mm/z3fold.c

   1 /*
   2  * z3fold.c
   3  *
   4  * Author: Vitaly Wool <vitaly.wool@konsulko.com>
   5  * Copyright (C) 2016, Sony Mobile Communications Inc.
   6  *
   7  * This implementation is based on zbud written by Seth Jennings.
   8  *
   9  * z3fold is an special purpose allocator for storing compressed pages. It
  10  * can store up to three compressed pages per page which improves the
  11  * compression ratio of zbud while retaining its main concepts (e. g. always
  12  * storing an integral number of objects per page) and simplicity.
  13  * It still has simple and deterministic reclaim properties that make it
  14  * preferable to a higher density approach (with no requirement on integral
  15  * number of object per page) when reclaim is used.
  16  *
  17  * As in zbud, pages are divided into "chunks".  The size of the chunks is
  18  * fixed at compile time and is determined by NCHUNKS_ORDER below.
  19  *
  20  * z3fold doesn't export any API and is meant to be used via zpool API.
  21  */
  22
  23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  24
  25 #include <linux/atomic.h>
  26 #include <linux/sched.h>
  27 #include <linux/list.h>
  28 #include <linux/mm.h>
  29 #include <linux/module.h>
  30 #include <linux/percpu.h>
  31 #include <linux/preempt.h>
  32 #include <linux/workqueue.h>
  33 #include <linux/slab.h>
  34 #include <linux/spinlock.h>
  35 #include <linux/zpool.h>
  36
  37 /*
  38  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
  39  * adjusting internal fragmentation.  It also determines the number of
  40  * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
  41  * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
  42  * in the beginning of an allocated page are occupied by z3fold header, so
  43  * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
  44  * which shows the max number of free chunks in z3fold page, also there will
  45  * be 63, or 62, respectively, freelists per pool.
  46  */
  47 #define NCHUNKS_ORDER   6
  48
  49 #define CHUNK_SHIFT     (PAGE_SHIFT - NCHUNKS_ORDER)
  50 #define CHUNK_SIZE      (1 << CHUNK_SHIFT)
  51 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
  52 #define ZHDR_CHUNKS     (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
  53 #define TOTAL_CHUNKS    (PAGE_SIZE >> CHUNK_SHIFT)
  54 #define NCHUNKS         ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
  55
  56 #define BUDDY_MASK      (0x3)
  57 #define BUDDY_SHIFT     2
  58 #define SLOTS_ALIGN     (0x40)
  59
  60 /*****************
  61  * Structures
  62 *****************/
  63 struct z3fold_pool;
  64 struct z3fold_ops {
  65         int (*evict)(struct z3fold_pool *pool, unsigned long handle);
  66 };
  67
  68 enum buddy {
  69         HEADLESS = 0,
  70         FIRST,
  71         MIDDLE,
  72         LAST,
  73         BUDDIES_MAX = LAST
  74 };
  75
  76 struct z3fold_buddy_slots {
  77         /*
  78          * we are using BUDDY_MASK in handle_to_buddy etc. so there should
  79          * be enough slots to hold all possible variants
  80          */
  81         unsigned long slot[BUDDY_MASK + 1];
  82         unsigned long pool; /* back link + flags */
  83 };
  84 #define HANDLE_FLAG_MASK        (0x03)
  85
  86 /*
  87  * struct z3fold_header - z3fold page metadata occupying first chunks of each
  88  *                      z3fold page, except for HEADLESS pages
  89  * @buddy:              links the z3fold page into the relevant list in the
  90  *                      pool
  91  * @page_lock:          per-page lock
  92  * @refcount:           reference count for the z3fold page
  93  * @work:               work_struct for page layout optimization
  94  * @slots:              pointer to the structure holding buddy slots
  95  * @cpu:                CPU which this page "belongs" to
  96  * @first_chunks:       the size of the first buddy in chunks, 0 if free
  97  * @middle_chunks:      the size of the middle buddy in chunks, 0 if free
  98  * @last_chunks:        the size of the last buddy in chunks, 0 if free
  99  * @first_num:          the starting number (for the first handle)
 100  */
 101 struct z3fold_header {
 102         struct list_head buddy;
 103         spinlock_t page_lock;
 104         struct kref refcount;
 105         struct work_struct work;
 106         struct z3fold_buddy_slots *slots;
 107         short cpu;
 108         unsigned short first_chunks;
 109         unsigned short middle_chunks;
 110         unsigned short last_chunks;
 111         unsigned short start_middle;
 112         unsigned short first_num:2;
 113 };
 114
 115 /**
 116  * struct z3fold_pool - stores metadata for each z3fold pool
 117  * @name:       pool name
 118  * @lock:       protects pool unbuddied/lru lists
 119  * @stale_lock: protects pool stale page list
 120  * @unbuddied:  per-cpu array of lists tracking z3fold pages that contain 2-
 121  *              buddies; the list each z3fold page is added to depends on
 122  *              the size of its free region.
 123  * @lru:        list tracking the z3fold pages in LRU order by most recently
 124  *              added buddy.
 125  * @stale:      list of pages marked for freeing
 126  * @pages_nr:   number of z3fold pages in the pool.
 127  * @c_handle:   cache for z3fold_buddy_slots allocation
 128  * @ops:        pointer to a structure of user defined operations specified at
 129  *              pool creation time.
 130  * @compact_wq: workqueue for page layout background optimization
 131  * @release_wq: workqueue for safe page release
 132  * @work:       work_struct for safe page release
 133  *
 134  * This structure is allocated at pool creation time and maintains metadata
 135  * pertaining to a particular z3fold pool.
 136  */
 137 struct z3fold_pool {
 138         const char *name;
 139         spinlock_t lock;
 140         spinlock_t stale_lock;
 141         struct list_head *unbuddied;
 142         struct list_head lru;
 143         struct list_head stale;
 144         atomic64_t pages_nr;
 145         struct kmem_cache *c_handle;
 146         const struct z3fold_ops *ops;
 147         struct zpool *zpool;
 148         const struct zpool_ops *zpool_ops;
 149         struct workqueue_struct *compact_wq;
 150         struct workqueue_struct *release_wq;
 151         struct work_struct work;
 152 };
 153
 154 /*
 155  * Internal z3fold page flags
 156  */
 157 enum z3fold_page_flags {
 158         PAGE_HEADLESS = 0,
 159         MIDDLE_CHUNK_MAPPED,
 160         NEEDS_COMPACTING,
 161         PAGE_STALE,
 162         PAGE_CLAIMED, /* by either reclaim or free */
 163 };
 164
 165 /*****************
 166  * Helpers
 167 *****************/
 168
 169 /* Converts an allocation size in bytes to size in z3fold chunks */
 170 static int size_to_chunks(size_t size)
 171 {
 172         return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
 173 }
 174
 175 #define for_each_unbuddied_list(_iter, _begin) \
 176         for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
 177
 178 static void compact_page_work(struct work_struct *w);
 179
 180 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool)
 181 {
 182         struct z3fold_buddy_slots *slots = kmem_cache_alloc(pool->c_handle,
 183                                                         GFP_KERNEL);
 184
 185         if (slots) {
 186                 memset(slots->slot, 0, sizeof(slots->slot));
 187                 slots->pool = (unsigned long)pool;
 188         }
 189
 190         return slots;
 191 }
 192
 193 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
 194 {
 195         return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
 196 }
 197
 198 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 199 {
 200         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 201 }
 202
 203 static inline void free_handle(unsigned long handle)
 204 {
 205         struct z3fold_buddy_slots *slots;
 206         int i;
 207         bool is_free;
 208
 209         if (handle & (1 << PAGE_HEADLESS))
 210                 return;
 211
 212         WARN_ON(*(unsigned long *)handle == 0);
 213         *(unsigned long *)handle = 0;
 214         slots = handle_to_slots(handle);
 215         is_free = true;
 216         for (i = 0; i <= BUDDY_MASK; i++) {
 217                 if (slots->slot[i]) {
 218                         is_free = false;
 219                         break;
 220                 }
 221         }
 222
 223         if (is_free) {
 224                 struct z3fold_pool *pool = slots_to_pool(slots);
 225
 226                 kmem_cache_free(pool->c_handle, slots);
 227         }
 228 }
 229
 230 /* Initializes the z3fold header of a newly allocated z3fold page */
 231 static struct z3fold_header *init_z3fold_page(struct page *page,
 232                                         struct z3fold_pool *pool)
 233 {
 234         struct z3fold_header *zhdr = page_address(page);
 235         struct z3fold_buddy_slots *slots = alloc_slots(pool);
 236
 237         if (!slots)
 238                 return NULL;
 239
 240         INIT_LIST_HEAD(&page->lru);
 241         clear_bit(PAGE_HEADLESS, &page->private);
 242         clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
 243         clear_bit(NEEDS_COMPACTING, &page->private);
 244         clear_bit(PAGE_STALE, &page->private);
 245         clear_bit(PAGE_CLAIMED, &page->private);
 246
 247         spin_lock_init(&zhdr->page_lock);
 248         kref_init(&zhdr->refcount);
 249         zhdr->first_chunks = 0;
 250         zhdr->middle_chunks = 0;
 251         zhdr->last_chunks = 0;
 252         zhdr->first_num = 0;
 253         zhdr->start_middle = 0;
 254         zhdr->cpu = -1;
 255         zhdr->slots = slots;
 256         INIT_LIST_HEAD(&zhdr->buddy);
 257         INIT_WORK(&zhdr->work, compact_page_work);
 258         return zhdr;
 259 }
 260
 261 /* Resets the struct page fields and frees the page */
 262 static void free_z3fold_page(struct page *page)
 263 {
 264         __free_page(page);
 265 }
 266
 267 /* Lock a z3fold page */
 268 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 269 {
 270         spin_lock(&zhdr->page_lock);
 271 }
 272
 273 /* Try to lock a z3fold page */
 274 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 275 {
 276         return spin_trylock(&zhdr->page_lock);
 277 }
 278
 279 /* Unlock a z3fold page */
 280 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
 281 {
 282         spin_unlock(&zhdr->page_lock);
 283 }
 284
 285 /* Helper function to build the index */
 286 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 287 {
 288         return (bud + zhdr->first_num) & BUDDY_MASK;
 289 }
 290
 291 /*
 292  * Encodes the handle of a particular buddy within a z3fold page
 293  * Pool lock should be held as this function accesses first_num
 294  */
 295 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 296 {
 297         struct z3fold_buddy_slots *slots;
 298         unsigned long h = (unsigned long)zhdr;
 299         int idx = 0;
 300
 301         /*
 302          * For a headless page, its handle is its pointer with the extra
 303          * PAGE_HEADLESS bit set
 304          */
 305         if (bud == HEADLESS)
 306                 return h | (1 << PAGE_HEADLESS);
 307
 308         /* otherwise, return pointer to encoded handle */
 309         idx = __idx(zhdr, bud);
 310         h += idx;
 311         if (bud == LAST)
 312                 h |= (zhdr->last_chunks << BUDDY_SHIFT);
 313
 314         slots = zhdr->slots;
 315         slots->slot[idx] = h;
 316         return (unsigned long)&slots->slot[idx];
 317 }
 318
 319 /* Returns the z3fold page where a given handle is stored */
 320 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
 321 {
 322         unsigned long addr = handle;
 323
 324         if (!(addr & (1 << PAGE_HEADLESS)))
 325                 addr = *(unsigned long *)handle;
 326
 327         return (struct z3fold_header *)(addr & PAGE_MASK);
 328 }
 329
 330 /* only for LAST bud, returns zero otherwise */
 331 static unsigned short handle_to_chunks(unsigned long handle)
 332 {
 333         unsigned long addr = *(unsigned long *)handle;
 334
 335         return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 336 }
 337
 338 /*
 339  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
 340  *  but that doesn't matter. because the masking will result in the
 341  *  correct buddy number.
 342  */
 343 static enum buddy handle_to_buddy(unsigned long handle)
 344 {
 345         struct z3fold_header *zhdr;
 346         unsigned long addr;
 347
 348         WARN_ON(handle & (1 << PAGE_HEADLESS));
 349         addr = *(unsigned long *)handle;
 350         zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 351         return (addr - zhdr->first_num) & BUDDY_MASK;
 352 }
 353
 354 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
 355 {
 356         return slots_to_pool(zhdr->slots);
 357 }
 358
 359 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 360 {
 361         struct page *page = virt_to_page(zhdr);
 362         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 363
 364         WARN_ON(!list_empty(&zhdr->buddy));
 365         set_bit(PAGE_STALE, &page->private);
 366         clear_bit(NEEDS_COMPACTING, &page->private);
 367         spin_lock(&pool->lock);
 368         if (!list_empty(&page->lru))
 369                 list_del(&page->lru);
 370         spin_unlock(&pool->lock);
 371         if (locked)
 372                 z3fold_page_unlock(zhdr);
 373         spin_lock(&pool->stale_lock);
 374         list_add(&zhdr->buddy, &pool->stale);
 375         queue_work(pool->release_wq, &pool->work);
 376         spin_unlock(&pool->stale_lock);
 377 }
 378
 379 static void __attribute__((__unused__))
 380                         release_z3fold_page(struct kref *ref)
 381 {
 382         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 383                                                 refcount);
 384         __release_z3fold_page(zhdr, false);
 385 }
 386
 387 static void release_z3fold_page_locked(struct kref *ref)
 388 {
 389         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 390                                                 refcount);
 391         WARN_ON(z3fold_page_trylock(zhdr));
 392         __release_z3fold_page(zhdr, true);
 393 }
 394
 395 static void release_z3fold_page_locked_list(struct kref *ref)
 396 {
 397         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 398                                                refcount);
 399         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 400         spin_lock(&pool->lock);
 401         list_del_init(&zhdr->buddy);
 402         spin_unlock(&pool->lock);
 403
 404         WARN_ON(z3fold_page_trylock(zhdr));
 405         __release_z3fold_page(zhdr, true);
 406 }
 407
 408 static void free_pages_work(struct work_struct *w)
 409 {
 410         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
 411
 412         spin_lock(&pool->stale_lock);
 413         while (!list_empty(&pool->stale)) {
 414                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
 415                                                 struct z3fold_header, buddy);
 416                 struct page *page = virt_to_page(zhdr);
 417
 418                 list_del(&zhdr->buddy);
 419                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
 420                         continue;
 421                 spin_unlock(&pool->stale_lock);
 422                 cancel_work_sync(&zhdr->work);
 423                 free_z3fold_page(page);
 424                 cond_resched();
 425                 spin_lock(&pool->stale_lock);
 426         }
 427         spin_unlock(&pool->stale_lock);
 428 }
 429
 430 /*
 431  * Returns the number of free chunks in a z3fold page.
 432  * NB: can't be used with HEADLESS pages.
 433  */
 434 static int num_free_chunks(struct z3fold_header *zhdr)
 435 {
 436         int nfree;
 437         /*
 438          * If there is a middle object, pick up the bigger free space
 439          * either before or after it. Otherwise just subtract the number
 440          * of chunks occupied by the first and the last objects.
 441          */
 442         if (zhdr->middle_chunks != 0) {
 443                 int nfree_before = zhdr->first_chunks ?
 444                         0 : zhdr->start_middle - ZHDR_CHUNKS;
 445                 int nfree_after = zhdr->last_chunks ?
 446                         0 : TOTAL_CHUNKS -
 447                                 (zhdr->start_middle + zhdr->middle_chunks);
 448                 nfree = max(nfree_before, nfree_after);
 449         } else
 450                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 451         return nfree;
 452 }
 453
 454 /* Add to the appropriate unbuddied list */
 455 static inline void add_to_unbuddied(struct z3fold_pool *pool,
 456                                 struct z3fold_header *zhdr)
 457 {
 458         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
 459                         zhdr->middle_chunks == 0) {
 460                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
 461
 462                 int freechunks = num_free_chunks(zhdr);
 463                 spin_lock(&pool->lock);
 464                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
 465                 spin_unlock(&pool->lock);
 466                 zhdr->cpu = smp_processor_id();
 467                 put_cpu_ptr(pool->unbuddied);
 468         }
 469 }
 470
 471 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 472                                 unsigned short dst_chunk)
 473 {
 474         void *beg = zhdr;
 475         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
 476                        beg + (zhdr->start_middle << CHUNK_SHIFT),
 477                        zhdr->middle_chunks << CHUNK_SHIFT);
 478 }
 479
 480 #define BIG_CHUNK_GAP   3
 481 /* Has to be called with lock held */
 482 static int z3fold_compact_page(struct z3fold_header *zhdr)
 483 {
 484         struct page *page = virt_to_page(zhdr);
 485
 486         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
 487                 return 0; /* can't move middle chunk, it's used */
 488
 489         if (zhdr->middle_chunks == 0)
 490                 return 0; /* nothing to compact */
 491
 492         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 493                 /* move to the beginning */
 494                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
 495                 zhdr->first_chunks = zhdr->middle_chunks;
 496                 zhdr->middle_chunks = 0;
 497                 zhdr->start_middle = 0;
 498                 zhdr->first_num++;
 499                 return 1;
 500         }
 501
 502         /*
 503          * moving data is expensive, so let's only do that if
 504          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
 505          */
 506         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
 507             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
 508                         BIG_CHUNK_GAP) {
 509                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
 510                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 511                 return 1;
 512         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
 513                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
 514                                         + zhdr->middle_chunks) >=
 515                         BIG_CHUNK_GAP) {
 516                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
 517                         zhdr->middle_chunks;
 518                 mchunk_memmove(zhdr, new_start);
 519                 zhdr->start_middle = new_start;
 520                 return 1;
 521         }
 522
 523         return 0;
 524 }
 525
 526 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 527 {
 528         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 529         struct page *page;
 530
 531         page = virt_to_page(zhdr);
 532         if (locked)
 533                 WARN_ON(z3fold_page_trylock(zhdr));
 534         else
 535                 z3fold_page_lock(zhdr);
 536         if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
 537                 z3fold_page_unlock(zhdr);
 538                 return;
 539         }
 540         spin_lock(&pool->lock);
 541         list_del_init(&zhdr->buddy);
 542         spin_unlock(&pool->lock);
 543
 544         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 545                 atomic64_dec(&pool->pages_nr);
 546                 return;
 547         }
 548
 549         z3fold_compact_page(zhdr);
 550         add_to_unbuddied(pool, zhdr);
 551         z3fold_page_unlock(zhdr);
 552 }
 553
 554 static void compact_page_work(struct work_struct *w)
 555 {
 556         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
 557                                                 work);
 558
 559         do_compact_page(zhdr, false);
 560 }
 561
 562 /* returns _locked_ z3fold page header or NULL */
 563 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
 564                                                 size_t size, bool can_sleep)
 565 {
 566         struct z3fold_header *zhdr = NULL;
 567         struct page *page;
 568         struct list_head *unbuddied;
 569         int chunks = size_to_chunks(size), i;
 570
 571 lookup:
 572         /* First, try to find an unbuddied z3fold page. */
 573         unbuddied = get_cpu_ptr(pool->unbuddied);
 574         for_each_unbuddied_list(i, chunks) {
 575                 struct list_head *l = &unbuddied[i];
 576
 577                 zhdr = list_first_entry_or_null(READ_ONCE(l),
 578                                         struct z3fold_header, buddy);
 579
 580                 if (!zhdr)
 581                         continue;
 582
 583                 /* Re-check under lock. */
 584                 spin_lock(&pool->lock);
 585                 l = &unbuddied[i];
 586                 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
 587                                                 struct z3fold_header, buddy)) ||
 588                     !z3fold_page_trylock(zhdr)) {
 589                         spin_unlock(&pool->lock);
 590                         zhdr = NULL;
 591                         put_cpu_ptr(pool->unbuddied);
 592                         if (can_sleep)
 593                                 cond_resched();
 594                         goto lookup;
 595                 }
 596                 list_del_init(&zhdr->buddy);
 597                 zhdr->cpu = -1;
 598                 spin_unlock(&pool->lock);
 599
 600                 page = virt_to_page(zhdr);
 601                 if (test_bit(NEEDS_COMPACTING, &page->private)) {
 602                         z3fold_page_unlock(zhdr);
 603                         zhdr = NULL;
 604                         put_cpu_ptr(pool->unbuddied);
 605                         if (can_sleep)
 606                                 cond_resched();
 607                         goto lookup;
 608                 }
 609
 610                 /*
 611                  * this page could not be removed from its unbuddied
 612                  * list while pool lock was held, and then we've taken
 613                  * page lock so kref_put could not be called before
 614                  * we got here, so it's safe to just call kref_get()
 615                  */
 616                 kref_get(&zhdr->refcount);
 617                 break;
 618         }
 619         put_cpu_ptr(pool->unbuddied);
 620
 621         if (!zhdr) {
 622                 int cpu;
 623
 624                 /* look for _exact_ match on other cpus' lists */
 625                 for_each_online_cpu(cpu) {
 626                         struct list_head *l;
 627
 628                         unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
 629                         spin_lock(&pool->lock);
 630                         l = &unbuddied[chunks];
 631
 632                         zhdr = list_first_entry_or_null(READ_ONCE(l),
 633                                                 struct z3fold_header, buddy);
 634
 635                         if (!zhdr || !z3fold_page_trylock(zhdr)) {
 636                                 spin_unlock(&pool->lock);
 637                                 zhdr = NULL;
 638                                 continue;
 639                         }
 640                         list_del_init(&zhdr->buddy);
 641                         zhdr->cpu = -1;
 642                         spin_unlock(&pool->lock);
 643
 644                         page = virt_to_page(zhdr);
 645                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
 646                                 z3fold_page_unlock(zhdr);
 647                                 zhdr = NULL;
 648                                 if (can_sleep)
 649                                         cond_resched();
 650                                 continue;
 651                         }
 652                         kref_get(&zhdr->refcount);
 653                         break;
 654                 }
 655         }
 656
 657         return zhdr;
 658 }
 659
 660 /*
 661  * API Functions
 662  */
 663
 664 /**
 665  * z3fold_create_pool() - create a new z3fold pool
 666  * @name:       pool name
 667  * @gfp:        gfp flags when allocating the z3fold pool structure
 668  * @ops:        user-defined operations for the z3fold pool
 669  *
 670  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
 671  * failed.
 672  */
 673 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
 674                 const struct z3fold_ops *ops)
 675 {
 676         struct z3fold_pool *pool = NULL;
 677         int i, cpu;
 678
 679         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
 680         if (!pool)
 681                 goto out;
 682         pool->c_handle = kmem_cache_create("z3fold_handle",
 683                                 sizeof(struct z3fold_buddy_slots),
 684                                 SLOTS_ALIGN, 0, NULL);
 685         if (!pool->c_handle)
 686                 goto out_c;
 687         spin_lock_init(&pool->lock);
 688         spin_lock_init(&pool->stale_lock);
 689         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
 690         if (!pool->unbuddied)
 691                 goto out_pool;
 692         for_each_possible_cpu(cpu) {
 693                 struct list_head *unbuddied =
 694                                 per_cpu_ptr(pool->unbuddied, cpu);
 695                 for_each_unbuddied_list(i, 0)
 696                         INIT_LIST_HEAD(&unbuddied[i]);
 697         }
 698         INIT_LIST_HEAD(&pool->lru);
 699         INIT_LIST_HEAD(&pool->stale);
 700         atomic64_set(&pool->pages_nr, 0);
 701         pool->name = name;
 702         pool->compact_wq = create_singlethread_workqueue(pool->name);
 703         if (!pool->compact_wq)
 704                 goto out_unbuddied;
 705         pool->release_wq = create_singlethread_workqueue(pool->name);
 706         if (!pool->release_wq)
 707                 goto out_wq;
 708         INIT_WORK(&pool->work, free_pages_work);
 709         pool->ops = ops;
 710         return pool;
 711
 712 out_wq:
 713         destroy_workqueue(pool->compact_wq);
 714 out_unbuddied:
 715         free_percpu(pool->unbuddied);
 716 out_pool:
 717         kmem_cache_destroy(pool->c_handle);
 718 out_c:
 719         kfree(pool);
 720 out:
 721         return NULL;
 722 }
 723
 724 /**
 725  * z3fold_destroy_pool() - destroys an existing z3fold pool
 726  * @pool:       the z3fold pool to be destroyed
 727  *
 728  * The pool should be emptied before this function is called.
 729  */
 730 static void z3fold_destroy_pool(struct z3fold_pool *pool)
 731 {
 732         kmem_cache_destroy(pool->c_handle);
 733         destroy_workqueue(pool->release_wq);
 734         destroy_workqueue(pool->compact_wq);
 735         kfree(pool);
 736 }
 737
 738 /**
 739  * z3fold_alloc() - allocates a region of a given size
 740  * @pool:       z3fold pool from which to allocate
 741  * @size:       size in bytes of the desired allocation
 742  * @gfp:        gfp flags used if the pool needs to grow
 743  * @handle:     handle of the new allocation
 744  *
 745  * This function will attempt to find a free region in the pool large enough to
 746  * satisfy the allocation request.  A search of the unbuddied lists is
 747  * performed first. If no suitable free region is found, then a new page is
 748  * allocated and added to the pool to satisfy the request.
 749  *
 750  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
 751  * as z3fold pool pages.
 752  *
 753  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
 754  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
 755  * a new page.
 756  */
 757 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 758                         unsigned long *handle)
 759 {
 760         int chunks = size_to_chunks(size);
 761         struct z3fold_header *zhdr = NULL;
 762         struct page *page = NULL;
 763         enum buddy bud;
 764         bool can_sleep = gfpflags_allow_blocking(gfp);
 765
 766         if (!size || (gfp & __GFP_HIGHMEM))
 767                 return -EINVAL;
 768
 769         if (size > PAGE_SIZE)
 770                 return -ENOSPC;
 771
 772         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
 773                 bud = HEADLESS;
 774         else {
 775 retry:
 776                 zhdr = __z3fold_alloc(pool, size, can_sleep);
 777                 if (zhdr) {
 778                         if (zhdr->first_chunks == 0) {
 779                                 if (zhdr->middle_chunks != 0 &&
 780                                     chunks >= zhdr->start_middle)
 781                                         bud = LAST;
 782                                 else
 783                                         bud = FIRST;
 784                         } else if (zhdr->last_chunks == 0)
 785                                 bud = LAST;
 786                         else if (zhdr->middle_chunks == 0)
 787                                 bud = MIDDLE;
 788                         else {
 789                                 if (kref_put(&zhdr->refcount,
 790                                              release_z3fold_page_locked))
 791                                         atomic64_dec(&pool->pages_nr);
 792                                 else
 793                                         z3fold_page_unlock(zhdr);
 794                                 pr_err("No free chunks in unbuddied\n");
 795                                 WARN_ON(1);
 796                                 goto retry;
 797                         }
 798                         page = virt_to_page(zhdr);
 799                         goto found;
 800                 }
 801                 bud = FIRST;
 802         }
 803
 804         page = NULL;
 805         if (can_sleep) {
 806                 spin_lock(&pool->stale_lock);
 807                 zhdr = list_first_entry_or_null(&pool->stale,
 808                                                 struct z3fold_header, buddy);
 809                 /*
 810                  * Before allocating a page, let's see if we can take one from
 811                  * the stale pages list. cancel_work_sync() can sleep so we
 812                  * limit this case to the contexts where we can sleep
 813                  */
 814                 if (zhdr) {
 815                         list_del(&zhdr->buddy);
 816                         spin_unlock(&pool->stale_lock);
 817                         cancel_work_sync(&zhdr->work);
 818                         page = virt_to_page(zhdr);
 819                 } else {
 820                         spin_unlock(&pool->stale_lock);
 821                 }
 822         }
 823         if (!page)
 824                 page = alloc_page(gfp);
 825
 826         if (!page)
 827                 return -ENOMEM;
 828
 829         zhdr = init_z3fold_page(page, pool);
 830         if (!zhdr) {
 831                 __free_page(page);
 832                 return -ENOMEM;
 833         }
 834         atomic64_inc(&pool->pages_nr);
 835
 836         if (bud == HEADLESS) {
 837                 set_bit(PAGE_HEADLESS, &page->private);
 838                 goto headless;
 839         }
 840         z3fold_page_lock(zhdr);
 841
 842 found:
 843         if (bud == FIRST)
 844                 zhdr->first_chunks = chunks;
 845         else if (bud == LAST)
 846                 zhdr->last_chunks = chunks;
 847         else {
 848                 zhdr->middle_chunks = chunks;
 849                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 850         }
 851         add_to_unbuddied(pool, zhdr);
 852
 853 headless:
 854         spin_lock(&pool->lock);
 855         /* Add/move z3fold page to beginning of LRU */
 856         if (!list_empty(&page->lru))
 857                 list_del(&page->lru);
 858
 859         list_add(&page->lru, &pool->lru);
 860
 861         *handle = encode_handle(zhdr, bud);
 862         spin_unlock(&pool->lock);
 863         if (bud != HEADLESS)
 864                 z3fold_page_unlock(zhdr);
 865
 866         return 0;
 867 }
 868
 869 /**
 870  * z3fold_free() - frees the allocation associated with the given handle
 871  * @pool:       pool in which the allocation resided
 872  * @handle:     handle associated with the allocation returned by z3fold_alloc()
 873  *
 874  * In the case that the z3fold page in which the allocation resides is under
 875  * reclaim, as indicated by the PG_reclaim flag being set, this function
 876  * only sets the first|last_chunks to 0.  The page is actually freed
 877  * once both buddies are evicted (see z3fold_reclaim_page() below).
 878  */
 879 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 880 {
 881         struct z3fold_header *zhdr;
 882         struct page *page;
 883         enum buddy bud;
 884
 885         zhdr = handle_to_z3fold_header(handle);
 886         page = virt_to_page(zhdr);
 887
 888         if (test_bit(PAGE_HEADLESS, &page->private)) {
 889                 /* if a headless page is under reclaim, just leave.
 890                  * NB: we use test_and_set_bit for a reason: if the bit
 891                  * has not been set before, we release this page
 892                  * immediately so we don't care about its value any more.
 893                  */
 894                 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
 895                         spin_lock(&pool->lock);
 896                         list_del(&page->lru);
 897                         spin_unlock(&pool->lock);
 898                         free_z3fold_page(page);
 899                         atomic64_dec(&pool->pages_nr);
 900                 }
 901                 return;
 902         }
 903
 904         /* Non-headless case */
 905         z3fold_page_lock(zhdr);
 906         bud = handle_to_buddy(handle);
 907
 908         switch (bud) {
 909         case FIRST:
 910                 zhdr->first_chunks = 0;
 911                 break;
 912         case MIDDLE:
 913                 zhdr->middle_chunks = 0;
 914                 break;
 915         case LAST:
 916                 zhdr->last_chunks = 0;
 917                 break;
 918         default:
 919                 pr_err("%s: unknown bud %d\n", __func__, bud);
 920                 WARN_ON(1);
 921                 z3fold_page_unlock(zhdr);
 922                 return;
 923         }
 924
 925         free_handle(handle);
 926         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
 927                 atomic64_dec(&pool->pages_nr);
 928                 return;
 929         }
 930         if (test_bit(PAGE_CLAIMED, &page->private)) {
 931                 z3fold_page_unlock(zhdr);
 932                 return;
 933         }
 934         if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
 935                 z3fold_page_unlock(zhdr);
 936                 return;
 937         }
 938         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
 939                 spin_lock(&pool->lock);
 940                 list_del_init(&zhdr->buddy);
 941                 spin_unlock(&pool->lock);
 942                 zhdr->cpu = -1;
 943                 kref_get(&zhdr->refcount);
 944                 do_compact_page(zhdr, true);
 945                 return;
 946         }
 947         kref_get(&zhdr->refcount);
 948         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
 949         z3fold_page_unlock(zhdr);
 950 }
 951
 952 /**
 953  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
 954  * @pool:       pool from which a page will attempt to be evicted
 955  * @retries:    number of pages on the LRU list for which eviction will
 956  *              be attempted before failing
 957  *
 958  * z3fold reclaim is different from normal system reclaim in that it is done
 959  * from the bottom, up. This is because only the bottom layer, z3fold, has
 960  * information on how the allocations are organized within each z3fold page.
 961  * This has the potential to create interesting locking situations between
 962  * z3fold and the user, however.
 963  *
 964  * To avoid these, this is how z3fold_reclaim_page() should be called:
 965  *
 966  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
 967  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
 968  * call the user-defined eviction handler with the pool and handle as
 969  * arguments.
 970  *
 971  * If the handle can not be evicted, the eviction handler should return
 972  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
 973  * appropriate list and try the next z3fold page on the LRU up to
 974  * a user defined number of retries.
 975  *
 976  * If the handle is successfully evicted, the eviction handler should
 977  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
 978  * contains logic to delay freeing the page if the page is under reclaim,
 979  * as indicated by the setting of the PG_reclaim flag on the underlying page.
 980  *
 981  * If all buddies in the z3fold page are successfully evicted, then the
 982  * z3fold page can be freed.
 983  *
 984  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
 985  * no pages to evict or an eviction handler is not registered, -EAGAIN if
 986  * the retry limit was hit.
 987  */
 988 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
 989 {
 990         int i, ret = 0;
 991         struct z3fold_header *zhdr = NULL;
 992         struct page *page = NULL;
 993         struct list_head *pos;
 994         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
 995
 996         spin_lock(&pool->lock);
 997         if (!pool->ops || !pool->ops->evict || retries == 0) {
 998                 spin_unlock(&pool->lock);
 999                 return -EINVAL;
1000         }
1001         for (i = 0; i < retries; i++) {
1002                 if (list_empty(&pool->lru)) {
1003                         spin_unlock(&pool->lock);
1004                         return -EINVAL;
1005                 }
1006                 list_for_each_prev(pos, &pool->lru) {
1007                         page = list_entry(pos, struct page, lru);
1008
1009                         /* this bit could have been set by free, in which case
1010                          * we pass over to the next page in the pool.
1011                          */
1012                         if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1013                                 continue;
1014
1015                         zhdr = page_address(page);
1016                         if (test_bit(PAGE_HEADLESS, &page->private))
1017                                 break;
1018
1019                         if (!z3fold_page_trylock(zhdr)) {
1020                                 zhdr = NULL;
1021                                 continue; /* can't evict at this point */
1022                         }
1023                         kref_get(&zhdr->refcount);
1024                         list_del_init(&zhdr->buddy);
1025                         zhdr->cpu = -1;
1026                         break;
1027                 }
1028
1029                 if (!zhdr)
1030                         break;
1031
1032                 list_del_init(&page->lru);
1033                 spin_unlock(&pool->lock);
1034
1035                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1036                         /*
1037                          * We need encode the handles before unlocking, since
1038                          * we can race with free that will set
1039                          * (first|last)_chunks to 0
1040                          */
1041                         first_handle = 0;
1042                         last_handle = 0;
1043                         middle_handle = 0;
1044                         if (zhdr->first_chunks)
1045                                 first_handle = encode_handle(zhdr, FIRST);
1046                         if (zhdr->middle_chunks)
1047                                 middle_handle = encode_handle(zhdr, MIDDLE);
1048                         if (zhdr->last_chunks)
1049                                 last_handle = encode_handle(zhdr, LAST);
1050                         /*
1051                          * it's safe to unlock here because we hold a
1052                          * reference to this page
1053                          */
1054                         z3fold_page_unlock(zhdr);
1055                 } else {
1056                         first_handle = encode_handle(zhdr, HEADLESS);
1057                         last_handle = middle_handle = 0;
1058                 }
1059
1060                 /* Issue the eviction callback(s) */
1061                 if (middle_handle) {
1062                         ret = pool->ops->evict(pool, middle_handle);
1063                         if (ret)
1064                                 goto next;
1065                 }
1066                 if (first_handle) {
1067                         ret = pool->ops->evict(pool, first_handle);
1068                         if (ret)
1069                                 goto next;
1070                 }
1071                 if (last_handle) {
1072                         ret = pool->ops->evict(pool, last_handle);
1073                         if (ret)
1074                                 goto next;
1075                 }
1076 next:
1077                 if (test_bit(PAGE_HEADLESS, &page->private)) {
1078                         if (ret == 0) {
1079                                 free_z3fold_page(page);
1080                                 atomic64_dec(&pool->pages_nr);
1081                                 return 0;
1082                         }
1083                         spin_lock(&pool->lock);
1084                         list_add(&page->lru, &pool->lru);
1085                         spin_unlock(&pool->lock);
1086                 } else {
1087                         z3fold_page_lock(zhdr);
1088                         clear_bit(PAGE_CLAIMED, &page->private);
1089                         if (kref_put(&zhdr->refcount,
1090                                         release_z3fold_page_locked)) {
1091                                 atomic64_dec(&pool->pages_nr);
1092                                 return 0;
1093                         }
1094                         /*
1095                          * if we are here, the page is still not completely
1096                          * free. Take the global pool lock then to be able
1097                          * to add it back to the lru list
1098                          */
1099                         spin_lock(&pool->lock);
1100                         list_add(&page->lru, &pool->lru);
1101                         spin_unlock(&pool->lock);
1102                         z3fold_page_unlock(zhdr);
1103                 }
1104
1105                 /* We started off locked to we need to lock the pool back */
1106                 spin_lock(&pool->lock);
1107         }
1108         spin_unlock(&pool->lock);
1109         return -EAGAIN;
1110 }
1111
1112 /**
1113  * z3fold_map() - maps the allocation associated with the given handle
1114  * @pool:       pool in which the allocation resides
1115  * @handle:     handle associated with the allocation to be mapped
1116  *
1117  * Extracts the buddy number from handle and constructs the pointer to the
1118  * correct starting chunk within the page.
1119  *
1120  * Returns: a pointer to the mapped allocation
1121  */
1122 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1123 {
1124         struct z3fold_header *zhdr;
1125         struct page *page;
1126         void *addr;
1127         enum buddy buddy;
1128
1129         zhdr = handle_to_z3fold_header(handle);
1130         addr = zhdr;
1131         page = virt_to_page(zhdr);
1132
1133         if (test_bit(PAGE_HEADLESS, &page->private))
1134                 goto out;
1135
1136         z3fold_page_lock(zhdr);
1137         buddy = handle_to_buddy(handle);
1138         switch (buddy) {
1139         case FIRST:
1140                 addr += ZHDR_SIZE_ALIGNED;
1141                 break;
1142         case MIDDLE:
1143                 addr += zhdr->start_middle << CHUNK_SHIFT;
1144                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1145                 break;
1146         case LAST:
1147                 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1148                 break;
1149         default:
1150                 pr_err("unknown buddy id %d\n", buddy);
1151                 WARN_ON(1);
1152                 addr = NULL;
1153                 break;
1154         }
1155
1156         z3fold_page_unlock(zhdr);
1157 out:
1158         return addr;
1159 }
1160
1161 /**
1162  * z3fold_unmap() - unmaps the allocation associated with the given handle
1163  * @pool:       pool in which the allocation resides
1164  * @handle:     handle associated with the allocation to be unmapped
1165  */
1166 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1167 {
1168         struct z3fold_header *zhdr;
1169         struct page *page;
1170         enum buddy buddy;
1171
1172         zhdr = handle_to_z3fold_header(handle);
1173         page = virt_to_page(zhdr);
1174
1175         if (test_bit(PAGE_HEADLESS, &page->private))
1176                 return;
1177
1178         z3fold_page_lock(zhdr);
1179         buddy = handle_to_buddy(handle);
1180         if (buddy == MIDDLE)
1181                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1182         z3fold_page_unlock(zhdr);
1183 }
1184
1185 /**
1186  * z3fold_get_pool_size() - gets the z3fold pool size in pages
1187  * @pool:       pool whose size is being queried
1188  *
1189  * Returns: size in pages of the given pool.
1190  */
1191 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1192 {
1193         return atomic64_read(&pool->pages_nr);
1194 }
1195
1196 /*****************
1197  * zpool
1198  ****************/
1199
1200 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1201 {
1202         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1203                 return pool->zpool_ops->evict(pool->zpool, handle);
1204         else
1205                 return -ENOENT;
1206 }
1207
1208 static const struct z3fold_ops z3fold_zpool_ops = {
1209         .evict =        z3fold_zpool_evict
1210 };
1211
1212 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1213                                const struct zpool_ops *zpool_ops,
1214                                struct zpool *zpool)
1215 {
1216         struct z3fold_pool *pool;
1217
1218         pool = z3fold_create_pool(name, gfp,
1219                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1220         if (pool) {
1221                 pool->zpool = zpool;
1222                 pool->zpool_ops = zpool_ops;
1223         }
1224         return pool;
1225 }
1226
1227 static void z3fold_zpool_destroy(void *pool)
1228 {
1229         z3fold_destroy_pool(pool);
1230 }
1231
1232 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1233                         unsigned long *handle)
1234 {
1235         return z3fold_alloc(pool, size, gfp, handle);
1236 }
1237 static void z3fold_zpool_free(void *pool, unsigned long handle)
1238 {
1239         z3fold_free(pool, handle);
1240 }
1241
1242 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1243                         unsigned int *reclaimed)
1244 {
1245         unsigned int total = 0;
1246         int ret = -EINVAL;
1247
1248         while (total < pages) {
1249                 ret = z3fold_reclaim_page(pool, 8);
1250                 if (ret < 0)
1251                         break;
1252                 total++;
1253         }
1254
1255         if (reclaimed)
1256                 *reclaimed = total;
1257
1258         return ret;
1259 }
1260
1261 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1262                         enum zpool_mapmode mm)
1263 {
1264         return z3fold_map(pool, handle);
1265 }
1266 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1267 {
1268         z3fold_unmap(pool, handle);
1269 }
1270
1271 static u64 z3fold_zpool_total_size(void *pool)
1272 {
1273         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1274 }
1275
1276 static struct zpool_driver z3fold_zpool_driver = {
1277         .type =         "z3fold",
1278         .owner =        THIS_MODULE,
1279         .create =       z3fold_zpool_create,
1280         .destroy =      z3fold_zpool_destroy,
1281         .malloc =       z3fold_zpool_malloc,
1282         .free =         z3fold_zpool_free,
1283         .shrink =       z3fold_zpool_shrink,
1284         .map =          z3fold_zpool_map,
1285         .unmap =        z3fold_zpool_unmap,
1286         .total_size =   z3fold_zpool_total_size,
1287 };
1288
1289 MODULE_ALIAS("zpool-z3fold");
1290
1291 static int __init init_z3fold(void)
1292 {
1293         /* Make sure the z3fold header is not larger than the page size */
1294         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1295         zpool_register_driver(&z3fold_zpool_driver);
1296
1297         return 0;
1298 }
1299
1300 static void __exit exit_z3fold(void)
1301 {
1302         zpool_unregister_driver(&z3fold_zpool_driver);
1303 }
1304
1305 module_init(init_z3fold);
1306 module_exit(exit_z3fold);
1307
1308 MODULE_LICENSE("GPL");
1309 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1310 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");