git.oblomov.eu Git - linux-2.6/blob - 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 <linux/blkdev.h>
  24 #include "ctree.h"
  25 #include "disk-io.h"
  26 #include "transaction.h"
  27 #include "locking.h"
  28 #include "ref-cache.h"
  29 #include "tree-log.h"
  30
  31 static int total_trans = 0;
  32 extern struct kmem_cache *btrfs_trans_handle_cachep;
  33 extern struct kmem_cache *btrfs_transaction_cachep;
  34
  35 #define BTRFS_ROOT_TRANS_TAG 0
  36
  37 static noinline void put_transaction(struct btrfs_transaction *transaction)
  38 {
  39         WARN_ON(transaction->use_count == 0);
  40         transaction->use_count--;
  41         if (transaction->use_count == 0) {
  42                 WARN_ON(total_trans == 0);
  43                 total_trans--;
  44                 list_del_init(&transaction->list);
  45                 memset(transaction, 0, sizeof(*transaction));
  46                 kmem_cache_free(btrfs_transaction_cachep, transaction);
  47         }
  48 }
  49
  50 /*
  51  * either allocate a new transaction or hop into the existing one
  52  */
  53 static noinline int join_transaction(struct btrfs_root *root)
  54 {
  55         struct btrfs_transaction *cur_trans;
  56         cur_trans = root->fs_info->running_transaction;
  57         if (!cur_trans) {
  58                 cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
  59                                              GFP_NOFS);
  60                 total_trans++;
  61                 BUG_ON(!cur_trans);
  62                 root->fs_info->generation++;
  63                 root->fs_info->last_alloc = 0;
  64                 root->fs_info->last_data_alloc = 0;
  65                 cur_trans->num_writers = 1;
  66                 cur_trans->num_joined = 0;
  67                 cur_trans->transid = root->fs_info->generation;
  68                 init_waitqueue_head(&cur_trans->writer_wait);
  69                 init_waitqueue_head(&cur_trans->commit_wait);
  70                 cur_trans->in_commit = 0;
  71                 cur_trans->blocked = 0;
  72                 cur_trans->use_count = 1;
  73                 cur_trans->commit_done = 0;
  74                 cur_trans->start_time = get_seconds();
  75                 INIT_LIST_HEAD(&cur_trans->pending_snapshots);
  76                 list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
  77                 extent_io_tree_init(&cur_trans->dirty_pages,
  78                                      root->fs_info->btree_inode->i_mapping,
  79                                      GFP_NOFS);
  80                 spin_lock(&root->fs_info->new_trans_lock);
  81                 root->fs_info->running_transaction = cur_trans;
  82                 spin_unlock(&root->fs_info->new_trans_lock);
  83         } else {
  84                 cur_trans->num_writers++;
  85                 cur_trans->num_joined++;
  86         }
  87
  88         return 0;
  89 }
  90
  91 /*
  92  * this does all the record keeping required to make sure that a
  93  * reference counted root is properly recorded in a given transaction.
  94  * This is required to make sure the old root from before we joined the transaction
  95  * is deleted when the transaction commits
  96  */
  97 noinline int btrfs_record_root_in_trans(struct btrfs_root *root)
  98 {
  99         struct btrfs_dirty_root *dirty;
 100         u64 running_trans_id = root->fs_info->running_transaction->transid;
 101         if (root->ref_cows && root->last_trans < running_trans_id) {
 102                 WARN_ON(root == root->fs_info->extent_root);
 103                 if (root->root_item.refs != 0) {
 104                         radix_tree_tag_set(&root->fs_info->fs_roots_radix,
 105                                    (unsigned long)root->root_key.objectid,
 106                                    BTRFS_ROOT_TRANS_TAG);
 107
 108                         dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 109                         BUG_ON(!dirty);
 110                         dirty->root = kmalloc(sizeof(*dirty->root), GFP_NOFS);
 111                         BUG_ON(!dirty->root);
 112                         dirty->latest_root = root;
 113                         INIT_LIST_HEAD(&dirty->list);
 114
 115                         root->commit_root = btrfs_root_node(root);
 116
 117                         memcpy(dirty->root, root, sizeof(*root));
 118                         spin_lock_init(&dirty->root->node_lock);
 119                         spin_lock_init(&dirty->root->list_lock);
 120                         mutex_init(&dirty->root->objectid_mutex);
 121                         mutex_init(&dirty->root->log_mutex);
 122                         INIT_LIST_HEAD(&dirty->root->dead_list);
 123                         dirty->root->node = root->commit_root;
 124                         dirty->root->commit_root = NULL;
 125
 126                         spin_lock(&root->list_lock);
 127                         list_add(&dirty->root->dead_list, &root->dead_list);
 128                         spin_unlock(&root->list_lock);
 129
 130                         root->dirty_root = dirty;
 131                 } else {
 132                         WARN_ON(1);
 133                 }
 134                 root->last_trans = running_trans_id;
 135         }
 136         return 0;
 137 }
 138
 139 /* wait for commit against the current transaction to become unblocked
 140  * when this is done, it is safe to start a new transaction, but the current
 141  * transaction might not be fully on disk.
 142  */
 143 static void wait_current_trans(struct btrfs_root *root)
 144 {
 145         struct btrfs_transaction *cur_trans;
 146
 147         cur_trans = root->fs_info->running_transaction;
 148         if (cur_trans && cur_trans->blocked) {
 149                 DEFINE_WAIT(wait);
 150                 cur_trans->use_count++;
 151                 while(1) {
 152                         prepare_to_wait(&root->fs_info->transaction_wait, &wait,
 153                                         TASK_UNINTERRUPTIBLE);
 154                         if (cur_trans->blocked) {
 155                                 mutex_unlock(&root->fs_info->trans_mutex);
 156                                 schedule();
 157                                 mutex_lock(&root->fs_info->trans_mutex);
 158                                 finish_wait(&root->fs_info->transaction_wait,
 159                                             &wait);
 160                         } else {
 161                                 finish_wait(&root->fs_info->transaction_wait,
 162                                             &wait);
 163                                 break;
 164                         }
 165                 }
 166                 put_transaction(cur_trans);
 167         }
 168 }
 169
 170 static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
 171                                              int num_blocks, int wait)
 172 {
 173         struct btrfs_trans_handle *h =
 174                 kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
 175         int ret;
 176
 177         mutex_lock(&root->fs_info->trans_mutex);
 178         if (!root->fs_info->log_root_recovering &&
 179             ((wait == 1 && !root->fs_info->open_ioctl_trans) || wait == 2))
 180                 wait_current_trans(root);
 181         ret = join_transaction(root);
 182         BUG_ON(ret);
 183
 184         btrfs_record_root_in_trans(root);
 185         h->transid = root->fs_info->running_transaction->transid;
 186         h->transaction = root->fs_info->running_transaction;
 187         h->blocks_reserved = num_blocks;
 188         h->blocks_used = 0;
 189         h->block_group = NULL;
 190         h->alloc_exclude_nr = 0;
 191         h->alloc_exclude_start = 0;
 192         root->fs_info->running_transaction->use_count++;
 193         mutex_unlock(&root->fs_info->trans_mutex);
 194         return h;
 195 }
 196
 197 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 198                                                    int num_blocks)
 199 {
 200         return start_transaction(root, num_blocks, 1);
 201 }
 202 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
 203                                                    int num_blocks)
 204 {
 205         return start_transaction(root, num_blocks, 0);
 206 }
 207
 208 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
 209                                                          int num_blocks)
 210 {
 211         return start_transaction(r, num_blocks, 2);
 212 }
 213
 214 /* wait for a transaction commit to be fully complete */
 215 static noinline int wait_for_commit(struct btrfs_root *root,
 216                                     struct btrfs_transaction *commit)
 217 {
 218         DEFINE_WAIT(wait);
 219         mutex_lock(&root->fs_info->trans_mutex);
 220         while(!commit->commit_done) {
 221                 prepare_to_wait(&commit->commit_wait, &wait,
 222                                 TASK_UNINTERRUPTIBLE);
 223                 if (commit->commit_done)
 224                         break;
 225                 mutex_unlock(&root->fs_info->trans_mutex);
 226                 schedule();
 227                 mutex_lock(&root->fs_info->trans_mutex);
 228         }
 229         mutex_unlock(&root->fs_info->trans_mutex);
 230         finish_wait(&commit->commit_wait, &wait);
 231         return 0;
 232 }
 233
 234 /*
 235  * rate limit against the drop_snapshot code.  This helps to slow down new operations
 236  * if the drop_snapshot code isn't able to keep up.
 237  */
 238 static void throttle_on_drops(struct btrfs_root *root)
 239 {
 240         struct btrfs_fs_info *info = root->fs_info;
 241         int harder_count = 0;
 242
 243 harder:
 244         if (atomic_read(&info->throttles)) {
 245                 DEFINE_WAIT(wait);
 246                 int thr;
 247                 thr = atomic_read(&info->throttle_gen);
 248
 249                 do {
 250                         prepare_to_wait(&info->transaction_throttle,
 251                                         &wait, TASK_UNINTERRUPTIBLE);
 252                         if (!atomic_read(&info->throttles)) {
 253                                 finish_wait(&info->transaction_throttle, &wait);
 254                                 break;
 255                         }
 256                         schedule();
 257                         finish_wait(&info->transaction_throttle, &wait);
 258                 } while (thr == atomic_read(&info->throttle_gen));
 259                 harder_count++;
 260
 261                 if (root->fs_info->total_ref_cache_size > 1 * 1024 * 1024 &&
 262                     harder_count < 2)
 263                         goto harder;
 264
 265                 if (root->fs_info->total_ref_cache_size > 5 * 1024 * 1024 &&
 266                     harder_count < 10)
 267                         goto harder;
 268
 269                 if (root->fs_info->total_ref_cache_size > 10 * 1024 * 1024 &&
 270                     harder_count < 20)
 271                         goto harder;
 272         }
 273 }
 274
 275 void btrfs_throttle(struct btrfs_root *root)
 276 {
 277         mutex_lock(&root->fs_info->trans_mutex);
 278         if (!root->fs_info->open_ioctl_trans)
 279                 wait_current_trans(root);
 280         mutex_unlock(&root->fs_info->trans_mutex);
 281
 282         throttle_on_drops(root);
 283 }
 284
 285 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 286                           struct btrfs_root *root, int throttle)
 287 {
 288         struct btrfs_transaction *cur_trans;
 289         struct btrfs_fs_info *info = root->fs_info;
 290
 291         mutex_lock(&info->trans_mutex);
 292         cur_trans = info->running_transaction;
 293         WARN_ON(cur_trans != trans->transaction);
 294         WARN_ON(cur_trans->num_writers < 1);
 295         cur_trans->num_writers--;
 296
 297         if (waitqueue_active(&cur_trans->writer_wait))
 298                 wake_up(&cur_trans->writer_wait);
 299         put_transaction(cur_trans);
 300         mutex_unlock(&info->trans_mutex);
 301         memset(trans, 0, sizeof(*trans));
 302         kmem_cache_free(btrfs_trans_handle_cachep, trans);
 303
 304         if (throttle)
 305                 throttle_on_drops(root);
 306
 307         return 0;
 308 }
 309
 310 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
 311                           struct btrfs_root *root)
 312 {
 313         return __btrfs_end_transaction(trans, root, 0);
 314 }
 315
 316 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
 317                                    struct btrfs_root *root)
 318 {
 319         return __btrfs_end_transaction(trans, root, 1);
 320 }
 321
 322 /*
 323  * when btree blocks are allocated, they have some corresponding bits set for
 324  * them in one of two extent_io trees.  This is used to make sure all of
 325  * those extents are on disk for transaction or log commit
 326  */
 327 int btrfs_write_and_wait_marked_extents(struct btrfs_root *root,
 328                                         struct extent_io_tree *dirty_pages)
 329 {
 330         int ret;
 331         int err = 0;
 332         int werr = 0;
 333         struct page *page;
 334         struct inode *btree_inode = root->fs_info->btree_inode;
 335         u64 start = 0;
 336         u64 end;
 337         unsigned long index;
 338
 339         while(1) {
 340                 ret = find_first_extent_bit(dirty_pages, start, &start, &end,
 341                                             EXTENT_DIRTY);
 342                 if (ret)
 343                         break;
 344                 while(start <= end) {
 345                         cond_resched();
 346
 347                         index = start >> PAGE_CACHE_SHIFT;
 348                         start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
 349                         page = find_get_page(btree_inode->i_mapping, index);
 350                         if (!page)
 351                                 continue;
 352
 353                         btree_lock_page_hook(page);
 354                         if (!page->mapping) {
 355                                 unlock_page(page);
 356                                 page_cache_release(page);
 357                                 continue;
 358                         }
 359
 360                         if (PageWriteback(page)) {
 361                                 if (PageDirty(page))
 362                                         wait_on_page_writeback(page);
 363                                 else {
 364                                         unlock_page(page);
 365                                         page_cache_release(page);
 366                                         continue;
 367                                 }
 368                         }
 369                         err = write_one_page(page, 0);
 370                         if (err)
 371                                 werr = err;
 372                         page_cache_release(page);
 373                 }
 374         }
 375         while(1) {
 376                 ret = find_first_extent_bit(dirty_pages, 0, &start, &end,
 377                                             EXTENT_DIRTY);
 378                 if (ret)
 379                         break;
 380
 381                 clear_extent_dirty(dirty_pages, start, end, GFP_NOFS);
 382                 while(start <= end) {
 383                         index = start >> PAGE_CACHE_SHIFT;
 384                         start = (u64)(index + 1) << PAGE_CACHE_SHIFT;
 385                         page = find_get_page(btree_inode->i_mapping, index);
 386                         if (!page)
 387                                 continue;
 388                         if (PageDirty(page)) {
 389                                 btree_lock_page_hook(page);
 390                                 wait_on_page_writeback(page);
 391                                 err = write_one_page(page, 0);
 392                                 if (err)
 393                                         werr = err;
 394                         }
 395                         wait_on_page_writeback(page);
 396                         page_cache_release(page);
 397                         cond_resched();
 398                 }
 399         }
 400         if (err)
 401                 werr = err;
 402         return werr;
 403 }
 404
 405 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
 406                                      struct btrfs_root *root)
 407 {
 408         if (!trans || !trans->transaction) {
 409                 struct inode *btree_inode;
 410                 btree_inode = root->fs_info->btree_inode;
 411                 return filemap_write_and_wait(btree_inode->i_mapping);
 412         }
 413         return btrfs_write_and_wait_marked_extents(root,
 414                                            &trans->transaction->dirty_pages);
 415 }
 416
 417 /*
 418  * this is used to update the root pointer in the tree of tree roots.
 419  *
 420  * But, in the case of the extent allocation tree, updating the root
 421  * pointer may allocate blocks which may change the root of the extent
 422  * allocation tree.
 423  *
 424  * So, this loops and repeats and makes sure the cowonly root didn't
 425  * change while the root pointer was being updated in the metadata.
 426  */
 427 static int update_cowonly_root(struct btrfs_trans_handle *trans,
 428                                struct btrfs_root *root)
 429 {
 430         int ret;
 431         u64 old_root_bytenr;
 432         struct btrfs_root *tree_root = root->fs_info->tree_root;
 433
 434         btrfs_extent_post_op(trans, root);
 435         btrfs_write_dirty_block_groups(trans, root);
 436         btrfs_extent_post_op(trans, root);
 437
 438         while(1) {
 439                 old_root_bytenr = btrfs_root_bytenr(&root->root_item);
 440                 if (old_root_bytenr == root->node->start)
 441                         break;
 442                 btrfs_set_root_bytenr(&root->root_item,
 443                                        root->node->start);
 444                 btrfs_set_root_level(&root->root_item,
 445                                      btrfs_header_level(root->node));
 446                 btrfs_set_root_generation(&root->root_item, trans->transid);
 447
 448                 btrfs_extent_post_op(trans, root);
 449
 450                 ret = btrfs_update_root(trans, tree_root,
 451                                         &root->root_key,
 452                                         &root->root_item);
 453                 BUG_ON(ret);
 454                 btrfs_write_dirty_block_groups(trans, root);
 455                 btrfs_extent_post_op(trans, root);
 456         }
 457         return 0;
 458 }
 459
 460 /*
 461  * update all the cowonly tree roots on disk
 462  */
 463 int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,
 464                             struct btrfs_root *root)
 465 {
 466         struct btrfs_fs_info *fs_info = root->fs_info;
 467         struct list_head *next;
 468         struct extent_buffer *eb;
 469
 470         btrfs_extent_post_op(trans, fs_info->tree_root);
 471
 472         eb = btrfs_lock_root_node(fs_info->tree_root);
 473         btrfs_cow_block(trans, fs_info->tree_root, eb, NULL, 0, &eb, 0);
 474         btrfs_tree_unlock(eb);
 475         free_extent_buffer(eb);
 476
 477         btrfs_extent_post_op(trans, fs_info->tree_root);
 478
 479         while(!list_empty(&fs_info->dirty_cowonly_roots)) {
 480                 next = fs_info->dirty_cowonly_roots.next;
 481                 list_del_init(next);
 482                 root = list_entry(next, struct btrfs_root, dirty_list);
 483
 484                 update_cowonly_root(trans, root);
 485         }
 486         return 0;
 487 }
 488
 489 /*
 490  * dead roots are old snapshots that need to be deleted.  This allocates
 491  * a dirty root struct and adds it into the list of dead roots that need to
 492  * be deleted
 493  */
 494 int btrfs_add_dead_root(struct btrfs_root *root, struct btrfs_root *latest)
 495 {
 496         struct btrfs_dirty_root *dirty;
 497
 498         dirty = kmalloc(sizeof(*dirty), GFP_NOFS);
 499         if (!dirty)
 500                 return -ENOMEM;
 501         dirty->root = root;
 502         dirty->latest_root = latest;
 503
 504         mutex_lock(&root->fs_info->trans_mutex);
 505         list_add(&dirty->list, &latest->fs_info->dead_roots);
 506         mutex_unlock(&root->fs_info->trans_mutex);
 507         return 0;
 508 }
 509
 510 /*
 511  * at transaction commit time we need to schedule the old roots for
 512  * deletion via btrfs_drop_snapshot.  This runs through all the
 513  * reference counted roots that were modified in the current
 514  * transaction and puts them into the drop list
 515  */
 516 static noinline int add_dirty_roots(struct btrfs_trans_handle *trans,
 517                                     struct radix_tree_root *radix,
 518                                     struct list_head *list)
 519 {
 520         struct btrfs_dirty_root *dirty;
 521         struct btrfs_root *gang[8];
 522         struct btrfs_root *root;
 523         int i;
 524         int ret;
 525         int err = 0;
 526         u32 refs;
 527
 528         while(1) {
 529                 ret = radix_tree_gang_lookup_tag(radix, (void **)gang, 0,
 530                                                  ARRAY_SIZE(gang),
 531                                                  BTRFS_ROOT_TRANS_TAG);
 532                 if (ret == 0)
 533                         break;
 534                 for (i = 0; i < ret; i++) {
 535                         root = gang[i];
 536                         radix_tree_tag_clear(radix,
 537                                      (unsigned long)root->root_key.objectid,
 538                                      BTRFS_ROOT_TRANS_TAG);
 539
 540                         BUG_ON(!root->ref_tree);
 541                         dirty = root->dirty_root;
 542
 543                         btrfs_free_log(trans, root);
 544                         btrfs_free_reloc_root(trans, root);
 545
 546                         if (root->commit_root == root->node) {
 547                                 WARN_ON(root->node->start !=
 548                                         btrfs_root_bytenr(&root->root_item));
 549
 550                                 free_extent_buffer(root->commit_root);
 551                                 root->commit_root = NULL;
 552                                 root->dirty_root = NULL;
 553
 554                                 spin_lock(&root->list_lock);
 555                                 list_del_init(&dirty->root->dead_list);
 556                                 spin_unlock(&root->list_lock);
 557
 558                                 kfree(dirty->root);
 559                                 kfree(dirty);
 560
 561                                 /* make sure to update the root on disk
 562                                  * so we get any updates to the block used
 563                                  * counts
 564                                  */
 565                                 err = btrfs_update_root(trans,
 566                                                 root->fs_info->tree_root,
 567                                                 &root->root_key,
 568                                                 &root->root_item);
 569                                 continue;
 570                         }
 571
 572                         memset(&root->root_item.drop_progress, 0,
 573                                sizeof(struct btrfs_disk_key));
 574                         root->root_item.drop_level = 0;
 575                         root->commit_root = NULL;
 576                         root->dirty_root = NULL;
 577                         root->root_key.offset = root->fs_info->generation;
 578                         btrfs_set_root_bytenr(&root->root_item,
 579                                               root->node->start);
 580                         btrfs_set_root_level(&root->root_item,
 581                                              btrfs_header_level(root->node));
 582                         btrfs_set_root_generation(&root->root_item,
 583                                                   root->root_key.offset);
 584
 585                         err = btrfs_insert_root(trans, root->fs_info->tree_root,
 586                                                 &root->root_key,
 587                                                 &root->root_item);
 588                         if (err)
 589                                 break;
 590
 591                         refs = btrfs_root_refs(&dirty->root->root_item);
 592                         btrfs_set_root_refs(&dirty->root->root_item, refs - 1);
 593                         err = btrfs_update_root(trans, root->fs_info->tree_root,
 594                                                 &dirty->root->root_key,
 595                                                 &dirty->root->root_item);
 596
 597                         BUG_ON(err);
 598                         if (refs == 1) {
 599                                 list_add(&dirty->list, list);
 600                         } else {
 601                                 WARN_ON(1);
 602                                 free_extent_buffer(dirty->root->node);
 603                                 kfree(dirty->root);
 604                                 kfree(dirty);
 605                         }
 606                 }
 607         }
 608         return err;
 609 }
 610
 611 /*
 612  * defrag a given btree.  If cacheonly == 1, this won't read from the disk,
 613  * otherwise every leaf in the btree is read and defragged.
 614  */
 615 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 616 {
 617         struct btrfs_fs_info *info = root->fs_info;
 618         int ret;
 619         struct btrfs_trans_handle *trans;
 620         unsigned long nr;
 621
 622         smp_mb();
 623         if (root->defrag_running)
 624                 return 0;
 625         trans = btrfs_start_transaction(root, 1);
 626         while (1) {
 627                 root->defrag_running = 1;
 628                 ret = btrfs_defrag_leaves(trans, root, cacheonly);
 629                 nr = trans->blocks_used;
 630                 btrfs_end_transaction(trans, root);
 631                 btrfs_btree_balance_dirty(info->tree_root, nr);
 632                 cond_resched();
 633
 634                 trans = btrfs_start_transaction(root, 1);
 635                 if (root->fs_info->closing || ret != -EAGAIN)
 636                         break;
 637         }
 638         root->defrag_running = 0;
 639         smp_mb();
 640         btrfs_end_transaction(trans, root);
 641         return 0;
 642 }
 643
 644 /*
 645  * Given a list of roots that need to be deleted, call btrfs_drop_snapshot on
 646  * all of them
 647  */
 648 static noinline int drop_dirty_roots(struct btrfs_root *tree_root,
 649                                      struct list_head *list)
 650 {
 651         struct btrfs_dirty_root *dirty;
 652         struct btrfs_trans_handle *trans;
 653         unsigned long nr;
 654         u64 num_bytes;
 655         u64 bytes_used;
 656         u64 max_useless;
 657         int ret = 0;
 658         int err;
 659
 660         while(!list_empty(list)) {
 661                 struct btrfs_root *root;
 662
 663                 dirty = list_entry(list->prev, struct btrfs_dirty_root, list);
 664                 list_del_init(&dirty->list);
 665
 666                 num_bytes = btrfs_root_used(&dirty->root->root_item);
 667                 root = dirty->latest_root;
 668                 atomic_inc(&root->fs_info->throttles);
 669
 670                 while(1) {
 671                         trans = btrfs_start_transaction(tree_root, 1);
 672                         mutex_lock(&root->fs_info->drop_mutex);
 673                         ret = btrfs_drop_snapshot(trans, dirty->root);
 674                         if (ret != -EAGAIN) {
 675                                 break;
 676                         }
 677                         mutex_unlock(&root->fs_info->drop_mutex);
 678
 679                         err = btrfs_update_root(trans,
 680                                         tree_root,
 681                                         &dirty->root->root_key,
 682                                         &dirty->root->root_item);
 683                         if (err)
 684                                 ret = err;
 685                         nr = trans->blocks_used;
 686                         ret = btrfs_end_transaction(trans, tree_root);
 687                         BUG_ON(ret);
 688
 689                         btrfs_btree_balance_dirty(tree_root, nr);
 690                         cond_resched();
 691                 }
 692                 BUG_ON(ret);
 693                 atomic_dec(&root->fs_info->throttles);
 694                 wake_up(&root->fs_info->transaction_throttle);
 695
 696                 num_bytes -= btrfs_root_used(&dirty->root->root_item);
 697                 bytes_used = btrfs_root_used(&root->root_item);
 698                 if (num_bytes) {
 699                         btrfs_record_root_in_trans(root);
 700                         btrfs_set_root_used(&root->root_item,
 701                                             bytes_used - num_bytes);
 702                 }
 703
 704                 ret = btrfs_del_root(trans, tree_root, &dirty->root->root_key);
 705                 if (ret) {
 706                         BUG();
 707                         break;
 708                 }
 709                 mutex_unlock(&root->fs_info->drop_mutex);
 710
 711                 spin_lock(&root->list_lock);
 712                 list_del_init(&dirty->root->dead_list);
 713                 if (!list_empty(&root->dead_list)) {
 714                         struct btrfs_root *oldest;
 715                         oldest = list_entry(root->dead_list.prev,
 716                                             struct btrfs_root, dead_list);
 717                         max_useless = oldest->root_key.offset - 1;
 718                 } else {
 719                         max_useless = root->root_key.offset - 1;
 720                 }
 721                 spin_unlock(&root->list_lock);
 722
 723                 nr = trans->blocks_used;
 724                 ret = btrfs_end_transaction(trans, tree_root);
 725                 BUG_ON(ret);
 726
 727                 ret = btrfs_remove_leaf_refs(root, max_useless, 0);
 728                 BUG_ON(ret);
 729
 730                 free_extent_buffer(dirty->root->node);
 731                 kfree(dirty->root);
 732                 kfree(dirty);
 733
 734                 btrfs_btree_balance_dirty(tree_root, nr);
 735                 cond_resched();
 736         }
 737         return ret;
 738 }
 739
 740 /*
 741  * new snapshots need to be created at a very specific time in the
 742  * transaction commit.  This does the actual creation
 743  */
 744 static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 745                                    struct btrfs_fs_info *fs_info,
 746                                    struct btrfs_pending_snapshot *pending)
 747 {
 748         struct btrfs_key key;
 749         struct btrfs_root_item *new_root_item;
 750         struct btrfs_root *tree_root = fs_info->tree_root;
 751         struct btrfs_root *root = pending->root;
 752         struct extent_buffer *tmp;
 753         struct extent_buffer *old;
 754         int ret;
 755         u64 objectid;
 756
 757         new_root_item = kmalloc(sizeof(*new_root_item), GFP_NOFS);
 758         if (!new_root_item) {
 759                 ret = -ENOMEM;
 760                 goto fail;
 761         }
 762         ret = btrfs_find_free_objectid(trans, tree_root, 0, &objectid);
 763         if (ret)
 764                 goto fail;
 765
 766         btrfs_record_root_in_trans(root);
 767         btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
 768         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
 769
 770         key.objectid = objectid;
 771         key.offset = trans->transid;
 772         btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
 773
 774         old = btrfs_lock_root_node(root);
 775         btrfs_cow_block(trans, root, old, NULL, 0, &old, 0);
 776
 777         btrfs_copy_root(trans, root, old, &tmp, objectid);
 778         btrfs_tree_unlock(old);
 779         free_extent_buffer(old);
 780
 781         btrfs_set_root_bytenr(new_root_item, tmp->start);
 782         btrfs_set_root_level(new_root_item, btrfs_header_level(tmp));
 783         btrfs_set_root_generation(new_root_item, trans->transid);
 784         ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
 785                                 new_root_item);
 786         btrfs_tree_unlock(tmp);
 787         free_extent_buffer(tmp);
 788         if (ret)
 789                 goto fail;
 790
 791         key.offset = (u64)-1;
 792         memcpy(&pending->root_key, &key, sizeof(key));
 793 fail:
 794         kfree(new_root_item);
 795         return ret;
 796 }
 797
 798 static noinline int finish_pending_snapshot(struct btrfs_fs_info *fs_info,
 799                                    struct btrfs_pending_snapshot *pending)
 800 {
 801         int ret;
 802         int namelen;
 803         u64 index = 0;
 804         struct btrfs_trans_handle *trans;
 805         struct inode *parent_inode;
 806         struct inode *inode;
 807         struct btrfs_root *parent_root;
 808
 809         parent_inode = pending->dentry->d_parent->d_inode;
 810         parent_root = BTRFS_I(parent_inode)->root;
 811         trans = btrfs_start_transaction(parent_root, 1);
 812
 813         /*
 814          * insert the directory item
 815          */
 816         namelen = strlen(pending->name);
 817         ret = btrfs_set_inode_index(parent_inode, &index);
 818         ret = btrfs_insert_dir_item(trans, parent_root,
 819                             pending->name, namelen,
 820                             parent_inode->i_ino,
 821                             &pending->root_key, BTRFS_FT_DIR, index);
 822
 823         if (ret)
 824                 goto fail;
 825
 826         /* add the backref first */
 827         ret = btrfs_add_root_ref(trans, parent_root->fs_info->tree_root,
 828                                  pending->root_key.objectid,
 829                                  BTRFS_ROOT_BACKREF_KEY,
 830                                  parent_root->root_key.objectid,
 831                                  parent_inode->i_ino, index, pending->name,
 832                                  namelen);
 833
 834         BUG_ON(ret);
 835
 836         /* now add the forward ref */
 837         ret = btrfs_add_root_ref(trans, parent_root->fs_info->tree_root,
 838                                  parent_root->root_key.objectid,
 839                                  BTRFS_ROOT_REF_KEY,
 840                                  pending->root_key.objectid,
 841                                  parent_inode->i_ino, index, pending->name,
 842                                  namelen);
 843
 844         inode = btrfs_lookup_dentry(parent_inode, pending->dentry);
 845         d_instantiate(pending->dentry, inode);
 846 fail:
 847         btrfs_end_transaction(trans, fs_info->fs_root);
 848         return ret;
 849 }
 850
 851 /*
 852  * create all the snapshots we've scheduled for creation
 853  */
 854 static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans,
 855                                              struct btrfs_fs_info *fs_info)
 856 {
 857         struct btrfs_pending_snapshot *pending;
 858         struct list_head *head = &trans->transaction->pending_snapshots;
 859         struct list_head *cur;
 860         int ret;
 861
 862         list_for_each(cur, head) {
 863                 pending = list_entry(cur, struct btrfs_pending_snapshot, list);
 864                 ret = create_pending_snapshot(trans, fs_info, pending);
 865                 BUG_ON(ret);
 866         }
 867         return 0;
 868 }
 869
 870 static noinline int finish_pending_snapshots(struct btrfs_trans_handle *trans,
 871                                              struct btrfs_fs_info *fs_info)
 872 {
 873         struct btrfs_pending_snapshot *pending;
 874         struct list_head *head = &trans->transaction->pending_snapshots;
 875         int ret;
 876
 877         while(!list_empty(head)) {
 878                 pending = list_entry(head->next,
 879                                      struct btrfs_pending_snapshot, list);
 880                 ret = finish_pending_snapshot(fs_info, pending);
 881                 BUG_ON(ret);
 882                 list_del(&pending->list);
 883                 kfree(pending->name);
 884                 kfree(pending);
 885         }
 886         return 0;
 887 }
 888
 889 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 890                              struct btrfs_root *root)
 891 {
 892         unsigned long joined = 0;
 893         unsigned long timeout = 1;
 894         struct btrfs_transaction *cur_trans;
 895         struct btrfs_transaction *prev_trans = NULL;
 896         struct btrfs_root *chunk_root = root->fs_info->chunk_root;
 897         struct list_head dirty_fs_roots;
 898         struct extent_io_tree *pinned_copy;
 899         DEFINE_WAIT(wait);
 900         int ret;
 901
 902         INIT_LIST_HEAD(&dirty_fs_roots);
 903         mutex_lock(&root->fs_info->trans_mutex);
 904         if (trans->transaction->in_commit) {
 905                 cur_trans = trans->transaction;
 906                 trans->transaction->use_count++;
 907                 mutex_unlock(&root->fs_info->trans_mutex);
 908                 btrfs_end_transaction(trans, root);
 909
 910                 ret = wait_for_commit(root, cur_trans);
 911                 BUG_ON(ret);
 912
 913                 mutex_lock(&root->fs_info->trans_mutex);
 914                 put_transaction(cur_trans);
 915                 mutex_unlock(&root->fs_info->trans_mutex);
 916
 917                 return 0;
 918         }
 919
 920         pinned_copy = kmalloc(sizeof(*pinned_copy), GFP_NOFS);
 921         if (!pinned_copy)
 922                 return -ENOMEM;
 923
 924         extent_io_tree_init(pinned_copy,
 925                              root->fs_info->btree_inode->i_mapping, GFP_NOFS);
 926
 927         trans->transaction->in_commit = 1;
 928         trans->transaction->blocked = 1;
 929         cur_trans = trans->transaction;
 930         if (cur_trans->list.prev != &root->fs_info->trans_list) {
 931                 prev_trans = list_entry(cur_trans->list.prev,
 932                                         struct btrfs_transaction, list);
 933                 if (!prev_trans->commit_done) {
 934                         prev_trans->use_count++;
 935                         mutex_unlock(&root->fs_info->trans_mutex);
 936
 937                         wait_for_commit(root, prev_trans);
 938
 939                         mutex_lock(&root->fs_info->trans_mutex);
 940                         put_transaction(prev_trans);
 941                 }
 942         }
 943
 944         do {
 945                 int snap_pending = 0;
 946                 joined = cur_trans->num_joined;
 947                 if (!list_empty(&trans->transaction->pending_snapshots))
 948                         snap_pending = 1;
 949
 950                 WARN_ON(cur_trans != trans->transaction);
 951                 prepare_to_wait(&cur_trans->writer_wait, &wait,
 952                                 TASK_UNINTERRUPTIBLE);
 953
 954                 if (cur_trans->num_writers > 1)
 955                         timeout = MAX_SCHEDULE_TIMEOUT;
 956                 else
 957                         timeout = 1;
 958
 959                 mutex_unlock(&root->fs_info->trans_mutex);
 960
 961                 if (snap_pending) {
 962                         ret = btrfs_wait_ordered_extents(root, 1);
 963                         BUG_ON(ret);
 964                 }
 965
 966                 schedule_timeout(timeout);
 967
 968                 mutex_lock(&root->fs_info->trans_mutex);
 969                 finish_wait(&cur_trans->writer_wait, &wait);
 970         } while (cur_trans->num_writers > 1 ||
 971                  (cur_trans->num_joined != joined));
 972
 973         ret = create_pending_snapshots(trans, root->fs_info);
 974         BUG_ON(ret);
 975
 976         WARN_ON(cur_trans != trans->transaction);
 977
 978         /* btrfs_commit_tree_roots is responsible for getting the
 979          * various roots consistent with each other.  Every pointer
 980          * in the tree of tree roots has to point to the most up to date
 981          * root for every subvolume and other tree.  So, we have to keep
 982          * the tree logging code from jumping in and changing any
 983          * of the trees.
 984          *
 985          * At this point in the commit, there can't be any tree-log
 986          * writers, but a little lower down we drop the trans mutex
 987          * and let new people in.  By holding the tree_log_mutex
 988          * from now until after the super is written, we avoid races
 989          * with the tree-log code.
 990          */
 991         mutex_lock(&root->fs_info->tree_log_mutex);
 992         /*
 993          * keep tree reloc code from adding new reloc trees
 994          */
 995         mutex_lock(&root->fs_info->tree_reloc_mutex);
 996
 997
 998         ret = add_dirty_roots(trans, &root->fs_info->fs_roots_radix,
 999                               &dirty_fs_roots);
1000         BUG_ON(ret);
1001
1002         /* add_dirty_roots gets rid of all the tree log roots, it is now
1003          * safe to free the root of tree log roots
1004          */
1005         btrfs_free_log_root_tree(trans, root->fs_info);
1006
1007         ret = btrfs_commit_tree_roots(trans, root);
1008         BUG_ON(ret);
1009
1010         cur_trans = root->fs_info->running_transaction;
1011         spin_lock(&root->fs_info->new_trans_lock);
1012         root->fs_info->running_transaction = NULL;
1013         spin_unlock(&root->fs_info->new_trans_lock);
1014         btrfs_set_super_generation(&root->fs_info->super_copy,
1015                                    cur_trans->transid);
1016         btrfs_set_super_root(&root->fs_info->super_copy,
1017                              root->fs_info->tree_root->node->start);
1018         btrfs_set_super_root_level(&root->fs_info->super_copy,
1019                            btrfs_header_level(root->fs_info->tree_root->node));
1020
1021         btrfs_set_super_chunk_root(&root->fs_info->super_copy,
1022                                    chunk_root->node->start);
1023         btrfs_set_super_chunk_root_level(&root->fs_info->super_copy,
1024                                          btrfs_header_level(chunk_root->node));
1025         btrfs_set_super_chunk_root_generation(&root->fs_info->super_copy,
1026                                 btrfs_header_generation(chunk_root->node));
1027
1028         if (!root->fs_info->log_root_recovering) {
1029                 btrfs_set_super_log_root(&root->fs_info->super_copy, 0);
1030                 btrfs_set_super_log_root_level(&root->fs_info->super_copy, 0);
1031         }
1032
1033         memcpy(&root->fs_info->super_for_commit, &root->fs_info->super_copy,
1034                sizeof(root->fs_info->super_copy));
1035
1036         btrfs_copy_pinned(root, pinned_copy);
1037
1038         trans->transaction->blocked = 0;
1039         wake_up(&root->fs_info->transaction_throttle);
1040         wake_up(&root->fs_info->transaction_wait);
1041
1042         mutex_unlock(&root->fs_info->trans_mutex);
1043         ret = btrfs_write_and_wait_transaction(trans, root);
1044         BUG_ON(ret);
1045         write_ctree_super(trans, root);
1046
1047         /*
1048          * the super is written, we can safely allow the tree-loggers
1049          * to go about their business
1050          */
1051         mutex_unlock(&root->fs_info->tree_log_mutex);
1052
1053         btrfs_finish_extent_commit(trans, root, pinned_copy);
1054         kfree(pinned_copy);
1055
1056         btrfs_drop_dead_reloc_roots(root);
1057         mutex_unlock(&root->fs_info->tree_reloc_mutex);
1058
1059         /* do the directory inserts of any pending snapshot creations */
1060         finish_pending_snapshots(trans, root->fs_info);
1061
1062         mutex_lock(&root->fs_info->trans_mutex);
1063
1064         cur_trans->commit_done = 1;
1065         root->fs_info->last_trans_committed = cur_trans->transid;
1066         wake_up(&cur_trans->commit_wait);
1067
1068         put_transaction(cur_trans);
1069         put_transaction(cur_trans);
1070
1071         list_splice_init(&dirty_fs_roots, &root->fs_info->dead_roots);
1072         if (root->fs_info->closing)
1073                 list_splice_init(&root->fs_info->dead_roots, &dirty_fs_roots);
1074
1075         mutex_unlock(&root->fs_info->trans_mutex);
1076
1077         kmem_cache_free(btrfs_trans_handle_cachep, trans);
1078
1079         if (root->fs_info->closing) {
1080                 drop_dirty_roots(root->fs_info->tree_root, &dirty_fs_roots);
1081         }
1082         return ret;
1083 }
1084
1085 /*
1086  * interface function to delete all the snapshots we have scheduled for deletion
1087  */
1088 int btrfs_clean_old_snapshots(struct btrfs_root *root)
1089 {
1090         struct list_head dirty_roots;
1091         INIT_LIST_HEAD(&dirty_roots);
1092 again:
1093         mutex_lock(&root->fs_info->trans_mutex);
1094         list_splice_init(&root->fs_info->dead_roots, &dirty_roots);
1095         mutex_unlock(&root->fs_info->trans_mutex);
1096
1097         if (!list_empty(&dirty_roots)) {
1098                 drop_dirty_roots(root, &dirty_roots);
1099                 goto again;
1100         }
1101         return 0;
1102 }