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 bdev_handle *bdev_handle;
 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_handle = bdev_open_by_path(device_path, BLK_OPEN_WRITE,
 261                                         fs_info->bdev_holder, NULL);
 262         if (IS_ERR(bdev_handle)) {
 263                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
 264                 return PTR_ERR(bdev_handle);
 265         }
 266         bdev = bdev_handle->bdev;
 267
 268         if (!btrfs_check_device_zone_type(fs_info, bdev)) {
 269                 btrfs_err(fs_info,
 270                 "dev-replace: zoned type of target device mismatch with filesystem");
 271                 ret = -EINVAL;
 272                 goto error;
 273         }
 274
 275         sync_blockdev(bdev);
 276
 277         list_for_each_entry(device, &fs_devices->devices, dev_list) {
 278                 if (device->bdev == bdev) {
 279                         btrfs_err(fs_info,
 280                                   "target device is in the filesystem!");
 281                         ret = -EEXIST;
 282                         goto error;
 283                 }
 284         }
 285
 286
 287         if (bdev_nr_bytes(bdev) < btrfs_device_get_total_bytes(srcdev)) {
 288                 btrfs_err(fs_info,
 289                           "target device is smaller than source device!");
 290                 ret = -EINVAL;
 291                 goto error;
 292         }
 293
 294
 295         device = btrfs_alloc_device(NULL, &devid, NULL, device_path);
 296         if (IS_ERR(device)) {
 297                 ret = PTR_ERR(device);
 298                 goto error;
 299         }
 300
 301         ret = lookup_bdev(device_path, &device->devt);
 302         if (ret)
 303                 goto error;
 304
 305         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 306         device->generation = 0;
 307         device->io_width = fs_info->sectorsize;
 308         device->io_align = fs_info->sectorsize;
 309         device->sector_size = fs_info->sectorsize;
 310         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
 311         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
 312         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 313         device->commit_total_bytes = srcdev->commit_total_bytes;
 314         device->commit_bytes_used = device->bytes_used;
 315         device->fs_info = fs_info;
 316         device->bdev = bdev;
 317         device->bdev_handle = bdev_handle;
 318         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 319         set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 320         device->dev_stats_valid = 1;
 321         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 322         device->fs_devices = fs_devices;
 323
 324         ret = btrfs_get_dev_zone_info(device, false);
 325         if (ret)
 326                 goto error;
 327
 328         mutex_lock(&fs_devices->device_list_mutex);
 329         list_add(&device->dev_list, &fs_devices->devices);
 330         fs_devices->num_devices++;
 331         fs_devices->open_devices++;
 332         mutex_unlock(&fs_devices->device_list_mutex);
 333
 334         *device_out = device;
 335         return 0;
 336
 337 error:
 338         bdev_release(bdev_handle);
 339         return ret;
 340 }
 341
 342 /*
 343  * called from commit_transaction. Writes changed device replace state to
 344  * disk.
 345  */
 346 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
 347 {
 348         struct btrfs_fs_info *fs_info = trans->fs_info;
 349         int ret;
 350         struct btrfs_root *dev_root = fs_info->dev_root;
 351         struct btrfs_path *path;
 352         struct btrfs_key key;
 353         struct extent_buffer *eb;
 354         struct btrfs_dev_replace_item *ptr;
 355         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 356
 357         down_read(&dev_replace->rwsem);
 358         if (!dev_replace->is_valid ||
 359             !dev_replace->item_needs_writeback) {
 360                 up_read(&dev_replace->rwsem);
 361                 return 0;
 362         }
 363         up_read(&dev_replace->rwsem);
 364
 365         key.objectid = 0;
 366         key.type = BTRFS_DEV_REPLACE_KEY;
 367         key.offset = 0;
 368
 369         path = btrfs_alloc_path();
 370         if (!path) {
 371                 ret = -ENOMEM;
 372                 goto out;
 373         }
 374         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
 375         if (ret < 0) {
 376                 btrfs_warn(fs_info,
 377                            "error %d while searching for dev_replace item!",
 378                            ret);
 379                 goto out;
 380         }
 381
 382         if (ret == 0 &&
 383             btrfs_item_size(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 384                 /*
 385                  * need to delete old one and insert a new one.
 386                  * Since no attempt is made to recover any old state, if the
 387                  * dev_replace state is 'running', the data on the target
 388                  * drive is lost.
 389                  * It would be possible to recover the state: just make sure
 390                  * that the beginning of the item is never changed and always
 391                  * contains all the essential information. Then read this
 392                  * minimal set of information and use it as a base for the
 393                  * new state.
 394                  */
 395                 ret = btrfs_del_item(trans, dev_root, path);
 396                 if (ret != 0) {
 397                         btrfs_warn(fs_info,
 398                                    "delete too small dev_replace item failed %d!",
 399                                    ret);
 400                         goto out;
 401                 }
 402                 ret = 1;
 403         }
 404
 405         if (ret == 1) {
 406                 /* need to insert a new item */
 407                 btrfs_release_path(path);
 408                 ret = btrfs_insert_empty_item(trans, dev_root, path,
 409                                               &key, sizeof(*ptr));
 410                 if (ret < 0) {
 411                         btrfs_warn(fs_info,
 412                                    "insert dev_replace item failed %d!", ret);
 413                         goto out;
 414                 }
 415         }
 416
 417         eb = path->nodes[0];
 418         ptr = btrfs_item_ptr(eb, path->slots[0],
 419                              struct btrfs_dev_replace_item);
 420
 421         down_write(&dev_replace->rwsem);
 422         if (dev_replace->srcdev)
 423                 btrfs_set_dev_replace_src_devid(eb, ptr,
 424                         dev_replace->srcdev->devid);
 425         else
 426                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 427         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 428                 dev_replace->cont_reading_from_srcdev_mode);
 429         btrfs_set_dev_replace_replace_state(eb, ptr,
 430                 dev_replace->replace_state);
 431         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 432         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 433         btrfs_set_dev_replace_num_write_errors(eb, ptr,
 434                 atomic64_read(&dev_replace->num_write_errors));
 435         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 436                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 437         dev_replace->cursor_left_last_write_of_item =
 438                 dev_replace->cursor_left;
 439         btrfs_set_dev_replace_cursor_left(eb, ptr,
 440                 dev_replace->cursor_left_last_write_of_item);
 441         btrfs_set_dev_replace_cursor_right(eb, ptr,
 442                 dev_replace->cursor_right);
 443         dev_replace->item_needs_writeback = 0;
 444         up_write(&dev_replace->rwsem);
 445
 446         btrfs_mark_buffer_dirty(trans, eb);
 447
 448 out:
 449         btrfs_free_path(path);
 450
 451         return ret;
 452 }
 453
 454 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 455                                     struct btrfs_device *src_dev)
 456 {
 457         struct btrfs_path *path;
 458         struct btrfs_key key;
 459         struct btrfs_key found_key;
 460         struct btrfs_root *root = fs_info->dev_root;
 461         struct btrfs_dev_extent *dev_extent = NULL;
 462         struct btrfs_block_group *cache;
 463         struct btrfs_trans_handle *trans;
 464         int iter_ret = 0;
 465         int ret = 0;
 466         u64 chunk_offset;
 467
 468         /* Do not use "to_copy" on non zoned filesystem for now */
 469         if (!btrfs_is_zoned(fs_info))
 470                 return 0;
 471
 472         mutex_lock(&fs_info->chunk_mutex);
 473
 474         /* Ensure we don't have pending new block group */
 475         spin_lock(&fs_info->trans_lock);
 476         while (fs_info->running_transaction &&
 477                !list_empty(&fs_info->running_transaction->dev_update_list)) {
 478                 spin_unlock(&fs_info->trans_lock);
 479                 mutex_unlock(&fs_info->chunk_mutex);
 480                 trans = btrfs_attach_transaction(root);
 481                 if (IS_ERR(trans)) {
 482                         ret = PTR_ERR(trans);
 483                         mutex_lock(&fs_info->chunk_mutex);
 484                         if (ret == -ENOENT) {
 485                                 spin_lock(&fs_info->trans_lock);
 486                                 continue;
 487                         } else {
 488                                 goto unlock;
 489                         }
 490                 }
 491
 492                 ret = btrfs_commit_transaction(trans);
 493                 mutex_lock(&fs_info->chunk_mutex);
 494                 if (ret)
 495                         goto unlock;
 496
 497                 spin_lock(&fs_info->trans_lock);
 498         }
 499         spin_unlock(&fs_info->trans_lock);
 500
 501         path = btrfs_alloc_path();
 502         if (!path) {
 503                 ret = -ENOMEM;
 504                 goto unlock;
 505         }
 506
 507         path->reada = READA_FORWARD;
 508         path->search_commit_root = 1;
 509         path->skip_locking = 1;
 510
 511         key.objectid = src_dev->devid;
 512         key.type = BTRFS_DEV_EXTENT_KEY;
 513         key.offset = 0;
 514
 515         btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 516                 struct extent_buffer *leaf = path->nodes[0];
 517
 518                 if (found_key.objectid != src_dev->devid)
 519                         break;
 520
 521                 if (found_key.type != BTRFS_DEV_EXTENT_KEY)
 522                         break;
 523
 524                 if (found_key.offset < key.offset)
 525                         break;
 526
 527                 dev_extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
 528
 529                 chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
 530
 531                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 532                 if (!cache)
 533                         continue;
 534
 535                 set_bit(BLOCK_GROUP_FLAG_TO_COPY, &cache->runtime_flags);
 536                 btrfs_put_block_group(cache);
 537         }
 538         if (iter_ret < 0)
 539                 ret = iter_ret;
 540
 541         btrfs_free_path(path);
 542 unlock:
 543         mutex_unlock(&fs_info->chunk_mutex);
 544
 545         return ret;
 546 }
 547
 548 bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev,
 549                                       struct btrfs_block_group *cache,
 550                                       u64 physical)
 551 {
 552         struct btrfs_fs_info *fs_info = cache->fs_info;
 553         struct extent_map *em;
 554         struct map_lookup *map;
 555         u64 chunk_offset = cache->start;
 556         int num_extents, cur_extent;
 557         int i;
 558
 559         /* Do not use "to_copy" on non zoned filesystem for now */
 560         if (!btrfs_is_zoned(fs_info))
 561                 return true;
 562
 563         spin_lock(&cache->lock);
 564         if (test_bit(BLOCK_GROUP_FLAG_REMOVED, &cache->runtime_flags)) {
 565                 spin_unlock(&cache->lock);
 566                 return true;
 567         }
 568         spin_unlock(&cache->lock);
 569
 570         em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
 571         ASSERT(!IS_ERR(em));
 572         map = em->map_lookup;
 573
 574         num_extents = 0;
 575         cur_extent = 0;
 576         for (i = 0; i < map->num_stripes; i++) {
 577                 /* We have more device extent to copy */
 578                 if (srcdev != map->stripes[i].dev)
 579                         continue;
 580
 581                 num_extents++;
 582                 if (physical == map->stripes[i].physical)
 583                         cur_extent = i;
 584         }
 585
 586         free_extent_map(em);
 587
 588         if (num_extents > 1 && cur_extent < num_extents - 1) {
 589                 /*
 590                  * Has more stripes on this device. Keep this block group
 591                  * readonly until we finish all the stripes.
 592                  */
 593                 return false;
 594         }
 595
 596         /* Last stripe on this device */
 597         clear_bit(BLOCK_GROUP_FLAG_TO_COPY, &cache->runtime_flags);
 598
 599         return true;
 600 }
 601
 602 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 603                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
 604                 int read_src)
 605 {
 606         struct btrfs_root *root = fs_info->dev_root;
 607         struct btrfs_trans_handle *trans;
 608         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 609         int ret;
 610         struct btrfs_device *tgt_device = NULL;
 611         struct btrfs_device *src_device = NULL;
 612
 613         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
 614                                                   srcdev_name);
 615         if (IS_ERR(src_device))
 616                 return PTR_ERR(src_device);
 617
 618         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
 619                 btrfs_warn_in_rcu(fs_info,
 620           "cannot replace device %s (devid %llu) due to active swapfile",
 621                         btrfs_dev_name(src_device), src_device->devid);
 622                 return -ETXTBSY;
 623         }
 624
 625         /*
 626          * Here we commit the transaction to make sure commit_total_bytes
 627          * of all the devices are updated.
 628          */
 629         trans = btrfs_attach_transaction(root);
 630         if (!IS_ERR(trans)) {
 631                 ret = btrfs_commit_transaction(trans);
 632                 if (ret)
 633                         return ret;
 634         } else if (PTR_ERR(trans) != -ENOENT) {
 635                 return PTR_ERR(trans);
 636         }
 637
 638         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
 639                                             src_device, &tgt_device);
 640         if (ret)
 641                 return ret;
 642
 643         ret = mark_block_group_to_copy(fs_info, src_device);
 644         if (ret)
 645                 return ret;
 646
 647         down_write(&dev_replace->rwsem);
 648         switch (dev_replace->replace_state) {
 649         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 650         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 651         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 652                 break;
 653         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 654         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 655                 ASSERT(0);
 656                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 657                 up_write(&dev_replace->rwsem);
 658                 goto leave;
 659         }
 660
 661         dev_replace->cont_reading_from_srcdev_mode = read_src;
 662         dev_replace->srcdev = src_device;
 663         dev_replace->tgtdev = tgt_device;
 664
 665         btrfs_info_in_rcu(fs_info,
 666                       "dev_replace from %s (devid %llu) to %s started",
 667                       btrfs_dev_name(src_device),
 668                       src_device->devid,
 669                       btrfs_dev_name(tgt_device));
 670
 671         /*
 672          * from now on, the writes to the srcdev are all duplicated to
 673          * go to the tgtdev as well (refer to btrfs_map_block()).
 674          */
 675         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 676         dev_replace->time_started = ktime_get_real_seconds();
 677         dev_replace->cursor_left = 0;
 678         dev_replace->committed_cursor_left = 0;
 679         dev_replace->cursor_left_last_write_of_item = 0;
 680         dev_replace->cursor_right = 0;
 681         dev_replace->is_valid = 1;
 682         dev_replace->item_needs_writeback = 1;
 683         atomic64_set(&dev_replace->num_write_errors, 0);
 684         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 685         up_write(&dev_replace->rwsem);
 686
 687         ret = btrfs_sysfs_add_device(tgt_device);
 688         if (ret)
 689                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
 690
 691         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 692
 693         /*
 694          * Commit dev_replace state and reserve 1 item for it.
 695          * This is crucial to ensure we won't miss copying extents for new block
 696          * groups that are allocated after we started the device replace, and
 697          * must be done after setting up the device replace state.
 698          */
 699         trans = btrfs_start_transaction(root, 1);
 700         if (IS_ERR(trans)) {
 701                 ret = PTR_ERR(trans);
 702                 down_write(&dev_replace->rwsem);
 703                 dev_replace->replace_state =
 704                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 705                 dev_replace->srcdev = NULL;
 706                 dev_replace->tgtdev = NULL;
 707                 up_write(&dev_replace->rwsem);
 708                 goto leave;
 709         }
 710
 711         ret = btrfs_commit_transaction(trans);
 712         WARN_ON(ret);
 713
 714         /* the disk copy procedure reuses the scrub code */
 715         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 716                               btrfs_device_get_total_bytes(src_device),
 717                               &dev_replace->scrub_progress, 0, 1);
 718
 719         ret = btrfs_dev_replace_finishing(fs_info, ret);
 720         if (ret == -EINPROGRESS)
 721                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
 722
 723         return ret;
 724
 725 leave:
 726         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 727         return ret;
 728 }
 729
 730 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 731                             struct btrfs_ioctl_dev_replace_args *args)
 732 {
 733         int ret;
 734
 735         switch (args->start.cont_reading_from_srcdev_mode) {
 736         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 737         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 738                 break;
 739         default:
 740                 return -EINVAL;
 741         }
 742
 743         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 744             args->start.tgtdev_name[0] == '\0')
 745                 return -EINVAL;
 746
 747         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 748                                         args->start.srcdevid,
 749                                         args->start.srcdev_name,
 750                                         args->start.cont_reading_from_srcdev_mode);
 751         args->result = ret;
 752         /* don't warn if EINPROGRESS, someone else might be running scrub */
 753         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
 754             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
 755                 return 0;
 756
 757         return ret;
 758 }
 759
 760 /*
 761  * blocked until all in-flight bios operations are finished.
 762  */
 763 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
 764 {
 765         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 766         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
 767                    &fs_info->dev_replace.bio_counter));
 768 }
 769
 770 /*
 771  * we have removed target device, it is safe to allow new bios request.
 772  */
 773 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
 774 {
 775         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 776         wake_up(&fs_info->dev_replace.replace_wait);
 777 }
 778
 779 /*
 780  * When finishing the device replace, before swapping the source device with the
 781  * target device we must update the chunk allocation state in the target device,
 782  * as it is empty because replace works by directly copying the chunks and not
 783  * through the normal chunk allocation path.
 784  */
 785 static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
 786                                         struct btrfs_device *tgtdev)
 787 {
 788         struct extent_state *cached_state = NULL;
 789         u64 start = 0;
 790         u64 found_start;
 791         u64 found_end;
 792         int ret = 0;
 793
 794         lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
 795
 796         while (find_first_extent_bit(&srcdev->alloc_state, start,
 797                                      &found_start, &found_end,
 798                                      CHUNK_ALLOCATED, &cached_state)) {
 799                 ret = set_extent_bit(&tgtdev->alloc_state, found_start,
 800                                      found_end, CHUNK_ALLOCATED, NULL);
 801                 if (ret)
 802                         break;
 803                 start = found_end + 1;
 804         }
 805
 806         free_extent_state(cached_state);
 807         return ret;
 808 }
 809
 810 static void btrfs_dev_replace_update_device_in_mapping_tree(
 811                                                 struct btrfs_fs_info *fs_info,
 812                                                 struct btrfs_device *srcdev,
 813                                                 struct btrfs_device *tgtdev)
 814 {
 815         struct extent_map_tree *em_tree = &fs_info->mapping_tree;
 816         struct extent_map *em;
 817         struct map_lookup *map;
 818         u64 start = 0;
 819         int i;
 820
 821         write_lock(&em_tree->lock);
 822         do {
 823                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
 824                 if (!em)
 825                         break;
 826                 map = em->map_lookup;
 827                 for (i = 0; i < map->num_stripes; i++)
 828                         if (srcdev == map->stripes[i].dev)
 829                                 map->stripes[i].dev = tgtdev;
 830                 start = em->start + em->len;
 831                 free_extent_map(em);
 832         } while (start);
 833         write_unlock(&em_tree->lock);
 834 }
 835
 836 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 837                                        int scrub_ret)
 838 {
 839         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 840         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 841         struct btrfs_device *tgt_device;
 842         struct btrfs_device *src_device;
 843         struct btrfs_root *root = fs_info->tree_root;
 844         u8 uuid_tmp[BTRFS_UUID_SIZE];
 845         struct btrfs_trans_handle *trans;
 846         int ret = 0;
 847
 848         /* don't allow cancel or unmount to disturb the finishing procedure */
 849         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 850
 851         down_read(&dev_replace->rwsem);
 852         /* was the operation canceled, or is it finished? */
 853         if (dev_replace->replace_state !=
 854             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 855                 up_read(&dev_replace->rwsem);
 856                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 857                 return 0;
 858         }
 859
 860         tgt_device = dev_replace->tgtdev;
 861         src_device = dev_replace->srcdev;
 862         up_read(&dev_replace->rwsem);
 863
 864         /*
 865          * flush all outstanding I/O and inode extent mappings before the
 866          * copy operation is declared as being finished
 867          */
 868         ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 869         if (ret) {
 870                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 871                 return ret;
 872         }
 873         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 874
 875         /*
 876          * We have to use this loop approach because at this point src_device
 877          * has to be available for transaction commit to complete, yet new
 878          * chunks shouldn't be allocated on the device.
 879          */
 880         while (1) {
 881                 trans = btrfs_start_transaction(root, 0);
 882                 if (IS_ERR(trans)) {
 883                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 884                         return PTR_ERR(trans);
 885                 }
 886                 ret = btrfs_commit_transaction(trans);
 887                 WARN_ON(ret);
 888
 889                 /* Prevent write_all_supers() during the finishing procedure */
 890                 mutex_lock(&fs_devices->device_list_mutex);
 891                 /* Prevent new chunks being allocated on the source device */
 892                 mutex_lock(&fs_info->chunk_mutex);
 893
 894                 if (!list_empty(&src_device->post_commit_list)) {
 895                         mutex_unlock(&fs_devices->device_list_mutex);
 896                         mutex_unlock(&fs_info->chunk_mutex);
 897                 } else {
 898                         break;
 899                 }
 900         }
 901
 902         down_write(&dev_replace->rwsem);
 903         dev_replace->replace_state =
 904                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 905                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 906         dev_replace->tgtdev = NULL;
 907         dev_replace->srcdev = NULL;
 908         dev_replace->time_stopped = ktime_get_real_seconds();
 909         dev_replace->item_needs_writeback = 1;
 910
 911         /*
 912          * Update allocation state in the new device and replace the old device
 913          * with the new one in the mapping tree.
 914          */
 915         if (!scrub_ret) {
 916                 scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
 917                 if (scrub_ret)
 918                         goto error;
 919                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 920                                                                 src_device,
 921                                                                 tgt_device);
 922         } else {
 923                 if (scrub_ret != -ECANCELED)
 924                         btrfs_err_in_rcu(fs_info,
 925                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 926                                  btrfs_dev_name(src_device),
 927                                  src_device->devid,
 928                                  btrfs_dev_name(tgt_device), scrub_ret);
 929 error:
 930                 up_write(&dev_replace->rwsem);
 931                 mutex_unlock(&fs_info->chunk_mutex);
 932                 mutex_unlock(&fs_devices->device_list_mutex);
 933                 btrfs_rm_dev_replace_blocked(fs_info);
 934                 if (tgt_device)
 935                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 936                 btrfs_rm_dev_replace_unblocked(fs_info);
 937                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 938
 939                 return scrub_ret;
 940         }
 941
 942         btrfs_info_in_rcu(fs_info,
 943                           "dev_replace from %s (devid %llu) to %s finished",
 944                           btrfs_dev_name(src_device),
 945                           src_device->devid,
 946                           btrfs_dev_name(tgt_device));
 947         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 948         tgt_device->devid = src_device->devid;
 949         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 950         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 951         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 952         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 953         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
 954         btrfs_device_set_disk_total_bytes(tgt_device,
 955                                           src_device->disk_total_bytes);
 956         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 957         tgt_device->commit_bytes_used = src_device->bytes_used;
 958
 959         btrfs_assign_next_active_device(src_device, tgt_device);
 960
 961         list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
 962         fs_devices->rw_devices++;
 963
 964         up_write(&dev_replace->rwsem);
 965         btrfs_rm_dev_replace_blocked(fs_info);
 966
 967         btrfs_rm_dev_replace_remove_srcdev(src_device);
 968
 969         btrfs_rm_dev_replace_unblocked(fs_info);
 970
 971         /*
 972          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
 973          * update on-disk dev stats value during commit transaction
 974          */
 975         atomic_inc(&tgt_device->dev_stats_ccnt);
 976
 977         /*
 978          * this is again a consistent state where no dev_replace procedure
 979          * is running, the target device is part of the filesystem, the
 980          * source device is not part of the filesystem anymore and its 1st
 981          * superblock is scratched out so that it is no longer marked to
 982          * belong to this filesystem.
 983          */
 984         mutex_unlock(&fs_info->chunk_mutex);
 985         mutex_unlock(&fs_devices->device_list_mutex);
 986
 987         /* replace the sysfs entry */
 988         btrfs_sysfs_remove_device(src_device);
 989         btrfs_sysfs_update_devid(tgt_device);
 990         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
 991                 btrfs_scratch_superblocks(fs_info, src_device->bdev,
 992                                           src_device->name->str);
 993
 994         /* write back the superblocks */
 995         trans = btrfs_start_transaction(root, 0);
 996         if (!IS_ERR(trans))
 997                 btrfs_commit_transaction(trans);
 998
 999         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1000
1001         btrfs_rm_dev_replace_free_srcdev(src_device);
1002
1003         return 0;
1004 }
1005
1006 /*
1007  * Read progress of device replace status according to the state and last
1008  * stored position. The value format is the same as for
1009  * btrfs_dev_replace::progress_1000
1010  */
1011 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
1012 {
1013         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1014         u64 ret = 0;
1015
1016         switch (dev_replace->replace_state) {
1017         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1018         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1019                 ret = 0;
1020                 break;
1021         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1022                 ret = 1000;
1023                 break;
1024         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1025         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1026                 ret = div64_u64(dev_replace->cursor_left,
1027                                 div_u64(btrfs_device_get_total_bytes(
1028                                                 dev_replace->srcdev), 1000));
1029                 break;
1030         }
1031
1032         return ret;
1033 }
1034
1035 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
1036                               struct btrfs_ioctl_dev_replace_args *args)
1037 {
1038         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1039
1040         down_read(&dev_replace->rwsem);
1041         /* even if !dev_replace_is_valid, the values are good enough for
1042          * the replace_status ioctl */
1043         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1044         args->status.replace_state = dev_replace->replace_state;
1045         args->status.time_started = dev_replace->time_started;
1046         args->status.time_stopped = dev_replace->time_stopped;
1047         args->status.num_write_errors =
1048                 atomic64_read(&dev_replace->num_write_errors);
1049         args->status.num_uncorrectable_read_errors =
1050                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
1051         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
1052         up_read(&dev_replace->rwsem);
1053 }
1054
1055 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
1056 {
1057         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1058         struct btrfs_device *tgt_device = NULL;
1059         struct btrfs_device *src_device = NULL;
1060         struct btrfs_trans_handle *trans;
1061         struct btrfs_root *root = fs_info->tree_root;
1062         int result;
1063         int ret;
1064
1065         if (sb_rdonly(fs_info->sb))
1066                 return -EROFS;
1067
1068         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1069         down_write(&dev_replace->rwsem);
1070         switch (dev_replace->replace_state) {
1071         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1072         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1073         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1074                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1075                 up_write(&dev_replace->rwsem);
1076                 break;
1077         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1078                 tgt_device = dev_replace->tgtdev;
1079                 src_device = dev_replace->srcdev;
1080                 up_write(&dev_replace->rwsem);
1081                 ret = btrfs_scrub_cancel(fs_info);
1082                 if (ret < 0) {
1083                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1084                 } else {
1085                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1086                         /*
1087                          * btrfs_dev_replace_finishing() will handle the
1088                          * cleanup part
1089                          */
1090                         btrfs_info_in_rcu(fs_info,
1091                                 "dev_replace from %s (devid %llu) to %s canceled",
1092                                 btrfs_dev_name(src_device), src_device->devid,
1093                                 btrfs_dev_name(tgt_device));
1094                 }
1095                 break;
1096         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1097                 /*
1098                  * Scrub doing the replace isn't running so we need to do the
1099                  * cleanup step of btrfs_dev_replace_finishing() here
1100                  */
1101                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1102                 tgt_device = dev_replace->tgtdev;
1103                 src_device = dev_replace->srcdev;
1104                 dev_replace->tgtdev = NULL;
1105                 dev_replace->srcdev = NULL;
1106                 dev_replace->replace_state =
1107                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
1108                 dev_replace->time_stopped = ktime_get_real_seconds();
1109                 dev_replace->item_needs_writeback = 1;
1110
1111                 up_write(&dev_replace->rwsem);
1112
1113                 /* Scrub for replace must not be running in suspended state */
1114                 btrfs_scrub_cancel(fs_info);
1115
1116                 trans = btrfs_start_transaction(root, 0);
1117                 if (IS_ERR(trans)) {
1118                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1119                         return PTR_ERR(trans);
1120                 }
1121                 ret = btrfs_commit_transaction(trans);
1122                 WARN_ON(ret);
1123
1124                 btrfs_info_in_rcu(fs_info,
1125                 "suspended dev_replace from %s (devid %llu) to %s canceled",
1126                         btrfs_dev_name(src_device), src_device->devid,
1127                         btrfs_dev_name(tgt_device));
1128
1129                 if (tgt_device)
1130                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
1131                 break;
1132         default:
1133                 up_write(&dev_replace->rwsem);
1134                 result = -EINVAL;
1135         }
1136
1137         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1138         return result;
1139 }
1140
1141 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
1142 {
1143         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1144
1145         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1146         down_write(&dev_replace->rwsem);
1147
1148         switch (dev_replace->replace_state) {
1149         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1150         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1151         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1152         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1153                 break;
1154         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1155                 dev_replace->replace_state =
1156                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1157                 dev_replace->time_stopped = ktime_get_real_seconds();
1158                 dev_replace->item_needs_writeback = 1;
1159                 btrfs_info(fs_info, "suspending dev_replace for unmount");
1160                 break;
1161         }
1162
1163         up_write(&dev_replace->rwsem);
1164         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1165 }
1166
1167 /* resume dev_replace procedure that was interrupted by unmount */
1168 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
1169 {
1170         struct task_struct *task;
1171         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1172
1173         down_write(&dev_replace->rwsem);
1174
1175         switch (dev_replace->replace_state) {
1176         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1177         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1178         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1179                 up_write(&dev_replace->rwsem);
1180                 return 0;
1181         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1182                 break;
1183         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1184                 dev_replace->replace_state =
1185                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1186                 break;
1187         }
1188         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1189                 btrfs_info(fs_info,
1190                            "cannot continue dev_replace, tgtdev is missing");
1191                 btrfs_info(fs_info,
1192                            "you may cancel the operation after 'mount -o degraded'");
1193                 dev_replace->replace_state =
1194                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1195                 up_write(&dev_replace->rwsem);
1196                 return 0;
1197         }
1198         up_write(&dev_replace->rwsem);
1199
1200         /*
1201          * This could collide with a paused balance, but the exclusive op logic
1202          * should never allow both to start and pause. We don't want to allow
1203          * dev-replace to start anyway.
1204          */
1205         if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
1206                 down_write(&dev_replace->rwsem);
1207                 dev_replace->replace_state =
1208                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1209                 up_write(&dev_replace->rwsem);
1210                 btrfs_info(fs_info,
1211                 "cannot resume dev-replace, other exclusive operation running");
1212                 return 0;
1213         }
1214
1215         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1216         return PTR_ERR_OR_ZERO(task);
1217 }
1218
1219 static int btrfs_dev_replace_kthread(void *data)
1220 {
1221         struct btrfs_fs_info *fs_info = data;
1222         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1223         u64 progress;
1224         int ret;
1225
1226         progress = btrfs_dev_replace_progress(fs_info);
1227         progress = div_u64(progress, 10);
1228         btrfs_info_in_rcu(fs_info,
1229                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1230                 btrfs_dev_name(dev_replace->srcdev),
1231                 dev_replace->srcdev->devid,
1232                 btrfs_dev_name(dev_replace->tgtdev),
1233                 (unsigned int)progress);
1234
1235         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1236                               dev_replace->committed_cursor_left,
1237                               btrfs_device_get_total_bytes(dev_replace->srcdev),
1238                               &dev_replace->scrub_progress, 0, 1);
1239         ret = btrfs_dev_replace_finishing(fs_info, ret);
1240         WARN_ON(ret && ret != -ECANCELED);
1241
1242         btrfs_exclop_finish(fs_info);
1243         return 0;
1244 }
1245
1246 int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1247 {
1248         if (!dev_replace->is_valid)
1249                 return 0;
1250
1251         switch (dev_replace->replace_state) {
1252         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1253         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1254         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1255                 return 0;
1256         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1257         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1258                 /*
1259                  * return true even if tgtdev is missing (this is
1260                  * something that can happen if the dev_replace
1261                  * procedure is suspended by an umount and then
1262                  * the tgtdev is missing (or "btrfs dev scan") was
1263                  * not called and the filesystem is remounted
1264                  * in degraded state. This does not stop the
1265                  * dev_replace procedure. It needs to be canceled
1266                  * manually if the cancellation is wanted.
1267                  */
1268                 break;
1269         }
1270         return 1;
1271 }
1272
1273 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1274 {
1275         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1276         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1277 }
1278
1279 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1280 {
1281         while (1) {
1282                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1283                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1284                                      &fs_info->fs_state)))
1285                         break;
1286
1287                 btrfs_bio_counter_dec(fs_info);
1288                 wait_event(fs_info->dev_replace.replace_wait,
1289                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1290                                      &fs_info->fs_state));
1291         }
1292 }