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  * @pool:               pointer to the containing pool
 105  * @cpu:                CPU which this page "belongs" to
 106  * @first_chunks:       the size of the first buddy in chunks, 0 if free
 107  * @middle_chunks:      the size of the middle buddy in chunks, 0 if free
 108  * @last_chunks:        the size of the last buddy in chunks, 0 if free
 109  * @first_num:          the starting number (for the first handle)
 110  * @mapped_count:       the number of objects currently mapped
 111  */
 112 struct z3fold_header {
 113         struct list_head buddy;
 114         spinlock_t page_lock;
 115         struct kref refcount;
 116         struct work_struct work;
 117         struct z3fold_buddy_slots *slots;
 118         struct z3fold_pool *pool;
 119         short cpu;
 120         unsigned short first_chunks;
 121         unsigned short middle_chunks;
 122         unsigned short last_chunks;
 123         unsigned short start_middle;
 124         unsigned short first_num:2;
 125         unsigned short mapped_count:2;
 126 };
 127
 128 /**
 129  * struct z3fold_pool - stores metadata for each z3fold pool
 130  * @name:       pool name
 131  * @lock:       protects pool unbuddied/lru lists
 132  * @stale_lock: protects pool stale page list
 133  * @unbuddied:  per-cpu array of lists tracking z3fold pages that contain 2-
 134  *              buddies; the list each z3fold page is added to depends on
 135  *              the size of its free region.
 136  * @lru:        list tracking the z3fold pages in LRU order by most recently
 137  *              added buddy.
 138  * @stale:      list of pages marked for freeing
 139  * @pages_nr:   number of z3fold pages in the pool.
 140  * @c_handle:   cache for z3fold_buddy_slots allocation
 141  * @ops:        pointer to a structure of user defined operations specified at
 142  *              pool creation time.
 143  * @compact_wq: workqueue for page layout background optimization
 144  * @release_wq: workqueue for safe page release
 145  * @work:       work_struct for safe page release
 146  * @inode:      inode for z3fold pseudo filesystem
 147  *
 148  * This structure is allocated at pool creation time and maintains metadata
 149  * pertaining to a particular z3fold pool.
 150  */
 151 struct z3fold_pool {
 152         const char *name;
 153         spinlock_t lock;
 154         spinlock_t stale_lock;
 155         struct list_head *unbuddied;
 156         struct list_head lru;
 157         struct list_head stale;
 158         atomic64_t pages_nr;
 159         struct kmem_cache *c_handle;
 160         const struct z3fold_ops *ops;
 161         struct zpool *zpool;
 162         const struct zpool_ops *zpool_ops;
 163         struct workqueue_struct *compact_wq;
 164         struct workqueue_struct *release_wq;
 165         struct work_struct work;
 166         struct inode *inode;
 167 };
 168
 169 /*
 170  * Internal z3fold page flags
 171  */
 172 enum z3fold_page_flags {
 173         PAGE_HEADLESS = 0,
 174         MIDDLE_CHUNK_MAPPED,
 175         NEEDS_COMPACTING,
 176         PAGE_STALE,
 177         PAGE_CLAIMED, /* by either reclaim or free */
 178 };
 179
 180 /*****************
 181  * Helpers
 182 *****************/
 183
 184 /* Converts an allocation size in bytes to size in z3fold chunks */
 185 static int size_to_chunks(size_t size)
 186 {
 187         return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
 188 }
 189
 190 #define for_each_unbuddied_list(_iter, _begin) \
 191         for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
 192
 193 static void compact_page_work(struct work_struct *w);
 194
 195 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
 196                                                         gfp_t gfp)
 197 {
 198         struct z3fold_buddy_slots *slots;
 199
 200         slots = kmem_cache_alloc(pool->c_handle,
 201                                  (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
 202
 203         if (slots) {
 204                 memset(slots->slot, 0, sizeof(slots->slot));
 205                 slots->pool = (unsigned long)pool;
 206         }
 207
 208         return slots;
 209 }
 210
 211 static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
 212 {
 213         return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
 214 }
 215
 216 static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 217 {
 218         return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 219 }
 220
 221 static inline void free_handle(unsigned long handle)
 222 {
 223         struct z3fold_buddy_slots *slots;
 224         int i;
 225         bool is_free;
 226
 227         if (handle & (1 << PAGE_HEADLESS))
 228                 return;
 229
 230         WARN_ON(*(unsigned long *)handle == 0);
 231         *(unsigned long *)handle = 0;
 232         slots = handle_to_slots(handle);
 233         is_free = true;
 234         for (i = 0; i <= BUDDY_MASK; i++) {
 235                 if (slots->slot[i]) {
 236                         is_free = false;
 237                         break;
 238                 }
 239         }
 240
 241         if (is_free) {
 242                 struct z3fold_pool *pool = slots_to_pool(slots);
 243
 244                 kmem_cache_free(pool->c_handle, slots);
 245         }
 246 }
 247
 248 static struct dentry *z3fold_do_mount(struct file_system_type *fs_type,
 249                                 int flags, const char *dev_name, void *data)
 250 {
 251         static const struct dentry_operations ops = {
 252                 .d_dname = simple_dname,
 253         };
 254
 255         return mount_pseudo(fs_type, "z3fold:", NULL, &ops, 0x33);
 256 }
 257
 258 static struct file_system_type z3fold_fs = {
 259         .name           = "z3fold",
 260         .mount          = z3fold_do_mount,
 261         .kill_sb        = kill_anon_super,
 262 };
 263
 264 static struct vfsmount *z3fold_mnt;
 265 static int z3fold_mount(void)
 266 {
 267         int ret = 0;
 268
 269         z3fold_mnt = kern_mount(&z3fold_fs);
 270         if (IS_ERR(z3fold_mnt))
 271                 ret = PTR_ERR(z3fold_mnt);
 272
 273         return ret;
 274 }
 275
 276 static void z3fold_unmount(void)
 277 {
 278         kern_unmount(z3fold_mnt);
 279 }
 280
 281 static const struct address_space_operations z3fold_aops;
 282 static int z3fold_register_migration(struct z3fold_pool *pool)
 283 {
 284         pool->inode = alloc_anon_inode(z3fold_mnt->mnt_sb);
 285         if (IS_ERR(pool->inode)) {
 286                 pool->inode = NULL;
 287                 return 1;
 288         }
 289
 290         pool->inode->i_mapping->private_data = pool;
 291         pool->inode->i_mapping->a_ops = &z3fold_aops;
 292         return 0;
 293 }
 294
 295 static void z3fold_unregister_migration(struct z3fold_pool *pool)
 296 {
 297         if (pool->inode)
 298                 iput(pool->inode);
 299  }
 300
 301 /* Initializes the z3fold header of a newly allocated z3fold page */
 302 static struct z3fold_header *init_z3fold_page(struct page *page,
 303                                         struct z3fold_pool *pool, gfp_t gfp)
 304 {
 305         struct z3fold_header *zhdr = page_address(page);
 306         struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp);
 307
 308         if (!slots)
 309                 return NULL;
 310
 311         INIT_LIST_HEAD(&page->lru);
 312         clear_bit(PAGE_HEADLESS, &page->private);
 313         clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
 314         clear_bit(NEEDS_COMPACTING, &page->private);
 315         clear_bit(PAGE_STALE, &page->private);
 316         clear_bit(PAGE_CLAIMED, &page->private);
 317
 318         spin_lock_init(&zhdr->page_lock);
 319         kref_init(&zhdr->refcount);
 320         zhdr->first_chunks = 0;
 321         zhdr->middle_chunks = 0;
 322         zhdr->last_chunks = 0;
 323         zhdr->first_num = 0;
 324         zhdr->start_middle = 0;
 325         zhdr->cpu = -1;
 326         zhdr->slots = slots;
 327         zhdr->pool = pool;
 328         INIT_LIST_HEAD(&zhdr->buddy);
 329         INIT_WORK(&zhdr->work, compact_page_work);
 330         return zhdr;
 331 }
 332
 333 /* Resets the struct page fields and frees the page */
 334 static void free_z3fold_page(struct page *page, bool headless)
 335 {
 336         if (!headless) {
 337                 lock_page(page);
 338                 __ClearPageMovable(page);
 339                 unlock_page(page);
 340         }
 341         ClearPagePrivate(page);
 342         __free_page(page);
 343 }
 344
 345 /* Lock a z3fold page */
 346 static inline void z3fold_page_lock(struct z3fold_header *zhdr)
 347 {
 348         spin_lock(&zhdr->page_lock);
 349 }
 350
 351 /* Try to lock a z3fold page */
 352 static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
 353 {
 354         return spin_trylock(&zhdr->page_lock);
 355 }
 356
 357 /* Unlock a z3fold page */
 358 static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
 359 {
 360         spin_unlock(&zhdr->page_lock);
 361 }
 362
 363 /* Helper function to build the index */
 364 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 365 {
 366         return (bud + zhdr->first_num) & BUDDY_MASK;
 367 }
 368
 369 /*
 370  * Encodes the handle of a particular buddy within a z3fold page
 371  * Pool lock should be held as this function accesses first_num
 372  */
 373 static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 374 {
 375         struct z3fold_buddy_slots *slots;
 376         unsigned long h = (unsigned long)zhdr;
 377         int idx = 0;
 378
 379         /*
 380          * For a headless page, its handle is its pointer with the extra
 381          * PAGE_HEADLESS bit set
 382          */
 383         if (bud == HEADLESS)
 384                 return h | (1 << PAGE_HEADLESS);
 385
 386         /* otherwise, return pointer to encoded handle */
 387         idx = __idx(zhdr, bud);
 388         h += idx;
 389         if (bud == LAST)
 390                 h |= (zhdr->last_chunks << BUDDY_SHIFT);
 391
 392         slots = zhdr->slots;
 393         slots->slot[idx] = h;
 394         return (unsigned long)&slots->slot[idx];
 395 }
 396
 397 /* Returns the z3fold page where a given handle is stored */
 398 static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
 399 {
 400         unsigned long addr = h;
 401
 402         if (!(addr & (1 << PAGE_HEADLESS)))
 403                 addr = *(unsigned long *)h;
 404
 405         return (struct z3fold_header *)(addr & PAGE_MASK);
 406 }
 407
 408 /* only for LAST bud, returns zero otherwise */
 409 static unsigned short handle_to_chunks(unsigned long handle)
 410 {
 411         unsigned long addr = *(unsigned long *)handle;
 412
 413         return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 414 }
 415
 416 /*
 417  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
 418  *  but that doesn't matter. because the masking will result in the
 419  *  correct buddy number.
 420  */
 421 static enum buddy handle_to_buddy(unsigned long handle)
 422 {
 423         struct z3fold_header *zhdr;
 424         unsigned long addr;
 425
 426         WARN_ON(handle & (1 << PAGE_HEADLESS));
 427         addr = *(unsigned long *)handle;
 428         zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 429         return (addr - zhdr->first_num) & BUDDY_MASK;
 430 }
 431
 432 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
 433 {
 434         return zhdr->pool;
 435 }
 436
 437 static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 438 {
 439         struct page *page = virt_to_page(zhdr);
 440         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 441
 442         WARN_ON(!list_empty(&zhdr->buddy));
 443         set_bit(PAGE_STALE, &page->private);
 444         clear_bit(NEEDS_COMPACTING, &page->private);
 445         spin_lock(&pool->lock);
 446         if (!list_empty(&page->lru))
 447                 list_del_init(&page->lru);
 448         spin_unlock(&pool->lock);
 449         if (locked)
 450                 z3fold_page_unlock(zhdr);
 451         spin_lock(&pool->stale_lock);
 452         list_add(&zhdr->buddy, &pool->stale);
 453         queue_work(pool->release_wq, &pool->work);
 454         spin_unlock(&pool->stale_lock);
 455 }
 456
 457 static void __attribute__((__unused__))
 458                         release_z3fold_page(struct kref *ref)
 459 {
 460         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 461                                                 refcount);
 462         __release_z3fold_page(zhdr, false);
 463 }
 464
 465 static void release_z3fold_page_locked(struct kref *ref)
 466 {
 467         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 468                                                 refcount);
 469         WARN_ON(z3fold_page_trylock(zhdr));
 470         __release_z3fold_page(zhdr, true);
 471 }
 472
 473 static void release_z3fold_page_locked_list(struct kref *ref)
 474 {
 475         struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 476                                                refcount);
 477         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 478         spin_lock(&pool->lock);
 479         list_del_init(&zhdr->buddy);
 480         spin_unlock(&pool->lock);
 481
 482         WARN_ON(z3fold_page_trylock(zhdr));
 483         __release_z3fold_page(zhdr, true);
 484 }
 485
 486 static void free_pages_work(struct work_struct *w)
 487 {
 488         struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
 489
 490         spin_lock(&pool->stale_lock);
 491         while (!list_empty(&pool->stale)) {
 492                 struct z3fold_header *zhdr = list_first_entry(&pool->stale,
 493                                                 struct z3fold_header, buddy);
 494                 struct page *page = virt_to_page(zhdr);
 495
 496                 list_del(&zhdr->buddy);
 497                 if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
 498                         continue;
 499                 spin_unlock(&pool->stale_lock);
 500                 cancel_work_sync(&zhdr->work);
 501                 free_z3fold_page(page, false);
 502                 cond_resched();
 503                 spin_lock(&pool->stale_lock);
 504         }
 505         spin_unlock(&pool->stale_lock);
 506 }
 507
 508 /*
 509  * Returns the number of free chunks in a z3fold page.
 510  * NB: can't be used with HEADLESS pages.
 511  */
 512 static int num_free_chunks(struct z3fold_header *zhdr)
 513 {
 514         int nfree;
 515         /*
 516          * If there is a middle object, pick up the bigger free space
 517          * either before or after it. Otherwise just subtract the number
 518          * of chunks occupied by the first and the last objects.
 519          */
 520         if (zhdr->middle_chunks != 0) {
 521                 int nfree_before = zhdr->first_chunks ?
 522                         0 : zhdr->start_middle - ZHDR_CHUNKS;
 523                 int nfree_after = zhdr->last_chunks ?
 524                         0 : TOTAL_CHUNKS -
 525                                 (zhdr->start_middle + zhdr->middle_chunks);
 526                 nfree = max(nfree_before, nfree_after);
 527         } else
 528                 nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 529         return nfree;
 530 }
 531
 532 /* Add to the appropriate unbuddied list */
 533 static inline void add_to_unbuddied(struct z3fold_pool *pool,
 534                                 struct z3fold_header *zhdr)
 535 {
 536         if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
 537                         zhdr->middle_chunks == 0) {
 538                 struct list_head *unbuddied = get_cpu_ptr(pool->unbuddied);
 539
 540                 int freechunks = num_free_chunks(zhdr);
 541                 spin_lock(&pool->lock);
 542                 list_add(&zhdr->buddy, &unbuddied[freechunks]);
 543                 spin_unlock(&pool->lock);
 544                 zhdr->cpu = smp_processor_id();
 545                 put_cpu_ptr(pool->unbuddied);
 546         }
 547 }
 548
 549 static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 550                                 unsigned short dst_chunk)
 551 {
 552         void *beg = zhdr;
 553         return memmove(beg + (dst_chunk << CHUNK_SHIFT),
 554                        beg + (zhdr->start_middle << CHUNK_SHIFT),
 555                        zhdr->middle_chunks << CHUNK_SHIFT);
 556 }
 557
 558 #define BIG_CHUNK_GAP   3
 559 /* Has to be called with lock held */
 560 static int z3fold_compact_page(struct z3fold_header *zhdr)
 561 {
 562         struct page *page = virt_to_page(zhdr);
 563
 564         if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
 565                 return 0; /* can't move middle chunk, it's used */
 566
 567         if (unlikely(PageIsolated(page)))
 568                 return 0;
 569
 570         if (zhdr->middle_chunks == 0)
 571                 return 0; /* nothing to compact */
 572
 573         if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
 574                 /* move to the beginning */
 575                 mchunk_memmove(zhdr, ZHDR_CHUNKS);
 576                 zhdr->first_chunks = zhdr->middle_chunks;
 577                 zhdr->middle_chunks = 0;
 578                 zhdr->start_middle = 0;
 579                 zhdr->first_num++;
 580                 return 1;
 581         }
 582
 583         /*
 584          * moving data is expensive, so let's only do that if
 585          * there's substantial gain (at least BIG_CHUNK_GAP chunks)
 586          */
 587         if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
 588             zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
 589                         BIG_CHUNK_GAP) {
 590                 mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
 591                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 592                 return 1;
 593         } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
 594                    TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
 595                                         + zhdr->middle_chunks) >=
 596                         BIG_CHUNK_GAP) {
 597                 unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
 598                         zhdr->middle_chunks;
 599                 mchunk_memmove(zhdr, new_start);
 600                 zhdr->start_middle = new_start;
 601                 return 1;
 602         }
 603
 604         return 0;
 605 }
 606
 607 static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 608 {
 609         struct z3fold_pool *pool = zhdr_to_pool(zhdr);
 610         struct page *page;
 611
 612         page = virt_to_page(zhdr);
 613         if (locked)
 614                 WARN_ON(z3fold_page_trylock(zhdr));
 615         else
 616                 z3fold_page_lock(zhdr);
 617         if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
 618                 z3fold_page_unlock(zhdr);
 619                 return;
 620         }
 621         spin_lock(&pool->lock);
 622         list_del_init(&zhdr->buddy);
 623         spin_unlock(&pool->lock);
 624
 625         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
 626                 atomic64_dec(&pool->pages_nr);
 627                 return;
 628         }
 629
 630         if (unlikely(PageIsolated(page) ||
 631                      test_bit(PAGE_STALE, &page->private))) {
 632                 z3fold_page_unlock(zhdr);
 633                 return;
 634         }
 635
 636         z3fold_compact_page(zhdr);
 637         add_to_unbuddied(pool, zhdr);
 638         z3fold_page_unlock(zhdr);
 639 }
 640
 641 static void compact_page_work(struct work_struct *w)
 642 {
 643         struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
 644                                                 work);
 645
 646         do_compact_page(zhdr, false);
 647 }
 648
 649 /* returns _locked_ z3fold page header or NULL */
 650 static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
 651                                                 size_t size, bool can_sleep)
 652 {
 653         struct z3fold_header *zhdr = NULL;
 654         struct page *page;
 655         struct list_head *unbuddied;
 656         int chunks = size_to_chunks(size), i;
 657
 658 lookup:
 659         /* First, try to find an unbuddied z3fold page. */
 660         unbuddied = get_cpu_ptr(pool->unbuddied);
 661         for_each_unbuddied_list(i, chunks) {
 662                 struct list_head *l = &unbuddied[i];
 663
 664                 zhdr = list_first_entry_or_null(READ_ONCE(l),
 665                                         struct z3fold_header, buddy);
 666
 667                 if (!zhdr)
 668                         continue;
 669
 670                 /* Re-check under lock. */
 671                 spin_lock(&pool->lock);
 672                 l = &unbuddied[i];
 673                 if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
 674                                                 struct z3fold_header, buddy)) ||
 675                     !z3fold_page_trylock(zhdr)) {
 676                         spin_unlock(&pool->lock);
 677                         zhdr = NULL;
 678                         put_cpu_ptr(pool->unbuddied);
 679                         if (can_sleep)
 680                                 cond_resched();
 681                         goto lookup;
 682                 }
 683                 list_del_init(&zhdr->buddy);
 684                 zhdr->cpu = -1;
 685                 spin_unlock(&pool->lock);
 686
 687                 page = virt_to_page(zhdr);
 688                 if (test_bit(NEEDS_COMPACTING, &page->private)) {
 689                         z3fold_page_unlock(zhdr);
 690                         zhdr = NULL;
 691                         put_cpu_ptr(pool->unbuddied);
 692                         if (can_sleep)
 693                                 cond_resched();
 694                         goto lookup;
 695                 }
 696
 697                 /*
 698                  * this page could not be removed from its unbuddied
 699                  * list while pool lock was held, and then we've taken
 700                  * page lock so kref_put could not be called before
 701                  * we got here, so it's safe to just call kref_get()
 702                  */
 703                 kref_get(&zhdr->refcount);
 704                 break;
 705         }
 706         put_cpu_ptr(pool->unbuddied);
 707
 708         if (!zhdr) {
 709                 int cpu;
 710
 711                 /* look for _exact_ match on other cpus' lists */
 712                 for_each_online_cpu(cpu) {
 713                         struct list_head *l;
 714
 715                         unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
 716                         spin_lock(&pool->lock);
 717                         l = &unbuddied[chunks];
 718
 719                         zhdr = list_first_entry_or_null(READ_ONCE(l),
 720                                                 struct z3fold_header, buddy);
 721
 722                         if (!zhdr || !z3fold_page_trylock(zhdr)) {
 723                                 spin_unlock(&pool->lock);
 724                                 zhdr = NULL;
 725                                 continue;
 726                         }
 727                         list_del_init(&zhdr->buddy);
 728                         zhdr->cpu = -1;
 729                         spin_unlock(&pool->lock);
 730
 731                         page = virt_to_page(zhdr);
 732                         if (test_bit(NEEDS_COMPACTING, &page->private)) {
 733                                 z3fold_page_unlock(zhdr);
 734                                 zhdr = NULL;
 735                                 if (can_sleep)
 736                                         cond_resched();
 737                                 continue;
 738                         }
 739                         kref_get(&zhdr->refcount);
 740                         break;
 741                 }
 742         }
 743
 744         return zhdr;
 745 }
 746
 747 /*
 748  * API Functions
 749  */
 750
 751 /**
 752  * z3fold_create_pool() - create a new z3fold pool
 753  * @name:       pool name
 754  * @gfp:        gfp flags when allocating the z3fold pool structure
 755  * @ops:        user-defined operations for the z3fold pool
 756  *
 757  * Return: pointer to the new z3fold pool or NULL if the metadata allocation
 758  * failed.
 759  */
 760 static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp,
 761                 const struct z3fold_ops *ops)
 762 {
 763         struct z3fold_pool *pool = NULL;
 764         int i, cpu;
 765
 766         pool = kzalloc(sizeof(struct z3fold_pool), gfp);
 767         if (!pool)
 768                 goto out;
 769         pool->c_handle = kmem_cache_create("z3fold_handle",
 770                                 sizeof(struct z3fold_buddy_slots),
 771                                 SLOTS_ALIGN, 0, NULL);
 772         if (!pool->c_handle)
 773                 goto out_c;
 774         spin_lock_init(&pool->lock);
 775         spin_lock_init(&pool->stale_lock);
 776         pool->unbuddied = __alloc_percpu(sizeof(struct list_head)*NCHUNKS, 2);
 777         if (!pool->unbuddied)
 778                 goto out_pool;
 779         for_each_possible_cpu(cpu) {
 780                 struct list_head *unbuddied =
 781                                 per_cpu_ptr(pool->unbuddied, cpu);
 782                 for_each_unbuddied_list(i, 0)
 783                         INIT_LIST_HEAD(&unbuddied[i]);
 784         }
 785         INIT_LIST_HEAD(&pool->lru);
 786         INIT_LIST_HEAD(&pool->stale);
 787         atomic64_set(&pool->pages_nr, 0);
 788         pool->name = name;
 789         pool->compact_wq = create_singlethread_workqueue(pool->name);
 790         if (!pool->compact_wq)
 791                 goto out_unbuddied;
 792         pool->release_wq = create_singlethread_workqueue(pool->name);
 793         if (!pool->release_wq)
 794                 goto out_wq;
 795         if (z3fold_register_migration(pool))
 796                 goto out_rwq;
 797         INIT_WORK(&pool->work, free_pages_work);
 798         pool->ops = ops;
 799         return pool;
 800
 801 out_rwq:
 802         destroy_workqueue(pool->release_wq);
 803 out_wq:
 804         destroy_workqueue(pool->compact_wq);
 805 out_unbuddied:
 806         free_percpu(pool->unbuddied);
 807 out_pool:
 808         kmem_cache_destroy(pool->c_handle);
 809 out_c:
 810         kfree(pool);
 811 out:
 812         return NULL;
 813 }
 814
 815 /**
 816  * z3fold_destroy_pool() - destroys an existing z3fold pool
 817  * @pool:       the z3fold pool to be destroyed
 818  *
 819  * The pool should be emptied before this function is called.
 820  */
 821 static void z3fold_destroy_pool(struct z3fold_pool *pool)
 822 {
 823         kmem_cache_destroy(pool->c_handle);
 824         z3fold_unregister_migration(pool);
 825         destroy_workqueue(pool->release_wq);
 826         destroy_workqueue(pool->compact_wq);
 827         kfree(pool);
 828 }
 829
 830 /**
 831  * z3fold_alloc() - allocates a region of a given size
 832  * @pool:       z3fold pool from which to allocate
 833  * @size:       size in bytes of the desired allocation
 834  * @gfp:        gfp flags used if the pool needs to grow
 835  * @handle:     handle of the new allocation
 836  *
 837  * This function will attempt to find a free region in the pool large enough to
 838  * satisfy the allocation request.  A search of the unbuddied lists is
 839  * performed first. If no suitable free region is found, then a new page is
 840  * allocated and added to the pool to satisfy the request.
 841  *
 842  * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
 843  * as z3fold pool pages.
 844  *
 845  * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
 846  * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
 847  * a new page.
 848  */
 849 static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
 850                         unsigned long *handle)
 851 {
 852         int chunks = size_to_chunks(size);
 853         struct z3fold_header *zhdr = NULL;
 854         struct page *page = NULL;
 855         enum buddy bud;
 856         bool can_sleep = gfpflags_allow_blocking(gfp);
 857
 858         if (!size)
 859                 return -EINVAL;
 860
 861         if (size > PAGE_SIZE)
 862                 return -ENOSPC;
 863
 864         if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
 865                 bud = HEADLESS;
 866         else {
 867 retry:
 868                 zhdr = __z3fold_alloc(pool, size, can_sleep);
 869                 if (zhdr) {
 870                         if (zhdr->first_chunks == 0) {
 871                                 if (zhdr->middle_chunks != 0 &&
 872                                     chunks >= zhdr->start_middle)
 873                                         bud = LAST;
 874                                 else
 875                                         bud = FIRST;
 876                         } else if (zhdr->last_chunks == 0)
 877                                 bud = LAST;
 878                         else if (zhdr->middle_chunks == 0)
 879                                 bud = MIDDLE;
 880                         else {
 881                                 if (kref_put(&zhdr->refcount,
 882                                              release_z3fold_page_locked))
 883                                         atomic64_dec(&pool->pages_nr);
 884                                 else
 885                                         z3fold_page_unlock(zhdr);
 886                                 pr_err("No free chunks in unbuddied\n");
 887                                 WARN_ON(1);
 888                                 goto retry;
 889                         }
 890                         page = virt_to_page(zhdr);
 891                         goto found;
 892                 }
 893                 bud = FIRST;
 894         }
 895
 896         page = NULL;
 897         if (can_sleep) {
 898                 spin_lock(&pool->stale_lock);
 899                 zhdr = list_first_entry_or_null(&pool->stale,
 900                                                 struct z3fold_header, buddy);
 901                 /*
 902                  * Before allocating a page, let's see if we can take one from
 903                  * the stale pages list. cancel_work_sync() can sleep so we
 904                  * limit this case to the contexts where we can sleep
 905                  */
 906                 if (zhdr) {
 907                         list_del(&zhdr->buddy);
 908                         spin_unlock(&pool->stale_lock);
 909                         cancel_work_sync(&zhdr->work);
 910                         page = virt_to_page(zhdr);
 911                 } else {
 912                         spin_unlock(&pool->stale_lock);
 913                 }
 914         }
 915         if (!page)
 916                 page = alloc_page(gfp);
 917
 918         if (!page)
 919                 return -ENOMEM;
 920
 921         zhdr = init_z3fold_page(page, pool, gfp);
 922         if (!zhdr) {
 923                 __free_page(page);
 924                 return -ENOMEM;
 925         }
 926         atomic64_inc(&pool->pages_nr);
 927
 928         if (bud == HEADLESS) {
 929                 set_bit(PAGE_HEADLESS, &page->private);
 930                 goto headless;
 931         }
 932         if (can_sleep) {
 933                 lock_page(page);
 934                 __SetPageMovable(page, pool->inode->i_mapping);
 935                 unlock_page(page);
 936         } else {
 937                 if (trylock_page(page)) {
 938                         __SetPageMovable(page, pool->inode->i_mapping);
 939                         unlock_page(page);
 940                 }
 941         }
 942         z3fold_page_lock(zhdr);
 943
 944 found:
 945         if (bud == FIRST)
 946                 zhdr->first_chunks = chunks;
 947         else if (bud == LAST)
 948                 zhdr->last_chunks = chunks;
 949         else {
 950                 zhdr->middle_chunks = chunks;
 951                 zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
 952         }
 953         add_to_unbuddied(pool, zhdr);
 954
 955 headless:
 956         spin_lock(&pool->lock);
 957         /* Add/move z3fold page to beginning of LRU */
 958         if (!list_empty(&page->lru))
 959                 list_del(&page->lru);
 960
 961         list_add(&page->lru, &pool->lru);
 962
 963         *handle = encode_handle(zhdr, bud);
 964         spin_unlock(&pool->lock);
 965         if (bud != HEADLESS)
 966                 z3fold_page_unlock(zhdr);
 967
 968         return 0;
 969 }
 970
 971 /**
 972  * z3fold_free() - frees the allocation associated with the given handle
 973  * @pool:       pool in which the allocation resided
 974  * @handle:     handle associated with the allocation returned by z3fold_alloc()
 975  *
 976  * In the case that the z3fold page in which the allocation resides is under
 977  * reclaim, as indicated by the PG_reclaim flag being set, this function
 978  * only sets the first|last_chunks to 0.  The page is actually freed
 979  * once both buddies are evicted (see z3fold_reclaim_page() below).
 980  */
 981 static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 982 {
 983         struct z3fold_header *zhdr;
 984         struct page *page;
 985         enum buddy bud;
 986
 987         zhdr = handle_to_z3fold_header(handle);
 988         page = virt_to_page(zhdr);
 989
 990         if (test_bit(PAGE_HEADLESS, &page->private)) {
 991                 /* if a headless page is under reclaim, just leave.
 992                  * NB: we use test_and_set_bit for a reason: if the bit
 993                  * has not been set before, we release this page
 994                  * immediately so we don't care about its value any more.
 995                  */
 996                 if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
 997                         spin_lock(&pool->lock);
 998                         list_del(&page->lru);
 999                         spin_unlock(&pool->lock);
1000                         free_z3fold_page(page, true);
1001                         atomic64_dec(&pool->pages_nr);
1002                 }
1003                 return;
1004         }
1005
1006         /* Non-headless case */
1007         z3fold_page_lock(zhdr);
1008         bud = handle_to_buddy(handle);
1009
1010         switch (bud) {
1011         case FIRST:
1012                 zhdr->first_chunks = 0;
1013                 break;
1014         case MIDDLE:
1015                 zhdr->middle_chunks = 0;
1016                 break;
1017         case LAST:
1018                 zhdr->last_chunks = 0;
1019                 break;
1020         default:
1021                 pr_err("%s: unknown bud %d\n", __func__, bud);
1022                 WARN_ON(1);
1023                 z3fold_page_unlock(zhdr);
1024                 return;
1025         }
1026
1027         free_handle(handle);
1028         if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
1029                 atomic64_dec(&pool->pages_nr);
1030                 return;
1031         }
1032         if (test_bit(PAGE_CLAIMED, &page->private)) {
1033                 z3fold_page_unlock(zhdr);
1034                 return;
1035         }
1036         if (unlikely(PageIsolated(page)) ||
1037             test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
1038                 z3fold_page_unlock(zhdr);
1039                 return;
1040         }
1041         if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
1042                 spin_lock(&pool->lock);
1043                 list_del_init(&zhdr->buddy);
1044                 spin_unlock(&pool->lock);
1045                 zhdr->cpu = -1;
1046                 kref_get(&zhdr->refcount);
1047                 do_compact_page(zhdr, true);
1048                 return;
1049         }
1050         kref_get(&zhdr->refcount);
1051         queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
1052         z3fold_page_unlock(zhdr);
1053 }
1054
1055 /**
1056  * z3fold_reclaim_page() - evicts allocations from a pool page and frees it
1057  * @pool:       pool from which a page will attempt to be evicted
1058  * @retries:    number of pages on the LRU list for which eviction will
1059  *              be attempted before failing
1060  *
1061  * z3fold reclaim is different from normal system reclaim in that it is done
1062  * from the bottom, up. This is because only the bottom layer, z3fold, has
1063  * information on how the allocations are organized within each z3fold page.
1064  * This has the potential to create interesting locking situations between
1065  * z3fold and the user, however.
1066  *
1067  * To avoid these, this is how z3fold_reclaim_page() should be called:
1068  *
1069  * The user detects a page should be reclaimed and calls z3fold_reclaim_page().
1070  * z3fold_reclaim_page() will remove a z3fold page from the pool LRU list and
1071  * call the user-defined eviction handler with the pool and handle as
1072  * arguments.
1073  *
1074  * If the handle can not be evicted, the eviction handler should return
1075  * non-zero. z3fold_reclaim_page() will add the z3fold page back to the
1076  * appropriate list and try the next z3fold page on the LRU up to
1077  * a user defined number of retries.
1078  *
1079  * If the handle is successfully evicted, the eviction handler should
1080  * return 0 _and_ should have called z3fold_free() on the handle. z3fold_free()
1081  * contains logic to delay freeing the page if the page is under reclaim,
1082  * as indicated by the setting of the PG_reclaim flag on the underlying page.
1083  *
1084  * If all buddies in the z3fold page are successfully evicted, then the
1085  * z3fold page can be freed.
1086  *
1087  * Returns: 0 if page is successfully freed, otherwise -EINVAL if there are
1088  * no pages to evict or an eviction handler is not registered, -EAGAIN if
1089  * the retry limit was hit.
1090  */
1091 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
1092 {
1093         int i, ret = 0;
1094         struct z3fold_header *zhdr = NULL;
1095         struct page *page = NULL;
1096         struct list_head *pos;
1097         unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
1098
1099         spin_lock(&pool->lock);
1100         if (!pool->ops || !pool->ops->evict || retries == 0) {
1101                 spin_unlock(&pool->lock);
1102                 return -EINVAL;
1103         }
1104         for (i = 0; i < retries; i++) {
1105                 if (list_empty(&pool->lru)) {
1106                         spin_unlock(&pool->lock);
1107                         return -EINVAL;
1108                 }
1109                 list_for_each_prev(pos, &pool->lru) {
1110                         page = list_entry(pos, struct page, lru);
1111
1112                         /* this bit could have been set by free, in which case
1113                          * we pass over to the next page in the pool.
1114                          */
1115                         if (test_and_set_bit(PAGE_CLAIMED, &page->private))
1116                                 continue;
1117
1118                         if (unlikely(PageIsolated(page)))
1119                                 continue;
1120                         if (test_bit(PAGE_HEADLESS, &page->private))
1121                                 break;
1122
1123                         zhdr = page_address(page);
1124                         if (!z3fold_page_trylock(zhdr)) {
1125                                 zhdr = NULL;
1126                                 continue; /* can't evict at this point */
1127                         }
1128                         kref_get(&zhdr->refcount);
1129                         list_del_init(&zhdr->buddy);
1130                         zhdr->cpu = -1;
1131                         break;
1132                 }
1133
1134                 if (!zhdr)
1135                         break;
1136
1137                 list_del_init(&page->lru);
1138                 spin_unlock(&pool->lock);
1139
1140                 if (!test_bit(PAGE_HEADLESS, &page->private)) {
1141                         /*
1142                          * We need encode the handles before unlocking, since
1143                          * we can race with free that will set
1144                          * (first|last)_chunks to 0
1145                          */
1146                         first_handle = 0;
1147                         last_handle = 0;
1148                         middle_handle = 0;
1149                         if (zhdr->first_chunks)
1150                                 first_handle = encode_handle(zhdr, FIRST);
1151                         if (zhdr->middle_chunks)
1152                                 middle_handle = encode_handle(zhdr, MIDDLE);
1153                         if (zhdr->last_chunks)
1154                                 last_handle = encode_handle(zhdr, LAST);
1155                         /*
1156                          * it's safe to unlock here because we hold a
1157                          * reference to this page
1158                          */
1159                         z3fold_page_unlock(zhdr);
1160                 } else {
1161                         first_handle = encode_handle(zhdr, HEADLESS);
1162                         last_handle = middle_handle = 0;
1163                 }
1164
1165                 /* Issue the eviction callback(s) */
1166                 if (middle_handle) {
1167                         ret = pool->ops->evict(pool, middle_handle);
1168                         if (ret)
1169                                 goto next;
1170                 }
1171                 if (first_handle) {
1172                         ret = pool->ops->evict(pool, first_handle);
1173                         if (ret)
1174                                 goto next;
1175                 }
1176                 if (last_handle) {
1177                         ret = pool->ops->evict(pool, last_handle);
1178                         if (ret)
1179                                 goto next;
1180                 }
1181 next:
1182                 if (test_bit(PAGE_HEADLESS, &page->private)) {
1183                         if (ret == 0) {
1184                                 free_z3fold_page(page, true);
1185                                 atomic64_dec(&pool->pages_nr);
1186                                 return 0;
1187                         }
1188                         spin_lock(&pool->lock);
1189                         list_add(&page->lru, &pool->lru);
1190                         spin_unlock(&pool->lock);
1191                 } else {
1192                         z3fold_page_lock(zhdr);
1193                         clear_bit(PAGE_CLAIMED, &page->private);
1194                         if (kref_put(&zhdr->refcount,
1195                                         release_z3fold_page_locked)) {
1196                                 atomic64_dec(&pool->pages_nr);
1197                                 return 0;
1198                         }
1199                         /*
1200                          * if we are here, the page is still not completely
1201                          * free. Take the global pool lock then to be able
1202                          * to add it back to the lru list
1203                          */
1204                         spin_lock(&pool->lock);
1205                         list_add(&page->lru, &pool->lru);
1206                         spin_unlock(&pool->lock);
1207                         z3fold_page_unlock(zhdr);
1208                 }
1209
1210                 /* We started off locked to we need to lock the pool back */
1211                 spin_lock(&pool->lock);
1212         }
1213         spin_unlock(&pool->lock);
1214         return -EAGAIN;
1215 }
1216
1217 /**
1218  * z3fold_map() - maps the allocation associated with the given handle
1219  * @pool:       pool in which the allocation resides
1220  * @handle:     handle associated with the allocation to be mapped
1221  *
1222  * Extracts the buddy number from handle and constructs the pointer to the
1223  * correct starting chunk within the page.
1224  *
1225  * Returns: a pointer to the mapped allocation
1226  */
1227 static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
1228 {
1229         struct z3fold_header *zhdr;
1230         struct page *page;
1231         void *addr;
1232         enum buddy buddy;
1233
1234         zhdr = handle_to_z3fold_header(handle);
1235         addr = zhdr;
1236         page = virt_to_page(zhdr);
1237
1238         if (test_bit(PAGE_HEADLESS, &page->private))
1239                 goto out;
1240
1241         z3fold_page_lock(zhdr);
1242         buddy = handle_to_buddy(handle);
1243         switch (buddy) {
1244         case FIRST:
1245                 addr += ZHDR_SIZE_ALIGNED;
1246                 break;
1247         case MIDDLE:
1248                 addr += zhdr->start_middle << CHUNK_SHIFT;
1249                 set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1250                 break;
1251         case LAST:
1252                 addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
1253                 break;
1254         default:
1255                 pr_err("unknown buddy id %d\n", buddy);
1256                 WARN_ON(1);
1257                 addr = NULL;
1258                 break;
1259         }
1260
1261         if (addr)
1262                 zhdr->mapped_count++;
1263         z3fold_page_unlock(zhdr);
1264 out:
1265         return addr;
1266 }
1267
1268 /**
1269  * z3fold_unmap() - unmaps the allocation associated with the given handle
1270  * @pool:       pool in which the allocation resides
1271  * @handle:     handle associated with the allocation to be unmapped
1272  */
1273 static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
1274 {
1275         struct z3fold_header *zhdr;
1276         struct page *page;
1277         enum buddy buddy;
1278
1279         zhdr = handle_to_z3fold_header(handle);
1280         page = virt_to_page(zhdr);
1281
1282         if (test_bit(PAGE_HEADLESS, &page->private))
1283                 return;
1284
1285         z3fold_page_lock(zhdr);
1286         buddy = handle_to_buddy(handle);
1287         if (buddy == MIDDLE)
1288                 clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
1289         zhdr->mapped_count--;
1290         z3fold_page_unlock(zhdr);
1291 }
1292
1293 /**
1294  * z3fold_get_pool_size() - gets the z3fold pool size in pages
1295  * @pool:       pool whose size is being queried
1296  *
1297  * Returns: size in pages of the given pool.
1298  */
1299 static u64 z3fold_get_pool_size(struct z3fold_pool *pool)
1300 {
1301         return atomic64_read(&pool->pages_nr);
1302 }
1303
1304 static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
1305 {
1306         struct z3fold_header *zhdr;
1307         struct z3fold_pool *pool;
1308
1309         VM_BUG_ON_PAGE(!PageMovable(page), page);
1310         VM_BUG_ON_PAGE(PageIsolated(page), page);
1311
1312         if (test_bit(PAGE_HEADLESS, &page->private))
1313                 return false;
1314
1315         zhdr = page_address(page);
1316         z3fold_page_lock(zhdr);
1317         if (test_bit(NEEDS_COMPACTING, &page->private) ||
1318             test_bit(PAGE_STALE, &page->private))
1319                 goto out;
1320
1321         pool = zhdr_to_pool(zhdr);
1322
1323         if (zhdr->mapped_count == 0) {
1324                 kref_get(&zhdr->refcount);
1325                 if (!list_empty(&zhdr->buddy))
1326                         list_del_init(&zhdr->buddy);
1327                 spin_lock(&pool->lock);
1328                 if (!list_empty(&page->lru))
1329                         list_del(&page->lru);
1330                 spin_unlock(&pool->lock);
1331                 z3fold_page_unlock(zhdr);
1332                 return true;
1333         }
1334 out:
1335         z3fold_page_unlock(zhdr);
1336         return false;
1337 }
1338
1339 static int z3fold_page_migrate(struct address_space *mapping, struct page *newpage,
1340                                struct page *page, enum migrate_mode mode)
1341 {
1342         struct z3fold_header *zhdr, *new_zhdr;
1343         struct z3fold_pool *pool;
1344         struct address_space *new_mapping;
1345
1346         VM_BUG_ON_PAGE(!PageMovable(page), page);
1347         VM_BUG_ON_PAGE(!PageIsolated(page), page);
1348         VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
1349
1350         zhdr = page_address(page);
1351         pool = zhdr_to_pool(zhdr);
1352
1353         if (!z3fold_page_trylock(zhdr)) {
1354                 return -EAGAIN;
1355         }
1356         if (zhdr->mapped_count != 0) {
1357                 z3fold_page_unlock(zhdr);
1358                 return -EBUSY;
1359         }
1360         if (work_pending(&zhdr->work)) {
1361                 z3fold_page_unlock(zhdr);
1362                 return -EAGAIN;
1363         }
1364         new_zhdr = page_address(newpage);
1365         memcpy(new_zhdr, zhdr, PAGE_SIZE);
1366         newpage->private = page->private;
1367         page->private = 0;
1368         z3fold_page_unlock(zhdr);
1369         spin_lock_init(&new_zhdr->page_lock);
1370         INIT_WORK(&new_zhdr->work, compact_page_work);
1371         /*
1372          * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
1373          * so we only have to reinitialize it.
1374          */
1375         INIT_LIST_HEAD(&new_zhdr->buddy);
1376         new_mapping = page_mapping(page);
1377         __ClearPageMovable(page);
1378         ClearPagePrivate(page);
1379
1380         get_page(newpage);
1381         z3fold_page_lock(new_zhdr);
1382         if (new_zhdr->first_chunks)
1383                 encode_handle(new_zhdr, FIRST);
1384         if (new_zhdr->last_chunks)
1385                 encode_handle(new_zhdr, LAST);
1386         if (new_zhdr->middle_chunks)
1387                 encode_handle(new_zhdr, MIDDLE);
1388         set_bit(NEEDS_COMPACTING, &newpage->private);
1389         new_zhdr->cpu = smp_processor_id();
1390         spin_lock(&pool->lock);
1391         list_add(&newpage->lru, &pool->lru);
1392         spin_unlock(&pool->lock);
1393         __SetPageMovable(newpage, new_mapping);
1394         z3fold_page_unlock(new_zhdr);
1395
1396         queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
1397
1398         page_mapcount_reset(page);
1399         put_page(page);
1400         return 0;
1401 }
1402
1403 static void z3fold_page_putback(struct page *page)
1404 {
1405         struct z3fold_header *zhdr;
1406         struct z3fold_pool *pool;
1407
1408         zhdr = page_address(page);
1409         pool = zhdr_to_pool(zhdr);
1410
1411         z3fold_page_lock(zhdr);
1412         if (!list_empty(&zhdr->buddy))
1413                 list_del_init(&zhdr->buddy);
1414         INIT_LIST_HEAD(&page->lru);
1415         if (kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
1416                 atomic64_dec(&pool->pages_nr);
1417                 return;
1418         }
1419         spin_lock(&pool->lock);
1420         list_add(&page->lru, &pool->lru);
1421         spin_unlock(&pool->lock);
1422         z3fold_page_unlock(zhdr);
1423 }
1424
1425 static const struct address_space_operations z3fold_aops = {
1426         .isolate_page = z3fold_page_isolate,
1427         .migratepage = z3fold_page_migrate,
1428         .putback_page = z3fold_page_putback,
1429 };
1430
1431 /*****************
1432  * zpool
1433  ****************/
1434
1435 static int z3fold_zpool_evict(struct z3fold_pool *pool, unsigned long handle)
1436 {
1437         if (pool->zpool && pool->zpool_ops && pool->zpool_ops->evict)
1438                 return pool->zpool_ops->evict(pool->zpool, handle);
1439         else
1440                 return -ENOENT;
1441 }
1442
1443 static const struct z3fold_ops z3fold_zpool_ops = {
1444         .evict =        z3fold_zpool_evict
1445 };
1446
1447 static void *z3fold_zpool_create(const char *name, gfp_t gfp,
1448                                const struct zpool_ops *zpool_ops,
1449                                struct zpool *zpool)
1450 {
1451         struct z3fold_pool *pool;
1452
1453         pool = z3fold_create_pool(name, gfp,
1454                                 zpool_ops ? &z3fold_zpool_ops : NULL);
1455         if (pool) {
1456                 pool->zpool = zpool;
1457                 pool->zpool_ops = zpool_ops;
1458         }
1459         return pool;
1460 }
1461
1462 static void z3fold_zpool_destroy(void *pool)
1463 {
1464         z3fold_destroy_pool(pool);
1465 }
1466
1467 static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
1468                         unsigned long *handle)
1469 {
1470         return z3fold_alloc(pool, size, gfp, handle);
1471 }
1472 static void z3fold_zpool_free(void *pool, unsigned long handle)
1473 {
1474         z3fold_free(pool, handle);
1475 }
1476
1477 static int z3fold_zpool_shrink(void *pool, unsigned int pages,
1478                         unsigned int *reclaimed)
1479 {
1480         unsigned int total = 0;
1481         int ret = -EINVAL;
1482
1483         while (total < pages) {
1484                 ret = z3fold_reclaim_page(pool, 8);
1485                 if (ret < 0)
1486                         break;
1487                 total++;
1488         }
1489
1490         if (reclaimed)
1491                 *reclaimed = total;
1492
1493         return ret;
1494 }
1495
1496 static void *z3fold_zpool_map(void *pool, unsigned long handle,
1497                         enum zpool_mapmode mm)
1498 {
1499         return z3fold_map(pool, handle);
1500 }
1501 static void z3fold_zpool_unmap(void *pool, unsigned long handle)
1502 {
1503         z3fold_unmap(pool, handle);
1504 }
1505
1506 static u64 z3fold_zpool_total_size(void *pool)
1507 {
1508         return z3fold_get_pool_size(pool) * PAGE_SIZE;
1509 }
1510
1511 static struct zpool_driver z3fold_zpool_driver = {
1512         .type =         "z3fold",
1513         .owner =        THIS_MODULE,
1514         .create =       z3fold_zpool_create,
1515         .destroy =      z3fold_zpool_destroy,
1516         .malloc =       z3fold_zpool_malloc,
1517         .free =         z3fold_zpool_free,
1518         .shrink =       z3fold_zpool_shrink,
1519         .map =          z3fold_zpool_map,
1520         .unmap =        z3fold_zpool_unmap,
1521         .total_size =   z3fold_zpool_total_size,
1522 };
1523
1524 MODULE_ALIAS("zpool-z3fold");
1525
1526 static int __init init_z3fold(void)
1527 {
1528         int ret;
1529
1530         /* Make sure the z3fold header is not larger than the page size */
1531         BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE);
1532         ret = z3fold_mount();
1533         if (ret)
1534                 return ret;
1535
1536         zpool_register_driver(&z3fold_zpool_driver);
1537
1538         return 0;
1539 }
1540
1541 static void __exit exit_z3fold(void)
1542 {
1543         z3fold_unmount();
1544         zpool_unregister_driver(&z3fold_zpool_driver);
1545 }
1546
1547 module_init(init_z3fold);
1548 module_exit(exit_z3fold);
1549
1550 MODULE_LICENSE("GPL");
1551 MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
1552 MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");