mm/zswap.c

   1 /*
   2  * zswap.c - zswap driver file
   3  *
   4  * zswap is a backend for frontswap that takes pages that are in the process
   5  * of being swapped out and attempts to compress and store them in a
   6  * RAM-based memory pool.  This can result in a significant I/O reduction on
   7  * the swap device and, in the case where decompressing from RAM is faster
   8  * than reading from the swap device, can also improve workload performance.
   9  *
  10  * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21 */
  22
  23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  24
  25 #include <linux/module.h>
  26 #include <linux/cpu.h>
  27 #include <linux/highmem.h>
  28 #include <linux/slab.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/types.h>
  31 #include <linux/atomic.h>
  32 #include <linux/frontswap.h>
  33 #include <linux/rbtree.h>
  34 #include <linux/swap.h>
  35 #include <linux/crypto.h>
  36 #include <linux/mempool.h>
  37 #include <linux/zpool.h>
  38
  39 #include <linux/mm_types.h>
  40 #include <linux/page-flags.h>
  41 #include <linux/swapops.h>
  42 #include <linux/writeback.h>
  43 #include <linux/pagemap.h>
  44
  45 /*********************************
  46 * statistics
  47 **********************************/
  48 /* Total bytes used by the compressed storage */
  49 static u64 zswap_pool_total_size;
  50 /* The number of compressed pages currently stored in zswap */
  51 static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  52
  53 /*
  54  * The statistics below are not protected from concurrent access for
  55  * performance reasons so they may not be a 100% accurate.  However,
  56  * they do provide useful information on roughly how many times a
  57  * certain event is occurring.
  58 */
  59
  60 /* Pool limit was hit (see zswap_max_pool_percent) */
  61 static u64 zswap_pool_limit_hit;
  62 /* Pages written back when pool limit was reached */
  63 static u64 zswap_written_back_pages;
  64 /* Store failed due to a reclaim failure after pool limit was reached */
  65 static u64 zswap_reject_reclaim_fail;
  66 /* Compressed page was too big for the allocator to (optimally) store */
  67 static u64 zswap_reject_compress_poor;
  68 /* Store failed because underlying allocator could not get memory */
  69 static u64 zswap_reject_alloc_fail;
  70 /* Store failed because the entry metadata could not be allocated (rare) */
  71 static u64 zswap_reject_kmemcache_fail;
  72 /* Duplicate store was encountered (rare) */
  73 static u64 zswap_duplicate_entry;
  74
  75 /*********************************
  76 * tunables
  77 **********************************/
  78 /* Enable/disable zswap (disabled by default, fixed at boot for now) */
  79 static bool zswap_enabled __read_mostly;
  80 module_param_named(enabled, zswap_enabled, bool, 0444);
  81
  82 /* Compressor to be used by zswap (fixed at boot for now) */
  83 #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
  84 static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
  85 module_param_named(compressor, zswap_compressor, charp, 0444);
  86
  87 /* The maximum percentage of memory that the compressed pool can occupy */
  88 static unsigned int zswap_max_pool_percent = 20;
  89 module_param_named(max_pool_percent,
  90                         zswap_max_pool_percent, uint, 0644);
  91
  92 /* Compressed storage to use */
  93 #define ZSWAP_ZPOOL_DEFAULT "zbud"
  94 static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
  95 module_param_named(zpool, zswap_zpool_type, charp, 0444);
  96
  97 /* zpool is shared by all of zswap backend  */
  98 static struct zpool *zswap_pool;
  99
 100 /*********************************
 101 * compression functions
 102 **********************************/
 103 /* per-cpu compression transforms */
 104 static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
 105
 106 enum comp_op {
 107         ZSWAP_COMPOP_COMPRESS,
 108         ZSWAP_COMPOP_DECOMPRESS
 109 };
 110
 111 static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
 112                                 u8 *dst, unsigned int *dlen)
 113 {
 114         struct crypto_comp *tfm;
 115         int ret;
 116
 117         tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
 118         switch (op) {
 119         case ZSWAP_COMPOP_COMPRESS:
 120                 ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
 121                 break;
 122         case ZSWAP_COMPOP_DECOMPRESS:
 123                 ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
 124                 break;
 125         default:
 126                 ret = -EINVAL;
 127         }
 128
 129         put_cpu();
 130         return ret;
 131 }
 132
 133 static int __init zswap_comp_init(void)
 134 {
 135         if (!crypto_has_comp(zswap_compressor, 0, 0)) {
 136                 pr_info("%s compressor not available\n", zswap_compressor);
 137                 /* fall back to default compressor */
 138                 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
 139                 if (!crypto_has_comp(zswap_compressor, 0, 0))
 140                         /* can't even load the default compressor */
 141                         return -ENODEV;
 142         }
 143         pr_info("using %s compressor\n", zswap_compressor);
 144
 145         /* alloc percpu transforms */
 146         zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
 147         if (!zswap_comp_pcpu_tfms)
 148                 return -ENOMEM;
 149         return 0;
 150 }
 151
 152 static void zswap_comp_exit(void)
 153 {
 154         /* free percpu transforms */
 155         if (zswap_comp_pcpu_tfms)
 156                 free_percpu(zswap_comp_pcpu_tfms);
 157 }
 158
 159 /*********************************
 160 * data structures
 161 **********************************/
 162 /*
 163  * struct zswap_entry
 164  *
 165  * This structure contains the metadata for tracking a single compressed
 166  * page within zswap.
 167  *
 168  * rbnode - links the entry into red-black tree for the appropriate swap type
 169  * refcount - the number of outstanding reference to the entry. This is needed
 170  *            to protect against premature freeing of the entry by code
 171  *            concurrent calls to load, invalidate, and writeback.  The lock
 172  *            for the zswap_tree structure that contains the entry must
 173  *            be held while changing the refcount.  Since the lock must
 174  *            be held, there is no reason to also make refcount atomic.
 175  * offset - the swap offset for the entry.  Index into the red-black tree.
 176  * handle - zpool allocation handle that stores the compressed page data
 177  * length - the length in bytes of the compressed page data.  Needed during
 178  *          decompression
 179  */
 180 struct zswap_entry {
 181         struct rb_node rbnode;
 182         pgoff_t offset;
 183         int refcount;
 184         unsigned int length;
 185         unsigned long handle;
 186 };
 187
 188 struct zswap_header {
 189         swp_entry_t swpentry;
 190 };
 191
 192 /*
 193  * The tree lock in the zswap_tree struct protects a few things:
 194  * - the rbtree
 195  * - the refcount field of each entry in the tree
 196  */
 197 struct zswap_tree {
 198         struct rb_root rbroot;
 199         spinlock_t lock;
 200 };
 201
 202 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 203
 204 /*********************************
 205 * zswap entry functions
 206 **********************************/
 207 static struct kmem_cache *zswap_entry_cache;
 208
 209 static int zswap_entry_cache_create(void)
 210 {
 211         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
 212         return zswap_entry_cache == NULL;
 213 }
 214
 215 static void __init zswap_entry_cache_destroy(void)
 216 {
 217         kmem_cache_destroy(zswap_entry_cache);
 218 }
 219
 220 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
 221 {
 222         struct zswap_entry *entry;
 223         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
 224         if (!entry)
 225                 return NULL;
 226         entry->refcount = 1;
 227         RB_CLEAR_NODE(&entry->rbnode);
 228         return entry;
 229 }
 230
 231 static void zswap_entry_cache_free(struct zswap_entry *entry)
 232 {
 233         kmem_cache_free(zswap_entry_cache, entry);
 234 }
 235
 236 /*********************************
 237 * rbtree functions
 238 **********************************/
 239 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
 240 {
 241         struct rb_node *node = root->rb_node;
 242         struct zswap_entry *entry;
 243
 244         while (node) {
 245                 entry = rb_entry(node, struct zswap_entry, rbnode);
 246                 if (entry->offset > offset)
 247                         node = node->rb_left;
 248                 else if (entry->offset < offset)
 249                         node = node->rb_right;
 250                 else
 251                         return entry;
 252         }
 253         return NULL;
 254 }
 255
 256 /*
 257  * In the case that a entry with the same offset is found, a pointer to
 258  * the existing entry is stored in dupentry and the function returns -EEXIST
 259  */
 260 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
 261                         struct zswap_entry **dupentry)
 262 {
 263         struct rb_node **link = &root->rb_node, *parent = NULL;
 264         struct zswap_entry *myentry;
 265
 266         while (*link) {
 267                 parent = *link;
 268                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
 269                 if (myentry->offset > entry->offset)
 270                         link = &(*link)->rb_left;
 271                 else if (myentry->offset < entry->offset)
 272                         link = &(*link)->rb_right;
 273                 else {
 274                         *dupentry = myentry;
 275                         return -EEXIST;
 276                 }
 277         }
 278         rb_link_node(&entry->rbnode, parent, link);
 279         rb_insert_color(&entry->rbnode, root);
 280         return 0;
 281 }
 282
 283 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
 284 {
 285         if (!RB_EMPTY_NODE(&entry->rbnode)) {
 286                 rb_erase(&entry->rbnode, root);
 287                 RB_CLEAR_NODE(&entry->rbnode);
 288         }
 289 }
 290
 291 /*
 292  * Carries out the common pattern of freeing and entry's zpool allocation,
 293  * freeing the entry itself, and decrementing the number of stored pages.
 294  */
 295 static void zswap_free_entry(struct zswap_entry *entry)
 296 {
 297         zpool_free(zswap_pool, entry->handle);
 298         zswap_entry_cache_free(entry);
 299         atomic_dec(&zswap_stored_pages);
 300         zswap_pool_total_size = zpool_get_total_size(zswap_pool);
 301 }
 302
 303 /* caller must hold the tree lock */
 304 static void zswap_entry_get(struct zswap_entry *entry)
 305 {
 306         entry->refcount++;
 307 }
 308
 309 /* caller must hold the tree lock
 310 * remove from the tree and free it, if nobody reference the entry
 311 */
 312 static void zswap_entry_put(struct zswap_tree *tree,
 313                         struct zswap_entry *entry)
 314 {
 315         int refcount = --entry->refcount;
 316
 317         BUG_ON(refcount < 0);
 318         if (refcount == 0) {
 319                 zswap_rb_erase(&tree->rbroot, entry);
 320                 zswap_free_entry(entry);
 321         }
 322 }
 323
 324 /* caller must hold the tree lock */
 325 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 326                                 pgoff_t offset)
 327 {
 328         struct zswap_entry *entry = NULL;
 329
 330         entry = zswap_rb_search(root, offset);
 331         if (entry)
 332                 zswap_entry_get(entry);
 333
 334         return entry;
 335 }
 336
 337 /*********************************
 338 * per-cpu code
 339 **********************************/
 340 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 341
 342 static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
 343 {
 344         struct crypto_comp *tfm;
 345         u8 *dst;
 346
 347         switch (action) {
 348         case CPU_UP_PREPARE:
 349                 tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
 350                 if (IS_ERR(tfm)) {
 351                         pr_err("can't allocate compressor transform\n");
 352                         return NOTIFY_BAD;
 353                 }
 354                 *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
 355                 dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 356                 if (!dst) {
 357                         pr_err("can't allocate compressor buffer\n");
 358                         crypto_free_comp(tfm);
 359                         *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
 360                         return NOTIFY_BAD;
 361                 }
 362                 per_cpu(zswap_dstmem, cpu) = dst;
 363                 break;
 364         case CPU_DEAD:
 365         case CPU_UP_CANCELED:
 366                 tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
 367                 if (tfm) {
 368                         crypto_free_comp(tfm);
 369                         *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
 370                 }
 371                 dst = per_cpu(zswap_dstmem, cpu);
 372                 kfree(dst);
 373                 per_cpu(zswap_dstmem, cpu) = NULL;
 374                 break;
 375         default:
 376                 break;
 377         }
 378         return NOTIFY_OK;
 379 }
 380
 381 static int zswap_cpu_notifier(struct notifier_block *nb,
 382                                 unsigned long action, void *pcpu)
 383 {
 384         unsigned long cpu = (unsigned long)pcpu;
 385         return __zswap_cpu_notifier(action, cpu);
 386 }
 387
 388 static struct notifier_block zswap_cpu_notifier_block = {
 389         .notifier_call = zswap_cpu_notifier
 390 };
 391
 392 static int zswap_cpu_init(void)
 393 {
 394         unsigned long cpu;
 395
 396         cpu_notifier_register_begin();
 397         for_each_online_cpu(cpu)
 398                 if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
 399                         goto cleanup;
 400         __register_cpu_notifier(&zswap_cpu_notifier_block);
 401         cpu_notifier_register_done();
 402         return 0;
 403
 404 cleanup:
 405         for_each_online_cpu(cpu)
 406                 __zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
 407         cpu_notifier_register_done();
 408         return -ENOMEM;
 409 }
 410
 411 /*********************************
 412 * helpers
 413 **********************************/
 414 static bool zswap_is_full(void)
 415 {
 416         return totalram_pages * zswap_max_pool_percent / 100 <
 417                 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 418 }
 419
 420 /*********************************
 421 * writeback code
 422 **********************************/
 423 /* return enum for zswap_get_swap_cache_page */
 424 enum zswap_get_swap_ret {
 425         ZSWAP_SWAPCACHE_NEW,
 426         ZSWAP_SWAPCACHE_EXIST,
 427         ZSWAP_SWAPCACHE_FAIL,
 428 };
 429
 430 /*
 431  * zswap_get_swap_cache_page
 432  *
 433  * This is an adaption of read_swap_cache_async()
 434  *
 435  * This function tries to find a page with the given swap entry
 436  * in the swapper_space address space (the swap cache).  If the page
 437  * is found, it is returned in retpage.  Otherwise, a page is allocated,
 438  * added to the swap cache, and returned in retpage.
 439  *
 440  * If success, the swap cache page is returned in retpage
 441  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
 442  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
 443  *     the new page is added to swapcache and locked
 444  * Returns ZSWAP_SWAPCACHE_FAIL on error
 445  */
 446 static int zswap_get_swap_cache_page(swp_entry_t entry,
 447                                 struct page **retpage)
 448 {
 449         struct page *found_page, *new_page = NULL;
 450         struct address_space *swapper_space = swap_address_space(entry);
 451         int err;
 452
 453         *retpage = NULL;
 454         do {
 455                 /*
 456                  * First check the swap cache.  Since this is normally
 457                  * called after lookup_swap_cache() failed, re-calling
 458                  * that would confuse statistics.
 459                  */
 460                 found_page = find_get_page(swapper_space, entry.val);
 461                 if (found_page)
 462                         break;
 463
 464                 /*
 465                  * Get a new page to read into from swap.
 466                  */
 467                 if (!new_page) {
 468                         new_page = alloc_page(GFP_KERNEL);
 469                         if (!new_page)
 470                                 break; /* Out of memory */
 471                 }
 472
 473                 /*
 474                  * call radix_tree_preload() while we can wait.
 475                  */
 476                 err = radix_tree_preload(GFP_KERNEL);
 477                 if (err)
 478                         break;
 479
 480                 /*
 481                  * Swap entry may have been freed since our caller observed it.
 482                  */
 483                 err = swapcache_prepare(entry);
 484                 if (err == -EEXIST) { /* seems racy */
 485                         radix_tree_preload_end();
 486                         continue;
 487                 }
 488                 if (err) { /* swp entry is obsolete ? */
 489                         radix_tree_preload_end();
 490                         break;
 491                 }
 492
 493                 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
 494                 __set_page_locked(new_page);
 495                 SetPageSwapBacked(new_page);
 496                 err = __add_to_swap_cache(new_page, entry);
 497                 if (likely(!err)) {
 498                         radix_tree_preload_end();
 499                         lru_cache_add_anon(new_page);
 500                         *retpage = new_page;
 501                         return ZSWAP_SWAPCACHE_NEW;
 502                 }
 503                 radix_tree_preload_end();
 504                 ClearPageSwapBacked(new_page);
 505                 __clear_page_locked(new_page);
 506                 /*
 507                  * add_to_swap_cache() doesn't return -EEXIST, so we can safely
 508                  * clear SWAP_HAS_CACHE flag.
 509                  */
 510                 swapcache_free(entry);
 511         } while (err != -ENOMEM);
 512
 513         if (new_page)
 514                 page_cache_release(new_page);
 515         if (!found_page)
 516                 return ZSWAP_SWAPCACHE_FAIL;
 517         *retpage = found_page;
 518         return ZSWAP_SWAPCACHE_EXIST;
 519 }
 520
 521 /*
 522  * Attempts to free an entry by adding a page to the swap cache,
 523  * decompressing the entry data into the page, and issuing a
 524  * bio write to write the page back to the swap device.
 525  *
 526  * This can be thought of as a "resumed writeback" of the page
 527  * to the swap device.  We are basically resuming the same swap
 528  * writeback path that was intercepted with the frontswap_store()
 529  * in the first place.  After the page has been decompressed into
 530  * the swap cache, the compressed version stored by zswap can be
 531  * freed.
 532  */
 533 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 534 {
 535         struct zswap_header *zhdr;
 536         swp_entry_t swpentry;
 537         struct zswap_tree *tree;
 538         pgoff_t offset;
 539         struct zswap_entry *entry;
 540         struct page *page;
 541         u8 *src, *dst;
 542         unsigned int dlen;
 543         int ret;
 544         struct writeback_control wbc = {
 545                 .sync_mode = WB_SYNC_NONE,
 546         };
 547
 548         /* extract swpentry from data */
 549         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
 550         swpentry = zhdr->swpentry; /* here */
 551         zpool_unmap_handle(pool, handle);
 552         tree = zswap_trees[swp_type(swpentry)];
 553         offset = swp_offset(swpentry);
 554
 555         /* find and ref zswap entry */
 556         spin_lock(&tree->lock);
 557         entry = zswap_entry_find_get(&tree->rbroot, offset);
 558         if (!entry) {
 559                 /* entry was invalidated */
 560                 spin_unlock(&tree->lock);
 561                 return 0;
 562         }
 563         spin_unlock(&tree->lock);
 564         BUG_ON(offset != entry->offset);
 565
 566         /* try to allocate swap cache page */
 567         switch (zswap_get_swap_cache_page(swpentry, &page)) {
 568         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 569                 ret = -ENOMEM;
 570                 goto fail;
 571
 572         case ZSWAP_SWAPCACHE_EXIST:
 573                 /* page is already in the swap cache, ignore for now */
 574                 page_cache_release(page);
 575                 ret = -EEXIST;
 576                 goto fail;
 577
 578         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 579                 /* decompress */
 580                 dlen = PAGE_SIZE;
 581                 src = (u8 *)zpool_map_handle(zswap_pool, entry->handle,
 582                                 ZPOOL_MM_RO) + sizeof(struct zswap_header);
 583                 dst = kmap_atomic(page);
 584                 ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
 585                                 entry->length, dst, &dlen);
 586                 kunmap_atomic(dst);
 587                 zpool_unmap_handle(zswap_pool, entry->handle);
 588                 BUG_ON(ret);
 589                 BUG_ON(dlen != PAGE_SIZE);
 590
 591                 /* page is up to date */
 592                 SetPageUptodate(page);
 593         }
 594
 595         /* move it to the tail of the inactive list after end_writeback */
 596         SetPageReclaim(page);
 597
 598         /* start writeback */
 599         __swap_writepage(page, &wbc, end_swap_bio_write);
 600         page_cache_release(page);
 601         zswap_written_back_pages++;
 602
 603         spin_lock(&tree->lock);
 604         /* drop local reference */
 605         zswap_entry_put(tree, entry);
 606
 607         /*
 608         * There are two possible situations for entry here:
 609         * (1) refcount is 1(normal case),  entry is valid and on the tree
 610         * (2) refcount is 0, entry is freed and not on the tree
 611         *     because invalidate happened during writeback
 612         *  search the tree and free the entry if find entry
 613         */
 614         if (entry == zswap_rb_search(&tree->rbroot, offset))
 615                 zswap_entry_put(tree, entry);
 616         spin_unlock(&tree->lock);
 617
 618         goto end;
 619
 620         /*
 621         * if we get here due to ZSWAP_SWAPCACHE_EXIST
 622         * a load may happening concurrently
 623         * it is safe and okay to not free the entry
 624         * if we free the entry in the following put
 625         * it it either okay to return !0
 626         */
 627 fail:
 628         spin_lock(&tree->lock);
 629         zswap_entry_put(tree, entry);
 630         spin_unlock(&tree->lock);
 631
 632 end:
 633         return ret;
 634 }
 635
 636 /*********************************
 637 * frontswap hooks
 638 **********************************/
 639 /* attempts to compress and store an single page */
 640 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 641                                 struct page *page)
 642 {
 643         struct zswap_tree *tree = zswap_trees[type];
 644         struct zswap_entry *entry, *dupentry;
 645         int ret;
 646         unsigned int dlen = PAGE_SIZE, len;
 647         unsigned long handle;
 648         char *buf;
 649         u8 *src, *dst;
 650         struct zswap_header *zhdr;
 651
 652         if (!tree) {
 653                 ret = -ENODEV;
 654                 goto reject;
 655         }
 656
 657         /* reclaim space if needed */
 658         if (zswap_is_full()) {
 659                 zswap_pool_limit_hit++;
 660                 if (zpool_shrink(zswap_pool, 1, NULL)) {
 661                         zswap_reject_reclaim_fail++;
 662                         ret = -ENOMEM;
 663                         goto reject;
 664                 }
 665         }
 666
 667         /* allocate entry */
 668         entry = zswap_entry_cache_alloc(GFP_KERNEL);
 669         if (!entry) {
 670                 zswap_reject_kmemcache_fail++;
 671                 ret = -ENOMEM;
 672                 goto reject;
 673         }
 674
 675         /* compress */
 676         dst = get_cpu_var(zswap_dstmem);
 677         src = kmap_atomic(page);
 678         ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
 679         kunmap_atomic(src);
 680         if (ret) {
 681                 ret = -EINVAL;
 682                 goto freepage;
 683         }
 684
 685         /* store */
 686         len = dlen + sizeof(struct zswap_header);
 687         ret = zpool_malloc(zswap_pool, len, __GFP_NORETRY | __GFP_NOWARN,
 688                 &handle);
 689         if (ret == -ENOSPC) {
 690                 zswap_reject_compress_poor++;
 691                 goto freepage;
 692         }
 693         if (ret) {
 694                 zswap_reject_alloc_fail++;
 695                 goto freepage;
 696         }
 697         zhdr = zpool_map_handle(zswap_pool, handle, ZPOOL_MM_RW);
 698         zhdr->swpentry = swp_entry(type, offset);
 699         buf = (u8 *)(zhdr + 1);
 700         memcpy(buf, dst, dlen);
 701         zpool_unmap_handle(zswap_pool, handle);
 702         put_cpu_var(zswap_dstmem);
 703
 704         /* populate entry */
 705         entry->offset = offset;
 706         entry->handle = handle;
 707         entry->length = dlen;
 708
 709         /* map */
 710         spin_lock(&tree->lock);
 711         do {
 712                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
 713                 if (ret == -EEXIST) {
 714                         zswap_duplicate_entry++;
 715                         /* remove from rbtree */
 716                         zswap_rb_erase(&tree->rbroot, dupentry);
 717                         zswap_entry_put(tree, dupentry);
 718                 }
 719         } while (ret == -EEXIST);
 720         spin_unlock(&tree->lock);
 721
 722         /* update stats */
 723         atomic_inc(&zswap_stored_pages);
 724         zswap_pool_total_size = zpool_get_total_size(zswap_pool);
 725
 726         return 0;
 727
 728 freepage:
 729         put_cpu_var(zswap_dstmem);
 730         zswap_entry_cache_free(entry);
 731 reject:
 732         return ret;
 733 }
 734
 735 /*
 736  * returns 0 if the page was successfully decompressed
 737  * return -1 on entry not found or error
 738 */
 739 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 740                                 struct page *page)
 741 {
 742         struct zswap_tree *tree = zswap_trees[type];
 743         struct zswap_entry *entry;
 744         u8 *src, *dst;
 745         unsigned int dlen;
 746         int ret;
 747
 748         /* find */
 749         spin_lock(&tree->lock);
 750         entry = zswap_entry_find_get(&tree->rbroot, offset);
 751         if (!entry) {
 752                 /* entry was written back */
 753                 spin_unlock(&tree->lock);
 754                 return -1;
 755         }
 756         spin_unlock(&tree->lock);
 757
 758         /* decompress */
 759         dlen = PAGE_SIZE;
 760         src = (u8 *)zpool_map_handle(zswap_pool, entry->handle,
 761                         ZPOOL_MM_RO) + sizeof(struct zswap_header);
 762         dst = kmap_atomic(page);
 763         ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
 764                 dst, &dlen);
 765         kunmap_atomic(dst);
 766         zpool_unmap_handle(zswap_pool, entry->handle);
 767         BUG_ON(ret);
 768
 769         spin_lock(&tree->lock);
 770         zswap_entry_put(tree, entry);
 771         spin_unlock(&tree->lock);
 772
 773         return 0;
 774 }
 775
 776 /* frees an entry in zswap */
 777 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
 778 {
 779         struct zswap_tree *tree = zswap_trees[type];
 780         struct zswap_entry *entry;
 781
 782         /* find */
 783         spin_lock(&tree->lock);
 784         entry = zswap_rb_search(&tree->rbroot, offset);
 785         if (!entry) {
 786                 /* entry was written back */
 787                 spin_unlock(&tree->lock);
 788                 return;
 789         }
 790
 791         /* remove from rbtree */
 792         zswap_rb_erase(&tree->rbroot, entry);
 793
 794         /* drop the initial reference from entry creation */
 795         zswap_entry_put(tree, entry);
 796
 797         spin_unlock(&tree->lock);
 798 }
 799
 800 /* frees all zswap entries for the given swap type */
 801 static void zswap_frontswap_invalidate_area(unsigned type)
 802 {
 803         struct zswap_tree *tree = zswap_trees[type];
 804         struct zswap_entry *entry, *n;
 805
 806         if (!tree)
 807                 return;
 808
 809         /* walk the tree and free everything */
 810         spin_lock(&tree->lock);
 811         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
 812                 zswap_free_entry(entry);
 813         tree->rbroot = RB_ROOT;
 814         spin_unlock(&tree->lock);
 815         kfree(tree);
 816         zswap_trees[type] = NULL;
 817 }
 818
 819 static struct zpool_ops zswap_zpool_ops = {
 820         .evict = zswap_writeback_entry
 821 };
 822
 823 static void zswap_frontswap_init(unsigned type)
 824 {
 825         struct zswap_tree *tree;
 826
 827         tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
 828         if (!tree) {
 829                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
 830                 return;
 831         }
 832
 833         tree->rbroot = RB_ROOT;
 834         spin_lock_init(&tree->lock);
 835         zswap_trees[type] = tree;
 836 }
 837
 838 static struct frontswap_ops zswap_frontswap_ops = {
 839         .store = zswap_frontswap_store,
 840         .load = zswap_frontswap_load,
 841         .invalidate_page = zswap_frontswap_invalidate_page,
 842         .invalidate_area = zswap_frontswap_invalidate_area,
 843         .init = zswap_frontswap_init
 844 };
 845
 846 /*********************************
 847 * debugfs functions
 848 **********************************/
 849 #ifdef CONFIG_DEBUG_FS
 850 #include <linux/debugfs.h>
 851
 852 static struct dentry *zswap_debugfs_root;
 853
 854 static int __init zswap_debugfs_init(void)
 855 {
 856         if (!debugfs_initialized())
 857                 return -ENODEV;
 858
 859         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
 860         if (!zswap_debugfs_root)
 861                 return -ENOMEM;
 862
 863         debugfs_create_u64("pool_limit_hit", S_IRUGO,
 864                         zswap_debugfs_root, &zswap_pool_limit_hit);
 865         debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
 866                         zswap_debugfs_root, &zswap_reject_reclaim_fail);
 867         debugfs_create_u64("reject_alloc_fail", S_IRUGO,
 868                         zswap_debugfs_root, &zswap_reject_alloc_fail);
 869         debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
 870                         zswap_debugfs_root, &zswap_reject_kmemcache_fail);
 871         debugfs_create_u64("reject_compress_poor", S_IRUGO,
 872                         zswap_debugfs_root, &zswap_reject_compress_poor);
 873         debugfs_create_u64("written_back_pages", S_IRUGO,
 874                         zswap_debugfs_root, &zswap_written_back_pages);
 875         debugfs_create_u64("duplicate_entry", S_IRUGO,
 876                         zswap_debugfs_root, &zswap_duplicate_entry);
 877         debugfs_create_u64("pool_total_size", S_IRUGO,
 878                         zswap_debugfs_root, &zswap_pool_total_size);
 879         debugfs_create_atomic_t("stored_pages", S_IRUGO,
 880                         zswap_debugfs_root, &zswap_stored_pages);
 881
 882         return 0;
 883 }
 884
 885 static void __exit zswap_debugfs_exit(void)
 886 {
 887         debugfs_remove_recursive(zswap_debugfs_root);
 888 }
 889 #else
 890 static int __init zswap_debugfs_init(void)
 891 {
 892         return 0;
 893 }
 894
 895 static void __exit zswap_debugfs_exit(void) { }
 896 #endif
 897
 898 /*********************************
 899 * module init and exit
 900 **********************************/
 901 static int __init init_zswap(void)
 902 {
 903         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN;
 904
 905         if (!zswap_enabled)
 906                 return 0;
 907
 908         pr_info("loading zswap\n");
 909
 910         zswap_pool = zpool_create_pool(zswap_zpool_type, gfp, &zswap_zpool_ops);
 911         if (!zswap_pool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
 912                 pr_info("%s zpool not available\n", zswap_zpool_type);
 913                 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
 914                 zswap_pool = zpool_create_pool(zswap_zpool_type, gfp,
 915                                         &zswap_zpool_ops);
 916         }
 917         if (!zswap_pool) {
 918                 pr_err("%s zpool not available\n", zswap_zpool_type);
 919                 pr_err("zpool creation failed\n");
 920                 goto error;
 921         }
 922         pr_info("using %s pool\n", zswap_zpool_type);
 923
 924         if (zswap_entry_cache_create()) {
 925                 pr_err("entry cache creation failed\n");
 926                 goto cachefail;
 927         }
 928         if (zswap_comp_init()) {
 929                 pr_err("compressor initialization failed\n");
 930                 goto compfail;
 931         }
 932         if (zswap_cpu_init()) {
 933                 pr_err("per-cpu initialization failed\n");
 934                 goto pcpufail;
 935         }
 936
 937         frontswap_register_ops(&zswap_frontswap_ops);
 938         if (zswap_debugfs_init())
 939                 pr_warn("debugfs initialization failed\n");
 940         return 0;
 941 pcpufail:
 942         zswap_comp_exit();
 943 compfail:
 944         zswap_entry_cache_destroy();
 945 cachefail:
 946         zpool_destroy_pool(zswap_pool);
 947 error:
 948         return -ENOMEM;
 949 }
 950 /* must be late so crypto has time to come up */
 951 late_initcall(init_zswap);
 952
 953 MODULE_LICENSE("GPL");
 954 MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
 955 MODULE_DESCRIPTION("Compressed cache for swap pages");