fs/btrfs/dev-replace.c

   1 /*
   2  * Copyright (C) STRATO AG 2012.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18 #include <linux/sched.h>
  19 #include <linux/bio.h>
  20 #include <linux/slab.h>
  21 #include <linux/buffer_head.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/random.h>
  24 #include <linux/iocontext.h>
  25 #include <linux/capability.h>
  26 #include <linux/kthread.h>
  27 #include <linux/math64.h>
  28 #include <asm/div64.h>
  29 #include "compat.h"
  30 #include "ctree.h"
  31 #include "extent_map.h"
  32 #include "disk-io.h"
  33 #include "transaction.h"
  34 #include "print-tree.h"
  35 #include "volumes.h"
  36 #include "async-thread.h"
  37 #include "check-integrity.h"
  38 #include "rcu-string.h"
  39 #include "dev-replace.h"
  40
  41 static u64 btrfs_get_seconds_since_1970(void);
  42 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
  43                                        int scrub_ret);
  44 static void btrfs_dev_replace_update_device_in_mapping_tree(
  45                                                 struct btrfs_fs_info *fs_info,
  46                                                 struct btrfs_device *srcdev,
  47                                                 struct btrfs_device *tgtdev);
  48 static int btrfs_dev_replace_find_srcdev(struct btrfs_root *root, u64 srcdevid,
  49                                          char *srcdev_name,
  50                                          struct btrfs_device **device);
  51 static u64 __btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info);
  52 static int btrfs_dev_replace_kthread(void *data);
  53 static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info);
  54
  55
  56 int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
  57 {
  58         struct btrfs_key key;
  59         struct btrfs_root *dev_root = fs_info->dev_root;
  60         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
  61         struct extent_buffer *eb;
  62         int slot;
  63         int ret = 0;
  64         struct btrfs_path *path = NULL;
  65         int item_size;
  66         struct btrfs_dev_replace_item *ptr;
  67         u64 src_devid;
  68
  69         path = btrfs_alloc_path();
  70         if (!path) {
  71                 ret = -ENOMEM;
  72                 goto out;
  73         }
  74
  75         key.objectid = 0;
  76         key.type = BTRFS_DEV_REPLACE_KEY;
  77         key.offset = 0;
  78         ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
  79         if (ret) {
  80 no_valid_dev_replace_entry_found:
  81                 ret = 0;
  82                 dev_replace->replace_state =
  83                         BTRFS_DEV_REPLACE_ITEM_STATE_NEVER_STARTED;
  84                 dev_replace->cont_reading_from_srcdev_mode =
  85                     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
  86                 dev_replace->replace_state = 0;
  87                 dev_replace->time_started = 0;
  88                 dev_replace->time_stopped = 0;
  89                 atomic64_set(&dev_replace->num_write_errors, 0);
  90                 atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
  91                 dev_replace->cursor_left = 0;
  92                 dev_replace->committed_cursor_left = 0;
  93                 dev_replace->cursor_left_last_write_of_item = 0;
  94                 dev_replace->cursor_right = 0;
  95                 dev_replace->srcdev = NULL;
  96                 dev_replace->tgtdev = NULL;
  97                 dev_replace->is_valid = 0;
  98                 dev_replace->item_needs_writeback = 0;
  99                 goto out;
 100         }
 101         slot = path->slots[0];
 102         eb = path->nodes[0];
 103         item_size = btrfs_item_size_nr(eb, slot);
 104         ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 105
 106         if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 107                 pr_warn("btrfs: dev_replace entry found has unexpected size, ignore entry\n");
 108                 goto no_valid_dev_replace_entry_found;
 109         }
 110
 111         src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 112         dev_replace->cont_reading_from_srcdev_mode =
 113                 btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 114         dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 115         dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 116         dev_replace->time_stopped =
 117                 btrfs_dev_replace_time_stopped(eb, ptr);
 118         atomic64_set(&dev_replace->num_write_errors,
 119                      btrfs_dev_replace_num_write_errors(eb, ptr));
 120         atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 121                      btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 122         dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 123         dev_replace->committed_cursor_left = dev_replace->cursor_left;
 124         dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
 125         dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
 126         dev_replace->is_valid = 1;
 127
 128         dev_replace->item_needs_writeback = 0;
 129         switch (dev_replace->replace_state) {
 130         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 131         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 132         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 133                 dev_replace->srcdev = NULL;
 134                 dev_replace->tgtdev = NULL;
 135                 break;
 136         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 137         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 138                 dev_replace->srcdev = btrfs_find_device(fs_info, src_devid,
 139                                                         NULL, NULL);
 140                 dev_replace->tgtdev = btrfs_find_device(fs_info,
 141                                                         BTRFS_DEV_REPLACE_DEVID,
 142                                                         NULL, NULL);
 143                 /*
 144                  * allow 'btrfs dev replace_cancel' if src/tgt device is
 145                  * missing
 146                  */
 147                 if (!dev_replace->srcdev &&
 148                     !btrfs_test_opt(dev_root, DEGRADED)) {
 149                         ret = -EIO;
 150                         pr_warn("btrfs: cannot mount because device replace operation is ongoing and\n" "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?\n",
 151                                 (unsigned long long)src_devid);
 152                 }
 153                 if (!dev_replace->tgtdev &&
 154                     !btrfs_test_opt(dev_root, DEGRADED)) {
 155                         ret = -EIO;
 156                         pr_warn("btrfs: cannot mount because device replace operation is ongoing and\n" "tgtdev (devid %llu) is missing, need to run btrfs dev scan?\n",
 157                                 (unsigned long long)BTRFS_DEV_REPLACE_DEVID);
 158                 }
 159                 if (dev_replace->tgtdev) {
 160                         if (dev_replace->srcdev) {
 161                                 dev_replace->tgtdev->total_bytes =
 162                                         dev_replace->srcdev->total_bytes;
 163                                 dev_replace->tgtdev->disk_total_bytes =
 164                                         dev_replace->srcdev->disk_total_bytes;
 165                                 dev_replace->tgtdev->bytes_used =
 166                                         dev_replace->srcdev->bytes_used;
 167                         }
 168                         dev_replace->tgtdev->is_tgtdev_for_dev_replace = 1;
 169                         btrfs_init_dev_replace_tgtdev_for_resume(fs_info,
 170                                 dev_replace->tgtdev);
 171                 }
 172                 break;
 173         }
 174
 175 out:
 176         if (path)
 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_lock(dev_replace);
 197         if (!dev_replace->is_valid ||
 198             !dev_replace->item_needs_writeback) {
 199                 btrfs_dev_replace_unlock(dev_replace);
 200                 return 0;
 201         }
 202         btrfs_dev_replace_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                 pr_warn("btrfs: error %d while searching for dev_replace item!\n",
 216                         ret);
 217                 goto out;
 218         }
 219
 220         if (ret == 0 &&
 221             btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 222                 /*
 223                  * need to delete old one and insert a new one.
 224                  * Since no attempt is made to recover any old state, if the
 225                  * dev_replace state is 'running', the data on the target
 226                  * drive is lost.
 227                  * It would be possible to recover the state: just make sure
 228                  * that the beginning of the item is never changed and always
 229                  * contains all the essential information. Then read this
 230                  * minimal set of information and use it as a base for the
 231                  * new state.
 232                  */
 233                 ret = btrfs_del_item(trans, dev_root, path);
 234                 if (ret != 0) {
 235                         pr_warn("btrfs: delete too small dev_replace item failed %d!\n",
 236                                 ret);
 237                         goto out;
 238                 }
 239                 ret = 1;
 240         }
 241
 242         if (ret == 1) {
 243                 /* need to insert a new item */
 244                 btrfs_release_path(path);
 245                 ret = btrfs_insert_empty_item(trans, dev_root, path,
 246                                               &key, sizeof(*ptr));
 247                 if (ret < 0) {
 248                         pr_warn("btrfs: insert dev_replace item failed %d!\n",
 249                                 ret);
 250                         goto out;
 251                 }
 252         }
 253
 254         eb = path->nodes[0];
 255         ptr = btrfs_item_ptr(eb, path->slots[0],
 256                              struct btrfs_dev_replace_item);
 257
 258         btrfs_dev_replace_lock(dev_replace);
 259         if (dev_replace->srcdev)
 260                 btrfs_set_dev_replace_src_devid(eb, ptr,
 261                         dev_replace->srcdev->devid);
 262         else
 263                 btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 264         btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 265                 dev_replace->cont_reading_from_srcdev_mode);
 266         btrfs_set_dev_replace_replace_state(eb, ptr,
 267                 dev_replace->replace_state);
 268         btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 269         btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 270         btrfs_set_dev_replace_num_write_errors(eb, ptr,
 271                 atomic64_read(&dev_replace->num_write_errors));
 272         btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 273                 atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 274         dev_replace->cursor_left_last_write_of_item =
 275                 dev_replace->cursor_left;
 276         btrfs_set_dev_replace_cursor_left(eb, ptr,
 277                 dev_replace->cursor_left_last_write_of_item);
 278         btrfs_set_dev_replace_cursor_right(eb, ptr,
 279                 dev_replace->cursor_right);
 280         dev_replace->item_needs_writeback = 0;
 281         btrfs_dev_replace_unlock(dev_replace);
 282
 283         btrfs_mark_buffer_dirty(eb);
 284
 285 out:
 286         btrfs_free_path(path);
 287
 288         return ret;
 289 }
 290
 291 void btrfs_after_dev_replace_commit(struct btrfs_fs_info *fs_info)
 292 {
 293         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 294
 295         dev_replace->committed_cursor_left =
 296                 dev_replace->cursor_left_last_write_of_item;
 297 }
 298
 299 static u64 btrfs_get_seconds_since_1970(void)
 300 {
 301         struct timespec t = CURRENT_TIME_SEC;
 302
 303         return t.tv_sec;
 304 }
 305
 306 int btrfs_dev_replace_start(struct btrfs_root *root,
 307                             struct btrfs_ioctl_dev_replace_args *args)
 308 {
 309         struct btrfs_trans_handle *trans;
 310         struct btrfs_fs_info *fs_info = root->fs_info;
 311         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 312         int ret;
 313         struct btrfs_device *tgt_device = NULL;
 314         struct btrfs_device *src_device = NULL;
 315
 316         switch (args->start.cont_reading_from_srcdev_mode) {
 317         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 318         case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 319                 break;
 320         default:
 321                 return -EINVAL;
 322         }
 323
 324         if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 325             args->start.tgtdev_name[0] == '\0')
 326                 return -EINVAL;
 327
 328         mutex_lock(&fs_info->volume_mutex);
 329         ret = btrfs_init_dev_replace_tgtdev(root, args->start.tgtdev_name,
 330                                             &tgt_device);
 331         if (ret) {
 332                 pr_err("btrfs: target device %s is invalid!\n",
 333                        args->start.tgtdev_name);
 334                 mutex_unlock(&fs_info->volume_mutex);
 335                 return -EINVAL;
 336         }
 337
 338         ret = btrfs_dev_replace_find_srcdev(root, args->start.srcdevid,
 339                                             args->start.srcdev_name,
 340                                             &src_device);
 341         mutex_unlock(&fs_info->volume_mutex);
 342         if (ret) {
 343                 ret = -EINVAL;
 344                 goto leave_no_lock;
 345         }
 346
 347         if (tgt_device->total_bytes < src_device->total_bytes) {
 348                 pr_err("btrfs: target device is smaller than source device!\n");
 349                 ret = -EINVAL;
 350                 goto leave_no_lock;
 351         }
 352
 353         btrfs_dev_replace_lock(dev_replace);
 354         switch (dev_replace->replace_state) {
 355         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 356         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 357         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 358                 break;
 359         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 360         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 361                 args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 362                 goto leave;
 363         }
 364
 365         dev_replace->cont_reading_from_srcdev_mode =
 366                 args->start.cont_reading_from_srcdev_mode;
 367         WARN_ON(!src_device);
 368         dev_replace->srcdev = src_device;
 369         WARN_ON(!tgt_device);
 370         dev_replace->tgtdev = tgt_device;
 371
 372         printk_in_rcu(KERN_INFO
 373                       "btrfs: dev_replace from %s (devid %llu) to %s) started\n",
 374                       src_device->missing ? "<missing disk>" :
 375                         rcu_str_deref(src_device->name),
 376                       src_device->devid,
 377                       rcu_str_deref(tgt_device->name));
 378
 379         tgt_device->total_bytes = src_device->total_bytes;
 380         tgt_device->disk_total_bytes = src_device->disk_total_bytes;
 381         tgt_device->bytes_used = src_device->bytes_used;
 382
 383         /*
 384          * from now on, the writes to the srcdev are all duplicated to
 385          * go to the tgtdev as well (refer to btrfs_map_block()).
 386          */
 387         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 388         dev_replace->time_started = btrfs_get_seconds_since_1970();
 389         dev_replace->cursor_left = 0;
 390         dev_replace->committed_cursor_left = 0;
 391         dev_replace->cursor_left_last_write_of_item = 0;
 392         dev_replace->cursor_right = 0;
 393         dev_replace->is_valid = 1;
 394         dev_replace->item_needs_writeback = 1;
 395         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
 396         btrfs_dev_replace_unlock(dev_replace);
 397
 398         btrfs_wait_ordered_extents(root, 0);
 399
 400         /* force writing the updated state information to disk */
 401         trans = btrfs_start_transaction(root, 0);
 402         if (IS_ERR(trans)) {
 403                 ret = PTR_ERR(trans);
 404                 btrfs_dev_replace_lock(dev_replace);
 405                 goto leave;
 406         }
 407
 408         ret = btrfs_commit_transaction(trans, root);
 409         WARN_ON(ret);
 410
 411         /* the disk copy procedure reuses the scrub code */
 412         ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 413                               src_device->total_bytes,
 414                               &dev_replace->scrub_progress, 0, 1);
 415
 416         ret = btrfs_dev_replace_finishing(root->fs_info, ret);
 417         WARN_ON(ret);
 418
 419         return 0;
 420
 421 leave:
 422         dev_replace->srcdev = NULL;
 423         dev_replace->tgtdev = NULL;
 424         btrfs_dev_replace_unlock(dev_replace);
 425 leave_no_lock:
 426         if (tgt_device)
 427                 btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
 428         return ret;
 429 }
 430
 431 static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 432                                        int scrub_ret)
 433 {
 434         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 435         struct btrfs_device *tgt_device;
 436         struct btrfs_device *src_device;
 437         struct btrfs_root *root = fs_info->tree_root;
 438         u8 uuid_tmp[BTRFS_UUID_SIZE];
 439         struct btrfs_trans_handle *trans;
 440         int ret = 0;
 441
 442         /* don't allow cancel or unmount to disturb the finishing procedure */
 443         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 444
 445         btrfs_dev_replace_lock(dev_replace);
 446         /* was the operation canceled, or is it finished? */
 447         if (dev_replace->replace_state !=
 448             BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 449                 btrfs_dev_replace_unlock(dev_replace);
 450                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 451                 return 0;
 452         }
 453
 454         tgt_device = dev_replace->tgtdev;
 455         src_device = dev_replace->srcdev;
 456         btrfs_dev_replace_unlock(dev_replace);
 457
 458         /* replace old device with new one in mapping tree */
 459         if (!scrub_ret)
 460                 btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 461                                                                 src_device,
 462                                                                 tgt_device);
 463
 464         /*
 465          * flush all outstanding I/O and inode extent mappings before the
 466          * copy operation is declared as being finished
 467          */
 468         ret = btrfs_start_delalloc_inodes(root, 0);
 469         if (ret) {
 470                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 471                 return ret;
 472         }
 473         btrfs_wait_ordered_extents(root, 0);
 474
 475         trans = btrfs_start_transaction(root, 0);
 476         if (IS_ERR(trans)) {
 477                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 478                 return PTR_ERR(trans);
 479         }
 480         ret = btrfs_commit_transaction(trans, root);
 481         WARN_ON(ret);
 482
 483         /* keep away write_all_supers() during the finishing procedure */
 484         mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
 485         btrfs_dev_replace_lock(dev_replace);
 486         dev_replace->replace_state =
 487                 scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 488                           : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 489         dev_replace->tgtdev = NULL;
 490         dev_replace->srcdev = NULL;
 491         dev_replace->time_stopped = btrfs_get_seconds_since_1970();
 492         dev_replace->item_needs_writeback = 1;
 493
 494         if (scrub_ret) {
 495                 printk_in_rcu(KERN_ERR
 496                               "btrfs: btrfs_scrub_dev(%s, %llu, %s) failed %d\n",
 497                               src_device->missing ? "<missing disk>" :
 498                                 rcu_str_deref(src_device->name),
 499                               src_device->devid,
 500                               rcu_str_deref(tgt_device->name), scrub_ret);
 501                 btrfs_dev_replace_unlock(dev_replace);
 502                 mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 503                 if (tgt_device)
 504                         btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
 505                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 506
 507                 return 0;
 508         }
 509
 510         printk_in_rcu(KERN_INFO
 511                       "btrfs: dev_replace from %s (devid %llu) to %s) finished\n",
 512                       src_device->missing ? "<missing disk>" :
 513                         rcu_str_deref(src_device->name),
 514                       src_device->devid,
 515                       rcu_str_deref(tgt_device->name));
 516         tgt_device->is_tgtdev_for_dev_replace = 0;
 517         tgt_device->devid = src_device->devid;
 518         src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 519         tgt_device->bytes_used = src_device->bytes_used;
 520         memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 521         memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 522         memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 523         tgt_device->total_bytes = src_device->total_bytes;
 524         tgt_device->disk_total_bytes = src_device->disk_total_bytes;
 525         tgt_device->bytes_used = src_device->bytes_used;
 526         if (fs_info->sb->s_bdev == src_device->bdev)
 527                 fs_info->sb->s_bdev = tgt_device->bdev;
 528         if (fs_info->fs_devices->latest_bdev == src_device->bdev)
 529                 fs_info->fs_devices->latest_bdev = tgt_device->bdev;
 530         list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
 531
 532         btrfs_rm_dev_replace_srcdev(fs_info, src_device);
 533         if (src_device->bdev) {
 534                 /* zero out the old super */
 535                 btrfs_scratch_superblock(src_device);
 536         }
 537         /*
 538          * this is again a consistent state where no dev_replace procedure
 539          * is running, the target device is part of the filesystem, the
 540          * source device is not part of the filesystem anymore and its 1st
 541          * superblock is scratched out so that it is no longer marked to
 542          * belong to this filesystem.
 543          */
 544         btrfs_dev_replace_unlock(dev_replace);
 545         mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
 546
 547         /* write back the superblocks */
 548         trans = btrfs_start_transaction(root, 0);
 549         if (!IS_ERR(trans))
 550                 btrfs_commit_transaction(trans, root);
 551
 552         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 553
 554         return 0;
 555 }
 556
 557 static void btrfs_dev_replace_update_device_in_mapping_tree(
 558                                                 struct btrfs_fs_info *fs_info,
 559                                                 struct btrfs_device *srcdev,
 560                                                 struct btrfs_device *tgtdev)
 561 {
 562         struct extent_map_tree *em_tree = &fs_info->mapping_tree.map_tree;
 563         struct extent_map *em;
 564         struct map_lookup *map;
 565         u64 start = 0;
 566         int i;
 567
 568         write_lock(&em_tree->lock);
 569         do {
 570                 em = lookup_extent_mapping(em_tree, start, (u64)-1);
 571                 if (!em)
 572                         break;
 573                 map = (struct map_lookup *)em->bdev;
 574                 for (i = 0; i < map->num_stripes; i++)
 575                         if (srcdev == map->stripes[i].dev)
 576                                 map->stripes[i].dev = tgtdev;
 577                 start = em->start + em->len;
 578                 free_extent_map(em);
 579         } while (start);
 580         write_unlock(&em_tree->lock);
 581 }
 582
 583 static int btrfs_dev_replace_find_srcdev(struct btrfs_root *root, u64 srcdevid,
 584                                          char *srcdev_name,
 585                                          struct btrfs_device **device)
 586 {
 587         int ret;
 588
 589         if (srcdevid) {
 590                 ret = 0;
 591                 *device = btrfs_find_device(root->fs_info, srcdevid, NULL,
 592                                             NULL);
 593                 if (!*device)
 594                         ret = -ENOENT;
 595         } else {
 596                 ret = btrfs_find_device_missing_or_by_path(root, srcdev_name,
 597                                                            device);
 598         }
 599         return ret;
 600 }
 601
 602 void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
 603                               struct btrfs_ioctl_dev_replace_args *args)
 604 {
 605         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 606
 607         btrfs_dev_replace_lock(dev_replace);
 608         /* even if !dev_replace_is_valid, the values are good enough for
 609          * the replace_status ioctl */
 610         args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
 611         args->status.replace_state = dev_replace->replace_state;
 612         args->status.time_started = dev_replace->time_started;
 613         args->status.time_stopped = dev_replace->time_stopped;
 614         args->status.num_write_errors =
 615                 atomic64_read(&dev_replace->num_write_errors);
 616         args->status.num_uncorrectable_read_errors =
 617                 atomic64_read(&dev_replace->num_uncorrectable_read_errors);
 618         switch (dev_replace->replace_state) {
 619         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 620         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 621                 args->status.progress_1000 = 0;
 622                 break;
 623         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 624                 args->status.progress_1000 = 1000;
 625                 break;
 626         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 627         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 628                 args->status.progress_1000 = div64_u64(dev_replace->cursor_left,
 629                         div64_u64(dev_replace->srcdev->total_bytes, 1000));
 630                 break;
 631         }
 632         btrfs_dev_replace_unlock(dev_replace);
 633 }
 634
 635 int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info,
 636                              struct btrfs_ioctl_dev_replace_args *args)
 637 {
 638         args->result = __btrfs_dev_replace_cancel(fs_info);
 639         return 0;
 640 }
 641
 642 static u64 __btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
 643 {
 644         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 645         struct btrfs_device *tgt_device = NULL;
 646         struct btrfs_trans_handle *trans;
 647         struct btrfs_root *root = fs_info->tree_root;
 648         u64 result;
 649         int ret;
 650
 651         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 652         btrfs_dev_replace_lock(dev_replace);
 653         switch (dev_replace->replace_state) {
 654         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 655         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 656         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 657                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
 658                 btrfs_dev_replace_unlock(dev_replace);
 659                 goto leave;
 660         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 661         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 662                 result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
 663                 tgt_device = dev_replace->tgtdev;
 664                 dev_replace->tgtdev = NULL;
 665                 dev_replace->srcdev = NULL;
 666                 break;
 667         }
 668         dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
 669         dev_replace->time_stopped = btrfs_get_seconds_since_1970();
 670         dev_replace->item_needs_writeback = 1;
 671         btrfs_dev_replace_unlock(dev_replace);
 672         btrfs_scrub_cancel(fs_info);
 673
 674         trans = btrfs_start_transaction(root, 0);
 675         if (IS_ERR(trans)) {
 676                 mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 677                 return PTR_ERR(trans);
 678         }
 679         ret = btrfs_commit_transaction(trans, root);
 680         WARN_ON(ret);
 681         if (tgt_device)
 682                 btrfs_destroy_dev_replace_tgtdev(fs_info, tgt_device);
 683
 684 leave:
 685         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 686         return result;
 687 }
 688
 689 void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
 690 {
 691         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 692
 693         mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 694         btrfs_dev_replace_lock(dev_replace);
 695         switch (dev_replace->replace_state) {
 696         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 697         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 698         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 699         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 700                 break;
 701         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 702                 dev_replace->replace_state =
 703                         BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
 704                 dev_replace->time_stopped = btrfs_get_seconds_since_1970();
 705                 dev_replace->item_needs_writeback = 1;
 706                 pr_info("btrfs: suspending dev_replace for unmount\n");
 707                 break;
 708         }
 709
 710         btrfs_dev_replace_unlock(dev_replace);
 711         mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 712 }
 713
 714 /* resume dev_replace procedure that was interrupted by unmount */
 715 int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
 716 {
 717         struct task_struct *task;
 718         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 719
 720         btrfs_dev_replace_lock(dev_replace);
 721         switch (dev_replace->replace_state) {
 722         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 723         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 724         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 725                 btrfs_dev_replace_unlock(dev_replace);
 726                 return 0;
 727         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 728                 break;
 729         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 730                 dev_replace->replace_state =
 731                         BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 732                 break;
 733         }
 734         if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
 735                 pr_info("btrfs: cannot continue dev_replace, tgtdev is missing\n"
 736                         "btrfs: you may cancel the operation after 'mount -o degraded'\n");
 737                 btrfs_dev_replace_unlock(dev_replace);
 738                 return 0;
 739         }
 740         btrfs_dev_replace_unlock(dev_replace);
 741
 742         WARN_ON(atomic_xchg(
 743                 &fs_info->mutually_exclusive_operation_running, 1));
 744         task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
 745         return PTR_RET(task);
 746 }
 747
 748 static int btrfs_dev_replace_kthread(void *data)
 749 {
 750         struct btrfs_fs_info *fs_info = data;
 751         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 752         struct btrfs_ioctl_dev_replace_args *status_args;
 753         u64 progress;
 754
 755         status_args = kzalloc(sizeof(*status_args), GFP_NOFS);
 756         if (status_args) {
 757                 btrfs_dev_replace_status(fs_info, status_args);
 758                 progress = status_args->status.progress_1000;
 759                 kfree(status_args);
 760                 do_div(progress, 10);
 761                 printk_in_rcu(KERN_INFO
 762                               "btrfs: continuing dev_replace from %s (devid %llu) to %s @%u%%\n",
 763                               dev_replace->srcdev->missing ? "<missing disk>" :
 764                                 rcu_str_deref(dev_replace->srcdev->name),
 765                               dev_replace->srcdev->devid,
 766                               dev_replace->tgtdev ?
 767                                 rcu_str_deref(dev_replace->tgtdev->name) :
 768                                 "<missing target disk>",
 769                               (unsigned int)progress);
 770         }
 771         btrfs_dev_replace_continue_on_mount(fs_info);
 772         atomic_set(&fs_info->mutually_exclusive_operation_running, 0);
 773
 774         return 0;
 775 }
 776
 777 static int btrfs_dev_replace_continue_on_mount(struct btrfs_fs_info *fs_info)
 778 {
 779         struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 780         int ret;
 781
 782         ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
 783                               dev_replace->committed_cursor_left,
 784                               dev_replace->srcdev->total_bytes,
 785                               &dev_replace->scrub_progress, 0, 1);
 786         ret = btrfs_dev_replace_finishing(fs_info, ret);
 787         WARN_ON(ret);
 788         return 0;
 789 }
 790
 791 int btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
 792 {
 793         if (!dev_replace->is_valid)
 794                 return 0;
 795
 796         switch (dev_replace->replace_state) {
 797         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 798         case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 799         case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 800                 return 0;
 801         case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 802         case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 803                 /*
 804                  * return true even if tgtdev is missing (this is
 805                  * something that can happen if the dev_replace
 806                  * procedure is suspended by an umount and then
 807                  * the tgtdev is missing (or "btrfs dev scan") was
 808                  * not called and the the filesystem is remounted
 809                  * in degraded state. This does not stop the
 810                  * dev_replace procedure. It needs to be canceled
 811                  * manually if the cancelation is wanted.
 812                  */
 813                 break;
 814         }
 815         return 1;
 816 }
 817
 818 void btrfs_dev_replace_lock(struct btrfs_dev_replace *dev_replace)
 819 {
 820         /* the beginning is just an optimization for the typical case */
 821         if (atomic_read(&dev_replace->nesting_level) == 0) {
 822 acquire_lock:
 823                 /* this is not a nested case where the same thread
 824                  * is trying to acqurire the same lock twice */
 825                 mutex_lock(&dev_replace->lock);
 826                 mutex_lock(&dev_replace->lock_management_lock);
 827                 dev_replace->lock_owner = current->pid;
 828                 atomic_inc(&dev_replace->nesting_level);
 829                 mutex_unlock(&dev_replace->lock_management_lock);
 830                 return;
 831         }
 832
 833         mutex_lock(&dev_replace->lock_management_lock);
 834         if (atomic_read(&dev_replace->nesting_level) > 0 &&
 835             dev_replace->lock_owner == current->pid) {
 836                 WARN_ON(!mutex_is_locked(&dev_replace->lock));
 837                 atomic_inc(&dev_replace->nesting_level);
 838                 mutex_unlock(&dev_replace->lock_management_lock);
 839                 return;
 840         }
 841
 842         mutex_unlock(&dev_replace->lock_management_lock);
 843         goto acquire_lock;
 844 }
 845
 846 void btrfs_dev_replace_unlock(struct btrfs_dev_replace *dev_replace)
 847 {
 848         WARN_ON(!mutex_is_locked(&dev_replace->lock));
 849         mutex_lock(&dev_replace->lock_management_lock);
 850         WARN_ON(atomic_read(&dev_replace->nesting_level) < 1);
 851         WARN_ON(dev_replace->lock_owner != current->pid);
 852         atomic_dec(&dev_replace->nesting_level);
 853         if (atomic_read(&dev_replace->nesting_level) == 0) {
 854                 dev_replace->lock_owner = 0;
 855                 mutex_unlock(&dev_replace->lock_management_lock);
 856                 mutex_unlock(&dev_replace->lock);
 857         } else {
 858                 mutex_unlock(&dev_replace->lock_management_lock);
 859         }
 860 }