drivers/block/zram/zram_drv.c

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *               2012, 2013 Minchan Kim
   6  *
   7  * This code is released using a dual license strategy: BSD/GPL
   8  * You can choose the licence that better fits your requirements.
   9  *
  10  * Released under the terms of 3-clause BSD License
  11  * Released under the terms of GNU General Public License Version 2.0
  12  *
  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/backing-dev.h>
  29 #include <linux/string.h>
  30 #include <linux/vmalloc.h>
  31 #include <linux/err.h>
  32 #include <linux/idr.h>
  33 #include <linux/sysfs.h>
  34 #include <linux/cpuhotplug.h>
  35
  36 #include "zram_drv.h"
  37
  38 static DEFINE_IDR(zram_index_idr);
  39 /* idr index must be protected */
  40 static DEFINE_MUTEX(zram_index_mutex);
  41
  42 static int zram_major;
  43 static const char *default_compressor = "lzo";
  44
  45 /* Module params (documentation at end) */
  46 static unsigned int num_devices = 1;
  47
  48 static inline bool init_done(struct zram *zram)
  49 {
  50         return zram->disksize;
  51 }
  52
  53 static inline struct zram *dev_to_zram(struct device *dev)
  54 {
  55         return (struct zram *)dev_to_disk(dev)->private_data;
  56 }
  57
  58 /* flag operations require table entry bit_spin_lock() being held */
  59 static int zram_test_flag(struct zram_meta *meta, u32 index,
  60                         enum zram_pageflags flag)
  61 {
  62         return meta->table[index].value & BIT(flag);
  63 }
  64
  65 static void zram_set_flag(struct zram_meta *meta, u32 index,
  66                         enum zram_pageflags flag)
  67 {
  68         meta->table[index].value |= BIT(flag);
  69 }
  70
  71 static void zram_clear_flag(struct zram_meta *meta, u32 index,
  72                         enum zram_pageflags flag)
  73 {
  74         meta->table[index].value &= ~BIT(flag);
  75 }
  76
  77 static inline void zram_set_element(struct zram_meta *meta, u32 index,
  78                         unsigned long element)
  79 {
  80         meta->table[index].element = element;
  81 }
  82
  83 static inline void zram_clear_element(struct zram_meta *meta, u32 index)
  84 {
  85         meta->table[index].element = 0;
  86 }
  87
  88 static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
  89 {
  90         return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
  91 }
  92
  93 static void zram_set_obj_size(struct zram_meta *meta,
  94                                         u32 index, size_t size)
  95 {
  96         unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
  97
  98         meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
  99 }
 100
 101 static inline bool is_partial_io(struct bio_vec *bvec)
 102 {
 103         return bvec->bv_len != PAGE_SIZE;
 104 }
 105
 106 static void zram_revalidate_disk(struct zram *zram)
 107 {
 108         revalidate_disk(zram->disk);
 109         /* revalidate_disk reset the BDI_CAP_STABLE_WRITES so set again */
 110         zram->disk->queue->backing_dev_info->capabilities |=
 111                 BDI_CAP_STABLE_WRITES;
 112 }
 113
 114 /*
 115  * Check if request is within bounds and aligned on zram logical blocks.
 116  */
 117 static inline bool valid_io_request(struct zram *zram,
 118                 sector_t start, unsigned int size)
 119 {
 120         u64 end, bound;
 121
 122         /* unaligned request */
 123         if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
 124                 return false;
 125         if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
 126                 return false;
 127
 128         end = start + (size >> SECTOR_SHIFT);
 129         bound = zram->disksize >> SECTOR_SHIFT;
 130         /* out of range range */
 131         if (unlikely(start >= bound || end > bound || start > end))
 132                 return false;
 133
 134         /* I/O request is valid */
 135         return true;
 136 }
 137
 138 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 139 {
 140         if (*offset + bvec->bv_len >= PAGE_SIZE)
 141                 (*index)++;
 142         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 143 }
 144
 145 static inline void update_used_max(struct zram *zram,
 146                                         const unsigned long pages)
 147 {
 148         unsigned long old_max, cur_max;
 149
 150         old_max = atomic_long_read(&zram->stats.max_used_pages);
 151
 152         do {
 153                 cur_max = old_max;
 154                 if (pages > cur_max)
 155                         old_max = atomic_long_cmpxchg(
 156                                 &zram->stats.max_used_pages, cur_max, pages);
 157         } while (old_max != cur_max);
 158 }
 159
 160 static inline void zram_fill_page(char *ptr, unsigned long len,
 161                                         unsigned long value)
 162 {
 163         int i;
 164         unsigned long *page = (unsigned long *)ptr;
 165
 166         WARN_ON_ONCE(!IS_ALIGNED(len, sizeof(unsigned long)));
 167
 168         if (likely(value == 0)) {
 169                 memset(ptr, 0, len);
 170         } else {
 171                 for (i = 0; i < len / sizeof(*page); i++)
 172                         page[i] = value;
 173         }
 174 }
 175
 176 static bool page_same_filled(void *ptr, unsigned long *element)
 177 {
 178         unsigned int pos;
 179         unsigned long *page;
 180
 181         page = (unsigned long *)ptr;
 182
 183         for (pos = 0; pos < PAGE_SIZE / sizeof(*page) - 1; pos++) {
 184                 if (page[pos] != page[pos + 1])
 185                         return false;
 186         }
 187
 188         *element = page[pos];
 189
 190         return true;
 191 }
 192
 193 static void handle_same_page(struct bio_vec *bvec, unsigned long element)
 194 {
 195         struct page *page = bvec->bv_page;
 196         void *user_mem;
 197
 198         user_mem = kmap_atomic(page);
 199         zram_fill_page(user_mem + bvec->bv_offset, bvec->bv_len, element);
 200         kunmap_atomic(user_mem);
 201
 202         flush_dcache_page(page);
 203 }
 204
 205 static ssize_t initstate_show(struct device *dev,
 206                 struct device_attribute *attr, char *buf)
 207 {
 208         u32 val;
 209         struct zram *zram = dev_to_zram(dev);
 210
 211         down_read(&zram->init_lock);
 212         val = init_done(zram);
 213         up_read(&zram->init_lock);
 214
 215         return scnprintf(buf, PAGE_SIZE, "%u\n", val);
 216 }
 217
 218 static ssize_t disksize_show(struct device *dev,
 219                 struct device_attribute *attr, char *buf)
 220 {
 221         struct zram *zram = dev_to_zram(dev);
 222
 223         return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
 224 }
 225
 226 static ssize_t mem_limit_store(struct device *dev,
 227                 struct device_attribute *attr, const char *buf, size_t len)
 228 {
 229         u64 limit;
 230         char *tmp;
 231         struct zram *zram = dev_to_zram(dev);
 232
 233         limit = memparse(buf, &tmp);
 234         if (buf == tmp) /* no chars parsed, invalid input */
 235                 return -EINVAL;
 236
 237         down_write(&zram->init_lock);
 238         zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
 239         up_write(&zram->init_lock);
 240
 241         return len;
 242 }
 243
 244 static ssize_t mem_used_max_store(struct device *dev,
 245                 struct device_attribute *attr, const char *buf, size_t len)
 246 {
 247         int err;
 248         unsigned long val;
 249         struct zram *zram = dev_to_zram(dev);
 250
 251         err = kstrtoul(buf, 10, &val);
 252         if (err || val != 0)
 253                 return -EINVAL;
 254
 255         down_read(&zram->init_lock);
 256         if (init_done(zram)) {
 257                 struct zram_meta *meta = zram->meta;
 258                 atomic_long_set(&zram->stats.max_used_pages,
 259                                 zs_get_total_pages(meta->mem_pool));
 260         }
 261         up_read(&zram->init_lock);
 262
 263         return len;
 264 }
 265
 266 /*
 267  * We switched to per-cpu streams and this attr is not needed anymore.
 268  * However, we will keep it around for some time, because:
 269  * a) we may revert per-cpu streams in the future
 270  * b) it's visible to user space and we need to follow our 2 years
 271  *    retirement rule; but we already have a number of 'soon to be
 272  *    altered' attrs, so max_comp_streams need to wait for the next
 273  *    layoff cycle.
 274  */
 275 static ssize_t max_comp_streams_show(struct device *dev,
 276                 struct device_attribute *attr, char *buf)
 277 {
 278         return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus());
 279 }
 280
 281 static ssize_t max_comp_streams_store(struct device *dev,
 282                 struct device_attribute *attr, const char *buf, size_t len)
 283 {
 284         return len;
 285 }
 286
 287 static ssize_t comp_algorithm_show(struct device *dev,
 288                 struct device_attribute *attr, char *buf)
 289 {
 290         size_t sz;
 291         struct zram *zram = dev_to_zram(dev);
 292
 293         down_read(&zram->init_lock);
 294         sz = zcomp_available_show(zram->compressor, buf);
 295         up_read(&zram->init_lock);
 296
 297         return sz;
 298 }
 299
 300 static ssize_t comp_algorithm_store(struct device *dev,
 301                 struct device_attribute *attr, const char *buf, size_t len)
 302 {
 303         struct zram *zram = dev_to_zram(dev);
 304         char compressor[CRYPTO_MAX_ALG_NAME];
 305         size_t sz;
 306
 307         strlcpy(compressor, buf, sizeof(compressor));
 308         /* ignore trailing newline */
 309         sz = strlen(compressor);
 310         if (sz > 0 && compressor[sz - 1] == '\n')
 311                 compressor[sz - 1] = 0x00;
 312
 313         if (!zcomp_available_algorithm(compressor))
 314                 return -EINVAL;
 315
 316         down_write(&zram->init_lock);
 317         if (init_done(zram)) {
 318                 up_write(&zram->init_lock);
 319                 pr_info("Can't change algorithm for initialized device\n");
 320                 return -EBUSY;
 321         }
 322
 323         strlcpy(zram->compressor, compressor, sizeof(compressor));
 324         up_write(&zram->init_lock);
 325         return len;
 326 }
 327
 328 static ssize_t compact_store(struct device *dev,
 329                 struct device_attribute *attr, const char *buf, size_t len)
 330 {
 331         struct zram *zram = dev_to_zram(dev);
 332         struct zram_meta *meta;
 333
 334         down_read(&zram->init_lock);
 335         if (!init_done(zram)) {
 336                 up_read(&zram->init_lock);
 337                 return -EINVAL;
 338         }
 339
 340         meta = zram->meta;
 341         zs_compact(meta->mem_pool);
 342         up_read(&zram->init_lock);
 343
 344         return len;
 345 }
 346
 347 static ssize_t io_stat_show(struct device *dev,
 348                 struct device_attribute *attr, char *buf)
 349 {
 350         struct zram *zram = dev_to_zram(dev);
 351         ssize_t ret;
 352
 353         down_read(&zram->init_lock);
 354         ret = scnprintf(buf, PAGE_SIZE,
 355                         "%8llu %8llu %8llu %8llu\n",
 356                         (u64)atomic64_read(&zram->stats.failed_reads),
 357                         (u64)atomic64_read(&zram->stats.failed_writes),
 358                         (u64)atomic64_read(&zram->stats.invalid_io),
 359                         (u64)atomic64_read(&zram->stats.notify_free));
 360         up_read(&zram->init_lock);
 361
 362         return ret;
 363 }
 364
 365 static ssize_t mm_stat_show(struct device *dev,
 366                 struct device_attribute *attr, char *buf)
 367 {
 368         struct zram *zram = dev_to_zram(dev);
 369         struct zs_pool_stats pool_stats;
 370         u64 orig_size, mem_used = 0;
 371         long max_used;
 372         ssize_t ret;
 373
 374         memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats));
 375
 376         down_read(&zram->init_lock);
 377         if (init_done(zram)) {
 378                 mem_used = zs_get_total_pages(zram->meta->mem_pool);
 379                 zs_pool_stats(zram->meta->mem_pool, &pool_stats);
 380         }
 381
 382         orig_size = atomic64_read(&zram->stats.pages_stored);
 383         max_used = atomic_long_read(&zram->stats.max_used_pages);
 384
 385         ret = scnprintf(buf, PAGE_SIZE,
 386                         "%8llu %8llu %8llu %8lu %8ld %8llu %8lu\n",
 387                         orig_size << PAGE_SHIFT,
 388                         (u64)atomic64_read(&zram->stats.compr_data_size),
 389                         mem_used << PAGE_SHIFT,
 390                         zram->limit_pages << PAGE_SHIFT,
 391                         max_used << PAGE_SHIFT,
 392                         (u64)atomic64_read(&zram->stats.same_pages),
 393                         pool_stats.pages_compacted);
 394         up_read(&zram->init_lock);
 395
 396         return ret;
 397 }
 398
 399 static ssize_t debug_stat_show(struct device *dev,
 400                 struct device_attribute *attr, char *buf)
 401 {
 402         int version = 1;
 403         struct zram *zram = dev_to_zram(dev);
 404         ssize_t ret;
 405
 406         down_read(&zram->init_lock);
 407         ret = scnprintf(buf, PAGE_SIZE,
 408                         "version: %d\n%8llu\n",
 409                         version,
 410                         (u64)atomic64_read(&zram->stats.writestall));
 411         up_read(&zram->init_lock);
 412
 413         return ret;
 414 }
 415
 416 static DEVICE_ATTR_RO(io_stat);
 417 static DEVICE_ATTR_RO(mm_stat);
 418 static DEVICE_ATTR_RO(debug_stat);
 419
 420 static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 421 {
 422         size_t num_pages = disksize >> PAGE_SHIFT;
 423         size_t index;
 424
 425         /* Free all pages that are still in this zram device */
 426         for (index = 0; index < num_pages; index++) {
 427                 unsigned long handle = meta->table[index].handle;
 428                 /*
 429                  * No memory is allocated for same element filled pages.
 430                  * Simply clear same page flag.
 431                  */
 432                 if (!handle || zram_test_flag(meta, index, ZRAM_SAME))
 433                         continue;
 434
 435                 zs_free(meta->mem_pool, handle);
 436         }
 437
 438         zs_destroy_pool(meta->mem_pool);
 439         vfree(meta->table);
 440         kfree(meta);
 441 }
 442
 443 static struct zram_meta *zram_meta_alloc(char *pool_name, u64 disksize)
 444 {
 445         size_t num_pages;
 446         struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 447
 448         if (!meta)
 449                 return NULL;
 450
 451         num_pages = disksize >> PAGE_SHIFT;
 452         meta->table = vzalloc(num_pages * sizeof(*meta->table));
 453         if (!meta->table) {
 454                 pr_err("Error allocating zram address table\n");
 455                 goto out_error;
 456         }
 457
 458         meta->mem_pool = zs_create_pool(pool_name);
 459         if (!meta->mem_pool) {
 460                 pr_err("Error creating memory pool\n");
 461                 goto out_error;
 462         }
 463
 464         return meta;
 465
 466 out_error:
 467         vfree(meta->table);
 468         kfree(meta);
 469         return NULL;
 470 }
 471
 472 /*
 473  * To protect concurrent access to the same index entry,
 474  * caller should hold this table index entry's bit_spinlock to
 475  * indicate this index entry is accessing.
 476  */
 477 static void zram_free_page(struct zram *zram, size_t index)
 478 {
 479         struct zram_meta *meta = zram->meta;
 480         unsigned long handle = meta->table[index].handle;
 481
 482         /*
 483          * No memory is allocated for same element filled pages.
 484          * Simply clear same page flag.
 485          */
 486         if (zram_test_flag(meta, index, ZRAM_SAME)) {
 487                 zram_clear_flag(meta, index, ZRAM_SAME);
 488                 zram_clear_element(meta, index);
 489                 atomic64_dec(&zram->stats.same_pages);
 490                 return;
 491         }
 492
 493         if (!handle)
 494                 return;
 495
 496         zs_free(meta->mem_pool, handle);
 497
 498         atomic64_sub(zram_get_obj_size(meta, index),
 499                         &zram->stats.compr_data_size);
 500         atomic64_dec(&zram->stats.pages_stored);
 501
 502         meta->table[index].handle = 0;
 503         zram_set_obj_size(meta, index, 0);
 504 }
 505
 506 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 507 {
 508         int ret = 0;
 509         unsigned char *cmem;
 510         struct zram_meta *meta = zram->meta;
 511         unsigned long handle;
 512         unsigned int size;
 513
 514         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 515         handle = meta->table[index].handle;
 516         size = zram_get_obj_size(meta, index);
 517
 518         if (!handle || zram_test_flag(meta, index, ZRAM_SAME)) {
 519                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 520                 zram_fill_page(mem, PAGE_SIZE, meta->table[index].element);
 521                 return 0;
 522         }
 523
 524         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 525         if (size == PAGE_SIZE) {
 526                 memcpy(mem, cmem, PAGE_SIZE);
 527         } else {
 528                 struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp);
 529
 530                 ret = zcomp_decompress(zstrm, cmem, size, mem);
 531                 zcomp_stream_put(zram->comp);
 532         }
 533         zs_unmap_object(meta->mem_pool, handle);
 534         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 535
 536         /* Should NEVER happen. Return bio error if it does. */
 537         if (unlikely(ret)) {
 538                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 539                 return ret;
 540         }
 541
 542         return 0;
 543 }
 544
 545 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 546                           u32 index, int offset)
 547 {
 548         int ret;
 549         struct page *page;
 550         unsigned char *user_mem, *uncmem = NULL;
 551         struct zram_meta *meta = zram->meta;
 552         page = bvec->bv_page;
 553
 554         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 555         if (unlikely(!meta->table[index].handle) ||
 556                         zram_test_flag(meta, index, ZRAM_SAME)) {
 557                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 558                 handle_same_page(bvec, meta->table[index].element);
 559                 return 0;
 560         }
 561         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 562
 563         if (is_partial_io(bvec))
 564                 /* Use  a temporary buffer to decompress the page */
 565                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 566
 567         user_mem = kmap_atomic(page);
 568         if (!is_partial_io(bvec))
 569                 uncmem = user_mem;
 570
 571         if (!uncmem) {
 572                 pr_err("Unable to allocate temp memory\n");
 573                 ret = -ENOMEM;
 574                 goto out_cleanup;
 575         }
 576
 577         ret = zram_decompress_page(zram, uncmem, index);
 578         /* Should NEVER happen. Return bio error if it does. */
 579         if (unlikely(ret))
 580                 goto out_cleanup;
 581
 582         if (is_partial_io(bvec))
 583                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 584                                 bvec->bv_len);
 585
 586         flush_dcache_page(page);
 587         ret = 0;
 588 out_cleanup:
 589         kunmap_atomic(user_mem);
 590         if (is_partial_io(bvec))
 591                 kfree(uncmem);
 592         return ret;
 593 }
 594
 595 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 596                            int offset)
 597 {
 598         int ret = 0;
 599         unsigned int clen;
 600         unsigned long handle = 0;
 601         struct page *page;
 602         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 603         struct zram_meta *meta = zram->meta;
 604         struct zcomp_strm *zstrm = NULL;
 605         unsigned long alloced_pages;
 606         unsigned long element;
 607
 608         page = bvec->bv_page;
 609         if (is_partial_io(bvec)) {
 610                 /*
 611                  * This is a partial IO. We need to read the full page
 612                  * before to write the changes.
 613                  */
 614                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 615                 if (!uncmem) {
 616                         ret = -ENOMEM;
 617                         goto out;
 618                 }
 619                 ret = zram_decompress_page(zram, uncmem, index);
 620                 if (ret)
 621                         goto out;
 622         }
 623
 624 compress_again:
 625         user_mem = kmap_atomic(page);
 626         if (is_partial_io(bvec)) {
 627                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 628                        bvec->bv_len);
 629                 kunmap_atomic(user_mem);
 630                 user_mem = NULL;
 631         } else {
 632                 uncmem = user_mem;
 633         }
 634
 635         if (page_same_filled(uncmem, &element)) {
 636                 if (user_mem)
 637                         kunmap_atomic(user_mem);
 638                 /* Free memory associated with this sector now. */
 639                 bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 640                 zram_free_page(zram, index);
 641                 zram_set_flag(meta, index, ZRAM_SAME);
 642                 zram_set_element(meta, index, element);
 643                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 644
 645                 atomic64_inc(&zram->stats.same_pages);
 646                 ret = 0;
 647                 goto out;
 648         }
 649
 650         zstrm = zcomp_stream_get(zram->comp);
 651         ret = zcomp_compress(zstrm, uncmem, &clen);
 652         if (!is_partial_io(bvec)) {
 653                 kunmap_atomic(user_mem);
 654                 user_mem = NULL;
 655                 uncmem = NULL;
 656         }
 657
 658         if (unlikely(ret)) {
 659                 pr_err("Compression failed! err=%d\n", ret);
 660                 goto out;
 661         }
 662
 663         src = zstrm->buffer;
 664         if (unlikely(clen > max_zpage_size)) {
 665                 clen = PAGE_SIZE;
 666                 if (is_partial_io(bvec))
 667                         src = uncmem;
 668         }
 669
 670         /*
 671          * handle allocation has 2 paths:
 672          * a) fast path is executed with preemption disabled (for
 673          *  per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
 674          *  since we can't sleep;
 675          * b) slow path enables preemption and attempts to allocate
 676          *  the page with __GFP_DIRECT_RECLAIM bit set. we have to
 677          *  put per-cpu compression stream and, thus, to re-do
 678          *  the compression once handle is allocated.
 679          *
 680          * if we have a 'non-null' handle here then we are coming
 681          * from the slow path and handle has already been allocated.
 682          */
 683         if (!handle)
 684                 handle = zs_malloc(meta->mem_pool, clen,
 685                                 __GFP_KSWAPD_RECLAIM |
 686                                 __GFP_NOWARN |
 687                                 __GFP_HIGHMEM |
 688                                 __GFP_MOVABLE);
 689         if (!handle) {
 690                 zcomp_stream_put(zram->comp);
 691                 zstrm = NULL;
 692
 693                 atomic64_inc(&zram->stats.writestall);
 694
 695                 handle = zs_malloc(meta->mem_pool, clen,
 696                                 GFP_NOIO | __GFP_HIGHMEM |
 697                                 __GFP_MOVABLE);
 698                 if (handle)
 699                         goto compress_again;
 700
 701                 pr_err("Error allocating memory for compressed page: %u, size=%u\n",
 702                         index, clen);
 703                 ret = -ENOMEM;
 704                 goto out;
 705         }
 706
 707         alloced_pages = zs_get_total_pages(meta->mem_pool);
 708         update_used_max(zram, alloced_pages);
 709
 710         if (zram->limit_pages && alloced_pages > zram->limit_pages) {
 711                 zs_free(meta->mem_pool, handle);
 712                 ret = -ENOMEM;
 713                 goto out;
 714         }
 715
 716         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
 717
 718         if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 719                 src = kmap_atomic(page);
 720                 memcpy(cmem, src, PAGE_SIZE);
 721                 kunmap_atomic(src);
 722         } else {
 723                 memcpy(cmem, src, clen);
 724         }
 725
 726         zcomp_stream_put(zram->comp);
 727         zstrm = NULL;
 728         zs_unmap_object(meta->mem_pool, handle);
 729
 730         /*
 731          * Free memory associated with this sector
 732          * before overwriting unused sectors.
 733          */
 734         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 735         zram_free_page(zram, index);
 736
 737         meta->table[index].handle = handle;
 738         zram_set_obj_size(meta, index, clen);
 739         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 740
 741         /* Update stats */
 742         atomic64_add(clen, &zram->stats.compr_data_size);
 743         atomic64_inc(&zram->stats.pages_stored);
 744 out:
 745         if (zstrm)
 746                 zcomp_stream_put(zram->comp);
 747         if (is_partial_io(bvec))
 748                 kfree(uncmem);
 749         return ret;
 750 }
 751
 752 /*
 753  * zram_bio_discard - handler on discard request
 754  * @index: physical block index in PAGE_SIZE units
 755  * @offset: byte offset within physical block
 756  */
 757 static void zram_bio_discard(struct zram *zram, u32 index,
 758                              int offset, struct bio *bio)
 759 {
 760         size_t n = bio->bi_iter.bi_size;
 761         struct zram_meta *meta = zram->meta;
 762
 763         /*
 764          * zram manages data in physical block size units. Because logical block
 765          * size isn't identical with physical block size on some arch, we
 766          * could get a discard request pointing to a specific offset within a
 767          * certain physical block.  Although we can handle this request by
 768          * reading that physiclal block and decompressing and partially zeroing
 769          * and re-compressing and then re-storing it, this isn't reasonable
 770          * because our intent with a discard request is to save memory.  So
 771          * skipping this logical block is appropriate here.
 772          */
 773         if (offset) {
 774                 if (n <= (PAGE_SIZE - offset))
 775                         return;
 776
 777                 n -= (PAGE_SIZE - offset);
 778                 index++;
 779         }
 780
 781         while (n >= PAGE_SIZE) {
 782                 bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 783                 zram_free_page(zram, index);
 784                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 785                 atomic64_inc(&zram->stats.notify_free);
 786                 index++;
 787                 n -= PAGE_SIZE;
 788         }
 789 }
 790
 791 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 792                         int offset, bool is_write)
 793 {
 794         unsigned long start_time = jiffies;
 795         int rw_acct = is_write ? REQ_OP_WRITE : REQ_OP_READ;
 796         int ret;
 797
 798         generic_start_io_acct(rw_acct, bvec->bv_len >> SECTOR_SHIFT,
 799                         &zram->disk->part0);
 800
 801         if (!is_write) {
 802                 atomic64_inc(&zram->stats.num_reads);
 803                 ret = zram_bvec_read(zram, bvec, index, offset);
 804         } else {
 805                 atomic64_inc(&zram->stats.num_writes);
 806                 ret = zram_bvec_write(zram, bvec, index, offset);
 807         }
 808
 809         generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);
 810
 811         if (unlikely(ret)) {
 812                 if (!is_write)
 813                         atomic64_inc(&zram->stats.failed_reads);
 814                 else
 815                         atomic64_inc(&zram->stats.failed_writes);
 816         }
 817
 818         return ret;
 819 }
 820
 821 static void __zram_make_request(struct zram *zram, struct bio *bio)
 822 {
 823         int offset;
 824         u32 index;
 825         struct bio_vec bvec;
 826         struct bvec_iter iter;
 827
 828         index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
 829         offset = (bio->bi_iter.bi_sector &
 830                   (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 831
 832         switch (bio_op(bio)) {
 833         case REQ_OP_DISCARD:
 834         case REQ_OP_WRITE_ZEROES:
 835                 zram_bio_discard(zram, index, offset, bio);
 836                 bio_endio(bio);
 837                 return;
 838         default:
 839                 break;
 840         }
 841
 842         bio_for_each_segment(bvec, bio, iter) {
 843                 int max_transfer_size = PAGE_SIZE - offset;
 844
 845                 if (bvec.bv_len > max_transfer_size) {
 846                         /*
 847                          * zram_bvec_rw() can only make operation on a single
 848                          * zram page. Split the bio vector.
 849                          */
 850                         struct bio_vec bv;
 851
 852                         bv.bv_page = bvec.bv_page;
 853                         bv.bv_len = max_transfer_size;
 854                         bv.bv_offset = bvec.bv_offset;
 855
 856                         if (zram_bvec_rw(zram, &bv, index, offset,
 857                                          op_is_write(bio_op(bio))) < 0)
 858                                 goto out;
 859
 860                         bv.bv_len = bvec.bv_len - max_transfer_size;
 861                         bv.bv_offset += max_transfer_size;
 862                         if (zram_bvec_rw(zram, &bv, index + 1, 0,
 863                                          op_is_write(bio_op(bio))) < 0)
 864                                 goto out;
 865                 } else
 866                         if (zram_bvec_rw(zram, &bvec, index, offset,
 867                                          op_is_write(bio_op(bio))) < 0)
 868                                 goto out;
 869
 870                 update_position(&index, &offset, &bvec);
 871         }
 872
 873         bio_endio(bio);
 874         return;
 875
 876 out:
 877         bio_io_error(bio);
 878 }
 879
 880 /*
 881  * Handler function for all zram I/O requests.
 882  */
 883 static blk_qc_t zram_make_request(struct request_queue *queue, struct bio *bio)
 884 {
 885         struct zram *zram = queue->queuedata;
 886
 887         blk_queue_split(queue, &bio, queue->bio_split);
 888
 889         if (!valid_io_request(zram, bio->bi_iter.bi_sector,
 890                                         bio->bi_iter.bi_size)) {
 891                 atomic64_inc(&zram->stats.invalid_io);
 892                 goto error;
 893         }
 894
 895         __zram_make_request(zram, bio);
 896         return BLK_QC_T_NONE;
 897
 898 error:
 899         bio_io_error(bio);
 900         return BLK_QC_T_NONE;
 901 }
 902
 903 static void zram_slot_free_notify(struct block_device *bdev,
 904                                 unsigned long index)
 905 {
 906         struct zram *zram;
 907         struct zram_meta *meta;
 908
 909         zram = bdev->bd_disk->private_data;
 910         meta = zram->meta;
 911
 912         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 913         zram_free_page(zram, index);
 914         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 915         atomic64_inc(&zram->stats.notify_free);
 916 }
 917
 918 static int zram_rw_page(struct block_device *bdev, sector_t sector,
 919                        struct page *page, bool is_write)
 920 {
 921         int offset, err = -EIO;
 922         u32 index;
 923         struct zram *zram;
 924         struct bio_vec bv;
 925
 926         zram = bdev->bd_disk->private_data;
 927
 928         if (!valid_io_request(zram, sector, PAGE_SIZE)) {
 929                 atomic64_inc(&zram->stats.invalid_io);
 930                 err = -EINVAL;
 931                 goto out;
 932         }
 933
 934         index = sector >> SECTORS_PER_PAGE_SHIFT;
 935         offset = (sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 936
 937         bv.bv_page = page;
 938         bv.bv_len = PAGE_SIZE;
 939         bv.bv_offset = 0;
 940
 941         err = zram_bvec_rw(zram, &bv, index, offset, is_write);
 942 out:
 943         /*
 944          * If I/O fails, just return error(ie, non-zero) without
 945          * calling page_endio.
 946          * It causes resubmit the I/O with bio request by upper functions
 947          * of rw_page(e.g., swap_readpage, __swap_writepage) and
 948          * bio->bi_end_io does things to handle the error
 949          * (e.g., SetPageError, set_page_dirty and extra works).
 950          */
 951         if (err == 0)
 952                 page_endio(page, is_write, 0);
 953         return err;
 954 }
 955
 956 static void zram_reset_device(struct zram *zram)
 957 {
 958         struct zram_meta *meta;
 959         struct zcomp *comp;
 960         u64 disksize;
 961
 962         down_write(&zram->init_lock);
 963
 964         zram->limit_pages = 0;
 965
 966         if (!init_done(zram)) {
 967                 up_write(&zram->init_lock);
 968                 return;
 969         }
 970
 971         meta = zram->meta;
 972         comp = zram->comp;
 973         disksize = zram->disksize;
 974
 975         /* Reset stats */
 976         memset(&zram->stats, 0, sizeof(zram->stats));
 977         zram->disksize = 0;
 978
 979         set_capacity(zram->disk, 0);
 980         part_stat_set_all(&zram->disk->part0, 0);
 981
 982         up_write(&zram->init_lock);
 983         /* I/O operation under all of CPU are done so let's free */
 984         zram_meta_free(meta, disksize);
 985         zcomp_destroy(comp);
 986 }
 987
 988 static ssize_t disksize_store(struct device *dev,
 989                 struct device_attribute *attr, const char *buf, size_t len)
 990 {
 991         u64 disksize;
 992         struct zcomp *comp;
 993         struct zram_meta *meta;
 994         struct zram *zram = dev_to_zram(dev);
 995         int err;
 996
 997         disksize = memparse(buf, NULL);
 998         if (!disksize)
 999                 return -EINVAL;
1000
1001         disksize = PAGE_ALIGN(disksize);
1002         meta = zram_meta_alloc(zram->disk->disk_name, disksize);
1003         if (!meta)
1004                 return -ENOMEM;
1005
1006         comp = zcomp_create(zram->compressor);
1007         if (IS_ERR(comp)) {
1008                 pr_err("Cannot initialise %s compressing backend\n",
1009                                 zram->compressor);
1010                 err = PTR_ERR(comp);
1011                 goto out_free_meta;
1012         }
1013
1014         down_write(&zram->init_lock);
1015         if (init_done(zram)) {
1016                 pr_info("Cannot change disksize for initialized device\n");
1017                 err = -EBUSY;
1018                 goto out_destroy_comp;
1019         }
1020
1021         zram->meta = meta;
1022         zram->comp = comp;
1023         zram->disksize = disksize;
1024         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
1025         zram_revalidate_disk(zram);
1026         up_write(&zram->init_lock);
1027
1028         return len;
1029
1030 out_destroy_comp:
1031         up_write(&zram->init_lock);
1032         zcomp_destroy(comp);
1033 out_free_meta:
1034         zram_meta_free(meta, disksize);
1035         return err;
1036 }
1037
1038 static ssize_t reset_store(struct device *dev,
1039                 struct device_attribute *attr, const char *buf, size_t len)
1040 {
1041         int ret;
1042         unsigned short do_reset;
1043         struct zram *zram;
1044         struct block_device *bdev;
1045
1046         ret = kstrtou16(buf, 10, &do_reset);
1047         if (ret)
1048                 return ret;
1049
1050         if (!do_reset)
1051                 return -EINVAL;
1052
1053         zram = dev_to_zram(dev);
1054         bdev = bdget_disk(zram->disk, 0);
1055         if (!bdev)
1056                 return -ENOMEM;
1057
1058         mutex_lock(&bdev->bd_mutex);
1059         /* Do not reset an active device or claimed device */
1060         if (bdev->bd_openers || zram->claim) {
1061                 mutex_unlock(&bdev->bd_mutex);
1062                 bdput(bdev);
1063                 return -EBUSY;
1064         }
1065
1066         /* From now on, anyone can't open /dev/zram[0-9] */
1067         zram->claim = true;
1068         mutex_unlock(&bdev->bd_mutex);
1069
1070         /* Make sure all the pending I/O are finished */
1071         fsync_bdev(bdev);
1072         zram_reset_device(zram);
1073         zram_revalidate_disk(zram);
1074         bdput(bdev);
1075
1076         mutex_lock(&bdev->bd_mutex);
1077         zram->claim = false;
1078         mutex_unlock(&bdev->bd_mutex);
1079
1080         return len;
1081 }
1082
1083 static int zram_open(struct block_device *bdev, fmode_t mode)
1084 {
1085         int ret = 0;
1086         struct zram *zram;
1087
1088         WARN_ON(!mutex_is_locked(&bdev->bd_mutex));
1089
1090         zram = bdev->bd_disk->private_data;
1091         /* zram was claimed to reset so open request fails */
1092         if (zram->claim)
1093                 ret = -EBUSY;
1094
1095         return ret;
1096 }
1097
1098 static const struct block_device_operations zram_devops = {
1099         .open = zram_open,
1100         .swap_slot_free_notify = zram_slot_free_notify,
1101         .rw_page = zram_rw_page,
1102         .owner = THIS_MODULE
1103 };
1104
1105 static DEVICE_ATTR_WO(compact);
1106 static DEVICE_ATTR_RW(disksize);
1107 static DEVICE_ATTR_RO(initstate);
1108 static DEVICE_ATTR_WO(reset);
1109 static DEVICE_ATTR_WO(mem_limit);
1110 static DEVICE_ATTR_WO(mem_used_max);
1111 static DEVICE_ATTR_RW(max_comp_streams);
1112 static DEVICE_ATTR_RW(comp_algorithm);
1113
1114 static struct attribute *zram_disk_attrs[] = {
1115         &dev_attr_disksize.attr,
1116         &dev_attr_initstate.attr,
1117         &dev_attr_reset.attr,
1118         &dev_attr_compact.attr,
1119         &dev_attr_mem_limit.attr,
1120         &dev_attr_mem_used_max.attr,
1121         &dev_attr_max_comp_streams.attr,
1122         &dev_attr_comp_algorithm.attr,
1123         &dev_attr_io_stat.attr,
1124         &dev_attr_mm_stat.attr,
1125         &dev_attr_debug_stat.attr,
1126         NULL,
1127 };
1128
1129 static struct attribute_group zram_disk_attr_group = {
1130         .attrs = zram_disk_attrs,
1131 };
1132
1133 /*
1134  * Allocate and initialize new zram device. the function returns
1135  * '>= 0' device_id upon success, and negative value otherwise.
1136  */
1137 static int zram_add(void)
1138 {
1139         struct zram *zram;
1140         struct request_queue *queue;
1141         int ret, device_id;
1142
1143         zram = kzalloc(sizeof(struct zram), GFP_KERNEL);
1144         if (!zram)
1145                 return -ENOMEM;
1146
1147         ret = idr_alloc(&zram_index_idr, zram, 0, 0, GFP_KERNEL);
1148         if (ret < 0)
1149                 goto out_free_dev;
1150         device_id = ret;
1151
1152         init_rwsem(&zram->init_lock);
1153
1154         queue = blk_alloc_queue(GFP_KERNEL);
1155         if (!queue) {
1156                 pr_err("Error allocating disk queue for device %d\n",
1157                         device_id);
1158                 ret = -ENOMEM;
1159                 goto out_free_idr;
1160         }
1161
1162         blk_queue_make_request(queue, zram_make_request);
1163
1164         /* gendisk structure */
1165         zram->disk = alloc_disk(1);
1166         if (!zram->disk) {
1167                 pr_err("Error allocating disk structure for device %d\n",
1168                         device_id);
1169                 ret = -ENOMEM;
1170                 goto out_free_queue;
1171         }
1172
1173         zram->disk->major = zram_major;
1174         zram->disk->first_minor = device_id;
1175         zram->disk->fops = &zram_devops;
1176         zram->disk->queue = queue;
1177         zram->disk->queue->queuedata = zram;
1178         zram->disk->private_data = zram;
1179         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
1180
1181         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
1182         set_capacity(zram->disk, 0);
1183         /* zram devices sort of resembles non-rotational disks */
1184         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
1185         queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);
1186         /*
1187          * To ensure that we always get PAGE_SIZE aligned
1188          * and n*PAGE_SIZED sized I/O requests.
1189          */
1190         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
1191         blk_queue_logical_block_size(zram->disk->queue,
1192                                         ZRAM_LOGICAL_BLOCK_SIZE);
1193         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
1194         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
1195         zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
1196         zram->disk->queue->limits.max_sectors = SECTORS_PER_PAGE;
1197         zram->disk->queue->limits.chunk_sectors = 0;
1198         blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
1199         queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
1200
1201         /*
1202          * zram_bio_discard() will clear all logical blocks if logical block
1203          * size is identical with physical block size(PAGE_SIZE). But if it is
1204          * different, we will skip discarding some parts of logical blocks in
1205          * the part of the request range which isn't aligned to physical block
1206          * size.  So we can't ensure that all discarded logical blocks are
1207          * zeroed.
1208          */
1209         if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
1210                 blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);
1211
1212         add_disk(zram->disk);
1213
1214         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
1215                                 &zram_disk_attr_group);
1216         if (ret < 0) {
1217                 pr_err("Error creating sysfs group for device %d\n",
1218                                 device_id);
1219                 goto out_free_disk;
1220         }
1221         strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
1222         zram->meta = NULL;
1223
1224         pr_info("Added device: %s\n", zram->disk->disk_name);
1225         return device_id;
1226
1227 out_free_disk:
1228         del_gendisk(zram->disk);
1229         put_disk(zram->disk);
1230 out_free_queue:
1231         blk_cleanup_queue(queue);
1232 out_free_idr:
1233         idr_remove(&zram_index_idr, device_id);
1234 out_free_dev:
1235         kfree(zram);
1236         return ret;
1237 }
1238
1239 static int zram_remove(struct zram *zram)
1240 {
1241         struct block_device *bdev;
1242
1243         bdev = bdget_disk(zram->disk, 0);
1244         if (!bdev)
1245                 return -ENOMEM;
1246
1247         mutex_lock(&bdev->bd_mutex);
1248         if (bdev->bd_openers || zram->claim) {
1249                 mutex_unlock(&bdev->bd_mutex);
1250                 bdput(bdev);
1251                 return -EBUSY;
1252         }
1253
1254         zram->claim = true;
1255         mutex_unlock(&bdev->bd_mutex);
1256
1257         /*
1258          * Remove sysfs first, so no one will perform a disksize
1259          * store while we destroy the devices. This also helps during
1260          * hot_remove -- zram_reset_device() is the last holder of
1261          * ->init_lock, no later/concurrent disksize_store() or any
1262          * other sysfs handlers are possible.
1263          */
1264         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
1265                         &zram_disk_attr_group);
1266
1267         /* Make sure all the pending I/O are finished */
1268         fsync_bdev(bdev);
1269         zram_reset_device(zram);
1270         bdput(bdev);
1271
1272         pr_info("Removed device: %s\n", zram->disk->disk_name);
1273
1274         blk_cleanup_queue(zram->disk->queue);
1275         del_gendisk(zram->disk);
1276         put_disk(zram->disk);
1277         kfree(zram);
1278         return 0;
1279 }
1280
1281 /* zram-control sysfs attributes */
1282 static ssize_t hot_add_show(struct class *class,
1283                         struct class_attribute *attr,
1284                         char *buf)
1285 {
1286         int ret;
1287
1288         mutex_lock(&zram_index_mutex);
1289         ret = zram_add();
1290         mutex_unlock(&zram_index_mutex);
1291
1292         if (ret < 0)
1293                 return ret;
1294         return scnprintf(buf, PAGE_SIZE, "%d\n", ret);
1295 }
1296
1297 static ssize_t hot_remove_store(struct class *class,
1298                         struct class_attribute *attr,
1299                         const char *buf,
1300                         size_t count)
1301 {
1302         struct zram *zram;
1303         int ret, dev_id;
1304
1305         /* dev_id is gendisk->first_minor, which is `int' */
1306         ret = kstrtoint(buf, 10, &dev_id);
1307         if (ret)
1308                 return ret;
1309         if (dev_id < 0)
1310                 return -EINVAL;
1311
1312         mutex_lock(&zram_index_mutex);
1313
1314         zram = idr_find(&zram_index_idr, dev_id);
1315         if (zram) {
1316                 ret = zram_remove(zram);
1317                 if (!ret)
1318                         idr_remove(&zram_index_idr, dev_id);
1319         } else {
1320                 ret = -ENODEV;
1321         }
1322
1323         mutex_unlock(&zram_index_mutex);
1324         return ret ? ret : count;
1325 }
1326
1327 /*
1328  * NOTE: hot_add attribute is not the usual read-only sysfs attribute. In a
1329  * sense that reading from this file does alter the state of your system -- it
1330  * creates a new un-initialized zram device and returns back this device's
1331  * device_id (or an error code if it fails to create a new device).
1332  */
1333 static struct class_attribute zram_control_class_attrs[] = {
1334         __ATTR(hot_add, 0400, hot_add_show, NULL),
1335         __ATTR_WO(hot_remove),
1336         __ATTR_NULL,
1337 };
1338
1339 static struct class zram_control_class = {
1340         .name           = "zram-control",
1341         .owner          = THIS_MODULE,
1342         .class_attrs    = zram_control_class_attrs,
1343 };
1344
1345 static int zram_remove_cb(int id, void *ptr, void *data)
1346 {
1347         zram_remove(ptr);
1348         return 0;
1349 }
1350
1351 static void destroy_devices(void)
1352 {
1353         class_unregister(&zram_control_class);
1354         idr_for_each(&zram_index_idr, &zram_remove_cb, NULL);
1355         idr_destroy(&zram_index_idr);
1356         unregister_blkdev(zram_major, "zram");
1357         cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE);
1358 }
1359
1360 static int __init zram_init(void)
1361 {
1362         int ret;
1363
1364         ret = cpuhp_setup_state_multi(CPUHP_ZCOMP_PREPARE, "block/zram:prepare",
1365                                       zcomp_cpu_up_prepare, zcomp_cpu_dead);
1366         if (ret < 0)
1367                 return ret;
1368
1369         ret = class_register(&zram_control_class);
1370         if (ret) {
1371                 pr_err("Unable to register zram-control class\n");
1372                 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE);
1373                 return ret;
1374         }
1375
1376         zram_major = register_blkdev(0, "zram");
1377         if (zram_major <= 0) {
1378                 pr_err("Unable to get major number\n");
1379                 class_unregister(&zram_control_class);
1380                 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE);
1381                 return -EBUSY;
1382         }
1383
1384         while (num_devices != 0) {
1385                 mutex_lock(&zram_index_mutex);
1386                 ret = zram_add();
1387                 mutex_unlock(&zram_index_mutex);
1388                 if (ret < 0)
1389                         goto out_error;
1390                 num_devices--;
1391         }
1392
1393         return 0;
1394
1395 out_error:
1396         destroy_devices();
1397         return ret;
1398 }
1399
1400 static void __exit zram_exit(void)
1401 {
1402         destroy_devices();
1403 }
1404
1405 module_init(zram_init);
1406 module_exit(zram_exit);
1407
1408 module_param(num_devices, uint, 0);
1409 MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
1410
1411 MODULE_LICENSE("Dual BSD/GPL");
1412 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
1413 MODULE_DESCRIPTION("Compressed RAM Block Device");