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 contans 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_key key;
  74         struct btrfs_root *dev_root = fs_info->dev_root;
  75         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
  76         struct extent_buffer *eb;
  77         int slot;
  78         int ret = 0;
  79         struct btrfs_path *path = NULL;
  80         int item_size;
  81         struct btrfs_dev_replace_item *ptr;
  82         u64 src_devid;
  83
  84         path = btrfs_alloc_path();
  85         if (!path) {
  86                 ret = -ENOMEM;
  87                 goto out;
  88         }
  89
  90         key.objectid = 0;
  91         key.type = BTRFS_DEV_REPLACE_KEY;
  92         key.offset = 0;
  93         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
  94         if (ret) {
  95 no_valid_dev_replace_entry_found:
  96                 /*
  97                  * We don't have a replace item or it's corrupted.  If there is
  98                  * a replace target, fail the mount.
  99                  */
 100                 if (btrfs_find_device(fs_info->fs_devices,
 101                                       BTRFS_DEV_REPLACE_DEVID, NULL, NULL)) {
 102                         btrfs_err(fs_info,
 103                         "found replace target device without a valid replace item");
 104                         ret = -EUCLEAN;
 105                         goto out;
 106                 }
 107                 ret = 0;
 108                 dev_replace->replace_state =
 109                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 110                 dev_replace->cont_reading_from_srcdev_mode =
 111                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 112                 dev_replace->time_started = 0;
 113                 dev_replace->time_stopped = 0;
 114                 atomic64_set(&dev_replace->num_write_errors, 0);
 115                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 116                 dev_replace->cursor_left = 0;
 117                 dev_replace->committed_cursor_left = 0;
 118                 dev_replace->cursor_left_last_write_of_item = 0;
 119                 dev_replace->cursor_right = 0;
 120                 dev_replace->srcdev = NULL;
 121                 dev_replace->tgtdev = NULL;
 122                 dev_replace->is_valid = 0;
 123                 dev_replace->item_needs_writeback = 0;
 124                 goto out;
 125         }
 126         slot = path->slots[0];
 127         eb = path->nodes[0];
 128         item_size = btrfs_item_size_nr(eb, slot);
 129         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 130
 131         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 132                 btrfs_warn(fs_info,
 133                         "dev_replace entry found has unexpected size, ignore entry");
 134                 goto no_valid_dev_replace_entry_found;
 135         }
 136
 137         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 138         dev_replace->cont_reading_from_srcdev_mode =
 139                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 140         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 141         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 142         dev_replace->time_stopped =
 143                 btrfs_dev_replace_time_stopped(eb, ptr);
 144         atomic64_set(&dev_replace->num_write_errors,
 145                      btrfs_dev_replace_num_write_errors(eb, ptr));
 146         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 147                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 148         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 149         dev_replace->committed_cursor_left = dev_replace->cursor_left;
 150         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
 151         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
 152         dev_replace->is_valid = 1;
 153
 154         dev_replace->item_needs_writeback = 0;
 155         switch (dev_replace->replace_state) {
 156         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 157         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 158         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 159                 /*
 160                  * We don't have an active replace item but if there is a
 161                  * replace target, fail the mount.
 162                  */
 163                 if (btrfs_find_device(fs_info->fs_devices,
 164                                       BTRFS_DEV_REPLACE_DEVID, NULL, NULL)) {
 165                         btrfs_err(fs_info,
 166                         "replace devid present without an active replace item");
 167                         ret = -EUCLEAN;
 168                 } else {
 169                         dev_replace->srcdev = NULL;
 170                         dev_replace->tgtdev = NULL;
 171                 }
 172                 break;
 173         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 174         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 175                 dev_replace->srcdev = btrfs_find_device(fs_info->fs_devices,
 176                                                 src_devid, NULL, NULL);
 177                 dev_replace->tgtdev = btrfs_find_device(fs_info->fs_devices,
 178                                                         BTRFS_DEV_REPLACE_DEVID,
 179                                                         NULL, NULL);
 180                 /*
 181                  * allow 'btrfs dev replace_cancel' if src/tgt device is
 182                  * missing
 183                  */
 184                 if (!dev_replace->srcdev &&
 185                     !btrfs_test_opt(fs_info, DEGRADED)) {
 186                         ret = -EIO;
 187                         btrfs_warn(fs_info,
 188                            "cannot mount because device replace operation is ongoing and");
 189                         btrfs_warn(fs_info,
 190                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 191                            src_devid);
 192                 }
 193                 if (!dev_replace->tgtdev &&
 194                     !btrfs_test_opt(fs_info, DEGRADED)) {
 195                         ret = -EIO;
 196                         btrfs_warn(fs_info,
 197                            "cannot mount because device replace operation is ongoing and");
 198                         btrfs_warn(fs_info,
 199                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 200                                 BTRFS_DEV_REPLACE_DEVID);
 201                 }
 202                 if (dev_replace->tgtdev) {
 203                         if (dev_replace->srcdev) {
 204                                 dev_replace->tgtdev->total_bytes =
 205                                         dev_replace->srcdev->total_bytes;
 206                                 dev_replace->tgtdev->disk_total_bytes =
 207                                         dev_replace->srcdev->disk_total_bytes;
 208                                 dev_replace->tgtdev->commit_total_bytes =
 209                                         dev_replace->srcdev->commit_total_bytes;
 210                                 dev_replace->tgtdev->bytes_used =
 211                                         dev_replace->srcdev->bytes_used;
 212                                 dev_replace->tgtdev->commit_bytes_used =
 213                                         dev_replace->srcdev->commit_bytes_used;
 214                         }
 215                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
 216                                 &dev_replace->tgtdev->dev_state);
 217
 218                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
 219                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
 220                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
 221                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
 222                         dev_replace->tgtdev->fs_info = fs_info;
 223                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
 224                                 &dev_replace->tgtdev->dev_state);
 225                 }
 226                 break;
 227         }
 228
 229 out:
 230         btrfs_free_path(path);
 231         return ret;
 232 }
 233
 234 /*
 235  * Initialize a new device for device replace target from a given source dev
 236  * and path.
 237  *
 238  * Return 0 and new device in @device_out, otherwise return < 0
 239  */
 240 static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 241                                   const char *device_path,
 242                                   struct btrfs_device *srcdev,
 243                                   struct btrfs_device **device_out)
 244 {
 245         struct btrfs_device *device;
 246         struct block_device *bdev;
 247         struct rcu_string *name;
 248         u64 devid = BTRFS_DEV_REPLACE_DEVID;
 249         int ret = 0;
 250
 251         *device_out = NULL;
 252         if (srcdev->fs_devices->seeding) {
 253                 btrfs_err(fs_info, "the filesystem is a seed filesystem!");
 254                 return -EINVAL;
 255         }
 256
 257         bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
 258                                   fs_info->bdev_holder);
 259         if (IS_ERR(bdev)) {
 260                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
 261                 return PTR_ERR(bdev);
 262         }
 263
 264         if (!btrfs_check_device_zone_type(fs_info, bdev)) {
 265                 btrfs_err(fs_info,
 266                 "dev-replace: zoned type of target device mismatch with filesystem");
 267                 ret = -EINVAL;
 268                 goto error;
 269         }
 270
 271         sync_blockdev(bdev);
 272
 273         list_for_each_entry(device, &fs_info->fs_devices->devices, dev_list) {
 274                 if (device->bdev == bdev) {
 275                         btrfs_err(fs_info,
 276                                   "target device is in the filesystem!");
 277                         ret = -EEXIST;
 278                         goto error;
 279                 }
 280         }
 281
 282
 283         if (i_size_read(bdev->bd_inode) <
 284             btrfs_device_get_total_bytes(srcdev)) {
 285                 btrfs_err(fs_info,
 286                           "target device is smaller than source device!");
 287                 ret = -EINVAL;
 288                 goto error;
 289         }
 290
 291
 292         device = btrfs_alloc_device(NULL, &devid, NULL);
 293         if (IS_ERR(device)) {
 294                 ret = PTR_ERR(device);
 295                 goto error;
 296         }
 297
 298         name = rcu_string_strdup(device_path, GFP_KERNEL);
 299         if (!name) {
 300                 btrfs_free_device(device);
 301                 ret = -ENOMEM;
 302                 goto error;
 303         }
 304         rcu_assign_pointer(device->name, name);
 305
 306         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 307         device->generation = 0;
 308         device->io_width = fs_info->sectorsize;
 309         device->io_align = fs_info->sectorsize;
 310         device->sector_size = fs_info->sectorsize;
 311         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
 312         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
 313         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 314         device->commit_total_bytes = srcdev->commit_total_bytes;
 315         device->commit_bytes_used = device->bytes_used;
 316         device->fs_info = fs_info;
 317         device->bdev = bdev;
 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->mode = FMODE_EXCL;
 321         device->dev_stats_valid = 1;
 322         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 323         device->fs_devices = fs_info->fs_devices;
 324
 325         ret = btrfs_get_dev_zone_info(device);
 326         if (ret)
 327                 goto error;
 328
 329         mutex_lock(&fs_info->fs_devices->device_list_mutex);
 330         list_add(&device->dev_list, &fs_info->fs_devices->devices);
 331         fs_info->fs_devices->num_devices++;
 332         fs_info->fs_devices->open_devices++;
 333         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 334
 335         *device_out = device;
 336         return 0;
 337
 338 error:
 339         blkdev_put(bdev, FMODE_EXCL);
 340         return ret;
 341 }
 342
 343 /*
 344  * called from commit_transaction. Writes changed device replace state to
 345  * disk.
 346  */
 347 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
 348 {
 349         struct btrfs_fs_info *fs_info = trans->fs_info;
 350         int ret;
 351         struct btrfs_root *dev_root = fs_info->dev_root;
 352         struct btrfs_path *path;
 353         struct btrfs_key key;
 354         struct extent_buffer *eb;
 355         struct btrfs_dev_replace_item *ptr;
 356         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 357
 358         down_read(&dev_replace->rwsem);
 359         if (!dev_replace->is_valid ||
 360             !dev_replace->item_needs_writeback) {
 361                 up_read(&dev_replace->rwsem);
 362                 return 0;
 363         }
 364         up_read(&dev_replace->rwsem);
 365
 366         key.objectid = 0;
 367         key.type = BTRFS_DEV_REPLACE_KEY;
 368         key.offset = 0;
 369
 370         path = btrfs_alloc_path();
 371         if (!path) {
 372                 ret = -ENOMEM;
 373                 goto out;
 374         }
 375         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
 376         if (ret < 0) {
 377                 btrfs_warn(fs_info,
 378                            "error %d while searching for dev_replace item!",
 379                            ret);
 380                 goto out;
 381         }
 382
 383         if (ret == 0 &&
 384             btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 385                 /*
 386                  * need to delete old one and insert a new one.
 387                  * Since no attempt is made to recover any old state, if the
 388                  * dev_replace state is 'running', the data on the target
 389                  * drive is lost.
 390                  * It would be possible to recover the state: just make sure
 391                  * that the beginning of the item is never changed and always
 392                  * contains all the essential information. Then read this
 393                  * minimal set of information and use it as a base for the
 394                  * new state.
 395                  */
 396                 ret = btrfs_del_item(trans, dev_root, path);
 397                 if (ret != 0) {
 398                         btrfs_warn(fs_info,
 399                                    "delete too small dev_replace item failed %d!",
 400                                    ret);
 401                         goto out;
 402                 }
 403                 ret = 1;
 404         }
 405
 406         if (ret == 1) {
 407                 /* need to insert a new item */
 408                 btrfs_release_path(path);
 409                 ret = btrfs_insert_empty_item(trans, dev_root, path,
 410                                               &key, sizeof(*ptr));
 411                 if (ret < 0) {
 412                         btrfs_warn(fs_info,
 413                                    "insert dev_replace item failed %d!", ret);
 414                         goto out;
 415                 }
 416         }
 417
 418         eb = path->nodes[0];
 419         ptr = btrfs_item_ptr(eb, path->slots[0],
 420                              struct btrfs_dev_replace_item);
 421
 422         down_write(&dev_replace->rwsem);
 423         if (dev_replace->srcdev)
 424                 btrfs_set_dev_replace_src_devid(eb, ptr,
 425                         dev_replace->srcdev->devid);
 426         else
 427                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 428         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 429                 dev_replace->cont_reading_from_srcdev_mode);
 430         btrfs_set_dev_replace_replace_state(eb, ptr,
 431                 dev_replace->replace_state);
 432         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 433         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 434         btrfs_set_dev_replace_num_write_errors(eb, ptr,
 435                 atomic64_read(&dev_replace->num_write_errors));
 436         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 437                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 438         dev_replace->cursor_left_last_write_of_item =
 439                 dev_replace->cursor_left;
 440         btrfs_set_dev_replace_cursor_left(eb, ptr,
 441                 dev_replace->cursor_left_last_write_of_item);
 442         btrfs_set_dev_replace_cursor_right(eb, ptr,
 443                 dev_replace->cursor_right);
 444         dev_replace->item_needs_writeback = 0;
 445         up_write(&dev_replace->rwsem);
 446
 447         btrfs_mark_buffer_dirty(eb);
 448
 449 out:
 450         btrfs_free_path(path);
 451
 452         return ret;
 453 }
 454
 455 static char* btrfs_dev_name(struct btrfs_device *device)
 456 {
 457         if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
 458                 return "<missing disk>";
 459         else
 460                 return rcu_str_deref(device->name);
 461 }
 462
 463 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 464                                     struct btrfs_device *src_dev)
 465 {
 466         struct btrfs_path *path;
 467         struct btrfs_key key;
 468         struct btrfs_key found_key;
 469         struct btrfs_root *root = fs_info->dev_root;
 470         struct btrfs_dev_extent *dev_extent = NULL;
 471         struct btrfs_block_group *cache;
 472         struct btrfs_trans_handle *trans;
 473         int ret = 0;
 474         u64 chunk_offset;
 475
 476         /* Do not use "to_copy" on non zoned filesystem for now */
 477         if (!btrfs_is_zoned(fs_info))
 478                 return 0;
 479
 480         mutex_lock(&fs_info->chunk_mutex);
 481
 482         /* Ensure we don't have pending new block group */
 483         spin_lock(&fs_info->trans_lock);
 484         while (fs_info->running_transaction &&
 485                !list_empty(&fs_info->running_transaction->dev_update_list)) {
 486                 spin_unlock(&fs_info->trans_lock);
 487                 mutex_unlock(&fs_info->chunk_mutex);
 488                 trans = btrfs_attach_transaction(root);
 489                 if (IS_ERR(trans)) {
 490                         ret = PTR_ERR(trans);
 491                         mutex_lock(&fs_info->chunk_mutex);
 492                         if (ret == -ENOENT) {
 493                                 spin_lock(&fs_info->trans_lock);
 494                                 continue;
 495                         } else {
 496                                 goto unlock;
 497                         }
 498                 }
 499
 500                 ret = btrfs_commit_transaction(trans);
 501                 mutex_lock(&fs_info->chunk_mutex);
 502                 if (ret)
 503                         goto unlock;
 504
 505                 spin_lock(&fs_info->trans_lock);
 506         }
 507         spin_unlock(&fs_info->trans_lock);
 508
 509         path = btrfs_alloc_path();
 510         if (!path) {
 511                 ret = -ENOMEM;
 512                 goto unlock;
 513         }
 514
 515         path->reada = READA_FORWARD;
 516         path->search_commit_root = 1;
 517         path->skip_locking = 1;
 518
 519         key.objectid = src_dev->devid;
 520         key.type = BTRFS_DEV_EXTENT_KEY;
 521         key.offset = 0;
 522
 523         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 524         if (ret < 0)
 525                 goto free_path;
 526         if (ret > 0) {
 527                 if (path->slots[0] >=
 528                     btrfs_header_nritems(path->nodes[0])) {
 529                         ret = btrfs_next_leaf(root, path);
 530                         if (ret < 0)
 531                                 goto free_path;
 532                         if (ret > 0) {
 533                                 ret = 0;
 534                                 goto free_path;
 535                         }
 536                 } else {
 537                         ret = 0;
 538                 }
 539         }
 540
 541         while (1) {
 542                 struct extent_buffer *leaf = path->nodes[0];
 543                 int slot = path->slots[0];
 544
 545                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 546
 547                 if (found_key.objectid != src_dev->devid)
 548                         break;
 549
 550                 if (found_key.type != BTRFS_DEV_EXTENT_KEY)
 551                         break;
 552
 553                 if (found_key.offset < key.offset)
 554                         break;
 555
 556                 dev_extent = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
 557
 558                 chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
 559
 560                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 561                 if (!cache)
 562                         goto skip;
 563
 564                 spin_lock(&cache->lock);
 565                 cache->to_copy = 1;
 566                 spin_unlock(&cache->lock);
 567
 568                 btrfs_put_block_group(cache);
 569
 570 skip:
 571                 ret = btrfs_next_item(root, path);
 572                 if (ret != 0) {
 573                         if (ret > 0)
 574                                 ret = 0;
 575                         break;
 576                 }
 577         }
 578
 579 free_path:
 580         btrfs_free_path(path);
 581 unlock:
 582         mutex_unlock(&fs_info->chunk_mutex);
 583
 584         return ret;
 585 }
 586
 587 bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev,
 588                                       struct btrfs_block_group *cache,
 589                                       u64 physical)
 590 {
 591         struct btrfs_fs_info *fs_info = cache->fs_info;
 592         struct extent_map *em;
 593         struct map_lookup *map;
 594         u64 chunk_offset = cache->start;
 595         int num_extents, cur_extent;
 596         int i;
 597
 598         /* Do not use "to_copy" on non zoned filesystem for now */
 599         if (!btrfs_is_zoned(fs_info))
 600                 return true;
 601
 602         spin_lock(&cache->lock);
 603         if (cache->removed) {
 604                 spin_unlock(&cache->lock);
 605                 return true;
 606         }
 607         spin_unlock(&cache->lock);
 608
 609         em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
 610         ASSERT(!IS_ERR(em));
 611         map = em->map_lookup;
 612
 613         num_extents = cur_extent = 0;
 614         for (i = 0; i < map->num_stripes; i++) {
 615                 /* We have more device extent to copy */
 616                 if (srcdev != map->stripes[i].dev)
 617                         continue;
 618
 619                 num_extents++;
 620                 if (physical == map->stripes[i].physical)
 621                         cur_extent = i;
 622         }
 623
 624         free_extent_map(em);
 625
 626         if (num_extents > 1 && cur_extent < num_extents - 1) {
 627                 /*
 628                  * Has more stripes on this device. Keep this block group
 629                  * readonly until we finish all the stripes.
 630                  */
 631                 return false;
 632         }
 633
 634         /* Last stripe on this device */
 635         spin_lock(&cache->lock);
 636         cache->to_copy = 0;
 637         spin_unlock(&cache->lock);
 638
 639         return true;
 640 }
 641
 642 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 643                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
 644                 int read_src)
 645 {
 646         struct btrfs_root *root = fs_info->dev_root;
 647         struct btrfs_trans_handle *trans;
 648         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 649         int ret;
 650         struct btrfs_device *tgt_device = NULL;
 651         struct btrfs_device *src_device = NULL;
 652
 653         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
 654                                                   srcdev_name);
 655         if (IS_ERR(src_device))
 656                 return PTR_ERR(src_device);
 657
 658         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
 659                 btrfs_warn_in_rcu(fs_info,
 660           "cannot replace device %s (devid %llu) due to active swapfile",
 661                         btrfs_dev_name(src_device), src_device->devid);
 662                 return -ETXTBSY;
 663         }
 664
 665         /*
 666          * Here we commit the transaction to make sure commit_total_bytes
 667          * of all the devices are updated.
 668          */
 669         trans = btrfs_attach_transaction(root);
 670         if (!IS_ERR(trans)) {
 671                 ret = btrfs_commit_transaction(trans);
 672                 if (ret)
 673                         return ret;
 674         } else if (PTR_ERR(trans) != -ENOENT) {
 675                 return PTR_ERR(trans);
 676         }
 677
 678         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
 679                                             src_device, &tgt_device);
 680         if (ret)
 681                 return ret;
 682
 683         ret = mark_block_group_to_copy(fs_info, src_device);
 684         if (ret)
 685                 return ret;
 686
 687         down_write(&dev_replace->rwsem);
 688         switch (dev_replace->replace_state) {
 689         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 690         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 691         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 692                 break;
 693         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 694         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 695                 ASSERT(0);
 696                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 697                 up_write(&dev_replace->rwsem);
 698                 goto leave;
 699         }
 700
 701         dev_replace->cont_reading_from_srcdev_mode = read_src;
 702         dev_replace->srcdev = src_device;
 703         dev_replace->tgtdev = tgt_device;
 704
 705         btrfs_info_in_rcu(fs_info,
 706                       "dev_replace from %s (devid %llu) to %s started",
 707                       btrfs_dev_name(src_device),
 708                       src_device->devid,
 709                       rcu_str_deref(tgt_device->name));
 710
 711         /*
 712          * from now on, the writes to the srcdev are all duplicated to
 713          * go to the tgtdev as well (refer to btrfs_map_block()).
 714          */
 715         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 716         dev_replace->time_started = ktime_get_real_seconds();
 717         dev_replace->cursor_left = 0;
 718         dev_replace->committed_cursor_left = 0;
 719         dev_replace->cursor_left_last_write_of_item = 0;
 720         dev_replace->cursor_right = 0;
 721         dev_replace->is_valid = 1;
 722         dev_replace->item_needs_writeback = 1;
 723         atomic64_set(&dev_replace->num_write_errors, 0);
 724         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 725         up_write(&dev_replace->rwsem);
 726
 727         ret = btrfs_sysfs_add_device(tgt_device);
 728         if (ret)
 729                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
 730
 731         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 732
 733         /* Commit dev_replace state and reserve 1 item for it. */
 734         trans = btrfs_start_transaction(root, 1);
 735         if (IS_ERR(trans)) {
 736                 ret = PTR_ERR(trans);
 737                 down_write(&dev_replace->rwsem);
 738                 dev_replace->replace_state =
 739                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 740                 dev_replace->srcdev = NULL;
 741                 dev_replace->tgtdev = NULL;
 742                 up_write(&dev_replace->rwsem);
 743                 goto leave;
 744         }
 745
 746         ret = btrfs_commit_transaction(trans);
 747         WARN_ON(ret);
 748
 749         /* the disk copy procedure reuses the scrub code */
 750         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 751                               btrfs_device_get_total_bytes(src_device),
 752                               &dev_replace->scrub_progress, 0, 1);
 753
 754         ret = btrfs_dev_replace_finishing(fs_info, ret);
 755         if (ret == -EINPROGRESS)
 756                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
 757
 758         return ret;
 759
 760 leave:
 761         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 762         return ret;
 763 }
 764
 765 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 766                             struct btrfs_ioctl_dev_replace_args *args)
 767 {
 768         int ret;
 769
 770         switch (args->start.cont_reading_from_srcdev_mode) {
 771         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 772         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 773                 break;
 774         default:
 775                 return -EINVAL;
 776         }
 777
 778         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 779             args->start.tgtdev_name[0] == '\0')
 780                 return -EINVAL;
 781
 782         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 783                                         args->start.srcdevid,
 784                                         args->start.srcdev_name,
 785                                         args->start.cont_reading_from_srcdev_mode);
 786         args->result = ret;
 787         /* don't warn if EINPROGRESS, someone else might be running scrub */
 788         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
 789             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
 790                 return 0;
 791
 792         return ret;
 793 }
 794
 795 /*
 796  * blocked until all in-flight bios operations are finished.
 797  */
 798 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
 799 {
 800         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 801         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
 802                    &fs_info->dev_replace.bio_counter));
 803 }
 804
 805 /*
 806  * we have removed target device, it is safe to allow new bios request.
 807  */
 808 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
 809 {
 810         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 811         wake_up(&fs_info->dev_replace.replace_wait);
 812 }
 813
 814 /*
 815  * When finishing the device replace, before swapping the source device with the
 816  * target device we must update the chunk allocation state in the target device,
 817  * as it is empty because replace works by directly copying the chunks and not
 818  * through the normal chunk allocation path.
 819  */
 820 static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
 821                                         struct btrfs_device *tgtdev)
 822 {
 823         struct extent_state *cached_state = NULL;
 824         u64 start = 0;
 825         u64 found_start;
 826         u64 found_end;
 827         int ret = 0;
 828
 829         lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
 830
 831         while (!find_first_extent_bit(&srcdev->alloc_state, start,
 832                                       &found_start, &found_end,
 833                                       CHUNK_ALLOCATED, &cached_state)) {
 834                 ret = set_extent_bits(&tgtdev->alloc_state, found_start,
 835                                       found_end, CHUNK_ALLOCATED);
 836                 if (ret)
 837                         break;
 838                 start = found_end + 1;
 839         }
 840
 841         free_extent_state(cached_state);
 842         return ret;
 843 }
 844
 845 static void btrfs_dev_replace_update_device_in_mapping_tree(
 846                                                 struct btrfs_fs_info *fs_info,
 847                                                 struct btrfs_device *srcdev,
 848                                                 struct btrfs_device *tgtdev)
 849 {
 850         struct extent_map_tree *em_tree = &fs_info->mapping_tree;
 851         struct extent_map *em;
 852         struct map_lookup *map;
 853         u64 start = 0;
 854         int i;
 855
 856         write_lock(&em_tree->lock);
 857         do {
 858                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
 859                 if (!em)
 860                         break;
 861                 map = em->map_lookup;
 862                 for (i = 0; i < map->num_stripes; i++)
 863                         if (srcdev == map->stripes[i].dev)
 864                                 map->stripes[i].dev = tgtdev;
 865                 start = em->start + em->len;
 866                 free_extent_map(em);
 867         } while (start);
 868         write_unlock(&em_tree->lock);
 869 }
 870
 871 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 872                                        int scrub_ret)
 873 {
 874         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 875         struct btrfs_device *tgt_device;
 876         struct btrfs_device *src_device;
 877         struct btrfs_root *root = fs_info->tree_root;
 878         u8 uuid_tmp[BTRFS_UUID_SIZE];
 879         struct btrfs_trans_handle *trans;
 880         int ret = 0;
 881
 882         /* don't allow cancel or unmount to disturb the finishing procedure */
 883         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 884
 885         down_read(&dev_replace->rwsem);
 886         /* was the operation canceled, or is it finished? */
 887         if (dev_replace->replace_state !=
 888             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 889                 up_read(&dev_replace->rwsem);
 890                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 891                 return 0;
 892         }
 893
 894         tgt_device = dev_replace->tgtdev;
 895         src_device = dev_replace->srcdev;
 896         up_read(&dev_replace->rwsem);
 897
 898         /*
 899          * flush all outstanding I/O and inode extent mappings before the
 900          * copy operation is declared as being finished
 901          */
 902         ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
 903         if (ret) {
 904                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 905                 return ret;
 906         }
 907         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 908
 909         if (!scrub_ret)
 910                 btrfs_reada_remove_dev(src_device);
 911
 912         /*
 913          * We have to use this loop approach because at this point src_device
 914          * has to be available for transaction commit to complete, yet new
 915          * chunks shouldn't be allocated on the device.
 916          */
 917         while (1) {
 918                 trans = btrfs_start_transaction(root, 0);
 919                 if (IS_ERR(trans)) {
 920                         btrfs_reada_undo_remove_dev(src_device);
 921                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 922                         return PTR_ERR(trans);
 923                 }
 924                 ret = btrfs_commit_transaction(trans);
 925                 WARN_ON(ret);
 926
 927                 /* Prevent write_all_supers() during the finishing procedure */
 928                 mutex_lock(&fs_info->fs_devices->device_list_mutex);
 929                 /* Prevent new chunks being allocated on the source device */
 930                 mutex_lock(&fs_info->chunk_mutex);
 931
 932                 if (!list_empty(&src_device->post_commit_list)) {
 933                         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 934                         mutex_unlock(&fs_info->chunk_mutex);
 935                 } else {
 936                         break;
 937                 }
 938         }
 939
 940         down_write(&dev_replace->rwsem);
 941         dev_replace->replace_state =
 942                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 943                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 944         dev_replace->tgtdev = NULL;
 945         dev_replace->srcdev = NULL;
 946         dev_replace->time_stopped = ktime_get_real_seconds();
 947         dev_replace->item_needs_writeback = 1;
 948
 949         /*
 950          * Update allocation state in the new device and replace the old device
 951          * with the new one in the mapping tree.
 952          */
 953         if (!scrub_ret) {
 954                 scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
 955                 if (scrub_ret)
 956                         goto error;
 957                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 958                                                                 src_device,
 959                                                                 tgt_device);
 960         } else {
 961                 if (scrub_ret != -ECANCELED)
 962                         btrfs_err_in_rcu(fs_info,
 963                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 964                                  btrfs_dev_name(src_device),
 965                                  src_device->devid,
 966                                  rcu_str_deref(tgt_device->name), scrub_ret);
 967 error:
 968                 up_write(&dev_replace->rwsem);
 969                 mutex_unlock(&fs_info->chunk_mutex);
 970                 mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 971                 btrfs_reada_undo_remove_dev(src_device);
 972                 btrfs_rm_dev_replace_blocked(fs_info);
 973                 if (tgt_device)
 974                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
 975                 btrfs_rm_dev_replace_unblocked(fs_info);
 976                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 977
 978                 return scrub_ret;
 979         }
 980
 981         btrfs_info_in_rcu(fs_info,
 982                           "dev_replace from %s (devid %llu) to %s finished",
 983                           btrfs_dev_name(src_device),
 984                           src_device->devid,
 985                           rcu_str_deref(tgt_device->name));
 986         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 987         tgt_device->devid = src_device->devid;
 988         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 989         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 990         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 991         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 992         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
 993         btrfs_device_set_disk_total_bytes(tgt_device,
 994                                           src_device->disk_total_bytes);
 995         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 996         tgt_device->commit_bytes_used = src_device->bytes_used;
 997
 998         btrfs_assign_next_active_device(src_device, tgt_device);
 999
1000         list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
1001         fs_info->fs_devices->rw_devices++;
1002
1003         up_write(&dev_replace->rwsem);
1004         btrfs_rm_dev_replace_blocked(fs_info);
1005
1006         btrfs_rm_dev_replace_remove_srcdev(src_device);
1007
1008         btrfs_rm_dev_replace_unblocked(fs_info);
1009
1010         /*
1011          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
1012          * update on-disk dev stats value during commit transaction
1013          */
1014         atomic_inc(&tgt_device->dev_stats_ccnt);
1015
1016         /*
1017          * this is again a consistent state where no dev_replace procedure
1018          * is running, the target device is part of the filesystem, the
1019          * source device is not part of the filesystem anymore and its 1st
1020          * superblock is scratched out so that it is no longer marked to
1021          * belong to this filesystem.
1022          */
1023         mutex_unlock(&fs_info->chunk_mutex);
1024         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
1025
1026         /* replace the sysfs entry */
1027         btrfs_sysfs_remove_device(src_device);
1028         btrfs_sysfs_update_devid(tgt_device);
1029         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
1030                 btrfs_scratch_superblocks(fs_info, src_device->bdev,
1031                                           src_device->name->str);
1032
1033         /* write back the superblocks */
1034         trans = btrfs_start_transaction(root, 0);
1035         if (!IS_ERR(trans))
1036                 btrfs_commit_transaction(trans);
1037
1038         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1039
1040         btrfs_rm_dev_replace_free_srcdev(src_device);
1041
1042         return 0;
1043 }
1044
1045 /*
1046  * Read progress of device replace status according to the state and last
1047  * stored position. The value format is the same as for
1048  * btrfs_dev_replace::progress_1000
1049  */
1050 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
1051 {
1052         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1053         u64 ret = 0;
1054
1055         switch (dev_replace->replace_state) {
1056         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1057         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1058                 ret = 0;
1059                 break;
1060         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1061                 ret = 1000;
1062                 break;
1063         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1064         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1065                 ret = div64_u64(dev_replace->cursor_left,
1066                                 div_u64(btrfs_device_get_total_bytes(
1067                                                 dev_replace->srcdev), 1000));
1068                 break;
1069         }
1070
1071         return ret;
1072 }
1073
1074 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
1075                               struct btrfs_ioctl_dev_replace_args *args)
1076 {
1077         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1078
1079         down_read(&dev_replace->rwsem);
1080         /* even if !dev_replace_is_valid, the values are good enough for
1081          * the replace_status ioctl */
1082         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1083         args->status.replace_state = dev_replace->replace_state;
1084         args->status.time_started = dev_replace->time_started;
1085         args->status.time_stopped = dev_replace->time_stopped;
1086         args->status.num_write_errors =
1087                 atomic64_read(&dev_replace->num_write_errors);
1088         args->status.num_uncorrectable_read_errors =
1089                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
1090         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
1091         up_read(&dev_replace->rwsem);
1092 }
1093
1094 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
1095 {
1096         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1097         struct btrfs_device *tgt_device = NULL;
1098         struct btrfs_device *src_device = NULL;
1099         struct btrfs_trans_handle *trans;
1100         struct btrfs_root *root = fs_info->tree_root;
1101         int result;
1102         int ret;
1103
1104         if (sb_rdonly(fs_info->sb))
1105                 return -EROFS;
1106
1107         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1108         down_write(&dev_replace->rwsem);
1109         switch (dev_replace->replace_state) {
1110         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1111         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1112         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1113                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1114                 up_write(&dev_replace->rwsem);
1115                 break;
1116         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1117                 tgt_device = dev_replace->tgtdev;
1118                 src_device = dev_replace->srcdev;
1119                 up_write(&dev_replace->rwsem);
1120                 ret = btrfs_scrub_cancel(fs_info);
1121                 if (ret < 0) {
1122                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1123                 } else {
1124                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1125                         /*
1126                          * btrfs_dev_replace_finishing() will handle the
1127                          * cleanup part
1128                          */
1129                         btrfs_info_in_rcu(fs_info,
1130                                 "dev_replace from %s (devid %llu) to %s canceled",
1131                                 btrfs_dev_name(src_device), src_device->devid,
1132                                 btrfs_dev_name(tgt_device));
1133                 }
1134                 break;
1135         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1136                 /*
1137                  * Scrub doing the replace isn't running so we need to do the
1138                  * cleanup step of btrfs_dev_replace_finishing() here
1139                  */
1140                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1141                 tgt_device = dev_replace->tgtdev;
1142                 src_device = dev_replace->srcdev;
1143                 dev_replace->tgtdev = NULL;
1144                 dev_replace->srcdev = NULL;
1145                 dev_replace->replace_state =
1146                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
1147                 dev_replace->time_stopped = ktime_get_real_seconds();
1148                 dev_replace->item_needs_writeback = 1;
1149
1150                 up_write(&dev_replace->rwsem);
1151
1152                 /* Scrub for replace must not be running in suspended state */
1153                 ret = btrfs_scrub_cancel(fs_info);
1154                 ASSERT(ret != -ENOTCONN);
1155
1156                 trans = btrfs_start_transaction(root, 0);
1157                 if (IS_ERR(trans)) {
1158                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1159                         return PTR_ERR(trans);
1160                 }
1161                 ret = btrfs_commit_transaction(trans);
1162                 WARN_ON(ret);
1163
1164                 btrfs_info_in_rcu(fs_info,
1165                 "suspended dev_replace from %s (devid %llu) to %s canceled",
1166                         btrfs_dev_name(src_device), src_device->devid,
1167                         btrfs_dev_name(tgt_device));
1168
1169                 if (tgt_device)
1170                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
1171                 break;
1172         default:
1173                 up_write(&dev_replace->rwsem);
1174                 result = -EINVAL;
1175         }
1176
1177         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1178         return result;
1179 }
1180
1181 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
1182 {
1183         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1184
1185         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1186         down_write(&dev_replace->rwsem);
1187
1188         switch (dev_replace->replace_state) {
1189         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1190         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1191         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1192         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1193                 break;
1194         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1195                 dev_replace->replace_state =
1196                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1197                 dev_replace->time_stopped = ktime_get_real_seconds();
1198                 dev_replace->item_needs_writeback = 1;
1199                 btrfs_info(fs_info, "suspending dev_replace for unmount");
1200                 break;
1201         }
1202
1203         up_write(&dev_replace->rwsem);
1204         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1205 }
1206
1207 /* resume dev_replace procedure that was interrupted by unmount */
1208 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
1209 {
1210         struct task_struct *task;
1211         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1212
1213         down_write(&dev_replace->rwsem);
1214
1215         switch (dev_replace->replace_state) {
1216         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1217         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1218         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1219                 up_write(&dev_replace->rwsem);
1220                 return 0;
1221         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1222                 break;
1223         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1224                 dev_replace->replace_state =
1225                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1226                 break;
1227         }
1228         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1229                 btrfs_info(fs_info,
1230                            "cannot continue dev_replace, tgtdev is missing");
1231                 btrfs_info(fs_info,
1232                            "you may cancel the operation after 'mount -o degraded'");
1233                 dev_replace->replace_state =
1234                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1235                 up_write(&dev_replace->rwsem);
1236                 return 0;
1237         }
1238         up_write(&dev_replace->rwsem);
1239
1240         /*
1241          * This could collide with a paused balance, but the exclusive op logic
1242          * should never allow both to start and pause. We don't want to allow
1243          * dev-replace to start anyway.
1244          */
1245         if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
1246                 down_write(&dev_replace->rwsem);
1247                 dev_replace->replace_state =
1248                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1249                 up_write(&dev_replace->rwsem);
1250                 btrfs_info(fs_info,
1251                 "cannot resume dev-replace, other exclusive operation running");
1252                 return 0;
1253         }
1254
1255         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1256         return PTR_ERR_OR_ZERO(task);
1257 }
1258
1259 static int btrfs_dev_replace_kthread(void *data)
1260 {
1261         struct btrfs_fs_info *fs_info = data;
1262         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1263         u64 progress;
1264         int ret;
1265
1266         progress = btrfs_dev_replace_progress(fs_info);
1267         progress = div_u64(progress, 10);
1268         btrfs_info_in_rcu(fs_info,
1269                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1270                 btrfs_dev_name(dev_replace->srcdev),
1271                 dev_replace->srcdev->devid,
1272                 btrfs_dev_name(dev_replace->tgtdev),
1273                 (unsigned int)progress);
1274
1275         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1276                               dev_replace->committed_cursor_left,
1277                               btrfs_device_get_total_bytes(dev_replace->srcdev),
1278                               &dev_replace->scrub_progress, 0, 1);
1279         ret = btrfs_dev_replace_finishing(fs_info, ret);
1280         WARN_ON(ret && ret != -ECANCELED);
1281
1282         btrfs_exclop_finish(fs_info);
1283         return 0;
1284 }
1285
1286 int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1287 {
1288         if (!dev_replace->is_valid)
1289                 return 0;
1290
1291         switch (dev_replace->replace_state) {
1292         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1293         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1294         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1295                 return 0;
1296         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1297         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1298                 /*
1299                  * return true even if tgtdev is missing (this is
1300                  * something that can happen if the dev_replace
1301                  * procedure is suspended by an umount and then
1302                  * the tgtdev is missing (or "btrfs dev scan") was
1303                  * not called and the filesystem is remounted
1304                  * in degraded state. This does not stop the
1305                  * dev_replace procedure. It needs to be canceled
1306                  * manually if the cancellation is wanted.
1307                  */
1308                 break;
1309         }
1310         return 1;
1311 }
1312
1313 void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
1314 {
1315         percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1316 }
1317
1318 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1319 {
1320         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1321         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1322 }
1323
1324 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1325 {
1326         while (1) {
1327                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1328                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1329                                      &fs_info->fs_state)))
1330                         break;
1331
1332                 btrfs_bio_counter_dec(fs_info);
1333                 wait_event(fs_info->dev_replace.replace_wait,
1334                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1335                                      &fs_info->fs_state));
1336         }
1337 }