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 "ctree.h"
  26 #include "disk-io.h"
  27 #include "transaction.h"
  28 #include "locking.h"
  29 #include "tree-log.h"
  30 #include "inode-map.h"
  31
  32 #define BTRFS_ROOT_TRANS_TAG 0
  33
  34 static noinline void put_transaction(struct btrfs_transaction *transaction)
  35 {
  36         WARN_ON(atomic_read(&transaction->use_count) == 0);
  37         if (atomic_dec_and_test(&transaction->use_count)) {
  38                 memset(transaction, 0, sizeof(*transaction));
  39                 kmem_cache_free(btrfs_transaction_cachep, transaction);
  40         }
  41 }
  42
  43 static noinline void switch_commit_root(struct btrfs_root *root)
  44 {
  45         free_extent_buffer(root->commit_root);
  46         root->commit_root = btrfs_root_node(root);
  47 }
  48
  49 /*
  50  * either allocate a new transaction or hop into the existing one
  51  */
  52 static noinline int join_transaction(struct btrfs_root *root)
  53 {
  54         struct btrfs_transaction *cur_trans;
  55         cur_trans = root->fs_info->running_transaction;
  56         if (!cur_trans) {
  57                 cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
  58                                              GFP_NOFS);
  59                 if (!cur_trans)
  60                         return -ENOMEM;
  61                 root->fs_info->generation++;
  62                 atomic_set(&cur_trans->num_writers, 1);
  63                 cur_trans->num_joined = 0;
  64                 cur_trans->transid = root->fs_info->generation;
  65                 init_waitqueue_head(&cur_trans->writer_wait);
  66                 init_waitqueue_head(&cur_trans->commit_wait);
  67                 cur_trans->in_commit = 0;
  68                 cur_trans->blocked = 0;
  69                 atomic_set(&cur_trans->use_count, 1);
  70                 cur_trans->commit_done = 0;
  71                 cur_trans->start_time = get_seconds();
  72
  73                 cur_trans->delayed_refs.root = RB_ROOT;
  74                 cur_trans->delayed_refs.num_entries = 0;
  75                 cur_trans->delayed_refs.num_heads_ready = 0;
  76                 cur_trans->delayed_refs.num_heads = 0;
  77                 cur_trans->delayed_refs.flushing = 0;
  78                 cur_trans->delayed_refs.run_delayed_start = 0;
  79                 spin_lock_init(&cur_trans->delayed_refs.lock);
  80
  81                 INIT_LIST_HEAD(&cur_trans->pending_snapshots);
  82                 list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
  83                 extent_io_tree_init(&cur_trans->dirty_pages,
  84                                      root->fs_info->btree_inode->i_mapping,
  85                                      GFP_NOFS);
  86                 spin_lock(&root->fs_info->new_trans_lock);
  87                 root->fs_info->running_transaction = cur_trans;
  88                 spin_unlock(&root->fs_info->new_trans_lock);
  89         } else {
  90                 atomic_inc(&cur_trans->num_writers);
  91                 cur_trans->num_joined++;
  92         }
  93
  94         return 0;
  95 }
  96
  97 /*
  98  * this does all the record keeping required to make sure that a reference
  99  * counted root is properly recorded in a given transaction.  This is required
 100  * to make sure the old root from before we joined the transaction is deleted
 101  * when the transaction commits
 102  */
 103 static noinline int record_root_in_trans(struct btrfs_trans_handle *trans,
 104                                          struct btrfs_root *root)
 105 {
 106         if (root->ref_cows && root->last_trans < trans->transid) {
 107                 WARN_ON(root == root->fs_info->extent_root);
 108                 WARN_ON(root->commit_root != root->node);
 109
 110                 radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 111                            (unsigned long)root->root_key.objectid,
 112                            BTRFS_ROOT_TRANS_TAG);
 113                 root->last_trans = trans->transid;
 114                 btrfs_init_reloc_root(trans, root);
 115         }
 116         return 0;
 117 }
 118
 119 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
 120                                struct btrfs_root *root)
 121 {
 122         if (!root->ref_cows)
 123                 return 0;
 124
 125         mutex_lock(&root->fs_info->trans_mutex);
 126         if (root->last_trans == trans->transid) {
 127                 mutex_unlock(&root->fs_info->trans_mutex);
 128                 return 0;
 129         }
 130
 131         record_root_in_trans(trans, root);
 132         mutex_unlock(&root->fs_info->trans_mutex);
 133         return 0;
 134 }
 135
 136 /* wait for commit against the current transaction to become unblocked
 137  * when this is done, it is safe to start a new transaction, but the current
 138  * transaction might not be fully on disk.
 139  */
 140 static void wait_current_trans(struct btrfs_root *root)
 141 {
 142         struct btrfs_transaction *cur_trans;
 143
 144         cur_trans = root->fs_info->running_transaction;
 145         if (cur_trans && cur_trans->blocked) {
 146                 DEFINE_WAIT(wait);
 147                 atomic_inc(&cur_trans->use_count);
 148                 while (1) {
 149                         prepare_to_wait(&root->fs_info->transaction_wait, &wait,
 150                                         TASK_UNINTERRUPTIBLE);
 151                         if (!cur_trans->blocked)
 152                                 break;
 153                         mutex_unlock(&root->fs_info->trans_mutex);
 154                         schedule();
 155                         mutex_lock(&root->fs_info->trans_mutex);
 156                 }
 157                 finish_wait(&root->fs_info->transaction_wait, &wait);
 158                 put_transaction(cur_trans);
 159         }
 160 }
 161
 162 enum btrfs_trans_type {
 163         TRANS_START,
 164         TRANS_JOIN,
 165         TRANS_USERSPACE,
 166         TRANS_JOIN_NOLOCK,
 167 };
 168
 169 static int may_wait_transaction(struct btrfs_root *root, int type)
 170 {
 171         if (!root->fs_info->log_root_recovering &&
 172             ((type == TRANS_START && !root->fs_info->open_ioctl_trans) ||
 173              type == TRANS_USERSPACE))
 174                 return 1;
 175         return 0;
 176 }
 177
 178 static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
 179                                                     u64 num_items, int type)
 180 {
 181         struct btrfs_trans_handle *h;
 182         struct btrfs_transaction *cur_trans;
 183         int retries = 0;
 184         int ret;
 185
 186         if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
 187                 return ERR_PTR(-EROFS);
 188 again:
 189         h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
 190         if (!h)
 191                 return ERR_PTR(-ENOMEM);
 192
 193         if (type != TRANS_JOIN_NOLOCK)
 194                 mutex_lock(&root->fs_info->trans_mutex);
 195         if (may_wait_transaction(root, type))
 196                 wait_current_trans(root);
 197
 198         ret = join_transaction(root);
 199         if (ret < 0) {
 200                 kmem_cache_free(btrfs_trans_handle_cachep, h);
 201                 if (type != TRANS_JOIN_NOLOCK)
 202                         mutex_unlock(&root->fs_info->trans_mutex);
 203                 return ERR_PTR(ret);
 204         }
 205
 206         cur_trans = root->fs_info->running_transaction;
 207         atomic_inc(&cur_trans->use_count);
 208         if (type != TRANS_JOIN_NOLOCK)
 209                 mutex_unlock(&root->fs_info->trans_mutex);
 210
 211         h->transid = cur_trans->transid;
 212         h->transaction = cur_trans;
 213         h->blocks_used = 0;
 214         h->block_group = 0;
 215         h->bytes_reserved = 0;
 216         h->delayed_ref_updates = 0;
 217         h->block_rsv = NULL;
 218
 219         smp_mb();
 220         if (cur_trans->blocked && may_wait_transaction(root, type)) {
 221                 btrfs_commit_transaction(h, root);
 222                 goto again;
 223         }
 224
 225         if (num_items > 0) {
 226                 ret = btrfs_trans_reserve_metadata(h, root, num_items);
 227                 if (ret == -EAGAIN && !retries) {
 228                         retries++;
 229                         btrfs_commit_transaction(h, root);
 230                         goto again;
 231                 } else if (ret == -EAGAIN) {
 232                         /*
 233                          * We have already retried and got EAGAIN, so really we
 234                          * don't have space, so set ret to -ENOSPC.
 235                          */
 236                         ret = -ENOSPC;
 237                 }
 238
 239                 if (ret < 0) {
 240                         btrfs_end_transaction(h, root);
 241                         return ERR_PTR(ret);
 242                 }
 243         }
 244
 245         if (type != TRANS_JOIN_NOLOCK)
 246                 mutex_lock(&root->fs_info->trans_mutex);
 247         record_root_in_trans(h, root);
 248         if (type != TRANS_JOIN_NOLOCK)
 249                 mutex_unlock(&root->fs_info->trans_mutex);
 250
 251         if (!current->journal_info && type != TRANS_USERSPACE)
 252                 current->journal_info = h;
 253         return h;
 254 }
 255
 256 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 257                                                    int num_items)
 258 {
 259         return start_transaction(root, num_items, TRANS_START);
 260 }
 261 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
 262                                                    int num_blocks)
 263 {
 264         return start_transaction(root, 0, TRANS_JOIN);
 265 }
 266
 267 struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root,
 268                                                           int num_blocks)
 269 {
 270         return start_transaction(root, 0, TRANS_JOIN_NOLOCK);
 271 }
 272
 273 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
 274                                                          int num_blocks)
 275 {
 276         return start_transaction(r, 0, TRANS_USERSPACE);
 277 }
 278
 279 /* wait for a transaction commit to be fully complete */
 280 static noinline int wait_for_commit(struct btrfs_root *root,
 281                                     struct btrfs_transaction *commit)
 282 {
 283         DEFINE_WAIT(wait);
 284         mutex_lock(&root->fs_info->trans_mutex);
 285         while (!commit->commit_done) {
 286                 prepare_to_wait(&commit->commit_wait, &wait,
 287                                 TASK_UNINTERRUPTIBLE);
 288                 if (commit->commit_done)
 289                         break;
 290                 mutex_unlock(&root->fs_info->trans_mutex);
 291                 schedule();
 292                 mutex_lock(&root->fs_info->trans_mutex);
 293         }
 294         mutex_unlock(&root->fs_info->trans_mutex);
 295         finish_wait(&commit->commit_wait, &wait);
 296         return 0;
 297 }
 298
 299 int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
 300 {
 301         struct btrfs_transaction *cur_trans = NULL, *t;
 302         int ret;
 303
 304         mutex_lock(&root->fs_info->trans_mutex);
 305
 306         ret = 0;
 307         if (transid) {
 308                 if (transid <= root->fs_info->last_trans_committed)
 309                         goto out_unlock;
 310
 311                 /* find specified transaction */
 312                 list_for_each_entry(t, &root->fs_info->trans_list, list) {
 313                         if (t->transid == transid) {
 314                                 cur_trans = t;
 315                                 break;
 316                         }
 317                         if (t->transid > transid)
 318                                 break;
 319                 }
 320                 ret = -EINVAL;
 321                 if (!cur_trans)
 322                         goto out_unlock;  /* bad transid */
 323         } else {
 324                 /* find newest transaction that is committing | committed */
 325                 list_for_each_entry_reverse(t, &root->fs_info->trans_list,
 326                                             list) {
 327                         if (t->in_commit) {
 328                                 if (t->commit_done)
 329                                         goto out_unlock;
 330                                 cur_trans = t;
 331                                 break;
 332                         }
 333                 }
 334                 if (!cur_trans)
 335                         goto out_unlock;  /* nothing committing|committed */
 336         }
 337
 338         atomic_inc(&cur_trans->use_count);
 339         mutex_unlock(&root->fs_info->trans_mutex);
 340
 341         wait_for_commit(root, cur_trans);
 342
 343         mutex_lock(&root->fs_info->trans_mutex);
 344         put_transaction(cur_trans);
 345         ret = 0;
 346 out_unlock:
 347         mutex_unlock(&root->fs_info->trans_mutex);
 348         return ret;
 349 }
 350
 351 #if 0
 352 /*
 353  * rate limit against the drop_snapshot code.  This helps to slow down new
 354  * operations if the drop_snapshot code isn't able to keep up.
 355  */
 356 static void throttle_on_drops(struct btrfs_root *root)
 357 {
 358         struct btrfs_fs_info *info = root->fs_info;
 359         int harder_count = 0;
 360
 361 harder:
 362         if (atomic_read(&info->throttles)) {
 363                 DEFINE_WAIT(wait);
 364                 int thr;
 365                 thr = atomic_read(&info->throttle_gen);
 366
 367                 do {
 368                         prepare_to_wait(&info->transaction_throttle,
 369                                         &wait, TASK_UNINTERRUPTIBLE);
 370                         if (!atomic_read(&info->throttles)) {
 371                                 finish_wait(&info->transaction_throttle, &wait);
 372                                 break;
 373                         }
 374                         schedule();
 375                         finish_wait(&info->transaction_throttle, &wait);
 376                 } while (thr == atomic_read(&info->throttle_gen));
 377                 harder_count++;
 378
 379                 if (root->fs_info->total_ref_cache_size > 1 * 1024 * 1024 &&
 380                     harder_count < 2)
 381                         goto harder;
 382
 383                 if (root->fs_info->total_ref_cache_size > 5 * 1024 * 1024 &&
 384                     harder_count < 10)
 385                         goto harder;
 386
 387                 if (root->fs_info->total_ref_cache_size > 10 * 1024 * 1024 &&
 388                     harder_count < 20)
 389                         goto harder;
 390         }
 391 }
 392 #endif
 393
 394 void btrfs_throttle(struct btrfs_root *root)
 395 {
 396         mutex_lock(&root->fs_info->trans_mutex);
 397         if (!root->fs_info->open_ioctl_trans)
 398                 wait_current_trans(root);
 399         mutex_unlock(&root->fs_info->trans_mutex);
 400 }
 401
 402 static int should_end_transaction(struct btrfs_trans_handle *trans,
 403                                   struct btrfs_root *root)
 404 {
 405         int ret;
 406         ret = btrfs_block_rsv_check(trans, root,
 407                                     &root->fs_info->global_block_rsv, 0, 5);
 408         return ret ? 1 : 0;
 409 }
 410
 411 int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
 412                                  struct btrfs_root *root)
 413 {
 414         struct btrfs_transaction *cur_trans = trans->transaction;
 415         int updates;
 416
 417         if (cur_trans->blocked || cur_trans->delayed_refs.flushing)
 418                 return 1;
 419
 420         updates = trans->delayed_ref_updates;
 421         trans->delayed_ref_updates = 0;
 422         if (updates)
 423                 btrfs_run_delayed_refs(trans, root, updates);
 424
 425         return should_end_transaction(trans, root);
 426 }
 427
 428 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 429                           struct btrfs_root *root, int throttle, int lock)
 430 {
 431         struct btrfs_transaction *cur_trans = trans->transaction;
 432         struct btrfs_fs_info *info = root->fs_info;
 433         int count = 0;
 434
 435         while (count < 4) {
 436                 unsigned long cur = trans->delayed_ref_updates;
 437                 trans->delayed_ref_updates = 0;
 438                 if (cur &&
 439                     trans->transaction->delayed_refs.num_heads_ready > 64) {
 440                         trans->delayed_ref_updates = 0;
 441
 442                         /*
 443                          * do a full flush if the transaction is trying
 444                          * to close
 445                          */
 446                         if (trans->transaction->delayed_refs.flushing)
 447                                 cur = 0;
 448                         btrfs_run_delayed_refs(trans, root, cur);
 449                 } else {
 450                         break;
 451                 }
 452                 count++;
 453         }
 454
 455         btrfs_trans_release_metadata(trans, root);
 456
 457         if (lock && !root->fs_info->open_ioctl_trans &&
 458             should_end_transaction(trans, root))
 459                 trans->transaction->blocked = 1;
 460
 461         if (lock && cur_trans->blocked && !cur_trans->in_commit) {
 462                 if (throttle)
 463                         return btrfs_commit_transaction(trans, root);
 464                 else
 465                         wake_up_process(info->transaction_kthread);
 466         }
 467
 468         WARN_ON(cur_trans != info->running_transaction);
 469         WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
 470         atomic_dec(&cur_trans->num_writers);
 471
 472         smp_mb();
 473         if (waitqueue_active(&cur_trans->writer_wait))
 474                 wake_up(&cur_trans->writer_wait);
 475         put_transaction(cur_trans);
 476
 477         if (current->journal_info == trans)
 478                 current->journal_info = NULL;
 479         memset(trans, 0, sizeof(*trans));
 480         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 481
 482         if (throttle)
 483                 btrfs_run_delayed_iputs(root);
 484
 485         return 0;
 486 }
 487
 488 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 489                           struct btrfs_root *root)
 490 {
 491         return __btrfs_end_transaction(trans, root, 0, 1);
 492 }
 493
 494 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
 495                                    struct btrfs_root *root)
 496 {
 497         return __btrfs_end_transaction(trans, root, 1, 1);
 498 }
 499
 500 int btrfs_end_transaction_nolock(struct btrfs_trans_handle *trans,
 501                                  struct btrfs_root *root)
 502 {
 503         return __btrfs_end_transaction(trans, root, 0, 0);
 504 }
 505
 506 /*
 507  * when btree blocks are allocated, they have some corresponding bits set for
 508  * them in one of two extent_io trees.  This is used to make sure all of
 509  * those extents are sent to disk but does not wait on them
 510  */
 511 int btrfs_write_marked_extents(struct btrfs_root *root,
 512                                struct extent_io_tree *dirty_pages, int mark)
 513 {
 514         int ret;
 515         int err = 0;
 516         int werr = 0;
 517         struct page *page;
 518         struct inode *btree_inode = root->fs_info->btree_inode;
 519         u64 start = 0;
 520         u64 end;
 521         unsigned long index;
 522
 523         while (1) {
 524                 ret = find_first_extent_bit(dirty_pages, start, &start, &end,
 525                                             mark);
 526                 if (ret)
 527                         break;
 528                 while (start <= end) {
 529                         cond_resched();
 530
 531                         index = start >> PAGE_CACHE_SHIFT;
 532                         start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
 533                         page = find_get_page(btree_inode->i_mapping, index);
 534                         if (!page)
 535                                 continue;
 536
 537                         btree_lock_page_hook(page);
 538                         if (!page->mapping) {
 539                                 unlock_page(page);
 540                                 page_cache_release(page);
 541                                 continue;
 542                         }
 543
 544                         if (PageWriteback(page)) {
 545                                 if (PageDirty(page))
 546                                         wait_on_page_writeback(page);
 547                                 else {
 548                                         unlock_page(page);
 549                                         page_cache_release(page);
 550                                         continue;
 551                                 }
 552                         }
 553                         err = write_one_page(page, 0);
 554                         if (err)
 555                                 werr = err;
 556                         page_cache_release(page);
 557                 }
 558         }
 559         if (err)
 560                 werr = err;
 561         return werr;
 562 }
 563
 564 /*
 565  * when btree blocks are allocated, they have some corresponding bits set for
 566  * them in one of two extent_io trees.  This is used to make sure all of
 567  * those extents are on disk for transaction or log commit.  We wait
 568  * on all the pages and clear them from the dirty pages state tree
 569  */
 570 int btrfs_wait_marked_extents(struct btrfs_root *root,
 571                               struct extent_io_tree *dirty_pages, int mark)
 572 {
 573         int ret;
 574         int err = 0;
 575         int werr = 0;
 576         struct page *page;
 577         struct inode *btree_inode = root->fs_info->btree_inode;
 578         u64 start = 0;
 579         u64 end;
 580         unsigned long index;
 581
 582         while (1) {
 583                 ret = find_first_extent_bit(dirty_pages, start, &start, &end,
 584                                             mark);
 585                 if (ret)
 586                         break;
 587
 588                 clear_extent_bits(dirty_pages, start, end, mark, GFP_NOFS);
 589                 while (start <= end) {
 590                         index = start >> PAGE_CACHE_SHIFT;
 591                         start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
 592                         page = find_get_page(btree_inode->i_mapping, index);
 593                         if (!page)
 594                                 continue;
 595                         if (PageDirty(page)) {
 596                                 btree_lock_page_hook(page);
 597                                 wait_on_page_writeback(page);
 598                                 err = write_one_page(page, 0);
 599                                 if (err)
 600                                         werr = err;
 601                         }
 602                         wait_on_page_writeback(page);
 603                         page_cache_release(page);
 604                         cond_resched();
 605                 }
 606         }
 607         if (err)
 608                 werr = err;
 609         return werr;
 610 }
 611
 612 /*
 613  * when btree blocks are allocated, they have some corresponding bits set for
 614  * them in one of two extent_io trees.  This is used to make sure all of
 615  * those extents are on disk for transaction or log commit
 616  */
 617 int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
 618                                 struct extent_io_tree *dirty_pages, int mark)
 619 {
 620         int ret;
 621         int ret2;
 622
 623         ret = btrfs_write_marked_extents(root, dirty_pages, mark);
 624         ret2 = btrfs_wait_marked_extents(root, dirty_pages, mark);
 625         return ret || ret2;
 626 }
 627
 628 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 629                                      struct btrfs_root *root)
 630 {
 631         if (!trans || !trans->transaction) {
 632                 struct inode *btree_inode;
 633                 btree_inode = root->fs_info->btree_inode;
 634                 return filemap_write_and_wait(btree_inode->i_mapping);
 635         }
 636         return btrfs_write_and_wait_marked_extents(root,
 637                                            &trans->transaction->dirty_pages,
 638                                            EXTENT_DIRTY);
 639 }
 640
 641 /*
 642  * this is used to update the root pointer in the tree of tree roots.
 643  *
 644  * But, in the case of the extent allocation tree, updating the root
 645  * pointer may allocate blocks which may change the root of the extent
 646  * allocation tree.
 647  *
 648  * So, this loops and repeats and makes sure the cowonly root didn't
 649  * change while the root pointer was being updated in the metadata.
 650  */
 651 static int update_cowonly_root(struct btrfs_trans_handle *trans,
 652                                struct btrfs_root *root)
 653 {
 654         int ret;
 655         u64 old_root_bytenr;
 656         u64 old_root_used;
 657         struct btrfs_root *tree_root = root->fs_info->tree_root;
 658
 659         old_root_used = btrfs_root_used(&root->root_item);
 660         btrfs_write_dirty_block_groups(trans, root);
 661
 662         while (1) {
 663                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
 664                 if (old_root_bytenr == root->node->start &&
 665                     old_root_used == btrfs_root_used(&root->root_item))
 666                         break;
 667
 668                 btrfs_set_root_node(&root->root_item, root->node);
 669                 ret = btrfs_update_root(trans, tree_root,
 670                                         &root->root_key,
 671                                         &root->root_item);
 672                 BUG_ON(ret);
 673
 674                 old_root_used = btrfs_root_used(&root->root_item);
 675                 ret = btrfs_write_dirty_block_groups(trans, root);
 676                 BUG_ON(ret);
 677         }
 678
 679         if (root != root->fs_info->extent_root)
 680                 switch_commit_root(root);
 681
 682         return 0;
 683 }
 684
 685 /*
 686  * update all the cowonly tree roots on disk
 687  */
 688 static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
 689                                          struct btrfs_root *root)
 690 {
 691         struct btrfs_fs_info *fs_info = root->fs_info;
 692         struct list_head *next;
 693         struct extent_buffer *eb;
 694         int ret;
 695
 696         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 697         BUG_ON(ret);
 698
 699         eb = btrfs_lock_root_node(fs_info->tree_root);
 700         btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb);
 701         btrfs_tree_unlock(eb);
 702         free_extent_buffer(eb);
 703
 704         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
 705         BUG_ON(ret);
 706
 707         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
 708                 next = fs_info->dirty_cowonly_roots.next;
 709                 list_del_init(next);
 710                 root = list_entry(next, struct btrfs_root, dirty_list);
 711
 712                 update_cowonly_root(trans, root);
 713         }
 714
 715         down_write(&fs_info->extent_commit_sem);
 716         switch_commit_root(fs_info->extent_root);
 717         up_write(&fs_info->extent_commit_sem);
 718
 719         return 0;
 720 }
 721
 722 /*
 723  * dead roots are old snapshots that need to be deleted.  This allocates
 724  * a dirty root struct and adds it into the list of dead roots that need to
 725  * be deleted
 726  */
 727 int btrfs_add_dead_root(struct btrfs_root *root)
 728 {
 729         mutex_lock(&root->fs_info->trans_mutex);
 730         list_add(&root->root_list, &root->fs_info->dead_roots);
 731         mutex_unlock(&root->fs_info->trans_mutex);
 732         return 0;
 733 }
 734
 735 /*
 736  * update all the cowonly tree roots on disk
 737  */
 738 static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
 739                                     struct btrfs_root *root)
 740 {
 741         struct btrfs_root *gang[8];
 742         struct btrfs_fs_info *fs_info = root->fs_info;
 743         int i;
 744         int ret;
 745         int err = 0;
 746
 747         while (1) {
 748                 ret = radix_tree_gang_lookup_tag(&fs_info->fs_roots_radix,
 749                                                  (void **)gang, 0,
 750                                                  ARRAY_SIZE(gang),
 751                                                  BTRFS_ROOT_TRANS_TAG);
 752                 if (ret == 0)
 753                         break;
 754                 for (i = 0; i < ret; i++) {
 755                         root = gang[i];
 756                         radix_tree_tag_clear(&fs_info->fs_roots_radix,
 757                                         (unsigned long)root->root_key.objectid,
 758                                         BTRFS_ROOT_TRANS_TAG);
 759
 760                         btrfs_free_log(trans, root);
 761                         btrfs_update_reloc_root(trans, root);
 762                         btrfs_orphan_commit_root(trans, root);
 763
 764                         if (root->commit_root != root->node) {
 765                                 mutex_lock(&root->fs_commit_mutex);
 766                                 switch_commit_root(root);
 767                                 btrfs_unpin_free_ino(root);
 768                                 mutex_unlock(&root->fs_commit_mutex);
 769
 770                                 btrfs_set_root_node(&root->root_item,
 771                                                     root->node);
 772                         }
 773
 774                         err = btrfs_update_root(trans, fs_info->tree_root,
 775                                                 &root->root_key,
 776                                                 &root->root_item);
 777                         if (err)
 778                                 break;
 779                 }
 780         }
 781         return err;
 782 }
 783
 784 /*
 785  * defrag a given btree.  If cacheonly == 1, this won't read from the disk,
 786  * otherwise every leaf in the btree is read and defragged.
 787  */
 788 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 789 {
 790         struct btrfs_fs_info *info = root->fs_info;
 791         struct btrfs_trans_handle *trans;
 792         int ret;
 793         unsigned long nr;
 794
 795         if (xchg(&root->defrag_running, 1))
 796                 return 0;
 797
 798         while (1) {
 799                 trans = btrfs_start_transaction(root, 0);
 800                 if (IS_ERR(trans))
 801                         return PTR_ERR(trans);
 802
 803                 ret = btrfs_defrag_leaves(trans, root, cacheonly);
 804
 805                 nr = trans->blocks_used;
 806                 btrfs_end_transaction(trans, root);
 807                 btrfs_btree_balance_dirty(info->tree_root, nr);
 808                 cond_resched();
 809
 810                 if (root->fs_info->closing || ret != -EAGAIN)
 811                         break;
 812         }
 813         root->defrag_running = 0;
 814         return ret;
 815 }
 816
 817 #if 0
 818 /*
 819  * when dropping snapshots, we generate a ton of delayed refs, and it makes
 820  * sense not to join the transaction while it is trying to flush the current
 821  * queue of delayed refs out.
 822  *
 823  * This is used by the drop snapshot code only
 824  */
 825 static noinline int wait_transaction_pre_flush(struct btrfs_fs_info *info)
 826 {
 827         DEFINE_WAIT(wait);
 828
 829         mutex_lock(&info->trans_mutex);
 830         while (info->running_transaction &&
 831                info->running_transaction->delayed_refs.flushing) {
 832                 prepare_to_wait(&info->transaction_wait, &wait,
 833                                 TASK_UNINTERRUPTIBLE);
 834                 mutex_unlock(&info->trans_mutex);
 835
 836                 schedule();
 837
 838                 mutex_lock(&info->trans_mutex);
 839                 finish_wait(&info->transaction_wait, &wait);
 840         }
 841         mutex_unlock(&info->trans_mutex);
 842         return 0;
 843 }
 844
 845 /*
 846  * Given a list of roots that need to be deleted, call btrfs_drop_snapshot on
 847  * all of them
 848  */
 849 int btrfs_drop_dead_root(struct btrfs_root *root)
 850 {
 851         struct btrfs_trans_handle *trans;
 852         struct btrfs_root *tree_root = root->fs_info->tree_root;
 853         unsigned long nr;
 854         int ret;
 855
 856         while (1) {
 857                 /*
 858                  * we don't want to jump in and create a bunch of
 859                  * delayed refs if the transaction is starting to close
 860                  */
 861                 wait_transaction_pre_flush(tree_root->fs_info);
 862                 trans = btrfs_start_transaction(tree_root, 1);
 863
 864                 /*
 865                  * we've joined a transaction, make sure it isn't
 866                  * closing right now
 867                  */
 868                 if (trans->transaction->delayed_refs.flushing) {
 869                         btrfs_end_transaction(trans, tree_root);
 870                         continue;
 871                 }
 872
 873                 ret = btrfs_drop_snapshot(trans, root);
 874                 if (ret != -EAGAIN)
 875                         break;
 876
 877                 ret = btrfs_update_root(trans, tree_root,
 878                                         &root->root_key,
 879                                         &root->root_item);
 880                 if (ret)
 881                         break;
 882
 883                 nr = trans->blocks_used;
 884                 ret = btrfs_end_transaction(trans, tree_root);
 885                 BUG_ON(ret);
 886
 887                 btrfs_btree_balance_dirty(tree_root, nr);
 888                 cond_resched();
 889         }
 890         BUG_ON(ret);
 891
 892         ret = btrfs_del_root(trans, tree_root, &root->root_key);
 893         BUG_ON(ret);
 894
 895         nr = trans->blocks_used;
 896         ret = btrfs_end_transaction(trans, tree_root);
 897         BUG_ON(ret);
 898
 899         free_extent_buffer(root->node);
 900         free_extent_buffer(root->commit_root);
 901         kfree(root);
 902
 903         btrfs_btree_balance_dirty(tree_root, nr);
 904         return ret;
 905 }
 906 #endif
 907
 908 /*
 909  * new snapshots need to be created at a very specific time in the
 910  * transaction commit.  This does the actual creation
 911  */
 912 static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 913                                    struct btrfs_fs_info *fs_info,
 914                                    struct btrfs_pending_snapshot *pending)
 915 {
 916         struct btrfs_key key;
 917         struct btrfs_root_item *new_root_item;
 918         struct btrfs_root *tree_root = fs_info->tree_root;
 919         struct btrfs_root *root = pending->root;
 920         struct btrfs_root *parent_root;
 921         struct inode *parent_inode;
 922         struct dentry *parent;
 923         struct dentry *dentry;
 924         struct extent_buffer *tmp;
 925         struct extent_buffer *old;
 926         int ret;
 927         u64 to_reserve = 0;
 928         u64 index = 0;
 929         u64 objectid;
 930         u64 root_flags;
 931
 932         new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
 933         if (!new_root_item) {
 934                 pending->error = -ENOMEM;
 935                 goto fail;
 936         }
 937
 938         ret = btrfs_find_free_objectid(tree_root, &objectid);
 939         if (ret) {
 940                 pending->error = ret;
 941                 goto fail;
 942         }
 943
 944         btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
 945         btrfs_orphan_pre_snapshot(trans, pending, &to_reserve);
 946
 947         if (to_reserve > 0) {
 948                 ret = btrfs_block_rsv_add(trans, root, &pending->block_rsv,
 949                                           to_reserve);
 950                 if (ret) {
 951                         pending->error = ret;
 952                         goto fail;
 953                 }
 954         }
 955
 956         key.objectid = objectid;
 957         key.offset = (u64)-1;
 958         key.type = BTRFS_ROOT_ITEM_KEY;
 959
 960         trans->block_rsv = &pending->block_rsv;
 961
 962         dentry = pending->dentry;
 963         parent = dget_parent(dentry);
 964         parent_inode = parent->d_inode;
 965         parent_root = BTRFS_I(parent_inode)->root;
 966         record_root_in_trans(trans, parent_root);
 967
 968         /*
 969          * insert the directory item
 970          */
 971         ret = btrfs_set_inode_index(parent_inode, &index);
 972         BUG_ON(ret);
 973         ret = btrfs_insert_dir_item(trans, parent_root,
 974                                 dentry->d_name.name, dentry->d_name.len,
 975                                 btrfs_ino(parent_inode), &key,
 976                                 BTRFS_FT_DIR, index);
 977         BUG_ON(ret);
 978
 979         btrfs_i_size_write(parent_inode, parent_inode->i_size +
 980                                          dentry->d_name.len * 2);
 981         ret = btrfs_update_inode(trans, parent_root, parent_inode);
 982         BUG_ON(ret);
 983
 984         record_root_in_trans(trans, root);
 985         btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
 986         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
 987         btrfs_check_and_init_root_item(new_root_item);
 988
 989         root_flags = btrfs_root_flags(new_root_item);
 990         if (pending->readonly)
 991                 root_flags |= BTRFS_ROOT_SUBVOL_RDONLY;
 992         else
 993                 root_flags &= ~BTRFS_ROOT_SUBVOL_RDONLY;
 994         btrfs_set_root_flags(new_root_item, root_flags);
 995
 996         old = btrfs_lock_root_node(root);
 997         btrfs_cow_block(trans, root, old, NULL, 0, &old);
 998         btrfs_set_lock_blocking(old);
 999
1000         btrfs_copy_root(trans, root, old, &tmp, objectid);
1001         btrfs_tree_unlock(old);
1002         free_extent_buffer(old);
1003
1004         btrfs_set_root_node(new_root_item, tmp);
1005         /* record when the snapshot was created in key.offset */
1006         key.offset = trans->transid;
1007         ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
1008         btrfs_tree_unlock(tmp);
1009         free_extent_buffer(tmp);
1010         BUG_ON(ret);
1011
1012         /*
1013          * insert root back/forward references
1014          */
1015         ret = btrfs_add_root_ref(trans, tree_root, objectid,
1016                                  parent_root->root_key.objectid,
1017                                  btrfs_ino(parent_inode), index,
1018                                  dentry->d_name.name, dentry->d_name.len);
1019         BUG_ON(ret);
1020         dput(parent);
1021
1022         key.offset = (u64)-1;
1023         pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
1024         BUG_ON(IS_ERR(pending->snap));
1025
1026         btrfs_reloc_post_snapshot(trans, pending);
1027         btrfs_orphan_post_snapshot(trans, pending);
1028 fail:
1029         kfree(new_root_item);
1030         btrfs_block_rsv_release(root, &pending->block_rsv, (u64)-1);
1031         return 0;
1032 }
1033
1034 /*
1035  * create all the snapshots we've scheduled for creation
1036  */
1037 static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
1038                                              struct btrfs_fs_info *fs_info)
1039 {
1040         struct btrfs_pending_snapshot *pending;
1041         struct list_head *head = &trans->transaction->pending_snapshots;
1042         int ret;
1043
1044         list_for_each_entry(pending, head, list) {
1045                 ret = create_pending_snapshot(trans, fs_info, pending);
1046                 BUG_ON(ret);
1047         }
1048         return 0;
1049 }
1050
1051 static void update_super_roots(struct btrfs_root *root)
1052 {
1053         struct btrfs_root_item *root_item;
1054         struct btrfs_super_block *super;
1055
1056         super = &root->fs_info->super_copy;
1057
1058         root_item = &root->fs_info->chunk_root->root_item;
1059         super->chunk_root = root_item->bytenr;
1060         super->chunk_root_generation = root_item->generation;
1061         super->chunk_root_level = root_item->level;
1062
1063         root_item = &root->fs_info->tree_root->root_item;
1064         super->root = root_item->bytenr;
1065         super->generation = root_item->generation;
1066         super->root_level = root_item->level;
1067         if (super->cache_generation != 0 || btrfs_test_opt(root, SPACE_CACHE))
1068                 super->cache_generation = root_item->generation;
1069 }
1070
1071 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
1072 {
1073         int ret = 0;
1074         spin_lock(&info->new_trans_lock);
1075         if (info->running_transaction)
1076                 ret = info->running_transaction->in_commit;
1077         spin_unlock(&info->new_trans_lock);
1078         return ret;
1079 }
1080
1081 int btrfs_transaction_blocked(struct btrfs_fs_info *info)
1082 {
1083         int ret = 0;
1084         spin_lock(&info->new_trans_lock);
1085         if (info->running_transaction)
1086                 ret = info->running_transaction->blocked;
1087         spin_unlock(&info->new_trans_lock);
1088         return ret;
1089 }
1090
1091 /*
1092  * wait for the current transaction commit to start and block subsequent
1093  * transaction joins
1094  */
1095 static void wait_current_trans_commit_start(struct btrfs_root *root,
1096                                             struct btrfs_transaction *trans)
1097 {
1098         DEFINE_WAIT(wait);
1099
1100         if (trans->in_commit)
1101                 return;
1102
1103         while (1) {
1104                 prepare_to_wait(&root->fs_info->transaction_blocked_wait, &wait,
1105                                 TASK_UNINTERRUPTIBLE);
1106                 if (trans->in_commit) {
1107                         finish_wait(&root->fs_info->transaction_blocked_wait,
1108                                     &wait);
1109                         break;
1110                 }
1111                 mutex_unlock(&root->fs_info->trans_mutex);
1112                 schedule();
1113                 mutex_lock(&root->fs_info->trans_mutex);
1114                 finish_wait(&root->fs_info->transaction_blocked_wait, &wait);
1115         }
1116 }
1117
1118 /*
1119  * wait for the current transaction to start and then become unblocked.
1120  * caller holds ref.
1121  */
1122 static void wait_current_trans_commit_start_and_unblock(struct btrfs_root *root,
1123                                          struct btrfs_transaction *trans)
1124 {
1125         DEFINE_WAIT(wait);
1126
1127         if (trans->commit_done || (trans->in_commit && !trans->blocked))
1128                 return;
1129
1130         while (1) {
1131                 prepare_to_wait(&root->fs_info->transaction_wait, &wait,
1132                                 TASK_UNINTERRUPTIBLE);
1133                 if (trans->commit_done ||
1134                     (trans->in_commit && !trans->blocked)) {
1135                         finish_wait(&root->fs_info->transaction_wait,
1136                                     &wait);
1137                         break;
1138                 }
1139                 mutex_unlock(&root->fs_info->trans_mutex);
1140                 schedule();
1141                 mutex_lock(&root->fs_info->trans_mutex);
1142                 finish_wait(&root->fs_info->transaction_wait,
1143                             &wait);
1144         }
1145 }
1146
1147 /*
1148  * commit transactions asynchronously. once btrfs_commit_transaction_async
1149  * returns, any subsequent transaction will not be allowed to join.
1150  */
1151 struct btrfs_async_commit {
1152         struct btrfs_trans_handle *newtrans;
1153         struct btrfs_root *root;
1154         struct delayed_work work;
1155 };
1156
1157 static void do_async_commit(struct work_struct *work)
1158 {
1159         struct btrfs_async_commit *ac =
1160                 container_of(work, struct btrfs_async_commit, work.work);
1161
1162         btrfs_commit_transaction(ac->newtrans, ac->root);
1163         kfree(ac);
1164 }
1165
1166 int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
1167                                    struct btrfs_root *root,
1168                                    int wait_for_unblock)
1169 {
1170         struct btrfs_async_commit *ac;
1171         struct btrfs_transaction *cur_trans;
1172
1173         ac = kmalloc(sizeof(*ac), GFP_NOFS);
1174         if (!ac)
1175                 return -ENOMEM;
1176
1177         INIT_DELAYED_WORK(&ac->work, do_async_commit);
1178         ac->root = root;
1179         ac->newtrans = btrfs_join_transaction(root, 0);
1180         if (IS_ERR(ac->newtrans)) {
1181                 int err = PTR_ERR(ac->newtrans);
1182                 kfree(ac);
1183                 return err;
1184         }
1185
1186         /* take transaction reference */
1187         mutex_lock(&root->fs_info->trans_mutex);
1188         cur_trans = trans->transaction;
1189         atomic_inc(&cur_trans->use_count);
1190         mutex_unlock(&root->fs_info->trans_mutex);
1191
1192         btrfs_end_transaction(trans, root);
1193         schedule_delayed_work(&ac->work, 0);
1194
1195         /* wait for transaction to start and unblock */
1196         mutex_lock(&root->fs_info->trans_mutex);
1197         if (wait_for_unblock)
1198                 wait_current_trans_commit_start_and_unblock(root, cur_trans);
1199         else
1200                 wait_current_trans_commit_start(root, cur_trans);
1201         put_transaction(cur_trans);
1202         mutex_unlock(&root->fs_info->trans_mutex);
1203
1204         return 0;
1205 }
1206
1207 /*
1208  * btrfs_transaction state sequence:
1209  *    in_commit = 0, blocked = 0  (initial)
1210  *    in_commit = 1, blocked = 1
1211  *    blocked = 0
1212  *    commit_done = 1
1213  */
1214 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
1215                              struct btrfs_root *root)
1216 {
1217         unsigned long joined = 0;
1218         struct btrfs_transaction *cur_trans;
1219         struct btrfs_transaction *prev_trans = NULL;
1220         DEFINE_WAIT(wait);
1221         int ret;
1222         int should_grow = 0;
1223         unsigned long now = get_seconds();
1224         int flush_on_commit = btrfs_test_opt(root, FLUSHONCOMMIT);
1225
1226         btrfs_run_ordered_operations(root, 0);
1227
1228         /* make a pass through all the delayed refs we have so far
1229          * any runnings procs may add more while we are here
1230          */
1231         ret = btrfs_run_delayed_refs(trans, root, 0);
1232         BUG_ON(ret);
1233
1234         btrfs_trans_release_metadata(trans, root);
1235
1236         cur_trans = trans->transaction;
1237         /*
1238          * set the flushing flag so procs in this transaction have to
1239          * start sending their work down.
1240          */
1241         cur_trans->delayed_refs.flushing = 1;
1242
1243         ret = btrfs_run_delayed_refs(trans, root, 0);
1244         BUG_ON(ret);
1245
1246         mutex_lock(&root->fs_info->trans_mutex);
1247         if (cur_trans->in_commit) {
1248                 atomic_inc(&cur_trans->use_count);
1249                 mutex_unlock(&root->fs_info->trans_mutex);
1250                 btrfs_end_transaction(trans, root);
1251
1252                 ret = wait_for_commit(root, cur_trans);
1253                 BUG_ON(ret);
1254
1255                 mutex_lock(&root->fs_info->trans_mutex);
1256                 put_transaction(cur_trans);
1257                 mutex_unlock(&root->fs_info->trans_mutex);
1258
1259                 return 0;
1260         }
1261
1262         trans->transaction->in_commit = 1;
1263         trans->transaction->blocked = 1;
1264         wake_up(&root->fs_info->transaction_blocked_wait);
1265
1266         if (cur_trans->list.prev != &root->fs_info->trans_list) {
1267                 prev_trans = list_entry(cur_trans->list.prev,
1268                                         struct btrfs_transaction, list);
1269                 if (!prev_trans->commit_done) {
1270                         atomic_inc(&prev_trans->use_count);
1271                         mutex_unlock(&root->fs_info->trans_mutex);
1272
1273                         wait_for_commit(root, prev_trans);
1274
1275                         mutex_lock(&root->fs_info->trans_mutex);
1276                         put_transaction(prev_trans);
1277                 }
1278         }
1279
1280         if (now < cur_trans->start_time || now - cur_trans->start_time < 1)
1281                 should_grow = 1;
1282
1283         do {
1284                 int snap_pending = 0;
1285                 joined = cur_trans->num_joined;
1286                 if (!list_empty(&trans->transaction->pending_snapshots))
1287                         snap_pending = 1;
1288
1289                 WARN_ON(cur_trans != trans->transaction);
1290                 mutex_unlock(&root->fs_info->trans_mutex);
1291
1292                 if (flush_on_commit || snap_pending) {
1293                         btrfs_start_delalloc_inodes(root, 1);
1294                         ret = btrfs_wait_ordered_extents(root, 0, 1);
1295                         BUG_ON(ret);
1296                 }
1297
1298                 /*
1299                  * rename don't use btrfs_join_transaction, so, once we
1300                  * set the transaction to blocked above, we aren't going
1301                  * to get any new ordered operations.  We can safely run
1302                  * it here and no for sure that nothing new will be added
1303                  * to the list
1304                  */
1305                 btrfs_run_ordered_operations(root, 1);
1306
1307                 prepare_to_wait(&cur_trans->writer_wait, &wait,
1308                                 TASK_UNINTERRUPTIBLE);
1309
1310                 smp_mb();
1311                 if (atomic_read(&cur_trans->num_writers) > 1)
1312                         schedule_timeout(MAX_SCHEDULE_TIMEOUT);
1313                 else if (should_grow)
1314                         schedule_timeout(1);
1315
1316                 mutex_lock(&root->fs_info->trans_mutex);
1317                 finish_wait(&cur_trans->writer_wait, &wait);
1318         } while (atomic_read(&cur_trans->num_writers) > 1 ||
1319                  (should_grow && cur_trans->num_joined != joined));
1320
1321         ret = create_pending_snapshots(trans, root->fs_info);
1322         BUG_ON(ret);
1323
1324         ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
1325         BUG_ON(ret);
1326
1327         WARN_ON(cur_trans != trans->transaction);
1328
1329         /* btrfs_commit_tree_roots is responsible for getting the
1330          * various roots consistent with each other.  Every pointer
1331          * in the tree of tree roots has to point to the most up to date
1332          * root for every subvolume and other tree.  So, we have to keep
1333          * the tree logging code from jumping in and changing any
1334          * of the trees.
1335          *
1336          * At this point in the commit, there can't be any tree-log
1337          * writers, but a little lower down we drop the trans mutex
1338          * and let new people in.  By holding the tree_log_mutex
1339          * from now until after the super is written, we avoid races
1340          * with the tree-log code.
1341          */
1342         mutex_lock(&root->fs_info->tree_log_mutex);
1343
1344         ret = commit_fs_roots(trans, root);
1345         BUG_ON(ret);
1346
1347         /* commit_fs_roots gets rid of all the tree log roots, it is now
1348          * safe to free the root of tree log roots
1349          */
1350         btrfs_free_log_root_tree(trans, root->fs_info);
1351
1352         ret = commit_cowonly_roots(trans, root);
1353         BUG_ON(ret);
1354
1355         btrfs_prepare_extent_commit(trans, root);
1356
1357         cur_trans = root->fs_info->running_transaction;
1358         spin_lock(&root->fs_info->new_trans_lock);
1359         root->fs_info->running_transaction = NULL;
1360         spin_unlock(&root->fs_info->new_trans_lock);
1361
1362         btrfs_set_root_node(&root->fs_info->tree_root->root_item,
1363                             root->fs_info->tree_root->node);
1364         switch_commit_root(root->fs_info->tree_root);
1365
1366         btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
1367                             root->fs_info->chunk_root->node);
1368         switch_commit_root(root->fs_info->chunk_root);
1369
1370         update_super_roots(root);
1371
1372         if (!root->fs_info->log_root_recovering) {
1373                 btrfs_set_super_log_root(&root->fs_info->super_copy, 0);
1374                 btrfs_set_super_log_root_level(&root->fs_info->super_copy, 0);
1375         }
1376
1377         memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
1378                sizeof(root->fs_info->super_copy));
1379
1380         trans->transaction->blocked = 0;
1381
1382         wake_up(&root->fs_info->transaction_wait);
1383
1384         mutex_unlock(&root->fs_info->trans_mutex);
1385         ret = btrfs_write_and_wait_transaction(trans, root);
1386         BUG_ON(ret);
1387         write_ctree_super(trans, root, 0);
1388
1389         /*
1390          * the super is written, we can safely allow the tree-loggers
1391          * to go about their business
1392          */
1393         mutex_unlock(&root->fs_info->tree_log_mutex);
1394
1395         btrfs_finish_extent_commit(trans, root);
1396
1397         mutex_lock(&root->fs_info->trans_mutex);
1398
1399         cur_trans->commit_done = 1;
1400
1401         root->fs_info->last_trans_committed = cur_trans->transid;
1402
1403         wake_up(&cur_trans->commit_wait);
1404
1405         list_del_init(&cur_trans->list);
1406         put_transaction(cur_trans);
1407         put_transaction(cur_trans);
1408
1409         trace_btrfs_transaction_commit(root);
1410
1411         mutex_unlock(&root->fs_info->trans_mutex);
1412
1413         if (current->journal_info == trans)
1414                 current->journal_info = NULL;
1415
1416         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1417
1418         if (current != root->fs_info->transaction_kthread)
1419                 btrfs_run_delayed_iputs(root);
1420
1421         return ret;
1422 }
1423
1424 /*
1425  * interface function to delete all the snapshots we have scheduled for deletion
1426  */
1427 int btrfs_clean_old_snapshots(struct btrfs_root *root)
1428 {
1429         LIST_HEAD(list);
1430         struct btrfs_fs_info *fs_info = root->fs_info;
1431
1432         mutex_lock(&fs_info->trans_mutex);
1433         list_splice_init(&fs_info->dead_roots, &list);
1434         mutex_unlock(&fs_info->trans_mutex);
1435
1436         while (!list_empty(&list)) {
1437                 root = list_entry(list.next, struct btrfs_root, root_list);
1438                 list_del(&root->root_list);
1439
1440                 if (btrfs_header_backref_rev(root->node) <
1441                     BTRFS_MIXED_BACKREF_REV)
1442                         btrfs_drop_snapshot(root, NULL, 0);
1443                 else
1444                         btrfs_drop_snapshot(root, NULL, 1);
1445         }
1446         return 0;
1447 }