL;
1778		fg[1] = ZS_ALMOST_EMPTY;
1779	}
1780
1781	for (i = 0; i < 2; i++) {
1782		zspage = list_first_entry_or_null(&class->fullness_list[fg[i]],
1783							struct zspage, list);
1784		if (zspage) {
1785			VM_BUG_ON(is_zspage_isolated(zspage));
1786			remove_zspage(class, zspage, fg[i]);
1787			return zspage;
1788		}
1789	}
1790
1791	return zspage;
1792}
1793
1794/*
1795 * putback_zspage - add @zspage into right class's fullness list
1796 * @class: destination class
1797 * @zspage: target page
1798 *
1799 * Return @zspage's fullness_group
1800 */
1801static enum fullness_group putback_zspage(struct size_class *class,
1802			struct zspage *zspage)
1803{
1804	enum fullness_group fullness;
1805
1806	VM_BUG_ON(is_zspage_isolated(zspage));
1807
1808	fullness = get_fullness_group(class, zspage);
1809	insert_zspage(class, zspage, fullness);
1810	set_zspage_mapping(zspage, class->index, fullness);
1811
1812	return fullness;
1813}
1814
1815#ifdef CONFIG_COMPACTION
1816static struct dentry *zs_mount(struct file_system_type *fs_type,
1817				int flags, const char *dev_name, void *data)
 
 
 
1818{
1819	static const struct dentry_operations ops = {
1820		.d_dname = simple_dname,
1821	};
 
 
 
1822
1823	return mount_pseudo(fs_type, "zsmalloc:", NULL, &ops, ZSMALLOC_MAGIC);
 
 
1824}
1825
1826static struct file_system_type zsmalloc_fs = {
1827	.name		= "zsmalloc",
1828	.mount		= zs_mount,
1829	.kill_sb	= kill_anon_super,
1830};
1831
1832static int zsmalloc_mount(void)
1833{
1834	int ret = 0;
1835
1836	zsmalloc_mnt = kern_mount(&zsmalloc_fs);
1837	if (IS_ERR(zsmalloc_mnt))
1838		ret = PTR_ERR(zsmalloc_mnt);
1839
1840	return ret;
1841}
1842
1843static void zsmalloc_unmount(void)
1844{
1845	kern_unmount(zsmalloc_mnt);
1846}
1847
1848static void migrate_lock_init(struct zspage *zspage)
1849{
1850	rwlock_init(&zspage->lock);
1851}
1852
1853static void migrate_read_lock(struct zspage *zspage)
1854{
1855	read_lock(&zspage->lock);
1856}
1857
1858static void migrate_read_unlock(struct zspage *zspage)
1859{
1860	read_unlock(&zspage->lock);
1861}
1862
1863static void migrate_write_lock(struct zspage *zspage)
1864{
1865	write_lock(&zspage->lock);
1866}
1867
1868static void migrate_write_unlock(struct zspage *zspage)
1869{
1870	write_unlock(&zspage->lock);
1871}
1872
1873/* Number of isolated subpage for *page migration* in this zspage */
1874static void inc_zspage_isolation(struct zspage *zspage)
1875{
1876	zspage->isolated++;
1877}
1878
1879static void dec_zspage_isolation(struct zspage *zspage)
1880{
1881	zspage->isolated--;
1882}
1883
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1884static void replace_sub_page(struct size_class *class, struct zspage *zspage,
1885				struct page *newpage, struct page *oldpage)
1886{
1887	struct page *page;
1888	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
1889	int idx = 0;
1890
1891	page = get_first_page(zspage);
1892	do {
1893		if (page == oldpage)
1894			pages[idx] = newpage;
1895		else
1896			pages[idx] = page;
1897		idx++;
1898	} while ((page = get_next_page(page)) != NULL);
1899
1900	create_page_chain(class, zspage, pages);
1901	set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
1902	if (unlikely(PageHugeObject(oldpage)))
1903		newpage->index = oldpage->index;
1904	__SetPageMovable(newpage, page_mapping(oldpage));
1905}
1906
1907bool zs_page_isolate(struct page *page, isolate_mode_t mode)
1908{
1909	struct zs_pool *pool;
1910	struct size_class *class;
1911	int class_idx;
1912	enum fullness_group fullness;
1913	struct zspage *zspage;
1914	struct address_space *mapping;
1915
1916	/*
1917	 * Page is locked so zspage couldn't be destroyed. For detail, look at
1918	 * lock_zspage in free_zspage.
1919	 */
1920	VM_BUG_ON_PAGE(!PageMovable(page), page);
1921	VM_BUG_ON_PAGE(PageIsolated(page), page);
1922
1923	zspage = get_zspage(page);
1924
1925	/*
1926	 * Without class lock, fullness could be stale while class_idx is okay
1927	 * because class_idx is constant unless page is freed so we should get
1928	 * fullness again under class lock.
1929	 */
1930	get_zspage_mapping(zspage, &class_idx, &fullness);
1931	mapping = page_mapping(page);
1932	pool = mapping->private_data;
1933	class = pool->size_class[class_idx];
1934
1935	spin_lock(&class->lock);
1936	if (get_zspage_inuse(zspage) == 0) {
1937		spin_unlock(&class->lock);
1938		return false;
1939	}
1940
1941	/* zspage is isolated for object migration */
1942	if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1943		spin_unlock(&class->lock);
1944		return false;
1945	}
1946
1947	/*
1948	 * If this is first time isolation for the zspage, isolate zspage from
1949	 * size_class to prevent further object allocation from the zspage.
1950	 */
1951	if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1952		get_zspage_mapping(zspage, &class_idx, &fullness);
 
1953		remove_zspage(class, zspage, fullness);
1954	}
1955
1956	inc_zspage_isolation(zspage);
1957	spin_unlock(&class->lock);
1958
1959	return true;
1960}
1961
1962int zs_page_migrate(struct address_space *mapping, struct page *newpage,
1963		struct page *page, enum migrate_mode mode)
1964{
1965	struct zs_pool *pool;
1966	struct size_class *class;
1967	int class_idx;
1968	enum fullness_group fullness;
1969	struct zspage *zspage;
1970	struct page *dummy;
1971	void *s_addr, *d_addr, *addr;
1972	int offset, pos;
1973	unsigned long handle, head;
1974	unsigned long old_obj, new_obj;
1975	unsigned int obj_idx;
1976	int ret = -EAGAIN;
1977
1978	/*
1979	 * We cannot support the _NO_COPY case here, because copy needs to
1980	 * happen under the zs lock, which does not work with
1981	 * MIGRATE_SYNC_NO_COPY workflow.
1982	 */
1983	if (mode == MIGRATE_SYNC_NO_COPY)
1984		return -EINVAL;
1985
1986	VM_BUG_ON_PAGE(!PageMovable(page), page);
1987	VM_BUG_ON_PAGE(!PageIsolated(page), page);
1988
1989	zspage = get_zspage(page);
1990
1991	/* Concurrent compactor cannot migrate any subpage in zspage */
1992	migrate_write_lock(zspage);
1993	get_zspage_mapping(zspage, &class_idx, &fullness);
1994	pool = mapping->private_data;
1995	class = pool->size_class[class_idx];
1996	offset = get_first_obj_offset(page);
1997
1998	spin_lock(&class->lock);
1999	if (!get_zspage_inuse(zspage)) {
2000		/*
2001		 * Set "offset" to end of the page so that every loops
2002		 * skips unnecessary object scanning.
2003		 */
2004		offset = PAGE_SIZE;
2005	}
2006
2007	pos = offset;
2008	s_addr = kmap_atomic(page);
2009	while (pos < PAGE_SIZE) {
2010		head = obj_to_head(page, s_addr + pos);
2011		if (head & OBJ_ALLOCATED_TAG) {
2012			handle = head & ~OBJ_ALLOCATED_TAG;
2013			if (!trypin_tag(handle))
2014				goto unpin_objects;
2015		}
2016		pos += class->size;
2017	}
2018
2019	/*
2020	 * Here, any user cannot access all objects in the zspage so let's move.
2021	 */
2022	d_addr = kmap_atomic(newpage);
2023	memcpy(d_addr, s_addr, PAGE_SIZE);
2024	kunmap_atomic(d_addr);
2025
2026	for (addr = s_addr + offset; addr < s_addr + pos;
2027					addr += class->size) {
2028		head = obj_to_head(page, addr);
2029		if (head & OBJ_ALLOCATED_TAG) {
2030			handle = head & ~OBJ_ALLOCATED_TAG;
2031			if (!testpin_tag(handle))
2032				BUG();
2033
2034			old_obj = handle_to_obj(handle);
2035			obj_to_location(old_obj, &dummy, &obj_idx);
2036			new_obj = (unsigned long)location_to_obj(newpage,
2037								obj_idx);
2038			new_obj |= BIT(HANDLE_PIN_BIT);
2039			record_obj(handle, new_obj);
2040		}
2041	}
2042
2043	replace_sub_page(class, zspage, newpage, page);
2044	get_page(newpage);
2045
2046	dec_zspage_isolation(zspage);
2047
2048	/*
2049	 * Page migration is done so let's putback isolated zspage to
2050	 * the list if @page is final isolated subpage in the zspage.
2051	 */
2052	if (!is_zspage_isolated(zspage))
2053		putback_zspage(class, zspage);
 
 
 
 
 
 
 
 
 
 
 
 
 
2054
2055	reset_page(page);
2056	put_page(page);
2057	page = newpage;
2058
2059	ret = MIGRATEPAGE_SUCCESS;
2060unpin_objects:
2061	for (addr = s_addr + offset; addr < s_addr + pos;
2062						addr += class->size) {
2063		head = obj_to_head(page, addr);
2064		if (head & OBJ_ALLOCATED_TAG) {
2065			handle = head & ~OBJ_ALLOCATED_TAG;
2066			if (!testpin_tag(handle))
2067				BUG();
2068			unpin_tag(handle);
2069		}
2070	}
2071	kunmap_atomic(s_addr);
2072	spin_unlock(&class->lock);
2073	migrate_write_unlock(zspage);
2074
2075	return ret;
2076}
2077
2078void zs_page_putback(struct page *page)
2079{
2080	struct zs_pool *pool;
2081	struct size_class *class;
2082	int class_idx;
2083	enum fullness_group fg;
2084	struct address_space *mapping;
2085	struct zspage *zspage;
2086
2087	VM_BUG_ON_PAGE(!PageMovable(page), page);
2088	VM_BUG_ON_PAGE(!PageIsolated(page), page);
2089
2090	zspage = get_zspage(page);
2091	get_zspage_mapping(zspage, &class_idx, &fg);
2092	mapping = page_mapping(page);
2093	pool = mapping->private_data;
2094	class = pool->size_class[class_idx];
2095
2096	spin_lock(&class->lock);
2097	dec_zspage_isolation(zspage);
2098	if (!is_zspage_isolated(zspage)) {
2099		fg = putback_zspage(class, zspage);
2100		/*
2101		 * Due to page_lock, we cannot free zspage immediately
2102		 * so let's defer.
2103		 */
2104		if (fg == ZS_EMPTY)
2105			schedule_work(&pool->free_work);
2106	}
2107	spin_unlock(&class->lock);
2108}
2109
2110const struct address_space_operations zsmalloc_aops = {
2111	.isolate_page = zs_page_isolate,
2112	.migratepage = zs_page_migrate,
2113	.putback_page = zs_page_putback,
2114};
2115
2116static int zs_register_migration(struct zs_pool *pool)
2117{
2118	pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
2119	if (IS_ERR(pool->inode)) {
2120		pool->inode = NULL;
2121		return 1;
2122	}
2123
2124	pool->inode->i_mapping->private_data = pool;
2125	pool->inode->i_mapping->a_ops = &zsmalloc_aops;
2126	return 0;
2127}
2128
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2129static void zs_unregister_migration(struct zs_pool *pool)
2130{
 
 
 
 
 
 
 
 
 
2131	flush_work(&pool->free_work);
2132	iput(pool->inode);
2133}
2134
2135/*
2136 * Caller should hold page_lock of all pages in the zspage
2137 * In here, we cannot use zspage meta data.
2138 */
2139static void async_free_zspage(struct work_struct *work)
2140{
2141	int i;
2142	struct size_class *class;
2143	unsigned int class_idx;
2144	enum fullness_group fullness;
2145	struct zspage *zspage, *tmp;
2146	LIST_HEAD(free_pages);
2147	struct zs_pool *pool = container_of(work, struct zs_pool,
2148					free_work);
2149
2150	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2151		class = pool->size_class[i];
2152		if (class->index != i)
2153			continue;
2154
2155		spin_lock(&class->lock);
2156		list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages);
2157		spin_unlock(&class->lock);
2158	}
2159
2160
2161	list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
2162		list_del(&zspage->list);
2163		lock_zspage(zspage);
2164
2165		get_zspage_mapping(zspage, &class_idx, &fullness);
2166		VM_BUG_ON(fullness != ZS_EMPTY);
2167		class = pool->size_class[class_idx];
2168		spin_lock(&class->lock);
2169		__free_zspage(pool, pool->size_class[class_idx], zspage);
2170		spin_unlock(&class->lock);
2171	}
2172};
2173
2174static void kick_deferred_free(struct zs_pool *pool)
2175{
2176	schedule_work(&pool->free_work);
2177}
2178
2179static void init_deferred_free(struct zs_pool *pool)
2180{
2181	INIT_WORK(&pool->free_work, async_free_zspage);
2182}
2183
2184static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
2185{
2186	struct page *page = get_first_page(zspage);
2187
2188	do {
2189		WARN_ON(!trylock_page(page));
2190		__SetPageMovable(page, pool->inode->i_mapping);
2191		unlock_page(page);
2192	} while ((page = get_next_page(page)) != NULL);
2193}
2194#endif
2195
2196/*
2197 *
2198 * Based on the number of unused allocated objects calculate
2199 * and return the number of pages that we can free.
2200 */
2201static unsigned long zs_can_compact(struct size_class *class)
2202{
2203	unsigned long obj_wasted;
2204	unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
2205	unsigned long obj_used = zs_stat_get(class, OBJ_USED);
2206
2207	if (obj_allocated <= obj_used)
2208		return 0;
2209
2210	obj_wasted = obj_allocated - obj_used;
2211	obj_wasted /= class->objs_per_zspage;
2212
2213	return obj_wasted * class->pages_per_zspage;
2214}
2215
2216static void __zs_compact(struct zs_pool *pool, struct size_class *class)
2217{
2218	struct zs_compact_control cc;
2219	struct zspage *src_zspage;
2220	struct zspage *dst_zspage = NULL;
2221
2222	spin_lock(&class->lock);
2223	while ((src_zspage = isolate_zspage(class, true))) {
2224
2225		if (!zs_can_compact(class))
2226			break;
2227
2228		cc.obj_idx = 0;
2229		cc.s_page = get_first_page(src_zspage);
2230
2231		while ((dst_zspage = isolate_zspage(class, false))) {
2232			cc.d_page = get_first_page(dst_zspage);
2233			/*
2234			 * If there is no more space in dst_page, resched
2235			 * and see if anyone had allocated another zspage.
2236			 */
2237			if (!migrate_zspage(pool, class, &cc))
2238				break;
2239
2240			putback_zspage(class, dst_zspage);
2241		}
2242
2243		/* Stop if we couldn't find slot */
2244		if (dst_zspage == NULL)
2245			break;
2246
2247		putback_zspage(class, dst_zspage);
2248		if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
2249			free_zspage(pool, class, src_zspage);
2250			pool->stats.pages_compacted += class->pages_per_zspage;
2251		}
2252		spin_unlock(&class->lock);
2253		cond_resched();
2254		spin_lock(&class->lock);
2255	}
2256
2257	if (src_zspage)
2258		putback_zspage(class, src_zspage);
2259
2260	spin_unlock(&class->lock);
2261}
2262
2263unsigned long zs_compact(struct zs_pool *pool)
2264{
2265	int i;
2266	struct size_class *class;
2267
2268	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2269		class = pool->size_class[i];
2270		if (!class)
2271			continue;
2272		if (class->index != i)
2273			continue;
2274		__zs_compact(pool, class);
2275	}
2276
2277	return pool->stats.pages_compacted;
2278}
2279EXPORT_SYMBOL_GPL(zs_compact);
2280
2281void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
2282{
2283	memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
2284}
2285EXPORT_SYMBOL_GPL(zs_pool_stats);
2286
2287static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
2288		struct shrink_control *sc)
2289{
2290	unsigned long pages_freed;
2291	struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2292			shrinker);
2293
2294	pages_freed = pool->stats.pages_compacted;
2295	/*
2296	 * Compact classes and calculate compaction delta.
2297	 * Can run concurrently with a manually triggered
2298	 * (by user) compaction.
2299	 */
2300	pages_freed = zs_compact(pool) - pages_freed;
2301
2302	return pages_freed ? pages_freed : SHRINK_STOP;
2303}
2304
2305static unsigned long zs_shrinker_count(struct shrinker *shrinker,
2306		struct shrink_control *sc)
2307{
2308	int i;
2309	struct size_class *class;
2310	unsigned long pages_to_free = 0;
2311	struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2312			shrinker);
2313
2314	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2315		class = pool->size_class[i];
2316		if (!class)
2317			continue;
2318		if (class->index != i)
2319			continue;
2320
2321		pages_to_free += zs_can_compact(class);
2322	}
2323
2324	return pages_to_free;
2325}
2326
2327static void zs_unregister_shrinker(struct zs_pool *pool)
2328{
2329	unregister_shrinker(&pool->shrinker);
2330}
2331
2332static int zs_register_shrinker(struct zs_pool *pool)
2333{
2334	pool->shrinker.scan_objects = zs_shrinker_scan;
2335	pool->shrinker.count_objects = zs_shrinker_count;
2336	pool->shrinker.batch = 0;
2337	pool->shrinker.seeks = DEFAULT_SEEKS;
2338
2339	return register_shrinker(&pool->shrinker);
2340}
2341
2342/**
2343 * zs_create_pool - Creates an allocation pool to work from.
2344 * @name: pool name to be created
2345 *
2346 * This function must be called before anything when using
2347 * the zsmalloc allocator.
2348 *
2349 * On success, a pointer to the newly created pool is returned,
2350 * otherwise NULL.
2351 */
2352struct zs_pool *zs_create_pool(const char *name)
2353{
2354	int i;
2355	struct zs_pool *pool;
2356	struct size_class *prev_class = NULL;
2357
2358	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
2359	if (!pool)
2360		return NULL;
2361
2362	init_deferred_free(pool);
2363
2364	pool->name = kstrdup(name, GFP_KERNEL);
2365	if (!pool->name)
2366		goto err;
 
 
 
 
2367
2368	if (create_cache(pool))
2369		goto err;
2370
2371	/*
2372	 * Iterate reversely, because, size of size_class that we want to use
2373	 * for merging should be larger or equal to current size.
2374	 */
2375	for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2376		int size;
2377		int pages_per_zspage;
2378		int objs_per_zspage;
2379		struct size_class *class;
2380		int fullness = 0;
2381
2382		size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
2383		if (size > ZS_MAX_ALLOC_SIZE)
2384			size = ZS_MAX_ALLOC_SIZE;
2385		pages_per_zspage = get_pages_per_zspage(size);
2386		objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
2387
2388		/*
2389		 * We iterate from biggest down to smallest classes,
2390		 * so huge_class_size holds the size of the first huge
2391		 * class. Any object bigger than or equal to that will
2392		 * endup in the huge class.
2393		 */
2394		if (pages_per_zspage != 1 && objs_per_zspage != 1 &&
2395				!huge_class_size) {
2396			huge_class_size = size;
2397			/*
2398			 * The object uses ZS_HANDLE_SIZE bytes to store the
2399			 * handle. We need to subtract it, because zs_malloc()
2400			 * unconditionally adds handle size before it performs
2401			 * size class search - so object may be smaller than
2402			 * huge class size, yet it still can end up in the huge
2403			 * class because it grows by ZS_HANDLE_SIZE extra bytes
2404			 * right before class lookup.
2405			 */
2406			huge_class_size -= (ZS_HANDLE_SIZE - 1);
2407		}
2408
2409		/*
2410		 * size_class is used for normal zsmalloc operation such
2411		 * as alloc/free for that size. Although it is natural that we
2412		 * have one size_class for each size, there is a chance that we
2413		 * can get more memory utilization if we use one size_class for
2414		 * many different sizes whose size_class have same
2415		 * characteristics. So, we makes size_class point to
2416		 * previous size_class if possible.
2417		 */
2418		if (prev_class) {
2419			if (can_merge(prev_class, pages_per_zspage, objs_per_zspage)) {
2420				pool->size_class[i] = prev_class;
2421				continue;
2422			}
2423		}
2424
2425		class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
2426		if (!class)
2427			goto err;
2428
2429		class->size = size;
2430		class->index = i;
2431		class->pages_per_zspage = pages_per_zspage;
2432		class->objs_per_zspage = objs_per_zspage;
2433		spin_lock_init(&class->lock);
2434		pool->size_class[i] = class;
2435		for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS;
2436							fullness++)
2437			INIT_LIST_HEAD(&class->fullness_list[fullness]);
2438
2439		prev_class = class;
2440	}
2441
2442	/* debug only, don't abort if it fails */
2443	zs_pool_stat_create(pool, name);
2444
2445	if (zs_register_migration(pool))
2446		goto err;
2447
2448	/*
2449	 * Not critical since shrinker is only used to trigger internal
2450	 * defragmentation of the pool which is pretty optional thing.  If
2451	 * registration fails we still can use the pool normally and user can
2452	 * trigger compaction manually. Thus, ignore return code.
2453	 */
2454	zs_register_shrinker(pool);
2455
2456	return pool;
2457
2458err:
2459	zs_destroy_pool(pool);
2460	return NULL;
2461}
2462EXPORT_SYMBOL_GPL(zs_create_pool);
2463
2464void zs_destroy_pool(struct zs_pool *pool)
2465{
2466	int i;
2467
2468	zs_unregister_shrinker(pool);
2469	zs_unregister_migration(pool);
2470	zs_pool_stat_destroy(pool);
2471
2472	for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2473		int fg;
2474		struct size_class *class = pool->size_class[i];
2475
2476		if (!class)
2477			continue;
2478
2479		if (class->index != i)
2480			continue;
2481
2482		for (fg = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) {
2483			if (!list_empty(&class->fullness_list[fg])) {
2484				pr_info("Freeing non-empty class with size %db, fullness group %d\n",
2485					class->size, fg);
2486			}
2487		}
2488		kfree(class);
2489	}
2490
2491	destroy_cache(pool);
2492	kfree(pool->name);
2493	kfree(pool);
2494}
2495EXPORT_SYMBOL_GPL(zs_destroy_pool);
2496
2497static int __init zs_init(void)
2498{
2499	int ret;
2500
2501	ret = zsmalloc_mount();
2502	if (ret)
2503		goto out;
2504
2505	ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
2506				zs_cpu_prepare, zs_cpu_dead);
2507	if (ret)
2508		goto hp_setup_fail;
2509
2510#ifdef CONFIG_ZPOOL
2511	zpool_register_driver(&zs_zpool_driver);
2512#endif
2513
2514	zs_stat_init();
2515
2516	return 0;
2517
2518hp_setup_fail:
2519	zsmalloc_unmount();
2520out:
2521	return ret;
2522}
2523
2524static void __exit zs_exit(void)
2525{
2526#ifdef CONFIG_ZPOOL
2527	zpool_unregister_driver(&zs_zpool_driver);
2528#endif
2529	zsmalloc_unmount();
2530	cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
2531
2532	zs_stat_exit();
2533}
2534
2535module_init(zs_init);
2536module_exit(zs_exit);
2537
2538MODULE_LICENSE("Dual BSD/GPL");
2539MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");