drivers/staging/zram/zram_drv.c

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #define KMSG_COMPONENT "zram"
  16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  17
  18 #include <linux/module.h>
  19 #include <linux/kernel.h>
  20 #include <linux/bio.h>
  21 #include <linux/bitops.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/buffer_head.h>
  24 #include <linux/device.h>
  25 #include <linux/genhd.h>
  26 #include <linux/highmem.h>
  27 #include <linux/slab.h>
  28 #include <linux/lzo.h>
  29 #include <linux/string.h>
  30 #include <linux/vmalloc.h>
  31
  32 #include "zram_drv.h"
  33
  34 /* Globals */
  35 static int zram_major;
  36 struct zram *devices;
  37
  38 /* Module params (documentation at end) */
  39 unsigned int num_devices;
  40
  41 static void zram_stat_inc(u32 *v)
  42 {
  43         *v = *v + 1;
  44 }
  45
  46 static void zram_stat_dec(u32 *v)
  47 {
  48         *v = *v - 1;
  49 }
  50
  51 static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
  52 {
  53         spin_lock(&zram->stat64_lock);
  54         *v = *v + inc;
  55         spin_unlock(&zram->stat64_lock);
  56 }
  57
  58 static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
  59 {
  60         spin_lock(&zram->stat64_lock);
  61         *v = *v - dec;
  62         spin_unlock(&zram->stat64_lock);
  63 }
  64
  65 static void zram_stat64_inc(struct zram *zram, u64 *v)
  66 {
  67         zram_stat64_add(zram, v, 1);
  68 }
  69
  70 static int zram_test_flag(struct zram *zram, u32 index,
  71                         enum zram_pageflags flag)
  72 {
  73         return zram->table[index].flags & BIT(flag);
  74 }
  75
  76 static void zram_set_flag(struct zram *zram, u32 index,
  77                         enum zram_pageflags flag)
  78 {
  79         zram->table[index].flags |= BIT(flag);
  80 }
  81
  82 static void zram_clear_flag(struct zram *zram, u32 index,
  83                         enum zram_pageflags flag)
  84 {
  85         zram->table[index].flags &= ~BIT(flag);
  86 }
  87
  88 static int page_zero_filled(void *ptr)
  89 {
  90         unsigned int pos;
  91         unsigned long *page;
  92
  93         page = (unsigned long *)ptr;
  94
  95         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
  96                 if (page[pos])
  97                         return 0;
  98         }
  99
 100         return 1;
 101 }
 102
 103 static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
 104 {
 105         if (!zram->disksize) {
 106                 pr_info(
 107                 "disk size not provided. You can use disksize_kb module "
 108                 "param to specify size.\nUsing default: (%u%% of RAM).\n",
 109                 default_disksize_perc_ram
 110                 );
 111                 zram->disksize = default_disksize_perc_ram *
 112                                         (totalram_bytes / 100);
 113         }
 114
 115         if (zram->disksize > 2 * (totalram_bytes)) {
 116                 pr_info(
 117                 "There is little point creating a zram of greater than "
 118                 "twice the size of memory since we expect a 2:1 compression "
 119                 "ratio. Note that zram uses about 0.1%% of the size of "
 120                 "the disk when not in use so a huge zram is "
 121                 "wasteful.\n"
 122                 "\tMemory Size: %zu kB\n"
 123                 "\tSize you selected: %llu kB\n"
 124                 "Continuing anyway ...\n",
 125                 totalram_bytes >> 10, zram->disksize
 126                 );
 127         }
 128
 129         zram->disksize &= PAGE_MASK;
 130 }
 131
 132 static void zram_free_page(struct zram *zram, size_t index)
 133 {
 134         u32 clen;
 135         void *obj;
 136
 137         struct page *page = zram->table[index].page;
 138         u32 offset = zram->table[index].offset;
 139
 140         if (unlikely(!page)) {
 141                 /*
 142                  * No memory is allocated for zero filled pages.
 143                  * Simply clear zero page flag.
 144                  */
 145                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 146                         zram_clear_flag(zram, index, ZRAM_ZERO);
 147                         zram_stat_dec(&zram->stats.pages_zero);
 148                 }
 149                 return;
 150         }
 151
 152         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 153                 clen = PAGE_SIZE;
 154                 __free_page(page);
 155                 zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
 156                 zram_stat_dec(&zram->stats.pages_expand);
 157                 goto out;
 158         }
 159
 160         obj = kmap_atomic(page, KM_USER0) + offset;
 161         clen = xv_get_object_size(obj) - sizeof(struct zobj_header);
 162         kunmap_atomic(obj, KM_USER0);
 163
 164         xv_free(zram->mem_pool, page, offset);
 165         if (clen <= PAGE_SIZE / 2)
 166                 zram_stat_dec(&zram->stats.good_compress);
 167
 168 out:
 169         zram_stat64_sub(zram, &zram->stats.compr_size, clen);
 170         zram_stat_dec(&zram->stats.pages_stored);
 171
 172         zram->table[index].page = NULL;
 173         zram->table[index].offset = 0;
 174 }
 175
 176 static void handle_zero_page(struct page *page)
 177 {
 178         void *user_mem;
 179
 180         user_mem = kmap_atomic(page, KM_USER0);
 181         memset(user_mem, 0, PAGE_SIZE);
 182         kunmap_atomic(user_mem, KM_USER0);
 183
 184         flush_dcache_page(page);
 185 }
 186
 187 static void handle_uncompressed_page(struct zram *zram,
 188                                 struct page *page, u32 index)
 189 {
 190         unsigned char *user_mem, *cmem;
 191
 192         user_mem = kmap_atomic(page, KM_USER0);
 193         cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 194                         zram->table[index].offset;
 195
 196         memcpy(user_mem, cmem, PAGE_SIZE);
 197         kunmap_atomic(user_mem, KM_USER0);
 198         kunmap_atomic(cmem, KM_USER1);
 199
 200         flush_dcache_page(page);
 201 }
 202
 203 static int zram_read(struct zram *zram, struct bio *bio)
 204 {
 205
 206         int i;
 207         u32 index;
 208         struct bio_vec *bvec;
 209
 210         if (unlikely(!zram->init_done)) {
 211                 set_bit(BIO_UPTODATE, &bio->bi_flags);
 212                 bio_endio(bio, 0);
 213                 return 0;
 214         }
 215
 216         zram_stat64_inc(zram, &zram->stats.num_reads);
 217         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 218
 219         bio_for_each_segment(bvec, bio, i) {
 220                 int ret;
 221                 size_t clen;
 222                 struct page *page;
 223                 struct zobj_header *zheader;
 224                 unsigned char *user_mem, *cmem;
 225
 226                 page = bvec->bv_page;
 227
 228                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 229                         handle_zero_page(page);
 230                         continue;
 231                 }
 232
 233                 /* Requested page is not present in compressed area */
 234                 if (unlikely(!zram->table[index].page)) {
 235                         pr_debug("Read before write: sector=%lu, size=%u",
 236                                 (ulong)(bio->bi_sector), bio->bi_size);
 237                         /* Do nothing */
 238                         continue;
 239                 }
 240
 241                 /* Page is stored uncompressed since it's incompressible */
 242                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 243                         handle_uncompressed_page(zram, page, index);
 244                         continue;
 245                 }
 246
 247                 user_mem = kmap_atomic(page, KM_USER0);
 248                 clen = PAGE_SIZE;
 249
 250                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 251                                 zram->table[index].offset;
 252
 253                 ret = lzo1x_decompress_safe(
 254                         cmem + sizeof(*zheader),
 255                         xv_get_object_size(cmem) - sizeof(*zheader),
 256                         user_mem, &clen);
 257
 258                 kunmap_atomic(user_mem, KM_USER0);
 259                 kunmap_atomic(cmem, KM_USER1);
 260
 261                 /* Should NEVER happen. Return bio error if it does. */
 262                 if (unlikely(ret != LZO_E_OK)) {
 263                         pr_err("Decompression failed! err=%d, page=%u\n",
 264                                 ret, index);
 265                         zram_stat64_inc(zram, &zram->stats.failed_reads);
 266                         goto out;
 267                 }
 268
 269                 flush_dcache_page(page);
 270                 index++;
 271         }
 272
 273         set_bit(BIO_UPTODATE, &bio->bi_flags);
 274         bio_endio(bio, 0);
 275         return 0;
 276
 277 out:
 278         bio_io_error(bio);
 279         return 0;
 280 }
 281
 282 static int zram_write(struct zram *zram, struct bio *bio)
 283 {
 284         int i, ret;
 285         u32 index;
 286         struct bio_vec *bvec;
 287
 288         if (unlikely(!zram->init_done)) {
 289                 ret = zram_init_device(zram);
 290                 if (ret)
 291                         goto out;
 292         }
 293
 294         zram_stat64_inc(zram, &zram->stats.num_writes);
 295         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 296
 297         bio_for_each_segment(bvec, bio, i) {
 298                 u32 offset;
 299                 size_t clen;
 300                 struct zobj_header *zheader;
 301                 struct page *page, *page_store;
 302                 unsigned char *user_mem, *cmem, *src;
 303
 304                 page = bvec->bv_page;
 305                 src = zram->compress_buffer;
 306
 307                 /*
 308                  * System overwrites unused sectors. Free memory associated
 309                  * with this sector now.
 310                  */
 311                 if (zram->table[index].page ||
 312                                 zram_test_flag(zram, index, ZRAM_ZERO))
 313                         zram_free_page(zram, index);
 314
 315                 mutex_lock(&zram->lock);
 316
 317                 user_mem = kmap_atomic(page, KM_USER0);
 318                 if (page_zero_filled(user_mem)) {
 319                         kunmap_atomic(user_mem, KM_USER0);
 320                         mutex_unlock(&zram->lock);
 321                         zram_stat_inc(&zram->stats.pages_zero);
 322                         zram_set_flag(zram, index, ZRAM_ZERO);
 323                         continue;
 324                 }
 325
 326                 ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
 327                                         zram->compress_workmem);
 328
 329                 kunmap_atomic(user_mem, KM_USER0);
 330
 331                 if (unlikely(ret != LZO_E_OK)) {
 332                         mutex_unlock(&zram->lock);
 333                         pr_err("Compression failed! err=%d\n", ret);
 334                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 335                         goto out;
 336                 }
 337
 338                 /*
 339                  * Page is incompressible. Store it as-is (uncompressed)
 340                  * since we do not want to return too many disk write
 341                  * errors which has side effect of hanging the system.
 342                  */
 343                 if (unlikely(clen > max_zpage_size)) {
 344                         clen = PAGE_SIZE;
 345                         page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
 346                         if (unlikely(!page_store)) {
 347                                 mutex_unlock(&zram->lock);
 348                                 pr_info("Error allocating memory for "
 349                                         "incompressible page: %u\n", index);
 350                                 zram_stat64_inc(zram,
 351                                         &zram->stats.failed_writes);
 352                                 goto out;
 353                         }
 354
 355                         offset = 0;
 356                         zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
 357                         zram_stat_inc(&zram->stats.pages_expand);
 358                         zram->table[index].page = page_store;
 359                         src = kmap_atomic(page, KM_USER0);
 360                         goto memstore;
 361                 }
 362
 363                 if (xv_malloc(zram->mem_pool, clen + sizeof(*zheader),
 364                                 &zram->table[index].page, &offset,
 365                                 GFP_NOIO | __GFP_HIGHMEM)) {
 366                         mutex_unlock(&zram->lock);
 367                         pr_info("Error allocating memory for compressed "
 368                                 "page: %u, size=%zu\n", index, clen);
 369                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 370                         goto out;
 371                 }
 372
 373 memstore:
 374                 zram->table[index].offset = offset;
 375
 376                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 377                                 zram->table[index].offset;
 378
 379 #if 0
 380                 /* Back-reference needed for memory defragmentation */
 381                 if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
 382                         zheader = (struct zobj_header *)cmem;
 383                         zheader->table_idx = index;
 384                         cmem += sizeof(*zheader);
 385                 }
 386 #endif
 387
 388                 memcpy(cmem, src, clen);
 389
 390                 kunmap_atomic(cmem, KM_USER1);
 391                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 392                         kunmap_atomic(src, KM_USER0);
 393
 394                 /* Update stats */
 395                 zram_stat64_add(zram, &zram->stats.compr_size, clen);
 396                 zram_stat_inc(&zram->stats.pages_stored);
 397                 if (clen <= PAGE_SIZE / 2)
 398                         zram_stat_inc(&zram->stats.good_compress);
 399
 400                 mutex_unlock(&zram->lock);
 401                 index++;
 402         }
 403
 404         set_bit(BIO_UPTODATE, &bio->bi_flags);
 405         bio_endio(bio, 0);
 406         return 0;
 407
 408 out:
 409         bio_io_error(bio);
 410         return 0;
 411 }
 412
 413 /*
 414  * Check if request is within bounds and page aligned.
 415  */
 416 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 417 {
 418         if (unlikely(
 419                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 420                 (bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
 421                 (bio->bi_size & (PAGE_SIZE - 1)))) {
 422
 423                 return 0;
 424         }
 425
 426         /* I/O request is valid */
 427         return 1;
 428 }
 429
 430 /*
 431  * Handler function for all zram I/O requests.
 432  */
 433 static int zram_make_request(struct request_queue *queue, struct bio *bio)
 434 {
 435         int ret = 0;
 436         struct zram *zram = queue->queuedata;
 437
 438         if (!valid_io_request(zram, bio)) {
 439                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 440                 bio_io_error(bio);
 441                 return 0;
 442         }
 443
 444         switch (bio_data_dir(bio)) {
 445         case READ:
 446                 ret = zram_read(zram, bio);
 447                 break;
 448
 449         case WRITE:
 450                 ret = zram_write(zram, bio);
 451                 break;
 452         }
 453
 454         return ret;
 455 }
 456
 457 void zram_reset_device(struct zram *zram)
 458 {
 459         size_t index;
 460
 461         mutex_lock(&zram->init_lock);
 462         zram->init_done = 0;
 463
 464         /* Free various per-device buffers */
 465         kfree(zram->compress_workmem);
 466         free_pages((unsigned long)zram->compress_buffer, 1);
 467
 468         zram->compress_workmem = NULL;
 469         zram->compress_buffer = NULL;
 470
 471         /* Free all pages that are still in this zram device */
 472         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 473                 struct page *page;
 474                 u16 offset;
 475
 476                 page = zram->table[index].page;
 477                 offset = zram->table[index].offset;
 478
 479                 if (!page)
 480                         continue;
 481
 482                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 483                         __free_page(page);
 484                 else
 485                         xv_free(zram->mem_pool, page, offset);
 486         }
 487
 488         vfree(zram->table);
 489         zram->table = NULL;
 490
 491         xv_destroy_pool(zram->mem_pool);
 492         zram->mem_pool = NULL;
 493
 494         /* Reset stats */
 495         memset(&zram->stats, 0, sizeof(zram->stats));
 496
 497         zram->disksize = 0;
 498         mutex_unlock(&zram->init_lock);
 499 }
 500
 501 int zram_init_device(struct zram *zram)
 502 {
 503         int ret;
 504         size_t num_pages;
 505
 506         mutex_lock(&zram->init_lock);
 507
 508         if (zram->init_done) {
 509                 mutex_unlock(&zram->init_lock);
 510                 return 0;
 511         }
 512
 513         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 514
 515         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 516         if (!zram->compress_workmem) {
 517                 pr_err("Error allocating compressor working memory!\n");
 518                 ret = -ENOMEM;
 519                 goto fail;
 520         }
 521
 522         zram->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
 523         if (!zram->compress_buffer) {
 524                 pr_err("Error allocating compressor buffer space\n");
 525                 ret = -ENOMEM;
 526                 goto fail;
 527         }
 528
 529         num_pages = zram->disksize >> PAGE_SHIFT;
 530         zram->table = vmalloc(num_pages * sizeof(*zram->table));
 531         if (!zram->table) {
 532                 pr_err("Error allocating zram address table\n");
 533                 /* To prevent accessing table entries during cleanup */
 534                 zram->disksize = 0;
 535                 ret = -ENOMEM;
 536                 goto fail;
 537         }
 538         memset(zram->table, 0, num_pages * sizeof(*zram->table));
 539
 540         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 541
 542         /* zram devices sort of resembles non-rotational disks */
 543         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 544
 545         zram->mem_pool = xv_create_pool();
 546         if (!zram->mem_pool) {
 547                 pr_err("Error creating memory pool\n");
 548                 ret = -ENOMEM;
 549                 goto fail;
 550         }
 551
 552         zram->init_done = 1;
 553         mutex_unlock(&zram->init_lock);
 554
 555         pr_debug("Initialization done!\n");
 556         return 0;
 557
 558 fail:
 559         mutex_unlock(&zram->init_lock);
 560         zram_reset_device(zram);
 561
 562         pr_err("Initialization failed: err=%d\n", ret);
 563         return ret;
 564 }
 565
 566 void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
 567 {
 568         struct zram *zram;
 569
 570         zram = bdev->bd_disk->private_data;
 571         zram_free_page(zram, index);
 572         zram_stat64_inc(zram, &zram->stats.notify_free);
 573 }
 574
 575 static const struct block_device_operations zram_devops = {
 576         .swap_slot_free_notify = zram_slot_free_notify,
 577         .owner = THIS_MODULE
 578 };
 579
 580 static int create_device(struct zram *zram, int device_id)
 581 {
 582         int ret = 0;
 583
 584         mutex_init(&zram->lock);
 585         mutex_init(&zram->init_lock);
 586         spin_lock_init(&zram->stat64_lock);
 587
 588         zram->queue = blk_alloc_queue(GFP_KERNEL);
 589         if (!zram->queue) {
 590                 pr_err("Error allocating disk queue for device %d\n",
 591                         device_id);
 592                 ret = -ENOMEM;
 593                 goto out;
 594         }
 595
 596         blk_queue_make_request(zram->queue, zram_make_request);
 597         zram->queue->queuedata = zram;
 598
 599          /* gendisk structure */
 600         zram->disk = alloc_disk(1);
 601         if (!zram->disk) {
 602                 blk_cleanup_queue(zram->queue);
 603                 pr_warning("Error allocating disk structure for device %d\n",
 604                         device_id);
 605                 ret = -ENOMEM;
 606                 goto out;
 607         }
 608
 609         zram->disk->major = zram_major;
 610         zram->disk->first_minor = device_id;
 611         zram->disk->fops = &zram_devops;
 612         zram->disk->queue = zram->queue;
 613         zram->disk->private_data = zram;
 614         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 615
 616         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 617         set_capacity(zram->disk, 0);
 618
 619         /*
 620          * To ensure that we always get PAGE_SIZE aligned
 621          * and n*PAGE_SIZED sized I/O requests.
 622          */
 623         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 624         blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
 625         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 626         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 627
 628         add_disk(zram->disk);
 629
 630 #ifdef CONFIG_SYSFS
 631         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 632                                 &zram_disk_attr_group);
 633         if (ret < 0) {
 634                 pr_warning("Error creating sysfs group");
 635                 goto out;
 636         }
 637 #endif
 638
 639         zram->init_done = 0;
 640
 641 out:
 642         return ret;
 643 }
 644
 645 static void destroy_device(struct zram *zram)
 646 {
 647 #ifdef CONFIG_SYSFS
 648         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 649                         &zram_disk_attr_group);
 650 #endif
 651
 652         if (zram->disk) {
 653                 del_gendisk(zram->disk);
 654                 put_disk(zram->disk);
 655         }
 656
 657         if (zram->queue)
 658                 blk_cleanup_queue(zram->queue);
 659 }
 660
 661 static int __init zram_init(void)
 662 {
 663         int ret, dev_id;
 664
 665         if (num_devices > max_num_devices) {
 666                 pr_warning("Invalid value for num_devices: %u\n",
 667                                 num_devices);
 668                 ret = -EINVAL;
 669                 goto out;
 670         }
 671
 672         zram_major = register_blkdev(0, "zram");
 673         if (zram_major <= 0) {
 674                 pr_warning("Unable to get major number\n");
 675                 ret = -EBUSY;
 676                 goto out;
 677         }
 678
 679         if (!num_devices) {
 680                 pr_info("num_devices not specified. Using default: 1\n");
 681                 num_devices = 1;
 682         }
 683
 684         /* Allocate the device array and initialize each one */
 685         pr_info("Creating %u devices ...\n", num_devices);
 686         devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 687         if (!devices) {
 688                 ret = -ENOMEM;
 689                 goto unregister;
 690         }
 691
 692         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 693                 ret = create_device(&devices[dev_id], dev_id);
 694                 if (ret)
 695                         goto free_devices;
 696         }
 697
 698         return 0;
 699
 700 free_devices:
 701         while (dev_id)
 702                 destroy_device(&devices[--dev_id]);
 703         kfree(devices);
 704 unregister:
 705         unregister_blkdev(zram_major, "zram");
 706 out:
 707         return ret;
 708 }
 709
 710 static void __exit zram_exit(void)
 711 {
 712         int i;
 713         struct zram *zram;
 714
 715         for (i = 0; i < num_devices; i++) {
 716                 zram = &devices[i];
 717
 718                 destroy_device(zram);
 719                 if (zram->init_done)
 720                         zram_reset_device(zram);
 721         }
 722
 723         unregister_blkdev(zram_major, "zram");
 724
 725         kfree(devices);
 726         pr_debug("Cleanup done!\n");
 727 }
 728
 729 module_param(num_devices, uint, 0);
 730 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 731
 732 module_init(zram_init);
 733 module_exit(zram_exit);
 734
 735 MODULE_LICENSE("Dual BSD/GPL");
 736 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 737 MODULE_DESCRIPTION("Compressed RAM Block Device");