mm/z3fold.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * z3fold.c
   4  *
   5  * Author: Vitaly Wool <vitaly.wool@konsulko.com>
   6  * Copyright (C) 2016, Sony Mobile Communications Inc.
   7  *
   8  * This implementation is based on zbud written by Seth Jennings.
   9  *
  10  * z3fold is an special purpose allocator for storing compressed pages. It
  11  * can store up to three compressed pages per page which improves the
  12  * compression ratio of zbud while retaining its main concepts (e. g. always
  13  * storing an integral number of objects per page) and simplicity.
  14  * It still has simple and deterministic reclaim properties that make it
  15  * preferable to a higher density approach (with no requirement on integral
  16  * number of object per page) when reclaim is used.
  17  *
  18  * As in zbud, pages are divided into "chunks".  The size of the chunks is
  19  * fixed at compile time and is determined by NCHUNKS_ORDER below.
  20  *
  21  * z3fold doesn't export any API and is meant to be used via zpool API.
  22  */
  23
  24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  25
  26 #include <linux/atomic.h>
  27 #include <linux/sched.h>
  28 #include <linux/cpumask.h>
  29 #include <linux/dcache.h>
  30 #include <linux/list.h>
  31 #include <linux/mm.h>
  32 #include <linux/module.h>
  33 #include <linux/page-flags.h>
  34 #include <linux/migrate.h>
  35 #include <linux/node.h>
  36 #include <linux/compaction.h>
  37 #include <linux/percpu.h>
  38 #include <linux/mount.h>
  39 #include <linux/fs.h>
  40 #include <linux/preempt.h>
  41 #include <linux/workqueue.h>
  42 #include <linux/slab.h>
  43 #include <linux/spinlock.h>
  44 #include <linux/zpool.h>
  45
  46 /*
  47  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
  48  * adjusting internal fragmentation.  It also determines the number of
  49  * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
  50  * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
  51  * in the beginning of an allocated page are occupied by z3fold header, so
  52  * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
  53  * which shows the max number of free chunks in z3fold page, also there will
  54  * be 63, or 62, respectively, freelists per pool.
  55  */
  56 #define NCHUNKS_ORDER   6
  57
  58 #define CHUNK_SHIFT     (PAGE_SHIFT - NCHUNKS_ORDER)
  59 #define CHUNK_SIZE      (1 << CHUNK_SHIFT)
  60 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
  61 #define ZHDR_CHUNKS     (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
  62 #define TOTAL_CHUNKS    (PAGE_SIZE >> CHUNK_SHIFT)
  63 #define NCHUNKS         ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
  64
  65 #define BUDDY_MASK      (0x3)
  66 #define BUDDY_SHIFT     2
  67 #define SLOTS_ALIGN     (0x40)
  68
  69 /*****************
  70  * Structures
  71 *****************/
  72 struct z3fold_pool;
  73 struct z3fold_ops {
  74         int (*evict)(struct z3fold_pool *pool, unsigned long handle);
  75 };
  76
  77 enum buddy {
  78         HEADLESS = 0,
  79         FIRST,
  80         MIDDLE,
  81         LAST,
  82         BUDDIES_MAX = LAST
  83 };
  84
  85 struct z3fold_buddy_slots {
  86         /*
  87          * we are using BUDDY_MASK in handle_to_buddy etc. so there should
  88          * be enough slots to hold all possible variants
  89          */
  90         unsigned long slot[BUDDY_MASK + 1];
  91         unsigned long pool; /* back link + flags */
  92 };
  93 #define HANDLE_FLAG_MASK        (0x03)
  94
  95 /*
  96  * struct z3fold_header - z3fold page metadata occupying first chunks of each
  97  *                      z3fold page, except for HEADLESS pages
  98  * @buddy:              links the z3fold page into the relevant list in the
  99  *                      pool
 100  * @page_lock:          per-page lock
 101  * @refcount:           reference count for the z3fold page
 102  * @work:               work_struct for page layout optimization
 103  * @slots:              pointer to the structure holding buddy slots
 104  * @cpu:                CPU which this page "belongs" to
 105  * @first_chunks:       the size of the first buddy in chunks, 0 if free
 106  * @middle_chunks:      the size of the middle buddy in chunks, 0 if free
 107  * @last_chunks:        the size of the last buddy in chunks, 0 if free
 108  * @first_num:          the starting number (for the first handle)
 109  * @mapped_count:       the number of objects currently mapped
 110  */
 111 struct z3fold_header {
 112         struct list_head buddy;
 113         spinlock_t page_lock;
 114         struct kref refcount;
 115         struct work_struct work;
 116         struct z3fold_buddy_slots *slots;
 117         short cpu;
 118         unsigned short first_chunks;
 119         unsigned short middle_chunks;
 120         unsigned short last_chunks;
 121         unsigned short start_middle;
 122         unsigned short first_num:2;
 123         unsigned short mapped_count:2;
 124 };
 125
 126 /**
 127  * struct z3fold_pool - stores metadata for each z3fold pool
 128  * @name:       pool name
 129  * @lock:       protects pool unbuddied/lru lists
 130  * @stale_lock: protects pool stale page list
 131  * @unbuddied:  per-cpu array of lists tracking z3fold pages that contain 2-
 132  *              buddies; the list each z3fold page is added to depends on
 133  *              the size of its free region.
 134  * @lru:        list tracking the z3fold pages in LRU order by most recently
 135  *              added buddy.
 136  * @stale:      list of pages marked for freeing
 137  * @pages_nr:   number of z3fold pages in the pool.
 138  * @c_handle:   cache for z3fold_buddy_slots allocation
 139  * @ops:        pointer to a structure of user defined operations specified at
 140  *              pool creation time.
 141  * @compact_wq: workqueue for page layout background optimization
 142  * @release_wq: workqueue for safe page release
 143  * @work:       work_struct for safe page release
 144  * @inode:      inode for z3fold pseudo filesystem
 145  *
 146  * This structure is allocated at pool creation time and maintains metadata
 147  * pertaining to a particular z3fold pool.
 148  */
 149 struct z3fold_pool {
 150         const char *name;
 151         spinlock_t lock;
 152         spinlock_t stale_lock;
 153         struct list_head *unbuddied;
 154         struct list_head lru;
 155         struct list_head stale;
 156         atomic64_t pages_nr;
 157         struct kmem_cache *c_handle;
 158         const struct z3fold_ops *ops;
 159         struct zpool *zpool;
 160         const struct zpool_ops *zpool_ops;
 161         struct workqueue_struct *compact_wq;
 162         struct workqueue_struct *release_wq;
 163         struct work_struct work;
 164         struct inode *inode;
 165 };
 166
 167 /*
 168  * Internal z3fold page flags
 169  */
 170 enum z3fold_page_flags {
 171         PAGE_HEADLESS = 0,
 172         MIDDLE_CHUNK_MAPPED,
 173         NEEDS_COMPACTING,
 174         PAGE_STALE,
 175         PAGE_CLAIMED, /* by either reclaim or free */
 176 };
 177
 178 /*****************
 179  * Helpers
 180 *****************/
 181
 182 /* Converts an allocation size in bytes to size in z3fold chunks */
 183 static int size_to_chunks(size_t size)
 184 {
 185         return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
 186 }
 187
 188 #define for_each_unbuddied_list(_iter, _begin) \
 189         for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
 190
 191 static void compact_page_work(struct work_struct *w);
 192
 193 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool)
 194 {
 195         struct z3fold_buddy_slots *slots = kmem_cache_alloc(pool->c_handle,
 196                                                         GFP_KERNEL);
 197
 198         if (slots) {
 199                 memset(slots->slot, 0, sizeof(slots->slot));
 200                 slots->pool = (unsigned long)pool;
 201         }
 202
 203         return slots;
 204 }
 205
 206 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
 207 {
 208         return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
 209 }
 210
 211 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 212 {
 213         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 214 }
 215
 216 static inline void free_handle(unsigned long handle)
 217 {
 218         struct z3fold_buddy_slots *slots;
 219         int i;
 220         bool is_free;
 221
 222         if (handle & (1 << PAGE_HEADLESS))
 223                 return;
 224
 225         WARN_ON(*(unsigned long *)handle == 0);
 226         *(unsigned long *)handle = 0;
 227         slots = handle_to_slots(handle);
 228         is_free = true;
 229         for (i = 0; i <= BUDDY_MASK; i++) {
 230                 if (slots->slot[i]) {
 231                         is_free = false;
 232                         break;
 233                 }
 234         }
 235
 236         if (is_free) {
 237                 struct z3fold_pool *pool = slots_to_pool(slots);
 238
 239                 kmem_cache_free(pool->c_handle, slots);
 240         }
 241 }
 242
 243 static struct dentry *z3fold_do_mount(struct file_system_type *fs_type,
 244                                 int flags, const char *dev_name, void *data)
 245 {
 246         static const struct dentry_operations ops = {
 247                 .d_dname = simple_dname,
 248         };
 249
 250         return mount_pseudo(fs_type, "z3fold:", NULL, &ops, 0x33);
 251 }
 252
 253 static struct file_system_type z3fold_fs = {
 254         .name           = "z3fold",
 255         .mount          = z3fold_do_mount,
 256         .kill_sb        = kill_anon_super,
 257 };
 258
 259 static struct vfsmount *z3fold_mnt;
 260 static int z3fold_mount(void)
 261 {
 262         int ret = 0;
 263
 264         z3fold_mnt = kern_mount(&z3fold_fs);
 265         if (IS_ERR(z3fold_mnt))
 266                 ret = PTR_ERR(z3fold_mnt);
 267
 268         return ret;
 269 }
 270
 271 static void z3fold_unmount(void)
 272 {
 273         kern_unmount(z3fold_mnt);
 274 }
 275
 276 static const struct address_space_operations z3fold_aops;
 277 static int z3fold_register_migration(struct z3fold_pool *pool)
 278 {
 279         pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
 280         if (IS_ERR(pool->inode)) {
 281                 pool->inode = NULL;
 282                 return 1;
 283         }
 284
 285         pool->inode->i_mapping->private_data = pool;
 286         pool->inode->i_mapping->a_ops = &z3fold_aops;
 287         return 0;
 288 }
 289
 290 static void z3fold_unregister_migration(struct z3fold_pool *pool)
 291 {
 292         if (pool->inode)
 293                 iput(pool->inode);
 294  }
 295
 296 /* Initializes the z3fold header of a newly allocated z3fold page */
 297 static struct z3fold_header *init_z3fold_page(struct page *page,
 298                                         struct z3fold_pool *pool)
 299 {
 300         struct z3fold_header *zhdr = page_address(page);
 301         struct z3fold_buddy_slots *slots = alloc_slots(pool);
 302
 303         if (!slots)
 304                 return NULL;
 305
 306         INIT_LIST_HEAD(&page->lru);
 307         clear_bit(PAGE_HEADLESS, &page->private);
 308         clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
 309         clear_bit(NEEDS_COMPACTING, &page->private);
 310         clear_bit(PAGE_STALE, &page->private);
 311         clear_bit(PAGE_CLAIMED, &page->private);
 312
 313         spin_lock_init(&zhdr->page_lock);
 314         kref_init(&zhdr->refcount);
 315         zhdr->first_chunks = 0;
 316         zhdr->middle_chunks = 0;
 317         zhdr->last_chunks = 0;
 318         zhdr->first_num = 0;
 319         zhdr->start_middle = 0;
 320         zhdr->cpu = -1;
 321         zhdr->slots = slots;
 322         INIT_LIST_HEAD(&zhdr->buddy);
 323         INIT_WORK(&zhdr->work, compact_page_work);
 324         return zhdr;
 325 }
 326
 327 /* Resets the struct page fields and frees the page */
 328 static void free_z3fold_page(struct page *page, bool headless)
 329 {
 330         if (!headless) {
 331                 lock_page(page);
 332                 __ClearPageMovable(page);
 333                 unlock_page(page);
 334         }
 335         ClearPagePrivate(page);
 336         __free_page(page);
 337 }
 338
 339 /* Lock a z3fold page */
 340 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 341 {
 342         spin_lock(&zhdr->page_lock);
 343 }
 344
 345 /* Try to lock a z3fold page */
 346 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 347 {
 348         return spin_trylock(&zhdr->page_lock);
 349 }
 350
 351 /* Unlock a z3fold page */
 352 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
 353 {
 354         spin_unlock(&zhdr->page_lock);
 355 }
 356
 357 /* Helper function to build the index */
 358 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 359 {
 360         return (bud + zhdr->first_num) & BUDDY_MASK;
 361 }
 362
 363 /*
 364  * Encodes the handle of a particular buddy within a z3fold page
 365  * Pool lock should be held as this function accesses first_num
 366  */
 367 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 368 {
 369         struct z3fold_buddy_slots *slots;
 370         unsigned long h = (unsigned long)zhdr;
 371         int idx = 0;
 372
 373         /*
 374          * For a headless page, its handle is its pointer with the extra
 375          * PAGE_HEADLESS bit set
 376          */
 377         if (bud == HEADLESS)
 378                 return h | (1 << PAGE_HEADLESS);
 379
 380         /* otherwise, return pointer to encoded handle */
 381         idx = __idx(zhdr, bud);
 382         h += idx;
 383         if (bud == LAST)
 384                 h |= (zhdr->last_chunks << BUDDY_SHIFT);
 385
 386         slots = zhdr->slots;
 387         slots->slot[idx] = h;
 388         return (unsigned long)&slots->slot[idx];
 389 }
 390
 391 /* Returns the z3fold page where a given handle is stored */
 392 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
 393 {
 394         unsigned long addr = h;
 395
 396         if (!(addr & (1 << PAGE_HEADLESS)))
 397                 addr = *(unsigned long *)h;
 398
 399         return (struct z3fold_header *)(addr & PAGE_MASK);
 400 }
 401
 402 /* only for LAST bud, returns zero otherwise */
 403 static unsigned short handle_to_chunks(unsigned long handle)
 404 {
 405         unsigned long addr = *(unsigned long *)handle;
 406
 407         return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 408 }
 409
 410 /*
 411  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
 412  *  but that doesn't matter. because the masking will result in the
 413  *  correct buddy number.
 414  */
 415 static enum buddy handle_to_buddy(unsigned long handle)
 416 {
 417         struct z3fold_header *zhdr;
 418         unsigned long addr;
 419
 420         WARN_ON(handle & (1 << PAGE_HEADLESS));
 421         addr = *(unsigned long *)handle;
 422         zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 423         return (addr - zhdr->first_num) & BUDDY_MASK;
 424 }
 425
 426 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
 427 {
 428         return slots_to_pool(zhdr->slots);
 429 }
 430
 431 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 432 {
 433         struct page *page = virt_to_page(zhdr);
 434         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 435
 436         WARN_ON(!list_empty(&zhdr->buddy));
 437         set_bit(PAGE_STALE, &page->private);
 438         clear_bit(NEEDS_COMPACTING, &page->private);
 439         spin_lock(&pool->lock);
 440         if (!list_empty(&page->lru))
 441                 list_del_init(&page->lru);
 442         spin_unlock(&pool->lock);
 443         if (locked)
 444                 z3fold_page_unlock(zhdr);
 445         spin_lock(&pool->stale_lock);
 446         list_add(&zhdr->buddy, &pool->stale);
 447         queue_work(pool->release_wq, &pool->work);
 448         spin_unlock(&pool->stale_lock);
 449 }
 450
 451 static void __attribute__((__unused__))
 452                         release_z3fold_page(struct kref *ref)
 453 {
 454         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 455                                                 refcount);
 456         __release_z3fold_page(zhdr, false);
 457 }
 458
 459 static void release_z3fold_page_locked(struct kref *ref)
 460 {
 461         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 462                                                 refcount);
 463         WARN_ON(z3fold_page_trylock(zhdr));
 464         __release_z3fold_page(zhdr, true);
 465 }
 466
 467 static void release_z3fold_page_locked_list(struct kref *ref)
 468 {
 469         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 470                                                refcount);
 471         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 472         spin_lock(&pool->lock);
 473         list_del_init(&zhdr->buddy);
 474         spin_unlock(&pool->lock);
 475
 476         WARN_ON(z3fold_page_trylock(zhdr));
 477         __release_z3fold_page(zhdr, true);
 478 }
 479
 480 static void free_pages_work(struct work_struct *w)
 481 {
 482         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
 483
 484         spin_lock(&pool->stale_lock);
 485         while (!list_empty(&pool->stale)) {
 486                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
 487                                                 struct z3fold_header, buddy);
 488                 struct page *page = virt_to_page(zhdr);
 489
 490                 list_del(&zhdr->buddy);
 491                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
 492                         continue;
 493                 spin_unlock(&pool->stale_lock);
 494                 cancel_work_sync(&zhdr->work);
 495                 free_z3fold_page(page, false);
 496                 cond_resched();
 497                 spin_lock(&pool->stale_lock);
 498         }
 499         spin_unlock(&pool->stale_lock);
 500 }
 501
 502 /*
 503  * Returns the number of free chunks in a z3fold page.
 504  * NB: can't be used with HEADLESS pages.
 505  */
 506 static int num_free_chunks(struct z3fold_header *zhdr)
 507 {
 508         int nfree;
 509         /*
 510          * If there is a middle object, pick up the bigger free space
 511          * either before or after it. Otherwise just subtract the number
 512          * of chunks occupied by the first and the last objects.
 513          */
 514         if (zhdr->middle_chunks != 0) {
 515                 int nfree_before = zhdr->first_chunks ?
 516                         0 : zhdr->start_middle - ZHDR_CHUNKS;
 517                 int nfree_after = zhdr->last_chunks ?
 518                         0 : TOTAL_CHUNKS -
 519                                 (zhdr->start_middle + zhdr->middle_chunks);
 520                 nfree = max(nfree_before, nfree_after);
 521         } else
 522                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 523         return nfree;
 524 }
 525
 526 /* Add to the appropriate unbuddied list */
 527 static inline void add_to_unbuddied(struct z3fold_pool *pool,
 528                                 struct z3fold_header *zhdr)
 529 {
 530         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
 531                         zhdr->middle_chunks == 0) {
 532                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
 533
 534                 int freechunks = num_free_chunks(zhdr);
 535                 spin_lock(&pool->lock);
 536                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
 537                 spin_unlock(&pool->lock);
 538                 zhdr->cpu = smp_processor_id();
 539                 put_cpu_ptr(pool->unbuddied);
 540         }
 541 }
 542
 543 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 544                                 unsigned short dst_chunk)
 545 {
 546         void *beg = zhdr;
 547         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
 548                        beg + (zhdr->start_middle << CHUNK_SHIFT),
 549                        zhdr->middle_chunks << CHUNK_SHIFT);
 550 }
 551
 552 #define BIG_CHUNK_GAP   3
 553 /* Has to be called with lock held */
 554 static int z3fold_compact_page(struct z3fold_header *zhdr)
 555 {
 556         struct page *page = virt_to_page(zhdr);
 557
 558         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
 559                 return 0; /* can't move middle chunk, it's used */
 560
 561         if (unlikely(PageIsolated(page)))
 562                 return 0;
 563
 564         if (zhdr->middle_chunks == 0)
 565                 return 0; /* nothing to compact */
 566
 567         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 568                 /* move to the beginning */
 569                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
 570                 zhdr->first_chunks = zhdr->middle_chunks;
 571                 zhdr->middle_chunks = 0;
 572                 zhdr->start_middle = 0;
 573                 zhdr->first_num++;
 574                 return 1;
 575         }
 576
 577         /*
 578          * moving data is expensive, so let's only do that if
 579          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
 580          */
 581         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
 582             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
 583                         BIG_CHUNK_GAP) {
 584                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
 585                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 586                 return 1;
 587         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
 588                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
 589                                         + zhdr->middle_chunks) >=
 590                         BIG_CHUNK_GAP) {
 591                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
 592                         zhdr->middle_chunks;
 593                 mchunk_memmove(zhdr, new_start);
 594                 zhdr->start_middle = new_start;
 595                 return 1;
 596         }
 597
 598         return 0;
 599 }
 600
 601 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 602 {
 603         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 604         struct page *page;
 605
 606         page = virt_to_page(zhdr);
 607         if (locked)
 608                 WARN_ON(z3fold_page_trylock(zhdr));
 609         else
 610                 z3fold_page_lock(zhdr);
 611         if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
 612                 z3fold_page_unlock(zhdr);
 613                 return;
 614         }
 615         spin_lock(&pool->lock);
 616         list_del_init(&zhdr->buddy);
 617         spin_unlock(&pool->lock);
 618
 619         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 620                 atomic64_dec(&pool->pages_nr);
 621                 return;
 622         }
 623
 624         if (unlikely(PageIsolated(page) ||
 625                      test_bit(PAGE_STALE, &page->private))) {
 626                 z3fold_page_unlock(zhdr);
 627                 return;
 628         }
 629
 630         z3fold_compact_page(zhdr);
 631         add_to_unbuddied(pool, zhdr);
 632         z3fold_page_unlock(zhdr);
 633 }
 634
 635 static void compact_page_work(struct work_struct *w)
 636 {
 637         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
 638                                                 work);
 639
 640         do_compact_page(zhdr, false);
 641 }
 642
 643 /* returns _locked_ z3fold page header or NULL */
 644 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
 645                                                 size_t size, bool can_sleep)
 646 {
 647         struct z3fold_header *zhdr = NULL;
 648         struct page *page;
 649         struct list_head *unbuddied;
 650         int chunks = size_to_chunks(size), i;
 651
 652 lookup:
 653         /* First, try to find an unbuddied z3fold page. */
 654         unbuddied = get_cpu_ptr(pool->unbuddied);
 655         for_each_unbuddied_list(i, chunks) {
 656                 struct list_head *l = &unbuddied[i];
 657
 658                 zhdr = list_first_entry_or_null(READ_ONCE(l),
 659                                         struct z3fold_header, buddy);
 660
 661                 if (!zhdr)
 662                         continue;
 663
 664                 /* Re-check under lock. */
 665                 spin_lock(&pool->lock);
 666                 l = &unbuddied[i];
 667                 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
 668                                                 struct z3fold_header, buddy)) ||
 669                     !z3fold_page_trylock(zhdr)) {
 670                         spin_unlock(&pool->lock);
 671                         zhdr = NULL;
 672                         put_cpu_ptr(pool->unbuddied);
 673                         if (can_sleep)
 674                                 cond_resched();
 675                         goto lookup;
 676                 }
 677                 list_del_init(&zhdr->buddy);
 678                 zhdr->cpu = -1;
 679                 spin_unlock(&pool->lock);
 680
 681                 page = virt_to_page(zhdr);
 682                 if (test_bit(NEEDS_COMPACTING, &page->private)) {
 683                         z3fold_page_unlock(zhdr);
 684                         zhdr = NULL;
 685                         put_cpu_ptr(pool->unbuddied);
 686                         if (can_sleep)
 687                                 cond_resched();
 688                         goto lookup;
 689                 }
 690
 691                 /*
 692                  * this page could not be removed from its unbuddied
 693                  * list while pool lock was held, and then we've taken
 694                  * page lock so kref_put could not be called before
 695                  * we got here, so it's safe to just call kref_get()
 696                  */
 697                 kref_get(&zhdr->refcount);
 698                 break;
 699         }
 700         put_cpu_ptr(pool->unbuddied);
 701
 702         if (!zhdr) {
 703                 int cpu;
 704
 705                 /* look for _exact_ match on other cpus' lists */
 706                 for_each_online_cpu(cpu) {
 707                         struct list_head *l;
 708
 709                         unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
 710                         spin_lock(&pool->lock);
 711                         l = &unbuddied[chunks];
 712
 713                         zhdr = list_first_entry_or_null(READ_ONCE(l),
 714                                                 struct z3fold_header, buddy);
 715
 716                         if (!zhdr || !z3fold_page_trylock(zhdr)) {
 717                                 spin_unlock(&pool->lock);
 718                                 zhdr = NULL;
 719                                 continue;
 720                         }
 721                         list_del_init(&zhdr->buddy);
 722                         zhdr->cpu = -1;
 723                         spin_unlock(&pool->lock);
 724
 725                         page = virt_to_page(zhdr);
 726                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
 727                                 z3fold_page_unlock(zhdr);
 728                                 zhdr = NULL;
 729                                 if (can_sleep)
 730                                         cond_resched();
 731                                 continue;
 732                         }
 733                         kref_get(&zhdr->refcount);
 734                         break;
 735                 }
 736         }
 737
 738         return zhdr;
 739 }
 740
 741 /*
 742  * API Functions
 743  */
 744
 745 /**
 746  * z3fold_create_pool() - create a new z3fold pool
 747  * @name:       pool name
 748  * @gfp:        gfp flags when allocating the z3fold pool structure
 749  * @ops:        user-defined operations for the z3fold pool
 750  *
 751  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
 752  * failed.
 753  */
 754 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
 755                 const struct z3fold_ops *ops)
 756 {
 757         struct z3fold_pool *pool = NULL;
 758         int i, cpu;
 759
 760         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
 761         if (!pool)
 762                 goto out;
 763         pool->c_handle = kmem_cache_create("z3fold_handle",
 764                                 sizeof(struct z3fold_buddy_slots),
 765                                 SLOTS_ALIGN, 0, NULL);
 766         if (!pool->c_handle)
 767                 goto out_c;
 768         spin_lock_init(&pool->lock);
 769         spin_lock_init(&pool->stale_lock);
 770         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
 771         if (!pool->unbuddied)
 772                 goto out_pool;
 773         for_each_possible_cpu(cpu) {
 774                 struct list_head *unbuddied =
 775                                 per_cpu_ptr(pool->unbuddied, cpu);
 776                 for_each_unbuddied_list(i, 0)
 777                         INIT_LIST_HEAD(&unbuddied[i]);
 778         }
 779         INIT_LIST_HEAD(&pool->lru);
 780         INIT_LIST_HEAD(&pool->stale);
 781         atomic64_set(&pool->pages_nr, 0);
 782         pool->name = name;
 783         pool->compact_wq = create_singlethread_workqueue(pool->name);
 784         if (!pool->compact_wq)
 785                 goto out_unbuddied;
 786         pool->release_wq = create_singlethread_workqueue(pool->name);
 787         if (!pool->release_wq)
 788                 goto out_wq;
 789         if (z3fold_register_migration(pool))
 790                 goto out_rwq;
 791         INIT_WORK(&pool->work, free_pages_work);
 792         pool->ops = ops;
 793         return pool;
 794
 795 out_rwq:
 796         destroy_workqueue(pool->release_wq);
 797 out_wq:
 798         destroy_workqueue(pool->compact_wq);
 799 out_unbuddied:
 800         free_percpu(pool->unbuddied);
 801 out_pool:
 802         kmem_cache_destroy(pool->c_handle);
 803 out_c:
 804         kfree(pool);
 805 out:
 806         return NULL;
 807 }
 808
 809 /**
 810  * z3fold_destroy_pool() - destroys an existing z3fold pool
 811  * @pool:       the z3fold pool to be destroyed
 812  *
 813  * The pool should be emptied before this function is called.
 814  */
 815 static void z3fold_destroy_pool(struct z3fold_pool *pool)
 816 {
 817         kmem_cache_destroy(pool->c_handle);
 818         z3fold_unregister_migration(pool);
 819         destroy_workqueue(pool->release_wq);
 820         destroy_workqueue(pool->compact_wq);
 821         kfree(pool);
 822 }
 823
 824 /**
 825  * z3fold_alloc() - allocates a region of a given size
 826  * @pool:       z3fold pool from which to allocate
 827  * @size:       size in bytes of the desired allocation
 828  * @gfp:        gfp flags used if the pool needs to grow
 829  * @handle:     handle of the new allocation
 830  *
 831  * This function will attempt to find a free region in the pool large enough to
 832  * satisfy the allocation request.  A search of the unbuddied lists is
 833  * performed first. If no suitable free region is found, then a new page is
 834  * allocated and added to the pool to satisfy the request.
 835  *
 836  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
 837  * as z3fold pool pages.
 838  *
 839  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
 840  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
 841  * a new page.
 842  */
 843 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 844                         unsigned long *handle)
 845 {
 846         int chunks = size_to_chunks(size);
 847         struct z3fold_header *zhdr = NULL;
 848         struct page *page = NULL;
 849         enum buddy bud;
 850         bool can_sleep = gfpflags_allow_blocking(gfp);
 851
 852         if (!size || (gfp & __GFP_HIGHMEM))
 853                 return -EINVAL;
 854
 855         if (size > PAGE_SIZE)
 856                 return -ENOSPC;
 857
 858         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
 859                 bud = HEADLESS;
 860         else {
 861 retry:
 862                 zhdr = __z3fold_alloc(pool, size, can_sleep);
 863                 if (zhdr) {
 864                         if (zhdr->first_chunks == 0) {
 865                                 if (zhdr->middle_chunks != 0 &&
 866                                     chunks >= zhdr->start_middle)
 867                                         bud = LAST;
 868                                 else
 869                                         bud = FIRST;
 870                         } else if (zhdr->last_chunks == 0)
 871                                 bud = LAST;
 872                         else if (zhdr->middle_chunks == 0)
 873                                 bud = MIDDLE;
 874                         else {
 875                                 if (kref_put(&zhdr->refcount,
 876                                              release_z3fold_page_locked))
 877                                         atomic64_dec(&pool->pages_nr);
 878                                 else
 879                                         z3fold_page_unlock(zhdr);
 880                                 pr_err("No free chunks in unbuddied\n");
 881                                 WARN_ON(1);
 882                                 goto retry;
 883                         }
 884                         page = virt_to_page(zhdr);
 885                         goto found;
 886                 }
 887                 bud = FIRST;
 888         }
 889
 890         page = NULL;
 891         if (can_sleep) {
 892                 spin_lock(&pool->stale_lock);
 893                 zhdr = list_first_entry_or_null(&pool->stale,
 894                                                 struct z3fold_header, buddy);
 895                 /*
 896                  * Before allocating a page, let's see if we can take one from
 897                  * the stale pages list. cancel_work_sync() can sleep so we
 898                  * limit this case to the contexts where we can sleep
 899                  */
 900                 if (zhdr) {
 901                         list_del(&zhdr->buddy);
 902                         spin_unlock(&pool->stale_lock);
 903                         cancel_work_sync(&zhdr->work);
 904                         page = virt_to_page(zhdr);
 905                 } else {
 906                         spin_unlock(&pool->stale_lock);
 907                 }
 908         }
 909         if (!page)
 910                 page = alloc_page(gfp);
 911
 912         if (!page)
 913                 return -ENOMEM;
 914
 915         zhdr = init_z3fold_page(page, pool);
 916         if (!zhdr) {
 917                 __free_page(page);
 918                 return -ENOMEM;
 919         }
 920         atomic64_inc(&pool->pages_nr);
 921
 922         if (bud == HEADLESS) {
 923                 set_bit(PAGE_HEADLESS, &page->private);
 924                 goto headless;
 925         }
 926         __SetPageMovable(page, pool->inode->i_mapping);
 927         z3fold_page_lock(zhdr);
 928
 929 found:
 930         if (bud == FIRST)
 931                 zhdr->first_chunks = chunks;
 932         else if (bud == LAST)
 933                 zhdr->last_chunks = chunks;
 934         else {
 935                 zhdr->middle_chunks = chunks;
 936                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 937         }
 938         add_to_unbuddied(pool, zhdr);
 939
 940 headless:
 941         spin_lock(&pool->lock);
 942         /* Add/move z3fold page to beginning of LRU */
 943         if (!list_empty(&page->lru))
 944                 list_del(&page->lru);
 945
 946         list_add(&page->lru, &pool->lru);
 947
 948         *handle = encode_handle(zhdr, bud);
 949         spin_unlock(&pool->lock);
 950         if (bud != HEADLESS)
 951                 z3fold_page_unlock(zhdr);
 952
 953         return 0;
 954 }
 955
 956 /**
 957  * z3fold_free() - frees the allocation associated with the given handle
 958  * @pool:       pool in which the allocation resided
 959  * @handle:     handle associated with the allocation returned by z3fold_alloc()
 960  *
 961  * In the case that the z3fold page in which the allocation resides is under
 962  * reclaim, as indicated by the PG_reclaim flag being set, this function
 963  * only sets the first|last_chunks to 0.  The page is actually freed
 964  * once both buddies are evicted (see z3fold_reclaim_page() below).
 965  */
 966 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 967 {
 968         struct z3fold_header *zhdr;
 969         struct page *page;
 970         enum buddy bud;
 971
 972         zhdr = handle_to_z3fold_header(handle);
 973         page = virt_to_page(zhdr);
 974
 975         if (test_bit(PAGE_HEADLESS, &page->private)) {
 976                 /* if a headless page is under reclaim, just leave.
 977                  * NB: we use test_and_set_bit for a reason: if the bit
 978                  * has not been set before, we release this page
 979                  * immediately so we don't care about its value any more.
 980                  */
 981                 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
 982                         spin_lock(&pool->lock);
 983                         list_del(&page->lru);
 984                         spin_unlock(&pool->lock);
 985                         free_z3fold_page(page, true);
 986                         atomic64_dec(&pool->pages_nr);
 987                 }
 988                 return;
 989         }
 990
 991         /* Non-headless case */
 992         z3fold_page_lock(zhdr);
 993         bud = handle_to_buddy(handle);
 994
 995         switch (bud) {
 996         case FIRST:
 997                 zhdr->first_chunks = 0;
 998                 break;
 999         case MIDDLE:
1000                 zhdr->middle_chunks = 0;
1001                 break;
1002         case LAST:
1003                 zhdr->last_chunks = 0;
1004                 break;
1005         default:
1006                 pr_err("%s: unknown bud %d\n", __func__, bud);
1007                 WARN_ON(1);
1008                 z3fold_page_unlock(zhdr);
1009                 return;
1010         }
1011
1012         free_handle(handle);
1013         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1014                 atomic64_dec(&pool->pages_nr);
1015                 return;
1016         }
1017         if (test_bit(PAGE_CLAIMED, &page->private)) {
1018                 z3fold_page_unlock(zhdr);
1019                 return;
1020         }
1021         if (unlikely(PageIsolated(page)) ||
1022             test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1023                 z3fold_page_unlock(zhdr);
1024                 return;
1025         }
1026         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1027                 spin_lock(&pool->lock);
1028                 list_del_init(&zhdr->buddy);
1029                 spin_unlock(&pool->lock);
1030                 zhdr->cpu = -1;
1031                 kref_get(&zhdr->refcount);
1032                 do_compact_page(zhdr, true);
1033                 return;
1034         }
1035         kref_get(&zhdr->refcount);
1036         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1037         z3fold_page_unlock(zhdr);
1038 }
1039
1040 /**
1041  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1042  * @pool:       pool from which a page will attempt to be evicted
1043  * @retries:    number of pages on the LRU list for which eviction will
1044  *              be attempted before failing
1045  *
1046  * z3fold reclaim is different from normal system reclaim in that it is done
1047  * from the bottom, up. This is because only the bottom layer, z3fold, has
1048  * information on how the allocations are organized within each z3fold page.
1049  * This has the potential to create interesting locking situations between
1050  * z3fold and the user, however.
1051  *
1052  * To avoid these, this is how z3fold_reclaim_page() should be called:
1053  *
1054  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1055  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1056  * call the user-defined eviction handler with the pool and handle as
1057  * arguments.
1058  *
1059  * If the handle can not be evicted, the eviction handler should return
1060  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1061  * appropriate list and try the next z3fold page on the LRU up to
1062  * a user defined number of retries.
1063  *
1064  * If the handle is successfully evicted, the eviction handler should
1065  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1066  * contains logic to delay freeing the page if the page is under reclaim,
1067  * as indicated by the setting of the PG_reclaim flag on the underlying page.
1068  *
1069  * If all buddies in the z3fold page are successfully evicted, then the
1070  * z3fold page can be freed.
1071  *
1072  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1073  * no pages to evict or an eviction handler is not registered, -EAGAIN if
1074  * the retry limit was hit.
1075  */
1076 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1077 {
1078         int i, ret = 0;
1079         struct z3fold_header *zhdr = NULL;
1080         struct page *page = NULL;
1081         struct list_head *pos;
1082         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1083
1084         spin_lock(&pool->lock);
1085         if (!pool->ops || !pool->ops->evict || retries == 0) {
1086                 spin_unlock(&pool->lock);
1087                 return -EINVAL;
1088         }
1089         for (i = 0; i < retries; i++) {
1090                 if (list_empty(&pool->lru)) {
1091                         spin_unlock(&pool->lock);
1092                         return -EINVAL;
1093                 }
1094                 list_for_each_prev(pos, &pool->lru) {
1095                         page = list_entry(pos, struct page, lru);
1096
1097                         /* this bit could have been set by free, in which case
1098                          * we pass over to the next page in the pool.
1099                          */
1100                         if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1101                                 continue;
1102
1103                         if (unlikely(PageIsolated(page)))
1104                                 continue;
1105                         if (test_bit(PAGE_HEADLESS, &page->private))
1106                                 break;
1107
1108                         zhdr = page_address(page);
1109                         if (!z3fold_page_trylock(zhdr)) {
1110                                 zhdr = NULL;
1111                                 continue; /* can't evict at this point */
1112                         }
1113                         kref_get(&zhdr->refcount);
1114                         list_del_init(&zhdr->buddy);
1115                         zhdr->cpu = -1;
1116                         break;
1117                 }
1118
1119                 if (!zhdr)
1120                         break;
1121
1122                 list_del_init(&page->lru);
1123                 spin_unlock(&pool->lock);
1124
1125                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1126                         /*
1127                          * We need encode the handles before unlocking, since
1128                          * we can race with free that will set
1129                          * (first|last)_chunks to 0
1130                          */
1131                         first_handle = 0;
1132                         last_handle = 0;
1133                         middle_handle = 0;
1134                         if (zhdr->first_chunks)
1135                                 first_handle = encode_handle(zhdr, FIRST);
1136                         if (zhdr->middle_chunks)
1137                                 middle_handle = encode_handle(zhdr, MIDDLE);
1138                         if (zhdr->last_chunks)
1139                                 last_handle = encode_handle(zhdr, LAST);
1140                         /*
1141                          * it's safe to unlock here because we hold a
1142                          * reference to this page
1143                          */
1144                         z3fold_page_unlock(zhdr);
1145                 } else {
1146                         first_handle = encode_handle(zhdr, HEADLESS);
1147                         last_handle = middle_handle = 0;
1148                 }
1149
1150                 /* Issue the eviction callback(s) */
1151                 if (middle_handle) {
1152                         ret = pool->ops->evict(pool, middle_handle);
1153                         if (ret)
1154                                 goto next;
1155                 }
1156                 if (first_handle) {
1157                         ret = pool->ops->evict(pool, first_handle);
1158                         if (ret)
1159                                 goto next;
1160                 }
1161                 if (last_handle) {
1162                         ret = pool->ops->evict(pool, last_handle);
1163                         if (ret)
1164                                 goto next;
1165                 }
1166 next:
1167                 if (test_bit(PAGE_HEADLESS, &page->private)) {
1168                         if (ret == 0) {
1169                                 free_z3fold_page(page, true);
1170                                 atomic64_dec(&pool->pages_nr);
1171                                 return 0;
1172                         }
1173                         spin_lock(&pool->lock);
1174                         list_add(&page->lru, &pool->lru);
1175                         spin_unlock(&pool->lock);
1176                 } else {
1177                         z3fold_page_lock(zhdr);
1178                         clear_bit(PAGE_CLAIMED, &page->private);
1179                         if (kref_put(&zhdr->refcount,
1180                                         release_z3fold_page_locked)) {
1181                                 atomic64_dec(&pool->pages_nr);
1182                                 return 0;
1183                         }
1184                         /*
1185                          * if we are here, the page is still not completely
1186                          * free. Take the global pool lock then to be able
1187                          * to add it back to the lru list
1188                          */
1189                         spin_lock(&pool->lock);
1190                         list_add(&page->lru, &pool->lru);
1191                         spin_unlock(&pool->lock);
1192                         z3fold_page_unlock(zhdr);
1193                 }
1194
1195                 /* We started off locked to we need to lock the pool back */
1196                 spin_lock(&pool->lock);
1197         }
1198         spin_unlock(&pool->lock);
1199         return -EAGAIN;
1200 }
1201
1202 /**
1203  * z3fold_map() - maps the allocation associated with the given handle
1204  * @pool:       pool in which the allocation resides
1205  * @handle:     handle associated with the allocation to be mapped
1206  *
1207  * Extracts the buddy number from handle and constructs the pointer to the
1208  * correct starting chunk within the page.
1209  *
1210  * Returns: a pointer to the mapped allocation
1211  */
1212 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1213 {
1214         struct z3fold_header *zhdr;
1215         struct page *page;
1216         void *addr;
1217         enum buddy buddy;
1218
1219         zhdr = handle_to_z3fold_header(handle);
1220         addr = zhdr;
1221         page = virt_to_page(zhdr);
1222
1223         if (test_bit(PAGE_HEADLESS, &page->private))
1224                 goto out;
1225
1226         z3fold_page_lock(zhdr);
1227         buddy = handle_to_buddy(handle);
1228         switch (buddy) {
1229         case FIRST:
1230                 addr += ZHDR_SIZE_ALIGNED;
1231                 break;
1232         case MIDDLE:
1233                 addr += zhdr->start_middle << CHUNK_SHIFT;
1234                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1235                 break;
1236         case LAST:
1237                 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1238                 break;
1239         default:
1240                 pr_err("unknown buddy id %d\n", buddy);
1241                 WARN_ON(1);
1242                 addr = NULL;
1243                 break;
1244         }
1245
1246         if (addr)
1247                 zhdr->mapped_count++;
1248         z3fold_page_unlock(zhdr);
1249 out:
1250         return addr;
1251 }
1252
1253 /**
1254  * z3fold_unmap() - unmaps the allocation associated with the given handle
1255  * @pool:       pool in which the allocation resides
1256  * @handle:     handle associated with the allocation to be unmapped
1257  */
1258 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1259 {
1260         struct z3fold_header *zhdr;
1261         struct page *page;
1262         enum buddy buddy;
1263
1264         zhdr = handle_to_z3fold_header(handle);
1265         page = virt_to_page(zhdr);
1266
1267         if (test_bit(PAGE_HEADLESS, &page->private))
1268                 return;
1269
1270         z3fold_page_lock(zhdr);
1271         buddy = handle_to_buddy(handle);
1272         if (buddy == MIDDLE)
1273                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1274         zhdr->mapped_count--;
1275         z3fold_page_unlock(zhdr);
1276 }
1277
1278 /**
1279  * z3fold_get_pool_size() - gets the z3fold pool size in pages
1280  * @pool:       pool whose size is being queried
1281  *
1282  * Returns: size in pages of the given pool.
1283  */
1284 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1285 {
1286         return atomic64_read(&pool->pages_nr);
1287 }
1288
1289 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1290 {
1291         struct z3fold_header *zhdr;
1292         struct z3fold_pool *pool;
1293
1294         VM_BUG_ON_PAGE(!PageMovable(page), page);
1295         VM_BUG_ON_PAGE(PageIsolated(page), page);
1296
1297         if (test_bit(PAGE_HEADLESS, &page->private))
1298                 return false;
1299
1300         zhdr = page_address(page);
1301         z3fold_page_lock(zhdr);
1302         if (test_bit(NEEDS_COMPACTING, &page->private) ||
1303             test_bit(PAGE_STALE, &page->private))
1304                 goto out;
1305
1306         pool = zhdr_to_pool(zhdr);
1307
1308         if (zhdr->mapped_count == 0) {
1309                 kref_get(&zhdr->refcount);
1310                 if (!list_empty(&zhdr->buddy))
1311                         list_del_init(&zhdr->buddy);
1312                 spin_lock(&pool->lock);
1313                 if (!list_empty(&page->lru))
1314                         list_del(&page->lru);
1315                 spin_unlock(&pool->lock);
1316                 z3fold_page_unlock(zhdr);
1317                 return true;
1318         }
1319 out:
1320         z3fold_page_unlock(zhdr);
1321         return false;
1322 }
1323
1324 static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1325                                struct page *page, enum migrate_mode mode)
1326 {
1327         struct z3fold_header *zhdr, *new_zhdr;
1328         struct z3fold_pool *pool;
1329         struct address_space *new_mapping;
1330
1331         VM_BUG_ON_PAGE(!PageMovable(page), page);
1332         VM_BUG_ON_PAGE(!PageIsolated(page), page);
1333
1334         zhdr = page_address(page);
1335         pool = zhdr_to_pool(zhdr);
1336
1337         if (!trylock_page(page))
1338                 return -EAGAIN;
1339
1340         if (!z3fold_page_trylock(zhdr)) {
1341                 unlock_page(page);
1342                 return -EAGAIN;
1343         }
1344         if (zhdr->mapped_count != 0) {
1345                 z3fold_page_unlock(zhdr);
1346                 unlock_page(page);
1347                 return -EBUSY;
1348         }
1349         new_zhdr = page_address(newpage);
1350         memcpy(new_zhdr, zhdr, PAGE_SIZE);
1351         newpage->private = page->private;
1352         page->private = 0;
1353         z3fold_page_unlock(zhdr);
1354         spin_lock_init(&new_zhdr->page_lock);
1355         new_mapping = page_mapping(page);
1356         __ClearPageMovable(page);
1357         ClearPagePrivate(page);
1358
1359         get_page(newpage);
1360         z3fold_page_lock(new_zhdr);
1361         if (new_zhdr->first_chunks)
1362                 encode_handle(new_zhdr, FIRST);
1363         if (new_zhdr->last_chunks)
1364                 encode_handle(new_zhdr, LAST);
1365         if (new_zhdr->middle_chunks)
1366                 encode_handle(new_zhdr, MIDDLE);
1367         set_bit(NEEDS_COMPACTING, &newpage->private);
1368         new_zhdr->cpu = smp_processor_id();
1369         spin_lock(&pool->lock);
1370         list_add(&newpage->lru, &pool->lru);
1371         spin_unlock(&pool->lock);
1372         __SetPageMovable(newpage, new_mapping);
1373         z3fold_page_unlock(new_zhdr);
1374
1375         queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1376
1377         page_mapcount_reset(page);
1378         unlock_page(page);
1379         put_page(page);
1380         return 0;
1381 }
1382
1383 static void z3fold_page_putback(struct page *page)
1384 {
1385         struct z3fold_header *zhdr;
1386         struct z3fold_pool *pool;
1387
1388         zhdr = page_address(page);
1389         pool = zhdr_to_pool(zhdr);
1390
1391         z3fold_page_lock(zhdr);
1392         if (!list_empty(&zhdr->buddy))
1393                 list_del_init(&zhdr->buddy);
1394         INIT_LIST_HEAD(&page->lru);
1395         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1396                 atomic64_dec(&pool->pages_nr);
1397                 return;
1398         }
1399         spin_lock(&pool->lock);
1400         list_add(&page->lru, &pool->lru);
1401         spin_unlock(&pool->lock);
1402         z3fold_page_unlock(zhdr);
1403 }
1404
1405 static const struct address_space_operations z3fold_aops = {
1406         .isolate_page = z3fold_page_isolate,
1407         .migratepage = z3fold_page_migrate,
1408         .putback_page = z3fold_page_putback,
1409 };
1410
1411 /*****************
1412  * zpool
1413  ****************/
1414
1415 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1416 {
1417         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1418                 return pool->zpool_ops->evict(pool->zpool, handle);
1419         else
1420                 return -ENOENT;
1421 }
1422
1423 static const struct z3fold_ops z3fold_zpool_ops = {
1424         .evict =        z3fold_zpool_evict
1425 };
1426
1427 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1428                                const struct zpool_ops *zpool_ops,
1429                                struct zpool *zpool)
1430 {
1431         struct z3fold_pool *pool;
1432
1433         pool = z3fold_create_pool(name, gfp,
1434                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1435         if (pool) {
1436                 pool->zpool = zpool;
1437                 pool->zpool_ops = zpool_ops;
1438         }
1439         return pool;
1440 }
1441
1442 static void z3fold_zpool_destroy(void *pool)
1443 {
1444         z3fold_destroy_pool(pool);
1445 }
1446
1447 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1448                         unsigned long *handle)
1449 {
1450         return z3fold_alloc(pool, size, gfp, handle);
1451 }
1452 static void z3fold_zpool_free(void *pool, unsigned long handle)
1453 {
1454         z3fold_free(pool, handle);
1455 }
1456
1457 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1458                         unsigned int *reclaimed)
1459 {
1460         unsigned int total = 0;
1461         int ret = -EINVAL;
1462
1463         while (total < pages) {
1464                 ret = z3fold_reclaim_page(pool, 8);
1465                 if (ret < 0)
1466                         break;
1467                 total++;
1468         }
1469
1470         if (reclaimed)
1471                 *reclaimed = total;
1472
1473         return ret;
1474 }
1475
1476 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1477                         enum zpool_mapmode mm)
1478 {
1479         return z3fold_map(pool, handle);
1480 }
1481 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1482 {
1483         z3fold_unmap(pool, handle);
1484 }
1485
1486 static u64 z3fold_zpool_total_size(void *pool)
1487 {
1488         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1489 }
1490
1491 static struct zpool_driver z3fold_zpool_driver = {
1492         .type =         "z3fold",
1493         .owner =        THIS_MODULE,
1494         .create =       z3fold_zpool_create,
1495         .destroy =      z3fold_zpool_destroy,
1496         .malloc =       z3fold_zpool_malloc,
1497         .free =         z3fold_zpool_free,
1498         .shrink =       z3fold_zpool_shrink,
1499         .map =          z3fold_zpool_map,
1500         .unmap =        z3fold_zpool_unmap,
1501         .total_size =   z3fold_zpool_total_size,
1502 };
1503
1504 MODULE_ALIAS("zpool-z3fold");
1505
1506 static int __init init_z3fold(void)
1507 {
1508         int ret;
1509
1510         /* Make sure the z3fold header is not larger than the page size */
1511         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1512         ret = z3fold_mount();
1513         if (ret)
1514                 return ret;
1515
1516         zpool_register_driver(&z3fold_zpool_driver);
1517
1518         return 0;
1519 }
1520
1521 static void __exit exit_z3fold(void)
1522 {
1523         z3fold_unmount();
1524         zpool_unregister_driver(&z3fold_zpool_driver);
1525 }
1526
1527 module_init(init_z3fold);
1528 module_exit(exit_z3fold);
1529
1530 MODULE_LICENSE("GPL");
1531 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1532 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");