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/list.h>
  30 #include <linux/mm.h>
  31 #include <linux/module.h>
  32 #include <linux/page-flags.h>
  33 #include <linux/migrate.h>
  34 #include <linux/node.h>
  35 #include <linux/compaction.h>
  36 #include <linux/percpu.h>
  37 #include <linux/mount.h>
  38 #include <linux/pseudo_fs.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 #include <linux/magic.h>
  46
  47 /*
  48  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
  49  * adjusting internal fragmentation.  It also determines the number of
  50  * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
  51  * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
  52  * in the beginning of an allocated page are occupied by z3fold header, so
  53  * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
  54  * which shows the max number of free chunks in z3fold page, also there will
  55  * be 63, or 62, respectively, freelists per pool.
  56  */
  57 #define NCHUNKS_ORDER   6
  58
  59 #define CHUNK_SHIFT     (PAGE_SHIFT - NCHUNKS_ORDER)
  60 #define CHUNK_SIZE      (1 << CHUNK_SHIFT)
  61 #define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
  62 #define ZHDR_CHUNKS     (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
  63 #define TOTAL_CHUNKS    (PAGE_SIZE >> CHUNK_SHIFT)
  64 #define NCHUNKS         ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
  65
  66 #define BUDDY_MASK      (0x3)
  67 #define BUDDY_SHIFT     2
  68 #define SLOTS_ALIGN     (0x40)
  69
  70 /*****************
  71  * Structures
  72 *****************/
  73 struct z3fold_pool;
  74 struct z3fold_ops {
  75         int (*evict)(struct z3fold_pool *pool, unsigned long handle);
  76 };
  77
  78 enum buddy {
  79         HEADLESS = 0,
  80         FIRST,
  81         MIDDLE,
  82         LAST,
  83         BUDDIES_MAX = LAST
  84 };
  85
  86 struct z3fold_buddy_slots {
  87         /*
  88          * we are using BUDDY_MASK in handle_to_buddy etc. so there should
  89          * be enough slots to hold all possible variants
  90          */
  91         unsigned long slot[BUDDY_MASK + 1];
  92         unsigned long pool; /* back link + flags */
  93 };
  94 #define HANDLE_FLAG_MASK        (0x03)
  95
  96 /*
  97  * struct z3fold_header - z3fold page metadata occupying first chunks of each
  98  *                      z3fold page, except for HEADLESS pages
  99  * @buddy:              links the z3fold page into the relevant list in the
 100  *                      pool
 101  * @page_lock:          per-page lock
 102  * @refcount:           reference count for the z3fold page
 103  * @work:               work_struct for page layout optimization
 104  * @slots:              pointer to the structure holding buddy slots
 105  * @pool:               pointer to the containing pool
 106  * @cpu:                CPU which this page "belongs" to
 107  * @first_chunks:       the size of the first buddy in chunks, 0 if free
 108  * @middle_chunks:      the size of the middle buddy in chunks, 0 if free
 109  * @last_chunks:        the size of the last buddy in chunks, 0 if free
 110  * @first_num:          the starting number (for the first handle)
 111  * @mapped_count:       the number of objects currently mapped
 112  */
 113 struct z3fold_header {
 114         struct list_head buddy;
 115         spinlock_t page_lock;
 116         struct kref refcount;
 117         struct work_struct work;
 118         struct z3fold_buddy_slots *slots;
 119         struct z3fold_pool *pool;
 120         short cpu;
 121         unsigned short first_chunks;
 122         unsigned short middle_chunks;
 123         unsigned short last_chunks;
 124         unsigned short start_middle;
 125         unsigned short first_num:2;
 126         unsigned short mapped_count:2;
 127 };
 128
 129 /**
 130  * struct z3fold_pool - stores metadata for each z3fold pool
 131  * @name:       pool name
 132  * @lock:       protects pool unbuddied/lru lists
 133  * @stale_lock: protects pool stale page list
 134  * @unbuddied:  per-cpu array of lists tracking z3fold pages that contain 2-
 135  *              buddies; the list each z3fold page is added to depends on
 136  *              the size of its free region.
 137  * @lru:        list tracking the z3fold pages in LRU order by most recently
 138  *              added buddy.
 139  * @stale:      list of pages marked for freeing
 140  * @pages_nr:   number of z3fold pages in the pool.
 141  * @c_handle:   cache for z3fold_buddy_slots allocation
 142  * @ops:        pointer to a structure of user defined operations specified at
 143  *              pool creation time.
 144  * @compact_wq: workqueue for page layout background optimization
 145  * @release_wq: workqueue for safe page release
 146  * @work:       work_struct for safe page release
 147  * @inode:      inode for z3fold pseudo filesystem
 148  *
 149  * This structure is allocated at pool creation time and maintains metadata
 150  * pertaining to a particular z3fold pool.
 151  */
 152 struct z3fold_pool {
 153         const char *name;
 154         spinlock_t lock;
 155         spinlock_t stale_lock;
 156         struct list_head *unbuddied;
 157         struct list_head lru;
 158         struct list_head stale;
 159         atomic64_t pages_nr;
 160         struct kmem_cache *c_handle;
 161         const struct z3fold_ops *ops;
 162         struct zpool *zpool;
 163         const struct zpool_ops *zpool_ops;
 164         struct workqueue_struct *compact_wq;
 165         struct workqueue_struct *release_wq;
 166         struct work_struct work;
 167         struct inode *inode;
 168 };
 169
 170 /*
 171  * Internal z3fold page flags
 172  */
 173 enum z3fold_page_flags {
 174         PAGE_HEADLESS = 0,
 175         MIDDLE_CHUNK_MAPPED,
 176         NEEDS_COMPACTING,
 177         PAGE_STALE,
 178         PAGE_CLAIMED, /* by either reclaim or free */
 179 };
 180
 181 /*****************
 182  * Helpers
 183 *****************/
 184
 185 /* Converts an allocation size in bytes to size in z3fold chunks */
 186 static int size_to_chunks(size_t size)
 187 {
 188         return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
 189 }
 190
 191 #define for_each_unbuddied_list(_iter, _begin) \
 192         for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
 193
 194 static void compact_page_work(struct work_struct *w);
 195
 196 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
 197                                                         gfp_t gfp)
 198 {
 199         struct z3fold_buddy_slots *slots;
 200
 201         slots = kmem_cache_alloc(pool->c_handle,
 202                                  (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
 203
 204         if (slots) {
 205                 memset(slots->slot, 0, sizeof(slots->slot));
 206                 slots->pool = (unsigned long)pool;
 207         }
 208
 209         return slots;
 210 }
 211
 212 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
 213 {
 214         return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
 215 }
 216
 217 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 218 {
 219         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 220 }
 221
 222 static inline void free_handle(unsigned long handle)
 223 {
 224         struct z3fold_buddy_slots *slots;
 225         int i;
 226         bool is_free;
 227
 228         if (handle & (1 << PAGE_HEADLESS))
 229                 return;
 230
 231         WARN_ON(*(unsigned long *)handle == 0);
 232         *(unsigned long *)handle = 0;
 233         slots = handle_to_slots(handle);
 234         is_free = true;
 235         for (i = 0; i <= BUDDY_MASK; i++) {
 236                 if (slots->slot[i]) {
 237                         is_free = false;
 238                         break;
 239                 }
 240         }
 241
 242         if (is_free) {
 243                 struct z3fold_pool *pool = slots_to_pool(slots);
 244
 245                 kmem_cache_free(pool->c_handle, slots);
 246         }
 247 }
 248
 249 static int z3fold_init_fs_context(struct fs_context *fc)
 250 {
 251         return init_pseudo(fc, Z3FOLD_MAGIC) ? 0 : -ENOMEM;
 252 }
 253
 254 static struct file_system_type z3fold_fs = {
 255         .name           = "z3fold",
 256         .init_fs_context = z3fold_init_fs_context,
 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         zhdr->pool = pool;
 324         INIT_LIST_HEAD(&zhdr->buddy);
 325         INIT_WORK(&zhdr->work, compact_page_work);
 326         return zhdr;
 327 }
 328
 329 /* Resets the struct page fields and frees the page */
 330 static void free_z3fold_page(struct page *page, bool headless)
 331 {
 332         if (!headless) {
 333                 lock_page(page);
 334                 __ClearPageMovable(page);
 335                 unlock_page(page);
 336         }
 337         ClearPagePrivate(page);
 338         __free_page(page);
 339 }
 340
 341 /* Lock a z3fold page */
 342 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 343 {
 344         spin_lock(&zhdr->page_lock);
 345 }
 346
 347 /* Try to lock a z3fold page */
 348 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 349 {
 350         return spin_trylock(&zhdr->page_lock);
 351 }
 352
 353 /* Unlock a z3fold page */
 354 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
 355 {
 356         spin_unlock(&zhdr->page_lock);
 357 }
 358
 359 /* Helper function to build the index */
 360 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 361 {
 362         return (bud + zhdr->first_num) & BUDDY_MASK;
 363 }
 364
 365 /*
 366  * Encodes the handle of a particular buddy within a z3fold page
 367  * Pool lock should be held as this function accesses first_num
 368  */
 369 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 370 {
 371         struct z3fold_buddy_slots *slots;
 372         unsigned long h = (unsigned long)zhdr;
 373         int idx = 0;
 374
 375         /*
 376          * For a headless page, its handle is its pointer with the extra
 377          * PAGE_HEADLESS bit set
 378          */
 379         if (bud == HEADLESS)
 380                 return h | (1 << PAGE_HEADLESS);
 381
 382         /* otherwise, return pointer to encoded handle */
 383         idx = __idx(zhdr, bud);
 384         h += idx;
 385         if (bud == LAST)
 386                 h |= (zhdr->last_chunks << BUDDY_SHIFT);
 387
 388         slots = zhdr->slots;
 389         slots->slot[idx] = h;
 390         return (unsigned long)&slots->slot[idx];
 391 }
 392
 393 /* Returns the z3fold page where a given handle is stored */
 394 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
 395 {
 396         unsigned long addr = h;
 397
 398         if (!(addr & (1 << PAGE_HEADLESS)))
 399                 addr = *(unsigned long *)h;
 400
 401         return (struct z3fold_header *)(addr & PAGE_MASK);
 402 }
 403
 404 /* only for LAST bud, returns zero otherwise */
 405 static unsigned short handle_to_chunks(unsigned long handle)
 406 {
 407         unsigned long addr = *(unsigned long *)handle;
 408
 409         return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 410 }
 411
 412 /*
 413  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
 414  *  but that doesn't matter. because the masking will result in the
 415  *  correct buddy number.
 416  */
 417 static enum buddy handle_to_buddy(unsigned long handle)
 418 {
 419         struct z3fold_header *zhdr;
 420         unsigned long addr;
 421
 422         WARN_ON(handle & (1 << PAGE_HEADLESS));
 423         addr = *(unsigned long *)handle;
 424         zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 425         return (addr - zhdr->first_num) & BUDDY_MASK;
 426 }
 427
 428 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
 429 {
 430         return zhdr->pool;
 431 }
 432
 433 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 434 {
 435         struct page *page = virt_to_page(zhdr);
 436         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 437
 438         WARN_ON(!list_empty(&zhdr->buddy));
 439         set_bit(PAGE_STALE, &page->private);
 440         clear_bit(NEEDS_COMPACTING, &page->private);
 441         spin_lock(&pool->lock);
 442         if (!list_empty(&page->lru))
 443                 list_del_init(&page->lru);
 444         spin_unlock(&pool->lock);
 445         if (locked)
 446                 z3fold_page_unlock(zhdr);
 447         spin_lock(&pool->stale_lock);
 448         list_add(&zhdr->buddy, &pool->stale);
 449         queue_work(pool->release_wq, &pool->work);
 450         spin_unlock(&pool->stale_lock);
 451 }
 452
 453 static void __attribute__((__unused__))
 454                         release_z3fold_page(struct kref *ref)
 455 {
 456         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 457                                                 refcount);
 458         __release_z3fold_page(zhdr, false);
 459 }
 460
 461 static void release_z3fold_page_locked(struct kref *ref)
 462 {
 463         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 464                                                 refcount);
 465         WARN_ON(z3fold_page_trylock(zhdr));
 466         __release_z3fold_page(zhdr, true);
 467 }
 468
 469 static void release_z3fold_page_locked_list(struct kref *ref)
 470 {
 471         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 472                                                refcount);
 473         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 474         spin_lock(&pool->lock);
 475         list_del_init(&zhdr->buddy);
 476         spin_unlock(&pool->lock);
 477
 478         WARN_ON(z3fold_page_trylock(zhdr));
 479         __release_z3fold_page(zhdr, true);
 480 }
 481
 482 static void free_pages_work(struct work_struct *w)
 483 {
 484         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
 485
 486         spin_lock(&pool->stale_lock);
 487         while (!list_empty(&pool->stale)) {
 488                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
 489                                                 struct z3fold_header, buddy);
 490                 struct page *page = virt_to_page(zhdr);
 491
 492                 list_del(&zhdr->buddy);
 493                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
 494                         continue;
 495                 spin_unlock(&pool->stale_lock);
 496                 cancel_work_sync(&zhdr->work);
 497                 free_z3fold_page(page, false);
 498                 cond_resched();
 499                 spin_lock(&pool->stale_lock);
 500         }
 501         spin_unlock(&pool->stale_lock);
 502 }
 503
 504 /*
 505  * Returns the number of free chunks in a z3fold page.
 506  * NB: can't be used with HEADLESS pages.
 507  */
 508 static int num_free_chunks(struct z3fold_header *zhdr)
 509 {
 510         int nfree;
 511         /*
 512          * If there is a middle object, pick up the bigger free space
 513          * either before or after it. Otherwise just subtract the number
 514          * of chunks occupied by the first and the last objects.
 515          */
 516         if (zhdr->middle_chunks != 0) {
 517                 int nfree_before = zhdr->first_chunks ?
 518                         0 : zhdr->start_middle - ZHDR_CHUNKS;
 519                 int nfree_after = zhdr->last_chunks ?
 520                         0 : TOTAL_CHUNKS -
 521                                 (zhdr->start_middle + zhdr->middle_chunks);
 522                 nfree = max(nfree_before, nfree_after);
 523         } else
 524                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 525         return nfree;
 526 }
 527
 528 /* Add to the appropriate unbuddied list */
 529 static inline void add_to_unbuddied(struct z3fold_pool *pool,
 530                                 struct z3fold_header *zhdr)
 531 {
 532         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
 533                         zhdr->middle_chunks == 0) {
 534                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
 535
 536                 int freechunks = num_free_chunks(zhdr);
 537                 spin_lock(&pool->lock);
 538                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
 539                 spin_unlock(&pool->lock);
 540                 zhdr->cpu = smp_processor_id();
 541                 put_cpu_ptr(pool->unbuddied);
 542         }
 543 }
 544
 545 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 546                                 unsigned short dst_chunk)
 547 {
 548         void *beg = zhdr;
 549         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
 550                        beg + (zhdr->start_middle << CHUNK_SHIFT),
 551                        zhdr->middle_chunks << CHUNK_SHIFT);
 552 }
 553
 554 #define BIG_CHUNK_GAP   3
 555 /* Has to be called with lock held */
 556 static int z3fold_compact_page(struct z3fold_header *zhdr)
 557 {
 558         struct page *page = virt_to_page(zhdr);
 559
 560         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
 561                 return 0; /* can't move middle chunk, it's used */
 562
 563         if (unlikely(PageIsolated(page)))
 564                 return 0;
 565
 566         if (zhdr->middle_chunks == 0)
 567                 return 0; /* nothing to compact */
 568
 569         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 570                 /* move to the beginning */
 571                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
 572                 zhdr->first_chunks = zhdr->middle_chunks;
 573                 zhdr->middle_chunks = 0;
 574                 zhdr->start_middle = 0;
 575                 zhdr->first_num++;
 576                 return 1;
 577         }
 578
 579         /*
 580          * moving data is expensive, so let's only do that if
 581          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
 582          */
 583         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
 584             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
 585                         BIG_CHUNK_GAP) {
 586                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
 587                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 588                 return 1;
 589         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
 590                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
 591                                         + zhdr->middle_chunks) >=
 592                         BIG_CHUNK_GAP) {
 593                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
 594                         zhdr->middle_chunks;
 595                 mchunk_memmove(zhdr, new_start);
 596                 zhdr->start_middle = new_start;
 597                 return 1;
 598         }
 599
 600         return 0;
 601 }
 602
 603 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 604 {
 605         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 606         struct page *page;
 607
 608         page = virt_to_page(zhdr);
 609         if (locked)
 610                 WARN_ON(z3fold_page_trylock(zhdr));
 611         else
 612                 z3fold_page_lock(zhdr);
 613         if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
 614                 z3fold_page_unlock(zhdr);
 615                 return;
 616         }
 617         spin_lock(&pool->lock);
 618         list_del_init(&zhdr->buddy);
 619         spin_unlock(&pool->lock);
 620
 621         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 622                 atomic64_dec(&pool->pages_nr);
 623                 return;
 624         }
 625
 626         if (unlikely(PageIsolated(page) ||
 627                      test_bit(PAGE_STALE, &page->private))) {
 628                 z3fold_page_unlock(zhdr);
 629                 return;
 630         }
 631
 632         z3fold_compact_page(zhdr);
 633         add_to_unbuddied(pool, zhdr);
 634         z3fold_page_unlock(zhdr);
 635 }
 636
 637 static void compact_page_work(struct work_struct *w)
 638 {
 639         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
 640                                                 work);
 641
 642         do_compact_page(zhdr, false);
 643 }
 644
 645 /* returns _locked_ z3fold page header or NULL */
 646 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
 647                                                 size_t size, bool can_sleep)
 648 {
 649         struct z3fold_header *zhdr = NULL;
 650         struct page *page;
 651         struct list_head *unbuddied;
 652         int chunks = size_to_chunks(size), i;
 653
 654 lookup:
 655         /* First, try to find an unbuddied z3fold page. */
 656         unbuddied = get_cpu_ptr(pool->unbuddied);
 657         for_each_unbuddied_list(i, chunks) {
 658                 struct list_head *l = &unbuddied[i];
 659
 660                 zhdr = list_first_entry_or_null(READ_ONCE(l),
 661                                         struct z3fold_header, buddy);
 662
 663                 if (!zhdr)
 664                         continue;
 665
 666                 /* Re-check under lock. */
 667                 spin_lock(&pool->lock);
 668                 l = &unbuddied[i];
 669                 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
 670                                                 struct z3fold_header, buddy)) ||
 671                     !z3fold_page_trylock(zhdr)) {
 672                         spin_unlock(&pool->lock);
 673                         zhdr = NULL;
 674                         put_cpu_ptr(pool->unbuddied);
 675                         if (can_sleep)
 676                                 cond_resched();
 677                         goto lookup;
 678                 }
 679                 list_del_init(&zhdr->buddy);
 680                 zhdr->cpu = -1;
 681                 spin_unlock(&pool->lock);
 682
 683                 page = virt_to_page(zhdr);
 684                 if (test_bit(NEEDS_COMPACTING, &page->private)) {
 685                         z3fold_page_unlock(zhdr);
 686                         zhdr = NULL;
 687                         put_cpu_ptr(pool->unbuddied);
 688                         if (can_sleep)
 689                                 cond_resched();
 690                         goto lookup;
 691                 }
 692
 693                 /*
 694                  * this page could not be removed from its unbuddied
 695                  * list while pool lock was held, and then we've taken
 696                  * page lock so kref_put could not be called before
 697                  * we got here, so it's safe to just call kref_get()
 698                  */
 699                 kref_get(&zhdr->refcount);
 700                 break;
 701         }
 702         put_cpu_ptr(pool->unbuddied);
 703
 704         if (!zhdr) {
 705                 int cpu;
 706
 707                 /* look for _exact_ match on other cpus' lists */
 708                 for_each_online_cpu(cpu) {
 709                         struct list_head *l;
 710
 711                         unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
 712                         spin_lock(&pool->lock);
 713                         l = &unbuddied[chunks];
 714
 715                         zhdr = list_first_entry_or_null(READ_ONCE(l),
 716                                                 struct z3fold_header, buddy);
 717
 718                         if (!zhdr || !z3fold_page_trylock(zhdr)) {
 719                                 spin_unlock(&pool->lock);
 720                                 zhdr = NULL;
 721                                 continue;
 722                         }
 723                         list_del_init(&zhdr->buddy);
 724                         zhdr->cpu = -1;
 725                         spin_unlock(&pool->lock);
 726
 727                         page = virt_to_page(zhdr);
 728                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
 729                                 z3fold_page_unlock(zhdr);
 730                                 zhdr = NULL;
 731                                 if (can_sleep)
 732                                         cond_resched();
 733                                 continue;
 734                         }
 735                         kref_get(&zhdr->refcount);
 736                         break;
 737                 }
 738         }
 739
 740         return zhdr;
 741 }
 742
 743 /*
 744  * API Functions
 745  */
 746
 747 /**
 748  * z3fold_create_pool() - create a new z3fold pool
 749  * @name:       pool name
 750  * @gfp:        gfp flags when allocating the z3fold pool structure
 751  * @ops:        user-defined operations for the z3fold pool
 752  *
 753  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
 754  * failed.
 755  */
 756 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
 757                 const struct z3fold_ops *ops)
 758 {
 759         struct z3fold_pool *pool = NULL;
 760         int i, cpu;
 761
 762         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
 763         if (!pool)
 764                 goto out;
 765         pool->c_handle = kmem_cache_create("z3fold_handle",
 766                                 sizeof(struct z3fold_buddy_slots),
 767                                 SLOTS_ALIGN, 0, NULL);
 768         if (!pool->c_handle)
 769                 goto out_c;
 770         spin_lock_init(&pool->lock);
 771         spin_lock_init(&pool->stale_lock);
 772         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
 773         if (!pool->unbuddied)
 774                 goto out_pool;
 775         for_each_possible_cpu(cpu) {
 776                 struct list_head *unbuddied =
 777                                 per_cpu_ptr(pool->unbuddied, cpu);
 778                 for_each_unbuddied_list(i, 0)
 779                         INIT_LIST_HEAD(&unbuddied[i]);
 780         }
 781         INIT_LIST_HEAD(&pool->lru);
 782         INIT_LIST_HEAD(&pool->stale);
 783         atomic64_set(&pool->pages_nr, 0);
 784         pool->name = name;
 785         pool->compact_wq = create_singlethread_workqueue(pool->name);
 786         if (!pool->compact_wq)
 787                 goto out_unbuddied;
 788         pool->release_wq = create_singlethread_workqueue(pool->name);
 789         if (!pool->release_wq)
 790                 goto out_wq;
 791         if (z3fold_register_migration(pool))
 792                 goto out_rwq;
 793         INIT_WORK(&pool->work, free_pages_work);
 794         pool->ops = ops;
 795         return pool;
 796
 797 out_rwq:
 798         destroy_workqueue(pool->release_wq);
 799 out_wq:
 800         destroy_workqueue(pool->compact_wq);
 801 out_unbuddied:
 802         free_percpu(pool->unbuddied);
 803 out_pool:
 804         kmem_cache_destroy(pool->c_handle);
 805 out_c:
 806         kfree(pool);
 807 out:
 808         return NULL;
 809 }
 810
 811 /**
 812  * z3fold_destroy_pool() - destroys an existing z3fold pool
 813  * @pool:       the z3fold pool to be destroyed
 814  *
 815  * The pool should be emptied before this function is called.
 816  */
 817 static void z3fold_destroy_pool(struct z3fold_pool *pool)
 818 {
 819         kmem_cache_destroy(pool->c_handle);
 820
 821         /*
 822          * We need to destroy pool->compact_wq before pool->release_wq,
 823          * as any pending work on pool->compact_wq will call
 824          * queue_work(pool->release_wq, &pool->work).
 825          *
 826          * There are still outstanding pages until both workqueues are drained,
 827          * so we cannot unregister migration until then.
 828          */
 829
 830         destroy_workqueue(pool->compact_wq);
 831         destroy_workqueue(pool->release_wq);
 832         z3fold_unregister_migration(pool);
 833         kfree(pool);
 834 }
 835
 836 /**
 837  * z3fold_alloc() - allocates a region of a given size
 838  * @pool:       z3fold pool from which to allocate
 839  * @size:       size in bytes of the desired allocation
 840  * @gfp:        gfp flags used if the pool needs to grow
 841  * @handle:     handle of the new allocation
 842  *
 843  * This function will attempt to find a free region in the pool large enough to
 844  * satisfy the allocation request.  A search of the unbuddied lists is
 845  * performed first. If no suitable free region is found, then a new page is
 846  * allocated and added to the pool to satisfy the request.
 847  *
 848  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
 849  * as z3fold pool pages.
 850  *
 851  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
 852  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
 853  * a new page.
 854  */
 855 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 856                         unsigned long *handle)
 857 {
 858         int chunks = size_to_chunks(size);
 859         struct z3fold_header *zhdr = NULL;
 860         struct page *page = NULL;
 861         enum buddy bud;
 862         bool can_sleep = gfpflags_allow_blocking(gfp);
 863
 864         if (!size)
 865                 return -EINVAL;
 866
 867         if (size > PAGE_SIZE)
 868                 return -ENOSPC;
 869
 870         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
 871                 bud = HEADLESS;
 872         else {
 873 retry:
 874                 zhdr = __z3fold_alloc(pool, size, can_sleep);
 875                 if (zhdr) {
 876                         if (zhdr->first_chunks == 0) {
 877                                 if (zhdr->middle_chunks != 0 &&
 878                                     chunks >= zhdr->start_middle)
 879                                         bud = LAST;
 880                                 else
 881                                         bud = FIRST;
 882                         } else if (zhdr->last_chunks == 0)
 883                                 bud = LAST;
 884                         else if (zhdr->middle_chunks == 0)
 885                                 bud = MIDDLE;
 886                         else {
 887                                 if (kref_put(&zhdr->refcount,
 888                                              release_z3fold_page_locked))
 889                                         atomic64_dec(&pool->pages_nr);
 890                                 else
 891                                         z3fold_page_unlock(zhdr);
 892                                 pr_err("No free chunks in unbuddied\n");
 893                                 WARN_ON(1);
 894                                 goto retry;
 895                         }
 896                         page = virt_to_page(zhdr);
 897                         goto found;
 898                 }
 899                 bud = FIRST;
 900         }
 901
 902         page = NULL;
 903         if (can_sleep) {
 904                 spin_lock(&pool->stale_lock);
 905                 zhdr = list_first_entry_or_null(&pool->stale,
 906                                                 struct z3fold_header, buddy);
 907                 /*
 908                  * Before allocating a page, let's see if we can take one from
 909                  * the stale pages list. cancel_work_sync() can sleep so we
 910                  * limit this case to the contexts where we can sleep
 911                  */
 912                 if (zhdr) {
 913                         list_del(&zhdr->buddy);
 914                         spin_unlock(&pool->stale_lock);
 915                         cancel_work_sync(&zhdr->work);
 916                         page = virt_to_page(zhdr);
 917                 } else {
 918                         spin_unlock(&pool->stale_lock);
 919                 }
 920         }
 921         if (!page)
 922                 page = alloc_page(gfp);
 923
 924         if (!page)
 925                 return -ENOMEM;
 926
 927         zhdr = init_z3fold_page(page, pool, gfp);
 928         if (!zhdr) {
 929                 __free_page(page);
 930                 return -ENOMEM;
 931         }
 932         atomic64_inc(&pool->pages_nr);
 933
 934         if (bud == HEADLESS) {
 935                 set_bit(PAGE_HEADLESS, &page->private);
 936                 goto headless;
 937         }
 938         if (can_sleep) {
 939                 lock_page(page);
 940                 __SetPageMovable(page, pool->inode->i_mapping);
 941                 unlock_page(page);
 942         } else {
 943                 if (trylock_page(page)) {
 944                         __SetPageMovable(page, pool->inode->i_mapping);
 945                         unlock_page(page);
 946                 }
 947         }
 948         z3fold_page_lock(zhdr);
 949
 950 found:
 951         if (bud == FIRST)
 952                 zhdr->first_chunks = chunks;
 953         else if (bud == LAST)
 954                 zhdr->last_chunks = chunks;
 955         else {
 956                 zhdr->middle_chunks = chunks;
 957                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 958         }
 959         add_to_unbuddied(pool, zhdr);
 960
 961 headless:
 962         spin_lock(&pool->lock);
 963         /* Add/move z3fold page to beginning of LRU */
 964         if (!list_empty(&page->lru))
 965                 list_del(&page->lru);
 966
 967         list_add(&page->lru, &pool->lru);
 968
 969         *handle = encode_handle(zhdr, bud);
 970         spin_unlock(&pool->lock);
 971         if (bud != HEADLESS)
 972                 z3fold_page_unlock(zhdr);
 973
 974         return 0;
 975 }
 976
 977 /**
 978  * z3fold_free() - frees the allocation associated with the given handle
 979  * @pool:       pool in which the allocation resided
 980  * @handle:     handle associated with the allocation returned by z3fold_alloc()
 981  *
 982  * In the case that the z3fold page in which the allocation resides is under
 983  * reclaim, as indicated by the PG_reclaim flag being set, this function
 984  * only sets the first|last_chunks to 0.  The page is actually freed
 985  * once both buddies are evicted (see z3fold_reclaim_page() below).
 986  */
 987 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 988 {
 989         struct z3fold_header *zhdr;
 990         struct page *page;
 991         enum buddy bud;
 992
 993         zhdr = handle_to_z3fold_header(handle);
 994         page = virt_to_page(zhdr);
 995
 996         if (test_bit(PAGE_HEADLESS, &page->private)) {
 997                 /* if a headless page is under reclaim, just leave.
 998                  * NB: we use test_and_set_bit for a reason: if the bit
 999                  * has not been set before, we release this page
1000                  * immediately so we don't care about its value any more.
1001                  */
1002                 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
1003                         spin_lock(&pool->lock);
1004                         list_del(&page->lru);
1005                         spin_unlock(&pool->lock);
1006                         free_z3fold_page(page, true);
1007                         atomic64_dec(&pool->pages_nr);
1008                 }
1009                 return;
1010         }
1011
1012         /* Non-headless case */
1013         z3fold_page_lock(zhdr);
1014         bud = handle_to_buddy(handle);
1015
1016         switch (bud) {
1017         case FIRST:
1018                 zhdr->first_chunks = 0;
1019                 break;
1020         case MIDDLE:
1021                 zhdr->middle_chunks = 0;
1022                 break;
1023         case LAST:
1024                 zhdr->last_chunks = 0;
1025                 break;
1026         default:
1027                 pr_err("%s: unknown bud %d\n", __func__, bud);
1028                 WARN_ON(1);
1029                 z3fold_page_unlock(zhdr);
1030                 return;
1031         }
1032
1033         free_handle(handle);
1034         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1035                 atomic64_dec(&pool->pages_nr);
1036                 return;
1037         }
1038         if (test_bit(PAGE_CLAIMED, &page->private)) {
1039                 z3fold_page_unlock(zhdr);
1040                 return;
1041         }
1042         if (unlikely(PageIsolated(page)) ||
1043             test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1044                 z3fold_page_unlock(zhdr);
1045                 return;
1046         }
1047         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1048                 spin_lock(&pool->lock);
1049                 list_del_init(&zhdr->buddy);
1050                 spin_unlock(&pool->lock);
1051                 zhdr->cpu = -1;
1052                 kref_get(&zhdr->refcount);
1053                 do_compact_page(zhdr, true);
1054                 return;
1055         }
1056         kref_get(&zhdr->refcount);
1057         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1058         z3fold_page_unlock(zhdr);
1059 }
1060
1061 /**
1062  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1063  * @pool:       pool from which a page will attempt to be evicted
1064  * @retries:    number of pages on the LRU list for which eviction will
1065  *              be attempted before failing
1066  *
1067  * z3fold reclaim is different from normal system reclaim in that it is done
1068  * from the bottom, up. This is because only the bottom layer, z3fold, has
1069  * information on how the allocations are organized within each z3fold page.
1070  * This has the potential to create interesting locking situations between
1071  * z3fold and the user, however.
1072  *
1073  * To avoid these, this is how z3fold_reclaim_page() should be called:
1074  *
1075  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1076  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1077  * call the user-defined eviction handler with the pool and handle as
1078  * arguments.
1079  *
1080  * If the handle can not be evicted, the eviction handler should return
1081  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1082  * appropriate list and try the next z3fold page on the LRU up to
1083  * a user defined number of retries.
1084  *
1085  * If the handle is successfully evicted, the eviction handler should
1086  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1087  * contains logic to delay freeing the page if the page is under reclaim,
1088  * as indicated by the setting of the PG_reclaim flag on the underlying page.
1089  *
1090  * If all buddies in the z3fold page are successfully evicted, then the
1091  * z3fold page can be freed.
1092  *
1093  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1094  * no pages to evict or an eviction handler is not registered, -EAGAIN if
1095  * the retry limit was hit.
1096  */
1097 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1098 {
1099         int i, ret = 0;
1100         struct z3fold_header *zhdr = NULL;
1101         struct page *page = NULL;
1102         struct list_head *pos;
1103         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1104
1105         spin_lock(&pool->lock);
1106         if (!pool->ops || !pool->ops->evict || retries == 0) {
1107                 spin_unlock(&pool->lock);
1108                 return -EINVAL;
1109         }
1110         for (i = 0; i < retries; i++) {
1111                 if (list_empty(&pool->lru)) {
1112                         spin_unlock(&pool->lock);
1113                         return -EINVAL;
1114                 }
1115                 list_for_each_prev(pos, &pool->lru) {
1116                         page = list_entry(pos, struct page, lru);
1117
1118                         /* this bit could have been set by free, in which case
1119                          * we pass over to the next page in the pool.
1120                          */
1121                         if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1122                                 continue;
1123
1124                         if (unlikely(PageIsolated(page)))
1125                                 continue;
1126                         if (test_bit(PAGE_HEADLESS, &page->private))
1127                                 break;
1128
1129                         zhdr = page_address(page);
1130                         if (!z3fold_page_trylock(zhdr)) {
1131                                 zhdr = NULL;
1132                                 continue; /* can't evict at this point */
1133                         }
1134                         kref_get(&zhdr->refcount);
1135                         list_del_init(&zhdr->buddy);
1136                         zhdr->cpu = -1;
1137                         break;
1138                 }
1139
1140                 if (!zhdr)
1141                         break;
1142
1143                 list_del_init(&page->lru);
1144                 spin_unlock(&pool->lock);
1145
1146                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1147                         /*
1148                          * We need encode the handles before unlocking, since
1149                          * we can race with free that will set
1150                          * (first|last)_chunks to 0
1151                          */
1152                         first_handle = 0;
1153                         last_handle = 0;
1154                         middle_handle = 0;
1155                         if (zhdr->first_chunks)
1156                                 first_handle = encode_handle(zhdr, FIRST);
1157                         if (zhdr->middle_chunks)
1158                                 middle_handle = encode_handle(zhdr, MIDDLE);
1159                         if (zhdr->last_chunks)
1160                                 last_handle = encode_handle(zhdr, LAST);
1161                         /*
1162                          * it's safe to unlock here because we hold a
1163                          * reference to this page
1164                          */
1165                         z3fold_page_unlock(zhdr);
1166                 } else {
1167                         first_handle = encode_handle(zhdr, HEADLESS);
1168                         last_handle = middle_handle = 0;
1169                 }
1170
1171                 /* Issue the eviction callback(s) */
1172                 if (middle_handle) {
1173                         ret = pool->ops->evict(pool, middle_handle);
1174                         if (ret)
1175                                 goto next;
1176                 }
1177                 if (first_handle) {
1178                         ret = pool->ops->evict(pool, first_handle);
1179                         if (ret)
1180                                 goto next;
1181                 }
1182                 if (last_handle) {
1183                         ret = pool->ops->evict(pool, last_handle);
1184                         if (ret)
1185                                 goto next;
1186                 }
1187 next:
1188                 if (test_bit(PAGE_HEADLESS, &page->private)) {
1189                         if (ret == 0) {
1190                                 free_z3fold_page(page, true);
1191                                 atomic64_dec(&pool->pages_nr);
1192                                 return 0;
1193                         }
1194                         spin_lock(&pool->lock);
1195                         list_add(&page->lru, &pool->lru);
1196                         spin_unlock(&pool->lock);
1197                 } else {
1198                         z3fold_page_lock(zhdr);
1199                         clear_bit(PAGE_CLAIMED, &page->private);
1200                         if (kref_put(&zhdr->refcount,
1201                                         release_z3fold_page_locked)) {
1202                                 atomic64_dec(&pool->pages_nr);
1203                                 return 0;
1204                         }
1205                         /*
1206                          * if we are here, the page is still not completely
1207                          * free. Take the global pool lock then to be able
1208                          * to add it back to the lru list
1209                          */
1210                         spin_lock(&pool->lock);
1211                         list_add(&page->lru, &pool->lru);
1212                         spin_unlock(&pool->lock);
1213                         z3fold_page_unlock(zhdr);
1214                 }
1215
1216                 /* We started off locked to we need to lock the pool back */
1217                 spin_lock(&pool->lock);
1218         }
1219         spin_unlock(&pool->lock);
1220         return -EAGAIN;
1221 }
1222
1223 /**
1224  * z3fold_map() - maps the allocation associated with the given handle
1225  * @pool:       pool in which the allocation resides
1226  * @handle:     handle associated with the allocation to be mapped
1227  *
1228  * Extracts the buddy number from handle and constructs the pointer to the
1229  * correct starting chunk within the page.
1230  *
1231  * Returns: a pointer to the mapped allocation
1232  */
1233 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1234 {
1235         struct z3fold_header *zhdr;
1236         struct page *page;
1237         void *addr;
1238         enum buddy buddy;
1239
1240         zhdr = handle_to_z3fold_header(handle);
1241         addr = zhdr;
1242         page = virt_to_page(zhdr);
1243
1244         if (test_bit(PAGE_HEADLESS, &page->private))
1245                 goto out;
1246
1247         z3fold_page_lock(zhdr);
1248         buddy = handle_to_buddy(handle);
1249         switch (buddy) {
1250         case FIRST:
1251                 addr += ZHDR_SIZE_ALIGNED;
1252                 break;
1253         case MIDDLE:
1254                 addr += zhdr->start_middle << CHUNK_SHIFT;
1255                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1256                 break;
1257         case LAST:
1258                 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1259                 break;
1260         default:
1261                 pr_err("unknown buddy id %d\n", buddy);
1262                 WARN_ON(1);
1263                 addr = NULL;
1264                 break;
1265         }
1266
1267         if (addr)
1268                 zhdr->mapped_count++;
1269         z3fold_page_unlock(zhdr);
1270 out:
1271         return addr;
1272 }
1273
1274 /**
1275  * z3fold_unmap() - unmaps the allocation associated with the given handle
1276  * @pool:       pool in which the allocation resides
1277  * @handle:     handle associated with the allocation to be unmapped
1278  */
1279 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1280 {
1281         struct z3fold_header *zhdr;
1282         struct page *page;
1283         enum buddy buddy;
1284
1285         zhdr = handle_to_z3fold_header(handle);
1286         page = virt_to_page(zhdr);
1287
1288         if (test_bit(PAGE_HEADLESS, &page->private))
1289                 return;
1290
1291         z3fold_page_lock(zhdr);
1292         buddy = handle_to_buddy(handle);
1293         if (buddy == MIDDLE)
1294                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1295         zhdr->mapped_count--;
1296         z3fold_page_unlock(zhdr);
1297 }
1298
1299 /**
1300  * z3fold_get_pool_size() - gets the z3fold pool size in pages
1301  * @pool:       pool whose size is being queried
1302  *
1303  * Returns: size in pages of the given pool.
1304  */
1305 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1306 {
1307         return atomic64_read(&pool->pages_nr);
1308 }
1309
1310 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1311 {
1312         struct z3fold_header *zhdr;
1313         struct z3fold_pool *pool;
1314
1315         VM_BUG_ON_PAGE(!PageMovable(page), page);
1316         VM_BUG_ON_PAGE(PageIsolated(page), page);
1317
1318         if (test_bit(PAGE_HEADLESS, &page->private))
1319                 return false;
1320
1321         zhdr = page_address(page);
1322         z3fold_page_lock(zhdr);
1323         if (test_bit(NEEDS_COMPACTING, &page->private) ||
1324             test_bit(PAGE_STALE, &page->private))
1325                 goto out;
1326
1327         pool = zhdr_to_pool(zhdr);
1328
1329         if (zhdr->mapped_count == 0) {
1330                 kref_get(&zhdr->refcount);
1331                 if (!list_empty(&zhdr->buddy))
1332                         list_del_init(&zhdr->buddy);
1333                 spin_lock(&pool->lock);
1334                 if (!list_empty(&page->lru))
1335                         list_del(&page->lru);
1336                 spin_unlock(&pool->lock);
1337                 z3fold_page_unlock(zhdr);
1338                 return true;
1339         }
1340 out:
1341         z3fold_page_unlock(zhdr);
1342         return false;
1343 }
1344
1345 static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1346                                struct page *page, enum migrate_mode mode)
1347 {
1348         struct z3fold_header *zhdr, *new_zhdr;
1349         struct z3fold_pool *pool;
1350         struct address_space *new_mapping;
1351
1352         VM_BUG_ON_PAGE(!PageMovable(page), page);
1353         VM_BUG_ON_PAGE(!PageIsolated(page), page);
1354         VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1355
1356         zhdr = page_address(page);
1357         pool = zhdr_to_pool(zhdr);
1358
1359         if (!z3fold_page_trylock(zhdr)) {
1360                 return -EAGAIN;
1361         }
1362         if (zhdr->mapped_count != 0) {
1363                 z3fold_page_unlock(zhdr);
1364                 return -EBUSY;
1365         }
1366         if (work_pending(&zhdr->work)) {
1367                 z3fold_page_unlock(zhdr);
1368                 return -EAGAIN;
1369         }
1370         new_zhdr = page_address(newpage);
1371         memcpy(new_zhdr, zhdr, PAGE_SIZE);
1372         newpage->private = page->private;
1373         page->private = 0;
1374         z3fold_page_unlock(zhdr);
1375         spin_lock_init(&new_zhdr->page_lock);
1376         INIT_WORK(&new_zhdr->work, compact_page_work);
1377         /*
1378          * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1379          * so we only have to reinitialize it.
1380          */
1381         INIT_LIST_HEAD(&new_zhdr->buddy);
1382         new_mapping = page_mapping(page);
1383         __ClearPageMovable(page);
1384         ClearPagePrivate(page);
1385
1386         get_page(newpage);
1387         z3fold_page_lock(new_zhdr);
1388         if (new_zhdr->first_chunks)
1389                 encode_handle(new_zhdr, FIRST);
1390         if (new_zhdr->last_chunks)
1391                 encode_handle(new_zhdr, LAST);
1392         if (new_zhdr->middle_chunks)
1393                 encode_handle(new_zhdr, MIDDLE);
1394         set_bit(NEEDS_COMPACTING, &newpage->private);
1395         new_zhdr->cpu = smp_processor_id();
1396         spin_lock(&pool->lock);
1397         list_add(&newpage->lru, &pool->lru);
1398         spin_unlock(&pool->lock);
1399         __SetPageMovable(newpage, new_mapping);
1400         z3fold_page_unlock(new_zhdr);
1401
1402         queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1403
1404         page_mapcount_reset(page);
1405         put_page(page);
1406         return 0;
1407 }
1408
1409 static void z3fold_page_putback(struct page *page)
1410 {
1411         struct z3fold_header *zhdr;
1412         struct z3fold_pool *pool;
1413
1414         zhdr = page_address(page);
1415         pool = zhdr_to_pool(zhdr);
1416
1417         z3fold_page_lock(zhdr);
1418         if (!list_empty(&zhdr->buddy))
1419                 list_del_init(&zhdr->buddy);
1420         INIT_LIST_HEAD(&page->lru);
1421         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1422                 atomic64_dec(&pool->pages_nr);
1423                 return;
1424         }
1425         spin_lock(&pool->lock);
1426         list_add(&page->lru, &pool->lru);
1427         spin_unlock(&pool->lock);
1428         z3fold_page_unlock(zhdr);
1429 }
1430
1431 static const struct address_space_operations z3fold_aops = {
1432         .isolate_page = z3fold_page_isolate,
1433         .migratepage = z3fold_page_migrate,
1434         .putback_page = z3fold_page_putback,
1435 };
1436
1437 /*****************
1438  * zpool
1439  ****************/
1440
1441 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1442 {
1443         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1444                 return pool->zpool_ops->evict(pool->zpool, handle);
1445         else
1446                 return -ENOENT;
1447 }
1448
1449 static const struct z3fold_ops z3fold_zpool_ops = {
1450         .evict =        z3fold_zpool_evict
1451 };
1452
1453 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1454                                const struct zpool_ops *zpool_ops,
1455                                struct zpool *zpool)
1456 {
1457         struct z3fold_pool *pool;
1458
1459         pool = z3fold_create_pool(name, gfp,
1460                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1461         if (pool) {
1462                 pool->zpool = zpool;
1463                 pool->zpool_ops = zpool_ops;
1464         }
1465         return pool;
1466 }
1467
1468 static void z3fold_zpool_destroy(void *pool)
1469 {
1470         z3fold_destroy_pool(pool);
1471 }
1472
1473 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1474                         unsigned long *handle)
1475 {
1476         return z3fold_alloc(pool, size, gfp, handle);
1477 }
1478 static void z3fold_zpool_free(void *pool, unsigned long handle)
1479 {
1480         z3fold_free(pool, handle);
1481 }
1482
1483 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1484                         unsigned int *reclaimed)
1485 {
1486         unsigned int total = 0;
1487         int ret = -EINVAL;
1488
1489         while (total < pages) {
1490                 ret = z3fold_reclaim_page(pool, 8);
1491                 if (ret < 0)
1492                         break;
1493                 total++;
1494         }
1495
1496         if (reclaimed)
1497                 *reclaimed = total;
1498
1499         return ret;
1500 }
1501
1502 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1503                         enum zpool_mapmode mm)
1504 {
1505         return z3fold_map(pool, handle);
1506 }
1507 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1508 {
1509         z3fold_unmap(pool, handle);
1510 }
1511
1512 static u64 z3fold_zpool_total_size(void *pool)
1513 {
1514         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1515 }
1516
1517 static struct zpool_driver z3fold_zpool_driver = {
1518         .type =         "z3fold",
1519         .owner =        THIS_MODULE,
1520         .create =       z3fold_zpool_create,
1521         .destroy =      z3fold_zpool_destroy,
1522         .malloc =       z3fold_zpool_malloc,
1523         .free =         z3fold_zpool_free,
1524         .shrink =       z3fold_zpool_shrink,
1525         .map =          z3fold_zpool_map,
1526         .unmap =        z3fold_zpool_unmap,
1527         .total_size =   z3fold_zpool_total_size,
1528 };
1529
1530 MODULE_ALIAS("zpool-z3fold");
1531
1532 static int __init init_z3fold(void)
1533 {
1534         int ret;
1535
1536         /* Make sure the z3fold header is not larger than the page size */
1537         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1538         ret = z3fold_mount();
1539         if (ret)
1540                 return ret;
1541
1542         zpool_register_driver(&z3fold_zpool_driver);
1543
1544         return 0;
1545 }
1546
1547 static void __exit exit_z3fold(void)
1548 {
1549         z3fold_unmount();
1550         zpool_unregister_driver(&z3fold_zpool_driver);
1551 }
1552
1553 module_init(init_z3fold);
1554 module_exit(exit_z3fold);
1555
1556 MODULE_LICENSE("GPL");
1557 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1558 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");