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_bytenr(&extent_root->root_item);
 209                 if (old_extent_block == extent_root->node->start)
 210                         break;
 211                 btrfs_set_root_bytenr(&extent_root->root_item,
 212                                       extent_root->node->start);
 213                 btrfs_set_root_level(&extent_root->root_item,
 214                                      btrfs_header_level(extent_root->node));
 215                 ret = btrfs_update_root(trans, tree_root,
 216                                         &extent_root->root_key,
 217                                         &extent_root->root_item);
 218                 BUG_ON(ret);
 219                 btrfs_write_dirty_block_groups(trans, extent_root);
 220         }
 221         return 0;
 222 }
 223
 224 static int wait_for_commit(struct btrfs_root *root,
 225                            struct btrfs_transaction *commit)
 226 {
 227         DEFINE_WAIT(wait);
 228         mutex_lock(&root->fs_info->trans_mutex);
 229         while(!commit->commit_done) {
 230                 prepare_to_wait(&commit->commit_wait, &wait,
 231                                 TASK_UNINTERRUPTIBLE);
 232                 if (commit->commit_done)
 233                         break;
 234                 mutex_unlock(&root->fs_info->trans_mutex);
 235                 schedule();
 236                 mutex_lock(&root->fs_info->trans_mutex);
 237         }
 238         mutex_unlock(&root->fs_info->trans_mutex);
 239         finish_wait(&commit->commit_wait, &wait);
 240         return 0;
 241 }
 242
 243 struct dirty_root {
 244         struct list_head list;
 245         struct btrfs_root *root;
 246         struct btrfs_root *latest_root;
 247 };
 248
 249 int btrfs_add_dead_root(struct btrfs_root *root,
 250                         struct btrfs_root *latest,
 251                         struct list_head *dead_list)
 252 {
 253         struct dirty_root *dirty;
 254
 255         dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 256         if (!dirty)
 257                 return -ENOMEM;
 258         dirty->root = root;
 259         dirty->latest_root = latest;
 260         list_add(&dirty->list, dead_list);
 261         return 0;
 262 }
 263
 264 static int add_dirty_roots(struct btrfs_trans_handle *trans,
 265                            struct radix_tree_root *radix,
 266                            struct list_head *list)
 267 {
 268         struct dirty_root *dirty;
 269         struct btrfs_root *gang[8];
 270         struct btrfs_root *root;
 271         int i;
 272         int ret;
 273         int err = 0;
 274         u32 refs;
 275
 276         while(1) {
 277                 ret = radix_tree_gang_lookup_tag(radix, (void **)gang, 0,
 278                                                  ARRAY_SIZE(gang),
 279                                                  BTRFS_ROOT_TRANS_TAG);
 280                 if (ret == 0)
 281                         break;
 282                 for (i = 0; i < ret; i++) {
 283                         root = gang[i];
 284                         radix_tree_tag_clear(radix,
 285                                      (unsigned long)root->root_key.objectid,
 286                                      BTRFS_ROOT_TRANS_TAG);
 287                         if (root->commit_root == root->node) {
 288                                 WARN_ON(root->node->start !=
 289                                         btrfs_root_bytenr(&root->root_item));
 290                                 free_extent_buffer(root->commit_root);
 291                                 root->commit_root = NULL;
 292
 293                                 /* make sure to update the root on disk
 294                                  * so we get any updates to the block used
 295                                  * counts
 296                                  */
 297                                 err = btrfs_update_root(trans,
 298                                                 root->fs_info->tree_root,
 299                                                 &root->root_key,
 300                                                 &root->root_item);
 301                                 continue;
 302                         }
 303                         dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 304                         BUG_ON(!dirty);
 305                         dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
 306                         BUG_ON(!dirty->root);
 307
 308                         memset(&root->root_item.drop_progress, 0,
 309                                sizeof(struct btrfs_disk_key));
 310                         root->root_item.drop_level = 0;
 311
 312                         memcpy(dirty->root, root, sizeof(*root));
 313                         dirty->root->node = root->commit_root;
 314                         dirty->latest_root = root;
 315                         root->commit_root = NULL;
 316
 317                         root->root_key.offset = root->fs_info->generation;
 318                         btrfs_set_root_bytenr(&root->root_item,
 319                                               root->node->start);
 320                         btrfs_set_root_level(&root->root_item,
 321                                              btrfs_header_level(root->node));
 322                         err = btrfs_insert_root(trans, root->fs_info->tree_root,
 323                                                 &root->root_key,
 324                                                 &root->root_item);
 325                         if (err)
 326                                 break;
 327
 328                         refs = btrfs_root_refs(&dirty->root->root_item);
 329                         btrfs_set_root_refs(&dirty->root->root_item, refs - 1);
 330                         err = btrfs_update_root(trans, root->fs_info->tree_root,
 331                                                 &dirty->root->root_key,
 332                                                 &dirty->root->root_item);
 333
 334                         BUG_ON(err);
 335                         if (refs == 1) {
 336                                 list_add(&dirty->list, list);
 337                         } else {
 338                                 WARN_ON(1);
 339                                 kfree(dirty->root);
 340                                 kfree(dirty);
 341                         }
 342                 }
 343         }
 344         return err;
 345 }
 346
 347 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 348 {
 349         struct btrfs_fs_info *info = root->fs_info;
 350         int ret;
 351         struct btrfs_trans_handle *trans;
 352         unsigned long nr;
 353
 354         if (root->defrag_running)
 355                 return 0;
 356
 357         trans = btrfs_start_transaction(root, 1);
 358         while (0) {
 359                 root->defrag_running = 1;
 360                 ret = btrfs_defrag_leaves(trans, root, cacheonly);
 361                 nr = trans->blocks_used;
 362                 btrfs_end_transaction(trans, root);
 363                 mutex_unlock(&info->fs_mutex);
 364
 365                 btrfs_btree_balance_dirty(info->tree_root, nr);
 366                 cond_resched();
 367
 368                 mutex_lock(&info->fs_mutex);
 369                 trans = btrfs_start_transaction(root, 1);
 370                 if (ret != -EAGAIN)
 371                         break;
 372         }
 373         root->defrag_running = 0;
 374         radix_tree_tag_clear(&info->fs_roots_radix,
 375                      (unsigned long)root->root_key.objectid,
 376                      BTRFS_ROOT_DEFRAG_TAG);
 377         btrfs_end_transaction(trans, root);
 378         return 0;
 379 }
 380
 381 int btrfs_defrag_dirty_roots(struct btrfs_fs_info *info)
 382 {
 383         struct btrfs_root *gang[1];
 384         struct btrfs_root *root;
 385         int i;
 386         int ret;
 387         int err = 0;
 388         u64 last = 0;
 389
 390         while(1) {
 391                 ret = radix_tree_gang_lookup_tag(&info->fs_roots_radix,
 392                                                  (void **)gang, last,
 393                                                  ARRAY_SIZE(gang),
 394                                                  BTRFS_ROOT_DEFRAG_TAG);
 395                 if (ret == 0)
 396                         break;
 397                 for (i = 0; i < ret; i++) {
 398                         root = gang[i];
 399                         last = root->root_key.objectid + 1;
 400                         btrfs_defrag_root(root, 1);
 401                 }
 402         }
 403         // btrfs_defrag_root(info->extent_root, 1);
 404         return err;
 405 }
 406
 407 static int drop_dirty_roots(struct btrfs_root *tree_root,
 408                             struct list_head *list)
 409 {
 410         struct dirty_root *dirty;
 411         struct btrfs_trans_handle *trans;
 412         unsigned long nr;
 413         u64 num_bytes;
 414         u64 bytes_used;
 415         int ret = 0;
 416         int err;
 417
 418         while(!list_empty(list)) {
 419                 struct btrfs_root *root;
 420
 421                 mutex_lock(&tree_root->fs_info->fs_mutex);
 422                 dirty = list_entry(list->next, struct dirty_root, list);
 423                 list_del_init(&dirty->list);
 424
 425                 num_bytes = btrfs_root_used(&dirty->root->root_item);
 426                 root = dirty->latest_root;
 427
 428                 while(1) {
 429                         trans = btrfs_start_transaction(tree_root, 1);
 430                         ret = btrfs_drop_snapshot(trans, dirty->root);
 431                         if (ret != -EAGAIN) {
 432                                 break;
 433                         }
 434
 435                         err = btrfs_update_root(trans,
 436                                         tree_root,
 437                                         &dirty->root->root_key,
 438                                         &dirty->root->root_item);
 439                         if (err)
 440                                 ret = err;
 441                         nr = trans->blocks_used;
 442                         ret = btrfs_end_transaction(trans, tree_root);
 443                         BUG_ON(ret);
 444                         mutex_unlock(&tree_root->fs_info->fs_mutex);
 445                         btrfs_btree_balance_dirty(tree_root, nr);
 446                         schedule();
 447
 448                         mutex_lock(&tree_root->fs_info->fs_mutex);
 449                 }
 450                 BUG_ON(ret);
 451
 452                 num_bytes -= btrfs_root_used(&dirty->root->root_item);
 453                 bytes_used = btrfs_root_used(&root->root_item);
 454                 if (num_bytes) {
 455                         record_root_in_trans(root);
 456                         btrfs_set_root_used(&root->root_item,
 457                                             bytes_used - num_bytes);
 458                 }
 459                 ret = btrfs_del_root(trans, tree_root, &dirty->root->root_key);
 460                 if (ret) {
 461                         BUG();
 462                         break;
 463                 }
 464                 nr = trans->blocks_used;
 465                 ret = btrfs_end_transaction(trans, tree_root);
 466                 BUG_ON(ret);
 467
 468                 free_extent_buffer(dirty->root->node);
 469                 kfree(dirty->root);
 470                 kfree(dirty);
 471                 mutex_unlock(&tree_root->fs_info->fs_mutex);
 472
 473                 btrfs_btree_balance_dirty(tree_root, nr);
 474                 schedule();
 475         }
 476         return ret;
 477 }
 478
 479 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 480                              struct btrfs_root *root)
 481 {
 482         unsigned long joined = 0;
 483         unsigned long timeout = 1;
 484         struct btrfs_transaction *cur_trans;
 485         struct btrfs_transaction *prev_trans = NULL;
 486         struct list_head dirty_fs_roots;
 487         struct extent_map_tree pinned_copy;
 488         DEFINE_WAIT(wait);
 489         int ret;
 490
 491         extent_map_tree_init(&pinned_copy,
 492                              root->fs_info->btree_inode->i_mapping, GFP_NOFS);
 493         INIT_LIST_HEAD(&dirty_fs_roots);
 494
 495         mutex_lock(&root->fs_info->trans_mutex);
 496         if (trans->transaction->in_commit) {
 497                 cur_trans = trans->transaction;
 498                 trans->transaction->use_count++;
 499                 mutex_unlock(&root->fs_info->trans_mutex);
 500                 btrfs_end_transaction(trans, root);
 501
 502                 mutex_unlock(&root->fs_info->fs_mutex);
 503                 ret = wait_for_commit(root, cur_trans);
 504                 BUG_ON(ret);
 505
 506                 mutex_lock(&root->fs_info->trans_mutex);
 507                 put_transaction(cur_trans);
 508                 mutex_unlock(&root->fs_info->trans_mutex);
 509
 510                 mutex_lock(&root->fs_info->fs_mutex);
 511                 return 0;
 512         }
 513         trans->transaction->in_commit = 1;
 514         cur_trans = trans->transaction;
 515         if (cur_trans->list.prev != &root->fs_info->trans_list) {
 516                 prev_trans = list_entry(cur_trans->list.prev,
 517                                         struct btrfs_transaction, list);
 518                 if (!prev_trans->commit_done) {
 519                         prev_trans->use_count++;
 520                         mutex_unlock(&root->fs_info->fs_mutex);
 521                         mutex_unlock(&root->fs_info->trans_mutex);
 522
 523                         wait_for_commit(root, prev_trans);
 524
 525                         mutex_lock(&root->fs_info->fs_mutex);
 526                         mutex_lock(&root->fs_info->trans_mutex);
 527                         put_transaction(prev_trans);
 528                 }
 529         }
 530
 531         do {
 532                 joined = cur_trans->num_joined;
 533                 WARN_ON(cur_trans != trans->transaction);
 534                 prepare_to_wait(&cur_trans->writer_wait, &wait,
 535                                 TASK_UNINTERRUPTIBLE);
 536
 537                 if (cur_trans->num_writers > 1)
 538                         timeout = MAX_SCHEDULE_TIMEOUT;
 539                 else
 540                         timeout = 1;
 541
 542                 mutex_unlock(&root->fs_info->fs_mutex);
 543                 mutex_unlock(&root->fs_info->trans_mutex);
 544
 545                 schedule_timeout(timeout);
 546
 547                 mutex_lock(&root->fs_info->fs_mutex);
 548                 mutex_lock(&root->fs_info->trans_mutex);
 549                 finish_wait(&cur_trans->writer_wait, &wait);
 550         } while (cur_trans->num_writers > 1 ||
 551                  (cur_trans->num_joined != joined));
 552
 553         WARN_ON(cur_trans != trans->transaction);
 554         ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
 555                               &dirty_fs_roots);
 556         BUG_ON(ret);
 557
 558         ret = btrfs_commit_tree_roots(trans, root);
 559         BUG_ON(ret);
 560
 561         cur_trans = root->fs_info->running_transaction;
 562         root->fs_info->running_transaction = NULL;
 563         btrfs_set_super_generation(&root->fs_info->super_copy,
 564                                    cur_trans->transid);
 565         btrfs_set_super_root(&root->fs_info->super_copy,
 566                              root->fs_info->tree_root->node->start);
 567         btrfs_set_super_root_level(&root->fs_info->super_copy,
 568                            btrfs_header_level(root->fs_info->tree_root->node));
 569
 570         write_extent_buffer(root->fs_info->sb_buffer,
 571                             &root->fs_info->super_copy, 0,
 572                             sizeof(root->fs_info->super_copy));
 573
 574         btrfs_copy_pinned(root, &pinned_copy);
 575
 576         mutex_unlock(&root->fs_info->trans_mutex);
 577         mutex_unlock(&root->fs_info->fs_mutex);
 578         ret = btrfs_write_and_wait_transaction(trans, root);
 579         BUG_ON(ret);
 580         write_ctree_super(trans, root);
 581         mutex_lock(&root->fs_info->fs_mutex);
 582         btrfs_finish_extent_commit(trans, root, &pinned_copy);
 583         mutex_lock(&root->fs_info->trans_mutex);
 584         cur_trans->commit_done = 1;
 585         root->fs_info->last_trans_committed = cur_trans->transid;
 586         wake_up(&cur_trans->commit_wait);
 587         put_transaction(cur_trans);
 588         put_transaction(cur_trans);
 589
 590         if (root->fs_info->closing)
 591                 list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);
 592         else
 593                 list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);
 594
 595         mutex_unlock(&root->fs_info->trans_mutex);
 596         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 597
 598         if (root->fs_info->closing) {
 599                 mutex_unlock(&root->fs_info->fs_mutex);
 600                 drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
 601                 mutex_lock(&root->fs_info->fs_mutex);
 602         }
 603         return ret;
 604 }
 605
 606 int btrfs_clean_old_snapshots(struct btrfs_root *root)
 607 {
 608         struct list_head dirty_roots;
 609         INIT_LIST_HEAD(&dirty_roots);
 610
 611         mutex_lock(&root->fs_info->trans_mutex);
 612         list_splice_init(&root->fs_info->dead_roots, &dirty_roots);
 613         mutex_unlock(&root->fs_info->trans_mutex);
 614
 615         if (!list_empty(&dirty_roots)) {
 616                 drop_dirty_roots(root, &dirty_roots);
 617         }
 618         return 0;
 619 }
 620 void btrfs_transaction_cleaner(struct work_struct *work)
 621 {
 622         struct btrfs_fs_info *fs_info = container_of(work,
 623                                                      struct btrfs_fs_info,
 624                                                      trans_work.work);
 625
 626         struct btrfs_root *root = fs_info->tree_root;
 627         struct btrfs_transaction *cur;
 628         struct btrfs_trans_handle *trans;
 629         unsigned long now;
 630         unsigned long delay = HZ * 30;
 631         int ret;
 632
 633         mutex_lock(&root->fs_info->fs_mutex);
 634         mutex_lock(&root->fs_info->trans_mutex);
 635         cur = root->fs_info->running_transaction;
 636         if (!cur) {
 637                 mutex_unlock(&root->fs_info->trans_mutex);
 638                 goto out;
 639         }
 640         now = get_seconds();
 641         if (now < cur->start_time || now - cur->start_time < 30) {
 642                 mutex_unlock(&root->fs_info->trans_mutex);
 643                 delay = HZ * 5;
 644                 goto out;
 645         }
 646         mutex_unlock(&root->fs_info->trans_mutex);
 647         btrfs_defrag_dirty_roots(root->fs_info);
 648         trans = btrfs_start_transaction(root, 1);
 649         ret = btrfs_commit_transaction(trans, root);
 650 out:
 651         mutex_unlock(&root->fs_info->fs_mutex);
 652         btrfs_clean_old_snapshots(root);
 653         btrfs_transaction_queue_work(root, delay);
 654 }
 655
 656 void btrfs_transaction_queue_work(struct btrfs_root *root, int delay)
 657 {
 658         queue_delayed_work(trans_wq, &root->fs_info->trans_work, delay);
 659 }
 660
 661 void btrfs_transaction_flush_work(struct btrfs_root *root)
 662 {
 663         cancel_rearming_delayed_workqueue(trans_wq, &root->fs_info->trans_work);
 664         flush_workqueue(trans_wq);
 665 }
 666
 667 void __init btrfs_init_transaction_sys(void)
 668 {
 669         trans_wq = create_workqueue("btrfs");
 670 }
 671
 672 void __exit btrfs_exit_transaction_sys(void)
 673 {
 674         destroy_workqueue(trans_wq);
 675 }
 676