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 #ifdef CONFIG_ZRAM_DEBUG
  19 #define DEBUG
  20 #endif
  21
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/bio.h>
  25 #include <linux/bitops.h>
  26 #include <linux/blkdev.h>
  27 #include <linux/buffer_head.h>
  28 #include <linux/device.h>
  29 #include <linux/genhd.h>
  30 #include <linux/highmem.h>
  31 #include <linux/slab.h>
  32 #include <linux/lzo.h>
  33 #include <linux/string.h>
  34 #include <linux/vmalloc.h>
  35
  36 #include "zram_drv.h"
  37
  38 /* Globals */
  39 static int zram_major;
  40 static struct zram *zram_devices;
  41
  42 /* Module params (documentation at end) */
  43 static unsigned int num_devices = 1;
  44
  45 static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
  46 {
  47         spin_lock(&zram->stat64_lock);
  48         *v = *v + inc;
  49         spin_unlock(&zram->stat64_lock);
  50 }
  51
  52 static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
  53 {
  54         spin_lock(&zram->stat64_lock);
  55         *v = *v - dec;
  56         spin_unlock(&zram->stat64_lock);
  57 }
  58
  59 static void zram_stat64_inc(struct zram *zram, u64 *v)
  60 {
  61         zram_stat64_add(zram, v, 1);
  62 }
  63
  64 static int zram_test_flag(struct zram_meta *meta, u32 index,
  65                         enum zram_pageflags flag)
  66 {
  67         return meta->table[index].flags & BIT(flag);
  68 }
  69
  70 static void zram_set_flag(struct zram_meta *meta, u32 index,
  71                         enum zram_pageflags flag)
  72 {
  73         meta->table[index].flags |= BIT(flag);
  74 }
  75
  76 static void zram_clear_flag(struct zram_meta *meta, u32 index,
  77                         enum zram_pageflags flag)
  78 {
  79         meta->table[index].flags &= ~BIT(flag);
  80 }
  81
  82 static int page_zero_filled(void *ptr)
  83 {
  84         unsigned int pos;
  85         unsigned long *page;
  86
  87         page = (unsigned long *)ptr;
  88
  89         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
  90                 if (page[pos])
  91                         return 0;
  92         }
  93
  94         return 1;
  95 }
  96
  97 static void zram_free_page(struct zram *zram, size_t index)
  98 {
  99         struct zram_meta *meta = zram->meta;
 100         unsigned long handle = meta->table[index].handle;
 101         u16 size = meta->table[index].size;
 102
 103         if (unlikely(!handle)) {
 104                 /*
 105                  * No memory is allocated for zero filled pages.
 106                  * Simply clear zero page flag.
 107                  */
 108                 if (zram_test_flag(meta, index, ZRAM_ZERO)) {
 109                         zram_clear_flag(meta, index, ZRAM_ZERO);
 110                         zram->stats.pages_zero--;
 111                 }
 112                 return;
 113         }
 114
 115         if (unlikely(size > max_zpage_size))
 116                 zram->stats.bad_compress--;
 117
 118         zs_free(meta->mem_pool, handle);
 119
 120         if (size <= PAGE_SIZE / 2)
 121                 zram->stats.good_compress--;
 122
 123         zram_stat64_sub(zram, &zram->stats.compr_size,
 124                         meta->table[index].size);
 125         zram->stats.pages_stored--;
 126
 127         meta->table[index].handle = 0;
 128         meta->table[index].size = 0;
 129 }
 130
 131 static inline int is_partial_io(struct bio_vec *bvec)
 132 {
 133         return bvec->bv_len != PAGE_SIZE;
 134 }
 135
 136 static void handle_zero_page(struct bio_vec *bvec)
 137 {
 138         struct page *page = bvec->bv_page;
 139         void *user_mem;
 140
 141         user_mem = kmap_atomic(page);
 142         if (is_partial_io(bvec))
 143                 memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
 144         else
 145                 clear_page(user_mem);
 146         kunmap_atomic(user_mem);
 147
 148         flush_dcache_page(page);
 149 }
 150
 151 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 152 {
 153         int ret = LZO_E_OK;
 154         size_t clen = PAGE_SIZE;
 155         unsigned char *cmem;
 156         struct zram_meta *meta = zram->meta;
 157         unsigned long handle = meta->table[index].handle;
 158
 159         if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
 160                 clear_page(mem);
 161                 return 0;
 162         }
 163
 164         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 165         if (meta->table[index].size == PAGE_SIZE)
 166                 copy_page(mem, cmem);
 167         else
 168                 ret = lzo1x_decompress_safe(cmem, meta->table[index].size,
 169                                                 mem, &clen);
 170         zs_unmap_object(meta->mem_pool, handle);
 171
 172         /* Should NEVER happen. Return bio error if it does. */
 173         if (unlikely(ret != LZO_E_OK)) {
 174                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 175                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 176                 return ret;
 177         }
 178
 179         return 0;
 180 }
 181
 182 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 183                           u32 index, int offset, struct bio *bio)
 184 {
 185         int ret;
 186         struct page *page;
 187         unsigned char *user_mem, *uncmem = NULL;
 188         struct zram_meta *meta = zram->meta;
 189         page = bvec->bv_page;
 190
 191         if (unlikely(!meta->table[index].handle) ||
 192                         zram_test_flag(meta, index, ZRAM_ZERO)) {
 193                 handle_zero_page(bvec);
 194                 return 0;
 195         }
 196
 197         if (is_partial_io(bvec))
 198                 /* Use  a temporary buffer to decompress the page */
 199                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 200
 201         user_mem = kmap_atomic(page);
 202         if (!is_partial_io(bvec))
 203                 uncmem = user_mem;
 204
 205         if (!uncmem) {
 206                 pr_info("Unable to allocate temp memory\n");
 207                 ret = -ENOMEM;
 208                 goto out_cleanup;
 209         }
 210
 211         ret = zram_decompress_page(zram, uncmem, index);
 212         /* Should NEVER happen. Return bio error if it does. */
 213         if (unlikely(ret != LZO_E_OK))
 214                 goto out_cleanup;
 215
 216         if (is_partial_io(bvec))
 217                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 218                                 bvec->bv_len);
 219
 220         flush_dcache_page(page);
 221         ret = 0;
 222 out_cleanup:
 223         kunmap_atomic(user_mem);
 224         if (is_partial_io(bvec))
 225                 kfree(uncmem);
 226         return ret;
 227 }
 228
 229 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 230                            int offset)
 231 {
 232         int ret = 0;
 233         size_t clen;
 234         unsigned long handle;
 235         struct page *page;
 236         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 237         struct zram_meta *meta = zram->meta;
 238
 239         page = bvec->bv_page;
 240         src = meta->compress_buffer;
 241
 242         if (is_partial_io(bvec)) {
 243                 /*
 244                  * This is a partial IO. We need to read the full page
 245                  * before to write the changes.
 246                  */
 247                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 248                 if (!uncmem) {
 249                         ret = -ENOMEM;
 250                         goto out;
 251                 }
 252                 ret = zram_decompress_page(zram, uncmem, index);
 253                 if (ret)
 254                         goto out;
 255         }
 256
 257         /*
 258          * System overwrites unused sectors. Free memory associated
 259          * with this sector now.
 260          */
 261         if (meta->table[index].handle ||
 262             zram_test_flag(meta, index, ZRAM_ZERO))
 263                 zram_free_page(zram, index);
 264
 265         user_mem = kmap_atomic(page);
 266
 267         if (is_partial_io(bvec)) {
 268                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 269                        bvec->bv_len);
 270                 kunmap_atomic(user_mem);
 271                 user_mem = NULL;
 272         } else {
 273                 uncmem = user_mem;
 274         }
 275
 276         if (page_zero_filled(uncmem)) {
 277                 kunmap_atomic(user_mem);
 278                 zram->stats.pages_zero++;
 279                 zram_set_flag(meta, index, ZRAM_ZERO);
 280                 ret = 0;
 281                 goto out;
 282         }
 283
 284         ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
 285                                meta->compress_workmem);
 286
 287         if (!is_partial_io(bvec)) {
 288                 kunmap_atomic(user_mem);
 289                 user_mem = NULL;
 290                 uncmem = NULL;
 291         }
 292
 293         if (unlikely(ret != LZO_E_OK)) {
 294                 pr_err("Compression failed! err=%d\n", ret);
 295                 goto out;
 296         }
 297
 298         if (unlikely(clen > max_zpage_size)) {
 299                 zram->stats.bad_compress++;
 300                 clen = PAGE_SIZE;
 301                 src = NULL;
 302                 if (is_partial_io(bvec))
 303                         src = uncmem;
 304         }
 305
 306         handle = zs_malloc(meta->mem_pool, clen);
 307         if (!handle) {
 308                 pr_info("Error allocating memory for compressed page: %u, size=%zu\n",
 309                         index, clen);
 310                 ret = -ENOMEM;
 311                 goto out;
 312         }
 313         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
 314
 315         if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 316                 src = kmap_atomic(page);
 317                 copy_page(cmem, src);
 318                 kunmap_atomic(src);
 319         } else {
 320                 memcpy(cmem, src, clen);
 321         }
 322
 323         zs_unmap_object(meta->mem_pool, handle);
 324
 325         meta->table[index].handle = handle;
 326         meta->table[index].size = clen;
 327
 328         /* Update stats */
 329         zram_stat64_add(zram, &zram->stats.compr_size, clen);
 330         zram->stats.pages_stored++;
 331         if (clen <= PAGE_SIZE / 2)
 332                 zram->stats.good_compress++;
 333
 334 out:
 335         if (is_partial_io(bvec))
 336                 kfree(uncmem);
 337
 338         if (ret)
 339                 zram_stat64_inc(zram, &zram->stats.failed_writes);
 340         return ret;
 341 }
 342
 343 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 344                         int offset, struct bio *bio, int rw)
 345 {
 346         int ret;
 347
 348         if (rw == READ) {
 349                 down_read(&zram->lock);
 350                 ret = zram_bvec_read(zram, bvec, index, offset, bio);
 351                 up_read(&zram->lock);
 352         } else {
 353                 down_write(&zram->lock);
 354                 ret = zram_bvec_write(zram, bvec, index, offset);
 355                 up_write(&zram->lock);
 356         }
 357
 358         return ret;
 359 }
 360
 361 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 362 {
 363         if (*offset + bvec->bv_len >= PAGE_SIZE)
 364                 (*index)++;
 365         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 366 }
 367
 368 static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
 369 {
 370         int i, offset;
 371         u32 index;
 372         struct bio_vec *bvec;
 373
 374         switch (rw) {
 375         case READ:
 376                 zram_stat64_inc(zram, &zram->stats.num_reads);
 377                 break;
 378         case WRITE:
 379                 zram_stat64_inc(zram, &zram->stats.num_writes);
 380                 break;
 381         }
 382
 383         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 384         offset = (bio->bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 385
 386         bio_for_each_segment(bvec, bio, i) {
 387                 int max_transfer_size = PAGE_SIZE - offset;
 388
 389                 if (bvec->bv_len > max_transfer_size) {
 390                         /*
 391                          * zram_bvec_rw() can only make operation on a single
 392                          * zram page. Split the bio vector.
 393                          */
 394                         struct bio_vec bv;
 395
 396                         bv.bv_page = bvec->bv_page;
 397                         bv.bv_len = max_transfer_size;
 398                         bv.bv_offset = bvec->bv_offset;
 399
 400                         if (zram_bvec_rw(zram, &bv, index, offset, bio, rw) < 0)
 401                                 goto out;
 402
 403                         bv.bv_len = bvec->bv_len - max_transfer_size;
 404                         bv.bv_offset += max_transfer_size;
 405                         if (zram_bvec_rw(zram, &bv, index+1, 0, bio, rw) < 0)
 406                                 goto out;
 407                 } else
 408                         if (zram_bvec_rw(zram, bvec, index, offset, bio, rw)
 409                             < 0)
 410                                 goto out;
 411
 412                 update_position(&index, &offset, bvec);
 413         }
 414
 415         set_bit(BIO_UPTODATE, &bio->bi_flags);
 416         bio_endio(bio, 0);
 417         return;
 418
 419 out:
 420         bio_io_error(bio);
 421 }
 422
 423 /*
 424  * Check if request is within bounds and aligned on zram logical blocks.
 425  */
 426 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 427 {
 428         u64 start, end, bound;
 429
 430         /* unaligned request */
 431         if (unlikely(bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
 432                 return 0;
 433         if (unlikely(bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
 434                 return 0;
 435
 436         start = bio->bi_sector;
 437         end = start + (bio->bi_size >> SECTOR_SHIFT);
 438         bound = zram->disksize >> SECTOR_SHIFT;
 439         /* out of range range */
 440         if (unlikely(start >= bound || end >= bound || start > end))
 441                 return 0;
 442
 443         /* I/O request is valid */
 444         return 1;
 445 }
 446
 447 /*
 448  * Handler function for all zram I/O requests.
 449  */
 450 static void zram_make_request(struct request_queue *queue, struct bio *bio)
 451 {
 452         struct zram *zram = queue->queuedata;
 453
 454         down_read(&zram->init_lock);
 455         if (unlikely(!zram->init_done))
 456                 goto error;
 457
 458         if (!valid_io_request(zram, bio)) {
 459                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 460                 goto error;
 461         }
 462
 463         __zram_make_request(zram, bio, bio_data_dir(bio));
 464         up_read(&zram->init_lock);
 465
 466         return;
 467
 468 error:
 469         up_read(&zram->init_lock);
 470         bio_io_error(bio);
 471 }
 472
 473 static void __zram_reset_device(struct zram *zram)
 474 {
 475         size_t index;
 476         struct zram_meta *meta;
 477
 478         if (!zram->init_done)
 479                 return;
 480
 481         meta = zram->meta;
 482         zram->init_done = 0;
 483
 484         /* Free all pages that are still in this zram device */
 485         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 486                 unsigned long handle = meta->table[index].handle;
 487                 if (!handle)
 488                         continue;
 489
 490                 zs_free(meta->mem_pool, handle);
 491         }
 492
 493         zram_meta_free(zram->meta);
 494         zram->meta = NULL;
 495         /* Reset stats */
 496         memset(&zram->stats, 0, sizeof(zram->stats));
 497
 498         zram->disksize = 0;
 499         set_capacity(zram->disk, 0);
 500 }
 501
 502 void zram_reset_device(struct zram *zram)
 503 {
 504         down_write(&zram->init_lock);
 505         __zram_reset_device(zram);
 506         up_write(&zram->init_lock);
 507 }
 508
 509 void zram_meta_free(struct zram_meta *meta)
 510 {
 511         zs_destroy_pool(meta->mem_pool);
 512         kfree(meta->compress_workmem);
 513         free_pages((unsigned long)meta->compress_buffer, 1);
 514         vfree(meta->table);
 515         kfree(meta);
 516 }
 517
 518 struct zram_meta *zram_meta_alloc(u64 disksize)
 519 {
 520         size_t num_pages;
 521         struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 522         if (!meta)
 523                 goto out;
 524
 525         meta->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 526         if (!meta->compress_workmem)
 527                 goto free_meta;
 528
 529         meta->compress_buffer =
 530                 (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
 531         if (!meta->compress_buffer) {
 532                 pr_err("Error allocating compressor buffer space\n");
 533                 goto free_workmem;
 534         }
 535
 536         num_pages = disksize >> PAGE_SHIFT;
 537         meta->table = vzalloc(num_pages * sizeof(*meta->table));
 538         if (!meta->table) {
 539                 pr_err("Error allocating zram address table\n");
 540                 goto free_buffer;
 541         }
 542
 543         meta->mem_pool = zs_create_pool(GFP_NOIO | __GFP_HIGHMEM);
 544         if (!meta->mem_pool) {
 545                 pr_err("Error creating memory pool\n");
 546                 goto free_table;
 547         }
 548
 549         return meta;
 550
 551 free_table:
 552         vfree(meta->table);
 553 free_buffer:
 554         free_pages((unsigned long)meta->compress_buffer, 1);
 555 free_workmem:
 556         kfree(meta->compress_workmem);
 557 free_meta:
 558         kfree(meta);
 559         meta = NULL;
 560 out:
 561         return meta;
 562 }
 563
 564 void zram_init_device(struct zram *zram, struct zram_meta *meta)
 565 {
 566         if (zram->disksize > 2 * (totalram_pages << PAGE_SHIFT)) {
 567                 pr_info(
 568                 "There is little point creating a zram of greater than "
 569                 "twice the size of memory since we expect a 2:1 compression "
 570                 "ratio. Note that zram uses about 0.1%% of the size of "
 571                 "the disk when not in use so a huge zram is "
 572                 "wasteful.\n"
 573                 "\tMemory Size: %lu kB\n"
 574                 "\tSize you selected: %llu kB\n"
 575                 "Continuing anyway ...\n",
 576                 (totalram_pages << PAGE_SHIFT) >> 10, zram->disksize >> 10
 577                 );
 578         }
 579
 580         /* zram devices sort of resembles non-rotational disks */
 581         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 582
 583         zram->meta = meta;
 584         zram->init_done = 1;
 585
 586         pr_debug("Initialization done!\n");
 587 }
 588
 589 static void zram_slot_free_notify(struct block_device *bdev,
 590                                 unsigned long index)
 591 {
 592         struct zram *zram;
 593
 594         zram = bdev->bd_disk->private_data;
 595         down_write(&zram->lock);
 596         zram_free_page(zram, index);
 597         up_write(&zram->lock);
 598         zram_stat64_inc(zram, &zram->stats.notify_free);
 599 }
 600
 601 static const struct block_device_operations zram_devops = {
 602         .swap_slot_free_notify = zram_slot_free_notify,
 603         .owner = THIS_MODULE
 604 };
 605
 606 static int create_device(struct zram *zram, int device_id)
 607 {
 608         int ret = -ENOMEM;
 609
 610         init_rwsem(&zram->lock);
 611         init_rwsem(&zram->init_lock);
 612         spin_lock_init(&zram->stat64_lock);
 613
 614         zram->queue = blk_alloc_queue(GFP_KERNEL);
 615         if (!zram->queue) {
 616                 pr_err("Error allocating disk queue for device %d\n",
 617                         device_id);
 618                 goto out;
 619         }
 620
 621         blk_queue_make_request(zram->queue, zram_make_request);
 622         zram->queue->queuedata = zram;
 623
 624          /* gendisk structure */
 625         zram->disk = alloc_disk(1);
 626         if (!zram->disk) {
 627                 pr_warn("Error allocating disk structure for device %d\n",
 628                         device_id);
 629                 goto out_free_queue;
 630         }
 631
 632         zram->disk->major = zram_major;
 633         zram->disk->first_minor = device_id;
 634         zram->disk->fops = &zram_devops;
 635         zram->disk->queue = zram->queue;
 636         zram->disk->private_data = zram;
 637         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 638
 639         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 640         set_capacity(zram->disk, 0);
 641
 642         /*
 643          * To ensure that we always get PAGE_SIZE aligned
 644          * and n*PAGE_SIZED sized I/O requests.
 645          */
 646         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 647         blk_queue_logical_block_size(zram->disk->queue,
 648                                         ZRAM_LOGICAL_BLOCK_SIZE);
 649         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 650         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 651
 652         add_disk(zram->disk);
 653
 654         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 655                                 &zram_disk_attr_group);
 656         if (ret < 0) {
 657                 pr_warn("Error creating sysfs group");
 658                 goto out_free_disk;
 659         }
 660
 661         zram->init_done = 0;
 662         return 0;
 663
 664 out_free_disk:
 665         del_gendisk(zram->disk);
 666         put_disk(zram->disk);
 667 out_free_queue:
 668         blk_cleanup_queue(zram->queue);
 669 out:
 670         return ret;
 671 }
 672
 673 static void destroy_device(struct zram *zram)
 674 {
 675         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 676                         &zram_disk_attr_group);
 677
 678         if (zram->disk) {
 679                 del_gendisk(zram->disk);
 680                 put_disk(zram->disk);
 681         }
 682
 683         if (zram->queue)
 684                 blk_cleanup_queue(zram->queue);
 685 }
 686
 687 static int __init zram_init(void)
 688 {
 689         int ret, dev_id;
 690
 691         if (num_devices > max_num_devices) {
 692                 pr_warn("Invalid value for num_devices: %u\n",
 693                                 num_devices);
 694                 ret = -EINVAL;
 695                 goto out;
 696         }
 697
 698         zram_major = register_blkdev(0, "zram");
 699         if (zram_major <= 0) {
 700                 pr_warn("Unable to get major number\n");
 701                 ret = -EBUSY;
 702                 goto out;
 703         }
 704
 705         /* Allocate the device array and initialize each one */
 706         zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 707         if (!zram_devices) {
 708                 ret = -ENOMEM;
 709                 goto unregister;
 710         }
 711
 712         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 713                 ret = create_device(&zram_devices[dev_id], dev_id);
 714                 if (ret)
 715                         goto free_devices;
 716         }
 717
 718         pr_info("Created %u device(s) ...\n", num_devices);
 719
 720         return 0;
 721
 722 free_devices:
 723         while (dev_id)
 724                 destroy_device(&zram_devices[--dev_id]);
 725         kfree(zram_devices);
 726 unregister:
 727         unregister_blkdev(zram_major, "zram");
 728 out:
 729         return ret;
 730 }
 731
 732 static void __exit zram_exit(void)
 733 {
 734         int i;
 735         struct zram *zram;
 736
 737         for (i = 0; i < num_devices; i++) {
 738                 zram = &zram_devices[i];
 739
 740                 get_disk(zram->disk);
 741                 destroy_device(zram);
 742                 zram_reset_device(zram);
 743                 put_disk(zram->disk);
 744         }
 745
 746         unregister_blkdev(zram_major, "zram");
 747
 748         kfree(zram_devices);
 749         pr_debug("Cleanup done!\n");
 750 }
 751
 752 module_param(num_devices, uint, 0);
 753 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 754
 755 module_init(zram_init);
 756 module_exit(zram_exit);
 757
 758 MODULE_LICENSE("Dual BSD/GPL");
 759 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 760 MODULE_DESCRIPTION("Compressed RAM Block Device");