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_bvec_read(struct zram *zram, struct bio_vec *bvec,
 187                           u32 index, int offset, struct bio *bio)
 188 {
 189         int ret;
 190         size_t clen;
 191         struct page *page;
 192         unsigned char *user_mem, *cmem, *uncmem = NULL;
 193
 194         page = bvec->bv_page;
 195
 196         if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 197                 handle_zero_page(bvec);
 198                 return 0;
 199         }
 200
 201         /* Requested page is not present in compressed area */
 202         if (unlikely(!zram->table[index].handle)) {
 203                 pr_debug("Read before write: sector=%lu, size=%u",
 204                          (ulong)(bio->bi_sector), bio->bi_size);
 205                 handle_zero_page(bvec);
 206                 return 0;
 207         }
 208
 209         if (is_partial_io(bvec)) {
 210                 /* Use  a temporary buffer to decompress the page */
 211                 uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
 212                 if (!uncmem) {
 213                         pr_info("Error allocating temp memory!\n");
 214                         return -ENOMEM;
 215                 }
 216         }
 217
 218         user_mem = kmap_atomic(page);
 219         if (!is_partial_io(bvec))
 220                 uncmem = user_mem;
 221         clen = PAGE_SIZE;
 222
 223         cmem = zs_map_object(zram->mem_pool, zram->table[index].handle);
 224
 225         ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
 226                                     uncmem, &clen);
 227
 228         if (is_partial_io(bvec)) {
 229                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 230                        bvec->bv_len);
 231                 kfree(uncmem);
 232         }
 233
 234         zs_unmap_object(zram->mem_pool, zram->table[index].handle);
 235         kunmap_atomic(user_mem);
 236
 237         /* Should NEVER happen. Return bio error if it does. */
 238         if (unlikely(ret != LZO_E_OK)) {
 239                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 240                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 241                 return ret;
 242         }
 243
 244         flush_dcache_page(page);
 245
 246         return 0;
 247 }
 248
 249 static int zram_read_before_write(struct zram *zram, char *mem, u32 index)
 250 {
 251         int ret;
 252         size_t clen = PAGE_SIZE;
 253         unsigned char *cmem;
 254         unsigned long handle = zram->table[index].handle;
 255
 256         if (zram_test_flag(zram, index, ZRAM_ZERO) || !handle) {
 257                 memset(mem, 0, PAGE_SIZE);
 258                 return 0;
 259         }
 260
 261         cmem = zs_map_object(zram->mem_pool, handle);
 262         ret = lzo1x_decompress_safe(cmem, zram->table[index].size,
 263                                     mem, &clen);
 264         zs_unmap_object(zram->mem_pool, handle);
 265
 266         /* Should NEVER happen. Return bio error if it does. */
 267         if (unlikely(ret != LZO_E_OK)) {
 268                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 269                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 270                 return ret;
 271         }
 272
 273         return 0;
 274 }
 275
 276 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 277                            int offset)
 278 {
 279         int ret;
 280         size_t clen;
 281         unsigned long handle;
 282         struct page *page;
 283         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 284
 285         page = bvec->bv_page;
 286         src = zram->compress_buffer;
 287
 288         if (is_partial_io(bvec)) {
 289                 /*
 290                  * This is a partial IO. We need to read the full page
 291                  * before to write the changes.
 292                  */
 293                 uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
 294                 if (!uncmem) {
 295                         pr_info("Error allocating temp memory!\n");
 296                         ret = -ENOMEM;
 297                         goto out;
 298                 }
 299                 ret = zram_read_before_write(zram, uncmem, index);
 300                 if (ret) {
 301                         kfree(uncmem);
 302                         goto out;
 303                 }
 304         }
 305
 306         /*
 307          * System overwrites unused sectors. Free memory associated
 308          * with this sector now.
 309          */
 310         if (zram->table[index].handle ||
 311             zram_test_flag(zram, index, ZRAM_ZERO))
 312                 zram_free_page(zram, index);
 313
 314         user_mem = kmap_atomic(page);
 315
 316         if (is_partial_io(bvec))
 317                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 318                        bvec->bv_len);
 319         else
 320                 uncmem = user_mem;
 321
 322         if (page_zero_filled(uncmem)) {
 323                 kunmap_atomic(user_mem);
 324                 if (is_partial_io(bvec))
 325                         kfree(uncmem);
 326                 zram_stat_inc(&zram->stats.pages_zero);
 327                 zram_set_flag(zram, index, ZRAM_ZERO);
 328                 ret = 0;
 329                 goto out;
 330         }
 331
 332         ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
 333                                zram->compress_workmem);
 334
 335         kunmap_atomic(user_mem);
 336         if (is_partial_io(bvec))
 337                         kfree(uncmem);
 338
 339         if (unlikely(ret != LZO_E_OK)) {
 340                 pr_err("Compression failed! err=%d\n", ret);
 341                 goto out;
 342         }
 343
 344         if (unlikely(clen > max_zpage_size))
 345                 zram_stat_inc(&zram->stats.bad_compress);
 346
 347         handle = zs_malloc(zram->mem_pool, clen);
 348         if (!handle) {
 349                 pr_info("Error allocating memory for compressed "
 350                         "page: %u, size=%zu\n", index, clen);
 351                 ret = -ENOMEM;
 352                 goto out;
 353         }
 354         cmem = zs_map_object(zram->mem_pool, handle);
 355
 356         memcpy(cmem, src, clen);
 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         return 0;
 370
 371 out:
 372         if (ret)
 373                 zram_stat64_inc(zram, &zram->stats.failed_writes);
 374         return ret;
 375 }
 376
 377 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 378                         int offset, struct bio *bio, int rw)
 379 {
 380         int ret;
 381
 382         if (rw == READ) {
 383                 down_read(&zram->lock);
 384                 ret = zram_bvec_read(zram, bvec, index, offset, bio);
 385                 up_read(&zram->lock);
 386         } else {
 387                 down_write(&zram->lock);
 388                 ret = zram_bvec_write(zram, bvec, index, offset);
 389                 up_write(&zram->lock);
 390         }
 391
 392         return ret;
 393 }
 394
 395 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 396 {
 397         if (*offset + bvec->bv_len >= PAGE_SIZE)
 398                 (*index)++;
 399         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 400 }
 401
 402 static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
 403 {
 404         int i, offset;
 405         u32 index;
 406         struct bio_vec *bvec;
 407
 408         switch (rw) {
 409         case READ:
 410                 zram_stat64_inc(zram, &zram->stats.num_reads);
 411                 break;
 412         case WRITE:
 413                 zram_stat64_inc(zram, &zram->stats.num_writes);
 414                 break;
 415         }
 416
 417         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 418         offset = (bio->bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 419
 420         bio_for_each_segment(bvec, bio, i) {
 421                 int max_transfer_size = PAGE_SIZE - offset;
 422
 423                 if (bvec->bv_len > max_transfer_size) {
 424                         /*
 425                          * zram_bvec_rw() can only make operation on a single
 426                          * zram page. Split the bio vector.
 427                          */
 428                         struct bio_vec bv;
 429
 430                         bv.bv_page = bvec->bv_page;
 431                         bv.bv_len = max_transfer_size;
 432                         bv.bv_offset = bvec->bv_offset;
 433
 434                         if (zram_bvec_rw(zram, &bv, index, offset, bio, rw) < 0)
 435                                 goto out;
 436
 437                         bv.bv_len = bvec->bv_len - max_transfer_size;
 438                         bv.bv_offset += max_transfer_size;
 439                         if (zram_bvec_rw(zram, &bv, index+1, 0, bio, rw) < 0)
 440                                 goto out;
 441                 } else
 442                         if (zram_bvec_rw(zram, bvec, index, offset, bio, rw)
 443                             < 0)
 444                                 goto out;
 445
 446                 update_position(&index, &offset, bvec);
 447         }
 448
 449         set_bit(BIO_UPTODATE, &bio->bi_flags);
 450         bio_endio(bio, 0);
 451         return;
 452
 453 out:
 454         bio_io_error(bio);
 455 }
 456
 457 /*
 458  * Check if request is within bounds and aligned on zram logical blocks.
 459  */
 460 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 461 {
 462         if (unlikely(
 463                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 464                 (bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)) ||
 465                 (bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))) {
 466
 467                 return 0;
 468         }
 469
 470         /* I/O request is valid */
 471         return 1;
 472 }
 473
 474 /*
 475  * Handler function for all zram I/O requests.
 476  */
 477 static void zram_make_request(struct request_queue *queue, struct bio *bio)
 478 {
 479         struct zram *zram = queue->queuedata;
 480
 481         if (unlikely(!zram->init_done) && zram_init_device(zram))
 482                 goto error;
 483
 484         down_read(&zram->init_lock);
 485         if (unlikely(!zram->init_done))
 486                 goto error_unlock;
 487
 488         if (!valid_io_request(zram, bio)) {
 489                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 490                 goto error_unlock;
 491         }
 492
 493         __zram_make_request(zram, bio, bio_data_dir(bio));
 494         up_read(&zram->init_lock);
 495
 496         return;
 497
 498 error_unlock:
 499         up_read(&zram->init_lock);
 500 error:
 501         bio_io_error(bio);
 502 }
 503
 504 void __zram_reset_device(struct zram *zram)
 505 {
 506         size_t index;
 507
 508         zram->init_done = 0;
 509
 510         /* Free various per-device buffers */
 511         kfree(zram->compress_workmem);
 512         free_pages((unsigned long)zram->compress_buffer, 1);
 513
 514         zram->compress_workmem = NULL;
 515         zram->compress_buffer = NULL;
 516
 517         /* Free all pages that are still in this zram device */
 518         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 519                 unsigned long handle = zram->table[index].handle;
 520                 if (!handle)
 521                         continue;
 522
 523                 zs_free(zram->mem_pool, handle);
 524         }
 525
 526         vfree(zram->table);
 527         zram->table = NULL;
 528
 529         zs_destroy_pool(zram->mem_pool);
 530         zram->mem_pool = NULL;
 531
 532         /* Reset stats */
 533         memset(&zram->stats, 0, sizeof(zram->stats));
 534
 535         zram->disksize = 0;
 536 }
 537
 538 void zram_reset_device(struct zram *zram)
 539 {
 540         down_write(&zram->init_lock);
 541         __zram_reset_device(zram);
 542         up_write(&zram->init_lock);
 543 }
 544
 545 int zram_init_device(struct zram *zram)
 546 {
 547         int ret;
 548         size_t num_pages;
 549
 550         down_write(&zram->init_lock);
 551
 552         if (zram->init_done) {
 553                 up_write(&zram->init_lock);
 554                 return 0;
 555         }
 556
 557         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 558
 559         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 560         if (!zram->compress_workmem) {
 561                 pr_err("Error allocating compressor working memory!\n");
 562                 ret = -ENOMEM;
 563                 goto fail_no_table;
 564         }
 565
 566         zram->compress_buffer =
 567                 (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
 568         if (!zram->compress_buffer) {
 569                 pr_err("Error allocating compressor buffer space\n");
 570                 ret = -ENOMEM;
 571                 goto fail_no_table;
 572         }
 573
 574         num_pages = zram->disksize >> PAGE_SHIFT;
 575         zram->table = vzalloc(num_pages * sizeof(*zram->table));
 576         if (!zram->table) {
 577                 pr_err("Error allocating zram address table\n");
 578                 ret = -ENOMEM;
 579                 goto fail_no_table;
 580         }
 581
 582         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 583
 584         /* zram devices sort of resembles non-rotational disks */
 585         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 586
 587         zram->mem_pool = zs_create_pool("zram", GFP_NOIO | __GFP_HIGHMEM);
 588         if (!zram->mem_pool) {
 589                 pr_err("Error creating memory pool\n");
 590                 ret = -ENOMEM;
 591                 goto fail;
 592         }
 593
 594         zram->init_done = 1;
 595         up_write(&zram->init_lock);
 596
 597         pr_debug("Initialization done!\n");
 598         return 0;
 599
 600 fail_no_table:
 601         /* To prevent accessing table entries during cleanup */
 602         zram->disksize = 0;
 603 fail:
 604         __zram_reset_device(zram);
 605         up_write(&zram->init_lock);
 606         pr_err("Initialization failed: err=%d\n", ret);
 607         return ret;
 608 }
 609
 610 static void zram_slot_free_notify(struct block_device *bdev,
 611                                 unsigned long index)
 612 {
 613         struct zram *zram;
 614
 615         zram = bdev->bd_disk->private_data;
 616         zram_free_page(zram, index);
 617         zram_stat64_inc(zram, &zram->stats.notify_free);
 618 }
 619
 620 static const struct block_device_operations zram_devops = {
 621         .swap_slot_free_notify = zram_slot_free_notify,
 622         .owner = THIS_MODULE
 623 };
 624
 625 static int create_device(struct zram *zram, int device_id)
 626 {
 627         int ret = 0;
 628
 629         init_rwsem(&zram->lock);
 630         init_rwsem(&zram->init_lock);
 631         spin_lock_init(&zram->stat64_lock);
 632
 633         zram->queue = blk_alloc_queue(GFP_KERNEL);
 634         if (!zram->queue) {
 635                 pr_err("Error allocating disk queue for device %d\n",
 636                         device_id);
 637                 ret = -ENOMEM;
 638                 goto out;
 639         }
 640
 641         blk_queue_make_request(zram->queue, zram_make_request);
 642         zram->queue->queuedata = zram;
 643
 644          /* gendisk structure */
 645         zram->disk = alloc_disk(1);
 646         if (!zram->disk) {
 647                 blk_cleanup_queue(zram->queue);
 648                 pr_warning("Error allocating disk structure for device %d\n",
 649                         device_id);
 650                 ret = -ENOMEM;
 651                 goto out;
 652         }
 653
 654         zram->disk->major = zram_major;
 655         zram->disk->first_minor = device_id;
 656         zram->disk->fops = &zram_devops;
 657         zram->disk->queue = zram->queue;
 658         zram->disk->private_data = zram;
 659         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 660
 661         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 662         set_capacity(zram->disk, 0);
 663
 664         /*
 665          * To ensure that we always get PAGE_SIZE aligned
 666          * and n*PAGE_SIZED sized I/O requests.
 667          */
 668         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 669         blk_queue_logical_block_size(zram->disk->queue,
 670                                         ZRAM_LOGICAL_BLOCK_SIZE);
 671         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 672         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 673
 674         add_disk(zram->disk);
 675
 676         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 677                                 &zram_disk_attr_group);
 678         if (ret < 0) {
 679                 pr_warning("Error creating sysfs group");
 680                 goto out;
 681         }
 682
 683         zram->init_done = 0;
 684
 685 out:
 686         return ret;
 687 }
 688
 689 static void destroy_device(struct zram *zram)
 690 {
 691         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 692                         &zram_disk_attr_group);
 693
 694         if (zram->disk) {
 695                 del_gendisk(zram->disk);
 696                 put_disk(zram->disk);
 697         }
 698
 699         if (zram->queue)
 700                 blk_cleanup_queue(zram->queue);
 701 }
 702
 703 unsigned int zram_get_num_devices(void)
 704 {
 705         return num_devices;
 706 }
 707
 708 static int __init zram_init(void)
 709 {
 710         int ret, dev_id;
 711
 712         if (num_devices > max_num_devices) {
 713                 pr_warning("Invalid value for num_devices: %u\n",
 714                                 num_devices);
 715                 ret = -EINVAL;
 716                 goto out;
 717         }
 718
 719         zram_major = register_blkdev(0, "zram");
 720         if (zram_major <= 0) {
 721                 pr_warning("Unable to get major number\n");
 722                 ret = -EBUSY;
 723                 goto out;
 724         }
 725
 726         if (!num_devices) {
 727                 pr_info("num_devices not specified. Using default: 1\n");
 728                 num_devices = 1;
 729         }
 730
 731         /* Allocate the device array and initialize each one */
 732         pr_info("Creating %u devices ...\n", num_devices);
 733         zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 734         if (!zram_devices) {
 735                 ret = -ENOMEM;
 736                 goto unregister;
 737         }
 738
 739         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 740                 ret = create_device(&zram_devices[dev_id], dev_id);
 741                 if (ret)
 742                         goto free_devices;
 743         }
 744
 745         return 0;
 746
 747 free_devices:
 748         while (dev_id)
 749                 destroy_device(&zram_devices[--dev_id]);
 750         kfree(zram_devices);
 751 unregister:
 752         unregister_blkdev(zram_major, "zram");
 753 out:
 754         return ret;
 755 }
 756
 757 static void __exit zram_exit(void)
 758 {
 759         int i;
 760         struct zram *zram;
 761
 762         for (i = 0; i < num_devices; i++) {
 763                 zram = &zram_devices[i];
 764
 765                 destroy_device(zram);
 766                 if (zram->init_done)
 767                         zram_reset_device(zram);
 768         }
 769
 770         unregister_blkdev(zram_major, "zram");
 771
 772         kfree(zram_devices);
 773         pr_debug("Cleanup done!\n");
 774 }
 775
 776 module_param(num_devices, uint, 0);
 777 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 778
 779 module_init(zram_init);
 780 module_exit(zram_exit);
 781
 782 MODULE_LICENSE("Dual BSD/GPL");
 783 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 784 MODULE_DESCRIPTION("Compressed RAM Block Device");