drivers/block/zram/zram_drv.c

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *               2012, 2013 Minchan Kim
   6  *
   7  * This code is released using a dual license strategy: BSD/GPL
   8  * You can choose the licence that better fits your requirements.
   9  *
  10  * Released under the terms of 3-clause BSD License
  11  * Released under the terms of GNU General Public License Version 2.0
  12  *
  13  */
  14
  15 #define KMSG_COMPONENT "zram"
  16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  17
  18 #include <linux/module.h>
  19 #include <linux/kernel.h>
  20 #include <linux/bio.h>
  21 #include <linux/bitops.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/buffer_head.h>
  24 #include <linux/device.h>
  25 #include <linux/genhd.h>
  26 #include <linux/highmem.h>
  27 #include <linux/slab.h>
  28 #include <linux/backing-dev.h>
  29 #include <linux/string.h>
  30 #include <linux/vmalloc.h>
  31 #include <linux/err.h>
  32 #include <linux/idr.h>
  33 #include <linux/sysfs.h>
  34 #include <linux/debugfs.h>
  35 #include <linux/cpuhotplug.h>
  36 #include <linux/part_stat.h>
  37
  38 #include "zram_drv.h"
  39
  40 static DEFINE_IDR(zram_index_idr);
  41 /* idr index must be protected */
  42 static DEFINE_MUTEX(zram_index_mutex);
  43
  44 static int zram_major;
  45 static const char *default_compressor = CONFIG_ZRAM_DEF_COMP;
  46
  47 /* Module params (documentation at end) */
  48 static unsigned int num_devices = 1;
  49 /*
  50  * Pages that compress to sizes equals or greater than this are stored
  51  * uncompressed in memory.
  52  */
  53 static size_t huge_class_size;
  54
  55 static const struct block_device_operations zram_devops;
  56 static const struct block_device_operations zram_wb_devops;
  57
  58 static void zram_free_page(struct zram *zram, size_t index);
  59 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
  60                                 u32 index, int offset, struct bio *bio);
  61
  62
  63 static int zram_slot_trylock(struct zram *zram, u32 index)
  64 {
  65         return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags);
  66 }
  67
  68 static void zram_slot_lock(struct zram *zram, u32 index)
  69 {
  70         bit_spin_lock(ZRAM_LOCK, &zram->table[index].flags);
  71 }
  72
  73 static void zram_slot_unlock(struct zram *zram, u32 index)
  74 {
  75         bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags);
  76 }
  77
  78 static inline bool init_done(struct zram *zram)
  79 {
  80         return zram->disksize;
  81 }
  82
  83 static inline struct zram *dev_to_zram(struct device *dev)
  84 {
  85         return (struct zram *)dev_to_disk(dev)->private_data;
  86 }
  87
  88 static unsigned long zram_get_handle(struct zram *zram, u32 index)
  89 {
  90         return zram->table[index].handle;
  91 }
  92
  93 static void zram_set_handle(struct zram *zram, u32 index, unsigned long handle)
  94 {
  95         zram->table[index].handle = handle;
  96 }
  97
  98 /* flag operations require table entry bit_spin_lock() being held */
  99 static bool zram_test_flag(struct zram *zram, u32 index,
 100                         enum zram_pageflags flag)
 101 {
 102         return zram->table[index].flags & BIT(flag);
 103 }
 104
 105 static void zram_set_flag(struct zram *zram, u32 index,
 106                         enum zram_pageflags flag)
 107 {
 108         zram->table[index].flags |= BIT(flag);
 109 }
 110
 111 static void zram_clear_flag(struct zram *zram, u32 index,
 112                         enum zram_pageflags flag)
 113 {
 114         zram->table[index].flags &= ~BIT(flag);
 115 }
 116
 117 static inline void zram_set_element(struct zram *zram, u32 index,
 118                         unsigned long element)
 119 {
 120         zram->table[index].element = element;
 121 }
 122
 123 static unsigned long zram_get_element(struct zram *zram, u32 index)
 124 {
 125         return zram->table[index].element;
 126 }
 127
 128 static size_t zram_get_obj_size(struct zram *zram, u32 index)
 129 {
 130         return zram->table[index].flags & (BIT(ZRAM_FLAG_SHIFT) - 1);
 131 }
 132
 133 static void zram_set_obj_size(struct zram *zram,
 134                                         u32 index, size_t size)
 135 {
 136         unsigned long flags = zram->table[index].flags >> ZRAM_FLAG_SHIFT;
 137
 138         zram->table[index].flags = (flags << ZRAM_FLAG_SHIFT) | size;
 139 }
 140
 141 static inline bool zram_allocated(struct zram *zram, u32 index)
 142 {
 143         return zram_get_obj_size(zram, index) ||
 144                         zram_test_flag(zram, index, ZRAM_SAME) ||
 145                         zram_test_flag(zram, index, ZRAM_WB);
 146 }
 147
 148 #if PAGE_SIZE != 4096
 149 static inline bool is_partial_io(struct bio_vec *bvec)
 150 {
 151         return bvec->bv_len != PAGE_SIZE;
 152 }
 153 #else
 154 static inline bool is_partial_io(struct bio_vec *bvec)
 155 {
 156         return false;
 157 }
 158 #endif
 159
 160 /*
 161  * Check if request is within bounds and aligned on zram logical blocks.
 162  */
 163 static inline bool valid_io_request(struct zram *zram,
 164                 sector_t start, unsigned int size)
 165 {
 166         u64 end, bound;
 167
 168         /* unaligned request */
 169         if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
 170                 return false;
 171         if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
 172                 return false;
 173
 174         end = start + (size >> SECTOR_SHIFT);
 175         bound = zram->disksize >> SECTOR_SHIFT;
 176         /* out of range range */
 177         if (unlikely(start >= bound || end > bound || start > end))
 178                 return false;
 179
 180         /* I/O request is valid */
 181         return true;
 182 }
 183
 184 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 185 {
 186         *index  += (*offset + bvec->bv_len) / PAGE_SIZE;
 187         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 188 }
 189
 190 static inline void update_used_max(struct zram *zram,
 191                                         const unsigned long pages)
 192 {
 193         unsigned long old_max, cur_max;
 194
 195         old_max = atomic_long_read(&zram->stats.max_used_pages);
 196
 197         do {
 198                 cur_max = old_max;
 199                 if (pages > cur_max)
 200                         old_max = atomic_long_cmpxchg(
 201                                 &zram->stats.max_used_pages, cur_max, pages);
 202         } while (old_max != cur_max);
 203 }
 204
 205 static inline void zram_fill_page(void *ptr, unsigned long len,
 206                                         unsigned long value)
 207 {
 208         WARN_ON_ONCE(!IS_ALIGNED(len, sizeof(unsigned long)));
 209         memset_l(ptr, value, len / sizeof(unsigned long));
 210 }
 211
 212 static bool page_same_filled(void *ptr, unsigned long *element)
 213 {
 214         unsigned long *page;
 215         unsigned long val;
 216         unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1;
 217
 218         page = (unsigned long *)ptr;
 219         val = page[0];
 220
 221         if (val != page[last_pos])
 222                 return false;
 223
 224         for (pos = 1; pos < last_pos; pos++) {
 225                 if (val != page[pos])
 226                         return false;
 227         }
 228
 229         *element = val;
 230
 231         return true;
 232 }
 233
 234 static ssize_t initstate_show(struct device *dev,
 235                 struct device_attribute *attr, char *buf)
 236 {
 237         u32 val;
 238         struct zram *zram = dev_to_zram(dev);
 239
 240         down_read(&zram->init_lock);
 241         val = init_done(zram);
 242         up_read(&zram->init_lock);
 243
 244         return scnprintf(buf, PAGE_SIZE, "%u\n", val);
 245 }
 246
 247 static ssize_t disksize_show(struct device *dev,
 248                 struct device_attribute *attr, char *buf)
 249 {
 250         struct zram *zram = dev_to_zram(dev);
 251
 252         return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
 253 }
 254
 255 static ssize_t mem_limit_store(struct device *dev,
 256                 struct device_attribute *attr, const char *buf, size_t len)
 257 {
 258         u64 limit;
 259         char *tmp;
 260         struct zram *zram = dev_to_zram(dev);
 261
 262         limit = memparse(buf, &tmp);
 263         if (buf == tmp) /* no chars parsed, invalid input */
 264                 return -EINVAL;
 265
 266         down_write(&zram->init_lock);
 267         zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
 268         up_write(&zram->init_lock);
 269
 270         return len;
 271 }
 272
 273 static ssize_t mem_used_max_store(struct device *dev,
 274                 struct device_attribute *attr, const char *buf, size_t len)
 275 {
 276         int err;
 277         unsigned long val;
 278         struct zram *zram = dev_to_zram(dev);
 279
 280         err = kstrtoul(buf, 10, &val);
 281         if (err || val != 0)
 282                 return -EINVAL;
 283
 284         down_read(&zram->init_lock);
 285         if (init_done(zram)) {
 286                 atomic_long_set(&zram->stats.max_used_pages,
 287                                 zs_get_total_pages(zram->mem_pool));
 288         }
 289         up_read(&zram->init_lock);
 290
 291         return len;
 292 }
 293
 294 static ssize_t idle_store(struct device *dev,
 295                 struct device_attribute *attr, const char *buf, size_t len)
 296 {
 297         struct zram *zram = dev_to_zram(dev);
 298         unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
 299         int index;
 300
 301         if (!sysfs_streq(buf, "all"))
 302                 return -EINVAL;
 303
 304         down_read(&zram->init_lock);
 305         if (!init_done(zram)) {
 306                 up_read(&zram->init_lock);
 307                 return -EINVAL;
 308         }
 309
 310         for (index = 0; index < nr_pages; index++) {
 311                 /*
 312                  * Do not mark ZRAM_UNDER_WB slot as ZRAM_IDLE to close race.
 313                  * See the comment in writeback_store.
 314                  */
 315                 zram_slot_lock(zram, index);
 316                 if (zram_allocated(zram, index) &&
 317                                 !zram_test_flag(zram, index, ZRAM_UNDER_WB))
 318                         zram_set_flag(zram, index, ZRAM_IDLE);
 319                 zram_slot_unlock(zram, index);
 320         }
 321
 322         up_read(&zram->init_lock);
 323
 324         return len;
 325 }
 326
 327 #ifdef CONFIG_ZRAM_WRITEBACK
 328 static ssize_t writeback_limit_enable_store(struct device *dev,
 329                 struct device_attribute *attr, const char *buf, size_t len)
 330 {
 331         struct zram *zram = dev_to_zram(dev);
 332         u64 val;
 333         ssize_t ret = -EINVAL;
 334
 335         if (kstrtoull(buf, 10, &val))
 336                 return ret;
 337
 338         down_read(&zram->init_lock);
 339         spin_lock(&zram->wb_limit_lock);
 340         zram->wb_limit_enable = val;
 341         spin_unlock(&zram->wb_limit_lock);
 342         up_read(&zram->init_lock);
 343         ret = len;
 344
 345         return ret;
 346 }
 347
 348 static ssize_t writeback_limit_enable_show(struct device *dev,
 349                 struct device_attribute *attr, char *buf)
 350 {
 351         bool val;
 352         struct zram *zram = dev_to_zram(dev);
 353
 354         down_read(&zram->init_lock);
 355         spin_lock(&zram->wb_limit_lock);
 356         val = zram->wb_limit_enable;
 357         spin_unlock(&zram->wb_limit_lock);
 358         up_read(&zram->init_lock);
 359
 360         return scnprintf(buf, PAGE_SIZE, "%d\n", val);
 361 }
 362
 363 static ssize_t writeback_limit_store(struct device *dev,
 364                 struct device_attribute *attr, const char *buf, size_t len)
 365 {
 366         struct zram *zram = dev_to_zram(dev);
 367         u64 val;
 368         ssize_t ret = -EINVAL;
 369
 370         if (kstrtoull(buf, 10, &val))
 371                 return ret;
 372
 373         down_read(&zram->init_lock);
 374         spin_lock(&zram->wb_limit_lock);
 375         zram->bd_wb_limit = val;
 376         spin_unlock(&zram->wb_limit_lock);
 377         up_read(&zram->init_lock);
 378         ret = len;
 379
 380         return ret;
 381 }
 382
 383 static ssize_t writeback_limit_show(struct device *dev,
 384                 struct device_attribute *attr, char *buf)
 385 {
 386         u64 val;
 387         struct zram *zram = dev_to_zram(dev);
 388
 389         down_read(&zram->init_lock);
 390         spin_lock(&zram->wb_limit_lock);
 391         val = zram->bd_wb_limit;
 392         spin_unlock(&zram->wb_limit_lock);
 393         up_read(&zram->init_lock);
 394
 395         return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
 396 }
 397
 398 static void reset_bdev(struct zram *zram)
 399 {
 400         struct block_device *bdev;
 401
 402         if (!zram->backing_dev)
 403                 return;
 404
 405         bdev = zram->bdev;
 406         blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 407         /* hope filp_close flush all of IO */
 408         filp_close(zram->backing_dev, NULL);
 409         zram->backing_dev = NULL;
 410         zram->bdev = NULL;
 411         zram->disk->fops = &zram_devops;
 412         kvfree(zram->bitmap);
 413         zram->bitmap = NULL;
 414 }
 415
 416 static ssize_t backing_dev_show(struct device *dev,
 417                 struct device_attribute *attr, char *buf)
 418 {
 419         struct file *file;
 420         struct zram *zram = dev_to_zram(dev);
 421         char *p;
 422         ssize_t ret;
 423
 424         down_read(&zram->init_lock);
 425         file = zram->backing_dev;
 426         if (!file) {
 427                 memcpy(buf, "none\n", 5);
 428                 up_read(&zram->init_lock);
 429                 return 5;
 430         }
 431
 432         p = file_path(file, buf, PAGE_SIZE - 1);
 433         if (IS_ERR(p)) {
 434                 ret = PTR_ERR(p);
 435                 goto out;
 436         }
 437
 438         ret = strlen(p);
 439         memmove(buf, p, ret);
 440         buf[ret++] = '\n';
 441 out:
 442         up_read(&zram->init_lock);
 443         return ret;
 444 }
 445
 446 static ssize_t backing_dev_store(struct device *dev,
 447                 struct device_attribute *attr, const char *buf, size_t len)
 448 {
 449         char *file_name;
 450         size_t sz;
 451         struct file *backing_dev = NULL;
 452         struct inode *inode;
 453         struct address_space *mapping;
 454         unsigned int bitmap_sz;
 455         unsigned long nr_pages, *bitmap = NULL;
 456         struct block_device *bdev = NULL;
 457         int err;
 458         struct zram *zram = dev_to_zram(dev);
 459
 460         file_name = kmalloc(PATH_MAX, GFP_KERNEL);
 461         if (!file_name)
 462                 return -ENOMEM;
 463
 464         down_write(&zram->init_lock);
 465         if (init_done(zram)) {
 466                 pr_info("Can't setup backing device for initialized device\n");
 467                 err = -EBUSY;
 468                 goto out;
 469         }
 470
 471         strlcpy(file_name, buf, PATH_MAX);
 472         /* ignore trailing newline */
 473         sz = strlen(file_name);
 474         if (sz > 0 && file_name[sz - 1] == '\n')
 475                 file_name[sz - 1] = 0x00;
 476
 477         backing_dev = filp_open(file_name, O_RDWR|O_LARGEFILE, 0);
 478         if (IS_ERR(backing_dev)) {
 479                 err = PTR_ERR(backing_dev);
 480                 backing_dev = NULL;
 481                 goto out;
 482         }
 483
 484         mapping = backing_dev->f_mapping;
 485         inode = mapping->host;
 486
 487         /* Support only block device in this moment */
 488         if (!S_ISBLK(inode->i_mode)) {
 489                 err = -ENOTBLK;
 490                 goto out;
 491         }
 492
 493         bdev = blkdev_get_by_dev(inode->i_rdev,
 494                         FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram);
 495         if (IS_ERR(bdev)) {
 496                 err = PTR_ERR(bdev);
 497                 bdev = NULL;
 498                 goto out;
 499         }
 500
 501         nr_pages = i_size_read(inode) >> PAGE_SHIFT;
 502         bitmap_sz = BITS_TO_LONGS(nr_pages) * sizeof(long);
 503         bitmap = kvzalloc(bitmap_sz, GFP_KERNEL);
 504         if (!bitmap) {
 505                 err = -ENOMEM;
 506                 goto out;
 507         }
 508
 509         reset_bdev(zram);
 510
 511         zram->bdev = bdev;
 512         zram->backing_dev = backing_dev;
 513         zram->bitmap = bitmap;
 514         zram->nr_pages = nr_pages;
 515         /*
 516          * With writeback feature, zram does asynchronous IO so it's no longer
 517          * synchronous device so let's remove synchronous io flag. Othewise,
 518          * upper layer(e.g., swap) could wait IO completion rather than
 519          * (submit and return), which will cause system sluggish.
 520          * Furthermore, when the IO function returns(e.g., swap_readpage),
 521          * upper layer expects IO was done so it could deallocate the page
 522          * freely but in fact, IO is going on so finally could cause
 523          * use-after-free when the IO is really done.
 524          */
 525         zram->disk->fops = &zram_wb_devops;
 526         up_write(&zram->init_lock);
 527
 528         pr_info("setup backing device %s\n", file_name);
 529         kfree(file_name);
 530
 531         return len;
 532 out:
 533         kvfree(bitmap);
 534
 535         if (bdev)
 536                 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
 537
 538         if (backing_dev)
 539                 filp_close(backing_dev, NULL);
 540
 541         up_write(&zram->init_lock);
 542
 543         kfree(file_name);
 544
 545         return err;
 546 }
 547
 548 static unsigned long alloc_block_bdev(struct zram *zram)
 549 {
 550         unsigned long blk_idx = 1;
 551 retry:
 552         /* skip 0 bit to confuse zram.handle = 0 */
 553         blk_idx = find_next_zero_bit(zram->bitmap, zram->nr_pages, blk_idx);
 554         if (blk_idx == zram->nr_pages)
 555                 return 0;
 556
 557         if (test_and_set_bit(blk_idx, zram->bitmap))
 558                 goto retry;
 559
 560         atomic64_inc(&zram->stats.bd_count);
 561         return blk_idx;
 562 }
 563
 564 static void free_block_bdev(struct zram *zram, unsigned long blk_idx)
 565 {
 566         int was_set;
 567
 568         was_set = test_and_clear_bit(blk_idx, zram->bitmap);
 569         WARN_ON_ONCE(!was_set);
 570         atomic64_dec(&zram->stats.bd_count);
 571 }
 572
 573 static void zram_page_end_io(struct bio *bio)
 574 {
 575         struct page *page = bio_first_page_all(bio);
 576
 577         page_endio(page, op_is_write(bio_op(bio)),
 578                         blk_status_to_errno(bio->bi_status));
 579         bio_put(bio);
 580 }
 581
 582 /*
 583  * Returns 1 if the submission is successful.
 584  */
 585 static int read_from_bdev_async(struct zram *zram, struct bio_vec *bvec,
 586                         unsigned long entry, struct bio *parent)
 587 {
 588         struct bio *bio;
 589
 590         bio = bio_alloc(GFP_ATOMIC, 1);
 591         if (!bio)
 592                 return -ENOMEM;
 593
 594         bio->bi_iter.bi_sector = entry * (PAGE_SIZE >> 9);
 595         bio_set_dev(bio, zram->bdev);
 596         if (!bio_add_page(bio, bvec->bv_page, bvec->bv_len, bvec->bv_offset)) {
 597                 bio_put(bio);
 598                 return -EIO;
 599         }
 600
 601         if (!parent) {
 602                 bio->bi_opf = REQ_OP_READ;
 603                 bio->bi_end_io = zram_page_end_io;
 604         } else {
 605                 bio->bi_opf = parent->bi_opf;
 606                 bio_chain(bio, parent);
 607         }
 608
 609         submit_bio(bio);
 610         return 1;
 611 }
 612
 613 #define PAGE_WB_SIG "page_index="
 614
 615 #define PAGE_WRITEBACK 0
 616 #define HUGE_WRITEBACK 1
 617 #define IDLE_WRITEBACK 2
 618
 619
 620 static ssize_t writeback_store(struct device *dev,
 621                 struct device_attribute *attr, const char *buf, size_t len)
 622 {
 623         struct zram *zram = dev_to_zram(dev);
 624         unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
 625         unsigned long index = 0;
 626         struct bio bio;
 627         struct bio_vec bio_vec;
 628         struct page *page;
 629         ssize_t ret = len;
 630         int mode, err;
 631         unsigned long blk_idx = 0;
 632
 633         if (sysfs_streq(buf, "idle"))
 634                 mode = IDLE_WRITEBACK;
 635         else if (sysfs_streq(buf, "huge"))
 636                 mode = HUGE_WRITEBACK;
 637         else {
 638                 if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1))
 639                         return -EINVAL;
 640
 641                 if (kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index) ||
 642                                 index >= nr_pages)
 643                         return -EINVAL;
 644
 645                 nr_pages = 1;
 646                 mode = PAGE_WRITEBACK;
 647         }
 648
 649         down_read(&zram->init_lock);
 650         if (!init_done(zram)) {
 651                 ret = -EINVAL;
 652                 goto release_init_lock;
 653         }
 654
 655         if (!zram->backing_dev) {
 656                 ret = -ENODEV;
 657                 goto release_init_lock;
 658         }
 659
 660         page = alloc_page(GFP_KERNEL);
 661         if (!page) {
 662                 ret = -ENOMEM;
 663                 goto release_init_lock;
 664         }
 665
 666         for (; nr_pages != 0; index++, nr_pages--) {
 667                 struct bio_vec bvec;
 668
 669                 bvec.bv_page = page;
 670                 bvec.bv_len = PAGE_SIZE;
 671                 bvec.bv_offset = 0;
 672
 673                 spin_lock(&zram->wb_limit_lock);
 674                 if (zram->wb_limit_enable && !zram->bd_wb_limit) {
 675                         spin_unlock(&zram->wb_limit_lock);
 676                         ret = -EIO;
 677                         break;
 678                 }
 679                 spin_unlock(&zram->wb_limit_lock);
 680
 681                 if (!blk_idx) {
 682                         blk_idx = alloc_block_bdev(zram);
 683                         if (!blk_idx) {
 684                                 ret = -ENOSPC;
 685                                 break;
 686                         }
 687                 }
 688
 689                 zram_slot_lock(zram, index);
 690                 if (!zram_allocated(zram, index))
 691                         goto next;
 692
 693                 if (zram_test_flag(zram, index, ZRAM_WB) ||
 694                                 zram_test_flag(zram, index, ZRAM_SAME) ||
 695                                 zram_test_flag(zram, index, ZRAM_UNDER_WB))
 696                         goto next;
 697
 698                 if (mode == IDLE_WRITEBACK &&
 699                           !zram_test_flag(zram, index, ZRAM_IDLE))
 700                         goto next;
 701                 if (mode == HUGE_WRITEBACK &&
 702                           !zram_test_flag(zram, index, ZRAM_HUGE))
 703                         goto next;
 704                 /*
 705                  * Clearing ZRAM_UNDER_WB is duty of caller.
 706                  * IOW, zram_free_page never clear it.
 707                  */
 708                 zram_set_flag(zram, index, ZRAM_UNDER_WB);
 709                 /* Need for hugepage writeback racing */
 710                 zram_set_flag(zram, index, ZRAM_IDLE);
 711                 zram_slot_unlock(zram, index);
 712                 if (zram_bvec_read(zram, &bvec, index, 0, NULL)) {
 713                         zram_slot_lock(zram, index);
 714                         zram_clear_flag(zram, index, ZRAM_UNDER_WB);
 715                         zram_clear_flag(zram, index, ZRAM_IDLE);
 716                         zram_slot_unlock(zram, index);
 717                         continue;
 718                 }
 719
 720                 bio_init(&bio, &bio_vec, 1);
 721                 bio_set_dev(&bio, zram->bdev);
 722                 bio.bi_iter.bi_sector = blk_idx * (PAGE_SIZE >> 9);
 723                 bio.bi_opf = REQ_OP_WRITE | REQ_SYNC;
 724
 725                 bio_add_page(&bio, bvec.bv_page, bvec.bv_len,
 726                                 bvec.bv_offset);
 727                 /*
 728                  * XXX: A single page IO would be inefficient for write
 729                  * but it would be not bad as starter.
 730                  */
 731                 err = submit_bio_wait(&bio);
 732                 if (err) {
 733                         zram_slot_lock(zram, index);
 734                         zram_clear_flag(zram, index, ZRAM_UNDER_WB);
 735                         zram_clear_flag(zram, index, ZRAM_IDLE);
 736                         zram_slot_unlock(zram, index);
 737                         /*
 738                          * Return last IO error unless every IO were
 739                          * not suceeded.
 740                          */
 741                         ret = err;
 742                         continue;
 743                 }
 744
 745                 atomic64_inc(&zram->stats.bd_writes);
 746                 /*
 747                  * We released zram_slot_lock so need to check if the slot was
 748                  * changed. If there is freeing for the slot, we can catch it
 749                  * easily by zram_allocated.
 750                  * A subtle case is the slot is freed/reallocated/marked as
 751                  * ZRAM_IDLE again. To close the race, idle_store doesn't
 752                  * mark ZRAM_IDLE once it found the slot was ZRAM_UNDER_WB.
 753                  * Thus, we could close the race by checking ZRAM_IDLE bit.
 754                  */
 755                 zram_slot_lock(zram, index);
 756                 if (!zram_allocated(zram, index) ||
 757                           !zram_test_flag(zram, index, ZRAM_IDLE)) {
 758                         zram_clear_flag(zram, index, ZRAM_UNDER_WB);
 759                         zram_clear_flag(zram, index, ZRAM_IDLE);
 760                         goto next;
 761                 }
 762
 763                 zram_free_page(zram, index);
 764                 zram_clear_flag(zram, index, ZRAM_UNDER_WB);
 765                 zram_set_flag(zram, index, ZRAM_WB);
 766                 zram_set_element(zram, index, blk_idx);
 767                 blk_idx = 0;
 768                 atomic64_inc(&zram->stats.pages_stored);
 769                 spin_lock(&zram->wb_limit_lock);
 770                 if (zram->wb_limit_enable && zram->bd_wb_limit > 0)
 771                         zram->bd_wb_limit -=  1UL << (PAGE_SHIFT - 12);
 772                 spin_unlock(&zram->wb_limit_lock);
 773 next:
 774                 zram_slot_unlock(zram, index);
 775         }
 776
 777         if (blk_idx)
 778                 free_block_bdev(zram, blk_idx);
 779         __free_page(page);
 780 release_init_lock:
 781         up_read(&zram->init_lock);
 782
 783         return ret;
 784 }
 785
 786 struct zram_work {
 787         struct work_struct work;
 788         struct zram *zram;
 789         unsigned long entry;
 790         struct bio *bio;
 791         struct bio_vec bvec;
 792 };
 793
 794 #if PAGE_SIZE != 4096
 795 static void zram_sync_read(struct work_struct *work)
 796 {
 797         struct zram_work *zw = container_of(work, struct zram_work, work);
 798         struct zram *zram = zw->zram;
 799         unsigned long entry = zw->entry;
 800         struct bio *bio = zw->bio;
 801
 802         read_from_bdev_async(zram, &zw->bvec, entry, bio);
 803 }
 804
 805 /*
 806  * Block layer want one ->submit_bio to be active at a time, so if we use
 807  * chained IO with parent IO in same context, it's a deadlock. To avoid that,
 808  * use a worker thread context.
 809  */
 810 static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec,
 811                                 unsigned long entry, struct bio *bio)
 812 {
 813         struct zram_work work;
 814
 815         work.bvec = *bvec;
 816         work.zram = zram;
 817         work.entry = entry;
 818         work.bio = bio;
 819
 820         INIT_WORK_ONSTACK(&work.work, zram_sync_read);
 821         queue_work(system_unbound_wq, &work.work);
 822         flush_work(&work.work);
 823         destroy_work_on_stack(&work.work);
 824
 825         return 1;
 826 }
 827 #else
 828 static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec,
 829                                 unsigned long entry, struct bio *bio)
 830 {
 831         WARN_ON(1);
 832         return -EIO;
 833 }
 834 #endif
 835
 836 static int read_from_bdev(struct zram *zram, struct bio_vec *bvec,
 837                         unsigned long entry, struct bio *parent, bool sync)
 838 {
 839         atomic64_inc(&zram->stats.bd_reads);
 840         if (sync)
 841                 return read_from_bdev_sync(zram, bvec, entry, parent);
 842         else
 843                 return read_from_bdev_async(zram, bvec, entry, parent);
 844 }
 845 #else
 846 static inline void reset_bdev(struct zram *zram) {};
 847 static int read_from_bdev(struct zram *zram, struct bio_vec *bvec,
 848                         unsigned long entry, struct bio *parent, bool sync)
 849 {
 850         return -EIO;
 851 }
 852
 853 static void free_block_bdev(struct zram *zram, unsigned long blk_idx) {};
 854 #endif
 855
 856 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
 857
 858 static struct dentry *zram_debugfs_root;
 859
 860 static void zram_debugfs_create(void)
 861 {
 862         zram_debugfs_root = debugfs_create_dir("zram", NULL);
 863 }
 864
 865 static void zram_debugfs_destroy(void)
 866 {
 867         debugfs_remove_recursive(zram_debugfs_root);
 868 }
 869
 870 static void zram_accessed(struct zram *zram, u32 index)
 871 {
 872         zram_clear_flag(zram, index, ZRAM_IDLE);
 873         zram->table[index].ac_time = ktime_get_boottime();
 874 }
 875
 876 static ssize_t read_block_state(struct file *file, char __user *buf,
 877                                 size_t count, loff_t *ppos)
 878 {
 879         char *kbuf;
 880         ssize_t index, written = 0;
 881         struct zram *zram = file->private_data;
 882         unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
 883         struct timespec64 ts;
 884
 885         kbuf = kvmalloc(count, GFP_KERNEL);
 886         if (!kbuf)
 887                 return -ENOMEM;
 888
 889         down_read(&zram->init_lock);
 890         if (!init_done(zram)) {
 891                 up_read(&zram->init_lock);
 892                 kvfree(kbuf);
 893                 return -EINVAL;
 894         }
 895
 896         for (index = *ppos; index < nr_pages; index++) {
 897                 int copied;
 898
 899                 zram_slot_lock(zram, index);
 900                 if (!zram_allocated(zram, index))
 901                         goto next;
 902
 903                 ts = ktime_to_timespec64(zram->table[index].ac_time);
 904                 copied = snprintf(kbuf + written, count,
 905                         "%12zd %12lld.%06lu %c%c%c%c\n",
 906                         index, (s64)ts.tv_sec,
 907                         ts.tv_nsec / NSEC_PER_USEC,
 908                         zram_test_flag(zram, index, ZRAM_SAME) ? 's' : '.',
 909                         zram_test_flag(zram, index, ZRAM_WB) ? 'w' : '.',
 910                         zram_test_flag(zram, index, ZRAM_HUGE) ? 'h' : '.',
 911                         zram_test_flag(zram, index, ZRAM_IDLE) ? 'i' : '.');
 912
 913                 if (count < copied) {
 914                         zram_slot_unlock(zram, index);
 915                         break;
 916                 }
 917                 written += copied;
 918                 count -= copied;
 919 next:
 920                 zram_slot_unlock(zram, index);
 921                 *ppos += 1;
 922         }
 923
 924         up_read(&zram->init_lock);
 925         if (copy_to_user(buf, kbuf, written))
 926                 written = -EFAULT;
 927         kvfree(kbuf);
 928
 929         return written;
 930 }
 931
 932 static const struct file_operations proc_zram_block_state_op = {
 933         .open = simple_open,
 934         .read = read_block_state,
 935         .llseek = default_llseek,
 936 };
 937
 938 static void zram_debugfs_register(struct zram *zram)
 939 {
 940         if (!zram_debugfs_root)
 941                 return;
 942
 943         zram->debugfs_dir = debugfs_create_dir(zram->disk->disk_name,
 944                                                 zram_debugfs_root);
 945         debugfs_create_file("block_state", 0400, zram->debugfs_dir,
 946                                 zram, &proc_zram_block_state_op);
 947 }
 948
 949 static void zram_debugfs_unregister(struct zram *zram)
 950 {
 951         debugfs_remove_recursive(zram->debugfs_dir);
 952 }
 953 #else
 954 static void zram_debugfs_create(void) {};
 955 static void zram_debugfs_destroy(void) {};
 956 static void zram_accessed(struct zram *zram, u32 index)
 957 {
 958         zram_clear_flag(zram, index, ZRAM_IDLE);
 959 };
 960 static void zram_debugfs_register(struct zram *zram) {};
 961 static void zram_debugfs_unregister(struct zram *zram) {};
 962 #endif
 963
 964 /*
 965  * We switched to per-cpu streams and this attr is not needed anymore.
 966  * However, we will keep it around for some time, because:
 967  * a) we may revert per-cpu streams in the future
 968  * b) it's visible to user space and we need to follow our 2 years
 969  *    retirement rule; but we already have a number of 'soon to be
 970  *    altered' attrs, so max_comp_streams need to wait for the next
 971  *    layoff cycle.
 972  */
 973 static ssize_t max_comp_streams_show(struct device *dev,
 974                 struct device_attribute *attr, char *buf)
 975 {
 976         return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus());
 977 }
 978
 979 static ssize_t max_comp_streams_store(struct device *dev,
 980                 struct device_attribute *attr, const char *buf, size_t len)
 981 {
 982         return len;
 983 }
 984
 985 static ssize_t comp_algorithm_show(struct device *dev,
 986                 struct device_attribute *attr, char *buf)
 987 {
 988         size_t sz;
 989         struct zram *zram = dev_to_zram(dev);
 990
 991         down_read(&zram->init_lock);
 992         sz = zcomp_available_show(zram->compressor, buf);
 993         up_read(&zram->init_lock);
 994
 995         return sz;
 996 }
 997
 998 static ssize_t comp_algorithm_store(struct device *dev,
 999                 struct device_attribute *attr, const char *buf, size_t len)
1000 {
1001         struct zram *zram = dev_to_zram(dev);
1002         char compressor[ARRAY_SIZE(zram->compressor)];
1003         size_t sz;
1004
1005         strlcpy(compressor, buf, sizeof(compressor));
1006         /* ignore trailing newline */
1007         sz = strlen(compressor);
1008         if (sz > 0 && compressor[sz - 1] == '\n')
1009                 compressor[sz - 1] = 0x00;
1010
1011         if (!zcomp_available_algorithm(compressor))
1012                 return -EINVAL;
1013
1014         down_write(&zram->init_lock);
1015         if (init_done(zram)) {
1016                 up_write(&zram->init_lock);
1017                 pr_info("Can't change algorithm for initialized device\n");
1018                 return -EBUSY;
1019         }
1020
1021         strcpy(zram->compressor, compressor);
1022         up_write(&zram->init_lock);
1023         return len;
1024 }
1025
1026 static ssize_t compact_store(struct device *dev,
1027                 struct device_attribute *attr, const char *buf, size_t len)
1028 {
1029         struct zram *zram = dev_to_zram(dev);
1030
1031         down_read(&zram->init_lock);
1032         if (!init_done(zram)) {
1033                 up_read(&zram->init_lock);
1034                 return -EINVAL;
1035         }
1036
1037         zs_compact(zram->mem_pool);
1038         up_read(&zram->init_lock);
1039
1040         return len;
1041 }
1042
1043 static ssize_t io_stat_show(struct device *dev,
1044                 struct device_attribute *attr, char *buf)
1045 {
1046         struct zram *zram = dev_to_zram(dev);
1047         ssize_t ret;
1048
1049         down_read(&zram->init_lock);
1050         ret = scnprintf(buf, PAGE_SIZE,
1051                         "%8llu %8llu %8llu %8llu\n",
1052                         (u64)atomic64_read(&zram->stats.failed_reads),
1053                         (u64)atomic64_read(&zram->stats.failed_writes),
1054                         (u64)atomic64_read(&zram->stats.invalid_io),
1055                         (u64)atomic64_read(&zram->stats.notify_free));
1056         up_read(&zram->init_lock);
1057
1058         return ret;
1059 }
1060
1061 static ssize_t mm_stat_show(struct device *dev,
1062                 struct device_attribute *attr, char *buf)
1063 {
1064         struct zram *zram = dev_to_zram(dev);
1065         struct zs_pool_stats pool_stats;
1066         u64 orig_size, mem_used = 0;
1067         long max_used;
1068         ssize_t ret;
1069
1070         memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats));
1071
1072         down_read(&zram->init_lock);
1073         if (init_done(zram)) {
1074                 mem_used = zs_get_total_pages(zram->mem_pool);
1075                 zs_pool_stats(zram->mem_pool, &pool_stats);
1076         }
1077
1078         orig_size = atomic64_read(&zram->stats.pages_stored);
1079         max_used = atomic_long_read(&zram->stats.max_used_pages);
1080
1081         ret = scnprintf(buf, PAGE_SIZE,
1082                         "%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu %8llu\n",
1083                         orig_size << PAGE_SHIFT,
1084                         (u64)atomic64_read(&zram->stats.compr_data_size),
1085                         mem_used << PAGE_SHIFT,
1086                         zram->limit_pages << PAGE_SHIFT,
1087                         max_used << PAGE_SHIFT,
1088                         (u64)atomic64_read(&zram->stats.same_pages),
1089                         atomic_long_read(&pool_stats.pages_compacted),
1090                         (u64)atomic64_read(&zram->stats.huge_pages),
1091                         (u64)atomic64_read(&zram->stats.huge_pages_since));
1092         up_read(&zram->init_lock);
1093
1094         return ret;
1095 }
1096
1097 #ifdef CONFIG_ZRAM_WRITEBACK
1098 #define FOUR_K(x) ((x) * (1 << (PAGE_SHIFT - 12)))
1099 static ssize_t bd_stat_show(struct device *dev,
1100                 struct device_attribute *attr, char *buf)
1101 {
1102         struct zram *zram = dev_to_zram(dev);
1103         ssize_t ret;
1104
1105         down_read(&zram->init_lock);
1106         ret = scnprintf(buf, PAGE_SIZE,
1107                 "%8llu %8llu %8llu\n",
1108                         FOUR_K((u64)atomic64_read(&zram->stats.bd_count)),
1109                         FOUR_K((u64)atomic64_read(&zram->stats.bd_reads)),
1110                         FOUR_K((u64)atomic64_read(&zram->stats.bd_writes)));
1111         up_read(&zram->init_lock);
1112
1113         return ret;
1114 }
1115 #endif
1116
1117 static ssize_t debug_stat_show(struct device *dev,
1118                 struct device_attribute *attr, char *buf)
1119 {
1120         int version = 1;
1121         struct zram *zram = dev_to_zram(dev);
1122         ssize_t ret;
1123
1124         down_read(&zram->init_lock);
1125         ret = scnprintf(buf, PAGE_SIZE,
1126                         "version: %d\n%8llu %8llu\n",
1127                         version,
1128                         (u64)atomic64_read(&zram->stats.writestall),
1129                         (u64)atomic64_read(&zram->stats.miss_free));
1130         up_read(&zram->init_lock);
1131
1132         return ret;
1133 }
1134
1135 static DEVICE_ATTR_RO(io_stat);
1136 static DEVICE_ATTR_RO(mm_stat);
1137 #ifdef CONFIG_ZRAM_WRITEBACK
1138 static DEVICE_ATTR_RO(bd_stat);
1139 #endif
1140 static DEVICE_ATTR_RO(debug_stat);
1141
1142 static void zram_meta_free(struct zram *zram, u64 disksize)
1143 {
1144         size_t num_pages = disksize >> PAGE_SHIFT;
1145         size_t index;
1146
1147         /* Free all pages that are still in this zram device */
1148         for (index = 0; index < num_pages; index++)
1149                 zram_free_page(zram, index);
1150
1151         zs_destroy_pool(zram->mem_pool);
1152         vfree(zram->table);
1153 }
1154
1155 static bool zram_meta_alloc(struct zram *zram, u64 disksize)
1156 {
1157         size_t num_pages;
1158
1159         num_pages = disksize >> PAGE_SHIFT;
1160         zram->table = vzalloc(array_size(num_pages, sizeof(*zram->table)));
1161         if (!zram->table)
1162                 return false;
1163
1164         zram->mem_pool = zs_create_pool(zram->disk->disk_name);
1165         if (!zram->mem_pool) {
1166                 vfree(zram->table);
1167                 return false;
1168         }
1169
1170         if (!huge_class_size)
1171                 huge_class_size = zs_huge_class_size(zram->mem_pool);
1172         return true;
1173 }
1174
1175 /*
1176  * To protect concurrent access to the same index entry,
1177  * caller should hold this table index entry's bit_spinlock to
1178  * indicate this index entry is accessing.
1179  */
1180 static void zram_free_page(struct zram *zram, size_t index)
1181 {
1182         unsigned long handle;
1183
1184 #ifdef CONFIG_ZRAM_MEMORY_TRACKING
1185         zram->table[index].ac_time = 0;
1186 #endif
1187         if (zram_test_flag(zram, index, ZRAM_IDLE))
1188                 zram_clear_flag(zram, index, ZRAM_IDLE);
1189
1190         if (zram_test_flag(zram, index, ZRAM_HUGE)) {
1191                 zram_clear_flag(zram, index, ZRAM_HUGE);
1192                 atomic64_dec(&zram->stats.huge_pages);
1193         }
1194
1195         if (zram_test_flag(zram, index, ZRAM_WB)) {
1196                 zram_clear_flag(zram, index, ZRAM_WB);
1197                 free_block_bdev(zram, zram_get_element(zram, index));
1198                 goto out;
1199         }
1200
1201         /*
1202          * No memory is allocated for same element filled pages.
1203          * Simply clear same page flag.
1204          */
1205         if (zram_test_flag(zram, index, ZRAM_SAME)) {
1206                 zram_clear_flag(zram, index, ZRAM_SAME);
1207                 atomic64_dec(&zram->stats.same_pages);
1208                 goto out;
1209         }
1210
1211         handle = zram_get_handle(zram, index);
1212         if (!handle)
1213                 return;
1214
1215         zs_free(zram->mem_pool, handle);
1216
1217         atomic64_sub(zram_get_obj_size(zram, index),
1218                         &zram->stats.compr_data_size);
1219 out:
1220         atomic64_dec(&zram->stats.pages_stored);
1221         zram_set_handle(zram, index, 0);
1222         zram_set_obj_size(zram, index, 0);
1223         WARN_ON_ONCE(zram->table[index].flags &
1224                 ~(1UL << ZRAM_LOCK | 1UL << ZRAM_UNDER_WB));
1225 }
1226
1227 static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
1228                                 struct bio *bio, bool partial_io)
1229 {
1230         struct zcomp_strm *zstrm;
1231         unsigned long handle;
1232         unsigned int size;
1233         void *src, *dst;
1234         int ret;
1235
1236         zram_slot_lock(zram, index);
1237         if (zram_test_flag(zram, index, ZRAM_WB)) {
1238                 struct bio_vec bvec;
1239
1240                 zram_slot_unlock(zram, index);
1241
1242                 bvec.bv_page = page;
1243                 bvec.bv_len = PAGE_SIZE;
1244                 bvec.bv_offset = 0;
1245                 return read_from_bdev(zram, &bvec,
1246                                 zram_get_element(zram, index),
1247                                 bio, partial_io);
1248         }
1249
1250         handle = zram_get_handle(zram, index);
1251         if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) {
1252                 unsigned long value;
1253                 void *mem;
1254
1255                 value = handle ? zram_get_element(zram, index) : 0;
1256                 mem = kmap_atomic(page);
1257                 zram_fill_page(mem, PAGE_SIZE, value);
1258                 kunmap_atomic(mem);
1259                 zram_slot_unlock(zram, index);
1260                 return 0;
1261         }
1262
1263         size = zram_get_obj_size(zram, index);
1264
1265         if (size != PAGE_SIZE)
1266                 zstrm = zcomp_stream_get(zram->comp);
1267
1268         src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
1269         if (size == PAGE_SIZE) {
1270                 dst = kmap_atomic(page);
1271                 memcpy(dst, src, PAGE_SIZE);
1272                 kunmap_atomic(dst);
1273                 ret = 0;
1274         } else {
1275                 dst = kmap_atomic(page);
1276                 ret = zcomp_decompress(zstrm, src, size, dst);
1277                 kunmap_atomic(dst);
1278                 zcomp_stream_put(zram->comp);
1279         }
1280         zs_unmap_object(zram->mem_pool, handle);
1281         zram_slot_unlock(zram, index);
1282
1283         /* Should NEVER happen. Return bio error if it does. */
1284         if (WARN_ON(ret))
1285                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
1286
1287         return ret;
1288 }
1289
1290 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
1291                                 u32 index, int offset, struct bio *bio)
1292 {
1293         int ret;
1294         struct page *page;
1295
1296         page = bvec->bv_page;
1297         if (is_partial_io(bvec)) {
1298                 /* Use a temporary buffer to decompress the page */
1299                 page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
1300                 if (!page)
1301                         return -ENOMEM;
1302         }
1303
1304         ret = __zram_bvec_read(zram, page, index, bio, is_partial_io(bvec));
1305         if (unlikely(ret))
1306                 goto out;
1307
1308         if (is_partial_io(bvec)) {
1309                 void *dst = kmap_atomic(bvec->bv_page);
1310                 void *src = kmap_atomic(page);
1311
1312                 memcpy(dst + bvec->bv_offset, src + offset, bvec->bv_len);
1313                 kunmap_atomic(src);
1314                 kunmap_atomic(dst);
1315         }
1316 out:
1317         if (is_partial_io(bvec))
1318                 __free_page(page);
1319
1320         return ret;
1321 }
1322
1323 static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
1324                                 u32 index, struct bio *bio)
1325 {
1326         int ret = 0;
1327         unsigned long alloced_pages;
1328         unsigned long handle = 0;
1329         unsigned int comp_len = 0;
1330         void *src, *dst, *mem;
1331         struct zcomp_strm *zstrm;
1332         struct page *page = bvec->bv_page;
1333         unsigned long element = 0;
1334         enum zram_pageflags flags = 0;
1335
1336         mem = kmap_atomic(page);
1337         if (page_same_filled(mem, &element)) {
1338                 kunmap_atomic(mem);
1339                 /* Free memory associated with this sector now. */
1340                 flags = ZRAM_SAME;
1341                 atomic64_inc(&zram->stats.same_pages);
1342                 goto out;
1343         }
1344         kunmap_atomic(mem);
1345
1346 compress_again:
1347         zstrm = zcomp_stream_get(zram->comp);
1348         src = kmap_atomic(page);
1349         ret = zcomp_compress(zstrm, src, &comp_len);
1350         kunmap_atomic(src);
1351
1352         if (unlikely(ret)) {
1353                 zcomp_stream_put(zram->comp);
1354                 pr_err("Compression failed! err=%d\n", ret);
1355                 zs_free(zram->mem_pool, handle);
1356                 return ret;
1357         }
1358
1359         if (comp_len >= huge_class_size)
1360                 comp_len = PAGE_SIZE;
1361         /*
1362          * handle allocation has 2 paths:
1363          * a) fast path is executed with preemption disabled (for
1364          *  per-cpu streams) and has __GFP_DIRECT_RECLAIM bit clear,
1365          *  since we can't sleep;
1366          * b) slow path enables preemption and attempts to allocate
1367          *  the page with __GFP_DIRECT_RECLAIM bit set. we have to
1368          *  put per-cpu compression stream and, thus, to re-do
1369          *  the compression once handle is allocated.
1370          *
1371          * if we have a 'non-null' handle here then we are coming
1372          * from the slow path and handle has already been allocated.
1373          */
1374         if (!handle)
1375                 handle = zs_malloc(zram->mem_pool, comp_len,
1376                                 __GFP_KSWAPD_RECLAIM |
1377                                 __GFP_NOWARN |
1378                                 __GFP_HIGHMEM |
1379                                 __GFP_MOVABLE);
1380         if (!handle) {
1381                 zcomp_stream_put(zram->comp);
1382                 atomic64_inc(&zram->stats.writestall);
1383                 handle = zs_malloc(zram->mem_pool, comp_len,
1384                                 GFP_NOIO | __GFP_HIGHMEM |
1385                                 __GFP_MOVABLE);
1386                 if (handle)
1387                         goto compress_again;
1388                 return -ENOMEM;
1389         }
1390
1391         alloced_pages = zs_get_total_pages(zram->mem_pool);
1392         update_used_max(zram, alloced_pages);
1393
1394         if (zram->limit_pages && alloced_pages > zram->limit_pages) {
1395                 zcomp_stream_put(zram->comp);
1396                 zs_free(zram->mem_pool, handle);
1397                 return -ENOMEM;
1398         }
1399
1400         dst = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
1401
1402         src = zstrm->buffer;
1403         if (comp_len == PAGE_SIZE)
1404                 src = kmap_atomic(page);
1405         memcpy(dst, src, comp_len);
1406         if (comp_len == PAGE_SIZE)
1407                 kunmap_atomic(src);
1408
1409         zcomp_stream_put(zram->comp);
1410         zs_unmap_object(zram->mem_pool, handle);
1411         atomic64_add(comp_len, &zram->stats.compr_data_size);
1412 out:
1413         /*
1414          * Free memory associated with this sector
1415          * before overwriting unused sectors.
1416          */
1417         zram_slot_lock(zram, index);
1418         zram_free_page(zram, index);
1419
1420         if (comp_len == PAGE_SIZE) {
1421                 zram_set_flag(zram, index, ZRAM_HUGE);
1422                 atomic64_inc(&zram->stats.huge_pages);
1423                 atomic64_inc(&zram->stats.huge_pages_since);
1424         }
1425
1426         if (flags) {
1427                 zram_set_flag(zram, index, flags);
1428                 zram_set_element(zram, index, element);
1429         }  else {
1430                 zram_set_handle(zram, index, handle);
1431                 zram_set_obj_size(zram, index, comp_len);
1432         }
1433         zram_slot_unlock(zram, index);
1434
1435         /* Update stats */
1436         atomic64_inc(&zram->stats.pages_stored);
1437         return ret;
1438 }
1439
1440 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
1441                                 u32 index, int offset, struct bio *bio)
1442 {
1443         int ret;
1444         struct page *page = NULL;
1445         void *src;
1446         struct bio_vec vec;
1447
1448         vec = *bvec;
1449         if (is_partial_io(bvec)) {
1450                 void *dst;
1451                 /*
1452                  * This is a partial IO. We need to read the full page
1453                  * before to write the changes.
1454                  */
1455                 page = alloc_page(GFP_NOIO|__GFP_HIGHMEM);
1456                 if (!page)
1457                         return -ENOMEM;
1458
1459                 ret = __zram_bvec_read(zram, page, index, bio, true);
1460                 if (ret)
1461                         goto out;
1462
1463                 src = kmap_atomic(bvec->bv_page);
1464                 dst = kmap_atomic(page);
1465                 memcpy(dst + offset, src + bvec->bv_offset, bvec->bv_len);
1466                 kunmap_atomic(dst);
1467                 kunmap_atomic(src);
1468
1469                 vec.bv_page = page;
1470                 vec.bv_len = PAGE_SIZE;
1471                 vec.bv_offset = 0;
1472         }
1473
1474         ret = __zram_bvec_write(zram, &vec, index, bio);
1475 out:
1476         if (is_partial_io(bvec))
1477                 __free_page(page);
1478         return ret;
1479 }
1480
1481 /*
1482  * zram_bio_discard - handler on discard request
1483  * @index: physical block index in PAGE_SIZE units
1484  * @offset: byte offset within physical block
1485  */
1486 static void zram_bio_discard(struct zram *zram, u32 index,
1487                              int offset, struct bio *bio)
1488 {
1489         size_t n = bio->bi_iter.bi_size;
1490
1491         /*
1492          * zram manages data in physical block size units. Because logical block
1493          * size isn't identical with physical block size on some arch, we
1494          * could get a discard request pointing to a specific offset within a
1495          * certain physical block.  Although we can handle this request by
1496          * reading that physiclal block and decompressing and partially zeroing
1497          * and re-compressing and then re-storing it, this isn't reasonable
1498          * because our intent with a discard request is to save memory.  So
1499          * skipping this logical block is appropriate here.
1500          */
1501         if (offset) {
1502                 if (n <= (PAGE_SIZE - offset))
1503                         return;
1504
1505                 n -= (PAGE_SIZE - offset);
1506                 index++;
1507         }
1508
1509         while (n >= PAGE_SIZE) {
1510                 zram_slot_lock(zram, index);
1511                 zram_free_page(zram, index);
1512                 zram_slot_unlock(zram, index);
1513                 atomic64_inc(&zram->stats.notify_free);
1514                 index++;
1515                 n -= PAGE_SIZE;
1516         }
1517 }
1518
1519 /*
1520  * Returns errno if it has some problem. Otherwise return 0 or 1.
1521  * Returns 0 if IO request was done synchronously
1522  * Returns 1 if IO request was successfully submitted.
1523  */
1524 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
1525                         int offset, unsigned int op, struct bio *bio)
1526 {
1527         int ret;
1528
1529         if (!op_is_write(op)) {
1530                 atomic64_inc(&zram->stats.num_reads);
1531                 ret = zram_bvec_read(zram, bvec, index, offset, bio);
1532                 flush_dcache_page(bvec->bv_page);
1533         } else {
1534                 atomic64_inc(&zram->stats.num_writes);
1535                 ret = zram_bvec_write(zram, bvec, index, offset, bio);
1536         }
1537
1538         zram_slot_lock(zram, index);
1539         zram_accessed(zram, index);
1540         zram_slot_unlock(zram, index);
1541
1542         if (unlikely(ret < 0)) {
1543                 if (!op_is_write(op))
1544                         atomic64_inc(&zram->stats.failed_reads);
1545                 else
1546                         atomic64_inc(&zram->stats.failed_writes);
1547         }
1548
1549         return ret;
1550 }
1551
1552 static void __zram_make_request(struct zram *zram, struct bio *bio)
1553 {
1554         int offset;
1555         u32 index;
1556         struct bio_vec bvec;
1557         struct bvec_iter iter;
1558         unsigned long start_time;
1559
1560         index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
1561         offset = (bio->bi_iter.bi_sector &
1562                   (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
1563
1564         switch (bio_op(bio)) {
1565         case REQ_OP_DISCARD:
1566         case REQ_OP_WRITE_ZEROES:
1567                 zram_bio_discard(zram, index, offset, bio);
1568                 bio_endio(bio);
1569                 return;
1570         default:
1571                 break;
1572         }
1573
1574         start_time = bio_start_io_acct(bio);
1575         bio_for_each_segment(bvec, bio, iter) {
1576                 struct bio_vec bv = bvec;
1577                 unsigned int unwritten = bvec.bv_len;
1578
1579                 do {
1580                         bv.bv_len = min_t(unsigned int, PAGE_SIZE - offset,
1581                                                         unwritten);
1582                         if (zram_bvec_rw(zram, &bv, index, offset,
1583                                          bio_op(bio), bio) < 0) {
1584                                 bio->bi_status = BLK_STS_IOERR;
1585                                 break;
1586                         }
1587
1588                         bv.bv_offset += bv.bv_len;
1589                         unwritten -= bv.bv_len;
1590
1591                         update_position(&index, &offset, &bv);
1592                 } while (unwritten);
1593         }
1594         bio_end_io_acct(bio, start_time);
1595         bio_endio(bio);
1596 }
1597
1598 /*
1599  * Handler function for all zram I/O requests.
1600  */
1601 static blk_qc_t zram_submit_bio(struct bio *bio)
1602 {
1603         struct zram *zram = bio->bi_bdev->bd_disk->private_data;
1604
1605         if (!valid_io_request(zram, bio->bi_iter.bi_sector,
1606                                         bio->bi_iter.bi_size)) {
1607                 atomic64_inc(&zram->stats.invalid_io);
1608                 goto error;
1609         }
1610
1611         __zram_make_request(zram, bio);
1612         return BLK_QC_T_NONE;
1613
1614 error:
1615         bio_io_error(bio);
1616         return BLK_QC_T_NONE;
1617 }
1618
1619 static void zram_slot_free_notify(struct block_device *bdev,
1620                                 unsigned long index)
1621 {
1622         struct zram *zram;
1623
1624         zram = bdev->bd_disk->private_data;
1625
1626         atomic64_inc(&zram->stats.notify_free);
1627         if (!zram_slot_trylock(zram, index)) {
1628                 atomic64_inc(&zram->stats.miss_free);
1629                 return;
1630         }
1631
1632         zram_free_page(zram, index);
1633         zram_slot_unlock(zram, index);
1634 }
1635
1636 static int zram_rw_page(struct block_device *bdev, sector_t sector,
1637                        struct page *page, unsigned int op)
1638 {
1639         int offset, ret;
1640         u32 index;
1641         struct zram *zram;
1642         struct bio_vec bv;
1643         unsigned long start_time;
1644
1645         if (PageTransHuge(page))
1646                 return -ENOTSUPP;
1647         zram = bdev->bd_disk->private_data;
1648
1649         if (!valid_io_request(zram, sector, PAGE_SIZE)) {
1650                 atomic64_inc(&zram->stats.invalid_io);
1651                 ret = -EINVAL;
1652                 goto out;
1653         }
1654
1655         index = sector >> SECTORS_PER_PAGE_SHIFT;
1656         offset = (sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
1657
1658         bv.bv_page = page;
1659         bv.bv_len = PAGE_SIZE;
1660         bv.bv_offset = 0;
1661
1662         start_time = disk_start_io_acct(bdev->bd_disk, SECTORS_PER_PAGE, op);
1663         ret = zram_bvec_rw(zram, &bv, index, offset, op, NULL);
1664         disk_end_io_acct(bdev->bd_disk, op, start_time);
1665 out:
1666         /*
1667          * If I/O fails, just return error(ie, non-zero) without
1668          * calling page_endio.
1669          * It causes resubmit the I/O with bio request by upper functions
1670          * of rw_page(e.g., swap_readpage, __swap_writepage) and
1671          * bio->bi_end_io does things to handle the error
1672          * (e.g., SetPageError, set_page_dirty and extra works).
1673          */
1674         if (unlikely(ret < 0))
1675                 return ret;
1676
1677         switch (ret) {
1678         case 0:
1679                 page_endio(page, op_is_write(op), 0);
1680                 break;
1681         case 1:
1682                 ret = 0;
1683                 break;
1684         default:
1685                 WARN_ON(1);
1686         }
1687         return ret;
1688 }
1689
1690 static void zram_reset_device(struct zram *zram)
1691 {
1692         struct zcomp *comp;
1693         u64 disksize;
1694
1695         down_write(&zram->init_lock);
1696
1697         zram->limit_pages = 0;
1698
1699         if (!init_done(zram)) {
1700                 up_write(&zram->init_lock);
1701                 return;
1702         }
1703
1704         comp = zram->comp;
1705         disksize = zram->disksize;
1706         zram->disksize = 0;
1707
1708         set_capacity_and_notify(zram->disk, 0);
1709         part_stat_set_all(zram->disk->part0, 0);
1710
1711         up_write(&zram->init_lock);
1712         /* I/O operation under all of CPU are done so let's free */
1713         zram_meta_free(zram, disksize);
1714         memset(&zram->stats, 0, sizeof(zram->stats));
1715         zcomp_destroy(comp);
1716         reset_bdev(zram);
1717 }
1718
1719 static ssize_t disksize_store(struct device *dev,
1720                 struct device_attribute *attr, const char *buf, size_t len)
1721 {
1722         u64 disksize;
1723         struct zcomp *comp;
1724         struct zram *zram = dev_to_zram(dev);
1725         int err;
1726
1727         disksize = memparse(buf, NULL);
1728         if (!disksize)
1729                 return -EINVAL;
1730
1731         down_write(&zram->init_lock);
1732         if (init_done(zram)) {
1733                 pr_info("Cannot change disksize for initialized device\n");
1734                 err = -EBUSY;
1735                 goto out_unlock;
1736         }
1737
1738         disksize = PAGE_ALIGN(disksize);
1739         if (!zram_meta_alloc(zram, disksize)) {
1740                 err = -ENOMEM;
1741                 goto out_unlock;
1742         }
1743
1744         comp = zcomp_create(zram->compressor);
1745         if (IS_ERR(comp)) {
1746                 pr_err("Cannot initialise %s compressing backend\n",
1747                                 zram->compressor);
1748                 err = PTR_ERR(comp);
1749                 goto out_free_meta;
1750         }
1751
1752         zram->comp = comp;
1753         zram->disksize = disksize;
1754         set_capacity_and_notify(zram->disk, zram->disksize >> SECTOR_SHIFT);
1755         up_write(&zram->init_lock);
1756
1757         return len;
1758
1759 out_free_meta:
1760         zram_meta_free(zram, disksize);
1761 out_unlock:
1762         up_write(&zram->init_lock);
1763         return err;
1764 }
1765
1766 static ssize_t reset_store(struct device *dev,
1767                 struct device_attribute *attr, const char *buf, size_t len)
1768 {
1769         int ret;
1770         unsigned short do_reset;
1771         struct zram *zram;
1772         struct block_device *bdev;
1773
1774         ret = kstrtou16(buf, 10, &do_reset);
1775         if (ret)
1776                 return ret;
1777
1778         if (!do_reset)
1779                 return -EINVAL;
1780
1781         zram = dev_to_zram(dev);
1782         bdev = zram->disk->part0;
1783
1784         mutex_lock(&bdev->bd_mutex);
1785         /* Do not reset an active device or claimed device */
1786         if (bdev->bd_openers || zram->claim) {
1787                 mutex_unlock(&bdev->bd_mutex);
1788                 return -EBUSY;
1789         }
1790
1791         /* From now on, anyone can't open /dev/zram[0-9] */
1792         zram->claim = true;
1793         mutex_unlock(&bdev->bd_mutex);
1794
1795         /* Make sure all the pending I/O are finished */
1796         fsync_bdev(bdev);
1797         zram_reset_device(zram);
1798
1799         mutex_lock(&bdev->bd_mutex);
1800         zram->claim = false;
1801         mutex_unlock(&bdev->bd_mutex);
1802
1803         return len;
1804 }
1805
1806 static int zram_open(struct block_device *bdev, fmode_t mode)
1807 {
1808         int ret = 0;
1809         struct zram *zram;
1810
1811         WARN_ON(!mutex_is_locked(&bdev->bd_mutex));
1812
1813         zram = bdev->bd_disk->private_data;
1814         /* zram was claimed to reset so open request fails */
1815         if (zram->claim)
1816                 ret = -EBUSY;
1817
1818         return ret;
1819 }
1820
1821 static const struct block_device_operations zram_devops = {
1822         .open = zram_open,
1823         .submit_bio = zram_submit_bio,
1824         .swap_slot_free_notify = zram_slot_free_notify,
1825         .rw_page = zram_rw_page,
1826         .owner = THIS_MODULE
1827 };
1828
1829 static const struct block_device_operations zram_wb_devops = {
1830         .open = zram_open,
1831         .submit_bio = zram_submit_bio,
1832         .swap_slot_free_notify = zram_slot_free_notify,
1833         .owner = THIS_MODULE
1834 };
1835
1836 static DEVICE_ATTR_WO(compact);
1837 static DEVICE_ATTR_RW(disksize);
1838 static DEVICE_ATTR_RO(initstate);
1839 static DEVICE_ATTR_WO(reset);
1840 static DEVICE_ATTR_WO(mem_limit);
1841 static DEVICE_ATTR_WO(mem_used_max);
1842 static DEVICE_ATTR_WO(idle);
1843 static DEVICE_ATTR_RW(max_comp_streams);
1844 static DEVICE_ATTR_RW(comp_algorithm);
1845 #ifdef CONFIG_ZRAM_WRITEBACK
1846 static DEVICE_ATTR_RW(backing_dev);
1847 static DEVICE_ATTR_WO(writeback);
1848 static DEVICE_ATTR_RW(writeback_limit);
1849 static DEVICE_ATTR_RW(writeback_limit_enable);
1850 #endif
1851
1852 static struct attribute *zram_disk_attrs[] = {
1853         &dev_attr_disksize.attr,
1854         &dev_attr_initstate.attr,
1855         &dev_attr_reset.attr,
1856         &dev_attr_compact.attr,
1857         &dev_attr_mem_limit.attr,
1858         &dev_attr_mem_used_max.attr,
1859         &dev_attr_idle.attr,
1860         &dev_attr_max_comp_streams.attr,
1861         &dev_attr_comp_algorithm.attr,
1862 #ifdef CONFIG_ZRAM_WRITEBACK
1863         &dev_attr_backing_dev.attr,
1864         &dev_attr_writeback.attr,
1865         &dev_attr_writeback_limit.attr,
1866         &dev_attr_writeback_limit_enable.attr,
1867 #endif
1868         &dev_attr_io_stat.attr,
1869         &dev_attr_mm_stat.attr,
1870 #ifdef CONFIG_ZRAM_WRITEBACK
1871         &dev_attr_bd_stat.attr,
1872 #endif
1873         &dev_attr_debug_stat.attr,
1874         NULL,
1875 };
1876
1877 static const struct attribute_group zram_disk_attr_group = {
1878         .attrs = zram_disk_attrs,
1879 };
1880
1881 static const struct attribute_group *zram_disk_attr_groups[] = {
1882         &zram_disk_attr_group,
1883         NULL,
1884 };
1885
1886 /*
1887  * Allocate and initialize new zram device. the function returns
1888  * '>= 0' device_id upon success, and negative value otherwise.
1889  */
1890 static int zram_add(void)
1891 {
1892         struct zram *zram;
1893         struct request_queue *queue;
1894         int ret, device_id;
1895
1896         zram = kzalloc(sizeof(struct zram), GFP_KERNEL);
1897         if (!zram)
1898                 return -ENOMEM;
1899
1900         ret = idr_alloc(&zram_index_idr, zram, 0, 0, GFP_KERNEL);
1901         if (ret < 0)
1902                 goto out_free_dev;
1903         device_id = ret;
1904
1905         init_rwsem(&zram->init_lock);
1906 #ifdef CONFIG_ZRAM_WRITEBACK
1907         spin_lock_init(&zram->wb_limit_lock);
1908 #endif
1909         queue = blk_alloc_queue(NUMA_NO_NODE);
1910         if (!queue) {
1911                 pr_err("Error allocating disk queue for device %d\n",
1912                         device_id);
1913                 ret = -ENOMEM;
1914                 goto out_free_idr;
1915         }
1916
1917         /* gendisk structure */
1918         zram->disk = alloc_disk(1);
1919         if (!zram->disk) {
1920                 pr_err("Error allocating disk structure for device %d\n",
1921                         device_id);
1922                 ret = -ENOMEM;
1923                 goto out_free_queue;
1924         }
1925
1926         zram->disk->major = zram_major;
1927         zram->disk->first_minor = device_id;
1928         zram->disk->fops = &zram_devops;
1929         zram->disk->queue = queue;
1930         zram->disk->private_data = zram;
1931         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
1932
1933         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
1934         set_capacity(zram->disk, 0);
1935         /* zram devices sort of resembles non-rotational disks */
1936         blk_queue_flag_set(QUEUE_FLAG_NONROT, zram->disk->queue);
1937         blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);
1938
1939         /*
1940          * To ensure that we always get PAGE_SIZE aligned
1941          * and n*PAGE_SIZED sized I/O requests.
1942          */
1943         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
1944         blk_queue_logical_block_size(zram->disk->queue,
1945                                         ZRAM_LOGICAL_BLOCK_SIZE);
1946         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
1947         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
1948         zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
1949         blk_queue_max_discard_sectors(zram->disk->queue, UINT_MAX);
1950         blk_queue_flag_set(QUEUE_FLAG_DISCARD, zram->disk->queue);
1951
1952         /*
1953          * zram_bio_discard() will clear all logical blocks if logical block
1954          * size is identical with physical block size(PAGE_SIZE). But if it is
1955          * different, we will skip discarding some parts of logical blocks in
1956          * the part of the request range which isn't aligned to physical block
1957          * size.  So we can't ensure that all discarded logical blocks are
1958          * zeroed.
1959          */
1960         if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
1961                 blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);
1962
1963         blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, zram->disk->queue);
1964         device_add_disk(NULL, zram->disk, zram_disk_attr_groups);
1965
1966         strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
1967
1968         zram_debugfs_register(zram);
1969         pr_info("Added device: %s\n", zram->disk->disk_name);
1970         return device_id;
1971
1972 out_free_queue:
1973         blk_cleanup_queue(queue);
1974 out_free_idr:
1975         idr_remove(&zram_index_idr, device_id);
1976 out_free_dev:
1977         kfree(zram);
1978         return ret;
1979 }
1980
1981 static int zram_remove(struct zram *zram)
1982 {
1983         struct block_device *bdev = zram->disk->part0;
1984
1985         mutex_lock(&bdev->bd_mutex);
1986         if (bdev->bd_openers || zram->claim) {
1987                 mutex_unlock(&bdev->bd_mutex);
1988                 return -EBUSY;
1989         }
1990
1991         zram->claim = true;
1992         mutex_unlock(&bdev->bd_mutex);
1993
1994         zram_debugfs_unregister(zram);
1995
1996         /* Make sure all the pending I/O are finished */
1997         fsync_bdev(bdev);
1998         zram_reset_device(zram);
1999
2000         pr_info("Removed device: %s\n", zram->disk->disk_name);
2001
2002         del_gendisk(zram->disk);
2003         blk_cleanup_queue(zram->disk->queue);
2004         put_disk(zram->disk);
2005         kfree(zram);
2006         return 0;
2007 }
2008
2009 /* zram-control sysfs attributes */
2010
2011 /*
2012  * NOTE: hot_add attribute is not the usual read-only sysfs attribute. In a
2013  * sense that reading from this file does alter the state of your system -- it
2014  * creates a new un-initialized zram device and returns back this device's
2015  * device_id (or an error code if it fails to create a new device).
2016  */
2017 static ssize_t hot_add_show(struct class *class,
2018                         struct class_attribute *attr,
2019                         char *buf)
2020 {
2021         int ret;
2022
2023         mutex_lock(&zram_index_mutex);
2024         ret = zram_add();
2025         mutex_unlock(&zram_index_mutex);
2026
2027         if (ret < 0)
2028                 return ret;
2029         return scnprintf(buf, PAGE_SIZE, "%d\n", ret);
2030 }
2031 static struct class_attribute class_attr_hot_add =
2032         __ATTR(hot_add, 0400, hot_add_show, NULL);
2033
2034 static ssize_t hot_remove_store(struct class *class,
2035                         struct class_attribute *attr,
2036                         const char *buf,
2037                         size_t count)
2038 {
2039         struct zram *zram;
2040         int ret, dev_id;
2041
2042         /* dev_id is gendisk->first_minor, which is `int' */
2043         ret = kstrtoint(buf, 10, &dev_id);
2044         if (ret)
2045                 return ret;
2046         if (dev_id < 0)
2047                 return -EINVAL;
2048
2049         mutex_lock(&zram_index_mutex);
2050
2051         zram = idr_find(&zram_index_idr, dev_id);
2052         if (zram) {
2053                 ret = zram_remove(zram);
2054                 if (!ret)
2055                         idr_remove(&zram_index_idr, dev_id);
2056         } else {
2057                 ret = -ENODEV;
2058         }
2059
2060         mutex_unlock(&zram_index_mutex);
2061         return ret ? ret : count;
2062 }
2063 static CLASS_ATTR_WO(hot_remove);
2064
2065 static struct attribute *zram_control_class_attrs[] = {
2066         &class_attr_hot_add.attr,
2067         &class_attr_hot_remove.attr,
2068         NULL,
2069 };
2070 ATTRIBUTE_GROUPS(zram_control_class);
2071
2072 static struct class zram_control_class = {
2073         .name           = "zram-control",
2074         .owner          = THIS_MODULE,
2075         .class_groups   = zram_control_class_groups,
2076 };
2077
2078 static int zram_remove_cb(int id, void *ptr, void *data)
2079 {
2080         zram_remove(ptr);
2081         return 0;
2082 }
2083
2084 static void destroy_devices(void)
2085 {
2086         class_unregister(&zram_control_class);
2087         idr_for_each(&zram_index_idr, &zram_remove_cb, NULL);
2088         zram_debugfs_destroy();
2089         idr_destroy(&zram_index_idr);
2090         unregister_blkdev(zram_major, "zram");
2091         cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE);
2092 }
2093
2094 static int __init zram_init(void)
2095 {
2096         int ret;
2097
2098         ret = cpuhp_setup_state_multi(CPUHP_ZCOMP_PREPARE, "block/zram:prepare",
2099                                       zcomp_cpu_up_prepare, zcomp_cpu_dead);
2100         if (ret < 0)
2101                 return ret;
2102
2103         ret = class_register(&zram_control_class);
2104         if (ret) {
2105                 pr_err("Unable to register zram-control class\n");
2106                 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE);
2107                 return ret;
2108         }
2109
2110         zram_debugfs_create();
2111         zram_major = register_blkdev(0, "zram");
2112         if (zram_major <= 0) {
2113                 pr_err("Unable to get major number\n");
2114                 class_unregister(&zram_control_class);
2115                 cpuhp_remove_multi_state(CPUHP_ZCOMP_PREPARE);
2116                 return -EBUSY;
2117         }
2118
2119         while (num_devices != 0) {
2120                 mutex_lock(&zram_index_mutex);
2121                 ret = zram_add();
2122                 mutex_unlock(&zram_index_mutex);
2123                 if (ret < 0)
2124                         goto out_error;
2125                 num_devices--;
2126         }
2127
2128         return 0;
2129
2130 out_error:
2131         destroy_devices();
2132         return ret;
2133 }
2134
2135 static void __exit zram_exit(void)
2136 {
2137         destroy_devices();
2138 }
2139
2140 module_init(zram_init);
2141 module_exit(zram_exit);
2142
2143 module_param(num_devices, uint, 0);
2144 MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices");
2145
2146 MODULE_LICENSE("Dual BSD/GPL");
2147 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
2148 MODULE_DESCRIPTION("Compressed RAM Block Device");