Pileus Git - ~andy/linux/blob - 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                 bio_endio(bio, -ENXIO);
 212                 return 0;
 213         }
 214
 215         zram_stat64_inc(zram, &zram->stats.num_reads);
 216         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 217
 218         bio_for_each_segment(bvec, bio, i) {
 219                 int ret;
 220                 size_t clen;
 221                 struct page *page;
 222                 struct zobj_header *zheader;
 223                 unsigned char *user_mem, *cmem;
 224
 225                 page = bvec->bv_page;
 226
 227                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 228                         handle_zero_page(page);
 229                         continue;
 230                 }
 231
 232                 /* Requested page is not present in compressed area */
 233                 if (unlikely(!zram->table[index].page)) {
 234                         pr_debug("Read before write: sector=%lu, size=%u",
 235                                 (ulong)(bio->bi_sector), bio->bi_size);
 236                         /* Do nothing */
 237                         continue;
 238                 }
 239
 240                 /* Page is stored uncompressed since it's incompressible */
 241                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 242                         handle_uncompressed_page(zram, page, index);
 243                         continue;
 244                 }
 245
 246                 user_mem = kmap_atomic(page, KM_USER0);
 247                 clen = PAGE_SIZE;
 248
 249                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 250                                 zram->table[index].offset;
 251
 252                 ret = lzo1x_decompress_safe(
 253                         cmem + sizeof(*zheader),
 254                         xv_get_object_size(cmem) - sizeof(*zheader),
 255                         user_mem, &clen);
 256
 257                 kunmap_atomic(user_mem, KM_USER0);
 258                 kunmap_atomic(cmem, KM_USER1);
 259
 260                 /* Should NEVER happen. Return bio error if it does. */
 261                 if (unlikely(ret != LZO_E_OK)) {
 262                         pr_err("Decompression failed! err=%d, page=%u\n",
 263                                 ret, index);
 264                         zram_stat64_inc(zram, &zram->stats.failed_reads);
 265                         goto out;
 266                 }
 267
 268                 flush_dcache_page(page);
 269                 index++;
 270         }
 271
 272         set_bit(BIO_UPTODATE, &bio->bi_flags);
 273         bio_endio(bio, 0);
 274         return 0;
 275
 276 out:
 277         bio_io_error(bio);
 278         return 0;
 279 }
 280
 281 static int zram_write(struct zram *zram, struct bio *bio)
 282 {
 283         int i, ret;
 284         u32 index;
 285         struct bio_vec *bvec;
 286
 287         if (unlikely(!zram->init_done)) {
 288                 ret = zram_init_device(zram);
 289                 if (ret)
 290                         goto out;
 291         }
 292
 293         zram_stat64_inc(zram, &zram->stats.num_writes);
 294         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 295
 296         bio_for_each_segment(bvec, bio, i) {
 297                 u32 offset;
 298                 size_t clen;
 299                 struct zobj_header *zheader;
 300                 struct page *page, *page_store;
 301                 unsigned char *user_mem, *cmem, *src;
 302
 303                 page = bvec->bv_page;
 304                 src = zram->compress_buffer;
 305
 306                 /*
 307                  * System overwrites unused sectors. Free memory associated
 308                  * with this sector now.
 309                  */
 310                 if (zram->table[index].page ||
 311                                 zram_test_flag(zram, index, ZRAM_ZERO))
 312                         zram_free_page(zram, index);
 313
 314                 mutex_lock(&zram->lock);
 315
 316                 user_mem = kmap_atomic(page, KM_USER0);
 317                 if (page_zero_filled(user_mem)) {
 318                         kunmap_atomic(user_mem, KM_USER0);
 319                         mutex_unlock(&zram->lock);
 320                         zram_stat_inc(&zram->stats.pages_zero);
 321                         zram_set_flag(zram, index, ZRAM_ZERO);
 322                         continue;
 323                 }
 324
 325                 ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
 326                                         zram->compress_workmem);
 327
 328                 kunmap_atomic(user_mem, KM_USER0);
 329
 330                 if (unlikely(ret != LZO_E_OK)) {
 331                         mutex_unlock(&zram->lock);
 332                         pr_err("Compression failed! err=%d\n", ret);
 333                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 334                         goto out;
 335                 }
 336
 337                 /*
 338                  * Page is incompressible. Store it as-is (uncompressed)
 339                  * since we do not want to return too many disk write
 340                  * errors which has side effect of hanging the system.
 341                  */
 342                 if (unlikely(clen > max_zpage_size)) {
 343                         clen = PAGE_SIZE;
 344                         page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
 345                         if (unlikely(!page_store)) {
 346                                 mutex_unlock(&zram->lock);
 347                                 pr_info("Error allocating memory for "
 348                                         "incompressible page: %u\n", index);
 349                                 zram_stat64_inc(zram,
 350                                         &zram->stats.failed_writes);
 351                                 goto out;
 352                         }
 353
 354                         offset = 0;
 355                         zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
 356                         zram_stat_inc(&zram->stats.pages_expand);
 357                         zram->table[index].page = page_store;
 358                         src = kmap_atomic(page, KM_USER0);
 359                         goto memstore;
 360                 }
 361
 362                 if (xv_malloc(zram->mem_pool, clen + sizeof(*zheader),
 363                                 &zram->table[index].page, &offset,
 364                                 GFP_NOIO | __GFP_HIGHMEM)) {
 365                         mutex_unlock(&zram->lock);
 366                         pr_info("Error allocating memory for compressed "
 367                                 "page: %u, size=%zu\n", index, clen);
 368                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 369                         goto out;
 370                 }
 371
 372 memstore:
 373                 zram->table[index].offset = offset;
 374
 375                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 376                                 zram->table[index].offset;
 377
 378 #if 0
 379                 /* Back-reference needed for memory defragmentation */
 380                 if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
 381                         zheader = (struct zobj_header *)cmem;
 382                         zheader->table_idx = index;
 383                         cmem += sizeof(*zheader);
 384                 }
 385 #endif
 386
 387                 memcpy(cmem, src, clen);
 388
 389                 kunmap_atomic(cmem, KM_USER1);
 390                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 391                         kunmap_atomic(src, KM_USER0);
 392
 393                 /* Update stats */
 394                 zram_stat64_add(zram, &zram->stats.compr_size, clen);
 395                 zram_stat_inc(&zram->stats.pages_stored);
 396                 if (clen <= PAGE_SIZE / 2)
 397                         zram_stat_inc(&zram->stats.good_compress);
 398
 399                 mutex_unlock(&zram->lock);
 400                 index++;
 401         }
 402
 403         set_bit(BIO_UPTODATE, &bio->bi_flags);
 404         bio_endio(bio, 0);
 405         return 0;
 406
 407 out:
 408         bio_io_error(bio);
 409         return 0;
 410 }
 411
 412 /*
 413  * Check if request is within bounds and page aligned.
 414  */
 415 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 416 {
 417         if (unlikely(
 418                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 419                 (bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
 420                 (bio->bi_size & (PAGE_SIZE - 1)))) {
 421
 422                 return 0;
 423         }
 424
 425         /* I/O request is valid */
 426         return 1;
 427 }
 428
 429 /*
 430  * Handler function for all zram I/O requests.
 431  */
 432 static int zram_make_request(struct request_queue *queue, struct bio *bio)
 433 {
 434         int ret = 0;
 435         struct zram *zram = queue->queuedata;
 436
 437         if (!valid_io_request(zram, bio)) {
 438                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 439                 bio_io_error(bio);
 440                 return 0;
 441         }
 442
 443         switch (bio_data_dir(bio)) {
 444         case READ:
 445                 ret = zram_read(zram, bio);
 446                 break;
 447
 448         case WRITE:
 449                 ret = zram_write(zram, bio);
 450                 break;
 451         }
 452
 453         return ret;
 454 }
 455
 456 void zram_reset_device(struct zram *zram)
 457 {
 458         size_t index;
 459
 460         mutex_lock(&zram->init_lock);
 461         zram->init_done = 0;
 462
 463         /* Free various per-device buffers */
 464         kfree(zram->compress_workmem);
 465         free_pages((unsigned long)zram->compress_buffer, 1);
 466
 467         zram->compress_workmem = NULL;
 468         zram->compress_buffer = NULL;
 469
 470         /* Free all pages that are still in this zram device */
 471         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 472                 struct page *page;
 473                 u16 offset;
 474
 475                 page = zram->table[index].page;
 476                 offset = zram->table[index].offset;
 477
 478                 if (!page)
 479                         continue;
 480
 481                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 482                         __free_page(page);
 483                 else
 484                         xv_free(zram->mem_pool, page, offset);
 485         }
 486
 487         vfree(zram->table);
 488         zram->table = NULL;
 489
 490         xv_destroy_pool(zram->mem_pool);
 491         zram->mem_pool = NULL;
 492
 493         /* Reset stats */
 494         memset(&zram->stats, 0, sizeof(zram->stats));
 495
 496         zram->disksize = 0;
 497         mutex_unlock(&zram->init_lock);
 498 }
 499
 500 int zram_init_device(struct zram *zram)
 501 {
 502         int ret;
 503         size_t num_pages;
 504
 505         mutex_lock(&zram->init_lock);
 506
 507         if (zram->init_done) {
 508                 mutex_unlock(&zram->init_lock);
 509                 return 0;
 510         }
 511
 512         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 513
 514         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 515         if (!zram->compress_workmem) {
 516                 pr_err("Error allocating compressor working memory!\n");
 517                 ret = -ENOMEM;
 518                 goto fail;
 519         }
 520
 521         zram->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
 522         if (!zram->compress_buffer) {
 523                 pr_err("Error allocating compressor buffer space\n");
 524                 ret = -ENOMEM;
 525                 goto fail;
 526         }
 527
 528         num_pages = zram->disksize >> PAGE_SHIFT;
 529         zram->table = vzalloc(num_pages * sizeof(*zram->table));
 530         if (!zram->table) {
 531                 pr_err("Error allocating zram address table\n");
 532                 /* To prevent accessing table entries during cleanup */
 533                 zram->disksize = 0;
 534                 ret = -ENOMEM;
 535                 goto fail;
 536         }
 537
 538         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 539
 540         /* zram devices sort of resembles non-rotational disks */
 541         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 542
 543         zram->mem_pool = xv_create_pool();
 544         if (!zram->mem_pool) {
 545                 pr_err("Error creating memory pool\n");
 546                 ret = -ENOMEM;
 547                 goto fail;
 548         }
 549
 550         zram->init_done = 1;
 551         mutex_unlock(&zram->init_lock);
 552
 553         pr_debug("Initialization done!\n");
 554         return 0;
 555
 556 fail:
 557         mutex_unlock(&zram->init_lock);
 558         zram_reset_device(zram);
 559
 560         pr_err("Initialization failed: err=%d\n", ret);
 561         return ret;
 562 }
 563
 564 void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
 565 {
 566         struct zram *zram;
 567
 568         zram = bdev->bd_disk->private_data;
 569         zram_free_page(zram, index);
 570         zram_stat64_inc(zram, &zram->stats.notify_free);
 571 }
 572
 573 static const struct block_device_operations zram_devops = {
 574         .swap_slot_free_notify = zram_slot_free_notify,
 575         .owner = THIS_MODULE
 576 };
 577
 578 static int create_device(struct zram *zram, int device_id)
 579 {
 580         int ret = 0;
 581
 582         mutex_init(&zram->lock);
 583         mutex_init(&zram->init_lock);
 584         spin_lock_init(&zram->stat64_lock);
 585
 586         zram->queue = blk_alloc_queue(GFP_KERNEL);
 587         if (!zram->queue) {
 588                 pr_err("Error allocating disk queue for device %d\n",
 589                         device_id);
 590                 ret = -ENOMEM;
 591                 goto out;
 592         }
 593
 594         blk_queue_make_request(zram->queue, zram_make_request);
 595         zram->queue->queuedata = zram;
 596
 597          /* gendisk structure */
 598         zram->disk = alloc_disk(1);
 599         if (!zram->disk) {
 600                 blk_cleanup_queue(zram->queue);
 601                 pr_warning("Error allocating disk structure for device %d\n",
 602                         device_id);
 603                 ret = -ENOMEM;
 604                 goto out;
 605         }
 606
 607         zram->disk->major = zram_major;
 608         zram->disk->first_minor = device_id;
 609         zram->disk->fops = &zram_devops;
 610         zram->disk->queue = zram->queue;
 611         zram->disk->private_data = zram;
 612         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 613
 614         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 615         set_capacity(zram->disk, 0);
 616
 617         /*
 618          * To ensure that we always get PAGE_SIZE aligned
 619          * and n*PAGE_SIZED sized I/O requests.
 620          */
 621         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 622         blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
 623         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 624         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 625
 626         add_disk(zram->disk);
 627
 628         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 629                                 &zram_disk_attr_group);
 630         if (ret < 0) {
 631                 pr_warning("Error creating sysfs group");
 632                 goto out;
 633         }
 634
 635         zram->init_done = 0;
 636
 637 out:
 638         return ret;
 639 }
 640
 641 static void destroy_device(struct zram *zram)
 642 {
 643         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 644                         &zram_disk_attr_group);
 645
 646         if (zram->disk) {
 647                 del_gendisk(zram->disk);
 648                 put_disk(zram->disk);
 649         }
 650
 651         if (zram->queue)
 652                 blk_cleanup_queue(zram->queue);
 653 }
 654
 655 static int __init zram_init(void)
 656 {
 657         int ret, dev_id;
 658
 659         if (num_devices > max_num_devices) {
 660                 pr_warning("Invalid value for num_devices: %u\n",
 661                                 num_devices);
 662                 ret = -EINVAL;
 663                 goto out;
 664         }
 665
 666         zram_major = register_blkdev(0, "zram");
 667         if (zram_major <= 0) {
 668                 pr_warning("Unable to get major number\n");
 669                 ret = -EBUSY;
 670                 goto out;
 671         }
 672
 673         if (!num_devices) {
 674                 pr_info("num_devices not specified. Using default: 1\n");
 675                 num_devices = 1;
 676         }
 677
 678         /* Allocate the device array and initialize each one */
 679         pr_info("Creating %u devices ...\n", num_devices);
 680         devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 681         if (!devices) {
 682                 ret = -ENOMEM;
 683                 goto unregister;
 684         }
 685
 686         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 687                 ret = create_device(&devices[dev_id], dev_id);
 688                 if (ret)
 689                         goto free_devices;
 690         }
 691
 692         return 0;
 693
 694 free_devices:
 695         while (dev_id)
 696                 destroy_device(&devices[--dev_id]);
 697         kfree(devices);
 698 unregister:
 699         unregister_blkdev(zram_major, "zram");
 700 out:
 701         return ret;
 702 }
 703
 704 static void __exit zram_exit(void)
 705 {
 706         int i;
 707         struct zram *zram;
 708
 709         for (i = 0; i < num_devices; i++) {
 710                 zram = &devices[i];
 711
 712                 destroy_device(zram);
 713                 if (zram->init_done)
 714                         zram_reset_device(zram);
 715         }
 716
 717         unregister_blkdev(zram_major, "zram");
 718
 719         kfree(devices);
 720         pr_debug("Cleanup done!\n");
 721 }
 722
 723 module_param(num_devices, uint, 0);
 724 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 725
 726 module_init(zram_init);
 727 module_exit(zram_exit);
 728
 729 MODULE_LICENSE("Dual BSD/GPL");
 730 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 731 MODULE_DESCRIPTION("Compressed RAM Block Device");