fs/btrfs/transaction.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/fs.h>
  20 #include <linux/slab.h>
  21 #include <linux/sched.h>
  22 #include <linux/writeback.h>
  23 #include <linux/pagemap.h>
  24 #include <linux/blkdev.h>
  25 #include <linux/uuid.h>
  26 #include "ctree.h"
  27 #include "disk-io.h"
  28 #include "transaction.h"
  29 #include "locking.h"
  30 #include "tree-log.h"
  31 #include "inode-map.h"
  32 #include "volumes.h"
  33 #include "dev-replace.h"
  34 #include "qgroup.h"
  35
  36 #define BTRFS_ROOT_TRANS_TAG 0
  37
  38 static unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {
  39         [TRANS_STATE_RUNNING]           = 0U,
  40         [TRANS_STATE_BLOCKED]           = (__TRANS_USERSPACE |
  41                                            __TRANS_START),
  42         [TRANS_STATE_COMMIT_START]      = (__TRANS_USERSPACE |
  43                                            __TRANS_START |
  44                                            __TRANS_ATTACH),
  45         [TRANS_STATE_COMMIT_DOING]      = (__TRANS_USERSPACE |
  46                                            __TRANS_START |
  47                                            __TRANS_ATTACH |
  48                                            __TRANS_JOIN),
  49         [TRANS_STATE_UNBLOCKED]         = (__TRANS_USERSPACE |
  50                                            __TRANS_START |
  51                                            __TRANS_ATTACH |
  52                                            __TRANS_JOIN |
  53                                            __TRANS_JOIN_NOLOCK),
  54         [TRANS_STATE_COMPLETED]         = (__TRANS_USERSPACE |
  55                                            __TRANS_START |
  56                                            __TRANS_ATTACH |
  57                                            __TRANS_JOIN |
  58                                            __TRANS_JOIN_NOLOCK),
  59 };
  60
  61 void btrfs_put_transaction(struct btrfs_transaction *transaction)
  62 {
  63         WARN_ON(atomic_read(&transaction->use_count) == 0);
  64         if (atomic_dec_and_test(&transaction->use_count)) {
  65                 BUG_ON(!list_empty(&transaction->list));
  66                 WARN_ON(!RB_EMPTY_ROOT(&transaction->delayed_refs.href_root));
  67                 while (!list_empty(&transaction->pending_chunks)) {
  68                         struct extent_map *em;
  69
  70                         em = list_first_entry(&transaction->pending_chunks,
  71                                               struct extent_map, list);
  72                         list_del_init(&em->list);
  73                         free_extent_map(em);
  74                 }
  75                 kmem_cache_free(btrfs_transaction_cachep, transaction);
  76         }
  77 }
  78
  79 static noinline void switch_commit_roots(struct btrfs_transaction *trans,
  80                                          struct btrfs_fs_info *fs_info)
  81 {
  82         struct btrfs_root *root, *tmp;
  83
  84         down_write(&fs_info->commit_root_sem);
  85         list_for_each_entry_safe(root, tmp, &trans->switch_commits,
  86                                  dirty_list) {
  87                 list_del_init(&root->dirty_list);
  88                 free_extent_buffer(root->commit_root);
  89                 root->commit_root = btrfs_root_node(root);
  90                 if (is_fstree(root->objectid))
  91                         btrfs_unpin_free_ino(root);
  92         }
  93         up_write(&fs_info->commit_root_sem);
  94 }
  95
  96 static inline void extwriter_counter_inc(struct btrfs_transaction *trans,
  97                                          unsigned int type)
  98 {
  99         if (type & TRANS_EXTWRITERS)
 100                 atomic_inc(&trans->num_extwriters);
 101 }
 102
 103 static inline void extwriter_counter_dec(struct btrfs_transaction *trans,
 104                                          unsigned int type)
 105 {
 106         if (type & TRANS_EXTWRITERS)
 107                 atomic_dec(&trans->num_extwriters);
 108 }
 109
 110 static inline void extwriter_counter_init(struct btrfs_transaction *trans,
 111                                           unsigned int type)
 112 {
 113         atomic_set(&trans->num_extwriters, ((type & TRANS_EXTWRITERS) ? 1 : 0));
 114 }
 115
 116 static inline int extwriter_counter_read(struct btrfs_transaction *trans)
 117 {
 118         return atomic_read(&trans->num_extwriters);
 119 }
 120
 121 /*
 122  * either allocate a new transaction or hop into the existing one
 123  */
 124 static noinline int join_transaction(struct btrfs_root *root, unsigned int type)
 125 {
 126         struct btrfs_transaction *cur_trans;
 127         struct btrfs_fs_info *fs_info = root->fs_info;
 128
 129         spin_lock(&fs_info->trans_lock);
 130 loop:
 131         /* The file system has been taken offline. No new transactions. */
 132         if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
 133                 spin_unlock(&fs_info->trans_lock);
 134                 return -EROFS;
 135         }
 136
 137         cur_trans = fs_info->running_transaction;
 138         if (cur_trans) {
 139                 if (cur_trans->aborted) {
 140                         spin_unlock(&fs_info->trans_lock);
 141                         return cur_trans->aborted;
 142                 }
 143                 if (btrfs_blocked_trans_types[cur_trans->state] & type) {
 144                         spin_unlock(&fs_info->trans_lock);
 145                         return -EBUSY;
 146                 }
 147                 atomic_inc(&cur_trans->use_count);
 148                 atomic_inc(&cur_trans->num_writers);
 149                 extwriter_counter_inc(cur_trans, type);
 150                 spin_unlock(&fs_info->trans_lock);
 151                 return 0;
 152         }
 153         spin_unlock(&fs_info->trans_lock);
 154
 155         /*
 156          * If we are ATTACH, we just want to catch the current transaction,
 157          * and commit it. If there is no transaction, just return ENOENT.
 158          */
 159         if (type == TRANS_ATTACH)
 160                 return -ENOENT;
 161
 162         /*
 163          * JOIN_NOLOCK only happens during the transaction commit, so
 164          * it is impossible that ->running_transaction is NULL
 165          */
 166         BUG_ON(type == TRANS_JOIN_NOLOCK);
 167
 168         cur_trans = kmem_cache_alloc(btrfs_transaction_cachep, GFP_NOFS);
 169         if (!cur_trans)
 170                 return -ENOMEM;
 171
 172         spin_lock(&fs_info->trans_lock);
 173         if (fs_info->running_transaction) {
 174                 /*
 175                  * someone started a transaction after we unlocked.  Make sure
 176                  * to redo the checks above
 177                  */
 178                 kmem_cache_free(btrfs_transaction_cachep, cur_trans);
 179                 goto loop;
 180         } else if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
 181                 spin_unlock(&fs_info->trans_lock);
 182                 kmem_cache_free(btrfs_transaction_cachep, cur_trans);
 183                 return -EROFS;
 184         }
 185
 186         atomic_set(&cur_trans->num_writers, 1);
 187         extwriter_counter_init(cur_trans, type);
 188         init_waitqueue_head(&cur_trans->writer_wait);
 189         init_waitqueue_head(&cur_trans->commit_wait);
 190         cur_trans->state = TRANS_STATE_RUNNING;
 191         /*
 192          * One for this trans handle, one so it will live on until we
 193          * commit the transaction.
 194          */
 195         atomic_set(&cur_trans->use_count, 2);
 196         cur_trans->start_time = get_seconds();
 197
 198         cur_trans->delayed_refs.href_root = RB_ROOT;
 199         atomic_set(&cur_trans->delayed_refs.num_entries, 0);
 200         cur_trans->delayed_refs.num_heads_ready = 0;
 201         cur_trans->delayed_refs.num_heads = 0;
 202         cur_trans->delayed_refs.flushing = 0;
 203         cur_trans->delayed_refs.run_delayed_start = 0;
 204
 205         /*
 206          * although the tree mod log is per file system and not per transaction,
 207          * the log must never go across transaction boundaries.
 208          */
 209         smp_mb();
 210         if (!list_empty(&fs_info->tree_mod_seq_list))
 211                 WARN(1, KERN_ERR "BTRFS: tree_mod_seq_list not empty when "
 212                         "creating a fresh transaction\n");
 213         if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log))
 214                 WARN(1, KERN_ERR "BTRFS: tree_mod_log rb tree not empty when "
 215                         "creating a fresh transaction\n");
 216         atomic64_set(&fs_info->tree_mod_seq, 0);
 217
 218         spin_lock_init(&cur_trans->delayed_refs.lock);
 219
 220         INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 221         INIT_LIST_HEAD(&cur_trans->pending_chunks);
 222         INIT_LIST_HEAD(&cur_trans->switch_commits);
 223         list_add_tail(&cur_trans->list, &fs_info->trans_list);
 224         extent_io_tree_init(&cur_trans->dirty_pages,
 225                              fs_info->btree_inode->i_mapping);
 226         fs_info->generation++;
 227         cur_trans->transid = fs_info->generation;
 228         fs_info->running_transaction = cur_trans;
 229         cur_trans->aborted = 0;
 230         spin_unlock(&fs_info->trans_lock);
 231
 232         return 0;
 233 }
 234
 235 /*
 236  * this does all the record keeping required to make sure that a reference
 237  * counted root is properly recorded in a given transaction.  This is required
 238  * to make sure the old root from before we joined the transaction is deleted
 239  * when the transaction commits
 240  */
 241 static int record_root_in_trans(struct btrfs_trans_handle *trans,
 242                                struct btrfs_root *root)
 243 {
 244         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 245             root->last_trans < trans->transid) {
 246                 WARN_ON(root == root->fs_info->extent_root);
 247                 WARN_ON(root->commit_root != root->node);
 248
 249                 /*
 250                  * see below for IN_TRANS_SETUP usage rules
 251                  * we have the reloc mutex held now, so there
 252                  * is only one writer in this function
 253                  */
 254                 set_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state);
 255
 256                 /* make sure readers find IN_TRANS_SETUP before
 257                  * they find our root->last_trans update
 258                  */
 259                 smp_wmb();
 260
 261                 spin_lock(&root->fs_info->fs_roots_radix_lock);
 262                 if (root->last_trans == trans->transid) {
 263                         spin_unlock(&root->fs_info->fs_roots_radix_lock);
 264                         return 0;
 265                 }
 266                 radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 267                            (unsigned long)root->root_key.objectid,
 268                            BTRFS_ROOT_TRANS_TAG);
 269                 spin_unlock(&root->fs_info->fs_roots_radix_lock);
 270                 root->last_trans = trans->transid;
 271
 272                 /* this is pretty tricky.  We don't want to
 273                  * take the relocation lock in btrfs_record_root_in_trans
 274                  * unless we're really doing the first setup for this root in
 275                  * this transaction.
 276                  *
 277                  * Normally we'd use root->last_trans as a flag to decide
 278                  * if we want to take the expensive mutex.
 279                  *
 280                  * But, we have to set root->last_trans before we
 281                  * init the relocation root, otherwise, we trip over warnings
 282                  * in ctree.c.  The solution used here is to flag ourselves
 283                  * with root IN_TRANS_SETUP.  When this is 1, we're still
 284                  * fixing up the reloc trees and everyone must wait.
 285                  *
 286                  * When this is zero, they can trust root->last_trans and fly
 287                  * through btrfs_record_root_in_trans without having to take the
 288                  * lock.  smp_wmb() makes sure that all the writes above are
 289                  * done before we pop in the zero below
 290                  */
 291                 btrfs_init_reloc_root(trans, root);
 292                 smp_mb__before_atomic();
 293                 clear_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state);
 294         }
 295         return 0;
 296 }
 297
 298
 299 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
 300                                struct btrfs_root *root)
 301 {
 302         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 303                 return 0;
 304
 305         /*
 306          * see record_root_in_trans for comments about IN_TRANS_SETUP usage
 307          * and barriers
 308          */
 309         smp_rmb();
 310         if (root->last_trans == trans->transid &&
 311             !test_bit(BTRFS_ROOT_IN_TRANS_SETUP, &root->state))
 312                 return 0;
 313
 314         mutex_lock(&root->fs_info->reloc_mutex);
 315         record_root_in_trans(trans, root);
 316         mutex_unlock(&root->fs_info->reloc_mutex);
 317
 318         return 0;
 319 }
 320
 321 static inline int is_transaction_blocked(struct btrfs_transaction *trans)
 322 {
 323         return (trans->state >= TRANS_STATE_BLOCKED &&
 324                 trans->state < TRANS_STATE_UNBLOCKED &&
 325                 !trans->aborted);
 326 }
 327
 328 /* wait for commit against the current transaction to become unblocked
 329  * when this is done, it is safe to start a new transaction, but the current
 330  * transaction might not be fully on disk.
 331  */
 332 static void wait_current_trans(struct btrfs_root *root)
 333 {
 334         struct btrfs_transaction *cur_trans;
 335
 336         spin_lock(&root->fs_info->trans_lock);
 337         cur_trans = root->fs_info->running_transaction;
 338         if (cur_trans && is_transaction_blocked(cur_trans)) {
 339                 atomic_inc(&cur_trans->use_count);
 340                 spin_unlock(&root->fs_info->trans_lock);
 341
 342                 wait_event(root->fs_info->transaction_wait,
 343                            cur_trans->state >= TRANS_STATE_UNBLOCKED ||
 344                            cur_trans->aborted);
 345                 btrfs_put_transaction(cur_trans);
 346         } else {
 347                 spin_unlock(&root->fs_info->trans_lock);
 348         }
 349 }
 350
 351 static int may_wait_transaction(struct btrfs_root *root, int type)
 352 {
 353         if (root->fs_info->log_root_recovering)
 354                 return 0;
 355
 356         if (type == TRANS_USERSPACE)
 357                 return 1;
 358
 359         if (type == TRANS_START &&
 360             !atomic_read(&root->fs_info->open_ioctl_trans))
 361                 return 1;
 362
 363         return 0;
 364 }
 365
 366 static inline bool need_reserve_reloc_root(struct btrfs_root *root)
 367 {
 368         if (!root->fs_info->reloc_ctl ||
 369             !test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
 370             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
 371             root->reloc_root)
 372                 return false;
 373
 374         return true;
 375 }
 376
 377 static struct btrfs_trans_handle *
 378 start_transaction(struct btrfs_root *root, u64 num_items, unsigned int type,
 379                   enum btrfs_reserve_flush_enum flush)
 380 {
 381         struct btrfs_trans_handle *h;
 382         struct btrfs_transaction *cur_trans;
 383         u64 num_bytes = 0;
 384         u64 qgroup_reserved = 0;
 385         bool reloc_reserved = false;
 386         int ret;
 387
 388         /* Send isn't supposed to start transactions. */
 389         ASSERT(current->journal_info != (void *)BTRFS_SEND_TRANS_STUB);
 390
 391         if (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state))
 392                 return ERR_PTR(-EROFS);
 393
 394         if (current->journal_info) {
 395                 WARN_ON(type & TRANS_EXTWRITERS);
 396                 h = current->journal_info;
 397                 h->use_count++;
 398                 WARN_ON(h->use_count > 2);
 399                 h->orig_rsv = h->block_rsv;
 400                 h->block_rsv = NULL;
 401                 goto got_it;
 402         }
 403
 404         /*
 405          * Do the reservation before we join the transaction so we can do all
 406          * the appropriate flushing if need be.
 407          */
 408         if (num_items > 0 && root != root->fs_info->chunk_root) {
 409                 if (root->fs_info->quota_enabled &&
 410                     is_fstree(root->root_key.objectid)) {
 411                         qgroup_reserved = num_items * root->leafsize;
 412                         ret = btrfs_qgroup_reserve(root, qgroup_reserved);
 413                         if (ret)
 414                                 return ERR_PTR(ret);
 415                 }
 416
 417                 num_bytes = btrfs_calc_trans_metadata_size(root, num_items);
 418                 /*
 419                  * Do the reservation for the relocation root creation
 420                  */
 421                 if (unlikely(need_reserve_reloc_root(root))) {
 422                         num_bytes += root->nodesize;
 423                         reloc_reserved = true;
 424                 }
 425
 426                 ret = btrfs_block_rsv_add(root,
 427                                           &root->fs_info->trans_block_rsv,
 428                                           num_bytes, flush);
 429                 if (ret)
 430                         goto reserve_fail;
 431         }
 432 again:
 433         h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
 434         if (!h) {
 435                 ret = -ENOMEM;
 436                 goto alloc_fail;
 437         }
 438
 439         /*
 440          * If we are JOIN_NOLOCK we're already committing a transaction and
 441          * waiting on this guy, so we don't need to do the sb_start_intwrite
 442          * because we're already holding a ref.  We need this because we could
 443          * have raced in and did an fsync() on a file which can kick a commit
 444          * and then we deadlock with somebody doing a freeze.
 445          *
 446          * If we are ATTACH, it means we just want to catch the current
 447          * transaction and commit it, so we needn't do sb_start_intwrite().
 448          */
 449         if (type & __TRANS_FREEZABLE)
 450                 sb_start_intwrite(root->fs_info->sb);
 451
 452         if (may_wait_transaction(root, type))
 453                 wait_current_trans(root);
 454
 455         do {
 456                 ret = join_transaction(root, type);
 457                 if (ret == -EBUSY) {
 458                         wait_current_trans(root);
 459                         if (unlikely(type == TRANS_ATTACH))
 460                                 ret = -ENOENT;
 461                 }
 462         } while (ret == -EBUSY);
 463
 464         if (ret < 0) {
 465                 /* We must get the transaction if we are JOIN_NOLOCK. */
 466                 BUG_ON(type == TRANS_JOIN_NOLOCK);
 467                 goto join_fail;
 468         }
 469
 470         cur_trans = root->fs_info->running_transaction;
 471
 472         h->transid = cur_trans->transid;
 473         h->transaction = cur_trans;
 474         h->blocks_used = 0;
 475         h->bytes_reserved = 0;
 476         h->root = root;
 477         h->delayed_ref_updates = 0;
 478         h->use_count = 1;
 479         h->adding_csums = 0;
 480         h->block_rsv = NULL;
 481         h->orig_rsv = NULL;
 482         h->aborted = 0;
 483         h->qgroup_reserved = 0;
 484         h->delayed_ref_elem.seq = 0;
 485         h->type = type;
 486         h->allocating_chunk = false;
 487         h->reloc_reserved = false;
 488         h->sync = false;
 489         INIT_LIST_HEAD(&h->qgroup_ref_list);
 490         INIT_LIST_HEAD(&h->new_bgs);
 491
 492         smp_mb();
 493         if (cur_trans->state >= TRANS_STATE_BLOCKED &&
 494             may_wait_transaction(root, type)) {
 495                 current->journal_info = h;
 496                 btrfs_commit_transaction(h, root);
 497                 goto again;
 498         }
 499
 500         if (num_bytes) {
 501                 trace_btrfs_space_reservation(root->fs_info, "transaction",
 502                                               h->transid, num_bytes, 1);
 503                 h->block_rsv = &root->fs_info->trans_block_rsv;
 504                 h->bytes_reserved = num_bytes;
 505                 h->reloc_reserved = reloc_reserved;
 506         }
 507         h->qgroup_reserved = qgroup_reserved;
 508
 509 got_it:
 510         btrfs_record_root_in_trans(h, root);
 511
 512         if (!current->journal_info && type != TRANS_USERSPACE)
 513                 current->journal_info = h;
 514         return h;
 515
 516 join_fail:
 517         if (type & __TRANS_FREEZABLE)
 518                 sb_end_intwrite(root->fs_info->sb);
 519         kmem_cache_free(btrfs_trans_handle_cachep, h);
 520 alloc_fail:
 521         if (num_bytes)
 522                 btrfs_block_rsv_release(root, &root->fs_info->trans_block_rsv,
 523                                         num_bytes);
 524 reserve_fail:
 525         if (qgroup_reserved)
 526                 btrfs_qgroup_free(root, qgroup_reserved);
 527         return ERR_PTR(ret);
 528 }
 529
 530 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 531                                                    int num_items)
 532 {
 533         return start_transaction(root, num_items, TRANS_START,
 534                                  BTRFS_RESERVE_FLUSH_ALL);
 535 }
 536
 537 struct btrfs_trans_handle *btrfs_start_transaction_lflush(
 538                                         struct btrfs_root *root, int num_items)
 539 {
 540         return start_transaction(root, num_items, TRANS_START,
 541                                  BTRFS_RESERVE_FLUSH_LIMIT);
 542 }
 543
 544 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)
 545 {
 546         return start_transaction(root, 0, TRANS_JOIN, 0);
 547 }
 548
 549 struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root)
 550 {
 551         return start_transaction(root, 0, TRANS_JOIN_NOLOCK, 0);
 552 }
 553
 554 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root)
 555 {
 556         return start_transaction(root, 0, TRANS_USERSPACE, 0);
 557 }
 558
 559 /*
 560  * btrfs_attach_transaction() - catch the running transaction
 561  *
 562  * It is used when we want to commit the current the transaction, but
 563  * don't want to start a new one.
 564  *
 565  * Note: If this function return -ENOENT, it just means there is no
 566  * running transaction. But it is possible that the inactive transaction
 567  * is still in the memory, not fully on disk. If you hope there is no
 568  * inactive transaction in the fs when -ENOENT is returned, you should
 569  * invoke
 570  *     btrfs_attach_transaction_barrier()
 571  */
 572 struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root)
 573 {
 574         return start_transaction(root, 0, TRANS_ATTACH, 0);
 575 }
 576
 577 /*
 578  * btrfs_attach_transaction_barrier() - catch the running transaction
 579  *
 580  * It is similar to the above function, the differentia is this one
 581  * will wait for all the inactive transactions until they fully
 582  * complete.
 583  */
 584 struct btrfs_trans_handle *
 585 btrfs_attach_transaction_barrier(struct btrfs_root *root)
 586 {
 587         struct btrfs_trans_handle *trans;
 588
 589         trans = start_transaction(root, 0, TRANS_ATTACH, 0);
 590         if (IS_ERR(trans) && PTR_ERR(trans) == -ENOENT)
 591                 btrfs_wait_for_commit(root, 0);
 592
 593         return trans;
 594 }
 595
 596 /* wait for a transaction commit to be fully complete */
 597 static noinline void wait_for_commit(struct btrfs_root *root,
 598                                     struct btrfs_transaction *commit)
 599 {
 600         wait_event(commit->commit_wait, commit->state == TRANS_STATE_COMPLETED);
 601 }
 602
 603 int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
 604 {
 605         struct btrfs_transaction *cur_trans = NULL, *t;
 606         int ret = 0;
 607
 608         if (transid) {
 609                 if (transid <= root->fs_info->last_trans_committed)
 610                         goto out;
 611
 612                 ret = -EINVAL;
 613                 /* find specified transaction */
 614                 spin_lock(&root->fs_info->trans_lock);
 615                 list_for_each_entry(t, &root->fs_info->trans_list, list) {
 616                         if (t->transid == transid) {
 617                                 cur_trans = t;
 618                                 atomic_inc(&cur_trans->use_count);
 619                                 ret = 0;
 620                                 break;
 621                         }
 622                         if (t->transid > transid) {
 623                                 ret = 0;
 624                                 break;
 625                         }
 626                 }
 627                 spin_unlock(&root->fs_info->trans_lock);
 628                 /* The specified transaction doesn't exist */
 629                 if (!cur_trans)
 630                         goto out;
 631         } else {
 632                 /* find newest transaction that is committing | committed */
 633                 spin_lock(&root->fs_info->trans_lock);
 634                 list_for_each_entry_reverse(t, &root->fs_info->trans_list,
 635                                             list) {
 636                         if (t->state >= TRANS_STATE_COMMIT_START) {
 637                                 if (t->state == TRANS_STATE_COMPLETED)
 638                                         break;
 639                                 cur_trans = t;
 640                                 atomic_inc(&cur_trans->use_count);
 641                                 break;
 642                         }
 643                 }
 644                 spin_unlock(&root->fs_info->trans_lock);
 645                 if (!cur_trans)
 646                         goto out;  /* nothing committing|committed */
 647         }
 648
 649         wait_for_commit(root, cur_trans);
 650         btrfs_put_transaction(cur_trans);
 651 out:
 652         return ret;
 653 }
 654
 655 void btrfs_throttle(struct btrfs_root *root)
 656 {
 657         if (!atomic_read(&root->fs_info->open_ioctl_trans))
 658                 wait_current_trans(root);
 659 }
 660
 661 static int should_end_transaction(struct btrfs_trans_handle *trans,
 662                                   struct btrfs_root *root)
 663 {
 664         if (root->fs_info->global_block_rsv.space_info->full &&
 665             btrfs_check_space_for_delayed_refs(trans, root))
 666                 return 1;
 667
 668         return !!btrfs_block_rsv_check(root, &root->fs_info->global_block_rsv, 5);
 669 }
 670
 671 int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
 672                                  struct btrfs_root *root)
 673 {
 674         struct btrfs_transaction *cur_trans = trans->transaction;
 675         int updates;
 676         int err;
 677
 678         smp_mb();
 679         if (cur_trans->state >= TRANS_STATE_BLOCKED ||
 680             cur_trans->delayed_refs.flushing)
 681                 return 1;
 682
 683         updates = trans->delayed_ref_updates;
 684         trans->delayed_ref_updates = 0;
 685         if (updates) {
 686                 err = btrfs_run_delayed_refs(trans, root, updates);
 687                 if (err) /* Error code will also eval true */
 688                         return err;
 689         }
 690
 691         return should_end_transaction(trans, root);
 692 }
 693
 694 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 695                           struct btrfs_root *root, int throttle)
 696 {
 697         struct btrfs_transaction *cur_trans = trans->transaction;
 698         struct btrfs_fs_info *info = root->fs_info;
 699         unsigned long cur = trans->delayed_ref_updates;
 700         int lock = (trans->type != TRANS_JOIN_NOLOCK);
 701         int err = 0;
 702         int must_run_delayed_refs = 0;
 703
 704         if (trans->use_count > 1) {
 705                 trans->use_count--;
 706                 trans->block_rsv = trans->orig_rsv;
 707                 return 0;
 708         }
 709
 710         btrfs_trans_release_metadata(trans, root);
 711         trans->block_rsv = NULL;
 712
 713         if (!list_empty(&trans->new_bgs))
 714                 btrfs_create_pending_block_groups(trans, root);
 715
 716         trans->delayed_ref_updates = 0;
 717         if (!trans->sync) {
 718                 must_run_delayed_refs =
 719                         btrfs_should_throttle_delayed_refs(trans, root);
 720                 cur = max_t(unsigned long, cur, 32);
 721
 722                 /*
 723                  * don't make the caller wait if they are from a NOLOCK
 724                  * or ATTACH transaction, it will deadlock with commit
 725                  */
 726                 if (must_run_delayed_refs == 1 &&
 727                     (trans->type & (__TRANS_JOIN_NOLOCK | __TRANS_ATTACH)))
 728                         must_run_delayed_refs = 2;
 729         }
 730
 731         if (trans->qgroup_reserved) {
 732                 /*
 733                  * the same root has to be passed here between start_transaction
 734                  * and end_transaction. Subvolume quota depends on this.
 735                  */
 736                 btrfs_qgroup_free(trans->root, trans->qgroup_reserved);
 737                 trans->qgroup_reserved = 0;
 738         }
 739
 740         btrfs_trans_release_metadata(trans, root);
 741         trans->block_rsv = NULL;
 742
 743         if (!list_empty(&trans->new_bgs))
 744                 btrfs_create_pending_block_groups(trans, root);
 745
 746         if (lock && !atomic_read(&root->fs_info->open_ioctl_trans) &&
 747             should_end_transaction(trans, root) &&
 748             ACCESS_ONCE(cur_trans->state) == TRANS_STATE_RUNNING) {
 749                 spin_lock(&info->trans_lock);
 750                 if (cur_trans->state == TRANS_STATE_RUNNING)
 751                         cur_trans->state = TRANS_STATE_BLOCKED;
 752                 spin_unlock(&info->trans_lock);
 753         }
 754
 755         if (lock && ACCESS_ONCE(cur_trans->state) == TRANS_STATE_BLOCKED) {
 756                 if (throttle)
 757                         return btrfs_commit_transaction(trans, root);
 758                 else
 759                         wake_up_process(info->transaction_kthread);
 760         }
 761
 762         if (trans->type & __TRANS_FREEZABLE)
 763                 sb_end_intwrite(root->fs_info->sb);
 764
 765         WARN_ON(cur_trans != info->running_transaction);
 766         WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
 767         atomic_dec(&cur_trans->num_writers);
 768         extwriter_counter_dec(cur_trans, trans->type);
 769
 770         smp_mb();
 771         if (waitqueue_active(&cur_trans->writer_wait))
 772                 wake_up(&cur_trans->writer_wait);
 773         btrfs_put_transaction(cur_trans);
 774
 775         if (current->journal_info == trans)
 776                 current->journal_info = NULL;
 777
 778         if (throttle)
 779                 btrfs_run_delayed_iputs(root);
 780
 781         if (trans->aborted ||
 782             test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state)) {
 783                 wake_up_process(info->transaction_kthread);
 784                 err = -EIO;
 785         }
 786         assert_qgroups_uptodate(trans);
 787
 788         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 789         if (must_run_delayed_refs) {
 790                 btrfs_async_run_delayed_refs(root, cur,
 791                                              must_run_delayed_refs == 1);
 792         }
 793         return err;
 794 }
 795
 796 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 797                           struct btrfs_root *root)
 798 {
 799         return __btrfs_end_transaction(trans, root, 0);
 800 }
 801
 802 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
 803                                    struct btrfs_root *root)
 804 {
 805         return __btrfs_end_transaction(trans, root, 1);
 806 }
 807
 808 /*
 809  * when btree blocks are allocated, they have some corresponding bits set for
 810  * them in one of two extent_io trees.  This is used to make sure all of
 811  * those extents are sent to disk but does not wait on them
 812  */
 813 int btrfs_write_marked_extents(struct btrfs_root *root,
 814                                struct extent_io_tree *dirty_pages, int mark)
 815 {
 816         int err = 0;
 817         int werr = 0;
 818         struct address_space *mapping = root->fs_info->btree_inode->i_mapping;
 819         struct extent_state *cached_state = NULL;
 820         u64 start = 0;
 821         u64 end;
 822
 823         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
 824                                       mark, &cached_state)) {
 825                 convert_extent_bit(dirty_pages, start, end, EXTENT_NEED_WAIT,
 826                                    mark, &cached_state, GFP_NOFS);
 827                 cached_state = NULL;
 828                 err = filemap_fdatawrite_range(mapping, start, end);
 829                 if (err)
 830                         werr = err;
 831                 cond_resched();
 832                 start = end + 1;
 833         }
 834         if (err)
 835                 werr = err;
 836         return werr;
 837 }
 838
 839 /*
 840  * when btree blocks are allocated, they have some corresponding bits set for
 841  * them in one of two extent_io trees.  This is used to make sure all of
 842  * those extents are on disk for transaction or log commit.  We wait
 843  * on all the pages and clear them from the dirty pages state tree
 844  */
 845 int btrfs_wait_marked_extents(struct btrfs_root *root,
 846                               struct extent_io_tree *dirty_pages, int mark)
 847 {
 848         int err = 0;
 849         int werr = 0;
 850         struct address_space *mapping = root->fs_info->btree_inode->i_mapping;
 851         struct extent_state *cached_state = NULL;
 852         u64 start = 0;
 853         u64 end;
 854
 855         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
 856                                       EXTENT_NEED_WAIT, &cached_state)) {
 857                 clear_extent_bit(dirty_pages, start, end, EXTENT_NEED_WAIT,
 858                                  0, 0, &cached_state, GFP_NOFS);
 859                 err = filemap_fdatawait_range(mapping, start, end);
 860                 if (err)
 861                         werr = err;
 862                 cond_resched();
 863                 start = end + 1;
 864         }
 865         if (err)
 866                 werr = err;
 867         return werr;
 868 }
 869
 870 /*
 871  * when btree blocks are allocated, they have some corresponding bits set for
 872  * them in one of two extent_io trees.  This is used to make sure all of
 873  * those extents are on disk for transaction or log commit
 874  */
 875 static int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
 876                                 struct extent_io_tree *dirty_pages, int mark)
 877 {
 878         int ret;
 879         int ret2;
 880         struct blk_plug plug;
 881
 882         blk_start_plug(&plug);
 883         ret = btrfs_write_marked_extents(root, dirty_pages, mark);
 884         blk_finish_plug(&plug);
 885         ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
 886
 887         if (ret)
 888                 return ret;
 889         if (ret2)
 890                 return ret2;
 891         return 0;
 892 }
 893
 894 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 895                                      struct btrfs_root *root)
 896 {
 897         if (!trans || !trans->transaction) {
 898                 struct inode *btree_inode;
 899                 btree_inode = root->fs_info->btree_inode;
 900                 return filemap_write_and_wait(btree_inode->i_mapping);
 901         }
 902         return btrfs_write_and_wait_marked_extents(root,
 903                                            &trans->transaction->dirty_pages,
 904                                            EXTENT_DIRTY);
 905 }
 906
 907 /*
 908  * this is used to update the root pointer in the tree of tree roots.
 909  *
 910  * But, in the case of the extent allocation tree, updating the root
 911  * pointer may allocate blocks which may change the root of the extent
 912  * allocation tree.
 913  *
 914  * So, this loops and repeats and makes sure the cowonly root didn't
 915  * change while the root pointer was being updated in the metadata.
 916  */
 917 static int update_cowonly_root(struct btrfs_trans_handle *trans,
 918                                struct btrfs_root *root)
 919 {
 920         int ret;
 921         u64 old_root_bytenr;
 922         u64 old_root_used;
 923         struct btrfs_root *tree_root = root->fs_info->tree_root;
 924
 925         old_root_used = btrfs_root_used(&root->root_item);
 926         btrfs_write_dirty_block_groups(trans, root);
 927
 928         while (1) {
 929                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
 930                 if (old_root_bytenr == root->node->start &&
 931                     old_root_used == btrfs_root_used(&root->root_item))
 932                         break;
 933
 934                 btrfs_set_root_node(&root->root_item, root->node);
 935                 ret = btrfs_update_root(trans, tree_root,
 936                                         &root->root_key,
 937                                         &root->root_item);
 938                 if (ret)
 939                         return ret;
 940
 941                 old_root_used = btrfs_root_used(&root->root_item);
 942                 ret = btrfs_write_dirty_block_groups(trans, root);
 943                 if (ret)
 944                         return ret;
 945         }
 946
 947         return 0;
 948 }
 949
 950 /*
 951  * update all the cowonly tree roots on disk
 952  *
 953  * The error handling in this function may not be obvious. Any of the
 954  * failures will cause the file system to go offline. We still need
 955  * to clean up the delayed refs.
 956  */
 957 static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
 958                                          struct btrfs_root *root)
 959 {
 960         struct btrfs_fs_info *fs_info = root->fs_info;
 961         struct list_head *next;
 962         struct extent_buffer *eb;
 963         int ret;
 964
 965         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 966         if (ret)
 967                 return ret;
 968
 969         eb = btrfs_lock_root_node(fs_info->tree_root);
 970         ret = btrfs_cow_block(trans, fs_info->tree_root, eb, NULL,
 971                               0, &eb);
 972         btrfs_tree_unlock(eb);
 973         free_extent_buffer(eb);
 974
 975         if (ret)
 976                 return ret;
 977
 978         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 979         if (ret)
 980                 return ret;
 981
 982         ret = btrfs_run_dev_stats(trans, root->fs_info);
 983         if (ret)
 984                 return ret;
 985         ret = btrfs_run_dev_replace(trans, root->fs_info);
 986         if (ret)
 987                 return ret;
 988         ret = btrfs_run_qgroups(trans, root->fs_info);
 989         if (ret)
 990                 return ret;
 991
 992         /* run_qgroups might have added some more refs */
 993         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 994         if (ret)
 995                 return ret;
 996
 997         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
 998                 next = fs_info->dirty_cowonly_roots.next;
 999                 list_del_init(next);
1000                 root = list_entry(next, struct btrfs_root, dirty_list);
1001
1002                 if (root != fs_info->extent_root)
1003                         list_add_tail(&root->dirty_list,
1004                                       &trans->transaction->switch_commits);
1005                 ret = update_cowonly_root(trans, root);
1006                 if (ret)
1007                         return ret;
1008         }
1009
1010         list_add_tail(&fs_info->extent_root->dirty_list,
1011                       &trans->transaction->switch_commits);
1012         btrfs_after_dev_replace_commit(fs_info);
1013
1014         return 0;
1015 }
1016
1017 /*
1018  * dead roots are old snapshots that need to be deleted.  This allocates
1019  * a dirty root struct and adds it into the list of dead roots that need to
1020  * be deleted
1021  */
1022 void btrfs_add_dead_root(struct btrfs_root *root)
1023 {
1024         spin_lock(&root->fs_info->trans_lock);
1025         if (list_empty(&root->root_list))
1026                 list_add_tail(&root->root_list, &root->fs_info->dead_roots);
1027         spin_unlock(&root->fs_info->trans_lock);
1028 }
1029
1030 /*
1031  * update all the cowonly tree roots on disk
1032  */
1033 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
1034                                     struct btrfs_root *root)
1035 {
1036         struct btrfs_root *gang[8];
1037         struct btrfs_fs_info *fs_info = root->fs_info;
1038         int i;
1039         int ret;
1040         int err = 0;
1041
1042         spin_lock(&fs_info->fs_roots_radix_lock);
1043         while (1) {
1044                 ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
1045                                                  (void **)gang, 0,
1046                                                  ARRAY_SIZE(gang),
1047                                                  BTRFS_ROOT_TRANS_TAG);
1048                 if (ret == 0)
1049                         break;
1050                 for (i = 0; i < ret; i++) {
1051                         root = gang[i];
1052                         radix_tree_tag_clear(&fs_info->fs_roots_radix,
1053                                         (unsigned long)root->root_key.objectid,
1054                                         BTRFS_ROOT_TRANS_TAG);
1055                         spin_unlock(&fs_info->fs_roots_radix_lock);
1056
1057                         btrfs_free_log(trans, root);
1058                         btrfs_update_reloc_root(trans, root);
1059                         btrfs_orphan_commit_root(trans, root);
1060
1061                         btrfs_save_ino_cache(root, trans);
1062
1063                         /* see comments in should_cow_block() */
1064                         clear_bit(BTRFS_ROOT_FORCE_COW, &root->state);
1065                         smp_mb__after_atomic();
1066
1067                         if (root->commit_root != root->node) {
1068                                 list_add_tail(&root->dirty_list,
1069                                         &trans->transaction->switch_commits);
1070                                 btrfs_set_root_node(&root->root_item,
1071                                                     root->node);
1072                         }
1073
1074                         err = btrfs_update_root(trans, fs_info->tree_root,
1075                                                 &root->root_key,
1076                                                 &root->root_item);
1077                         spin_lock(&fs_info->fs_roots_radix_lock);
1078                         if (err)
1079                                 break;
1080                 }
1081         }
1082         spin_unlock(&fs_info->fs_roots_radix_lock);
1083         return err;
1084 }
1085
1086 /*
1087  * defrag a given btree.
1088  * Every leaf in the btree is read and defragged.
1089  */
1090 int btrfs_defrag_root(struct btrfs_root *root)
1091 {
1092         struct btrfs_fs_info *info = root->fs_info;
1093         struct btrfs_trans_handle *trans;
1094         int ret;
1095
1096         if (test_and_set_bit(BTRFS_ROOT_DEFRAG_RUNNING, &root->state))
1097                 return 0;
1098
1099         while (1) {
1100                 trans = btrfs_start_transaction(root, 0);
1101                 if (IS_ERR(trans))
1102                         return PTR_ERR(trans);
1103
1104                 ret = btrfs_defrag_leaves(trans, root);
1105
1106                 btrfs_end_transaction(trans, root);
1107                 btrfs_btree_balance_dirty(info->tree_root);
1108                 cond_resched();
1109
1110                 if (btrfs_fs_closing(root->fs_info) || ret != -EAGAIN)
1111                         break;
1112
1113                 if (btrfs_defrag_cancelled(root->fs_info)) {
1114                         pr_debug("BTRFS: defrag_root cancelled\n");
1115                         ret = -EAGAIN;
1116                         break;
1117                 }
1118         }
1119         clear_bit(BTRFS_ROOT_DEFRAG_RUNNING, &root->state);
1120         return ret;
1121 }
1122
1123 /*
1124  * new snapshots need to be created at a very specific time in the
1125  * transaction commit.  This does the actual creation.
1126  *
1127  * Note:
1128  * If the error which may affect the commitment of the current transaction
1129  * happens, we should return the error number. If the error which just affect
1130  * the creation of the pending snapshots, just return 0.
1131  */
1132 static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
1133                                    struct btrfs_fs_info *fs_info,
1134                                    struct btrfs_pending_snapshot *pending)
1135 {
1136         struct btrfs_key key;
1137         struct btrfs_root_item *new_root_item;
1138         struct btrfs_root *tree_root = fs_info->tree_root;
1139         struct btrfs_root *root = pending->root;
1140         struct btrfs_root *parent_root;
1141         struct btrfs_block_rsv *rsv;
1142         struct inode *parent_inode;
1143         struct btrfs_path *path;
1144         struct btrfs_dir_item *dir_item;
1145         struct dentry *dentry;
1146         struct extent_buffer *tmp;
1147         struct extent_buffer *old;
1148         struct timespec cur_time = CURRENT_TIME;
1149         int ret = 0;
1150         u64 to_reserve = 0;
1151         u64 index = 0;
1152         u64 objectid;
1153         u64 root_flags;
1154         uuid_le new_uuid;
1155
1156         path = btrfs_alloc_path();
1157         if (!path) {
1158                 pending->error = -ENOMEM;
1159                 return 0;
1160         }
1161
1162         new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
1163         if (!new_root_item) {
1164                 pending->error = -ENOMEM;
1165                 goto root_item_alloc_fail;
1166         }
1167
1168         pending->error = btrfs_find_free_objectid(tree_root, &objectid);
1169         if (pending->error)
1170                 goto no_free_objectid;
1171
1172         btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
1173
1174         if (to_reserve > 0) {
1175                 pending->error = btrfs_block_rsv_add(root,
1176                                                      &pending->block_rsv,
1177                                                      to_reserve,
1178                                                      BTRFS_RESERVE_NO_FLUSH);
1179                 if (pending->error)
1180                         goto no_free_objectid;
1181         }
1182
1183         key.objectid = objectid;
1184         key.offset = (u64)-1;
1185         key.type = BTRFS_ROOT_ITEM_KEY;
1186
1187         rsv = trans->block_rsv;
1188         trans->block_rsv = &pending->block_rsv;
1189         trans->bytes_reserved = trans->block_rsv->reserved;
1190
1191         dentry = pending->dentry;
1192         parent_inode = pending->dir;
1193         parent_root = BTRFS_I(parent_inode)->root;
1194         record_root_in_trans(trans, parent_root);
1195
1196         /*
1197          * insert the directory item
1198          */
1199         ret = btrfs_set_inode_index(parent_inode, &index);
1200         BUG_ON(ret); /* -ENOMEM */
1201
1202         /* check if there is a file/dir which has the same name. */
1203         dir_item = btrfs_lookup_dir_item(NULL, parent_root, path,
1204                                          btrfs_ino(parent_inode),
1205                                          dentry->d_name.name,
1206                                          dentry->d_name.len, 0);
1207         if (dir_item != NULL && !IS_ERR(dir_item)) {
1208                 pending->error = -EEXIST;
1209                 goto dir_item_existed;
1210         } else if (IS_ERR(dir_item)) {
1211                 ret = PTR_ERR(dir_item);
1212                 btrfs_abort_transaction(trans, root, ret);
1213                 goto fail;
1214         }
1215         btrfs_release_path(path);
1216
1217         /*
1218          * pull in the delayed directory update
1219          * and the delayed inode item
1220          * otherwise we corrupt the FS during
1221          * snapshot
1222          */
1223         ret = btrfs_run_delayed_items(trans, root);
1224         if (ret) {      /* Transaction aborted */
1225                 btrfs_abort_transaction(trans, root, ret);
1226                 goto fail;
1227         }
1228
1229         record_root_in_trans(trans, root);
1230         btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
1231         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
1232         btrfs_check_and_init_root_item(new_root_item);
1233
1234         root_flags = btrfs_root_flags(new_root_item);
1235         if (pending->readonly)
1236                 root_flags |= BTRFS_ROOT_SUBVOL_RDONLY;
1237         else
1238                 root_flags &= ~BTRFS_ROOT_SUBVOL_RDONLY;
1239         btrfs_set_root_flags(new_root_item, root_flags);
1240
1241         btrfs_set_root_generation_v2(new_root_item,
1242                         trans->transid);
1243         uuid_le_gen(&new_uuid);
1244         memcpy(new_root_item->uuid, new_uuid.b, BTRFS_UUID_SIZE);
1245         memcpy(new_root_item->parent_uuid, root->root_item.uuid,
1246                         BTRFS_UUID_SIZE);
1247         if (!(root_flags & BTRFS_ROOT_SUBVOL_RDONLY)) {
1248                 memset(new_root_item->received_uuid, 0,
1249                        sizeof(new_root_item->received_uuid));
1250                 memset(&new_root_item->stime, 0, sizeof(new_root_item->stime));
1251                 memset(&new_root_item->rtime, 0, sizeof(new_root_item->rtime));
1252                 btrfs_set_root_stransid(new_root_item, 0);
1253                 btrfs_set_root_rtransid(new_root_item, 0);
1254         }
1255         btrfs_set_stack_timespec_sec(&new_root_item->otime, cur_time.tv_sec);
1256         btrfs_set_stack_timespec_nsec(&new_root_item->otime, cur_time.tv_nsec);
1257         btrfs_set_root_otransid(new_root_item, trans->transid);
1258
1259         old = btrfs_lock_root_node(root);
1260         ret = btrfs_cow_block(trans, root, old, NULL, 0, &old);
1261         if (ret) {
1262                 btrfs_tree_unlock(old);
1263                 free_extent_buffer(old);
1264                 btrfs_abort_transaction(trans, root, ret);
1265                 goto fail;
1266         }
1267
1268         btrfs_set_lock_blocking(old);
1269
1270         ret = btrfs_copy_root(trans, root, old, &tmp, objectid);
1271         /* clean up in any case */
1272         btrfs_tree_unlock(old);
1273         free_extent_buffer(old);
1274         if (ret) {
1275                 btrfs_abort_transaction(trans, root, ret);
1276                 goto fail;
1277         }
1278
1279         /*
1280          * We need to flush delayed refs in order to make sure all of our quota
1281          * operations have been done before we call btrfs_qgroup_inherit.
1282          */
1283         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1284         if (ret) {
1285                 btrfs_abort_transaction(trans, root, ret);
1286                 goto fail;
1287         }
1288
1289         ret = btrfs_qgroup_inherit(trans, fs_info,
1290                                    root->root_key.objectid,
1291                                    objectid, pending->inherit);
1292         if (ret) {
1293                 btrfs_abort_transaction(trans, root, ret);
1294                 goto fail;
1295         }
1296
1297         /* see comments in should_cow_block() */
1298         set_bit(BTRFS_ROOT_FORCE_COW, &root->state);
1299         smp_wmb();
1300
1301         btrfs_set_root_node(new_root_item, tmp);
1302         /* record when the snapshot was created in key.offset */
1303         key.offset = trans->transid;
1304         ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
1305         btrfs_tree_unlock(tmp);
1306         free_extent_buffer(tmp);
1307         if (ret) {
1308                 btrfs_abort_transaction(trans, root, ret);
1309                 goto fail;
1310         }
1311
1312         /*
1313          * insert root back/forward references
1314          */
1315         ret = btrfs_add_root_ref(trans, tree_root, objectid,
1316                                  parent_root->root_key.objectid,
1317                                  btrfs_ino(parent_inode), index,
1318                                  dentry->d_name.name, dentry->d_name.len);
1319         if (ret) {
1320                 btrfs_abort_transaction(trans, root, ret);
1321                 goto fail;
1322         }
1323
1324         key.offset = (u64)-1;
1325         pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
1326         if (IS_ERR(pending->snap)) {
1327                 ret = PTR_ERR(pending->snap);
1328                 btrfs_abort_transaction(trans, root, ret);
1329                 goto fail;
1330         }
1331
1332         ret = btrfs_reloc_post_snapshot(trans, pending);
1333         if (ret) {
1334                 btrfs_abort_transaction(trans, root, ret);
1335                 goto fail;
1336         }
1337
1338         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1339         if (ret) {
1340                 btrfs_abort_transaction(trans, root, ret);
1341                 goto fail;
1342         }
1343
1344         ret = btrfs_insert_dir_item(trans, parent_root,
1345                                     dentry->d_name.name, dentry->d_name.len,
1346                                     parent_inode, &key,
1347                                     BTRFS_FT_DIR, index);
1348         /* We have check then name at the beginning, so it is impossible. */
1349         BUG_ON(ret == -EEXIST || ret == -EOVERFLOW);
1350         if (ret) {
1351                 btrfs_abort_transaction(trans, root, ret);
1352                 goto fail;
1353         }
1354
1355         btrfs_i_size_write(parent_inode, parent_inode->i_size +
1356                                          dentry->d_name.len * 2);
1357         parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
1358         ret = btrfs_update_inode_fallback(trans, parent_root, parent_inode);
1359         if (ret) {
1360                 btrfs_abort_transaction(trans, root, ret);
1361                 goto fail;
1362         }
1363         ret = btrfs_uuid_tree_add(trans, fs_info->uuid_root, new_uuid.b,
1364                                   BTRFS_UUID_KEY_SUBVOL, objectid);
1365         if (ret) {
1366                 btrfs_abort_transaction(trans, root, ret);
1367                 goto fail;
1368         }
1369         if (!btrfs_is_empty_uuid(new_root_item->received_uuid)) {
1370                 ret = btrfs_uuid_tree_add(trans, fs_info->uuid_root,
1371                                           new_root_item->received_uuid,
1372                                           BTRFS_UUID_KEY_RECEIVED_SUBVOL,
1373                                           objectid);
1374                 if (ret && ret != -EEXIST) {
1375                         btrfs_abort_transaction(trans, root, ret);
1376                         goto fail;
1377                 }
1378         }
1379 fail:
1380         pending->error = ret;
1381 dir_item_existed:
1382         trans->block_rsv = rsv;
1383         trans->bytes_reserved = 0;
1384 no_free_objectid:
1385         kfree(new_root_item);
1386 root_item_alloc_fail:
1387         btrfs_free_path(path);
1388         return ret;
1389 }
1390
1391 /*
1392  * create all the snapshots we've scheduled for creation
1393  */
1394 static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
1395                                              struct btrfs_fs_info *fs_info)
1396 {
1397         struct btrfs_pending_snapshot *pending, *next;
1398         struct list_head *head = &trans->transaction->pending_snapshots;
1399         int ret = 0;
1400
1401         list_for_each_entry_safe(pending, next, head, list) {
1402                 list_del(&pending->list);
1403                 ret = create_pending_snapshot(trans, fs_info, pending);
1404                 if (ret)
1405                         break;
1406         }
1407         return ret;
1408 }
1409
1410 static void update_super_roots(struct btrfs_root *root)
1411 {
1412         struct btrfs_root_item *root_item;
1413         struct btrfs_super_block *super;
1414
1415         super = root->fs_info->super_copy;
1416
1417         root_item = &root->fs_info->chunk_root->root_item;
1418         super->chunk_root = root_item->bytenr;
1419         super->chunk_root_generation = root_item->generation;
1420         super->chunk_root_level = root_item->level;
1421
1422         root_item = &root->fs_info->tree_root->root_item;
1423         super->root = root_item->bytenr;
1424         super->generation = root_item->generation;
1425         super->root_level = root_item->level;
1426         if (btrfs_test_opt(root, SPACE_CACHE))
1427                 super->cache_generation = root_item->generation;
1428         if (root->fs_info->update_uuid_tree_gen)
1429                 super->uuid_tree_generation = root_item->generation;
1430 }
1431
1432 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
1433 {
1434         struct btrfs_transaction *trans;
1435         int ret = 0;
1436
1437         spin_lock(&info->trans_lock);
1438         trans = info->running_transaction;
1439         if (trans)
1440                 ret = (trans->state >= TRANS_STATE_COMMIT_START);
1441         spin_unlock(&info->trans_lock);
1442         return ret;
1443 }
1444
1445 int btrfs_transaction_blocked(struct btrfs_fs_info *info)
1446 {
1447         struct btrfs_transaction *trans;
1448         int ret = 0;
1449
1450         spin_lock(&info->trans_lock);
1451         trans = info->running_transaction;
1452         if (trans)
1453                 ret = is_transaction_blocked(trans);
1454         spin_unlock(&info->trans_lock);
1455         return ret;
1456 }
1457
1458 /*
1459  * wait for the current transaction commit to start and block subsequent
1460  * transaction joins
1461  */
1462 static void wait_current_trans_commit_start(struct btrfs_root *root,
1463                                             struct btrfs_transaction *trans)
1464 {
1465         wait_event(root->fs_info->transaction_blocked_wait,
1466                    trans->state >= TRANS_STATE_COMMIT_START ||
1467                    trans->aborted);
1468 }
1469
1470 /*
1471  * wait for the current transaction to start and then become unblocked.
1472  * caller holds ref.
1473  */
1474 static void wait_current_trans_commit_start_and_unblock(struct btrfs_root *root,
1475                                          struct btrfs_transaction *trans)
1476 {
1477         wait_event(root->fs_info->transaction_wait,
1478                    trans->state >= TRANS_STATE_UNBLOCKED ||
1479                    trans->aborted);
1480 }
1481
1482 /*
1483  * commit transactions asynchronously. once btrfs_commit_transaction_async
1484  * returns, any subsequent transaction will not be allowed to join.
1485  */
1486 struct btrfs_async_commit {
1487         struct btrfs_trans_handle *newtrans;
1488         struct btrfs_root *root;
1489         struct work_struct work;
1490 };
1491
1492 static void do_async_commit(struct work_struct *work)
1493 {
1494         struct btrfs_async_commit *ac =
1495                 container_of(work, struct btrfs_async_commit, work);
1496
1497         /*
1498          * We've got freeze protection passed with the transaction.
1499          * Tell lockdep about it.
1500          */
1501         if (ac->newtrans->type & __TRANS_FREEZABLE)
1502                 rwsem_acquire_read(
1503                      &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1504                      0, 1, _THIS_IP_);
1505
1506         current->journal_info = ac->newtrans;
1507
1508         btrfs_commit_transaction(ac->newtrans, ac->root);
1509         kfree(ac);
1510 }
1511
1512 int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
1513                                    struct btrfs_root *root,
1514                                    int wait_for_unblock)
1515 {
1516         struct btrfs_async_commit *ac;
1517         struct btrfs_transaction *cur_trans;
1518
1519         ac = kmalloc(sizeof(*ac), GFP_NOFS);
1520         if (!ac)
1521                 return -ENOMEM;
1522
1523         INIT_WORK(&ac->work, do_async_commit);
1524         ac->root = root;
1525         ac->newtrans = btrfs_join_transaction(root);
1526         if (IS_ERR(ac->newtrans)) {
1527                 int err = PTR_ERR(ac->newtrans);
1528                 kfree(ac);
1529                 return err;
1530         }
1531
1532         /* take transaction reference */
1533         cur_trans = trans->transaction;
1534         atomic_inc(&cur_trans->use_count);
1535
1536         btrfs_end_transaction(trans, root);
1537
1538         /*
1539          * Tell lockdep we've released the freeze rwsem, since the
1540          * async commit thread will be the one to unlock it.
1541          */
1542         if (ac->newtrans->type & __TRANS_FREEZABLE)
1543                 rwsem_release(
1544                         &root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1545                         1, _THIS_IP_);
1546
1547         schedule_work(&ac->work);
1548
1549         /* wait for transaction to start and unblock */
1550         if (wait_for_unblock)
1551                 wait_current_trans_commit_start_and_unblock(root, cur_trans);
1552         else
1553                 wait_current_trans_commit_start(root, cur_trans);
1554
1555         if (current->journal_info == trans)
1556                 current->journal_info = NULL;
1557
1558         btrfs_put_transaction(cur_trans);
1559         return 0;
1560 }
1561
1562
1563 static void cleanup_transaction(struct btrfs_trans_handle *trans,
1564                                 struct btrfs_root *root, int err)
1565 {
1566         struct btrfs_transaction *cur_trans = trans->transaction;
1567         DEFINE_WAIT(wait);
1568
1569         WARN_ON(trans->use_count > 1);
1570
1571         btrfs_abort_transaction(trans, root, err);
1572
1573         spin_lock(&root->fs_info->trans_lock);
1574
1575         /*
1576          * If the transaction is removed from the list, it means this
1577          * transaction has been committed successfully, so it is impossible
1578          * to call the cleanup function.
1579          */
1580         BUG_ON(list_empty(&cur_trans->list));
1581
1582         list_del_init(&cur_trans->list);
1583         if (cur_trans == root->fs_info->running_transaction) {
1584                 cur_trans->state = TRANS_STATE_COMMIT_DOING;
1585                 spin_unlock(&root->fs_info->trans_lock);
1586                 wait_event(cur_trans->writer_wait,
1587                            atomic_read(&cur_trans->num_writers) == 1);
1588
1589                 spin_lock(&root->fs_info->trans_lock);
1590         }
1591         spin_unlock(&root->fs_info->trans_lock);
1592
1593         btrfs_cleanup_one_transaction(trans->transaction, root);
1594
1595         spin_lock(&root->fs_info->trans_lock);
1596         if (cur_trans == root->fs_info->running_transaction)
1597                 root->fs_info->running_transaction = NULL;
1598         spin_unlock(&root->fs_info->trans_lock);
1599
1600         if (trans->type & __TRANS_FREEZABLE)
1601                 sb_end_intwrite(root->fs_info->sb);
1602         btrfs_put_transaction(cur_trans);
1603         btrfs_put_transaction(cur_trans);
1604
1605         trace_btrfs_transaction_commit(root);
1606
1607         if (current->journal_info == trans)
1608                 current->journal_info = NULL;
1609         btrfs_scrub_cancel(root->fs_info);
1610
1611         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1612 }
1613
1614 static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
1615 {
1616         if (btrfs_test_opt(fs_info->tree_root, FLUSHONCOMMIT))
1617                 return btrfs_start_delalloc_roots(fs_info, 1, -1);
1618         return 0;
1619 }
1620
1621 static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
1622 {
1623         if (btrfs_test_opt(fs_info->tree_root, FLUSHONCOMMIT))
1624                 btrfs_wait_ordered_roots(fs_info, -1);
1625 }
1626
1627 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
1628                              struct btrfs_root *root)
1629 {
1630         struct btrfs_transaction *cur_trans = trans->transaction;
1631         struct btrfs_transaction *prev_trans = NULL;
1632         int ret;
1633
1634         /* Stop the commit early if ->aborted is set */
1635         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1636                 ret = cur_trans->aborted;
1637                 btrfs_end_transaction(trans, root);
1638                 return ret;
1639         }
1640
1641         /* make a pass through all the delayed refs we have so far
1642          * any runnings procs may add more while we are here
1643          */
1644         ret = btrfs_run_delayed_refs(trans, root, 0);
1645         if (ret) {
1646                 btrfs_end_transaction(trans, root);
1647                 return ret;
1648         }
1649
1650         btrfs_trans_release_metadata(trans, root);
1651         trans->block_rsv = NULL;
1652         if (trans->qgroup_reserved) {
1653                 btrfs_qgroup_free(root, trans->qgroup_reserved);
1654                 trans->qgroup_reserved = 0;
1655         }
1656
1657         cur_trans = trans->transaction;
1658
1659         /*
1660          * set the flushing flag so procs in this transaction have to
1661          * start sending their work down.
1662          */
1663         cur_trans->delayed_refs.flushing = 1;
1664         smp_wmb();
1665
1666         if (!list_empty(&trans->new_bgs))
1667                 btrfs_create_pending_block_groups(trans, root);
1668
1669         ret = btrfs_run_delayed_refs(trans, root, 0);
1670         if (ret) {
1671                 btrfs_end_transaction(trans, root);
1672                 return ret;
1673         }
1674
1675         spin_lock(&root->fs_info->trans_lock);
1676         if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
1677                 spin_unlock(&root->fs_info->trans_lock);
1678                 atomic_inc(&cur_trans->use_count);
1679                 ret = btrfs_end_transaction(trans, root);
1680
1681                 wait_for_commit(root, cur_trans);
1682
1683                 btrfs_put_transaction(cur_trans);
1684
1685                 return ret;
1686         }
1687
1688         cur_trans->state = TRANS_STATE_COMMIT_START;
1689         wake_up(&root->fs_info->transaction_blocked_wait);
1690
1691         if (cur_trans->list.prev != &root->fs_info->trans_list) {
1692                 prev_trans = list_entry(cur_trans->list.prev,
1693                                         struct btrfs_transaction, list);
1694                 if (prev_trans->state != TRANS_STATE_COMPLETED) {
1695                         atomic_inc(&prev_trans->use_count);
1696                         spin_unlock(&root->fs_info->trans_lock);
1697
1698                         wait_for_commit(root, prev_trans);
1699
1700                         btrfs_put_transaction(prev_trans);
1701                 } else {
1702                         spin_unlock(&root->fs_info->trans_lock);
1703                 }
1704         } else {
1705                 spin_unlock(&root->fs_info->trans_lock);
1706         }
1707
1708         extwriter_counter_dec(cur_trans, trans->type);
1709
1710         ret = btrfs_start_delalloc_flush(root->fs_info);
1711         if (ret)
1712                 goto cleanup_transaction;
1713
1714         ret = btrfs_run_delayed_items(trans, root);
1715         if (ret)
1716                 goto cleanup_transaction;
1717
1718         wait_event(cur_trans->writer_wait,
1719                    extwriter_counter_read(cur_trans) == 0);
1720
1721         /* some pending stuffs might be added after the previous flush. */
1722         ret = btrfs_run_delayed_items(trans, root);
1723         if (ret)
1724                 goto cleanup_transaction;
1725
1726         btrfs_wait_delalloc_flush(root->fs_info);
1727
1728         btrfs_scrub_pause(root);
1729         /*
1730          * Ok now we need to make sure to block out any other joins while we
1731          * commit the transaction.  We could have started a join before setting
1732          * COMMIT_DOING so make sure to wait for num_writers to == 1 again.
1733          */
1734         spin_lock(&root->fs_info->trans_lock);
1735         cur_trans->state = TRANS_STATE_COMMIT_DOING;
1736         spin_unlock(&root->fs_info->trans_lock);
1737         wait_event(cur_trans->writer_wait,
1738                    atomic_read(&cur_trans->num_writers) == 1);
1739
1740         /* ->aborted might be set after the previous check, so check it */
1741         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1742                 ret = cur_trans->aborted;
1743                 goto scrub_continue;
1744         }
1745         /*
1746          * the reloc mutex makes sure that we stop
1747          * the balancing code from coming in and moving
1748          * extents around in the middle of the commit
1749          */
1750         mutex_lock(&root->fs_info->reloc_mutex);
1751
1752         /*
1753          * We needn't worry about the delayed items because we will
1754          * deal with them in create_pending_snapshot(), which is the
1755          * core function of the snapshot creation.
1756          */
1757         ret = create_pending_snapshots(trans, root->fs_info);
1758         if (ret) {
1759                 mutex_unlock(&root->fs_info->reloc_mutex);
1760                 goto scrub_continue;
1761         }
1762
1763         /*
1764          * We insert the dir indexes of the snapshots and update the inode
1765          * of the snapshots' parents after the snapshot creation, so there
1766          * are some delayed items which are not dealt with. Now deal with
1767          * them.
1768          *
1769          * We needn't worry that this operation will corrupt the snapshots,
1770          * because all the tree which are snapshoted will be forced to COW
1771          * the nodes and leaves.
1772          */
1773         ret = btrfs_run_delayed_items(trans, root);
1774         if (ret) {
1775                 mutex_unlock(&root->fs_info->reloc_mutex);
1776                 goto scrub_continue;
1777         }
1778
1779         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1780         if (ret) {
1781                 mutex_unlock(&root->fs_info->reloc_mutex);
1782                 goto scrub_continue;
1783         }
1784
1785         /*
1786          * make sure none of the code above managed to slip in a
1787          * delayed item
1788          */
1789         btrfs_assert_delayed_root_empty(root);
1790
1791         WARN_ON(cur_trans != trans->transaction);
1792
1793         /* btrfs_commit_tree_roots is responsible for getting the
1794          * various roots consistent with each other.  Every pointer
1795          * in the tree of tree roots has to point to the most up to date
1796          * root for every subvolume and other tree.  So, we have to keep
1797          * the tree logging code from jumping in and changing any
1798          * of the trees.
1799          *
1800          * At this point in the commit, there can't be any tree-log
1801          * writers, but a little lower down we drop the trans mutex
1802          * and let new people in.  By holding the tree_log_mutex
1803          * from now until after the super is written, we avoid races
1804          * with the tree-log code.
1805          */
1806         mutex_lock(&root->fs_info->tree_log_mutex);
1807
1808         ret = commit_fs_roots(trans, root);
1809         if (ret) {
1810                 mutex_unlock(&root->fs_info->tree_log_mutex);
1811                 mutex_unlock(&root->fs_info->reloc_mutex);
1812                 goto scrub_continue;
1813         }
1814
1815         /*
1816          * Since the transaction is done, we should set the inode map cache flag
1817          * before any other comming transaction.
1818          */
1819         if (btrfs_test_opt(root, CHANGE_INODE_CACHE))
1820                 btrfs_set_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
1821         else
1822                 btrfs_clear_opt(root->fs_info->mount_opt, INODE_MAP_CACHE);
1823
1824         /* commit_fs_roots gets rid of all the tree log roots, it is now
1825          * safe to free the root of tree log roots
1826          */
1827         btrfs_free_log_root_tree(trans, root->fs_info);
1828
1829         ret = commit_cowonly_roots(trans, root);
1830         if (ret) {
1831                 mutex_unlock(&root->fs_info->tree_log_mutex);
1832                 mutex_unlock(&root->fs_info->reloc_mutex);
1833                 goto scrub_continue;
1834         }
1835
1836         /*
1837          * The tasks which save the space cache and inode cache may also
1838          * update ->aborted, check it.
1839          */
1840         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1841                 ret = cur_trans->aborted;
1842                 mutex_unlock(&root->fs_info->tree_log_mutex);
1843                 mutex_unlock(&root->fs_info->reloc_mutex);
1844                 goto scrub_continue;
1845         }
1846
1847         btrfs_prepare_extent_commit(trans, root);
1848
1849         cur_trans = root->fs_info->running_transaction;
1850
1851         btrfs_set_root_node(&root->fs_info->tree_root->root_item,
1852                             root->fs_info->tree_root->node);
1853         list_add_tail(&root->fs_info->tree_root->dirty_list,
1854                       &cur_trans->switch_commits);
1855
1856         btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
1857                             root->fs_info->chunk_root->node);
1858         list_add_tail(&root->fs_info->chunk_root->dirty_list,
1859                       &cur_trans->switch_commits);
1860
1861         switch_commit_roots(cur_trans, root->fs_info);
1862
1863         assert_qgroups_uptodate(trans);
1864         update_super_roots(root);
1865
1866         btrfs_set_super_log_root(root->fs_info->super_copy, 0);
1867         btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);
1868         memcpy(root->fs_info->super_for_commit, root->fs_info->super_copy,
1869                sizeof(*root->fs_info->super_copy));
1870
1871         spin_lock(&root->fs_info->trans_lock);
1872         cur_trans->state = TRANS_STATE_UNBLOCKED;
1873         root->fs_info->running_transaction = NULL;
1874         spin_unlock(&root->fs_info->trans_lock);
1875         mutex_unlock(&root->fs_info->reloc_mutex);
1876
1877         wake_up(&root->fs_info->transaction_wait);
1878
1879         ret = btrfs_write_and_wait_transaction(trans, root);
1880         if (ret) {
1881                 btrfs_error(root->fs_info, ret,
1882                             "Error while writing out transaction");
1883                 mutex_unlock(&root->fs_info->tree_log_mutex);
1884                 goto scrub_continue;
1885         }
1886
1887         ret = write_ctree_super(trans, root, 0);
1888         if (ret) {
1889                 mutex_unlock(&root->fs_info->tree_log_mutex);
1890                 goto scrub_continue;
1891         }
1892
1893         /*
1894          * the super is written, we can safely allow the tree-loggers
1895          * to go about their business
1896          */
1897         mutex_unlock(&root->fs_info->tree_log_mutex);
1898
1899         btrfs_finish_extent_commit(trans, root);
1900
1901         root->fs_info->last_trans_committed = cur_trans->transid;
1902         /*
1903          * We needn't acquire the lock here because there is no other task
1904          * which can change it.
1905          */
1906         cur_trans->state = TRANS_STATE_COMPLETED;
1907         wake_up(&cur_trans->commit_wait);
1908
1909         spin_lock(&root->fs_info->trans_lock);
1910         list_del_init(&cur_trans->list);
1911         spin_unlock(&root->fs_info->trans_lock);
1912
1913         btrfs_put_transaction(cur_trans);
1914         btrfs_put_transaction(cur_trans);
1915
1916         if (trans->type & __TRANS_FREEZABLE)
1917                 sb_end_intwrite(root->fs_info->sb);
1918
1919         trace_btrfs_transaction_commit(root);
1920
1921         btrfs_scrub_continue(root);
1922
1923         if (current->journal_info == trans)
1924                 current->journal_info = NULL;
1925
1926         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1927
1928         if (current != root->fs_info->transaction_kthread)
1929                 btrfs_run_delayed_iputs(root);
1930
1931         return ret;
1932
1933 scrub_continue:
1934         btrfs_scrub_continue(root);
1935 cleanup_transaction:
1936         btrfs_trans_release_metadata(trans, root);
1937         trans->block_rsv = NULL;
1938         if (trans->qgroup_reserved) {
1939                 btrfs_qgroup_free(root, trans->qgroup_reserved);
1940                 trans->qgroup_reserved = 0;
1941         }
1942         btrfs_warn(root->fs_info, "Skipping commit of aborted transaction.");
1943         if (current->journal_info == trans)
1944                 current->journal_info = NULL;
1945         cleanup_transaction(trans, root, ret);
1946
1947         return ret;
1948 }
1949
1950 /*
1951  * return < 0 if error
1952  * 0 if there are no more dead_roots at the time of call
1953  * 1 there are more to be processed, call me again
1954  *
1955  * The return value indicates there are certainly more snapshots to delete, but
1956  * if there comes a new one during processing, it may return 0. We don't mind,
1957  * because btrfs_commit_super will poke cleaner thread and it will process it a
1958  * few seconds later.
1959  */
1960 int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
1961 {
1962         int ret;
1963         struct btrfs_fs_info *fs_info = root->fs_info;
1964
1965         spin_lock(&fs_info->trans_lock);
1966         if (list_empty(&fs_info->dead_roots)) {
1967                 spin_unlock(&fs_info->trans_lock);
1968                 return 0;
1969         }
1970         root = list_first_entry(&fs_info->dead_roots,
1971                         struct btrfs_root, root_list);
1972         list_del_init(&root->root_list);
1973         spin_unlock(&fs_info->trans_lock);
1974
1975         pr_debug("BTRFS: cleaner removing %llu\n", root->objectid);
1976
1977         btrfs_kill_all_delayed_nodes(root);
1978
1979         if (btrfs_header_backref_rev(root->node) <
1980                         BTRFS_MIXED_BACKREF_REV)
1981                 ret = btrfs_drop_snapshot(root, NULL, 0, 0);
1982         else
1983                 ret = btrfs_drop_snapshot(root, NULL, 1, 0);
1984         /*
1985          * If we encounter a transaction abort during snapshot cleaning, we
1986          * don't want to crash here
1987          */
1988         return (ret < 0) ? 0 : 1;
1989 }