drivers/md/dm-writecache.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2018 Red Hat. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/vmalloc.h>
  12 #include <linux/kthread.h>
  13 #include <linux/dm-io.h>
  14 #include <linux/dm-kcopyd.h>
  15 #include <linux/dax.h>
  16 #include <linux/pfn_t.h>
  17 #include <linux/libnvdimm.h>
  18
  19 #define DM_MSG_PREFIX "writecache"
  20
  21 #define HIGH_WATERMARK                  50
  22 #define LOW_WATERMARK                   45
  23 #define MAX_WRITEBACK_JOBS              0
  24 #define ENDIO_LATENCY                   16
  25 #define WRITEBACK_LATENCY               64
  26 #define AUTOCOMMIT_BLOCKS_SSD           65536
  27 #define AUTOCOMMIT_BLOCKS_PMEM          64
  28 #define AUTOCOMMIT_MSEC                 1000
  29 #define MAX_AGE_DIV                     16
  30 #define MAX_AGE_UNSPECIFIED             -1UL
  31
  32 #define BITMAP_GRANULARITY      65536
  33 #if BITMAP_GRANULARITY < PAGE_SIZE
  34 #undef BITMAP_GRANULARITY
  35 #define BITMAP_GRANULARITY      PAGE_SIZE
  36 #endif
  37
  38 #if IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API) && IS_ENABLED(CONFIG_DAX_DRIVER)
  39 #define DM_WRITECACHE_HAS_PMEM
  40 #endif
  41
  42 #ifdef DM_WRITECACHE_HAS_PMEM
  43 #define pmem_assign(dest, src)                                  \
  44 do {                                                            \
  45         typeof(dest) uniq = (src);                              \
  46         memcpy_flushcache(&(dest), &uniq, sizeof(dest));        \
  47 } while (0)
  48 #else
  49 #define pmem_assign(dest, src)  ((dest) = (src))
  50 #endif
  51
  52 #if defined(__HAVE_ARCH_MEMCPY_MCSAFE) && defined(DM_WRITECACHE_HAS_PMEM)
  53 #define DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
  54 #endif
  55
  56 #define MEMORY_SUPERBLOCK_MAGIC         0x23489321
  57 #define MEMORY_SUPERBLOCK_VERSION       1
  58
  59 struct wc_memory_entry {
  60         __le64 original_sector;
  61         __le64 seq_count;
  62 };
  63
  64 struct wc_memory_superblock {
  65         union {
  66                 struct {
  67                         __le32 magic;
  68                         __le32 version;
  69                         __le32 block_size;
  70                         __le32 pad;
  71                         __le64 n_blocks;
  72                         __le64 seq_count;
  73                 };
  74                 __le64 padding[8];
  75         };
  76         struct wc_memory_entry entries[0];
  77 };
  78
  79 struct wc_entry {
  80         struct rb_node rb_node;
  81         struct list_head lru;
  82         unsigned short wc_list_contiguous;
  83         bool write_in_progress
  84 #if BITS_PER_LONG == 64
  85                 :1
  86 #endif
  87         ;
  88         unsigned long index
  89 #if BITS_PER_LONG == 64
  90                 :47
  91 #endif
  92         ;
  93         unsigned long age;
  94 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
  95         uint64_t original_sector;
  96         uint64_t seq_count;
  97 #endif
  98 };
  99
 100 #ifdef DM_WRITECACHE_HAS_PMEM
 101 #define WC_MODE_PMEM(wc)                        ((wc)->pmem_mode)
 102 #define WC_MODE_FUA(wc)                         ((wc)->writeback_fua)
 103 #else
 104 #define WC_MODE_PMEM(wc)                        false
 105 #define WC_MODE_FUA(wc)                         false
 106 #endif
 107 #define WC_MODE_SORT_FREELIST(wc)               (!WC_MODE_PMEM(wc))
 108
 109 struct dm_writecache {
 110         struct mutex lock;
 111         struct list_head lru;
 112         union {
 113                 struct list_head freelist;
 114                 struct {
 115                         struct rb_root freetree;
 116                         struct wc_entry *current_free;
 117                 };
 118         };
 119         struct rb_root tree;
 120
 121         size_t freelist_size;
 122         size_t writeback_size;
 123         size_t freelist_high_watermark;
 124         size_t freelist_low_watermark;
 125         unsigned long max_age;
 126
 127         unsigned uncommitted_blocks;
 128         unsigned autocommit_blocks;
 129         unsigned max_writeback_jobs;
 130
 131         int error;
 132
 133         unsigned long autocommit_jiffies;
 134         struct timer_list autocommit_timer;
 135         struct wait_queue_head freelist_wait;
 136
 137         struct timer_list max_age_timer;
 138
 139         atomic_t bio_in_progress[2];
 140         struct wait_queue_head bio_in_progress_wait[2];
 141
 142         struct dm_target *ti;
 143         struct dm_dev *dev;
 144         struct dm_dev *ssd_dev;
 145         sector_t start_sector;
 146         void *memory_map;
 147         uint64_t memory_map_size;
 148         size_t metadata_sectors;
 149         size_t n_blocks;
 150         uint64_t seq_count;
 151         void *block_start;
 152         struct wc_entry *entries;
 153         unsigned block_size;
 154         unsigned char block_size_bits;
 155
 156         bool pmem_mode:1;
 157         bool writeback_fua:1;
 158
 159         bool overwrote_committed:1;
 160         bool memory_vmapped:1;
 161
 162         bool high_wm_percent_set:1;
 163         bool low_wm_percent_set:1;
 164         bool max_writeback_jobs_set:1;
 165         bool autocommit_blocks_set:1;
 166         bool autocommit_time_set:1;
 167         bool writeback_fua_set:1;
 168         bool flush_on_suspend:1;
 169         bool cleaner:1;
 170
 171         unsigned writeback_all;
 172         struct workqueue_struct *writeback_wq;
 173         struct work_struct writeback_work;
 174         struct work_struct flush_work;
 175
 176         struct dm_io_client *dm_io;
 177
 178         raw_spinlock_t endio_list_lock;
 179         struct list_head endio_list;
 180         struct task_struct *endio_thread;
 181
 182         struct task_struct *flush_thread;
 183         struct bio_list flush_list;
 184
 185         struct dm_kcopyd_client *dm_kcopyd;
 186         unsigned long *dirty_bitmap;
 187         unsigned dirty_bitmap_size;
 188
 189         struct bio_set bio_set;
 190         mempool_t copy_pool;
 191 };
 192
 193 #define WB_LIST_INLINE          16
 194
 195 struct writeback_struct {
 196         struct list_head endio_entry;
 197         struct dm_writecache *wc;
 198         struct wc_entry **wc_list;
 199         unsigned wc_list_n;
 200         struct wc_entry *wc_list_inline[WB_LIST_INLINE];
 201         struct bio bio;
 202 };
 203
 204 struct copy_struct {
 205         struct list_head endio_entry;
 206         struct dm_writecache *wc;
 207         struct wc_entry *e;
 208         unsigned n_entries;
 209         int error;
 210 };
 211
 212 DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(dm_writecache_throttle,
 213                                             "A percentage of time allocated for data copying");
 214
 215 static void wc_lock(struct dm_writecache *wc)
 216 {
 217         mutex_lock(&wc->lock);
 218 }
 219
 220 static void wc_unlock(struct dm_writecache *wc)
 221 {
 222         mutex_unlock(&wc->lock);
 223 }
 224
 225 #ifdef DM_WRITECACHE_HAS_PMEM
 226 static int persistent_memory_claim(struct dm_writecache *wc)
 227 {
 228         int r;
 229         loff_t s;
 230         long p, da;
 231         pfn_t pfn;
 232         int id;
 233         struct page **pages;
 234
 235         wc->memory_vmapped = false;
 236
 237         s = wc->memory_map_size;
 238         p = s >> PAGE_SHIFT;
 239         if (!p) {
 240                 r = -EINVAL;
 241                 goto err1;
 242         }
 243         if (p != s >> PAGE_SHIFT) {
 244                 r = -EOVERFLOW;
 245                 goto err1;
 246         }
 247
 248         id = dax_read_lock();
 249
 250         da = dax_direct_access(wc->ssd_dev->dax_dev, 0, p, &wc->memory_map, &pfn);
 251         if (da < 0) {
 252                 wc->memory_map = NULL;
 253                 r = da;
 254                 goto err2;
 255         }
 256         if (!pfn_t_has_page(pfn)) {
 257                 wc->memory_map = NULL;
 258                 r = -EOPNOTSUPP;
 259                 goto err2;
 260         }
 261         if (da != p) {
 262                 long i;
 263                 wc->memory_map = NULL;
 264                 pages = kvmalloc_array(p, sizeof(struct page *), GFP_KERNEL);
 265                 if (!pages) {
 266                         r = -ENOMEM;
 267                         goto err2;
 268                 }
 269                 i = 0;
 270                 do {
 271                         long daa;
 272                         daa = dax_direct_access(wc->ssd_dev->dax_dev, i, p - i,
 273                                                 NULL, &pfn);
 274                         if (daa <= 0) {
 275                                 r = daa ? daa : -EINVAL;
 276                                 goto err3;
 277                         }
 278                         if (!pfn_t_has_page(pfn)) {
 279                                 r = -EOPNOTSUPP;
 280                                 goto err3;
 281                         }
 282                         while (daa-- && i < p) {
 283                                 pages[i++] = pfn_t_to_page(pfn);
 284                                 pfn.val++;
 285                                 if (!(i & 15))
 286                                         cond_resched();
 287                         }
 288                 } while (i < p);
 289                 wc->memory_map = vmap(pages, p, VM_MAP, PAGE_KERNEL);
 290                 if (!wc->memory_map) {
 291                         r = -ENOMEM;
 292                         goto err3;
 293                 }
 294                 kvfree(pages);
 295                 wc->memory_vmapped = true;
 296         }
 297
 298         dax_read_unlock(id);
 299
 300         wc->memory_map += (size_t)wc->start_sector << SECTOR_SHIFT;
 301         wc->memory_map_size -= (size_t)wc->start_sector << SECTOR_SHIFT;
 302
 303         return 0;
 304 err3:
 305         kvfree(pages);
 306 err2:
 307         dax_read_unlock(id);
 308 err1:
 309         return r;
 310 }
 311 #else
 312 static int persistent_memory_claim(struct dm_writecache *wc)
 313 {
 314         BUG();
 315 }
 316 #endif
 317
 318 static void persistent_memory_release(struct dm_writecache *wc)
 319 {
 320         if (wc->memory_vmapped)
 321                 vunmap(wc->memory_map - ((size_t)wc->start_sector << SECTOR_SHIFT));
 322 }
 323
 324 static struct page *persistent_memory_page(void *addr)
 325 {
 326         if (is_vmalloc_addr(addr))
 327                 return vmalloc_to_page(addr);
 328         else
 329                 return virt_to_page(addr);
 330 }
 331
 332 static unsigned persistent_memory_page_offset(void *addr)
 333 {
 334         return (unsigned long)addr & (PAGE_SIZE - 1);
 335 }
 336
 337 static void persistent_memory_flush_cache(void *ptr, size_t size)
 338 {
 339         if (is_vmalloc_addr(ptr))
 340                 flush_kernel_vmap_range(ptr, size);
 341 }
 342
 343 static void persistent_memory_invalidate_cache(void *ptr, size_t size)
 344 {
 345         if (is_vmalloc_addr(ptr))
 346                 invalidate_kernel_vmap_range(ptr, size);
 347 }
 348
 349 static struct wc_memory_superblock *sb(struct dm_writecache *wc)
 350 {
 351         return wc->memory_map;
 352 }
 353
 354 static struct wc_memory_entry *memory_entry(struct dm_writecache *wc, struct wc_entry *e)
 355 {
 356         return &sb(wc)->entries[e->index];
 357 }
 358
 359 static void *memory_data(struct dm_writecache *wc, struct wc_entry *e)
 360 {
 361         return (char *)wc->block_start + (e->index << wc->block_size_bits);
 362 }
 363
 364 static sector_t cache_sector(struct dm_writecache *wc, struct wc_entry *e)
 365 {
 366         return wc->start_sector + wc->metadata_sectors +
 367                 ((sector_t)e->index << (wc->block_size_bits - SECTOR_SHIFT));
 368 }
 369
 370 static uint64_t read_original_sector(struct dm_writecache *wc, struct wc_entry *e)
 371 {
 372 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 373         return e->original_sector;
 374 #else
 375         return le64_to_cpu(memory_entry(wc, e)->original_sector);
 376 #endif
 377 }
 378
 379 static uint64_t read_seq_count(struct dm_writecache *wc, struct wc_entry *e)
 380 {
 381 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 382         return e->seq_count;
 383 #else
 384         return le64_to_cpu(memory_entry(wc, e)->seq_count);
 385 #endif
 386 }
 387
 388 static void clear_seq_count(struct dm_writecache *wc, struct wc_entry *e)
 389 {
 390 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 391         e->seq_count = -1;
 392 #endif
 393         pmem_assign(memory_entry(wc, e)->seq_count, cpu_to_le64(-1));
 394 }
 395
 396 static void write_original_sector_seq_count(struct dm_writecache *wc, struct wc_entry *e,
 397                                             uint64_t original_sector, uint64_t seq_count)
 398 {
 399         struct wc_memory_entry me;
 400 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 401         e->original_sector = original_sector;
 402         e->seq_count = seq_count;
 403 #endif
 404         me.original_sector = cpu_to_le64(original_sector);
 405         me.seq_count = cpu_to_le64(seq_count);
 406         pmem_assign(*memory_entry(wc, e), me);
 407 }
 408
 409 #define writecache_error(wc, err, msg, arg...)                          \
 410 do {                                                                    \
 411         if (!cmpxchg(&(wc)->error, 0, err))                             \
 412                 DMERR(msg, ##arg);                                      \
 413         wake_up(&(wc)->freelist_wait);                                  \
 414 } while (0)
 415
 416 #define writecache_has_error(wc)        (unlikely(READ_ONCE((wc)->error)))
 417
 418 static void writecache_flush_all_metadata(struct dm_writecache *wc)
 419 {
 420         if (!WC_MODE_PMEM(wc))
 421                 memset(wc->dirty_bitmap, -1, wc->dirty_bitmap_size);
 422 }
 423
 424 static void writecache_flush_region(struct dm_writecache *wc, void *ptr, size_t size)
 425 {
 426         if (!WC_MODE_PMEM(wc))
 427                 __set_bit(((char *)ptr - (char *)wc->memory_map) / BITMAP_GRANULARITY,
 428                           wc->dirty_bitmap);
 429 }
 430
 431 static void writecache_disk_flush(struct dm_writecache *wc, struct dm_dev *dev);
 432
 433 struct io_notify {
 434         struct dm_writecache *wc;
 435         struct completion c;
 436         atomic_t count;
 437 };
 438
 439 static void writecache_notify_io(unsigned long error, void *context)
 440 {
 441         struct io_notify *endio = context;
 442
 443         if (unlikely(error != 0))
 444                 writecache_error(endio->wc, -EIO, "error writing metadata");
 445         BUG_ON(atomic_read(&endio->count) <= 0);
 446         if (atomic_dec_and_test(&endio->count))
 447                 complete(&endio->c);
 448 }
 449
 450 static void writecache_wait_for_ios(struct dm_writecache *wc, int direction)
 451 {
 452         wait_event(wc->bio_in_progress_wait[direction],
 453                    !atomic_read(&wc->bio_in_progress[direction]));
 454 }
 455
 456 static void ssd_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
 457 {
 458         struct dm_io_region region;
 459         struct dm_io_request req;
 460         struct io_notify endio = {
 461                 wc,
 462                 COMPLETION_INITIALIZER_ONSTACK(endio.c),
 463                 ATOMIC_INIT(1),
 464         };
 465         unsigned bitmap_bits = wc->dirty_bitmap_size * 8;
 466         unsigned i = 0;
 467
 468         while (1) {
 469                 unsigned j;
 470                 i = find_next_bit(wc->dirty_bitmap, bitmap_bits, i);
 471                 if (unlikely(i == bitmap_bits))
 472                         break;
 473                 j = find_next_zero_bit(wc->dirty_bitmap, bitmap_bits, i);
 474
 475                 region.bdev = wc->ssd_dev->bdev;
 476                 region.sector = (sector_t)i * (BITMAP_GRANULARITY >> SECTOR_SHIFT);
 477                 region.count = (sector_t)(j - i) * (BITMAP_GRANULARITY >> SECTOR_SHIFT);
 478
 479                 if (unlikely(region.sector >= wc->metadata_sectors))
 480                         break;
 481                 if (unlikely(region.sector + region.count > wc->metadata_sectors))
 482                         region.count = wc->metadata_sectors - region.sector;
 483
 484                 region.sector += wc->start_sector;
 485                 atomic_inc(&endio.count);
 486                 req.bi_op = REQ_OP_WRITE;
 487                 req.bi_op_flags = REQ_SYNC;
 488                 req.mem.type = DM_IO_VMA;
 489                 req.mem.ptr.vma = (char *)wc->memory_map + (size_t)i * BITMAP_GRANULARITY;
 490                 req.client = wc->dm_io;
 491                 req.notify.fn = writecache_notify_io;
 492                 req.notify.context = &endio;
 493
 494                 /* writing via async dm-io (implied by notify.fn above) won't return an error */
 495                 (void) dm_io(&req, 1, &region, NULL);
 496                 i = j;
 497         }
 498
 499         writecache_notify_io(0, &endio);
 500         wait_for_completion_io(&endio.c);
 501
 502         if (wait_for_ios)
 503                 writecache_wait_for_ios(wc, WRITE);
 504
 505         writecache_disk_flush(wc, wc->ssd_dev);
 506
 507         memset(wc->dirty_bitmap, 0, wc->dirty_bitmap_size);
 508 }
 509
 510 static void ssd_commit_superblock(struct dm_writecache *wc)
 511 {
 512         int r;
 513         struct dm_io_region region;
 514         struct dm_io_request req;
 515
 516         region.bdev = wc->ssd_dev->bdev;
 517         region.sector = 0;
 518         region.count = PAGE_SIZE;
 519
 520         if (unlikely(region.sector + region.count > wc->metadata_sectors))
 521                 region.count = wc->metadata_sectors - region.sector;
 522
 523         region.sector += wc->start_sector;
 524
 525         req.bi_op = REQ_OP_WRITE;
 526         req.bi_op_flags = REQ_SYNC | REQ_FUA;
 527         req.mem.type = DM_IO_VMA;
 528         req.mem.ptr.vma = (char *)wc->memory_map;
 529         req.client = wc->dm_io;
 530         req.notify.fn = NULL;
 531         req.notify.context = NULL;
 532
 533         r = dm_io(&req, 1, &region, NULL);
 534         if (unlikely(r))
 535                 writecache_error(wc, r, "error writing superblock");
 536 }
 537
 538 static void writecache_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
 539 {
 540         if (WC_MODE_PMEM(wc))
 541                 pmem_wmb();
 542         else
 543                 ssd_commit_flushed(wc, wait_for_ios);
 544 }
 545
 546 static void writecache_disk_flush(struct dm_writecache *wc, struct dm_dev *dev)
 547 {
 548         int r;
 549         struct dm_io_region region;
 550         struct dm_io_request req;
 551
 552         region.bdev = dev->bdev;
 553         region.sector = 0;
 554         region.count = 0;
 555         req.bi_op = REQ_OP_WRITE;
 556         req.bi_op_flags = REQ_PREFLUSH;
 557         req.mem.type = DM_IO_KMEM;
 558         req.mem.ptr.addr = NULL;
 559         req.client = wc->dm_io;
 560         req.notify.fn = NULL;
 561
 562         r = dm_io(&req, 1, &region, NULL);
 563         if (unlikely(r))
 564                 writecache_error(wc, r, "error flushing metadata: %d", r);
 565 }
 566
 567 #define WFE_RETURN_FOLLOWING    1
 568 #define WFE_LOWEST_SEQ          2
 569
 570 static struct wc_entry *writecache_find_entry(struct dm_writecache *wc,
 571                                               uint64_t block, int flags)
 572 {
 573         struct wc_entry *e;
 574         struct rb_node *node = wc->tree.rb_node;
 575
 576         if (unlikely(!node))
 577                 return NULL;
 578
 579         while (1) {
 580                 e = container_of(node, struct wc_entry, rb_node);
 581                 if (read_original_sector(wc, e) == block)
 582                         break;
 583
 584                 node = (read_original_sector(wc, e) >= block ?
 585                         e->rb_node.rb_left : e->rb_node.rb_right);
 586                 if (unlikely(!node)) {
 587                         if (!(flags & WFE_RETURN_FOLLOWING))
 588                                 return NULL;
 589                         if (read_original_sector(wc, e) >= block) {
 590                                 return e;
 591                         } else {
 592                                 node = rb_next(&e->rb_node);
 593                                 if (unlikely(!node))
 594                                         return NULL;
 595                                 e = container_of(node, struct wc_entry, rb_node);
 596                                 return e;
 597                         }
 598                 }
 599         }
 600
 601         while (1) {
 602                 struct wc_entry *e2;
 603                 if (flags & WFE_LOWEST_SEQ)
 604                         node = rb_prev(&e->rb_node);
 605                 else
 606                         node = rb_next(&e->rb_node);
 607                 if (unlikely(!node))
 608                         return e;
 609                 e2 = container_of(node, struct wc_entry, rb_node);
 610                 if (read_original_sector(wc, e2) != block)
 611                         return e;
 612                 e = e2;
 613         }
 614 }
 615
 616 static void writecache_insert_entry(struct dm_writecache *wc, struct wc_entry *ins)
 617 {
 618         struct wc_entry *e;
 619         struct rb_node **node = &wc->tree.rb_node, *parent = NULL;
 620
 621         while (*node) {
 622                 e = container_of(*node, struct wc_entry, rb_node);
 623                 parent = &e->rb_node;
 624                 if (read_original_sector(wc, e) > read_original_sector(wc, ins))
 625                         node = &parent->rb_left;
 626                 else
 627                         node = &parent->rb_right;
 628         }
 629         rb_link_node(&ins->rb_node, parent, node);
 630         rb_insert_color(&ins->rb_node, &wc->tree);
 631         list_add(&ins->lru, &wc->lru);
 632         ins->age = jiffies;
 633 }
 634
 635 static void writecache_unlink(struct dm_writecache *wc, struct wc_entry *e)
 636 {
 637         list_del(&e->lru);
 638         rb_erase(&e->rb_node, &wc->tree);
 639 }
 640
 641 static void writecache_add_to_freelist(struct dm_writecache *wc, struct wc_entry *e)
 642 {
 643         if (WC_MODE_SORT_FREELIST(wc)) {
 644                 struct rb_node **node = &wc->freetree.rb_node, *parent = NULL;
 645                 if (unlikely(!*node))
 646                         wc->current_free = e;
 647                 while (*node) {
 648                         parent = *node;
 649                         if (&e->rb_node < *node)
 650                                 node = &parent->rb_left;
 651                         else
 652                                 node = &parent->rb_right;
 653                 }
 654                 rb_link_node(&e->rb_node, parent, node);
 655                 rb_insert_color(&e->rb_node, &wc->freetree);
 656         } else {
 657                 list_add_tail(&e->lru, &wc->freelist);
 658         }
 659         wc->freelist_size++;
 660 }
 661
 662 static inline void writecache_verify_watermark(struct dm_writecache *wc)
 663 {
 664         if (unlikely(wc->freelist_size + wc->writeback_size <= wc->freelist_high_watermark))
 665                 queue_work(wc->writeback_wq, &wc->writeback_work);
 666 }
 667
 668 static void writecache_max_age_timer(struct timer_list *t)
 669 {
 670         struct dm_writecache *wc = from_timer(wc, t, max_age_timer);
 671
 672         if (!dm_suspended(wc->ti) && !writecache_has_error(wc)) {
 673                 queue_work(wc->writeback_wq, &wc->writeback_work);
 674                 mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);
 675         }
 676 }
 677
 678 static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc, sector_t expected_sector)
 679 {
 680         struct wc_entry *e;
 681
 682         if (WC_MODE_SORT_FREELIST(wc)) {
 683                 struct rb_node *next;
 684                 if (unlikely(!wc->current_free))
 685                         return NULL;
 686                 e = wc->current_free;
 687                 if (expected_sector != (sector_t)-1 && unlikely(cache_sector(wc, e) != expected_sector))
 688                         return NULL;
 689                 next = rb_next(&e->rb_node);
 690                 rb_erase(&e->rb_node, &wc->freetree);
 691                 if (unlikely(!next))
 692                         next = rb_first(&wc->freetree);
 693                 wc->current_free = next ? container_of(next, struct wc_entry, rb_node) : NULL;
 694         } else {
 695                 if (unlikely(list_empty(&wc->freelist)))
 696                         return NULL;
 697                 e = container_of(wc->freelist.next, struct wc_entry, lru);
 698                 if (expected_sector != (sector_t)-1 && unlikely(cache_sector(wc, e) != expected_sector))
 699                         return NULL;
 700                 list_del(&e->lru);
 701         }
 702         wc->freelist_size--;
 703
 704         writecache_verify_watermark(wc);
 705
 706         return e;
 707 }
 708
 709 static void writecache_free_entry(struct dm_writecache *wc, struct wc_entry *e)
 710 {
 711         writecache_unlink(wc, e);
 712         writecache_add_to_freelist(wc, e);
 713         clear_seq_count(wc, e);
 714         writecache_flush_region(wc, memory_entry(wc, e), sizeof(struct wc_memory_entry));
 715         if (unlikely(waitqueue_active(&wc->freelist_wait)))
 716                 wake_up(&wc->freelist_wait);
 717 }
 718
 719 static void writecache_wait_on_freelist(struct dm_writecache *wc)
 720 {
 721         DEFINE_WAIT(wait);
 722
 723         prepare_to_wait(&wc->freelist_wait, &wait, TASK_UNINTERRUPTIBLE);
 724         wc_unlock(wc);
 725         io_schedule();
 726         finish_wait(&wc->freelist_wait, &wait);
 727         wc_lock(wc);
 728 }
 729
 730 static void writecache_poison_lists(struct dm_writecache *wc)
 731 {
 732         /*
 733          * Catch incorrect access to these values while the device is suspended.
 734          */
 735         memset(&wc->tree, -1, sizeof wc->tree);
 736         wc->lru.next = LIST_POISON1;
 737         wc->lru.prev = LIST_POISON2;
 738         wc->freelist.next = LIST_POISON1;
 739         wc->freelist.prev = LIST_POISON2;
 740 }
 741
 742 static void writecache_flush_entry(struct dm_writecache *wc, struct wc_entry *e)
 743 {
 744         writecache_flush_region(wc, memory_entry(wc, e), sizeof(struct wc_memory_entry));
 745         if (WC_MODE_PMEM(wc))
 746                 writecache_flush_region(wc, memory_data(wc, e), wc->block_size);
 747 }
 748
 749 static bool writecache_entry_is_committed(struct dm_writecache *wc, struct wc_entry *e)
 750 {
 751         return read_seq_count(wc, e) < wc->seq_count;
 752 }
 753
 754 static void writecache_flush(struct dm_writecache *wc)
 755 {
 756         struct wc_entry *e, *e2;
 757         bool need_flush_after_free;
 758
 759         wc->uncommitted_blocks = 0;
 760         del_timer(&wc->autocommit_timer);
 761
 762         if (list_empty(&wc->lru))
 763                 return;
 764
 765         e = container_of(wc->lru.next, struct wc_entry, lru);
 766         if (writecache_entry_is_committed(wc, e)) {
 767                 if (wc->overwrote_committed) {
 768                         writecache_wait_for_ios(wc, WRITE);
 769                         writecache_disk_flush(wc, wc->ssd_dev);
 770                         wc->overwrote_committed = false;
 771                 }
 772                 return;
 773         }
 774         while (1) {
 775                 writecache_flush_entry(wc, e);
 776                 if (unlikely(e->lru.next == &wc->lru))
 777                         break;
 778                 e2 = container_of(e->lru.next, struct wc_entry, lru);
 779                 if (writecache_entry_is_committed(wc, e2))
 780                         break;
 781                 e = e2;
 782                 cond_resched();
 783         }
 784         writecache_commit_flushed(wc, true);
 785
 786         wc->seq_count++;
 787         pmem_assign(sb(wc)->seq_count, cpu_to_le64(wc->seq_count));
 788         if (WC_MODE_PMEM(wc))
 789                 writecache_commit_flushed(wc, false);
 790         else
 791                 ssd_commit_superblock(wc);
 792
 793         wc->overwrote_committed = false;
 794
 795         need_flush_after_free = false;
 796         while (1) {
 797                 /* Free another committed entry with lower seq-count */
 798                 struct rb_node *rb_node = rb_prev(&e->rb_node);
 799
 800                 if (rb_node) {
 801                         e2 = container_of(rb_node, struct wc_entry, rb_node);
 802                         if (read_original_sector(wc, e2) == read_original_sector(wc, e) &&
 803                             likely(!e2->write_in_progress)) {
 804                                 writecache_free_entry(wc, e2);
 805                                 need_flush_after_free = true;
 806                         }
 807                 }
 808                 if (unlikely(e->lru.prev == &wc->lru))
 809                         break;
 810                 e = container_of(e->lru.prev, struct wc_entry, lru);
 811                 cond_resched();
 812         }
 813
 814         if (need_flush_after_free)
 815                 writecache_commit_flushed(wc, false);
 816 }
 817
 818 static void writecache_flush_work(struct work_struct *work)
 819 {
 820         struct dm_writecache *wc = container_of(work, struct dm_writecache, flush_work);
 821
 822         wc_lock(wc);
 823         writecache_flush(wc);
 824         wc_unlock(wc);
 825 }
 826
 827 static void writecache_autocommit_timer(struct timer_list *t)
 828 {
 829         struct dm_writecache *wc = from_timer(wc, t, autocommit_timer);
 830         if (!writecache_has_error(wc))
 831                 queue_work(wc->writeback_wq, &wc->flush_work);
 832 }
 833
 834 static void writecache_schedule_autocommit(struct dm_writecache *wc)
 835 {
 836         if (!timer_pending(&wc->autocommit_timer))
 837                 mod_timer(&wc->autocommit_timer, jiffies + wc->autocommit_jiffies);
 838 }
 839
 840 static void writecache_discard(struct dm_writecache *wc, sector_t start, sector_t end)
 841 {
 842         struct wc_entry *e;
 843         bool discarded_something = false;
 844
 845         e = writecache_find_entry(wc, start, WFE_RETURN_FOLLOWING | WFE_LOWEST_SEQ);
 846         if (unlikely(!e))
 847                 return;
 848
 849         while (read_original_sector(wc, e) < end) {
 850                 struct rb_node *node = rb_next(&e->rb_node);
 851
 852                 if (likely(!e->write_in_progress)) {
 853                         if (!discarded_something) {
 854                                 if (!WC_MODE_PMEM(wc)) {
 855                                         writecache_wait_for_ios(wc, READ);
 856                                         writecache_wait_for_ios(wc, WRITE);
 857                                 }
 858                                 discarded_something = true;
 859                         }
 860                         if (!writecache_entry_is_committed(wc, e))
 861                                 wc->uncommitted_blocks--;
 862                         writecache_free_entry(wc, e);
 863                 }
 864
 865                 if (unlikely(!node))
 866                         break;
 867
 868                 e = container_of(node, struct wc_entry, rb_node);
 869         }
 870
 871         if (discarded_something)
 872                 writecache_commit_flushed(wc, false);
 873 }
 874
 875 static bool writecache_wait_for_writeback(struct dm_writecache *wc)
 876 {
 877         if (wc->writeback_size) {
 878                 writecache_wait_on_freelist(wc);
 879                 return true;
 880         }
 881         return false;
 882 }
 883
 884 static void writecache_suspend(struct dm_target *ti)
 885 {
 886         struct dm_writecache *wc = ti->private;
 887         bool flush_on_suspend;
 888
 889         del_timer_sync(&wc->autocommit_timer);
 890         del_timer_sync(&wc->max_age_timer);
 891
 892         wc_lock(wc);
 893         writecache_flush(wc);
 894         flush_on_suspend = wc->flush_on_suspend;
 895         if (flush_on_suspend) {
 896                 wc->flush_on_suspend = false;
 897                 wc->writeback_all++;
 898                 queue_work(wc->writeback_wq, &wc->writeback_work);
 899         }
 900         wc_unlock(wc);
 901
 902         drain_workqueue(wc->writeback_wq);
 903
 904         wc_lock(wc);
 905         if (flush_on_suspend)
 906                 wc->writeback_all--;
 907         while (writecache_wait_for_writeback(wc));
 908
 909         if (WC_MODE_PMEM(wc))
 910                 persistent_memory_flush_cache(wc->memory_map, wc->memory_map_size);
 911
 912         writecache_poison_lists(wc);
 913
 914         wc_unlock(wc);
 915 }
 916
 917 static int writecache_alloc_entries(struct dm_writecache *wc)
 918 {
 919         size_t b;
 920
 921         if (wc->entries)
 922                 return 0;
 923         wc->entries = vmalloc(array_size(sizeof(struct wc_entry), wc->n_blocks));
 924         if (!wc->entries)
 925                 return -ENOMEM;
 926         for (b = 0; b < wc->n_blocks; b++) {
 927                 struct wc_entry *e = &wc->entries[b];
 928                 e->index = b;
 929                 e->write_in_progress = false;
 930                 cond_resched();
 931         }
 932
 933         return 0;
 934 }
 935
 936 static int writecache_read_metadata(struct dm_writecache *wc, sector_t n_sectors)
 937 {
 938         struct dm_io_region region;
 939         struct dm_io_request req;
 940
 941         region.bdev = wc->ssd_dev->bdev;
 942         region.sector = wc->start_sector;
 943         region.count = n_sectors;
 944         req.bi_op = REQ_OP_READ;
 945         req.bi_op_flags = REQ_SYNC;
 946         req.mem.type = DM_IO_VMA;
 947         req.mem.ptr.vma = (char *)wc->memory_map;
 948         req.client = wc->dm_io;
 949         req.notify.fn = NULL;
 950
 951         return dm_io(&req, 1, &region, NULL);
 952 }
 953
 954 static void writecache_resume(struct dm_target *ti)
 955 {
 956         struct dm_writecache *wc = ti->private;
 957         size_t b;
 958         bool need_flush = false;
 959         __le64 sb_seq_count;
 960         int r;
 961
 962         wc_lock(wc);
 963
 964         if (WC_MODE_PMEM(wc)) {
 965                 persistent_memory_invalidate_cache(wc->memory_map, wc->memory_map_size);
 966         } else {
 967                 r = writecache_read_metadata(wc, wc->metadata_sectors);
 968                 if (r) {
 969                         size_t sb_entries_offset;
 970                         writecache_error(wc, r, "unable to read metadata: %d", r);
 971                         sb_entries_offset = offsetof(struct wc_memory_superblock, entries);
 972                         memset((char *)wc->memory_map + sb_entries_offset, -1,
 973                                (wc->metadata_sectors << SECTOR_SHIFT) - sb_entries_offset);
 974                 }
 975         }
 976
 977         wc->tree = RB_ROOT;
 978         INIT_LIST_HEAD(&wc->lru);
 979         if (WC_MODE_SORT_FREELIST(wc)) {
 980                 wc->freetree = RB_ROOT;
 981                 wc->current_free = NULL;
 982         } else {
 983                 INIT_LIST_HEAD(&wc->freelist);
 984         }
 985         wc->freelist_size = 0;
 986
 987         r = memcpy_mcsafe(&sb_seq_count, &sb(wc)->seq_count, sizeof(uint64_t));
 988         if (r) {
 989                 writecache_error(wc, r, "hardware memory error when reading superblock: %d", r);
 990                 sb_seq_count = cpu_to_le64(0);
 991         }
 992         wc->seq_count = le64_to_cpu(sb_seq_count);
 993
 994 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 995         for (b = 0; b < wc->n_blocks; b++) {
 996                 struct wc_entry *e = &wc->entries[b];
 997                 struct wc_memory_entry wme;
 998                 if (writecache_has_error(wc)) {
 999                         e->original_sector = -1;
1000                         e->seq_count = -1;
1001                         continue;
1002                 }
1003                 r = memcpy_mcsafe(&wme, memory_entry(wc, e), sizeof(struct wc_memory_entry));
1004                 if (r) {
1005                         writecache_error(wc, r, "hardware memory error when reading metadata entry %lu: %d",
1006                                          (unsigned long)b, r);
1007                         e->original_sector = -1;
1008                         e->seq_count = -1;
1009                 } else {
1010                         e->original_sector = le64_to_cpu(wme.original_sector);
1011                         e->seq_count = le64_to_cpu(wme.seq_count);
1012                 }
1013                 cond_resched();
1014         }
1015 #endif
1016         for (b = 0; b < wc->n_blocks; b++) {
1017                 struct wc_entry *e = &wc->entries[b];
1018                 if (!writecache_entry_is_committed(wc, e)) {
1019                         if (read_seq_count(wc, e) != -1) {
1020 erase_this:
1021                                 clear_seq_count(wc, e);
1022                                 need_flush = true;
1023                         }
1024                         writecache_add_to_freelist(wc, e);
1025                 } else {
1026                         struct wc_entry *old;
1027
1028                         old = writecache_find_entry(wc, read_original_sector(wc, e), 0);
1029                         if (!old) {
1030                                 writecache_insert_entry(wc, e);
1031                         } else {
1032                                 if (read_seq_count(wc, old) == read_seq_count(wc, e)) {
1033                                         writecache_error(wc, -EINVAL,
1034                                                  "two identical entries, position %llu, sector %llu, sequence %llu",
1035                                                  (unsigned long long)b, (unsigned long long)read_original_sector(wc, e),
1036                                                  (unsigned long long)read_seq_count(wc, e));
1037                                 }
1038                                 if (read_seq_count(wc, old) > read_seq_count(wc, e)) {
1039                                         goto erase_this;
1040                                 } else {
1041                                         writecache_free_entry(wc, old);
1042                                         writecache_insert_entry(wc, e);
1043                                         need_flush = true;
1044                                 }
1045                         }
1046                 }
1047                 cond_resched();
1048         }
1049
1050         if (need_flush) {
1051                 writecache_flush_all_metadata(wc);
1052                 writecache_commit_flushed(wc, false);
1053         }
1054
1055         writecache_verify_watermark(wc);
1056
1057         if (wc->max_age != MAX_AGE_UNSPECIFIED)
1058                 mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);
1059
1060         wc_unlock(wc);
1061 }
1062
1063 static int process_flush_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
1064 {
1065         if (argc != 1)
1066                 return -EINVAL;
1067
1068         wc_lock(wc);
1069         if (dm_suspended(wc->ti)) {
1070                 wc_unlock(wc);
1071                 return -EBUSY;
1072         }
1073         if (writecache_has_error(wc)) {
1074                 wc_unlock(wc);
1075                 return -EIO;
1076         }
1077
1078         writecache_flush(wc);
1079         wc->writeback_all++;
1080         queue_work(wc->writeback_wq, &wc->writeback_work);
1081         wc_unlock(wc);
1082
1083         flush_workqueue(wc->writeback_wq);
1084
1085         wc_lock(wc);
1086         wc->writeback_all--;
1087         if (writecache_has_error(wc)) {
1088                 wc_unlock(wc);
1089                 return -EIO;
1090         }
1091         wc_unlock(wc);
1092
1093         return 0;
1094 }
1095
1096 static int process_flush_on_suspend_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
1097 {
1098         if (argc != 1)
1099                 return -EINVAL;
1100
1101         wc_lock(wc);
1102         wc->flush_on_suspend = true;
1103         wc_unlock(wc);
1104
1105         return 0;
1106 }
1107
1108 static void activate_cleaner(struct dm_writecache *wc)
1109 {
1110         wc->flush_on_suspend = true;
1111         wc->cleaner = true;
1112         wc->freelist_high_watermark = wc->n_blocks;
1113         wc->freelist_low_watermark = wc->n_blocks;
1114 }
1115
1116 static int process_cleaner_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
1117 {
1118         if (argc != 1)
1119                 return -EINVAL;
1120
1121         wc_lock(wc);
1122         activate_cleaner(wc);
1123         if (!dm_suspended(wc->ti))
1124                 writecache_verify_watermark(wc);
1125         wc_unlock(wc);
1126
1127         return 0;
1128 }
1129
1130 static int writecache_message(struct dm_target *ti, unsigned argc, char **argv,
1131                               char *result, unsigned maxlen)
1132 {
1133         int r = -EINVAL;
1134         struct dm_writecache *wc = ti->private;
1135
1136         if (!strcasecmp(argv[0], "flush"))
1137                 r = process_flush_mesg(argc, argv, wc);
1138         else if (!strcasecmp(argv[0], "flush_on_suspend"))
1139                 r = process_flush_on_suspend_mesg(argc, argv, wc);
1140         else if (!strcasecmp(argv[0], "cleaner"))
1141                 r = process_cleaner_mesg(argc, argv, wc);
1142         else
1143                 DMERR("unrecognised message received: %s", argv[0]);
1144
1145         return r;
1146 }
1147
1148 static void memcpy_flushcache_optimized(void *dest, void *source, size_t size)
1149 {
1150         /*
1151          * clflushopt performs better with block size 1024, 2048, 4096
1152          * non-temporal stores perform better with block size 512
1153          *
1154          * block size   512             1024            2048            4096
1155          * movnti       496 MB/s        642 MB/s        725 MB/s        744 MB/s
1156          * clflushopt   373 MB/s        688 MB/s        1.1 GB/s        1.2 GB/s
1157          *
1158          * We see that movnti performs better for 512-byte blocks, and
1159          * clflushopt performs better for 1024-byte and larger blocks. So, we
1160          * prefer clflushopt for sizes >= 768.
1161          *
1162          * NOTE: this happens to be the case now (with dm-writecache's single
1163          * threaded model) but re-evaluate this once memcpy_flushcache() is
1164          * enabled to use movdir64b which might invalidate this performance
1165          * advantage seen with cache-allocating-writes plus flushing.
1166          */
1167 #ifdef CONFIG_X86
1168         if (static_cpu_has(X86_FEATURE_CLFLUSHOPT) &&
1169             likely(boot_cpu_data.x86_clflush_size == 64) &&
1170             likely(size >= 768)) {
1171                 do {
1172                         memcpy((void *)dest, (void *)source, 64);
1173                         clflushopt((void *)dest);
1174                         dest += 64;
1175                         source += 64;
1176                         size -= 64;
1177                 } while (size >= 64);
1178                 return;
1179         }
1180 #endif
1181         memcpy_flushcache(dest, source, size);
1182 }
1183
1184 static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data)
1185 {
1186         void *buf;
1187         unsigned long flags;
1188         unsigned size;
1189         int rw = bio_data_dir(bio);
1190         unsigned remaining_size = wc->block_size;
1191
1192         do {
1193                 struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
1194                 buf = bvec_kmap_irq(&bv, &flags);
1195                 size = bv.bv_len;
1196                 if (unlikely(size > remaining_size))
1197                         size = remaining_size;
1198
1199                 if (rw == READ) {
1200                         int r;
1201                         r = memcpy_mcsafe(buf, data, size);
1202                         flush_dcache_page(bio_page(bio));
1203                         if (unlikely(r)) {
1204                                 writecache_error(wc, r, "hardware memory error when reading data: %d", r);
1205                                 bio->bi_status = BLK_STS_IOERR;
1206                         }
1207                 } else {
1208                         flush_dcache_page(bio_page(bio));
1209                         memcpy_flushcache_optimized(data, buf, size);
1210                 }
1211
1212                 bvec_kunmap_irq(buf, &flags);
1213
1214                 data = (char *)data + size;
1215                 remaining_size -= size;
1216                 bio_advance(bio, size);
1217         } while (unlikely(remaining_size));
1218 }
1219
1220 static int writecache_flush_thread(void *data)
1221 {
1222         struct dm_writecache *wc = data;
1223
1224         while (1) {
1225                 struct bio *bio;
1226
1227                 wc_lock(wc);
1228                 bio = bio_list_pop(&wc->flush_list);
1229                 if (!bio) {
1230                         set_current_state(TASK_INTERRUPTIBLE);
1231                         wc_unlock(wc);
1232
1233                         if (unlikely(kthread_should_stop())) {
1234                                 set_current_state(TASK_RUNNING);
1235                                 break;
1236                         }
1237
1238                         schedule();
1239                         continue;
1240                 }
1241
1242                 if (bio_op(bio) == REQ_OP_DISCARD) {
1243                         writecache_discard(wc, bio->bi_iter.bi_sector,
1244                                            bio_end_sector(bio));
1245                         wc_unlock(wc);
1246                         bio_set_dev(bio, wc->dev->bdev);
1247                         submit_bio_noacct(bio);
1248                 } else {
1249                         writecache_flush(wc);
1250                         wc_unlock(wc);
1251                         if (writecache_has_error(wc))
1252                                 bio->bi_status = BLK_STS_IOERR;
1253                         bio_endio(bio);
1254                 }
1255         }
1256
1257         return 0;
1258 }
1259
1260 static void writecache_offload_bio(struct dm_writecache *wc, struct bio *bio)
1261 {
1262         if (bio_list_empty(&wc->flush_list))
1263                 wake_up_process(wc->flush_thread);
1264         bio_list_add(&wc->flush_list, bio);
1265 }
1266
1267 static int writecache_map(struct dm_target *ti, struct bio *bio)
1268 {
1269         struct wc_entry *e;
1270         struct dm_writecache *wc = ti->private;
1271
1272         bio->bi_private = NULL;
1273
1274         wc_lock(wc);
1275
1276         if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
1277                 if (writecache_has_error(wc))
1278                         goto unlock_error;
1279                 if (WC_MODE_PMEM(wc)) {
1280                         writecache_flush(wc);
1281                         if (writecache_has_error(wc))
1282                                 goto unlock_error;
1283                         goto unlock_submit;
1284                 } else {
1285                         writecache_offload_bio(wc, bio);
1286                         goto unlock_return;
1287                 }
1288         }
1289
1290         bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
1291
1292         if (unlikely((((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
1293                                 (wc->block_size / 512 - 1)) != 0)) {
1294                 DMERR("I/O is not aligned, sector %llu, size %u, block size %u",
1295                       (unsigned long long)bio->bi_iter.bi_sector,
1296                       bio->bi_iter.bi_size, wc->block_size);
1297                 goto unlock_error;
1298         }
1299
1300         if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
1301                 if (writecache_has_error(wc))
1302                         goto unlock_error;
1303                 if (WC_MODE_PMEM(wc)) {
1304                         writecache_discard(wc, bio->bi_iter.bi_sector, bio_end_sector(bio));
1305                         goto unlock_remap_origin;
1306                 } else {
1307                         writecache_offload_bio(wc, bio);
1308                         goto unlock_return;
1309                 }
1310         }
1311
1312         if (bio_data_dir(bio) == READ) {
1313 read_next_block:
1314                 e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
1315                 if (e && read_original_sector(wc, e) == bio->bi_iter.bi_sector) {
1316                         if (WC_MODE_PMEM(wc)) {
1317                                 bio_copy_block(wc, bio, memory_data(wc, e));
1318                                 if (bio->bi_iter.bi_size)
1319                                         goto read_next_block;
1320                                 goto unlock_submit;
1321                         } else {
1322                                 dm_accept_partial_bio(bio, wc->block_size >> SECTOR_SHIFT);
1323                                 bio_set_dev(bio, wc->ssd_dev->bdev);
1324                                 bio->bi_iter.bi_sector = cache_sector(wc, e);
1325                                 if (!writecache_entry_is_committed(wc, e))
1326                                         writecache_wait_for_ios(wc, WRITE);
1327                                 goto unlock_remap;
1328                         }
1329                 } else {
1330                         if (e) {
1331                                 sector_t next_boundary =
1332                                         read_original_sector(wc, e) - bio->bi_iter.bi_sector;
1333                                 if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
1334                                         dm_accept_partial_bio(bio, next_boundary);
1335                                 }
1336                         }
1337                         goto unlock_remap_origin;
1338                 }
1339         } else {
1340                 do {
1341                         bool found_entry = false;
1342                         if (writecache_has_error(wc))
1343                                 goto unlock_error;
1344                         e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);
1345                         if (e) {
1346                                 if (!writecache_entry_is_committed(wc, e))
1347                                         goto bio_copy;
1348                                 if (!WC_MODE_PMEM(wc) && !e->write_in_progress) {
1349                                         wc->overwrote_committed = true;
1350                                         goto bio_copy;
1351                                 }
1352                                 found_entry = true;
1353                         } else {
1354                                 if (unlikely(wc->cleaner))
1355                                         goto direct_write;
1356                         }
1357                         e = writecache_pop_from_freelist(wc, (sector_t)-1);
1358                         if (unlikely(!e)) {
1359                                 if (!found_entry) {
1360 direct_write:
1361                                         e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
1362                                         if (e) {
1363                                                 sector_t next_boundary = read_original_sector(wc, e) - bio->bi_iter.bi_sector;
1364                                                 BUG_ON(!next_boundary);
1365                                                 if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
1366                                                         dm_accept_partial_bio(bio, next_boundary);
1367                                                 }
1368                                         }
1369                                         goto unlock_remap_origin;
1370                                 }
1371                                 writecache_wait_on_freelist(wc);
1372                                 continue;
1373                         }
1374                         write_original_sector_seq_count(wc, e, bio->bi_iter.bi_sector, wc->seq_count);
1375                         writecache_insert_entry(wc, e);
1376                         wc->uncommitted_blocks++;
1377 bio_copy:
1378                         if (WC_MODE_PMEM(wc)) {
1379                                 bio_copy_block(wc, bio, memory_data(wc, e));
1380                         } else {
1381                                 unsigned bio_size = wc->block_size;
1382                                 sector_t start_cache_sec = cache_sector(wc, e);
1383                                 sector_t current_cache_sec = start_cache_sec + (bio_size >> SECTOR_SHIFT);
1384
1385                                 while (bio_size < bio->bi_iter.bi_size) {
1386                                         struct wc_entry *f = writecache_pop_from_freelist(wc, current_cache_sec);
1387                                         if (!f)
1388                                                 break;
1389                                         write_original_sector_seq_count(wc, f, bio->bi_iter.bi_sector +
1390                                                                         (bio_size >> SECTOR_SHIFT), wc->seq_count);
1391                                         writecache_insert_entry(wc, f);
1392                                         wc->uncommitted_blocks++;
1393                                         bio_size += wc->block_size;
1394                                         current_cache_sec += wc->block_size >> SECTOR_SHIFT;
1395                                 }
1396
1397                                 bio_set_dev(bio, wc->ssd_dev->bdev);
1398                                 bio->bi_iter.bi_sector = start_cache_sec;
1399                                 dm_accept_partial_bio(bio, bio_size >> SECTOR_SHIFT);
1400
1401                                 if (unlikely(wc->uncommitted_blocks >= wc->autocommit_blocks)) {
1402                                         wc->uncommitted_blocks = 0;
1403                                         queue_work(wc->writeback_wq, &wc->flush_work);
1404                                 } else {
1405                                         writecache_schedule_autocommit(wc);
1406                                 }
1407                                 goto unlock_remap;
1408                         }
1409                 } while (bio->bi_iter.bi_size);
1410
1411                 if (unlikely(bio->bi_opf & REQ_FUA ||
1412                              wc->uncommitted_blocks >= wc->autocommit_blocks))
1413                         writecache_flush(wc);
1414                 else
1415                         writecache_schedule_autocommit(wc);
1416                 goto unlock_submit;
1417         }
1418
1419 unlock_remap_origin:
1420         bio_set_dev(bio, wc->dev->bdev);
1421         wc_unlock(wc);
1422         return DM_MAPIO_REMAPPED;
1423
1424 unlock_remap:
1425         /* make sure that writecache_end_io decrements bio_in_progress: */
1426         bio->bi_private = (void *)1;
1427         atomic_inc(&wc->bio_in_progress[bio_data_dir(bio)]);
1428         wc_unlock(wc);
1429         return DM_MAPIO_REMAPPED;
1430
1431 unlock_submit:
1432         wc_unlock(wc);
1433         bio_endio(bio);
1434         return DM_MAPIO_SUBMITTED;
1435
1436 unlock_return:
1437         wc_unlock(wc);
1438         return DM_MAPIO_SUBMITTED;
1439
1440 unlock_error:
1441         wc_unlock(wc);
1442         bio_io_error(bio);
1443         return DM_MAPIO_SUBMITTED;
1444 }
1445
1446 static int writecache_end_io(struct dm_target *ti, struct bio *bio, blk_status_t *status)
1447 {
1448         struct dm_writecache *wc = ti->private;
1449
1450         if (bio->bi_private != NULL) {
1451                 int dir = bio_data_dir(bio);
1452                 if (atomic_dec_and_test(&wc->bio_in_progress[dir]))
1453                         if (unlikely(waitqueue_active(&wc->bio_in_progress_wait[dir])))
1454                                 wake_up(&wc->bio_in_progress_wait[dir]);
1455         }
1456         return 0;
1457 }
1458
1459 static int writecache_iterate_devices(struct dm_target *ti,
1460                                       iterate_devices_callout_fn fn, void *data)
1461 {
1462         struct dm_writecache *wc = ti->private;
1463
1464         return fn(ti, wc->dev, 0, ti->len, data);
1465 }
1466
1467 static void writecache_io_hints(struct dm_target *ti, struct queue_limits *limits)
1468 {
1469         struct dm_writecache *wc = ti->private;
1470
1471         if (limits->logical_block_size < wc->block_size)
1472                 limits->logical_block_size = wc->block_size;
1473
1474         if (limits->physical_block_size < wc->block_size)
1475                 limits->physical_block_size = wc->block_size;
1476
1477         if (limits->io_min < wc->block_size)
1478                 limits->io_min = wc->block_size;
1479 }
1480
1481
1482 static void writecache_writeback_endio(struct bio *bio)
1483 {
1484         struct writeback_struct *wb = container_of(bio, struct writeback_struct, bio);
1485         struct dm_writecache *wc = wb->wc;
1486         unsigned long flags;
1487
1488         raw_spin_lock_irqsave(&wc->endio_list_lock, flags);
1489         if (unlikely(list_empty(&wc->endio_list)))
1490                 wake_up_process(wc->endio_thread);
1491         list_add_tail(&wb->endio_entry, &wc->endio_list);
1492         raw_spin_unlock_irqrestore(&wc->endio_list_lock, flags);
1493 }
1494
1495 static void writecache_copy_endio(int read_err, unsigned long write_err, void *ptr)
1496 {
1497         struct copy_struct *c = ptr;
1498         struct dm_writecache *wc = c->wc;
1499
1500         c->error = likely(!(read_err | write_err)) ? 0 : -EIO;
1501
1502         raw_spin_lock_irq(&wc->endio_list_lock);
1503         if (unlikely(list_empty(&wc->endio_list)))
1504                 wake_up_process(wc->endio_thread);
1505         list_add_tail(&c->endio_entry, &wc->endio_list);
1506         raw_spin_unlock_irq(&wc->endio_list_lock);
1507 }
1508
1509 static void __writecache_endio_pmem(struct dm_writecache *wc, struct list_head *list)
1510 {
1511         unsigned i;
1512         struct writeback_struct *wb;
1513         struct wc_entry *e;
1514         unsigned long n_walked = 0;
1515
1516         do {
1517                 wb = list_entry(list->next, struct writeback_struct, endio_entry);
1518                 list_del(&wb->endio_entry);
1519
1520                 if (unlikely(wb->bio.bi_status != BLK_STS_OK))
1521                         writecache_error(wc, blk_status_to_errno(wb->bio.bi_status),
1522                                         "write error %d", wb->bio.bi_status);
1523                 i = 0;
1524                 do {
1525                         e = wb->wc_list[i];
1526                         BUG_ON(!e->write_in_progress);
1527                         e->write_in_progress = false;
1528                         INIT_LIST_HEAD(&e->lru);
1529                         if (!writecache_has_error(wc))
1530                                 writecache_free_entry(wc, e);
1531                         BUG_ON(!wc->writeback_size);
1532                         wc->writeback_size--;
1533                         n_walked++;
1534                         if (unlikely(n_walked >= ENDIO_LATENCY)) {
1535                                 writecache_commit_flushed(wc, false);
1536                                 wc_unlock(wc);
1537                                 wc_lock(wc);
1538                                 n_walked = 0;
1539                         }
1540                 } while (++i < wb->wc_list_n);
1541
1542                 if (wb->wc_list != wb->wc_list_inline)
1543                         kfree(wb->wc_list);
1544                 bio_put(&wb->bio);
1545         } while (!list_empty(list));
1546 }
1547
1548 static void __writecache_endio_ssd(struct dm_writecache *wc, struct list_head *list)
1549 {
1550         struct copy_struct *c;
1551         struct wc_entry *e;
1552
1553         do {
1554                 c = list_entry(list->next, struct copy_struct, endio_entry);
1555                 list_del(&c->endio_entry);
1556
1557                 if (unlikely(c->error))
1558                         writecache_error(wc, c->error, "copy error");
1559
1560                 e = c->e;
1561                 do {
1562                         BUG_ON(!e->write_in_progress);
1563                         e->write_in_progress = false;
1564                         INIT_LIST_HEAD(&e->lru);
1565                         if (!writecache_has_error(wc))
1566                                 writecache_free_entry(wc, e);
1567
1568                         BUG_ON(!wc->writeback_size);
1569                         wc->writeback_size--;
1570                         e++;
1571                 } while (--c->n_entries);
1572                 mempool_free(c, &wc->copy_pool);
1573         } while (!list_empty(list));
1574 }
1575
1576 static int writecache_endio_thread(void *data)
1577 {
1578         struct dm_writecache *wc = data;
1579
1580         while (1) {
1581                 struct list_head list;
1582
1583                 raw_spin_lock_irq(&wc->endio_list_lock);
1584                 if (!list_empty(&wc->endio_list))
1585                         goto pop_from_list;
1586                 set_current_state(TASK_INTERRUPTIBLE);
1587                 raw_spin_unlock_irq(&wc->endio_list_lock);
1588
1589                 if (unlikely(kthread_should_stop())) {
1590                         set_current_state(TASK_RUNNING);
1591                         break;
1592                 }
1593
1594                 schedule();
1595
1596                 continue;
1597
1598 pop_from_list:
1599                 list = wc->endio_list;
1600                 list.next->prev = list.prev->next = &list;
1601                 INIT_LIST_HEAD(&wc->endio_list);
1602                 raw_spin_unlock_irq(&wc->endio_list_lock);
1603
1604                 if (!WC_MODE_FUA(wc))
1605                         writecache_disk_flush(wc, wc->dev);
1606
1607                 wc_lock(wc);
1608
1609                 if (WC_MODE_PMEM(wc)) {
1610                         __writecache_endio_pmem(wc, &list);
1611                 } else {
1612                         __writecache_endio_ssd(wc, &list);
1613                         writecache_wait_for_ios(wc, READ);
1614                 }
1615
1616                 writecache_commit_flushed(wc, false);
1617
1618                 wc_unlock(wc);
1619         }
1620
1621         return 0;
1622 }
1623
1624 static bool wc_add_block(struct writeback_struct *wb, struct wc_entry *e, gfp_t gfp)
1625 {
1626         struct dm_writecache *wc = wb->wc;
1627         unsigned block_size = wc->block_size;
1628         void *address = memory_data(wc, e);
1629
1630         persistent_memory_flush_cache(address, block_size);
1631         return bio_add_page(&wb->bio, persistent_memory_page(address),
1632                             block_size, persistent_memory_page_offset(address)) != 0;
1633 }
1634
1635 struct writeback_list {
1636         struct list_head list;
1637         size_t size;
1638 };
1639
1640 static void __writeback_throttle(struct dm_writecache *wc, struct writeback_list *wbl)
1641 {
1642         if (unlikely(wc->max_writeback_jobs)) {
1643                 if (READ_ONCE(wc->writeback_size) - wbl->size >= wc->max_writeback_jobs) {
1644                         wc_lock(wc);
1645                         while (wc->writeback_size - wbl->size >= wc->max_writeback_jobs)
1646                                 writecache_wait_on_freelist(wc);
1647                         wc_unlock(wc);
1648                 }
1649         }
1650         cond_resched();
1651 }
1652
1653 static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeback_list *wbl)
1654 {
1655         struct wc_entry *e, *f;
1656         struct bio *bio;
1657         struct writeback_struct *wb;
1658         unsigned max_pages;
1659
1660         while (wbl->size) {
1661                 wbl->size--;
1662                 e = container_of(wbl->list.prev, struct wc_entry, lru);
1663                 list_del(&e->lru);
1664
1665                 max_pages = e->wc_list_contiguous;
1666
1667                 bio = bio_alloc_bioset(GFP_NOIO, max_pages, &wc->bio_set);
1668                 wb = container_of(bio, struct writeback_struct, bio);
1669                 wb->wc = wc;
1670                 bio->bi_end_io = writecache_writeback_endio;
1671                 bio_set_dev(bio, wc->dev->bdev);
1672                 bio->bi_iter.bi_sector = read_original_sector(wc, e);
1673                 if (max_pages <= WB_LIST_INLINE ||
1674                     unlikely(!(wb->wc_list = kmalloc_array(max_pages, sizeof(struct wc_entry *),
1675                                                            GFP_NOIO | __GFP_NORETRY |
1676                                                            __GFP_NOMEMALLOC | __GFP_NOWARN)))) {
1677                         wb->wc_list = wb->wc_list_inline;
1678                         max_pages = WB_LIST_INLINE;
1679                 }
1680
1681                 BUG_ON(!wc_add_block(wb, e, GFP_NOIO));
1682
1683                 wb->wc_list[0] = e;
1684                 wb->wc_list_n = 1;
1685
1686                 while (wbl->size && wb->wc_list_n < max_pages) {
1687                         f = container_of(wbl->list.prev, struct wc_entry, lru);
1688                         if (read_original_sector(wc, f) !=
1689                             read_original_sector(wc, e) + (wc->block_size >> SECTOR_SHIFT))
1690                                 break;
1691                         if (!wc_add_block(wb, f, GFP_NOWAIT | __GFP_NOWARN))
1692                                 break;
1693                         wbl->size--;
1694                         list_del(&f->lru);
1695                         wb->wc_list[wb->wc_list_n++] = f;
1696                         e = f;
1697                 }
1698                 bio_set_op_attrs(bio, REQ_OP_WRITE, WC_MODE_FUA(wc) * REQ_FUA);
1699                 if (writecache_has_error(wc)) {
1700                         bio->bi_status = BLK_STS_IOERR;
1701                         bio_endio(bio);
1702                 } else {
1703                         submit_bio(bio);
1704                 }
1705
1706                 __writeback_throttle(wc, wbl);
1707         }
1708 }
1709
1710 static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writeback_list *wbl)
1711 {
1712         struct wc_entry *e, *f;
1713         struct dm_io_region from, to;
1714         struct copy_struct *c;
1715
1716         while (wbl->size) {
1717                 unsigned n_sectors;
1718
1719                 wbl->size--;
1720                 e = container_of(wbl->list.prev, struct wc_entry, lru);
1721                 list_del(&e->lru);
1722
1723                 n_sectors = e->wc_list_contiguous << (wc->block_size_bits - SECTOR_SHIFT);
1724
1725                 from.bdev = wc->ssd_dev->bdev;
1726                 from.sector = cache_sector(wc, e);
1727                 from.count = n_sectors;
1728                 to.bdev = wc->dev->bdev;
1729                 to.sector = read_original_sector(wc, e);
1730                 to.count = n_sectors;
1731
1732                 c = mempool_alloc(&wc->copy_pool, GFP_NOIO);
1733                 c->wc = wc;
1734                 c->e = e;
1735                 c->n_entries = e->wc_list_contiguous;
1736
1737                 while ((n_sectors -= wc->block_size >> SECTOR_SHIFT)) {
1738                         wbl->size--;
1739                         f = container_of(wbl->list.prev, struct wc_entry, lru);
1740                         BUG_ON(f != e + 1);
1741                         list_del(&f->lru);
1742                         e = f;
1743                 }
1744
1745                 dm_kcopyd_copy(wc->dm_kcopyd, &from, 1, &to, 0, writecache_copy_endio, c);
1746
1747                 __writeback_throttle(wc, wbl);
1748         }
1749 }
1750
1751 static void writecache_writeback(struct work_struct *work)
1752 {
1753         struct dm_writecache *wc = container_of(work, struct dm_writecache, writeback_work);
1754         struct blk_plug plug;
1755         struct wc_entry *f, *g, *e = NULL;
1756         struct rb_node *node, *next_node;
1757         struct list_head skipped;
1758         struct writeback_list wbl;
1759         unsigned long n_walked;
1760
1761         wc_lock(wc);
1762 restart:
1763         if (writecache_has_error(wc)) {
1764                 wc_unlock(wc);
1765                 return;
1766         }
1767
1768         if (unlikely(wc->writeback_all)) {
1769                 if (writecache_wait_for_writeback(wc))
1770                         goto restart;
1771         }
1772
1773         if (wc->overwrote_committed) {
1774                 writecache_wait_for_ios(wc, WRITE);
1775         }
1776
1777         n_walked = 0;
1778         INIT_LIST_HEAD(&skipped);
1779         INIT_LIST_HEAD(&wbl.list);
1780         wbl.size = 0;
1781         while (!list_empty(&wc->lru) &&
1782                (wc->writeback_all ||
1783                 wc->freelist_size + wc->writeback_size <= wc->freelist_low_watermark ||
1784                 (jiffies - container_of(wc->lru.prev, struct wc_entry, lru)->age >=
1785                  wc->max_age - wc->max_age / MAX_AGE_DIV))) {
1786
1787                 n_walked++;
1788                 if (unlikely(n_walked > WRITEBACK_LATENCY) &&
1789                     likely(!wc->writeback_all) && likely(!dm_suspended(wc->ti))) {
1790                         queue_work(wc->writeback_wq, &wc->writeback_work);
1791                         break;
1792                 }
1793
1794                 if (unlikely(wc->writeback_all)) {
1795                         if (unlikely(!e)) {
1796                                 writecache_flush(wc);
1797                                 e = container_of(rb_first(&wc->tree), struct wc_entry, rb_node);
1798                         } else
1799                                 e = g;
1800                 } else
1801                         e = container_of(wc->lru.prev, struct wc_entry, lru);
1802                 BUG_ON(e->write_in_progress);
1803                 if (unlikely(!writecache_entry_is_committed(wc, e))) {
1804                         writecache_flush(wc);
1805                 }
1806                 node = rb_prev(&e->rb_node);
1807                 if (node) {
1808                         f = container_of(node, struct wc_entry, rb_node);
1809                         if (unlikely(read_original_sector(wc, f) ==
1810                                      read_original_sector(wc, e))) {
1811                                 BUG_ON(!f->write_in_progress);
1812                                 list_del(&e->lru);
1813                                 list_add(&e->lru, &skipped);
1814                                 cond_resched();
1815                                 continue;
1816                         }
1817                 }
1818                 wc->writeback_size++;
1819                 list_del(&e->lru);
1820                 list_add(&e->lru, &wbl.list);
1821                 wbl.size++;
1822                 e->write_in_progress = true;
1823                 e->wc_list_contiguous = 1;
1824
1825                 f = e;
1826
1827                 while (1) {
1828                         next_node = rb_next(&f->rb_node);
1829                         if (unlikely(!next_node))
1830                                 break;
1831                         g = container_of(next_node, struct wc_entry, rb_node);
1832                         if (unlikely(read_original_sector(wc, g) ==
1833                             read_original_sector(wc, f))) {
1834                                 f = g;
1835                                 continue;
1836                         }
1837                         if (read_original_sector(wc, g) !=
1838                             read_original_sector(wc, f) + (wc->block_size >> SECTOR_SHIFT))
1839                                 break;
1840                         if (unlikely(g->write_in_progress))
1841                                 break;
1842                         if (unlikely(!writecache_entry_is_committed(wc, g)))
1843                                 break;
1844
1845                         if (!WC_MODE_PMEM(wc)) {
1846                                 if (g != f + 1)
1847                                         break;
1848                         }
1849
1850                         n_walked++;
1851                         //if (unlikely(n_walked > WRITEBACK_LATENCY) && likely(!wc->writeback_all))
1852                         //      break;
1853
1854                         wc->writeback_size++;
1855                         list_del(&g->lru);
1856                         list_add(&g->lru, &wbl.list);
1857                         wbl.size++;
1858                         g->write_in_progress = true;
1859                         g->wc_list_contiguous = BIO_MAX_PAGES;
1860                         f = g;
1861                         e->wc_list_contiguous++;
1862                         if (unlikely(e->wc_list_contiguous == BIO_MAX_PAGES)) {
1863                                 if (unlikely(wc->writeback_all)) {
1864                                         next_node = rb_next(&f->rb_node);
1865                                         if (likely(next_node))
1866                                                 g = container_of(next_node, struct wc_entry, rb_node);
1867                                 }
1868                                 break;
1869                         }
1870                 }
1871                 cond_resched();
1872         }
1873
1874         if (!list_empty(&skipped)) {
1875                 list_splice_tail(&skipped, &wc->lru);
1876                 /*
1877                  * If we didn't do any progress, we must wait until some
1878                  * writeback finishes to avoid burning CPU in a loop
1879                  */
1880                 if (unlikely(!wbl.size))
1881                         writecache_wait_for_writeback(wc);
1882         }
1883
1884         wc_unlock(wc);
1885
1886         blk_start_plug(&plug);
1887
1888         if (WC_MODE_PMEM(wc))
1889                 __writecache_writeback_pmem(wc, &wbl);
1890         else
1891                 __writecache_writeback_ssd(wc, &wbl);
1892
1893         blk_finish_plug(&plug);
1894
1895         if (unlikely(wc->writeback_all)) {
1896                 wc_lock(wc);
1897                 while (writecache_wait_for_writeback(wc));
1898                 wc_unlock(wc);
1899         }
1900 }
1901
1902 static int calculate_memory_size(uint64_t device_size, unsigned block_size,
1903                                  size_t *n_blocks_p, size_t *n_metadata_blocks_p)
1904 {
1905         uint64_t n_blocks, offset;
1906         struct wc_entry e;
1907
1908         n_blocks = device_size;
1909         do_div(n_blocks, block_size + sizeof(struct wc_memory_entry));
1910
1911         while (1) {
1912                 if (!n_blocks)
1913                         return -ENOSPC;
1914                 /* Verify the following entries[n_blocks] won't overflow */
1915                 if (n_blocks >= ((size_t)-sizeof(struct wc_memory_superblock) /
1916                                  sizeof(struct wc_memory_entry)))
1917                         return -EFBIG;
1918                 offset = offsetof(struct wc_memory_superblock, entries[n_blocks]);
1919                 offset = (offset + block_size - 1) & ~(uint64_t)(block_size - 1);
1920                 if (offset + n_blocks * block_size <= device_size)
1921                         break;
1922                 n_blocks--;
1923         }
1924
1925         /* check if the bit field overflows */
1926         e.index = n_blocks;
1927         if (e.index != n_blocks)
1928                 return -EFBIG;
1929
1930         if (n_blocks_p)
1931                 *n_blocks_p = n_blocks;
1932         if (n_metadata_blocks_p)
1933                 *n_metadata_blocks_p = offset >> __ffs(block_size);
1934         return 0;
1935 }
1936
1937 static int init_memory(struct dm_writecache *wc)
1938 {
1939         size_t b;
1940         int r;
1941
1942         r = calculate_memory_size(wc->memory_map_size, wc->block_size, &wc->n_blocks, NULL);
1943         if (r)
1944                 return r;
1945
1946         r = writecache_alloc_entries(wc);
1947         if (r)
1948                 return r;
1949
1950         for (b = 0; b < ARRAY_SIZE(sb(wc)->padding); b++)
1951                 pmem_assign(sb(wc)->padding[b], cpu_to_le64(0));
1952         pmem_assign(sb(wc)->version, cpu_to_le32(MEMORY_SUPERBLOCK_VERSION));
1953         pmem_assign(sb(wc)->block_size, cpu_to_le32(wc->block_size));
1954         pmem_assign(sb(wc)->n_blocks, cpu_to_le64(wc->n_blocks));
1955         pmem_assign(sb(wc)->seq_count, cpu_to_le64(0));
1956
1957         for (b = 0; b < wc->n_blocks; b++) {
1958                 write_original_sector_seq_count(wc, &wc->entries[b], -1, -1);
1959                 cond_resched();
1960         }
1961
1962         writecache_flush_all_metadata(wc);
1963         writecache_commit_flushed(wc, false);
1964         pmem_assign(sb(wc)->magic, cpu_to_le32(MEMORY_SUPERBLOCK_MAGIC));
1965         writecache_flush_region(wc, &sb(wc)->magic, sizeof sb(wc)->magic);
1966         writecache_commit_flushed(wc, false);
1967
1968         return 0;
1969 }
1970
1971 static void writecache_dtr(struct dm_target *ti)
1972 {
1973         struct dm_writecache *wc = ti->private;
1974
1975         if (!wc)
1976                 return;
1977
1978         if (wc->endio_thread)
1979                 kthread_stop(wc->endio_thread);
1980
1981         if (wc->flush_thread)
1982                 kthread_stop(wc->flush_thread);
1983
1984         bioset_exit(&wc->bio_set);
1985
1986         mempool_exit(&wc->copy_pool);
1987
1988         if (wc->writeback_wq)
1989                 destroy_workqueue(wc->writeback_wq);
1990
1991         if (wc->dev)
1992                 dm_put_device(ti, wc->dev);
1993
1994         if (wc->ssd_dev)
1995                 dm_put_device(ti, wc->ssd_dev);
1996
1997         if (wc->entries)
1998                 vfree(wc->entries);
1999
2000         if (wc->memory_map) {
2001                 if (WC_MODE_PMEM(wc))
2002                         persistent_memory_release(wc);
2003                 else
2004                         vfree(wc->memory_map);
2005         }
2006
2007         if (wc->dm_kcopyd)
2008                 dm_kcopyd_client_destroy(wc->dm_kcopyd);
2009
2010         if (wc->dm_io)
2011                 dm_io_client_destroy(wc->dm_io);
2012
2013         if (wc->dirty_bitmap)
2014                 vfree(wc->dirty_bitmap);
2015
2016         kfree(wc);
2017 }
2018
2019 static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)
2020 {
2021         struct dm_writecache *wc;
2022         struct dm_arg_set as;
2023         const char *string;
2024         unsigned opt_params;
2025         size_t offset, data_size;
2026         int i, r;
2027         char dummy;
2028         int high_wm_percent = HIGH_WATERMARK;
2029         int low_wm_percent = LOW_WATERMARK;
2030         uint64_t x;
2031         struct wc_memory_superblock s;
2032
2033         static struct dm_arg _args[] = {
2034                 {0, 10, "Invalid number of feature args"},
2035         };
2036
2037         as.argc = argc;
2038         as.argv = argv;
2039
2040         wc = kzalloc(sizeof(struct dm_writecache), GFP_KERNEL);
2041         if (!wc) {
2042                 ti->error = "Cannot allocate writecache structure";
2043                 r = -ENOMEM;
2044                 goto bad;
2045         }
2046         ti->private = wc;
2047         wc->ti = ti;
2048
2049         mutex_init(&wc->lock);
2050         wc->max_age = MAX_AGE_UNSPECIFIED;
2051         writecache_poison_lists(wc);
2052         init_waitqueue_head(&wc->freelist_wait);
2053         timer_setup(&wc->autocommit_timer, writecache_autocommit_timer, 0);
2054         timer_setup(&wc->max_age_timer, writecache_max_age_timer, 0);
2055
2056         for (i = 0; i < 2; i++) {
2057                 atomic_set(&wc->bio_in_progress[i], 0);
2058                 init_waitqueue_head(&wc->bio_in_progress_wait[i]);
2059         }
2060
2061         wc->dm_io = dm_io_client_create();
2062         if (IS_ERR(wc->dm_io)) {
2063                 r = PTR_ERR(wc->dm_io);
2064                 ti->error = "Unable to allocate dm-io client";
2065                 wc->dm_io = NULL;
2066                 goto bad;
2067         }
2068
2069         wc->writeback_wq = alloc_workqueue("writecache-writeback", WQ_MEM_RECLAIM, 1);
2070         if (!wc->writeback_wq) {
2071                 r = -ENOMEM;
2072                 ti->error = "Could not allocate writeback workqueue";
2073                 goto bad;
2074         }
2075         INIT_WORK(&wc->writeback_work, writecache_writeback);
2076         INIT_WORK(&wc->flush_work, writecache_flush_work);
2077
2078         raw_spin_lock_init(&wc->endio_list_lock);
2079         INIT_LIST_HEAD(&wc->endio_list);
2080         wc->endio_thread = kthread_create(writecache_endio_thread, wc, "writecache_endio");
2081         if (IS_ERR(wc->endio_thread)) {
2082                 r = PTR_ERR(wc->endio_thread);
2083                 wc->endio_thread = NULL;
2084                 ti->error = "Couldn't spawn endio thread";
2085                 goto bad;
2086         }
2087         wake_up_process(wc->endio_thread);
2088
2089         /*
2090          * Parse the mode (pmem or ssd)
2091          */
2092         string = dm_shift_arg(&as);
2093         if (!string)
2094                 goto bad_arguments;
2095
2096         if (!strcasecmp(string, "s")) {
2097                 wc->pmem_mode = false;
2098         } else if (!strcasecmp(string, "p")) {
2099 #ifdef DM_WRITECACHE_HAS_PMEM
2100                 wc->pmem_mode = true;
2101                 wc->writeback_fua = true;
2102 #else
2103                 /*
2104                  * If the architecture doesn't support persistent memory or
2105                  * the kernel doesn't support any DAX drivers, this driver can
2106                  * only be used in SSD-only mode.
2107                  */
2108                 r = -EOPNOTSUPP;
2109                 ti->error = "Persistent memory or DAX not supported on this system";
2110                 goto bad;
2111 #endif
2112         } else {
2113                 goto bad_arguments;
2114         }
2115
2116         if (WC_MODE_PMEM(wc)) {
2117                 r = bioset_init(&wc->bio_set, BIO_POOL_SIZE,
2118                                 offsetof(struct writeback_struct, bio),
2119                                 BIOSET_NEED_BVECS);
2120                 if (r) {
2121                         ti->error = "Could not allocate bio set";
2122                         goto bad;
2123                 }
2124         } else {
2125                 r = mempool_init_kmalloc_pool(&wc->copy_pool, 1, sizeof(struct copy_struct));
2126                 if (r) {
2127                         ti->error = "Could not allocate mempool";
2128                         goto bad;
2129                 }
2130         }
2131
2132         /*
2133          * Parse the origin data device
2134          */
2135         string = dm_shift_arg(&as);
2136         if (!string)
2137                 goto bad_arguments;
2138         r = dm_get_device(ti, string, dm_table_get_mode(ti->table), &wc->dev);
2139         if (r) {
2140                 ti->error = "Origin data device lookup failed";
2141                 goto bad;
2142         }
2143
2144         /*
2145          * Parse cache data device (be it pmem or ssd)
2146          */
2147         string = dm_shift_arg(&as);
2148         if (!string)
2149                 goto bad_arguments;
2150
2151         r = dm_get_device(ti, string, dm_table_get_mode(ti->table), &wc->ssd_dev);
2152         if (r) {
2153                 ti->error = "Cache data device lookup failed";
2154                 goto bad;
2155         }
2156         wc->memory_map_size = i_size_read(wc->ssd_dev->bdev->bd_inode);
2157
2158         /*
2159          * Parse the cache block size
2160          */
2161         string = dm_shift_arg(&as);
2162         if (!string)
2163                 goto bad_arguments;
2164         if (sscanf(string, "%u%c", &wc->block_size, &dummy) != 1 ||
2165             wc->block_size < 512 || wc->block_size > PAGE_SIZE ||
2166             (wc->block_size & (wc->block_size - 1))) {
2167                 r = -EINVAL;
2168                 ti->error = "Invalid block size";
2169                 goto bad;
2170         }
2171         if (wc->block_size < bdev_logical_block_size(wc->dev->bdev) ||
2172             wc->block_size < bdev_logical_block_size(wc->ssd_dev->bdev)) {
2173                 r = -EINVAL;
2174                 ti->error = "Block size is smaller than device logical block size";
2175                 goto bad;
2176         }
2177         wc->block_size_bits = __ffs(wc->block_size);
2178
2179         wc->max_writeback_jobs = MAX_WRITEBACK_JOBS;
2180         wc->autocommit_blocks = !WC_MODE_PMEM(wc) ? AUTOCOMMIT_BLOCKS_SSD : AUTOCOMMIT_BLOCKS_PMEM;
2181         wc->autocommit_jiffies = msecs_to_jiffies(AUTOCOMMIT_MSEC);
2182
2183         /*
2184          * Parse optional arguments
2185          */
2186         r = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
2187         if (r)
2188                 goto bad;
2189
2190         while (opt_params) {
2191                 string = dm_shift_arg(&as), opt_params--;
2192                 if (!strcasecmp(string, "start_sector") && opt_params >= 1) {
2193                         unsigned long long start_sector;
2194                         string = dm_shift_arg(&as), opt_params--;
2195                         if (sscanf(string, "%llu%c", &start_sector, &dummy) != 1)
2196                                 goto invalid_optional;
2197                         wc->start_sector = start_sector;
2198                         if (wc->start_sector != start_sector ||
2199                             wc->start_sector >= wc->memory_map_size >> SECTOR_SHIFT)
2200                                 goto invalid_optional;
2201                 } else if (!strcasecmp(string, "high_watermark") && opt_params >= 1) {
2202                         string = dm_shift_arg(&as), opt_params--;
2203                         if (sscanf(string, "%d%c", &high_wm_percent, &dummy) != 1)
2204                                 goto invalid_optional;
2205                         if (high_wm_percent < 0 || high_wm_percent > 100)
2206                                 goto invalid_optional;
2207                         wc->high_wm_percent_set = true;
2208                 } else if (!strcasecmp(string, "low_watermark") && opt_params >= 1) {
2209                         string = dm_shift_arg(&as), opt_params--;
2210                         if (sscanf(string, "%d%c", &low_wm_percent, &dummy) != 1)
2211                                 goto invalid_optional;
2212                         if (low_wm_percent < 0 || low_wm_percent > 100)
2213                                 goto invalid_optional;
2214                         wc->low_wm_percent_set = true;
2215                 } else if (!strcasecmp(string, "writeback_jobs") && opt_params >= 1) {
2216                         string = dm_shift_arg(&as), opt_params--;
2217                         if (sscanf(string, "%u%c", &wc->max_writeback_jobs, &dummy) != 1)
2218                                 goto invalid_optional;
2219                         wc->max_writeback_jobs_set = true;
2220                 } else if (!strcasecmp(string, "autocommit_blocks") && opt_params >= 1) {
2221                         string = dm_shift_arg(&as), opt_params--;
2222                         if (sscanf(string, "%u%c", &wc->autocommit_blocks, &dummy) != 1)
2223                                 goto invalid_optional;
2224                         wc->autocommit_blocks_set = true;
2225                 } else if (!strcasecmp(string, "autocommit_time") && opt_params >= 1) {
2226                         unsigned autocommit_msecs;
2227                         string = dm_shift_arg(&as), opt_params--;
2228                         if (sscanf(string, "%u%c", &autocommit_msecs, &dummy) != 1)
2229                                 goto invalid_optional;
2230                         if (autocommit_msecs > 3600000)
2231                                 goto invalid_optional;
2232                         wc->autocommit_jiffies = msecs_to_jiffies(autocommit_msecs);
2233                         wc->autocommit_time_set = true;
2234                 } else if (!strcasecmp(string, "max_age") && opt_params >= 1) {
2235                         unsigned max_age_msecs;
2236                         string = dm_shift_arg(&as), opt_params--;
2237                         if (sscanf(string, "%u%c", &max_age_msecs, &dummy) != 1)
2238                                 goto invalid_optional;
2239                         if (max_age_msecs > 86400000)
2240                                 goto invalid_optional;
2241                         wc->max_age = msecs_to_jiffies(max_age_msecs);
2242                 } else if (!strcasecmp(string, "cleaner")) {
2243                         wc->cleaner = true;
2244                 } else if (!strcasecmp(string, "fua")) {
2245                         if (WC_MODE_PMEM(wc)) {
2246                                 wc->writeback_fua = true;
2247                                 wc->writeback_fua_set = true;
2248                         } else goto invalid_optional;
2249                 } else if (!strcasecmp(string, "nofua")) {
2250                         if (WC_MODE_PMEM(wc)) {
2251                                 wc->writeback_fua = false;
2252                                 wc->writeback_fua_set = true;
2253                         } else goto invalid_optional;
2254                 } else {
2255 invalid_optional:
2256                         r = -EINVAL;
2257                         ti->error = "Invalid optional argument";
2258                         goto bad;
2259                 }
2260         }
2261
2262         if (high_wm_percent < low_wm_percent) {
2263                 r = -EINVAL;
2264                 ti->error = "High watermark must be greater than or equal to low watermark";
2265                 goto bad;
2266         }
2267
2268         if (WC_MODE_PMEM(wc)) {
2269                 if (!dax_synchronous(wc->ssd_dev->dax_dev)) {
2270                         r = -EOPNOTSUPP;
2271                         ti->error = "Asynchronous persistent memory not supported as pmem cache";
2272                         goto bad;
2273                 }
2274
2275                 r = persistent_memory_claim(wc);
2276                 if (r) {
2277                         ti->error = "Unable to map persistent memory for cache";
2278                         goto bad;
2279                 }
2280         } else {
2281                 size_t n_blocks, n_metadata_blocks;
2282                 uint64_t n_bitmap_bits;
2283
2284                 wc->memory_map_size -= (uint64_t)wc->start_sector << SECTOR_SHIFT;
2285
2286                 bio_list_init(&wc->flush_list);
2287                 wc->flush_thread = kthread_create(writecache_flush_thread, wc, "dm_writecache_flush");
2288                 if (IS_ERR(wc->flush_thread)) {
2289                         r = PTR_ERR(wc->flush_thread);
2290                         wc->flush_thread = NULL;
2291                         ti->error = "Couldn't spawn flush thread";
2292                         goto bad;
2293                 }
2294                 wake_up_process(wc->flush_thread);
2295
2296                 r = calculate_memory_size(wc->memory_map_size, wc->block_size,
2297                                           &n_blocks, &n_metadata_blocks);
2298                 if (r) {
2299                         ti->error = "Invalid device size";
2300                         goto bad;
2301                 }
2302
2303                 n_bitmap_bits = (((uint64_t)n_metadata_blocks << wc->block_size_bits) +
2304                                  BITMAP_GRANULARITY - 1) / BITMAP_GRANULARITY;
2305                 /* this is limitation of test_bit functions */
2306                 if (n_bitmap_bits > 1U << 31) {
2307                         r = -EFBIG;
2308                         ti->error = "Invalid device size";
2309                         goto bad;
2310                 }
2311
2312                 wc->memory_map = vmalloc(n_metadata_blocks << wc->block_size_bits);
2313                 if (!wc->memory_map) {
2314                         r = -ENOMEM;
2315                         ti->error = "Unable to allocate memory for metadata";
2316                         goto bad;
2317                 }
2318
2319                 wc->dm_kcopyd = dm_kcopyd_client_create(&dm_kcopyd_throttle);
2320                 if (IS_ERR(wc->dm_kcopyd)) {
2321                         r = PTR_ERR(wc->dm_kcopyd);
2322                         ti->error = "Unable to allocate dm-kcopyd client";
2323                         wc->dm_kcopyd = NULL;
2324                         goto bad;
2325                 }
2326
2327                 wc->metadata_sectors = n_metadata_blocks << (wc->block_size_bits - SECTOR_SHIFT);
2328                 wc->dirty_bitmap_size = (n_bitmap_bits + BITS_PER_LONG - 1) /
2329                         BITS_PER_LONG * sizeof(unsigned long);
2330                 wc->dirty_bitmap = vzalloc(wc->dirty_bitmap_size);
2331                 if (!wc->dirty_bitmap) {
2332                         r = -ENOMEM;
2333                         ti->error = "Unable to allocate dirty bitmap";
2334                         goto bad;
2335                 }
2336
2337                 r = writecache_read_metadata(wc, wc->block_size >> SECTOR_SHIFT);
2338                 if (r) {
2339                         ti->error = "Unable to read first block of metadata";
2340                         goto bad;
2341                 }
2342         }
2343
2344         r = memcpy_mcsafe(&s, sb(wc), sizeof(struct wc_memory_superblock));
2345         if (r) {
2346                 ti->error = "Hardware memory error when reading superblock";
2347                 goto bad;
2348         }
2349         if (!le32_to_cpu(s.magic) && !le32_to_cpu(s.version)) {
2350                 r = init_memory(wc);
2351                 if (r) {
2352                         ti->error = "Unable to initialize device";
2353                         goto bad;
2354                 }
2355                 r = memcpy_mcsafe(&s, sb(wc), sizeof(struct wc_memory_superblock));
2356                 if (r) {
2357                         ti->error = "Hardware memory error when reading superblock";
2358                         goto bad;
2359                 }
2360         }
2361
2362         if (le32_to_cpu(s.magic) != MEMORY_SUPERBLOCK_MAGIC) {
2363                 ti->error = "Invalid magic in the superblock";
2364                 r = -EINVAL;
2365                 goto bad;
2366         }
2367
2368         if (le32_to_cpu(s.version) != MEMORY_SUPERBLOCK_VERSION) {
2369                 ti->error = "Invalid version in the superblock";
2370                 r = -EINVAL;
2371                 goto bad;
2372         }
2373
2374         if (le32_to_cpu(s.block_size) != wc->block_size) {
2375                 ti->error = "Block size does not match superblock";
2376                 r = -EINVAL;
2377                 goto bad;
2378         }
2379
2380         wc->n_blocks = le64_to_cpu(s.n_blocks);
2381
2382         offset = wc->n_blocks * sizeof(struct wc_memory_entry);
2383         if (offset / sizeof(struct wc_memory_entry) != le64_to_cpu(sb(wc)->n_blocks)) {
2384 overflow:
2385                 ti->error = "Overflow in size calculation";
2386                 r = -EINVAL;
2387                 goto bad;
2388         }
2389         offset += sizeof(struct wc_memory_superblock);
2390         if (offset < sizeof(struct wc_memory_superblock))
2391                 goto overflow;
2392         offset = (offset + wc->block_size - 1) & ~(size_t)(wc->block_size - 1);
2393         data_size = wc->n_blocks * (size_t)wc->block_size;
2394         if (!offset || (data_size / wc->block_size != wc->n_blocks) ||
2395             (offset + data_size < offset))
2396                 goto overflow;
2397         if (offset + data_size > wc->memory_map_size) {
2398                 ti->error = "Memory area is too small";
2399                 r = -EINVAL;
2400                 goto bad;
2401         }
2402
2403         wc->metadata_sectors = offset >> SECTOR_SHIFT;
2404         wc->block_start = (char *)sb(wc) + offset;
2405
2406         x = (uint64_t)wc->n_blocks * (100 - high_wm_percent);
2407         x += 50;
2408         do_div(x, 100);
2409         wc->freelist_high_watermark = x;
2410         x = (uint64_t)wc->n_blocks * (100 - low_wm_percent);
2411         x += 50;
2412         do_div(x, 100);
2413         wc->freelist_low_watermark = x;
2414
2415         if (wc->cleaner)
2416                 activate_cleaner(wc);
2417
2418         r = writecache_alloc_entries(wc);
2419         if (r) {
2420                 ti->error = "Cannot allocate memory";
2421                 goto bad;
2422         }
2423
2424         ti->num_flush_bios = 1;
2425         ti->flush_supported = true;
2426         ti->num_discard_bios = 1;
2427
2428         if (WC_MODE_PMEM(wc))
2429                 persistent_memory_flush_cache(wc->memory_map, wc->memory_map_size);
2430
2431         return 0;
2432
2433 bad_arguments:
2434         r = -EINVAL;
2435         ti->error = "Bad arguments";
2436 bad:
2437         writecache_dtr(ti);
2438         return r;
2439 }
2440
2441 static void writecache_status(struct dm_target *ti, status_type_t type,
2442                               unsigned status_flags, char *result, unsigned maxlen)
2443 {
2444         struct dm_writecache *wc = ti->private;
2445         unsigned extra_args;
2446         unsigned sz = 0;
2447         uint64_t x;
2448
2449         switch (type) {
2450         case STATUSTYPE_INFO:
2451                 DMEMIT("%ld %llu %llu %llu", writecache_has_error(wc),
2452                        (unsigned long long)wc->n_blocks, (unsigned long long)wc->freelist_size,
2453                        (unsigned long long)wc->writeback_size);
2454                 break;
2455         case STATUSTYPE_TABLE:
2456                 DMEMIT("%c %s %s %u ", WC_MODE_PMEM(wc) ? 'p' : 's',
2457                                 wc->dev->name, wc->ssd_dev->name, wc->block_size);
2458                 extra_args = 0;
2459                 if (wc->start_sector)
2460                         extra_args += 2;
2461                 if (wc->high_wm_percent_set && !wc->cleaner)
2462                         extra_args += 2;
2463                 if (wc->low_wm_percent_set && !wc->cleaner)
2464                         extra_args += 2;
2465                 if (wc->max_writeback_jobs_set)
2466                         extra_args += 2;
2467                 if (wc->autocommit_blocks_set)
2468                         extra_args += 2;
2469                 if (wc->autocommit_time_set)
2470                         extra_args += 2;
2471                 if (wc->cleaner)
2472                         extra_args++;
2473                 if (wc->writeback_fua_set)
2474                         extra_args++;
2475
2476                 DMEMIT("%u", extra_args);
2477                 if (wc->start_sector)
2478                         DMEMIT(" start_sector %llu", (unsigned long long)wc->start_sector);
2479                 if (wc->high_wm_percent_set && !wc->cleaner) {
2480                         x = (uint64_t)wc->freelist_high_watermark * 100;
2481                         x += wc->n_blocks / 2;
2482                         do_div(x, (size_t)wc->n_blocks);
2483                         DMEMIT(" high_watermark %u", 100 - (unsigned)x);
2484                 }
2485                 if (wc->low_wm_percent_set && !wc->cleaner) {
2486                         x = (uint64_t)wc->freelist_low_watermark * 100;
2487                         x += wc->n_blocks / 2;
2488                         do_div(x, (size_t)wc->n_blocks);
2489                         DMEMIT(" low_watermark %u", 100 - (unsigned)x);
2490                 }
2491                 if (wc->max_writeback_jobs_set)
2492                         DMEMIT(" writeback_jobs %u", wc->max_writeback_jobs);
2493                 if (wc->autocommit_blocks_set)
2494                         DMEMIT(" autocommit_blocks %u", wc->autocommit_blocks);
2495                 if (wc->autocommit_time_set)
2496                         DMEMIT(" autocommit_time %u", jiffies_to_msecs(wc->autocommit_jiffies));
2497                 if (wc->max_age != MAX_AGE_UNSPECIFIED)
2498                         DMEMIT(" max_age %u", jiffies_to_msecs(wc->max_age));
2499                 if (wc->cleaner)
2500                         DMEMIT(" cleaner");
2501                 if (wc->writeback_fua_set)
2502                         DMEMIT(" %sfua", wc->writeback_fua ? "" : "no");
2503                 break;
2504         }
2505 }
2506
2507 static struct target_type writecache_target = {
2508         .name                   = "writecache",
2509         .version                = {1, 3, 0},
2510         .module                 = THIS_MODULE,
2511         .ctr                    = writecache_ctr,
2512         .dtr                    = writecache_dtr,
2513         .status                 = writecache_status,
2514         .postsuspend            = writecache_suspend,
2515         .resume                 = writecache_resume,
2516         .message                = writecache_message,
2517         .map                    = writecache_map,
2518         .end_io                 = writecache_end_io,
2519         .iterate_devices        = writecache_iterate_devices,
2520         .io_hints               = writecache_io_hints,
2521 };
2522
2523 static int __init dm_writecache_init(void)
2524 {
2525         int r;
2526
2527         r = dm_register_target(&writecache_target);
2528         if (r < 0) {
2529                 DMERR("register failed %d", r);
2530                 return r;
2531         }
2532
2533         return 0;
2534 }
2535
2536 static void __exit dm_writecache_exit(void)
2537 {
2538         dm_unregister_target(&writecache_target);
2539 }
2540
2541 module_init(dm_writecache_init);
2542 module_exit(dm_writecache_exit);
2543
2544 MODULE_DESCRIPTION(DM_NAME " writecache target");
2545 MODULE_AUTHOR("Mikulas Patocka <[email protected]>");
2546 MODULE_LICENSE("GPL");