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 "rcu-string.h"
  22 #include "dev-replace.h"
  23 #include "sysfs.h"
  24 #include "zoned.h"
  25 #include "block-group.h"
  26
  27 /*
  28  * Device replace overview
  29  *
  30  * [Objective]
  31  * To copy all extents (both new and on-disk) from source device to target
  32  * device, while still keeping the filesystem read-write.
  33  *
  34  * [Method]
  35  * There are two main methods involved:
  36  *
  37  * - Write duplication
  38  *
  39  *   All new writes will be written to both target and source devices, so even
  40  *   if replace gets canceled, sources device still contains up-to-date data.
  41  *
  42  *   Location:          handle_ops_on_dev_replace() from __btrfs_map_block()
  43  *   Start:             btrfs_dev_replace_start()
  44  *   End:               btrfs_dev_replace_finishing()
  45  *   Content:           Latest data/metadata
  46  *
  47  * - Copy existing extents
  48  *
  49  *   This happens by re-using scrub facility, as scrub also iterates through
  50  *   existing extents from commit root.
  51  *
  52  *   Location:          scrub_write_block_to_dev_replace() from
  53  *                      scrub_block_complete()
  54  *   Content:           Data/meta from commit root.
  55  *
  56  * Due to the content difference, we need to avoid nocow write when dev-replace
  57  * is happening.  This is done by marking the block group read-only and waiting
  58  * for NOCOW writes.
  59  *
  60  * After replace is done, the finishing part is done by swapping the target and
  61  * source devices.
  62  *
  63  *   Location:          btrfs_dev_replace_update_device_in_mapping_tree() from
  64  *                      btrfs_dev_replace_finishing()
  65  */
  66
  67 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
  68                                        int scrub_ret);
  69 static int btrfs_dev_replace_kthread(void *data);
  70
  71 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
  72 {
  73         struct btrfs_dev_lookup_args args = { .devid = BTRFS_DEV_REPLACE_DEVID };
  74         struct btrfs_key key;
  75         struct btrfs_root *dev_root = fs_info->dev_root;
  76         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
  77         struct extent_buffer *eb;
  78         int slot;
  79         int ret = 0;
  80         struct btrfs_path *path = NULL;
  81         int item_size;
  82         struct btrfs_dev_replace_item *ptr;
  83         u64 src_devid;
  84
  85         if (!dev_root)
  86                 return 0;
  87
  88         path = btrfs_alloc_path();
  89         if (!path) {
  90                 ret = -ENOMEM;
  91                 goto out;
  92         }
  93
  94         key.objectid = 0;
  95         key.type = BTRFS_DEV_REPLACE_KEY;
  96         key.offset = 0;
  97         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
  98         if (ret) {
  99 no_valid_dev_replace_entry_found:
 100                 /*
 101                  * We don't have a replace item or it's corrupted.  If there is
 102                  * a replace target, fail the mount.
 103                  */
 104                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
 105                         btrfs_err(fs_info,
 106                         "found replace target device without a valid replace item");
 107                         ret = -EUCLEAN;
 108                         goto out;
 109                 }
 110                 ret = 0;
 111                 dev_replace->replace_state =
 112                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 113                 dev_replace->cont_reading_from_srcdev_mode =
 114                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 115                 dev_replace->time_started = 0;
 116                 dev_replace->time_stopped = 0;
 117                 atomic64_set(&dev_replace->num_write_errors, 0);
 118                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 119                 dev_replace->cursor_left = 0;
 120                 dev_replace->committed_cursor_left = 0;
 121                 dev_replace->cursor_left_last_write_of_item = 0;
 122                 dev_replace->cursor_right = 0;
 123                 dev_replace->srcdev = NULL;
 124                 dev_replace->tgtdev = NULL;
 125                 dev_replace->is_valid = 0;
 126                 dev_replace->item_needs_writeback = 0;
 127                 goto out;
 128         }
 129         slot = path->slots[0];
 130         eb = path->nodes[0];
 131         item_size = btrfs_item_size(eb, slot);
 132         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 133
 134         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 135                 btrfs_warn(fs_info,
 136                         "dev_replace entry found has unexpected size, ignore entry");
 137                 goto no_valid_dev_replace_entry_found;
 138         }
 139
 140         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 141         dev_replace->cont_reading_from_srcdev_mode =
 142                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 143         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 144         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 145         dev_replace->time_stopped =
 146                 btrfs_dev_replace_time_stopped(eb, ptr);
 147         atomic64_set(&dev_replace->num_write_errors,
 148                      btrfs_dev_replace_num_write_errors(eb, ptr));
 149         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 150                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 151         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 152         dev_replace->committed_cursor_left = dev_replace->cursor_left;
 153         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
 154         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
 155         dev_replace->is_valid = 1;
 156
 157         dev_replace->item_needs_writeback = 0;
 158         switch (dev_replace->replace_state) {
 159         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 160         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 161         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 162                 /*
 163                  * We don't have an active replace item but if there is a
 164                  * replace target, fail the mount.
 165                  */
 166                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
 167                         btrfs_err(fs_info,
 168                         "replace devid present without an active replace item");
 169                         ret = -EUCLEAN;
 170                 } else {
 171                         dev_replace->srcdev = NULL;
 172                         dev_replace->tgtdev = NULL;
 173                 }
 174                 break;
 175         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 176         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 177                 dev_replace->tgtdev = btrfs_find_device(fs_info->fs_devices, &args);
 178                 args.devid = src_devid;
 179                 dev_replace->srcdev = btrfs_find_device(fs_info->fs_devices, &args);
 180
 181                 /*
 182                  * allow 'btrfs dev replace_cancel' if src/tgt device is
 183                  * missing
 184                  */
 185                 if (!dev_replace->srcdev &&
 186                     !btrfs_test_opt(fs_info, DEGRADED)) {
 187                         ret = -EIO;
 188                         btrfs_warn(fs_info,
 189                            "cannot mount because device replace operation is ongoing and");
 190                         btrfs_warn(fs_info,
 191                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 192                            src_devid);
 193                 }
 194                 if (!dev_replace->tgtdev &&
 195                     !btrfs_test_opt(fs_info, DEGRADED)) {
 196                         ret = -EIO;
 197                         btrfs_warn(fs_info,
 198                            "cannot mount because device replace operation is ongoing and");
 199                         btrfs_warn(fs_info,
 200                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 201                                 BTRFS_DEV_REPLACE_DEVID);
 202                 }
 203                 if (dev_replace->tgtdev) {
 204                         if (dev_replace->srcdev) {
 205                                 dev_replace->tgtdev->total_bytes =
 206                                         dev_replace->srcdev->total_bytes;
 207                                 dev_replace->tgtdev->disk_total_bytes =
 208                                         dev_replace->srcdev->disk_total_bytes;
 209                                 dev_replace->tgtdev->commit_total_bytes =
 210                                         dev_replace->srcdev->commit_total_bytes;
 211                                 dev_replace->tgtdev->bytes_used =
 212                                         dev_replace->srcdev->bytes_used;
 213                                 dev_replace->tgtdev->commit_bytes_used =
 214                                         dev_replace->srcdev->commit_bytes_used;
 215                         }
 216                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
 217                                 &dev_replace->tgtdev->dev_state);
 218
 219                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
 220                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
 221                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
 222                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
 223                         dev_replace->tgtdev->fs_info = fs_info;
 224                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
 225                                 &dev_replace->tgtdev->dev_state);
 226                 }
 227                 break;
 228         }
 229
 230 out:
 231         btrfs_free_path(path);
 232         return ret;
 233 }
 234
 235 /*
 236  * Initialize a new device for device replace target from a given source dev
 237  * and path.
 238  *
 239  * Return 0 and new device in @device_out, otherwise return < 0
 240  */
 241 static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 242                                   const char *device_path,
 243                                   struct btrfs_device *srcdev,
 244                                   struct btrfs_device **device_out)
 245 {
 246         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 247         struct btrfs_device *device;
 248         struct block_device *bdev;
 249         struct rcu_string *name;
 250         u64 devid = BTRFS_DEV_REPLACE_DEVID;
 251         int ret = 0;
 252
 253         *device_out = NULL;
 254         if (srcdev->fs_devices->seeding) {
 255                 btrfs_err(fs_info, "the filesystem is a seed filesystem!");
 256                 return -EINVAL;
 257         }
 258
 259         bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
 260                                   fs_info->bdev_holder);
 261         if (IS_ERR(bdev)) {
 262                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
 263                 return PTR_ERR(bdev);
 264         }
 265
 266         if (!btrfs_check_device_zone_type(fs_info, bdev)) {
 267                 btrfs_err(fs_info,
 268                 "dev-replace: zoned type of target device mismatch with filesystem");
 269                 ret = -EINVAL;
 270                 goto error;
 271         }
 272
 273         sync_blockdev(bdev);
 274
 275         list_for_each_entry(device, &fs_devices->devices, dev_list) {
 276                 if (device->bdev == bdev) {
 277                         btrfs_err(fs_info,
 278                                   "target device is in the filesystem!");
 279                         ret = -EEXIST;
 280                         goto error;
 281                 }
 282         }
 283
 284
 285         if (bdev_nr_bytes(bdev) < btrfs_device_get_total_bytes(srcdev)) {
 286                 btrfs_err(fs_info,
 287                           "target device is smaller than source device!");
 288                 ret = -EINVAL;
 289                 goto error;
 290         }
 291
 292
 293         device = btrfs_alloc_device(NULL, &devid, NULL);
 294         if (IS_ERR(device)) {
 295                 ret = PTR_ERR(device);
 296                 goto error;
 297         }
 298
 299         name = rcu_string_strdup(device_path, GFP_KERNEL);
 300         if (!name) {
 301                 btrfs_free_device(device);
 302                 ret = -ENOMEM;
 303                 goto error;
 304         }
 305         rcu_assign_pointer(device->name, name);
 306         ret = lookup_bdev(device_path, &device->devt);
 307         if (ret)
 308                 goto error;
 309
 310         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 311         device->generation = 0;
 312         device->io_width = fs_info->sectorsize;
 313         device->io_align = fs_info->sectorsize;
 314         device->sector_size = fs_info->sectorsize;
 315         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
 316         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
 317         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 318         device->commit_total_bytes = srcdev->commit_total_bytes;
 319         device->commit_bytes_used = device->bytes_used;
 320         device->fs_info = fs_info;
 321         device->bdev = bdev;
 322         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 323         set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 324         device->mode = FMODE_EXCL;
 325         device->dev_stats_valid = 1;
 326         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 327         device->fs_devices = fs_devices;
 328
 329         ret = btrfs_get_dev_zone_info(device, false);
 330         if (ret)
 331                 goto error;
 332
 333         mutex_lock(&fs_devices->device_list_mutex);
 334         list_add(&device->dev_list, &fs_devices->devices);
 335         fs_devices->num_devices++;
 336         fs_devices->open_devices++;
 337         mutex_unlock(&fs_devices->device_list_mutex);
 338
 339         *device_out = device;
 340         return 0;
 341
 342 error:
 343         blkdev_put(bdev, FMODE_EXCL);
 344         return ret;
 345 }
 346
 347 /*
 348  * called from commit_transaction. Writes changed device replace state to
 349  * disk.
 350  */
 351 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
 352 {
 353         struct btrfs_fs_info *fs_info = trans->fs_info;
 354         int ret;
 355         struct btrfs_root *dev_root = fs_info->dev_root;
 356         struct btrfs_path *path;
 357         struct btrfs_key key;
 358         struct extent_buffer *eb;
 359         struct btrfs_dev_replace_item *ptr;
 360         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 361
 362         down_read(&dev_replace->rwsem);
 363         if (!dev_replace->is_valid ||
 364             !dev_replace->item_needs_writeback) {
 365                 up_read(&dev_replace->rwsem);
 366                 return 0;
 367         }
 368         up_read(&dev_replace->rwsem);
 369
 370         key.objectid = 0;
 371         key.type = BTRFS_DEV_REPLACE_KEY;
 372         key.offset = 0;
 373
 374         path = btrfs_alloc_path();
 375         if (!path) {
 376                 ret = -ENOMEM;
 377                 goto out;
 378         }
 379         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
 380         if (ret < 0) {
 381                 btrfs_warn(fs_info,
 382                            "error %d while searching for dev_replace item!",
 383                            ret);
 384                 goto out;
 385         }
 386
 387         if (ret == 0 &&
 388             btrfs_item_size(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 389                 /*
 390                  * need to delete old one and insert a new one.
 391                  * Since no attempt is made to recover any old state, if the
 392                  * dev_replace state is 'running', the data on the target
 393                  * drive is lost.
 394                  * It would be possible to recover the state: just make sure
 395                  * that the beginning of the item is never changed and always
 396                  * contains all the essential information. Then read this
 397                  * minimal set of information and use it as a base for the
 398                  * new state.
 399                  */
 400                 ret = btrfs_del_item(trans, dev_root, path);
 401                 if (ret != 0) {
 402                         btrfs_warn(fs_info,
 403                                    "delete too small dev_replace item failed %d!",
 404                                    ret);
 405                         goto out;
 406                 }
 407                 ret = 1;
 408         }
 409
 410         if (ret == 1) {
 411                 /* need to insert a new item */
 412                 btrfs_release_path(path);
 413                 ret = btrfs_insert_empty_item(trans, dev_root, path,
 414                                               &key, sizeof(*ptr));
 415                 if (ret < 0) {
 416                         btrfs_warn(fs_info,
 417                                    "insert dev_replace item failed %d!", ret);
 418                         goto out;
 419                 }
 420         }
 421
 422         eb = path->nodes[0];
 423         ptr = btrfs_item_ptr(eb, path->slots[0],
 424                              struct btrfs_dev_replace_item);
 425
 426         down_write(&dev_replace->rwsem);
 427         if (dev_replace->srcdev)
 428                 btrfs_set_dev_replace_src_devid(eb, ptr,
 429                         dev_replace->srcdev->devid);
 430         else
 431                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 432         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 433                 dev_replace->cont_reading_from_srcdev_mode);
 434         btrfs_set_dev_replace_replace_state(eb, ptr,
 435                 dev_replace->replace_state);
 436         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 437         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 438         btrfs_set_dev_replace_num_write_errors(eb, ptr,
 439                 atomic64_read(&dev_replace->num_write_errors));
 440         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 441                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 442         dev_replace->cursor_left_last_write_of_item =
 443                 dev_replace->cursor_left;
 444         btrfs_set_dev_replace_cursor_left(eb, ptr,
 445                 dev_replace->cursor_left_last_write_of_item);
 446         btrfs_set_dev_replace_cursor_right(eb, ptr,
 447                 dev_replace->cursor_right);
 448         dev_replace->item_needs_writeback = 0;
 449         up_write(&dev_replace->rwsem);
 450
 451         btrfs_mark_buffer_dirty(eb);
 452
 453 out:
 454         btrfs_free_path(path);
 455
 456         return ret;
 457 }
 458
 459 static char* btrfs_dev_name(struct btrfs_device *device)
 460 {
 461         if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
 462                 return "<missing disk>";
 463         else
 464                 return rcu_str_deref(device->name);
 465 }
 466
 467 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 468                                     struct btrfs_device *src_dev)
 469 {
 470         struct btrfs_path *path;
 471         struct btrfs_key key;
 472         struct btrfs_key found_key;
 473         struct btrfs_root *root = fs_info->dev_root;
 474         struct btrfs_dev_extent *dev_extent = NULL;
 475         struct btrfs_block_group *cache;
 476         struct btrfs_trans_handle *trans;
 477         int iter_ret = 0;
 478         int ret = 0;
 479         u64 chunk_offset;
 480
 481         /* Do not use "to_copy" on non zoned filesystem for now */
 482         if (!btrfs_is_zoned(fs_info))
 483                 return 0;
 484
 485         mutex_lock(&fs_info->chunk_mutex);
 486
 487         /* Ensure we don't have pending new block group */
 488         spin_lock(&fs_info->trans_lock);
 489         while (fs_info->running_transaction &&
 490                !list_empty(&fs_info->running_transaction->dev_update_list)) {
 491                 spin_unlock(&fs_info->trans_lock);
 492                 mutex_unlock(&fs_info->chunk_mutex);
 493                 trans = btrfs_attach_transaction(root);
 494                 if (IS_ERR(trans)) {
 495                         ret = PTR_ERR(trans);
 496                         mutex_lock(&fs_info->chunk_mutex);
 497                         if (ret == -ENOENT) {
 498                                 spin_lock(&fs_info->trans_lock);
 499                                 continue;
 500                         } else {
 501                                 goto unlock;
 502                         }
 503                 }
 504
 505                 ret = btrfs_commit_transaction(trans);
 506                 mutex_lock(&fs_info->chunk_mutex);
 507                 if (ret)
 508                         goto unlock;
 509
 510                 spin_lock(&fs_info->trans_lock);
 511         }
 512         spin_unlock(&fs_info->trans_lock);
 513
 514         path = btrfs_alloc_path();
 515         if (!path) {
 516                 ret = -ENOMEM;
 517                 goto unlock;
 518         }
 519
 520         path->reada = READA_FORWARD;
 521         path->search_commit_root = 1;
 522         path->skip_locking = 1;
 523
 524         key.objectid = src_dev->devid;
 525         key.type = BTRFS_DEV_EXTENT_KEY;
 526         key.offset = 0;
 527
 528         btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 529                 struct extent_buffer *leaf = path->nodes[0];
 530
 531                 if (found_key.objectid != src_dev->devid)
 532                         break;
 533
 534                 if (found_key.type != BTRFS_DEV_EXTENT_KEY)
 535                         break;
 536
 537                 if (found_key.offset < key.offset)
 538                         break;
 539
 540                 dev_extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
 541
 542                 chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
 543
 544                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 545                 if (!cache)
 546                         continue;
 547
 548                 spin_lock(&cache->lock);
 549                 cache->to_copy = 1;
 550                 spin_unlock(&cache->lock);
 551
 552                 btrfs_put_block_group(cache);
 553         }
 554         if (iter_ret < 0)
 555                 ret = iter_ret;
 556
 557         btrfs_free_path(path);
 558 unlock:
 559         mutex_unlock(&fs_info->chunk_mutex);
 560
 561         return ret;
 562 }
 563
 564 bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev,
 565                                       struct btrfs_block_group *cache,
 566                                       u64 physical)
 567 {
 568         struct btrfs_fs_info *fs_info = cache->fs_info;
 569         struct extent_map *em;
 570         struct map_lookup *map;
 571         u64 chunk_offset = cache->start;
 572         int num_extents, cur_extent;
 573         int i;
 574
 575         /* Do not use "to_copy" on non zoned filesystem for now */
 576         if (!btrfs_is_zoned(fs_info))
 577                 return true;
 578
 579         spin_lock(&cache->lock);
 580         if (cache->removed) {
 581                 spin_unlock(&cache->lock);
 582                 return true;
 583         }
 584         spin_unlock(&cache->lock);
 585
 586         em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
 587         ASSERT(!IS_ERR(em));
 588         map = em->map_lookup;
 589
 590         num_extents = cur_extent = 0;
 591         for (i = 0; i < map->num_stripes; i++) {
 592                 /* We have more device extent to copy */
 593                 if (srcdev != map->stripes[i].dev)
 594                         continue;
 595
 596                 num_extents++;
 597                 if (physical == map->stripes[i].physical)
 598                         cur_extent = i;
 599         }
 600
 601         free_extent_map(em);
 602
 603         if (num_extents > 1 && cur_extent < num_extents - 1) {
 604                 /*
 605                  * Has more stripes on this device. Keep this block group
 606                  * readonly until we finish all the stripes.
 607                  */
 608                 return false;
 609         }
 610
 611         /* Last stripe on this device */
 612         spin_lock(&cache->lock);
 613         cache->to_copy = 0;
 614         spin_unlock(&cache->lock);
 615
 616         return true;
 617 }
 618
 619 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 620                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
 621                 int read_src)
 622 {
 623         struct btrfs_root *root = fs_info->dev_root;
 624         struct btrfs_trans_handle *trans;
 625         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 626         int ret;
 627         struct btrfs_device *tgt_device = NULL;
 628         struct btrfs_device *src_device = NULL;
 629
 630         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
 631                                                   srcdev_name);
 632         if (IS_ERR(src_device))
 633                 return PTR_ERR(src_device);
 634
 635         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
 636                 btrfs_warn_in_rcu(fs_info,
 637           "cannot replace device %s (devid %llu) due to active swapfile",
 638                         btrfs_dev_name(src_device), src_device->devid);
 639                 return -ETXTBSY;
 640         }
 641
 642         /*
 643          * Here we commit the transaction to make sure commit_total_bytes
 644          * of all the devices are updated.
 645          */
 646         trans = btrfs_attach_transaction(root);
 647         if (!IS_ERR(trans)) {
 648                 ret = btrfs_commit_transaction(trans);
 649                 if (ret)
 650                         return ret;
 651         } else if (PTR_ERR(trans) != -ENOENT) {
 652                 return PTR_ERR(trans);
 653         }
 654
 655         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
 656                                             src_device, &tgt_device);
 657         if (ret)
 658                 return ret;
 659
 660         ret = mark_block_group_to_copy(fs_info, src_device);
 661         if (ret)
 662                 return ret;
 663
 664         down_write(&dev_replace->rwsem);
 665         switch (dev_replace->replace_state) {
 666         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 667         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 668         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 669                 break;
 670         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 671         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 672                 ASSERT(0);
 673                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 674                 up_write(&dev_replace->rwsem);
 675                 goto leave;
 676         }
 677
 678         dev_replace->cont_reading_from_srcdev_mode = read_src;
 679         dev_replace->srcdev = src_device;
 680         dev_replace->tgtdev = tgt_device;
 681
 682         btrfs_info_in_rcu(fs_info,
 683                       "dev_replace from %s (devid %llu) to %s started",
 684                       btrfs_dev_name(src_device),
 685                       src_device->devid,
 686                       rcu_str_deref(tgt_device->name));
 687
 688         /*
 689          * from now on, the writes to the srcdev are all duplicated to
 690          * go to the tgtdev as well (refer to btrfs_map_block()).
 691          */
 692         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 693         dev_replace->time_started = ktime_get_real_seconds();
 694         dev_replace->cursor_left = 0;
 695         dev_replace->committed_cursor_left = 0;
 696         dev_replace->cursor_left_last_write_of_item = 0;
 697         dev_replace->cursor_right = 0;
 698         dev_replace->is_valid = 1;
 699         dev_replace->item_needs_writeback = 1;
 700         atomic64_set(&dev_replace->num_write_errors, 0);
 701         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 702         up_write(&dev_replace->rwsem);
 703
 704         ret = btrfs_sysfs_add_device(tgt_device);
 705         if (ret)
 706                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
 707
 708         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 709
 710         /*
 711          * Commit dev_replace state and reserve 1 item for it.
 712          * This is crucial to ensure we won't miss copying extents for new block
 713          * groups that are allocated after we started the device replace, and
 714          * must be done after setting up the device replace state.
 715          */
 716         trans = btrfs_start_transaction(root, 1);
 717         if (IS_ERR(trans)) {
 718                 ret = PTR_ERR(trans);
 719                 down_write(&dev_replace->rwsem);
 720                 dev_replace->replace_state =
 721                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 722                 dev_replace->srcdev = NULL;
 723                 dev_replace->tgtdev = NULL;
 724                 up_write(&dev_replace->rwsem);
 725                 goto leave;
 726         }
 727
 728         ret = btrfs_commit_transaction(trans);
 729         WARN_ON(ret);
 730
 731         /* the disk copy procedure reuses the scrub code */
 732         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 733                               btrfs_device_get_total_bytes(src_device),
 734                               &dev_replace->scrub_progress, 0, 1);
 735
 736         ret = btrfs_dev_replace_finishing(fs_info, ret);
 737         if (ret == -EINPROGRESS)
 738                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
 739
 740         return ret;
 741
 742 leave:
 743         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 744         return ret;
 745 }
 746
 747 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 748                             struct btrfs_ioctl_dev_replace_args *args)
 749 {
 750         int ret;
 751
 752         switch (args->start.cont_reading_from_srcdev_mode) {
 753         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 754         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 755                 break;
 756         default:
 757                 return -EINVAL;
 758         }
 759
 760         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 761             args->start.tgtdev_name[0] == '\0')
 762                 return -EINVAL;
 763
 764         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 765                                         args->start.srcdevid,
 766                                         args->start.srcdev_name,
 767                                         args->start.cont_reading_from_srcdev_mode);
 768         args->result = ret;
 769         /* don't warn if EINPROGRESS, someone else might be running scrub */
 770         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
 771             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
 772                 return 0;
 773
 774         return ret;
 775 }
 776
 777 /*
 778  * blocked until all in-flight bios operations are finished.
 779  */
 780 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
 781 {
 782         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 783         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
 784                    &fs_info->dev_replace.bio_counter));
 785 }
 786
 787 /*
 788  * we have removed target device, it is safe to allow new bios request.
 789  */
 790 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
 791 {
 792         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 793         wake_up(&fs_info->dev_replace.replace_wait);
 794 }
 795
 796 /*
 797  * When finishing the device replace, before swapping the source device with the
 798  * target device we must update the chunk allocation state in the target device,
 799  * as it is empty because replace works by directly copying the chunks and not
 800  * through the normal chunk allocation path.
 801  */
 802 static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
 803                                         struct btrfs_device *tgtdev)
 804 {
 805         struct extent_state *cached_state = NULL;
 806         u64 start = 0;
 807         u64 found_start;
 808         u64 found_end;
 809         int ret = 0;
 810
 811         lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
 812
 813         while (!find_first_extent_bit(&srcdev->alloc_state, start,
 814                                       &found_start, &found_end,
 815                                       CHUNK_ALLOCATED, &cached_state)) {
 816                 ret = set_extent_bits(&tgtdev->alloc_state, found_start,
 817                                       found_end, CHUNK_ALLOCATED);
 818                 if (ret)
 819                         break;
 820                 start = found_end + 1;
 821         }
 822
 823         free_extent_state(cached_state);
 824         return ret;
 825 }
 826
 827 static void btrfs_dev_replace_update_device_in_mapping_tree(
 828                                                 struct btrfs_fs_info *fs_info,
 829                                                 struct btrfs_device *srcdev,
 830                                                 struct btrfs_device *tgtdev)
 831 {
 832         struct extent_map_tree *em_tree = &fs_info->mapping_tree;
 833         struct extent_map *em;
 834         struct map_lookup *map;
 835         u64 start = 0;
 836         int i;
 837
 838         write_lock(&em_tree->lock);
 839         do {
 840                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
 841                 if (!em)
 842                         break;
 843                 map = em->map_lookup;
 844                 for (i = 0; i < map->num_stripes; i++)
 845                         if (srcdev == map->stripes[i].dev)
 846                                 map->stripes[i].dev = tgtdev;
 847                 start = em->start + em->len;
 848                 free_extent_map(em);
 849         } while (start);
 850         write_unlock(&em_tree->lock);
 851 }
 852
 853 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 854                                        int scrub_ret)
 855 {
 856         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 857         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 858         struct btrfs_device *tgt_device;
 859         struct btrfs_device *src_device;
 860         struct btrfs_root *root = fs_info->tree_root;
 861         u8 uuid_tmp[BTRFS_UUID_SIZE];
 862         struct btrfs_trans_handle *trans;
 863         int ret = 0;
 864
 865         /* don't allow cancel or unmount to disturb the finishing procedure */
 866         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 867
 868         down_read(&dev_replace->rwsem);
 869         /* was the operation canceled, or is it finished? */
 870         if (dev_replace->replace_state !=
 871             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 872                 up_read(&dev_replace->rwsem);
 873                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 874                 return 0;
 875         }
 876
 877         tgt_device = dev_replace->tgtdev;
 878         src_device = dev_replace->srcdev;
 879         up_read(&dev_replace->rwsem);
 880
 881         /*
 882          * flush all outstanding I/O and inode extent mappings before the
 883          * copy operation is declared as being finished
 884          */
 885         ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 886         if (ret) {
 887                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 888                 return ret;
 889         }
 890         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 891
 892         /*
 893          * We have to use this loop approach because at this point src_device
 894          * has to be available for transaction commit to complete, yet new
 895          * chunks shouldn't be allocated on the device.
 896          */
 897         while (1) {
 898                 trans = btrfs_start_transaction(root, 0);
 899                 if (IS_ERR(trans)) {
 900                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 901                         return PTR_ERR(trans);
 902                 }
 903                 ret = btrfs_commit_transaction(trans);
 904                 WARN_ON(ret);
 905
 906                 /* Prevent write_all_supers() during the finishing procedure */
 907                 mutex_lock(&fs_devices->device_list_mutex);
 908                 /* Prevent new chunks being allocated on the source device */
 909                 mutex_lock(&fs_info->chunk_mutex);
 910
 911                 if (!list_empty(&src_device->post_commit_list)) {
 912                         mutex_unlock(&fs_devices->device_list_mutex);
 913                         mutex_unlock(&fs_info->chunk_mutex);
 914                 } else {
 915                         break;
 916                 }
 917         }
 918
 919         down_write(&dev_replace->rwsem);
 920         dev_replace->replace_state =
 921                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 922                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 923         dev_replace->tgtdev = NULL;
 924         dev_replace->srcdev = NULL;
 925         dev_replace->time_stopped = ktime_get_real_seconds();
 926         dev_replace->item_needs_writeback = 1;
 927
 928         /*
 929          * Update allocation state in the new device and replace the old device
 930          * with the new one in the mapping tree.
 931          */
 932         if (!scrub_ret) {
 933                 scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
 934                 if (scrub_ret)
 935                         goto error;
 936                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 937                                                                 src_device,
 938                                                                 tgt_device);
 939         } else {
 940                 if (scrub_ret != -ECANCELED)
 941                         btrfs_err_in_rcu(fs_info,
 942                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 943                                  btrfs_dev_name(src_device),
 944                                  src_device->devid,
 945                                  rcu_str_deref(tgt_device->name), scrub_ret);
 946 error:
 947                 up_write(&dev_replace->rwsem);
 948                 mutex_unlock(&fs_info->chunk_mutex);
 949                 mutex_unlock(&fs_devices->device_list_mutex);
 950                 btrfs_rm_dev_replace_blocked(fs_info);
 951                 if (tgt_device)
 952                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 953                 btrfs_rm_dev_replace_unblocked(fs_info);
 954                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 955
 956                 return scrub_ret;
 957         }
 958
 959         btrfs_info_in_rcu(fs_info,
 960                           "dev_replace from %s (devid %llu) to %s finished",
 961                           btrfs_dev_name(src_device),
 962                           src_device->devid,
 963                           rcu_str_deref(tgt_device->name));
 964         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 965         tgt_device->devid = src_device->devid;
 966         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 967         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 968         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 969         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 970         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
 971         btrfs_device_set_disk_total_bytes(tgt_device,
 972                                           src_device->disk_total_bytes);
 973         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 974         tgt_device->commit_bytes_used = src_device->bytes_used;
 975
 976         btrfs_assign_next_active_device(src_device, tgt_device);
 977
 978         list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
 979         fs_devices->rw_devices++;
 980
 981         up_write(&dev_replace->rwsem);
 982         btrfs_rm_dev_replace_blocked(fs_info);
 983
 984         btrfs_rm_dev_replace_remove_srcdev(src_device);
 985
 986         btrfs_rm_dev_replace_unblocked(fs_info);
 987
 988         /*
 989          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
 990          * update on-disk dev stats value during commit transaction
 991          */
 992         atomic_inc(&tgt_device->dev_stats_ccnt);
 993
 994         /*
 995          * this is again a consistent state where no dev_replace procedure
 996          * is running, the target device is part of the filesystem, the
 997          * source device is not part of the filesystem anymore and its 1st
 998          * superblock is scratched out so that it is no longer marked to
 999          * belong to this filesystem.
1000          */
1001         mutex_unlock(&fs_info->chunk_mutex);
1002         mutex_unlock(&fs_devices->device_list_mutex);
1003
1004         /* replace the sysfs entry */
1005         btrfs_sysfs_remove_device(src_device);
1006         btrfs_sysfs_update_devid(tgt_device);
1007         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
1008                 btrfs_scratch_superblocks(fs_info, src_device->bdev,
1009                                           src_device->name->str);
1010
1011         /* write back the superblocks */
1012         trans = btrfs_start_transaction(root, 0);
1013         if (!IS_ERR(trans))
1014                 btrfs_commit_transaction(trans);
1015
1016         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1017
1018         btrfs_rm_dev_replace_free_srcdev(src_device);
1019
1020         return 0;
1021 }
1022
1023 /*
1024  * Read progress of device replace status according to the state and last
1025  * stored position. The value format is the same as for
1026  * btrfs_dev_replace::progress_1000
1027  */
1028 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
1029 {
1030         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1031         u64 ret = 0;
1032
1033         switch (dev_replace->replace_state) {
1034         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1035         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1036                 ret = 0;
1037                 break;
1038         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1039                 ret = 1000;
1040                 break;
1041         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1042         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1043                 ret = div64_u64(dev_replace->cursor_left,
1044                                 div_u64(btrfs_device_get_total_bytes(
1045                                                 dev_replace->srcdev), 1000));
1046                 break;
1047         }
1048
1049         return ret;
1050 }
1051
1052 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
1053                               struct btrfs_ioctl_dev_replace_args *args)
1054 {
1055         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1056
1057         down_read(&dev_replace->rwsem);
1058         /* even if !dev_replace_is_valid, the values are good enough for
1059          * the replace_status ioctl */
1060         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1061         args->status.replace_state = dev_replace->replace_state;
1062         args->status.time_started = dev_replace->time_started;
1063         args->status.time_stopped = dev_replace->time_stopped;
1064         args->status.num_write_errors =
1065                 atomic64_read(&dev_replace->num_write_errors);
1066         args->status.num_uncorrectable_read_errors =
1067                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
1068         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
1069         up_read(&dev_replace->rwsem);
1070 }
1071
1072 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
1073 {
1074         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1075         struct btrfs_device *tgt_device = NULL;
1076         struct btrfs_device *src_device = NULL;
1077         struct btrfs_trans_handle *trans;
1078         struct btrfs_root *root = fs_info->tree_root;
1079         int result;
1080         int ret;
1081
1082         if (sb_rdonly(fs_info->sb))
1083                 return -EROFS;
1084
1085         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1086         down_write(&dev_replace->rwsem);
1087         switch (dev_replace->replace_state) {
1088         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1089         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1090         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1091                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1092                 up_write(&dev_replace->rwsem);
1093                 break;
1094         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1095                 tgt_device = dev_replace->tgtdev;
1096                 src_device = dev_replace->srcdev;
1097                 up_write(&dev_replace->rwsem);
1098                 ret = btrfs_scrub_cancel(fs_info);
1099                 if (ret < 0) {
1100                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1101                 } else {
1102                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1103                         /*
1104                          * btrfs_dev_replace_finishing() will handle the
1105                          * cleanup part
1106                          */
1107                         btrfs_info_in_rcu(fs_info,
1108                                 "dev_replace from %s (devid %llu) to %s canceled",
1109                                 btrfs_dev_name(src_device), src_device->devid,
1110                                 btrfs_dev_name(tgt_device));
1111                 }
1112                 break;
1113         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1114                 /*
1115                  * Scrub doing the replace isn't running so we need to do the
1116                  * cleanup step of btrfs_dev_replace_finishing() here
1117                  */
1118                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1119                 tgt_device = dev_replace->tgtdev;
1120                 src_device = dev_replace->srcdev;
1121                 dev_replace->tgtdev = NULL;
1122                 dev_replace->srcdev = NULL;
1123                 dev_replace->replace_state =
1124                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
1125                 dev_replace->time_stopped = ktime_get_real_seconds();
1126                 dev_replace->item_needs_writeback = 1;
1127
1128                 up_write(&dev_replace->rwsem);
1129
1130                 /* Scrub for replace must not be running in suspended state */
1131                 ret = btrfs_scrub_cancel(fs_info);
1132                 ASSERT(ret != -ENOTCONN);
1133
1134                 trans = btrfs_start_transaction(root, 0);
1135                 if (IS_ERR(trans)) {
1136                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1137                         return PTR_ERR(trans);
1138                 }
1139                 ret = btrfs_commit_transaction(trans);
1140                 WARN_ON(ret);
1141
1142                 btrfs_info_in_rcu(fs_info,
1143                 "suspended dev_replace from %s (devid %llu) to %s canceled",
1144                         btrfs_dev_name(src_device), src_device->devid,
1145                         btrfs_dev_name(tgt_device));
1146
1147                 if (tgt_device)
1148                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
1149                 break;
1150         default:
1151                 up_write(&dev_replace->rwsem);
1152                 result = -EINVAL;
1153         }
1154
1155         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1156         return result;
1157 }
1158
1159 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
1160 {
1161         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1162
1163         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1164         down_write(&dev_replace->rwsem);
1165
1166         switch (dev_replace->replace_state) {
1167         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1168         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1169         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1170         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1171                 break;
1172         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1173                 dev_replace->replace_state =
1174                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1175                 dev_replace->time_stopped = ktime_get_real_seconds();
1176                 dev_replace->item_needs_writeback = 1;
1177                 btrfs_info(fs_info, "suspending dev_replace for unmount");
1178                 break;
1179         }
1180
1181         up_write(&dev_replace->rwsem);
1182         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1183 }
1184
1185 /* resume dev_replace procedure that was interrupted by unmount */
1186 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
1187 {
1188         struct task_struct *task;
1189         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1190
1191         down_write(&dev_replace->rwsem);
1192
1193         switch (dev_replace->replace_state) {
1194         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1195         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1196         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1197                 up_write(&dev_replace->rwsem);
1198                 return 0;
1199         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1200                 break;
1201         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1202                 dev_replace->replace_state =
1203                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1204                 break;
1205         }
1206         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1207                 btrfs_info(fs_info,
1208                            "cannot continue dev_replace, tgtdev is missing");
1209                 btrfs_info(fs_info,
1210                            "you may cancel the operation after 'mount -o degraded'");
1211                 dev_replace->replace_state =
1212                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1213                 up_write(&dev_replace->rwsem);
1214                 return 0;
1215         }
1216         up_write(&dev_replace->rwsem);
1217
1218         /*
1219          * This could collide with a paused balance, but the exclusive op logic
1220          * should never allow both to start and pause. We don't want to allow
1221          * dev-replace to start anyway.
1222          */
1223         if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
1224                 down_write(&dev_replace->rwsem);
1225                 dev_replace->replace_state =
1226                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1227                 up_write(&dev_replace->rwsem);
1228                 btrfs_info(fs_info,
1229                 "cannot resume dev-replace, other exclusive operation running");
1230                 return 0;
1231         }
1232
1233         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1234         return PTR_ERR_OR_ZERO(task);
1235 }
1236
1237 static int btrfs_dev_replace_kthread(void *data)
1238 {
1239         struct btrfs_fs_info *fs_info = data;
1240         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1241         u64 progress;
1242         int ret;
1243
1244         progress = btrfs_dev_replace_progress(fs_info);
1245         progress = div_u64(progress, 10);
1246         btrfs_info_in_rcu(fs_info,
1247                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1248                 btrfs_dev_name(dev_replace->srcdev),
1249                 dev_replace->srcdev->devid,
1250                 btrfs_dev_name(dev_replace->tgtdev),
1251                 (unsigned int)progress);
1252
1253         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1254                               dev_replace->committed_cursor_left,
1255                               btrfs_device_get_total_bytes(dev_replace->srcdev),
1256                               &dev_replace->scrub_progress, 0, 1);
1257         ret = btrfs_dev_replace_finishing(fs_info, ret);
1258         WARN_ON(ret && ret != -ECANCELED);
1259
1260         btrfs_exclop_finish(fs_info);
1261         return 0;
1262 }
1263
1264 int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1265 {
1266         if (!dev_replace->is_valid)
1267                 return 0;
1268
1269         switch (dev_replace->replace_state) {
1270         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1271         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1272         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1273                 return 0;
1274         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1275         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1276                 /*
1277                  * return true even if tgtdev is missing (this is
1278                  * something that can happen if the dev_replace
1279                  * procedure is suspended by an umount and then
1280                  * the tgtdev is missing (or "btrfs dev scan") was
1281                  * not called and the filesystem is remounted
1282                  * in degraded state. This does not stop the
1283                  * dev_replace procedure. It needs to be canceled
1284                  * manually if the cancellation is wanted.
1285                  */
1286                 break;
1287         }
1288         return 1;
1289 }
1290
1291 void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
1292 {
1293         percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1294 }
1295
1296 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1297 {
1298         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1299         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1300 }
1301
1302 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1303 {
1304         while (1) {
1305                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1306                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1307                                      &fs_info->fs_state)))
1308                         break;
1309
1310                 btrfs_bio_counter_dec(fs_info);
1311                 wait_event(fs_info->dev_replace.replace_wait,
1312                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1313                                      &fs_info->fs_state));
1314         }
1315 }