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 struct zram *zram_devices;
  41
  42 /* Module params (documentation at end) */
  43 static unsigned int num_devices;
  44
  45 static void zram_stat_inc(u32 *v)
  46 {
  47         *v = *v + 1;
  48 }
  49
  50 static void zram_stat_dec(u32 *v)
  51 {
  52         *v = *v - 1;
  53 }
  54
  55 static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
  56 {
  57         spin_lock(&zram->stat64_lock);
  58         *v = *v + inc;
  59         spin_unlock(&zram->stat64_lock);
  60 }
  61
  62 static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
  63 {
  64         spin_lock(&zram->stat64_lock);
  65         *v = *v - dec;
  66         spin_unlock(&zram->stat64_lock);
  67 }
  68
  69 static void zram_stat64_inc(struct zram *zram, u64 *v)
  70 {
  71         zram_stat64_add(zram, v, 1);
  72 }
  73
  74 static int zram_test_flag(struct zram *zram, u32 index,
  75                         enum zram_pageflags flag)
  76 {
  77         return zram->table[index].flags & BIT(flag);
  78 }
  79
  80 static void zram_set_flag(struct zram *zram, u32 index,
  81                         enum zram_pageflags flag)
  82 {
  83         zram->table[index].flags |= BIT(flag);
  84 }
  85
  86 static void zram_clear_flag(struct zram *zram, u32 index,
  87                         enum zram_pageflags flag)
  88 {
  89         zram->table[index].flags &= ~BIT(flag);
  90 }
  91
  92 static int page_zero_filled(void *ptr)
  93 {
  94         unsigned int pos;
  95         unsigned long *page;
  96
  97         page = (unsigned long *)ptr;
  98
  99         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
 100                 if (page[pos])
 101                         return 0;
 102         }
 103
 104         return 1;
 105 }
 106
 107 static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
 108 {
 109         if (!zram->disksize) {
 110                 pr_info(
 111                 "disk size not provided. You can use disksize_kb module "
 112                 "param to specify size.\nUsing default: (%u%% of RAM).\n",
 113                 default_disksize_perc_ram
 114                 );
 115                 zram->disksize = default_disksize_perc_ram *
 116                                         (totalram_bytes / 100);
 117         }
 118
 119         if (zram->disksize > 2 * (totalram_bytes)) {
 120                 pr_info(
 121                 "There is little point creating a zram of greater than "
 122                 "twice the size of memory since we expect a 2:1 compression "
 123                 "ratio. Note that zram uses about 0.1%% of the size of "
 124                 "the disk when not in use so a huge zram is "
 125                 "wasteful.\n"
 126                 "\tMemory Size: %zu kB\n"
 127                 "\tSize you selected: %llu kB\n"
 128                 "Continuing anyway ...\n",
 129                 totalram_bytes >> 10, zram->disksize
 130                 );
 131         }
 132
 133         zram->disksize &= PAGE_MASK;
 134 }
 135
 136 static void zram_free_page(struct zram *zram, size_t index)
 137 {
 138         unsigned long handle = zram->table[index].handle;
 139         u16 size = zram->table[index].size;
 140
 141         if (unlikely(!handle)) {
 142                 /*
 143                  * No memory is allocated for zero filled pages.
 144                  * Simply clear zero page flag.
 145                  */
 146                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 147                         zram_clear_flag(zram, index, ZRAM_ZERO);
 148                         zram_stat_dec(&zram->stats.pages_zero);
 149                 }
 150                 return;
 151         }
 152
 153         if (unlikely(size > max_zpage_size))
 154                 zram_stat_dec(&zram->stats.bad_compress);
 155
 156         zs_free(zram->mem_pool, handle);
 157
 158         if (size <= PAGE_SIZE / 2)
 159                 zram_stat_dec(&zram->stats.good_compress);
 160
 161         zram_stat64_sub(zram, &zram->stats.compr_size,
 162                         zram->table[index].size);
 163         zram_stat_dec(&zram->stats.pages_stored);
 164
 165         zram->table[index].handle = 0;
 166         zram->table[index].size = 0;
 167 }
 168
 169 static void handle_zero_page(struct bio_vec *bvec)
 170 {
 171         struct page *page = bvec->bv_page;
 172         void *user_mem;
 173
 174         user_mem = kmap_atomic(page);
 175         memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
 176         kunmap_atomic(user_mem);
 177
 178         flush_dcache_page(page);
 179 }
 180
 181 static inline int is_partial_io(struct bio_vec *bvec)
 182 {
 183         return bvec->bv_len != PAGE_SIZE;
 184 }
 185
 186 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 187 {
 188         int ret = LZO_E_OK;
 189         size_t clen = PAGE_SIZE;
 190         unsigned char *cmem;
 191         unsigned long handle = zram->table[index].handle;
 192
 193         if (!handle || zram_test_flag(zram, index, ZRAM_ZERO)) {
 194                 memset(mem, 0, PAGE_SIZE);
 195                 return 0;
 196         }
 197
 198         cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
 199         if (zram->table[index].size == PAGE_SIZE)
 200                 memcpy(mem, cmem, PAGE_SIZE);
 201         else
 202                 ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
 203                                                 mem, &clen);
 204         zs_unmap_object(zram->mem_pool, handle);
 205
 206         /* Should NEVER happen. Return bio error if it does. */
 207         if (unlikely(ret != LZO_E_OK)) {
 208                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 209                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 210                 return ret;
 211         }
 212
 213         return 0;
 214 }
 215
 216 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 217                           u32 index, int offset, struct bio *bio)
 218 {
 219         int ret;
 220         struct page *page;
 221         unsigned char *user_mem, *uncmem = NULL;
 222
 223         page = bvec->bv_page;
 224
 225         if (unlikely(!zram->table[index].handle) ||
 226                         zram_test_flag(zram, index, ZRAM_ZERO)) {
 227                 handle_zero_page(bvec);
 228                 return 0;
 229         }
 230
 231         user_mem = kmap_atomic(page);
 232         if (is_partial_io(bvec))
 233                 /* Use  a temporary buffer to decompress the page */
 234                 uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
 235         else
 236                 uncmem = user_mem;
 237
 238         if (!uncmem) {
 239                 pr_info("Unable to allocate temp memory\n");
 240                 ret = -ENOMEM;
 241                 goto out_cleanup;
 242         }
 243
 244         ret = zram_decompress_page(zram, uncmem, index);
 245         /* Should NEVER happen. Return bio error if it does. */
 246         if (unlikely(ret != LZO_E_OK)) {
 247                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 248                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 249                 goto out_cleanup;
 250         }
 251
 252         if (is_partial_io(bvec))
 253                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 254                                 bvec->bv_len);
 255
 256         flush_dcache_page(page);
 257         ret = 0;
 258 out_cleanup:
 259         kunmap_atomic(user_mem);
 260         if (is_partial_io(bvec))
 261                 kfree(uncmem);
 262         return ret;
 263 }
 264
 265 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 266                            int offset)
 267 {
 268         int ret = 0;
 269         size_t clen;
 270         unsigned long handle;
 271         struct page *page;
 272         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 273
 274         page = bvec->bv_page;
 275         src = zram->compress_buffer;
 276
 277         if (is_partial_io(bvec)) {
 278                 /*
 279                  * This is a partial IO. We need to read the full page
 280                  * before to write the changes.
 281                  */
 282                 uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
 283                 if (!uncmem) {
 284                         pr_info("Error allocating temp memory!\n");
 285                         ret = -ENOMEM;
 286                         goto out;
 287                 }
 288                 ret = zram_decompress_page(zram, uncmem, index);
 289                 if (ret)
 290                         goto out;
 291         }
 292
 293         /*
 294          * System overwrites unused sectors. Free memory associated
 295          * with this sector now.
 296          */
 297         if (zram->table[index].handle ||
 298             zram_test_flag(zram, index, ZRAM_ZERO))
 299                 zram_free_page(zram, index);
 300
 301         user_mem = kmap_atomic(page);
 302
 303         if (is_partial_io(bvec)) {
 304                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 305                        bvec->bv_len);
 306                 kunmap_atomic(user_mem);
 307                 user_mem = NULL;
 308         } else {
 309                 uncmem = user_mem;
 310         }
 311
 312         if (page_zero_filled(uncmem)) {
 313                 if (!is_partial_io(bvec))
 314                         kunmap_atomic(user_mem);
 315                 zram_stat_inc(&zram->stats.pages_zero);
 316                 zram_set_flag(zram, index, ZRAM_ZERO);
 317                 ret = 0;
 318                 goto out;
 319         }
 320
 321         ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
 322                                zram->compress_workmem);
 323
 324         if (!is_partial_io(bvec)) {
 325                 kunmap_atomic(user_mem);
 326                 user_mem = NULL;
 327                 uncmem = NULL;
 328         }
 329
 330         if (unlikely(ret != LZO_E_OK)) {
 331                 pr_err("Compression failed! err=%d\n", ret);
 332                 goto out;
 333         }
 334
 335         if (unlikely(clen > max_zpage_size)) {
 336                 zram_stat_inc(&zram->stats.bad_compress);
 337                 clen = PAGE_SIZE;
 338                 src = NULL;
 339                 if (is_partial_io(bvec))
 340                         src = uncmem;
 341         }
 342
 343         handle = zs_malloc(zram->mem_pool, clen);
 344         if (!handle) {
 345                 pr_info("Error allocating memory for compressed "
 346                         "page: %u, size=%zu\n", index, clen);
 347                 ret = -ENOMEM;
 348                 goto out;
 349         }
 350         cmem = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
 351
 352         if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
 353                 src = kmap_atomic(page);
 354         memcpy(cmem, src, clen);
 355         if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
 356                 kunmap_atomic(src);
 357
 358         zs_unmap_object(zram->mem_pool, handle);
 359
 360         zram->table[index].handle = handle;
 361         zram->table[index].size = clen;
 362
 363         /* Update stats */
 364         zram_stat64_add(zram, &zram->stats.compr_size, clen);
 365         zram_stat_inc(&zram->stats.pages_stored);
 366         if (clen <= PAGE_SIZE / 2)
 367                 zram_stat_inc(&zram->stats.good_compress);
 368
 369 out:
 370         if (is_partial_io(bvec))
 371                 kfree(uncmem);
 372
 373         if (ret)
 374                 zram_stat64_inc(zram, &zram->stats.failed_writes);
 375         return ret;
 376 }
 377
 378 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 379                         int offset, struct bio *bio, int rw)
 380 {
 381         int ret;
 382
 383         if (rw == READ) {
 384                 down_read(&zram->lock);
 385                 ret = zram_bvec_read(zram, bvec, index, offset, bio);
 386                 up_read(&zram->lock);
 387         } else {
 388                 down_write(&zram->lock);
 389                 ret = zram_bvec_write(zram, bvec, index, offset);
 390                 up_write(&zram->lock);
 391         }
 392
 393         return ret;
 394 }
 395
 396 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 397 {
 398         if (*offset + bvec->bv_len >= PAGE_SIZE)
 399                 (*index)++;
 400         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 401 }
 402
 403 static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
 404 {
 405         int i, offset;
 406         u32 index;
 407         struct bio_vec *bvec;
 408
 409         switch (rw) {
 410         case READ:
 411                 zram_stat64_inc(zram, &zram->stats.num_reads);
 412                 break;
 413         case WRITE:
 414                 zram_stat64_inc(zram, &zram->stats.num_writes);
 415                 break;
 416         }
 417
 418         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 419         offset = (bio->bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 420
 421         bio_for_each_segment(bvec, bio, i) {
 422                 int max_transfer_size = PAGE_SIZE - offset;
 423
 424                 if (bvec->bv_len > max_transfer_size) {
 425                         /*
 426                          * zram_bvec_rw() can only make operation on a single
 427                          * zram page. Split the bio vector.
 428                          */
 429                         struct bio_vec bv;
 430
 431                         bv.bv_page = bvec->bv_page;
 432                         bv.bv_len = max_transfer_size;
 433                         bv.bv_offset = bvec->bv_offset;
 434
 435                         if (zram_bvec_rw(zram, &bv, index, offset, bio, rw) < 0)
 436                                 goto out;
 437
 438                         bv.bv_len = bvec->bv_len - max_transfer_size;
 439                         bv.bv_offset += max_transfer_size;
 440                         if (zram_bvec_rw(zram, &bv, index+1, 0, bio, rw) < 0)
 441                                 goto out;
 442                 } else
 443                         if (zram_bvec_rw(zram, bvec, index, offset, bio, rw)
 444                             < 0)
 445                                 goto out;
 446
 447                 update_position(&index, &offset, bvec);
 448         }
 449
 450         set_bit(BIO_UPTODATE, &bio->bi_flags);
 451         bio_endio(bio, 0);
 452         return;
 453
 454 out:
 455         bio_io_error(bio);
 456 }
 457
 458 /*
 459  * Check if request is within bounds and aligned on zram logical blocks.
 460  */
 461 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 462 {
 463         if (unlikely(
 464                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 465                 (bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)) ||
 466                 (bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))) {
 467
 468                 return 0;
 469         }
 470
 471         /* I/O request is valid */
 472         return 1;
 473 }
 474
 475 /*
 476  * Handler function for all zram I/O requests.
 477  */
 478 static void zram_make_request(struct request_queue *queue, struct bio *bio)
 479 {
 480         struct zram *zram = queue->queuedata;
 481
 482         if (unlikely(!zram->init_done) && zram_init_device(zram))
 483                 goto error;
 484
 485         down_read(&zram->init_lock);
 486         if (unlikely(!zram->init_done))
 487                 goto error_unlock;
 488
 489         if (!valid_io_request(zram, bio)) {
 490                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 491                 goto error_unlock;
 492         }
 493
 494         __zram_make_request(zram, bio, bio_data_dir(bio));
 495         up_read(&zram->init_lock);
 496
 497         return;
 498
 499 error_unlock:
 500         up_read(&zram->init_lock);
 501 error:
 502         bio_io_error(bio);
 503 }
 504
 505 void __zram_reset_device(struct zram *zram)
 506 {
 507         size_t index;
 508
 509         zram->init_done = 0;
 510
 511         /* Free various per-device buffers */
 512         kfree(zram->compress_workmem);
 513         free_pages((unsigned long)zram->compress_buffer, 1);
 514
 515         zram->compress_workmem = NULL;
 516         zram->compress_buffer = NULL;
 517
 518         /* Free all pages that are still in this zram device */
 519         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 520                 unsigned long handle = zram->table[index].handle;
 521                 if (!handle)
 522                         continue;
 523
 524                 zs_free(zram->mem_pool, handle);
 525         }
 526
 527         vfree(zram->table);
 528         zram->table = NULL;
 529
 530         zs_destroy_pool(zram->mem_pool);
 531         zram->mem_pool = NULL;
 532
 533         /* Reset stats */
 534         memset(&zram->stats, 0, sizeof(zram->stats));
 535
 536         zram->disksize = 0;
 537 }
 538
 539 void zram_reset_device(struct zram *zram)
 540 {
 541         down_write(&zram->init_lock);
 542         __zram_reset_device(zram);
 543         up_write(&zram->init_lock);
 544 }
 545
 546 int zram_init_device(struct zram *zram)
 547 {
 548         int ret;
 549         size_t num_pages;
 550
 551         down_write(&zram->init_lock);
 552
 553         if (zram->init_done) {
 554                 up_write(&zram->init_lock);
 555                 return 0;
 556         }
 557
 558         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 559
 560         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 561         if (!zram->compress_workmem) {
 562                 pr_err("Error allocating compressor working memory!\n");
 563                 ret = -ENOMEM;
 564                 goto fail_no_table;
 565         }
 566
 567         zram->compress_buffer =
 568                 (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
 569         if (!zram->compress_buffer) {
 570                 pr_err("Error allocating compressor buffer space\n");
 571                 ret = -ENOMEM;
 572                 goto fail_no_table;
 573         }
 574
 575         num_pages = zram->disksize >> PAGE_SHIFT;
 576         zram->table = vzalloc(num_pages * sizeof(*zram->table));
 577         if (!zram->table) {
 578                 pr_err("Error allocating zram address table\n");
 579                 ret = -ENOMEM;
 580                 goto fail_no_table;
 581         }
 582
 583         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 584
 585         /* zram devices sort of resembles non-rotational disks */
 586         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 587
 588         zram->mem_pool = zs_create_pool("zram", GFP_NOIO | __GFP_HIGHMEM);
 589         if (!zram->mem_pool) {
 590                 pr_err("Error creating memory pool\n");
 591                 ret = -ENOMEM;
 592                 goto fail;
 593         }
 594
 595         zram->init_done = 1;
 596         up_write(&zram->init_lock);
 597
 598         pr_debug("Initialization done!\n");
 599         return 0;
 600
 601 fail_no_table:
 602         /* To prevent accessing table entries during cleanup */
 603         zram->disksize = 0;
 604 fail:
 605         __zram_reset_device(zram);
 606         up_write(&zram->init_lock);
 607         pr_err("Initialization failed: err=%d\n", ret);
 608         return ret;
 609 }
 610
 611 static void zram_slot_free_notify(struct block_device *bdev,
 612                                 unsigned long index)
 613 {
 614         struct zram *zram;
 615
 616         zram = bdev->bd_disk->private_data;
 617         zram_free_page(zram, index);
 618         zram_stat64_inc(zram, &zram->stats.notify_free);
 619 }
 620
 621 static const struct block_device_operations zram_devops = {
 622         .swap_slot_free_notify = zram_slot_free_notify,
 623         .owner = THIS_MODULE
 624 };
 625
 626 static int create_device(struct zram *zram, int device_id)
 627 {
 628         int ret = 0;
 629
 630         init_rwsem(&zram->lock);
 631         init_rwsem(&zram->init_lock);
 632         spin_lock_init(&zram->stat64_lock);
 633
 634         zram->queue = blk_alloc_queue(GFP_KERNEL);
 635         if (!zram->queue) {
 636                 pr_err("Error allocating disk queue for device %d\n",
 637                         device_id);
 638                 ret = -ENOMEM;
 639                 goto out;
 640         }
 641
 642         blk_queue_make_request(zram->queue, zram_make_request);
 643         zram->queue->queuedata = zram;
 644
 645          /* gendisk structure */
 646         zram->disk = alloc_disk(1);
 647         if (!zram->disk) {
 648                 blk_cleanup_queue(zram->queue);
 649                 pr_warn("Error allocating disk structure for device %d\n",
 650                         device_id);
 651                 ret = -ENOMEM;
 652                 goto out;
 653         }
 654
 655         zram->disk->major = zram_major;
 656         zram->disk->first_minor = device_id;
 657         zram->disk->fops = &zram_devops;
 658         zram->disk->queue = zram->queue;
 659         zram->disk->private_data = zram;
 660         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 661
 662         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 663         set_capacity(zram->disk, 0);
 664
 665         /*
 666          * To ensure that we always get PAGE_SIZE aligned
 667          * and n*PAGE_SIZED sized I/O requests.
 668          */
 669         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 670         blk_queue_logical_block_size(zram->disk->queue,
 671                                         ZRAM_LOGICAL_BLOCK_SIZE);
 672         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 673         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 674
 675         add_disk(zram->disk);
 676
 677         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 678                                 &zram_disk_attr_group);
 679         if (ret < 0) {
 680                 pr_warn("Error creating sysfs group");
 681                 goto out;
 682         }
 683
 684         zram->init_done = 0;
 685
 686 out:
 687         return ret;
 688 }
 689
 690 static void destroy_device(struct zram *zram)
 691 {
 692         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 693                         &zram_disk_attr_group);
 694
 695         if (zram->disk) {
 696                 del_gendisk(zram->disk);
 697                 put_disk(zram->disk);
 698         }
 699
 700         if (zram->queue)
 701                 blk_cleanup_queue(zram->queue);
 702 }
 703
 704 unsigned int zram_get_num_devices(void)
 705 {
 706         return num_devices;
 707 }
 708
 709 static int __init zram_init(void)
 710 {
 711         int ret, dev_id;
 712
 713         if (num_devices > max_num_devices) {
 714                 pr_warn("Invalid value for num_devices: %u\n",
 715                                 num_devices);
 716                 ret = -EINVAL;
 717                 goto out;
 718         }
 719
 720         zram_major = register_blkdev(0, "zram");
 721         if (zram_major <= 0) {
 722                 pr_warn("Unable to get major number\n");
 723                 ret = -EBUSY;
 724                 goto out;
 725         }
 726
 727         if (!num_devices) {
 728                 pr_info("num_devices not specified. Using default: 1\n");
 729                 num_devices = 1;
 730         }
 731
 732         /* Allocate the device array and initialize each one */
 733         pr_info("Creating %u devices ...\n", num_devices);
 734         zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 735         if (!zram_devices) {
 736                 ret = -ENOMEM;
 737                 goto unregister;
 738         }
 739
 740         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 741                 ret = create_device(&zram_devices[dev_id], dev_id);
 742                 if (ret)
 743                         goto free_devices;
 744         }
 745
 746         return 0;
 747
 748 free_devices:
 749         while (dev_id)
 750                 destroy_device(&zram_devices[--dev_id]);
 751         kfree(zram_devices);
 752 unregister:
 753         unregister_blkdev(zram_major, "zram");
 754 out:
 755         return ret;
 756 }
 757
 758 static void __exit zram_exit(void)
 759 {
 760         int i;
 761         struct zram *zram;
 762
 763         for (i = 0; i < num_devices; i++) {
 764                 zram = &zram_devices[i];
 765
 766                 destroy_device(zram);
 767                 if (zram->init_done)
 768                         zram_reset_device(zram);
 769         }
 770
 771         unregister_blkdev(zram_major, "zram");
 772
 773         kfree(zram_devices);
 774         pr_debug("Cleanup done!\n");
 775 }
 776
 777 module_param(num_devices, uint, 0);
 778 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 779
 780 module_init(zram_init);
 781 module_exit(zram_exit);
 782
 783 MODULE_LICENSE("Dual BSD/GPL");
 784 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 785 MODULE_DESCRIPTION("Compressed RAM Block Device");