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 "check-integrity.h"
  21 #include "dev-replace.h"
  22 #include "sysfs.h"
  23 #include "zoned.h"
  24 #include "block-group.h"
  25 #include "fs.h"
  26 #include "accessors.h"
  27 #include "scrub.h"
  28
  29 /*
  30  * Device replace overview
  31  *
  32  * [Objective]
  33  * To copy all extents (both new and on-disk) from source device to target
  34  * device, while still keeping the filesystem read-write.
  35  *
  36  * [Method]
  37  * There are two main methods involved:
  38  *
  39  * - Write duplication
  40  *
  41  *   All new writes will be written to both target and source devices, so even
  42  *   if replace gets canceled, sources device still contains up-to-date data.
  43  *
  44  *   Location:          handle_ops_on_dev_replace() from __btrfs_map_block()
  45  *   Start:             btrfs_dev_replace_start()
  46  *   End:               btrfs_dev_replace_finishing()
  47  *   Content:           Latest data/metadata
  48  *
  49  * - Copy existing extents
  50  *
  51  *   This happens by re-using scrub facility, as scrub also iterates through
  52  *   existing extents from commit root.
  53  *
  54  *   Location:          scrub_write_block_to_dev_replace() from
  55  *                      scrub_block_complete()
  56  *   Content:           Data/meta from commit root.
  57  *
  58  * Due to the content difference, we need to avoid nocow write when dev-replace
  59  * is happening.  This is done by marking the block group read-only and waiting
  60  * for NOCOW writes.
  61  *
  62  * After replace is done, the finishing part is done by swapping the target and
  63  * source devices.
  64  *
  65  *   Location:          btrfs_dev_replace_update_device_in_mapping_tree() from
  66  *                      btrfs_dev_replace_finishing()
  67  */
  68
  69 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
  70                                        int scrub_ret);
  71 static int btrfs_dev_replace_kthread(void *data);
  72
  73 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
  74 {
  75         struct btrfs_dev_lookup_args args = { .devid = BTRFS_DEV_REPLACE_DEVID };
  76         struct btrfs_key key;
  77         struct btrfs_root *dev_root = fs_info->dev_root;
  78         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
  79         struct extent_buffer *eb;
  80         int slot;
  81         int ret = 0;
  82         struct btrfs_path *path = NULL;
  83         int item_size;
  84         struct btrfs_dev_replace_item *ptr;
  85         u64 src_devid;
  86
  87         if (!dev_root)
  88                 return 0;
  89
  90         path = btrfs_alloc_path();
  91         if (!path) {
  92                 ret = -ENOMEM;
  93                 goto out;
  94         }
  95
  96         key.objectid = 0;
  97         key.type = BTRFS_DEV_REPLACE_KEY;
  98         key.offset = 0;
  99         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
 100         if (ret) {
 101 no_valid_dev_replace_entry_found:
 102                 /*
 103                  * We don't have a replace item or it's corrupted.  If there is
 104                  * a replace target, fail the mount.
 105                  */
 106                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
 107                         btrfs_err(fs_info,
 108                         "found replace target device without a valid replace item");
 109                         ret = -EUCLEAN;
 110                         goto out;
 111                 }
 112                 ret = 0;
 113                 dev_replace->replace_state =
 114                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 115                 dev_replace->cont_reading_from_srcdev_mode =
 116                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 117                 dev_replace->time_started = 0;
 118                 dev_replace->time_stopped = 0;
 119                 atomic64_set(&dev_replace->num_write_errors, 0);
 120                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 121                 dev_replace->cursor_left = 0;
 122                 dev_replace->committed_cursor_left = 0;
 123                 dev_replace->cursor_left_last_write_of_item = 0;
 124                 dev_replace->cursor_right = 0;
 125                 dev_replace->srcdev = NULL;
 126                 dev_replace->tgtdev = NULL;
 127                 dev_replace->is_valid = 0;
 128                 dev_replace->item_needs_writeback = 0;
 129                 goto out;
 130         }
 131         slot = path->slots[0];
 132         eb = path->nodes[0];
 133         item_size = btrfs_item_size(eb, slot);
 134         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 135
 136         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 137                 btrfs_warn(fs_info,
 138                         "dev_replace entry found has unexpected size, ignore entry");
 139                 goto no_valid_dev_replace_entry_found;
 140         }
 141
 142         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 143         dev_replace->cont_reading_from_srcdev_mode =
 144                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 145         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 146         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 147         dev_replace->time_stopped =
 148                 btrfs_dev_replace_time_stopped(eb, ptr);
 149         atomic64_set(&dev_replace->num_write_errors,
 150                      btrfs_dev_replace_num_write_errors(eb, ptr));
 151         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 152                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 153         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 154         dev_replace->committed_cursor_left = dev_replace->cursor_left;
 155         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
 156         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
 157         dev_replace->is_valid = 1;
 158
 159         dev_replace->item_needs_writeback = 0;
 160         switch (dev_replace->replace_state) {
 161         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 162         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 163         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 164                 /*
 165                  * We don't have an active replace item but if there is a
 166                  * replace target, fail the mount.
 167                  */
 168                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
 169                         btrfs_err(fs_info,
 170 "replace without active item, run 'device scan --forget' on the target device");
 171                         ret = -EUCLEAN;
 172                 } else {
 173                         dev_replace->srcdev = NULL;
 174                         dev_replace->tgtdev = NULL;
 175                 }
 176                 break;
 177         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 178         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 179                 dev_replace->tgtdev = btrfs_find_device(fs_info->fs_devices, &args);
 180                 args.devid = src_devid;
 181                 dev_replace->srcdev = btrfs_find_device(fs_info->fs_devices, &args);
 182
 183                 /*
 184                  * allow 'btrfs dev replace_cancel' if src/tgt device is
 185                  * missing
 186                  */
 187                 if (!dev_replace->srcdev &&
 188                     !btrfs_test_opt(fs_info, DEGRADED)) {
 189                         ret = -EIO;
 190                         btrfs_warn(fs_info,
 191                            "cannot mount because device replace operation is ongoing and");
 192                         btrfs_warn(fs_info,
 193                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 194                            src_devid);
 195                 }
 196                 if (!dev_replace->tgtdev &&
 197                     !btrfs_test_opt(fs_info, DEGRADED)) {
 198                         ret = -EIO;
 199                         btrfs_warn(fs_info,
 200                            "cannot mount because device replace operation is ongoing and");
 201                         btrfs_warn(fs_info,
 202                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 203                                 BTRFS_DEV_REPLACE_DEVID);
 204                 }
 205                 if (dev_replace->tgtdev) {
 206                         if (dev_replace->srcdev) {
 207                                 dev_replace->tgtdev->total_bytes =
 208                                         dev_replace->srcdev->total_bytes;
 209                                 dev_replace->tgtdev->disk_total_bytes =
 210                                         dev_replace->srcdev->disk_total_bytes;
 211                                 dev_replace->tgtdev->commit_total_bytes =
 212                                         dev_replace->srcdev->commit_total_bytes;
 213                                 dev_replace->tgtdev->bytes_used =
 214                                         dev_replace->srcdev->bytes_used;
 215                                 dev_replace->tgtdev->commit_bytes_used =
 216                                         dev_replace->srcdev->commit_bytes_used;
 217                         }
 218                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
 219                                 &dev_replace->tgtdev->dev_state);
 220
 221                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
 222                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
 223                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
 224                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
 225                         dev_replace->tgtdev->fs_info = fs_info;
 226                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
 227                                 &dev_replace->tgtdev->dev_state);
 228                 }
 229                 break;
 230         }
 231
 232 out:
 233         btrfs_free_path(path);
 234         return ret;
 235 }
 236
 237 /*
 238  * Initialize a new device for device replace target from a given source dev
 239  * and path.
 240  *
 241  * Return 0 and new device in @device_out, otherwise return < 0
 242  */
 243 static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 244                                   const char *device_path,
 245                                   struct btrfs_device *srcdev,
 246                                   struct btrfs_device **device_out)
 247 {
 248         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 249         struct btrfs_device *device;
 250         struct block_device *bdev;
 251         u64 devid = BTRFS_DEV_REPLACE_DEVID;
 252         int ret = 0;
 253
 254         *device_out = NULL;
 255         if (srcdev->fs_devices->seeding) {
 256                 btrfs_err(fs_info, "the filesystem is a seed filesystem!");
 257                 return -EINVAL;
 258         }
 259
 260         bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
 261                                   fs_info->bdev_holder);
 262         if (IS_ERR(bdev)) {
 263                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
 264                 return PTR_ERR(bdev);
 265         }
 266
 267         if (!btrfs_check_device_zone_type(fs_info, bdev)) {
 268                 btrfs_err(fs_info,
 269                 "dev-replace: zoned type of target device mismatch with filesystem");
 270                 ret = -EINVAL;
 271                 goto error;
 272         }
 273
 274         sync_blockdev(bdev);
 275
 276         list_for_each_entry(device, &fs_devices->devices, dev_list) {
 277                 if (device->bdev == bdev) {
 278                         btrfs_err(fs_info,
 279                                   "target device is in the filesystem!");
 280                         ret = -EEXIST;
 281                         goto error;
 282                 }
 283         }
 284
 285
 286         if (bdev_nr_bytes(bdev) < btrfs_device_get_total_bytes(srcdev)) {
 287                 btrfs_err(fs_info,
 288                           "target device is smaller than source device!");
 289                 ret = -EINVAL;
 290                 goto error;
 291         }
 292
 293
 294         device = btrfs_alloc_device(NULL, &devid, NULL, device_path);
 295         if (IS_ERR(device)) {
 296                 ret = PTR_ERR(device);
 297                 goto error;
 298         }
 299
 300         ret = lookup_bdev(device_path, &device->devt);
 301         if (ret)
 302                 goto error;
 303
 304         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 305         device->generation = 0;
 306         device->io_width = fs_info->sectorsize;
 307         device->io_align = fs_info->sectorsize;
 308         device->sector_size = fs_info->sectorsize;
 309         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
 310         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
 311         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 312         device->commit_total_bytes = srcdev->commit_total_bytes;
 313         device->commit_bytes_used = device->bytes_used;
 314         device->fs_info = fs_info;
 315         device->bdev = bdev;
 316         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 317         set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 318         device->mode = FMODE_EXCL;
 319         device->dev_stats_valid = 1;
 320         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 321         device->fs_devices = fs_devices;
 322
 323         ret = btrfs_get_dev_zone_info(device, false);
 324         if (ret)
 325                 goto error;
 326
 327         mutex_lock(&fs_devices->device_list_mutex);
 328         list_add(&device->dev_list, &fs_devices->devices);
 329         fs_devices->num_devices++;
 330         fs_devices->open_devices++;
 331         mutex_unlock(&fs_devices->device_list_mutex);
 332
 333         *device_out = device;
 334         return 0;
 335
 336 error:
 337         blkdev_put(bdev, FMODE_EXCL);
 338         return ret;
 339 }
 340
 341 /*
 342  * called from commit_transaction. Writes changed device replace state to
 343  * disk.
 344  */
 345 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
 346 {
 347         struct btrfs_fs_info *fs_info = trans->fs_info;
 348         int ret;
 349         struct btrfs_root *dev_root = fs_info->dev_root;
 350         struct btrfs_path *path;
 351         struct btrfs_key key;
 352         struct extent_buffer *eb;
 353         struct btrfs_dev_replace_item *ptr;
 354         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 355
 356         down_read(&dev_replace->rwsem);
 357         if (!dev_replace->is_valid ||
 358             !dev_replace->item_needs_writeback) {
 359                 up_read(&dev_replace->rwsem);
 360                 return 0;
 361         }
 362         up_read(&dev_replace->rwsem);
 363
 364         key.objectid = 0;
 365         key.type = BTRFS_DEV_REPLACE_KEY;
 366         key.offset = 0;
 367
 368         path = btrfs_alloc_path();
 369         if (!path) {
 370                 ret = -ENOMEM;
 371                 goto out;
 372         }
 373         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
 374         if (ret < 0) {
 375                 btrfs_warn(fs_info,
 376                            "error %d while searching for dev_replace item!",
 377                            ret);
 378                 goto out;
 379         }
 380
 381         if (ret == 0 &&
 382             btrfs_item_size(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 383                 /*
 384                  * need to delete old one and insert a new one.
 385                  * Since no attempt is made to recover any old state, if the
 386                  * dev_replace state is 'running', the data on the target
 387                  * drive is lost.
 388                  * It would be possible to recover the state: just make sure
 389                  * that the beginning of the item is never changed and always
 390                  * contains all the essential information. Then read this
 391                  * minimal set of information and use it as a base for the
 392                  * new state.
 393                  */
 394                 ret = btrfs_del_item(trans, dev_root, path);
 395                 if (ret != 0) {
 396                         btrfs_warn(fs_info,
 397                                    "delete too small dev_replace item failed %d!",
 398                                    ret);
 399                         goto out;
 400                 }
 401                 ret = 1;
 402         }
 403
 404         if (ret == 1) {
 405                 /* need to insert a new item */
 406                 btrfs_release_path(path);
 407                 ret = btrfs_insert_empty_item(trans, dev_root, path,
 408                                               &key, sizeof(*ptr));
 409                 if (ret < 0) {
 410                         btrfs_warn(fs_info,
 411                                    "insert dev_replace item failed %d!", ret);
 412                         goto out;
 413                 }
 414         }
 415
 416         eb = path->nodes[0];
 417         ptr = btrfs_item_ptr(eb, path->slots[0],
 418                              struct btrfs_dev_replace_item);
 419
 420         down_write(&dev_replace->rwsem);
 421         if (dev_replace->srcdev)
 422                 btrfs_set_dev_replace_src_devid(eb, ptr,
 423                         dev_replace->srcdev->devid);
 424         else
 425                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 426         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 427                 dev_replace->cont_reading_from_srcdev_mode);
 428         btrfs_set_dev_replace_replace_state(eb, ptr,
 429                 dev_replace->replace_state);
 430         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 431         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 432         btrfs_set_dev_replace_num_write_errors(eb, ptr,
 433                 atomic64_read(&dev_replace->num_write_errors));
 434         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 435                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 436         dev_replace->cursor_left_last_write_of_item =
 437                 dev_replace->cursor_left;
 438         btrfs_set_dev_replace_cursor_left(eb, ptr,
 439                 dev_replace->cursor_left_last_write_of_item);
 440         btrfs_set_dev_replace_cursor_right(eb, ptr,
 441                 dev_replace->cursor_right);
 442         dev_replace->item_needs_writeback = 0;
 443         up_write(&dev_replace->rwsem);
 444
 445         btrfs_mark_buffer_dirty(eb);
 446
 447 out:
 448         btrfs_free_path(path);
 449
 450         return ret;
 451 }
 452
 453 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 454                                     struct btrfs_device *src_dev)
 455 {
 456         struct btrfs_path *path;
 457         struct btrfs_key key;
 458         struct btrfs_key found_key;
 459         struct btrfs_root *root = fs_info->dev_root;
 460         struct btrfs_dev_extent *dev_extent = NULL;
 461         struct btrfs_block_group *cache;
 462         struct btrfs_trans_handle *trans;
 463         int iter_ret = 0;
 464         int ret = 0;
 465         u64 chunk_offset;
 466
 467         /* Do not use "to_copy" on non zoned filesystem for now */
 468         if (!btrfs_is_zoned(fs_info))
 469                 return 0;
 470
 471         mutex_lock(&fs_info->chunk_mutex);
 472
 473         /* Ensure we don't have pending new block group */
 474         spin_lock(&fs_info->trans_lock);
 475         while (fs_info->running_transaction &&
 476                !list_empty(&fs_info->running_transaction->dev_update_list)) {
 477                 spin_unlock(&fs_info->trans_lock);
 478                 mutex_unlock(&fs_info->chunk_mutex);
 479                 trans = btrfs_attach_transaction(root);
 480                 if (IS_ERR(trans)) {
 481                         ret = PTR_ERR(trans);
 482                         mutex_lock(&fs_info->chunk_mutex);
 483                         if (ret == -ENOENT) {
 484                                 spin_lock(&fs_info->trans_lock);
 485                                 continue;
 486                         } else {
 487                                 goto unlock;
 488                         }
 489                 }
 490
 491                 ret = btrfs_commit_transaction(trans);
 492                 mutex_lock(&fs_info->chunk_mutex);
 493                 if (ret)
 494                         goto unlock;
 495
 496                 spin_lock(&fs_info->trans_lock);
 497         }
 498         spin_unlock(&fs_info->trans_lock);
 499
 500         path = btrfs_alloc_path();
 501         if (!path) {
 502                 ret = -ENOMEM;
 503                 goto unlock;
 504         }
 505
 506         path->reada = READA_FORWARD;
 507         path->search_commit_root = 1;
 508         path->skip_locking = 1;
 509
 510         key.objectid = src_dev->devid;
 511         key.type = BTRFS_DEV_EXTENT_KEY;
 512         key.offset = 0;
 513
 514         btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 515                 struct extent_buffer *leaf = path->nodes[0];
 516
 517                 if (found_key.objectid != src_dev->devid)
 518                         break;
 519
 520                 if (found_key.type != BTRFS_DEV_EXTENT_KEY)
 521                         break;
 522
 523                 if (found_key.offset < key.offset)
 524                         break;
 525
 526                 dev_extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
 527
 528                 chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
 529
 530                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 531                 if (!cache)
 532                         continue;
 533
 534                 set_bit(BLOCK_GROUP_FLAG_TO_COPY, &cache->runtime_flags);
 535                 btrfs_put_block_group(cache);
 536         }
 537         if (iter_ret < 0)
 538                 ret = iter_ret;
 539
 540         btrfs_free_path(path);
 541 unlock:
 542         mutex_unlock(&fs_info->chunk_mutex);
 543
 544         return ret;
 545 }
 546
 547 bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev,
 548                                       struct btrfs_block_group *cache,
 549                                       u64 physical)
 550 {
 551         struct btrfs_fs_info *fs_info = cache->fs_info;
 552         struct extent_map *em;
 553         struct map_lookup *map;
 554         u64 chunk_offset = cache->start;
 555         int num_extents, cur_extent;
 556         int i;
 557
 558         /* Do not use "to_copy" on non zoned filesystem for now */
 559         if (!btrfs_is_zoned(fs_info))
 560                 return true;
 561
 562         spin_lock(&cache->lock);
 563         if (test_bit(BLOCK_GROUP_FLAG_REMOVED, &cache->runtime_flags)) {
 564                 spin_unlock(&cache->lock);
 565                 return true;
 566         }
 567         spin_unlock(&cache->lock);
 568
 569         em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
 570         ASSERT(!IS_ERR(em));
 571         map = em->map_lookup;
 572
 573         num_extents = 0;
 574         cur_extent = 0;
 575         for (i = 0; i < map->num_stripes; i++) {
 576                 /* We have more device extent to copy */
 577                 if (srcdev != map->stripes[i].dev)
 578                         continue;
 579
 580                 num_extents++;
 581                 if (physical == map->stripes[i].physical)
 582                         cur_extent = i;
 583         }
 584
 585         free_extent_map(em);
 586
 587         if (num_extents > 1 && cur_extent < num_extents - 1) {
 588                 /*
 589                  * Has more stripes on this device. Keep this block group
 590                  * readonly until we finish all the stripes.
 591                  */
 592                 return false;
 593         }
 594
 595         /* Last stripe on this device */
 596         clear_bit(BLOCK_GROUP_FLAG_TO_COPY, &cache->runtime_flags);
 597
 598         return true;
 599 }
 600
 601 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 602                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
 603                 int read_src)
 604 {
 605         struct btrfs_root *root = fs_info->dev_root;
 606         struct btrfs_trans_handle *trans;
 607         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 608         int ret;
 609         struct btrfs_device *tgt_device = NULL;
 610         struct btrfs_device *src_device = NULL;
 611
 612         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
 613                                                   srcdev_name);
 614         if (IS_ERR(src_device))
 615                 return PTR_ERR(src_device);
 616
 617         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
 618                 btrfs_warn_in_rcu(fs_info,
 619           "cannot replace device %s (devid %llu) due to active swapfile",
 620                         btrfs_dev_name(src_device), src_device->devid);
 621                 return -ETXTBSY;
 622         }
 623
 624         /*
 625          * Here we commit the transaction to make sure commit_total_bytes
 626          * of all the devices are updated.
 627          */
 628         trans = btrfs_attach_transaction(root);
 629         if (!IS_ERR(trans)) {
 630                 ret = btrfs_commit_transaction(trans);
 631                 if (ret)
 632                         return ret;
 633         } else if (PTR_ERR(trans) != -ENOENT) {
 634                 return PTR_ERR(trans);
 635         }
 636
 637         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
 638                                             src_device, &tgt_device);
 639         if (ret)
 640                 return ret;
 641
 642         ret = mark_block_group_to_copy(fs_info, src_device);
 643         if (ret)
 644                 return ret;
 645
 646         down_write(&dev_replace->rwsem);
 647         switch (dev_replace->replace_state) {
 648         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 649         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 650         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 651                 break;
 652         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 653         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 654                 ASSERT(0);
 655                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 656                 up_write(&dev_replace->rwsem);
 657                 goto leave;
 658         }
 659
 660         dev_replace->cont_reading_from_srcdev_mode = read_src;
 661         dev_replace->srcdev = src_device;
 662         dev_replace->tgtdev = tgt_device;
 663
 664         btrfs_info_in_rcu(fs_info,
 665                       "dev_replace from %s (devid %llu) to %s started",
 666                       btrfs_dev_name(src_device),
 667                       src_device->devid,
 668                       btrfs_dev_name(tgt_device));
 669
 670         /*
 671          * from now on, the writes to the srcdev are all duplicated to
 672          * go to the tgtdev as well (refer to btrfs_map_block()).
 673          */
 674         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 675         dev_replace->time_started = ktime_get_real_seconds();
 676         dev_replace->cursor_left = 0;
 677         dev_replace->committed_cursor_left = 0;
 678         dev_replace->cursor_left_last_write_of_item = 0;
 679         dev_replace->cursor_right = 0;
 680         dev_replace->is_valid = 1;
 681         dev_replace->item_needs_writeback = 1;
 682         atomic64_set(&dev_replace->num_write_errors, 0);
 683         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 684         up_write(&dev_replace->rwsem);
 685
 686         ret = btrfs_sysfs_add_device(tgt_device);
 687         if (ret)
 688                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
 689
 690         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 691
 692         /*
 693          * Commit dev_replace state and reserve 1 item for it.
 694          * This is crucial to ensure we won't miss copying extents for new block
 695          * groups that are allocated after we started the device replace, and
 696          * must be done after setting up the device replace state.
 697          */
 698         trans = btrfs_start_transaction(root, 1);
 699         if (IS_ERR(trans)) {
 700                 ret = PTR_ERR(trans);
 701                 down_write(&dev_replace->rwsem);
 702                 dev_replace->replace_state =
 703                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 704                 dev_replace->srcdev = NULL;
 705                 dev_replace->tgtdev = NULL;
 706                 up_write(&dev_replace->rwsem);
 707                 goto leave;
 708         }
 709
 710         ret = btrfs_commit_transaction(trans);
 711         WARN_ON(ret);
 712
 713         /* the disk copy procedure reuses the scrub code */
 714         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 715                               btrfs_device_get_total_bytes(src_device),
 716                               &dev_replace->scrub_progress, 0, 1);
 717
 718         ret = btrfs_dev_replace_finishing(fs_info, ret);
 719         if (ret == -EINPROGRESS)
 720                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
 721
 722         return ret;
 723
 724 leave:
 725         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 726         return ret;
 727 }
 728
 729 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 730                             struct btrfs_ioctl_dev_replace_args *args)
 731 {
 732         int ret;
 733
 734         switch (args->start.cont_reading_from_srcdev_mode) {
 735         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 736         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 737                 break;
 738         default:
 739                 return -EINVAL;
 740         }
 741
 742         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 743             args->start.tgtdev_name[0] == '\0')
 744                 return -EINVAL;
 745
 746         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 747                                         args->start.srcdevid,
 748                                         args->start.srcdev_name,
 749                                         args->start.cont_reading_from_srcdev_mode);
 750         args->result = ret;
 751         /* don't warn if EINPROGRESS, someone else might be running scrub */
 752         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
 753             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
 754                 return 0;
 755
 756         return ret;
 757 }
 758
 759 /*
 760  * blocked until all in-flight bios operations are finished.
 761  */
 762 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
 763 {
 764         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 765         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
 766                    &fs_info->dev_replace.bio_counter));
 767 }
 768
 769 /*
 770  * we have removed target device, it is safe to allow new bios request.
 771  */
 772 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
 773 {
 774         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 775         wake_up(&fs_info->dev_replace.replace_wait);
 776 }
 777
 778 /*
 779  * When finishing the device replace, before swapping the source device with the
 780  * target device we must update the chunk allocation state in the target device,
 781  * as it is empty because replace works by directly copying the chunks and not
 782  * through the normal chunk allocation path.
 783  */
 784 static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
 785                                         struct btrfs_device *tgtdev)
 786 {
 787         struct extent_state *cached_state = NULL;
 788         u64 start = 0;
 789         u64 found_start;
 790         u64 found_end;
 791         int ret = 0;
 792
 793         lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
 794
 795         while (!find_first_extent_bit(&srcdev->alloc_state, start,
 796                                       &found_start, &found_end,
 797                                       CHUNK_ALLOCATED, &cached_state)) {
 798                 ret = set_extent_bits(&tgtdev->alloc_state, found_start,
 799                                       found_end, CHUNK_ALLOCATED);
 800                 if (ret)
 801                         break;
 802                 start = found_end + 1;
 803         }
 804
 805         free_extent_state(cached_state);
 806         return ret;
 807 }
 808
 809 static void btrfs_dev_replace_update_device_in_mapping_tree(
 810                                                 struct btrfs_fs_info *fs_info,
 811                                                 struct btrfs_device *srcdev,
 812                                                 struct btrfs_device *tgtdev)
 813 {
 814         struct extent_map_tree *em_tree = &fs_info->mapping_tree;
 815         struct extent_map *em;
 816         struct map_lookup *map;
 817         u64 start = 0;
 818         int i;
 819
 820         write_lock(&em_tree->lock);
 821         do {
 822                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
 823                 if (!em)
 824                         break;
 825                 map = em->map_lookup;
 826                 for (i = 0; i < map->num_stripes; i++)
 827                         if (srcdev == map->stripes[i].dev)
 828                                 map->stripes[i].dev = tgtdev;
 829                 start = em->start + em->len;
 830                 free_extent_map(em);
 831         } while (start);
 832         write_unlock(&em_tree->lock);
 833 }
 834
 835 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 836                                        int scrub_ret)
 837 {
 838         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 839         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 840         struct btrfs_device *tgt_device;
 841         struct btrfs_device *src_device;
 842         struct btrfs_root *root = fs_info->tree_root;
 843         u8 uuid_tmp[BTRFS_UUID_SIZE];
 844         struct btrfs_trans_handle *trans;
 845         int ret = 0;
 846
 847         /* don't allow cancel or unmount to disturb the finishing procedure */
 848         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 849
 850         down_read(&dev_replace->rwsem);
 851         /* was the operation canceled, or is it finished? */
 852         if (dev_replace->replace_state !=
 853             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 854                 up_read(&dev_replace->rwsem);
 855                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 856                 return 0;
 857         }
 858
 859         tgt_device = dev_replace->tgtdev;
 860         src_device = dev_replace->srcdev;
 861         up_read(&dev_replace->rwsem);
 862
 863         /*
 864          * flush all outstanding I/O and inode extent mappings before the
 865          * copy operation is declared as being finished
 866          */
 867         ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 868         if (ret) {
 869                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 870                 return ret;
 871         }
 872         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 873
 874         /*
 875          * We have to use this loop approach because at this point src_device
 876          * has to be available for transaction commit to complete, yet new
 877          * chunks shouldn't be allocated on the device.
 878          */
 879         while (1) {
 880                 trans = btrfs_start_transaction(root, 0);
 881                 if (IS_ERR(trans)) {
 882                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 883                         return PTR_ERR(trans);
 884                 }
 885                 ret = btrfs_commit_transaction(trans);
 886                 WARN_ON(ret);
 887
 888                 /* Prevent write_all_supers() during the finishing procedure */
 889                 mutex_lock(&fs_devices->device_list_mutex);
 890                 /* Prevent new chunks being allocated on the source device */
 891                 mutex_lock(&fs_info->chunk_mutex);
 892
 893                 if (!list_empty(&src_device->post_commit_list)) {
 894                         mutex_unlock(&fs_devices->device_list_mutex);
 895                         mutex_unlock(&fs_info->chunk_mutex);
 896                 } else {
 897                         break;
 898                 }
 899         }
 900
 901         down_write(&dev_replace->rwsem);
 902         dev_replace->replace_state =
 903                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 904                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 905         dev_replace->tgtdev = NULL;
 906         dev_replace->srcdev = NULL;
 907         dev_replace->time_stopped = ktime_get_real_seconds();
 908         dev_replace->item_needs_writeback = 1;
 909
 910         /*
 911          * Update allocation state in the new device and replace the old device
 912          * with the new one in the mapping tree.
 913          */
 914         if (!scrub_ret) {
 915                 scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
 916                 if (scrub_ret)
 917                         goto error;
 918                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 919                                                                 src_device,
 920                                                                 tgt_device);
 921         } else {
 922                 if (scrub_ret != -ECANCELED)
 923                         btrfs_err_in_rcu(fs_info,
 924                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 925                                  btrfs_dev_name(src_device),
 926                                  src_device->devid,
 927                                  btrfs_dev_name(tgt_device), scrub_ret);
 928 error:
 929                 up_write(&dev_replace->rwsem);
 930                 mutex_unlock(&fs_info->chunk_mutex);
 931                 mutex_unlock(&fs_devices->device_list_mutex);
 932                 btrfs_rm_dev_replace_blocked(fs_info);
 933                 if (tgt_device)
 934                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 935                 btrfs_rm_dev_replace_unblocked(fs_info);
 936                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 937
 938                 return scrub_ret;
 939         }
 940
 941         btrfs_info_in_rcu(fs_info,
 942                           "dev_replace from %s (devid %llu) to %s finished",
 943                           btrfs_dev_name(src_device),
 944                           src_device->devid,
 945                           btrfs_dev_name(tgt_device));
 946         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 947         tgt_device->devid = src_device->devid;
 948         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 949         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 950         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 951         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 952         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
 953         btrfs_device_set_disk_total_bytes(tgt_device,
 954                                           src_device->disk_total_bytes);
 955         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 956         tgt_device->commit_bytes_used = src_device->bytes_used;
 957
 958         btrfs_assign_next_active_device(src_device, tgt_device);
 959
 960         list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
 961         fs_devices->rw_devices++;
 962
 963         up_write(&dev_replace->rwsem);
 964         btrfs_rm_dev_replace_blocked(fs_info);
 965
 966         btrfs_rm_dev_replace_remove_srcdev(src_device);
 967
 968         btrfs_rm_dev_replace_unblocked(fs_info);
 969
 970         /*
 971          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
 972          * update on-disk dev stats value during commit transaction
 973          */
 974         atomic_inc(&tgt_device->dev_stats_ccnt);
 975
 976         /*
 977          * this is again a consistent state where no dev_replace procedure
 978          * is running, the target device is part of the filesystem, the
 979          * source device is not part of the filesystem anymore and its 1st
 980          * superblock is scratched out so that it is no longer marked to
 981          * belong to this filesystem.
 982          */
 983         mutex_unlock(&fs_info->chunk_mutex);
 984         mutex_unlock(&fs_devices->device_list_mutex);
 985
 986         /* replace the sysfs entry */
 987         btrfs_sysfs_remove_device(src_device);
 988         btrfs_sysfs_update_devid(tgt_device);
 989         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
 990                 btrfs_scratch_superblocks(fs_info, src_device->bdev,
 991                                           src_device->name->str);
 992
 993         /* write back the superblocks */
 994         trans = btrfs_start_transaction(root, 0);
 995         if (!IS_ERR(trans))
 996                 btrfs_commit_transaction(trans);
 997
 998         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 999
1000         btrfs_rm_dev_replace_free_srcdev(src_device);
1001
1002         return 0;
1003 }
1004
1005 /*
1006  * Read progress of device replace status according to the state and last
1007  * stored position. The value format is the same as for
1008  * btrfs_dev_replace::progress_1000
1009  */
1010 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
1011 {
1012         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1013         u64 ret = 0;
1014
1015         switch (dev_replace->replace_state) {
1016         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1017         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1018                 ret = 0;
1019                 break;
1020         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1021                 ret = 1000;
1022                 break;
1023         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1024         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1025                 ret = div64_u64(dev_replace->cursor_left,
1026                                 div_u64(btrfs_device_get_total_bytes(
1027                                                 dev_replace->srcdev), 1000));
1028                 break;
1029         }
1030
1031         return ret;
1032 }
1033
1034 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
1035                               struct btrfs_ioctl_dev_replace_args *args)
1036 {
1037         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1038
1039         down_read(&dev_replace->rwsem);
1040         /* even if !dev_replace_is_valid, the values are good enough for
1041          * the replace_status ioctl */
1042         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1043         args->status.replace_state = dev_replace->replace_state;
1044         args->status.time_started = dev_replace->time_started;
1045         args->status.time_stopped = dev_replace->time_stopped;
1046         args->status.num_write_errors =
1047                 atomic64_read(&dev_replace->num_write_errors);
1048         args->status.num_uncorrectable_read_errors =
1049                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
1050         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
1051         up_read(&dev_replace->rwsem);
1052 }
1053
1054 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
1055 {
1056         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1057         struct btrfs_device *tgt_device = NULL;
1058         struct btrfs_device *src_device = NULL;
1059         struct btrfs_trans_handle *trans;
1060         struct btrfs_root *root = fs_info->tree_root;
1061         int result;
1062         int ret;
1063
1064         if (sb_rdonly(fs_info->sb))
1065                 return -EROFS;
1066
1067         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1068         down_write(&dev_replace->rwsem);
1069         switch (dev_replace->replace_state) {
1070         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1071         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1072         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1073                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1074                 up_write(&dev_replace->rwsem);
1075                 break;
1076         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1077                 tgt_device = dev_replace->tgtdev;
1078                 src_device = dev_replace->srcdev;
1079                 up_write(&dev_replace->rwsem);
1080                 ret = btrfs_scrub_cancel(fs_info);
1081                 if (ret < 0) {
1082                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1083                 } else {
1084                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1085                         /*
1086                          * btrfs_dev_replace_finishing() will handle the
1087                          * cleanup part
1088                          */
1089                         btrfs_info_in_rcu(fs_info,
1090                                 "dev_replace from %s (devid %llu) to %s canceled",
1091                                 btrfs_dev_name(src_device), src_device->devid,
1092                                 btrfs_dev_name(tgt_device));
1093                 }
1094                 break;
1095         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1096                 /*
1097                  * Scrub doing the replace isn't running so we need to do the
1098                  * cleanup step of btrfs_dev_replace_finishing() here
1099                  */
1100                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1101                 tgt_device = dev_replace->tgtdev;
1102                 src_device = dev_replace->srcdev;
1103                 dev_replace->tgtdev = NULL;
1104                 dev_replace->srcdev = NULL;
1105                 dev_replace->replace_state =
1106                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
1107                 dev_replace->time_stopped = ktime_get_real_seconds();
1108                 dev_replace->item_needs_writeback = 1;
1109
1110                 up_write(&dev_replace->rwsem);
1111
1112                 /* Scrub for replace must not be running in suspended state */
1113                 btrfs_scrub_cancel(fs_info);
1114
1115                 trans = btrfs_start_transaction(root, 0);
1116                 if (IS_ERR(trans)) {
1117                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1118                         return PTR_ERR(trans);
1119                 }
1120                 ret = btrfs_commit_transaction(trans);
1121                 WARN_ON(ret);
1122
1123                 btrfs_info_in_rcu(fs_info,
1124                 "suspended dev_replace from %s (devid %llu) to %s canceled",
1125                         btrfs_dev_name(src_device), src_device->devid,
1126                         btrfs_dev_name(tgt_device));
1127
1128                 if (tgt_device)
1129                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
1130                 break;
1131         default:
1132                 up_write(&dev_replace->rwsem);
1133                 result = -EINVAL;
1134         }
1135
1136         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1137         return result;
1138 }
1139
1140 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
1141 {
1142         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1143
1144         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1145         down_write(&dev_replace->rwsem);
1146
1147         switch (dev_replace->replace_state) {
1148         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1149         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1150         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1151         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1152                 break;
1153         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1154                 dev_replace->replace_state =
1155                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1156                 dev_replace->time_stopped = ktime_get_real_seconds();
1157                 dev_replace->item_needs_writeback = 1;
1158                 btrfs_info(fs_info, "suspending dev_replace for unmount");
1159                 break;
1160         }
1161
1162         up_write(&dev_replace->rwsem);
1163         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1164 }
1165
1166 /* resume dev_replace procedure that was interrupted by unmount */
1167 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
1168 {
1169         struct task_struct *task;
1170         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1171
1172         down_write(&dev_replace->rwsem);
1173
1174         switch (dev_replace->replace_state) {
1175         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1176         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1177         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1178                 up_write(&dev_replace->rwsem);
1179                 return 0;
1180         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1181                 break;
1182         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1183                 dev_replace->replace_state =
1184                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1185                 break;
1186         }
1187         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1188                 btrfs_info(fs_info,
1189                            "cannot continue dev_replace, tgtdev is missing");
1190                 btrfs_info(fs_info,
1191                            "you may cancel the operation after 'mount -o degraded'");
1192                 dev_replace->replace_state =
1193                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1194                 up_write(&dev_replace->rwsem);
1195                 return 0;
1196         }
1197         up_write(&dev_replace->rwsem);
1198
1199         /*
1200          * This could collide with a paused balance, but the exclusive op logic
1201          * should never allow both to start and pause. We don't want to allow
1202          * dev-replace to start anyway.
1203          */
1204         if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
1205                 down_write(&dev_replace->rwsem);
1206                 dev_replace->replace_state =
1207                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1208                 up_write(&dev_replace->rwsem);
1209                 btrfs_info(fs_info,
1210                 "cannot resume dev-replace, other exclusive operation running");
1211                 return 0;
1212         }
1213
1214         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1215         return PTR_ERR_OR_ZERO(task);
1216 }
1217
1218 static int btrfs_dev_replace_kthread(void *data)
1219 {
1220         struct btrfs_fs_info *fs_info = data;
1221         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1222         u64 progress;
1223         int ret;
1224
1225         progress = btrfs_dev_replace_progress(fs_info);
1226         progress = div_u64(progress, 10);
1227         btrfs_info_in_rcu(fs_info,
1228                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1229                 btrfs_dev_name(dev_replace->srcdev),
1230                 dev_replace->srcdev->devid,
1231                 btrfs_dev_name(dev_replace->tgtdev),
1232                 (unsigned int)progress);
1233
1234         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1235                               dev_replace->committed_cursor_left,
1236                               btrfs_device_get_total_bytes(dev_replace->srcdev),
1237                               &dev_replace->scrub_progress, 0, 1);
1238         ret = btrfs_dev_replace_finishing(fs_info, ret);
1239         WARN_ON(ret && ret != -ECANCELED);
1240
1241         btrfs_exclop_finish(fs_info);
1242         return 0;
1243 }
1244
1245 int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1246 {
1247         if (!dev_replace->is_valid)
1248                 return 0;
1249
1250         switch (dev_replace->replace_state) {
1251         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1252         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1253         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1254                 return 0;
1255         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1256         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1257                 /*
1258                  * return true even if tgtdev is missing (this is
1259                  * something that can happen if the dev_replace
1260                  * procedure is suspended by an umount and then
1261                  * the tgtdev is missing (or "btrfs dev scan") was
1262                  * not called and the filesystem is remounted
1263                  * in degraded state. This does not stop the
1264                  * dev_replace procedure. It needs to be canceled
1265                  * manually if the cancellation is wanted.
1266                  */
1267                 break;
1268         }
1269         return 1;
1270 }
1271
1272 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1273 {
1274         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1275         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1276 }
1277
1278 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1279 {
1280         while (1) {
1281                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1282                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1283                                      &fs_info->fs_state)))
1284                         break;
1285
1286                 btrfs_bio_counter_dec(fs_info);
1287                 wait_event(fs_info->dev_replace.replace_wait,
1288                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1289                                      &fs_info->fs_state));
1290         }
1291 }