Pileus Git - ~andy/linux/blob - drivers/staging/zram/zram_drv.c

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #define KMSG_COMPONENT "zram"
  16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  17
  18 #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         void *handle = zram->table[index].handle;
 139
 140         if (unlikely(!handle)) {
 141                 /*
 142                  * No memory is allocated for zero filled pages.
 143                  * Simply clear zero page flag.
 144                  */
 145                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 146                         zram_clear_flag(zram, index, ZRAM_ZERO);
 147                         zram_stat_dec(&zram->stats.pages_zero);
 148                 }
 149                 return;
 150         }
 151
 152         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 153                 __free_page(handle);
 154                 zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
 155                 zram_stat_dec(&zram->stats.pages_expand);
 156                 goto out;
 157         }
 158
 159         zs_free(zram->mem_pool, handle);
 160
 161         if (zram->table[index].size <= PAGE_SIZE / 2)
 162                 zram_stat_dec(&zram->stats.good_compress);
 163
 164 out:
 165         zram_stat64_sub(zram, &zram->stats.compr_size,
 166                         zram->table[index].size);
 167         zram_stat_dec(&zram->stats.pages_stored);
 168
 169         zram->table[index].handle = NULL;
 170         zram->table[index].size = 0;
 171 }
 172
 173 static void handle_zero_page(struct bio_vec *bvec)
 174 {
 175         struct page *page = bvec->bv_page;
 176         void *user_mem;
 177
 178         user_mem = kmap_atomic(page);
 179         memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
 180         kunmap_atomic(user_mem);
 181
 182         flush_dcache_page(page);
 183 }
 184
 185 static void handle_uncompressed_page(struct zram *zram, struct bio_vec *bvec,
 186                                      u32 index, int offset)
 187 {
 188         struct page *page = bvec->bv_page;
 189         unsigned char *user_mem, *cmem;
 190
 191         user_mem = kmap_atomic(page);
 192         cmem = kmap_atomic(zram->table[index].handle);
 193
 194         memcpy(user_mem + bvec->bv_offset, cmem + offset, bvec->bv_len);
 195         kunmap_atomic(cmem);
 196         kunmap_atomic(user_mem);
 197
 198         flush_dcache_page(page);
 199 }
 200
 201 static inline int is_partial_io(struct bio_vec *bvec)
 202 {
 203         return bvec->bv_len != PAGE_SIZE;
 204 }
 205
 206 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 207                           u32 index, int offset, struct bio *bio)
 208 {
 209         int ret;
 210         size_t clen;
 211         struct page *page;
 212         struct zobj_header *zheader;
 213         unsigned char *user_mem, *cmem, *uncmem = NULL;
 214
 215         page = bvec->bv_page;
 216
 217         if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 218                 handle_zero_page(bvec);
 219                 return 0;
 220         }
 221
 222         /* Requested page is not present in compressed area */
 223         if (unlikely(!zram->table[index].handle)) {
 224                 pr_debug("Read before write: sector=%lu, size=%u",
 225                          (ulong)(bio->bi_sector), bio->bi_size);
 226                 handle_zero_page(bvec);
 227                 return 0;
 228         }
 229
 230         /* Page is stored uncompressed since it's incompressible */
 231         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 232                 handle_uncompressed_page(zram, bvec, index, offset);
 233                 return 0;
 234         }
 235
 236         if (is_partial_io(bvec)) {
 237                 /* Use  a temporary buffer to decompress the page */
 238                 uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
 239                 if (!uncmem) {
 240                         pr_info("Error allocating temp memory!\n");
 241                         return -ENOMEM;
 242                 }
 243         }
 244
 245         user_mem = kmap_atomic(page);
 246         if (!is_partial_io(bvec))
 247                 uncmem = user_mem;
 248         clen = PAGE_SIZE;
 249
 250         cmem = zs_map_object(zram->mem_pool, zram->table[index].handle);
 251
 252         ret = lzo1x_decompress_safe(cmem + sizeof(*zheader),
 253                                     zram->table[index].size,
 254                                     uncmem, &clen);
 255
 256         if (is_partial_io(bvec)) {
 257                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 258                        bvec->bv_len);
 259                 kfree(uncmem);
 260         }
 261
 262         zs_unmap_object(zram->mem_pool, zram->table[index].handle);
 263         kunmap_atomic(user_mem);
 264
 265         /* Should NEVER happen. Return bio error if it does. */
 266         if (unlikely(ret != LZO_E_OK)) {
 267                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 268                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 269                 return ret;
 270         }
 271
 272         flush_dcache_page(page);
 273
 274         return 0;
 275 }
 276
 277 static int zram_read_before_write(struct zram *zram, char *mem, u32 index)
 278 {
 279         int ret;
 280         size_t clen = PAGE_SIZE;
 281         struct zobj_header *zheader;
 282         unsigned char *cmem;
 283
 284         if (zram_test_flag(zram, index, ZRAM_ZERO) ||
 285             !zram->table[index].handle) {
 286                 memset(mem, 0, PAGE_SIZE);
 287                 return 0;
 288         }
 289
 290         cmem = zs_map_object(zram->mem_pool, zram->table[index].handle);
 291
 292         /* Page is stored uncompressed since it's incompressible */
 293         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 294                 memcpy(mem, cmem, PAGE_SIZE);
 295                 kunmap_atomic(cmem);
 296                 return 0;
 297         }
 298
 299         ret = lzo1x_decompress_safe(cmem + sizeof(*zheader),
 300                                     zram->table[index].size,
 301                                     mem, &clen);
 302         zs_unmap_object(zram->mem_pool, zram->table[index].handle);
 303
 304         /* Should NEVER happen. Return bio error if it does. */
 305         if (unlikely(ret != LZO_E_OK)) {
 306                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 307                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 308                 return ret;
 309         }
 310
 311         return 0;
 312 }
 313
 314 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 315                            int offset)
 316 {
 317         int ret;
 318         u32 store_offset;
 319         size_t clen;
 320         void *handle;
 321         struct zobj_header *zheader;
 322         struct page *page, *page_store;
 323         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 324
 325         page = bvec->bv_page;
 326         src = zram->compress_buffer;
 327
 328         if (is_partial_io(bvec)) {
 329                 /*
 330                  * This is a partial IO. We need to read the full page
 331                  * before to write the changes.
 332                  */
 333                 uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
 334                 if (!uncmem) {
 335                         pr_info("Error allocating temp memory!\n");
 336                         ret = -ENOMEM;
 337                         goto out;
 338                 }
 339                 ret = zram_read_before_write(zram, uncmem, index);
 340                 if (ret) {
 341                         kfree(uncmem);
 342                         goto out;
 343                 }
 344         }
 345
 346         /*
 347          * System overwrites unused sectors. Free memory associated
 348          * with this sector now.
 349          */
 350         if (zram->table[index].handle ||
 351             zram_test_flag(zram, index, ZRAM_ZERO))
 352                 zram_free_page(zram, index);
 353
 354         user_mem = kmap_atomic(page);
 355
 356         if (is_partial_io(bvec))
 357                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 358                        bvec->bv_len);
 359         else
 360                 uncmem = user_mem;
 361
 362         if (page_zero_filled(uncmem)) {
 363                 kunmap_atomic(user_mem);
 364                 if (is_partial_io(bvec))
 365                         kfree(uncmem);
 366                 zram_stat_inc(&zram->stats.pages_zero);
 367                 zram_set_flag(zram, index, ZRAM_ZERO);
 368                 ret = 0;
 369                 goto out;
 370         }
 371
 372         ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
 373                                zram->compress_workmem);
 374
 375         kunmap_atomic(user_mem);
 376         if (is_partial_io(bvec))
 377                         kfree(uncmem);
 378
 379         if (unlikely(ret != LZO_E_OK)) {
 380                 pr_err("Compression failed! err=%d\n", ret);
 381                 goto out;
 382         }
 383
 384         /*
 385          * Page is incompressible. Store it as-is (uncompressed)
 386          * since we do not want to return too many disk write
 387          * errors which has side effect of hanging the system.
 388          */
 389         if (unlikely(clen > max_zpage_size)) {
 390                 clen = PAGE_SIZE;
 391                 page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
 392                 if (unlikely(!page_store)) {
 393                         pr_info("Error allocating memory for "
 394                                 "incompressible page: %u\n", index);
 395                         ret = -ENOMEM;
 396                         goto out;
 397                 }
 398
 399                 store_offset = 0;
 400                 zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
 401                 zram_stat_inc(&zram->stats.pages_expand);
 402                 handle = page_store;
 403                 src = kmap_atomic(page);
 404                 cmem = kmap_atomic(page_store);
 405                 goto memstore;
 406         }
 407
 408         handle = zs_malloc(zram->mem_pool, clen + sizeof(*zheader));
 409         if (!handle) {
 410                 pr_info("Error allocating memory for compressed "
 411                         "page: %u, size=%zu\n", index, clen);
 412                 ret = -ENOMEM;
 413                 goto out;
 414         }
 415         cmem = zs_map_object(zram->mem_pool, handle);
 416
 417 memstore:
 418 #if 0
 419         /* Back-reference needed for memory defragmentation */
 420         if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
 421                 zheader = (struct zobj_header *)cmem;
 422                 zheader->table_idx = index;
 423                 cmem += sizeof(*zheader);
 424         }
 425 #endif
 426
 427         memcpy(cmem, src, clen);
 428
 429         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 430                 kunmap_atomic(cmem);
 431                 kunmap_atomic(src);
 432         } else {
 433                 zs_unmap_object(zram->mem_pool, handle);
 434         }
 435
 436         zram->table[index].handle = handle;
 437         zram->table[index].size = clen;
 438
 439         /* Update stats */
 440         zram_stat64_add(zram, &zram->stats.compr_size, clen);
 441         zram_stat_inc(&zram->stats.pages_stored);
 442         if (clen <= PAGE_SIZE / 2)
 443                 zram_stat_inc(&zram->stats.good_compress);
 444
 445         return 0;
 446
 447 out:
 448         if (ret)
 449                 zram_stat64_inc(zram, &zram->stats.failed_writes);
 450         return ret;
 451 }
 452
 453 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 454                         int offset, struct bio *bio, int rw)
 455 {
 456         int ret;
 457
 458         if (rw == READ) {
 459                 down_read(&zram->lock);
 460                 ret = zram_bvec_read(zram, bvec, index, offset, bio);
 461                 up_read(&zram->lock);
 462         } else {
 463                 down_write(&zram->lock);
 464                 ret = zram_bvec_write(zram, bvec, index, offset);
 465                 up_write(&zram->lock);
 466         }
 467
 468         return ret;
 469 }
 470
 471 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 472 {
 473         if (*offset + bvec->bv_len >= PAGE_SIZE)
 474                 (*index)++;
 475         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 476 }
 477
 478 static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
 479 {
 480         int i, offset;
 481         u32 index;
 482         struct bio_vec *bvec;
 483
 484         switch (rw) {
 485         case READ:
 486                 zram_stat64_inc(zram, &zram->stats.num_reads);
 487                 break;
 488         case WRITE:
 489                 zram_stat64_inc(zram, &zram->stats.num_writes);
 490                 break;
 491         }
 492
 493         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 494         offset = (bio->bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 495
 496         bio_for_each_segment(bvec, bio, i) {
 497                 int max_transfer_size = PAGE_SIZE - offset;
 498
 499                 if (bvec->bv_len > max_transfer_size) {
 500                         /*
 501                          * zram_bvec_rw() can only make operation on a single
 502                          * zram page. Split the bio vector.
 503                          */
 504                         struct bio_vec bv;
 505
 506                         bv.bv_page = bvec->bv_page;
 507                         bv.bv_len = max_transfer_size;
 508                         bv.bv_offset = bvec->bv_offset;
 509
 510                         if (zram_bvec_rw(zram, &bv, index, offset, bio, rw) < 0)
 511                                 goto out;
 512
 513                         bv.bv_len = bvec->bv_len - max_transfer_size;
 514                         bv.bv_offset += max_transfer_size;
 515                         if (zram_bvec_rw(zram, &bv, index+1, 0, bio, rw) < 0)
 516                                 goto out;
 517                 } else
 518                         if (zram_bvec_rw(zram, bvec, index, offset, bio, rw)
 519                             < 0)
 520                                 goto out;
 521
 522                 update_position(&index, &offset, bvec);
 523         }
 524
 525         set_bit(BIO_UPTODATE, &bio->bi_flags);
 526         bio_endio(bio, 0);
 527         return;
 528
 529 out:
 530         bio_io_error(bio);
 531 }
 532
 533 /*
 534  * Check if request is within bounds and aligned on zram logical blocks.
 535  */
 536 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 537 {
 538         if (unlikely(
 539                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 540                 (bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)) ||
 541                 (bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))) {
 542
 543                 return 0;
 544         }
 545
 546         /* I/O request is valid */
 547         return 1;
 548 }
 549
 550 /*
 551  * Handler function for all zram I/O requests.
 552  */
 553 static void zram_make_request(struct request_queue *queue, struct bio *bio)
 554 {
 555         struct zram *zram = queue->queuedata;
 556
 557         if (unlikely(!zram->init_done) && zram_init_device(zram))
 558                 goto error;
 559
 560         down_read(&zram->init_lock);
 561         if (unlikely(!zram->init_done))
 562                 goto error_unlock;
 563
 564         if (!valid_io_request(zram, bio)) {
 565                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 566                 goto error_unlock;
 567         }
 568
 569         __zram_make_request(zram, bio, bio_data_dir(bio));
 570         up_read(&zram->init_lock);
 571
 572         return;
 573
 574 error_unlock:
 575         up_read(&zram->init_lock);
 576 error:
 577         bio_io_error(bio);
 578 }
 579
 580 void __zram_reset_device(struct zram *zram)
 581 {
 582         size_t index;
 583
 584         zram->init_done = 0;
 585
 586         /* Free various per-device buffers */
 587         kfree(zram->compress_workmem);
 588         free_pages((unsigned long)zram->compress_buffer, 1);
 589
 590         zram->compress_workmem = NULL;
 591         zram->compress_buffer = NULL;
 592
 593         /* Free all pages that are still in this zram device */
 594         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 595                 void *handle = zram->table[index].handle;
 596                 if (!handle)
 597                         continue;
 598
 599                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 600                         __free_page(handle);
 601                 else
 602                         zs_free(zram->mem_pool, handle);
 603         }
 604
 605         vfree(zram->table);
 606         zram->table = NULL;
 607
 608         zs_destroy_pool(zram->mem_pool);
 609         zram->mem_pool = NULL;
 610
 611         /* Reset stats */
 612         memset(&zram->stats, 0, sizeof(zram->stats));
 613
 614         zram->disksize = 0;
 615 }
 616
 617 void zram_reset_device(struct zram *zram)
 618 {
 619         down_write(&zram->init_lock);
 620         __zram_reset_device(zram);
 621         up_write(&zram->init_lock);
 622 }
 623
 624 int zram_init_device(struct zram *zram)
 625 {
 626         int ret;
 627         size_t num_pages;
 628
 629         down_write(&zram->init_lock);
 630
 631         if (zram->init_done) {
 632                 up_write(&zram->init_lock);
 633                 return 0;
 634         }
 635
 636         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 637
 638         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 639         if (!zram->compress_workmem) {
 640                 pr_err("Error allocating compressor working memory!\n");
 641                 ret = -ENOMEM;
 642                 goto fail_no_table;
 643         }
 644
 645         zram->compress_buffer =
 646                 (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
 647         if (!zram->compress_buffer) {
 648                 pr_err("Error allocating compressor buffer space\n");
 649                 ret = -ENOMEM;
 650                 goto fail_no_table;
 651         }
 652
 653         num_pages = zram->disksize >> PAGE_SHIFT;
 654         zram->table = vzalloc(num_pages * sizeof(*zram->table));
 655         if (!zram->table) {
 656                 pr_err("Error allocating zram address table\n");
 657                 ret = -ENOMEM;
 658                 goto fail_no_table;
 659         }
 660
 661         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 662
 663         /* zram devices sort of resembles non-rotational disks */
 664         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 665
 666         zram->mem_pool = zs_create_pool("zram", GFP_NOIO | __GFP_HIGHMEM);
 667         if (!zram->mem_pool) {
 668                 pr_err("Error creating memory pool\n");
 669                 ret = -ENOMEM;
 670                 goto fail;
 671         }
 672
 673         zram->init_done = 1;
 674         up_write(&zram->init_lock);
 675
 676         pr_debug("Initialization done!\n");
 677         return 0;
 678
 679 fail_no_table:
 680         /* To prevent accessing table entries during cleanup */
 681         zram->disksize = 0;
 682 fail:
 683         __zram_reset_device(zram);
 684         up_write(&zram->init_lock);
 685         pr_err("Initialization failed: err=%d\n", ret);
 686         return ret;
 687 }
 688
 689 static void zram_slot_free_notify(struct block_device *bdev,
 690                                 unsigned long index)
 691 {
 692         struct zram *zram;
 693
 694         zram = bdev->bd_disk->private_data;
 695         zram_free_page(zram, index);
 696         zram_stat64_inc(zram, &zram->stats.notify_free);
 697 }
 698
 699 static const struct block_device_operations zram_devops = {
 700         .swap_slot_free_notify = zram_slot_free_notify,
 701         .owner = THIS_MODULE
 702 };
 703
 704 static int create_device(struct zram *zram, int device_id)
 705 {
 706         int ret = 0;
 707
 708         init_rwsem(&zram->lock);
 709         init_rwsem(&zram->init_lock);
 710         spin_lock_init(&zram->stat64_lock);
 711
 712         zram->queue = blk_alloc_queue(GFP_KERNEL);
 713         if (!zram->queue) {
 714                 pr_err("Error allocating disk queue for device %d\n",
 715                         device_id);
 716                 ret = -ENOMEM;
 717                 goto out;
 718         }
 719
 720         blk_queue_make_request(zram->queue, zram_make_request);
 721         zram->queue->queuedata = zram;
 722
 723          /* gendisk structure */
 724         zram->disk = alloc_disk(1);
 725         if (!zram->disk) {
 726                 blk_cleanup_queue(zram->queue);
 727                 pr_warning("Error allocating disk structure for device %d\n",
 728                         device_id);
 729                 ret = -ENOMEM;
 730                 goto out;
 731         }
 732
 733         zram->disk->major = zram_major;
 734         zram->disk->first_minor = device_id;
 735         zram->disk->fops = &zram_devops;
 736         zram->disk->queue = zram->queue;
 737         zram->disk->private_data = zram;
 738         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 739
 740         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 741         set_capacity(zram->disk, 0);
 742
 743         /*
 744          * To ensure that we always get PAGE_SIZE aligned
 745          * and n*PAGE_SIZED sized I/O requests.
 746          */
 747         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 748         blk_queue_logical_block_size(zram->disk->queue,
 749                                         ZRAM_LOGICAL_BLOCK_SIZE);
 750         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 751         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 752
 753         add_disk(zram->disk);
 754
 755         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 756                                 &zram_disk_attr_group);
 757         if (ret < 0) {
 758                 pr_warning("Error creating sysfs group");
 759                 goto out;
 760         }
 761
 762         zram->init_done = 0;
 763
 764 out:
 765         return ret;
 766 }
 767
 768 static void destroy_device(struct zram *zram)
 769 {
 770         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 771                         &zram_disk_attr_group);
 772
 773         if (zram->disk) {
 774                 del_gendisk(zram->disk);
 775                 put_disk(zram->disk);
 776         }
 777
 778         if (zram->queue)
 779                 blk_cleanup_queue(zram->queue);
 780 }
 781
 782 unsigned int zram_get_num_devices(void)
 783 {
 784         return num_devices;
 785 }
 786
 787 static int __init zram_init(void)
 788 {
 789         int ret, dev_id;
 790
 791         if (num_devices > max_num_devices) {
 792                 pr_warning("Invalid value for num_devices: %u\n",
 793                                 num_devices);
 794                 ret = -EINVAL;
 795                 goto out;
 796         }
 797
 798         zram_major = register_blkdev(0, "zram");
 799         if (zram_major <= 0) {
 800                 pr_warning("Unable to get major number\n");
 801                 ret = -EBUSY;
 802                 goto out;
 803         }
 804
 805         if (!num_devices) {
 806                 pr_info("num_devices not specified. Using default: 1\n");
 807                 num_devices = 1;
 808         }
 809
 810         /* Allocate the device array and initialize each one */
 811         pr_info("Creating %u devices ...\n", num_devices);
 812         zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 813         if (!zram_devices) {
 814                 ret = -ENOMEM;
 815                 goto unregister;
 816         }
 817
 818         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 819                 ret = create_device(&zram_devices[dev_id], dev_id);
 820                 if (ret)
 821                         goto free_devices;
 822         }
 823
 824         return 0;
 825
 826 free_devices:
 827         while (dev_id)
 828                 destroy_device(&zram_devices[--dev_id]);
 829         kfree(zram_devices);
 830 unregister:
 831         unregister_blkdev(zram_major, "zram");
 832 out:
 833         return ret;
 834 }
 835
 836 static void __exit zram_exit(void)
 837 {
 838         int i;
 839         struct zram *zram;
 840
 841         for (i = 0; i < num_devices; i++) {
 842                 zram = &zram_devices[i];
 843
 844                 destroy_device(zram);
 845                 if (zram->init_done)
 846                         zram_reset_device(zram);
 847         }
 848
 849         unregister_blkdev(zram_major, "zram");
 850
 851         kfree(zram_devices);
 852         pr_debug("Cleanup done!\n");
 853 }
 854
 855 module_param(num_devices, uint, 0);
 856 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 857
 858 module_init(zram_init);
 859 module_exit(zram_exit);
 860
 861 MODULE_LICENSE("Dual BSD/GPL");
 862 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 863 MODULE_DESCRIPTION("Compressed RAM Block Device");