GNU Linux-libre 5.19-gnu
[releases.git] / fs / btrfs / dev-replace.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) STRATO AG 2012.  All rights reserved.
4  */
5
6 #include <linux/sched.h>
7 #include <linux/bio.h>
8 #include <linux/slab.h>
9 #include <linux/blkdev.h>
10 #include <linux/kthread.h>
11 #include <linux/math64.h>
12 #include "misc.h"
13 #include "ctree.h"
14 #include "extent_map.h"
15 #include "disk-io.h"
16 #include "transaction.h"
17 #include "print-tree.h"
18 #include "volumes.h"
19 #include "async-thread.h"
20 #include "check-integrity.h"
21 #include "rcu-string.h"
22 #include "dev-replace.h"
23 #include "sysfs.h"
24 #include "zoned.h"
25 #include "block-group.h"
26
27 /*
28  * Device replace overview
29  *
30  * [Objective]
31  * To copy all extents (both new and on-disk) from source device to target
32  * device, while still keeping the filesystem read-write.
33  *
34  * [Method]
35  * There are two main methods involved:
36  *
37  * - Write duplication
38  *
39  *   All new writes will be written to both target and source devices, so even
40  *   if replace gets canceled, sources device still contains up-to-date data.
41  *
42  *   Location:          handle_ops_on_dev_replace() from __btrfs_map_block()
43  *   Start:             btrfs_dev_replace_start()
44  *   End:               btrfs_dev_replace_finishing()
45  *   Content:           Latest data/metadata
46  *
47  * - Copy existing extents
48  *
49  *   This happens by re-using scrub facility, as scrub also iterates through
50  *   existing extents from commit root.
51  *
52  *   Location:          scrub_write_block_to_dev_replace() from
53  *                      scrub_block_complete()
54  *   Content:           Data/meta from commit root.
55  *
56  * Due to the content difference, we need to avoid nocow write when dev-replace
57  * is happening.  This is done by marking the block group read-only and waiting
58  * for NOCOW writes.
59  *
60  * After replace is done, the finishing part is done by swapping the target and
61  * source devices.
62  *
63  *   Location:          btrfs_dev_replace_update_device_in_mapping_tree() from
64  *                      btrfs_dev_replace_finishing()
65  */
66
67 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
68                                        int scrub_ret);
69 static int btrfs_dev_replace_kthread(void *data);
70
71 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
72 {
73         struct btrfs_dev_lookup_args args = { .devid = BTRFS_DEV_REPLACE_DEVID };
74         struct btrfs_key key;
75         struct btrfs_root *dev_root = fs_info->dev_root;
76         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
77         struct extent_buffer *eb;
78         int slot;
79         int ret = 0;
80         struct btrfs_path *path = NULL;
81         int item_size;
82         struct btrfs_dev_replace_item *ptr;
83         u64 src_devid;
84
85         if (!dev_root)
86                 return 0;
87
88         path = btrfs_alloc_path();
89         if (!path) {
90                 ret = -ENOMEM;
91                 goto out;
92         }
93
94         key.objectid = 0;
95         key.type = BTRFS_DEV_REPLACE_KEY;
96         key.offset = 0;
97         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
98         if (ret) {
99 no_valid_dev_replace_entry_found:
100                 /*
101                  * We don't have a replace item or it's corrupted.  If there is
102                  * a replace target, fail the mount.
103                  */
104                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
105                         btrfs_err(fs_info,
106                         "found replace target device without a valid replace item");
107                         ret = -EUCLEAN;
108                         goto out;
109                 }
110                 ret = 0;
111                 dev_replace->replace_state =
112                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
113                 dev_replace->cont_reading_from_srcdev_mode =
114                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
115                 dev_replace->time_started = 0;
116                 dev_replace->time_stopped = 0;
117                 atomic64_set(&dev_replace->num_write_errors, 0);
118                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
119                 dev_replace->cursor_left = 0;
120                 dev_replace->committed_cursor_left = 0;
121                 dev_replace->cursor_left_last_write_of_item = 0;
122                 dev_replace->cursor_right = 0;
123                 dev_replace->srcdev = NULL;
124                 dev_replace->tgtdev = NULL;
125                 dev_replace->is_valid = 0;
126                 dev_replace->item_needs_writeback = 0;
127                 goto out;
128         }
129         slot = path->slots[0];
130         eb = path->nodes[0];
131         item_size = btrfs_item_size(eb, slot);
132         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
133
134         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
135                 btrfs_warn(fs_info,
136                         "dev_replace entry found has unexpected size, ignore entry");
137                 goto no_valid_dev_replace_entry_found;
138         }
139
140         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
141         dev_replace->cont_reading_from_srcdev_mode =
142                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
143         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
144         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
145         dev_replace->time_stopped =
146                 btrfs_dev_replace_time_stopped(eb, ptr);
147         atomic64_set(&dev_replace->num_write_errors,
148                      btrfs_dev_replace_num_write_errors(eb, ptr));
149         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
150                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
151         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
152         dev_replace->committed_cursor_left = dev_replace->cursor_left;
153         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
154         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
155         dev_replace->is_valid = 1;
156
157         dev_replace->item_needs_writeback = 0;
158         switch (dev_replace->replace_state) {
159         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
160         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
161         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
162                 /*
163                  * We don't have an active replace item but if there is a
164                  * replace target, fail the mount.
165                  */
166                 if (btrfs_find_device(fs_info->fs_devices, &args)) {
167                         btrfs_err(fs_info,
168                         "replace devid present without an active replace item");
169                         ret = -EUCLEAN;
170                 } else {
171                         dev_replace->srcdev = NULL;
172                         dev_replace->tgtdev = NULL;
173                 }
174                 break;
175         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
176         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
177                 dev_replace->tgtdev = btrfs_find_device(fs_info->fs_devices, &args);
178                 args.devid = src_devid;
179                 dev_replace->srcdev = btrfs_find_device(fs_info->fs_devices, &args);
180
181                 /*
182                  * allow 'btrfs dev replace_cancel' if src/tgt device is
183                  * missing
184                  */
185                 if (!dev_replace->srcdev &&
186                     !btrfs_test_opt(fs_info, DEGRADED)) {
187                         ret = -EIO;
188                         btrfs_warn(fs_info,
189                            "cannot mount because device replace operation is ongoing and");
190                         btrfs_warn(fs_info,
191                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
192                            src_devid);
193                 }
194                 if (!dev_replace->tgtdev &&
195                     !btrfs_test_opt(fs_info, DEGRADED)) {
196                         ret = -EIO;
197                         btrfs_warn(fs_info,
198                            "cannot mount because device replace operation is ongoing and");
199                         btrfs_warn(fs_info,
200                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
201                                 BTRFS_DEV_REPLACE_DEVID);
202                 }
203                 if (dev_replace->tgtdev) {
204                         if (dev_replace->srcdev) {
205                                 dev_replace->tgtdev->total_bytes =
206                                         dev_replace->srcdev->total_bytes;
207                                 dev_replace->tgtdev->disk_total_bytes =
208                                         dev_replace->srcdev->disk_total_bytes;
209                                 dev_replace->tgtdev->commit_total_bytes =
210                                         dev_replace->srcdev->commit_total_bytes;
211                                 dev_replace->tgtdev->bytes_used =
212                                         dev_replace->srcdev->bytes_used;
213                                 dev_replace->tgtdev->commit_bytes_used =
214                                         dev_replace->srcdev->commit_bytes_used;
215                         }
216                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
217                                 &dev_replace->tgtdev->dev_state);
218
219                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
220                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
221                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
222                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
223                         dev_replace->tgtdev->fs_info = fs_info;
224                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
225                                 &dev_replace->tgtdev->dev_state);
226                 }
227                 break;
228         }
229
230 out:
231         btrfs_free_path(path);
232         return ret;
233 }
234
235 /*
236  * Initialize a new device for device replace target from a given source dev
237  * and path.
238  *
239  * Return 0 and new device in @device_out, otherwise return < 0
240  */
241 static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
242                                   const char *device_path,
243                                   struct btrfs_device *srcdev,
244                                   struct btrfs_device **device_out)
245 {
246         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
247         struct btrfs_device *device;
248         struct block_device *bdev;
249         struct rcu_string *name;
250         u64 devid = BTRFS_DEV_REPLACE_DEVID;
251         int ret = 0;
252
253         *device_out = NULL;
254         if (srcdev->fs_devices->seeding) {
255                 btrfs_err(fs_info, "the filesystem is a seed filesystem!");
256                 return -EINVAL;
257         }
258
259         bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
260                                   fs_info->bdev_holder);
261         if (IS_ERR(bdev)) {
262                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
263                 return PTR_ERR(bdev);
264         }
265
266         if (!btrfs_check_device_zone_type(fs_info, bdev)) {
267                 btrfs_err(fs_info,
268                 "dev-replace: zoned type of target device mismatch with filesystem");
269                 ret = -EINVAL;
270                 goto error;
271         }
272
273         sync_blockdev(bdev);
274
275         list_for_each_entry(device, &fs_devices->devices, dev_list) {
276                 if (device->bdev == bdev) {
277                         btrfs_err(fs_info,
278                                   "target device is in the filesystem!");
279                         ret = -EEXIST;
280                         goto error;
281                 }
282         }
283
284
285         if (bdev_nr_bytes(bdev) < btrfs_device_get_total_bytes(srcdev)) {
286                 btrfs_err(fs_info,
287                           "target device is smaller than source device!");
288                 ret = -EINVAL;
289                 goto error;
290         }
291
292
293         device = btrfs_alloc_device(NULL, &devid, NULL);
294         if (IS_ERR(device)) {
295                 ret = PTR_ERR(device);
296                 goto error;
297         }
298
299         name = rcu_string_strdup(device_path, GFP_KERNEL);
300         if (!name) {
301                 btrfs_free_device(device);
302                 ret = -ENOMEM;
303                 goto error;
304         }
305         rcu_assign_pointer(device->name, name);
306         ret = lookup_bdev(device_path, &device->devt);
307         if (ret)
308                 goto error;
309
310         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
311         device->generation = 0;
312         device->io_width = fs_info->sectorsize;
313         device->io_align = fs_info->sectorsize;
314         device->sector_size = fs_info->sectorsize;
315         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
316         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
317         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
318         device->commit_total_bytes = srcdev->commit_total_bytes;
319         device->commit_bytes_used = device->bytes_used;
320         device->fs_info = fs_info;
321         device->bdev = bdev;
322         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
323         set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
324         device->mode = FMODE_EXCL;
325         device->dev_stats_valid = 1;
326         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
327         device->fs_devices = fs_devices;
328
329         ret = btrfs_get_dev_zone_info(device, false);
330         if (ret)
331                 goto error;
332
333         mutex_lock(&fs_devices->device_list_mutex);
334         list_add(&device->dev_list, &fs_devices->devices);
335         fs_devices->num_devices++;
336         fs_devices->open_devices++;
337         mutex_unlock(&fs_devices->device_list_mutex);
338
339         *device_out = device;
340         return 0;
341
342 error:
343         blkdev_put(bdev, FMODE_EXCL);
344         return ret;
345 }
346
347 /*
348  * called from commit_transaction. Writes changed device replace state to
349  * disk.
350  */
351 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
352 {
353         struct btrfs_fs_info *fs_info = trans->fs_info;
354         int ret;
355         struct btrfs_root *dev_root = fs_info->dev_root;
356         struct btrfs_path *path;
357         struct btrfs_key key;
358         struct extent_buffer *eb;
359         struct btrfs_dev_replace_item *ptr;
360         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
361
362         down_read(&dev_replace->rwsem);
363         if (!dev_replace->is_valid ||
364             !dev_replace->item_needs_writeback) {
365                 up_read(&dev_replace->rwsem);
366                 return 0;
367         }
368         up_read(&dev_replace->rwsem);
369
370         key.objectid = 0;
371         key.type = BTRFS_DEV_REPLACE_KEY;
372         key.offset = 0;
373
374         path = btrfs_alloc_path();
375         if (!path) {
376                 ret = -ENOMEM;
377                 goto out;
378         }
379         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
380         if (ret < 0) {
381                 btrfs_warn(fs_info,
382                            "error %d while searching for dev_replace item!",
383                            ret);
384                 goto out;
385         }
386
387         if (ret == 0 &&
388             btrfs_item_size(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
389                 /*
390                  * need to delete old one and insert a new one.
391                  * Since no attempt is made to recover any old state, if the
392                  * dev_replace state is 'running', the data on the target
393                  * drive is lost.
394                  * It would be possible to recover the state: just make sure
395                  * that the beginning of the item is never changed and always
396                  * contains all the essential information. Then read this
397                  * minimal set of information and use it as a base for the
398                  * new state.
399                  */
400                 ret = btrfs_del_item(trans, dev_root, path);
401                 if (ret != 0) {
402                         btrfs_warn(fs_info,
403                                    "delete too small dev_replace item failed %d!",
404                                    ret);
405                         goto out;
406                 }
407                 ret = 1;
408         }
409
410         if (ret == 1) {
411                 /* need to insert a new item */
412                 btrfs_release_path(path);
413                 ret = btrfs_insert_empty_item(trans, dev_root, path,
414                                               &key, sizeof(*ptr));
415                 if (ret < 0) {
416                         btrfs_warn(fs_info,
417                                    "insert dev_replace item failed %d!", ret);
418                         goto out;
419                 }
420         }
421
422         eb = path->nodes[0];
423         ptr = btrfs_item_ptr(eb, path->slots[0],
424                              struct btrfs_dev_replace_item);
425
426         down_write(&dev_replace->rwsem);
427         if (dev_replace->srcdev)
428                 btrfs_set_dev_replace_src_devid(eb, ptr,
429                         dev_replace->srcdev->devid);
430         else
431                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
432         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
433                 dev_replace->cont_reading_from_srcdev_mode);
434         btrfs_set_dev_replace_replace_state(eb, ptr,
435                 dev_replace->replace_state);
436         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
437         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
438         btrfs_set_dev_replace_num_write_errors(eb, ptr,
439                 atomic64_read(&dev_replace->num_write_errors));
440         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
441                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
442         dev_replace->cursor_left_last_write_of_item =
443                 dev_replace->cursor_left;
444         btrfs_set_dev_replace_cursor_left(eb, ptr,
445                 dev_replace->cursor_left_last_write_of_item);
446         btrfs_set_dev_replace_cursor_right(eb, ptr,
447                 dev_replace->cursor_right);
448         dev_replace->item_needs_writeback = 0;
449         up_write(&dev_replace->rwsem);
450
451         btrfs_mark_buffer_dirty(eb);
452
453 out:
454         btrfs_free_path(path);
455
456         return ret;
457 }
458
459 static char* btrfs_dev_name(struct btrfs_device *device)
460 {
461         if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
462                 return "<missing disk>";
463         else
464                 return rcu_str_deref(device->name);
465 }
466
467 static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
468                                     struct btrfs_device *src_dev)
469 {
470         struct btrfs_path *path;
471         struct btrfs_key key;
472         struct btrfs_key found_key;
473         struct btrfs_root *root = fs_info->dev_root;
474         struct btrfs_dev_extent *dev_extent = NULL;
475         struct btrfs_block_group *cache;
476         struct btrfs_trans_handle *trans;
477         int iter_ret = 0;
478         int ret = 0;
479         u64 chunk_offset;
480
481         /* Do not use "to_copy" on non zoned filesystem for now */
482         if (!btrfs_is_zoned(fs_info))
483                 return 0;
484
485         mutex_lock(&fs_info->chunk_mutex);
486
487         /* Ensure we don't have pending new block group */
488         spin_lock(&fs_info->trans_lock);
489         while (fs_info->running_transaction &&
490                !list_empty(&fs_info->running_transaction->dev_update_list)) {
491                 spin_unlock(&fs_info->trans_lock);
492                 mutex_unlock(&fs_info->chunk_mutex);
493                 trans = btrfs_attach_transaction(root);
494                 if (IS_ERR(trans)) {
495                         ret = PTR_ERR(trans);
496                         mutex_lock(&fs_info->chunk_mutex);
497                         if (ret == -ENOENT) {
498                                 spin_lock(&fs_info->trans_lock);
499                                 continue;
500                         } else {
501                                 goto unlock;
502                         }
503                 }
504
505                 ret = btrfs_commit_transaction(trans);
506                 mutex_lock(&fs_info->chunk_mutex);
507                 if (ret)
508                         goto unlock;
509
510                 spin_lock(&fs_info->trans_lock);
511         }
512         spin_unlock(&fs_info->trans_lock);
513
514         path = btrfs_alloc_path();
515         if (!path) {
516                 ret = -ENOMEM;
517                 goto unlock;
518         }
519
520         path->reada = READA_FORWARD;
521         path->search_commit_root = 1;
522         path->skip_locking = 1;
523
524         key.objectid = src_dev->devid;
525         key.type = BTRFS_DEV_EXTENT_KEY;
526         key.offset = 0;
527
528         btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
529                 struct extent_buffer *leaf = path->nodes[0];
530
531                 if (found_key.objectid != src_dev->devid)
532                         break;
533
534                 if (found_key.type != BTRFS_DEV_EXTENT_KEY)
535                         break;
536
537                 if (found_key.offset < key.offset)
538                         break;
539
540                 dev_extent = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_extent);
541
542                 chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
543
544                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
545                 if (!cache)
546                         continue;
547
548                 spin_lock(&cache->lock);
549                 cache->to_copy = 1;
550                 spin_unlock(&cache->lock);
551
552                 btrfs_put_block_group(cache);
553         }
554         if (iter_ret < 0)
555                 ret = iter_ret;
556
557         btrfs_free_path(path);
558 unlock:
559         mutex_unlock(&fs_info->chunk_mutex);
560
561         return ret;
562 }
563
564 bool btrfs_finish_block_group_to_copy(struct btrfs_device *srcdev,
565                                       struct btrfs_block_group *cache,
566                                       u64 physical)
567 {
568         struct btrfs_fs_info *fs_info = cache->fs_info;
569         struct extent_map *em;
570         struct map_lookup *map;
571         u64 chunk_offset = cache->start;
572         int num_extents, cur_extent;
573         int i;
574
575         /* Do not use "to_copy" on non zoned filesystem for now */
576         if (!btrfs_is_zoned(fs_info))
577                 return true;
578
579         spin_lock(&cache->lock);
580         if (cache->removed) {
581                 spin_unlock(&cache->lock);
582                 return true;
583         }
584         spin_unlock(&cache->lock);
585
586         em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
587         ASSERT(!IS_ERR(em));
588         map = em->map_lookup;
589
590         num_extents = cur_extent = 0;
591         for (i = 0; i < map->num_stripes; i++) {
592                 /* We have more device extent to copy */
593                 if (srcdev != map->stripes[i].dev)
594                         continue;
595
596                 num_extents++;
597                 if (physical == map->stripes[i].physical)
598                         cur_extent = i;
599         }
600
601         free_extent_map(em);
602
603         if (num_extents > 1 && cur_extent < num_extents - 1) {
604                 /*
605                  * Has more stripes on this device. Keep this block group
606                  * readonly until we finish all the stripes.
607                  */
608                 return false;
609         }
610
611         /* Last stripe on this device */
612         spin_lock(&cache->lock);
613         cache->to_copy = 0;
614         spin_unlock(&cache->lock);
615
616         return true;
617 }
618
619 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
620                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
621                 int read_src)
622 {
623         struct btrfs_root *root = fs_info->dev_root;
624         struct btrfs_trans_handle *trans;
625         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
626         int ret;
627         struct btrfs_device *tgt_device = NULL;
628         struct btrfs_device *src_device = NULL;
629
630         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
631                                                   srcdev_name);
632         if (IS_ERR(src_device))
633                 return PTR_ERR(src_device);
634
635         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
636                 btrfs_warn_in_rcu(fs_info,
637           "cannot replace device %s (devid %llu) due to active swapfile",
638                         btrfs_dev_name(src_device), src_device->devid);
639                 return -ETXTBSY;
640         }
641
642         /*
643          * Here we commit the transaction to make sure commit_total_bytes
644          * of all the devices are updated.
645          */
646         trans = btrfs_attach_transaction(root);
647         if (!IS_ERR(trans)) {
648                 ret = btrfs_commit_transaction(trans);
649                 if (ret)
650                         return ret;
651         } else if (PTR_ERR(trans) != -ENOENT) {
652                 return PTR_ERR(trans);
653         }
654
655         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
656                                             src_device, &tgt_device);
657         if (ret)
658                 return ret;
659
660         ret = mark_block_group_to_copy(fs_info, src_device);
661         if (ret)
662                 return ret;
663
664         down_write(&dev_replace->rwsem);
665         switch (dev_replace->replace_state) {
666         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
667         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
668         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
669                 break;
670         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
671         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
672                 ASSERT(0);
673                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
674                 up_write(&dev_replace->rwsem);
675                 goto leave;
676         }
677
678         dev_replace->cont_reading_from_srcdev_mode = read_src;
679         dev_replace->srcdev = src_device;
680         dev_replace->tgtdev = tgt_device;
681
682         btrfs_info_in_rcu(fs_info,
683                       "dev_replace from %s (devid %llu) to %s started",
684                       btrfs_dev_name(src_device),
685                       src_device->devid,
686                       rcu_str_deref(tgt_device->name));
687
688         /*
689          * from now on, the writes to the srcdev are all duplicated to
690          * go to the tgtdev as well (refer to btrfs_map_block()).
691          */
692         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
693         dev_replace->time_started = ktime_get_real_seconds();
694         dev_replace->cursor_left = 0;
695         dev_replace->committed_cursor_left = 0;
696         dev_replace->cursor_left_last_write_of_item = 0;
697         dev_replace->cursor_right = 0;
698         dev_replace->is_valid = 1;
699         dev_replace->item_needs_writeback = 1;
700         atomic64_set(&dev_replace->num_write_errors, 0);
701         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
702         up_write(&dev_replace->rwsem);
703
704         ret = btrfs_sysfs_add_device(tgt_device);
705         if (ret)
706                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
707
708         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
709
710         /*
711          * Commit dev_replace state and reserve 1 item for it.
712          * This is crucial to ensure we won't miss copying extents for new block
713          * groups that are allocated after we started the device replace, and
714          * must be done after setting up the device replace state.
715          */
716         trans = btrfs_start_transaction(root, 1);
717         if (IS_ERR(trans)) {
718                 ret = PTR_ERR(trans);
719                 down_write(&dev_replace->rwsem);
720                 dev_replace->replace_state =
721                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
722                 dev_replace->srcdev = NULL;
723                 dev_replace->tgtdev = NULL;
724                 up_write(&dev_replace->rwsem);
725                 goto leave;
726         }
727
728         ret = btrfs_commit_transaction(trans);
729         WARN_ON(ret);
730
731         /* the disk copy procedure reuses the scrub code */
732         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
733                               btrfs_device_get_total_bytes(src_device),
734                               &dev_replace->scrub_progress, 0, 1);
735
736         ret = btrfs_dev_replace_finishing(fs_info, ret);
737         if (ret == -EINPROGRESS)
738                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
739
740         return ret;
741
742 leave:
743         btrfs_destroy_dev_replace_tgtdev(tgt_device);
744         return ret;
745 }
746
747 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
748                             struct btrfs_ioctl_dev_replace_args *args)
749 {
750         int ret;
751
752         switch (args->start.cont_reading_from_srcdev_mode) {
753         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
754         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
755                 break;
756         default:
757                 return -EINVAL;
758         }
759
760         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
761             args->start.tgtdev_name[0] == '\0')
762                 return -EINVAL;
763
764         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
765                                         args->start.srcdevid,
766                                         args->start.srcdev_name,
767                                         args->start.cont_reading_from_srcdev_mode);
768         args->result = ret;
769         /* don't warn if EINPROGRESS, someone else might be running scrub */
770         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
771             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
772                 return 0;
773
774         return ret;
775 }
776
777 /*
778  * blocked until all in-flight bios operations are finished.
779  */
780 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
781 {
782         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
783         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
784                    &fs_info->dev_replace.bio_counter));
785 }
786
787 /*
788  * we have removed target device, it is safe to allow new bios request.
789  */
790 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
791 {
792         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
793         wake_up(&fs_info->dev_replace.replace_wait);
794 }
795
796 /*
797  * When finishing the device replace, before swapping the source device with the
798  * target device we must update the chunk allocation state in the target device,
799  * as it is empty because replace works by directly copying the chunks and not
800  * through the normal chunk allocation path.
801  */
802 static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
803                                         struct btrfs_device *tgtdev)
804 {
805         struct extent_state *cached_state = NULL;
806         u64 start = 0;
807         u64 found_start;
808         u64 found_end;
809         int ret = 0;
810
811         lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
812
813         while (!find_first_extent_bit(&srcdev->alloc_state, start,
814                                       &found_start, &found_end,
815                                       CHUNK_ALLOCATED, &cached_state)) {
816                 ret = set_extent_bits(&tgtdev->alloc_state, found_start,
817                                       found_end, CHUNK_ALLOCATED);
818                 if (ret)
819                         break;
820                 start = found_end + 1;
821         }
822
823         free_extent_state(cached_state);
824         return ret;
825 }
826
827 static void btrfs_dev_replace_update_device_in_mapping_tree(
828                                                 struct btrfs_fs_info *fs_info,
829                                                 struct btrfs_device *srcdev,
830                                                 struct btrfs_device *tgtdev)
831 {
832         struct extent_map_tree *em_tree = &fs_info->mapping_tree;
833         struct extent_map *em;
834         struct map_lookup *map;
835         u64 start = 0;
836         int i;
837
838         write_lock(&em_tree->lock);
839         do {
840                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
841                 if (!em)
842                         break;
843                 map = em->map_lookup;
844                 for (i = 0; i < map->num_stripes; i++)
845                         if (srcdev == map->stripes[i].dev)
846                                 map->stripes[i].dev = tgtdev;
847                 start = em->start + em->len;
848                 free_extent_map(em);
849         } while (start);
850         write_unlock(&em_tree->lock);
851 }
852
853 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
854                                        int scrub_ret)
855 {
856         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
857         struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
858         struct btrfs_device *tgt_device;
859         struct btrfs_device *src_device;
860         struct btrfs_root *root = fs_info->tree_root;
861         u8 uuid_tmp[BTRFS_UUID_SIZE];
862         struct btrfs_trans_handle *trans;
863         int ret = 0;
864
865         /* don't allow cancel or unmount to disturb the finishing procedure */
866         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
867
868         down_read(&dev_replace->rwsem);
869         /* was the operation canceled, or is it finished? */
870         if (dev_replace->replace_state !=
871             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
872                 up_read(&dev_replace->rwsem);
873                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
874                 return 0;
875         }
876
877         tgt_device = dev_replace->tgtdev;
878         src_device = dev_replace->srcdev;
879         up_read(&dev_replace->rwsem);
880
881         /*
882          * flush all outstanding I/O and inode extent mappings before the
883          * copy operation is declared as being finished
884          */
885         ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
886         if (ret) {
887                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
888                 return ret;
889         }
890         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
891
892         /*
893          * We have to use this loop approach because at this point src_device
894          * has to be available for transaction commit to complete, yet new
895          * chunks shouldn't be allocated on the device.
896          */
897         while (1) {
898                 trans = btrfs_start_transaction(root, 0);
899                 if (IS_ERR(trans)) {
900                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
901                         return PTR_ERR(trans);
902                 }
903                 ret = btrfs_commit_transaction(trans);
904                 WARN_ON(ret);
905
906                 /* Prevent write_all_supers() during the finishing procedure */
907                 mutex_lock(&fs_devices->device_list_mutex);
908                 /* Prevent new chunks being allocated on the source device */
909                 mutex_lock(&fs_info->chunk_mutex);
910
911                 if (!list_empty(&src_device->post_commit_list)) {
912                         mutex_unlock(&fs_devices->device_list_mutex);
913                         mutex_unlock(&fs_info->chunk_mutex);
914                 } else {
915                         break;
916                 }
917         }
918
919         down_write(&dev_replace->rwsem);
920         dev_replace->replace_state =
921                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
922                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
923         dev_replace->tgtdev = NULL;
924         dev_replace->srcdev = NULL;
925         dev_replace->time_stopped = ktime_get_real_seconds();
926         dev_replace->item_needs_writeback = 1;
927
928         /*
929          * Update allocation state in the new device and replace the old device
930          * with the new one in the mapping tree.
931          */
932         if (!scrub_ret) {
933                 scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
934                 if (scrub_ret)
935                         goto error;
936                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
937                                                                 src_device,
938                                                                 tgt_device);
939         } else {
940                 if (scrub_ret != -ECANCELED)
941                         btrfs_err_in_rcu(fs_info,
942                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
943                                  btrfs_dev_name(src_device),
944                                  src_device->devid,
945                                  rcu_str_deref(tgt_device->name), scrub_ret);
946 error:
947                 up_write(&dev_replace->rwsem);
948                 mutex_unlock(&fs_info->chunk_mutex);
949                 mutex_unlock(&fs_devices->device_list_mutex);
950                 btrfs_rm_dev_replace_blocked(fs_info);
951                 if (tgt_device)
952                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
953                 btrfs_rm_dev_replace_unblocked(fs_info);
954                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
955
956                 return scrub_ret;
957         }
958
959         btrfs_info_in_rcu(fs_info,
960                           "dev_replace from %s (devid %llu) to %s finished",
961                           btrfs_dev_name(src_device),
962                           src_device->devid,
963                           rcu_str_deref(tgt_device->name));
964         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
965         tgt_device->devid = src_device->devid;
966         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
967         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
968         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
969         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
970         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
971         btrfs_device_set_disk_total_bytes(tgt_device,
972                                           src_device->disk_total_bytes);
973         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
974         tgt_device->commit_bytes_used = src_device->bytes_used;
975
976         btrfs_assign_next_active_device(src_device, tgt_device);
977
978         list_add(&tgt_device->dev_alloc_list, &fs_devices->alloc_list);
979         fs_devices->rw_devices++;
980
981         up_write(&dev_replace->rwsem);
982         btrfs_rm_dev_replace_blocked(fs_info);
983
984         btrfs_rm_dev_replace_remove_srcdev(src_device);
985
986         btrfs_rm_dev_replace_unblocked(fs_info);
987
988         /*
989          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
990          * update on-disk dev stats value during commit transaction
991          */
992         atomic_inc(&tgt_device->dev_stats_ccnt);
993
994         /*
995          * this is again a consistent state where no dev_replace procedure
996          * is running, the target device is part of the filesystem, the
997          * source device is not part of the filesystem anymore and its 1st
998          * superblock is scratched out so that it is no longer marked to
999          * belong to this filesystem.
1000          */
1001         mutex_unlock(&fs_info->chunk_mutex);
1002         mutex_unlock(&fs_devices->device_list_mutex);
1003
1004         /* replace the sysfs entry */
1005         btrfs_sysfs_remove_device(src_device);
1006         btrfs_sysfs_update_devid(tgt_device);
1007         if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
1008                 btrfs_scratch_superblocks(fs_info, src_device->bdev,
1009                                           src_device->name->str);
1010
1011         /* write back the superblocks */
1012         trans = btrfs_start_transaction(root, 0);
1013         if (!IS_ERR(trans))
1014                 btrfs_commit_transaction(trans);
1015
1016         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1017
1018         btrfs_rm_dev_replace_free_srcdev(src_device);
1019
1020         return 0;
1021 }
1022
1023 /*
1024  * Read progress of device replace status according to the state and last
1025  * stored position. The value format is the same as for
1026  * btrfs_dev_replace::progress_1000
1027  */
1028 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
1029 {
1030         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1031         u64 ret = 0;
1032
1033         switch (dev_replace->replace_state) {
1034         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1035         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1036                 ret = 0;
1037                 break;
1038         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1039                 ret = 1000;
1040                 break;
1041         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1042         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1043                 ret = div64_u64(dev_replace->cursor_left,
1044                                 div_u64(btrfs_device_get_total_bytes(
1045                                                 dev_replace->srcdev), 1000));
1046                 break;
1047         }
1048
1049         return ret;
1050 }
1051
1052 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
1053                               struct btrfs_ioctl_dev_replace_args *args)
1054 {
1055         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1056
1057         down_read(&dev_replace->rwsem);
1058         /* even if !dev_replace_is_valid, the values are good enough for
1059          * the replace_status ioctl */
1060         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1061         args->status.replace_state = dev_replace->replace_state;
1062         args->status.time_started = dev_replace->time_started;
1063         args->status.time_stopped = dev_replace->time_stopped;
1064         args->status.num_write_errors =
1065                 atomic64_read(&dev_replace->num_write_errors);
1066         args->status.num_uncorrectable_read_errors =
1067                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
1068         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
1069         up_read(&dev_replace->rwsem);
1070 }
1071
1072 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
1073 {
1074         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1075         struct btrfs_device *tgt_device = NULL;
1076         struct btrfs_device *src_device = NULL;
1077         struct btrfs_trans_handle *trans;
1078         struct btrfs_root *root = fs_info->tree_root;
1079         int result;
1080         int ret;
1081
1082         if (sb_rdonly(fs_info->sb))
1083                 return -EROFS;
1084
1085         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1086         down_write(&dev_replace->rwsem);
1087         switch (dev_replace->replace_state) {
1088         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1089         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1090         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1091                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1092                 up_write(&dev_replace->rwsem);
1093                 break;
1094         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1095                 tgt_device = dev_replace->tgtdev;
1096                 src_device = dev_replace->srcdev;
1097                 up_write(&dev_replace->rwsem);
1098                 ret = btrfs_scrub_cancel(fs_info);
1099                 if (ret < 0) {
1100                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
1101                 } else {
1102                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1103                         /*
1104                          * btrfs_dev_replace_finishing() will handle the
1105                          * cleanup part
1106                          */
1107                         btrfs_info_in_rcu(fs_info,
1108                                 "dev_replace from %s (devid %llu) to %s canceled",
1109                                 btrfs_dev_name(src_device), src_device->devid,
1110                                 btrfs_dev_name(tgt_device));
1111                 }
1112                 break;
1113         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1114                 /*
1115                  * Scrub doing the replace isn't running so we need to do the
1116                  * cleanup step of btrfs_dev_replace_finishing() here
1117                  */
1118                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
1119                 tgt_device = dev_replace->tgtdev;
1120                 src_device = dev_replace->srcdev;
1121                 dev_replace->tgtdev = NULL;
1122                 dev_replace->srcdev = NULL;
1123                 dev_replace->replace_state =
1124                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
1125                 dev_replace->time_stopped = ktime_get_real_seconds();
1126                 dev_replace->item_needs_writeback = 1;
1127
1128                 up_write(&dev_replace->rwsem);
1129
1130                 /* Scrub for replace must not be running in suspended state */
1131                 ret = btrfs_scrub_cancel(fs_info);
1132                 ASSERT(ret != -ENOTCONN);
1133
1134                 trans = btrfs_start_transaction(root, 0);
1135                 if (IS_ERR(trans)) {
1136                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1137                         return PTR_ERR(trans);
1138                 }
1139                 ret = btrfs_commit_transaction(trans);
1140                 WARN_ON(ret);
1141
1142                 btrfs_info_in_rcu(fs_info,
1143                 "suspended dev_replace from %s (devid %llu) to %s canceled",
1144                         btrfs_dev_name(src_device), src_device->devid,
1145                         btrfs_dev_name(tgt_device));
1146
1147                 if (tgt_device)
1148                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
1149                 break;
1150         default:
1151                 up_write(&dev_replace->rwsem);
1152                 result = -EINVAL;
1153         }
1154
1155         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1156         return result;
1157 }
1158
1159 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
1160 {
1161         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1162
1163         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
1164         down_write(&dev_replace->rwsem);
1165
1166         switch (dev_replace->replace_state) {
1167         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1168         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1169         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1170         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1171                 break;
1172         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1173                 dev_replace->replace_state =
1174                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1175                 dev_replace->time_stopped = ktime_get_real_seconds();
1176                 dev_replace->item_needs_writeback = 1;
1177                 btrfs_info(fs_info, "suspending dev_replace for unmount");
1178                 break;
1179         }
1180
1181         up_write(&dev_replace->rwsem);
1182         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
1183 }
1184
1185 /* resume dev_replace procedure that was interrupted by unmount */
1186 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
1187 {
1188         struct task_struct *task;
1189         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1190
1191         down_write(&dev_replace->rwsem);
1192
1193         switch (dev_replace->replace_state) {
1194         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1195         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1196         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1197                 up_write(&dev_replace->rwsem);
1198                 return 0;
1199         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1200                 break;
1201         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1202                 dev_replace->replace_state =
1203                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1204                 break;
1205         }
1206         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1207                 btrfs_info(fs_info,
1208                            "cannot continue dev_replace, tgtdev is missing");
1209                 btrfs_info(fs_info,
1210                            "you may cancel the operation after 'mount -o degraded'");
1211                 dev_replace->replace_state =
1212                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1213                 up_write(&dev_replace->rwsem);
1214                 return 0;
1215         }
1216         up_write(&dev_replace->rwsem);
1217
1218         /*
1219          * This could collide with a paused balance, but the exclusive op logic
1220          * should never allow both to start and pause. We don't want to allow
1221          * dev-replace to start anyway.
1222          */
1223         if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_DEV_REPLACE)) {
1224                 down_write(&dev_replace->rwsem);
1225                 dev_replace->replace_state =
1226                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1227                 up_write(&dev_replace->rwsem);
1228                 btrfs_info(fs_info,
1229                 "cannot resume dev-replace, other exclusive operation running");
1230                 return 0;
1231         }
1232
1233         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1234         return PTR_ERR_OR_ZERO(task);
1235 }
1236
1237 static int btrfs_dev_replace_kthread(void *data)
1238 {
1239         struct btrfs_fs_info *fs_info = data;
1240         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1241         u64 progress;
1242         int ret;
1243
1244         progress = btrfs_dev_replace_progress(fs_info);
1245         progress = div_u64(progress, 10);
1246         btrfs_info_in_rcu(fs_info,
1247                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1248                 btrfs_dev_name(dev_replace->srcdev),
1249                 dev_replace->srcdev->devid,
1250                 btrfs_dev_name(dev_replace->tgtdev),
1251                 (unsigned int)progress);
1252
1253         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1254                               dev_replace->committed_cursor_left,
1255                               btrfs_device_get_total_bytes(dev_replace->srcdev),
1256                               &dev_replace->scrub_progress, 0, 1);
1257         ret = btrfs_dev_replace_finishing(fs_info, ret);
1258         WARN_ON(ret && ret != -ECANCELED);
1259
1260         btrfs_exclop_finish(fs_info);
1261         return 0;
1262 }
1263
1264 int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1265 {
1266         if (!dev_replace->is_valid)
1267                 return 0;
1268
1269         switch (dev_replace->replace_state) {
1270         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1271         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1272         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1273                 return 0;
1274         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1275         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1276                 /*
1277                  * return true even if tgtdev is missing (this is
1278                  * something that can happen if the dev_replace
1279                  * procedure is suspended by an umount and then
1280                  * the tgtdev is missing (or "btrfs dev scan") was
1281                  * not called and the filesystem is remounted
1282                  * in degraded state. This does not stop the
1283                  * dev_replace procedure. It needs to be canceled
1284                  * manually if the cancellation is wanted.
1285                  */
1286                 break;
1287         }
1288         return 1;
1289 }
1290
1291 void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
1292 {
1293         percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1294 }
1295
1296 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1297 {
1298         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1299         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1300 }
1301
1302 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1303 {
1304         while (1) {
1305                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1306                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1307                                      &fs_info->fs_state)))
1308                         break;
1309
1310                 btrfs_bio_counter_dec(fs_info);
1311                 wait_event(fs_info->dev_replace.replace_wait,
1312                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1313                                      &fs_info->fs_state));
1314         }
1315 }