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TOMOYO Linux Cross Reference
Linux/fs/btrfs/dev-replace.c

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  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/buffer_head.h>
 10 #include <linux/blkdev.h>
 11 #include <linux/random.h>
 12 #include <linux/iocontext.h>
 13 #include <linux/capability.h>
 14 #include <linux/kthread.h>
 15 #include <linux/math64.h>
 16 #include <asm/div64.h>
 17 #include "ctree.h"
 18 #include "extent_map.h"
 19 #include "disk-io.h"
 20 #include "transaction.h"
 21 #include "print-tree.h"
 22 #include "volumes.h"
 23 #include "async-thread.h"
 24 #include "check-integrity.h"
 25 #include "rcu-string.h"
 26 #include "dev-replace.h"
 27 #include "sysfs.h"
 28 
 29 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 30                                        int scrub_ret);
 31 static void btrfs_dev_replace_update_device_in_mapping_tree(
 32                                                 struct btrfs_fs_info *fs_info,
 33                                                 struct btrfs_device *srcdev,
 34                                                 struct btrfs_device *tgtdev);
 35 static int btrfs_dev_replace_kthread(void *data);
 36 static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info);
 37 
 38 
 39 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
 40 {
 41         struct btrfs_key key;
 42         struct btrfs_root *dev_root = fs_info->dev_root;
 43         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 44         struct extent_buffer *eb;
 45         int slot;
 46         int ret = 0;
 47         struct btrfs_path *path = NULL;
 48         int item_size;
 49         struct btrfs_dev_replace_item *ptr;
 50         u64 src_devid;
 51 
 52         path = btrfs_alloc_path();
 53         if (!path) {
 54                 ret = -ENOMEM;
 55                 goto out;
 56         }
 57 
 58         key.objectid = 0;
 59         key.type = BTRFS_DEV_REPLACE_KEY;
 60         key.offset = 0;
 61         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
 62         if (ret) {
 63 no_valid_dev_replace_entry_found:
 64                 ret = 0;
 65                 dev_replace->replace_state =
 66                         BTRFS_DEV_REPLACE_ITEM_STATE_NEVER_STARTED;
 67                 dev_replace->cont_reading_from_srcdev_mode =
 68                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 69                 dev_replace->replace_state = 0;
 70                 dev_replace->time_started = 0;
 71                 dev_replace->time_stopped = 0;
 72                 atomic64_set(&dev_replace->num_write_errors, 0);
 73                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 74                 dev_replace->cursor_left = 0;
 75                 dev_replace->committed_cursor_left = 0;
 76                 dev_replace->cursor_left_last_write_of_item = 0;
 77                 dev_replace->cursor_right = 0;
 78                 dev_replace->srcdev = NULL;
 79                 dev_replace->tgtdev = NULL;
 80                 dev_replace->is_valid = 0;
 81                 dev_replace->item_needs_writeback = 0;
 82                 goto out;
 83         }
 84         slot = path->slots[0];
 85         eb = path->nodes[0];
 86         item_size = btrfs_item_size_nr(eb, slot);
 87         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 88 
 89         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 90                 btrfs_warn(fs_info,
 91                         "dev_replace entry found has unexpected size, ignore entry");
 92                 goto no_valid_dev_replace_entry_found;
 93         }
 94 
 95         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 96         dev_replace->cont_reading_from_srcdev_mode =
 97                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 98         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 99         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
100         dev_replace->time_stopped =
101                 btrfs_dev_replace_time_stopped(eb, ptr);
102         atomic64_set(&dev_replace->num_write_errors,
103                      btrfs_dev_replace_num_write_errors(eb, ptr));
104         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
105                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
106         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
107         dev_replace->committed_cursor_left = dev_replace->cursor_left;
108         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
109         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
110         dev_replace->is_valid = 1;
111 
112         dev_replace->item_needs_writeback = 0;
113         switch (dev_replace->replace_state) {
114         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
115         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
116         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
117                 dev_replace->srcdev = NULL;
118                 dev_replace->tgtdev = NULL;
119                 break;
120         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
121         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
122                 dev_replace->srcdev = btrfs_find_device(fs_info, src_devid,
123                                                         NULL, NULL);
124                 dev_replace->tgtdev = btrfs_find_device(fs_info,
125                                                         BTRFS_DEV_REPLACE_DEVID,
126                                                         NULL, NULL);
127                 /*
128                  * allow 'btrfs dev replace_cancel' if src/tgt device is
129                  * missing
130                  */
131                 if (!dev_replace->srcdev &&
132                     !btrfs_test_opt(fs_info, DEGRADED)) {
133                         ret = -EIO;
134                         btrfs_warn(fs_info,
135                            "cannot mount because device replace operation is ongoing and");
136                         btrfs_warn(fs_info,
137                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
138                            src_devid);
139                 }
140                 if (!dev_replace->tgtdev &&
141                     !btrfs_test_opt(fs_info, DEGRADED)) {
142                         ret = -EIO;
143                         btrfs_warn(fs_info,
144                            "cannot mount because device replace operation is ongoing and");
145                         btrfs_warn(fs_info,
146                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
147                                 BTRFS_DEV_REPLACE_DEVID);
148                 }
149                 if (dev_replace->tgtdev) {
150                         if (dev_replace->srcdev) {
151                                 dev_replace->tgtdev->total_bytes =
152                                         dev_replace->srcdev->total_bytes;
153                                 dev_replace->tgtdev->disk_total_bytes =
154                                         dev_replace->srcdev->disk_total_bytes;
155                                 dev_replace->tgtdev->commit_total_bytes =
156                                         dev_replace->srcdev->commit_total_bytes;
157                                 dev_replace->tgtdev->bytes_used =
158                                         dev_replace->srcdev->bytes_used;
159                                 dev_replace->tgtdev->commit_bytes_used =
160                                         dev_replace->srcdev->commit_bytes_used;
161                         }
162                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
163                                 &dev_replace->tgtdev->dev_state);
164 
165                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
166                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
167                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
168                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
169                         dev_replace->tgtdev->fs_info = fs_info;
170                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
171                                 &dev_replace->tgtdev->dev_state);
172                 }
173                 break;
174         }
175 
176 out:
177         btrfs_free_path(path);
178         return ret;
179 }
180 
181 /*
182  * called from commit_transaction. Writes changed device replace state to
183  * disk.
184  */
185 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans,
186                           struct btrfs_fs_info *fs_info)
187 {
188         int ret;
189         struct btrfs_root *dev_root = fs_info->dev_root;
190         struct btrfs_path *path;
191         struct btrfs_key key;
192         struct extent_buffer *eb;
193         struct btrfs_dev_replace_item *ptr;
194         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
195 
196         btrfs_dev_replace_read_lock(dev_replace);
197         if (!dev_replace->is_valid ||
198             !dev_replace->item_needs_writeback) {
199                 btrfs_dev_replace_read_unlock(dev_replace);
200                 return 0;
201         }
202         btrfs_dev_replace_read_unlock(dev_replace);
203 
204         key.objectid = 0;
205         key.type = BTRFS_DEV_REPLACE_KEY;
206         key.offset = 0;
207 
208         path = btrfs_alloc_path();
209         if (!path) {
210                 ret = -ENOMEM;
211                 goto out;
212         }
213         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
214         if (ret < 0) {
215                 btrfs_warn(fs_info,
216                            "error %d while searching for dev_replace item!",
217                            ret);
218                 goto out;
219         }
220 
221         if (ret == 0 &&
222             btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
223                 /*
224                  * need to delete old one and insert a new one.
225                  * Since no attempt is made to recover any old state, if the
226                  * dev_replace state is 'running', the data on the target
227                  * drive is lost.
228                  * It would be possible to recover the state: just make sure
229                  * that the beginning of the item is never changed and always
230                  * contains all the essential information. Then read this
231                  * minimal set of information and use it as a base for the
232                  * new state.
233                  */
234                 ret = btrfs_del_item(trans, dev_root, path);
235                 if (ret != 0) {
236                         btrfs_warn(fs_info,
237                                    "delete too small dev_replace item failed %d!",
238                                    ret);
239                         goto out;
240                 }
241                 ret = 1;
242         }
243 
244         if (ret == 1) {
245                 /* need to insert a new item */
246                 btrfs_release_path(path);
247                 ret = btrfs_insert_empty_item(trans, dev_root, path,
248                                               &key, sizeof(*ptr));
249                 if (ret < 0) {
250                         btrfs_warn(fs_info,
251                                    "insert dev_replace item failed %d!", ret);
252                         goto out;
253                 }
254         }
255 
256         eb = path->nodes[0];
257         ptr = btrfs_item_ptr(eb, path->slots[0],
258                              struct btrfs_dev_replace_item);
259 
260         btrfs_dev_replace_write_lock(dev_replace);
261         if (dev_replace->srcdev)
262                 btrfs_set_dev_replace_src_devid(eb, ptr,
263                         dev_replace->srcdev->devid);
264         else
265                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
266         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
267                 dev_replace->cont_reading_from_srcdev_mode);
268         btrfs_set_dev_replace_replace_state(eb, ptr,
269                 dev_replace->replace_state);
270         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
271         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
272         btrfs_set_dev_replace_num_write_errors(eb, ptr,
273                 atomic64_read(&dev_replace->num_write_errors));
274         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
275                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
276         dev_replace->cursor_left_last_write_of_item =
277                 dev_replace->cursor_left;
278         btrfs_set_dev_replace_cursor_left(eb, ptr,
279                 dev_replace->cursor_left_last_write_of_item);
280         btrfs_set_dev_replace_cursor_right(eb, ptr,
281                 dev_replace->cursor_right);
282         dev_replace->item_needs_writeback = 0;
283         btrfs_dev_replace_write_unlock(dev_replace);
284 
285         btrfs_mark_buffer_dirty(eb);
286 
287 out:
288         btrfs_free_path(path);
289 
290         return ret;
291 }
292 
293 void btrfs_after_dev_replace_commit(struct btrfs_fs_info *fs_info)
294 {
295         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
296 
297         dev_replace->committed_cursor_left =
298                 dev_replace->cursor_left_last_write_of_item;
299 }
300 
301 static char* btrfs_dev_name(struct btrfs_device *device)
302 {
303         if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
304                 return "<missing disk>";
305         else
306                 return rcu_str_deref(device->name);
307 }
308 
309 int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
310                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
311                 int read_src)
312 {
313         struct btrfs_root *root = fs_info->dev_root;
314         struct btrfs_trans_handle *trans;
315         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
316         int ret;
317         struct btrfs_device *tgt_device = NULL;
318         struct btrfs_device *src_device = NULL;
319 
320         /* the disk copy procedure reuses the scrub code */
321         mutex_lock(&fs_info->volume_mutex);
322         ret = btrfs_find_device_by_devspec(fs_info, srcdevid,
323                                             srcdev_name, &src_device);
324         if (ret) {
325                 mutex_unlock(&fs_info->volume_mutex);
326                 return ret;
327         }
328 
329         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
330                                             src_device, &tgt_device);
331         mutex_unlock(&fs_info->volume_mutex);
332         if (ret)
333                 return ret;
334 
335         /*
336          * Here we commit the transaction to make sure commit_total_bytes
337          * of all the devices are updated.
338          */
339         trans = btrfs_attach_transaction(root);
340         if (!IS_ERR(trans)) {
341                 ret = btrfs_commit_transaction(trans);
342                 if (ret)
343                         return ret;
344         } else if (PTR_ERR(trans) != -ENOENT) {
345                 return PTR_ERR(trans);
346         }
347 
348         btrfs_dev_replace_write_lock(dev_replace);
349         switch (dev_replace->replace_state) {
350         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
351         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
352         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
353                 break;
354         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
355         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
356                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
357                 goto leave;
358         }
359 
360         dev_replace->cont_reading_from_srcdev_mode = read_src;
361         WARN_ON(!src_device);
362         dev_replace->srcdev = src_device;
363         WARN_ON(!tgt_device);
364         dev_replace->tgtdev = tgt_device;
365 
366         btrfs_info_in_rcu(fs_info,
367                       "dev_replace from %s (devid %llu) to %s started",
368                       btrfs_dev_name(src_device),
369                       src_device->devid,
370                       rcu_str_deref(tgt_device->name));
371 
372         /*
373          * from now on, the writes to the srcdev are all duplicated to
374          * go to the tgtdev as well (refer to btrfs_map_block()).
375          */
376         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
377         dev_replace->time_started = get_seconds();
378         dev_replace->cursor_left = 0;
379         dev_replace->committed_cursor_left = 0;
380         dev_replace->cursor_left_last_write_of_item = 0;
381         dev_replace->cursor_right = 0;
382         dev_replace->is_valid = 1;
383         dev_replace->item_needs_writeback = 1;
384         atomic64_set(&dev_replace->num_write_errors, 0);
385         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
386         btrfs_dev_replace_write_unlock(dev_replace);
387 
388         ret = btrfs_sysfs_add_device_link(tgt_device->fs_devices, tgt_device);
389         if (ret)
390                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
391 
392         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
393 
394         /* force writing the updated state information to disk */
395         trans = btrfs_start_transaction(root, 0);
396         if (IS_ERR(trans)) {
397                 ret = PTR_ERR(trans);
398                 btrfs_dev_replace_write_lock(dev_replace);
399                 goto leave;
400         }
401 
402         ret = btrfs_commit_transaction(trans);
403         WARN_ON(ret);
404 
405         /* the disk copy procedure reuses the scrub code */
406         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
407                               btrfs_device_get_total_bytes(src_device),
408                               &dev_replace->scrub_progress, 0, 1);
409 
410         ret = btrfs_dev_replace_finishing(fs_info, ret);
411         if (ret == -EINPROGRESS) {
412                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
413         } else {
414                 WARN_ON(ret);
415         }
416 
417         return ret;
418 
419 leave:
420         dev_replace->srcdev = NULL;
421         dev_replace->tgtdev = NULL;
422         btrfs_dev_replace_write_unlock(dev_replace);
423         btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
424         return ret;
425 }
426 
427 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
428                             struct btrfs_ioctl_dev_replace_args *args)
429 {
430         int ret;
431 
432         switch (args->start.cont_reading_from_srcdev_mode) {
433         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
434         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
435                 break;
436         default:
437                 return -EINVAL;
438         }
439 
440         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
441             args->start.tgtdev_name[0] == '\0')
442                 return -EINVAL;
443 
444         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
445                                         args->start.srcdevid,
446                                         args->start.srcdev_name,
447                                         args->start.cont_reading_from_srcdev_mode);
448         args->result = ret;
449         /* don't warn if EINPROGRESS, someone else might be running scrub */
450         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS)
451                 ret = 0;
452 
453         return ret;
454 }
455 
456 /*
457  * blocked until all in-flight bios operations are finished.
458  */
459 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
460 {
461         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
462         wait_event(fs_info->replace_wait, !percpu_counter_sum(
463                    &fs_info->bio_counter));
464 }
465 
466 /*
467  * we have removed target device, it is safe to allow new bios request.
468  */
469 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
470 {
471         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
472         wake_up(&fs_info->replace_wait);
473 }
474 
475 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
476                                        int scrub_ret)
477 {
478         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
479         struct btrfs_device *tgt_device;
480         struct btrfs_device *src_device;
481         struct btrfs_root *root = fs_info->tree_root;
482         u8 uuid_tmp[BTRFS_UUID_SIZE];
483         struct btrfs_trans_handle *trans;
484         int ret = 0;
485 
486         /* don't allow cancel or unmount to disturb the finishing procedure */
487         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
488 
489         btrfs_dev_replace_read_lock(dev_replace);
490         /* was the operation canceled, or is it finished? */
491         if (dev_replace->replace_state !=
492             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
493                 btrfs_dev_replace_read_unlock(dev_replace);
494                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
495                 return 0;
496         }
497 
498         tgt_device = dev_replace->tgtdev;
499         src_device = dev_replace->srcdev;
500         btrfs_dev_replace_read_unlock(dev_replace);
501 
502         /*
503          * flush all outstanding I/O and inode extent mappings before the
504          * copy operation is declared as being finished
505          */
506         ret = btrfs_start_delalloc_roots(fs_info, 0, -1);
507         if (ret) {
508                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
509                 return ret;
510         }
511         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
512 
513         trans = btrfs_start_transaction(root, 0);
514         if (IS_ERR(trans)) {
515                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
516                 return PTR_ERR(trans);
517         }
518         ret = btrfs_commit_transaction(trans);
519         WARN_ON(ret);
520 
521         mutex_lock(&uuid_mutex);
522         /* keep away write_all_supers() during the finishing procedure */
523         mutex_lock(&fs_info->fs_devices->device_list_mutex);
524         mutex_lock(&fs_info->chunk_mutex);
525         btrfs_dev_replace_write_lock(dev_replace);
526         dev_replace->replace_state =
527                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
528                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
529         dev_replace->tgtdev = NULL;
530         dev_replace->srcdev = NULL;
531         dev_replace->time_stopped = get_seconds();
532         dev_replace->item_needs_writeback = 1;
533 
534         /* replace old device with new one in mapping tree */
535         if (!scrub_ret) {
536                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
537                                                                 src_device,
538                                                                 tgt_device);
539         } else {
540                 btrfs_err_in_rcu(fs_info,
541                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
542                                  btrfs_dev_name(src_device),
543                                  src_device->devid,
544                                  rcu_str_deref(tgt_device->name), scrub_ret);
545                 btrfs_dev_replace_write_unlock(dev_replace);
546                 mutex_unlock(&fs_info->chunk_mutex);
547                 mutex_unlock(&fs_info->fs_devices->device_list_mutex);
548                 mutex_unlock(&uuid_mutex);
549                 btrfs_rm_dev_replace_blocked(fs_info);
550                 if (tgt_device)
551                         btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
552                 btrfs_rm_dev_replace_unblocked(fs_info);
553                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
554 
555                 return scrub_ret;
556         }
557 
558         btrfs_info_in_rcu(fs_info,
559                           "dev_replace from %s (devid %llu) to %s finished",
560                           btrfs_dev_name(src_device),
561                           src_device->devid,
562                           rcu_str_deref(tgt_device->name));
563         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
564         tgt_device->devid = src_device->devid;
565         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
566         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
567         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
568         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
569         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
570         btrfs_device_set_disk_total_bytes(tgt_device,
571                                           src_device->disk_total_bytes);
572         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
573         ASSERT(list_empty(&src_device->resized_list));
574         tgt_device->commit_total_bytes = src_device->commit_total_bytes;
575         tgt_device->commit_bytes_used = src_device->bytes_used;
576 
577         btrfs_assign_next_active_device(fs_info, src_device, tgt_device);
578 
579         list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
580         fs_info->fs_devices->rw_devices++;
581 
582         btrfs_dev_replace_write_unlock(dev_replace);
583 
584         btrfs_rm_dev_replace_blocked(fs_info);
585 
586         btrfs_rm_dev_replace_remove_srcdev(fs_info, src_device);
587 
588         btrfs_rm_dev_replace_unblocked(fs_info);
589 
590         /*
591          * this is again a consistent state where no dev_replace procedure
592          * is running, the target device is part of the filesystem, the
593          * source device is not part of the filesystem anymore and its 1st
594          * superblock is scratched out so that it is no longer marked to
595          * belong to this filesystem.
596          */
597         mutex_unlock(&fs_info->chunk_mutex);
598         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
599         mutex_unlock(&uuid_mutex);
600 
601         /* replace the sysfs entry */
602         btrfs_sysfs_rm_device_link(fs_info->fs_devices, src_device);
603         btrfs_rm_dev_replace_free_srcdev(fs_info, src_device);
604 
605         /* write back the superblocks */
606         trans = btrfs_start_transaction(root, 0);
607         if (!IS_ERR(trans))
608                 btrfs_commit_transaction(trans);
609 
610         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
611 
612         return 0;
613 }
614 
615 static void btrfs_dev_replace_update_device_in_mapping_tree(
616                                                 struct btrfs_fs_info *fs_info,
617                                                 struct btrfs_device *srcdev,
618                                                 struct btrfs_device *tgtdev)
619 {
620         struct extent_map_tree *em_tree = &fs_info->mapping_tree.map_tree;
621         struct extent_map *em;
622         struct map_lookup *map;
623         u64 start = 0;
624         int i;
625 
626         write_lock(&em_tree->lock);
627         do {
628                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
629                 if (!em)
630                         break;
631                 map = em->map_lookup;
632                 for (i = 0; i < map->num_stripes; i++)
633                         if (srcdev == map->stripes[i].dev)
634                                 map->stripes[i].dev = tgtdev;
635                 start = em->start + em->len;
636                 free_extent_map(em);
637         } while (start);
638         write_unlock(&em_tree->lock);
639 }
640 
641 /*
642  * Read progress of device replace status according to the state and last
643  * stored position. The value format is the same as for
644  * btrfs_dev_replace::progress_1000
645  */
646 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
647 {
648         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
649         u64 ret = 0;
650 
651         switch (dev_replace->replace_state) {
652         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
653         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
654                 ret = 0;
655                 break;
656         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
657                 ret = 1000;
658                 break;
659         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
660         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
661                 ret = div64_u64(dev_replace->cursor_left,
662                                 div_u64(btrfs_device_get_total_bytes(
663                                                 dev_replace->srcdev), 1000));
664                 break;
665         }
666 
667         return ret;
668 }
669 
670 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
671                               struct btrfs_ioctl_dev_replace_args *args)
672 {
673         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
674 
675         btrfs_dev_replace_read_lock(dev_replace);
676         /* even if !dev_replace_is_valid, the values are good enough for
677          * the replace_status ioctl */
678         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
679         args->status.replace_state = dev_replace->replace_state;
680         args->status.time_started = dev_replace->time_started;
681         args->status.time_stopped = dev_replace->time_stopped;
682         args->status.num_write_errors =
683                 atomic64_read(&dev_replace->num_write_errors);
684         args->status.num_uncorrectable_read_errors =
685                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
686         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
687         btrfs_dev_replace_read_unlock(dev_replace);
688 }
689 
690 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
691 {
692         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
693         struct btrfs_device *tgt_device = NULL;
694         struct btrfs_device *src_device = NULL;
695         struct btrfs_trans_handle *trans;
696         struct btrfs_root *root = fs_info->tree_root;
697         int result;
698         int ret;
699 
700         if (sb_rdonly(fs_info->sb))
701                 return -EROFS;
702 
703         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
704         btrfs_dev_replace_write_lock(dev_replace);
705         switch (dev_replace->replace_state) {
706         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
707         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
708         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
709                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
710                 btrfs_dev_replace_write_unlock(dev_replace);
711                 goto leave;
712         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
713         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
714                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
715                 tgt_device = dev_replace->tgtdev;
716                 src_device = dev_replace->srcdev;
717                 dev_replace->tgtdev = NULL;
718                 dev_replace->srcdev = NULL;
719                 break;
720         }
721         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
722         dev_replace->time_stopped = get_seconds();
723         dev_replace->item_needs_writeback = 1;
724         btrfs_dev_replace_write_unlock(dev_replace);
725         btrfs_scrub_cancel(fs_info);
726 
727         trans = btrfs_start_transaction(root, 0);
728         if (IS_ERR(trans)) {
729                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
730                 return PTR_ERR(trans);
731         }
732         ret = btrfs_commit_transaction(trans);
733         WARN_ON(ret);
734 
735         btrfs_info_in_rcu(fs_info,
736                 "dev_replace from %s (devid %llu) to %s canceled",
737                 btrfs_dev_name(src_device), src_device->devid,
738                 btrfs_dev_name(tgt_device));
739 
740         if (tgt_device)
741                 btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
742 
743 leave:
744         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
745         return result;
746 }
747 
748 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
749 {
750         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
751 
752         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
753         btrfs_dev_replace_write_lock(dev_replace);
754         switch (dev_replace->replace_state) {
755         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
756         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
757         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
758         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
759                 break;
760         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
761                 dev_replace->replace_state =
762                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
763                 dev_replace->time_stopped = get_seconds();
764                 dev_replace->item_needs_writeback = 1;
765                 btrfs_info(fs_info, "suspending dev_replace for unmount");
766                 break;
767         }
768 
769         btrfs_dev_replace_write_unlock(dev_replace);
770         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
771 }
772 
773 /* resume dev_replace procedure that was interrupted by unmount */
774 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
775 {
776         struct task_struct *task;
777         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
778 
779         btrfs_dev_replace_write_lock(dev_replace);
780         switch (dev_replace->replace_state) {
781         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
782         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
783         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
784                 btrfs_dev_replace_write_unlock(dev_replace);
785                 return 0;
786         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
787                 break;
788         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
789                 dev_replace->replace_state =
790                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
791                 break;
792         }
793         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
794                 btrfs_info(fs_info,
795                            "cannot continue dev_replace, tgtdev is missing");
796                 btrfs_info(fs_info,
797                            "you may cancel the operation after 'mount -o degraded'");
798                 btrfs_dev_replace_write_unlock(dev_replace);
799                 return 0;
800         }
801         btrfs_dev_replace_write_unlock(dev_replace);
802 
803         WARN_ON(test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags));
804         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
805         return PTR_ERR_OR_ZERO(task);
806 }
807 
808 static int btrfs_dev_replace_kthread(void *data)
809 {
810         struct btrfs_fs_info *fs_info = data;
811         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
812         u64 progress;
813 
814         progress = btrfs_dev_replace_progress(fs_info);
815         progress = div_u64(progress, 10);
816         btrfs_info_in_rcu(fs_info,
817                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
818                 btrfs_dev_name(dev_replace->srcdev),
819                 dev_replace->srcdev->devid,
820                 btrfs_dev_name(dev_replace->tgtdev),
821                 (unsigned int)progress);
822 
823         btrfs_dev_replace_continue_on_mount(fs_info);
824         clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
825 
826         return 0;
827 }
828 
829 static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info)
830 {
831         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
832         int ret;
833 
834         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
835                               dev_replace->committed_cursor_left,
836                               btrfs_device_get_total_bytes(dev_replace->srcdev),
837                               &dev_replace->scrub_progress, 0, 1);
838         ret = btrfs_dev_replace_finishing(fs_info, ret);
839         WARN_ON(ret);
840         return 0;
841 }
842 
843 int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
844 {
845         if (!dev_replace->is_valid)
846                 return 0;
847 
848         switch (dev_replace->replace_state) {
849         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
850         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
851         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
852                 return 0;
853         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
854         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
855                 /*
856                  * return true even if tgtdev is missing (this is
857                  * something that can happen if the dev_replace
858                  * procedure is suspended by an umount and then
859                  * the tgtdev is missing (or "btrfs dev scan") was
860                  * not called and the the filesystem is remounted
861                  * in degraded state. This does not stop the
862                  * dev_replace procedure. It needs to be canceled
863                  * manually if the cancellation is wanted.
864                  */
865                 break;
866         }
867         return 1;
868 }
869 
870 void btrfs_dev_replace_read_lock(struct btrfs_dev_replace *dev_replace)
871 {
872         read_lock(&dev_replace->lock);
873         atomic_inc(&dev_replace->read_locks);
874 }
875 
876 void btrfs_dev_replace_read_unlock(struct btrfs_dev_replace *dev_replace)
877 {
878         ASSERT(atomic_read(&dev_replace->read_locks) > 0);
879         atomic_dec(&dev_replace->read_locks);
880         read_unlock(&dev_replace->lock);
881 }
882 
883 void btrfs_dev_replace_write_lock(struct btrfs_dev_replace *dev_replace)
884 {
885 again:
886         wait_event(dev_replace->read_lock_wq,
887                    atomic_read(&dev_replace->blocking_readers) == 0);
888         write_lock(&dev_replace->lock);
889         if (atomic_read(&dev_replace->blocking_readers)) {
890                 write_unlock(&dev_replace->lock);
891                 goto again;
892         }
893 }
894 
895 void btrfs_dev_replace_write_unlock(struct btrfs_dev_replace *dev_replace)
896 {
897         ASSERT(atomic_read(&dev_replace->blocking_readers) == 0);
898         write_unlock(&dev_replace->lock);
899 }
900 
901 /* inc blocking cnt and release read lock */
902 void btrfs_dev_replace_set_lock_blocking(
903                                         struct btrfs_dev_replace *dev_replace)
904 {
905         /* only set blocking for read lock */
906         ASSERT(atomic_read(&dev_replace->read_locks) > 0);
907         atomic_inc(&dev_replace->blocking_readers);
908         read_unlock(&dev_replace->lock);
909 }
910 
911 /* acquire read lock and dec blocking cnt */
912 void btrfs_dev_replace_clear_lock_blocking(
913                                         struct btrfs_dev_replace *dev_replace)
914 {
915         /* only set blocking for read lock */
916         ASSERT(atomic_read(&dev_replace->read_locks) > 0);
917         ASSERT(atomic_read(&dev_replace->blocking_readers) > 0);
918         read_lock(&dev_replace->lock);
919         if (atomic_dec_and_test(&dev_replace->blocking_readers) &&
920             waitqueue_active(&dev_replace->read_lock_wq))
921                 wake_up(&dev_replace->read_lock_wq);
922 }
923 
924 void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
925 {
926         percpu_counter_inc(&fs_info->bio_counter);
927 }
928 
929 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
930 {
931         percpu_counter_sub(&fs_info->bio_counter, amount);
932 
933         if (waitqueue_active(&fs_info->replace_wait))
934                 wake_up(&fs_info->replace_wait);
935 }
936 
937 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
938 {
939         while (1) {
940                 percpu_counter_inc(&fs_info->bio_counter);
941                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
942                                      &fs_info->fs_state)))
943                         break;
944 
945                 btrfs_bio_counter_dec(fs_info);
946                 wait_event(fs_info->replace_wait,
947                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
948                                      &fs_info->fs_state));
949         }
950 }
951 

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