kernel/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 static ssize_t max_comp_streams_show(struct device *dev,
 308                 struct device_attribute *attr, char *buf)
 309 {
 310         int val;
 311         struct zram *zram = dev_to_zram(dev);
 312
 313         down_read(&zram->init_lock);
 314         val = zram->max_comp_streams;
 315         up_read(&zram->init_lock);
 316
 317         return scnprintf(buf, PAGE_SIZE, "%d\n", val);
 318 }
 319
 320 static ssize_t max_comp_streams_store(struct device *dev,
 321                 struct device_attribute *attr, const char *buf, size_t len)
 322 {
 323         int num;
 324         struct zram *zram = dev_to_zram(dev);
 325         int ret;
 326
 327         ret = kstrtoint(buf, 0, &num);
 328         if (ret < 0)
 329                 return ret;
 330         if (num < 1)
 331                 return -EINVAL;
 332
 333         down_write(&zram->init_lock);
 334         if (init_done(zram)) {
 335                 if (!zcomp_set_max_streams(zram->comp, num)) {
 336                         pr_info("Cannot change max compression streams\n");
 337                         ret = -EINVAL;
 338                         goto out;
 339                 }
 340         }
 341
 342         zram->max_comp_streams = num;
 343         ret = len;
 344 out:
 345         up_write(&zram->init_lock);
 346         return ret;
 347 }
 348
 349 static ssize_t comp_algorithm_show(struct device *dev,
 350                 struct device_attribute *attr, char *buf)
 351 {
 352         size_t sz;
 353         struct zram *zram = dev_to_zram(dev);
 354
 355         down_read(&zram->init_lock);
 356         sz = zcomp_available_show(zram->compressor, buf);
 357         up_read(&zram->init_lock);
 358
 359         return sz;
 360 }
 361
 362 static ssize_t comp_algorithm_store(struct device *dev,
 363                 struct device_attribute *attr, const char *buf, size_t len)
 364 {
 365         struct zram *zram = dev_to_zram(dev);
 366         size_t sz;
 367
 368         if (!zcomp_available_algorithm(buf))
 369                 return -EINVAL;
 370
 371         down_write(&zram->init_lock);
 372         if (init_done(zram)) {
 373                 up_write(&zram->init_lock);
 374                 pr_info("Can't change algorithm for initialized device\n");
 375                 return -EBUSY;
 376         }
 377         strlcpy(zram->compressor, buf, sizeof(zram->compressor));
 378
 379         /* ignore trailing newline */
 380         sz = strlen(zram->compressor);
 381         if (sz > 0 && zram->compressor[sz - 1] == '\n')
 382                 zram->compressor[sz - 1] = 0x00;
 383
 384         up_write(&zram->init_lock);
 385         return len;
 386 }
 387
 388 static ssize_t compact_store(struct device *dev,
 389                 struct device_attribute *attr, const char *buf, size_t len)
 390 {
 391         struct zram *zram = dev_to_zram(dev);
 392         struct zram_meta *meta;
 393
 394         down_read(&zram->init_lock);
 395         if (!init_done(zram)) {
 396                 up_read(&zram->init_lock);
 397                 return -EINVAL;
 398         }
 399
 400         meta = zram->meta;
 401         zs_compact(meta->mem_pool);
 402         up_read(&zram->init_lock);
 403
 404         return len;
 405 }
 406
 407 static ssize_t io_stat_show(struct device *dev,
 408                 struct device_attribute *attr, char *buf)
 409 {
 410         struct zram *zram = dev_to_zram(dev);
 411         ssize_t ret;
 412
 413         down_read(&zram->init_lock);
 414         ret = scnprintf(buf, PAGE_SIZE,
 415                         "%8llu %8llu %8llu %8llu\n",
 416                         (u64)atomic64_read(&zram->stats.failed_reads),
 417                         (u64)atomic64_read(&zram->stats.failed_writes),
 418                         (u64)atomic64_read(&zram->stats.invalid_io),
 419                         (u64)atomic64_read(&zram->stats.notify_free));
 420         up_read(&zram->init_lock);
 421
 422         return ret;
 423 }
 424
 425 static ssize_t mm_stat_show(struct device *dev,
 426                 struct device_attribute *attr, char *buf)
 427 {
 428         struct zram *zram = dev_to_zram(dev);
 429         struct zs_pool_stats pool_stats;
 430         u64 orig_size, mem_used = 0;
 431         long max_used;
 432         ssize_t ret;
 433
 434         memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats));
 435
 436         down_read(&zram->init_lock);
 437         if (init_done(zram)) {
 438                 mem_used = zs_get_total_pages(zram->meta->mem_pool);
 439                 zs_pool_stats(zram->meta->mem_pool, &pool_stats);
 440         }
 441
 442         orig_size = atomic64_read(&zram->stats.pages_stored);
 443         max_used = atomic_long_read(&zram->stats.max_used_pages);
 444
 445         ret = scnprintf(buf, PAGE_SIZE,
 446                         "%8llu %8llu %8llu %8lu %8ld %8llu %8lu\n",
 447                         orig_size << PAGE_SHIFT,
 448                         (u64)atomic64_read(&zram->stats.compr_data_size),
 449                         mem_used << PAGE_SHIFT,
 450                         zram->limit_pages << PAGE_SHIFT,
 451                         max_used << PAGE_SHIFT,
 452                         (u64)atomic64_read(&zram->stats.zero_pages),
 453                         pool_stats.pages_compacted);
 454         up_read(&zram->init_lock);
 455
 456         return ret;
 457 }
 458
 459 static DEVICE_ATTR_RO(io_stat);
 460 static DEVICE_ATTR_RO(mm_stat);
 461 ZRAM_ATTR_RO(num_reads);
 462 ZRAM_ATTR_RO(num_writes);
 463 ZRAM_ATTR_RO(failed_reads);
 464 ZRAM_ATTR_RO(failed_writes);
 465 ZRAM_ATTR_RO(invalid_io);
 466 ZRAM_ATTR_RO(notify_free);
 467 ZRAM_ATTR_RO(zero_pages);
 468 ZRAM_ATTR_RO(compr_data_size);
 469
 470 static inline bool zram_meta_get(struct zram *zram)
 471 {
 472         if (atomic_inc_not_zero(&zram->refcount))
 473                 return true;
 474         return false;
 475 }
 476
 477 static inline void zram_meta_put(struct zram *zram)
 478 {
 479         atomic_dec(&zram->refcount);
 480 }
 481
 482 static void zram_meta_free(struct zram_meta *meta, u64 disksize)
 483 {
 484         size_t num_pages = disksize >> PAGE_SHIFT;
 485         size_t index;
 486
 487         /* Free all pages that are still in this zram device */
 488         for (index = 0; index < num_pages; index++) {
 489                 unsigned long handle = meta->table[index].handle;
 490
 491                 if (!handle)
 492                         continue;
 493
 494                 zs_free(meta->mem_pool, handle);
 495         }
 496
 497         zs_destroy_pool(meta->mem_pool);
 498         vfree(meta->table);
 499         kfree(meta);
 500 }
 501
 502 static struct zram_meta *zram_meta_alloc(char *pool_name, u64 disksize)
 503 {
 504         size_t num_pages;
 505         struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 506
 507         if (!meta)
 508                 return NULL;
 509
 510         num_pages = disksize >> PAGE_SHIFT;
 511         meta->table = vzalloc(num_pages * sizeof(*meta->table));
 512         if (!meta->table) {
 513                 pr_err("Error allocating zram address table\n");
 514                 goto out_error;
 515         }
 516
 517         meta->mem_pool = zs_create_pool(pool_name, GFP_NOIO | __GFP_HIGHMEM);
 518         if (!meta->mem_pool) {
 519                 pr_err("Error creating memory pool\n");
 520                 goto out_error;
 521         }
 522
 523         zram_meta_init_table_locks(meta, disksize);
 524
 525         return meta;
 526
 527 out_error:
 528         vfree(meta->table);
 529         kfree(meta);
 530         return NULL;
 531 }
 532
 533 /*
 534  * To protect concurrent access to the same index entry,
 535  * caller should hold this table index entry's bit_spinlock to
 536  * indicate this index entry is accessing.
 537  */
 538 static void zram_free_page(struct zram *zram, size_t index)
 539 {
 540         struct zram_meta *meta = zram->meta;
 541         unsigned long handle = meta->table[index].handle;
 542
 543         if (unlikely(!handle)) {
 544                 /*
 545                  * No memory is allocated for zero filled pages.
 546                  * Simply clear zero page flag.
 547                  */
 548                 if (zram_test_flag(meta, index, ZRAM_ZERO)) {
 549                         zram_clear_flag(meta, index, ZRAM_ZERO);
 550                         atomic64_dec(&zram->stats.zero_pages);
 551                 }
 552                 return;
 553         }
 554
 555         zs_free(meta->mem_pool, handle);
 556
 557         atomic64_sub(zram_get_obj_size(meta, index),
 558                         &zram->stats.compr_data_size);
 559         atomic64_dec(&zram->stats.pages_stored);
 560
 561         meta->table[index].handle = 0;
 562         zram_set_obj_size(meta, index, 0);
 563 }
 564
 565 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 566 {
 567         int ret = 0;
 568         unsigned char *cmem;
 569         struct zram_meta *meta = zram->meta;
 570         unsigned long handle;
 571         size_t size;
 572
 573         zram_lock_table(&meta->table[index]);
 574         handle = meta->table[index].handle;
 575         size = zram_get_obj_size(meta, index);
 576
 577         if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
 578                 zram_unlock_table(&meta->table[index]);
 579                 clear_page(mem);
 580                 return 0;
 581         }
 582
 583         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 584         if (size == PAGE_SIZE)
 585                 copy_page(mem, cmem);
 586         else
 587                 ret = zcomp_decompress(zram->comp, cmem, size, mem);
 588         zs_unmap_object(meta->mem_pool, handle);
 589         zram_unlock_table(&meta->table[index]);
 590
 591         /* Should NEVER happen. Return bio error if it does. */
 592         if (unlikely(ret)) {
 593                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 594                 return ret;
 595         }
 596
 597         return 0;
 598 }
 599
 600 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 601                           u32 index, int offset)
 602 {
 603         int ret;
 604         struct page *page;
 605         unsigned char *user_mem, *uncmem = NULL;
 606         struct zram_meta *meta = zram->meta;
 607         page = bvec->bv_page;
 608
 609         zram_lock_table(&meta->table[index]);
 610         if (unlikely(!meta->table[index].handle) ||
 611                         zram_test_flag(meta, index, ZRAM_ZERO)) {
 612                 zram_unlock_table(&meta->table[index]);
 613                 handle_zero_page(bvec);
 614                 return 0;
 615         }
 616         zram_unlock_table(&meta->table[index]);
 617
 618         if (is_partial_io(bvec))
 619                 /* Use  a temporary buffer to decompress the page */
 620                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 621
 622         user_mem = kmap_atomic(page);
 623         if (!is_partial_io(bvec))
 624                 uncmem = user_mem;
 625
 626         if (!uncmem) {
 627                 pr_err("Unable to allocate temp memory\n");
 628                 ret = -ENOMEM;
 629                 goto out_cleanup;
 630         }
 631
 632         ret = zram_decompress_page(zram, uncmem, index);
 633         /* Should NEVER happen. Return bio error if it does. */
 634         if (unlikely(ret))
 635                 goto out_cleanup;
 636
 637         if (is_partial_io(bvec))
 638                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 639                                 bvec->bv_len);
 640
 641         flush_dcache_page(page);
 642         ret = 0;
 643 out_cleanup:
 644         kunmap_atomic(user_mem);
 645         if (is_partial_io(bvec))
 646                 kfree(uncmem);
 647         return ret;
 648 }
 649
 650 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 651                            int offset)
 652 {
 653         int ret = 0;
 654         size_t clen;
 655         unsigned long handle;
 656         struct page *page;
 657         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 658         struct zram_meta *meta = zram->meta;
 659         struct zcomp_strm *zstrm = NULL;
 660         unsigned long alloced_pages;
 661
 662         page = bvec->bv_page;
 663         if (is_partial_io(bvec)) {
 664                 /*
 665                  * This is a partial IO. We need to read the full page
 666                  * before to write the changes.
 667                  */
 668                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 669                 if (!uncmem) {
 670                         ret = -ENOMEM;
 671                         goto out;
 672                 }
 673                 ret = zram_decompress_page(zram, uncmem, index);
 674                 if (ret)
 675                         goto out;
 676         }
 677
 678         zstrm = zcomp_strm_find(zram->comp);
 679         user_mem = kmap_atomic(page);
 680
 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                 zram_lock_table(&meta->table[index]);
 695                 zram_free_page(zram, index);
 696                 zram_set_flag(meta, index, ZRAM_ZERO);
 697                 zram_unlock_table(&meta->table[index]);
 698
 699                 atomic64_inc(&zram->stats.zero_pages);
 700                 ret = 0;
 701                 goto out;
 702         }
 703
 704         ret = zcomp_compress(zram->comp, zstrm, uncmem, &clen);
 705         if (!is_partial_io(bvec)) {
 706                 kunmap_atomic(user_mem);
 707                 user_mem = NULL;
 708                 uncmem = NULL;
 709         }
 710
 711         if (unlikely(ret)) {
 712                 pr_err("Compression failed! err=%d\n", ret);
 713                 goto out;
 714         }
 715         src = zstrm->buffer;
 716         if (unlikely(clen > max_zpage_size)) {
 717                 clen = PAGE_SIZE;
 718                 if (is_partial_io(bvec))
 719                         src = uncmem;
 720         }
 721
 722         handle = zs_malloc(meta->mem_pool, clen);
 723         if (!handle) {
 724                 pr_err("Error allocating memory for compressed page: %u, size=%zu\n",
 725                         index, clen);
 726                 ret = -ENOMEM;
 727                 goto out;
 728         }
 729
 730         alloced_pages = zs_get_total_pages(meta->mem_pool);
 731         update_used_max(zram, alloced_pages);
 732
 733         if (zram->limit_pages && alloced_pages > zram->limit_pages) {
 734                 zs_free(meta->mem_pool, handle);
 735                 ret = -ENOMEM;
 736                 goto out;
 737         }
 738
 739         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
 740
 741         if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 742                 src = kmap_atomic(page);
 743                 copy_page(cmem, src);
 744                 kunmap_atomic(src);
 745         } else {
 746                 memcpy(cmem, src, clen);
 747         }
 748
 749         zcomp_strm_release(zram->comp, zstrm);
 750         zstrm = NULL;
 751         zs_unmap_object(meta->mem_pool, handle);
 752
 753         /*
 754          * Free memory associated with this sector
 755          * before overwriting unused sectors.
 756          */
 757         zram_lock_table(&meta->table[index]);
 758         zram_free_page(zram, index);
 759
 760         meta->table[index].handle = handle;
 761         zram_set_obj_size(meta, index, clen);
 762         zram_unlock_table(&meta->table[index]);
 763
 764         /* Update stats */
 765         atomic64_add(clen, &zram->stats.compr_data_size);
 766         atomic64_inc(&zram->stats.pages_stored);
 767 out:
 768         if (zstrm)
 769                 zcomp_strm_release(zram->comp, zstrm);
 770         if (is_partial_io(bvec))
 771                 kfree(uncmem);
 772         return ret;
 773 }
 774
 775 /*
 776  * zram_bio_discard - handler on discard request
 777  * @index: physical block index in PAGE_SIZE units
 778  * @offset: byte offset within physical block
 779  */
 780 static void zram_bio_discard(struct zram *zram, u32 index,
 781                              int offset, struct bio *bio)
 782 {
 783         size_t n = bio->bi_iter.bi_size;
 784         struct zram_meta *meta = zram->meta;
 785
 786         /*
 787          * zram manages data in physical block size units. Because logical block
 788          * size isn't identical with physical block size on some arch, we
 789          * could get a discard request pointing to a specific offset within a
 790          * certain physical block.  Although we can handle this request by
 791          * reading that physiclal block and decompressing and partially zeroing
 792          * and re-compressing and then re-storing it, this isn't reasonable
 793          * because our intent with a discard request is to save memory.  So
 794          * skipping this logical block is appropriate here.
 795          */
 796         if (offset) {
 797                 if (n <= (PAGE_SIZE - offset))
 798                         return;
 799
 800                 n -= (PAGE_SIZE - offset);
 801                 index++;
 802         }
 803
 804         while (n >= PAGE_SIZE) {
 805                 zram_lock_table(&meta->table[index]);
 806                 zram_free_page(zram, index);
 807                 zram_unlock_table(&meta->table[index]);
 808                 atomic64_inc(&zram->stats.notify_free);
 809                 index++;
 810                 n -= PAGE_SIZE;
 811         }
 812 }
 813
 814 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 815                         int offset, int rw)
 816 {
 817         unsigned long start_time = jiffies;
 818         int ret;
 819
 820         generic_start_io_acct(rw, bvec->bv_len >> SECTOR_SHIFT,
 821                         &zram->disk->part0);
 822
 823         if (rw == READ) {
 824                 atomic64_inc(&zram->stats.num_reads);
 825                 ret = zram_bvec_read(zram, bvec, index, offset);
 826         } else {
 827                 atomic64_inc(&zram->stats.num_writes);
 828                 ret = zram_bvec_write(zram, bvec, index, offset);
 829         }
 830
 831         generic_end_io_acct(rw, &zram->disk->part0, start_time);
 832
 833         if (unlikely(ret)) {
 834                 if (rw == READ)
 835                         atomic64_inc(&zram->stats.failed_reads);
 836                 else
 837                         atomic64_inc(&zram->stats.failed_writes);
 838         }
 839
 840         return ret;
 841 }
 842
 843 static void __zram_make_request(struct zram *zram, struct bio *bio)
 844 {
 845         int offset, rw;
 846         u32 index;
 847         struct bio_vec bvec;
 848         struct bvec_iter iter;
 849
 850         index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
 851         offset = (bio->bi_iter.bi_sector &
 852                   (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 853
 854         if (unlikely(bio->bi_rw & REQ_DISCARD)) {
 855                 zram_bio_discard(zram, index, offset, bio);
 856                 bio_endio(bio);
 857                 return;
 858         }
 859
 860         rw = bio_data_dir(bio);
 861         bio_for_each_segment(bvec, bio, iter) {
 862                 int max_transfer_size = PAGE_SIZE - offset;
 863
 864                 if (bvec.bv_len > max_transfer_size) {
 865                         /*
 866                          * zram_bvec_rw() can only make operation on a single
 867                          * zram page. Split the bio vector.
 868                          */
 869                         struct bio_vec bv;
 870
 871                         bv.bv_page = bvec.bv_page;
 872                         bv.bv_len = max_transfer_size;
 873                         bv.bv_offset = bvec.bv_offset;
 874
 875                         if (zram_bvec_rw(zram, &bv, index, offset, rw) < 0)
 876                                 goto out;
 877
 878                         bv.bv_len = bvec.bv_len - max_transfer_size;
 879                         bv.bv_offset += max_transfer_size;
 880                         if (zram_bvec_rw(zram, &bv, index + 1, 0, rw) < 0)
 881                                 goto out;
 882                 } else
 883                         if (zram_bvec_rw(zram, &bvec, index, offset, rw) < 0)
 884                                 goto out;
 885
 886                 update_position(&index, &offset, &bvec);
 887         }
 888
 889         bio_endio(bio);
 890         return;
 891
 892 out:
 893         bio_io_error(bio);
 894 }
 895
 896 /*
 897  * Handler function for all zram I/O requests.
 898  */
 899 static blk_qc_t zram_make_request(struct request_queue *queue, struct bio *bio)
 900 {
 901         struct zram *zram = queue->queuedata;
 902
 903         if (unlikely(!zram_meta_get(zram)))
 904                 goto error;
 905
 906         blk_queue_split(queue, &bio, queue->bio_split);
 907
 908         if (!valid_io_request(zram, bio->bi_iter.bi_sector,
 909                                         bio->bi_iter.bi_size)) {
 910                 atomic64_inc(&zram->stats.invalid_io);
 911                 goto put_zram;
 912         }
 913
 914         __zram_make_request(zram, bio);
 915         zram_meta_put(zram);
 916         return BLK_QC_T_NONE;
 917 put_zram:
 918         zram_meta_put(zram);
 919 error:
 920         bio_io_error(bio);
 921         return BLK_QC_T_NONE;
 922 }
 923
 924 static void zram_slot_free_notify(struct block_device *bdev,
 925                                 unsigned long index)
 926 {
 927         struct zram *zram;
 928         struct zram_meta *meta;
 929
 930         zram = bdev->bd_disk->private_data;
 931         meta = zram->meta;
 932
 933         zram_lock_table(&meta->table[index]);
 934         zram_free_page(zram, index);
 935         zram_unlock_table(&meta->table[index]);
 936         atomic64_inc(&zram->stats.notify_free);
 937 }
 938
 939 static int zram_rw_page(struct block_device *bdev, sector_t sector,
 940                        struct page *page, int rw)
 941 {
 942         int offset, err = -EIO;
 943         u32 index;
 944         struct zram *zram;
 945         struct bio_vec bv;
 946
 947         zram = bdev->bd_disk->private_data;
 948         if (unlikely(!zram_meta_get(zram)))
 949                 goto out;
 950
 951         if (!valid_io_request(zram, sector, PAGE_SIZE)) {
 952                 atomic64_inc(&zram->stats.invalid_io);
 953                 err = -EINVAL;
 954                 goto put_zram;
 955         }
 956
 957         index = sector >> SECTORS_PER_PAGE_SHIFT;
 958         offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
 959
 960         bv.bv_page = page;
 961         bv.bv_len = PAGE_SIZE;
 962         bv.bv_offset = 0;
 963
 964         err = zram_bvec_rw(zram, &bv, index, offset, rw);
 965 put_zram:
 966         zram_meta_put(zram);
 967 out:
 968         /*
 969          * If I/O fails, just return error(ie, non-zero) without
 970          * calling page_endio.
 971          * It causes resubmit the I/O with bio request by upper functions
 972          * of rw_page(e.g., swap_readpage, __swap_writepage) and
 973          * bio->bi_end_io does things to handle the error
 974          * (e.g., SetPageError, set_page_dirty and extra works).
 975          */
 976         if (err == 0)
 977                 page_endio(page, rw, 0);
 978         return err;
 979 }
 980
 981 static void zram_reset_device(struct zram *zram)
 982 {
 983         struct zram_meta *meta;
 984         struct zcomp *comp;
 985         u64 disksize;
 986
 987         down_write(&zram->init_lock);
 988
 989         zram->limit_pages = 0;
 990
 991         if (!init_done(zram)) {
 992                 up_write(&zram->init_lock);
 993                 return;
 994         }
 995
 996         meta = zram->meta;
 997         comp = zram->comp;
 998         disksize = zram->disksize;
 999         /*
1000          * Refcount will go down to 0 eventually and r/w handler
1001          * cannot handle further I/O so it will bail out by
1002          * check zram_meta_get.
1003          */
1004         zram_meta_put(zram);
1005         /*
1006          * We want to free zram_meta in process context to avoid
1007          * deadlock between reclaim path and any other locks.
1008          */
1009         wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
1010
1011         /* Reset stats */
1012         memset(&zram->stats, 0, sizeof(zram->stats));
1013         zram->disksize = 0;
1014         zram->max_comp_streams = 1;
1015
1016         set_capacity(zram->disk, 0);
1017         part_stat_set_all(&zram->disk->part0, 0);
1018
1019         up_write(&zram->init_lock);
1020         /* I/O operation under all of CPU are done so let's free */
1021         zram_meta_free(meta, disksize);
1022         zcomp_destroy(comp);
1023 }
1024
1025 static ssize_t disksize_store(struct device *dev,
1026                 struct device_attribute *attr, const char *buf, size_t len)
1027 {
1028         u64 disksize;
1029         struct zcomp *comp;
1030         struct zram_meta *meta;
1031         struct zram *zram = dev_to_zram(dev);
1032         int err;
1033
1034         disksize = memparse(buf, NULL);
1035         if (!disksize)
1036                 return -EINVAL;
1037
1038         disksize = PAGE_ALIGN(disksize);
1039         meta = zram_meta_alloc(zram->disk->disk_name, disksize);
1040         if (!meta)
1041                 return -ENOMEM;
1042
1043         comp = zcomp_create(zram->compressor, zram->max_comp_streams);
1044         if (IS_ERR(comp)) {
1045                 pr_err("Cannot initialise %s compressing backend\n",
1046                                 zram->compressor);
1047                 err = PTR_ERR(comp);
1048                 goto out_free_meta;
1049         }
1050
1051         down_write(&zram->init_lock);
1052         if (init_done(zram)) {
1053                 pr_info("Cannot change disksize for initialized device\n");
1054                 err = -EBUSY;
1055                 goto out_destroy_comp;
1056         }
1057
1058         init_waitqueue_head(&zram->io_done);
1059         atomic_set(&zram->refcount, 1);
1060         zram->meta = meta;
1061         zram->comp = comp;
1062         zram->disksize = disksize;
1063         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
1064         up_write(&zram->init_lock);
1065
1066         /*
1067          * Revalidate disk out of the init_lock to avoid lockdep splat.
1068          * It's okay because disk's capacity is protected by init_lock
1069          * so that revalidate_disk always sees up-to-date capacity.
1070          */
1071         revalidate_disk(zram->disk);
1072
1073         return len;
1074
1075 out_destroy_comp:
1076         up_write(&zram->init_lock);
1077         zcomp_destroy(comp);
1078 out_free_meta:
1079         zram_meta_free(meta, disksize);
1080         return err;
1081 }
1082
1083 static ssize_t reset_store(struct device *dev,
1084                 struct device_attribute *attr, const char *buf, size_t len)
1085 {
1086         int ret;
1087         unsigned short do_reset;
1088         struct zram *zram;
1089         struct block_device *bdev;
1090
1091         ret = kstrtou16(buf, 10, &do_reset);
1092         if (ret)
1093                 return ret;
1094
1095         if (!do_reset)
1096                 return -EINVAL;
1097
1098         zram = dev_to_zram(dev);
1099         bdev = bdget_disk(zram->disk, 0);
1100         if (!bdev)
1101                 return -ENOMEM;
1102
1103         mutex_lock(&bdev->bd_mutex);
1104         /* Do not reset an active device or claimed device */
1105         if (bdev->bd_openers || zram->claim) {
1106                 mutex_unlock(&bdev->bd_mutex);
1107                 bdput(bdev);
1108                 return -EBUSY;
1109         }
1110
1111         /* From now on, anyone can't open /dev/zram[0-9] */
1112         zram->claim = true;
1113         mutex_unlock(&bdev->bd_mutex);
1114
1115         /* Make sure all the pending I/O are finished */
1116         fsync_bdev(bdev);
1117         zram_reset_device(zram);
1118         revalidate_disk(zram->disk);
1119         bdput(bdev);
1120
1121         mutex_lock(&bdev->bd_mutex);
1122         zram->claim = false;
1123         mutex_unlock(&bdev->bd_mutex);
1124
1125         return len;
1126 }
1127
1128 static int zram_open(struct block_device *bdev, fmode_t mode)
1129 {
1130         int ret = 0;
1131         struct zram *zram;
1132
1133         WARN_ON(!mutex_is_locked(&bdev->bd_mutex));
1134
1135         zram = bdev->bd_disk->private_data;
1136         /* zram was claimed to reset so open request fails */
1137         if (zram->claim)
1138                 ret = -EBUSY;
1139
1140         return ret;
1141 }
1142
1143 static const struct block_device_operations zram_devops = {
1144         .open = zram_open,
1145         .swap_slot_free_notify = zram_slot_free_notify,
1146         .rw_page = zram_rw_page,
1147         .owner = THIS_MODULE
1148 };
1149
1150 static DEVICE_ATTR_WO(compact);
1151 static DEVICE_ATTR_RW(disksize);
1152 static DEVICE_ATTR_RO(initstate);
1153 static DEVICE_ATTR_WO(reset);
1154 static DEVICE_ATTR_RO(orig_data_size);
1155 static DEVICE_ATTR_RO(mem_used_total);
1156 static DEVICE_ATTR_RW(mem_limit);
1157 static DEVICE_ATTR_RW(mem_used_max);
1158 static DEVICE_ATTR_RW(max_comp_streams);
1159 static DEVICE_ATTR_RW(comp_algorithm);
1160
1161 static struct attribute *zram_disk_attrs[] = {
1162         &dev_attr_disksize.attr,
1163         &dev_attr_initstate.attr,
1164         &dev_attr_reset.attr,
1165         &dev_attr_num_reads.attr,
1166         &dev_attr_num_writes.attr,
1167         &dev_attr_failed_reads.attr,
1168         &dev_attr_failed_writes.attr,
1169         &dev_attr_compact.attr,
1170         &dev_attr_invalid_io.attr,
1171         &dev_attr_notify_free.attr,
1172         &dev_attr_zero_pages.attr,
1173         &dev_attr_orig_data_size.attr,
1174         &dev_attr_compr_data_size.attr,
1175         &dev_attr_mem_used_total.attr,
1176         &dev_attr_mem_limit.attr,
1177         &dev_attr_mem_used_max.attr,
1178         &dev_attr_max_comp_streams.attr,
1179         &dev_attr_comp_algorithm.attr,
1180         &dev_attr_io_stat.attr,
1181         &dev_attr_mm_stat.attr,
1182         NULL,
1183 };
1184
1185 static struct attribute_group zram_disk_attr_group = {
1186         .attrs = zram_disk_attrs,
1187 };
1188
1189 /*
1190  * Allocate and initialize new zram device. the function returns
1191  * '>= 0' device_id upon success, and negative value otherwise.
1192  */
1193 static int zram_add(void)
1194 {
1195         struct zram *zram;
1196         struct request_queue *queue;
1197         int ret, device_id;
1198
1199         zram = kzalloc(sizeof(struct zram), GFP_KERNEL);
1200         if (!zram)
1201                 return -ENOMEM;
1202
1203         ret = idr_alloc(&zram_index_idr, zram, 0, 0, GFP_KERNEL);
1204         if (ret < 0)
1205                 goto out_free_dev;
1206         device_id = ret;
1207
1208         init_rwsem(&zram->init_lock);
1209
1210         queue = blk_alloc_queue(GFP_KERNEL);
1211         if (!queue) {
1212                 pr_err("Error allocating disk queue for device %d\n",
1213                         device_id);
1214                 ret = -ENOMEM;
1215                 goto out_free_idr;
1216         }
1217
1218         blk_queue_make_request(queue, zram_make_request);
1219
1220         /* gendisk structure */
1221         zram->disk = alloc_disk(1);
1222         if (!zram->disk) {
1223                 pr_err("Error allocating disk structure for device %d\n",
1224                         device_id);
1225                 ret = -ENOMEM;
1226                 goto out_free_queue;
1227         }
1228
1229         zram->disk->major = zram_major;
1230         zram->disk->first_minor = device_id;
1231         zram->disk->fops = &zram_devops;
1232         zram->disk->queue = queue;
1233         zram->disk->queue->queuedata = zram;
1234         zram->disk->private_data = zram;
1235         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
1236
1237         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
1238         set_capacity(zram->disk, 0);
1239         /* zram devices sort of resembles non-rotational disks */
1240         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
1241         queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);
1242         /*
1243          * To ensure that we always get PAGE_SIZE aligned
1244          * and n*PAGE_SIZED sized I/O requests.
1245          */
1246         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
1247         blk_queue_logical_block_size(zram->disk->queue,
1248                                         ZRAM_LOGICAL_BLOCK_SIZE);
1249         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
1250         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
1251         zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
1252         blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
1253         /*
1254          * zram_bio_discard() will clear all logical blocks if logical block
1255          * size is identical with physical block size(PAGE_SIZE). But if it is
1256          * different, we will skip discarding some parts of logical blocks in
1257          * the part of the request range which isn't aligned to physical block
1258          * size.  So we can't ensure that all discarded logical blocks are
1259          * zeroed.
1260          */
1261         if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
1262                 zram->disk->queue->limits.discard_zeroes_data = 1;
1263         else
1264                 zram->disk->queue->limits.discard_zeroes_data = 0;
1265         queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
1266
1267         add_disk(zram->disk);
1268
1269         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
1270                                 &zram_disk_attr_group);
1271         if (ret < 0) {
1272                 pr_err("Error creating sysfs group for device %d\n",
1273                                 device_id);
1274                 goto out_free_disk;
1275         }
1276         strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
1277         zram->meta = NULL;
1278         zram->max_comp_streams = 1;
1279
1280         pr_info("Added device: %s\n", zram->disk->disk_name);
1281         return device_id;
1282
1283 out_free_disk:
1284         del_gendisk(zram->disk);
1285         put_disk(zram->disk);
1286 out_free_queue:
1287         blk_cleanup_queue(queue);
1288 out_free_idr:
1289         idr_remove(&zram_index_idr, device_id);
1290 out_free_dev:
1291         kfree(zram);
1292         return ret;
1293 }
1294
1295 static int zram_remove(struct zram *zram)
1296 {
1297         struct block_device *bdev;
1298
1299         bdev = bdget_disk(zram->disk, 0);
1300         if (!bdev)
1301                 return -ENOMEM;
1302
1303         mutex_lock(&bdev->bd_mutex);
1304         if (bdev->bd_openers || zram->claim) {
1305                 mutex_unlock(&bdev->bd_mutex);
1306                 bdput(bdev);
1307                 return -EBUSY;
1308         }
1309
1310         zram->claim = true;
1311         mutex_unlock(&bdev->bd_mutex);
1312
1313         /*
1314          * Remove sysfs first, so no one will perform a disksize
1315          * store while we destroy the devices. This also helps during
1316          * hot_remove -- zram_reset_device() is the last holder of
1317          * ->init_lock, no later/concurrent disksize_store() or any
1318          * other sysfs handlers are possible.
1319          */
1320         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
1321                         &zram_disk_attr_group);
1322
1323         /* Make sure all the pending I/O are finished */
1324         fsync_bdev(bdev);
1325         zram_reset_device(zram);
1326         bdput(bdev);
1327
1328         pr_info("Removed device: %s\n", zram->disk->disk_name);
1329
1330         blk_cleanup_queue(zram->disk->queue);
1331         del_gendisk(zram->disk);
1332         put_disk(zram->disk);
1333         kfree(zram);
1334         return 0;
1335 }
1336
1337 /* zram-control sysfs attributes */
1338 static ssize_t hot_add_show(struct class *class,
1339                         struct class_attribute *attr,
1340                         char *buf)
1341 {
1342         int ret;
1343
1344         mutex_lock(&zram_index_mutex);
1345         ret = zram_add();
1346         mutex_unlock(&zram_index_mutex);
1347
1348         if (ret < 0)
1349                 return ret;
1350         return scnprintf(buf, PAGE_SIZE, "%d\n", ret);
1351 }
1352
1353 static ssize_t hot_remove_store(struct class *class,
1354                         struct class_attribute *attr,
1355                         const char *buf,
1356                         size_t count)
1357 {
1358         struct zram *zram;
1359         int ret, dev_id;
1360
1361         /* dev_id is gendisk->first_minor, which is `int' */
1362         ret = kstrtoint(buf, 10, &dev_id);
1363         if (ret)
1364                 return ret;
1365         if (dev_id < 0)
1366                 return -EINVAL;
1367
1368         mutex_lock(&zram_index_mutex);
1369
1370         zram = idr_find(&zram_index_idr, dev_id);
1371         if (zram) {
1372                 ret = zram_remove(zram);
1373                 if (!ret)
1374                         idr_remove(&zram_index_idr, dev_id);
1375         } else {
1376                 ret = -ENODEV;
1377         }
1378
1379         mutex_unlock(&zram_index_mutex);
1380         return ret ? ret : count;
1381 }
1382
1383 /*
1384  * NOTE: hot_add attribute is not the usual read-only sysfs attribute. In a
1385  * sense that reading from this file does alter the state of your system -- it
1386  * creates a new un-initialized zram device and returns back this device's
1387  * device_id (or an error code if it fails to create a new device).
1388  */
1389 static struct class_attribute zram_control_class_attrs[] = {
1390         __ATTR(hot_add, 0400, hot_add_show, NULL),
1391         __ATTR_WO(hot_remove),
1392         __ATTR_NULL,
1393 };
1394
1395 static struct class zram_control_class = {
1396         .name           = "zram-control",
1397         .owner          = THIS_MODULE,
1398         .class_attrs    = zram_control_class_attrs,
1399 };
1400
1401 static int zram_remove_cb(int id, void *ptr, void *data)
1402 {
1403         zram_remove(ptr);
1404         return 0;
1405 }
1406
1407 static void destroy_devices(void)
1408 {
1409         class_unregister(&zram_control_class);
1410         idr_for_each(&zram_index_idr, &zram_remove_cb, NULL);
1411         idr_destroy(&zram_index_idr);
1412         unregister_blkdev(zram_major, "zram");
1413 }
1414
1415 static int __init zram_init(void)
1416 {
1417         int ret;
1418
1419         ret = class_register(&zram_control_class);
1420         if (ret) {
1421                 pr_err("Unable to register zram-control class\n");
1422                 return ret;
1423         }
1424
1425         zram_major = register_blkdev(0, "zram");
1426         if (zram_major <= 0) {
1427                 pr_err("Unable to get major number\n");
1428                 class_unregister(&zram_control_class);
1429                 return -EBUSY;
1430         }
1431
1432         while (num_devices != 0) {
1433                 mutex_lock(&zram_index_mutex);
1434                 ret = zram_add();
1435                 mutex_unlock(&zram_index_mutex);
1436                 if (ret < 0)
1437                         goto out_error;
1438                 num_devices--;
1439         }
1440
1441         return 0;
1442
1443 out_error:
1444         destroy_devices();
1445         return ret;
1446 }
1447
1448 static void __exit zram_exit(void)
1449 {
1450         destroy_devices();
1451 }
1452
1453 module_init(zram_init);
1454 module_exit(zram_exit);
1455
1456 module_param(num_devices, uint, 0);
1457 MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
1458
1459 MODULE_LICENSE("Dual BSD/GPL");
1460 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
1461 MODULE_DESCRIPTION("Compressed RAM Block Device");