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         sector_t offset;
 235
 236         wc->memory_vmapped = false;
 237
 238         s = wc->memory_map_size;
 239         p = s >> PAGE_SHIFT;
 240         if (!p) {
 241                 r = -EINVAL;
 242                 goto err1;
 243         }
 244         if (p != s >> PAGE_SHIFT) {
 245                 r = -EOVERFLOW;
 246                 goto err1;
 247         }
 248
 249         offset = get_start_sect(wc->ssd_dev->bdev);
 250         if (offset & (PAGE_SIZE / 512 - 1)) {
 251                 r = -EINVAL;
 252                 goto err1;
 253         }
 254         offset >>= PAGE_SHIFT - 9;
 255
 256         id = dax_read_lock();
 257
 258         da = dax_direct_access(wc->ssd_dev->dax_dev, offset, p, &wc->memory_map, &pfn);
 259         if (da < 0) {
 260                 wc->memory_map = NULL;
 261                 r = da;
 262                 goto err2;
 263         }
 264         if (!pfn_t_has_page(pfn)) {
 265                 wc->memory_map = NULL;
 266                 r = -EOPNOTSUPP;
 267                 goto err2;
 268         }
 269         if (da != p) {
 270                 long i;
 271                 wc->memory_map = NULL;
 272                 pages = kvmalloc_array(p, sizeof(struct page *), GFP_KERNEL);
 273                 if (!pages) {
 274                         r = -ENOMEM;
 275                         goto err2;
 276                 }
 277                 i = 0;
 278                 do {
 279                         long daa;
 280                         daa = dax_direct_access(wc->ssd_dev->dax_dev, offset + i, p - i,
 281                                                 NULL, &pfn);
 282                         if (daa <= 0) {
 283                                 r = daa ? daa : -EINVAL;
 284                                 goto err3;
 285                         }
 286                         if (!pfn_t_has_page(pfn)) {
 287                                 r = -EOPNOTSUPP;
 288                                 goto err3;
 289                         }
 290                         while (daa-- && i < p) {
 291                                 pages[i++] = pfn_t_to_page(pfn);
 292                                 pfn.val++;
 293                                 if (!(i & 15))
 294                                         cond_resched();
 295                         }
 296                 } while (i < p);
 297                 wc->memory_map = vmap(pages, p, VM_MAP, PAGE_KERNEL);
 298                 if (!wc->memory_map) {
 299                         r = -ENOMEM;
 300                         goto err3;
 301                 }
 302                 kvfree(pages);
 303                 wc->memory_vmapped = true;
 304         }
 305
 306         dax_read_unlock(id);
 307
 308         wc->memory_map += (size_t)wc->start_sector << SECTOR_SHIFT;
 309         wc->memory_map_size -= (size_t)wc->start_sector << SECTOR_SHIFT;
 310
 311         return 0;
 312 err3:
 313         kvfree(pages);
 314 err2:
 315         dax_read_unlock(id);
 316 err1:
 317         return r;
 318 }
 319 #else
 320 static int persistent_memory_claim(struct dm_writecache *wc)
 321 {
 322         BUG();
 323 }
 324 #endif
 325
 326 static void persistent_memory_release(struct dm_writecache *wc)
 327 {
 328         if (wc->memory_vmapped)
 329                 vunmap(wc->memory_map - ((size_t)wc->start_sector << SECTOR_SHIFT));
 330 }
 331
 332 static struct page *persistent_memory_page(void *addr)
 333 {
 334         if (is_vmalloc_addr(addr))
 335                 return vmalloc_to_page(addr);
 336         else
 337                 return virt_to_page(addr);
 338 }
 339
 340 static unsigned persistent_memory_page_offset(void *addr)
 341 {
 342         return (unsigned long)addr & (PAGE_SIZE - 1);
 343 }
 344
 345 static void persistent_memory_flush_cache(void *ptr, size_t size)
 346 {
 347         if (is_vmalloc_addr(ptr))
 348                 flush_kernel_vmap_range(ptr, size);
 349 }
 350
 351 static void persistent_memory_invalidate_cache(void *ptr, size_t size)
 352 {
 353         if (is_vmalloc_addr(ptr))
 354                 invalidate_kernel_vmap_range(ptr, size);
 355 }
 356
 357 static struct wc_memory_superblock *sb(struct dm_writecache *wc)
 358 {
 359         return wc->memory_map;
 360 }
 361
 362 static struct wc_memory_entry *memory_entry(struct dm_writecache *wc, struct wc_entry *e)
 363 {
 364         return &sb(wc)->entries[e->index];
 365 }
 366
 367 static void *memory_data(struct dm_writecache *wc, struct wc_entry *e)
 368 {
 369         return (char *)wc->block_start + (e->index << wc->block_size_bits);
 370 }
 371
 372 static sector_t cache_sector(struct dm_writecache *wc, struct wc_entry *e)
 373 {
 374         return wc->start_sector + wc->metadata_sectors +
 375                 ((sector_t)e->index << (wc->block_size_bits - SECTOR_SHIFT));
 376 }
 377
 378 static uint64_t read_original_sector(struct dm_writecache *wc, struct wc_entry *e)
 379 {
 380 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 381         return e->original_sector;
 382 #else
 383         return le64_to_cpu(memory_entry(wc, e)->original_sector);
 384 #endif
 385 }
 386
 387 static uint64_t read_seq_count(struct dm_writecache *wc, struct wc_entry *e)
 388 {
 389 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 390         return e->seq_count;
 391 #else
 392         return le64_to_cpu(memory_entry(wc, e)->seq_count);
 393 #endif
 394 }
 395
 396 static void clear_seq_count(struct dm_writecache *wc, struct wc_entry *e)
 397 {
 398 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 399         e->seq_count = -1;
 400 #endif
 401         pmem_assign(memory_entry(wc, e)->seq_count, cpu_to_le64(-1));
 402 }
 403
 404 static void write_original_sector_seq_count(struct dm_writecache *wc, struct wc_entry *e,
 405                                             uint64_t original_sector, uint64_t seq_count)
 406 {
 407         struct wc_memory_entry me;
 408 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
 409         e->original_sector = original_sector;
 410         e->seq_count = seq_count;
 411 #endif
 412         me.original_sector = cpu_to_le64(original_sector);
 413         me.seq_count = cpu_to_le64(seq_count);
 414         pmem_assign(*memory_entry(wc, e), me);
 415 }
 416
 417 #define writecache_error(wc, err, msg, arg...)                          \
 418 do {                                                                    \
 419         if (!cmpxchg(&(wc)->error, 0, err))                             \
 420                 DMERR(msg, ##arg);                                      \
 421         wake_up(&(wc)->freelist_wait);                                  \
 422 } while (0)
 423
 424 #define writecache_has_error(wc)        (unlikely(READ_ONCE((wc)->error)))
 425
 426 static void writecache_flush_all_metadata(struct dm_writecache *wc)
 427 {
 428         if (!WC_MODE_PMEM(wc))
 429                 memset(wc->dirty_bitmap, -1, wc->dirty_bitmap_size);
 430 }
 431
 432 static void writecache_flush_region(struct dm_writecache *wc, void *ptr, size_t size)
 433 {
 434         if (!WC_MODE_PMEM(wc))
 435                 __set_bit(((char *)ptr - (char *)wc->memory_map) / BITMAP_GRANULARITY,
 436                           wc->dirty_bitmap);
 437 }
 438
 439 static void writecache_disk_flush(struct dm_writecache *wc, struct dm_dev *dev);
 440
 441 struct io_notify {
 442         struct dm_writecache *wc;
 443         struct completion c;
 444         atomic_t count;
 445 };
 446
 447 static void writecache_notify_io(unsigned long error, void *context)
 448 {
 449         struct io_notify *endio = context;
 450
 451         if (unlikely(error != 0))
 452                 writecache_error(endio->wc, -EIO, "error writing metadata");
 453         BUG_ON(atomic_read(&endio->count) <= 0);
 454         if (atomic_dec_and_test(&endio->count))
 455                 complete(&endio->c);
 456 }
 457
 458 static void writecache_wait_for_ios(struct dm_writecache *wc, int direction)
 459 {
 460         wait_event(wc->bio_in_progress_wait[direction],
 461                    !atomic_read(&wc->bio_in_progress[direction]));
 462 }
 463
 464 static void ssd_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
 465 {
 466         struct dm_io_region region;
 467         struct dm_io_request req;
 468         struct io_notify endio = {
 469                 wc,
 470                 COMPLETION_INITIALIZER_ONSTACK(endio.c),
 471                 ATOMIC_INIT(1),
 472         };
 473         unsigned bitmap_bits = wc->dirty_bitmap_size * 8;
 474         unsigned i = 0;
 475
 476         while (1) {
 477                 unsigned j;
 478                 i = find_next_bit(wc->dirty_bitmap, bitmap_bits, i);
 479                 if (unlikely(i == bitmap_bits))
 480                         break;
 481                 j = find_next_zero_bit(wc->dirty_bitmap, bitmap_bits, i);
 482
 483                 region.bdev = wc->ssd_dev->bdev;
 484                 region.sector = (sector_t)i * (BITMAP_GRANULARITY >> SECTOR_SHIFT);
 485                 region.count = (sector_t)(j - i) * (BITMAP_GRANULARITY >> SECTOR_SHIFT);
 486
 487                 if (unlikely(region.sector >= wc->metadata_sectors))
 488                         break;
 489                 if (unlikely(region.sector + region.count > wc->metadata_sectors))
 490                         region.count = wc->metadata_sectors - region.sector;
 491
 492                 region.sector += wc->start_sector;
 493                 atomic_inc(&endio.count);
 494                 req.bi_op = REQ_OP_WRITE;
 495                 req.bi_op_flags = REQ_SYNC;
 496                 req.mem.type = DM_IO_VMA;
 497                 req.mem.ptr.vma = (char *)wc->memory_map + (size_t)i * BITMAP_GRANULARITY;
 498                 req.client = wc->dm_io;
 499                 req.notify.fn = writecache_notify_io;
 500                 req.notify.context = &endio;
 501
 502                 /* writing via async dm-io (implied by notify.fn above) won't return an error */
 503                 (void) dm_io(&req, 1, &region, NULL);
 504                 i = j;
 505         }
 506
 507         writecache_notify_io(0, &endio);
 508         wait_for_completion_io(&endio.c);
 509
 510         if (wait_for_ios)
 511                 writecache_wait_for_ios(wc, WRITE);
 512
 513         writecache_disk_flush(wc, wc->ssd_dev);
 514
 515         memset(wc->dirty_bitmap, 0, wc->dirty_bitmap_size);
 516 }
 517
 518 static void ssd_commit_superblock(struct dm_writecache *wc)
 519 {
 520         int r;
 521         struct dm_io_region region;
 522         struct dm_io_request req;
 523
 524         region.bdev = wc->ssd_dev->bdev;
 525         region.sector = 0;
 526         region.count = PAGE_SIZE;
 527
 528         if (unlikely(region.sector + region.count > wc->metadata_sectors))
 529                 region.count = wc->metadata_sectors - region.sector;
 530
 531         region.sector += wc->start_sector;
 532
 533         req.bi_op = REQ_OP_WRITE;
 534         req.bi_op_flags = REQ_SYNC | REQ_FUA;
 535         req.mem.type = DM_IO_VMA;
 536         req.mem.ptr.vma = (char *)wc->memory_map;
 537         req.client = wc->dm_io;
 538         req.notify.fn = NULL;
 539         req.notify.context = NULL;
 540
 541         r = dm_io(&req, 1, &region, NULL);
 542         if (unlikely(r))
 543                 writecache_error(wc, r, "error writing superblock");
 544 }
 545
 546 static void writecache_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
 547 {
 548         if (WC_MODE_PMEM(wc))
 549                 pmem_wmb();
 550         else
 551                 ssd_commit_flushed(wc, wait_for_ios);
 552 }
 553
 554 static void writecache_disk_flush(struct dm_writecache *wc, struct dm_dev *dev)
 555 {
 556         int r;
 557         struct dm_io_region region;
 558         struct dm_io_request req;
 559
 560         region.bdev = dev->bdev;
 561         region.sector = 0;
 562         region.count = 0;
 563         req.bi_op = REQ_OP_WRITE;
 564         req.bi_op_flags = REQ_PREFLUSH;
 565         req.mem.type = DM_IO_KMEM;
 566         req.mem.ptr.addr = NULL;
 567         req.client = wc->dm_io;
 568         req.notify.fn = NULL;
 569
 570         r = dm_io(&req, 1, &region, NULL);
 571         if (unlikely(r))
 572                 writecache_error(wc, r, "error flushing metadata: %d", r);
 573 }
 574
 575 #define WFE_RETURN_FOLLOWING    1
 576 #define WFE_LOWEST_SEQ          2
 577
 578 static struct wc_entry *writecache_find_entry(struct dm_writecache *wc,
 579                                               uint64_t block, int flags)
 580 {
 581         struct wc_entry *e;
 582         struct rb_node *node = wc->tree.rb_node;
 583
 584         if (unlikely(!node))
 585                 return NULL;
 586
 587         while (1) {
 588                 e = container_of(node, struct wc_entry, rb_node);
 589                 if (read_original_sector(wc, e) == block)
 590                         break;
 591
 592                 node = (read_original_sector(wc, e) >= block ?
 593                         e->rb_node.rb_left : e->rb_node.rb_right);
 594                 if (unlikely(!node)) {
 595                         if (!(flags & WFE_RETURN_FOLLOWING))
 596                                 return NULL;
 597                         if (read_original_sector(wc, e) >= block) {
 598                                 return e;
 599                         } else {
 600                                 node = rb_next(&e->rb_node);
 601                                 if (unlikely(!node))
 602                                         return NULL;
 603                                 e = container_of(node, struct wc_entry, rb_node);
 604                                 return e;
 605                         }
 606                 }
 607         }
 608
 609         while (1) {
 610                 struct wc_entry *e2;
 611                 if (flags & WFE_LOWEST_SEQ)
 612                         node = rb_prev(&e->rb_node);
 613                 else
 614                         node = rb_next(&e->rb_node);
 615                 if (unlikely(!node))
 616                         return e;
 617                 e2 = container_of(node, struct wc_entry, rb_node);
 618                 if (read_original_sector(wc, e2) != block)
 619                         return e;
 620                 e = e2;
 621         }
 622 }
 623
 624 static void writecache_insert_entry(struct dm_writecache *wc, struct wc_entry *ins)
 625 {
 626         struct wc_entry *e;
 627         struct rb_node **node = &wc->tree.rb_node, *parent = NULL;
 628
 629         while (*node) {
 630                 e = container_of(*node, struct wc_entry, rb_node);
 631                 parent = &e->rb_node;
 632                 if (read_original_sector(wc, e) > read_original_sector(wc, ins))
 633                         node = &parent->rb_left;
 634                 else
 635                         node = &parent->rb_right;
 636         }
 637         rb_link_node(&ins->rb_node, parent, node);
 638         rb_insert_color(&ins->rb_node, &wc->tree);
 639         list_add(&ins->lru, &wc->lru);
 640         ins->age = jiffies;
 641 }
 642
 643 static void writecache_unlink(struct dm_writecache *wc, struct wc_entry *e)
 644 {
 645         list_del(&e->lru);
 646         rb_erase(&e->rb_node, &wc->tree);
 647 }
 648
 649 static void writecache_add_to_freelist(struct dm_writecache *wc, struct wc_entry *e)
 650 {
 651         if (WC_MODE_SORT_FREELIST(wc)) {
 652                 struct rb_node **node = &wc->freetree.rb_node, *parent = NULL;
 653                 if (unlikely(!*node))
 654                         wc->current_free = e;
 655                 while (*node) {
 656                         parent = *node;
 657                         if (&e->rb_node < *node)
 658                                 node = &parent->rb_left;
 659                         else
 660                                 node = &parent->rb_right;
 661                 }
 662                 rb_link_node(&e->rb_node, parent, node);
 663                 rb_insert_color(&e->rb_node, &wc->freetree);
 664         } else {
 665                 list_add_tail(&e->lru, &wc->freelist);
 666         }
 667         wc->freelist_size++;
 668 }
 669
 670 static inline void writecache_verify_watermark(struct dm_writecache *wc)
 671 {
 672         if (unlikely(wc->freelist_size + wc->writeback_size <= wc->freelist_high_watermark))
 673                 queue_work(wc->writeback_wq, &wc->writeback_work);
 674 }
 675
 676 static void writecache_max_age_timer(struct timer_list *t)
 677 {
 678         struct dm_writecache *wc = from_timer(wc, t, max_age_timer);
 679
 680         if (!dm_suspended(wc->ti) && !writecache_has_error(wc)) {
 681                 queue_work(wc->writeback_wq, &wc->writeback_work);
 682                 mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);
 683         }
 684 }
 685
 686 static struct wc_entry *writecache_pop_from_freelist(struct dm_writecache *wc, sector_t expected_sector)
 687 {
 688         struct wc_entry *e;
 689
 690         if (WC_MODE_SORT_FREELIST(wc)) {
 691                 struct rb_node *next;
 692                 if (unlikely(!wc->current_free))
 693                         return NULL;
 694                 e = wc->current_free;
 695                 if (expected_sector != (sector_t)-1 && unlikely(cache_sector(wc, e) != expected_sector))
 696                         return NULL;
 697                 next = rb_next(&e->rb_node);
 698                 rb_erase(&e->rb_node, &wc->freetree);
 699                 if (unlikely(!next))
 700                         next = rb_first(&wc->freetree);
 701                 wc->current_free = next ? container_of(next, struct wc_entry, rb_node) : NULL;
 702         } else {
 703                 if (unlikely(list_empty(&wc->freelist)))
 704                         return NULL;
 705                 e = container_of(wc->freelist.next, struct wc_entry, lru);
 706                 if (expected_sector != (sector_t)-1 && unlikely(cache_sector(wc, e) != expected_sector))
 707                         return NULL;
 708                 list_del(&e->lru);
 709         }
 710         wc->freelist_size--;
 711
 712         writecache_verify_watermark(wc);
 713
 714         return e;
 715 }
 716
 717 static void writecache_free_entry(struct dm_writecache *wc, struct wc_entry *e)
 718 {
 719         writecache_unlink(wc, e);
 720         writecache_add_to_freelist(wc, e);
 721         clear_seq_count(wc, e);
 722         writecache_flush_region(wc, memory_entry(wc, e), sizeof(struct wc_memory_entry));
 723         if (unlikely(waitqueue_active(&wc->freelist_wait)))
 724                 wake_up(&wc->freelist_wait);
 725 }
 726
 727 static void writecache_wait_on_freelist(struct dm_writecache *wc)
 728 {
 729         DEFINE_WAIT(wait);
 730
 731         prepare_to_wait(&wc->freelist_wait, &wait, TASK_UNINTERRUPTIBLE);
 732         wc_unlock(wc);
 733         io_schedule();
 734         finish_wait(&wc->freelist_wait, &wait);
 735         wc_lock(wc);
 736 }
 737
 738 static void writecache_poison_lists(struct dm_writecache *wc)
 739 {
 740         /*
 741          * Catch incorrect access to these values while the device is suspended.
 742          */
 743         memset(&wc->tree, -1, sizeof wc->tree);
 744         wc->lru.next = LIST_POISON1;
 745         wc->lru.prev = LIST_POISON2;
 746         wc->freelist.next = LIST_POISON1;
 747         wc->freelist.prev = LIST_POISON2;
 748 }
 749
 750 static void writecache_flush_entry(struct dm_writecache *wc, struct wc_entry *e)
 751 {
 752         writecache_flush_region(wc, memory_entry(wc, e), sizeof(struct wc_memory_entry));
 753         if (WC_MODE_PMEM(wc))
 754                 writecache_flush_region(wc, memory_data(wc, e), wc->block_size);
 755 }
 756
 757 static bool writecache_entry_is_committed(struct dm_writecache *wc, struct wc_entry *e)
 758 {
 759         return read_seq_count(wc, e) < wc->seq_count;
 760 }
 761
 762 static void writecache_flush(struct dm_writecache *wc)
 763 {
 764         struct wc_entry *e, *e2;
 765         bool need_flush_after_free;
 766
 767         wc->uncommitted_blocks = 0;
 768         del_timer(&wc->autocommit_timer);
 769
 770         if (list_empty(&wc->lru))
 771                 return;
 772
 773         e = container_of(wc->lru.next, struct wc_entry, lru);
 774         if (writecache_entry_is_committed(wc, e)) {
 775                 if (wc->overwrote_committed) {
 776                         writecache_wait_for_ios(wc, WRITE);
 777                         writecache_disk_flush(wc, wc->ssd_dev);
 778                         wc->overwrote_committed = false;
 779                 }
 780                 return;
 781         }
 782         while (1) {
 783                 writecache_flush_entry(wc, e);
 784                 if (unlikely(e->lru.next == &wc->lru))
 785                         break;
 786                 e2 = container_of(e->lru.next, struct wc_entry, lru);
 787                 if (writecache_entry_is_committed(wc, e2))
 788                         break;
 789                 e = e2;
 790                 cond_resched();
 791         }
 792         writecache_commit_flushed(wc, true);
 793
 794         wc->seq_count++;
 795         pmem_assign(sb(wc)->seq_count, cpu_to_le64(wc->seq_count));
 796         if (WC_MODE_PMEM(wc))
 797                 writecache_commit_flushed(wc, false);
 798         else
 799                 ssd_commit_superblock(wc);
 800
 801         wc->overwrote_committed = false;
 802
 803         need_flush_after_free = false;
 804         while (1) {
 805                 /* Free another committed entry with lower seq-count */
 806                 struct rb_node *rb_node = rb_prev(&e->rb_node);
 807
 808                 if (rb_node) {
 809                         e2 = container_of(rb_node, struct wc_entry, rb_node);
 810                         if (read_original_sector(wc, e2) == read_original_sector(wc, e) &&
 811                             likely(!e2->write_in_progress)) {
 812                                 writecache_free_entry(wc, e2);
 813                                 need_flush_after_free = true;
 814                         }
 815                 }
 816                 if (unlikely(e->lru.prev == &wc->lru))
 817                         break;
 818                 e = container_of(e->lru.prev, struct wc_entry, lru);
 819                 cond_resched();
 820         }
 821
 822         if (need_flush_after_free)
 823                 writecache_commit_flushed(wc, false);
 824 }
 825
 826 static void writecache_flush_work(struct work_struct *work)
 827 {
 828         struct dm_writecache *wc = container_of(work, struct dm_writecache, flush_work);
 829
 830         wc_lock(wc);
 831         writecache_flush(wc);
 832         wc_unlock(wc);
 833 }
 834
 835 static void writecache_autocommit_timer(struct timer_list *t)
 836 {
 837         struct dm_writecache *wc = from_timer(wc, t, autocommit_timer);
 838         if (!writecache_has_error(wc))
 839                 queue_work(wc->writeback_wq, &wc->flush_work);
 840 }
 841
 842 static void writecache_schedule_autocommit(struct dm_writecache *wc)
 843 {
 844         if (!timer_pending(&wc->autocommit_timer))
 845                 mod_timer(&wc->autocommit_timer, jiffies + wc->autocommit_jiffies);
 846 }
 847
 848 static void writecache_discard(struct dm_writecache *wc, sector_t start, sector_t end)
 849 {
 850         struct wc_entry *e;
 851         bool discarded_something = false;
 852
 853         e = writecache_find_entry(wc, start, WFE_RETURN_FOLLOWING | WFE_LOWEST_SEQ);
 854         if (unlikely(!e))
 855                 return;
 856
 857         while (read_original_sector(wc, e) < end) {
 858                 struct rb_node *node = rb_next(&e->rb_node);
 859
 860                 if (likely(!e->write_in_progress)) {
 861                         if (!discarded_something) {
 862                                 if (!WC_MODE_PMEM(wc)) {
 863                                         writecache_wait_for_ios(wc, READ);
 864                                         writecache_wait_for_ios(wc, WRITE);
 865                                 }
 866                                 discarded_something = true;
 867                         }
 868                         if (!writecache_entry_is_committed(wc, e))
 869                                 wc->uncommitted_blocks--;
 870                         writecache_free_entry(wc, e);
 871                 }
 872
 873                 if (unlikely(!node))
 874                         break;
 875
 876                 e = container_of(node, struct wc_entry, rb_node);
 877         }
 878
 879         if (discarded_something)
 880                 writecache_commit_flushed(wc, false);
 881 }
 882
 883 static bool writecache_wait_for_writeback(struct dm_writecache *wc)
 884 {
 885         if (wc->writeback_size) {
 886                 writecache_wait_on_freelist(wc);
 887                 return true;
 888         }
 889         return false;
 890 }
 891
 892 static void writecache_suspend(struct dm_target *ti)
 893 {
 894         struct dm_writecache *wc = ti->private;
 895         bool flush_on_suspend;
 896
 897         del_timer_sync(&wc->autocommit_timer);
 898         del_timer_sync(&wc->max_age_timer);
 899
 900         wc_lock(wc);
 901         writecache_flush(wc);
 902         flush_on_suspend = wc->flush_on_suspend;
 903         if (flush_on_suspend) {
 904                 wc->flush_on_suspend = false;
 905                 wc->writeback_all++;
 906                 queue_work(wc->writeback_wq, &wc->writeback_work);
 907         }
 908         wc_unlock(wc);
 909
 910         drain_workqueue(wc->writeback_wq);
 911
 912         wc_lock(wc);
 913         if (flush_on_suspend)
 914                 wc->writeback_all--;
 915         while (writecache_wait_for_writeback(wc));
 916
 917         if (WC_MODE_PMEM(wc))
 918                 persistent_memory_flush_cache(wc->memory_map, wc->memory_map_size);
 919
 920         writecache_poison_lists(wc);
 921
 922         wc_unlock(wc);
 923 }
 924
 925 static int writecache_alloc_entries(struct dm_writecache *wc)
 926 {
 927         size_t b;
 928
 929         if (wc->entries)
 930                 return 0;
 931         wc->entries = vmalloc(array_size(sizeof(struct wc_entry), wc->n_blocks));
 932         if (!wc->entries)
 933                 return -ENOMEM;
 934         for (b = 0; b < wc->n_blocks; b++) {
 935                 struct wc_entry *e = &wc->entries[b];
 936                 e->index = b;
 937                 e->write_in_progress = false;
 938                 cond_resched();
 939         }
 940
 941         return 0;
 942 }
 943
 944 static int writecache_read_metadata(struct dm_writecache *wc, sector_t n_sectors)
 945 {
 946         struct dm_io_region region;
 947         struct dm_io_request req;
 948
 949         region.bdev = wc->ssd_dev->bdev;
 950         region.sector = wc->start_sector;
 951         region.count = n_sectors;
 952         req.bi_op = REQ_OP_READ;
 953         req.bi_op_flags = REQ_SYNC;
 954         req.mem.type = DM_IO_VMA;
 955         req.mem.ptr.vma = (char *)wc->memory_map;
 956         req.client = wc->dm_io;
 957         req.notify.fn = NULL;
 958
 959         return dm_io(&req, 1, &region, NULL);
 960 }
 961
 962 static void writecache_resume(struct dm_target *ti)
 963 {
 964         struct dm_writecache *wc = ti->private;
 965         size_t b;
 966         bool need_flush = false;
 967         __le64 sb_seq_count;
 968         int r;
 969
 970         wc_lock(wc);
 971
 972         if (WC_MODE_PMEM(wc)) {
 973                 persistent_memory_invalidate_cache(wc->memory_map, wc->memory_map_size);
 974         } else {
 975                 r = writecache_read_metadata(wc, wc->metadata_sectors);
 976                 if (r) {
 977                         size_t sb_entries_offset;
 978                         writecache_error(wc, r, "unable to read metadata: %d", r);
 979                         sb_entries_offset = offsetof(struct wc_memory_superblock, entries);
 980                         memset((char *)wc->memory_map + sb_entries_offset, -1,
 981                                (wc->metadata_sectors << SECTOR_SHIFT) - sb_entries_offset);
 982                 }
 983         }
 984
 985         wc->tree = RB_ROOT;
 986         INIT_LIST_HEAD(&wc->lru);
 987         if (WC_MODE_SORT_FREELIST(wc)) {
 988                 wc->freetree = RB_ROOT;
 989                 wc->current_free = NULL;
 990         } else {
 991                 INIT_LIST_HEAD(&wc->freelist);
 992         }
 993         wc->freelist_size = 0;
 994
 995         r = memcpy_mcsafe(&sb_seq_count, &sb(wc)->seq_count, sizeof(uint64_t));
 996         if (r) {
 997                 writecache_error(wc, r, "hardware memory error when reading superblock: %d", r);
 998                 sb_seq_count = cpu_to_le64(0);
 999         }
1000         wc->seq_count = le64_to_cpu(sb_seq_count);
1001
1002 #ifdef DM_WRITECACHE_HANDLE_HARDWARE_ERRORS
1003         for (b = 0; b < wc->n_blocks; b++) {
1004                 struct wc_entry *e = &wc->entries[b];
1005                 struct wc_memory_entry wme;
1006                 if (writecache_has_error(wc)) {
1007                         e->original_sector = -1;
1008                         e->seq_count = -1;
1009                         continue;
1010                 }
1011                 r = memcpy_mcsafe(&wme, memory_entry(wc, e), sizeof(struct wc_memory_entry));
1012                 if (r) {
1013                         writecache_error(wc, r, "hardware memory error when reading metadata entry %lu: %d",
1014                                          (unsigned long)b, r);
1015                         e->original_sector = -1;
1016                         e->seq_count = -1;
1017                 } else {
1018                         e->original_sector = le64_to_cpu(wme.original_sector);
1019                         e->seq_count = le64_to_cpu(wme.seq_count);
1020                 }
1021                 cond_resched();
1022         }
1023 #endif
1024         for (b = 0; b < wc->n_blocks; b++) {
1025                 struct wc_entry *e = &wc->entries[b];
1026                 if (!writecache_entry_is_committed(wc, e)) {
1027                         if (read_seq_count(wc, e) != -1) {
1028 erase_this:
1029                                 clear_seq_count(wc, e);
1030                                 need_flush = true;
1031                         }
1032                         writecache_add_to_freelist(wc, e);
1033                 } else {
1034                         struct wc_entry *old;
1035
1036                         old = writecache_find_entry(wc, read_original_sector(wc, e), 0);
1037                         if (!old) {
1038                                 writecache_insert_entry(wc, e);
1039                         } else {
1040                                 if (read_seq_count(wc, old) == read_seq_count(wc, e)) {
1041                                         writecache_error(wc, -EINVAL,
1042                                                  "two identical entries, position %llu, sector %llu, sequence %llu",
1043                                                  (unsigned long long)b, (unsigned long long)read_original_sector(wc, e),
1044                                                  (unsigned long long)read_seq_count(wc, e));
1045                                 }
1046                                 if (read_seq_count(wc, old) > read_seq_count(wc, e)) {
1047                                         goto erase_this;
1048                                 } else {
1049                                         writecache_free_entry(wc, old);
1050                                         writecache_insert_entry(wc, e);
1051                                         need_flush = true;
1052                                 }
1053                         }
1054                 }
1055                 cond_resched();
1056         }
1057
1058         if (need_flush) {
1059                 writecache_flush_all_metadata(wc);
1060                 writecache_commit_flushed(wc, false);
1061         }
1062
1063         writecache_verify_watermark(wc);
1064
1065         if (wc->max_age != MAX_AGE_UNSPECIFIED)
1066                 mod_timer(&wc->max_age_timer, jiffies + wc->max_age / MAX_AGE_DIV);
1067
1068         wc_unlock(wc);
1069 }
1070
1071 static int process_flush_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
1072 {
1073         if (argc != 1)
1074                 return -EINVAL;
1075
1076         wc_lock(wc);
1077         if (dm_suspended(wc->ti)) {
1078                 wc_unlock(wc);
1079                 return -EBUSY;
1080         }
1081         if (writecache_has_error(wc)) {
1082                 wc_unlock(wc);
1083                 return -EIO;
1084         }
1085
1086         writecache_flush(wc);
1087         wc->writeback_all++;
1088         queue_work(wc->writeback_wq, &wc->writeback_work);
1089         wc_unlock(wc);
1090
1091         flush_workqueue(wc->writeback_wq);
1092
1093         wc_lock(wc);
1094         wc->writeback_all--;
1095         if (writecache_has_error(wc)) {
1096                 wc_unlock(wc);
1097                 return -EIO;
1098         }
1099         wc_unlock(wc);
1100
1101         return 0;
1102 }
1103
1104 static int process_flush_on_suspend_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
1105 {
1106         if (argc != 1)
1107                 return -EINVAL;
1108
1109         wc_lock(wc);
1110         wc->flush_on_suspend = true;
1111         wc_unlock(wc);
1112
1113         return 0;
1114 }
1115
1116 static void activate_cleaner(struct dm_writecache *wc)
1117 {
1118         wc->flush_on_suspend = true;
1119         wc->cleaner = true;
1120         wc->freelist_high_watermark = wc->n_blocks;
1121         wc->freelist_low_watermark = wc->n_blocks;
1122 }
1123
1124 static int process_cleaner_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
1125 {
1126         if (argc != 1)
1127                 return -EINVAL;
1128
1129         wc_lock(wc);
1130         activate_cleaner(wc);
1131         if (!dm_suspended(wc->ti))
1132                 writecache_verify_watermark(wc);
1133         wc_unlock(wc);
1134
1135         return 0;
1136 }
1137
1138 static int writecache_message(struct dm_target *ti, unsigned argc, char **argv,
1139                               char *result, unsigned maxlen)
1140 {
1141         int r = -EINVAL;
1142         struct dm_writecache *wc = ti->private;
1143
1144         if (!strcasecmp(argv[0], "flush"))
1145                 r = process_flush_mesg(argc, argv, wc);
1146         else if (!strcasecmp(argv[0], "flush_on_suspend"))
1147                 r = process_flush_on_suspend_mesg(argc, argv, wc);
1148         else if (!strcasecmp(argv[0], "cleaner"))
1149                 r = process_cleaner_mesg(argc, argv, wc);
1150         else
1151                 DMERR("unrecognised message received: %s", argv[0]);
1152
1153         return r;
1154 }
1155
1156 static void memcpy_flushcache_optimized(void *dest, void *source, size_t size)
1157 {
1158         /*
1159          * clflushopt performs better with block size 1024, 2048, 4096
1160          * non-temporal stores perform better with block size 512
1161          *
1162          * block size   512             1024            2048            4096
1163          * movnti       496 MB/s        642 MB/s        725 MB/s        744 MB/s
1164          * clflushopt   373 MB/s        688 MB/s        1.1 GB/s        1.2 GB/s
1165          *
1166          * We see that movnti performs better for 512-byte blocks, and
1167          * clflushopt performs better for 1024-byte and larger blocks. So, we
1168          * prefer clflushopt for sizes >= 768.
1169          *
1170          * NOTE: this happens to be the case now (with dm-writecache's single
1171          * threaded model) but re-evaluate this once memcpy_flushcache() is
1172          * enabled to use movdir64b which might invalidate this performance
1173          * advantage seen with cache-allocating-writes plus flushing.
1174          */
1175 #ifdef CONFIG_X86
1176         if (static_cpu_has(X86_FEATURE_CLFLUSHOPT) &&
1177             likely(boot_cpu_data.x86_clflush_size == 64) &&
1178             likely(size >= 768)) {
1179                 do {
1180                         memcpy((void *)dest, (void *)source, 64);
1181                         clflushopt((void *)dest);
1182                         dest += 64;
1183                         source += 64;
1184                         size -= 64;
1185                 } while (size >= 64);
1186                 return;
1187         }
1188 #endif
1189         memcpy_flushcache(dest, source, size);
1190 }
1191
1192 static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data)
1193 {
1194         void *buf;
1195         unsigned long flags;
1196         unsigned size;
1197         int rw = bio_data_dir(bio);
1198         unsigned remaining_size = wc->block_size;
1199
1200         do {
1201                 struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
1202                 buf = bvec_kmap_irq(&bv, &flags);
1203                 size = bv.bv_len;
1204                 if (unlikely(size > remaining_size))
1205                         size = remaining_size;
1206
1207                 if (rw == READ) {
1208                         int r;
1209                         r = memcpy_mcsafe(buf, data, size);
1210                         flush_dcache_page(bio_page(bio));
1211                         if (unlikely(r)) {
1212                                 writecache_error(wc, r, "hardware memory error when reading data: %d", r);
1213                                 bio->bi_status = BLK_STS_IOERR;
1214                         }
1215                 } else {
1216                         flush_dcache_page(bio_page(bio));
1217                         memcpy_flushcache_optimized(data, buf, size);
1218                 }
1219
1220                 bvec_kunmap_irq(buf, &flags);
1221
1222                 data = (char *)data + size;
1223                 remaining_size -= size;
1224                 bio_advance(bio, size);
1225         } while (unlikely(remaining_size));
1226 }
1227
1228 static int writecache_flush_thread(void *data)
1229 {
1230         struct dm_writecache *wc = data;
1231
1232         while (1) {
1233                 struct bio *bio;
1234
1235                 wc_lock(wc);
1236                 bio = bio_list_pop(&wc->flush_list);
1237                 if (!bio) {
1238                         set_current_state(TASK_INTERRUPTIBLE);
1239                         wc_unlock(wc);
1240
1241                         if (unlikely(kthread_should_stop())) {
1242                                 set_current_state(TASK_RUNNING);
1243                                 break;
1244                         }
1245
1246                         schedule();
1247                         continue;
1248                 }
1249
1250                 if (bio_op(bio) == REQ_OP_DISCARD) {
1251                         writecache_discard(wc, bio->bi_iter.bi_sector,
1252                                            bio_end_sector(bio));
1253                         wc_unlock(wc);
1254                         bio_set_dev(bio, wc->dev->bdev);
1255                         submit_bio_noacct(bio);
1256                 } else {
1257                         writecache_flush(wc);
1258                         wc_unlock(wc);
1259                         if (writecache_has_error(wc))
1260                                 bio->bi_status = BLK_STS_IOERR;
1261                         bio_endio(bio);
1262                 }
1263         }
1264
1265         return 0;
1266 }
1267
1268 static void writecache_offload_bio(struct dm_writecache *wc, struct bio *bio)
1269 {
1270         if (bio_list_empty(&wc->flush_list))
1271                 wake_up_process(wc->flush_thread);
1272         bio_list_add(&wc->flush_list, bio);
1273 }
1274
1275 static int writecache_map(struct dm_target *ti, struct bio *bio)
1276 {
1277         struct wc_entry *e;
1278         struct dm_writecache *wc = ti->private;
1279
1280         bio->bi_private = NULL;
1281
1282         wc_lock(wc);
1283
1284         if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
1285                 if (writecache_has_error(wc))
1286                         goto unlock_error;
1287                 if (WC_MODE_PMEM(wc)) {
1288                         writecache_flush(wc);
1289                         if (writecache_has_error(wc))
1290                                 goto unlock_error;
1291                         goto unlock_submit;
1292                 } else {
1293                         writecache_offload_bio(wc, bio);
1294                         goto unlock_return;
1295                 }
1296         }
1297
1298         bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
1299
1300         if (unlikely((((unsigned)bio->bi_iter.bi_sector | bio_sectors(bio)) &
1301                                 (wc->block_size / 512 - 1)) != 0)) {
1302                 DMERR("I/O is not aligned, sector %llu, size %u, block size %u",
1303                       (unsigned long long)bio->bi_iter.bi_sector,
1304                       bio->bi_iter.bi_size, wc->block_size);
1305                 goto unlock_error;
1306         }
1307
1308         if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {
1309                 if (writecache_has_error(wc))
1310                         goto unlock_error;
1311                 if (WC_MODE_PMEM(wc)) {
1312                         writecache_discard(wc, bio->bi_iter.bi_sector, bio_end_sector(bio));
1313                         goto unlock_remap_origin;
1314                 } else {
1315                         writecache_offload_bio(wc, bio);
1316                         goto unlock_return;
1317                 }
1318         }
1319
1320         if (bio_data_dir(bio) == READ) {
1321 read_next_block:
1322                 e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
1323                 if (e && read_original_sector(wc, e) == bio->bi_iter.bi_sector) {
1324                         if (WC_MODE_PMEM(wc)) {
1325                                 bio_copy_block(wc, bio, memory_data(wc, e));
1326                                 if (bio->bi_iter.bi_size)
1327                                         goto read_next_block;
1328                                 goto unlock_submit;
1329                         } else {
1330                                 dm_accept_partial_bio(bio, wc->block_size >> SECTOR_SHIFT);
1331                                 bio_set_dev(bio, wc->ssd_dev->bdev);
1332                                 bio->bi_iter.bi_sector = cache_sector(wc, e);
1333                                 if (!writecache_entry_is_committed(wc, e))
1334                                         writecache_wait_for_ios(wc, WRITE);
1335                                 goto unlock_remap;
1336                         }
1337                 } else {
1338                         if (e) {
1339                                 sector_t next_boundary =
1340                                         read_original_sector(wc, e) - bio->bi_iter.bi_sector;
1341                                 if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
1342                                         dm_accept_partial_bio(bio, next_boundary);
1343                                 }
1344                         }
1345                         goto unlock_remap_origin;
1346                 }
1347         } else {
1348                 do {
1349                         bool found_entry = false;
1350                         if (writecache_has_error(wc))
1351                                 goto unlock_error;
1352                         e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);
1353                         if (e) {
1354                                 if (!writecache_entry_is_committed(wc, e))
1355                                         goto bio_copy;
1356                                 if (!WC_MODE_PMEM(wc) && !e->write_in_progress) {
1357                                         wc->overwrote_committed = true;
1358                                         goto bio_copy;
1359                                 }
1360                                 found_entry = true;
1361                         } else {
1362                                 if (unlikely(wc->cleaner))
1363                                         goto direct_write;
1364                         }
1365                         e = writecache_pop_from_freelist(wc, (sector_t)-1);
1366                         if (unlikely(!e)) {
1367                                 if (!found_entry) {
1368 direct_write:
1369                                         e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
1370                                         if (e) {
1371                                                 sector_t next_boundary = read_original_sector(wc, e) - bio->bi_iter.bi_sector;
1372                                                 BUG_ON(!next_boundary);
1373                                                 if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
1374                                                         dm_accept_partial_bio(bio, next_boundary);
1375                                                 }
1376                                         }
1377                                         goto unlock_remap_origin;
1378                                 }
1379                                 writecache_wait_on_freelist(wc);
1380                                 continue;
1381                         }
1382                         write_original_sector_seq_count(wc, e, bio->bi_iter.bi_sector, wc->seq_count);
1383                         writecache_insert_entry(wc, e);
1384                         wc->uncommitted_blocks++;
1385 bio_copy:
1386                         if (WC_MODE_PMEM(wc)) {
1387                                 bio_copy_block(wc, bio, memory_data(wc, e));
1388                         } else {
1389                                 unsigned bio_size = wc->block_size;
1390                                 sector_t start_cache_sec = cache_sector(wc, e);
1391                                 sector_t current_cache_sec = start_cache_sec + (bio_size >> SECTOR_SHIFT);
1392
1393                                 while (bio_size < bio->bi_iter.bi_size) {
1394                                         struct wc_entry *f = writecache_pop_from_freelist(wc, current_cache_sec);
1395                                         if (!f)
1396                                                 break;
1397                                         write_original_sector_seq_count(wc, f, bio->bi_iter.bi_sector +
1398                                                                         (bio_size >> SECTOR_SHIFT), wc->seq_count);
1399                                         writecache_insert_entry(wc, f);
1400                                         wc->uncommitted_blocks++;
1401                                         bio_size += wc->block_size;
1402                                         current_cache_sec += wc->block_size >> SECTOR_SHIFT;
1403                                 }
1404
1405                                 bio_set_dev(bio, wc->ssd_dev->bdev);
1406                                 bio->bi_iter.bi_sector = start_cache_sec;
1407                                 dm_accept_partial_bio(bio, bio_size >> SECTOR_SHIFT);
1408
1409                                 if (unlikely(wc->uncommitted_blocks >= wc->autocommit_blocks)) {
1410                                         wc->uncommitted_blocks = 0;
1411                                         queue_work(wc->writeback_wq, &wc->flush_work);
1412                                 } else {
1413                                         writecache_schedule_autocommit(wc);
1414                                 }
1415                                 goto unlock_remap;
1416                         }
1417                 } while (bio->bi_iter.bi_size);
1418
1419                 if (unlikely(bio->bi_opf & REQ_FUA ||
1420                              wc->uncommitted_blocks >= wc->autocommit_blocks))
1421                         writecache_flush(wc);
1422                 else
1423                         writecache_schedule_autocommit(wc);
1424                 goto unlock_submit;
1425         }
1426
1427 unlock_remap_origin:
1428         bio_set_dev(bio, wc->dev->bdev);
1429         wc_unlock(wc);
1430         return DM_MAPIO_REMAPPED;
1431
1432 unlock_remap:
1433         /* make sure that writecache_end_io decrements bio_in_progress: */
1434         bio->bi_private = (void *)1;
1435         atomic_inc(&wc->bio_in_progress[bio_data_dir(bio)]);
1436         wc_unlock(wc);
1437         return DM_MAPIO_REMAPPED;
1438
1439 unlock_submit:
1440         wc_unlock(wc);
1441         bio_endio(bio);
1442         return DM_MAPIO_SUBMITTED;
1443
1444 unlock_return:
1445         wc_unlock(wc);
1446         return DM_MAPIO_SUBMITTED;
1447
1448 unlock_error:
1449         wc_unlock(wc);
1450         bio_io_error(bio);
1451         return DM_MAPIO_SUBMITTED;
1452 }
1453
1454 static int writecache_end_io(struct dm_target *ti, struct bio *bio, blk_status_t *status)
1455 {
1456         struct dm_writecache *wc = ti->private;
1457
1458         if (bio->bi_private != NULL) {
1459                 int dir = bio_data_dir(bio);
1460                 if (atomic_dec_and_test(&wc->bio_in_progress[dir]))
1461                         if (unlikely(waitqueue_active(&wc->bio_in_progress_wait[dir])))
1462                                 wake_up(&wc->bio_in_progress_wait[dir]);
1463         }
1464         return 0;
1465 }
1466
1467 static int writecache_iterate_devices(struct dm_target *ti,
1468                                       iterate_devices_callout_fn fn, void *data)
1469 {
1470         struct dm_writecache *wc = ti->private;
1471
1472         return fn(ti, wc->dev, 0, ti->len, data);
1473 }
1474
1475 static void writecache_io_hints(struct dm_target *ti, struct queue_limits *limits)
1476 {
1477         struct dm_writecache *wc = ti->private;
1478
1479         if (limits->logical_block_size < wc->block_size)
1480                 limits->logical_block_size = wc->block_size;
1481
1482         if (limits->physical_block_size < wc->block_size)
1483                 limits->physical_block_size = wc->block_size;
1484
1485         if (limits->io_min < wc->block_size)
1486                 limits->io_min = wc->block_size;
1487 }
1488
1489
1490 static void writecache_writeback_endio(struct bio *bio)
1491 {
1492         struct writeback_struct *wb = container_of(bio, struct writeback_struct, bio);
1493         struct dm_writecache *wc = wb->wc;
1494         unsigned long flags;
1495
1496         raw_spin_lock_irqsave(&wc->endio_list_lock, flags);
1497         if (unlikely(list_empty(&wc->endio_list)))
1498                 wake_up_process(wc->endio_thread);
1499         list_add_tail(&wb->endio_entry, &wc->endio_list);
1500         raw_spin_unlock_irqrestore(&wc->endio_list_lock, flags);
1501 }
1502
1503 static void writecache_copy_endio(int read_err, unsigned long write_err, void *ptr)
1504 {
1505         struct copy_struct *c = ptr;
1506         struct dm_writecache *wc = c->wc;
1507
1508         c->error = likely(!(read_err | write_err)) ? 0 : -EIO;
1509
1510         raw_spin_lock_irq(&wc->endio_list_lock);
1511         if (unlikely(list_empty(&wc->endio_list)))
1512                 wake_up_process(wc->endio_thread);
1513         list_add_tail(&c->endio_entry, &wc->endio_list);
1514         raw_spin_unlock_irq(&wc->endio_list_lock);
1515 }
1516
1517 static void __writecache_endio_pmem(struct dm_writecache *wc, struct list_head *list)
1518 {
1519         unsigned i;
1520         struct writeback_struct *wb;
1521         struct wc_entry *e;
1522         unsigned long n_walked = 0;
1523
1524         do {
1525                 wb = list_entry(list->next, struct writeback_struct, endio_entry);
1526                 list_del(&wb->endio_entry);
1527
1528                 if (unlikely(wb->bio.bi_status != BLK_STS_OK))
1529                         writecache_error(wc, blk_status_to_errno(wb->bio.bi_status),
1530                                         "write error %d", wb->bio.bi_status);
1531                 i = 0;
1532                 do {
1533                         e = wb->wc_list[i];
1534                         BUG_ON(!e->write_in_progress);
1535                         e->write_in_progress = false;
1536                         INIT_LIST_HEAD(&e->lru);
1537                         if (!writecache_has_error(wc))
1538                                 writecache_free_entry(wc, e);
1539                         BUG_ON(!wc->writeback_size);
1540                         wc->writeback_size--;
1541                         n_walked++;
1542                         if (unlikely(n_walked >= ENDIO_LATENCY)) {
1543                                 writecache_commit_flushed(wc, false);
1544                                 wc_unlock(wc);
1545                                 wc_lock(wc);
1546                                 n_walked = 0;
1547                         }
1548                 } while (++i < wb->wc_list_n);
1549
1550                 if (wb->wc_list != wb->wc_list_inline)
1551                         kfree(wb->wc_list);
1552                 bio_put(&wb->bio);
1553         } while (!list_empty(list));
1554 }
1555
1556 static void __writecache_endio_ssd(struct dm_writecache *wc, struct list_head *list)
1557 {
1558         struct copy_struct *c;
1559         struct wc_entry *e;
1560
1561         do {
1562                 c = list_entry(list->next, struct copy_struct, endio_entry);
1563                 list_del(&c->endio_entry);
1564
1565                 if (unlikely(c->error))
1566                         writecache_error(wc, c->error, "copy error");
1567
1568                 e = c->e;
1569                 do {
1570                         BUG_ON(!e->write_in_progress);
1571                         e->write_in_progress = false;
1572                         INIT_LIST_HEAD(&e->lru);
1573                         if (!writecache_has_error(wc))
1574                                 writecache_free_entry(wc, e);
1575
1576                         BUG_ON(!wc->writeback_size);
1577                         wc->writeback_size--;
1578                         e++;
1579                 } while (--c->n_entries);
1580                 mempool_free(c, &wc->copy_pool);
1581         } while (!list_empty(list));
1582 }
1583
1584 static int writecache_endio_thread(void *data)
1585 {
1586         struct dm_writecache *wc = data;
1587
1588         while (1) {
1589                 struct list_head list;
1590
1591                 raw_spin_lock_irq(&wc->endio_list_lock);
1592                 if (!list_empty(&wc->endio_list))
1593                         goto pop_from_list;
1594                 set_current_state(TASK_INTERRUPTIBLE);
1595                 raw_spin_unlock_irq(&wc->endio_list_lock);
1596
1597                 if (unlikely(kthread_should_stop())) {
1598                         set_current_state(TASK_RUNNING);
1599                         break;
1600                 }
1601
1602                 schedule();
1603
1604                 continue;
1605
1606 pop_from_list:
1607                 list = wc->endio_list;
1608                 list.next->prev = list.prev->next = &list;
1609                 INIT_LIST_HEAD(&wc->endio_list);
1610                 raw_spin_unlock_irq(&wc->endio_list_lock);
1611
1612                 if (!WC_MODE_FUA(wc))
1613                         writecache_disk_flush(wc, wc->dev);
1614
1615                 wc_lock(wc);
1616
1617                 if (WC_MODE_PMEM(wc)) {
1618                         __writecache_endio_pmem(wc, &list);
1619                 } else {
1620                         __writecache_endio_ssd(wc, &list);
1621                         writecache_wait_for_ios(wc, READ);
1622                 }
1623
1624                 writecache_commit_flushed(wc, false);
1625
1626                 wc_unlock(wc);
1627         }
1628
1629         return 0;
1630 }
1631
1632 static bool wc_add_block(struct writeback_struct *wb, struct wc_entry *e, gfp_t gfp)
1633 {
1634         struct dm_writecache *wc = wb->wc;
1635         unsigned block_size = wc->block_size;
1636         void *address = memory_data(wc, e);
1637
1638         persistent_memory_flush_cache(address, block_size);
1639         return bio_add_page(&wb->bio, persistent_memory_page(address),
1640                             block_size, persistent_memory_page_offset(address)) != 0;
1641 }
1642
1643 struct writeback_list {
1644         struct list_head list;
1645         size_t size;
1646 };
1647
1648 static void __writeback_throttle(struct dm_writecache *wc, struct writeback_list *wbl)
1649 {
1650         if (unlikely(wc->max_writeback_jobs)) {
1651                 if (READ_ONCE(wc->writeback_size) - wbl->size >= wc->max_writeback_jobs) {
1652                         wc_lock(wc);
1653                         while (wc->writeback_size - wbl->size >= wc->max_writeback_jobs)
1654                                 writecache_wait_on_freelist(wc);
1655                         wc_unlock(wc);
1656                 }
1657         }
1658         cond_resched();
1659 }
1660
1661 static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeback_list *wbl)
1662 {
1663         struct wc_entry *e, *f;
1664         struct bio *bio;
1665         struct writeback_struct *wb;
1666         unsigned max_pages;
1667
1668         while (wbl->size) {
1669                 wbl->size--;
1670                 e = container_of(wbl->list.prev, struct wc_entry, lru);
1671                 list_del(&e->lru);
1672
1673                 max_pages = e->wc_list_contiguous;
1674
1675                 bio = bio_alloc_bioset(GFP_NOIO, max_pages, &wc->bio_set);
1676                 wb = container_of(bio, struct writeback_struct, bio);
1677                 wb->wc = wc;
1678                 bio->bi_end_io = writecache_writeback_endio;
1679                 bio_set_dev(bio, wc->dev->bdev);
1680                 bio->bi_iter.bi_sector = read_original_sector(wc, e);
1681                 if (max_pages <= WB_LIST_INLINE ||
1682                     unlikely(!(wb->wc_list = kmalloc_array(max_pages, sizeof(struct wc_entry *),
1683                                                            GFP_NOIO | __GFP_NORETRY |
1684                                                            __GFP_NOMEMALLOC | __GFP_NOWARN)))) {
1685                         wb->wc_list = wb->wc_list_inline;
1686                         max_pages = WB_LIST_INLINE;
1687                 }
1688
1689                 BUG_ON(!wc_add_block(wb, e, GFP_NOIO));
1690
1691                 wb->wc_list[0] = e;
1692                 wb->wc_list_n = 1;
1693
1694                 while (wbl->size && wb->wc_list_n < max_pages) {
1695                         f = container_of(wbl->list.prev, struct wc_entry, lru);
1696                         if (read_original_sector(wc, f) !=
1697                             read_original_sector(wc, e) + (wc->block_size >> SECTOR_SHIFT))
1698                                 break;
1699                         if (!wc_add_block(wb, f, GFP_NOWAIT | __GFP_NOWARN))
1700                                 break;
1701                         wbl->size--;
1702                         list_del(&f->lru);
1703                         wb->wc_list[wb->wc_list_n++] = f;
1704                         e = f;
1705                 }
1706                 bio_set_op_attrs(bio, REQ_OP_WRITE, WC_MODE_FUA(wc) * REQ_FUA);
1707                 if (writecache_has_error(wc)) {
1708                         bio->bi_status = BLK_STS_IOERR;
1709                         bio_endio(bio);
1710                 } else {
1711                         submit_bio(bio);
1712                 }
1713
1714                 __writeback_throttle(wc, wbl);
1715         }
1716 }
1717
1718 static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writeback_list *wbl)
1719 {
1720         struct wc_entry *e, *f;
1721         struct dm_io_region from, to;
1722         struct copy_struct *c;
1723
1724         while (wbl->size) {
1725                 unsigned n_sectors;
1726
1727                 wbl->size--;
1728                 e = container_of(wbl->list.prev, struct wc_entry, lru);
1729                 list_del(&e->lru);
1730
1731                 n_sectors = e->wc_list_contiguous << (wc->block_size_bits - SECTOR_SHIFT);
1732
1733                 from.bdev = wc->ssd_dev->bdev;
1734                 from.sector = cache_sector(wc, e);
1735                 from.count = n_sectors;
1736                 to.bdev = wc->dev->bdev;
1737                 to.sector = read_original_sector(wc, e);
1738                 to.count = n_sectors;
1739
1740                 c = mempool_alloc(&wc->copy_pool, GFP_NOIO);
1741                 c->wc = wc;
1742                 c->e = e;
1743                 c->n_entries = e->wc_list_contiguous;
1744
1745                 while ((n_sectors -= wc->block_size >> SECTOR_SHIFT)) {
1746                         wbl->size--;
1747                         f = container_of(wbl->list.prev, struct wc_entry, lru);
1748                         BUG_ON(f != e + 1);
1749                         list_del(&f->lru);
1750                         e = f;
1751                 }
1752
1753                 dm_kcopyd_copy(wc->dm_kcopyd, &from, 1, &to, 0, writecache_copy_endio, c);
1754
1755                 __writeback_throttle(wc, wbl);
1756         }
1757 }
1758
1759 static void writecache_writeback(struct work_struct *work)
1760 {
1761         struct dm_writecache *wc = container_of(work, struct dm_writecache, writeback_work);
1762         struct blk_plug plug;
1763         struct wc_entry *f, *g, *e = NULL;
1764         struct rb_node *node, *next_node;
1765         struct list_head skipped;
1766         struct writeback_list wbl;
1767         unsigned long n_walked;
1768
1769         wc_lock(wc);
1770 restart:
1771         if (writecache_has_error(wc)) {
1772                 wc_unlock(wc);
1773                 return;
1774         }
1775
1776         if (unlikely(wc->writeback_all)) {
1777                 if (writecache_wait_for_writeback(wc))
1778                         goto restart;
1779         }
1780
1781         if (wc->overwrote_committed) {
1782                 writecache_wait_for_ios(wc, WRITE);
1783         }
1784
1785         n_walked = 0;
1786         INIT_LIST_HEAD(&skipped);
1787         INIT_LIST_HEAD(&wbl.list);
1788         wbl.size = 0;
1789         while (!list_empty(&wc->lru) &&
1790                (wc->writeback_all ||
1791                 wc->freelist_size + wc->writeback_size <= wc->freelist_low_watermark ||
1792                 (jiffies - container_of(wc->lru.prev, struct wc_entry, lru)->age >=
1793                  wc->max_age - wc->max_age / MAX_AGE_DIV))) {
1794
1795                 n_walked++;
1796                 if (unlikely(n_walked > WRITEBACK_LATENCY) &&
1797                     likely(!wc->writeback_all) && likely(!dm_suspended(wc->ti))) {
1798                         queue_work(wc->writeback_wq, &wc->writeback_work);
1799                         break;
1800                 }
1801
1802                 if (unlikely(wc->writeback_all)) {
1803                         if (unlikely(!e)) {
1804                                 writecache_flush(wc);
1805                                 e = container_of(rb_first(&wc->tree), struct wc_entry, rb_node);
1806                         } else
1807                                 e = g;
1808                 } else
1809                         e = container_of(wc->lru.prev, struct wc_entry, lru);
1810                 BUG_ON(e->write_in_progress);
1811                 if (unlikely(!writecache_entry_is_committed(wc, e))) {
1812                         writecache_flush(wc);
1813                 }
1814                 node = rb_prev(&e->rb_node);
1815                 if (node) {
1816                         f = container_of(node, struct wc_entry, rb_node);
1817                         if (unlikely(read_original_sector(wc, f) ==
1818                                      read_original_sector(wc, e))) {
1819                                 BUG_ON(!f->write_in_progress);
1820                                 list_del(&e->lru);
1821                                 list_add(&e->lru, &skipped);
1822                                 cond_resched();
1823                                 continue;
1824                         }
1825                 }
1826                 wc->writeback_size++;
1827                 list_del(&e->lru);
1828                 list_add(&e->lru, &wbl.list);
1829                 wbl.size++;
1830                 e->write_in_progress = true;
1831                 e->wc_list_contiguous = 1;
1832
1833                 f = e;
1834
1835                 while (1) {
1836                         next_node = rb_next(&f->rb_node);
1837                         if (unlikely(!next_node))
1838                                 break;
1839                         g = container_of(next_node, struct wc_entry, rb_node);
1840                         if (unlikely(read_original_sector(wc, g) ==
1841                             read_original_sector(wc, f))) {
1842                                 f = g;
1843                                 continue;
1844                         }
1845                         if (read_original_sector(wc, g) !=
1846                             read_original_sector(wc, f) + (wc->block_size >> SECTOR_SHIFT))
1847                                 break;
1848                         if (unlikely(g->write_in_progress))
1849                                 break;
1850                         if (unlikely(!writecache_entry_is_committed(wc, g)))
1851                                 break;
1852
1853                         if (!WC_MODE_PMEM(wc)) {
1854                                 if (g != f + 1)
1855                                         break;
1856                         }
1857
1858                         n_walked++;
1859                         //if (unlikely(n_walked > WRITEBACK_LATENCY) && likely(!wc->writeback_all))
1860                         //      break;
1861
1862                         wc->writeback_size++;
1863                         list_del(&g->lru);
1864                         list_add(&g->lru, &wbl.list);
1865                         wbl.size++;
1866                         g->write_in_progress = true;
1867                         g->wc_list_contiguous = BIO_MAX_PAGES;
1868                         f = g;
1869                         e->wc_list_contiguous++;
1870                         if (unlikely(e->wc_list_contiguous == BIO_MAX_PAGES)) {
1871                                 if (unlikely(wc->writeback_all)) {
1872                                         next_node = rb_next(&f->rb_node);
1873                                         if (likely(next_node))
1874                                                 g = container_of(next_node, struct wc_entry, rb_node);
1875                                 }
1876                                 break;
1877                         }
1878                 }
1879                 cond_resched();
1880         }
1881
1882         if (!list_empty(&skipped)) {
1883                 list_splice_tail(&skipped, &wc->lru);
1884                 /*
1885                  * If we didn't do any progress, we must wait until some
1886                  * writeback finishes to avoid burning CPU in a loop
1887                  */
1888                 if (unlikely(!wbl.size))
1889                         writecache_wait_for_writeback(wc);
1890         }
1891
1892         wc_unlock(wc);
1893
1894         blk_start_plug(&plug);
1895
1896         if (WC_MODE_PMEM(wc))
1897                 __writecache_writeback_pmem(wc, &wbl);
1898         else
1899                 __writecache_writeback_ssd(wc, &wbl);
1900
1901         blk_finish_plug(&plug);
1902
1903         if (unlikely(wc->writeback_all)) {
1904                 wc_lock(wc);
1905                 while (writecache_wait_for_writeback(wc));
1906                 wc_unlock(wc);
1907         }
1908 }
1909
1910 static int calculate_memory_size(uint64_t device_size, unsigned block_size,
1911                                  size_t *n_blocks_p, size_t *n_metadata_blocks_p)
1912 {
1913         uint64_t n_blocks, offset;
1914         struct wc_entry e;
1915
1916         n_blocks = device_size;
1917         do_div(n_blocks, block_size + sizeof(struct wc_memory_entry));
1918
1919         while (1) {
1920                 if (!n_blocks)
1921                         return -ENOSPC;
1922                 /* Verify the following entries[n_blocks] won't overflow */
1923                 if (n_blocks >= ((size_t)-sizeof(struct wc_memory_superblock) /
1924                                  sizeof(struct wc_memory_entry)))
1925                         return -EFBIG;
1926                 offset = offsetof(struct wc_memory_superblock, entries[n_blocks]);
1927                 offset = (offset + block_size - 1) & ~(uint64_t)(block_size - 1);
1928                 if (offset + n_blocks * block_size <= device_size)
1929                         break;
1930                 n_blocks--;
1931         }
1932
1933         /* check if the bit field overflows */
1934         e.index = n_blocks;
1935         if (e.index != n_blocks)
1936                 return -EFBIG;
1937
1938         if (n_blocks_p)
1939                 *n_blocks_p = n_blocks;
1940         if (n_metadata_blocks_p)
1941                 *n_metadata_blocks_p = offset >> __ffs(block_size);
1942         return 0;
1943 }
1944
1945 static int init_memory(struct dm_writecache *wc)
1946 {
1947         size_t b;
1948         int r;
1949
1950         r = calculate_memory_size(wc->memory_map_size, wc->block_size, &wc->n_blocks, NULL);
1951         if (r)
1952                 return r;
1953
1954         r = writecache_alloc_entries(wc);
1955         if (r)
1956                 return r;
1957
1958         for (b = 0; b < ARRAY_SIZE(sb(wc)->padding); b++)
1959                 pmem_assign(sb(wc)->padding[b], cpu_to_le64(0));
1960         pmem_assign(sb(wc)->version, cpu_to_le32(MEMORY_SUPERBLOCK_VERSION));
1961         pmem_assign(sb(wc)->block_size, cpu_to_le32(wc->block_size));
1962         pmem_assign(sb(wc)->n_blocks, cpu_to_le64(wc->n_blocks));
1963         pmem_assign(sb(wc)->seq_count, cpu_to_le64(0));
1964
1965         for (b = 0; b < wc->n_blocks; b++) {
1966                 write_original_sector_seq_count(wc, &wc->entries[b], -1, -1);
1967                 cond_resched();
1968         }
1969
1970         writecache_flush_all_metadata(wc);
1971         writecache_commit_flushed(wc, false);
1972         pmem_assign(sb(wc)->magic, cpu_to_le32(MEMORY_SUPERBLOCK_MAGIC));
1973         writecache_flush_region(wc, &sb(wc)->magic, sizeof sb(wc)->magic);
1974         writecache_commit_flushed(wc, false);
1975
1976         return 0;
1977 }
1978
1979 static void writecache_dtr(struct dm_target *ti)
1980 {
1981         struct dm_writecache *wc = ti->private;
1982
1983         if (!wc)
1984                 return;
1985
1986         if (wc->endio_thread)
1987                 kthread_stop(wc->endio_thread);
1988
1989         if (wc->flush_thread)
1990                 kthread_stop(wc->flush_thread);
1991
1992         bioset_exit(&wc->bio_set);
1993
1994         mempool_exit(&wc->copy_pool);
1995
1996         if (wc->writeback_wq)
1997                 destroy_workqueue(wc->writeback_wq);
1998
1999         if (wc->dev)
2000                 dm_put_device(ti, wc->dev);
2001
2002         if (wc->ssd_dev)
2003                 dm_put_device(ti, wc->ssd_dev);
2004
2005         if (wc->entries)
2006                 vfree(wc->entries);
2007
2008         if (wc->memory_map) {
2009                 if (WC_MODE_PMEM(wc))
2010                         persistent_memory_release(wc);
2011                 else
2012                         vfree(wc->memory_map);
2013         }
2014
2015         if (wc->dm_kcopyd)
2016                 dm_kcopyd_client_destroy(wc->dm_kcopyd);
2017
2018         if (wc->dm_io)
2019                 dm_io_client_destroy(wc->dm_io);
2020
2021         if (wc->dirty_bitmap)
2022                 vfree(wc->dirty_bitmap);
2023
2024         kfree(wc);
2025 }
2026
2027 static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)
2028 {
2029         struct dm_writecache *wc;
2030         struct dm_arg_set as;
2031         const char *string;
2032         unsigned opt_params;
2033         size_t offset, data_size;
2034         int i, r;
2035         char dummy;
2036         int high_wm_percent = HIGH_WATERMARK;
2037         int low_wm_percent = LOW_WATERMARK;
2038         uint64_t x;
2039         struct wc_memory_superblock s;
2040
2041         static struct dm_arg _args[] = {
2042                 {0, 10, "Invalid number of feature args"},
2043         };
2044
2045         as.argc = argc;
2046         as.argv = argv;
2047
2048         wc = kzalloc(sizeof(struct dm_writecache), GFP_KERNEL);
2049         if (!wc) {
2050                 ti->error = "Cannot allocate writecache structure";
2051                 r = -ENOMEM;
2052                 goto bad;
2053         }
2054         ti->private = wc;
2055         wc->ti = ti;
2056
2057         mutex_init(&wc->lock);
2058         wc->max_age = MAX_AGE_UNSPECIFIED;
2059         writecache_poison_lists(wc);
2060         init_waitqueue_head(&wc->freelist_wait);
2061         timer_setup(&wc->autocommit_timer, writecache_autocommit_timer, 0);
2062         timer_setup(&wc->max_age_timer, writecache_max_age_timer, 0);
2063
2064         for (i = 0; i < 2; i++) {
2065                 atomic_set(&wc->bio_in_progress[i], 0);
2066                 init_waitqueue_head(&wc->bio_in_progress_wait[i]);
2067         }
2068
2069         wc->dm_io = dm_io_client_create();
2070         if (IS_ERR(wc->dm_io)) {
2071                 r = PTR_ERR(wc->dm_io);
2072                 ti->error = "Unable to allocate dm-io client";
2073                 wc->dm_io = NULL;
2074                 goto bad;
2075         }
2076
2077         wc->writeback_wq = alloc_workqueue("writecache-writeback", WQ_MEM_RECLAIM, 1);
2078         if (!wc->writeback_wq) {
2079                 r = -ENOMEM;
2080                 ti->error = "Could not allocate writeback workqueue";
2081                 goto bad;
2082         }
2083         INIT_WORK(&wc->writeback_work, writecache_writeback);
2084         INIT_WORK(&wc->flush_work, writecache_flush_work);
2085
2086         raw_spin_lock_init(&wc->endio_list_lock);
2087         INIT_LIST_HEAD(&wc->endio_list);
2088         wc->endio_thread = kthread_create(writecache_endio_thread, wc, "writecache_endio");
2089         if (IS_ERR(wc->endio_thread)) {
2090                 r = PTR_ERR(wc->endio_thread);
2091                 wc->endio_thread = NULL;
2092                 ti->error = "Couldn't spawn endio thread";
2093                 goto bad;
2094         }
2095         wake_up_process(wc->endio_thread);
2096
2097         /*
2098          * Parse the mode (pmem or ssd)
2099          */
2100         string = dm_shift_arg(&as);
2101         if (!string)
2102                 goto bad_arguments;
2103
2104         if (!strcasecmp(string, "s")) {
2105                 wc->pmem_mode = false;
2106         } else if (!strcasecmp(string, "p")) {
2107 #ifdef DM_WRITECACHE_HAS_PMEM
2108                 wc->pmem_mode = true;
2109                 wc->writeback_fua = true;
2110 #else
2111                 /*
2112                  * If the architecture doesn't support persistent memory or
2113                  * the kernel doesn't support any DAX drivers, this driver can
2114                  * only be used in SSD-only mode.
2115                  */
2116                 r = -EOPNOTSUPP;
2117                 ti->error = "Persistent memory or DAX not supported on this system";
2118                 goto bad;
2119 #endif
2120         } else {
2121                 goto bad_arguments;
2122         }
2123
2124         if (WC_MODE_PMEM(wc)) {
2125                 r = bioset_init(&wc->bio_set, BIO_POOL_SIZE,
2126                                 offsetof(struct writeback_struct, bio),
2127                                 BIOSET_NEED_BVECS);
2128                 if (r) {
2129                         ti->error = "Could not allocate bio set";
2130                         goto bad;
2131                 }
2132         } else {
2133                 r = mempool_init_kmalloc_pool(&wc->copy_pool, 1, sizeof(struct copy_struct));
2134                 if (r) {
2135                         ti->error = "Could not allocate mempool";
2136                         goto bad;
2137                 }
2138         }
2139
2140         /*
2141          * Parse the origin data device
2142          */
2143         string = dm_shift_arg(&as);
2144         if (!string)
2145                 goto bad_arguments;
2146         r = dm_get_device(ti, string, dm_table_get_mode(ti->table), &wc->dev);
2147         if (r) {
2148                 ti->error = "Origin data device lookup failed";
2149                 goto bad;
2150         }
2151
2152         /*
2153          * Parse cache data device (be it pmem or ssd)
2154          */
2155         string = dm_shift_arg(&as);
2156         if (!string)
2157                 goto bad_arguments;
2158
2159         r = dm_get_device(ti, string, dm_table_get_mode(ti->table), &wc->ssd_dev);
2160         if (r) {
2161                 ti->error = "Cache data device lookup failed";
2162                 goto bad;
2163         }
2164         wc->memory_map_size = i_size_read(wc->ssd_dev->bdev->bd_inode);
2165
2166         /*
2167          * Parse the cache block size
2168          */
2169         string = dm_shift_arg(&as);
2170         if (!string)
2171                 goto bad_arguments;
2172         if (sscanf(string, "%u%c", &wc->block_size, &dummy) != 1 ||
2173             wc->block_size < 512 || wc->block_size > PAGE_SIZE ||
2174             (wc->block_size & (wc->block_size - 1))) {
2175                 r = -EINVAL;
2176                 ti->error = "Invalid block size";
2177                 goto bad;
2178         }
2179         if (wc->block_size < bdev_logical_block_size(wc->dev->bdev) ||
2180             wc->block_size < bdev_logical_block_size(wc->ssd_dev->bdev)) {
2181                 r = -EINVAL;
2182                 ti->error = "Block size is smaller than device logical block size";
2183                 goto bad;
2184         }
2185         wc->block_size_bits = __ffs(wc->block_size);
2186
2187         wc->max_writeback_jobs = MAX_WRITEBACK_JOBS;
2188         wc->autocommit_blocks = !WC_MODE_PMEM(wc) ? AUTOCOMMIT_BLOCKS_SSD : AUTOCOMMIT_BLOCKS_PMEM;
2189         wc->autocommit_jiffies = msecs_to_jiffies(AUTOCOMMIT_MSEC);
2190
2191         /*
2192          * Parse optional arguments
2193          */
2194         r = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
2195         if (r)
2196                 goto bad;
2197
2198         while (opt_params) {
2199                 string = dm_shift_arg(&as), opt_params--;
2200                 if (!strcasecmp(string, "start_sector") && opt_params >= 1) {
2201                         unsigned long long start_sector;
2202                         string = dm_shift_arg(&as), opt_params--;
2203                         if (sscanf(string, "%llu%c", &start_sector, &dummy) != 1)
2204                                 goto invalid_optional;
2205                         wc->start_sector = start_sector;
2206                         if (wc->start_sector != start_sector ||
2207                             wc->start_sector >= wc->memory_map_size >> SECTOR_SHIFT)
2208                                 goto invalid_optional;
2209                 } else if (!strcasecmp(string, "high_watermark") && opt_params >= 1) {
2210                         string = dm_shift_arg(&as), opt_params--;
2211                         if (sscanf(string, "%d%c", &high_wm_percent, &dummy) != 1)
2212                                 goto invalid_optional;
2213                         if (high_wm_percent < 0 || high_wm_percent > 100)
2214                                 goto invalid_optional;
2215                         wc->high_wm_percent_set = true;
2216                 } else if (!strcasecmp(string, "low_watermark") && opt_params >= 1) {
2217                         string = dm_shift_arg(&as), opt_params--;
2218                         if (sscanf(string, "%d%c", &low_wm_percent, &dummy) != 1)
2219                                 goto invalid_optional;
2220                         if (low_wm_percent < 0 || low_wm_percent > 100)
2221                                 goto invalid_optional;
2222                         wc->low_wm_percent_set = true;
2223                 } else if (!strcasecmp(string, "writeback_jobs") && opt_params >= 1) {
2224                         string = dm_shift_arg(&as), opt_params--;
2225                         if (sscanf(string, "%u%c", &wc->max_writeback_jobs, &dummy) != 1)
2226                                 goto invalid_optional;
2227                         wc->max_writeback_jobs_set = true;
2228                 } else if (!strcasecmp(string, "autocommit_blocks") && opt_params >= 1) {
2229                         string = dm_shift_arg(&as), opt_params--;
2230                         if (sscanf(string, "%u%c", &wc->autocommit_blocks, &dummy) != 1)
2231                                 goto invalid_optional;
2232                         wc->autocommit_blocks_set = true;
2233                 } else if (!strcasecmp(string, "autocommit_time") && opt_params >= 1) {
2234                         unsigned autocommit_msecs;
2235                         string = dm_shift_arg(&as), opt_params--;
2236                         if (sscanf(string, "%u%c", &autocommit_msecs, &dummy) != 1)
2237                                 goto invalid_optional;
2238                         if (autocommit_msecs > 3600000)
2239                                 goto invalid_optional;
2240                         wc->autocommit_jiffies = msecs_to_jiffies(autocommit_msecs);
2241                         wc->autocommit_time_set = true;
2242                 } else if (!strcasecmp(string, "max_age") && opt_params >= 1) {
2243                         unsigned max_age_msecs;
2244                         string = dm_shift_arg(&as), opt_params--;
2245                         if (sscanf(string, "%u%c", &max_age_msecs, &dummy) != 1)
2246                                 goto invalid_optional;
2247                         if (max_age_msecs > 86400000)
2248                                 goto invalid_optional;
2249                         wc->max_age = msecs_to_jiffies(max_age_msecs);
2250                 } else if (!strcasecmp(string, "cleaner")) {
2251                         wc->cleaner = true;
2252                 } else if (!strcasecmp(string, "fua")) {
2253                         if (WC_MODE_PMEM(wc)) {
2254                                 wc->writeback_fua = true;
2255                                 wc->writeback_fua_set = true;
2256                         } else goto invalid_optional;
2257                 } else if (!strcasecmp(string, "nofua")) {
2258                         if (WC_MODE_PMEM(wc)) {
2259                                 wc->writeback_fua = false;
2260                                 wc->writeback_fua_set = true;
2261                         } else goto invalid_optional;
2262                 } else {
2263 invalid_optional:
2264                         r = -EINVAL;
2265                         ti->error = "Invalid optional argument";
2266                         goto bad;
2267                 }
2268         }
2269
2270         if (high_wm_percent < low_wm_percent) {
2271                 r = -EINVAL;
2272                 ti->error = "High watermark must be greater than or equal to low watermark";
2273                 goto bad;
2274         }
2275
2276         if (WC_MODE_PMEM(wc)) {
2277                 if (!dax_synchronous(wc->ssd_dev->dax_dev)) {
2278                         r = -EOPNOTSUPP;
2279                         ti->error = "Asynchronous persistent memory not supported as pmem cache";
2280                         goto bad;
2281                 }
2282
2283                 r = persistent_memory_claim(wc);
2284                 if (r) {
2285                         ti->error = "Unable to map persistent memory for cache";
2286                         goto bad;
2287                 }
2288         } else {
2289                 size_t n_blocks, n_metadata_blocks;
2290                 uint64_t n_bitmap_bits;
2291
2292                 wc->memory_map_size -= (uint64_t)wc->start_sector << SECTOR_SHIFT;
2293
2294                 bio_list_init(&wc->flush_list);
2295                 wc->flush_thread = kthread_create(writecache_flush_thread, wc, "dm_writecache_flush");
2296                 if (IS_ERR(wc->flush_thread)) {
2297                         r = PTR_ERR(wc->flush_thread);
2298                         wc->flush_thread = NULL;
2299                         ti->error = "Couldn't spawn flush thread";
2300                         goto bad;
2301                 }
2302                 wake_up_process(wc->flush_thread);
2303
2304                 r = calculate_memory_size(wc->memory_map_size, wc->block_size,
2305                                           &n_blocks, &n_metadata_blocks);
2306                 if (r) {
2307                         ti->error = "Invalid device size";
2308                         goto bad;
2309                 }
2310
2311                 n_bitmap_bits = (((uint64_t)n_metadata_blocks << wc->block_size_bits) +
2312                                  BITMAP_GRANULARITY - 1) / BITMAP_GRANULARITY;
2313                 /* this is limitation of test_bit functions */
2314                 if (n_bitmap_bits > 1U << 31) {
2315                         r = -EFBIG;
2316                         ti->error = "Invalid device size";
2317                         goto bad;
2318                 }
2319
2320                 wc->memory_map = vmalloc(n_metadata_blocks << wc->block_size_bits);
2321                 if (!wc->memory_map) {
2322                         r = -ENOMEM;
2323                         ti->error = "Unable to allocate memory for metadata";
2324                         goto bad;
2325                 }
2326
2327                 wc->dm_kcopyd = dm_kcopyd_client_create(&dm_kcopyd_throttle);
2328                 if (IS_ERR(wc->dm_kcopyd)) {
2329                         r = PTR_ERR(wc->dm_kcopyd);
2330                         ti->error = "Unable to allocate dm-kcopyd client";
2331                         wc->dm_kcopyd = NULL;
2332                         goto bad;
2333                 }
2334
2335                 wc->metadata_sectors = n_metadata_blocks << (wc->block_size_bits - SECTOR_SHIFT);
2336                 wc->dirty_bitmap_size = (n_bitmap_bits + BITS_PER_LONG - 1) /
2337                         BITS_PER_LONG * sizeof(unsigned long);
2338                 wc->dirty_bitmap = vzalloc(wc->dirty_bitmap_size);
2339                 if (!wc->dirty_bitmap) {
2340                         r = -ENOMEM;
2341                         ti->error = "Unable to allocate dirty bitmap";
2342                         goto bad;
2343                 }
2344
2345                 r = writecache_read_metadata(wc, wc->block_size >> SECTOR_SHIFT);
2346                 if (r) {
2347                         ti->error = "Unable to read first block of metadata";
2348                         goto bad;
2349                 }
2350         }
2351
2352         r = memcpy_mcsafe(&s, sb(wc), sizeof(struct wc_memory_superblock));
2353         if (r) {
2354                 ti->error = "Hardware memory error when reading superblock";
2355                 goto bad;
2356         }
2357         if (!le32_to_cpu(s.magic) && !le32_to_cpu(s.version)) {
2358                 r = init_memory(wc);
2359                 if (r) {
2360                         ti->error = "Unable to initialize device";
2361                         goto bad;
2362                 }
2363                 r = memcpy_mcsafe(&s, sb(wc), sizeof(struct wc_memory_superblock));
2364                 if (r) {
2365                         ti->error = "Hardware memory error when reading superblock";
2366                         goto bad;
2367                 }
2368         }
2369
2370         if (le32_to_cpu(s.magic) != MEMORY_SUPERBLOCK_MAGIC) {
2371                 ti->error = "Invalid magic in the superblock";
2372                 r = -EINVAL;
2373                 goto bad;
2374         }
2375
2376         if (le32_to_cpu(s.version) != MEMORY_SUPERBLOCK_VERSION) {
2377                 ti->error = "Invalid version in the superblock";
2378                 r = -EINVAL;
2379                 goto bad;
2380         }
2381
2382         if (le32_to_cpu(s.block_size) != wc->block_size) {
2383                 ti->error = "Block size does not match superblock";
2384                 r = -EINVAL;
2385                 goto bad;
2386         }
2387
2388         wc->n_blocks = le64_to_cpu(s.n_blocks);
2389
2390         offset = wc->n_blocks * sizeof(struct wc_memory_entry);
2391         if (offset / sizeof(struct wc_memory_entry) != le64_to_cpu(sb(wc)->n_blocks)) {
2392 overflow:
2393                 ti->error = "Overflow in size calculation";
2394                 r = -EINVAL;
2395                 goto bad;
2396         }
2397         offset += sizeof(struct wc_memory_superblock);
2398         if (offset < sizeof(struct wc_memory_superblock))
2399                 goto overflow;
2400         offset = (offset + wc->block_size - 1) & ~(size_t)(wc->block_size - 1);
2401         data_size = wc->n_blocks * (size_t)wc->block_size;
2402         if (!offset || (data_size / wc->block_size != wc->n_blocks) ||
2403             (offset + data_size < offset))
2404                 goto overflow;
2405         if (offset + data_size > wc->memory_map_size) {
2406                 ti->error = "Memory area is too small";
2407                 r = -EINVAL;
2408                 goto bad;
2409         }
2410
2411         wc->metadata_sectors = offset >> SECTOR_SHIFT;
2412         wc->block_start = (char *)sb(wc) + offset;
2413
2414         x = (uint64_t)wc->n_blocks * (100 - high_wm_percent);
2415         x += 50;
2416         do_div(x, 100);
2417         wc->freelist_high_watermark = x;
2418         x = (uint64_t)wc->n_blocks * (100 - low_wm_percent);
2419         x += 50;
2420         do_div(x, 100);
2421         wc->freelist_low_watermark = x;
2422
2423         if (wc->cleaner)
2424                 activate_cleaner(wc);
2425
2426         r = writecache_alloc_entries(wc);
2427         if (r) {
2428                 ti->error = "Cannot allocate memory";
2429                 goto bad;
2430         }
2431
2432         ti->num_flush_bios = 1;
2433         ti->flush_supported = true;
2434         ti->num_discard_bios = 1;
2435
2436         if (WC_MODE_PMEM(wc))
2437                 persistent_memory_flush_cache(wc->memory_map, wc->memory_map_size);
2438
2439         return 0;
2440
2441 bad_arguments:
2442         r = -EINVAL;
2443         ti->error = "Bad arguments";
2444 bad:
2445         writecache_dtr(ti);
2446         return r;
2447 }
2448
2449 static void writecache_status(struct dm_target *ti, status_type_t type,
2450                               unsigned status_flags, char *result, unsigned maxlen)
2451 {
2452         struct dm_writecache *wc = ti->private;
2453         unsigned extra_args;
2454         unsigned sz = 0;
2455         uint64_t x;
2456
2457         switch (type) {
2458         case STATUSTYPE_INFO:
2459                 DMEMIT("%ld %llu %llu %llu", writecache_has_error(wc),
2460                        (unsigned long long)wc->n_blocks, (unsigned long long)wc->freelist_size,
2461                        (unsigned long long)wc->writeback_size);
2462                 break;
2463         case STATUSTYPE_TABLE:
2464                 DMEMIT("%c %s %s %u ", WC_MODE_PMEM(wc) ? 'p' : 's',
2465                                 wc->dev->name, wc->ssd_dev->name, wc->block_size);
2466                 extra_args = 0;
2467                 if (wc->start_sector)
2468                         extra_args += 2;
2469                 if (wc->high_wm_percent_set && !wc->cleaner)
2470                         extra_args += 2;
2471                 if (wc->low_wm_percent_set && !wc->cleaner)
2472                         extra_args += 2;
2473                 if (wc->max_writeback_jobs_set)
2474                         extra_args += 2;
2475                 if (wc->autocommit_blocks_set)
2476                         extra_args += 2;
2477                 if (wc->autocommit_time_set)
2478                         extra_args += 2;
2479                 if (wc->cleaner)
2480                         extra_args++;
2481                 if (wc->writeback_fua_set)
2482                         extra_args++;
2483
2484                 DMEMIT("%u", extra_args);
2485                 if (wc->start_sector)
2486                         DMEMIT(" start_sector %llu", (unsigned long long)wc->start_sector);
2487                 if (wc->high_wm_percent_set && !wc->cleaner) {
2488                         x = (uint64_t)wc->freelist_high_watermark * 100;
2489                         x += wc->n_blocks / 2;
2490                         do_div(x, (size_t)wc->n_blocks);
2491                         DMEMIT(" high_watermark %u", 100 - (unsigned)x);
2492                 }
2493                 if (wc->low_wm_percent_set && !wc->cleaner) {
2494                         x = (uint64_t)wc->freelist_low_watermark * 100;
2495                         x += wc->n_blocks / 2;
2496                         do_div(x, (size_t)wc->n_blocks);
2497                         DMEMIT(" low_watermark %u", 100 - (unsigned)x);
2498                 }
2499                 if (wc->max_writeback_jobs_set)
2500                         DMEMIT(" writeback_jobs %u", wc->max_writeback_jobs);
2501                 if (wc->autocommit_blocks_set)
2502                         DMEMIT(" autocommit_blocks %u", wc->autocommit_blocks);
2503                 if (wc->autocommit_time_set)
2504                         DMEMIT(" autocommit_time %u", jiffies_to_msecs(wc->autocommit_jiffies));
2505                 if (wc->max_age != MAX_AGE_UNSPECIFIED)
2506                         DMEMIT(" max_age %u", jiffies_to_msecs(wc->max_age));
2507                 if (wc->cleaner)
2508                         DMEMIT(" cleaner");
2509                 if (wc->writeback_fua_set)
2510                         DMEMIT(" %sfua", wc->writeback_fua ? "" : "no");
2511                 break;
2512         }
2513 }
2514
2515 static struct target_type writecache_target = {
2516         .name                   = "writecache",
2517         .version                = {1, 3, 0},
2518         .module                 = THIS_MODULE,
2519         .ctr                    = writecache_ctr,
2520         .dtr                    = writecache_dtr,
2521         .status                 = writecache_status,
2522         .postsuspend            = writecache_suspend,
2523         .resume                 = writecache_resume,
2524         .message                = writecache_message,
2525         .map                    = writecache_map,
2526         .end_io                 = writecache_end_io,
2527         .iterate_devices        = writecache_iterate_devices,
2528         .io_hints               = writecache_io_hints,
2529 };
2530
2531 static int __init dm_writecache_init(void)
2532 {
2533         int r;
2534
2535         r = dm_register_target(&writecache_target);
2536         if (r < 0) {
2537                 DMERR("register failed %d", r);
2538                 return r;
2539         }
2540
2541         return 0;
2542 }
2543
2544 static void __exit dm_writecache_exit(void)
2545 {
2546         dm_unregister_target(&writecache_target);
2547 }
2548
2549 module_init(dm_writecache_init);
2550 module_exit(dm_writecache_exit);
2551
2552 MODULE_DESCRIPTION(DM_NAME " writecache target");
2553 MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
2554 MODULE_LICENSE("GPL");