fs/btrfs/dev-replace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) STRATO AG 2012.  All rights reserved.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include <linux/bio.h>
   8 #include <linux/slab.h>
   9 #include <linux/blkdev.h>
  10 #include <linux/kthread.h>
  11 #include <linux/math64.h>
  12 #include "misc.h"
  13 #include "ctree.h"
  14 #include "extent_map.h"
  15 #include "disk-io.h"
  16 #include "transaction.h"
  17 #include "print-tree.h"
  18 #include "volumes.h"
  19 #include "async-thread.h"
  20 #include "dev-replace.h"
  21 #include "sysfs.h"
  22 #include "zoned.h"
  23 #include "block-group.h"
  24 #include "fs.h"
  25 #include "accessors.h"
  26 #include "scrub.h"
  27
  28 /*
  29  * Device replace overview
  30  *
  31  * [Objective]
  32  * To copy all extents (both new and on-disk) from source device to target
  33  * device, while still keeping the filesystem read-write.
  34  *
  35  * [Method]
  36  * There are two main methods involved:
  37  *
  38  * - Write duplication
  39  *
  40  *   All new writes will be written to both target and source devices, so even
  41  *   if replace gets canceled, sources device still contains up-to-date data.
  42  *
  43  *   Location:          handle_ops_on_dev_replace() from btrfs_map_block()
  44  *   Start:             btrfs_dev_replace_start()
  45  *   End:               btrfs_dev_replace_finishing()
  46  *   Content:           Latest data/metadata
  47  *
  48  * - Copy existing extents
  49  *
  50  *   This happens by re-using scrub facility, as scrub also iterates through
  51  *   existing extents from commit root.
  52  *
  53  *   Location:          scrub_write_block_to_dev_replace() from
  54  *                      scrub_block_complete()
  55  *   Content:           Data/meta from commit root.
  56  *
  57  * Due to the content difference, we need to avoid nocow write when dev-replace
  58  * is happening.  This is done by marking the block group read-only and waiting
  59  * for NOCOW writes.
  60  *
  61  * After replace is done, the finishing part is done by swapping the target and
  62  * source devices.
  63  *
  64  *   Location:          btrfs_dev_replace_update_device_in_mapping_tree() from
  65  *                      btrfs_dev_replace_finishing()
  66  */
  67
  68 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
  69                                        int scrub_ret);
  70 static int btrfs_dev_replace_kthread(void *data);
  71
  72 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
  73 {
  74         struct btrfs_dev_lookup_args args = { .devid = BTRFS_DEV_REPLACE_DEVID };
  75         struct btrfs_key key;
  76         struct btrfs_root *dev_root = fs_info->dev_root;
  77         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
  78         struct extent_buffer *eb;
  79         int slot;
  80         int ret = 0;
  81         struct btrfs_path *path = NULL;
  82         int item_size;
  83         struct btrfs_dev_replace_item *ptr;
  84         u64 src_devid;
  85
  86         if (!dev_root)
  87                 return 0;
  88
  89         path = btrfs_alloc_path();
  90         if (!path) {
  91                 ret = -ENOMEM;
  92                 goto out;
  93         }
  94
  95         key.objectid = 0;
  96         key.type = BTRFS_DEV_REPLACE_KEY;
  97         key.offset = 0;
  98         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
  99         if (ret) {
 100 no_valid_dev_replace_entry_found:
 101                 /*
 102                  * We don't have a replace item or it's corrupted.  If there is
 103                  * a replace target, fail the mount.
 104                  */
 105                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
 106                         btrfs_err(fs_info,
 107                         "found replace target device without a valid replace item");
 108                         ret = -EUCLEAN;
 109                         goto out;
 110                 }
 111                 ret = 0;
 112                 dev_replace->replace_state =
 113                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 114                 dev_replace->cont_reading_from_srcdev_mode =
 115                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 116                 dev_replace->time_started = 0;
 117                 dev_replace->time_stopped = 0;
 118                 atomic64_set(&dev_replace->num_write_errors, 0);
 119                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 120                 dev_replace->cursor_left = 0;
 121                 dev_replace->committed_cursor_left = 0;
 122                 dev_replace->cursor_left_last_write_of_item = 0;
 123                 dev_replace->cursor_right = 0;
 124                 dev_replace->srcdev = NULL;
 125                 dev_replace->tgtdev = NULL;
 126                 dev_replace->is_valid = 0;
 127                 dev_replace->item_needs_writeback = 0;
 128                 goto out;
 129         }
 130         slot = path->slots[0];
 131         eb = path->nodes[0];
 132         item_size = btrfs_item_size(eb, slot);
 133         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 134
 135         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 136                 btrfs_warn(fs_info,
 137                         "dev_replace entry found has unexpected size, ignore entry");
 138                 goto no_valid_dev_replace_entry_found;
 139         }
 140
 141         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 142         dev_replace->cont_reading_from_srcdev_mode =
 143                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 144         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 145         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 146         dev_replace->time_stopped =
 147                 btrfs_dev_replace_time_stopped(eb, ptr);
 148         atomic64_set(&dev_replace->num_write_errors,
 149                      btrfs_dev_replace_num_write_errors(eb, ptr));
 150         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 151                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 152         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 153         dev_replace->committed_cursor_left = dev_replace->cursor_left;
 154         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
 155         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
 156         dev_replace->is_valid = 1;
 157
 158         dev_replace->item_needs_writeback = 0;
 159         switch (dev_replace->replace_state) {
 160         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 161         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 162         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 163                 /*
 164                  * We don't have an active replace item but if there is a
 165                  * replace target, fail the mount.
 166                  */
 167                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
 168                         btrfs_err(fs_info,
 169 "replace without active item, run 'device scan --forget' on the target device");
 170                         ret = -EUCLEAN;
 171                 } else {
 172                         dev_replace->srcdev = NULL;
 173                         dev_replace->tgtdev = NULL;
 174                 }
 175                 break;
 176         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 177         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 178                 dev_replace->tgtdev = btrfs_find_device(fs_info->fs_devices, &args);
 179                 args.devid = src_devid;
 180                 dev_replace->srcdev = btrfs_find_device(fs_info->fs_devices, &args);
 181
 182                 /*
 183                  * allow 'btrfs dev replace_cancel' if src/tgt device is
 184                  * missing
 185                  */
 186                 if (!dev_replace->srcdev &&
 187                     !btrfs_test_opt(fs_info, DEGRADED)) {
 188                         ret = -EIO;
 189                         btrfs_warn(fs_info,
 190                            "cannot mount because device replace operation is ongoing and");
 191                         btrfs_warn(fs_info,
 192                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 193                            src_devid);
 194                 }
 195                 if (!dev_replace->tgtdev &&
 196                     !btrfs_test_opt(fs_info, DEGRADED)) {
 197                         ret = -EIO;
 198                         btrfs_warn(fs_info,
 199                            "cannot mount because device replace operation is ongoing and");
 200                         btrfs_warn(fs_info,
 201                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 202                                 BTRFS_DEV_REPLACE_DEVID);
 203                 }
 204                 if (dev_replace->tgtdev) {
 205                         if (dev_replace->srcdev) {
 206                                 dev_replace->tgtdev->total_bytes =
 207                                         dev_replace->srcdev->total_bytes;
 208                                 dev_replace->tgtdev->disk_total_bytes =
 209                                         dev_replace->srcdev->disk_total_bytes;
 210                                 dev_replace->tgtdev->commit_total_bytes =
 211                                         dev_replace->srcdev->commit_total_bytes;
 212                                 dev_replace->tgtdev->bytes_used =
 213                                         dev_replace->srcdev->bytes_used;
 214                                 dev_replace->tgtdev->commit_bytes_used =
 215                                         dev_replace->srcdev->commit_bytes_used;
 216                         }
 217                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
 218                                 &dev_replace->tgtdev->dev_state);
 219
 220                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
 221                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
 222                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
 223                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
 224                         dev_replace->tgtdev->fs_info = fs_info;
 225                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
 226                                 &dev_replace->tgtdev->dev_state);
 227                 }
 228                 break;
 229         }
 230
 231 out:
 232         btrfs_free_path(path);
 233         return ret;
 234 }
 235
 236 /*
 237  * Initialize a new device for device replace target from a given source dev
 238  * and path.
 239  *
 240  * Return 0 and new device in @device_out, otherwise return < 0
 241  */
 242 static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 243                                   const char *device_path,
 244                                   struct btrfs_device *srcdev,
 245                                   struct btrfs_device **device_out)
 246 {
 247         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 248         struct btrfs_device *device;
 249         struct block_device *bdev;
 250         u64 devid = BTRFS_DEV_REPLACE_DEVID;
 251         int ret = 0;
 252
 253         *device_out = NULL;
 254         if (srcdev->fs_devices->seeding) {
 255                 btrfs_err(fs_info, "the filesystem is a seed filesystem!");
 256                 return -EINVAL;
 257         }
 258
 259         bdev = blkdev_get_by_path(device_path, BLK_OPEN_WRITE,
 260                                   fs_info->bdev_holder, NULL);
 261         if (IS_ERR(bdev)) {
 262                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
 263                 return PTR_ERR(bdev);
 264         }
 265
 266         if (!btrfs_check_device_zone_type(fs_info, bdev)) {
 267                 btrfs_err(fs_info,
 268                 "dev-replace: zoned type of target device mismatch with filesystem");
 269                 ret = -EINVAL;
 270                 goto error;
 271         }
 272
 273         sync_blockdev(bdev);
 274
 275         list_for_each_entry(device, &fs_devices->devices, dev_list) {
 276                 if (device->bdev == bdev) {
 277                         btrfs_err(fs_info,
 278                                   "target device is in the filesystem!");
 279                         ret = -EEXIST;
 280                         goto error;
 281                 }
 282         }
 283
 284
 285         if (bdev_nr_bytes(bdev) < btrfs_device_get_total_bytes(srcdev)) {
 286                 btrfs_err(fs_info,
 287                           "target device is smaller than source device!");
 288                 ret = -EINVAL;
 289                 goto error;
 290         }
 291
 292
 293         device = btrfs_alloc_device(NULL, &devid, NULL, device_path);
 294         if (IS_ERR(device)) {
 295                 ret = PTR_ERR(device);
 296                 goto error;
 297         }
 298
 299         ret = lookup_bdev(device_path, &device->devt);
 300         if (ret)
 301                 goto error;
 302
 303         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 304         device->generation = 0;
 305         device->io_width = fs_info->sectorsize;
 306         device->io_align = fs_info->sectorsize;
 307         device->sector_size = fs_info->sectorsize;
 308         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
 309         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
 310         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 311         device->commit_total_bytes = srcdev->commit_total_bytes;
 312         device->commit_bytes_used = device->bytes_used;
 313         device->fs_info = fs_info;
 314         device->bdev = bdev;
 315         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 316         set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 317         device->holder = fs_info->bdev_holder;
 318         device->dev_stats_valid = 1;
 319         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 320         device->fs_devices = fs_devices;
 321
 322         ret = btrfs_get_dev_zone_info(device, false);
 323         if (ret)
 324                 goto error;
 325
 326         mutex_lock(&fs_devices->device_list_mutex);
 327         list_add(&device->dev_list, &fs_devices->devices);
 328         fs_devices->num_devices++;
 329         fs_devices->open_devices++;
 330         mutex_unlock(&fs_devices->device_list_mutex);
 331
 332         *device_out = device;
 333         return 0;
 334
 335 error:
 336         blkdev_put(bdev, fs_info->bdev_holder);
 337         return ret;
 338 }
 339
 340 /*
 341  * called from commit_transaction. Writes changed device replace state to
 342  * disk.
 343  */
 344 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
 345 {
 346         struct btrfs_fs_info *fs_info = trans->fs_info;
 347         int ret;
 348         struct btrfs_root *dev_root = fs_info->dev_root;
 349         struct btrfs_path *path;
 350         struct btrfs_key key;
 351         struct extent_buffer *eb;
 352         struct btrfs_dev_replace_item *ptr;
 353         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 354
 355         down_read(&dev_replace->rwsem);
 356         if (!dev_replace->is_valid ||
 357             !dev_replace->item_needs_writeback) {
 358                 up_read(&dev_replace->rwsem);
 359                 return 0;
 360         }
 361         up_read(&dev_replace->rwsem);
 362
 363         key.objectid = 0;
 364         key.type = BTRFS_DEV_REPLACE_KEY;
 365         key.offset = 0;
 366
 367         path = btrfs_alloc_path();
 368         if (!path) {
 369                 ret = -ENOMEM;
 370                 goto out;
 371         }
 372         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
 373         if (ret < 0) {
 374                 btrfs_warn(fs_info,
 375                            "error %d while searching for dev_replace item!",
 376                            ret);
 377                 goto out;
 378         }
 379
 380         if (ret == 0 &&
 381             btrfs_item_size(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 382                 /*
 383                  * need to delete old one and insert a new one.
 384                  * Since no attempt is made to recover any old state, if the
 385                  * dev_replace state is 'running', the data on the target
 386                  * drive is lost.
 387                  * It would be possible to recover the state: just make sure
 388                  * that the beginning of the item is never changed and always
 389                  * contains all the essential information. Then read this
 390                  * minimal set of information and use it as a base for the
 391                  * new state.
 392                  */
 393                 ret = btrfs_del_item(trans, dev_root, path);
 394                 if (ret != 0) {
 395                         btrfs_warn(fs_info,
 396                                    "delete too small dev_replace item failed %d!",
 397                                    ret);
 398                         goto out;
 399                 }
 400                 ret = 1;
 401         }
 402
 403         if (ret == 1) {
 404                 /* need to insert a new item */
 405                 btrfs_release_path(path);
 406                 ret = btrfs_insert_empty_item(trans, dev_root, path,
 407                                               &key, sizeof(*ptr));
 408                 if (ret < 0) {
 409                         btrfs_warn(fs_info,
 410                                    "insert dev_replace item failed %d!", ret);
 411                         goto out;
 412                 }
 413         }
 414
 415         eb = path->nodes[0];
 416         ptr = btrfs_item_ptr(eb, path->slots[0],
 417                              struct btrfs_dev_replace_item);
 418
 419         down_write(&dev_replace->rwsem);
 420         if (dev_replace->srcdev)
 421                 btrfs_set_dev_replace_src_devid(eb, ptr,
 422                         dev_replace->srcdev->devid);
 423         else
 424                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 425         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 426                 dev_replace->cont_reading_from_srcdev_mode);
 427         btrfs_set_dev_replace_replace_state(eb, ptr,
 428                 dev_replace->replace_state);
 429         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 430         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 431         btrfs_set_dev_replace_num_write_errors(eb, ptr,
 432                 atomic64_read(&dev_replace->num_write_errors));
 433         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 434                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 435         dev_replace->cursor_left_last_write_of_item =
 436                 dev_replace->cursor_left;
 437         btrfs_set_dev_replace_cursor_left(eb, ptr,
 438                 dev_replace->cursor_left_last_write_of_item);
 439         btrfs_set_dev_replace_cursor_right(eb, ptr,
 440                 dev_replace->cursor_right);
 441         dev_replace->item_needs_writeback = 0;
 442         up_write(&dev_replace->rwsem);
 443
 444         btrfs_mark_buffer_dirty(trans, eb);
 445
 446 out:
 447         btrfs_free_path(path);
 448
 449         return ret;
 450 }
 451
 452 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 453                                     struct btrfs_device *src_dev)
 454 {
 455         struct btrfs_path *path;
 456         struct btrfs_key key;
 457         struct btrfs_key found_key;
 458         struct btrfs_root *root = fs_info->dev_root;
 459         struct btrfs_dev_extent *dev_extent = NULL;
 460         struct btrfs_block_group *cache;
 461         struct btrfs_trans_handle *trans;
 462         int iter_ret = 0;
 463         int ret = 0;
 464         u64 chunk_offset;
 465
 466         /* Do not use "to_copy" on non zoned filesystem for now */
 467         if (!btrfs_is_zoned(fs_info))
 468                 return 0;
 469
 470         mutex_lock(&fs_info->chunk_mutex);
 471
 472         /* Ensure we don't have pending new block group */
 473         spin_lock(&fs_info->trans_lock);
 474         while (fs_info->running_transaction &&
 475                !list_empty(&fs_info->running_transaction->dev_update_list)) {
 476                 spin_unlock(&fs_info->trans_lock);
 477                 mutex_unlock(&fs_info->chunk_mutex);
 478                 trans = btrfs_attach_transaction(root);
 479                 if (IS_ERR(trans)) {
 480                         ret = PTR_ERR(trans);
 481                         mutex_lock(&fs_info->chunk_mutex);
 482                         if (ret == -ENOENT) {
 483                                 spin_lock(&fs_info->trans_lock);
 484                                 continue;
 485                         } else {
 486                                 goto unlock;
 487                         }
 488                 }
 489
 490                 ret = btrfs_commit_transaction(trans);
 491                 mutex_lock(&fs_info->chunk_mutex);
 492                 if (ret)
 493                         goto unlock;
 494
 495                 spin_lock(&fs_info->trans_lock);
 496         }
 497         spin_unlock(&fs_info->trans_lock);
 498
 499         path = btrfs_alloc_path();
 500         if (!path) {
 501                 ret = -ENOMEM;
 502                 goto unlock;
 503         }
 504
 505         path->reada = READA_FORWARD;
 506         path->search_commit_root = 1;
 507         path->skip_locking = 1;
 508
 509         key.objectid = src_dev->devid;
 510         key.type = BTRFS_DEV_EXTENT_KEY;
 511         key.offset = 0;
 512
 513         btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 514                 struct extent_buffer *leaf = path->nodes[0];
 515
 516                 if (found_key.objectid != src_dev->devid)
 517                         break;
 518
 519                 if (found_key.type != BTRFS_DEV_EXTENT_KEY)
 520                         break;
 521
 522                 if (found_key.offset < key.offset)
 523                         break;
 524
 525                 dev_extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
 526
 527                 chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
 528
 529                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 530                 if (!cache)
 531                         continue;
 532
 533                 set_bit(BLOCK_GROUP_FLAG_TO_COPY, &cache->runtime_flags);
 534                 btrfs_put_block_group(cache);
 535         }
 536         if (iter_ret < 0)
 537                 ret = iter_ret;
 538
 539         btrfs_free_path(path);
 540 unlock:
 541         mutex_unlock(&fs_info->chunk_mutex);
 542
 543         return ret;
 544 }
 545
 546 bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev,
 547                                       struct btrfs_block_group *cache,
 548                                       u64 physical)
 549 {
 550         struct btrfs_fs_info *fs_info = cache->fs_info;
 551         struct extent_map *em;
 552         struct map_lookup *map;
 553         u64 chunk_offset = cache->start;
 554         int num_extents, cur_extent;
 555         int i;
 556
 557         /* Do not use "to_copy" on non zoned filesystem for now */
 558         if (!btrfs_is_zoned(fs_info))
 559                 return true;
 560
 561         spin_lock(&cache->lock);
 562         if (test_bit(BLOCK_GROUP_FLAG_REMOVED, &cache->runtime_flags)) {
 563                 spin_unlock(&cache->lock);
 564                 return true;
 565         }
 566         spin_unlock(&cache->lock);
 567
 568         em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
 569         ASSERT(!IS_ERR(em));
 570         map = em->map_lookup;
 571
 572         num_extents = 0;
 573         cur_extent = 0;
 574         for (i = 0; i < map->num_stripes; i++) {
 575                 /* We have more device extent to copy */
 576                 if (srcdev != map->stripes[i].dev)
 577                         continue;
 578
 579                 num_extents++;
 580                 if (physical == map->stripes[i].physical)
 581                         cur_extent = i;
 582         }
 583
 584         free_extent_map(em);
 585
 586         if (num_extents > 1 && cur_extent < num_extents - 1) {
 587                 /*
 588                  * Has more stripes on this device. Keep this block group
 589                  * readonly until we finish all the stripes.
 590                  */
 591                 return false;
 592         }
 593
 594         /* Last stripe on this device */
 595         clear_bit(BLOCK_GROUP_FLAG_TO_COPY, &cache->runtime_flags);
 596
 597         return true;
 598 }
 599
 600 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 601                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
 602                 int read_src)
 603 {
 604         struct btrfs_root *root = fs_info->dev_root;
 605         struct btrfs_trans_handle *trans;
 606         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 607         int ret;
 608         struct btrfs_device *tgt_device = NULL;
 609         struct btrfs_device *src_device = NULL;
 610
 611         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
 612                                                   srcdev_name);
 613         if (IS_ERR(src_device))
 614                 return PTR_ERR(src_device);
 615
 616         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
 617                 btrfs_warn_in_rcu(fs_info,
 618           "cannot replace device %s (devid %llu) due to active swapfile",
 619                         btrfs_dev_name(src_device), src_device->devid);
 620                 return -ETXTBSY;
 621         }
 622
 623         /*
 624          * Here we commit the transaction to make sure commit_total_bytes
 625          * of all the devices are updated.
 626          */
 627         trans = btrfs_attach_transaction(root);
 628         if (!IS_ERR(trans)) {
 629                 ret = btrfs_commit_transaction(trans);
 630                 if (ret)
 631                         return ret;
 632         } else if (PTR_ERR(trans) != -ENOENT) {
 633                 return PTR_ERR(trans);
 634         }
 635
 636         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
 637                                             src_device, &tgt_device);
 638         if (ret)
 639                 return ret;
 640
 641         ret = mark_block_group_to_copy(fs_info, src_device);
 642         if (ret)
 643                 return ret;
 644
 645         down_write(&dev_replace->rwsem);
 646         switch (dev_replace->replace_state) {
 647         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 648         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 649         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 650                 break;
 651         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 652         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 653                 ASSERT(0);
 654                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 655                 up_write(&dev_replace->rwsem);
 656                 goto leave;
 657         }
 658
 659         dev_replace->cont_reading_from_srcdev_mode = read_src;
 660         dev_replace->srcdev = src_device;
 661         dev_replace->tgtdev = tgt_device;
 662
 663         btrfs_info_in_rcu(fs_info,
 664                       "dev_replace from %s (devid %llu) to %s started",
 665                       btrfs_dev_name(src_device),
 666                       src_device->devid,
 667                       btrfs_dev_name(tgt_device));
 668
 669         /*
 670          * from now on, the writes to the srcdev are all duplicated to
 671          * go to the tgtdev as well (refer to btrfs_map_block()).
 672          */
 673         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 674         dev_replace->time_started = ktime_get_real_seconds();
 675         dev_replace->cursor_left = 0;
 676         dev_replace->committed_cursor_left = 0;
 677         dev_replace->cursor_left_last_write_of_item = 0;
 678         dev_replace->cursor_right = 0;
 679         dev_replace->is_valid = 1;
 680         dev_replace->item_needs_writeback = 1;
 681         atomic64_set(&dev_replace->num_write_errors, 0);
 682         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 683         up_write(&dev_replace->rwsem);
 684
 685         ret = btrfs_sysfs_add_device(tgt_device);
 686         if (ret)
 687                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
 688
 689         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 690
 691         /*
 692          * Commit dev_replace state and reserve 1 item for it.
 693          * This is crucial to ensure we won't miss copying extents for new block
 694          * groups that are allocated after we started the device replace, and
 695          * must be done after setting up the device replace state.
 696          */
 697         trans = btrfs_start_transaction(root, 1);
 698         if (IS_ERR(trans)) {
 699                 ret = PTR_ERR(trans);
 700                 down_write(&dev_replace->rwsem);
 701                 dev_replace->replace_state =
 702                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 703                 dev_replace->srcdev = NULL;
 704                 dev_replace->tgtdev = NULL;
 705                 up_write(&dev_replace->rwsem);
 706                 goto leave;
 707         }
 708
 709         ret = btrfs_commit_transaction(trans);
 710         WARN_ON(ret);
 711
 712         /* the disk copy procedure reuses the scrub code */
 713         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 714                               btrfs_device_get_total_bytes(src_device),
 715                               &dev_replace->scrub_progress, 0, 1);
 716
 717         ret = btrfs_dev_replace_finishing(fs_info, ret);
 718         if (ret == -EINPROGRESS)
 719                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
 720
 721         return ret;
 722
 723 leave:
 724         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 725         return ret;
 726 }
 727
 728 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 729                             struct btrfs_ioctl_dev_replace_args *args)
 730 {
 731         int ret;
 732
 733         switch (args->start.cont_reading_from_srcdev_mode) {
 734         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 735         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 736                 break;
 737         default:
 738                 return -EINVAL;
 739         }
 740
 741         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 742             args->start.tgtdev_name[0] == '\0')
 743                 return -EINVAL;
 744
 745         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 746                                         args->start.srcdevid,
 747                                         args->start.srcdev_name,
 748                                         args->start.cont_reading_from_srcdev_mode);
 749         args->result = ret;
 750         /* don't warn if EINPROGRESS, someone else might be running scrub */
 751         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
 752             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
 753                 return 0;
 754
 755         return ret;
 756 }
 757
 758 /*
 759  * blocked until all in-flight bios operations are finished.
 760  */
 761 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
 762 {
 763         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 764         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
 765                    &fs_info->dev_replace.bio_counter));
 766 }
 767
 768 /*
 769  * we have removed target device, it is safe to allow new bios request.
 770  */
 771 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
 772 {
 773         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 774         wake_up(&fs_info->dev_replace.replace_wait);
 775 }
 776
 777 /*
 778  * When finishing the device replace, before swapping the source device with the
 779  * target device we must update the chunk allocation state in the target device,
 780  * as it is empty because replace works by directly copying the chunks and not
 781  * through the normal chunk allocation path.
 782  */
 783 static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
 784                                         struct btrfs_device *tgtdev)
 785 {
 786         struct extent_state *cached_state = NULL;
 787         u64 start = 0;
 788         u64 found_start;
 789         u64 found_end;
 790         int ret = 0;
 791
 792         lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
 793
 794         while (find_first_extent_bit(&srcdev->alloc_state, start,
 795                                      &found_start, &found_end,
 796                                      CHUNK_ALLOCATED, &cached_state)) {
 797                 ret = set_extent_bit(&tgtdev->alloc_state, found_start,
 798                                      found_end, CHUNK_ALLOCATED, NULL);
 799                 if (ret)
 800                         break;
 801                 start = found_end + 1;
 802         }
 803
 804         free_extent_state(cached_state);
 805         return ret;
 806 }
 807
 808 static void btrfs_dev_replace_update_device_in_mapping_tree(
 809                                                 struct btrfs_fs_info *fs_info,
 810                                                 struct btrfs_device *srcdev,
 811                                                 struct btrfs_device *tgtdev)
 812 {
 813         struct extent_map_tree *em_tree = &fs_info->mapping_tree;
 814         struct extent_map *em;
 815         struct map_lookup *map;
 816         u64 start = 0;
 817         int i;
 818
 819         write_lock(&em_tree->lock);
 820         do {
 821                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
 822                 if (!em)
 823                         break;
 824                 map = em->map_lookup;
 825                 for (i = 0; i < map->num_stripes; i++)
 826                         if (srcdev == map->stripes[i].dev)
 827                                 map->stripes[i].dev = tgtdev;
 828                 start = em->start + em->len;
 829                 free_extent_map(em);
 830         } while (start);
 831         write_unlock(&em_tree->lock);
 832 }
 833
 834 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 835                                        int scrub_ret)
 836 {
 837         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 838         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 839         struct btrfs_device *tgt_device;
 840         struct btrfs_device *src_device;
 841         struct btrfs_root *root = fs_info->tree_root;
 842         u8 uuid_tmp[BTRFS_UUID_SIZE];
 843         struct btrfs_trans_handle *trans;
 844         int ret = 0;
 845
 846         /* don't allow cancel or unmount to disturb the finishing procedure */
 847         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 848
 849         down_read(&dev_replace->rwsem);
 850         /* was the operation canceled, or is it finished? */
 851         if (dev_replace->replace_state !=
 852             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 853                 up_read(&dev_replace->rwsem);
 854                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 855                 return 0;
 856         }
 857
 858         tgt_device = dev_replace->tgtdev;
 859         src_device = dev_replace->srcdev;
 860         up_read(&dev_replace->rwsem);
 861
 862         /*
 863          * flush all outstanding I/O and inode extent mappings before the
 864          * copy operation is declared as being finished
 865          */
 866         ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 867         if (ret) {
 868                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 869                 return ret;
 870         }
 871         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 872
 873         /*
 874          * We have to use this loop approach because at this point src_device
 875          * has to be available for transaction commit to complete, yet new
 876          * chunks shouldn't be allocated on the device.
 877          */
 878         while (1) {
 879                 trans = btrfs_start_transaction(root, 0);
 880                 if (IS_ERR(trans)) {
 881                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 882                         return PTR_ERR(trans);
 883                 }
 884                 ret = btrfs_commit_transaction(trans);
 885                 WARN_ON(ret);
 886
 887                 /* Prevent write_all_supers() during the finishing procedure */
 888                 mutex_lock(&fs_devices->device_list_mutex);
 889                 /* Prevent new chunks being allocated on the source device */
 890                 mutex_lock(&fs_info->chunk_mutex);
 891
 892                 if (!list_empty(&src_device->post_commit_list)) {
 893                         mutex_unlock(&fs_devices->device_list_mutex);
 894                         mutex_unlock(&fs_info->chunk_mutex);
 895                 } else {
 896                         break;
 897                 }
 898         }
 899
 900         down_write(&dev_replace->rwsem);
 901         dev_replace->replace_state =
 902                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 903                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 904         dev_replace->tgtdev = NULL;
 905         dev_replace->srcdev = NULL;
 906         dev_replace->time_stopped = ktime_get_real_seconds();
 907         dev_replace->item_needs_writeback = 1;
 908
 909         /*
 910          * Update allocation state in the new device and replace the old device
 911          * with the new one in the mapping tree.
 912          */
 913         if (!scrub_ret) {
 914                 scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
 915                 if (scrub_ret)
 916                         goto error;
 917                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 918                                                                 src_device,
 919                                                                 tgt_device);
 920         } else {
 921                 if (scrub_ret != -ECANCELED)
 922                         btrfs_err_in_rcu(fs_info,
 923                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 924                                  btrfs_dev_name(src_device),
 925                                  src_device->devid,
 926                                  btrfs_dev_name(tgt_device), scrub_ret);
 927 error:
 928                 up_write(&dev_replace->rwsem);
 929                 mutex_unlock(&fs_info->chunk_mutex);
 930                 mutex_unlock(&fs_devices->device_list_mutex);
 931                 btrfs_rm_dev_replace_blocked(fs_info);
 932                 if (tgt_device)
 933                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 934                 btrfs_rm_dev_replace_unblocked(fs_info);
 935                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 936
 937                 return scrub_ret;
 938         }
 939
 940         btrfs_info_in_rcu(fs_info,
 941                           "dev_replace from %s (devid %llu) to %s finished",
 942                           btrfs_dev_name(src_device),
 943                           src_device->devid,
 944                           btrfs_dev_name(tgt_device));
 945         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 946         tgt_device->devid = src_device->devid;
 947         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 948         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 949         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 950         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 951         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
 952         btrfs_device_set_disk_total_bytes(tgt_device,
 953                                           src_device->disk_total_bytes);
 954         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 955         tgt_device->commit_bytes_used = src_device->bytes_used;
 956
 957         btrfs_assign_next_active_device(src_device, tgt_device);
 958
 959         list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
 960         fs_devices->rw_devices++;
 961
 962         up_write(&dev_replace->rwsem);
 963         btrfs_rm_dev_replace_blocked(fs_info);
 964
 965         btrfs_rm_dev_replace_remove_srcdev(src_device);
 966
 967         btrfs_rm_dev_replace_unblocked(fs_info);
 968
 969         /*
 970          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
 971          * update on-disk dev stats value during commit transaction
 972          */
 973         atomic_inc(&tgt_device->dev_stats_ccnt);
 974
 975         /*
 976          * this is again a consistent state where no dev_replace procedure
 977          * is running, the target device is part of the filesystem, the
 978          * source device is not part of the filesystem anymore and its 1st
 979          * superblock is scratched out so that it is no longer marked to
 980          * belong to this filesystem.
 981          */
 982         mutex_unlock(&fs_info->chunk_mutex);
 983         mutex_unlock(&fs_devices->device_list_mutex);
 984
 985         /* replace the sysfs entry */
 986         btrfs_sysfs_remove_device(src_device);
 987         btrfs_sysfs_update_devid(tgt_device);
 988         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
 989                 btrfs_scratch_superblocks(fs_info, src_device->bdev,
 990                                           src_device->name->str);
 991
 992         /* write back the superblocks */
 993         trans = btrfs_start_transaction(root, 0);
 994         if (!IS_ERR(trans))
 995                 btrfs_commit_transaction(trans);
 996
 997         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 998
 999         btrfs_rm_dev_replace_free_srcdev(src_device);
1000
1001         return 0;
1002 }
1003
1004 /*
1005  * Read progress of device replace status according to the state and last
1006  * stored position. The value format is the same as for
1007  * btrfs_dev_replace::progress_1000
1008  */
1009 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
1010 {
1011         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1012         u64 ret = 0;
1013
1014         switch (dev_replace->replace_state) {
1015         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1016         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1017                 ret = 0;
1018                 break;
1019         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1020                 ret = 1000;
1021                 break;
1022         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1023         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1024                 ret = div64_u64(dev_replace->cursor_left,
1025                                 div_u64(btrfs_device_get_total_bytes(
1026                                                 dev_replace->srcdev), 1000));
1027                 break;
1028         }
1029
1030         return ret;
1031 }
1032
1033 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
1034                               struct btrfs_ioctl_dev_replace_args *args)
1035 {
1036         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1037
1038         down_read(&dev_replace->rwsem);
1039         /* even if !dev_replace_is_valid, the values are good enough for
1040          * the replace_status ioctl */
1041         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1042         args->status.replace_state = dev_replace->replace_state;
1043         args->status.time_started = dev_replace->time_started;
1044         args->status.time_stopped = dev_replace->time_stopped;
1045         args->status.num_write_errors =
1046                 atomic64_read(&dev_replace->num_write_errors);
1047         args->status.num_uncorrectable_read_errors =
1048                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
1049         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
1050         up_read(&dev_replace->rwsem);
1051 }
1052
1053 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
1054 {
1055         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1056         struct btrfs_device *tgt_device = NULL;
1057         struct btrfs_device *src_device = NULL;
1058         struct btrfs_trans_handle *trans;
1059         struct btrfs_root *root = fs_info->tree_root;
1060         int result;
1061         int ret;
1062
1063         if (sb_rdonly(fs_info->sb))
1064                 return -EROFS;
1065
1066         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1067         down_write(&dev_replace->rwsem);
1068         switch (dev_replace->replace_state) {
1069         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1070         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1071         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1072                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1073                 up_write(&dev_replace->rwsem);
1074                 break;
1075         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1076                 tgt_device = dev_replace->tgtdev;
1077                 src_device = dev_replace->srcdev;
1078                 up_write(&dev_replace->rwsem);
1079                 ret = btrfs_scrub_cancel(fs_info);
1080                 if (ret < 0) {
1081                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1082                 } else {
1083                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1084                         /*
1085                          * btrfs_dev_replace_finishing() will handle the
1086                          * cleanup part
1087                          */
1088                         btrfs_info_in_rcu(fs_info,
1089                                 "dev_replace from %s (devid %llu) to %s canceled",
1090                                 btrfs_dev_name(src_device), src_device->devid,
1091                                 btrfs_dev_name(tgt_device));
1092                 }
1093                 break;
1094         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1095                 /*
1096                  * Scrub doing the replace isn't running so we need to do the
1097                  * cleanup step of btrfs_dev_replace_finishing() here
1098                  */
1099                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1100                 tgt_device = dev_replace->tgtdev;
1101                 src_device = dev_replace->srcdev;
1102                 dev_replace->tgtdev = NULL;
1103                 dev_replace->srcdev = NULL;
1104                 dev_replace->replace_state =
1105                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
1106                 dev_replace->time_stopped = ktime_get_real_seconds();
1107                 dev_replace->item_needs_writeback = 1;
1108
1109                 up_write(&dev_replace->rwsem);
1110
1111                 /* Scrub for replace must not be running in suspended state */
1112                 btrfs_scrub_cancel(fs_info);
1113
1114                 trans = btrfs_start_transaction(root, 0);
1115                 if (IS_ERR(trans)) {
1116                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1117                         return PTR_ERR(trans);
1118                 }
1119                 ret = btrfs_commit_transaction(trans);
1120                 WARN_ON(ret);
1121
1122                 btrfs_info_in_rcu(fs_info,
1123                 "suspended dev_replace from %s (devid %llu) to %s canceled",
1124                         btrfs_dev_name(src_device), src_device->devid,
1125                         btrfs_dev_name(tgt_device));
1126
1127                 if (tgt_device)
1128                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
1129                 break;
1130         default:
1131                 up_write(&dev_replace->rwsem);
1132                 result = -EINVAL;
1133         }
1134
1135         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1136         return result;
1137 }
1138
1139 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
1140 {
1141         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1142
1143         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1144         down_write(&dev_replace->rwsem);
1145
1146         switch (dev_replace->replace_state) {
1147         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1148         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1149         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1150         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1151                 break;
1152         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1153                 dev_replace->replace_state =
1154                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1155                 dev_replace->time_stopped = ktime_get_real_seconds();
1156                 dev_replace->item_needs_writeback = 1;
1157                 btrfs_info(fs_info, "suspending dev_replace for unmount");
1158                 break;
1159         }
1160
1161         up_write(&dev_replace->rwsem);
1162         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1163 }
1164
1165 /* resume dev_replace procedure that was interrupted by unmount */
1166 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
1167 {
1168         struct task_struct *task;
1169         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1170
1171         down_write(&dev_replace->rwsem);
1172
1173         switch (dev_replace->replace_state) {
1174         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1175         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1176         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1177                 up_write(&dev_replace->rwsem);
1178                 return 0;
1179         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1180                 break;
1181         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1182                 dev_replace->replace_state =
1183                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1184                 break;
1185         }
1186         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1187                 btrfs_info(fs_info,
1188                            "cannot continue dev_replace, tgtdev is missing");
1189                 btrfs_info(fs_info,
1190                            "you may cancel the operation after 'mount -o degraded'");
1191                 dev_replace->replace_state =
1192                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1193                 up_write(&dev_replace->rwsem);
1194                 return 0;
1195         }
1196         up_write(&dev_replace->rwsem);
1197
1198         /*
1199          * This could collide with a paused balance, but the exclusive op logic
1200          * should never allow both to start and pause. We don't want to allow
1201          * dev-replace to start anyway.
1202          */
1203         if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
1204                 down_write(&dev_replace->rwsem);
1205                 dev_replace->replace_state =
1206                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1207                 up_write(&dev_replace->rwsem);
1208                 btrfs_info(fs_info,
1209                 "cannot resume dev-replace, other exclusive operation running");
1210                 return 0;
1211         }
1212
1213         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1214         return PTR_ERR_OR_ZERO(task);
1215 }
1216
1217 static int btrfs_dev_replace_kthread(void *data)
1218 {
1219         struct btrfs_fs_info *fs_info = data;
1220         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1221         u64 progress;
1222         int ret;
1223
1224         progress = btrfs_dev_replace_progress(fs_info);
1225         progress = div_u64(progress, 10);
1226         btrfs_info_in_rcu(fs_info,
1227                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1228                 btrfs_dev_name(dev_replace->srcdev),
1229                 dev_replace->srcdev->devid,
1230                 btrfs_dev_name(dev_replace->tgtdev),
1231                 (unsigned int)progress);
1232
1233         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1234                               dev_replace->committed_cursor_left,
1235                               btrfs_device_get_total_bytes(dev_replace->srcdev),
1236                               &dev_replace->scrub_progress, 0, 1);
1237         ret = btrfs_dev_replace_finishing(fs_info, ret);
1238         WARN_ON(ret && ret != -ECANCELED);
1239
1240         btrfs_exclop_finish(fs_info);
1241         return 0;
1242 }
1243
1244 int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1245 {
1246         if (!dev_replace->is_valid)
1247                 return 0;
1248
1249         switch (dev_replace->replace_state) {
1250         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1251         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1252         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1253                 return 0;
1254         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1255         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1256                 /*
1257                  * return true even if tgtdev is missing (this is
1258                  * something that can happen if the dev_replace
1259                  * procedure is suspended by an umount and then
1260                  * the tgtdev is missing (or "btrfs dev scan") was
1261                  * not called and the filesystem is remounted
1262                  * in degraded state. This does not stop the
1263                  * dev_replace procedure. It needs to be canceled
1264                  * manually if the cancellation is wanted.
1265                  */
1266                 break;
1267         }
1268         return 1;
1269 }
1270
1271 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1272 {
1273         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1274         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1275 }
1276
1277 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1278 {
1279         while (1) {
1280                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1281                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1282                                      &fs_info->fs_state)))
1283                         break;
1284
1285                 btrfs_bio_counter_dec(fs_info);
1286                 wait_event(fs_info->dev_replace.replace_wait,
1287                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1288                                      &fs_info->fs_state));
1289         }
1290 }