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                                                         gfp_t gfp)
 195 {
 196         struct z3fold_buddy_slots *slots = kmem_cache_alloc(pool->c_handle,
 197                                                             gfp);
 198
 199         if (slots) {
 200                 memset(slots->slot, 0, sizeof(slots->slot));
 201                 slots->pool = (unsigned long)pool;
 202         }
 203
 204         return slots;
 205 }
 206
 207 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
 208 {
 209         return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
 210 }
 211
 212 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 213 {
 214         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 215 }
 216
 217 static inline void free_handle(unsigned long handle)
 218 {
 219         struct z3fold_buddy_slots *slots;
 220         int i;
 221         bool is_free;
 222
 223         if (handle & (1 << PAGE_HEADLESS))
 224                 return;
 225
 226         WARN_ON(*(unsigned long *)handle == 0);
 227         *(unsigned long *)handle = 0;
 228         slots = handle_to_slots(handle);
 229         is_free = true;
 230         for (i = 0; i <= BUDDY_MASK; i++) {
 231                 if (slots->slot[i]) {
 232                         is_free = false;
 233                         break;
 234                 }
 235         }
 236
 237         if (is_free) {
 238                 struct z3fold_pool *pool = slots_to_pool(slots);
 239
 240                 kmem_cache_free(pool->c_handle, slots);
 241         }
 242 }
 243
 244 static struct dentry *z3fold_do_mount(struct file_system_type *fs_type,
 245                                 int flags, const char *dev_name, void *data)
 246 {
 247         static const struct dentry_operations ops = {
 248                 .d_dname = simple_dname,
 249         };
 250
 251         return mount_pseudo(fs_type, "z3fold:", NULL, &ops, 0x33);
 252 }
 253
 254 static struct file_system_type z3fold_fs = {
 255         .name           = "z3fold",
 256         .mount          = z3fold_do_mount,
 257         .kill_sb        = kill_anon_super,
 258 };
 259
 260 static struct vfsmount *z3fold_mnt;
 261 static int z3fold_mount(void)
 262 {
 263         int ret = 0;
 264
 265         z3fold_mnt = kern_mount(&z3fold_fs);
 266         if (IS_ERR(z3fold_mnt))
 267                 ret = PTR_ERR(z3fold_mnt);
 268
 269         return ret;
 270 }
 271
 272 static void z3fold_unmount(void)
 273 {
 274         kern_unmount(z3fold_mnt);
 275 }
 276
 277 static const struct address_space_operations z3fold_aops;
 278 static int z3fold_register_migration(struct z3fold_pool *pool)
 279 {
 280         pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
 281         if (IS_ERR(pool->inode)) {
 282                 pool->inode = NULL;
 283                 return 1;
 284         }
 285
 286         pool->inode->i_mapping->private_data = pool;
 287         pool->inode->i_mapping->a_ops = &z3fold_aops;
 288         return 0;
 289 }
 290
 291 static void z3fold_unregister_migration(struct z3fold_pool *pool)
 292 {
 293         if (pool->inode)
 294                 iput(pool->inode);
 295  }
 296
 297 /* Initializes the z3fold header of a newly allocated z3fold page */
 298 static struct z3fold_header *init_z3fold_page(struct page *page,
 299                                         struct z3fold_pool *pool, gfp_t gfp)
 300 {
 301         struct z3fold_header *zhdr = page_address(page);
 302         struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp);
 303
 304         if (!slots)
 305                 return NULL;
 306
 307         INIT_LIST_HEAD(&page->lru);
 308         clear_bit(PAGE_HEADLESS, &page->private);
 309         clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
 310         clear_bit(NEEDS_COMPACTING, &page->private);
 311         clear_bit(PAGE_STALE, &page->private);
 312         clear_bit(PAGE_CLAIMED, &page->private);
 313
 314         spin_lock_init(&zhdr->page_lock);
 315         kref_init(&zhdr->refcount);
 316         zhdr->first_chunks = 0;
 317         zhdr->middle_chunks = 0;
 318         zhdr->last_chunks = 0;
 319         zhdr->first_num = 0;
 320         zhdr->start_middle = 0;
 321         zhdr->cpu = -1;
 322         zhdr->slots = slots;
 323         INIT_LIST_HEAD(&zhdr->buddy);
 324         INIT_WORK(&zhdr->work, compact_page_work);
 325         return zhdr;
 326 }
 327
 328 /* Resets the struct page fields and frees the page */
 329 static void free_z3fold_page(struct page *page, bool headless)
 330 {
 331         if (!headless) {
 332                 lock_page(page);
 333                 __ClearPageMovable(page);
 334                 unlock_page(page);
 335         }
 336         ClearPagePrivate(page);
 337         __free_page(page);
 338 }
 339
 340 /* Lock a z3fold page */
 341 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 342 {
 343         spin_lock(&zhdr->page_lock);
 344 }
 345
 346 /* Try to lock a z3fold page */
 347 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 348 {
 349         return spin_trylock(&zhdr->page_lock);
 350 }
 351
 352 /* Unlock a z3fold page */
 353 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
 354 {
 355         spin_unlock(&zhdr->page_lock);
 356 }
 357
 358 /* Helper function to build the index */
 359 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 360 {
 361         return (bud + zhdr->first_num) & BUDDY_MASK;
 362 }
 363
 364 /*
 365  * Encodes the handle of a particular buddy within a z3fold page
 366  * Pool lock should be held as this function accesses first_num
 367  */
 368 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 369 {
 370         struct z3fold_buddy_slots *slots;
 371         unsigned long h = (unsigned long)zhdr;
 372         int idx = 0;
 373
 374         /*
 375          * For a headless page, its handle is its pointer with the extra
 376          * PAGE_HEADLESS bit set
 377          */
 378         if (bud == HEADLESS)
 379                 return h | (1 << PAGE_HEADLESS);
 380
 381         /* otherwise, return pointer to encoded handle */
 382         idx = __idx(zhdr, bud);
 383         h += idx;
 384         if (bud == LAST)
 385                 h |= (zhdr->last_chunks << BUDDY_SHIFT);
 386
 387         slots = zhdr->slots;
 388         slots->slot[idx] = h;
 389         return (unsigned long)&slots->slot[idx];
 390 }
 391
 392 /* Returns the z3fold page where a given handle is stored */
 393 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
 394 {
 395         unsigned long addr = h;
 396
 397         if (!(addr & (1 << PAGE_HEADLESS)))
 398                 addr = *(unsigned long *)h;
 399
 400         return (struct z3fold_header *)(addr & PAGE_MASK);
 401 }
 402
 403 /* only for LAST bud, returns zero otherwise */
 404 static unsigned short handle_to_chunks(unsigned long handle)
 405 {
 406         unsigned long addr = *(unsigned long *)handle;
 407
 408         return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 409 }
 410
 411 /*
 412  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
 413  *  but that doesn't matter. because the masking will result in the
 414  *  correct buddy number.
 415  */
 416 static enum buddy handle_to_buddy(unsigned long handle)
 417 {
 418         struct z3fold_header *zhdr;
 419         unsigned long addr;
 420
 421         WARN_ON(handle & (1 << PAGE_HEADLESS));
 422         addr = *(unsigned long *)handle;
 423         zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 424         return (addr - zhdr->first_num) & BUDDY_MASK;
 425 }
 426
 427 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
 428 {
 429         return slots_to_pool(zhdr->slots);
 430 }
 431
 432 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 433 {
 434         struct page *page = virt_to_page(zhdr);
 435         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 436
 437         WARN_ON(!list_empty(&zhdr->buddy));
 438         set_bit(PAGE_STALE, &page->private);
 439         clear_bit(NEEDS_COMPACTING, &page->private);
 440         spin_lock(&pool->lock);
 441         if (!list_empty(&page->lru))
 442                 list_del_init(&page->lru);
 443         spin_unlock(&pool->lock);
 444         if (locked)
 445                 z3fold_page_unlock(zhdr);
 446         spin_lock(&pool->stale_lock);
 447         list_add(&zhdr->buddy, &pool->stale);
 448         queue_work(pool->release_wq, &pool->work);
 449         spin_unlock(&pool->stale_lock);
 450 }
 451
 452 static void __attribute__((__unused__))
 453                         release_z3fold_page(struct kref *ref)
 454 {
 455         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 456                                                 refcount);
 457         __release_z3fold_page(zhdr, false);
 458 }
 459
 460 static void release_z3fold_page_locked(struct kref *ref)
 461 {
 462         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 463                                                 refcount);
 464         WARN_ON(z3fold_page_trylock(zhdr));
 465         __release_z3fold_page(zhdr, true);
 466 }
 467
 468 static void release_z3fold_page_locked_list(struct kref *ref)
 469 {
 470         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 471                                                refcount);
 472         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 473         spin_lock(&pool->lock);
 474         list_del_init(&zhdr->buddy);
 475         spin_unlock(&pool->lock);
 476
 477         WARN_ON(z3fold_page_trylock(zhdr));
 478         __release_z3fold_page(zhdr, true);
 479 }
 480
 481 static void free_pages_work(struct work_struct *w)
 482 {
 483         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
 484
 485         spin_lock(&pool->stale_lock);
 486         while (!list_empty(&pool->stale)) {
 487                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
 488                                                 struct z3fold_header, buddy);
 489                 struct page *page = virt_to_page(zhdr);
 490
 491                 list_del(&zhdr->buddy);
 492                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
 493                         continue;
 494                 spin_unlock(&pool->stale_lock);
 495                 cancel_work_sync(&zhdr->work);
 496                 free_z3fold_page(page, false);
 497                 cond_resched();
 498                 spin_lock(&pool->stale_lock);
 499         }
 500         spin_unlock(&pool->stale_lock);
 501 }
 502
 503 /*
 504  * Returns the number of free chunks in a z3fold page.
 505  * NB: can't be used with HEADLESS pages.
 506  */
 507 static int num_free_chunks(struct z3fold_header *zhdr)
 508 {
 509         int nfree;
 510         /*
 511          * If there is a middle object, pick up the bigger free space
 512          * either before or after it. Otherwise just subtract the number
 513          * of chunks occupied by the first and the last objects.
 514          */
 515         if (zhdr->middle_chunks != 0) {
 516                 int nfree_before = zhdr->first_chunks ?
 517                         0 : zhdr->start_middle - ZHDR_CHUNKS;
 518                 int nfree_after = zhdr->last_chunks ?
 519                         0 : TOTAL_CHUNKS -
 520                                 (zhdr->start_middle + zhdr->middle_chunks);
 521                 nfree = max(nfree_before, nfree_after);
 522         } else
 523                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 524         return nfree;
 525 }
 526
 527 /* Add to the appropriate unbuddied list */
 528 static inline void add_to_unbuddied(struct z3fold_pool *pool,
 529                                 struct z3fold_header *zhdr)
 530 {
 531         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
 532                         zhdr->middle_chunks == 0) {
 533                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
 534
 535                 int freechunks = num_free_chunks(zhdr);
 536                 spin_lock(&pool->lock);
 537                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
 538                 spin_unlock(&pool->lock);
 539                 zhdr->cpu = smp_processor_id();
 540                 put_cpu_ptr(pool->unbuddied);
 541         }
 542 }
 543
 544 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 545                                 unsigned short dst_chunk)
 546 {
 547         void *beg = zhdr;
 548         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
 549                        beg + (zhdr->start_middle << CHUNK_SHIFT),
 550                        zhdr->middle_chunks << CHUNK_SHIFT);
 551 }
 552
 553 #define BIG_CHUNK_GAP   3
 554 /* Has to be called with lock held */
 555 static int z3fold_compact_page(struct z3fold_header *zhdr)
 556 {
 557         struct page *page = virt_to_page(zhdr);
 558
 559         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
 560                 return 0; /* can't move middle chunk, it's used */
 561
 562         if (unlikely(PageIsolated(page)))
 563                 return 0;
 564
 565         if (zhdr->middle_chunks == 0)
 566                 return 0; /* nothing to compact */
 567
 568         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 569                 /* move to the beginning */
 570                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
 571                 zhdr->first_chunks = zhdr->middle_chunks;
 572                 zhdr->middle_chunks = 0;
 573                 zhdr->start_middle = 0;
 574                 zhdr->first_num++;
 575                 return 1;
 576         }
 577
 578         /*
 579          * moving data is expensive, so let's only do that if
 580          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
 581          */
 582         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
 583             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
 584                         BIG_CHUNK_GAP) {
 585                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
 586                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 587                 return 1;
 588         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
 589                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
 590                                         + zhdr->middle_chunks) >=
 591                         BIG_CHUNK_GAP) {
 592                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
 593                         zhdr->middle_chunks;
 594                 mchunk_memmove(zhdr, new_start);
 595                 zhdr->start_middle = new_start;
 596                 return 1;
 597         }
 598
 599         return 0;
 600 }
 601
 602 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 603 {
 604         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 605         struct page *page;
 606
 607         page = virt_to_page(zhdr);
 608         if (locked)
 609                 WARN_ON(z3fold_page_trylock(zhdr));
 610         else
 611                 z3fold_page_lock(zhdr);
 612         if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
 613                 z3fold_page_unlock(zhdr);
 614                 return;
 615         }
 616         spin_lock(&pool->lock);
 617         list_del_init(&zhdr->buddy);
 618         spin_unlock(&pool->lock);
 619
 620         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 621                 atomic64_dec(&pool->pages_nr);
 622                 return;
 623         }
 624
 625         if (unlikely(PageIsolated(page) ||
 626                      test_bit(PAGE_STALE, &page->private))) {
 627                 z3fold_page_unlock(zhdr);
 628                 return;
 629         }
 630
 631         z3fold_compact_page(zhdr);
 632         add_to_unbuddied(pool, zhdr);
 633         z3fold_page_unlock(zhdr);
 634 }
 635
 636 static void compact_page_work(struct work_struct *w)
 637 {
 638         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
 639                                                 work);
 640
 641         do_compact_page(zhdr, false);
 642 }
 643
 644 /* returns _locked_ z3fold page header or NULL */
 645 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
 646                                                 size_t size, bool can_sleep)
 647 {
 648         struct z3fold_header *zhdr = NULL;
 649         struct page *page;
 650         struct list_head *unbuddied;
 651         int chunks = size_to_chunks(size), i;
 652
 653 lookup:
 654         /* First, try to find an unbuddied z3fold page. */
 655         unbuddied = get_cpu_ptr(pool->unbuddied);
 656         for_each_unbuddied_list(i, chunks) {
 657                 struct list_head *l = &unbuddied[i];
 658
 659                 zhdr = list_first_entry_or_null(READ_ONCE(l),
 660                                         struct z3fold_header, buddy);
 661
 662                 if (!zhdr)
 663                         continue;
 664
 665                 /* Re-check under lock. */
 666                 spin_lock(&pool->lock);
 667                 l = &unbuddied[i];
 668                 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
 669                                                 struct z3fold_header, buddy)) ||
 670                     !z3fold_page_trylock(zhdr)) {
 671                         spin_unlock(&pool->lock);
 672                         zhdr = NULL;
 673                         put_cpu_ptr(pool->unbuddied);
 674                         if (can_sleep)
 675                                 cond_resched();
 676                         goto lookup;
 677                 }
 678                 list_del_init(&zhdr->buddy);
 679                 zhdr->cpu = -1;
 680                 spin_unlock(&pool->lock);
 681
 682                 page = virt_to_page(zhdr);
 683                 if (test_bit(NEEDS_COMPACTING, &page->private)) {
 684                         z3fold_page_unlock(zhdr);
 685                         zhdr = NULL;
 686                         put_cpu_ptr(pool->unbuddied);
 687                         if (can_sleep)
 688                                 cond_resched();
 689                         goto lookup;
 690                 }
 691
 692                 /*
 693                  * this page could not be removed from its unbuddied
 694                  * list while pool lock was held, and then we've taken
 695                  * page lock so kref_put could not be called before
 696                  * we got here, so it's safe to just call kref_get()
 697                  */
 698                 kref_get(&zhdr->refcount);
 699                 break;
 700         }
 701         put_cpu_ptr(pool->unbuddied);
 702
 703         if (!zhdr) {
 704                 int cpu;
 705
 706                 /* look for _exact_ match on other cpus' lists */
 707                 for_each_online_cpu(cpu) {
 708                         struct list_head *l;
 709
 710                         unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
 711                         spin_lock(&pool->lock);
 712                         l = &unbuddied[chunks];
 713
 714                         zhdr = list_first_entry_or_null(READ_ONCE(l),
 715                                                 struct z3fold_header, buddy);
 716
 717                         if (!zhdr || !z3fold_page_trylock(zhdr)) {
 718                                 spin_unlock(&pool->lock);
 719                                 zhdr = NULL;
 720                                 continue;
 721                         }
 722                         list_del_init(&zhdr->buddy);
 723                         zhdr->cpu = -1;
 724                         spin_unlock(&pool->lock);
 725
 726                         page = virt_to_page(zhdr);
 727                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
 728                                 z3fold_page_unlock(zhdr);
 729                                 zhdr = NULL;
 730                                 if (can_sleep)
 731                                         cond_resched();
 732                                 continue;
 733                         }
 734                         kref_get(&zhdr->refcount);
 735                         break;
 736                 }
 737         }
 738
 739         return zhdr;
 740 }
 741
 742 /*
 743  * API Functions
 744  */
 745
 746 /**
 747  * z3fold_create_pool() - create a new z3fold pool
 748  * @name:       pool name
 749  * @gfp:        gfp flags when allocating the z3fold pool structure
 750  * @ops:        user-defined operations for the z3fold pool
 751  *
 752  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
 753  * failed.
 754  */
 755 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
 756                 const struct z3fold_ops *ops)
 757 {
 758         struct z3fold_pool *pool = NULL;
 759         int i, cpu;
 760
 761         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
 762         if (!pool)
 763                 goto out;
 764         pool->c_handle = kmem_cache_create("z3fold_handle",
 765                                 sizeof(struct z3fold_buddy_slots),
 766                                 SLOTS_ALIGN, 0, NULL);
 767         if (!pool->c_handle)
 768                 goto out_c;
 769         spin_lock_init(&pool->lock);
 770         spin_lock_init(&pool->stale_lock);
 771         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
 772         if (!pool->unbuddied)
 773                 goto out_pool;
 774         for_each_possible_cpu(cpu) {
 775                 struct list_head *unbuddied =
 776                                 per_cpu_ptr(pool->unbuddied, cpu);
 777                 for_each_unbuddied_list(i, 0)
 778                         INIT_LIST_HEAD(&unbuddied[i]);
 779         }
 780         INIT_LIST_HEAD(&pool->lru);
 781         INIT_LIST_HEAD(&pool->stale);
 782         atomic64_set(&pool->pages_nr, 0);
 783         pool->name = name;
 784         pool->compact_wq = create_singlethread_workqueue(pool->name);
 785         if (!pool->compact_wq)
 786                 goto out_unbuddied;
 787         pool->release_wq = create_singlethread_workqueue(pool->name);
 788         if (!pool->release_wq)
 789                 goto out_wq;
 790         if (z3fold_register_migration(pool))
 791                 goto out_rwq;
 792         INIT_WORK(&pool->work, free_pages_work);
 793         pool->ops = ops;
 794         return pool;
 795
 796 out_rwq:
 797         destroy_workqueue(pool->release_wq);
 798 out_wq:
 799         destroy_workqueue(pool->compact_wq);
 800 out_unbuddied:
 801         free_percpu(pool->unbuddied);
 802 out_pool:
 803         kmem_cache_destroy(pool->c_handle);
 804 out_c:
 805         kfree(pool);
 806 out:
 807         return NULL;
 808 }
 809
 810 /**
 811  * z3fold_destroy_pool() - destroys an existing z3fold pool
 812  * @pool:       the z3fold pool to be destroyed
 813  *
 814  * The pool should be emptied before this function is called.
 815  */
 816 static void z3fold_destroy_pool(struct z3fold_pool *pool)
 817 {
 818         kmem_cache_destroy(pool->c_handle);
 819         z3fold_unregister_migration(pool);
 820         destroy_workqueue(pool->release_wq);
 821         destroy_workqueue(pool->compact_wq);
 822         kfree(pool);
 823 }
 824
 825 /**
 826  * z3fold_alloc() - allocates a region of a given size
 827  * @pool:       z3fold pool from which to allocate
 828  * @size:       size in bytes of the desired allocation
 829  * @gfp:        gfp flags used if the pool needs to grow
 830  * @handle:     handle of the new allocation
 831  *
 832  * This function will attempt to find a free region in the pool large enough to
 833  * satisfy the allocation request.  A search of the unbuddied lists is
 834  * performed first. If no suitable free region is found, then a new page is
 835  * allocated and added to the pool to satisfy the request.
 836  *
 837  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
 838  * as z3fold pool pages.
 839  *
 840  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
 841  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
 842  * a new page.
 843  */
 844 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 845                         unsigned long *handle)
 846 {
 847         int chunks = size_to_chunks(size);
 848         struct z3fold_header *zhdr = NULL;
 849         struct page *page = NULL;
 850         enum buddy bud;
 851         bool can_sleep = gfpflags_allow_blocking(gfp);
 852
 853         if (!size || (gfp & __GFP_HIGHMEM))
 854                 return -EINVAL;
 855
 856         if (size > PAGE_SIZE)
 857                 return -ENOSPC;
 858
 859         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
 860                 bud = HEADLESS;
 861         else {
 862 retry:
 863                 zhdr = __z3fold_alloc(pool, size, can_sleep);
 864                 if (zhdr) {
 865                         if (zhdr->first_chunks == 0) {
 866                                 if (zhdr->middle_chunks != 0 &&
 867                                     chunks >= zhdr->start_middle)
 868                                         bud = LAST;
 869                                 else
 870                                         bud = FIRST;
 871                         } else if (zhdr->last_chunks == 0)
 872                                 bud = LAST;
 873                         else if (zhdr->middle_chunks == 0)
 874                                 bud = MIDDLE;
 875                         else {
 876                                 if (kref_put(&zhdr->refcount,
 877                                              release_z3fold_page_locked))
 878                                         atomic64_dec(&pool->pages_nr);
 879                                 else
 880                                         z3fold_page_unlock(zhdr);
 881                                 pr_err("No free chunks in unbuddied\n");
 882                                 WARN_ON(1);
 883                                 goto retry;
 884                         }
 885                         page = virt_to_page(zhdr);
 886                         goto found;
 887                 }
 888                 bud = FIRST;
 889         }
 890
 891         page = NULL;
 892         if (can_sleep) {
 893                 spin_lock(&pool->stale_lock);
 894                 zhdr = list_first_entry_or_null(&pool->stale,
 895                                                 struct z3fold_header, buddy);
 896                 /*
 897                  * Before allocating a page, let's see if we can take one from
 898                  * the stale pages list. cancel_work_sync() can sleep so we
 899                  * limit this case to the contexts where we can sleep
 900                  */
 901                 if (zhdr) {
 902                         list_del(&zhdr->buddy);
 903                         spin_unlock(&pool->stale_lock);
 904                         cancel_work_sync(&zhdr->work);
 905                         page = virt_to_page(zhdr);
 906                 } else {
 907                         spin_unlock(&pool->stale_lock);
 908                 }
 909         }
 910         if (!page)
 911                 page = alloc_page(gfp);
 912
 913         if (!page)
 914                 return -ENOMEM;
 915
 916         zhdr = init_z3fold_page(page, pool, gfp);
 917         if (!zhdr) {
 918                 __free_page(page);
 919                 return -ENOMEM;
 920         }
 921         atomic64_inc(&pool->pages_nr);
 922
 923         if (bud == HEADLESS) {
 924                 set_bit(PAGE_HEADLESS, &page->private);
 925                 goto headless;
 926         }
 927         if (can_sleep) {
 928                 lock_page(page);
 929                 __SetPageMovable(page, pool->inode->i_mapping);
 930                 unlock_page(page);
 931         } else {
 932                 if (trylock_page(page)) {
 933                         __SetPageMovable(page, pool->inode->i_mapping);
 934                         unlock_page(page);
 935                 }
 936         }
 937         z3fold_page_lock(zhdr);
 938
 939 found:
 940         if (bud == FIRST)
 941                 zhdr->first_chunks = chunks;
 942         else if (bud == LAST)
 943                 zhdr->last_chunks = chunks;
 944         else {
 945                 zhdr->middle_chunks = chunks;
 946                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 947         }
 948         add_to_unbuddied(pool, zhdr);
 949
 950 headless:
 951         spin_lock(&pool->lock);
 952         /* Add/move z3fold page to beginning of LRU */
 953         if (!list_empty(&page->lru))
 954                 list_del(&page->lru);
 955
 956         list_add(&page->lru, &pool->lru);
 957
 958         *handle = encode_handle(zhdr, bud);
 959         spin_unlock(&pool->lock);
 960         if (bud != HEADLESS)
 961                 z3fold_page_unlock(zhdr);
 962
 963         return 0;
 964 }
 965
 966 /**
 967  * z3fold_free() - frees the allocation associated with the given handle
 968  * @pool:       pool in which the allocation resided
 969  * @handle:     handle associated with the allocation returned by z3fold_alloc()
 970  *
 971  * In the case that the z3fold page in which the allocation resides is under
 972  * reclaim, as indicated by the PG_reclaim flag being set, this function
 973  * only sets the first|last_chunks to 0.  The page is actually freed
 974  * once both buddies are evicted (see z3fold_reclaim_page() below).
 975  */
 976 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 977 {
 978         struct z3fold_header *zhdr;
 979         struct page *page;
 980         enum buddy bud;
 981
 982         zhdr = handle_to_z3fold_header(handle);
 983         page = virt_to_page(zhdr);
 984
 985         if (test_bit(PAGE_HEADLESS, &page->private)) {
 986                 /* if a headless page is under reclaim, just leave.
 987                  * NB: we use test_and_set_bit for a reason: if the bit
 988                  * has not been set before, we release this page
 989                  * immediately so we don't care about its value any more.
 990                  */
 991                 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
 992                         spin_lock(&pool->lock);
 993                         list_del(&page->lru);
 994                         spin_unlock(&pool->lock);
 995                         free_z3fold_page(page, true);
 996                         atomic64_dec(&pool->pages_nr);
 997                 }
 998                 return;
 999         }
1000
1001         /* Non-headless case */
1002         z3fold_page_lock(zhdr);
1003         bud = handle_to_buddy(handle);
1004
1005         switch (bud) {
1006         case FIRST:
1007                 zhdr->first_chunks = 0;
1008                 break;
1009         case MIDDLE:
1010                 zhdr->middle_chunks = 0;
1011                 break;
1012         case LAST:
1013                 zhdr->last_chunks = 0;
1014                 break;
1015         default:
1016                 pr_err("%s: unknown bud %d\n", __func__, bud);
1017                 WARN_ON(1);
1018                 z3fold_page_unlock(zhdr);
1019                 return;
1020         }
1021
1022         free_handle(handle);
1023         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1024                 atomic64_dec(&pool->pages_nr);
1025                 return;
1026         }
1027         if (test_bit(PAGE_CLAIMED, &page->private)) {
1028                 z3fold_page_unlock(zhdr);
1029                 return;
1030         }
1031         if (unlikely(PageIsolated(page)) ||
1032             test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1033                 z3fold_page_unlock(zhdr);
1034                 return;
1035         }
1036         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1037                 spin_lock(&pool->lock);
1038                 list_del_init(&zhdr->buddy);
1039                 spin_unlock(&pool->lock);
1040                 zhdr->cpu = -1;
1041                 kref_get(&zhdr->refcount);
1042                 do_compact_page(zhdr, true);
1043                 return;
1044         }
1045         kref_get(&zhdr->refcount);
1046         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1047         z3fold_page_unlock(zhdr);
1048 }
1049
1050 /**
1051  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1052  * @pool:       pool from which a page will attempt to be evicted
1053  * @retries:    number of pages on the LRU list for which eviction will
1054  *              be attempted before failing
1055  *
1056  * z3fold reclaim is different from normal system reclaim in that it is done
1057  * from the bottom, up. This is because only the bottom layer, z3fold, has
1058  * information on how the allocations are organized within each z3fold page.
1059  * This has the potential to create interesting locking situations between
1060  * z3fold and the user, however.
1061  *
1062  * To avoid these, this is how z3fold_reclaim_page() should be called:
1063  *
1064  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1065  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1066  * call the user-defined eviction handler with the pool and handle as
1067  * arguments.
1068  *
1069  * If the handle can not be evicted, the eviction handler should return
1070  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1071  * appropriate list and try the next z3fold page on the LRU up to
1072  * a user defined number of retries.
1073  *
1074  * If the handle is successfully evicted, the eviction handler should
1075  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1076  * contains logic to delay freeing the page if the page is under reclaim,
1077  * as indicated by the setting of the PG_reclaim flag on the underlying page.
1078  *
1079  * If all buddies in the z3fold page are successfully evicted, then the
1080  * z3fold page can be freed.
1081  *
1082  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1083  * no pages to evict or an eviction handler is not registered, -EAGAIN if
1084  * the retry limit was hit.
1085  */
1086 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1087 {
1088         int i, ret = 0;
1089         struct z3fold_header *zhdr = NULL;
1090         struct page *page = NULL;
1091         struct list_head *pos;
1092         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1093
1094         spin_lock(&pool->lock);
1095         if (!pool->ops || !pool->ops->evict || retries == 0) {
1096                 spin_unlock(&pool->lock);
1097                 return -EINVAL;
1098         }
1099         for (i = 0; i < retries; i++) {
1100                 if (list_empty(&pool->lru)) {
1101                         spin_unlock(&pool->lock);
1102                         return -EINVAL;
1103                 }
1104                 list_for_each_prev(pos, &pool->lru) {
1105                         page = list_entry(pos, struct page, lru);
1106
1107                         /* this bit could have been set by free, in which case
1108                          * we pass over to the next page in the pool.
1109                          */
1110                         if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1111                                 continue;
1112
1113                         if (unlikely(PageIsolated(page)))
1114                                 continue;
1115                         if (test_bit(PAGE_HEADLESS, &page->private))
1116                                 break;
1117
1118                         zhdr = page_address(page);
1119                         if (!z3fold_page_trylock(zhdr)) {
1120                                 zhdr = NULL;
1121                                 continue; /* can't evict at this point */
1122                         }
1123                         kref_get(&zhdr->refcount);
1124                         list_del_init(&zhdr->buddy);
1125                         zhdr->cpu = -1;
1126                         break;
1127                 }
1128
1129                 if (!zhdr)
1130                         break;
1131
1132                 list_del_init(&page->lru);
1133                 spin_unlock(&pool->lock);
1134
1135                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1136                         /*
1137                          * We need encode the handles before unlocking, since
1138                          * we can race with free that will set
1139                          * (first|last)_chunks to 0
1140                          */
1141                         first_handle = 0;
1142                         last_handle = 0;
1143                         middle_handle = 0;
1144                         if (zhdr->first_chunks)
1145                                 first_handle = encode_handle(zhdr, FIRST);
1146                         if (zhdr->middle_chunks)
1147                                 middle_handle = encode_handle(zhdr, MIDDLE);
1148                         if (zhdr->last_chunks)
1149                                 last_handle = encode_handle(zhdr, LAST);
1150                         /*
1151                          * it's safe to unlock here because we hold a
1152                          * reference to this page
1153                          */
1154                         z3fold_page_unlock(zhdr);
1155                 } else {
1156                         first_handle = encode_handle(zhdr, HEADLESS);
1157                         last_handle = middle_handle = 0;
1158                 }
1159
1160                 /* Issue the eviction callback(s) */
1161                 if (middle_handle) {
1162                         ret = pool->ops->evict(pool, middle_handle);
1163                         if (ret)
1164                                 goto next;
1165                 }
1166                 if (first_handle) {
1167                         ret = pool->ops->evict(pool, first_handle);
1168                         if (ret)
1169                                 goto next;
1170                 }
1171                 if (last_handle) {
1172                         ret = pool->ops->evict(pool, last_handle);
1173                         if (ret)
1174                                 goto next;
1175                 }
1176 next:
1177                 if (test_bit(PAGE_HEADLESS, &page->private)) {
1178                         if (ret == 0) {
1179                                 free_z3fold_page(page, true);
1180                                 atomic64_dec(&pool->pages_nr);
1181                                 return 0;
1182                         }
1183                         spin_lock(&pool->lock);
1184                         list_add(&page->lru, &pool->lru);
1185                         spin_unlock(&pool->lock);
1186                 } else {
1187                         z3fold_page_lock(zhdr);
1188                         clear_bit(PAGE_CLAIMED, &page->private);
1189                         if (kref_put(&zhdr->refcount,
1190                                         release_z3fold_page_locked)) {
1191                                 atomic64_dec(&pool->pages_nr);
1192                                 return 0;
1193                         }
1194                         /*
1195                          * if we are here, the page is still not completely
1196                          * free. Take the global pool lock then to be able
1197                          * to add it back to the lru list
1198                          */
1199                         spin_lock(&pool->lock);
1200                         list_add(&page->lru, &pool->lru);
1201                         spin_unlock(&pool->lock);
1202                         z3fold_page_unlock(zhdr);
1203                 }
1204
1205                 /* We started off locked to we need to lock the pool back */
1206                 spin_lock(&pool->lock);
1207         }
1208         spin_unlock(&pool->lock);
1209         return -EAGAIN;
1210 }
1211
1212 /**
1213  * z3fold_map() - maps the allocation associated with the given handle
1214  * @pool:       pool in which the allocation resides
1215  * @handle:     handle associated with the allocation to be mapped
1216  *
1217  * Extracts the buddy number from handle and constructs the pointer to the
1218  * correct starting chunk within the page.
1219  *
1220  * Returns: a pointer to the mapped allocation
1221  */
1222 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1223 {
1224         struct z3fold_header *zhdr;
1225         struct page *page;
1226         void *addr;
1227         enum buddy buddy;
1228
1229         zhdr = handle_to_z3fold_header(handle);
1230         addr = zhdr;
1231         page = virt_to_page(zhdr);
1232
1233         if (test_bit(PAGE_HEADLESS, &page->private))
1234                 goto out;
1235
1236         z3fold_page_lock(zhdr);
1237         buddy = handle_to_buddy(handle);
1238         switch (buddy) {
1239         case FIRST:
1240                 addr += ZHDR_SIZE_ALIGNED;
1241                 break;
1242         case MIDDLE:
1243                 addr += zhdr->start_middle << CHUNK_SHIFT;
1244                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1245                 break;
1246         case LAST:
1247                 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1248                 break;
1249         default:
1250                 pr_err("unknown buddy id %d\n", buddy);
1251                 WARN_ON(1);
1252                 addr = NULL;
1253                 break;
1254         }
1255
1256         if (addr)
1257                 zhdr->mapped_count++;
1258         z3fold_page_unlock(zhdr);
1259 out:
1260         return addr;
1261 }
1262
1263 /**
1264  * z3fold_unmap() - unmaps the allocation associated with the given handle
1265  * @pool:       pool in which the allocation resides
1266  * @handle:     handle associated with the allocation to be unmapped
1267  */
1268 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1269 {
1270         struct z3fold_header *zhdr;
1271         struct page *page;
1272         enum buddy buddy;
1273
1274         zhdr = handle_to_z3fold_header(handle);
1275         page = virt_to_page(zhdr);
1276
1277         if (test_bit(PAGE_HEADLESS, &page->private))
1278                 return;
1279
1280         z3fold_page_lock(zhdr);
1281         buddy = handle_to_buddy(handle);
1282         if (buddy == MIDDLE)
1283                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1284         zhdr->mapped_count--;
1285         z3fold_page_unlock(zhdr);
1286 }
1287
1288 /**
1289  * z3fold_get_pool_size() - gets the z3fold pool size in pages
1290  * @pool:       pool whose size is being queried
1291  *
1292  * Returns: size in pages of the given pool.
1293  */
1294 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1295 {
1296         return atomic64_read(&pool->pages_nr);
1297 }
1298
1299 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1300 {
1301         struct z3fold_header *zhdr;
1302         struct z3fold_pool *pool;
1303
1304         VM_BUG_ON_PAGE(!PageMovable(page), page);
1305         VM_BUG_ON_PAGE(PageIsolated(page), page);
1306
1307         if (test_bit(PAGE_HEADLESS, &page->private))
1308                 return false;
1309
1310         zhdr = page_address(page);
1311         z3fold_page_lock(zhdr);
1312         if (test_bit(NEEDS_COMPACTING, &page->private) ||
1313             test_bit(PAGE_STALE, &page->private))
1314                 goto out;
1315
1316         pool = zhdr_to_pool(zhdr);
1317
1318         if (zhdr->mapped_count == 0) {
1319                 kref_get(&zhdr->refcount);
1320                 if (!list_empty(&zhdr->buddy))
1321                         list_del_init(&zhdr->buddy);
1322                 spin_lock(&pool->lock);
1323                 if (!list_empty(&page->lru))
1324                         list_del(&page->lru);
1325                 spin_unlock(&pool->lock);
1326                 z3fold_page_unlock(zhdr);
1327                 return true;
1328         }
1329 out:
1330         z3fold_page_unlock(zhdr);
1331         return false;
1332 }
1333
1334 static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1335                                struct page *page, enum migrate_mode mode)
1336 {
1337         struct z3fold_header *zhdr, *new_zhdr;
1338         struct z3fold_pool *pool;
1339         struct address_space *new_mapping;
1340
1341         VM_BUG_ON_PAGE(!PageMovable(page), page);
1342         VM_BUG_ON_PAGE(!PageIsolated(page), page);
1343         VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1344
1345         zhdr = page_address(page);
1346         pool = zhdr_to_pool(zhdr);
1347
1348         if (!trylock_page(page))
1349                 return -EAGAIN;
1350
1351         if (!z3fold_page_trylock(zhdr)) {
1352                 unlock_page(page);
1353                 return -EAGAIN;
1354         }
1355         if (zhdr->mapped_count != 0) {
1356                 z3fold_page_unlock(zhdr);
1357                 unlock_page(page);
1358                 return -EBUSY;
1359         }
1360         new_zhdr = page_address(newpage);
1361         memcpy(new_zhdr, zhdr, PAGE_SIZE);
1362         newpage->private = page->private;
1363         page->private = 0;
1364         z3fold_page_unlock(zhdr);
1365         spin_lock_init(&new_zhdr->page_lock);
1366         new_mapping = page_mapping(page);
1367         __ClearPageMovable(page);
1368         ClearPagePrivate(page);
1369
1370         get_page(newpage);
1371         z3fold_page_lock(new_zhdr);
1372         if (new_zhdr->first_chunks)
1373                 encode_handle(new_zhdr, FIRST);
1374         if (new_zhdr->last_chunks)
1375                 encode_handle(new_zhdr, LAST);
1376         if (new_zhdr->middle_chunks)
1377                 encode_handle(new_zhdr, MIDDLE);
1378         set_bit(NEEDS_COMPACTING, &newpage->private);
1379         new_zhdr->cpu = smp_processor_id();
1380         spin_lock(&pool->lock);
1381         list_add(&newpage->lru, &pool->lru);
1382         spin_unlock(&pool->lock);
1383         __SetPageMovable(newpage, new_mapping);
1384         z3fold_page_unlock(new_zhdr);
1385
1386         queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1387
1388         page_mapcount_reset(page);
1389         unlock_page(page);
1390         put_page(page);
1391         return 0;
1392 }
1393
1394 static void z3fold_page_putback(struct page *page)
1395 {
1396         struct z3fold_header *zhdr;
1397         struct z3fold_pool *pool;
1398
1399         zhdr = page_address(page);
1400         pool = zhdr_to_pool(zhdr);
1401
1402         z3fold_page_lock(zhdr);
1403         if (!list_empty(&zhdr->buddy))
1404                 list_del_init(&zhdr->buddy);
1405         INIT_LIST_HEAD(&page->lru);
1406         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1407                 atomic64_dec(&pool->pages_nr);
1408                 return;
1409         }
1410         spin_lock(&pool->lock);
1411         list_add(&page->lru, &pool->lru);
1412         spin_unlock(&pool->lock);
1413         z3fold_page_unlock(zhdr);
1414 }
1415
1416 static const struct address_space_operations z3fold_aops = {
1417         .isolate_page = z3fold_page_isolate,
1418         .migratepage = z3fold_page_migrate,
1419         .putback_page = z3fold_page_putback,
1420 };
1421
1422 /*****************
1423  * zpool
1424  ****************/
1425
1426 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1427 {
1428         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1429                 return pool->zpool_ops->evict(pool->zpool, handle);
1430         else
1431                 return -ENOENT;
1432 }
1433
1434 static const struct z3fold_ops z3fold_zpool_ops = {
1435         .evict =        z3fold_zpool_evict
1436 };
1437
1438 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1439                                const struct zpool_ops *zpool_ops,
1440                                struct zpool *zpool)
1441 {
1442         struct z3fold_pool *pool;
1443
1444         pool = z3fold_create_pool(name, gfp,
1445                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1446         if (pool) {
1447                 pool->zpool = zpool;
1448                 pool->zpool_ops = zpool_ops;
1449         }
1450         return pool;
1451 }
1452
1453 static void z3fold_zpool_destroy(void *pool)
1454 {
1455         z3fold_destroy_pool(pool);
1456 }
1457
1458 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1459                         unsigned long *handle)
1460 {
1461         return z3fold_alloc(pool, size, gfp, handle);
1462 }
1463 static void z3fold_zpool_free(void *pool, unsigned long handle)
1464 {
1465         z3fold_free(pool, handle);
1466 }
1467
1468 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1469                         unsigned int *reclaimed)
1470 {
1471         unsigned int total = 0;
1472         int ret = -EINVAL;
1473
1474         while (total < pages) {
1475                 ret = z3fold_reclaim_page(pool, 8);
1476                 if (ret < 0)
1477                         break;
1478                 total++;
1479         }
1480
1481         if (reclaimed)
1482                 *reclaimed = total;
1483
1484         return ret;
1485 }
1486
1487 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1488                         enum zpool_mapmode mm)
1489 {
1490         return z3fold_map(pool, handle);
1491 }
1492 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1493 {
1494         z3fold_unmap(pool, handle);
1495 }
1496
1497 static u64 z3fold_zpool_total_size(void *pool)
1498 {
1499         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1500 }
1501
1502 static struct zpool_driver z3fold_zpool_driver = {
1503         .type =         "z3fold",
1504         .owner =        THIS_MODULE,
1505         .create =       z3fold_zpool_create,
1506         .destroy =      z3fold_zpool_destroy,
1507         .malloc =       z3fold_zpool_malloc,
1508         .free =         z3fold_zpool_free,
1509         .shrink =       z3fold_zpool_shrink,
1510         .map =          z3fold_zpool_map,
1511         .unmap =        z3fold_zpool_unmap,
1512         .total_size =   z3fold_zpool_total_size,
1513 };
1514
1515 MODULE_ALIAS("zpool-z3fold");
1516
1517 static int __init init_z3fold(void)
1518 {
1519         int ret;
1520
1521         /* Make sure the z3fold header is not larger than the page size */
1522         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1523         ret = z3fold_mount();
1524         if (ret)
1525                 return ret;
1526
1527         zpool_register_driver(&z3fold_zpool_driver);
1528
1529         return 0;
1530 }
1531
1532 static void __exit exit_z3fold(void)
1533 {
1534         z3fold_unmount();
1535         zpool_unregister_driver(&z3fold_zpool_driver);
1536 }
1537
1538 module_init(init_z3fold);
1539 module_exit(exit_z3fold);
1540
1541 MODULE_LICENSE("GPL");
1542 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1543 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");