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/sched.h>
  21 #include <linux/writeback.h>
  22 #include <linux/pagemap.h>
  23 #include "ctree.h"
  24 #include "disk-io.h"
  25 #include "transaction.h"
  26
  27 static int total_trans = 0;
  28 extern struct kmem_cache *btrfs_trans_handle_cachep;
  29 extern struct kmem_cache *btrfs_transaction_cachep;
  30
  31 static struct workqueue_struct *trans_wq;
  32
  33 #define BTRFS_ROOT_TRANS_TAG 0
  34 #define BTRFS_ROOT_DEFRAG_TAG 1
  35
  36 static void put_transaction(struct btrfs_transaction *transaction)
  37 {
  38         WARN_ON(transaction->use_count == 0);
  39         transaction->use_count--;
  40         if (transaction->use_count == 0) {
  41                 WARN_ON(total_trans == 0);
  42                 total_trans--;
  43                 list_del_init(&transaction->list);
  44                 memset(transaction, 0, sizeof(*transaction));
  45                 kmem_cache_free(btrfs_transaction_cachep, transaction);
  46         }
  47 }
  48
  49 static int join_transaction(struct btrfs_root *root)
  50 {
  51         struct btrfs_transaction *cur_trans;
  52         cur_trans = root->fs_info->running_transaction;
  53         if (!cur_trans) {
  54                 cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
  55                                              GFP_NOFS);
  56                 total_trans++;
  57                 BUG_ON(!cur_trans);
  58                 root->fs_info->generation++;
  59                 root->fs_info->running_transaction = cur_trans;
  60                 cur_trans->num_writers = 1;
  61                 cur_trans->num_joined = 0;
  62                 cur_trans->transid = root->fs_info->generation;
  63                 init_waitqueue_head(&cur_trans->writer_wait);
  64                 init_waitqueue_head(&cur_trans->commit_wait);
  65                 cur_trans->in_commit = 0;
  66                 cur_trans->use_count = 1;
  67                 cur_trans->commit_done = 0;
  68                 cur_trans->start_time = get_seconds();
  69                 list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
  70                 extent_map_tree_init(&cur_trans->dirty_pages,
  71                                      root->fs_info->btree_inode->i_mapping,
  72                                      GFP_NOFS);
  73         } else {
  74                 cur_trans->num_writers++;
  75                 cur_trans->num_joined++;
  76         }
  77
  78         return 0;
  79 }
  80
  81 static int record_root_in_trans(struct btrfs_root *root)
  82 {
  83         u64 running_trans_id = root->fs_info->running_transaction->transid;
  84         if (root->ref_cows && root->last_trans < running_trans_id) {
  85                 WARN_ON(root == root->fs_info->extent_root);
  86                 if (root->root_item.refs != 0) {
  87                         radix_tree_tag_set(&root->fs_info->fs_roots_radix,
  88                                    (unsigned long)root->root_key.objectid,
  89                                    BTRFS_ROOT_TRANS_TAG);
  90                         radix_tree_tag_set(&root->fs_info->fs_roots_radix,
  91                                    (unsigned long)root->root_key.objectid,
  92                                    BTRFS_ROOT_DEFRAG_TAG);
  93                         root->commit_root = root->node;
  94                         extent_buffer_get(root->node);
  95                 } else {
  96                         WARN_ON(1);
  97                 }
  98                 root->last_trans = running_trans_id;
  99         }
 100         return 0;
 101 }
 102
 103 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 104                                                    int num_blocks)
 105 {
 106         struct btrfs_trans_handle *h =
 107                 kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
 108         int ret;
 109
 110         mutex_lock(&root->fs_info->trans_mutex);
 111         ret = join_transaction(root);
 112         BUG_ON(ret);
 113
 114         record_root_in_trans(root);
 115         h->transid = root->fs_info->running_transaction->transid;
 116         h->transaction = root->fs_info->running_transaction;
 117         h->blocks_reserved = num_blocks;
 118         h->blocks_used = 0;
 119         h->block_group = NULL;
 120         h->alloc_exclude_nr = 0;
 121         h->alloc_exclude_start = 0;
 122         root->fs_info->running_transaction->use_count++;
 123         mutex_unlock(&root->fs_info->trans_mutex);
 124         return h;
 125 }
 126
 127 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 128                           struct btrfs_root *root)
 129 {
 130         struct btrfs_transaction *cur_trans;
 131
 132         mutex_lock(&root->fs_info->trans_mutex);
 133         cur_trans = root->fs_info->running_transaction;
 134         WARN_ON(cur_trans != trans->transaction);
 135         WARN_ON(cur_trans->num_writers < 1);
 136         cur_trans->num_writers--;
 137         if (waitqueue_active(&cur_trans->writer_wait))
 138                 wake_up(&cur_trans->writer_wait);
 139         put_transaction(cur_trans);
 140         mutex_unlock(&root->fs_info->trans_mutex);
 141         memset(trans, 0, sizeof(*trans));
 142         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 143         return 0;
 144 }
 145
 146
 147 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 148                                      struct btrfs_root *root)
 149 {
 150         int ret;
 151         int err;
 152         int werr = 0;
 153         struct extent_map_tree *dirty_pages;
 154         struct page *page;
 155         struct inode *btree_inode = root->fs_info->btree_inode;
 156         u64 start;
 157         u64 end;
 158         unsigned long index;
 159
 160         if (!trans || !trans->transaction) {
 161                 return filemap_write_and_wait(btree_inode->i_mapping);
 162         }
 163         dirty_pages = &trans->transaction->dirty_pages;
 164         while(1) {
 165                 ret = find_first_extent_bit(dirty_pages, 0, &start, &end,
 166                                             EXTENT_DIRTY);
 167                 if (ret)
 168                         break;
 169                 clear_extent_dirty(dirty_pages, start, end, GFP_NOFS);
 170                 while(start <= end) {
 171                         index = start >> PAGE_CACHE_SHIFT;
 172                         start = (index + 1) << PAGE_CACHE_SHIFT;
 173                         page = find_lock_page(btree_inode->i_mapping, index);
 174                         if (!page)
 175                                 continue;
 176                         if (PageWriteback(page)) {
 177                                 if (PageDirty(page))
 178                                         wait_on_page_writeback(page);
 179                                 else {
 180                                         unlock_page(page);
 181                                         page_cache_release(page);
 182                                         continue;
 183                                 }
 184                         }
 185                         err = write_one_page(page, 0);
 186                         if (err)
 187                                 werr = err;
 188                         page_cache_release(page);
 189                 }
 190         }
 191         err = filemap_fdatawait(btree_inode->i_mapping);
 192         if (err)
 193                 werr = err;
 194         return werr;
 195 }
 196
 197 int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
 198                             struct btrfs_root *root)
 199 {
 200         int ret;
 201         u64 old_extent_block;
 202         struct btrfs_fs_info *fs_info = root->fs_info;
 203         struct btrfs_root *tree_root = fs_info->tree_root;
 204         struct btrfs_root *extent_root = fs_info->extent_root;
 205
 206         btrfs_write_dirty_block_groups(trans, extent_root);
 207         while(1) {
 208                 old_extent_block = btrfs_root_blocknr(&extent_root->root_item);
 209                 if (old_extent_block ==
 210                     extent_buffer_blocknr(extent_root->node))
 211                         break;
 212                 btrfs_set_root_blocknr(&extent_root->root_item,
 213                                extent_buffer_blocknr(extent_root->node));
 214                 ret = btrfs_update_root(trans, tree_root,
 215                                         &extent_root->root_key,
 216                                         &extent_root->root_item);
 217                 BUG_ON(ret);
 218                 btrfs_write_dirty_block_groups(trans, extent_root);
 219         }
 220         return 0;
 221 }
 222
 223 static int wait_for_commit(struct btrfs_root *root,
 224                            struct btrfs_transaction *commit)
 225 {
 226         DEFINE_WAIT(wait);
 227         mutex_lock(&root->fs_info->trans_mutex);
 228         while(!commit->commit_done) {
 229                 prepare_to_wait(&commit->commit_wait, &wait,
 230                                 TASK_UNINTERRUPTIBLE);
 231                 if (commit->commit_done)
 232                         break;
 233                 mutex_unlock(&root->fs_info->trans_mutex);
 234                 schedule();
 235                 mutex_lock(&root->fs_info->trans_mutex);
 236         }
 237         mutex_unlock(&root->fs_info->trans_mutex);
 238         finish_wait(&commit->commit_wait, &wait);
 239         return 0;
 240 }
 241
 242 struct dirty_root {
 243         struct list_head list;
 244         struct btrfs_root *root;
 245         struct btrfs_root *latest_root;
 246 };
 247
 248 int btrfs_add_dead_root(struct btrfs_root *root,
 249                         struct btrfs_root *latest,
 250                         struct list_head *dead_list)
 251 {
 252         struct dirty_root *dirty;
 253
 254         dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 255         if (!dirty)
 256                 return -ENOMEM;
 257         dirty->root = root;
 258         dirty->latest_root = latest;
 259         list_add(&dirty->list, dead_list);
 260         return 0;
 261 }
 262
 263 static int add_dirty_roots(struct btrfs_trans_handle *trans,
 264                            struct radix_tree_root *radix,
 265                            struct list_head *list)
 266 {
 267         struct dirty_root *dirty;
 268         struct btrfs_root *gang[8];
 269         struct btrfs_root *root;
 270         int i;
 271         int ret;
 272         int err = 0;
 273         u32 refs;
 274
 275         while(1) {
 276                 ret = radix_tree_gang_lookup_tag(radix, (void **)gang, 0,
 277                                                  ARRAY_SIZE(gang),
 278                                                  BTRFS_ROOT_TRANS_TAG);
 279                 if (ret == 0)
 280                         break;
 281                 for (i = 0; i < ret; i++) {
 282                         root = gang[i];
 283                         radix_tree_tag_clear(radix,
 284                                      (unsigned long)root->root_key.objectid,
 285                                      BTRFS_ROOT_TRANS_TAG);
 286                         if (root->commit_root == root->node) {
 287                                 WARN_ON(extent_buffer_blocknr(root->node) !=
 288                                         btrfs_root_blocknr(&root->root_item));
 289                                 free_extent_buffer(root->commit_root);
 290                                 root->commit_root = NULL;
 291
 292                                 /* make sure to update the root on disk
 293                                  * so we get any updates to the block used
 294                                  * counts
 295                                  */
 296                                 err = btrfs_update_root(trans,
 297                                                 root->fs_info->tree_root,
 298                                                 &root->root_key,
 299                                                 &root->root_item);
 300                                 continue;
 301                         }
 302                         dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 303                         BUG_ON(!dirty);
 304                         dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
 305                         BUG_ON(!dirty->root);
 306
 307                         memset(&root->root_item.drop_progress, 0,
 308                                sizeof(struct btrfs_disk_key));
 309                         root->root_item.drop_level = 0;
 310
 311                         memcpy(dirty->root, root, sizeof(*root));
 312                         dirty->root->node = root->commit_root;
 313                         dirty->latest_root = root;
 314                         root->commit_root = NULL;
 315
 316                         root->root_key.offset = root->fs_info->generation;
 317                         btrfs_set_root_blocknr(&root->root_item,
 318                                        extent_buffer_blocknr(root->node));
 319                         err = btrfs_insert_root(trans, root->fs_info->tree_root,
 320                                                 &root->root_key,
 321                                                 &root->root_item);
 322                         if (err)
 323                                 break;
 324
 325                         refs = btrfs_root_refs(&dirty->root->root_item);
 326                         btrfs_set_root_refs(&dirty->root->root_item, refs - 1);
 327                         err = btrfs_update_root(trans, root->fs_info->tree_root,
 328                                                 &dirty->root->root_key,
 329                                                 &dirty->root->root_item);
 330
 331                         BUG_ON(err);
 332                         if (refs == 1) {
 333                                 list_add(&dirty->list, list);
 334                         } else {
 335                                 WARN_ON(1);
 336                                 kfree(dirty->root);
 337                                 kfree(dirty);
 338                         }
 339                 }
 340         }
 341         return err;
 342 }
 343
 344 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 345 {
 346         struct btrfs_fs_info *info = root->fs_info;
 347         int ret;
 348         struct btrfs_trans_handle *trans;
 349         unsigned long nr;
 350
 351         if (root->defrag_running)
 352                 return 0;
 353
 354         trans = btrfs_start_transaction(root, 1);
 355         while (0) {
 356                 root->defrag_running = 1;
 357                 ret = btrfs_defrag_leaves(trans, root, cacheonly);
 358                 nr = trans->blocks_used;
 359                 btrfs_end_transaction(trans, root);
 360                 mutex_unlock(&info->fs_mutex);
 361
 362                 btrfs_btree_balance_dirty(info->tree_root, nr);
 363                 cond_resched();
 364
 365                 mutex_lock(&info->fs_mutex);
 366                 trans = btrfs_start_transaction(root, 1);
 367                 if (ret != -EAGAIN)
 368                         break;
 369         }
 370         root->defrag_running = 0;
 371         radix_tree_tag_clear(&info->fs_roots_radix,
 372                      (unsigned long)root->root_key.objectid,
 373                      BTRFS_ROOT_DEFRAG_TAG);
 374         btrfs_end_transaction(trans, root);
 375         return 0;
 376 }
 377
 378 int btrfs_defrag_dirty_roots(struct btrfs_fs_info *info)
 379 {
 380         struct btrfs_root *gang[1];
 381         struct btrfs_root *root;
 382         int i;
 383         int ret;
 384         int err = 0;
 385         u64 last = 0;
 386
 387         while(1) {
 388                 ret = radix_tree_gang_lookup_tag(&info->fs_roots_radix,
 389                                                  (void **)gang, last,
 390                                                  ARRAY_SIZE(gang),
 391                                                  BTRFS_ROOT_DEFRAG_TAG);
 392                 if (ret == 0)
 393                         break;
 394                 for (i = 0; i < ret; i++) {
 395                         root = gang[i];
 396                         last = root->root_key.objectid + 1;
 397                         btrfs_defrag_root(root, 1);
 398                 }
 399         }
 400         // btrfs_defrag_root(info->extent_root, 1);
 401         return err;
 402 }
 403
 404 static int drop_dirty_roots(struct btrfs_root *tree_root,
 405                             struct list_head *list)
 406 {
 407         struct dirty_root *dirty;
 408         struct btrfs_trans_handle *trans;
 409         unsigned long nr;
 410         u64 num_blocks;
 411         u64 blocks_used;
 412         int ret = 0;
 413         int err;
 414
 415         while(!list_empty(list)) {
 416                 struct btrfs_root *root;
 417
 418                 mutex_lock(&tree_root->fs_info->fs_mutex);
 419                 dirty = list_entry(list->next, struct dirty_root, list);
 420                 list_del_init(&dirty->list);
 421
 422                 num_blocks = btrfs_root_used(&dirty->root->root_item);
 423                 root = dirty->latest_root;
 424
 425                 while(1) {
 426                         trans = btrfs_start_transaction(tree_root, 1);
 427                         ret = btrfs_drop_snapshot(trans, dirty->root);
 428                         if (ret != -EAGAIN) {
 429                                 break;
 430                         }
 431
 432                         err = btrfs_update_root(trans,
 433                                         tree_root,
 434                                         &dirty->root->root_key,
 435                                         &dirty->root->root_item);
 436                         if (err)
 437                                 ret = err;
 438                         nr = trans->blocks_used;
 439                         ret = btrfs_end_transaction(trans, tree_root);
 440                         BUG_ON(ret);
 441                         mutex_unlock(&tree_root->fs_info->fs_mutex);
 442                         btrfs_btree_balance_dirty(tree_root, nr);
 443                         schedule();
 444
 445                         mutex_lock(&tree_root->fs_info->fs_mutex);
 446                 }
 447                 BUG_ON(ret);
 448
 449                 num_blocks -= btrfs_root_used(&dirty->root->root_item);
 450                 blocks_used = btrfs_root_used(&root->root_item);
 451                 if (num_blocks) {
 452                         record_root_in_trans(root);
 453                         btrfs_set_root_used(&root->root_item,
 454                                                    blocks_used - num_blocks);
 455                 }
 456                 ret = btrfs_del_root(trans, tree_root, &dirty->root->root_key);
 457                 if (ret) {
 458                         BUG();
 459                         break;
 460                 }
 461                 nr = trans->blocks_used;
 462                 ret = btrfs_end_transaction(trans, tree_root);
 463                 BUG_ON(ret);
 464
 465                 free_extent_buffer(dirty->root->node);
 466                 kfree(dirty->root);
 467                 kfree(dirty);
 468                 mutex_unlock(&tree_root->fs_info->fs_mutex);
 469
 470                 btrfs_btree_balance_dirty(tree_root, nr);
 471                 schedule();
 472         }
 473         return ret;
 474 }
 475
 476 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 477                              struct btrfs_root *root)
 478 {
 479         unsigned long joined = 0;
 480         unsigned long timeout = 1;
 481         struct btrfs_transaction *cur_trans;
 482         struct btrfs_transaction *prev_trans = NULL;
 483         struct list_head dirty_fs_roots;
 484         struct radix_tree_root pinned_copy;
 485         DEFINE_WAIT(wait);
 486         int ret;
 487
 488         init_bit_radix(&pinned_copy);
 489         INIT_LIST_HEAD(&dirty_fs_roots);
 490
 491         mutex_lock(&root->fs_info->trans_mutex);
 492         if (trans->transaction->in_commit) {
 493                 cur_trans = trans->transaction;
 494                 trans->transaction->use_count++;
 495                 mutex_unlock(&root->fs_info->trans_mutex);
 496                 btrfs_end_transaction(trans, root);
 497
 498                 mutex_unlock(&root->fs_info->fs_mutex);
 499                 ret = wait_for_commit(root, cur_trans);
 500                 BUG_ON(ret);
 501
 502                 mutex_lock(&root->fs_info->trans_mutex);
 503                 put_transaction(cur_trans);
 504                 mutex_unlock(&root->fs_info->trans_mutex);
 505
 506                 mutex_lock(&root->fs_info->fs_mutex);
 507                 return 0;
 508         }
 509         trans->transaction->in_commit = 1;
 510         cur_trans = trans->transaction;
 511         if (cur_trans->list.prev != &root->fs_info->trans_list) {
 512                 prev_trans = list_entry(cur_trans->list.prev,
 513                                         struct btrfs_transaction, list);
 514                 if (!prev_trans->commit_done) {
 515                         prev_trans->use_count++;
 516                         mutex_unlock(&root->fs_info->fs_mutex);
 517                         mutex_unlock(&root->fs_info->trans_mutex);
 518
 519                         wait_for_commit(root, prev_trans);
 520
 521                         mutex_lock(&root->fs_info->fs_mutex);
 522                         mutex_lock(&root->fs_info->trans_mutex);
 523                         put_transaction(prev_trans);
 524                 }
 525         }
 526
 527         do {
 528                 joined = cur_trans->num_joined;
 529                 WARN_ON(cur_trans != trans->transaction);
 530                 prepare_to_wait(&cur_trans->writer_wait, &wait,
 531                                 TASK_UNINTERRUPTIBLE);
 532
 533                 if (cur_trans->num_writers > 1)
 534                         timeout = MAX_SCHEDULE_TIMEOUT;
 535                 else
 536                         timeout = 1;
 537
 538                 mutex_unlock(&root->fs_info->fs_mutex);
 539                 mutex_unlock(&root->fs_info->trans_mutex);
 540
 541                 schedule_timeout(timeout);
 542
 543                 mutex_lock(&root->fs_info->fs_mutex);
 544                 mutex_lock(&root->fs_info->trans_mutex);
 545                 finish_wait(&cur_trans->writer_wait, &wait);
 546         } while (cur_trans->num_writers > 1 ||
 547                  (cur_trans->num_joined != joined));
 548
 549         WARN_ON(cur_trans != trans->transaction);
 550         ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
 551                               &dirty_fs_roots);
 552         BUG_ON(ret);
 553
 554         ret = btrfs_commit_tree_roots(trans, root);
 555         BUG_ON(ret);
 556
 557         cur_trans = root->fs_info->running_transaction;
 558         root->fs_info->running_transaction = NULL;
 559         btrfs_set_super_generation(&root->fs_info->super_copy,
 560                                    cur_trans->transid);
 561         btrfs_set_super_root(&root->fs_info->super_copy,
 562                      extent_buffer_blocknr(root->fs_info->tree_root->node));
 563
 564         write_extent_buffer(root->fs_info->sb_buffer,
 565                             &root->fs_info->super_copy, 0,
 566                             sizeof(root->fs_info->super_copy));
 567
 568         btrfs_copy_pinned(root, &pinned_copy);
 569
 570         mutex_unlock(&root->fs_info->trans_mutex);
 571         mutex_unlock(&root->fs_info->fs_mutex);
 572         ret = btrfs_write_and_wait_transaction(trans, root);
 573         BUG_ON(ret);
 574         write_ctree_super(trans, root);
 575         mutex_lock(&root->fs_info->fs_mutex);
 576         btrfs_finish_extent_commit(trans, root, &pinned_copy);
 577         mutex_lock(&root->fs_info->trans_mutex);
 578         cur_trans->commit_done = 1;
 579         root->fs_info->last_trans_committed = cur_trans->transid;
 580         wake_up(&cur_trans->commit_wait);
 581         put_transaction(cur_trans);
 582         put_transaction(cur_trans);
 583
 584         if (root->fs_info->closing)
 585                 list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);
 586         else
 587                 list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);
 588
 589         mutex_unlock(&root->fs_info->trans_mutex);
 590         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 591
 592         if (root->fs_info->closing) {
 593                 mutex_unlock(&root->fs_info->fs_mutex);
 594                 drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
 595                 mutex_lock(&root->fs_info->fs_mutex);
 596         }
 597         return ret;
 598 }
 599
 600 int btrfs_clean_old_snapshots(struct btrfs_root *root)
 601 {
 602         struct list_head dirty_roots;
 603         INIT_LIST_HEAD(&dirty_roots);
 604
 605         mutex_lock(&root->fs_info->trans_mutex);
 606         list_splice_init(&root->fs_info->dead_roots, &dirty_roots);
 607         mutex_unlock(&root->fs_info->trans_mutex);
 608
 609         if (!list_empty(&dirty_roots)) {
 610                 drop_dirty_roots(root, &dirty_roots);
 611         }
 612         return 0;
 613 }
 614 void btrfs_transaction_cleaner(struct work_struct *work)
 615 {
 616         struct btrfs_fs_info *fs_info = container_of(work,
 617                                                      struct btrfs_fs_info,
 618                                                      trans_work.work);
 619
 620         struct btrfs_root *root = fs_info->tree_root;
 621         struct btrfs_transaction *cur;
 622         struct btrfs_trans_handle *trans;
 623         unsigned long now;
 624         unsigned long delay = HZ * 30;
 625         int ret;
 626
 627         mutex_lock(&root->fs_info->fs_mutex);
 628         mutex_lock(&root->fs_info->trans_mutex);
 629         cur = root->fs_info->running_transaction;
 630         if (!cur) {
 631                 mutex_unlock(&root->fs_info->trans_mutex);
 632                 goto out;
 633         }
 634         now = get_seconds();
 635         if (now < cur->start_time || now - cur->start_time < 30) {
 636                 mutex_unlock(&root->fs_info->trans_mutex);
 637                 delay = HZ * 5;
 638                 goto out;
 639         }
 640         mutex_unlock(&root->fs_info->trans_mutex);
 641         btrfs_defrag_dirty_roots(root->fs_info);
 642         trans = btrfs_start_transaction(root, 1);
 643         ret = btrfs_commit_transaction(trans, root);
 644 out:
 645         mutex_unlock(&root->fs_info->fs_mutex);
 646         btrfs_clean_old_snapshots(root);
 647         btrfs_transaction_queue_work(root, delay);
 648 }
 649
 650 void btrfs_transaction_queue_work(struct btrfs_root *root, int delay)
 651 {
 652         queue_delayed_work(trans_wq, &root->fs_info->trans_work, delay);
 653 }
 654
 655 void btrfs_transaction_flush_work(struct btrfs_root *root)
 656 {
 657         cancel_rearming_delayed_workqueue(trans_wq, &root->fs_info->trans_work);
 658         flush_workqueue(trans_wq);
 659 }
 660
 661 void __init btrfs_init_transaction_sys(void)
 662 {
 663         trans_wq = create_workqueue("btrfs");
 664 }
 665
 666 void __exit btrfs_exit_transaction_sys(void)
 667 {
 668         destroy_workqueue(trans_wq);
 669 }
 670