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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/blkdev.h>
 10 #include <linux/kthread.h>
 11 #include <linux/math64.h>
 12 #include "ctree.h"
 13 #include "extent_map.h"
 14 #include "disk-io.h"
 15 #include "transaction.h"
 16 #include "print-tree.h"
 17 #include "volumes.h"
 18 #include "async-thread.h"
 19 #include "check-integrity.h"
 20 #include "rcu-string.h"
 21 #include "dev-replace.h"
 22 #include "sysfs.h"
 23 
 24 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 25                                        int scrub_ret);
 26 static void btrfs_dev_replace_update_device_in_mapping_tree(
 27                                                 struct btrfs_fs_info *fs_info,
 28                                                 struct btrfs_device *srcdev,
 29                                                 struct btrfs_device *tgtdev);
 30 static int btrfs_dev_replace_kthread(void *data);
 31 
 32 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
 33 {
 34         struct btrfs_key key;
 35         struct btrfs_root *dev_root = fs_info->dev_root;
 36         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 37         struct extent_buffer *eb;
 38         int slot;
 39         int ret = 0;
 40         struct btrfs_path *path = NULL;
 41         int item_size;
 42         struct btrfs_dev_replace_item *ptr;
 43         u64 src_devid;
 44 
 45         path = btrfs_alloc_path();
 46         if (!path) {
 47                 ret = -ENOMEM;
 48                 goto out;
 49         }
 50 
 51         key.objectid = 0;
 52         key.type = BTRFS_DEV_REPLACE_KEY;
 53         key.offset = 0;
 54         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
 55         if (ret) {
 56 no_valid_dev_replace_entry_found:
 57                 ret = 0;
 58                 dev_replace->replace_state =
 59                         BTRFS_DEV_REPLACE_ITEM_STATE_NEVER_STARTED;
 60                 dev_replace->cont_reading_from_srcdev_mode =
 61                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 62                 dev_replace->time_started = 0;
 63                 dev_replace->time_stopped = 0;
 64                 atomic64_set(&dev_replace->num_write_errors, 0);
 65                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 66                 dev_replace->cursor_left = 0;
 67                 dev_replace->committed_cursor_left = 0;
 68                 dev_replace->cursor_left_last_write_of_item = 0;
 69                 dev_replace->cursor_right = 0;
 70                 dev_replace->srcdev = NULL;
 71                 dev_replace->tgtdev = NULL;
 72                 dev_replace->is_valid = 0;
 73                 dev_replace->item_needs_writeback = 0;
 74                 goto out;
 75         }
 76         slot = path->slots[0];
 77         eb = path->nodes[0];
 78         item_size = btrfs_item_size_nr(eb, slot);
 79         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 80 
 81         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 82                 btrfs_warn(fs_info,
 83                         "dev_replace entry found has unexpected size, ignore entry");
 84                 goto no_valid_dev_replace_entry_found;
 85         }
 86 
 87         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 88         dev_replace->cont_reading_from_srcdev_mode =
 89                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 90         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 91         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 92         dev_replace->time_stopped =
 93                 btrfs_dev_replace_time_stopped(eb, ptr);
 94         atomic64_set(&dev_replace->num_write_errors,
 95                      btrfs_dev_replace_num_write_errors(eb, ptr));
 96         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 97                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 98         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 99         dev_replace->committed_cursor_left = dev_replace->cursor_left;
100         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
101         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
102         dev_replace->is_valid = 1;
103 
104         dev_replace->item_needs_writeback = 0;
105         switch (dev_replace->replace_state) {
106         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
107         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
108         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
109                 dev_replace->srcdev = NULL;
110                 dev_replace->tgtdev = NULL;
111                 break;
112         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
113         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
114                 dev_replace->srcdev = btrfs_find_device(fs_info, src_devid,
115                                                         NULL, NULL);
116                 dev_replace->tgtdev = btrfs_find_device(fs_info,
117                                                         BTRFS_DEV_REPLACE_DEVID,
118                                                         NULL, NULL);
119                 /*
120                  * allow 'btrfs dev replace_cancel' if src/tgt device is
121                  * missing
122                  */
123                 if (!dev_replace->srcdev &&
124                     !btrfs_test_opt(fs_info, DEGRADED)) {
125                         ret = -EIO;
126                         btrfs_warn(fs_info,
127                            "cannot mount because device replace operation is ongoing and");
128                         btrfs_warn(fs_info,
129                            "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
130                            src_devid);
131                 }
132                 if (!dev_replace->tgtdev &&
133                     !btrfs_test_opt(fs_info, DEGRADED)) {
134                         ret = -EIO;
135                         btrfs_warn(fs_info,
136                            "cannot mount because device replace operation is ongoing and");
137                         btrfs_warn(fs_info,
138                            "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
139                                 BTRFS_DEV_REPLACE_DEVID);
140                 }
141                 if (dev_replace->tgtdev) {
142                         if (dev_replace->srcdev) {
143                                 dev_replace->tgtdev->total_bytes =
144                                         dev_replace->srcdev->total_bytes;
145                                 dev_replace->tgtdev->disk_total_bytes =
146                                         dev_replace->srcdev->disk_total_bytes;
147                                 dev_replace->tgtdev->commit_total_bytes =
148                                         dev_replace->srcdev->commit_total_bytes;
149                                 dev_replace->tgtdev->bytes_used =
150                                         dev_replace->srcdev->bytes_used;
151                                 dev_replace->tgtdev->commit_bytes_used =
152                                         dev_replace->srcdev->commit_bytes_used;
153                         }
154                         set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
155                                 &dev_replace->tgtdev->dev_state);
156 
157                         WARN_ON(fs_info->fs_devices->rw_devices == 0);
158                         dev_replace->tgtdev->io_width = fs_info->sectorsize;
159                         dev_replace->tgtdev->io_align = fs_info->sectorsize;
160                         dev_replace->tgtdev->sector_size = fs_info->sectorsize;
161                         dev_replace->tgtdev->fs_info = fs_info;
162                         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
163                                 &dev_replace->tgtdev->dev_state);
164                 }
165                 break;
166         }
167 
168 out:
169         btrfs_free_path(path);
170         return ret;
171 }
172 
173 /*
174  * Initialize a new device for device replace target from a given source dev
175  * and path.
176  *
177  * Return 0 and new device in @device_out, otherwise return < 0
178  */
179 static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
180                                   const char *device_path,
181                                   struct btrfs_device *srcdev,
182                                   struct btrfs_device **device_out)
183 {
184         struct btrfs_device *device;
185         struct block_device *bdev;
186         struct list_head *devices;
187         struct rcu_string *name;
188         u64 devid = BTRFS_DEV_REPLACE_DEVID;
189         int ret = 0;
190 
191         *device_out = NULL;
192         if (fs_info->fs_devices->seeding) {
193                 btrfs_err(fs_info, "the filesystem is a seed filesystem!");
194                 return -EINVAL;
195         }
196 
197         bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
198                                   fs_info->bdev_holder);
199         if (IS_ERR(bdev)) {
200                 btrfs_err(fs_info, "target device %s is invalid!", device_path);
201                 return PTR_ERR(bdev);
202         }
203 
204         filemap_write_and_wait(bdev->bd_inode->i_mapping);
205 
206         devices = &fs_info->fs_devices->devices;
207         list_for_each_entry(device, devices, dev_list) {
208                 if (device->bdev == bdev) {
209                         btrfs_err(fs_info,
210                                   "target device is in the filesystem!");
211                         ret = -EEXIST;
212                         goto error;
213                 }
214         }
215 
216 
217         if (i_size_read(bdev->bd_inode) <
218             btrfs_device_get_total_bytes(srcdev)) {
219                 btrfs_err(fs_info,
220                           "target device is smaller than source device!");
221                 ret = -EINVAL;
222                 goto error;
223         }
224 
225 
226         device = btrfs_alloc_device(NULL, &devid, NULL);
227         if (IS_ERR(device)) {
228                 ret = PTR_ERR(device);
229                 goto error;
230         }
231 
232         name = rcu_string_strdup(device_path, GFP_KERNEL);
233         if (!name) {
234                 btrfs_free_device(device);
235                 ret = -ENOMEM;
236                 goto error;
237         }
238         rcu_assign_pointer(device->name, name);
239 
240         mutex_lock(&fs_info->fs_devices->device_list_mutex);
241         set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
242         device->generation = 0;
243         device->io_width = fs_info->sectorsize;
244         device->io_align = fs_info->sectorsize;
245         device->sector_size = fs_info->sectorsize;
246         device->total_bytes = btrfs_device_get_total_bytes(srcdev);
247         device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
248         device->bytes_used = btrfs_device_get_bytes_used(srcdev);
249         device->commit_total_bytes = srcdev->commit_total_bytes;
250         device->commit_bytes_used = device->bytes_used;
251         device->fs_info = fs_info;
252         device->bdev = bdev;
253         set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
254         set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
255         device->mode = FMODE_EXCL;
256         device->dev_stats_valid = 1;
257         set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
258         device->fs_devices = fs_info->fs_devices;
259         list_add(&device->dev_list, &fs_info->fs_devices->devices);
260         fs_info->fs_devices->num_devices++;
261         fs_info->fs_devices->open_devices++;
262         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
263 
264         *device_out = device;
265         return 0;
266 
267 error:
268         blkdev_put(bdev, FMODE_EXCL);
269         return ret;
270 }
271 
272 /*
273  * called from commit_transaction. Writes changed device replace state to
274  * disk.
275  */
276 int btrfs_run_dev_replace(struct btrfs_trans_handle *trans,
277                           struct btrfs_fs_info *fs_info)
278 {
279         int ret;
280         struct btrfs_root *dev_root = fs_info->dev_root;
281         struct btrfs_path *path;
282         struct btrfs_key key;
283         struct extent_buffer *eb;
284         struct btrfs_dev_replace_item *ptr;
285         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
286 
287         down_read(&dev_replace->rwsem);
288         if (!dev_replace->is_valid ||
289             !dev_replace->item_needs_writeback) {
290                 up_read(&dev_replace->rwsem);
291                 return 0;
292         }
293         up_read(&dev_replace->rwsem);
294 
295         key.objectid = 0;
296         key.type = BTRFS_DEV_REPLACE_KEY;
297         key.offset = 0;
298 
299         path = btrfs_alloc_path();
300         if (!path) {
301                 ret = -ENOMEM;
302                 goto out;
303         }
304         ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
305         if (ret < 0) {
306                 btrfs_warn(fs_info,
307                            "error %d while searching for dev_replace item!",
308                            ret);
309                 goto out;
310         }
311 
312         if (ret == 0 &&
313             btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
314                 /*
315                  * need to delete old one and insert a new one.
316                  * Since no attempt is made to recover any old state, if the
317                  * dev_replace state is 'running', the data on the target
318                  * drive is lost.
319                  * It would be possible to recover the state: just make sure
320                  * that the beginning of the item is never changed and always
321                  * contains all the essential information. Then read this
322                  * minimal set of information and use it as a base for the
323                  * new state.
324                  */
325                 ret = btrfs_del_item(trans, dev_root, path);
326                 if (ret != 0) {
327                         btrfs_warn(fs_info,
328                                    "delete too small dev_replace item failed %d!",
329                                    ret);
330                         goto out;
331                 }
332                 ret = 1;
333         }
334 
335         if (ret == 1) {
336                 /* need to insert a new item */
337                 btrfs_release_path(path);
338                 ret = btrfs_insert_empty_item(trans, dev_root, path,
339                                               &key, sizeof(*ptr));
340                 if (ret < 0) {
341                         btrfs_warn(fs_info,
342                                    "insert dev_replace item failed %d!", ret);
343                         goto out;
344                 }
345         }
346 
347         eb = path->nodes[0];
348         ptr = btrfs_item_ptr(eb, path->slots[0],
349                              struct btrfs_dev_replace_item);
350 
351         down_write(&dev_replace->rwsem);
352         if (dev_replace->srcdev)
353                 btrfs_set_dev_replace_src_devid(eb, ptr,
354                         dev_replace->srcdev->devid);
355         else
356                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
357         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
358                 dev_replace->cont_reading_from_srcdev_mode);
359         btrfs_set_dev_replace_replace_state(eb, ptr,
360                 dev_replace->replace_state);
361         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
362         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
363         btrfs_set_dev_replace_num_write_errors(eb, ptr,
364                 atomic64_read(&dev_replace->num_write_errors));
365         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
366                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
367         dev_replace->cursor_left_last_write_of_item =
368                 dev_replace->cursor_left;
369         btrfs_set_dev_replace_cursor_left(eb, ptr,
370                 dev_replace->cursor_left_last_write_of_item);
371         btrfs_set_dev_replace_cursor_right(eb, ptr,
372                 dev_replace->cursor_right);
373         dev_replace->item_needs_writeback = 0;
374         up_write(&dev_replace->rwsem);
375 
376         btrfs_mark_buffer_dirty(eb);
377 
378 out:
379         btrfs_free_path(path);
380 
381         return ret;
382 }
383 
384 static char* btrfs_dev_name(struct btrfs_device *device)
385 {
386         if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
387                 return "<missing disk>";
388         else
389                 return rcu_str_deref(device->name);
390 }
391 
392 static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
393                 const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
394                 int read_src)
395 {
396         struct btrfs_root *root = fs_info->dev_root;
397         struct btrfs_trans_handle *trans;
398         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
399         int ret;
400         struct btrfs_device *tgt_device = NULL;
401         struct btrfs_device *src_device = NULL;
402         bool need_unlock;
403 
404         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
405                                                   srcdev_name);
406         if (IS_ERR(src_device))
407                 return PTR_ERR(src_device);
408 
409         if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
410                 btrfs_warn_in_rcu(fs_info,
411           "cannot replace device %s (devid %llu) due to active swapfile",
412                         btrfs_dev_name(src_device), src_device->devid);
413                 return -ETXTBSY;
414         }
415 
416         ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
417                                             src_device, &tgt_device);
418         if (ret)
419                 return ret;
420 
421         /*
422          * Here we commit the transaction to make sure commit_total_bytes
423          * of all the devices are updated.
424          */
425         trans = btrfs_attach_transaction(root);
426         if (!IS_ERR(trans)) {
427                 ret = btrfs_commit_transaction(trans);
428                 if (ret)
429                         return ret;
430         } else if (PTR_ERR(trans) != -ENOENT) {
431                 return PTR_ERR(trans);
432         }
433 
434         need_unlock = true;
435         down_write(&dev_replace->rwsem);
436         switch (dev_replace->replace_state) {
437         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
438         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
439         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
440                 break;
441         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
442         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
443                 ASSERT(0);
444                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
445                 goto leave;
446         }
447 
448         dev_replace->cont_reading_from_srcdev_mode = read_src;
449         WARN_ON(!src_device);
450         dev_replace->srcdev = src_device;
451         dev_replace->tgtdev = tgt_device;
452 
453         btrfs_info_in_rcu(fs_info,
454                       "dev_replace from %s (devid %llu) to %s started",
455                       btrfs_dev_name(src_device),
456                       src_device->devid,
457                       rcu_str_deref(tgt_device->name));
458 
459         /*
460          * from now on, the writes to the srcdev are all duplicated to
461          * go to the tgtdev as well (refer to btrfs_map_block()).
462          */
463         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
464         dev_replace->time_started = ktime_get_real_seconds();
465         dev_replace->cursor_left = 0;
466         dev_replace->committed_cursor_left = 0;
467         dev_replace->cursor_left_last_write_of_item = 0;
468         dev_replace->cursor_right = 0;
469         dev_replace->is_valid = 1;
470         dev_replace->item_needs_writeback = 1;
471         atomic64_set(&dev_replace->num_write_errors, 0);
472         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
473         up_write(&dev_replace->rwsem);
474         need_unlock = false;
475 
476         ret = btrfs_sysfs_add_device_link(tgt_device->fs_devices, tgt_device);
477         if (ret)
478                 btrfs_err(fs_info, "kobj add dev failed %d", ret);
479 
480         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
481 
482         /* force writing the updated state information to disk */
483         trans = btrfs_start_transaction(root, 0);
484         if (IS_ERR(trans)) {
485                 ret = PTR_ERR(trans);
486                 need_unlock = true;
487                 down_write(&dev_replace->rwsem);
488                 dev_replace->replace_state =
489                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
490                 dev_replace->srcdev = NULL;
491                 dev_replace->tgtdev = NULL;
492                 goto leave;
493         }
494 
495         ret = btrfs_commit_transaction(trans);
496         WARN_ON(ret);
497 
498         /* the disk copy procedure reuses the scrub code */
499         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
500                               btrfs_device_get_total_bytes(src_device),
501                               &dev_replace->scrub_progress, 0, 1);
502 
503         ret = btrfs_dev_replace_finishing(fs_info, ret);
504         if (ret == -EINPROGRESS) {
505                 ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
506         } else if (ret != -ECANCELED) {
507                 WARN_ON(ret);
508         }
509 
510         return ret;
511 
512 leave:
513         if (need_unlock)
514                 up_write(&dev_replace->rwsem);
515         btrfs_destroy_dev_replace_tgtdev(tgt_device);
516         return ret;
517 }
518 
519 int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
520                             struct btrfs_ioctl_dev_replace_args *args)
521 {
522         int ret;
523 
524         switch (args->start.cont_reading_from_srcdev_mode) {
525         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
526         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
527                 break;
528         default:
529                 return -EINVAL;
530         }
531 
532         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
533             args->start.tgtdev_name[0] == '\0')
534                 return -EINVAL;
535 
536         ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
537                                         args->start.srcdevid,
538                                         args->start.srcdev_name,
539                                         args->start.cont_reading_from_srcdev_mode);
540         args->result = ret;
541         /* don't warn if EINPROGRESS, someone else might be running scrub */
542         if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
543             ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
544                 return 0;
545 
546         return ret;
547 }
548 
549 /*
550  * blocked until all in-flight bios operations are finished.
551  */
552 static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
553 {
554         set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
555         wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
556                    &fs_info->dev_replace.bio_counter));
557 }
558 
559 /*
560  * we have removed target device, it is safe to allow new bios request.
561  */
562 static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
563 {
564         clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
565         wake_up(&fs_info->dev_replace.replace_wait);
566 }
567 
568 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
569                                        int scrub_ret)
570 {
571         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
572         struct btrfs_device *tgt_device;
573         struct btrfs_device *src_device;
574         struct btrfs_root *root = fs_info->tree_root;
575         u8 uuid_tmp[BTRFS_UUID_SIZE];
576         struct btrfs_trans_handle *trans;
577         int ret = 0;
578 
579         /* don't allow cancel or unmount to disturb the finishing procedure */
580         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
581 
582         down_read(&dev_replace->rwsem);
583         /* was the operation canceled, or is it finished? */
584         if (dev_replace->replace_state !=
585             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
586                 up_read(&dev_replace->rwsem);
587                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
588                 return 0;
589         }
590 
591         tgt_device = dev_replace->tgtdev;
592         src_device = dev_replace->srcdev;
593         up_read(&dev_replace->rwsem);
594 
595         /*
596          * flush all outstanding I/O and inode extent mappings before the
597          * copy operation is declared as being finished
598          */
599         ret = btrfs_start_delalloc_roots(fs_info, -1);
600         if (ret) {
601                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
602                 return ret;
603         }
604         btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
605 
606         trans = btrfs_start_transaction(root, 0);
607         if (IS_ERR(trans)) {
608                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
609                 return PTR_ERR(trans);
610         }
611         ret = btrfs_commit_transaction(trans);
612         WARN_ON(ret);
613 
614         /* keep away write_all_supers() during the finishing procedure */
615         mutex_lock(&fs_info->fs_devices->device_list_mutex);
616         mutex_lock(&fs_info->chunk_mutex);
617         down_write(&dev_replace->rwsem);
618         dev_replace->replace_state =
619                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
620                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
621         dev_replace->tgtdev = NULL;
622         dev_replace->srcdev = NULL;
623         dev_replace->time_stopped = ktime_get_real_seconds();
624         dev_replace->item_needs_writeback = 1;
625 
626         /* replace old device with new one in mapping tree */
627         if (!scrub_ret) {
628                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
629                                                                 src_device,
630                                                                 tgt_device);
631         } else {
632                 if (scrub_ret != -ECANCELED)
633                         btrfs_err_in_rcu(fs_info,
634                                  "btrfs_scrub_dev(%s, %llu, %s) failed %d",
635                                  btrfs_dev_name(src_device),
636                                  src_device->devid,
637                                  rcu_str_deref(tgt_device->name), scrub_ret);
638                 up_write(&dev_replace->rwsem);
639                 mutex_unlock(&fs_info->chunk_mutex);
640                 mutex_unlock(&fs_info->fs_devices->device_list_mutex);
641                 btrfs_rm_dev_replace_blocked(fs_info);
642                 if (tgt_device)
643                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
644                 btrfs_rm_dev_replace_unblocked(fs_info);
645                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
646 
647                 return scrub_ret;
648         }
649 
650         btrfs_info_in_rcu(fs_info,
651                           "dev_replace from %s (devid %llu) to %s finished",
652                           btrfs_dev_name(src_device),
653                           src_device->devid,
654                           rcu_str_deref(tgt_device->name));
655         clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
656         tgt_device->devid = src_device->devid;
657         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
658         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
659         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
660         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
661         btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
662         btrfs_device_set_disk_total_bytes(tgt_device,
663                                           src_device->disk_total_bytes);
664         btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
665         ASSERT(list_empty(&src_device->resized_list));
666         tgt_device->commit_total_bytes = src_device->commit_total_bytes;
667         tgt_device->commit_bytes_used = src_device->bytes_used;
668 
669         btrfs_assign_next_active_device(src_device, tgt_device);
670 
671         list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
672         fs_info->fs_devices->rw_devices++;
673 
674         up_write(&dev_replace->rwsem);
675         btrfs_rm_dev_replace_blocked(fs_info);
676 
677         btrfs_rm_dev_replace_remove_srcdev(src_device);
678 
679         btrfs_rm_dev_replace_unblocked(fs_info);
680 
681         /*
682          * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
683          * update on-disk dev stats value during commit transaction
684          */
685         atomic_inc(&tgt_device->dev_stats_ccnt);
686 
687         /*
688          * this is again a consistent state where no dev_replace procedure
689          * is running, the target device is part of the filesystem, the
690          * source device is not part of the filesystem anymore and its 1st
691          * superblock is scratched out so that it is no longer marked to
692          * belong to this filesystem.
693          */
694         mutex_unlock(&fs_info->chunk_mutex);
695         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
696 
697         /* replace the sysfs entry */
698         btrfs_sysfs_rm_device_link(fs_info->fs_devices, src_device);
699         btrfs_rm_dev_replace_free_srcdev(fs_info, src_device);
700 
701         /* write back the superblocks */
702         trans = btrfs_start_transaction(root, 0);
703         if (!IS_ERR(trans))
704                 btrfs_commit_transaction(trans);
705 
706         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
707 
708         return 0;
709 }
710 
711 static void btrfs_dev_replace_update_device_in_mapping_tree(
712                                                 struct btrfs_fs_info *fs_info,
713                                                 struct btrfs_device *srcdev,
714                                                 struct btrfs_device *tgtdev)
715 {
716         struct extent_map_tree *em_tree = &fs_info->mapping_tree.map_tree;
717         struct extent_map *em;
718         struct map_lookup *map;
719         u64 start = 0;
720         int i;
721 
722         write_lock(&em_tree->lock);
723         do {
724                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
725                 if (!em)
726                         break;
727                 map = em->map_lookup;
728                 for (i = 0; i < map->num_stripes; i++)
729                         if (srcdev == map->stripes[i].dev)
730                                 map->stripes[i].dev = tgtdev;
731                 start = em->start + em->len;
732                 free_extent_map(em);
733         } while (start);
734         write_unlock(&em_tree->lock);
735 }
736 
737 /*
738  * Read progress of device replace status according to the state and last
739  * stored position. The value format is the same as for
740  * btrfs_dev_replace::progress_1000
741  */
742 static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
743 {
744         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
745         u64 ret = 0;
746 
747         switch (dev_replace->replace_state) {
748         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
749         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
750                 ret = 0;
751                 break;
752         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
753                 ret = 1000;
754                 break;
755         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
756         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
757                 ret = div64_u64(dev_replace->cursor_left,
758                                 div_u64(btrfs_device_get_total_bytes(
759                                                 dev_replace->srcdev), 1000));
760                 break;
761         }
762 
763         return ret;
764 }
765 
766 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
767                               struct btrfs_ioctl_dev_replace_args *args)
768 {
769         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
770 
771         down_read(&dev_replace->rwsem);
772         /* even if !dev_replace_is_valid, the values are good enough for
773          * the replace_status ioctl */
774         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
775         args->status.replace_state = dev_replace->replace_state;
776         args->status.time_started = dev_replace->time_started;
777         args->status.time_stopped = dev_replace->time_stopped;
778         args->status.num_write_errors =
779                 atomic64_read(&dev_replace->num_write_errors);
780         args->status.num_uncorrectable_read_errors =
781                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
782         args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
783         up_read(&dev_replace->rwsem);
784 }
785 
786 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
787 {
788         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
789         struct btrfs_device *tgt_device = NULL;
790         struct btrfs_device *src_device = NULL;
791         struct btrfs_trans_handle *trans;
792         struct btrfs_root *root = fs_info->tree_root;
793         int result;
794         int ret;
795 
796         if (sb_rdonly(fs_info->sb))
797                 return -EROFS;
798 
799         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
800         down_write(&dev_replace->rwsem);
801         switch (dev_replace->replace_state) {
802         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
803         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
804         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
805                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
806                 up_write(&dev_replace->rwsem);
807                 break;
808         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
809                 tgt_device = dev_replace->tgtdev;
810                 src_device = dev_replace->srcdev;
811                 up_write(&dev_replace->rwsem);
812                 ret = btrfs_scrub_cancel(fs_info);
813                 if (ret < 0) {
814                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
815                 } else {
816                         result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
817                         /*
818                          * btrfs_dev_replace_finishing() will handle the
819                          * cleanup part
820                          */
821                         btrfs_info_in_rcu(fs_info,
822                                 "dev_replace from %s (devid %llu) to %s canceled",
823                                 btrfs_dev_name(src_device), src_device->devid,
824                                 btrfs_dev_name(tgt_device));
825                 }
826                 break;
827         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
828                 /*
829                  * Scrub doing the replace isn't running so we need to do the
830                  * cleanup step of btrfs_dev_replace_finishing() here
831                  */
832                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
833                 tgt_device = dev_replace->tgtdev;
834                 src_device = dev_replace->srcdev;
835                 dev_replace->tgtdev = NULL;
836                 dev_replace->srcdev = NULL;
837                 dev_replace->replace_state =
838                                 BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
839                 dev_replace->time_stopped = ktime_get_real_seconds();
840                 dev_replace->item_needs_writeback = 1;
841 
842                 up_write(&dev_replace->rwsem);
843 
844                 /* Scrub for replace must not be running in suspended state */
845                 ret = btrfs_scrub_cancel(fs_info);
846                 ASSERT(ret != -ENOTCONN);
847 
848                 trans = btrfs_start_transaction(root, 0);
849                 if (IS_ERR(trans)) {
850                         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
851                         return PTR_ERR(trans);
852                 }
853                 ret = btrfs_commit_transaction(trans);
854                 WARN_ON(ret);
855 
856                 btrfs_info_in_rcu(fs_info,
857                 "suspended dev_replace from %s (devid %llu) to %s canceled",
858                         btrfs_dev_name(src_device), src_device->devid,
859                         btrfs_dev_name(tgt_device));
860 
861                 if (tgt_device)
862                         btrfs_destroy_dev_replace_tgtdev(tgt_device);
863                 break;
864         default:
865                 up_write(&dev_replace->rwsem);
866                 result = -EINVAL;
867         }
868 
869         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
870         return result;
871 }
872 
873 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
874 {
875         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
876 
877         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
878         down_write(&dev_replace->rwsem);
879 
880         switch (dev_replace->replace_state) {
881         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
882         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
883         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
884         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
885                 break;
886         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
887                 dev_replace->replace_state =
888                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
889                 dev_replace->time_stopped = ktime_get_real_seconds();
890                 dev_replace->item_needs_writeback = 1;
891                 btrfs_info(fs_info, "suspending dev_replace for unmount");
892                 break;
893         }
894 
895         up_write(&dev_replace->rwsem);
896         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
897 }
898 
899 /* resume dev_replace procedure that was interrupted by unmount */
900 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
901 {
902         struct task_struct *task;
903         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
904 
905         down_write(&dev_replace->rwsem);
906 
907         switch (dev_replace->replace_state) {
908         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
909         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
910         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
911                 up_write(&dev_replace->rwsem);
912                 return 0;
913         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
914                 break;
915         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
916                 dev_replace->replace_state =
917                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
918                 break;
919         }
920         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
921                 btrfs_info(fs_info,
922                            "cannot continue dev_replace, tgtdev is missing");
923                 btrfs_info(fs_info,
924                            "you may cancel the operation after 'mount -o degraded'");
925                 dev_replace->replace_state =
926                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
927                 up_write(&dev_replace->rwsem);
928                 return 0;
929         }
930         up_write(&dev_replace->rwsem);
931 
932         /*
933          * This could collide with a paused balance, but the exclusive op logic
934          * should never allow both to start and pause. We don't want to allow
935          * dev-replace to start anyway.
936          */
937         if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
938                 down_write(&dev_replace->rwsem);
939                 dev_replace->replace_state =
940                                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
941                 up_write(&dev_replace->rwsem);
942                 btrfs_info(fs_info,
943                 "cannot resume dev-replace, other exclusive operation running");
944                 return 0;
945         }
946 
947         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
948         return PTR_ERR_OR_ZERO(task);
949 }
950 
951 static int btrfs_dev_replace_kthread(void *data)
952 {
953         struct btrfs_fs_info *fs_info = data;
954         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
955         u64 progress;
956         int ret;
957 
958         progress = btrfs_dev_replace_progress(fs_info);
959         progress = div_u64(progress, 10);
960         btrfs_info_in_rcu(fs_info,
961                 "continuing dev_replace from %s (devid %llu) to target %s @%u%%",
962                 btrfs_dev_name(dev_replace->srcdev),
963                 dev_replace->srcdev->devid,
964                 btrfs_dev_name(dev_replace->tgtdev),
965                 (unsigned int)progress);
966 
967         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
968                               dev_replace->committed_cursor_left,
969                               btrfs_device_get_total_bytes(dev_replace->srcdev),
970                               &dev_replace->scrub_progress, 0, 1);
971         ret = btrfs_dev_replace_finishing(fs_info, ret);
972         WARN_ON(ret && ret != -ECANCELED);
973 
974         clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
975         return 0;
976 }
977 
978 int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
979 {
980         if (!dev_replace->is_valid)
981                 return 0;
982 
983         switch (dev_replace->replace_state) {
984         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
985         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
986         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
987                 return 0;
988         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
989         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
990                 /*
991                  * return true even if tgtdev is missing (this is
992                  * something that can happen if the dev_replace
993                  * procedure is suspended by an umount and then
994                  * the tgtdev is missing (or "btrfs dev scan") was
995                  * not called and the filesystem is remounted
996                  * in degraded state. This does not stop the
997                  * dev_replace procedure. It needs to be canceled
998                  * manually if the cancellation is wanted.
999                  */
1000                 break;
1001         }
1002         return 1;
1003 }
1004 
1005 void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
1006 {
1007         percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1008 }
1009 
1010 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1011 {
1012         percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1013         cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1014 }
1015 
1016 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1017 {
1018         while (1) {
1019                 percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1020                 if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1021                                      &fs_info->fs_state)))
1022                         break;
1023 
1024                 btrfs_bio_counter_dec(fs_info);
1025                 wait_event(fs_info->dev_replace.replace_wait,
1026                            !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1027                                      &fs_info->fs_state));
1028         }
1029 }
1030 

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