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 static struct zram *devices;
  37
  38 /* Module params (documentation at end) */
  39 static unsigned int num_devices;
  40
  41 static int zram_test_flag(struct zram *zram, u32 index,
  42                         enum zram_pageflags flag)
  43 {
  44         return zram->table[index].flags & BIT(flag);
  45 }
  46
  47 static void zram_set_flag(struct zram *zram, u32 index,
  48                         enum zram_pageflags flag)
  49 {
  50         zram->table[index].flags |= BIT(flag);
  51 }
  52
  53 static void zram_clear_flag(struct zram *zram, u32 index,
  54                         enum zram_pageflags flag)
  55 {
  56         zram->table[index].flags &= ~BIT(flag);
  57 }
  58
  59 static int page_zero_filled(void *ptr)
  60 {
  61         unsigned int pos;
  62         unsigned long *page;
  63
  64         page = (unsigned long *)ptr;
  65
  66         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
  67                 if (page[pos])
  68                         return 0;
  69         }
  70
  71         return 1;
  72 }
  73
  74 static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
  75 {
  76         if (!zram->disksize) {
  77                 pr_info(
  78                 "disk size not provided. You can use disksize_kb module "
  79                 "param to specify size.\nUsing default: (%u%% of RAM).\n",
  80                 default_disksize_perc_ram
  81                 );
  82                 zram->disksize = default_disksize_perc_ram *
  83                                         (totalram_bytes / 100);
  84         }
  85
  86         if (zram->disksize > 2 * (totalram_bytes)) {
  87                 pr_info(
  88                 "There is little point creating a zram of greater than "
  89                 "twice the size of memory since we expect a 2:1 compression "
  90                 "ratio. Note that zram uses about 0.1%% of the size of "
  91                 "the disk when not in use so a huge zram is "
  92                 "wasteful.\n"
  93                 "\tMemory Size: %zu kB\n"
  94                 "\tSize you selected: %zu kB\n"
  95                 "Continuing anyway ...\n",
  96                 totalram_bytes >> 10, zram->disksize
  97                 );
  98         }
  99
 100         zram->disksize &= PAGE_MASK;
 101 }
 102
 103 static void zram_ioctl_get_stats(struct zram *zram,
 104                         struct zram_ioctl_stats *s)
 105 {
 106         s->disksize = zram->disksize;
 107
 108 #if defined(CONFIG_ZRAM_STATS)
 109         {
 110         struct zram_stats *rs = &zram->stats;
 111         size_t succ_writes, mem_used;
 112         unsigned int good_compress_perc = 0, no_compress_perc = 0;
 113
 114         mem_used = xv_get_total_size_bytes(zram->mem_pool)
 115                         + (rs->pages_expand << PAGE_SHIFT);
 116         succ_writes = zram_stat64_read(zram, &rs->num_writes) -
 117                         zram_stat64_read(zram, &rs->failed_writes);
 118
 119         if (succ_writes && rs->pages_stored) {
 120                 good_compress_perc = rs->good_compress * 100
 121                                         / rs->pages_stored;
 122                 no_compress_perc = rs->pages_expand * 100
 123                                         / rs->pages_stored;
 124         }
 125
 126         s->num_reads = zram_stat64_read(zram, &rs->num_reads);
 127         s->num_writes = zram_stat64_read(zram, &rs->num_writes);
 128         s->failed_reads = zram_stat64_read(zram, &rs->failed_reads);
 129         s->failed_writes = zram_stat64_read(zram, &rs->failed_writes);
 130         s->invalid_io = zram_stat64_read(zram, &rs->invalid_io);
 131         s->notify_free = zram_stat64_read(zram, &rs->notify_free);
 132         s->pages_zero = rs->pages_zero;
 133
 134         s->good_compress_pct = good_compress_perc;
 135         s->pages_expand_pct = no_compress_perc;
 136
 137         s->pages_stored = rs->pages_stored;
 138         s->pages_used = mem_used >> PAGE_SHIFT;
 139         s->orig_data_size = rs->pages_stored << PAGE_SHIFT;
 140         s->compr_data_size = rs->compr_size;
 141         s->mem_used_total = mem_used;
 142         }
 143 #endif /* CONFIG_ZRAM_STATS */
 144 }
 145
 146 static void zram_free_page(struct zram *zram, size_t index)
 147 {
 148         u32 clen;
 149         void *obj;
 150
 151         struct page *page = zram->table[index].page;
 152         u32 offset = zram->table[index].offset;
 153
 154         if (unlikely(!page)) {
 155                 /*
 156                  * No memory is allocated for zero filled pages.
 157                  * Simply clear zero page flag.
 158                  */
 159                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 160                         zram_clear_flag(zram, index, ZRAM_ZERO);
 161                         zram_stat_dec(&zram->stats.pages_zero);
 162                 }
 163                 return;
 164         }
 165
 166         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 167                 clen = PAGE_SIZE;
 168                 __free_page(page);
 169                 zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
 170                 zram_stat_dec(&zram->stats.pages_expand);
 171                 goto out;
 172         }
 173
 174         obj = kmap_atomic(page, KM_USER0) + offset;
 175         clen = xv_get_object_size(obj) - sizeof(struct zobj_header);
 176         kunmap_atomic(obj, KM_USER0);
 177
 178         xv_free(zram->mem_pool, page, offset);
 179         if (clen <= PAGE_SIZE / 2)
 180                 zram_stat_dec(&zram->stats.good_compress);
 181
 182 out:
 183         zram->stats.compr_size -= clen;
 184         zram_stat_dec(&zram->stats.pages_stored);
 185
 186         zram->table[index].page = NULL;
 187         zram->table[index].offset = 0;
 188 }
 189
 190 static void handle_zero_page(struct page *page)
 191 {
 192         void *user_mem;
 193
 194         user_mem = kmap_atomic(page, KM_USER0);
 195         memset(user_mem, 0, PAGE_SIZE);
 196         kunmap_atomic(user_mem, KM_USER0);
 197
 198         flush_dcache_page(page);
 199 }
 200
 201 static void handle_uncompressed_page(struct zram *zram,
 202                                 struct page *page, u32 index)
 203 {
 204         unsigned char *user_mem, *cmem;
 205
 206         user_mem = kmap_atomic(page, KM_USER0);
 207         cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 208                         zram->table[index].offset;
 209
 210         memcpy(user_mem, cmem, PAGE_SIZE);
 211         kunmap_atomic(user_mem, KM_USER0);
 212         kunmap_atomic(cmem, KM_USER1);
 213
 214         flush_dcache_page(page);
 215 }
 216
 217 static int zram_read(struct zram *zram, struct bio *bio)
 218 {
 219
 220         int i;
 221         u32 index;
 222         struct bio_vec *bvec;
 223
 224         zram_stat64_inc(zram, &zram->stats.num_reads);
 225
 226         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 227         bio_for_each_segment(bvec, bio, i) {
 228                 int ret;
 229                 size_t clen;
 230                 struct page *page;
 231                 struct zobj_header *zheader;
 232                 unsigned char *user_mem, *cmem;
 233
 234                 page = bvec->bv_page;
 235
 236                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 237                         handle_zero_page(page);
 238                         continue;
 239                 }
 240
 241                 /* Requested page is not present in compressed area */
 242                 if (unlikely(!zram->table[index].page)) {
 243                         pr_debug("Read before write: sector=%lu, size=%u",
 244                                 (ulong)(bio->bi_sector), bio->bi_size);
 245                         /* Do nothing */
 246                         continue;
 247                 }
 248
 249                 /* Page is stored uncompressed since it's incompressible */
 250                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 251                         handle_uncompressed_page(zram, page, index);
 252                         continue;
 253                 }
 254
 255                 user_mem = kmap_atomic(page, KM_USER0);
 256                 clen = PAGE_SIZE;
 257
 258                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 259                                 zram->table[index].offset;
 260
 261                 ret = lzo1x_decompress_safe(
 262                         cmem + sizeof(*zheader),
 263                         xv_get_object_size(cmem) - sizeof(*zheader),
 264                         user_mem, &clen);
 265
 266                 kunmap_atomic(user_mem, KM_USER0);
 267                 kunmap_atomic(cmem, KM_USER1);
 268
 269                 /* Should NEVER happen. Return bio error if it does. */
 270                 if (unlikely(ret != LZO_E_OK)) {
 271                         pr_err("Decompression failed! err=%d, page=%u\n",
 272                                 ret, index);
 273                         zram_stat64_inc(zram, &zram->stats.failed_reads);
 274                         goto out;
 275                 }
 276
 277                 flush_dcache_page(page);
 278                 index++;
 279         }
 280
 281         set_bit(BIO_UPTODATE, &bio->bi_flags);
 282         bio_endio(bio, 0);
 283         return 0;
 284
 285 out:
 286         bio_io_error(bio);
 287         return 0;
 288 }
 289
 290 static int zram_write(struct zram *zram, struct bio *bio)
 291 {
 292         int i;
 293         u32 index;
 294         struct bio_vec *bvec;
 295
 296         zram_stat64_inc(zram, &zram->stats.num_writes);
 297
 298         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 299
 300         bio_for_each_segment(bvec, bio, i) {
 301                 int ret;
 302                 u32 offset;
 303                 size_t clen;
 304                 struct zobj_header *zheader;
 305                 struct page *page, *page_store;
 306                 unsigned char *user_mem, *cmem, *src;
 307
 308                 page = bvec->bv_page;
 309                 src = zram->compress_buffer;
 310
 311                 /*
 312                  * System overwrites unused sectors. Free memory associated
 313                  * with this sector now.
 314                  */
 315                 if (zram->table[index].page ||
 316                                 zram_test_flag(zram, index, ZRAM_ZERO))
 317                         zram_free_page(zram, index);
 318
 319                 mutex_lock(&zram->lock);
 320
 321                 user_mem = kmap_atomic(page, KM_USER0);
 322                 if (page_zero_filled(user_mem)) {
 323                         kunmap_atomic(user_mem, KM_USER0);
 324                         mutex_unlock(&zram->lock);
 325                         zram_stat_inc(&zram->stats.pages_zero);
 326                         zram_set_flag(zram, index, ZRAM_ZERO);
 327                         continue;
 328                 }
 329
 330                 ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
 331                                         zram->compress_workmem);
 332
 333                 kunmap_atomic(user_mem, KM_USER0);
 334
 335                 if (unlikely(ret != LZO_E_OK)) {
 336                         mutex_unlock(&zram->lock);
 337                         pr_err("Compression failed! err=%d\n", ret);
 338                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 339                         goto out;
 340                 }
 341
 342                 /*
 343                  * Page is incompressible. Store it as-is (uncompressed)
 344                  * since we do not want to return too many disk write
 345                  * errors which has side effect of hanging the system.
 346                  */
 347                 if (unlikely(clen > max_zpage_size)) {
 348                         clen = PAGE_SIZE;
 349                         page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
 350                         if (unlikely(!page_store)) {
 351                                 mutex_unlock(&zram->lock);
 352                                 pr_info("Error allocating memory for "
 353                                         "incompressible page: %u\n", index);
 354                                 zram_stat64_inc(zram,
 355                                         &zram->stats.failed_writes);
 356                                 goto out;
 357                         }
 358
 359                         offset = 0;
 360                         zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
 361                         zram_stat_inc(&zram->stats.pages_expand);
 362                         zram->table[index].page = page_store;
 363                         src = kmap_atomic(page, KM_USER0);
 364                         goto memstore;
 365                 }
 366
 367                 if (xv_malloc(zram->mem_pool, clen + sizeof(*zheader),
 368                                 &zram->table[index].page, &offset,
 369                                 GFP_NOIO | __GFP_HIGHMEM)) {
 370                         mutex_unlock(&zram->lock);
 371                         pr_info("Error allocating memory for compressed "
 372                                 "page: %u, size=%zu\n", index, clen);
 373                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 374                         goto out;
 375                 }
 376
 377 memstore:
 378                 zram->table[index].offset = offset;
 379
 380                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 381                                 zram->table[index].offset;
 382
 383 #if 0
 384                 /* Back-reference needed for memory defragmentation */
 385                 if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
 386                         zheader = (struct zobj_header *)cmem;
 387                         zheader->table_idx = index;
 388                         cmem += sizeof(*zheader);
 389                 }
 390 #endif
 391
 392                 memcpy(cmem, src, clen);
 393
 394                 kunmap_atomic(cmem, KM_USER1);
 395                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 396                         kunmap_atomic(src, KM_USER0);
 397
 398                 /* Update stats */
 399                 zram->stats.compr_size += clen;
 400                 zram_stat_inc(&zram->stats.pages_stored);
 401                 if (clen <= PAGE_SIZE / 2)
 402                         zram_stat_inc(&zram->stats.good_compress);
 403
 404                 mutex_unlock(&zram->lock);
 405                 index++;
 406         }
 407
 408         set_bit(BIO_UPTODATE, &bio->bi_flags);
 409         bio_endio(bio, 0);
 410         return 0;
 411
 412 out:
 413         bio_io_error(bio);
 414         return 0;
 415 }
 416
 417 /*
 418  * Check if request is within bounds and page aligned.
 419  */
 420 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 421 {
 422         if (unlikely(
 423                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 424                 (bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
 425                 (bio->bi_size & (PAGE_SIZE - 1)))) {
 426
 427                 return 0;
 428         }
 429
 430         /* I/O request is valid */
 431         return 1;
 432 }
 433
 434 /*
 435  * Handler function for all zram I/O requests.
 436  */
 437 static int zram_make_request(struct request_queue *queue, struct bio *bio)
 438 {
 439         int ret = 0;
 440         struct zram *zram = queue->queuedata;
 441
 442         if (unlikely(!zram->init_done)) {
 443                 bio_io_error(bio);
 444                 return 0;
 445         }
 446
 447         if (!valid_io_request(zram, bio)) {
 448                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 449                 bio_io_error(bio);
 450                 return 0;
 451         }
 452
 453         switch (bio_data_dir(bio)) {
 454         case READ:
 455                 ret = zram_read(zram, bio);
 456                 break;
 457
 458         case WRITE:
 459                 ret = zram_write(zram, bio);
 460                 break;
 461         }
 462
 463         return ret;
 464 }
 465
 466 static void reset_device(struct zram *zram)
 467 {
 468         size_t index;
 469
 470         /* Do not accept any new I/O request */
 471         zram->init_done = 0;
 472
 473         /* Free various per-device buffers */
 474         kfree(zram->compress_workmem);
 475         free_pages((unsigned long)zram->compress_buffer, 1);
 476
 477         zram->compress_workmem = NULL;
 478         zram->compress_buffer = NULL;
 479
 480         /* Free all pages that are still in this zram device */
 481         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 482                 struct page *page;
 483                 u16 offset;
 484
 485                 page = zram->table[index].page;
 486                 offset = zram->table[index].offset;
 487
 488                 if (!page)
 489                         continue;
 490
 491                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 492                         __free_page(page);
 493                 else
 494                         xv_free(zram->mem_pool, page, offset);
 495         }
 496
 497         vfree(zram->table);
 498         zram->table = NULL;
 499
 500         xv_destroy_pool(zram->mem_pool);
 501         zram->mem_pool = NULL;
 502
 503         /* Reset stats */
 504         memset(&zram->stats, 0, sizeof(zram->stats));
 505
 506         zram->disksize = 0;
 507 }
 508
 509 static int zram_ioctl_init_device(struct zram *zram)
 510 {
 511         int ret;
 512         size_t num_pages;
 513
 514         if (zram->init_done) {
 515                 pr_info("Device already initialized!\n");
 516                 return -EBUSY;
 517         }
 518
 519         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 520
 521         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 522         if (!zram->compress_workmem) {
 523                 pr_err("Error allocating compressor working memory!\n");
 524                 ret = -ENOMEM;
 525                 goto fail;
 526         }
 527
 528         zram->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
 529         if (!zram->compress_buffer) {
 530                 pr_err("Error allocating compressor buffer space\n");
 531                 ret = -ENOMEM;
 532                 goto fail;
 533         }
 534
 535         num_pages = zram->disksize >> PAGE_SHIFT;
 536         zram->table = vmalloc(num_pages * sizeof(*zram->table));
 537         if (!zram->table) {
 538                 pr_err("Error allocating zram address table\n");
 539                 /* To prevent accessing table entries during cleanup */
 540                 zram->disksize = 0;
 541                 ret = -ENOMEM;
 542                 goto fail;
 543         }
 544         memset(zram->table, 0, num_pages * sizeof(*zram->table));
 545
 546         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 547
 548         /* zram devices sort of resembles non-rotational disks */
 549         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 550
 551         zram->mem_pool = xv_create_pool();
 552         if (!zram->mem_pool) {
 553                 pr_err("Error creating memory pool\n");
 554                 ret = -ENOMEM;
 555                 goto fail;
 556         }
 557
 558         zram->init_done = 1;
 559
 560         pr_debug("Initialization done!\n");
 561         return 0;
 562
 563 fail:
 564         reset_device(zram);
 565
 566         pr_err("Initialization failed: err=%d\n", ret);
 567         return ret;
 568 }
 569
 570 static int zram_ioctl_reset_device(struct zram *zram)
 571 {
 572         if (zram->init_done)
 573                 reset_device(zram);
 574
 575         return 0;
 576 }
 577
 578 static int zram_ioctl(struct block_device *bdev, fmode_t mode,
 579                         unsigned int cmd, unsigned long arg)
 580 {
 581         int ret = 0;
 582         size_t disksize_kb;
 583
 584         struct zram *zram = bdev->bd_disk->private_data;
 585
 586         switch (cmd) {
 587         case ZRAMIO_SET_DISKSIZE_KB:
 588                 if (zram->init_done) {
 589                         ret = -EBUSY;
 590                         goto out;
 591                 }
 592                 if (copy_from_user(&disksize_kb, (void *)arg,
 593                                                 _IOC_SIZE(cmd))) {
 594                         ret = -EFAULT;
 595                         goto out;
 596                 }
 597                 zram->disksize = disksize_kb << 10;
 598                 pr_info("Disk size set to %zu kB\n", disksize_kb);
 599                 break;
 600
 601         case ZRAMIO_GET_STATS:
 602         {
 603                 struct zram_ioctl_stats *stats;
 604                 if (!zram->init_done) {
 605                         ret = -ENOTTY;
 606                         goto out;
 607                 }
 608                 stats = kzalloc(sizeof(*stats), GFP_KERNEL);
 609                 if (!stats) {
 610                         ret = -ENOMEM;
 611                         goto out;
 612                 }
 613                 zram_ioctl_get_stats(zram, stats);
 614                 if (copy_to_user((void *)arg, stats, sizeof(*stats))) {
 615                         kfree(stats);
 616                         ret = -EFAULT;
 617                         goto out;
 618                 }
 619                 kfree(stats);
 620                 break;
 621         }
 622         case ZRAMIO_INIT:
 623                 ret = zram_ioctl_init_device(zram);
 624                 break;
 625
 626         case ZRAMIO_RESET:
 627                 /* Do not reset an active device! */
 628                 if (bdev->bd_holders) {
 629                         ret = -EBUSY;
 630                         goto out;
 631                 }
 632
 633                 /* Make sure all pending I/O is finished */
 634                 if (bdev)
 635                         fsync_bdev(bdev);
 636
 637                 ret = zram_ioctl_reset_device(zram);
 638                 break;
 639
 640         default:
 641                 pr_info("Invalid ioctl %u\n", cmd);
 642                 ret = -ENOTTY;
 643         }
 644
 645 out:
 646         return ret;
 647 }
 648
 649 void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
 650 {
 651         struct zram *zram;
 652
 653         zram = bdev->bd_disk->private_data;
 654         zram_free_page(zram, index);
 655         zram_stat64_inc(zram, &zram->stats.notify_free);
 656 }
 657
 658 static const struct block_device_operations zram_devops = {
 659         .ioctl = zram_ioctl,
 660         .swap_slot_free_notify = zram_slot_free_notify,
 661         .owner = THIS_MODULE
 662 };
 663
 664 static int create_device(struct zram *zram, int device_id)
 665 {
 666         int ret = 0;
 667
 668         mutex_init(&zram->lock);
 669         spin_lock_init(&zram->stat64_lock);
 670
 671         zram->queue = blk_alloc_queue(GFP_KERNEL);
 672         if (!zram->queue) {
 673                 pr_err("Error allocating disk queue for device %d\n",
 674                         device_id);
 675                 ret = -ENOMEM;
 676                 goto out;
 677         }
 678
 679         blk_queue_make_request(zram->queue, zram_make_request);
 680         zram->queue->queuedata = zram;
 681
 682          /* gendisk structure */
 683         zram->disk = alloc_disk(1);
 684         if (!zram->disk) {
 685                 blk_cleanup_queue(zram->queue);
 686                 pr_warning("Error allocating disk structure for device %d\n",
 687                         device_id);
 688                 ret = -ENOMEM;
 689                 goto out;
 690         }
 691
 692         zram->disk->major = zram_major;
 693         zram->disk->first_minor = device_id;
 694         zram->disk->fops = &zram_devops;
 695         zram->disk->queue = zram->queue;
 696         zram->disk->private_data = zram;
 697         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 698
 699         /* Actual capacity set using ZRAMIO_SET_DISKSIZE_KB ioctl */
 700         set_capacity(zram->disk, 0);
 701
 702         /*
 703          * To ensure that we always get PAGE_SIZE aligned
 704          * and n*PAGE_SIZED sized I/O requests.
 705          */
 706         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 707         blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
 708         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 709         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 710
 711         add_disk(zram->disk);
 712
 713         zram->init_done = 0;
 714
 715 out:
 716         return ret;
 717 }
 718
 719 static void destroy_device(struct zram *zram)
 720 {
 721         if (zram->disk) {
 722                 del_gendisk(zram->disk);
 723                 put_disk(zram->disk);
 724         }
 725
 726         if (zram->queue)
 727                 blk_cleanup_queue(zram->queue);
 728 }
 729
 730 static int __init zram_init(void)
 731 {
 732         int ret, dev_id;
 733
 734         if (num_devices > max_num_devices) {
 735                 pr_warning("Invalid value for num_devices: %u\n",
 736                                 num_devices);
 737                 ret = -EINVAL;
 738                 goto out;
 739         }
 740
 741         zram_major = register_blkdev(0, "zram");
 742         if (zram_major <= 0) {
 743                 pr_warning("Unable to get major number\n");
 744                 ret = -EBUSY;
 745                 goto out;
 746         }
 747
 748         if (!num_devices) {
 749                 pr_info("num_devices not specified. Using default: 1\n");
 750                 num_devices = 1;
 751         }
 752
 753         /* Allocate the device array and initialize each one */
 754         pr_info("Creating %u devices ...\n", num_devices);
 755         devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 756         if (!devices) {
 757                 ret = -ENOMEM;
 758                 goto unregister;
 759         }
 760
 761         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 762                 ret = create_device(&devices[dev_id], dev_id);
 763                 if (ret)
 764                         goto free_devices;
 765         }
 766
 767         return 0;
 768
 769 free_devices:
 770         while (dev_id)
 771                 destroy_device(&devices[--dev_id]);
 772 unregister:
 773         unregister_blkdev(zram_major, "zram");
 774 out:
 775         return ret;
 776 }
 777
 778 static void __exit zram_exit(void)
 779 {
 780         int i;
 781         struct zram *zram;
 782
 783         for (i = 0; i < num_devices; i++) {
 784                 zram = &devices[i];
 785
 786                 destroy_device(zram);
 787                 if (zram->init_done)
 788                         reset_device(zram);
 789         }
 790
 791         unregister_blkdev(zram_major, "zram");
 792
 793         kfree(devices);
 794         pr_debug("Cleanup done!\n");
 795 }
 796
 797 module_param(num_devices, uint, 0);
 798 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 799
 800 module_init(zram_init);
 801 module_exit(zram_exit);
 802
 803 MODULE_LICENSE("Dual BSD/GPL");
 804 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 805 MODULE_DESCRIPTION("Compressed RAM Block Device");