linux/mm/zsmalloc.c
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   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 <linux/pgtable.h>
  43#include <asm/tlbflush.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/pseudo_fs.h>
  56#include <linux/migrate.h>
  57#include <linux/wait.h>
  58#include <linux/pagemap.h>
  59#include <linux/fs.h>
  60
  61#define ZSPAGE_MAGIC    0x58
  62
  63/*
  64 * This must be power of 2 and greater than or equal to sizeof(link_free).
  65 * These two conditions ensure that any 'struct link_free' itself doesn't
  66 * span more than 1 page which avoids complex case of mapping 2 pages simply
  67 * to restore link_free pointer values.
  68 */
  69#define ZS_ALIGN                8
  70
  71/*
  72 * A single 'zspage' is composed of up to 2^N discontiguous 0-order (single)
  73 * pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N.
  74 */
  75#define ZS_MAX_ZSPAGE_ORDER 2
  76#define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)
  77
  78#define ZS_HANDLE_SIZE (sizeof(unsigned long))
  79
  80/*
  81 * Object location (<PFN>, <obj_idx>) is encoded as
  82 * a single (unsigned long) handle value.
  83 *
  84 * Note that object index <obj_idx> starts from 0.
  85 *
  86 * This is made more complicated by various memory models and PAE.
  87 */
  88
  89#ifndef MAX_POSSIBLE_PHYSMEM_BITS
  90#ifdef MAX_PHYSMEM_BITS
  91#define MAX_POSSIBLE_PHYSMEM_BITS MAX_PHYSMEM_BITS
  92#else
  93/*
  94 * If this definition of MAX_PHYSMEM_BITS is used, OBJ_INDEX_BITS will just
  95 * be PAGE_SHIFT
  96 */
  97#define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG
  98#endif
  99#endif
 100
 101#define _PFN_BITS               (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
 102
 103/*
 104 * Memory for allocating for handle keeps object position by
 105 * encoding <page, obj_idx> and the encoded value has a room
 106 * in least bit(ie, look at obj_to_location).
 107 * We use the bit to synchronize between object access by
 108 * user and migration.
 109 */
 110#define HANDLE_PIN_BIT  0
 111
 112/*
 113 * Head in allocated object should have OBJ_ALLOCATED_TAG
 114 * to identify the object was allocated or not.
 115 * It's okay to add the status bit in the least bit because
 116 * header keeps handle which is 4byte-aligned address so we
 117 * have room for two bit at least.
 118 */
 119#define OBJ_ALLOCATED_TAG 1
 120#define OBJ_TAG_BITS 1
 121#define OBJ_INDEX_BITS  (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
 122#define OBJ_INDEX_MASK  ((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
 123
 124#define FULLNESS_BITS   2
 125#define CLASS_BITS      8
 126#define ISOLATED_BITS   3
 127#define MAGIC_VAL_BITS  8
 128
 129#define MAX(a, b) ((a) >= (b) ? (a) : (b))
 130/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
 131#define ZS_MIN_ALLOC_SIZE \
 132        MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
 133/* each chunk includes extra space to keep handle */
 134#define ZS_MAX_ALLOC_SIZE       PAGE_SIZE
 135
 136/*
 137 * On systems with 4K page size, this gives 255 size classes! There is a
 138 * trader-off here:
 139 *  - Large number of size classes is potentially wasteful as free page are
 140 *    spread across these classes
 141 *  - Small number of size classes causes large internal fragmentation
 142 *  - Probably its better to use specific size classes (empirically
 143 *    determined). NOTE: all those class sizes must be set as multiple of
 144 *    ZS_ALIGN to make sure link_free itself never has to span 2 pages.
 145 *
 146 *  ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
 147 *  (reason above)
 148 */
 149#define ZS_SIZE_CLASS_DELTA     (PAGE_SIZE >> CLASS_BITS)
 150#define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
 151                                      ZS_SIZE_CLASS_DELTA) + 1)
 152
 153enum fullness_group {
 154        ZS_EMPTY,
 155        ZS_ALMOST_EMPTY,
 156        ZS_ALMOST_FULL,
 157        ZS_FULL,
 158        NR_ZS_FULLNESS,
 159};
 160
 161enum zs_stat_type {
 162        CLASS_EMPTY,
 163        CLASS_ALMOST_EMPTY,
 164        CLASS_ALMOST_FULL,
 165        CLASS_FULL,
 166        OBJ_ALLOCATED,
 167        OBJ_USED,
 168        NR_ZS_STAT_TYPE,
 169};
 170
 171struct zs_size_stat {
 172        unsigned long objs[NR_ZS_STAT_TYPE];
 173};
 174
 175#ifdef CONFIG_ZSMALLOC_STAT
 176static struct dentry *zs_stat_root;
 177#endif
 178
 179#ifdef CONFIG_COMPACTION
 180static struct vfsmount *zsmalloc_mnt;
 181#endif
 182
 183/*
 184 * We assign a page to ZS_ALMOST_EMPTY fullness group when:
 185 *      n <= N / f, where
 186 * n = number of allocated objects
 187 * N = total number of objects zspage can store
 188 * f = fullness_threshold_frac
 189 *
 190 * Similarly, we assign zspage to:
 191 *      ZS_ALMOST_FULL  when n > N / f
 192 *      ZS_EMPTY        when n == 0
 193 *      ZS_FULL         when n == N
 194 *
 195 * (see: fix_fullness_group())
 196 */
 197static const int fullness_threshold_frac = 4;
 198static size_t huge_class_size;
 199
 200struct size_class {
 201        spinlock_t lock;
 202        struct list_head fullness_list[NR_ZS_FULLNESS];
 203        /*
 204         * Size of objects stored in this class. Must be multiple
 205         * of ZS_ALIGN.
 206         */
 207        int size;
 208        int objs_per_zspage;
 209        /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
 210        int pages_per_zspage;
 211
 212        unsigned int index;
 213        struct zs_size_stat stats;
 214};
 215
 216/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
 217static void SetPageHugeObject(struct page *page)
 218{
 219        SetPageOwnerPriv1(page);
 220}
 221
 222static void ClearPageHugeObject(struct page *page)
 223{
 224        ClearPageOwnerPriv1(page);
 225}
 226
 227static int PageHugeObject(struct page *page)
 228{
 229        return PageOwnerPriv1(page);
 230}
 231
 232/*
 233 * Placed within free objects to form a singly linked list.
 234 * For every zspage, zspage->freeobj gives head of this list.
 235 *
 236 * This must be power of 2 and less than or equal to ZS_ALIGN
 237 */
 238struct link_free {
 239        union {
 240                /*
 241                 * Free object index;
 242                 * It's valid for non-allocated object
 243                 */
 244                unsigned long next;
 245                /*
 246                 * Handle of allocated object.
 247                 */
 248                unsigned long handle;
 249        };
 250};
 251
 252struct zs_pool {
 253        const char *name;
 254
 255        struct size_class *size_class[ZS_SIZE_CLASSES];
 256        struct kmem_cache *handle_cachep;
 257        struct kmem_cache *zspage_cachep;
 258
 259        atomic_long_t pages_allocated;
 260
 261        struct zs_pool_stats stats;
 262
 263        /* Compact classes */
 264        struct shrinker shrinker;
 265
 266#ifdef CONFIG_ZSMALLOC_STAT
 267        struct dentry *stat_dentry;
 268#endif
 269#ifdef CONFIG_COMPACTION
 270        struct inode *inode;
 271        struct work_struct free_work;
 272        /* A wait queue for when migration races with async_free_zspage() */
 273        struct wait_queue_head migration_wait;
 274        atomic_long_t isolated_pages;
 275        bool destroying;
 276#endif
 277};
 278
 279struct zspage {
 280        struct {
 281                unsigned int fullness:FULLNESS_BITS;
 282                unsigned int class:CLASS_BITS + 1;
 283                unsigned int isolated:ISOLATED_BITS;
 284                unsigned int magic:MAGIC_VAL_BITS;
 285        };
 286        unsigned int inuse;
 287        unsigned int freeobj;
 288        struct page *first_page;
 289        struct list_head list; /* fullness list */
 290#ifdef CONFIG_COMPACTION
 291        rwlock_t lock;
 292#endif
 293};
 294
 295struct mapping_area {
 296        char *vm_buf; /* copy buffer for objects that span pages */
 297        char *vm_addr; /* address of kmap_atomic()'ed pages */
 298        enum zs_mapmode vm_mm; /* mapping mode */
 299};
 300
 301#ifdef CONFIG_COMPACTION
 302static int zs_register_migration(struct zs_pool *pool);
 303static void zs_unregister_migration(struct zs_pool *pool);
 304static void migrate_lock_init(struct zspage *zspage);
 305static void migrate_read_lock(struct zspage *zspage);
 306static void migrate_read_unlock(struct zspage *zspage);
 307static void kick_deferred_free(struct zs_pool *pool);
 308static void init_deferred_free(struct zs_pool *pool);
 309static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage);
 310#else
 311static int zsmalloc_mount(void) { return 0; }
 312static void zsmalloc_unmount(void) {}
 313static int zs_register_migration(struct zs_pool *pool) { return 0; }
 314static void zs_unregister_migration(struct zs_pool *pool) {}
 315static void migrate_lock_init(struct zspage *zspage) {}
 316static void migrate_read_lock(struct zspage *zspage) {}
 317static void migrate_read_unlock(struct zspage *zspage) {}
 318static void kick_deferred_free(struct zs_pool *pool) {}
 319static void init_deferred_free(struct zs_pool *pool) {}
 320static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage) {}
 321#endif
 322
 323static int create_cache(struct zs_pool *pool)
 324{
 325        pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
 326                                        0, 0, NULL);
 327        if (!pool->handle_cachep)
 328                return 1;
 329
 330        pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
 331                                        0, 0, NULL);
 332        if (!pool->zspage_cachep) {
 333                kmem_cache_destroy(pool->handle_cachep);
 334                pool->handle_cachep = NULL;
 335                return 1;
 336        }
 337
 338        return 0;
 339}
 340
 341static void destroy_cache(struct zs_pool *pool)
 342{
 343        kmem_cache_destroy(pool->handle_cachep);
 344        kmem_cache_destroy(pool->zspage_cachep);
 345}
 346
 347static unsigned long cache_alloc_handle(struct zs_pool *pool, gfp_t gfp)
 348{
 349        return (unsigned long)kmem_cache_alloc(pool->handle_cachep,
 350                        gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
 351}
 352
 353static void cache_free_handle(struct zs_pool *pool, unsigned long handle)
 354{
 355        kmem_cache_free(pool->handle_cachep, (void *)handle);
 356}
 357
 358static struct zspage *cache_alloc_zspage(struct zs_pool *pool, gfp_t flags)
 359{
 360        return kmem_cache_zalloc(pool->zspage_cachep,
 361                        flags & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
 362}
 363
 364static void cache_free_zspage(struct zs_pool *pool, struct zspage *zspage)
 365{
 366        kmem_cache_free(pool->zspage_cachep, zspage);
 367}
 368
 369static void record_obj(unsigned long handle, unsigned long obj)
 370{
 371        /*
 372         * lsb of @obj represents handle lock while other bits
 373         * represent object value the handle is pointing so
 374         * updating shouldn't do store tearing.
 375         */
 376        WRITE_ONCE(*(unsigned long *)handle, obj);
 377}
 378
 379/* zpool driver */
 380
 381#ifdef CONFIG_ZPOOL
 382
 383static void *zs_zpool_create(const char *name, gfp_t gfp,
 384                             const struct zpool_ops *zpool_ops,
 385                             struct zpool *zpool)
 386{
 387        /*
 388         * Ignore global gfp flags: zs_malloc() may be invoked from
 389         * different contexts and its caller must provide a valid
 390         * gfp mask.
 391         */
 392        return zs_create_pool(name);
 393}
 394
 395static void zs_zpool_destroy(void *pool)
 396{
 397        zs_destroy_pool(pool);
 398}
 399
 400static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
 401                        unsigned long *handle)
 402{
 403        *handle = zs_malloc(pool, size, gfp);
 404        return *handle ? 0 : -1;
 405}
 406static void zs_zpool_free(void *pool, unsigned long handle)
 407{
 408        zs_free(pool, handle);
 409}
 410
 411static void *zs_zpool_map(void *pool, unsigned long handle,
 412                        enum zpool_mapmode mm)
 413{
 414        enum zs_mapmode zs_mm;
 415
 416        switch (mm) {
 417        case ZPOOL_MM_RO:
 418                zs_mm = ZS_MM_RO;
 419                break;
 420        case ZPOOL_MM_WO:
 421                zs_mm = ZS_MM_WO;
 422                break;
 423        case ZPOOL_MM_RW:
 424        default:
 425                zs_mm = ZS_MM_RW;
 426                break;
 427        }
 428
 429        return zs_map_object(pool, handle, zs_mm);
 430}
 431static void zs_zpool_unmap(void *pool, unsigned long handle)
 432{
 433        zs_unmap_object(pool, handle);
 434}
 435
 436static u64 zs_zpool_total_size(void *pool)
 437{
 438        return zs_get_total_pages(pool) << PAGE_SHIFT;
 439}
 440
 441static struct zpool_driver zs_zpool_driver = {
 442        .type =                   "zsmalloc",
 443        .owner =                  THIS_MODULE,
 444        .create =                 zs_zpool_create,
 445        .destroy =                zs_zpool_destroy,
 446        .malloc_support_movable = true,
 447        .malloc =                 zs_zpool_malloc,
 448        .free =                   zs_zpool_free,
 449        .map =                    zs_zpool_map,
 450        .unmap =                  zs_zpool_unmap,
 451        .total_size =             zs_zpool_total_size,
 452};
 453
 454MODULE_ALIAS("zpool-zsmalloc");
 455#endif /* CONFIG_ZPOOL */
 456
 457/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
 458static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
 459
 460static bool is_zspage_isolated(struct zspage *zspage)
 461{
 462        return zspage->isolated;
 463}
 464
 465static __maybe_unused int is_first_page(struct page *page)
 466{
 467        return PagePrivate(page);
 468}
 469
 470/* Protected by class->lock */
 471static inline int get_zspage_inuse(struct zspage *zspage)
 472{
 473        return zspage->inuse;
 474}
 475
 476
 477static inline void mod_zspage_inuse(struct zspage *zspage, int val)
 478{
 479        zspage->inuse += val;
 480}
 481
 482static inline struct page *get_first_page(struct zspage *zspage)
 483{
 484        struct page *first_page = zspage->first_page;
 485
 486        VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
 487        return first_page;
 488}
 489
 490static inline int get_first_obj_offset(struct page *page)
 491{
 492        return page->units;
 493}
 494
 495static inline void set_first_obj_offset(struct page *page, int offset)
 496{
 497        page->units = offset;
 498}
 499
 500static inline unsigned int get_freeobj(struct zspage *zspage)
 501{
 502        return zspage->freeobj;
 503}
 504
 505static inline void set_freeobj(struct zspage *zspage, unsigned int obj)
 506{
 507        zspage->freeobj = obj;
 508}
 509
 510static void get_zspage_mapping(struct zspage *zspage,
 511                                unsigned int *class_idx,
 512                                enum fullness_group *fullness)
 513{
 514        BUG_ON(zspage->magic != ZSPAGE_MAGIC);
 515
 516        *fullness = zspage->fullness;
 517        *class_idx = zspage->class;
 518}
 519
 520static void set_zspage_mapping(struct zspage *zspage,
 521                                unsigned int class_idx,
 522                                enum fullness_group fullness)
 523{
 524        zspage->class = class_idx;
 525        zspage->fullness = fullness;
 526}
 527
 528/*
 529 * zsmalloc divides the pool into various size classes where each
 530 * class maintains a list of zspages where each zspage is divided
 531 * into equal sized chunks. Each allocation falls into one of these
 532 * classes depending on its size. This function returns index of the
 533 * size class which has chunk size big enough to hold the given size.
 534 */
 535static int get_size_class_index(int size)
 536{
 537        int idx = 0;
 538
 539        if (likely(size > ZS_MIN_ALLOC_SIZE))
 540                idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
 541                                ZS_SIZE_CLASS_DELTA);
 542
 543        return min_t(int, ZS_SIZE_CLASSES - 1, idx);
 544}
 545
 546/* type can be of enum type zs_stat_type or fullness_group */
 547static inline void zs_stat_inc(struct size_class *class,
 548                                int type, unsigned long cnt)
 549{
 550        class->stats.objs[type] += cnt;
 551}
 552
 553/* type can be of enum type zs_stat_type or fullness_group */
 554static inline void zs_stat_dec(struct size_class *class,
 555                                int type, unsigned long cnt)
 556{
 557        class->stats.objs[type] -= cnt;
 558}
 559
 560/* type can be of enum type zs_stat_type or fullness_group */
 561static inline unsigned long zs_stat_get(struct size_class *class,
 562                                int type)
 563{
 564        return class->stats.objs[type];
 565}
 566
 567#ifdef CONFIG_ZSMALLOC_STAT
 568
 569static void __init zs_stat_init(void)
 570{
 571        if (!debugfs_initialized()) {
 572                pr_warn("debugfs not available, stat dir not created\n");
 573                return;
 574        }
 575
 576        zs_stat_root = debugfs_create_dir("zsmalloc", NULL);
 577}
 578
 579static void __exit zs_stat_exit(void)
 580{
 581        debugfs_remove_recursive(zs_stat_root);
 582}
 583
 584static unsigned long zs_can_compact(struct size_class *class);
 585
 586static int zs_stats_size_show(struct seq_file *s, void *v)
 587{
 588        int i;
 589        struct zs_pool *pool = s->private;
 590        struct size_class *class;
 591        int objs_per_zspage;
 592        unsigned long class_almost_full, class_almost_empty;
 593        unsigned long obj_allocated, obj_used, pages_used, freeable;
 594        unsigned long total_class_almost_full = 0, total_class_almost_empty = 0;
 595        unsigned long total_objs = 0, total_used_objs = 0, total_pages = 0;
 596        unsigned long total_freeable = 0;
 597
 598        seq_printf(s, " %5s %5s %11s %12s %13s %10s %10s %16s %8s\n",
 599                        "class", "size", "almost_full", "almost_empty",
 600                        "obj_allocated", "obj_used", "pages_used",
 601                        "pages_per_zspage", "freeable");
 602
 603        for (i = 0; i < ZS_SIZE_CLASSES; i++) {
 604                class = pool->size_class[i];
 605
 606                if (class->index != i)
 607                        continue;
 608
 609                spin_lock(&class->lock);
 610                class_almost_full = zs_stat_get(class, CLASS_ALMOST_FULL);
 611                class_almost_empty = zs_stat_get(class, CLASS_ALMOST_EMPTY);
 612                obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
 613                obj_used = zs_stat_get(class, OBJ_USED);
 614                freeable = zs_can_compact(class);
 615                spin_unlock(&class->lock);
 616
 617                objs_per_zspage = class->objs_per_zspage;
 618                pages_used = obj_allocated / objs_per_zspage *
 619                                class->pages_per_zspage;
 620
 621                seq_printf(s, " %5u %5u %11lu %12lu %13lu"
 622                                " %10lu %10lu %16d %8lu\n",
 623                        i, class->size, class_almost_full, class_almost_empty,
 624                        obj_allocated, obj_used, pages_used,
 625                        class->pages_per_zspage, freeable);
 626
 627                total_class_almost_full += class_almost_full;
 628                total_class_almost_empty += class_almost_empty;
 629                total_objs += obj_allocated;
 630                total_used_objs += obj_used;
 631                total_pages += pages_used;
 632                total_freeable += freeable;
 633        }
 634
 635        seq_puts(s, "\n");
 636        seq_printf(s, " %5s %5s %11lu %12lu %13lu %10lu %10lu %16s %8lu\n",
 637                        "Total", "", total_class_almost_full,
 638                        total_class_almost_empty, total_objs,
 639                        total_used_objs, total_pages, "", total_freeable);
 640
 641        return 0;
 642}
 643DEFINE_SHOW_ATTRIBUTE(zs_stats_size);
 644
 645static void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 646{
 647        if (!zs_stat_root) {
 648                pr_warn("no root stat dir, not creating <%s> stat dir\n", name);
 649                return;
 650        }
 651
 652        pool->stat_dentry = debugfs_create_dir(name, zs_stat_root);
 653
 654        debugfs_create_file("classes", S_IFREG | 0444, pool->stat_dentry, pool,
 655                            &zs_stats_size_fops);
 656}
 657
 658static void zs_pool_stat_destroy(struct zs_pool *pool)
 659{
 660        debugfs_remove_recursive(pool->stat_dentry);
 661}
 662
 663#else /* CONFIG_ZSMALLOC_STAT */
 664static void __init zs_stat_init(void)
 665{
 666}
 667
 668static void __exit zs_stat_exit(void)
 669{
 670}
 671
 672static inline void zs_pool_stat_create(struct zs_pool *pool, const char *name)
 673{
 674}
 675
 676static inline void zs_pool_stat_destroy(struct zs_pool *pool)
 677{
 678}
 679#endif
 680
 681
 682/*
 683 * For each size class, zspages are divided into different groups
 684 * depending on how "full" they are. This was done so that we could
 685 * easily find empty or nearly empty zspages when we try to shrink
 686 * the pool (not yet implemented). This function returns fullness
 687 * status of the given page.
 688 */
 689static enum fullness_group get_fullness_group(struct size_class *class,
 690                                                struct zspage *zspage)
 691{
 692        int inuse, objs_per_zspage;
 693        enum fullness_group fg;
 694
 695        inuse = get_zspage_inuse(zspage);
 696        objs_per_zspage = class->objs_per_zspage;
 697
 698        if (inuse == 0)
 699                fg = ZS_EMPTY;
 700        else if (inuse == objs_per_zspage)
 701                fg = ZS_FULL;
 702        else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
 703                fg = ZS_ALMOST_EMPTY;
 704        else
 705                fg = ZS_ALMOST_FULL;
 706
 707        return fg;
 708}
 709
 710/*
 711 * Each size class maintains various freelists and zspages are assigned
 712 * to one of these freelists based on the number of live objects they
 713 * have. This functions inserts the given zspage into the freelist
 714 * identified by <class, fullness_group>.
 715 */
 716static void insert_zspage(struct size_class *class,
 717                                struct zspage *zspage,
 718                                enum fullness_group fullness)
 719{
 720        struct zspage *head;
 721
 722        zs_stat_inc(class, fullness, 1);
 723        head = list_first_entry_or_null(&class->fullness_list[fullness],
 724                                        struct zspage, list);
 725        /*
 726         * We want to see more ZS_FULL pages and less almost empty/full.
 727         * Put pages with higher ->inuse first.
 728         */
 729        if (head && get_zspage_inuse(zspage) < get_zspage_inuse(head))
 730                list_add(&zspage->list, &head->list);
 731        else
 732                list_add(&zspage->list, &class->fullness_list[fullness]);
 733}
 734
 735/*
 736 * This function removes the given zspage from the freelist identified
 737 * by <class, fullness_group>.
 738 */
 739static void remove_zspage(struct size_class *class,
 740                                struct zspage *zspage,
 741                                enum fullness_group fullness)
 742{
 743        VM_BUG_ON(list_empty(&class->fullness_list[fullness]));
 744        VM_BUG_ON(is_zspage_isolated(zspage));
 745
 746        list_del_init(&zspage->list);
 747        zs_stat_dec(class, fullness, 1);
 748}
 749
 750/*
 751 * Each size class maintains zspages in different fullness groups depending
 752 * on the number of live objects they contain. When allocating or freeing
 753 * objects, the fullness status of the page can change, say, from ALMOST_FULL
 754 * to ALMOST_EMPTY when freeing an object. This function checks if such
 755 * a status change has occurred for the given page and accordingly moves the
 756 * page from the freelist of the old fullness group to that of the new
 757 * fullness group.
 758 */
 759static enum fullness_group fix_fullness_group(struct size_class *class,
 760                                                struct zspage *zspage)
 761{
 762        int class_idx;
 763        enum fullness_group currfg, newfg;
 764
 765        get_zspage_mapping(zspage, &class_idx, &currfg);
 766        newfg = get_fullness_group(class, zspage);
 767        if (newfg == currfg)
 768                goto out;
 769
 770        if (!is_zspage_isolated(zspage)) {
 771                remove_zspage(class, zspage, currfg);
 772                insert_zspage(class, zspage, newfg);
 773        }
 774
 775        set_zspage_mapping(zspage, class_idx, newfg);
 776
 777out:
 778        return newfg;
 779}
 780
 781/*
 782 * We have to decide on how many pages to link together
 783 * to form a zspage for each size class. This is important
 784 * to reduce wastage due to unusable space left at end of
 785 * each zspage which is given as:
 786 *     wastage = Zp % class_size
 787 *     usage = Zp - wastage
 788 * where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
 789 *
 790 * For example, for size class of 3/8 * PAGE_SIZE, we should
 791 * link together 3 PAGE_SIZE sized pages to form a zspage
 792 * since then we can perfectly fit in 8 such objects.
 793 */
 794static int get_pages_per_zspage(int class_size)
 795{
 796        int i, max_usedpc = 0;
 797        /* zspage order which gives maximum used size per KB */
 798        int max_usedpc_order = 1;
 799
 800        for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
 801                int zspage_size;
 802                int waste, usedpc;
 803
 804                zspage_size = i * PAGE_SIZE;
 805                waste = zspage_size % class_size;
 806                usedpc = (zspage_size - waste) * 100 / zspage_size;
 807
 808                if (usedpc > max_usedpc) {
 809                        max_usedpc = usedpc;
 810                        max_usedpc_order = i;
 811                }
 812        }
 813
 814        return max_usedpc_order;
 815}
 816
 817static struct zspage *get_zspage(struct page *page)
 818{
 819        struct zspage *zspage = (struct zspage *)page_private(page);
 820
 821        BUG_ON(zspage->magic != ZSPAGE_MAGIC);
 822        return zspage;
 823}
 824
 825static struct page *get_next_page(struct page *page)
 826{
 827        if (unlikely(PageHugeObject(page)))
 828                return NULL;
 829
 830        return page->freelist;
 831}
 832
 833/**
 834 * obj_to_location - get (<page>, <obj_idx>) from encoded object value
 835 * @obj: the encoded object value
 836 * @page: page object resides in zspage
 837 * @obj_idx: object index
 838 */
 839static void obj_to_location(unsigned long obj, struct page **page,
 840                                unsigned int *obj_idx)
 841{
 842        obj >>= OBJ_TAG_BITS;
 843        *page = pfn_to_page(obj >> OBJ_INDEX_BITS);
 844        *obj_idx = (obj & OBJ_INDEX_MASK);
 845}
 846
 847/**
 848 * location_to_obj - get obj value encoded from (<page>, <obj_idx>)
 849 * @page: page object resides in zspage
 850 * @obj_idx: object index
 851 */
 852static unsigned long location_to_obj(struct page *page, unsigned int obj_idx)
 853{
 854        unsigned long obj;
 855
 856        obj = page_to_pfn(page) << OBJ_INDEX_BITS;
 857        obj |= obj_idx & OBJ_INDEX_MASK;
 858        obj <<= OBJ_TAG_BITS;
 859
 860        return obj;
 861}
 862
 863static unsigned long handle_to_obj(unsigned long handle)
 864{
 865        return *(unsigned long *)handle;
 866}
 867
 868static unsigned long obj_to_head(struct page *page, void *obj)
 869{
 870        if (unlikely(PageHugeObject(page))) {
 871                VM_BUG_ON_PAGE(!is_first_page(page), page);
 872                return page->index;
 873        } else
 874                return *(unsigned long *)obj;
 875}
 876
 877static inline int testpin_tag(unsigned long handle)
 878{
 879        return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
 880}
 881
 882static inline int trypin_tag(unsigned long handle)
 883{
 884        return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
 885}
 886
 887static void pin_tag(unsigned long handle) __acquires(bitlock)
 888{
 889        bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
 890}
 891
 892static void unpin_tag(unsigned long handle) __releases(bitlock)
 893{
 894        bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
 895}
 896
 897static void reset_page(struct page *page)
 898{
 899        __ClearPageMovable(page);
 900        ClearPagePrivate(page);
 901        set_page_private(page, 0);
 902        page_mapcount_reset(page);
 903        ClearPageHugeObject(page);
 904        page->freelist = NULL;
 905}
 906
 907static int trylock_zspage(struct zspage *zspage)
 908{
 909        struct page *cursor, *fail;
 910
 911        for (cursor = get_first_page(zspage); cursor != NULL; cursor =
 912                                        get_next_page(cursor)) {
 913                if (!trylock_page(cursor)) {
 914                        fail = cursor;
 915                        goto unlock;
 916                }
 917        }
 918
 919        return 1;
 920unlock:
 921        for (cursor = get_first_page(zspage); cursor != fail; cursor =
 922                                        get_next_page(cursor))
 923                unlock_page(cursor);
 924
 925        return 0;
 926}
 927
 928static void __free_zspage(struct zs_pool *pool, struct size_class *class,
 929                                struct zspage *zspage)
 930{
 931        struct page *page, *next;
 932        enum fullness_group fg;
 933        unsigned int class_idx;
 934
 935        get_zspage_mapping(zspage, &class_idx, &fg);
 936
 937        assert_spin_locked(&class->lock);
 938
 939        VM_BUG_ON(get_zspage_inuse(zspage));
 940        VM_BUG_ON(fg != ZS_EMPTY);
 941
 942        next = page = get_first_page(zspage);
 943        do {
 944                VM_BUG_ON_PAGE(!PageLocked(page), page);
 945                next = get_next_page(page);
 946                reset_page(page);
 947                unlock_page(page);
 948                dec_zone_page_state(page, NR_ZSPAGES);
 949                put_page(page);
 950                page = next;
 951        } while (page != NULL);
 952
 953        cache_free_zspage(pool, zspage);
 954
 955        zs_stat_dec(class, OBJ_ALLOCATED, class->objs_per_zspage);
 956        atomic_long_sub(class->pages_per_zspage,
 957                                        &pool->pages_allocated);
 958}
 959
 960static void free_zspage(struct zs_pool *pool, struct size_class *class,
 961                                struct zspage *zspage)
 962{
 963        VM_BUG_ON(get_zspage_inuse(zspage));
 964        VM_BUG_ON(list_empty(&zspage->list));
 965
 966        if (!trylock_zspage(zspage)) {
 967                kick_deferred_free(pool);
 968                return;
 969        }
 970
 971        remove_zspage(class, zspage, ZS_EMPTY);
 972        __free_zspage(pool, class, zspage);
 973}
 974
 975/* Initialize a newly allocated zspage */
 976static void init_zspage(struct size_class *class, struct zspage *zspage)
 977{
 978        unsigned int freeobj = 1;
 979        unsigned long off = 0;
 980        struct page *page = get_first_page(zspage);
 981
 982        while (page) {
 983                struct page *next_page;
 984                struct link_free *link;
 985                void *vaddr;
 986
 987                set_first_obj_offset(page, off);
 988
 989                vaddr = kmap_atomic(page);
 990                link = (struct link_free *)vaddr + off / sizeof(*link);
 991
 992                while ((off += class->size) < PAGE_SIZE) {
 993                        link->next = freeobj++ << OBJ_TAG_BITS;
 994                        link += class->size / sizeof(*link);
 995                }
 996
 997                /*
 998                 * We now come to the last (full or partial) object on this
 999                 * page, which must point to the first object on the next
1000                 * page (if present)
1001                 */
1002                next_page = get_next_page(page);
1003                if (next_page) {
1004                        link->next = freeobj++ << OBJ_TAG_BITS;
1005                } else {
1006                        /*
1007                         * Reset OBJ_TAG_BITS bit to last link to tell
1008                         * whether it's allocated object or not.
1009                         */
1010                        link->next = -1UL << OBJ_TAG_BITS;
1011                }
1012                kunmap_atomic(vaddr);
1013                page = next_page;
1014                off %= PAGE_SIZE;
1015        }
1016
1017        set_freeobj(zspage, 0);
1018}
1019
1020static void create_page_chain(struct size_class *class, struct zspage *zspage,
1021                                struct page *pages[])
1022{
1023        int i;
1024        struct page *page;
1025        struct page *prev_page = NULL;
1026        int nr_pages = class->pages_per_zspage;
1027
1028        /*
1029         * Allocate individual pages and link them together as:
1030         * 1. all pages are linked together using page->freelist
1031         * 2. each sub-page point to zspage using page->private
1032         *
1033         * we set PG_private to identify the first page (i.e. no other sub-page
1034         * has this flag set).
1035         */
1036        for (i = 0; i < nr_pages; i++) {
1037                page = pages[i];
1038                set_page_private(page, (unsigned long)zspage);
1039                page->freelist = NULL;
1040                if (i == 0) {
1041                        zspage->first_page = page;
1042                        SetPagePrivate(page);
1043                        if (unlikely(class->objs_per_zspage == 1 &&
1044                                        class->pages_per_zspage == 1))
1045                                SetPageHugeObject(page);
1046                } else {
1047                        prev_page->freelist = page;
1048                }
1049                prev_page = page;
1050        }
1051}
1052
1053/*
1054 * Allocate a zspage for the given size class
1055 */
1056static struct zspage *alloc_zspage(struct zs_pool *pool,
1057                                        struct size_class *class,
1058                                        gfp_t gfp)
1059{
1060        int i;
1061        struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
1062        struct zspage *zspage = cache_alloc_zspage(pool, gfp);
1063
1064        if (!zspage)
1065                return NULL;
1066
1067        zspage->magic = ZSPAGE_MAGIC;
1068        migrate_lock_init(zspage);
1069
1070        for (i = 0; i < class->pages_per_zspage; i++) {
1071                struct page *page;
1072
1073                page = alloc_page(gfp);
1074                if (!page) {
1075                        while (--i >= 0) {
1076                                dec_zone_page_state(pages[i], NR_ZSPAGES);
1077                                __free_page(pages[i]);
1078                        }
1079                        cache_free_zspage(pool, zspage);
1080                        return NULL;
1081                }
1082
1083                inc_zone_page_state(page, NR_ZSPAGES);
1084                pages[i] = page;
1085        }
1086
1087        create_page_chain(class, zspage, pages);
1088        init_zspage(class, zspage);
1089
1090        return zspage;
1091}
1092
1093static struct zspage *find_get_zspage(struct size_class *class)
1094{
1095        int i;
1096        struct zspage *zspage;
1097
1098        for (i = ZS_ALMOST_FULL; i >= ZS_EMPTY; i--) {
1099                zspage = list_first_entry_or_null(&class->fullness_list[i],
1100                                struct zspage, list);
1101                if (zspage)
1102                        break;
1103        }
1104
1105        return zspage;
1106}
1107
1108static inline int __zs_cpu_up(struct mapping_area *area)
1109{
1110        /*
1111         * Make sure we don't leak memory if a cpu UP notification
1112         * and zs_init() race and both call zs_cpu_up() on the same cpu
1113         */
1114        if (area->vm_buf)
1115                return 0;
1116        area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
1117        if (!area->vm_buf)
1118                return -ENOMEM;
1119        return 0;
1120}
1121
1122static inline void __zs_cpu_down(struct mapping_area *area)
1123{
1124        kfree(area->vm_buf);
1125        area->vm_buf = NULL;
1126}
1127
1128static void *__zs_map_object(struct mapping_area *area,
1129                        struct page *pages[2], int off, int size)
1130{
1131        int sizes[2];
1132        void *addr;
1133        char *buf = area->vm_buf;
1134
1135        /* disable page faults to match kmap_atomic() return conditions */
1136        pagefault_disable();
1137
1138        /* no read fastpath */
1139        if (area->vm_mm == ZS_MM_WO)
1140                goto out;
1141
1142        sizes[0] = PAGE_SIZE - off;
1143        sizes[1] = size - sizes[0];
1144
1145        /* copy object to per-cpu buffer */
1146        addr = kmap_atomic(pages[0]);
1147        memcpy(buf, addr + off, sizes[0]);
1148        kunmap_atomic(addr);
1149        addr = kmap_atomic(pages[1]);
1150        memcpy(buf + sizes[0], addr, sizes[1]);
1151        kunmap_atomic(addr);
1152out:
1153        return area->vm_buf;
1154}
1155
1156static void __zs_unmap_object(struct mapping_area *area,
1157                        struct page *pages[2], int off, int size)
1158{
1159        int sizes[2];
1160        void *addr;
1161        char *buf;
1162
1163        /* no write fastpath */
1164        if (area->vm_mm == ZS_MM_RO)
1165                goto out;
1166
1167        buf = area->vm_buf;
1168        buf = buf + ZS_HANDLE_SIZE;
1169        size -= ZS_HANDLE_SIZE;
1170        off += ZS_HANDLE_SIZE;
1171
1172        sizes[0] = PAGE_SIZE - off;
1173        sizes[1] = size - sizes[0];
1174
1175        /* copy per-cpu buffer to object */
1176        addr = kmap_atomic(pages[0]);
1177        memcpy(addr + off, buf, sizes[0]);
1178        kunmap_atomic(addr);
1179        addr = kmap_atomic(pages[1]);
1180        memcpy(addr, buf + sizes[0], sizes[1]);
1181        kunmap_atomic(addr);
1182
1183out:
1184        /* enable page faults to match kunmap_atomic() return conditions */
1185        pagefault_enable();
1186}
1187
1188static int zs_cpu_prepare(unsigned int cpu)
1189{
1190        struct mapping_area *area;
1191
1192        area = &per_cpu(zs_map_area, cpu);
1193        return __zs_cpu_up(area);
1194}
1195
1196static int zs_cpu_dead(unsigned int cpu)
1197{
1198        struct mapping_area *area;
1199
1200        area = &per_cpu(zs_map_area, cpu);
1201        __zs_cpu_down(area);
1202        return 0;
1203}
1204
1205static bool can_merge(struct size_class *prev, int pages_per_zspage,
1206                                        int objs_per_zspage)
1207{
1208        if (prev->pages_per_zspage == pages_per_zspage &&
1209                prev->objs_per_zspage == objs_per_zspage)
1210                return true;
1211
1212        return false;
1213}
1214
1215static bool zspage_full(struct size_class *class, struct zspage *zspage)
1216{
1217        return get_zspage_inuse(zspage) == class->objs_per_zspage;
1218}
1219
1220unsigned long zs_get_total_pages(struct zs_pool *pool)
1221{
1222        return atomic_long_read(&pool->pages_allocated);
1223}
1224EXPORT_SYMBOL_GPL(zs_get_total_pages);
1225
1226/**
1227 * zs_map_object - get address of allocated object from handle.
1228 * @pool: pool from which the object was allocated
1229 * @handle: handle returned from zs_malloc
1230 * @mm: mapping mode to use
1231 *
1232 * Before using an object allocated from zs_malloc, it must be mapped using
1233 * this function. When done with the object, it must be unmapped using
1234 * zs_unmap_object.
1235 *
1236 * Only one object can be mapped per cpu at a time. There is no protection
1237 * against nested mappings.
1238 *
1239 * This function returns with preemption and page faults disabled.
1240 */
1241void *zs_map_object(struct zs_pool *pool, unsigned long handle,
1242                        enum zs_mapmode mm)
1243{
1244        struct zspage *zspage;
1245        struct page *page;
1246        unsigned long obj, off;
1247        unsigned int obj_idx;
1248
1249        unsigned int class_idx;
1250        enum fullness_group fg;
1251        struct size_class *class;
1252        struct mapping_area *area;
1253        struct page *pages[2];
1254        void *ret;
1255
1256        /*
1257         * Because we use per-cpu mapping areas shared among the
1258         * pools/users, we can't allow mapping in interrupt context
1259         * because it can corrupt another users mappings.
1260         */
1261        BUG_ON(in_interrupt());
1262
1263        /* From now on, migration cannot move the object */
1264        pin_tag(handle);
1265
1266        obj = handle_to_obj(handle);
1267        obj_to_location(obj, &page, &obj_idx);
1268        zspage = get_zspage(page);
1269
1270        /* migration cannot move any subpage in this zspage */
1271        migrate_read_lock(zspage);
1272
1273        get_zspage_mapping(zspage, &class_idx, &fg);
1274        class = pool->size_class[class_idx];
1275        off = (class->size * obj_idx) & ~PAGE_MASK;
1276
1277        area = &get_cpu_var(zs_map_area);
1278        area->vm_mm = mm;
1279        if (off + class->size <= PAGE_SIZE) {
1280                /* this object is contained entirely within a page */
1281                area->vm_addr = kmap_atomic(page);
1282                ret = area->vm_addr + off;
1283                goto out;
1284        }
1285
1286        /* this object spans two pages */
1287        pages[0] = page;
1288        pages[1] = get_next_page(page);
1289        BUG_ON(!pages[1]);
1290
1291        ret = __zs_map_object(area, pages, off, class->size);
1292out:
1293        if (likely(!PageHugeObject(page)))
1294                ret += ZS_HANDLE_SIZE;
1295
1296        return ret;
1297}
1298EXPORT_SYMBOL_GPL(zs_map_object);
1299
1300void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
1301{
1302        struct zspage *zspage;
1303        struct page *page;
1304        unsigned long obj, off;
1305        unsigned int obj_idx;
1306
1307        unsigned int class_idx;
1308        enum fullness_group fg;
1309        struct size_class *class;
1310        struct mapping_area *area;
1311
1312        obj = handle_to_obj(handle);
1313        obj_to_location(obj, &page, &obj_idx);
1314        zspage = get_zspage(page);
1315        get_zspage_mapping(zspage, &class_idx, &fg);
1316        class = pool->size_class[class_idx];
1317        off = (class->size * obj_idx) & ~PAGE_MASK;
1318
1319        area = this_cpu_ptr(&zs_map_area);
1320        if (off + class->size <= PAGE_SIZE)
1321                kunmap_atomic(area->vm_addr);
1322        else {
1323                struct page *pages[2];
1324
1325                pages[0] = page;
1326                pages[1] = get_next_page(page);
1327                BUG_ON(!pages[1]);
1328
1329                __zs_unmap_object(area, pages, off, class->size);
1330        }
1331        put_cpu_var(zs_map_area);
1332
1333        migrate_read_unlock(zspage);
1334        unpin_tag(handle);
1335}
1336EXPORT_SYMBOL_GPL(zs_unmap_object);
1337
1338/**
1339 * zs_huge_class_size() - Returns the size (in bytes) of the first huge
1340 *                        zsmalloc &size_class.
1341 * @pool: zsmalloc pool to use
1342 *
1343 * The function returns the size of the first huge class - any object of equal
1344 * or bigger size will be stored in zspage consisting of a single physical
1345 * page.
1346 *
1347 * Context: Any context.
1348 *
1349 * Return: the size (in bytes) of the first huge zsmalloc &size_class.
1350 */
1351size_t zs_huge_class_size(struct zs_pool *pool)
1352{
1353        return huge_class_size;
1354}
1355EXPORT_SYMBOL_GPL(zs_huge_class_size);
1356
1357static unsigned long obj_malloc(struct size_class *class,
1358                                struct zspage *zspage, unsigned long handle)
1359{
1360        int i, nr_page, offset;
1361        unsigned long obj;
1362        struct link_free *link;
1363
1364        struct page *m_page;
1365        unsigned long m_offset;
1366        void *vaddr;
1367
1368        handle |= OBJ_ALLOCATED_TAG;
1369        obj = get_freeobj(zspage);
1370
1371        offset = obj * class->size;
1372        nr_page = offset >> PAGE_SHIFT;
1373        m_offset = offset & ~PAGE_MASK;
1374        m_page = get_first_page(zspage);
1375
1376        for (i = 0; i < nr_page; i++)
1377                m_page = get_next_page(m_page);
1378
1379        vaddr = kmap_atomic(m_page);
1380        link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1381        set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
1382        if (likely(!PageHugeObject(m_page)))
1383                /* record handle in the header of allocated chunk */
1384                link->handle = handle;
1385        else
1386                /* record handle to page->index */
1387                zspage->first_page->index = handle;
1388
1389        kunmap_atomic(vaddr);
1390        mod_zspage_inuse(zspage, 1);
1391        zs_stat_inc(class, OBJ_USED, 1);
1392
1393        obj = location_to_obj(m_page, obj);
1394
1395        return obj;
1396}
1397
1398
1399/**
1400 * zs_malloc - Allocate block of given size from pool.
1401 * @pool: pool to allocate from
1402 * @size: size of block to allocate
1403 * @gfp: gfp flags when allocating object
1404 *
1405 * On success, handle to the allocated object is returned,
1406 * otherwise 0.
1407 * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
1408 */
1409unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t gfp)
1410{
1411        unsigned long handle, obj;
1412        struct size_class *class;
1413        enum fullness_group newfg;
1414        struct zspage *zspage;
1415
1416        if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
1417                return 0;
1418
1419        handle = cache_alloc_handle(pool, gfp);
1420        if (!handle)
1421                return 0;
1422
1423        /* extra space in chunk to keep the handle */
1424        size += ZS_HANDLE_SIZE;
1425        class = pool->size_class[get_size_class_index(size)];
1426
1427        spin_lock(&class->lock);
1428        zspage = find_get_zspage(class);
1429        if (likely(zspage)) {
1430                obj = obj_malloc(class, zspage, handle);
1431                /* Now move the zspage to another fullness group, if required */
1432                fix_fullness_group(class, zspage);
1433                record_obj(handle, obj);
1434                spin_unlock(&class->lock);
1435
1436                return handle;
1437        }
1438
1439        spin_unlock(&class->lock);
1440
1441        zspage = alloc_zspage(pool, class, gfp);
1442        if (!zspage) {
1443                cache_free_handle(pool, handle);
1444                return 0;
1445        }
1446
1447        spin_lock(&class->lock);
1448        obj = obj_malloc(class, zspage, handle);
1449        newfg = get_fullness_group(class, zspage);
1450        insert_zspage(class, zspage, newfg);
1451        set_zspage_mapping(zspage, class->index, newfg);
1452        record_obj(handle, obj);
1453        atomic_long_add(class->pages_per_zspage,
1454                                &pool->pages_allocated);
1455        zs_stat_inc(class, OBJ_ALLOCATED, class->objs_per_zspage);
1456
1457        /* We completely set up zspage so mark them as movable */
1458        SetZsPageMovable(pool, zspage);
1459        spin_unlock(&class->lock);
1460
1461        return handle;
1462}
1463EXPORT_SYMBOL_GPL(zs_malloc);
1464
1465static void obj_free(struct size_class *class, unsigned long obj)
1466{
1467        struct link_free *link;
1468        struct zspage *zspage;
1469        struct page *f_page;
1470        unsigned long f_offset;
1471        unsigned int f_objidx;
1472        void *vaddr;
1473
1474        obj_to_location(obj, &f_page, &f_objidx);
1475        f_offset = (class->size * f_objidx) & ~PAGE_MASK;
1476        zspage = get_zspage(f_page);
1477
1478        vaddr = kmap_atomic(f_page);
1479
1480        /* Insert this object in containing zspage's freelist */
1481        link = (struct link_free *)(vaddr + f_offset);
1482        link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
1483        kunmap_atomic(vaddr);
1484        set_freeobj(zspage, f_objidx);
1485        mod_zspage_inuse(zspage, -1);
1486        zs_stat_dec(class, OBJ_USED, 1);
1487}
1488
1489void zs_free(struct zs_pool *pool, unsigned long handle)
1490{
1491        struct zspage *zspage;
1492        struct page *f_page;
1493        unsigned long obj;
1494        unsigned int f_objidx;
1495        int class_idx;
1496        struct size_class *class;
1497        enum fullness_group fullness;
1498        bool isolated;
1499
1500        if (unlikely(!handle))
1501                return;
1502
1503        pin_tag(handle);
1504        obj = handle_to_obj(handle);
1505        obj_to_location(obj, &f_page, &f_objidx);
1506        zspage = get_zspage(f_page);
1507
1508        migrate_read_lock(zspage);
1509
1510        get_zspage_mapping(zspage, &class_idx, &fullness);
1511        class = pool->size_class[class_idx];
1512
1513        spin_lock(&class->lock);
1514        obj_free(class, obj);
1515        fullness = fix_fullness_group(class, zspage);
1516        if (fullness != ZS_EMPTY) {
1517                migrate_read_unlock(zspage);
1518                goto out;
1519        }
1520
1521        isolated = is_zspage_isolated(zspage);
1522        migrate_read_unlock(zspage);
1523        /* If zspage is isolated, zs_page_putback will free the zspage */
1524        if (likely(!isolated))
1525                free_zspage(pool, class, zspage);
1526out:
1527
1528        spin_unlock(&class->lock);
1529        unpin_tag(handle);
1530        cache_free_handle(pool, handle);
1531}
1532EXPORT_SYMBOL_GPL(zs_free);
1533
1534static void zs_object_copy(struct size_class *class, unsigned long dst,
1535                                unsigned long src)
1536{
1537        struct page *s_page, *d_page;
1538        unsigned int s_objidx, d_objidx;
1539        unsigned long s_off, d_off;
1540        void *s_addr, *d_addr;
1541        int s_size, d_size, size;
1542        int written = 0;
1543
1544        s_size = d_size = class->size;
1545
1546        obj_to_location(src, &s_page, &s_objidx);
1547        obj_to_location(dst, &d_page, &d_objidx);
1548
1549        s_off = (class->size * s_objidx) & ~PAGE_MASK;
1550        d_off = (class->size * d_objidx) & ~PAGE_MASK;
1551
1552        if (s_off + class->size > PAGE_SIZE)
1553                s_size = PAGE_SIZE - s_off;
1554
1555        if (d_off + class->size > PAGE_SIZE)
1556                d_size = PAGE_SIZE - d_off;
1557
1558        s_addr = kmap_atomic(s_page);
1559        d_addr = kmap_atomic(d_page);
1560
1561        while (1) {
1562                size = min(s_size, d_size);
1563                memcpy(d_addr + d_off, s_addr + s_off, size);
1564                written += size;
1565
1566                if (written == class->size)
1567                        break;
1568
1569                s_off += size;
1570                s_size -= size;
1571                d_off += size;
1572                d_size -= size;
1573
1574                if (s_off >= PAGE_SIZE) {
1575                        kunmap_atomic(d_addr);
1576                        kunmap_atomic(s_addr);
1577                        s_page = get_next_page(s_page);
1578                        s_addr = kmap_atomic(s_page);
1579                        d_addr = kmap_atomic(d_page);
1580                        s_size = class->size - written;
1581                        s_off = 0;
1582                }
1583
1584                if (d_off >= PAGE_SIZE) {
1585                        kunmap_atomic(d_addr);
1586                        d_page = get_next_page(d_page);
1587                        d_addr = kmap_atomic(d_page);
1588                        d_size = class->size - written;
1589                        d_off = 0;
1590                }
1591        }
1592
1593        kunmap_atomic(d_addr);
1594        kunmap_atomic(s_addr);
1595}
1596
1597/*
1598 * Find alloced object in zspage from index object and
1599 * return handle.
1600 */
1601static unsigned long find_alloced_obj(struct size_class *class,
1602                                        struct page *page, int *obj_idx)
1603{
1604        unsigned long head;
1605        int offset = 0;
1606        int index = *obj_idx;
1607        unsigned long handle = 0;
1608        void *addr = kmap_atomic(page);
1609
1610        offset = get_first_obj_offset(page);
1611        offset += class->size * index;
1612
1613        while (offset < PAGE_SIZE) {
1614                head = obj_to_head(page, addr + offset);
1615                if (head & OBJ_ALLOCATED_TAG) {
1616                        handle = head & ~OBJ_ALLOCATED_TAG;
1617                        if (trypin_tag(handle))
1618                                break;
1619                        handle = 0;
1620                }
1621
1622                offset += class->size;
1623                index++;
1624        }
1625
1626        kunmap_atomic(addr);
1627
1628        *obj_idx = index;
1629
1630        return handle;
1631}
1632
1633struct zs_compact_control {
1634        /* Source spage for migration which could be a subpage of zspage */
1635        struct page *s_page;
1636        /* Destination page for migration which should be a first page
1637         * of zspage. */
1638        struct page *d_page;
1639         /* Starting object index within @s_page which used for live object
1640          * in the subpage. */
1641        int obj_idx;
1642};
1643
1644static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
1645                                struct zs_compact_control *cc)
1646{
1647        unsigned long used_obj, free_obj;
1648        unsigned long handle;
1649        struct page *s_page = cc->s_page;
1650        struct page *d_page = cc->d_page;
1651        int obj_idx = cc->obj_idx;
1652        int ret = 0;
1653
1654        while (1) {
1655                handle = find_alloced_obj(class, s_page, &obj_idx);
1656                if (!handle) {
1657                        s_page = get_next_page(s_page);
1658                        if (!s_page)
1659                                break;
1660                        obj_idx = 0;
1661                        continue;
1662                }
1663
1664                /* Stop if there is no more space */
1665                if (zspage_full(class, get_zspage(d_page))) {
1666                        unpin_tag(handle);
1667                        ret = -ENOMEM;
1668                        break;
1669                }
1670
1671                used_obj = handle_to_obj(handle);
1672                free_obj = obj_malloc(class, get_zspage(d_page), handle);
1673                zs_object_copy(class, free_obj, used_obj);
1674                obj_idx++;
1675                /*
1676                 * record_obj updates handle's value to free_obj and it will
1677                 * invalidate lock bit(ie, HANDLE_PIN_BIT) of handle, which
1678                 * breaks synchronization using pin_tag(e,g, zs_free) so
1679                 * let's keep the lock bit.
1680                 */
1681                free_obj |= BIT(HANDLE_PIN_BIT);
1682                record_obj(handle, free_obj);
1683                unpin_tag(handle);
1684                obj_free(class, used_obj);
1685        }
1686
1687        /* Remember last position in this iteration */
1688        cc->s_page = s_page;
1689        cc->obj_idx = obj_idx;
1690
1691        return ret;
1692}
1693
1694static struct zspage *isolate_zspage(struct size_class *class, bool source)
1695{
1696        int i;
1697        struct zspage *zspage;
1698        enum fullness_group fg[2] = {ZS_ALMOST_EMPTY, ZS_ALMOST_FULL};
1699
1700        if (!source) {
1701                fg[0] = ZS_ALMOST_FULL;
1702                fg[1] = ZS_ALMOST_EMPTY;
1703        }
1704
1705        for (i = 0; i < 2; i++) {
1706                zspage = list_first_entry_or_null(&class->fullness_list[fg[i]],
1707                                                        struct zspage, list);
1708                if (zspage) {
1709                        VM_BUG_ON(is_zspage_isolated(zspage));
1710                        remove_zspage(class, zspage, fg[i]);
1711                        return zspage;
1712                }
1713        }
1714
1715        return zspage;
1716}
1717
1718/*
1719 * putback_zspage - add @zspage into right class's fullness list
1720 * @class: destination class
1721 * @zspage: target page
1722 *
1723 * Return @zspage's fullness_group
1724 */
1725static enum fullness_group putback_zspage(struct size_class *class,
1726                        struct zspage *zspage)
1727{
1728        enum fullness_group fullness;
1729
1730        VM_BUG_ON(is_zspage_isolated(zspage));
1731
1732        fullness = get_fullness_group(class, zspage);
1733        insert_zspage(class, zspage, fullness);
1734        set_zspage_mapping(zspage, class->index, fullness);
1735
1736        return fullness;
1737}
1738
1739#ifdef CONFIG_COMPACTION
1740/*
1741 * To prevent zspage destroy during migration, zspage freeing should
1742 * hold locks of all pages in the zspage.
1743 */
1744static void lock_zspage(struct zspage *zspage)
1745{
1746        struct page *page = get_first_page(zspage);
1747
1748        do {
1749                lock_page(page);
1750        } while ((page = get_next_page(page)) != NULL);
1751}
1752
1753static int zs_init_fs_context(struct fs_context *fc)
1754{
1755        return init_pseudo(fc, ZSMALLOC_MAGIC) ? 0 : -ENOMEM;
1756}
1757
1758static struct file_system_type zsmalloc_fs = {
1759        .name           = "zsmalloc",
1760        .init_fs_context = zs_init_fs_context,
1761        .kill_sb        = kill_anon_super,
1762};
1763
1764static int zsmalloc_mount(void)
1765{
1766        int ret = 0;
1767
1768        zsmalloc_mnt = kern_mount(&zsmalloc_fs);
1769        if (IS_ERR(zsmalloc_mnt))
1770                ret = PTR_ERR(zsmalloc_mnt);
1771
1772        return ret;
1773}
1774
1775static void zsmalloc_unmount(void)
1776{
1777        kern_unmount(zsmalloc_mnt);
1778}
1779
1780static void migrate_lock_init(struct zspage *zspage)
1781{
1782        rwlock_init(&zspage->lock);
1783}
1784
1785static void migrate_read_lock(struct zspage *zspage) __acquires(&zspage->lock)
1786{
1787        read_lock(&zspage->lock);
1788}
1789
1790static void migrate_read_unlock(struct zspage *zspage) __releases(&zspage->lock)
1791{
1792        read_unlock(&zspage->lock);
1793}
1794
1795static void migrate_write_lock(struct zspage *zspage)
1796{
1797        write_lock(&zspage->lock);
1798}
1799
1800static void migrate_write_unlock(struct zspage *zspage)
1801{
1802        write_unlock(&zspage->lock);
1803}
1804
1805/* Number of isolated subpage for *page migration* in this zspage */
1806static void inc_zspage_isolation(struct zspage *zspage)
1807{
1808        zspage->isolated++;
1809}
1810
1811static void dec_zspage_isolation(struct zspage *zspage)
1812{
1813        zspage->isolated--;
1814}
1815
1816static void putback_zspage_deferred(struct zs_pool *pool,
1817                                    struct size_class *class,
1818                                    struct zspage *zspage)
1819{
1820        enum fullness_group fg;
1821
1822        fg = putback_zspage(class, zspage);
1823        if (fg == ZS_EMPTY)
1824                schedule_work(&pool->free_work);
1825
1826}
1827
1828static inline void zs_pool_dec_isolated(struct zs_pool *pool)
1829{
1830        VM_BUG_ON(atomic_long_read(&pool->isolated_pages) <= 0);
1831        atomic_long_dec(&pool->isolated_pages);
1832        /*
1833         * There's no possibility of racing, since wait_for_isolated_drain()
1834         * checks the isolated count under &class->lock after enqueuing
1835         * on migration_wait.
1836         */
1837        if (atomic_long_read(&pool->isolated_pages) == 0 && pool->destroying)
1838                wake_up_all(&pool->migration_wait);
1839}
1840
1841static void replace_sub_page(struct size_class *class, struct zspage *zspage,
1842                                struct page *newpage, struct page *oldpage)
1843{
1844        struct page *page;
1845        struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE] = {NULL, };
1846        int idx = 0;
1847
1848        page = get_first_page(zspage);
1849        do {
1850                if (page == oldpage)
1851                        pages[idx] = newpage;
1852                else
1853                        pages[idx] = page;
1854                idx++;
1855        } while ((page = get_next_page(page)) != NULL);
1856
1857        create_page_chain(class, zspage, pages);
1858        set_first_obj_offset(newpage, get_first_obj_offset(oldpage));
1859        if (unlikely(PageHugeObject(oldpage)))
1860                newpage->index = oldpage->index;
1861        __SetPageMovable(newpage, page_mapping(oldpage));
1862}
1863
1864static bool zs_page_isolate(struct page *page, isolate_mode_t mode)
1865{
1866        struct zs_pool *pool;
1867        struct size_class *class;
1868        int class_idx;
1869        enum fullness_group fullness;
1870        struct zspage *zspage;
1871        struct address_space *mapping;
1872
1873        /*
1874         * Page is locked so zspage couldn't be destroyed. For detail, look at
1875         * lock_zspage in free_zspage.
1876         */
1877        VM_BUG_ON_PAGE(!PageMovable(page), page);
1878        VM_BUG_ON_PAGE(PageIsolated(page), page);
1879
1880        zspage = get_zspage(page);
1881
1882        /*
1883         * Without class lock, fullness could be stale while class_idx is okay
1884         * because class_idx is constant unless page is freed so we should get
1885         * fullness again under class lock.
1886         */
1887        get_zspage_mapping(zspage, &class_idx, &fullness);
1888        mapping = page_mapping(page);
1889        pool = mapping->private_data;
1890        class = pool->size_class[class_idx];
1891
1892        spin_lock(&class->lock);
1893        if (get_zspage_inuse(zspage) == 0) {
1894                spin_unlock(&class->lock);
1895                return false;
1896        }
1897
1898        /* zspage is isolated for object migration */
1899        if (list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1900                spin_unlock(&class->lock);
1901                return false;
1902        }
1903
1904        /*
1905         * If this is first time isolation for the zspage, isolate zspage from
1906         * size_class to prevent further object allocation from the zspage.
1907         */
1908        if (!list_empty(&zspage->list) && !is_zspage_isolated(zspage)) {
1909                get_zspage_mapping(zspage, &class_idx, &fullness);
1910                atomic_long_inc(&pool->isolated_pages);
1911                remove_zspage(class, zspage, fullness);
1912        }
1913
1914        inc_zspage_isolation(zspage);
1915        spin_unlock(&class->lock);
1916
1917        return true;
1918}
1919
1920static int zs_page_migrate(struct address_space *mapping, struct page *newpage,
1921                struct page *page, enum migrate_mode mode)
1922{
1923        struct zs_pool *pool;
1924        struct size_class *class;
1925        int class_idx;
1926        enum fullness_group fullness;
1927        struct zspage *zspage;
1928        struct page *dummy;
1929        void *s_addr, *d_addr, *addr;
1930        int offset, pos;
1931        unsigned long handle, head;
1932        unsigned long old_obj, new_obj;
1933        unsigned int obj_idx;
1934        int ret = -EAGAIN;
1935
1936        /*
1937         * We cannot support the _NO_COPY case here, because copy needs to
1938         * happen under the zs lock, which does not work with
1939         * MIGRATE_SYNC_NO_COPY workflow.
1940         */
1941        if (mode == MIGRATE_SYNC_NO_COPY)
1942                return -EINVAL;
1943
1944        VM_BUG_ON_PAGE(!PageMovable(page), page);
1945        VM_BUG_ON_PAGE(!PageIsolated(page), page);
1946
1947        zspage = get_zspage(page);
1948
1949        /* Concurrent compactor cannot migrate any subpage in zspage */
1950        migrate_write_lock(zspage);
1951        get_zspage_mapping(zspage, &class_idx, &fullness);
1952        pool = mapping->private_data;
1953        class = pool->size_class[class_idx];
1954        offset = get_first_obj_offset(page);
1955
1956        spin_lock(&class->lock);
1957        if (!get_zspage_inuse(zspage)) {
1958                /*
1959                 * Set "offset" to end of the page so that every loops
1960                 * skips unnecessary object scanning.
1961                 */
1962                offset = PAGE_SIZE;
1963        }
1964
1965        pos = offset;
1966        s_addr = kmap_atomic(page);
1967        while (pos < PAGE_SIZE) {
1968                head = obj_to_head(page, s_addr + pos);
1969                if (head & OBJ_ALLOCATED_TAG) {
1970                        handle = head & ~OBJ_ALLOCATED_TAG;
1971                        if (!trypin_tag(handle))
1972                                goto unpin_objects;
1973                }
1974                pos += class->size;
1975        }
1976
1977        /*
1978         * Here, any user cannot access all objects in the zspage so let's move.
1979         */
1980        d_addr = kmap_atomic(newpage);
1981        memcpy(d_addr, s_addr, PAGE_SIZE);
1982        kunmap_atomic(d_addr);
1983
1984        for (addr = s_addr + offset; addr < s_addr + pos;
1985                                        addr += class->size) {
1986                head = obj_to_head(page, addr);
1987                if (head & OBJ_ALLOCATED_TAG) {
1988                        handle = head & ~OBJ_ALLOCATED_TAG;
1989                        BUG_ON(!testpin_tag(handle));
1990
1991                        old_obj = handle_to_obj(handle);
1992                        obj_to_location(old_obj, &dummy, &obj_idx);
1993                        new_obj = (unsigned long)location_to_obj(newpage,
1994                                                                obj_idx);
1995                        new_obj |= BIT(HANDLE_PIN_BIT);
1996                        record_obj(handle, new_obj);
1997                }
1998        }
1999
2000        replace_sub_page(class, zspage, newpage, page);
2001        get_page(newpage);
2002
2003        dec_zspage_isolation(zspage);
2004
2005        /*
2006         * Page migration is done so let's putback isolated zspage to
2007         * the list if @page is final isolated subpage in the zspage.
2008         */
2009        if (!is_zspage_isolated(zspage)) {
2010                /*
2011                 * We cannot race with zs_destroy_pool() here because we wait
2012                 * for isolation to hit zero before we start destroying.
2013                 * Also, we ensure that everyone can see pool->destroying before
2014                 * we start waiting.
2015                 */
2016                putback_zspage_deferred(pool, class, zspage);
2017                zs_pool_dec_isolated(pool);
2018        }
2019
2020        if (page_zone(newpage) != page_zone(page)) {
2021                dec_zone_page_state(page, NR_ZSPAGES);
2022                inc_zone_page_state(newpage, NR_ZSPAGES);
2023        }
2024
2025        reset_page(page);
2026        put_page(page);
2027        page = newpage;
2028
2029        ret = MIGRATEPAGE_SUCCESS;
2030unpin_objects:
2031        for (addr = s_addr + offset; addr < s_addr + pos;
2032                                                addr += class->size) {
2033                head = obj_to_head(page, addr);
2034                if (head & OBJ_ALLOCATED_TAG) {
2035                        handle = head & ~OBJ_ALLOCATED_TAG;
2036                        BUG_ON(!testpin_tag(handle));
2037                        unpin_tag(handle);
2038                }
2039        }
2040        kunmap_atomic(s_addr);
2041        spin_unlock(&class->lock);
2042        migrate_write_unlock(zspage);
2043
2044        return ret;
2045}
2046
2047static void zs_page_putback(struct page *page)
2048{
2049        struct zs_pool *pool;
2050        struct size_class *class;
2051        int class_idx;
2052        enum fullness_group fg;
2053        struct address_space *mapping;
2054        struct zspage *zspage;
2055
2056        VM_BUG_ON_PAGE(!PageMovable(page), page);
2057        VM_BUG_ON_PAGE(!PageIsolated(page), page);
2058
2059        zspage = get_zspage(page);
2060        get_zspage_mapping(zspage, &class_idx, &fg);
2061        mapping = page_mapping(page);
2062        pool = mapping->private_data;
2063        class = pool->size_class[class_idx];
2064
2065        spin_lock(&class->lock);
2066        dec_zspage_isolation(zspage);
2067        if (!is_zspage_isolated(zspage)) {
2068                /*
2069                 * Due to page_lock, we cannot free zspage immediately
2070                 * so let's defer.
2071                 */
2072                putback_zspage_deferred(pool, class, zspage);
2073                zs_pool_dec_isolated(pool);
2074        }
2075        spin_unlock(&class->lock);
2076}
2077
2078static const struct address_space_operations zsmalloc_aops = {
2079        .isolate_page = zs_page_isolate,
2080        .migratepage = zs_page_migrate,
2081        .putback_page = zs_page_putback,
2082};
2083
2084static int zs_register_migration(struct zs_pool *pool)
2085{
2086        pool->inode = alloc_anon_inode(zsmalloc_mnt->mnt_sb);
2087        if (IS_ERR(pool->inode)) {
2088                pool->inode = NULL;
2089                return 1;
2090        }
2091
2092        pool->inode->i_mapping->private_data = pool;
2093        pool->inode->i_mapping->a_ops = &zsmalloc_aops;
2094        return 0;
2095}
2096
2097static bool pool_isolated_are_drained(struct zs_pool *pool)
2098{
2099        return atomic_long_read(&pool->isolated_pages) == 0;
2100}
2101
2102/* Function for resolving migration */
2103static void wait_for_isolated_drain(struct zs_pool *pool)
2104{
2105
2106        /*
2107         * We're in the process of destroying the pool, so there are no
2108         * active allocations. zs_page_isolate() fails for completely free
2109         * zspages, so we need only wait for the zs_pool's isolated
2110         * count to hit zero.
2111         */
2112        wait_event(pool->migration_wait,
2113                   pool_isolated_are_drained(pool));
2114}
2115
2116static void zs_unregister_migration(struct zs_pool *pool)
2117{
2118        pool->destroying = true;
2119        /*
2120         * We need a memory barrier here to ensure global visibility of
2121         * pool->destroying. Thus pool->isolated pages will either be 0 in which
2122         * case we don't care, or it will be > 0 and pool->destroying will
2123         * ensure that we wake up once isolation hits 0.
2124         */
2125        smp_mb();
2126        wait_for_isolated_drain(pool); /* This can block */
2127        flush_work(&pool->free_work);
2128        iput(pool->inode);
2129}
2130
2131/*
2132 * Caller should hold page_lock of all pages in the zspage
2133 * In here, we cannot use zspage meta data.
2134 */
2135static void async_free_zspage(struct work_struct *work)
2136{
2137        int i;
2138        struct size_class *class;
2139        unsigned int class_idx;
2140        enum fullness_group fullness;
2141        struct zspage *zspage, *tmp;
2142        LIST_HEAD(free_pages);
2143        struct zs_pool *pool = container_of(work, struct zs_pool,
2144                                        free_work);
2145
2146        for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2147                class = pool->size_class[i];
2148                if (class->index != i)
2149                        continue;
2150
2151                spin_lock(&class->lock);
2152                list_splice_init(&class->fullness_list[ZS_EMPTY], &free_pages);
2153                spin_unlock(&class->lock);
2154        }
2155
2156
2157        list_for_each_entry_safe(zspage, tmp, &free_pages, list) {
2158                list_del(&zspage->list);
2159                lock_zspage(zspage);
2160
2161                get_zspage_mapping(zspage, &class_idx, &fullness);
2162                VM_BUG_ON(fullness != ZS_EMPTY);
2163                class = pool->size_class[class_idx];
2164                spin_lock(&class->lock);
2165                __free_zspage(pool, class, zspage);
2166                spin_unlock(&class->lock);
2167        }
2168};
2169
2170static void kick_deferred_free(struct zs_pool *pool)
2171{
2172        schedule_work(&pool->free_work);
2173}
2174
2175static void init_deferred_free(struct zs_pool *pool)
2176{
2177        INIT_WORK(&pool->free_work, async_free_zspage);
2178}
2179
2180static void SetZsPageMovable(struct zs_pool *pool, struct zspage *zspage)
2181{
2182        struct page *page = get_first_page(zspage);
2183
2184        do {
2185                WARN_ON(!trylock_page(page));
2186                __SetPageMovable(page, pool->inode->i_mapping);
2187                unlock_page(page);
2188        } while ((page = get_next_page(page)) != NULL);
2189}
2190#endif
2191
2192/*
2193 *
2194 * Based on the number of unused allocated objects calculate
2195 * and return the number of pages that we can free.
2196 */
2197static unsigned long zs_can_compact(struct size_class *class)
2198{
2199        unsigned long obj_wasted;
2200        unsigned long obj_allocated = zs_stat_get(class, OBJ_ALLOCATED);
2201        unsigned long obj_used = zs_stat_get(class, OBJ_USED);
2202
2203        if (obj_allocated <= obj_used)
2204                return 0;
2205
2206        obj_wasted = obj_allocated - obj_used;
2207        obj_wasted /= class->objs_per_zspage;
2208
2209        return obj_wasted * class->pages_per_zspage;
2210}
2211
2212static unsigned long __zs_compact(struct zs_pool *pool,
2213                                  struct size_class *class)
2214{
2215        struct zs_compact_control cc;
2216        struct zspage *src_zspage;
2217        struct zspage *dst_zspage = NULL;
2218        unsigned long pages_freed = 0;
2219
2220        spin_lock(&class->lock);
2221        while ((src_zspage = isolate_zspage(class, true))) {
2222
2223                if (!zs_can_compact(class))
2224                        break;
2225
2226                cc.obj_idx = 0;
2227                cc.s_page = get_first_page(src_zspage);
2228
2229                while ((dst_zspage = isolate_zspage(class, false))) {
2230                        cc.d_page = get_first_page(dst_zspage);
2231                        /*
2232                         * If there is no more space in dst_page, resched
2233                         * and see if anyone had allocated another zspage.
2234                         */
2235                        if (!migrate_zspage(pool, class, &cc))
2236                                break;
2237
2238                        putback_zspage(class, dst_zspage);
2239                }
2240
2241                /* Stop if we couldn't find slot */
2242                if (dst_zspage == NULL)
2243                        break;
2244
2245                putback_zspage(class, dst_zspage);
2246                if (putback_zspage(class, src_zspage) == ZS_EMPTY) {
2247                        free_zspage(pool, class, src_zspage);
2248                        pages_freed += class->pages_per_zspage;
2249                }
2250                spin_unlock(&class->lock);
2251                cond_resched();
2252                spin_lock(&class->lock);
2253        }
2254
2255        if (src_zspage)
2256                putback_zspage(class, src_zspage);
2257
2258        spin_unlock(&class->lock);
2259
2260        return pages_freed;
2261}
2262
2263unsigned long zs_compact(struct zs_pool *pool)
2264{
2265        int i;
2266        struct size_class *class;
2267        unsigned long pages_freed = 0;
2268
2269        for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2270                class = pool->size_class[i];
2271                if (!class)
2272                        continue;
2273                if (class->index != i)
2274                        continue;
2275                pages_freed += __zs_compact(pool, class);
2276        }
2277        atomic_long_add(pages_freed, &pool->stats.pages_compacted);
2278
2279        return pages_freed;
2280}
2281EXPORT_SYMBOL_GPL(zs_compact);
2282
2283void zs_pool_stats(struct zs_pool *pool, struct zs_pool_stats *stats)
2284{
2285        memcpy(stats, &pool->stats, sizeof(struct zs_pool_stats));
2286}
2287EXPORT_SYMBOL_GPL(zs_pool_stats);
2288
2289static unsigned long zs_shrinker_scan(struct shrinker *shrinker,
2290                struct shrink_control *sc)
2291{
2292        unsigned long pages_freed;
2293        struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2294                        shrinker);
2295
2296        /*
2297         * Compact classes and calculate compaction delta.
2298         * Can run concurrently with a manually triggered
2299         * (by user) compaction.
2300         */
2301        pages_freed = zs_compact(pool);
2302
2303        return pages_freed ? pages_freed : SHRINK_STOP;
2304}
2305
2306static unsigned long zs_shrinker_count(struct shrinker *shrinker,
2307                struct shrink_control *sc)
2308{
2309        int i;
2310        struct size_class *class;
2311        unsigned long pages_to_free = 0;
2312        struct zs_pool *pool = container_of(shrinker, struct zs_pool,
2313                        shrinker);
2314
2315        for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2316                class = pool->size_class[i];
2317                if (!class)
2318                        continue;
2319                if (class->index != i)
2320                        continue;
2321
2322                pages_to_free += zs_can_compact(class);
2323        }
2324
2325        return pages_to_free;
2326}
2327
2328static void zs_unregister_shrinker(struct zs_pool *pool)
2329{
2330        unregister_shrinker(&pool->shrinker);
2331}
2332
2333static int zs_register_shrinker(struct zs_pool *pool)
2334{
2335        pool->shrinker.scan_objects = zs_shrinker_scan;
2336        pool->shrinker.count_objects = zs_shrinker_count;
2337        pool->shrinker.batch = 0;
2338        pool->shrinker.seeks = DEFAULT_SEEKS;
2339
2340        return register_shrinker(&pool->shrinker);
2341}
2342
2343/**
2344 * zs_create_pool - Creates an allocation pool to work from.
2345 * @name: pool name to be created
2346 *
2347 * This function must be called before anything when using
2348 * the zsmalloc allocator.
2349 *
2350 * On success, a pointer to the newly created pool is returned,
2351 * otherwise NULL.
2352 */
2353struct zs_pool *zs_create_pool(const char *name)
2354{
2355        int i;
2356        struct zs_pool *pool;
2357        struct size_class *prev_class = NULL;
2358
2359        pool = kzalloc(sizeof(*pool), GFP_KERNEL);
2360        if (!pool)
2361                return NULL;
2362
2363        init_deferred_free(pool);
2364
2365        pool->name = kstrdup(name, GFP_KERNEL);
2366        if (!pool->name)
2367                goto err;
2368
2369#ifdef CONFIG_COMPACTION
2370        init_waitqueue_head(&pool->migration_wait);
2371#endif
2372
2373        if (create_cache(pool))
2374                goto err;
2375
2376        /*
2377         * Iterate reversely, because, size of size_class that we want to use
2378         * for merging should be larger or equal to current size.
2379         */
2380        for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
2381                int size;
2382                int pages_per_zspage;
2383                int objs_per_zspage;
2384                struct size_class *class;
2385                int fullness = 0;
2386
2387                size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
2388                if (size > ZS_MAX_ALLOC_SIZE)
2389                        size = ZS_MAX_ALLOC_SIZE;
2390                pages_per_zspage = get_pages_per_zspage(size);
2391                objs_per_zspage = pages_per_zspage * PAGE_SIZE / size;
2392
2393                /*
2394                 * We iterate from biggest down to smallest classes,
2395                 * so huge_class_size holds the size of the first huge
2396                 * class. Any object bigger than or equal to that will
2397                 * endup in the huge class.
2398                 */
2399                if (pages_per_zspage != 1 && objs_per_zspage != 1 &&
2400                                !huge_class_size) {
2401                        huge_class_size = size;
2402                        /*
2403                         * The object uses ZS_HANDLE_SIZE bytes to store the
2404                         * handle. We need to subtract it, because zs_malloc()
2405                         * unconditionally adds handle size before it performs
2406                         * size class search - so object may be smaller than
2407                         * huge class size, yet it still can end up in the huge
2408                         * class because it grows by ZS_HANDLE_SIZE extra bytes
2409                         * right before class lookup.
2410                         */
2411                        huge_class_size -= (ZS_HANDLE_SIZE - 1);
2412                }
2413
2414                /*
2415                 * size_class is used for normal zsmalloc operation such
2416                 * as alloc/free for that size. Although it is natural that we
2417                 * have one size_class for each size, there is a chance that we
2418                 * can get more memory utilization if we use one size_class for
2419                 * many different sizes whose size_class have same
2420                 * characteristics. So, we makes size_class point to
2421                 * previous size_class if possible.
2422                 */
2423                if (prev_class) {
2424                        if (can_merge(prev_class, pages_per_zspage, objs_per_zspage)) {
2425                                pool->size_class[i] = prev_class;
2426                                continue;
2427                        }
2428                }
2429
2430                class = kzalloc(sizeof(struct size_class), GFP_KERNEL);
2431                if (!class)
2432                        goto err;
2433
2434                class->size = size;
2435                class->index = i;
2436                class->pages_per_zspage = pages_per_zspage;
2437                class->objs_per_zspage = objs_per_zspage;
2438                spin_lock_init(&class->lock);
2439                pool->size_class[i] = class;
2440                for (fullness = ZS_EMPTY; fullness < NR_ZS_FULLNESS;
2441                                                        fullness++)
2442                        INIT_LIST_HEAD(&class->fullness_list[fullness]);
2443
2444                prev_class = class;
2445        }
2446
2447        /* debug only, don't abort if it fails */
2448        zs_pool_stat_create(pool, name);
2449
2450        if (zs_register_migration(pool))
2451                goto err;
2452
2453        /*
2454         * Not critical since shrinker is only used to trigger internal
2455         * defragmentation of the pool which is pretty optional thing.  If
2456         * registration fails we still can use the pool normally and user can
2457         * trigger compaction manually. Thus, ignore return code.
2458         */
2459        zs_register_shrinker(pool);
2460
2461        return pool;
2462
2463err:
2464        zs_destroy_pool(pool);
2465        return NULL;
2466}
2467EXPORT_SYMBOL_GPL(zs_create_pool);
2468
2469void zs_destroy_pool(struct zs_pool *pool)
2470{
2471        int i;
2472
2473        zs_unregister_shrinker(pool);
2474        zs_unregister_migration(pool);
2475        zs_pool_stat_destroy(pool);
2476
2477        for (i = 0; i < ZS_SIZE_CLASSES; i++) {
2478                int fg;
2479                struct size_class *class = pool->size_class[i];
2480
2481                if (!class)
2482                        continue;
2483
2484                if (class->index != i)
2485                        continue;
2486
2487                for (fg = ZS_EMPTY; fg < NR_ZS_FULLNESS; fg++) {
2488                        if (!list_empty(&class->fullness_list[fg])) {
2489                                pr_info("Freeing non-empty class with size %db, fullness group %d\n",
2490                                        class->size, fg);
2491                        }
2492                }
2493                kfree(class);
2494        }
2495
2496        destroy_cache(pool);
2497        kfree(pool->name);
2498        kfree(pool);
2499}
2500EXPORT_SYMBOL_GPL(zs_destroy_pool);
2501
2502static int __init zs_init(void)
2503{
2504        int ret;
2505
2506        ret = zsmalloc_mount();
2507        if (ret)
2508                goto out;
2509
2510        ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
2511                                zs_cpu_prepare, zs_cpu_dead);
2512        if (ret)
2513                goto hp_setup_fail;
2514
2515#ifdef CONFIG_ZPOOL
2516        zpool_register_driver(&zs_zpool_driver);
2517#endif
2518
2519        zs_stat_init();
2520
2521        return 0;
2522
2523hp_setup_fail:
2524        zsmalloc_unmount();
2525out:
2526        return ret;
2527}
2528
2529static void __exit zs_exit(void)
2530{
2531#ifdef CONFIG_ZPOOL
2532        zpool_unregister_driver(&zs_zpool_driver);
2533#endif
2534        zsmalloc_unmount();
2535        cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
2536
2537        zs_stat_exit();
2538}
2539
2540module_init(zs_init);
2541module_exit(zs_exit);
2542
2543MODULE_LICENSE("Dual BSD/GPL");
2544MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
2545
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