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