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/string.h>
  29 #include <linux/vmalloc.h>
  30 #include <linux/err.h>
  31 #include <linux/idr.h>
  32 #include <linux/sysfs.h>
  33
  34 #include "zram_drv.h"
  35
  36 static DEFINE_IDR(zram_index_idr);
  37 /* idr index must be protected */
  38 static DEFINE_MUTEX(zram_index_mutex);
  39
  40 static int zram_major;
  41 static const char *default_compressor = "lzo";
  42
  43 /* Module params (documentation at end) */
  44 static unsigned int num_devices = 1;
  45
  46 static inline void deprecated_attr_warn(const char *name)
  47 {
  48         pr_warn_once("%d (%s) Attribute %s (and others) will be removed. %s\n",
  49                         task_pid_nr(current),
  50                         current->comm,
  51                         name,
  52                         "See zram documentation.");
  53 }
  54
  55 #define ZRAM_ATTR_RO(name)                                              \
  56 static ssize_t name##_show(struct device *d,                            \
  57                                 struct device_attribute *attr, char *b) \
  58 {                                                                       \
  59         struct zram *zram = dev_to_zram(d);                             \
  60                                                                         \
  61         deprecated_attr_warn(__stringify(name));                        \
  62         return scnprintf(b, PAGE_SIZE, "%llu\n",                        \
  63                 (u64)atomic64_read(&zram->stats.name));                 \
  64 }                                                                       \
  65 static DEVICE_ATTR_RO(name);
  66
  67 static inline bool init_done(struct zram *zram)
  68 {
  69         return zram->disksize;
  70 }
  71
  72 static inline struct zram *dev_to_zram(struct device *dev)
  73 {
  74         return (struct zram *)dev_to_disk(dev)->private_data;
  75 }
  76
  77 /* flag operations require table entry bit_spin_lock() being held */
  78 static int zram_test_flag(struct zram_meta *meta, u32 index,
  79                         enum zram_pageflags flag)
  80 {
  81         return meta->table[index].value & BIT(flag);
  82 }
  83
  84 static void zram_set_flag(struct zram_meta *meta, u32 index,
  85                         enum zram_pageflags flag)
  86 {
  87         meta->table[index].value |= BIT(flag);
  88 }
  89
  90 static void zram_clear_flag(struct zram_meta *meta, u32 index,
  91                         enum zram_pageflags flag)
  92 {
  93         meta->table[index].value &= ~BIT(flag);
  94 }
  95
  96 static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
  97 {
  98         return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
  99 }
 100
 101 static void zram_set_obj_size(struct zram_meta *meta,
 102                                         u32 index, size_t size)
 103 {
 104         unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
 105
 106         meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
 107 }
 108
 109 static inline bool is_partial_io(struct bio_vec *bvec)
 110 {
 111         return bvec->bv_len != PAGE_SIZE;
 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 bool page_zero_filled(void *ptr)
 161 {
 162         unsigned int pos;
 163         unsigned long *page;
 164
 165         page = (unsigned long *)ptr;
 166
 167         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
 168                 if (page[pos])
 169                         return false;
 170         }
 171
 172         return true;
 173 }
 174
 175 static void handle_zero_page(struct bio_vec *bvec)
 176 {
 177         struct page *page = bvec->bv_page;
 178         void *user_mem;
 179
 180         user_mem = kmap_atomic(page);
 181         if (is_partial_io(bvec))
 182                 memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
 183         else
 184                 clear_page(user_mem);
 185         kunmap_atomic(user_mem);
 186
 187         flush_dcache_page(page);
 188 }
 189
 190 static ssize_t initstate_show(struct device *dev,
 191                 struct device_attribute *attr, char *buf)
 192 {
 193         u32 val;
 194         struct zram *zram = dev_to_zram(dev);
 195
 196         down_read(&zram->init_lock);
 197         val = init_done(zram);
 198         up_read(&zram->init_lock);
 199
 200         return scnprintf(buf, PAGE_SIZE, "%u\n", val);
 201 }
 202
 203 static ssize_t disksize_show(struct device *dev,
 204                 struct device_attribute *attr, char *buf)
 205 {
 206         struct zram *zram = dev_to_zram(dev);
 207
 208         return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
 209 }
 210
 211 static ssize_t orig_data_size_show(struct device *dev,
 212                 struct device_attribute *attr, char *buf)
 213 {
 214         struct zram *zram = dev_to_zram(dev);
 215
 216         deprecated_attr_warn("orig_data_size");
 217         return scnprintf(buf, PAGE_SIZE, "%llu\n",
 218                 (u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
 219 }
 220
 221 static ssize_t mem_used_total_show(struct device *dev,
 222                 struct device_attribute *attr, char *buf)
 223 {
 224         u64 val = 0;
 225         struct zram *zram = dev_to_zram(dev);
 226
 227         deprecated_attr_warn("mem_used_total");
 228         down_read(&zram->init_lock);
 229         if (init_done(zram)) {
 230                 struct zram_meta *meta = zram->meta;
 231                 val = zs_get_total_pages(meta->mem_pool);
 232         }
 233         up_read(&zram->init_lock);
 234
 235         return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
 236 }
 237
 238 static ssize_t mem_limit_show(struct device *dev,
 239                 struct device_attribute *attr, char *buf)
 240 {
 241         u64 val;
 242         struct zram *zram = dev_to_zram(dev);
 243
 244         deprecated_attr_warn("mem_limit");
 245         down_read(&zram->init_lock);
 246         val = zram->limit_pages;
 247         up_read(&zram->init_lock);
 248
 249         return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
 250 }
 251
 252 static ssize_t mem_limit_store(struct device *dev,
 253                 struct device_attribute *attr, const char *buf, size_t len)
 254 {
 255         u64 limit;
 256         char *tmp;
 257         struct zram *zram = dev_to_zram(dev);
 258
 259         limit = memparse(buf, &tmp);
 260         if (buf == tmp) /* no chars parsed, invalid input */
 261                 return -EINVAL;
 262
 263         down_write(&zram->init_lock);
 264         zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
 265         up_write(&zram->init_lock);
 266
 267         return len;
 268 }
 269
 270 static ssize_t mem_used_max_show(struct device *dev,
 271                 struct device_attribute *attr, char *buf)
 272 {
 273         u64 val = 0;
 274         struct zram *zram = dev_to_zram(dev);
 275
 276         deprecated_attr_warn("mem_used_max");
 277         down_read(&zram->init_lock);
 278         if (init_done(zram))
 279                 val = atomic_long_read(&zram->stats.max_used_pages);
 280         up_read(&zram->init_lock);
 281
 282         return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
 283 }
 284
 285 static ssize_t mem_used_max_store(struct device *dev,
 286                 struct device_attribute *attr, const char *buf, size_t len)
 287 {
 288         int err;
 289         unsigned long val;
 290         struct zram *zram = dev_to_zram(dev);
 291
 292         err = kstrtoul(buf, 10, &val);
 293         if (err || val != 0)
 294                 return -EINVAL;
 295
 296         down_read(&zram->init_lock);
 297         if (init_done(zram)) {
 298                 struct zram_meta *meta = zram->meta;
 299                 atomic_long_set(&zram->stats.max_used_pages,
 300                                 zs_get_total_pages(meta->mem_pool));
 301         }
 302         up_read(&zram->init_lock);
 303
 304         return len;
 305 }
 306
 307 /*
 308  * We switched to per-cpu streams and this attr is not needed anymore.
 309  * However, we will keep it around for some time, because:
 310  * a) we may revert per-cpu streams in the future
 311  * b) it's visible to user space and we need to follow our 2 years
 312  *    retirement rule; but we already have a number of 'soon to be
 313  *    altered' attrs, so max_comp_streams need to wait for the next
 314  *    layoff cycle.
 315  */
 316 static ssize_t max_comp_streams_show(struct device *dev,
 317                 struct device_attribute *attr, char *buf)
 318 {
 319         return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus());
 320 }
 321
 322 static ssize_t max_comp_streams_store(struct device *dev,
 323                 struct device_attribute *attr, const char *buf, size_t len)
 324 {
 325         return len;
 326 }
 327
 328 static ssize_t comp_algorithm_show(struct device *dev,
 329                 struct device_attribute *attr, char *buf)
 330 {
 331         size_t sz;
 332         struct zram *zram = dev_to_zram(dev);
 333
 334         down_read(&zram->init_lock);
 335         sz = zcomp_available_show(zram->compressor, buf);
 336         up_read(&zram->init_lock);
 337
 338         return sz;
 339 }
 340
 341 static ssize_t comp_algorithm_store(struct device *dev,
 342                 struct device_attribute *attr, const char *buf, size_t len)
 343 {
 344         struct zram *zram = dev_to_zram(dev);
 345         char compressor[CRYPTO_MAX_ALG_NAME];
 346         size_t sz;
 347
 348         strlcpy(compressor, buf, sizeof(compressor));
 349         /* ignore trailing newline */
 350         sz = strlen(compressor);
 351         if (sz > 0 && compressor[sz - 1] == '\n')
 352                 compressor[sz - 1] = 0x00;
 353
 354         if (!zcomp_available_algorithm(compressor))
 355                 return -EINVAL;
 356
 357         down_write(&zram->init_lock);
 358         if (init_done(zram)) {
 359                 up_write(&zram->init_lock);
 360                 pr_info("Can't change algorithm for initialized device\n");
 361                 return -EBUSY;
 362         }
 363
 364         strlcpy(zram->compressor, compressor, sizeof(compressor));
 365         up_write(&zram->init_lock);
 366         return len;
 367 }
 368
 369 static ssize_t compact_store(struct device *dev,
 370                 struct device_attribute *attr, const char *buf, size_t len)
 371 {
 372         struct zram *zram = dev_to_zram(dev);
 373         struct zram_meta *meta;
 374
 375         down_read(&zram->init_lock);
 376         if (!init_done(zram)) {
 377                 up_read(&zram->init_lock);
 378                 return -EINVAL;
 379         }
 380
 381         meta = zram->meta;
 382         zs_compact(meta->mem_pool);
 383         up_read(&zram->init_lock);
 384
 385         return len;
 386 }
 387
 388 static ssize_t io_stat_show(struct device *dev,
 389                 struct device_attribute *attr, char *buf)
 390 {
 391         struct zram *zram = dev_to_zram(dev);
 392         ssize_t ret;
 393
 394         down_read(&zram->init_lock);
 395         ret = scnprintf(buf, PAGE_SIZE,
 396                         "%8llu %8llu %8llu %8llu\n",
 397                         (u64)atomic64_read(&zram->stats.failed_reads),
 398                         (u64)atomic64_read(&zram->stats.failed_writes),
 399                         (u64)atomic64_read(&zram->stats.invalid_io),
 400                         (u64)atomic64_read(&zram->stats.notify_free));
 401         up_read(&zram->init_lock);
 402
 403         return ret;
 404 }
 405
 406 static ssize_t mm_stat_show(struct device *dev,
 407                 struct device_attribute *attr, char *buf)
 408 {
 409         struct zram *zram = dev_to_zram(dev);
 410         struct zs_pool_stats pool_stats;
 411         u64 orig_size, mem_used = 0;
 412         long max_used;
 413         ssize_t ret;
 414
 415         memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats));
 416
 417         down_read(&zram->init_lock);
 418         if (init_done(zram)) {
 419                 mem_used = zs_get_total_pages(zram->meta->mem_pool);
 420                 zs_pool_stats(zram->meta->mem_pool, &pool_stats);
 421         }
 422
 423         orig_size = atomic64_read(&zram->stats.pages_stored);
 424         max_used = atomic_long_read(&zram->stats.max_used_pages);
 425
 426         ret = scnprintf(buf, PAGE_SIZE,
 427                         "%8llu %8llu %8llu %8lu %8ld %8llu %8lu\n",
 428                         orig_size << PAGE_SHIFT,
 429                         (u64)atomic64_read(&zram->stats.compr_data_size),
 430                         mem_used << PAGE_SHIFT,
 431                         zram->limit_pages << PAGE_SHIFT,
 432                         max_used << PAGE_SHIFT,
 433                         (u64)atomic64_read(&zram->stats.zero_pages),
 434                         pool_stats.pages_compacted);
 435         up_read(&zram->init_lock);
 436
 437         return ret;
 438 }
 439
 440 static ssize_t debug_stat_show(struct device *dev,
 441                 struct device_attribute *attr, char *buf)
 442 {
 443         int version = 1;
 444         struct zram *zram = dev_to_zram(dev);
 445         ssize_t ret;
 446
 447         down_read(&zram->init_lock);
 448         ret = scnprintf(buf, PAGE_SIZE,
 449                         "version: %d\n%8llu\n",
 450                         version,
 451                         (u64)atomic64_read(&zram->stats.writestall));
 452         up_read(&zram->init_lock);
 453
 454         return ret;
 455 }
 456
 457 static DEVICE_ATTR_RO(io_stat);
 458 static DEVICE_ATTR_RO(mm_stat);
 459 static DEVICE_ATTR_RO(debug_stat);
 460 ZRAM_ATTR_RO(num_reads);
 461 ZRAM_ATTR_RO(num_writes);
 462 ZRAM_ATTR_RO(failed_reads);
 463 ZRAM_ATTR_RO(failed_writes);
 464 ZRAM_ATTR_RO(invalid_io);
 465 ZRAM_ATTR_RO(notify_free);
 466 ZRAM_ATTR_RO(zero_pages);
 467 ZRAM_ATTR_RO(compr_data_size);
 468
 469 static inline bool zram_meta_get(struct zram *zram)
 470 {
 471         if (atomic_inc_not_zero(&zram->refcount))
 472                 return true;
 473         return false;
 474 }
 475
 476 static inline void zram_meta_put(struct zram *zram)
 477 {
 478         atomic_dec(&zram->refcount);
 479 }
 480
 481 static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 482 {
 483         size_t num_pages = disksize >> PAGE_SHIFT;
 484         size_t index;
 485
 486         /* Free all pages that are still in this zram device */
 487         for (index = 0; index < num_pages; index++) {
 488                 unsigned long handle = meta->table[index].handle;
 489
 490                 if (!handle)
 491                         continue;
 492
 493                 zs_free(meta->mem_pool, handle);
 494         }
 495
 496         zs_destroy_pool(meta->mem_pool);
 497         vfree(meta->table);
 498         kfree(meta);
 499 }
 500
 501 static struct zram_meta *zram_meta_alloc(char *pool_name, u64 disksize)
 502 {
 503         size_t num_pages;
 504         struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 505
 506         if (!meta)
 507                 return NULL;
 508
 509         num_pages = disksize >> PAGE_SHIFT;
 510         meta->table = vzalloc(num_pages * sizeof(*meta->table));
 511         if (!meta->table) {
 512                 pr_err("Error allocating zram address table\n");
 513                 goto out_error;
 514         }
 515
 516         meta->mem_pool = zs_create_pool(pool_name);
 517         if (!meta->mem_pool) {
 518                 pr_err("Error creating memory pool\n");
 519                 goto out_error;
 520         }
 521
 522         return meta;
 523
 524 out_error:
 525         vfree(meta->table);
 526         kfree(meta);
 527         return NULL;
 528 }
 529
 530 /*
 531  * To protect concurrent access to the same index entry,
 532  * caller should hold this table index entry's bit_spinlock to
 533  * indicate this index entry is accessing.
 534  */
 535 static void zram_free_page(struct zram *zram, size_t index)
 536 {
 537         struct zram_meta *meta = zram->meta;
 538         unsigned long handle = meta->table[index].handle;
 539
 540         if (unlikely(!handle)) {
 541                 /*
 542                  * No memory is allocated for zero filled pages.
 543                  * Simply clear zero page flag.
 544                  */
 545                 if (zram_test_flag(meta, index, ZRAM_ZERO)) {
 546                         zram_clear_flag(meta, index, ZRAM_ZERO);
 547                         atomic64_dec(&zram->stats.zero_pages);
 548                 }
 549                 return;
 550         }
 551
 552         zs_free(meta->mem_pool, handle);
 553
 554         atomic64_sub(zram_get_obj_size(meta, index),
 555                         &zram->stats.compr_data_size);
 556         atomic64_dec(&zram->stats.pages_stored);
 557
 558         meta->table[index].handle = 0;
 559         zram_set_obj_size(meta, index, 0);
 560 }
 561
 562 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 563 {
 564         int ret = 0;
 565         unsigned char *cmem;
 566         struct zram_meta *meta = zram->meta;
 567         unsigned long handle;
 568         unsigned int size;
 569
 570         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 571         handle = meta->table[index].handle;
 572         size = zram_get_obj_size(meta, index);
 573
 574         if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
 575                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 576                 clear_page(mem);
 577                 return 0;
 578         }
 579
 580         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 581         if (size == PAGE_SIZE) {
 582                 copy_page(mem, cmem);
 583         } else {
 584                 struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp);
 585
 586                 ret = zcomp_decompress(zstrm, cmem, size, mem);
 587                 zcomp_stream_put(zram->comp);
 588         }
 589         zs_unmap_object(meta->mem_pool, handle);
 590         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 591
 592         /* Should NEVER happen. Return bio error if it does. */
 593         if (unlikely(ret)) {
 594                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 595                 return ret;
 596         }
 597
 598         return 0;
 599 }
 600
 601 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 602                           u32 index, int offset)
 603 {
 604         int ret;
 605         struct page *page;
 606         unsigned char *user_mem, *uncmem = NULL;
 607         struct zram_meta *meta = zram->meta;
 608         page = bvec->bv_page;
 609
 610         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 611         if (unlikely(!meta->table[index].handle) ||
 612                         zram_test_flag(meta, index, ZRAM_ZERO)) {
 613                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 614                 handle_zero_page(bvec);
 615                 return 0;
 616         }
 617         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 618
 619         if (is_partial_io(bvec))
 620                 /* Use  a temporary buffer to decompress the page */
 621                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 622
 623         user_mem = kmap_atomic(page);
 624         if (!is_partial_io(bvec))
 625                 uncmem = user_mem;
 626
 627         if (!uncmem) {
 628                 pr_err("Unable to allocate temp memory\n");
 629                 ret = -ENOMEM;
 630                 goto out_cleanup;
 631         }
 632
 633         ret = zram_decompress_page(zram, uncmem, index);
 634         /* Should NEVER happen. Return bio error if it does. */
 635         if (unlikely(ret))
 636                 goto out_cleanup;
 637
 638         if (is_partial_io(bvec))
 639                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 640                                 bvec->bv_len);
 641
 642         flush_dcache_page(page);
 643         ret = 0;
 644 out_cleanup:
 645         kunmap_atomic(user_mem);
 646         if (is_partial_io(bvec))
 647                 kfree(uncmem);
 648         return ret;
 649 }
 650
 651 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 652                            int offset)
 653 {
 654         int ret = 0;
 655         unsigned int clen;
 656         unsigned long handle = 0;
 657         struct page *page;
 658         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 659         struct zram_meta *meta = zram->meta;
 660         struct zcomp_strm *zstrm = NULL;
 661         unsigned long alloced_pages;
 662
 663         page = bvec->bv_page;
 664         if (is_partial_io(bvec)) {
 665                 /*
 666                  * This is a partial IO. We need to read the full page
 667                  * before to write the changes.
 668                  */
 669                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 670                 if (!uncmem) {
 671                         ret = -ENOMEM;
 672                         goto out;
 673                 }
 674                 ret = zram_decompress_page(zram, uncmem, index);
 675                 if (ret)
 676                         goto out;
 677         }
 678
 679 compress_again:
 680         user_mem = kmap_atomic(page);
 681         if (is_partial_io(bvec)) {
 682                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 683                        bvec->bv_len);
 684                 kunmap_atomic(user_mem);
 685                 user_mem = NULL;
 686         } else {
 687                 uncmem = user_mem;
 688         }
 689
 690         if (page_zero_filled(uncmem)) {
 691                 if (user_mem)
 692                         kunmap_atomic(user_mem);
 693                 /* Free memory associated with this sector now. */
 694                 bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 695                 zram_free_page(zram, index);
 696                 zram_set_flag(meta, index, ZRAM_ZERO);
 697                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 698
 699                 atomic64_inc(&zram->stats.zero_pages);
 700                 ret = 0;
 701                 goto out;
 702         }
 703
 704         zstrm = zcomp_stream_get(zram->comp);
 705         ret = zcomp_compress(zstrm, uncmem, &clen);
 706         if (!is_partial_io(bvec)) {
 707                 kunmap_atomic(user_mem);
 708                 user_mem = NULL;
 709                 uncmem = NULL;
 710         }
 711
 712         if (unlikely(ret)) {
 713                 pr_err("Compression failed! err=%d\n", ret);
 714                 goto out;
 715         }
 716
 717         src = zstrm->buffer;
 718         if (unlikely(clen > max_zpage_size)) {
 719                 clen = PAGE_SIZE;
 720                 if (is_partial_io(bvec))
 721                         src = uncmem;
 722         }
 723
 724         /*
 725          * handle allocation has 2 paths:
 726          * a) fast path is executed with preemption disabled (for
 727          *  per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
 728          *  since we can't sleep;
 729          * b) slow path enables preemption and attempts to allocate
 730          *  the page with __GFP_DIRECT_RECLAIM bit set. we have to
 731          *  put per-cpu compression stream and, thus, to re-do
 732          *  the compression once handle is allocated.
 733          *
 734          * if we have a 'non-null' handle here then we are coming
 735          * from the slow path and handle has already been allocated.
 736          */
 737         if (!handle)
 738                 handle = zs_malloc(meta->mem_pool, clen,
 739                                 __GFP_KSWAPD_RECLAIM |
 740                                 __GFP_NOWARN |
 741                                 __GFP_HIGHMEM |
 742                                 __GFP_MOVABLE);
 743         if (!handle) {
 744                 zcomp_stream_put(zram->comp);
 745                 zstrm = NULL;
 746
 747                 atomic64_inc(&zram->stats.writestall);
 748
 749                 handle = zs_malloc(meta->mem_pool, clen,
 750                                 GFP_NOIO | __GFP_HIGHMEM |
 751                                 __GFP_MOVABLE);
 752                 if (handle)
 753                         goto compress_again;
 754
 755                 pr_err("Error allocating memory for compressed page: %u, size=%u\n",
 756                         index, clen);
 757                 ret = -ENOMEM;
 758                 goto out;
 759         }
 760
 761         alloced_pages = zs_get_total_pages(meta->mem_pool);
 762         update_used_max(zram, alloced_pages);
 763
 764         if (zram->limit_pages && alloced_pages > zram->limit_pages) {
 765                 zs_free(meta->mem_pool, handle);
 766                 ret = -ENOMEM;
 767                 goto out;
 768         }
 769
 770         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
 771
 772         if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 773                 src = kmap_atomic(page);
 774                 copy_page(cmem, src);
 775                 kunmap_atomic(src);
 776         } else {
 777                 memcpy(cmem, src, clen);
 778         }
 779
 780         zcomp_stream_put(zram->comp);
 781         zstrm = NULL;
 782         zs_unmap_object(meta->mem_pool, handle);
 783
 784         /*
 785          * Free memory associated with this sector
 786          * before overwriting unused sectors.
 787          */
 788         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 789         zram_free_page(zram, index);
 790
 791         meta->table[index].handle = handle;
 792         zram_set_obj_size(meta, index, clen);
 793         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 794
 795         /* Update stats */
 796         atomic64_add(clen, &zram->stats.compr_data_size);
 797         atomic64_inc(&zram->stats.pages_stored);
 798 out:
 799         if (zstrm)
 800                 zcomp_stream_put(zram->comp);
 801         if (is_partial_io(bvec))
 802                 kfree(uncmem);
 803         return ret;
 804 }
 805
 806 /*
 807  * zram_bio_discard - handler on discard request
 808  * @index: physical block index in PAGE_SIZE units
 809  * @offset: byte offset within physical block
 810  */
 811 static void zram_bio_discard(struct zram *zram, u32 index,
 812                              int offset, struct bio *bio)
 813 {
 814         size_t n = bio->bi_iter.bi_size;
 815         struct zram_meta *meta = zram->meta;
 816
 817         /*
 818          * zram manages data in physical block size units. Because logical block
 819          * size isn't identical with physical block size on some arch, we
 820          * could get a discard request pointing to a specific offset within a
 821          * certain physical block.  Although we can handle this request by
 822          * reading that physiclal block and decompressing and partially zeroing
 823          * and re-compressing and then re-storing it, this isn't reasonable
 824          * because our intent with a discard request is to save memory.  So
 825          * skipping this logical block is appropriate here.
 826          */
 827         if (offset) {
 828                 if (n <= (PAGE_SIZE - offset))
 829                         return;
 830
 831                 n -= (PAGE_SIZE - offset);
 832                 index++;
 833         }
 834
 835         while (n >= PAGE_SIZE) {
 836                 bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 837                 zram_free_page(zram, index);
 838                 bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 839                 atomic64_inc(&zram->stats.notify_free);
 840                 index++;
 841                 n -= PAGE_SIZE;
 842         }
 843 }
 844
 845 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 846                         int offset, bool is_write)
 847 {
 848         unsigned long start_time = jiffies;
 849         int rw_acct = is_write ? REQ_OP_WRITE : REQ_OP_READ;
 850         int ret;
 851
 852         generic_start_io_acct(rw_acct, bvec->bv_len >> SECTOR_SHIFT,
 853                         &zram->disk->part0);
 854
 855         if (!is_write) {
 856                 atomic64_inc(&zram->stats.num_reads);
 857                 ret = zram_bvec_read(zram, bvec, index, offset);
 858         } else {
 859                 atomic64_inc(&zram->stats.num_writes);
 860                 ret = zram_bvec_write(zram, bvec, index, offset);
 861         }
 862
 863         generic_end_io_acct(rw_acct, &zram->disk->part0, start_time);
 864
 865         if (unlikely(ret)) {
 866                 if (!is_write)
 867                         atomic64_inc(&zram->stats.failed_reads);
 868                 else
 869                         atomic64_inc(&zram->stats.failed_writes);
 870         }
 871
 872         return ret;
 873 }
 874
 875 static void __zram_make_request(struct zram *zram, struct bio *bio)
 876 {
 877         int offset;
 878         u32 index;
 879         struct bio_vec bvec;
 880         struct bvec_iter iter;
 881
 882         index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
 883         offset = (bio->bi_iter.bi_sector &
 884                   (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 885
 886         if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
 887                 zram_bio_discard(zram, index, offset, bio);
 888                 bio_endio(bio);
 889                 return;
 890         }
 891
 892         bio_for_each_segment(bvec, bio, iter) {
 893                 int max_transfer_size = PAGE_SIZE - offset;
 894
 895                 if (bvec.bv_len > max_transfer_size) {
 896                         /*
 897                          * zram_bvec_rw() can only make operation on a single
 898                          * zram page. Split the bio vector.
 899                          */
 900                         struct bio_vec bv;
 901
 902                         bv.bv_page = bvec.bv_page;
 903                         bv.bv_len = max_transfer_size;
 904                         bv.bv_offset = bvec.bv_offset;
 905
 906                         if (zram_bvec_rw(zram, &bv, index, offset,
 907                                          op_is_write(bio_op(bio))) < 0)
 908                                 goto out;
 909
 910                         bv.bv_len = bvec.bv_len - max_transfer_size;
 911                         bv.bv_offset += max_transfer_size;
 912                         if (zram_bvec_rw(zram, &bv, index + 1, 0,
 913                                          op_is_write(bio_op(bio))) < 0)
 914                                 goto out;
 915                 } else
 916                         if (zram_bvec_rw(zram, &bvec, index, offset,
 917                                          op_is_write(bio_op(bio))) < 0)
 918                                 goto out;
 919
 920                 update_position(&index, &offset, &bvec);
 921         }
 922
 923         bio_endio(bio);
 924         return;
 925
 926 out:
 927         bio_io_error(bio);
 928 }
 929
 930 /*
 931  * Handler function for all zram I/O requests.
 932  */
 933 static blk_qc_t zram_make_request(struct request_queue *queue, struct bio *bio)
 934 {
 935         struct zram *zram = queue->queuedata;
 936
 937         if (unlikely(!zram_meta_get(zram)))
 938                 goto error;
 939
 940         blk_queue_split(queue, &bio, queue->bio_split);
 941
 942         if (!valid_io_request(zram, bio->bi_iter.bi_sector,
 943                                         bio->bi_iter.bi_size)) {
 944                 atomic64_inc(&zram->stats.invalid_io);
 945                 goto put_zram;
 946         }
 947
 948         __zram_make_request(zram, bio);
 949         zram_meta_put(zram);
 950         return BLK_QC_T_NONE;
 951 put_zram:
 952         zram_meta_put(zram);
 953 error:
 954         bio_io_error(bio);
 955         return BLK_QC_T_NONE;
 956 }
 957
 958 static void zram_slot_free_notify(struct block_device *bdev,
 959                                 unsigned long index)
 960 {
 961         struct zram *zram;
 962         struct zram_meta *meta;
 963
 964         zram = bdev->bd_disk->private_data;
 965         meta = zram->meta;
 966
 967         bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 968         zram_free_page(zram, index);
 969         bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
 970         atomic64_inc(&zram->stats.notify_free);
 971 }
 972
 973 static int zram_rw_page(struct block_device *bdev, sector_t sector,
 974                        struct page *page, bool is_write)
 975 {
 976         int offset, err = -EIO;
 977         u32 index;
 978         struct zram *zram;
 979         struct bio_vec bv;
 980
 981         zram = bdev->bd_disk->private_data;
 982         if (unlikely(!zram_meta_get(zram)))
 983                 goto out;
 984
 985         if (!valid_io_request(zram, sector, PAGE_SIZE)) {
 986                 atomic64_inc(&zram->stats.invalid_io);
 987                 err = -EINVAL;
 988                 goto put_zram;
 989         }
 990
 991         index = sector >> SECTORS_PER_PAGE_SHIFT;
 992         offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
 993
 994         bv.bv_page = page;
 995         bv.bv_len = PAGE_SIZE;
 996         bv.bv_offset = 0;
 997
 998         err = zram_bvec_rw(zram, &bv, index, offset, is_write);
 999 put_zram:
1000         zram_meta_put(zram);
1001 out:
1002         /*
1003          * If I/O fails, just return error(ie, non-zero) without
1004          * calling page_endio.
1005          * It causes resubmit the I/O with bio request by upper functions
1006          * of rw_page(e.g., swap_readpage, __swap_writepage) and
1007          * bio->bi_end_io does things to handle the error
1008          * (e.g., SetPageError, set_page_dirty and extra works).
1009          */
1010         if (err == 0)
1011                 page_endio(page, is_write, 0);
1012         return err;
1013 }
1014
1015 static void zram_reset_device(struct zram *zram)
1016 {
1017         struct zram_meta *meta;
1018         struct zcomp *comp;
1019         u64 disksize;
1020
1021         down_write(&zram->init_lock);
1022
1023         zram->limit_pages = 0;
1024
1025         if (!init_done(zram)) {
1026                 up_write(&zram->init_lock);
1027                 return;
1028         }
1029
1030         meta = zram->meta;
1031         comp = zram->comp;
1032         disksize = zram->disksize;
1033         /*
1034          * Refcount will go down to 0 eventually and r/w handler
1035          * cannot handle further I/O so it will bail out by
1036          * check zram_meta_get.
1037          */
1038         zram_meta_put(zram);
1039         /*
1040          * We want to free zram_meta in process context to avoid
1041          * deadlock between reclaim path and any other locks.
1042          */
1043         wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
1044
1045         /* Reset stats */
1046         memset(&zram->stats, 0, sizeof(zram->stats));
1047         zram->disksize = 0;
1048
1049         set_capacity(zram->disk, 0);
1050         part_stat_set_all(&zram->disk->part0, 0);
1051
1052         up_write(&zram->init_lock);
1053         /* I/O operation under all of CPU are done so let's free */
1054         zram_meta_free(meta, disksize);
1055         zcomp_destroy(comp);
1056 }
1057
1058 static ssize_t disksize_store(struct device *dev,
1059                 struct device_attribute *attr, const char *buf, size_t len)
1060 {
1061         u64 disksize;
1062         struct zcomp *comp;
1063         struct zram_meta *meta;
1064         struct zram *zram = dev_to_zram(dev);
1065         int err;
1066
1067         disksize = memparse(buf, NULL);
1068         if (!disksize)
1069                 return -EINVAL;
1070
1071         disksize = PAGE_ALIGN(disksize);
1072         meta = zram_meta_alloc(zram->disk->disk_name, disksize);
1073         if (!meta)
1074                 return -ENOMEM;
1075
1076         comp = zcomp_create(zram->compressor);
1077         if (IS_ERR(comp)) {
1078                 pr_err("Cannot initialise %s compressing backend\n",
1079                                 zram->compressor);
1080                 err = PTR_ERR(comp);
1081                 goto out_free_meta;
1082         }
1083
1084         down_write(&zram->init_lock);
1085         if (init_done(zram)) {
1086                 pr_info("Cannot change disksize for initialized device\n");
1087                 err = -EBUSY;
1088                 goto out_destroy_comp;
1089         }
1090
1091         init_waitqueue_head(&zram->io_done);
1092         atomic_set(&zram->refcount, 1);
1093         zram->meta = meta;
1094         zram->comp = comp;
1095         zram->disksize = disksize;
1096         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
1097         up_write(&zram->init_lock);
1098
1099         /*
1100          * Revalidate disk out of the init_lock to avoid lockdep splat.
1101          * It's okay because disk's capacity is protected by init_lock
1102          * so that revalidate_disk always sees up-to-date capacity.
1103          */
1104         revalidate_disk(zram->disk);
1105
1106         return len;
1107
1108 out_destroy_comp:
1109         up_write(&zram->init_lock);
1110         zcomp_destroy(comp);
1111 out_free_meta:
1112         zram_meta_free(meta, disksize);
1113         return err;
1114 }
1115
1116 static ssize_t reset_store(struct device *dev,
1117                 struct device_attribute *attr, const char *buf, size_t len)
1118 {
1119         int ret;
1120         unsigned short do_reset;
1121         struct zram *zram;
1122         struct block_device *bdev;
1123
1124         ret = kstrtou16(buf, 10, &do_reset);
1125         if (ret)
1126                 return ret;
1127
1128         if (!do_reset)
1129                 return -EINVAL;
1130
1131         zram = dev_to_zram(dev);
1132         bdev = bdget_disk(zram->disk, 0);
1133         if (!bdev)
1134                 return -ENOMEM;
1135
1136         mutex_lock(&bdev->bd_mutex);
1137         /* Do not reset an active device or claimed device */
1138         if (bdev->bd_openers || zram->claim) {
1139                 mutex_unlock(&bdev->bd_mutex);
1140                 bdput(bdev);
1141                 return -EBUSY;
1142         }
1143
1144         /* From now on, anyone can't open /dev/zram[0-9] */
1145         zram->claim = true;
1146         mutex_unlock(&bdev->bd_mutex);
1147
1148         /* Make sure all the pending I/O are finished */
1149         fsync_bdev(bdev);
1150         zram_reset_device(zram);
1151         revalidate_disk(zram->disk);
1152         bdput(bdev);
1153
1154         mutex_lock(&bdev->bd_mutex);
1155         zram->claim = false;
1156         mutex_unlock(&bdev->bd_mutex);
1157
1158         return len;
1159 }
1160
1161 static int zram_open(struct block_device *bdev, fmode_t mode)
1162 {
1163         int ret = 0;
1164         struct zram *zram;
1165
1166         WARN_ON(!mutex_is_locked(&bdev->bd_mutex));
1167
1168         zram = bdev->bd_disk->private_data;
1169         /* zram was claimed to reset so open request fails */
1170         if (zram->claim)
1171                 ret = -EBUSY;
1172
1173         return ret;
1174 }
1175
1176 static const struct block_device_operations zram_devops = {
1177         .open = zram_open,
1178         .swap_slot_free_notify = zram_slot_free_notify,
1179         .rw_page = zram_rw_page,
1180         .owner = THIS_MODULE
1181 };
1182
1183 static DEVICE_ATTR_WO(compact);
1184 static DEVICE_ATTR_RW(disksize);
1185 static DEVICE_ATTR_RO(initstate);
1186 static DEVICE_ATTR_WO(reset);
1187 static DEVICE_ATTR_RO(orig_data_size);
1188 static DEVICE_ATTR_RO(mem_used_total);
1189 static DEVICE_ATTR_RW(mem_limit);
1190 static DEVICE_ATTR_RW(mem_used_max);
1191 static DEVICE_ATTR_RW(max_comp_streams);
1192 static DEVICE_ATTR_RW(comp_algorithm);
1193
1194 static struct attribute *zram_disk_attrs[] = {
1195         &dev_attr_disksize.attr,
1196         &dev_attr_initstate.attr,
1197         &dev_attr_reset.attr,
1198         &dev_attr_num_reads.attr,
1199         &dev_attr_num_writes.attr,
1200         &dev_attr_failed_reads.attr,
1201         &dev_attr_failed_writes.attr,
1202         &dev_attr_compact.attr,
1203         &dev_attr_invalid_io.attr,
1204         &dev_attr_notify_free.attr,
1205         &dev_attr_zero_pages.attr,
1206         &dev_attr_orig_data_size.attr,
1207         &dev_attr_compr_data_size.attr,
1208         &dev_attr_mem_used_total.attr,
1209         &dev_attr_mem_limit.attr,
1210         &dev_attr_mem_used_max.attr,
1211         &dev_attr_max_comp_streams.attr,
1212         &dev_attr_comp_algorithm.attr,
1213         &dev_attr_io_stat.attr,
1214         &dev_attr_mm_stat.attr,
1215         &dev_attr_debug_stat.attr,
1216         NULL,
1217 };
1218
1219 static struct attribute_group zram_disk_attr_group = {
1220         .attrs = zram_disk_attrs,
1221 };
1222
1223 /*
1224  * Allocate and initialize new zram device. the function returns
1225  * '>= 0' device_id upon success, and negative value otherwise.
1226  */
1227 static int zram_add(void)
1228 {
1229         struct zram *zram;
1230         struct request_queue *queue;
1231         int ret, device_id;
1232
1233         zram = kzalloc(sizeof(struct zram), GFP_KERNEL);
1234         if (!zram)
1235                 return -ENOMEM;
1236
1237         ret = idr_alloc(&zram_index_idr, zram, 0, 0, GFP_KERNEL);
1238         if (ret < 0)
1239                 goto out_free_dev;
1240         device_id = ret;
1241
1242         init_rwsem(&zram->init_lock);
1243
1244         queue = blk_alloc_queue(GFP_KERNEL);
1245         if (!queue) {
1246                 pr_err("Error allocating disk queue for device %d\n",
1247                         device_id);
1248                 ret = -ENOMEM;
1249                 goto out_free_idr;
1250         }
1251
1252         blk_queue_make_request(queue, zram_make_request);
1253
1254         /* gendisk structure */
1255         zram->disk = alloc_disk(1);
1256         if (!zram->disk) {
1257                 pr_err("Error allocating disk structure for device %d\n",
1258                         device_id);
1259                 ret = -ENOMEM;
1260                 goto out_free_queue;
1261         }
1262
1263         zram->disk->major = zram_major;
1264         zram->disk->first_minor = device_id;
1265         zram->disk->fops = &zram_devops;
1266         zram->disk->queue = queue;
1267         zram->disk->queue->queuedata = zram;
1268         zram->disk->private_data = zram;
1269         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
1270
1271         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
1272         set_capacity(zram->disk, 0);
1273         /* zram devices sort of resembles non-rotational disks */
1274         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
1275         queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);
1276         /*
1277          * To ensure that we always get PAGE_SIZE aligned
1278          * and n*PAGE_SIZED sized I/O requests.
1279          */
1280         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
1281         blk_queue_logical_block_size(zram->disk->queue,
1282                                         ZRAM_LOGICAL_BLOCK_SIZE);
1283         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
1284         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
1285         zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
1286         blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
1287         /*
1288          * zram_bio_discard() will clear all logical blocks if logical block
1289          * size is identical with physical block size(PAGE_SIZE). But if it is
1290          * different, we will skip discarding some parts of logical blocks in
1291          * the part of the request range which isn't aligned to physical block
1292          * size.  So we can't ensure that all discarded logical blocks are
1293          * zeroed.
1294          */
1295         if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
1296                 zram->disk->queue->limits.discard_zeroes_data = 1;
1297         else
1298                 zram->disk->queue->limits.discard_zeroes_data = 0;
1299         queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
1300
1301         add_disk(zram->disk);
1302
1303         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
1304                                 &zram_disk_attr_group);
1305         if (ret < 0) {
1306                 pr_err("Error creating sysfs group for device %d\n",
1307                                 device_id);
1308                 goto out_free_disk;
1309         }
1310         strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
1311         zram->meta = NULL;
1312
1313         pr_info("Added device: %s\n", zram->disk->disk_name);
1314         return device_id;
1315
1316 out_free_disk:
1317         del_gendisk(zram->disk);
1318         put_disk(zram->disk);
1319 out_free_queue:
1320         blk_cleanup_queue(queue);
1321 out_free_idr:
1322         idr_remove(&zram_index_idr, device_id);
1323 out_free_dev:
1324         kfree(zram);
1325         return ret;
1326 }
1327
1328 static int zram_remove(struct zram *zram)
1329 {
1330         struct block_device *bdev;
1331
1332         bdev = bdget_disk(zram->disk, 0);
1333         if (!bdev)
1334                 return -ENOMEM;
1335
1336         mutex_lock(&bdev->bd_mutex);
1337         if (bdev->bd_openers || zram->claim) {
1338                 mutex_unlock(&bdev->bd_mutex);
1339                 bdput(bdev);
1340                 return -EBUSY;
1341         }
1342
1343         zram->claim = true;
1344         mutex_unlock(&bdev->bd_mutex);
1345
1346         /*
1347          * Remove sysfs first, so no one will perform a disksize
1348          * store while we destroy the devices. This also helps during
1349          * hot_remove -- zram_reset_device() is the last holder of
1350          * ->init_lock, no later/concurrent disksize_store() or any
1351          * other sysfs handlers are possible.
1352          */
1353         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
1354                         &zram_disk_attr_group);
1355
1356         /* Make sure all the pending I/O are finished */
1357         fsync_bdev(bdev);
1358         zram_reset_device(zram);
1359         bdput(bdev);
1360
1361         pr_info("Removed device: %s\n", zram->disk->disk_name);
1362
1363         blk_cleanup_queue(zram->disk->queue);
1364         del_gendisk(zram->disk);
1365         put_disk(zram->disk);
1366         kfree(zram);
1367         return 0;
1368 }
1369
1370 /* zram-control sysfs attributes */
1371 static ssize_t hot_add_show(struct class *class,
1372                         struct class_attribute *attr,
1373                         char *buf)
1374 {
1375         int ret;
1376
1377         mutex_lock(&zram_index_mutex);
1378         ret = zram_add();
1379         mutex_unlock(&zram_index_mutex);
1380
1381         if (ret < 0)
1382                 return ret;
1383         return scnprintf(buf, PAGE_SIZE, "%d\n", ret);
1384 }
1385
1386 static ssize_t hot_remove_store(struct class *class,
1387                         struct class_attribute *attr,
1388                         const char *buf,
1389                         size_t count)
1390 {
1391         struct zram *zram;
1392         int ret, dev_id;
1393
1394         /* dev_id is gendisk->first_minor, which is `int' */
1395         ret = kstrtoint(buf, 10, &dev_id);
1396         if (ret)
1397                 return ret;
1398         if (dev_id < 0)
1399                 return -EINVAL;
1400
1401         mutex_lock(&zram_index_mutex);
1402
1403         zram = idr_find(&zram_index_idr, dev_id);
1404         if (zram) {
1405                 ret = zram_remove(zram);
1406                 idr_remove(&zram_index_idr, dev_id);
1407         } else {
1408                 ret = -ENODEV;
1409         }
1410
1411         mutex_unlock(&zram_index_mutex);
1412         return ret ? ret : count;
1413 }
1414
1415 static struct class_attribute zram_control_class_attrs[] = {
1416         __ATTR_RO(hot_add),
1417         __ATTR_WO(hot_remove),
1418         __ATTR_NULL,
1419 };
1420
1421 static struct class zram_control_class = {
1422         .name           = "zram-control",
1423         .owner          = THIS_MODULE,
1424         .class_attrs    = zram_control_class_attrs,
1425 };
1426
1427 static int zram_remove_cb(int id, void *ptr, void *data)
1428 {
1429         zram_remove(ptr);
1430         return 0;
1431 }
1432
1433 static void destroy_devices(void)
1434 {
1435         class_unregister(&zram_control_class);
1436         idr_for_each(&zram_index_idr, &zram_remove_cb, NULL);
1437         idr_destroy(&zram_index_idr);
1438         unregister_blkdev(zram_major, "zram");
1439 }
1440
1441 static int __init zram_init(void)
1442 {
1443         int ret;
1444
1445         ret = class_register(&zram_control_class);
1446         if (ret) {
1447                 pr_err("Unable to register zram-control class\n");
1448                 return ret;
1449         }
1450
1451         zram_major = register_blkdev(0, "zram");
1452         if (zram_major <= 0) {
1453                 pr_err("Unable to get major number\n");
1454                 class_unregister(&zram_control_class);
1455                 return -EBUSY;
1456         }
1457
1458         while (num_devices != 0) {
1459                 mutex_lock(&zram_index_mutex);
1460                 ret = zram_add();
1461                 mutex_unlock(&zram_index_mutex);
1462                 if (ret < 0)
1463                         goto out_error;
1464                 num_devices--;
1465         }
1466
1467         return 0;
1468
1469 out_error:
1470         destroy_devices();
1471         return ret;
1472 }
1473
1474 static void __exit zram_exit(void)
1475 {
1476         destroy_devices();
1477 }
1478
1479 module_init(zram_init);
1480 module_exit(zram_exit);
1481
1482 module_param(num_devices, uint, 0);
1483 MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
1484
1485 MODULE_LICENSE("Dual BSD/GPL");
1486 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
1487 MODULE_DESCRIPTION("Compressed RAM Block Device");