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
  35 #define BTRFS_ROOT_TRANS_TAG 0
  36
  37 static unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {
  38         [TRANS_STATE_RUNNING]           = 0U,
  39         [TRANS_STATE_BLOCKED]           = (__TRANS_USERSPACE |
  40                                            __TRANS_START),
  41         [TRANS_STATE_COMMIT_START]      = (__TRANS_USERSPACE |
  42                                            __TRANS_START |
  43                                            __TRANS_ATTACH),
  44         [TRANS_STATE_COMMIT_DOING]      = (__TRANS_USERSPACE |
  45                                            __TRANS_START |
  46                                            __TRANS_ATTACH |
  47                                            __TRANS_JOIN),
  48         [TRANS_STATE_UNBLOCKED]         = (__TRANS_USERSPACE |
  49                                            __TRANS_START |
  50                                            __TRANS_ATTACH |
  51                                            __TRANS_JOIN |
  52                                            __TRANS_JOIN_NOLOCK),
  53         [TRANS_STATE_COMPLETED]         = (__TRANS_USERSPACE |
  54                                            __TRANS_START |
  55                                            __TRANS_ATTACH |
  56                                            __TRANS_JOIN |
  57                                            __TRANS_JOIN_NOLOCK),
  58 };
  59
  60 void btrfs_put_transaction(struct btrfs_transaction *transaction)
  61 {
  62         WARN_ON(atomic_read(&transaction->use_count) == 0);
  63         if (atomic_dec_and_test(&transaction->use_count)) {
  64                 BUG_ON(!list_empty(&transaction->list));
  65                 WARN_ON(transaction->delayed_refs.root.rb_node);
  66                 while (!list_empty(&transaction->pending_chunks)) {
  67                         struct extent_map *em;
  68
  69                         em = list_first_entry(&transaction->pending_chunks,
  70                                               struct extent_map, list);
  71                         list_del_init(&em->list);
  72                         free_extent_map(em);
  73                 }
  74                 kmem_cache_free(btrfs_transaction_cachep, transaction);
  75         }
  76 }
  77
  78 static noinline void switch_commit_root(struct btrfs_root *root)
  79 {
  80         free_extent_buffer(root->commit_root);
  81         root->commit_root = btrfs_root_node(root);
  82 }
  83
  84 static inline void extwriter_counter_inc(struct btrfs_transaction *trans,
  85                                          unsigned int type)
  86 {
  87         if (type & TRANS_EXTWRITERS)
  88                 atomic_inc(&trans->num_extwriters);
  89 }
  90
  91 static inline void extwriter_counter_dec(struct btrfs_transaction *trans,
  92                                          unsigned int type)
  93 {
  94         if (type & TRANS_EXTWRITERS)
  95                 atomic_dec(&trans->num_extwriters);
  96 }
  97
  98 static inline void extwriter_counter_init(struct btrfs_transaction *trans,
  99                                           unsigned int type)
 100 {
 101         atomic_set(&trans->num_extwriters, ((type & TRANS_EXTWRITERS) ? 1 : 0));
 102 }
 103
 104 static inline int extwriter_counter_read(struct btrfs_transaction *trans)
 105 {
 106         return atomic_read(&trans->num_extwriters);
 107 }
 108
 109 /*
 110  * either allocate a new transaction or hop into the existing one
 111  */
 112 static noinline int join_transaction(struct btrfs_root *root, unsigned int type)
 113 {
 114         struct btrfs_transaction *cur_trans;
 115         struct btrfs_fs_info *fs_info = root->fs_info;
 116
 117         spin_lock(&fs_info->trans_lock);
 118 loop:
 119         /* The file system has been taken offline. No new transactions. */
 120         if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
 121                 spin_unlock(&fs_info->trans_lock);
 122                 return -EROFS;
 123         }
 124
 125         cur_trans = fs_info->running_transaction;
 126         if (cur_trans) {
 127                 if (cur_trans->aborted) {
 128                         spin_unlock(&fs_info->trans_lock);
 129                         return cur_trans->aborted;
 130                 }
 131                 if (btrfs_blocked_trans_types[cur_trans->state] & type) {
 132                         spin_unlock(&fs_info->trans_lock);
 133                         return -EBUSY;
 134                 }
 135                 atomic_inc(&cur_trans->use_count);
 136                 atomic_inc(&cur_trans->num_writers);
 137                 extwriter_counter_inc(cur_trans, type);
 138                 spin_unlock(&fs_info->trans_lock);
 139                 return 0;
 140         }
 141         spin_unlock(&fs_info->trans_lock);
 142
 143         /*
 144          * If we are ATTACH, we just want to catch the current transaction,
 145          * and commit it. If there is no transaction, just return ENOENT.
 146          */
 147         if (type == TRANS_ATTACH)
 148                 return -ENOENT;
 149
 150         /*
 151          * JOIN_NOLOCK only happens during the transaction commit, so
 152          * it is impossible that ->running_transaction is NULL
 153          */
 154         BUG_ON(type == TRANS_JOIN_NOLOCK);
 155
 156         cur_trans = kmem_cache_alloc(btrfs_transaction_cachep, GFP_NOFS);
 157         if (!cur_trans)
 158                 return -ENOMEM;
 159
 160         spin_lock(&fs_info->trans_lock);
 161         if (fs_info->running_transaction) {
 162                 /*
 163                  * someone started a transaction after we unlocked.  Make sure
 164                  * to redo the checks above
 165                  */
 166                 kmem_cache_free(btrfs_transaction_cachep, cur_trans);
 167                 goto loop;
 168         } else if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
 169                 spin_unlock(&fs_info->trans_lock);
 170                 kmem_cache_free(btrfs_transaction_cachep, cur_trans);
 171                 return -EROFS;
 172         }
 173
 174         atomic_set(&cur_trans->num_writers, 1);
 175         extwriter_counter_init(cur_trans, type);
 176         init_waitqueue_head(&cur_trans->writer_wait);
 177         init_waitqueue_head(&cur_trans->commit_wait);
 178         cur_trans->state = TRANS_STATE_RUNNING;
 179         /*
 180          * One for this trans handle, one so it will live on until we
 181          * commit the transaction.
 182          */
 183         atomic_set(&cur_trans->use_count, 2);
 184         cur_trans->start_time = get_seconds();
 185
 186         cur_trans->delayed_refs.root = RB_ROOT;
 187         cur_trans->delayed_refs.num_entries = 0;
 188         cur_trans->delayed_refs.num_heads_ready = 0;
 189         cur_trans->delayed_refs.num_heads = 0;
 190         cur_trans->delayed_refs.flushing = 0;
 191         cur_trans->delayed_refs.run_delayed_start = 0;
 192
 193         /*
 194          * although the tree mod log is per file system and not per transaction,
 195          * the log must never go across transaction boundaries.
 196          */
 197         smp_mb();
 198         if (!list_empty(&fs_info->tree_mod_seq_list))
 199                 WARN(1, KERN_ERR "btrfs: tree_mod_seq_list not empty when "
 200                         "creating a fresh transaction\n");
 201         if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log))
 202                 WARN(1, KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
 203                         "creating a fresh transaction\n");
 204         atomic64_set(&fs_info->tree_mod_seq, 0);
 205
 206         spin_lock_init(&cur_trans->delayed_refs.lock);
 207         atomic_set(&cur_trans->delayed_refs.procs_running_refs, 0);
 208         atomic_set(&cur_trans->delayed_refs.ref_seq, 0);
 209         init_waitqueue_head(&cur_trans->delayed_refs.wait);
 210
 211         INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 212         INIT_LIST_HEAD(&cur_trans->ordered_operations);
 213         INIT_LIST_HEAD(&cur_trans->pending_chunks);
 214         list_add_tail(&cur_trans->list, &fs_info->trans_list);
 215         extent_io_tree_init(&cur_trans->dirty_pages,
 216                              fs_info->btree_inode->i_mapping);
 217         fs_info->generation++;
 218         cur_trans->transid = fs_info->generation;
 219         fs_info->running_transaction = cur_trans;
 220         cur_trans->aborted = 0;
 221         spin_unlock(&fs_info->trans_lock);
 222
 223         return 0;
 224 }
 225
 226 /*
 227  * this does all the record keeping required to make sure that a reference
 228  * counted root is properly recorded in a given transaction.  This is required
 229  * to make sure the old root from before we joined the transaction is deleted
 230  * when the transaction commits
 231  */
 232 static int record_root_in_trans(struct btrfs_trans_handle *trans,
 233                                struct btrfs_root *root)
 234 {
 235         if (root->ref_cows && root->last_trans < trans->transid) {
 236                 WARN_ON(root == root->fs_info->extent_root);
 237                 WARN_ON(root->commit_root != root->node);
 238
 239                 /*
 240                  * see below for in_trans_setup usage rules
 241                  * we have the reloc mutex held now, so there
 242                  * is only one writer in this function
 243                  */
 244                 root->in_trans_setup = 1;
 245
 246                 /* make sure readers find in_trans_setup before
 247                  * they find our root->last_trans update
 248                  */
 249                 smp_wmb();
 250
 251                 spin_lock(&root->fs_info->fs_roots_radix_lock);
 252                 if (root->last_trans == trans->transid) {
 253                         spin_unlock(&root->fs_info->fs_roots_radix_lock);
 254                         return 0;
 255                 }
 256                 radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 257                            (unsigned long)root->root_key.objectid,
 258                            BTRFS_ROOT_TRANS_TAG);
 259                 spin_unlock(&root->fs_info->fs_roots_radix_lock);
 260                 root->last_trans = trans->transid;
 261
 262                 /* this is pretty tricky.  We don't want to
 263                  * take the relocation lock in btrfs_record_root_in_trans
 264                  * unless we're really doing the first setup for this root in
 265                  * this transaction.
 266                  *
 267                  * Normally we'd use root->last_trans as a flag to decide
 268                  * if we want to take the expensive mutex.
 269                  *
 270                  * But, we have to set root->last_trans before we
 271                  * init the relocation root, otherwise, we trip over warnings
 272                  * in ctree.c.  The solution used here is to flag ourselves
 273                  * with root->in_trans_setup.  When this is 1, we're still
 274                  * fixing up the reloc trees and everyone must wait.
 275                  *
 276                  * When this is zero, they can trust root->last_trans and fly
 277                  * through btrfs_record_root_in_trans without having to take the
 278                  * lock.  smp_wmb() makes sure that all the writes above are
 279                  * done before we pop in the zero below
 280                  */
 281                 btrfs_init_reloc_root(trans, root);
 282                 smp_wmb();
 283                 root->in_trans_setup = 0;
 284         }
 285         return 0;
 286 }
 287
 288
 289 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
 290                                struct btrfs_root *root)
 291 {
 292         if (!root->ref_cows)
 293                 return 0;
 294
 295         /*
 296          * see record_root_in_trans for comments about in_trans_setup usage
 297          * and barriers
 298          */
 299         smp_rmb();
 300         if (root->last_trans == trans->transid &&
 301             !root->in_trans_setup)
 302                 return 0;
 303
 304         mutex_lock(&root->fs_info->reloc_mutex);
 305         record_root_in_trans(trans, root);
 306         mutex_unlock(&root->fs_info->reloc_mutex);
 307
 308         return 0;
 309 }
 310
 311 static inline int is_transaction_blocked(struct btrfs_transaction *trans)
 312 {
 313         return (trans->state >= TRANS_STATE_BLOCKED &&
 314                 trans->state < TRANS_STATE_UNBLOCKED &&
 315                 !trans->aborted);
 316 }
 317
 318 /* wait for commit against the current transaction to become unblocked
 319  * when this is done, it is safe to start a new transaction, but the current
 320  * transaction might not be fully on disk.
 321  */
 322 static void wait_current_trans(struct btrfs_root *root)
 323 {
 324         struct btrfs_transaction *cur_trans;
 325
 326         spin_lock(&root->fs_info->trans_lock);
 327         cur_trans = root->fs_info->running_transaction;
 328         if (cur_trans && is_transaction_blocked(cur_trans)) {
 329                 atomic_inc(&cur_trans->use_count);
 330                 spin_unlock(&root->fs_info->trans_lock);
 331
 332                 wait_event(root->fs_info->transaction_wait,
 333                            cur_trans->state >= TRANS_STATE_UNBLOCKED ||
 334                            cur_trans->aborted);
 335                 btrfs_put_transaction(cur_trans);
 336         } else {
 337                 spin_unlock(&root->fs_info->trans_lock);
 338         }
 339 }
 340
 341 static int may_wait_transaction(struct btrfs_root *root, int type)
 342 {
 343         if (root->fs_info->log_root_recovering)
 344                 return 0;
 345
 346         if (type == TRANS_USERSPACE)
 347                 return 1;
 348
 349         if (type == TRANS_START &&
 350             !atomic_read(&root->fs_info->open_ioctl_trans))
 351                 return 1;
 352
 353         return 0;
 354 }
 355
 356 static inline bool need_reserve_reloc_root(struct btrfs_root *root)
 357 {
 358         if (!root->fs_info->reloc_ctl ||
 359             !root->ref_cows ||
 360             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
 361             root->reloc_root)
 362                 return false;
 363
 364         return true;
 365 }
 366
 367 static struct btrfs_trans_handle *
 368 start_transaction(struct btrfs_root *root, u64 num_items, unsigned int type,
 369                   enum btrfs_reserve_flush_enum flush)
 370 {
 371         struct btrfs_trans_handle *h;
 372         struct btrfs_transaction *cur_trans;
 373         u64 num_bytes = 0;
 374         u64 qgroup_reserved = 0;
 375         bool reloc_reserved = false;
 376         int ret;
 377
 378         if (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state))
 379                 return ERR_PTR(-EROFS);
 380
 381         if (current->journal_info) {
 382                 WARN_ON(type & TRANS_EXTWRITERS);
 383                 h = current->journal_info;
 384                 h->use_count++;
 385                 WARN_ON(h->use_count > 2);
 386                 h->orig_rsv = h->block_rsv;
 387                 h->block_rsv = NULL;
 388                 goto got_it;
 389         }
 390
 391         /*
 392          * Do the reservation before we join the transaction so we can do all
 393          * the appropriate flushing if need be.
 394          */
 395         if (num_items > 0 && root != root->fs_info->chunk_root) {
 396                 if (root->fs_info->quota_enabled &&
 397                     is_fstree(root->root_key.objectid)) {
 398                         qgroup_reserved = num_items * root->leafsize;
 399                         ret = btrfs_qgroup_reserve(root, qgroup_reserved);
 400                         if (ret)
 401                                 return ERR_PTR(ret);
 402                 }
 403
 404                 num_bytes = btrfs_calc_trans_metadata_size(root, num_items);
 405                 /*
 406                  * Do the reservation for the relocation root creation
 407                  */
 408                 if (unlikely(need_reserve_reloc_root(root))) {
 409                         num_bytes += root->nodesize;
 410                         reloc_reserved = true;
 411                 }
 412
 413                 ret = btrfs_block_rsv_add(root,
 414                                           &root->fs_info->trans_block_rsv,
 415                                           num_bytes, flush);
 416                 if (ret)
 417                         goto reserve_fail;
 418         }
 419 again:
 420         h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
 421         if (!h) {
 422                 ret = -ENOMEM;
 423                 goto alloc_fail;
 424         }
 425
 426         /*
 427          * If we are JOIN_NOLOCK we're already committing a transaction and
 428          * waiting on this guy, so we don't need to do the sb_start_intwrite
 429          * because we're already holding a ref.  We need this because we could
 430          * have raced in and did an fsync() on a file which can kick a commit
 431          * and then we deadlock with somebody doing a freeze.
 432          *
 433          * If we are ATTACH, it means we just want to catch the current
 434          * transaction and commit it, so we needn't do sb_start_intwrite().
 435          */
 436         if (type & __TRANS_FREEZABLE)
 437                 sb_start_intwrite(root->fs_info->sb);
 438
 439         if (may_wait_transaction(root, type))
 440                 wait_current_trans(root);
 441
 442         do {
 443                 ret = join_transaction(root, type);
 444                 if (ret == -EBUSY) {
 445                         wait_current_trans(root);
 446                         if (unlikely(type == TRANS_ATTACH))
 447                                 ret = -ENOENT;
 448                 }
 449         } while (ret == -EBUSY);
 450
 451         if (ret < 0) {
 452                 /* We must get the transaction if we are JOIN_NOLOCK. */
 453                 BUG_ON(type == TRANS_JOIN_NOLOCK);
 454                 goto join_fail;
 455         }
 456
 457         cur_trans = root->fs_info->running_transaction;
 458
 459         h->transid = cur_trans->transid;
 460         h->transaction = cur_trans;
 461         h->blocks_used = 0;
 462         h->bytes_reserved = 0;
 463         h->root = root;
 464         h->delayed_ref_updates = 0;
 465         h->use_count = 1;
 466         h->adding_csums = 0;
 467         h->block_rsv = NULL;
 468         h->orig_rsv = NULL;
 469         h->aborted = 0;
 470         h->qgroup_reserved = 0;
 471         h->delayed_ref_elem.seq = 0;
 472         h->type = type;
 473         h->allocating_chunk = false;
 474         h->reloc_reserved = false;
 475         INIT_LIST_HEAD(&h->qgroup_ref_list);
 476         INIT_LIST_HEAD(&h->new_bgs);
 477
 478         smp_mb();
 479         if (cur_trans->state >= TRANS_STATE_BLOCKED &&
 480             may_wait_transaction(root, type)) {
 481                 btrfs_commit_transaction(h, root);
 482                 goto again;
 483         }
 484
 485         if (num_bytes) {
 486                 trace_btrfs_space_reservation(root->fs_info, "transaction",
 487                                               h->transid, num_bytes, 1);
 488                 h->block_rsv = &root->fs_info->trans_block_rsv;
 489                 h->bytes_reserved = num_bytes;
 490                 h->reloc_reserved = reloc_reserved;
 491         }
 492         h->qgroup_reserved = qgroup_reserved;
 493
 494 got_it:
 495         btrfs_record_root_in_trans(h, root);
 496
 497         if (!current->journal_info && type != TRANS_USERSPACE)
 498                 current->journal_info = h;
 499         return h;
 500
 501 join_fail:
 502         if (type & __TRANS_FREEZABLE)
 503                 sb_end_intwrite(root->fs_info->sb);
 504         kmem_cache_free(btrfs_trans_handle_cachep, h);
 505 alloc_fail:
 506         if (num_bytes)
 507                 btrfs_block_rsv_release(root, &root->fs_info->trans_block_rsv,
 508                                         num_bytes);
 509 reserve_fail:
 510         if (qgroup_reserved)
 511                 btrfs_qgroup_free(root, qgroup_reserved);
 512         return ERR_PTR(ret);
 513 }
 514
 515 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 516                                                    int num_items)
 517 {
 518         return start_transaction(root, num_items, TRANS_START,
 519                                  BTRFS_RESERVE_FLUSH_ALL);
 520 }
 521
 522 struct btrfs_trans_handle *btrfs_start_transaction_lflush(
 523                                         struct btrfs_root *root, int num_items)
 524 {
 525         return start_transaction(root, num_items, TRANS_START,
 526                                  BTRFS_RESERVE_FLUSH_LIMIT);
 527 }
 528
 529 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)
 530 {
 531         return start_transaction(root, 0, TRANS_JOIN, 0);
 532 }
 533
 534 struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root)
 535 {
 536         return start_transaction(root, 0, TRANS_JOIN_NOLOCK, 0);
 537 }
 538
 539 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root)
 540 {
 541         return start_transaction(root, 0, TRANS_USERSPACE, 0);
 542 }
 543
 544 /*
 545  * btrfs_attach_transaction() - catch the running transaction
 546  *
 547  * It is used when we want to commit the current the transaction, but
 548  * don't want to start a new one.
 549  *
 550  * Note: If this function return -ENOENT, it just means there is no
 551  * running transaction. But it is possible that the inactive transaction
 552  * is still in the memory, not fully on disk. If you hope there is no
 553  * inactive transaction in the fs when -ENOENT is returned, you should
 554  * invoke
 555  *     btrfs_attach_transaction_barrier()
 556  */
 557 struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root)
 558 {
 559         return start_transaction(root, 0, TRANS_ATTACH, 0);
 560 }
 561
 562 /*
 563  * btrfs_attach_transaction_barrier() - catch the running transaction
 564  *
 565  * It is similar to the above function, the differentia is this one
 566  * will wait for all the inactive transactions until they fully
 567  * complete.
 568  */
 569 struct btrfs_trans_handle *
 570 btrfs_attach_transaction_barrier(struct btrfs_root *root)
 571 {
 572         struct btrfs_trans_handle *trans;
 573
 574         trans = start_transaction(root, 0, TRANS_ATTACH, 0);
 575         if (IS_ERR(trans) && PTR_ERR(trans) == -ENOENT)
 576                 btrfs_wait_for_commit(root, 0);
 577
 578         return trans;
 579 }
 580
 581 /* wait for a transaction commit to be fully complete */
 582 static noinline void wait_for_commit(struct btrfs_root *root,
 583                                     struct btrfs_transaction *commit)
 584 {
 585         wait_event(commit->commit_wait, commit->state == TRANS_STATE_COMPLETED);
 586 }
 587
 588 int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
 589 {
 590         struct btrfs_transaction *cur_trans = NULL, *t;
 591         int ret = 0;
 592
 593         if (transid) {
 594                 if (transid <= root->fs_info->last_trans_committed)
 595                         goto out;
 596
 597                 ret = -EINVAL;
 598                 /* find specified transaction */
 599                 spin_lock(&root->fs_info->trans_lock);
 600                 list_for_each_entry(t, &root->fs_info->trans_list, list) {
 601                         if (t->transid == transid) {
 602                                 cur_trans = t;
 603                                 atomic_inc(&cur_trans->use_count);
 604                                 ret = 0;
 605                                 break;
 606                         }
 607                         if (t->transid > transid) {
 608                                 ret = 0;
 609                                 break;
 610                         }
 611                 }
 612                 spin_unlock(&root->fs_info->trans_lock);
 613                 /* The specified transaction doesn't exist */
 614                 if (!cur_trans)
 615                         goto out;
 616         } else {
 617                 /* find newest transaction that is committing | committed */
 618                 spin_lock(&root->fs_info->trans_lock);
 619                 list_for_each_entry_reverse(t, &root->fs_info->trans_list,
 620                                             list) {
 621                         if (t->state >= TRANS_STATE_COMMIT_START) {
 622                                 if (t->state == TRANS_STATE_COMPLETED)
 623                                         break;
 624                                 cur_trans = t;
 625                                 atomic_inc(&cur_trans->use_count);
 626                                 break;
 627                         }
 628                 }
 629                 spin_unlock(&root->fs_info->trans_lock);
 630                 if (!cur_trans)
 631                         goto out;  /* nothing committing|committed */
 632         }
 633
 634         wait_for_commit(root, cur_trans);
 635         btrfs_put_transaction(cur_trans);
 636 out:
 637         return ret;
 638 }
 639
 640 void btrfs_throttle(struct btrfs_root *root)
 641 {
 642         if (!atomic_read(&root->fs_info->open_ioctl_trans))
 643                 wait_current_trans(root);
 644 }
 645
 646 static int should_end_transaction(struct btrfs_trans_handle *trans,
 647                                   struct btrfs_root *root)
 648 {
 649         if (root->fs_info->global_block_rsv.space_info->full &&
 650             btrfs_should_throttle_delayed_refs(trans, root))
 651                 return 1;
 652
 653         return !!btrfs_block_rsv_check(root, &root->fs_info->global_block_rsv, 5);
 654 }
 655
 656 int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
 657                                  struct btrfs_root *root)
 658 {
 659         struct btrfs_transaction *cur_trans = trans->transaction;
 660         int updates;
 661         int err;
 662
 663         smp_mb();
 664         if (cur_trans->state >= TRANS_STATE_BLOCKED ||
 665             cur_trans->delayed_refs.flushing)
 666                 return 1;
 667
 668         updates = trans->delayed_ref_updates;
 669         trans->delayed_ref_updates = 0;
 670         if (updates) {
 671                 err = btrfs_run_delayed_refs(trans, root, updates);
 672                 if (err) /* Error code will also eval true */
 673                         return err;
 674         }
 675
 676         return should_end_transaction(trans, root);
 677 }
 678
 679 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 680                           struct btrfs_root *root, int throttle)
 681 {
 682         struct btrfs_transaction *cur_trans = trans->transaction;
 683         struct btrfs_fs_info *info = root->fs_info;
 684         unsigned long cur = trans->delayed_ref_updates;
 685         int lock = (trans->type != TRANS_JOIN_NOLOCK);
 686         int err = 0;
 687
 688         if (--trans->use_count) {
 689                 trans->block_rsv = trans->orig_rsv;
 690                 return 0;
 691         }
 692
 693         /*
 694          * do the qgroup accounting as early as possible
 695          */
 696         err = btrfs_delayed_refs_qgroup_accounting(trans, info);
 697
 698         btrfs_trans_release_metadata(trans, root);
 699         trans->block_rsv = NULL;
 700
 701         if (trans->qgroup_reserved) {
 702                 /*
 703                  * the same root has to be passed here between start_transaction
 704                  * and end_transaction. Subvolume quota depends on this.
 705                  */
 706                 btrfs_qgroup_free(trans->root, trans->qgroup_reserved);
 707                 trans->qgroup_reserved = 0;
 708         }
 709
 710         if (!list_empty(&trans->new_bgs))
 711                 btrfs_create_pending_block_groups(trans, root);
 712
 713         trans->delayed_ref_updates = 0;
 714         if (btrfs_should_throttle_delayed_refs(trans, root)) {
 715                 cur = max_t(unsigned long, cur, 1);
 716                 trans->delayed_ref_updates = 0;
 717                 btrfs_run_delayed_refs(trans, root, cur);
 718         }
 719
 720         btrfs_trans_release_metadata(trans, root);
 721         trans->block_rsv = NULL;
 722
 723         if (!list_empty(&trans->new_bgs))
 724                 btrfs_create_pending_block_groups(trans, root);
 725
 726         if (lock && !atomic_read(&root->fs_info->open_ioctl_trans) &&
 727             should_end_transaction(trans, root) &&
 728             ACCESS_ONCE(cur_trans->state) == TRANS_STATE_RUNNING) {
 729                 spin_lock(&info->trans_lock);
 730                 if (cur_trans->state == TRANS_STATE_RUNNING)
 731                         cur_trans->state = TRANS_STATE_BLOCKED;
 732                 spin_unlock(&info->trans_lock);
 733         }
 734
 735         if (lock && ACCESS_ONCE(cur_trans->state) == TRANS_STATE_BLOCKED) {
 736                 if (throttle) {
 737                         /*
 738                          * We may race with somebody else here so end up having
 739                          * to call end_transaction on ourselves again, so inc
 740                          * our use_count.
 741                          */
 742                         trans->use_count++;
 743                         return btrfs_commit_transaction(trans, root);
 744                 } else {
 745                         wake_up_process(info->transaction_kthread);
 746                 }
 747         }
 748
 749         if (trans->type & __TRANS_FREEZABLE)
 750                 sb_end_intwrite(root->fs_info->sb);
 751
 752         WARN_ON(cur_trans != info->running_transaction);
 753         WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
 754         atomic_dec(&cur_trans->num_writers);
 755         extwriter_counter_dec(cur_trans, trans->type);
 756
 757         smp_mb();
 758         if (waitqueue_active(&cur_trans->writer_wait))
 759                 wake_up(&cur_trans->writer_wait);
 760         btrfs_put_transaction(cur_trans);
 761
 762         if (current->journal_info == trans)
 763                 current->journal_info = NULL;
 764
 765         if (throttle)
 766                 btrfs_run_delayed_iputs(root);
 767
 768         if (trans->aborted ||
 769             test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state)) {
 770                 wake_up_process(info->transaction_kthread);
 771                 err = -EIO;
 772         }
 773         assert_qgroups_uptodate(trans);
 774
 775         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 776         return err;
 777 }
 778
 779 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 780                           struct btrfs_root *root)
 781 {
 782         return __btrfs_end_transaction(trans, root, 0);
 783 }
 784
 785 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
 786                                    struct btrfs_root *root)
 787 {
 788         return __btrfs_end_transaction(trans, root, 1);
 789 }
 790
 791 int btrfs_end_transaction_dmeta(struct btrfs_trans_handle *trans,
 792                                 struct btrfs_root *root)
 793 {
 794         return __btrfs_end_transaction(trans, root, 1);
 795 }
 796
 797 /*
 798  * when btree blocks are allocated, they have some corresponding bits set for
 799  * them in one of two extent_io trees.  This is used to make sure all of
 800  * those extents are sent to disk but does not wait on them
 801  */
 802 int btrfs_write_marked_extents(struct btrfs_root *root,
 803                                struct extent_io_tree *dirty_pages, int mark)
 804 {
 805         int err = 0;
 806         int werr = 0;
 807         struct address_space *mapping = root->fs_info->btree_inode->i_mapping;
 808         struct extent_state *cached_state = NULL;
 809         u64 start = 0;
 810         u64 end;
 811
 812         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
 813                                       mark, &cached_state)) {
 814                 convert_extent_bit(dirty_pages, start, end, EXTENT_NEED_WAIT,
 815                                    mark, &cached_state, GFP_NOFS);
 816                 cached_state = NULL;
 817                 err = filemap_fdatawrite_range(mapping, start, end);
 818                 if (err)
 819                         werr = err;
 820                 cond_resched();
 821                 start = end + 1;
 822         }
 823         if (err)
 824                 werr = err;
 825         return werr;
 826 }
 827
 828 /*
 829  * when btree blocks are allocated, they have some corresponding bits set for
 830  * them in one of two extent_io trees.  This is used to make sure all of
 831  * those extents are on disk for transaction or log commit.  We wait
 832  * on all the pages and clear them from the dirty pages state tree
 833  */
 834 int btrfs_wait_marked_extents(struct btrfs_root *root,
 835                               struct extent_io_tree *dirty_pages, int mark)
 836 {
 837         int err = 0;
 838         int werr = 0;
 839         struct address_space *mapping = root->fs_info->btree_inode->i_mapping;
 840         struct extent_state *cached_state = NULL;
 841         u64 start = 0;
 842         u64 end;
 843
 844         while (!find_first_extent_bit(dirty_pages, start, &start, &end,
 845                                       EXTENT_NEED_WAIT, &cached_state)) {
 846                 clear_extent_bit(dirty_pages, start, end, EXTENT_NEED_WAIT,
 847                                  0, 0, &cached_state, GFP_NOFS);
 848                 err = filemap_fdatawait_range(mapping, start, end);
 849                 if (err)
 850                         werr = err;
 851                 cond_resched();
 852                 start = end + 1;
 853         }
 854         if (err)
 855                 werr = err;
 856         return werr;
 857 }
 858
 859 /*
 860  * when btree blocks are allocated, they have some corresponding bits set for
 861  * them in one of two extent_io trees.  This is used to make sure all of
 862  * those extents are on disk for transaction or log commit
 863  */
 864 static int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
 865                                 struct extent_io_tree *dirty_pages, int mark)
 866 {
 867         int ret;
 868         int ret2;
 869         struct blk_plug plug;
 870
 871         blk_start_plug(&plug);
 872         ret = btrfs_write_marked_extents(root, dirty_pages, mark);
 873         blk_finish_plug(&plug);
 874         ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
 875
 876         if (ret)
 877                 return ret;
 878         if (ret2)
 879                 return ret2;
 880         return 0;
 881 }
 882
 883 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 884                                      struct btrfs_root *root)
 885 {
 886         if (!trans || !trans->transaction) {
 887                 struct inode *btree_inode;
 888                 btree_inode = root->fs_info->btree_inode;
 889                 return filemap_write_and_wait(btree_inode->i_mapping);
 890         }
 891         return btrfs_write_and_wait_marked_extents(root,
 892                                            &trans->transaction->dirty_pages,
 893                                            EXTENT_DIRTY);
 894 }
 895
 896 /*
 897  * this is used to update the root pointer in the tree of tree roots.
 898  *
 899  * But, in the case of the extent allocation tree, updating the root
 900  * pointer may allocate blocks which may change the root of the extent
 901  * allocation tree.
 902  *
 903  * So, this loops and repeats and makes sure the cowonly root didn't
 904  * change while the root pointer was being updated in the metadata.
 905  */
 906 static int update_cowonly_root(struct btrfs_trans_handle *trans,
 907                                struct btrfs_root *root)
 908 {
 909         int ret;
 910         u64 old_root_bytenr;
 911         u64 old_root_used;
 912         struct btrfs_root *tree_root = root->fs_info->tree_root;
 913
 914         old_root_used = btrfs_root_used(&root->root_item);
 915         btrfs_write_dirty_block_groups(trans, root);
 916
 917         while (1) {
 918                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
 919                 if (old_root_bytenr == root->node->start &&
 920                     old_root_used == btrfs_root_used(&root->root_item))
 921                         break;
 922
 923                 btrfs_set_root_node(&root->root_item, root->node);
 924                 ret = btrfs_update_root(trans, tree_root,
 925                                         &root->root_key,
 926                                         &root->root_item);
 927                 if (ret)
 928                         return ret;
 929
 930                 old_root_used = btrfs_root_used(&root->root_item);
 931                 ret = btrfs_write_dirty_block_groups(trans, root);
 932                 if (ret)
 933                         return ret;
 934         }
 935
 936         if (root != root->fs_info->extent_root)
 937                 switch_commit_root(root);
 938
 939         return 0;
 940 }
 941
 942 /*
 943  * update all the cowonly tree roots on disk
 944  *
 945  * The error handling in this function may not be obvious. Any of the
 946  * failures will cause the file system to go offline. We still need
 947  * to clean up the delayed refs.
 948  */
 949 static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
 950                                          struct btrfs_root *root)
 951 {
 952         struct btrfs_fs_info *fs_info = root->fs_info;
 953         struct list_head *next;
 954         struct extent_buffer *eb;
 955         int ret;
 956
 957         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 958         if (ret)
 959                 return ret;
 960
 961         eb = btrfs_lock_root_node(fs_info->tree_root);
 962         ret = btrfs_cow_block(trans, fs_info->tree_root, eb, NULL,
 963                               0, &eb);
 964         btrfs_tree_unlock(eb);
 965         free_extent_buffer(eb);
 966
 967         if (ret)
 968                 return ret;
 969
 970         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 971         if (ret)
 972                 return ret;
 973
 974         ret = btrfs_run_dev_stats(trans, root->fs_info);
 975         if (ret)
 976                 return ret;
 977         ret = btrfs_run_dev_replace(trans, root->fs_info);
 978         if (ret)
 979                 return ret;
 980         ret = btrfs_run_qgroups(trans, root->fs_info);
 981         if (ret)
 982                 return ret;
 983
 984         /* run_qgroups might have added some more refs */
 985         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 986         if (ret)
 987                 return ret;
 988
 989         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
 990                 next = fs_info->dirty_cowonly_roots.next;
 991                 list_del_init(next);
 992                 root = list_entry(next, struct btrfs_root, dirty_list);
 993
 994                 ret = update_cowonly_root(trans, root);
 995                 if (ret)
 996                         return ret;
 997         }
 998
 999         down_write(&fs_info->extent_commit_sem);
1000         switch_commit_root(fs_info->extent_root);
1001         up_write(&fs_info->extent_commit_sem);
1002
1003         btrfs_after_dev_replace_commit(fs_info);
1004
1005         return 0;
1006 }
1007
1008 /*
1009  * dead roots are old snapshots that need to be deleted.  This allocates
1010  * a dirty root struct and adds it into the list of dead roots that need to
1011  * be deleted
1012  */
1013 void btrfs_add_dead_root(struct btrfs_root *root)
1014 {
1015         spin_lock(&root->fs_info->trans_lock);
1016         if (list_empty(&root->root_list))
1017                 list_add_tail(&root->root_list, &root->fs_info->dead_roots);
1018         spin_unlock(&root->fs_info->trans_lock);
1019 }
1020
1021 /*
1022  * update all the cowonly tree roots on disk
1023  */
1024 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
1025                                     struct btrfs_root *root)
1026 {
1027         struct btrfs_root *gang[8];
1028         struct btrfs_fs_info *fs_info = root->fs_info;
1029         int i;
1030         int ret;
1031         int err = 0;
1032
1033         spin_lock(&fs_info->fs_roots_radix_lock);
1034         while (1) {
1035                 ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
1036                                                  (void **)gang, 0,
1037                                                  ARRAY_SIZE(gang),
1038                                                  BTRFS_ROOT_TRANS_TAG);
1039                 if (ret == 0)
1040                         break;
1041                 for (i = 0; i < ret; i++) {
1042                         root = gang[i];
1043                         radix_tree_tag_clear(&fs_info->fs_roots_radix,
1044                                         (unsigned long)root->root_key.objectid,
1045                                         BTRFS_ROOT_TRANS_TAG);
1046                         spin_unlock(&fs_info->fs_roots_radix_lock);
1047
1048                         btrfs_free_log(trans, root);
1049                         btrfs_update_reloc_root(trans, root);
1050                         btrfs_orphan_commit_root(trans, root);
1051
1052                         btrfs_save_ino_cache(root, trans);
1053
1054                         /* see comments in should_cow_block() */
1055                         root->force_cow = 0;
1056                         smp_wmb();
1057
1058                         if (root->commit_root != root->node) {
1059                                 mutex_lock(&root->fs_commit_mutex);
1060                                 switch_commit_root(root);
1061                                 btrfs_unpin_free_ino(root);
1062                                 mutex_unlock(&root->fs_commit_mutex);
1063
1064                                 btrfs_set_root_node(&root->root_item,
1065                                                     root->node);
1066                         }
1067
1068                         err = btrfs_update_root(trans, fs_info->tree_root,
1069                                                 &root->root_key,
1070                                                 &root->root_item);
1071                         spin_lock(&fs_info->fs_roots_radix_lock);
1072                         if (err)
1073                                 break;
1074                 }
1075         }
1076         spin_unlock(&fs_info->fs_roots_radix_lock);
1077         return err;
1078 }
1079
1080 /*
1081  * defrag a given btree.
1082  * Every leaf in the btree is read and defragged.
1083  */
1084 int btrfs_defrag_root(struct btrfs_root *root)
1085 {
1086         struct btrfs_fs_info *info = root->fs_info;
1087         struct btrfs_trans_handle *trans;
1088         int ret;
1089
1090         if (xchg(&root->defrag_running, 1))
1091                 return 0;
1092
1093         while (1) {
1094                 trans = btrfs_start_transaction(root, 0);
1095                 if (IS_ERR(trans))
1096                         return PTR_ERR(trans);
1097
1098                 ret = btrfs_defrag_leaves(trans, root);
1099
1100                 btrfs_end_transaction(trans, root);
1101                 btrfs_btree_balance_dirty(info->tree_root);
1102                 cond_resched();
1103
1104                 if (btrfs_fs_closing(root->fs_info) || ret != -EAGAIN)
1105                         break;
1106
1107                 if (btrfs_defrag_cancelled(root->fs_info)) {
1108                         printk(KERN_DEBUG "btrfs: defrag_root cancelled\n");
1109                         ret = -EAGAIN;
1110                         break;
1111                 }
1112         }
1113         root->defrag_running = 0;
1114         return ret;
1115 }
1116
1117 /*
1118  * new snapshots need to be created at a very specific time in the
1119  * transaction commit.  This does the actual creation.
1120  *
1121  * Note:
1122  * If the error which may affect the commitment of the current transaction
1123  * happens, we should return the error number. If the error which just affect
1124  * the creation of the pending snapshots, just return 0.
1125  */
1126 static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
1127                                    struct btrfs_fs_info *fs_info,
1128                                    struct btrfs_pending_snapshot *pending)
1129 {
1130         struct btrfs_key key;
1131         struct btrfs_root_item *new_root_item;
1132         struct btrfs_root *tree_root = fs_info->tree_root;
1133         struct btrfs_root *root = pending->root;
1134         struct btrfs_root *parent_root;
1135         struct btrfs_block_rsv *rsv;
1136         struct inode *parent_inode;
1137         struct btrfs_path *path;
1138         struct btrfs_dir_item *dir_item;
1139         struct dentry *dentry;
1140         struct extent_buffer *tmp;
1141         struct extent_buffer *old;
1142         struct timespec cur_time = CURRENT_TIME;
1143         int ret = 0;
1144         u64 to_reserve = 0;
1145         u64 index = 0;
1146         u64 objectid;
1147         u64 root_flags;
1148         uuid_le new_uuid;
1149
1150         path = btrfs_alloc_path();
1151         if (!path) {
1152                 pending->error = -ENOMEM;
1153                 return 0;
1154         }
1155
1156         new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
1157         if (!new_root_item) {
1158                 pending->error = -ENOMEM;
1159                 goto root_item_alloc_fail;
1160         }
1161
1162         pending->error = btrfs_find_free_objectid(tree_root, &objectid);
1163         if (pending->error)
1164                 goto no_free_objectid;
1165
1166         btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
1167
1168         if (to_reserve > 0) {
1169                 pending->error = btrfs_block_rsv_add(root,
1170                                                      &pending->block_rsv,
1171                                                      to_reserve,
1172                                                      BTRFS_RESERVE_NO_FLUSH);
1173                 if (pending->error)
1174                         goto no_free_objectid;
1175         }
1176
1177         pending->error = btrfs_qgroup_inherit(trans, fs_info,
1178                                               root->root_key.objectid,
1179                                               objectid, pending->inherit);
1180         if (pending->error)
1181                 goto no_free_objectid;
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         /* see comments in should_cow_block() */
1280         root->force_cow = 1;
1281         smp_wmb();
1282
1283         btrfs_set_root_node(new_root_item, tmp);
1284         /* record when the snapshot was created in key.offset */
1285         key.offset = trans->transid;
1286         ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
1287         btrfs_tree_unlock(tmp);
1288         free_extent_buffer(tmp);
1289         if (ret) {
1290                 btrfs_abort_transaction(trans, root, ret);
1291                 goto fail;
1292         }
1293
1294         /*
1295          * insert root back/forward references
1296          */
1297         ret = btrfs_add_root_ref(trans, tree_root, objectid,
1298                                  parent_root->root_key.objectid,
1299                                  btrfs_ino(parent_inode), index,
1300                                  dentry->d_name.name, dentry->d_name.len);
1301         if (ret) {
1302                 btrfs_abort_transaction(trans, root, ret);
1303                 goto fail;
1304         }
1305
1306         key.offset = (u64)-1;
1307         pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
1308         if (IS_ERR(pending->snap)) {
1309                 ret = PTR_ERR(pending->snap);
1310                 btrfs_abort_transaction(trans, root, ret);
1311                 goto fail;
1312         }
1313
1314         ret = btrfs_reloc_post_snapshot(trans, pending);
1315         if (ret) {
1316                 btrfs_abort_transaction(trans, root, ret);
1317                 goto fail;
1318         }
1319
1320         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1321         if (ret) {
1322                 btrfs_abort_transaction(trans, root, ret);
1323                 goto fail;
1324         }
1325
1326         ret = btrfs_insert_dir_item(trans, parent_root,
1327                                     dentry->d_name.name, dentry->d_name.len,
1328                                     parent_inode, &key,
1329                                     BTRFS_FT_DIR, index);
1330         /* We have check then name at the beginning, so it is impossible. */
1331         BUG_ON(ret == -EEXIST || ret == -EOVERFLOW);
1332         if (ret) {
1333                 btrfs_abort_transaction(trans, root, ret);
1334                 goto fail;
1335         }
1336
1337         btrfs_i_size_write(parent_inode, parent_inode->i_size +
1338                                          dentry->d_name.len * 2);
1339         parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
1340         ret = btrfs_update_inode_fallback(trans, parent_root, parent_inode);
1341         if (ret) {
1342                 btrfs_abort_transaction(trans, root, ret);
1343                 goto fail;
1344         }
1345         ret = btrfs_uuid_tree_add(trans, fs_info->uuid_root, new_uuid.b,
1346                                   BTRFS_UUID_KEY_SUBVOL, objectid);
1347         if (ret) {
1348                 btrfs_abort_transaction(trans, root, ret);
1349                 goto fail;
1350         }
1351         if (!btrfs_is_empty_uuid(new_root_item->received_uuid)) {
1352                 ret = btrfs_uuid_tree_add(trans, fs_info->uuid_root,
1353                                           new_root_item->received_uuid,
1354                                           BTRFS_UUID_KEY_RECEIVED_SUBVOL,
1355                                           objectid);
1356                 if (ret && ret != -EEXIST) {
1357                         btrfs_abort_transaction(trans, root, ret);
1358                         goto fail;
1359                 }
1360         }
1361 fail:
1362         pending->error = ret;
1363 dir_item_existed:
1364         trans->block_rsv = rsv;
1365         trans->bytes_reserved = 0;
1366 no_free_objectid:
1367         kfree(new_root_item);
1368 root_item_alloc_fail:
1369         btrfs_free_path(path);
1370         return ret;
1371 }
1372
1373 /*
1374  * create all the snapshots we've scheduled for creation
1375  */
1376 static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
1377                                              struct btrfs_fs_info *fs_info)
1378 {
1379         struct btrfs_pending_snapshot *pending, *next;
1380         struct list_head *head = &trans->transaction->pending_snapshots;
1381         int ret = 0;
1382
1383         list_for_each_entry_safe(pending, next, head, list) {
1384                 list_del(&pending->list);
1385                 ret = create_pending_snapshot(trans, fs_info, pending);
1386                 if (ret)
1387                         break;
1388         }
1389         return ret;
1390 }
1391
1392 static void update_super_roots(struct btrfs_root *root)
1393 {
1394         struct btrfs_root_item *root_item;
1395         struct btrfs_super_block *super;
1396
1397         super = root->fs_info->super_copy;
1398
1399         root_item = &root->fs_info->chunk_root->root_item;
1400         super->chunk_root = root_item->bytenr;
1401         super->chunk_root_generation = root_item->generation;
1402         super->chunk_root_level = root_item->level;
1403
1404         root_item = &root->fs_info->tree_root->root_item;
1405         super->root = root_item->bytenr;
1406         super->generation = root_item->generation;
1407         super->root_level = root_item->level;
1408         if (btrfs_test_opt(root, SPACE_CACHE))
1409                 super->cache_generation = root_item->generation;
1410         if (root->fs_info->update_uuid_tree_gen)
1411                 super->uuid_tree_generation = root_item->generation;
1412 }
1413
1414 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
1415 {
1416         struct btrfs_transaction *trans;
1417         int ret = 0;
1418
1419         spin_lock(&info->trans_lock);
1420         trans = info->running_transaction;
1421         if (trans)
1422                 ret = (trans->state >= TRANS_STATE_COMMIT_START);
1423         spin_unlock(&info->trans_lock);
1424         return ret;
1425 }
1426
1427 int btrfs_transaction_blocked(struct btrfs_fs_info *info)
1428 {
1429         struct btrfs_transaction *trans;
1430         int ret = 0;
1431
1432         spin_lock(&info->trans_lock);
1433         trans = info->running_transaction;
1434         if (trans)
1435                 ret = is_transaction_blocked(trans);
1436         spin_unlock(&info->trans_lock);
1437         return ret;
1438 }
1439
1440 /*
1441  * wait for the current transaction commit to start and block subsequent
1442  * transaction joins
1443  */
1444 static void wait_current_trans_commit_start(struct btrfs_root *root,
1445                                             struct btrfs_transaction *trans)
1446 {
1447         wait_event(root->fs_info->transaction_blocked_wait,
1448                    trans->state >= TRANS_STATE_COMMIT_START ||
1449                    trans->aborted);
1450 }
1451
1452 /*
1453  * wait for the current transaction to start and then become unblocked.
1454  * caller holds ref.
1455  */
1456 static void wait_current_trans_commit_start_and_unblock(struct btrfs_root *root,
1457                                          struct btrfs_transaction *trans)
1458 {
1459         wait_event(root->fs_info->transaction_wait,
1460                    trans->state >= TRANS_STATE_UNBLOCKED ||
1461                    trans->aborted);
1462 }
1463
1464 /*
1465  * commit transactions asynchronously. once btrfs_commit_transaction_async
1466  * returns, any subsequent transaction will not be allowed to join.
1467  */
1468 struct btrfs_async_commit {
1469         struct btrfs_trans_handle *newtrans;
1470         struct btrfs_root *root;
1471         struct work_struct work;
1472 };
1473
1474 static void do_async_commit(struct work_struct *work)
1475 {
1476         struct btrfs_async_commit *ac =
1477                 container_of(work, struct btrfs_async_commit, work);
1478
1479         /*
1480          * We've got freeze protection passed with the transaction.
1481          * Tell lockdep about it.
1482          */
1483         if (ac->newtrans->type & __TRANS_FREEZABLE)
1484                 rwsem_acquire_read(
1485                      &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1486                      0, 1, _THIS_IP_);
1487
1488         current->journal_info = ac->newtrans;
1489
1490         btrfs_commit_transaction(ac->newtrans, ac->root);
1491         kfree(ac);
1492 }
1493
1494 int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
1495                                    struct btrfs_root *root,
1496                                    int wait_for_unblock)
1497 {
1498         struct btrfs_async_commit *ac;
1499         struct btrfs_transaction *cur_trans;
1500
1501         ac = kmalloc(sizeof(*ac), GFP_NOFS);
1502         if (!ac)
1503                 return -ENOMEM;
1504
1505         INIT_WORK(&ac->work, do_async_commit);
1506         ac->root = root;
1507         ac->newtrans = btrfs_join_transaction(root);
1508         if (IS_ERR(ac->newtrans)) {
1509                 int err = PTR_ERR(ac->newtrans);
1510                 kfree(ac);
1511                 return err;
1512         }
1513
1514         /* take transaction reference */
1515         cur_trans = trans->transaction;
1516         atomic_inc(&cur_trans->use_count);
1517
1518         btrfs_end_transaction(trans, root);
1519
1520         /*
1521          * Tell lockdep we've released the freeze rwsem, since the
1522          * async commit thread will be the one to unlock it.
1523          */
1524         if (ac->newtrans->type & __TRANS_FREEZABLE)
1525                 rwsem_release(
1526                         &root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1527                         1, _THIS_IP_);
1528
1529         schedule_work(&ac->work);
1530
1531         /* wait for transaction to start and unblock */
1532         if (wait_for_unblock)
1533                 wait_current_trans_commit_start_and_unblock(root, cur_trans);
1534         else
1535                 wait_current_trans_commit_start(root, cur_trans);
1536
1537         if (current->journal_info == trans)
1538                 current->journal_info = NULL;
1539
1540         btrfs_put_transaction(cur_trans);
1541         return 0;
1542 }
1543
1544
1545 static void cleanup_transaction(struct btrfs_trans_handle *trans,
1546                                 struct btrfs_root *root, int err)
1547 {
1548         struct btrfs_transaction *cur_trans = trans->transaction;
1549         DEFINE_WAIT(wait);
1550
1551         WARN_ON(trans->use_count > 1);
1552
1553         btrfs_abort_transaction(trans, root, err);
1554
1555         spin_lock(&root->fs_info->trans_lock);
1556
1557         /*
1558          * If the transaction is removed from the list, it means this
1559          * transaction has been committed successfully, so it is impossible
1560          * to call the cleanup function.
1561          */
1562         BUG_ON(list_empty(&cur_trans->list));
1563
1564         list_del_init(&cur_trans->list);
1565         if (cur_trans == root->fs_info->running_transaction) {
1566                 cur_trans->state = TRANS_STATE_COMMIT_DOING;
1567                 spin_unlock(&root->fs_info->trans_lock);
1568                 wait_event(cur_trans->writer_wait,
1569                            atomic_read(&cur_trans->num_writers) == 1);
1570
1571                 spin_lock(&root->fs_info->trans_lock);
1572         }
1573         spin_unlock(&root->fs_info->trans_lock);
1574
1575         btrfs_cleanup_one_transaction(trans->transaction, root);
1576
1577         spin_lock(&root->fs_info->trans_lock);
1578         if (cur_trans == root->fs_info->running_transaction)
1579                 root->fs_info->running_transaction = NULL;
1580         spin_unlock(&root->fs_info->trans_lock);
1581
1582         if (trans->type & __TRANS_FREEZABLE)
1583                 sb_end_intwrite(root->fs_info->sb);
1584         btrfs_put_transaction(cur_trans);
1585         btrfs_put_transaction(cur_trans);
1586
1587         trace_btrfs_transaction_commit(root);
1588
1589         btrfs_scrub_continue(root);
1590
1591         if (current->journal_info == trans)
1592                 current->journal_info = NULL;
1593
1594         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1595 }
1596
1597 static int btrfs_flush_all_pending_stuffs(struct btrfs_trans_handle *trans,
1598                                           struct btrfs_root *root)
1599 {
1600         int ret;
1601
1602         ret = btrfs_run_delayed_items(trans, root);
1603         /*
1604          * running the delayed items may have added new refs. account
1605          * them now so that they hinder processing of more delayed refs
1606          * as little as possible.
1607          */
1608         if (ret) {
1609                 btrfs_delayed_refs_qgroup_accounting(trans, root->fs_info);
1610                 return ret;
1611         }
1612
1613         ret = btrfs_delayed_refs_qgroup_accounting(trans, root->fs_info);
1614         if (ret)
1615                 return ret;
1616
1617         /*
1618          * rename don't use btrfs_join_transaction, so, once we
1619          * set the transaction to blocked above, we aren't going
1620          * to get any new ordered operations.  We can safely run
1621          * it here and no for sure that nothing new will be added
1622          * to the list
1623          */
1624         ret = btrfs_run_ordered_operations(trans, root, 1);
1625
1626         return ret;
1627 }
1628
1629 static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
1630 {
1631         if (btrfs_test_opt(fs_info->tree_root, FLUSHONCOMMIT))
1632                 return btrfs_start_delalloc_roots(fs_info, 1);
1633         return 0;
1634 }
1635
1636 static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
1637 {
1638         if (btrfs_test_opt(fs_info->tree_root, FLUSHONCOMMIT))
1639                 btrfs_wait_ordered_roots(fs_info, -1);
1640 }
1641
1642 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
1643                              struct btrfs_root *root)
1644 {
1645         struct btrfs_transaction *cur_trans = trans->transaction;
1646         struct btrfs_transaction *prev_trans = NULL;
1647         int ret;
1648
1649         ret = btrfs_run_ordered_operations(trans, root, 0);
1650         if (ret) {
1651                 btrfs_abort_transaction(trans, root, ret);
1652                 btrfs_end_transaction(trans, root);
1653                 return ret;
1654         }
1655
1656         /* Stop the commit early if ->aborted is set */
1657         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1658                 ret = cur_trans->aborted;
1659                 btrfs_end_transaction(trans, root);
1660                 return ret;
1661         }
1662
1663         /* make a pass through all the delayed refs we have so far
1664          * any runnings procs may add more while we are here
1665          */
1666         ret = btrfs_run_delayed_refs(trans, root, 0);
1667         if (ret) {
1668                 btrfs_end_transaction(trans, root);
1669                 return ret;
1670         }
1671
1672         btrfs_trans_release_metadata(trans, root);
1673         trans->block_rsv = NULL;
1674         if (trans->qgroup_reserved) {
1675                 btrfs_qgroup_free(root, trans->qgroup_reserved);
1676                 trans->qgroup_reserved = 0;
1677         }
1678
1679         cur_trans = trans->transaction;
1680
1681         /*
1682          * set the flushing flag so procs in this transaction have to
1683          * start sending their work down.
1684          */
1685         cur_trans->delayed_refs.flushing = 1;
1686         smp_wmb();
1687
1688         if (!list_empty(&trans->new_bgs))
1689                 btrfs_create_pending_block_groups(trans, root);
1690
1691         ret = btrfs_run_delayed_refs(trans, root, 0);
1692         if (ret) {
1693                 btrfs_end_transaction(trans, root);
1694                 return ret;
1695         }
1696
1697         spin_lock(&root->fs_info->trans_lock);
1698         if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
1699                 spin_unlock(&root->fs_info->trans_lock);
1700                 atomic_inc(&cur_trans->use_count);
1701                 ret = btrfs_end_transaction(trans, root);
1702
1703                 wait_for_commit(root, cur_trans);
1704
1705                 btrfs_put_transaction(cur_trans);
1706
1707                 return ret;
1708         }
1709
1710         cur_trans->state = TRANS_STATE_COMMIT_START;
1711         wake_up(&root->fs_info->transaction_blocked_wait);
1712
1713         if (cur_trans->list.prev != &root->fs_info->trans_list) {
1714                 prev_trans = list_entry(cur_trans->list.prev,
1715                                         struct btrfs_transaction, list);
1716                 if (prev_trans->state != TRANS_STATE_COMPLETED) {
1717                         atomic_inc(&prev_trans->use_count);
1718                         spin_unlock(&root->fs_info->trans_lock);
1719
1720                         wait_for_commit(root, prev_trans);
1721
1722                         btrfs_put_transaction(prev_trans);
1723                 } else {
1724                         spin_unlock(&root->fs_info->trans_lock);
1725                 }
1726         } else {
1727                 spin_unlock(&root->fs_info->trans_lock);
1728         }
1729
1730         extwriter_counter_dec(cur_trans, trans->type);
1731
1732         ret = btrfs_start_delalloc_flush(root->fs_info);
1733         if (ret)
1734                 goto cleanup_transaction;
1735
1736         ret = btrfs_flush_all_pending_stuffs(trans, root);
1737         if (ret)
1738                 goto cleanup_transaction;
1739
1740         wait_event(cur_trans->writer_wait,
1741                    extwriter_counter_read(cur_trans) == 0);
1742
1743         /* some pending stuffs might be added after the previous flush. */
1744         ret = btrfs_flush_all_pending_stuffs(trans, root);
1745         if (ret)
1746                 goto cleanup_transaction;
1747
1748         btrfs_wait_delalloc_flush(root->fs_info);
1749         /*
1750          * Ok now we need to make sure to block out any other joins while we
1751          * commit the transaction.  We could have started a join before setting
1752          * COMMIT_DOING so make sure to wait for num_writers to == 1 again.
1753          */
1754         spin_lock(&root->fs_info->trans_lock);
1755         cur_trans->state = TRANS_STATE_COMMIT_DOING;
1756         spin_unlock(&root->fs_info->trans_lock);
1757         wait_event(cur_trans->writer_wait,
1758                    atomic_read(&cur_trans->num_writers) == 1);
1759
1760         /* ->aborted might be set after the previous check, so check it */
1761         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1762                 ret = cur_trans->aborted;
1763                 goto cleanup_transaction;
1764         }
1765         /*
1766          * the reloc mutex makes sure that we stop
1767          * the balancing code from coming in and moving
1768          * extents around in the middle of the commit
1769          */
1770         mutex_lock(&root->fs_info->reloc_mutex);
1771
1772         /*
1773          * We needn't worry about the delayed items because we will
1774          * deal with them in create_pending_snapshot(), which is the
1775          * core function of the snapshot creation.
1776          */
1777         ret = create_pending_snapshots(trans, root->fs_info);
1778         if (ret) {
1779                 mutex_unlock(&root->fs_info->reloc_mutex);
1780                 goto cleanup_transaction;
1781         }
1782
1783         /*
1784          * We insert the dir indexes of the snapshots and update the inode
1785          * of the snapshots' parents after the snapshot creation, so there
1786          * are some delayed items which are not dealt with. Now deal with
1787          * them.
1788          *
1789          * We needn't worry that this operation will corrupt the snapshots,
1790          * because all the tree which are snapshoted will be forced to COW
1791          * the nodes and leaves.
1792          */
1793         ret = btrfs_run_delayed_items(trans, root);
1794         if (ret) {
1795                 mutex_unlock(&root->fs_info->reloc_mutex);
1796                 goto cleanup_transaction;
1797         }
1798
1799         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1800         if (ret) {
1801                 mutex_unlock(&root->fs_info->reloc_mutex);
1802                 goto cleanup_transaction;
1803         }
1804
1805         /*
1806          * make sure none of the code above managed to slip in a
1807          * delayed item
1808          */
1809         btrfs_assert_delayed_root_empty(root);
1810
1811         WARN_ON(cur_trans != trans->transaction);
1812
1813         btrfs_scrub_pause(root);
1814         /* btrfs_commit_tree_roots is responsible for getting the
1815          * various roots consistent with each other.  Every pointer
1816          * in the tree of tree roots has to point to the most up to date
1817          * root for every subvolume and other tree.  So, we have to keep
1818          * the tree logging code from jumping in and changing any
1819          * of the trees.
1820          *
1821          * At this point in the commit, there can't be any tree-log
1822          * writers, but a little lower down we drop the trans mutex
1823          * and let new people in.  By holding the tree_log_mutex
1824          * from now until after the super is written, we avoid races
1825          * with the tree-log code.
1826          */
1827         mutex_lock(&root->fs_info->tree_log_mutex);
1828
1829         ret = commit_fs_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 cleanup_transaction;
1834         }
1835
1836         /* commit_fs_roots gets rid of all the tree log roots, it is now
1837          * safe to free the root of tree log roots
1838          */
1839         btrfs_free_log_root_tree(trans, root->fs_info);
1840
1841         ret = commit_cowonly_roots(trans, root);
1842         if (ret) {
1843                 mutex_unlock(&root->fs_info->tree_log_mutex);
1844                 mutex_unlock(&root->fs_info->reloc_mutex);
1845                 goto cleanup_transaction;
1846         }
1847
1848         /*
1849          * The tasks which save the space cache and inode cache may also
1850          * update ->aborted, check it.
1851          */
1852         if (unlikely(ACCESS_ONCE(cur_trans->aborted))) {
1853                 ret = cur_trans->aborted;
1854                 mutex_unlock(&root->fs_info->tree_log_mutex);
1855                 mutex_unlock(&root->fs_info->reloc_mutex);
1856                 goto cleanup_transaction;
1857         }
1858
1859         btrfs_prepare_extent_commit(trans, root);
1860
1861         cur_trans = root->fs_info->running_transaction;
1862
1863         btrfs_set_root_node(&root->fs_info->tree_root->root_item,
1864                             root->fs_info->tree_root->node);
1865         switch_commit_root(root->fs_info->tree_root);
1866
1867         btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
1868                             root->fs_info->chunk_root->node);
1869         switch_commit_root(root->fs_info->chunk_root);
1870
1871         assert_qgroups_uptodate(trans);
1872         update_super_roots(root);
1873
1874         btrfs_set_super_log_root(root->fs_info->super_copy, 0);
1875         btrfs_set_super_log_root_level(root->fs_info->super_copy, 0);
1876         memcpy(root->fs_info->super_for_commit, root->fs_info->super_copy,
1877                sizeof(*root->fs_info->super_copy));
1878
1879         spin_lock(&root->fs_info->trans_lock);
1880         cur_trans->state = TRANS_STATE_UNBLOCKED;
1881         root->fs_info->running_transaction = NULL;
1882         spin_unlock(&root->fs_info->trans_lock);
1883         mutex_unlock(&root->fs_info->reloc_mutex);
1884
1885         wake_up(&root->fs_info->transaction_wait);
1886
1887         ret = btrfs_write_and_wait_transaction(trans, root);
1888         if (ret) {
1889                 btrfs_error(root->fs_info, ret,
1890                             "Error while writing out transaction");
1891                 mutex_unlock(&root->fs_info->tree_log_mutex);
1892                 goto cleanup_transaction;
1893         }
1894
1895         ret = write_ctree_super(trans, root, 0);
1896         if (ret) {
1897                 mutex_unlock(&root->fs_info->tree_log_mutex);
1898                 goto cleanup_transaction;
1899         }
1900
1901         /*
1902          * the super is written, we can safely allow the tree-loggers
1903          * to go about their business
1904          */
1905         mutex_unlock(&root->fs_info->tree_log_mutex);
1906
1907         btrfs_finish_extent_commit(trans, root);
1908
1909         root->fs_info->last_trans_committed = cur_trans->transid;
1910         /*
1911          * We needn't acquire the lock here because there is no other task
1912          * which can change it.
1913          */
1914         cur_trans->state = TRANS_STATE_COMPLETED;
1915         wake_up(&cur_trans->commit_wait);
1916
1917         spin_lock(&root->fs_info->trans_lock);
1918         list_del_init(&cur_trans->list);
1919         spin_unlock(&root->fs_info->trans_lock);
1920
1921         btrfs_put_transaction(cur_trans);
1922         btrfs_put_transaction(cur_trans);
1923
1924         if (trans->type & __TRANS_FREEZABLE)
1925                 sb_end_intwrite(root->fs_info->sb);
1926
1927         trace_btrfs_transaction_commit(root);
1928
1929         btrfs_scrub_continue(root);
1930
1931         if (current->journal_info == trans)
1932                 current->journal_info = NULL;
1933
1934         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1935
1936         if (current != root->fs_info->transaction_kthread)
1937                 btrfs_run_delayed_iputs(root);
1938
1939         return ret;
1940
1941 cleanup_transaction:
1942         btrfs_trans_release_metadata(trans, root);
1943         trans->block_rsv = NULL;
1944         if (trans->qgroup_reserved) {
1945                 btrfs_qgroup_free(root, trans->qgroup_reserved);
1946                 trans->qgroup_reserved = 0;
1947         }
1948         btrfs_warn(root->fs_info, "Skipping commit of aborted transaction.");
1949         if (current->journal_info == trans)
1950                 current->journal_info = NULL;
1951         cleanup_transaction(trans, root, ret);
1952
1953         return ret;
1954 }
1955
1956 /*
1957  * return < 0 if error
1958  * 0 if there are no more dead_roots at the time of call
1959  * 1 there are more to be processed, call me again
1960  *
1961  * The return value indicates there are certainly more snapshots to delete, but
1962  * if there comes a new one during processing, it may return 0. We don't mind,
1963  * because btrfs_commit_super will poke cleaner thread and it will process it a
1964  * few seconds later.
1965  */
1966 int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
1967 {
1968         int ret;
1969         struct btrfs_fs_info *fs_info = root->fs_info;
1970
1971         spin_lock(&fs_info->trans_lock);
1972         if (list_empty(&fs_info->dead_roots)) {
1973                 spin_unlock(&fs_info->trans_lock);
1974                 return 0;
1975         }
1976         root = list_first_entry(&fs_info->dead_roots,
1977                         struct btrfs_root, root_list);
1978         list_del_init(&root->root_list);
1979         spin_unlock(&fs_info->trans_lock);
1980
1981         pr_debug("btrfs: cleaner removing %llu\n", root->objectid);
1982
1983         btrfs_kill_all_delayed_nodes(root);
1984
1985         if (btrfs_header_backref_rev(root->node) <
1986                         BTRFS_MIXED_BACKREF_REV)
1987                 ret = btrfs_drop_snapshot(root, NULL, 0, 0);
1988         else
1989                 ret = btrfs_drop_snapshot(root, NULL, 1, 0);
1990         /*
1991          * If we encounter a transaction abort during snapshot cleaning, we
1992          * don't want to crash here
1993          */
1994         return (ret < 0) ? 0 : 1;
1995 }