fs/btrfs/transaction.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2007 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/fs.h>
   7 #include <linux/slab.h>
   8 #include <linux/sched.h>
   9 #include <linux/writeback.h>
  10 #include <linux/pagemap.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/uuid.h>
  13 #include "misc.h"
  14 #include "ctree.h"
  15 #include "disk-io.h"
  16 #include "transaction.h"
  17 #include "locking.h"
  18 #include "tree-log.h"
  19 #include "volumes.h"
  20 #include "dev-replace.h"
  21 #include "qgroup.h"
  22 #include "block-group.h"
  23 #include "space-info.h"
  24 #include "zoned.h"
  25
  26 #define BTRFS_ROOT_TRANS_TAG 0
  27
  28 /*
  29  * Transaction states and transitions
  30  *
  31  * No running transaction (fs tree blocks are not modified)
  32  * |
  33  * | To next stage:
  34  * |  Call start_transaction() variants. Except btrfs_join_transaction_nostart().
  35  * V
  36  * Transaction N [[TRANS_STATE_RUNNING]]
  37  * |
  38  * | New trans handles can be attached to transaction N by calling all
  39  * | start_transaction() variants.
  40  * |
  41  * | To next stage:
  42  * |  Call btrfs_commit_transaction() on any trans handle attached to
  43  * |  transaction N
  44  * V
  45  * Transaction N [[TRANS_STATE_COMMIT_START]]
  46  * |
  47  * | Will wait for previous running transaction to completely finish if there
  48  * | is one
  49  * |
  50  * | Then one of the following happes:
  51  * | - Wait for all other trans handle holders to release.
  52  * |   The btrfs_commit_transaction() caller will do the commit work.
  53  * | - Wait for current transaction to be committed by others.
  54  * |   Other btrfs_commit_transaction() caller will do the commit work.
  55  * |
  56  * | At this stage, only btrfs_join_transaction*() variants can attach
  57  * | to this running transaction.
  58  * | All other variants will wait for current one to finish and attach to
  59  * | transaction N+1.
  60  * |
  61  * | To next stage:
  62  * |  Caller is chosen to commit transaction N, and all other trans handle
  63  * |  haven been released.
  64  * V
  65  * Transaction N [[TRANS_STATE_COMMIT_DOING]]
  66  * |
  67  * | The heavy lifting transaction work is started.
  68  * | From running delayed refs (modifying extent tree) to creating pending
  69  * | snapshots, running qgroups.
  70  * | In short, modify supporting trees to reflect modifications of subvolume
  71  * | trees.
  72  * |
  73  * | At this stage, all start_transaction() calls will wait for this
  74  * | transaction to finish and attach to transaction N+1.
  75  * |
  76  * | To next stage:
  77  * |  Until all supporting trees are updated.
  78  * V
  79  * Transaction N [[TRANS_STATE_UNBLOCKED]]
  80  * |                                                Transaction N+1
  81  * | All needed trees are modified, thus we only    [[TRANS_STATE_RUNNING]]
  82  * | need to write them back to disk and update     |
  83  * | super blocks.                                  |
  84  * |                                                |
  85  * | At this stage, new transaction is allowed to   |
  86  * | start.                                         |
  87  * | All new start_transaction() calls will be      |
  88  * | attached to transid N+1.                       |
  89  * |                                                |
  90  * | To next stage:                                 |
  91  * |  Until all tree blocks are super blocks are    |
  92  * |  written to block devices                      |
  93  * V                                                |
  94  * Transaction N [[TRANS_STATE_COMPLETED]]          V
  95  *   All tree blocks and super blocks are written.  Transaction N+1
  96  *   This transaction is finished and all its       [[TRANS_STATE_COMMIT_START]]
  97  *   data structures will be cleaned up.            | Life goes on
  98  */
  99 static const unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {
 100         [TRANS_STATE_RUNNING]           = 0U,
 101         [TRANS_STATE_COMMIT_START]      = (__TRANS_START | __TRANS_ATTACH),
 102         [TRANS_STATE_COMMIT_DOING]      = (__TRANS_START |
 103                                            __TRANS_ATTACH |
 104                                            __TRANS_JOIN |
 105                                            __TRANS_JOIN_NOSTART),
 106         [TRANS_STATE_UNBLOCKED]         = (__TRANS_START |
 107                                            __TRANS_ATTACH |
 108                                            __TRANS_JOIN |
 109                                            __TRANS_JOIN_NOLOCK |
 110                                            __TRANS_JOIN_NOSTART),
 111         [TRANS_STATE_SUPER_COMMITTED]   = (__TRANS_START |
 112                                            __TRANS_ATTACH |
 113                                            __TRANS_JOIN |
 114                                            __TRANS_JOIN_NOLOCK |
 115                                            __TRANS_JOIN_NOSTART),
 116         [TRANS_STATE_COMPLETED]         = (__TRANS_START |
 117                                            __TRANS_ATTACH |
 118                                            __TRANS_JOIN |
 119                                            __TRANS_JOIN_NOLOCK |
 120                                            __TRANS_JOIN_NOSTART),
 121 };
 122
 123 void btrfs_put_transaction(struct btrfs_transaction *transaction)
 124 {
 125         WARN_ON(refcount_read(&transaction->use_count) == 0);
 126         if (refcount_dec_and_test(&transaction->use_count)) {
 127                 BUG_ON(!list_empty(&transaction->list));
 128                 WARN_ON(!RB_EMPTY_ROOT(
 129                                 &transaction->delayed_refs.href_root.rb_root));
 130                 WARN_ON(!RB_EMPTY_ROOT(
 131                                 &transaction->delayed_refs.dirty_extent_root));
 132                 if (transaction->delayed_refs.pending_csums)
 133                         btrfs_err(transaction->fs_info,
 134                                   "pending csums is %llu",
 135                                   transaction->delayed_refs.pending_csums);
 136                 /*
 137                  * If any block groups are found in ->deleted_bgs then it's
 138                  * because the transaction was aborted and a commit did not
 139                  * happen (things failed before writing the new superblock
 140                  * and calling btrfs_finish_extent_commit()), so we can not
 141                  * discard the physical locations of the block groups.
 142                  */
 143                 while (!list_empty(&transaction->deleted_bgs)) {
 144                         struct btrfs_block_group *cache;
 145
 146                         cache = list_first_entry(&transaction->deleted_bgs,
 147                                                  struct btrfs_block_group,
 148                                                  bg_list);
 149                         list_del_init(&cache->bg_list);
 150                         btrfs_unfreeze_block_group(cache);
 151                         btrfs_put_block_group(cache);
 152                 }
 153                 WARN_ON(!list_empty(&transaction->dev_update_list));
 154                 kfree(transaction);
 155         }
 156 }
 157
 158 static noinline void switch_commit_roots(struct btrfs_trans_handle *trans)
 159 {
 160         struct btrfs_transaction *cur_trans = trans->transaction;
 161         struct btrfs_fs_info *fs_info = trans->fs_info;
 162         struct btrfs_root *root, *tmp;
 163         struct btrfs_caching_control *caching_ctl, *next;
 164
 165         down_write(&fs_info->commit_root_sem);
 166         list_for_each_entry_safe(root, tmp, &cur_trans->switch_commits,
 167                                  dirty_list) {
 168                 list_del_init(&root->dirty_list);
 169                 free_extent_buffer(root->commit_root);
 170                 root->commit_root = btrfs_root_node(root);
 171                 extent_io_tree_release(&root->dirty_log_pages);
 172                 btrfs_qgroup_clean_swapped_blocks(root);
 173         }
 174
 175         /* We can free old roots now. */
 176         spin_lock(&cur_trans->dropped_roots_lock);
 177         while (!list_empty(&cur_trans->dropped_roots)) {
 178                 root = list_first_entry(&cur_trans->dropped_roots,
 179                                         struct btrfs_root, root_list);
 180                 list_del_init(&root->root_list);
 181                 spin_unlock(&cur_trans->dropped_roots_lock);
 182                 btrfs_free_log(trans, root);
 183                 btrfs_drop_and_free_fs_root(fs_info, root);
 184                 spin_lock(&cur_trans->dropped_roots_lock);
 185         }
 186         spin_unlock(&cur_trans->dropped_roots_lock);
 187
 188         /*
 189          * We have to update the last_byte_to_unpin under the commit_root_sem,
 190          * at the same time we swap out the commit roots.
 191          *
 192          * This is because we must have a real view of the last spot the caching
 193          * kthreads were while caching.  Consider the following views of the
 194          * extent tree for a block group
 195          *
 196          * commit root
 197          * +----+----+----+----+----+----+----+
 198          * |\\\\|    |\\\\|\\\\|    |\\\\|\\\\|
 199          * +----+----+----+----+----+----+----+
 200          * 0    1    2    3    4    5    6    7
 201          *
 202          * new commit root
 203          * +----+----+----+----+----+----+----+
 204          * |    |    |    |\\\\|    |    |\\\\|
 205          * +----+----+----+----+----+----+----+
 206          * 0    1    2    3    4    5    6    7
 207          *
 208          * If the cache_ctl->progress was at 3, then we are only allowed to
 209          * unpin [0,1) and [2,3], because the caching thread has already
 210          * processed those extents.  We are not allowed to unpin [5,6), because
 211          * the caching thread will re-start it's search from 3, and thus find
 212          * the hole from [4,6) to add to the free space cache.
 213          */
 214         spin_lock(&fs_info->block_group_cache_lock);
 215         list_for_each_entry_safe(caching_ctl, next,
 216                                  &fs_info->caching_block_groups, list) {
 217                 struct btrfs_block_group *cache = caching_ctl->block_group;
 218
 219                 if (btrfs_block_group_done(cache)) {
 220                         cache->last_byte_to_unpin = (u64)-1;
 221                         list_del_init(&caching_ctl->list);
 222                         btrfs_put_caching_control(caching_ctl);
 223                 } else {
 224                         cache->last_byte_to_unpin = caching_ctl->progress;
 225                 }
 226         }
 227         spin_unlock(&fs_info->block_group_cache_lock);
 228         up_write(&fs_info->commit_root_sem);
 229 }
 230
 231 static inline void extwriter_counter_inc(struct btrfs_transaction *trans,
 232                                          unsigned int type)
 233 {
 234         if (type & TRANS_EXTWRITERS)
 235                 atomic_inc(&trans->num_extwriters);
 236 }
 237
 238 static inline void extwriter_counter_dec(struct btrfs_transaction *trans,
 239                                          unsigned int type)
 240 {
 241         if (type & TRANS_EXTWRITERS)
 242                 atomic_dec(&trans->num_extwriters);
 243 }
 244
 245 static inline void extwriter_counter_init(struct btrfs_transaction *trans,
 246                                           unsigned int type)
 247 {
 248         atomic_set(&trans->num_extwriters, ((type & TRANS_EXTWRITERS) ? 1 : 0));
 249 }
 250
 251 static inline int extwriter_counter_read(struct btrfs_transaction *trans)
 252 {
 253         return atomic_read(&trans->num_extwriters);
 254 }
 255
 256 /*
 257  * To be called after all the new block groups attached to the transaction
 258  * handle have been created (btrfs_create_pending_block_groups()).
 259  */
 260 void btrfs_trans_release_chunk_metadata(struct btrfs_trans_handle *trans)
 261 {
 262         struct btrfs_fs_info *fs_info = trans->fs_info;
 263         struct btrfs_transaction *cur_trans = trans->transaction;
 264
 265         if (!trans->chunk_bytes_reserved)
 266                 return;
 267
 268         WARN_ON_ONCE(!list_empty(&trans->new_bgs));
 269
 270         btrfs_block_rsv_release(fs_info, &fs_info->chunk_block_rsv,
 271                                 trans->chunk_bytes_reserved, NULL);
 272         atomic64_sub(trans->chunk_bytes_reserved, &cur_trans->chunk_bytes_reserved);
 273         cond_wake_up(&cur_trans->chunk_reserve_wait);
 274         trans->chunk_bytes_reserved = 0;
 275 }
 276
 277 /*
 278  * either allocate a new transaction or hop into the existing one
 279  */
 280 static noinline int join_transaction(struct btrfs_fs_info *fs_info,
 281                                      unsigned int type)
 282 {
 283         struct btrfs_transaction *cur_trans;
 284
 285         spin_lock(&fs_info->trans_lock);
 286 loop:
 287         /* The file system has been taken offline. No new transactions. */
 288         if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
 289                 spin_unlock(&fs_info->trans_lock);
 290                 return -EROFS;
 291         }
 292
 293         cur_trans = fs_info->running_transaction;
 294         if (cur_trans) {
 295                 if (TRANS_ABORTED(cur_trans)) {
 296                         spin_unlock(&fs_info->trans_lock);
 297                         return cur_trans->aborted;
 298                 }
 299                 if (btrfs_blocked_trans_types[cur_trans->state] & type) {
 300                         spin_unlock(&fs_info->trans_lock);
 301                         return -EBUSY;
 302                 }
 303                 refcount_inc(&cur_trans->use_count);
 304                 atomic_inc(&cur_trans->num_writers);
 305                 extwriter_counter_inc(cur_trans, type);
 306                 spin_unlock(&fs_info->trans_lock);
 307                 return 0;
 308         }
 309         spin_unlock(&fs_info->trans_lock);
 310
 311         /*
 312          * If we are ATTACH, we just want to catch the current transaction,
 313          * and commit it. If there is no transaction, just return ENOENT.
 314          */
 315         if (type == TRANS_ATTACH)
 316                 return -ENOENT;
 317
 318         /*
 319          * JOIN_NOLOCK only happens during the transaction commit, so
 320          * it is impossible that ->running_transaction is NULL
 321          */
 322         BUG_ON(type == TRANS_JOIN_NOLOCK);
 323
 324         cur_trans = kmalloc(sizeof(*cur_trans), GFP_NOFS);
 325         if (!cur_trans)
 326                 return -ENOMEM;
 327
 328         spin_lock(&fs_info->trans_lock);
 329         if (fs_info->running_transaction) {
 330                 /*
 331                  * someone started a transaction after we unlocked.  Make sure
 332                  * to redo the checks above
 333                  */
 334                 kfree(cur_trans);
 335                 goto loop;
 336         } else if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
 337                 spin_unlock(&fs_info->trans_lock);
 338                 kfree(cur_trans);
 339                 return -EROFS;
 340         }
 341
 342         cur_trans->fs_info = fs_info;
 343         atomic_set(&cur_trans->pending_ordered, 0);
 344         init_waitqueue_head(&cur_trans->pending_wait);
 345         atomic_set(&cur_trans->num_writers, 1);
 346         extwriter_counter_init(cur_trans, type);
 347         init_waitqueue_head(&cur_trans->writer_wait);
 348         init_waitqueue_head(&cur_trans->commit_wait);
 349         cur_trans->state = TRANS_STATE_RUNNING;
 350         /*
 351          * One for this trans handle, one so it will live on until we
 352          * commit the transaction.
 353          */
 354         refcount_set(&cur_trans->use_count, 2);
 355         cur_trans->flags = 0;
 356         cur_trans->start_time = ktime_get_seconds();
 357
 358         memset(&cur_trans->delayed_refs, 0, sizeof(cur_trans->delayed_refs));
 359
 360         cur_trans->delayed_refs.href_root = RB_ROOT_CACHED;
 361         cur_trans->delayed_refs.dirty_extent_root = RB_ROOT;
 362         atomic_set(&cur_trans->delayed_refs.num_entries, 0);
 363
 364         /*
 365          * although the tree mod log is per file system and not per transaction,
 366          * the log must never go across transaction boundaries.
 367          */
 368         smp_mb();
 369         if (!list_empty(&fs_info->tree_mod_seq_list))
 370                 WARN(1, KERN_ERR "BTRFS: tree_mod_seq_list not empty when creating a fresh transaction\n");
 371         if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log))
 372                 WARN(1, KERN_ERR "BTRFS: tree_mod_log rb tree not empty when creating a fresh transaction\n");
 373         atomic64_set(&fs_info->tree_mod_seq, 0);
 374
 375         spin_lock_init(&cur_trans->delayed_refs.lock);
 376
 377         INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 378         INIT_LIST_HEAD(&cur_trans->dev_update_list);
 379         INIT_LIST_HEAD(&cur_trans->switch_commits);
 380         INIT_LIST_HEAD(&cur_trans->dirty_bgs);
 381         INIT_LIST_HEAD(&cur_trans->io_bgs);
 382         INIT_LIST_HEAD(&cur_trans->dropped_roots);
 383         mutex_init(&cur_trans->cache_write_mutex);
 384         spin_lock_init(&cur_trans->dirty_bgs_lock);
 385         INIT_LIST_HEAD(&cur_trans->deleted_bgs);
 386         spin_lock_init(&cur_trans->dropped_roots_lock);
 387         INIT_LIST_HEAD(&cur_trans->releasing_ebs);
 388         spin_lock_init(&cur_trans->releasing_ebs_lock);
 389         atomic64_set(&cur_trans->chunk_bytes_reserved, 0);
 390         init_waitqueue_head(&cur_trans->chunk_reserve_wait);
 391         list_add_tail(&cur_trans->list, &fs_info->trans_list);
 392         extent_io_tree_init(fs_info, &cur_trans->dirty_pages,
 393                         IO_TREE_TRANS_DIRTY_PAGES, fs_info->btree_inode);
 394         extent_io_tree_init(fs_info, &cur_trans->pinned_extents,
 395                         IO_TREE_FS_PINNED_EXTENTS, NULL);
 396         fs_info->generation++;
 397         cur_trans->transid = fs_info->generation;
 398         fs_info->running_transaction = cur_trans;
 399         cur_trans->aborted = 0;
 400         spin_unlock(&fs_info->trans_lock);
 401
 402         return 0;
 403 }
 404
 405 /*
 406  * This does all the record keeping required to make sure that a shareable root
 407  * is properly recorded in a given transaction.  This is required to make sure
 408  * the old root from before we joined the transaction is deleted when the
 409  * transaction commits.
 410  */
 411 static int record_root_in_trans(struct btrfs_trans_handle *trans,
 412                                struct btrfs_root *root,
 413                                int force)
 414 {
 415         struct btrfs_fs_info *fs_info = root->fs_info;
 416
 417         if ((test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&
 418             root->last_trans < trans->transid) || force) {
 419                 WARN_ON(root == fs_info->extent_root);
 420                 WARN_ON(!force && root->commit_root != root->node);
 421
 422                 /*
 423                  * see below for IN_TRANS_SETUP usage rules
 424                  * we have the reloc mutex held now, so there
 425                  * is only one writer in this function
 426                  */
 427                 set_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state);
 428
 429                 /* make sure readers find IN_TRANS_SETUP before
 430                  * they find our root->last_trans update
 431                  */
 432                 smp_wmb();
 433
 434                 spin_lock(&fs_info->fs_roots_radix_lock);
 435                 if (root->last_trans == trans->transid && !force) {
 436                         spin_unlock(&fs_info->fs_roots_radix_lock);
 437                         return 0;
 438                 }
 439                 radix_tree_tag_set(&fs_info->fs_roots_radix,
 440                                    (unsigned long)root->root_key.objectid,
 441                                    BTRFS_ROOT_TRANS_TAG);
 442                 spin_unlock(&fs_info->fs_roots_radix_lock);
 443                 root->last_trans = trans->transid;
 444
 445                 /* this is pretty tricky.  We don't want to
 446                  * take the relocation lock in btrfs_record_root_in_trans
 447                  * unless we're really doing the first setup for this root in
 448                  * this transaction.
 449                  *
 450                  * Normally we'd use root->last_trans as a flag to decide
 451                  * if we want to take the expensive mutex.
 452                  *
 453                  * But, we have to set root->last_trans before we
 454                  * init the relocation root, otherwise, we trip over warnings
 455                  * in ctree.c.  The solution used here is to flag ourselves
 456                  * with root IN_TRANS_SETUP.  When this is 1, we're still
 457                  * fixing up the reloc trees and everyone must wait.
 458                  *
 459                  * When this is zero, they can trust root->last_trans and fly
 460                  * through btrfs_record_root_in_trans without having to take the
 461                  * lock.  smp_wmb() makes sure that all the writes above are
 462                  * done before we pop in the zero below
 463                  */
 464                 btrfs_init_reloc_root(trans, root);
 465                 smp_mb__before_atomic();
 466                 clear_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state);
 467         }
 468         return 0;
 469 }
 470
 471
 472 void btrfs_add_dropped_root(struct btrfs_trans_handle *trans,
 473                             struct btrfs_root *root)
 474 {
 475         struct btrfs_fs_info *fs_info = root->fs_info;
 476         struct btrfs_transaction *cur_trans = trans->transaction;
 477
 478         /* Add ourselves to the transaction dropped list */
 479         spin_lock(&cur_trans->dropped_roots_lock);
 480         list_add_tail(&root->root_list, &cur_trans->dropped_roots);
 481         spin_unlock(&cur_trans->dropped_roots_lock);
 482
 483         /* Make sure we don't try to update the root at commit time */
 484         spin_lock(&fs_info->fs_roots_radix_lock);
 485         radix_tree_tag_clear(&fs_info->fs_roots_radix,
 486                              (unsigned long)root->root_key.objectid,
 487                              BTRFS_ROOT_TRANS_TAG);
 488         spin_unlock(&fs_info->fs_roots_radix_lock);
 489 }
 490
 491 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
 492                                struct btrfs_root *root)
 493 {
 494         struct btrfs_fs_info *fs_info = root->fs_info;
 495
 496         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
 497                 return 0;
 498
 499         /*
 500          * see record_root_in_trans for comments about IN_TRANS_SETUP usage
 501          * and barriers
 502          */
 503         smp_rmb();
 504         if (root->last_trans == trans->transid &&
 505             !test_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state))
 506                 return 0;
 507
 508         mutex_lock(&fs_info->reloc_mutex);
 509         record_root_in_trans(trans, root, 0);
 510         mutex_unlock(&fs_info->reloc_mutex);
 511
 512         return 0;
 513 }
 514
 515 static inline int is_transaction_blocked(struct btrfs_transaction *trans)
 516 {
 517         return (trans->state >= TRANS_STATE_COMMIT_START &&
 518                 trans->state < TRANS_STATE_UNBLOCKED &&
 519                 !TRANS_ABORTED(trans));
 520 }
 521
 522 /* wait for commit against the current transaction to become unblocked
 523  * when this is done, it is safe to start a new transaction, but the current
 524  * transaction might not be fully on disk.
 525  */
 526 static void wait_current_trans(struct btrfs_fs_info *fs_info)
 527 {
 528         struct btrfs_transaction *cur_trans;
 529
 530         spin_lock(&fs_info->trans_lock);
 531         cur_trans = fs_info->running_transaction;
 532         if (cur_trans && is_transaction_blocked(cur_trans)) {
 533                 refcount_inc(&cur_trans->use_count);
 534                 spin_unlock(&fs_info->trans_lock);
 535
 536                 wait_event(fs_info->transaction_wait,
 537                            cur_trans->state >= TRANS_STATE_UNBLOCKED ||
 538                            TRANS_ABORTED(cur_trans));
 539                 btrfs_put_transaction(cur_trans);
 540         } else {
 541                 spin_unlock(&fs_info->trans_lock);
 542         }
 543 }
 544
 545 static int may_wait_transaction(struct btrfs_fs_info *fs_info, int type)
 546 {
 547         if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
 548                 return 0;
 549
 550         if (type == TRANS_START)
 551                 return 1;
 552
 553         return 0;
 554 }
 555
 556 static inline bool need_reserve_reloc_root(struct btrfs_root *root)
 557 {
 558         struct btrfs_fs_info *fs_info = root->fs_info;
 559
 560         if (!fs_info->reloc_ctl ||
 561             !test_bit(BTRFS_ROOT_SHAREABLE, &root->state) ||
 562             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
 563             root->reloc_root)
 564                 return false;
 565
 566         return true;
 567 }
 568
 569 static struct btrfs_trans_handle *
 570 start_transaction(struct btrfs_root *root, unsigned int num_items,
 571                   unsigned int type, enum btrfs_reserve_flush_enum flush,
 572                   bool enforce_qgroups)
 573 {
 574         struct btrfs_fs_info *fs_info = root->fs_info;
 575         struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
 576         struct btrfs_trans_handle *h;
 577         struct btrfs_transaction *cur_trans;
 578         u64 num_bytes = 0;
 579         u64 qgroup_reserved = 0;
 580         bool reloc_reserved = false;
 581         bool do_chunk_alloc = false;
 582         int ret;
 583
 584         /* Send isn't supposed to start transactions. */
 585         ASSERT(current->journal_info != BTRFS_SEND_TRANS_STUB);
 586
 587         if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
 588                 return ERR_PTR(-EROFS);
 589
 590         if (current->journal_info) {
 591                 WARN_ON(type & TRANS_EXTWRITERS);
 592                 h = current->journal_info;
 593                 refcount_inc(&h->use_count);
 594                 WARN_ON(refcount_read(&h->use_count) > 2);
 595                 h->orig_rsv = h->block_rsv;
 596                 h->block_rsv = NULL;
 597                 goto got_it;
 598         }
 599
 600         /*
 601          * Do the reservation before we join the transaction so we can do all
 602          * the appropriate flushing if need be.
 603          */
 604         if (num_items && root != fs_info->chunk_root) {
 605                 struct btrfs_block_rsv *rsv = &fs_info->trans_block_rsv;
 606                 u64 delayed_refs_bytes = 0;
 607
 608                 qgroup_reserved = num_items * fs_info->nodesize;
 609                 ret = btrfs_qgroup_reserve_meta_pertrans(root, qgroup_reserved,
 610                                 enforce_qgroups);
 611                 if (ret)
 612                         return ERR_PTR(ret);
 613
 614                 /*
 615                  * We want to reserve all the bytes we may need all at once, so
 616                  * we only do 1 enospc flushing cycle per transaction start.  We
 617                  * accomplish this by simply assuming we'll do 2 x num_items
 618                  * worth of delayed refs updates in this trans handle, and
 619                  * refill that amount for whatever is missing in the reserve.
 620                  */
 621                 num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items);
 622                 if (flush == BTRFS_RESERVE_FLUSH_ALL &&
 623                     delayed_refs_rsv->full == 0) {
 624                         delayed_refs_bytes = num_bytes;
 625                         num_bytes <<= 1;
 626                 }
 627
 628                 /*
 629                  * Do the reservation for the relocation root creation
 630                  */
 631                 if (need_reserve_reloc_root(root)) {
 632                         num_bytes += fs_info->nodesize;
 633                         reloc_reserved = true;
 634                 }
 635
 636                 ret = btrfs_block_rsv_add(root, rsv, num_bytes, flush);
 637                 if (ret)
 638                         goto reserve_fail;
 639                 if (delayed_refs_bytes) {
 640                         btrfs_migrate_to_delayed_refs_rsv(fs_info, rsv,
 641                                                           delayed_refs_bytes);
 642                         num_bytes -= delayed_refs_bytes;
 643                 }
 644
 645                 if (rsv->space_info->force_alloc)
 646                         do_chunk_alloc = true;
 647         } else if (num_items == 0 && flush == BTRFS_RESERVE_FLUSH_ALL &&
 648                    !delayed_refs_rsv->full) {
 649                 /*
 650                  * Some people call with btrfs_start_transaction(root, 0)
 651                  * because they can be throttled, but have some other mechanism
 652                  * for reserving space.  We still want these guys to refill the
 653                  * delayed block_rsv so just add 1 items worth of reservation
 654                  * here.
 655                  */
 656                 ret = btrfs_delayed_refs_rsv_refill(fs_info, flush);
 657                 if (ret)
 658                         goto reserve_fail;
 659         }
 660 again:
 661         h = kmem_cache_zalloc(btrfs_trans_handle_cachep, GFP_NOFS);
 662         if (!h) {
 663                 ret = -ENOMEM;
 664                 goto alloc_fail;
 665         }
 666
 667         /*
 668          * If we are JOIN_NOLOCK we're already committing a transaction and
 669          * waiting on this guy, so we don't need to do the sb_start_intwrite
 670          * because we're already holding a ref.  We need this because we could
 671          * have raced in and did an fsync() on a file which can kick a commit
 672          * and then we deadlock with somebody doing a freeze.
 673          *
 674          * If we are ATTACH, it means we just want to catch the current
 675          * transaction and commit it, so we needn't do sb_start_intwrite().
 676          */
 677         if (type & __TRANS_FREEZABLE)
 678                 sb_start_intwrite(fs_info->sb);
 679
 680         if (may_wait_transaction(fs_info, type))
 681                 wait_current_trans(fs_info);
 682
 683         do {
 684                 ret = join_transaction(fs_info, type);
 685                 if (ret == -EBUSY) {
 686                         wait_current_trans(fs_info);
 687                         if (unlikely(type == TRANS_ATTACH ||
 688                                      type == TRANS_JOIN_NOSTART))
 689                                 ret = -ENOENT;
 690                 }
 691         } while (ret == -EBUSY);
 692
 693         if (ret < 0)
 694                 goto join_fail;
 695
 696         cur_trans = fs_info->running_transaction;
 697
 698         h->transid = cur_trans->transid;
 699         h->transaction = cur_trans;
 700         h->root = root;
 701         refcount_set(&h->use_count, 1);
 702         h->fs_info = root->fs_info;
 703
 704         h->type = type;
 705         h->can_flush_pending_bgs = true;
 706         INIT_LIST_HEAD(&h->new_bgs);
 707
 708         smp_mb();
 709         if (cur_trans->state >= TRANS_STATE_COMMIT_START &&
 710             may_wait_transaction(fs_info, type)) {
 711                 current->journal_info = h;
 712                 btrfs_commit_transaction(h);
 713                 goto again;
 714         }
 715
 716         if (num_bytes) {
 717                 trace_btrfs_space_reservation(fs_info, "transaction",
 718                                               h->transid, num_bytes, 1);
 719                 h->block_rsv = &fs_info->trans_block_rsv;
 720                 h->bytes_reserved = num_bytes;
 721                 h->reloc_reserved = reloc_reserved;
 722         }
 723
 724 got_it:
 725         if (!current->journal_info)
 726                 current->journal_info = h;
 727
 728         /*
 729          * If the space_info is marked ALLOC_FORCE then we'll get upgraded to
 730          * ALLOC_FORCE the first run through, and then we won't allocate for
 731          * anybody else who races in later.  We don't care about the return
 732          * value here.
 733          */
 734         if (do_chunk_alloc && num_bytes) {
 735                 u64 flags = h->block_rsv->space_info->flags;
 736
 737                 btrfs_chunk_alloc(h, btrfs_get_alloc_profile(fs_info, flags),
 738                                   CHUNK_ALLOC_NO_FORCE);
 739         }
 740
 741         /*
 742          * btrfs_record_root_in_trans() needs to alloc new extents, and may
 743          * call btrfs_join_transaction() while we're also starting a
 744          * transaction.
 745          *
 746          * Thus it need to be called after current->journal_info initialized,
 747          * or we can deadlock.
 748          */
 749         ret = btrfs_record_root_in_trans(h, root);
 750         if (ret) {
 751                 /*
 752                  * The transaction handle is fully initialized and linked with
 753                  * other structures so it needs to be ended in case of errors,
 754                  * not just freed.
 755                  */
 756                 btrfs_end_transaction(h);
 757                 return ERR_PTR(ret);
 758         }
 759
 760         return h;
 761
 762 join_fail:
 763         if (type & __TRANS_FREEZABLE)
 764                 sb_end_intwrite(fs_info->sb);
 765         kmem_cache_free(btrfs_trans_handle_cachep, h);
 766 alloc_fail:
 767         if (num_bytes)
 768                 btrfs_block_rsv_release(fs_info, &fs_info->trans_block_rsv,
 769                                         num_bytes, NULL);
 770 reserve_fail:
 771         btrfs_qgroup_free_meta_pertrans(root, qgroup_reserved);
 772         return ERR_PTR(ret);
 773 }
 774
 775 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 776                                                    unsigned int num_items)
 777 {
 778         return start_transaction(root, num_items, TRANS_START,
 779                                  BTRFS_RESERVE_FLUSH_ALL, true);
 780 }
 781
 782 struct btrfs_trans_handle *btrfs_start_transaction_fallback_global_rsv(
 783                                         struct btrfs_root *root,
 784                                         unsigned int num_items)
 785 {
 786         return start_transaction(root, num_items, TRANS_START,
 787                                  BTRFS_RESERVE_FLUSH_ALL_STEAL, false);
 788 }
 789
 790 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)
 791 {
 792         return start_transaction(root, 0, TRANS_JOIN, BTRFS_RESERVE_NO_FLUSH,
 793                                  true);
 794 }
 795
 796 struct btrfs_trans_handle *btrfs_join_transaction_spacecache(struct btrfs_root *root)
 797 {
 798         return start_transaction(root, 0, TRANS_JOIN_NOLOCK,
 799                                  BTRFS_RESERVE_NO_FLUSH, true);
 800 }
 801
 802 /*
 803  * Similar to regular join but it never starts a transaction when none is
 804  * running or after waiting for the current one to finish.
 805  */
 806 struct btrfs_trans_handle *btrfs_join_transaction_nostart(struct btrfs_root *root)
 807 {
 808         return start_transaction(root, 0, TRANS_JOIN_NOSTART,
 809                                  BTRFS_RESERVE_NO_FLUSH, true);
 810 }
 811
 812 /*
 813  * btrfs_attach_transaction() - catch the running transaction
 814  *
 815  * It is used when we want to commit the current the transaction, but
 816  * don't want to start a new one.
 817  *
 818  * Note: If this function return -ENOENT, it just means there is no
 819  * running transaction. But it is possible that the inactive transaction
 820  * is still in the memory, not fully on disk. If you hope there is no
 821  * inactive transaction in the fs when -ENOENT is returned, you should
 822  * invoke
 823  *     btrfs_attach_transaction_barrier()
 824  */
 825 struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root)
 826 {
 827         return start_transaction(root, 0, TRANS_ATTACH,
 828                                  BTRFS_RESERVE_NO_FLUSH, true);
 829 }
 830
 831 /*
 832  * btrfs_attach_transaction_barrier() - catch the running transaction
 833  *
 834  * It is similar to the above function, the difference is this one
 835  * will wait for all the inactive transactions until they fully
 836  * complete.
 837  */
 838 struct btrfs_trans_handle *
 839 btrfs_attach_transaction_barrier(struct btrfs_root *root)
 840 {
 841         struct btrfs_trans_handle *trans;
 842
 843         trans = start_transaction(root, 0, TRANS_ATTACH,
 844                                   BTRFS_RESERVE_NO_FLUSH, true);
 845         if (trans == ERR_PTR(-ENOENT))
 846                 btrfs_wait_for_commit(root->fs_info, 0);
 847
 848         return trans;
 849 }
 850
 851 /* Wait for a transaction commit to reach at least the given state. */
 852 static noinline void wait_for_commit(struct btrfs_transaction *commit,
 853                                      const enum btrfs_trans_state min_state)
 854 {
 855         wait_event(commit->commit_wait, commit->state >= min_state);
 856 }
 857
 858 int btrfs_wait_for_commit(struct btrfs_fs_info *fs_info, u64 transid)
 859 {
 860         struct btrfs_transaction *cur_trans = NULL, *t;
 861         int ret = 0;
 862
 863         if (transid) {
 864                 if (transid <= fs_info->last_trans_committed)
 865                         goto out;
 866
 867                 /* find specified transaction */
 868                 spin_lock(&fs_info->trans_lock);
 869                 list_for_each_entry(t, &fs_info->trans_list, list) {
 870                         if (t->transid == transid) {
 871                                 cur_trans = t;
 872                                 refcount_inc(&cur_trans->use_count);
 873                                 ret = 0;
 874                                 break;
 875                         }
 876                         if (t->transid > transid) {
 877                                 ret = 0;
 878                                 break;
 879                         }
 880                 }
 881                 spin_unlock(&fs_info->trans_lock);
 882
 883                 /*
 884                  * The specified transaction doesn't exist, or we
 885                  * raced with btrfs_commit_transaction
 886                  */
 887                 if (!cur_trans) {
 888                         if (transid > fs_info->last_trans_committed)
 889                                 ret = -EINVAL;
 890                         goto out;
 891                 }
 892         } else {
 893                 /* find newest transaction that is committing | committed */
 894                 spin_lock(&fs_info->trans_lock);
 895                 list_for_each_entry_reverse(t, &fs_info->trans_list,
 896                                             list) {
 897                         if (t->state >= TRANS_STATE_COMMIT_START) {
 898                                 if (t->state == TRANS_STATE_COMPLETED)
 899                                         break;
 900                                 cur_trans = t;
 901                                 refcount_inc(&cur_trans->use_count);
 902                                 break;
 903                         }
 904                 }
 905                 spin_unlock(&fs_info->trans_lock);
 906                 if (!cur_trans)
 907                         goto out;  /* nothing committing|committed */
 908         }
 909
 910         wait_for_commit(cur_trans, TRANS_STATE_COMPLETED);
 911         btrfs_put_transaction(cur_trans);
 912 out:
 913         return ret;
 914 }
 915
 916 void btrfs_throttle(struct btrfs_fs_info *fs_info)
 917 {
 918         wait_current_trans(fs_info);
 919 }
 920
 921 static bool should_end_transaction(struct btrfs_trans_handle *trans)
 922 {
 923         struct btrfs_fs_info *fs_info = trans->fs_info;
 924
 925         if (btrfs_check_space_for_delayed_refs(fs_info))
 926                 return true;
 927
 928         return !!btrfs_block_rsv_check(&fs_info->global_block_rsv, 5);
 929 }
 930
 931 bool btrfs_should_end_transaction(struct btrfs_trans_handle *trans)
 932 {
 933         struct btrfs_transaction *cur_trans = trans->transaction;
 934
 935         if (cur_trans->state >= TRANS_STATE_COMMIT_START ||
 936             test_bit(BTRFS_DELAYED_REFS_FLUSHING, &cur_trans->delayed_refs.flags))
 937                 return true;
 938
 939         return should_end_transaction(trans);
 940 }
 941
 942 static void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans)
 943
 944 {
 945         struct btrfs_fs_info *fs_info = trans->fs_info;
 946
 947         if (!trans->block_rsv) {
 948                 ASSERT(!trans->bytes_reserved);
 949                 return;
 950         }
 951
 952         if (!trans->bytes_reserved)
 953                 return;
 954
 955         ASSERT(trans->block_rsv == &fs_info->trans_block_rsv);
 956         trace_btrfs_space_reservation(fs_info, "transaction",
 957                                       trans->transid, trans->bytes_reserved, 0);
 958         btrfs_block_rsv_release(fs_info, trans->block_rsv,
 959                                 trans->bytes_reserved, NULL);
 960         trans->bytes_reserved = 0;
 961 }
 962
 963 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 964                                    int throttle)
 965 {
 966         struct btrfs_fs_info *info = trans->fs_info;
 967         struct btrfs_transaction *cur_trans = trans->transaction;
 968         int err = 0;
 969
 970         if (refcount_read(&trans->use_count) > 1) {
 971                 refcount_dec(&trans->use_count);
 972                 trans->block_rsv = trans->orig_rsv;
 973                 return 0;
 974         }
 975
 976         btrfs_trans_release_metadata(trans);
 977         trans->block_rsv = NULL;
 978
 979         btrfs_create_pending_block_groups(trans);
 980
 981         btrfs_trans_release_chunk_metadata(trans);
 982
 983         if (trans->type & __TRANS_FREEZABLE)
 984                 sb_end_intwrite(info->sb);
 985
 986         WARN_ON(cur_trans != info->running_transaction);
 987         WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
 988         atomic_dec(&cur_trans->num_writers);
 989         extwriter_counter_dec(cur_trans, trans->type);
 990
 991         cond_wake_up(&cur_trans->writer_wait);
 992         btrfs_put_transaction(cur_trans);
 993
 994         if (current->journal_info == trans)
 995                 current->journal_info = NULL;
 996
 997         if (throttle)
 998                 btrfs_run_delayed_iputs(info);
 999
1000         if (TRANS_ABORTED(trans) ||
1001             test_bit(BTRFS_FS_STATE_ERROR, &info->fs_state)) {
1002                 wake_up_process(info->transaction_kthread);
1003                 if (TRANS_ABORTED(trans))
1004                         err = trans->aborted;
1005                 else
1006                         err = -EROFS;
1007         }
1008
1009         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1010         return err;
1011 }
1012
1013 int btrfs_end_transaction(struct btrfs_trans_handle *trans)
1014 {
1015         return __btrfs_end_transaction(trans, 0);
1016 }
1017
1018 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans)
1019 {
1020         return __btrfs_end_transaction(trans, 1);
1021 }
1022
1023 /*
1024  * when btree blocks are allocated, they have some corresponding bits set for
1025  * them in one of two extent_io trees.  This is used to make sure all of
1026  * those extents are sent to disk but does not wait on them
1027  */
1028 int btrfs_write_marked_extents(struct btrfs_fs_info *fs_info,
1029                                struct extent_io_tree *dirty_pages, int mark)
1030 {
1031         int err = 0;
1032         int werr = 0;
1033         struct address_space *mapping = fs_info->btree_inode->i_mapping;
1034         struct extent_state *cached_state = NULL;
1035         u64 start = 0;
1036         u64 end;
1037
1038         atomic_inc(&BTRFS_I(fs_info->btree_inode)->sync_writers);
1039         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
1040                                       mark, &cached_state)) {
1041                 bool wait_writeback = false;
1042
1043                 err = convert_extent_bit(dirty_pages, start, end,
1044                                          EXTENT_NEED_WAIT,
1045                                          mark, &cached_state);
1046                 /*
1047                  * convert_extent_bit can return -ENOMEM, which is most of the
1048                  * time a temporary error. So when it happens, ignore the error
1049                  * and wait for writeback of this range to finish - because we
1050                  * failed to set the bit EXTENT_NEED_WAIT for the range, a call
1051                  * to __btrfs_wait_marked_extents() would not know that
1052                  * writeback for this range started and therefore wouldn't
1053                  * wait for it to finish - we don't want to commit a
1054                  * superblock that points to btree nodes/leafs for which
1055                  * writeback hasn't finished yet (and without errors).
1056                  * We cleanup any entries left in the io tree when committing
1057                  * the transaction (through extent_io_tree_release()).
1058                  */
1059                 if (err == -ENOMEM) {
1060                         err = 0;
1061                         wait_writeback = true;
1062                 }
1063                 if (!err)
1064                         err = filemap_fdatawrite_range(mapping, start, end);
1065                 if (err)
1066                         werr = err;
1067                 else if (wait_writeback)
1068                         werr = filemap_fdatawait_range(mapping, start, end);
1069                 free_extent_state(cached_state);
1070                 cached_state = NULL;
1071                 cond_resched();
1072                 start = end + 1;
1073         }
1074         atomic_dec(&BTRFS_I(fs_info->btree_inode)->sync_writers);
1075         return werr;
1076 }
1077
1078 /*
1079  * when btree blocks are allocated, they have some corresponding bits set for
1080  * them in one of two extent_io trees.  This is used to make sure all of
1081  * those extents are on disk for transaction or log commit.  We wait
1082  * on all the pages and clear them from the dirty pages state tree
1083  */
1084 static int __btrfs_wait_marked_extents(struct btrfs_fs_info *fs_info,
1085                                        struct extent_io_tree *dirty_pages)
1086 {
1087         int err = 0;
1088         int werr = 0;
1089         struct address_space *mapping = fs_info->btree_inode->i_mapping;
1090         struct extent_state *cached_state = NULL;
1091         u64 start = 0;
1092         u64 end;
1093
1094         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
1095                                       EXTENT_NEED_WAIT, &cached_state)) {
1096                 /*
1097                  * Ignore -ENOMEM errors returned by clear_extent_bit().
1098                  * When committing the transaction, we'll remove any entries
1099                  * left in the io tree. For a log commit, we don't remove them
1100                  * after committing the log because the tree can be accessed
1101                  * concurrently - we do it only at transaction commit time when
1102                  * it's safe to do it (through extent_io_tree_release()).
1103                  */
1104                 err = clear_extent_bit(dirty_pages, start, end,
1105                                        EXTENT_NEED_WAIT, 0, 0, &cached_state);
1106                 if (err == -ENOMEM)
1107                         err = 0;
1108                 if (!err)
1109                         err = filemap_fdatawait_range(mapping, start, end);
1110                 if (err)
1111                         werr = err;
1112                 free_extent_state(cached_state);
1113                 cached_state = NULL;
1114                 cond_resched();
1115                 start = end + 1;
1116         }
1117         if (err)
1118                 werr = err;
1119         return werr;
1120 }
1121
1122 static int btrfs_wait_extents(struct btrfs_fs_info *fs_info,
1123                        struct extent_io_tree *dirty_pages)
1124 {
1125         bool errors = false;
1126         int err;
1127
1128         err = __btrfs_wait_marked_extents(fs_info, dirty_pages);
1129         if (test_and_clear_bit(BTRFS_FS_BTREE_ERR, &fs_info->flags))
1130                 errors = true;
1131
1132         if (errors && !err)
1133                 err = -EIO;
1134         return err;
1135 }
1136
1137 int btrfs_wait_tree_log_extents(struct btrfs_root *log_root, int mark)
1138 {
1139         struct btrfs_fs_info *fs_info = log_root->fs_info;
1140         struct extent_io_tree *dirty_pages = &log_root->dirty_log_pages;
1141         bool errors = false;
1142         int err;
1143
1144         ASSERT(log_root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID);
1145
1146         err = __btrfs_wait_marked_extents(fs_info, dirty_pages);
1147         if ((mark & EXTENT_DIRTY) &&
1148             test_and_clear_bit(BTRFS_FS_LOG1_ERR, &fs_info->flags))
1149                 errors = true;
1150
1151         if ((mark & EXTENT_NEW) &&
1152             test_and_clear_bit(BTRFS_FS_LOG2_ERR, &fs_info->flags))
1153                 errors = true;
1154
1155         if (errors && !err)
1156                 err = -EIO;
1157         return err;
1158 }
1159
1160 /*
1161  * When btree blocks are allocated the corresponding extents are marked dirty.
1162  * This function ensures such extents are persisted on disk for transaction or
1163  * log commit.
1164  *
1165  * @trans: transaction whose dirty pages we'd like to write
1166  */
1167 static int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans)
1168 {
1169         int ret;
1170         int ret2;
1171         struct extent_io_tree *dirty_pages = &trans->transaction->dirty_pages;
1172         struct btrfs_fs_info *fs_info = trans->fs_info;
1173         struct blk_plug plug;
1174
1175         blk_start_plug(&plug);
1176         ret = btrfs_write_marked_extents(fs_info, dirty_pages, EXTENT_DIRTY);
1177         blk_finish_plug(&plug);
1178         ret2 = btrfs_wait_extents(fs_info, dirty_pages);
1179
1180         extent_io_tree_release(&trans->transaction->dirty_pages);
1181
1182         if (ret)
1183                 return ret;
1184         else if (ret2)
1185                 return ret2;
1186         else
1187                 return 0;
1188 }
1189
1190 /*
1191  * this is used to update the root pointer in the tree of tree roots.
1192  *
1193  * But, in the case of the extent allocation tree, updating the root
1194  * pointer may allocate blocks which may change the root of the extent
1195  * allocation tree.
1196  *
1197  * So, this loops and repeats and makes sure the cowonly root didn't
1198  * change while the root pointer was being updated in the metadata.
1199  */
1200 static int update_cowonly_root(struct btrfs_trans_handle *trans,
1201                                struct btrfs_root *root)
1202 {
1203         int ret;
1204         u64 old_root_bytenr;
1205         u64 old_root_used;
1206         struct btrfs_fs_info *fs_info = root->fs_info;
1207         struct btrfs_root *tree_root = fs_info->tree_root;
1208
1209         old_root_used = btrfs_root_used(&root->root_item);
1210
1211         while (1) {
1212                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
1213                 if (old_root_bytenr == root->node->start &&
1214                     old_root_used == btrfs_root_used(&root->root_item))
1215                         break;
1216
1217                 btrfs_set_root_node(&root->root_item, root->node);
1218                 ret = btrfs_update_root(trans, tree_root,
1219                                         &root->root_key,
1220                                         &root->root_item);
1221                 if (ret)
1222                         return ret;
1223
1224                 old_root_used = btrfs_root_used(&root->root_item);
1225         }
1226
1227         return 0;
1228 }
1229
1230 /*
1231  * update all the cowonly tree roots on disk
1232  *
1233  * The error handling in this function may not be obvious. Any of the
1234  * failures will cause the file system to go offline. We still need
1235  * to clean up the delayed refs.
1236  */
1237 static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans)
1238 {
1239         struct btrfs_fs_info *fs_info = trans->fs_info;
1240         struct list_head *dirty_bgs = &trans->transaction->dirty_bgs;
1241         struct list_head *io_bgs = &trans->transaction->io_bgs;
1242         struct list_head *next;
1243         struct extent_buffer *eb;
1244         int ret;
1245
1246         eb = btrfs_lock_root_node(fs_info->tree_root);
1247         ret = btrfs_cow_block(trans, fs_info->tree_root, eb, NULL,
1248                               0, &eb, BTRFS_NESTING_COW);
1249         btrfs_tree_unlock(eb);
1250         free_extent_buffer(eb);
1251
1252         if (ret)
1253                 return ret;
1254
1255         ret = btrfs_run_dev_stats(trans);
1256         if (ret)
1257                 return ret;
1258         ret = btrfs_run_dev_replace(trans);
1259         if (ret)
1260                 return ret;
1261         ret = btrfs_run_qgroups(trans);
1262         if (ret)
1263                 return ret;
1264
1265         ret = btrfs_setup_space_cache(trans);
1266         if (ret)
1267                 return ret;
1268
1269 again:
1270         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
1271                 struct btrfs_root *root;
1272                 next = fs_info->dirty_cowonly_roots.next;
1273                 list_del_init(next);
1274                 root = list_entry(next, struct btrfs_root, dirty_list);
1275                 clear_bit(BTRFS_ROOT_DIRTY, &root->state);
1276
1277                 if (root != fs_info->extent_root)
1278                         list_add_tail(&root->dirty_list,
1279                                       &trans->transaction->switch_commits);
1280                 ret = update_cowonly_root(trans, root);
1281                 if (ret)
1282                         return ret;
1283         }
1284
1285         /* Now flush any delayed refs generated by updating all of the roots */
1286         ret = btrfs_run_delayed_refs(trans, (unsigned long)-1);
1287         if (ret)
1288                 return ret;
1289
1290         while (!list_empty(dirty_bgs) || !list_empty(io_bgs)) {
1291                 ret = btrfs_write_dirty_block_groups(trans);
1292                 if (ret)
1293                         return ret;
1294
1295                 /*
1296                  * We're writing the dirty block groups, which could generate
1297                  * delayed refs, which could generate more dirty block groups,
1298                  * so we want to keep this flushing in this loop to make sure
1299                  * everything gets run.
1300                  */
1301                 ret = btrfs_run_delayed_refs(trans, (unsigned long)-1);
1302                 if (ret)
1303                         return ret;
1304         }
1305
1306         if (!list_empty(&fs_info->dirty_cowonly_roots))
1307                 goto again;
1308
1309         list_add_tail(&fs_info->extent_root->dirty_list,
1310                       &trans->transaction->switch_commits);
1311
1312         /* Update dev-replace pointer once everything is committed */
1313         fs_info->dev_replace.committed_cursor_left =
1314                 fs_info->dev_replace.cursor_left_last_write_of_item;
1315
1316         return 0;
1317 }
1318
1319 /*
1320  * dead roots are old snapshots that need to be deleted.  This allocates
1321  * a dirty root struct and adds it into the list of dead roots that need to
1322  * be deleted
1323  */
1324 void btrfs_add_dead_root(struct btrfs_root *root)
1325 {
1326         struct btrfs_fs_info *fs_info = root->fs_info;
1327
1328         spin_lock(&fs_info->trans_lock);
1329         if (list_empty(&root->root_list)) {
1330                 btrfs_grab_root(root);
1331                 list_add_tail(&root->root_list, &fs_info->dead_roots);
1332         }
1333         spin_unlock(&fs_info->trans_lock);
1334 }
1335
1336 /*
1337  * update all the cowonly tree roots on disk
1338  */
1339 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
1340 {
1341         struct btrfs_fs_info *fs_info = trans->fs_info;
1342         struct btrfs_root *gang[8];
1343         int i;
1344         int ret;
1345
1346         spin_lock(&fs_info->fs_roots_radix_lock);
1347         while (1) {
1348                 ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
1349                                                  (void **)gang, 0,
1350                                                  ARRAY_SIZE(gang),
1351                                                  BTRFS_ROOT_TRANS_TAG);
1352                 if (ret == 0)
1353                         break;
1354                 for (i = 0; i < ret; i++) {
1355                         struct btrfs_root *root = gang[i];
1356                         int ret2;
1357
1358                         radix_tree_tag_clear(&fs_info->fs_roots_radix,
1359                                         (unsigned long)root->root_key.objectid,
1360                                         BTRFS_ROOT_TRANS_TAG);
1361                         spin_unlock(&fs_info->fs_roots_radix_lock);
1362
1363                         btrfs_free_log(trans, root);
1364                         btrfs_update_reloc_root(trans, root);
1365
1366                         /* see comments in should_cow_block() */
1367                         clear_bit(BTRFS_ROOT_FORCE_COW, &root->state);
1368                         smp_mb__after_atomic();
1369
1370                         if (root->commit_root != root->node) {
1371                                 list_add_tail(&root->dirty_list,
1372                                         &trans->transaction->switch_commits);
1373                                 btrfs_set_root_node(&root->root_item,
1374                                                     root->node);
1375                         }
1376
1377                         ret2 = btrfs_update_root(trans, fs_info->tree_root,
1378                                                 &root->root_key,
1379                                                 &root->root_item);
1380                         if (ret2)
1381                                 return ret2;
1382                         spin_lock(&fs_info->fs_roots_radix_lock);
1383                         btrfs_qgroup_free_meta_all_pertrans(root);
1384                 }
1385         }
1386         spin_unlock(&fs_info->fs_roots_radix_lock);
1387         return 0;
1388 }
1389
1390 /*
1391  * defrag a given btree.
1392  * Every leaf in the btree is read and defragged.
1393  */
1394 int btrfs_defrag_root(struct btrfs_root *root)
1395 {
1396         struct btrfs_fs_info *info = root->fs_info;
1397         struct btrfs_trans_handle *trans;
1398         int ret;
1399
1400         if (test_and_set_bit(BTRFS_ROOT_DEFRAG_RUNNING, &root->state))
1401                 return 0;
1402
1403         while (1) {
1404                 trans = btrfs_start_transaction(root, 0);
1405                 if (IS_ERR(trans))
1406                         return PTR_ERR(trans);
1407
1408                 ret = btrfs_defrag_leaves(trans, root);
1409
1410                 btrfs_end_transaction(trans);
1411                 btrfs_btree_balance_dirty(info);
1412                 cond_resched();
1413
1414                 if (btrfs_fs_closing(info) || ret != -EAGAIN)
1415                         break;
1416
1417                 if (btrfs_defrag_cancelled(info)) {
1418                         btrfs_debug(info, "defrag_root cancelled");
1419                         ret = -EAGAIN;
1420                         break;
1421                 }
1422         }
1423         clear_bit(BTRFS_ROOT_DEFRAG_RUNNING, &root->state);
1424         return ret;
1425 }
1426
1427 /*
1428  * Do all special snapshot related qgroup dirty hack.
1429  *
1430  * Will do all needed qgroup inherit and dirty hack like switch commit
1431  * roots inside one transaction and write all btree into disk, to make
1432  * qgroup works.
1433  */
1434 static int qgroup_account_snapshot(struct btrfs_trans_handle *trans,
1435                                    struct btrfs_root *src,
1436                                    struct btrfs_root *parent,
1437                                    struct btrfs_qgroup_inherit *inherit,
1438                                    u64 dst_objectid)
1439 {
1440         struct btrfs_fs_info *fs_info = src->fs_info;
1441         int ret;
1442
1443         /*
1444          * Save some performance in the case that qgroups are not
1445          * enabled. If this check races with the ioctl, rescan will
1446          * kick in anyway.
1447          */
1448         if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
1449                 return 0;
1450
1451         /*
1452          * Ensure dirty @src will be committed.  Or, after coming
1453          * commit_fs_roots() and switch_commit_roots(), any dirty but not
1454          * recorded root will never be updated again, causing an outdated root
1455          * item.
1456          */
1457         ret = record_root_in_trans(trans, src, 1);
1458         if (ret)
1459                 return ret;
1460
1461         /*
1462          * btrfs_qgroup_inherit relies on a consistent view of the usage for the
1463          * src root, so we must run the delayed refs here.
1464          *
1465          * However this isn't particularly fool proof, because there's no
1466          * synchronization keeping us from changing the tree after this point
1467          * before we do the qgroup_inherit, or even from making changes while
1468          * we're doing the qgroup_inherit.  But that's a problem for the future,
1469          * for now flush the delayed refs to narrow the race window where the
1470          * qgroup counters could end up wrong.
1471          */
1472         ret = btrfs_run_delayed_refs(trans, (unsigned long)-1);
1473         if (ret) {
1474                 btrfs_abort_transaction(trans, ret);
1475                 goto out;
1476         }
1477
1478         /*
1479          * We are going to commit transaction, see btrfs_commit_transaction()
1480          * comment for reason locking tree_log_mutex
1481          */
1482         mutex_lock(&fs_info->tree_log_mutex);
1483
1484         ret = commit_fs_roots(trans);
1485         if (ret)
1486                 goto out;
1487         ret = btrfs_qgroup_account_extents(trans);
1488         if (ret < 0)
1489                 goto out;
1490
1491         /* Now qgroup are all updated, we can inherit it to new qgroups */
1492         ret = btrfs_qgroup_inherit(trans, src->root_key.objectid, dst_objectid,
1493                                    inherit);
1494         if (ret < 0)
1495                 goto out;
1496
1497         /*
1498          * Now we do a simplified commit transaction, which will:
1499          * 1) commit all subvolume and extent tree
1500          *    To ensure all subvolume and extent tree have a valid
1501          *    commit_root to accounting later insert_dir_item()
1502          * 2) write all btree blocks onto disk
1503          *    This is to make sure later btree modification will be cowed
1504          *    Or commit_root can be populated and cause wrong qgroup numbers
1505          * In this simplified commit, we don't really care about other trees
1506          * like chunk and root tree, as they won't affect qgroup.
1507          * And we don't write super to avoid half committed status.
1508          */
1509         ret = commit_cowonly_roots(trans);
1510         if (ret)
1511                 goto out;
1512         switch_commit_roots(trans);
1513         ret = btrfs_write_and_wait_transaction(trans);
1514         if (ret)
1515                 btrfs_handle_fs_error(fs_info, ret,
1516                         "Error while writing out transaction for qgroup");
1517
1518 out:
1519         mutex_unlock(&fs_info->tree_log_mutex);
1520
1521         /*
1522          * Force parent root to be updated, as we recorded it before so its
1523          * last_trans == cur_transid.
1524          * Or it won't be committed again onto disk after later
1525          * insert_dir_item()
1526          */
1527         if (!ret)
1528                 ret = record_root_in_trans(trans, parent, 1);
1529         return ret;
1530 }
1531
1532 /*
1533  * new snapshots need to be created at a very specific time in the
1534  * transaction commit.  This does the actual creation.
1535  *
1536  * Note:
1537  * If the error which may affect the commitment of the current transaction
1538  * happens, we should return the error number. If the error which just affect
1539  * the creation of the pending snapshots, just return 0.
1540  */
1541 static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
1542                                    struct btrfs_pending_snapshot *pending)
1543 {
1544
1545         struct btrfs_fs_info *fs_info = trans->fs_info;
1546         struct btrfs_key key;
1547         struct btrfs_root_item *new_root_item;
1548         struct btrfs_root *tree_root = fs_info->tree_root;
1549         struct btrfs_root *root = pending->root;
1550         struct btrfs_root *parent_root;
1551         struct btrfs_block_rsv *rsv;
1552         struct inode *parent_inode;
1553         struct btrfs_path *path;
1554         struct btrfs_dir_item *dir_item;
1555         struct dentry *dentry;
1556         struct extent_buffer *tmp;
1557         struct extent_buffer *old;
1558         struct timespec64 cur_time;
1559         int ret = 0;
1560         u64 to_reserve = 0;
1561         u64 index = 0;
1562         u64 objectid;
1563         u64 root_flags;
1564
1565         ASSERT(pending->path);
1566         path = pending->path;
1567
1568         ASSERT(pending->root_item);
1569         new_root_item = pending->root_item;
1570
1571         pending->error = btrfs_get_free_objectid(tree_root, &objectid);
1572         if (pending->error)
1573                 goto no_free_objectid;
1574
1575         /*
1576          * Make qgroup to skip current new snapshot's qgroupid, as it is
1577          * accounted by later btrfs_qgroup_inherit().
1578          */
1579         btrfs_set_skip_qgroup(trans, objectid);
1580
1581         btrfs_reloc_pre_snapshot(pending, &to_reserve);
1582
1583         if (to_reserve > 0) {
1584                 pending->error = btrfs_block_rsv_add(root,
1585                                                      &pending->block_rsv,
1586                                                      to_reserve,
1587                                                      BTRFS_RESERVE_NO_FLUSH);
1588                 if (pending->error)
1589                         goto clear_skip_qgroup;
1590         }
1591
1592         key.objectid = objectid;
1593         key.offset = (u64)-1;
1594         key.type = BTRFS_ROOT_ITEM_KEY;
1595
1596         rsv = trans->block_rsv;
1597         trans->block_rsv = &pending->block_rsv;
1598         trans->bytes_reserved = trans->block_rsv->reserved;
1599         trace_btrfs_space_reservation(fs_info, "transaction",
1600                                       trans->transid,
1601                                       trans->bytes_reserved, 1);
1602         dentry = pending->dentry;
1603         parent_inode = pending->dir;
1604         parent_root = BTRFS_I(parent_inode)->root;
1605         record_root_in_trans(trans, parent_root, 0);
1606
1607         cur_time = current_time(parent_inode);
1608
1609         /*
1610          * insert the directory item
1611          */
1612         ret = btrfs_set_inode_index(BTRFS_I(parent_inode), &index);
1613         BUG_ON(ret); /* -ENOMEM */
1614
1615         /* check if there is a file/dir which has the same name. */
1616         dir_item = btrfs_lookup_dir_item(NULL, parent_root, path,
1617                                          btrfs_ino(BTRFS_I(parent_inode)),
1618                                          dentry->d_name.name,
1619                                          dentry->d_name.len, 0);
1620         if (dir_item != NULL && !IS_ERR(dir_item)) {
1621                 pending->error = -EEXIST;
1622                 goto dir_item_existed;
1623         } else if (IS_ERR(dir_item)) {
1624                 ret = PTR_ERR(dir_item);
1625                 btrfs_abort_transaction(trans, ret);
1626                 goto fail;
1627         }
1628         btrfs_release_path(path);
1629
1630         /*
1631          * pull in the delayed directory update
1632          * and the delayed inode item
1633          * otherwise we corrupt the FS during
1634          * snapshot
1635          */
1636         ret = btrfs_run_delayed_items(trans);
1637         if (ret) {      /* Transaction aborted */
1638                 btrfs_abort_transaction(trans, ret);
1639                 goto fail;
1640         }
1641
1642         record_root_in_trans(trans, root, 0);
1643         btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
1644         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
1645         btrfs_check_and_init_root_item(new_root_item);
1646
1647         root_flags = btrfs_root_flags(new_root_item);
1648         if (pending->readonly)
1649                 root_flags |= BTRFS_ROOT_SUBVOL_RDONLY;
1650         else
1651                 root_flags &= ~BTRFS_ROOT_SUBVOL_RDONLY;
1652         btrfs_set_root_flags(new_root_item, root_flags);
1653
1654         btrfs_set_root_generation_v2(new_root_item,
1655                         trans->transid);
1656         generate_random_guid(new_root_item->uuid);
1657         memcpy(new_root_item->parent_uuid, root->root_item.uuid,
1658                         BTRFS_UUID_SIZE);
1659         if (!(root_flags & BTRFS_ROOT_SUBVOL_RDONLY)) {
1660                 memset(new_root_item->received_uuid, 0,
1661                        sizeof(new_root_item->received_uuid));
1662                 memset(&new_root_item->stime, 0, sizeof(new_root_item->stime));
1663                 memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime));
1664                 btrfs_set_root_stransid(new_root_item, 0);
1665                 btrfs_set_root_rtransid(new_root_item, 0);
1666         }
1667         btrfs_set_stack_timespec_sec(&new_root_item->otime, cur_time.tv_sec);
1668         btrfs_set_stack_timespec_nsec(&new_root_item->otime, cur_time.tv_nsec);
1669         btrfs_set_root_otransid(new_root_item, trans->transid);
1670
1671         old = btrfs_lock_root_node(root);
1672         ret = btrfs_cow_block(trans, root, old, NULL, 0, &old,
1673                               BTRFS_NESTING_COW);
1674         if (ret) {
1675                 btrfs_tree_unlock(old);
1676                 free_extent_buffer(old);
1677                 btrfs_abort_transaction(trans, ret);
1678                 goto fail;
1679         }
1680
1681         ret = btrfs_copy_root(trans, root, old, &tmp, objectid);
1682         /* clean up in any case */
1683         btrfs_tree_unlock(old);
1684         free_extent_buffer(old);
1685         if (ret) {
1686                 btrfs_abort_transaction(trans, ret);
1687                 goto fail;
1688         }
1689         /* see comments in should_cow_block() */
1690         set_bit(BTRFS_ROOT_FORCE_COW, &root->state);
1691         smp_wmb();
1692
1693         btrfs_set_root_node(new_root_item, tmp);
1694         /* record when the snapshot was created in key.offset */
1695         key.offset = trans->transid;
1696         ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
1697         btrfs_tree_unlock(tmp);
1698         free_extent_buffer(tmp);
1699         if (ret) {
1700                 btrfs_abort_transaction(trans, ret);
1701                 goto fail;
1702         }
1703
1704         /*
1705          * insert root back/forward references
1706          */
1707         ret = btrfs_add_root_ref(trans, objectid,
1708                                  parent_root->root_key.objectid,
1709                                  btrfs_ino(BTRFS_I(parent_inode)), index,
1710                                  dentry->d_name.name, dentry->d_name.len);
1711         if (ret) {
1712                 btrfs_abort_transaction(trans, ret);
1713                 goto fail;
1714         }
1715
1716         key.offset = (u64)-1;
1717         pending->snap = btrfs_get_new_fs_root(fs_info, objectid, pending->anon_dev);
1718         if (IS_ERR(pending->snap)) {
1719                 ret = PTR_ERR(pending->snap);
1720                 pending->snap = NULL;
1721                 btrfs_abort_transaction(trans, ret);
1722                 goto fail;
1723         }
1724
1725         ret = btrfs_reloc_post_snapshot(trans, pending);
1726         if (ret) {
1727                 btrfs_abort_transaction(trans, ret);
1728                 goto fail;
1729         }
1730
1731         /*
1732          * Do special qgroup accounting for snapshot, as we do some qgroup
1733          * snapshot hack to do fast snapshot.
1734          * To co-operate with that hack, we do hack again.
1735          * Or snapshot will be greatly slowed down by a subtree qgroup rescan
1736          */
1737         ret = qgroup_account_snapshot(trans, root, parent_root,
1738                                       pending->inherit, objectid);
1739         if (ret < 0)
1740                 goto fail;
1741
1742         ret = btrfs_insert_dir_item(trans, dentry->d_name.name,
1743                                     dentry->d_name.len, BTRFS_I(parent_inode),
1744                                     &key, BTRFS_FT_DIR, index);
1745         /* We have check then name at the beginning, so it is impossible. */
1746         BUG_ON(ret == -EEXIST || ret == -EOVERFLOW);
1747         if (ret) {
1748                 btrfs_abort_transaction(trans, ret);
1749                 goto fail;
1750         }
1751
1752         btrfs_i_size_write(BTRFS_I(parent_inode), parent_inode->i_size +
1753                                          dentry->d_name.len * 2);
1754         parent_inode->i_mtime = parent_inode->i_ctime =
1755                 current_time(parent_inode);
1756         ret = btrfs_update_inode_fallback(trans, parent_root, BTRFS_I(parent_inode));
1757         if (ret) {
1758                 btrfs_abort_transaction(trans, ret);
1759                 goto fail;
1760         }
1761         ret = btrfs_uuid_tree_add(trans, new_root_item->uuid,
1762                                   BTRFS_UUID_KEY_SUBVOL,
1763                                   objectid);
1764         if (ret) {
1765                 btrfs_abort_transaction(trans, ret);
1766                 goto fail;
1767         }
1768         if (!btrfs_is_empty_uuid(new_root_item->received_uuid)) {
1769                 ret = btrfs_uuid_tree_add(trans, new_root_item->received_uuid,
1770                                           BTRFS_UUID_KEY_RECEIVED_SUBVOL,
1771                                           objectid);
1772                 if (ret && ret != -EEXIST) {
1773                         btrfs_abort_transaction(trans, ret);
1774                         goto fail;
1775                 }
1776         }
1777
1778 fail:
1779         pending->error = ret;
1780 dir_item_existed:
1781         trans->block_rsv = rsv;
1782         trans->bytes_reserved = 0;
1783 clear_skip_qgroup:
1784         btrfs_clear_skip_qgroup(trans);
1785 no_free_objectid:
1786         kfree(new_root_item);
1787         pending->root_item = NULL;
1788         btrfs_free_path(path);
1789         pending->path = NULL;
1790
1791         return ret;
1792 }
1793
1794 /*
1795  * create all the snapshots we've scheduled for creation
1796  */
1797 static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans)
1798 {
1799         struct btrfs_pending_snapshot *pending, *next;
1800         struct list_head *head = &trans->transaction->pending_snapshots;
1801         int ret = 0;
1802
1803         list_for_each_entry_safe(pending, next, head, list) {
1804                 list_del(&pending->list);
1805                 ret = create_pending_snapshot(trans, pending);
1806                 if (ret)
1807                         break;
1808         }
1809         return ret;
1810 }
1811
1812 static void update_super_roots(struct btrfs_fs_info *fs_info)
1813 {
1814         struct btrfs_root_item *root_item;
1815         struct btrfs_super_block *super;
1816
1817         super = fs_info->super_copy;
1818
1819         root_item = &fs_info->chunk_root->root_item;
1820         super->chunk_root = root_item->bytenr;
1821         super->chunk_root_generation = root_item->generation;
1822         super->chunk_root_level = root_item->level;
1823
1824         root_item = &fs_info->tree_root->root_item;
1825         super->root = root_item->bytenr;
1826         super->generation = root_item->generation;
1827         super->root_level = root_item->level;
1828         if (btrfs_test_opt(fs_info, SPACE_CACHE))
1829                 super->cache_generation = root_item->generation;
1830         else if (test_bit(BTRFS_FS_CLEANUP_SPACE_CACHE_V1, &fs_info->flags))
1831                 super->cache_generation = 0;
1832         if (test_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags))
1833                 super->uuid_tree_generation = root_item->generation;
1834 }
1835
1836 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
1837 {
1838         struct btrfs_transaction *trans;
1839         int ret = 0;
1840
1841         spin_lock(&info->trans_lock);
1842         trans = info->running_transaction;
1843         if (trans)
1844                 ret = (trans->state >= TRANS_STATE_COMMIT_START);
1845         spin_unlock(&info->trans_lock);
1846         return ret;
1847 }
1848
1849 int btrfs_transaction_blocked(struct btrfs_fs_info *info)
1850 {
1851         struct btrfs_transaction *trans;
1852         int ret = 0;
1853
1854         spin_lock(&info->trans_lock);
1855         trans = info->running_transaction;
1856         if (trans)
1857                 ret = is_transaction_blocked(trans);
1858         spin_unlock(&info->trans_lock);
1859         return ret;
1860 }
1861
1862 /*
1863  * wait for the current transaction commit to start and block subsequent
1864  * transaction joins
1865  */
1866 static void wait_current_trans_commit_start(struct btrfs_fs_info *fs_info,
1867                                             struct btrfs_transaction *trans)
1868 {
1869         wait_event(fs_info->transaction_blocked_wait,
1870                    trans->state >= TRANS_STATE_COMMIT_START ||
1871                    TRANS_ABORTED(trans));
1872 }
1873
1874 /*
1875  * wait for the current transaction to start and then become unblocked.
1876  * caller holds ref.
1877  */
1878 static void wait_current_trans_commit_start_and_unblock(
1879                                         struct btrfs_fs_info *fs_info,
1880                                         struct btrfs_transaction *trans)
1881 {
1882         wait_event(fs_info->transaction_wait,
1883                    trans->state >= TRANS_STATE_UNBLOCKED ||
1884                    TRANS_ABORTED(trans));
1885 }
1886
1887 /*
1888  * commit transactions asynchronously. once btrfs_commit_transaction_async
1889  * returns, any subsequent transaction will not be allowed to join.
1890  */
1891 struct btrfs_async_commit {
1892         struct btrfs_trans_handle *newtrans;
1893         struct work_struct work;
1894 };
1895
1896 static void do_async_commit(struct work_struct *work)
1897 {
1898         struct btrfs_async_commit *ac =
1899                 container_of(work, struct btrfs_async_commit, work);
1900
1901         /*
1902          * We've got freeze protection passed with the transaction.
1903          * Tell lockdep about it.
1904          */
1905         if (ac->newtrans->type & __TRANS_FREEZABLE)
1906                 __sb_writers_acquired(ac->newtrans->fs_info->sb, SB_FREEZE_FS);
1907
1908         current->journal_info = ac->newtrans;
1909
1910         btrfs_commit_transaction(ac->newtrans);
1911         kfree(ac);
1912 }
1913
1914 int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
1915                                    int wait_for_unblock)
1916 {
1917         struct btrfs_fs_info *fs_info = trans->fs_info;
1918         struct btrfs_async_commit *ac;
1919         struct btrfs_transaction *cur_trans;
1920
1921         ac = kmalloc(sizeof(*ac), GFP_NOFS);
1922         if (!ac)
1923                 return -ENOMEM;
1924
1925         INIT_WORK(&ac->work, do_async_commit);
1926         ac->newtrans = btrfs_join_transaction(trans->root);
1927         if (IS_ERR(ac->newtrans)) {
1928                 int err = PTR_ERR(ac->newtrans);
1929                 kfree(ac);
1930                 return err;
1931         }
1932
1933         /* take transaction reference */
1934         cur_trans = trans->transaction;
1935         refcount_inc(&cur_trans->use_count);
1936
1937         btrfs_end_transaction(trans);
1938
1939         /*
1940          * Tell lockdep we've released the freeze rwsem, since the
1941          * async commit thread will be the one to unlock it.
1942          */
1943         if (ac->newtrans->type & __TRANS_FREEZABLE)
1944                 __sb_writers_release(fs_info->sb, SB_FREEZE_FS);
1945
1946         schedule_work(&ac->work);
1947
1948         /* wait for transaction to start and unblock */
1949         if (wait_for_unblock)
1950                 wait_current_trans_commit_start_and_unblock(fs_info, cur_trans);
1951         else
1952                 wait_current_trans_commit_start(fs_info, cur_trans);
1953
1954         if (current->journal_info == trans)
1955                 current->journal_info = NULL;
1956
1957         btrfs_put_transaction(cur_trans);
1958         return 0;
1959 }
1960
1961
1962 static void cleanup_transaction(struct btrfs_trans_handle *trans, int err)
1963 {
1964         struct btrfs_fs_info *fs_info = trans->fs_info;
1965         struct btrfs_transaction *cur_trans = trans->transaction;
1966
1967         WARN_ON(refcount_read(&trans->use_count) > 1);
1968
1969         btrfs_abort_transaction(trans, err);
1970
1971         spin_lock(&fs_info->trans_lock);
1972
1973         /*
1974          * If the transaction is removed from the list, it means this
1975          * transaction has been committed successfully, so it is impossible
1976          * to call the cleanup function.
1977          */
1978         BUG_ON(list_empty(&cur_trans->list));
1979
1980         list_del_init(&cur_trans->list);
1981         if (cur_trans == fs_info->running_transaction) {
1982                 cur_trans->state = TRANS_STATE_COMMIT_DOING;
1983                 spin_unlock(&fs_info->trans_lock);
1984                 wait_event(cur_trans->writer_wait,
1985                            atomic_read(&cur_trans->num_writers) == 1);
1986
1987                 spin_lock(&fs_info->trans_lock);
1988         }
1989         spin_unlock(&fs_info->trans_lock);
1990
1991         btrfs_cleanup_one_transaction(trans->transaction, fs_info);
1992
1993         spin_lock(&fs_info->trans_lock);
1994         if (cur_trans == fs_info->running_transaction)
1995                 fs_info->running_transaction = NULL;
1996         spin_unlock(&fs_info->trans_lock);
1997
1998         if (trans->type & __TRANS_FREEZABLE)
1999                 sb_end_intwrite(fs_info->sb);
2000         btrfs_put_transaction(cur_trans);
2001         btrfs_put_transaction(cur_trans);
2002
2003         trace_btrfs_transaction_commit(trans->root);
2004
2005         if (current->journal_info == trans)
2006                 current->journal_info = NULL;
2007         btrfs_scrub_cancel(fs_info);
2008
2009         kmem_cache_free(btrfs_trans_handle_cachep, trans);
2010 }
2011
2012 /*
2013  * Release reserved delayed ref space of all pending block groups of the
2014  * transaction and remove them from the list
2015  */
2016 static void btrfs_cleanup_pending_block_groups(struct btrfs_trans_handle *trans)
2017 {
2018        struct btrfs_fs_info *fs_info = trans->fs_info;
2019        struct btrfs_block_group *block_group, *tmp;
2020
2021        list_for_each_entry_safe(block_group, tmp, &trans->new_bgs, bg_list) {
2022                btrfs_delayed_refs_rsv_release(fs_info, 1);
2023                list_del_init(&block_group->bg_list);
2024        }
2025 }
2026
2027 static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
2028 {
2029         /*
2030          * We use writeback_inodes_sb here because if we used
2031          * btrfs_start_delalloc_roots we would deadlock with fs freeze.
2032          * Currently are holding the fs freeze lock, if we do an async flush
2033          * we'll do btrfs_join_transaction() and deadlock because we need to
2034          * wait for the fs freeze lock.  Using the direct flushing we benefit
2035          * from already being in a transaction and our join_transaction doesn't
2036          * have to re-take the fs freeze lock.
2037          */
2038         if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
2039                 writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
2040         return 0;
2041 }
2042
2043 static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
2044 {
2045         if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
2046                 btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
2047 }
2048
2049 int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
2050 {
2051         struct btrfs_fs_info *fs_info = trans->fs_info;
2052         struct btrfs_transaction *cur_trans = trans->transaction;
2053         struct btrfs_transaction *prev_trans = NULL;
2054         int ret;
2055
2056         ASSERT(refcount_read(&trans->use_count) == 1);
2057
2058         /*
2059          * Some places just start a transaction to commit it.  We need to make
2060          * sure that if this commit fails that the abort code actually marks the
2061          * transaction as failed, so set trans->dirty to make the abort code do
2062          * the right thing.
2063          */
2064         trans->dirty = true;
2065
2066         /* Stop the commit early if ->aborted is set */
2067         if (TRANS_ABORTED(cur_trans)) {
2068                 ret = cur_trans->aborted;
2069                 btrfs_end_transaction(trans);
2070                 return ret;
2071         }
2072
2073         btrfs_trans_release_metadata(trans);
2074         trans->block_rsv = NULL;
2075
2076         /*
2077          * We only want one transaction commit doing the flushing so we do not
2078          * waste a bunch of time on lock contention on the extent root node.
2079          */
2080         if (!test_and_set_bit(BTRFS_DELAYED_REFS_FLUSHING,
2081                               &cur_trans->delayed_refs.flags)) {
2082                 /*
2083                  * Make a pass through all the delayed refs we have so far.
2084                  * Any running threads may add more while we are here.
2085                  */
2086                 ret = btrfs_run_delayed_refs(trans, 0);
2087                 if (ret) {
2088                         btrfs_end_transaction(trans);
2089                         return ret;
2090                 }
2091         }
2092
2093         btrfs_create_pending_block_groups(trans);
2094
2095         if (!test_bit(BTRFS_TRANS_DIRTY_BG_RUN, &cur_trans->flags)) {
2096                 int run_it = 0;
2097
2098                 /* this mutex is also taken before trying to set
2099                  * block groups readonly.  We need to make sure
2100                  * that nobody has set a block group readonly
2101                  * after a extents from that block group have been
2102                  * allocated for cache files.  btrfs_set_block_group_ro
2103                  * will wait for the transaction to commit if it
2104                  * finds BTRFS_TRANS_DIRTY_BG_RUN set.
2105                  *
2106                  * The BTRFS_TRANS_DIRTY_BG_RUN flag is also used to make sure
2107                  * only one process starts all the block group IO.  It wouldn't
2108                  * hurt to have more than one go through, but there's no
2109                  * real advantage to it either.
2110                  */
2111                 mutex_lock(&fs_info->ro_block_group_mutex);
2112                 if (!test_and_set_bit(BTRFS_TRANS_DIRTY_BG_RUN,
2113                                       &cur_trans->flags))
2114                         run_it = 1;
2115                 mutex_unlock(&fs_info->ro_block_group_mutex);
2116
2117                 if (run_it) {
2118                         ret = btrfs_start_dirty_block_groups(trans);
2119                         if (ret) {
2120                                 btrfs_end_transaction(trans);
2121                                 return ret;
2122                         }
2123                 }
2124         }
2125
2126         spin_lock(&fs_info->trans_lock);
2127         if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
2128                 enum btrfs_trans_state want_state = TRANS_STATE_COMPLETED;
2129
2130                 spin_unlock(&fs_info->trans_lock);
2131                 refcount_inc(&cur_trans->use_count);
2132
2133                 if (trans->in_fsync)
2134                         want_state = TRANS_STATE_SUPER_COMMITTED;
2135                 ret = btrfs_end_transaction(trans);
2136                 wait_for_commit(cur_trans, want_state);
2137
2138                 if (TRANS_ABORTED(cur_trans))
2139                         ret = cur_trans->aborted;
2140
2141                 btrfs_put_transaction(cur_trans);
2142
2143                 return ret;
2144         }
2145
2146         cur_trans->state = TRANS_STATE_COMMIT_START;
2147         wake_up(&fs_info->transaction_blocked_wait);
2148
2149         if (cur_trans->list.prev != &fs_info->trans_list) {
2150                 enum btrfs_trans_state want_state = TRANS_STATE_COMPLETED;
2151
2152                 if (trans->in_fsync)
2153                         want_state = TRANS_STATE_SUPER_COMMITTED;
2154
2155                 prev_trans = list_entry(cur_trans->list.prev,
2156                                         struct btrfs_transaction, list);
2157                 if (prev_trans->state < want_state) {
2158                         refcount_inc(&prev_trans->use_count);
2159                         spin_unlock(&fs_info->trans_lock);
2160
2161                         wait_for_commit(prev_trans, want_state);
2162
2163                         ret = READ_ONCE(prev_trans->aborted);
2164
2165                         btrfs_put_transaction(prev_trans);
2166                         if (ret)
2167                                 goto cleanup_transaction;
2168                 } else {
2169                         spin_unlock(&fs_info->trans_lock);
2170                 }
2171         } else {
2172                 spin_unlock(&fs_info->trans_lock);
2173                 /*
2174                  * The previous transaction was aborted and was already removed
2175                  * from the list of transactions at fs_info->trans_list. So we
2176                  * abort to prevent writing a new superblock that reflects a
2177                  * corrupt state (pointing to trees with unwritten nodes/leafs).
2178                  */
2179                 if (test_bit(BTRFS_FS_STATE_TRANS_ABORTED, &fs_info->fs_state)) {
2180                         ret = -EROFS;
2181                         goto cleanup_transaction;
2182                 }
2183         }
2184
2185         extwriter_counter_dec(cur_trans, trans->type);
2186
2187         ret = btrfs_start_delalloc_flush(fs_info);
2188         if (ret)
2189                 goto cleanup_transaction;
2190
2191         ret = btrfs_run_delayed_items(trans);
2192         if (ret)
2193                 goto cleanup_transaction;
2194
2195         wait_event(cur_trans->writer_wait,
2196                    extwriter_counter_read(cur_trans) == 0);
2197
2198         /* some pending stuffs might be added after the previous flush. */
2199         ret = btrfs_run_delayed_items(trans);
2200         if (ret)
2201                 goto cleanup_transaction;
2202
2203         btrfs_wait_delalloc_flush(fs_info);
2204
2205         /*
2206          * Wait for all ordered extents started by a fast fsync that joined this
2207          * transaction. Otherwise if this transaction commits before the ordered
2208          * extents complete we lose logged data after a power failure.
2209          */
2210         wait_event(cur_trans->pending_wait,
2211                    atomic_read(&cur_trans->pending_ordered) == 0);
2212
2213         btrfs_scrub_pause(fs_info);
2214         /*
2215          * Ok now we need to make sure to block out any other joins while we
2216          * commit the transaction.  We could have started a join before setting
2217          * COMMIT_DOING so make sure to wait for num_writers to == 1 again.
2218          */
2219         spin_lock(&fs_info->trans_lock);
2220         cur_trans->state = TRANS_STATE_COMMIT_DOING;
2221         spin_unlock(&fs_info->trans_lock);
2222         wait_event(cur_trans->writer_wait,
2223                    atomic_read(&cur_trans->num_writers) == 1);
2224
2225         if (TRANS_ABORTED(cur_trans)) {
2226                 ret = cur_trans->aborted;
2227                 goto scrub_continue;
2228         }
2229         /*
2230          * the reloc mutex makes sure that we stop
2231          * the balancing code from coming in and moving
2232          * extents around in the middle of the commit
2233          */
2234         mutex_lock(&fs_info->reloc_mutex);
2235
2236         /*
2237          * We needn't worry about the delayed items because we will
2238          * deal with them in create_pending_snapshot(), which is the
2239          * core function of the snapshot creation.
2240          */
2241         ret = create_pending_snapshots(trans);
2242         if (ret)
2243                 goto unlock_reloc;
2244
2245         /*
2246          * We insert the dir indexes of the snapshots and update the inode
2247          * of the snapshots' parents after the snapshot creation, so there
2248          * are some delayed items which are not dealt with. Now deal with
2249          * them.
2250          *
2251          * We needn't worry that this operation will corrupt the snapshots,
2252          * because all the tree which are snapshoted will be forced to COW
2253          * the nodes and leaves.
2254          */
2255         ret = btrfs_run_delayed_items(trans);
2256         if (ret)
2257                 goto unlock_reloc;
2258
2259         ret = btrfs_run_delayed_refs(trans, (unsigned long)-1);
2260         if (ret)
2261                 goto unlock_reloc;
2262
2263         /*
2264          * make sure none of the code above managed to slip in a
2265          * delayed item
2266          */
2267         btrfs_assert_delayed_root_empty(fs_info);
2268
2269         WARN_ON(cur_trans != trans->transaction);
2270
2271         /* btrfs_commit_tree_roots is responsible for getting the
2272          * various roots consistent with each other.  Every pointer
2273          * in the tree of tree roots has to point to the most up to date
2274          * root for every subvolume and other tree.  So, we have to keep
2275          * the tree logging code from jumping in and changing any
2276          * of the trees.
2277          *
2278          * At this point in the commit, there can't be any tree-log
2279          * writers, but a little lower down we drop the trans mutex
2280          * and let new people in.  By holding the tree_log_mutex
2281          * from now until after the super is written, we avoid races
2282          * with the tree-log code.
2283          */
2284         mutex_lock(&fs_info->tree_log_mutex);
2285
2286         ret = commit_fs_roots(trans);
2287         if (ret)
2288                 goto unlock_tree_log;
2289
2290         /*
2291          * Since the transaction is done, we can apply the pending changes
2292          * before the next transaction.
2293          */
2294         btrfs_apply_pending_changes(fs_info);
2295
2296         /* commit_fs_roots gets rid of all the tree log roots, it is now
2297          * safe to free the root of tree log roots
2298          */
2299         btrfs_free_log_root_tree(trans, fs_info);
2300
2301         /*
2302          * Since fs roots are all committed, we can get a quite accurate
2303          * new_roots. So let's do quota accounting.
2304          */
2305         ret = btrfs_qgroup_account_extents(trans);
2306         if (ret < 0)
2307                 goto unlock_tree_log;
2308
2309         ret = commit_cowonly_roots(trans);
2310         if (ret)
2311                 goto unlock_tree_log;
2312
2313         /*
2314          * The tasks which save the space cache and inode cache may also
2315          * update ->aborted, check it.
2316          */
2317         if (TRANS_ABORTED(cur_trans)) {
2318                 ret = cur_trans->aborted;
2319                 goto unlock_tree_log;
2320         }
2321
2322         cur_trans = fs_info->running_transaction;
2323
2324         btrfs_set_root_node(&fs_info->tree_root->root_item,
2325                             fs_info->tree_root->node);
2326         list_add_tail(&fs_info->tree_root->dirty_list,
2327                       &cur_trans->switch_commits);
2328
2329         btrfs_set_root_node(&fs_info->chunk_root->root_item,
2330                             fs_info->chunk_root->node);
2331         list_add_tail(&fs_info->chunk_root->dirty_list,
2332                       &cur_trans->switch_commits);
2333
2334         switch_commit_roots(trans);
2335
2336         ASSERT(list_empty(&cur_trans->dirty_bgs));
2337         ASSERT(list_empty(&cur_trans->io_bgs));
2338         update_super_roots(fs_info);
2339
2340         btrfs_set_super_log_root(fs_info->super_copy, 0);
2341         btrfs_set_super_log_root_level(fs_info->super_copy, 0);
2342         memcpy(fs_info->super_for_commit, fs_info->super_copy,
2343                sizeof(*fs_info->super_copy));
2344
2345         btrfs_commit_device_sizes(cur_trans);
2346
2347         clear_bit(BTRFS_FS_LOG1_ERR, &fs_info->flags);
2348         clear_bit(BTRFS_FS_LOG2_ERR, &fs_info->flags);
2349
2350         btrfs_trans_release_chunk_metadata(trans);
2351
2352         spin_lock(&fs_info->trans_lock);
2353         cur_trans->state = TRANS_STATE_UNBLOCKED;
2354         fs_info->running_transaction = NULL;
2355         spin_unlock(&fs_info->trans_lock);
2356         mutex_unlock(&fs_info->reloc_mutex);
2357
2358         wake_up(&fs_info->transaction_wait);
2359
2360         ret = btrfs_write_and_wait_transaction(trans);
2361         if (ret) {
2362                 btrfs_handle_fs_error(fs_info, ret,
2363                                       "Error while writing out transaction");
2364                 /*
2365                  * reloc_mutex has been unlocked, tree_log_mutex is still held
2366                  * but we can't jump to unlock_tree_log causing double unlock
2367                  */
2368                 mutex_unlock(&fs_info->tree_log_mutex);
2369                 goto scrub_continue;
2370         }
2371
2372         /*
2373          * At this point, we should have written all the tree blocks allocated
2374          * in this transaction. So it's now safe to free the redirtyied extent
2375          * buffers.
2376          */
2377         btrfs_free_redirty_list(cur_trans);
2378
2379         ret = write_all_supers(fs_info, 0);
2380         /*
2381          * the super is written, we can safely allow the tree-loggers
2382          * to go about their business
2383          */
2384         mutex_unlock(&fs_info->tree_log_mutex);
2385         if (ret)
2386                 goto scrub_continue;
2387
2388         /*
2389          * We needn't acquire the lock here because there is no other task
2390          * which can change it.
2391          */
2392         cur_trans->state = TRANS_STATE_SUPER_COMMITTED;
2393         wake_up(&cur_trans->commit_wait);
2394
2395         btrfs_finish_extent_commit(trans);
2396
2397         if (test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &cur_trans->flags))
2398                 btrfs_clear_space_info_full(fs_info);
2399
2400         fs_info->last_trans_committed = cur_trans->transid;
2401         /*
2402          * We needn't acquire the lock here because there is no other task
2403          * which can change it.
2404          */
2405         cur_trans->state = TRANS_STATE_COMPLETED;
2406         wake_up(&cur_trans->commit_wait);
2407
2408         spin_lock(&fs_info->trans_lock);
2409         list_del_init(&cur_trans->list);
2410         spin_unlock(&fs_info->trans_lock);
2411
2412         btrfs_put_transaction(cur_trans);
2413         btrfs_put_transaction(cur_trans);
2414
2415         if (trans->type & __TRANS_FREEZABLE)
2416                 sb_end_intwrite(fs_info->sb);
2417
2418         trace_btrfs_transaction_commit(trans->root);
2419
2420         btrfs_scrub_continue(fs_info);
2421
2422         if (current->journal_info == trans)
2423                 current->journal_info = NULL;
2424
2425         kmem_cache_free(btrfs_trans_handle_cachep, trans);
2426
2427         return ret;
2428
2429 unlock_tree_log:
2430         mutex_unlock(&fs_info->tree_log_mutex);
2431 unlock_reloc:
2432         mutex_unlock(&fs_info->reloc_mutex);
2433 scrub_continue:
2434         btrfs_scrub_continue(fs_info);
2435 cleanup_transaction:
2436         btrfs_trans_release_metadata(trans);
2437         btrfs_cleanup_pending_block_groups(trans);
2438         btrfs_trans_release_chunk_metadata(trans);
2439         trans->block_rsv = NULL;
2440         btrfs_warn(fs_info, "Skipping commit of aborted transaction.");
2441         if (current->journal_info == trans)
2442                 current->journal_info = NULL;
2443         cleanup_transaction(trans, ret);
2444
2445         return ret;
2446 }
2447
2448 /*
2449  * return < 0 if error
2450  * 0 if there are no more dead_roots at the time of call
2451  * 1 there are more to be processed, call me again
2452  *
2453  * The return value indicates there are certainly more snapshots to delete, but
2454  * if there comes a new one during processing, it may return 0. We don't mind,
2455  * because btrfs_commit_super will poke cleaner thread and it will process it a
2456  * few seconds later.
2457  */
2458 int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
2459 {
2460         int ret;
2461         struct btrfs_fs_info *fs_info = root->fs_info;
2462
2463         spin_lock(&fs_info->trans_lock);
2464         if (list_empty(&fs_info->dead_roots)) {
2465                 spin_unlock(&fs_info->trans_lock);
2466                 return 0;
2467         }
2468         root = list_first_entry(&fs_info->dead_roots,
2469                         struct btrfs_root, root_list);
2470         list_del_init(&root->root_list);
2471         spin_unlock(&fs_info->trans_lock);
2472
2473         btrfs_debug(fs_info, "cleaner removing %llu", root->root_key.objectid);
2474
2475         btrfs_kill_all_delayed_nodes(root);
2476
2477         if (btrfs_header_backref_rev(root->node) <
2478                         BTRFS_MIXED_BACKREF_REV)
2479                 ret = btrfs_drop_snapshot(root, 0, 0);
2480         else
2481                 ret = btrfs_drop_snapshot(root, 1, 0);
2482
2483         btrfs_put_root(root);
2484         return (ret < 0) ? 0 : 1;
2485 }
2486
2487 void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
2488 {
2489         unsigned long prev;
2490         unsigned long bit;
2491
2492         prev = xchg(&fs_info->pending_changes, 0);
2493         if (!prev)
2494                 return;
2495
2496         bit = 1 << BTRFS_PENDING_COMMIT;
2497         if (prev & bit)
2498                 btrfs_debug(fs_info, "pending commit done");
2499         prev &= ~bit;
2500
2501         if (prev)
2502                 btrfs_warn(fs_info,
2503                         "unknown pending changes left 0x%lx, ignoring", prev);
2504 }