fs/btrfs/relocation.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2009 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/writeback.h>
   9 #include <linux/blkdev.h>
  10 #include <linux/rbtree.h>
  11 #include <linux/slab.h>
  12 #include "ctree.h"
  13 #include "disk-io.h"
  14 #include "transaction.h"
  15 #include "volumes.h"
  16 #include "locking.h"
  17 #include "btrfs_inode.h"
  18 #include "async-thread.h"
  19 #include "free-space-cache.h"
  20 #include "inode-map.h"
  21 #include "qgroup.h"
  22 #include "print-tree.h"
  23
  24 /*
  25  * backref_node, mapping_node and tree_block start with this
  26  */
  27 struct tree_entry {
  28         struct rb_node rb_node;
  29         u64 bytenr;
  30 };
  31
  32 /*
  33  * present a tree block in the backref cache
  34  */
  35 struct backref_node {
  36         struct rb_node rb_node;
  37         u64 bytenr;
  38
  39         u64 new_bytenr;
  40         /* objectid of tree block owner, can be not uptodate */
  41         u64 owner;
  42         /* link to pending, changed or detached list */
  43         struct list_head list;
  44         /* list of upper level blocks reference this block */
  45         struct list_head upper;
  46         /* list of child blocks in the cache */
  47         struct list_head lower;
  48         /* NULL if this node is not tree root */
  49         struct btrfs_root *root;
  50         /* extent buffer got by COW the block */
  51         struct extent_buffer *eb;
  52         /* level of tree block */
  53         unsigned int level:8;
  54         /* is the block in non-reference counted tree */
  55         unsigned int cowonly:1;
  56         /* 1 if no child node in the cache */
  57         unsigned int lowest:1;
  58         /* is the extent buffer locked */
  59         unsigned int locked:1;
  60         /* has the block been processed */
  61         unsigned int processed:1;
  62         /* have backrefs of this block been checked */
  63         unsigned int checked:1;
  64         /*
  65          * 1 if corresponding block has been cowed but some upper
  66          * level block pointers may not point to the new location
  67          */
  68         unsigned int pending:1;
  69         /*
  70          * 1 if the backref node isn't connected to any other
  71          * backref node.
  72          */
  73         unsigned int detached:1;
  74 };
  75
  76 /*
  77  * present a block pointer in the backref cache
  78  */
  79 struct backref_edge {
  80         struct list_head list[2];
  81         struct backref_node *node[2];
  82 };
  83
  84 #define LOWER   0
  85 #define UPPER   1
  86 #define RELOCATION_RESERVED_NODES       256
  87
  88 struct backref_cache {
  89         /* red black tree of all backref nodes in the cache */
  90         struct rb_root rb_root;
  91         /* for passing backref nodes to btrfs_reloc_cow_block */
  92         struct backref_node *path[BTRFS_MAX_LEVEL];
  93         /*
  94          * list of blocks that have been cowed but some block
  95          * pointers in upper level blocks may not reflect the
  96          * new location
  97          */
  98         struct list_head pending[BTRFS_MAX_LEVEL];
  99         /* list of backref nodes with no child node */
 100         struct list_head leaves;
 101         /* list of blocks that have been cowed in current transaction */
 102         struct list_head changed;
 103         /* list of detached backref node. */
 104         struct list_head detached;
 105
 106         u64 last_trans;
 107
 108         int nr_nodes;
 109         int nr_edges;
 110 };
 111
 112 /*
 113  * map address of tree root to tree
 114  */
 115 struct mapping_node {
 116         struct rb_node rb_node;
 117         u64 bytenr;
 118         void *data;
 119 };
 120
 121 struct mapping_tree {
 122         struct rb_root rb_root;
 123         spinlock_t lock;
 124 };
 125
 126 /*
 127  * present a tree block to process
 128  */
 129 struct tree_block {
 130         struct rb_node rb_node;
 131         u64 bytenr;
 132         struct btrfs_key key;
 133         unsigned int level:8;
 134         unsigned int key_ready:1;
 135 };
 136
 137 #define MAX_EXTENTS 128
 138
 139 struct file_extent_cluster {
 140         u64 start;
 141         u64 end;
 142         u64 boundary[MAX_EXTENTS];
 143         unsigned int nr;
 144 };
 145
 146 struct reloc_control {
 147         /* block group to relocate */
 148         struct btrfs_block_group_cache *block_group;
 149         /* extent tree */
 150         struct btrfs_root *extent_root;
 151         /* inode for moving data */
 152         struct inode *data_inode;
 153
 154         struct btrfs_block_rsv *block_rsv;
 155
 156         struct backref_cache backref_cache;
 157
 158         struct file_extent_cluster cluster;
 159         /* tree blocks have been processed */
 160         struct extent_io_tree processed_blocks;
 161         /* map start of tree root to corresponding reloc tree */
 162         struct mapping_tree reloc_root_tree;
 163         /* list of reloc trees */
 164         struct list_head reloc_roots;
 165         /* size of metadata reservation for merging reloc trees */
 166         u64 merging_rsv_size;
 167         /* size of relocated tree nodes */
 168         u64 nodes_relocated;
 169         /* reserved size for block group relocation*/
 170         u64 reserved_bytes;
 171
 172         u64 search_start;
 173         u64 extents_found;
 174
 175         unsigned int stage:8;
 176         unsigned int create_reloc_tree:1;
 177         unsigned int merge_reloc_tree:1;
 178         unsigned int found_file_extent:1;
 179 };
 180
 181 /* stages of data relocation */
 182 #define MOVE_DATA_EXTENTS       0
 183 #define UPDATE_DATA_PTRS        1
 184
 185 static void remove_backref_node(struct backref_cache *cache,
 186                                 struct backref_node *node);
 187 static void __mark_block_processed(struct reloc_control *rc,
 188                                    struct backref_node *node);
 189
 190 static void mapping_tree_init(struct mapping_tree *tree)
 191 {
 192         tree->rb_root = RB_ROOT;
 193         spin_lock_init(&tree->lock);
 194 }
 195
 196 static void backref_cache_init(struct backref_cache *cache)
 197 {
 198         int i;
 199         cache->rb_root = RB_ROOT;
 200         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 201                 INIT_LIST_HEAD(&cache->pending[i]);
 202         INIT_LIST_HEAD(&cache->changed);
 203         INIT_LIST_HEAD(&cache->detached);
 204         INIT_LIST_HEAD(&cache->leaves);
 205 }
 206
 207 static void backref_cache_cleanup(struct backref_cache *cache)
 208 {
 209         struct backref_node *node;
 210         int i;
 211
 212         while (!list_empty(&cache->detached)) {
 213                 node = list_entry(cache->detached.next,
 214                                   struct backref_node, list);
 215                 remove_backref_node(cache, node);
 216         }
 217
 218         while (!list_empty(&cache->leaves)) {
 219                 node = list_entry(cache->leaves.next,
 220                                   struct backref_node, lower);
 221                 remove_backref_node(cache, node);
 222         }
 223
 224         cache->last_trans = 0;
 225
 226         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 227                 ASSERT(list_empty(&cache->pending[i]));
 228         ASSERT(list_empty(&cache->changed));
 229         ASSERT(list_empty(&cache->detached));
 230         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
 231         ASSERT(!cache->nr_nodes);
 232         ASSERT(!cache->nr_edges);
 233 }
 234
 235 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
 236 {
 237         struct backref_node *node;
 238
 239         node = kzalloc(sizeof(*node), GFP_NOFS);
 240         if (node) {
 241                 INIT_LIST_HEAD(&node->list);
 242                 INIT_LIST_HEAD(&node->upper);
 243                 INIT_LIST_HEAD(&node->lower);
 244                 RB_CLEAR_NODE(&node->rb_node);
 245                 cache->nr_nodes++;
 246         }
 247         return node;
 248 }
 249
 250 static void free_backref_node(struct backref_cache *cache,
 251                               struct backref_node *node)
 252 {
 253         if (node) {
 254                 cache->nr_nodes--;
 255                 kfree(node);
 256         }
 257 }
 258
 259 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
 260 {
 261         struct backref_edge *edge;
 262
 263         edge = kzalloc(sizeof(*edge), GFP_NOFS);
 264         if (edge)
 265                 cache->nr_edges++;
 266         return edge;
 267 }
 268
 269 static void free_backref_edge(struct backref_cache *cache,
 270                               struct backref_edge *edge)
 271 {
 272         if (edge) {
 273                 cache->nr_edges--;
 274                 kfree(edge);
 275         }
 276 }
 277
 278 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
 279                                    struct rb_node *node)
 280 {
 281         struct rb_node **p = &root->rb_node;
 282         struct rb_node *parent = NULL;
 283         struct tree_entry *entry;
 284
 285         while (*p) {
 286                 parent = *p;
 287                 entry = rb_entry(parent, struct tree_entry, rb_node);
 288
 289                 if (bytenr < entry->bytenr)
 290                         p = &(*p)->rb_left;
 291                 else if (bytenr > entry->bytenr)
 292                         p = &(*p)->rb_right;
 293                 else
 294                         return parent;
 295         }
 296
 297         rb_link_node(node, parent, p);
 298         rb_insert_color(node, root);
 299         return NULL;
 300 }
 301
 302 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
 303 {
 304         struct rb_node *n = root->rb_node;
 305         struct tree_entry *entry;
 306
 307         while (n) {
 308                 entry = rb_entry(n, struct tree_entry, rb_node);
 309
 310                 if (bytenr < entry->bytenr)
 311                         n = n->rb_left;
 312                 else if (bytenr > entry->bytenr)
 313                         n = n->rb_right;
 314                 else
 315                         return n;
 316         }
 317         return NULL;
 318 }
 319
 320 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
 321 {
 322
 323         struct btrfs_fs_info *fs_info = NULL;
 324         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
 325                                               rb_node);
 326         if (bnode->root)
 327                 fs_info = bnode->root->fs_info;
 328         btrfs_panic(fs_info, errno,
 329                     "Inconsistency in backref cache found at offset %llu",
 330                     bytenr);
 331 }
 332
 333 /*
 334  * walk up backref nodes until reach node presents tree root
 335  */
 336 static struct backref_node *walk_up_backref(struct backref_node *node,
 337                                             struct backref_edge *edges[],
 338                                             int *index)
 339 {
 340         struct backref_edge *edge;
 341         int idx = *index;
 342
 343         while (!list_empty(&node->upper)) {
 344                 edge = list_entry(node->upper.next,
 345                                   struct backref_edge, list[LOWER]);
 346                 edges[idx++] = edge;
 347                 node = edge->node[UPPER];
 348         }
 349         BUG_ON(node->detached);
 350         *index = idx;
 351         return node;
 352 }
 353
 354 /*
 355  * walk down backref nodes to find start of next reference path
 356  */
 357 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
 358                                               int *index)
 359 {
 360         struct backref_edge *edge;
 361         struct backref_node *lower;
 362         int idx = *index;
 363
 364         while (idx > 0) {
 365                 edge = edges[idx - 1];
 366                 lower = edge->node[LOWER];
 367                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 368                         idx--;
 369                         continue;
 370                 }
 371                 edge = list_entry(edge->list[LOWER].next,
 372                                   struct backref_edge, list[LOWER]);
 373                 edges[idx - 1] = edge;
 374                 *index = idx;
 375                 return edge->node[UPPER];
 376         }
 377         *index = 0;
 378         return NULL;
 379 }
 380
 381 static void unlock_node_buffer(struct backref_node *node)
 382 {
 383         if (node->locked) {
 384                 btrfs_tree_unlock(node->eb);
 385                 node->locked = 0;
 386         }
 387 }
 388
 389 static void drop_node_buffer(struct backref_node *node)
 390 {
 391         if (node->eb) {
 392                 unlock_node_buffer(node);
 393                 free_extent_buffer(node->eb);
 394                 node->eb = NULL;
 395         }
 396 }
 397
 398 static void drop_backref_node(struct backref_cache *tree,
 399                               struct backref_node *node)
 400 {
 401         BUG_ON(!list_empty(&node->upper));
 402
 403         drop_node_buffer(node);
 404         list_del(&node->list);
 405         list_del(&node->lower);
 406         if (!RB_EMPTY_NODE(&node->rb_node))
 407                 rb_erase(&node->rb_node, &tree->rb_root);
 408         free_backref_node(tree, node);
 409 }
 410
 411 /*
 412  * remove a backref node from the backref cache
 413  */
 414 static void remove_backref_node(struct backref_cache *cache,
 415                                 struct backref_node *node)
 416 {
 417         struct backref_node *upper;
 418         struct backref_edge *edge;
 419
 420         if (!node)
 421                 return;
 422
 423         BUG_ON(!node->lowest && !node->detached);
 424         while (!list_empty(&node->upper)) {
 425                 edge = list_entry(node->upper.next, struct backref_edge,
 426                                   list[LOWER]);
 427                 upper = edge->node[UPPER];
 428                 list_del(&edge->list[LOWER]);
 429                 list_del(&edge->list[UPPER]);
 430                 free_backref_edge(cache, edge);
 431
 432                 if (RB_EMPTY_NODE(&upper->rb_node)) {
 433                         BUG_ON(!list_empty(&node->upper));
 434                         drop_backref_node(cache, node);
 435                         node = upper;
 436                         node->lowest = 1;
 437                         continue;
 438                 }
 439                 /*
 440                  * add the node to leaf node list if no other
 441                  * child block cached.
 442                  */
 443                 if (list_empty(&upper->lower)) {
 444                         list_add_tail(&upper->lower, &cache->leaves);
 445                         upper->lowest = 1;
 446                 }
 447         }
 448
 449         drop_backref_node(cache, node);
 450 }
 451
 452 static void update_backref_node(struct backref_cache *cache,
 453                                 struct backref_node *node, u64 bytenr)
 454 {
 455         struct rb_node *rb_node;
 456         rb_erase(&node->rb_node, &cache->rb_root);
 457         node->bytenr = bytenr;
 458         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 459         if (rb_node)
 460                 backref_tree_panic(rb_node, -EEXIST, bytenr);
 461 }
 462
 463 /*
 464  * update backref cache after a transaction commit
 465  */
 466 static int update_backref_cache(struct btrfs_trans_handle *trans,
 467                                 struct backref_cache *cache)
 468 {
 469         struct backref_node *node;
 470         int level = 0;
 471
 472         if (cache->last_trans == 0) {
 473                 cache->last_trans = trans->transid;
 474                 return 0;
 475         }
 476
 477         if (cache->last_trans == trans->transid)
 478                 return 0;
 479
 480         /*
 481          * detached nodes are used to avoid unnecessary backref
 482          * lookup. transaction commit changes the extent tree.
 483          * so the detached nodes are no longer useful.
 484          */
 485         while (!list_empty(&cache->detached)) {
 486                 node = list_entry(cache->detached.next,
 487                                   struct backref_node, list);
 488                 remove_backref_node(cache, node);
 489         }
 490
 491         while (!list_empty(&cache->changed)) {
 492                 node = list_entry(cache->changed.next,
 493                                   struct backref_node, list);
 494                 list_del_init(&node->list);
 495                 BUG_ON(node->pending);
 496                 update_backref_node(cache, node, node->new_bytenr);
 497         }
 498
 499         /*
 500          * some nodes can be left in the pending list if there were
 501          * errors during processing the pending nodes.
 502          */
 503         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 504                 list_for_each_entry(node, &cache->pending[level], list) {
 505                         BUG_ON(!node->pending);
 506                         if (node->bytenr == node->new_bytenr)
 507                                 continue;
 508                         update_backref_node(cache, node, node->new_bytenr);
 509                 }
 510         }
 511
 512         cache->last_trans = 0;
 513         return 1;
 514 }
 515
 516
 517 static int should_ignore_root(struct btrfs_root *root)
 518 {
 519         struct btrfs_root *reloc_root;
 520
 521         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 522                 return 0;
 523
 524         reloc_root = root->reloc_root;
 525         if (!reloc_root)
 526                 return 0;
 527
 528         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
 529             root->fs_info->running_transaction->transid - 1)
 530                 return 0;
 531         /*
 532          * if there is reloc tree and it was created in previous
 533          * transaction backref lookup can find the reloc tree,
 534          * so backref node for the fs tree root is useless for
 535          * relocation.
 536          */
 537         return 1;
 538 }
 539 /*
 540  * find reloc tree by address of tree root
 541  */
 542 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
 543                                           u64 bytenr)
 544 {
 545         struct rb_node *rb_node;
 546         struct mapping_node *node;
 547         struct btrfs_root *root = NULL;
 548
 549         spin_lock(&rc->reloc_root_tree.lock);
 550         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
 551         if (rb_node) {
 552                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 553                 root = (struct btrfs_root *)node->data;
 554         }
 555         spin_unlock(&rc->reloc_root_tree.lock);
 556         return root;
 557 }
 558
 559 static int is_cowonly_root(u64 root_objectid)
 560 {
 561         if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
 562             root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
 563             root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
 564             root_objectid == BTRFS_DEV_TREE_OBJECTID ||
 565             root_objectid == BTRFS_TREE_LOG_OBJECTID ||
 566             root_objectid == BTRFS_CSUM_TREE_OBJECTID ||
 567             root_objectid == BTRFS_UUID_TREE_OBJECTID ||
 568             root_objectid == BTRFS_QUOTA_TREE_OBJECTID ||
 569             root_objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
 570                 return 1;
 571         return 0;
 572 }
 573
 574 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 575                                         u64 root_objectid)
 576 {
 577         struct btrfs_key key;
 578
 579         key.objectid = root_objectid;
 580         key.type = BTRFS_ROOT_ITEM_KEY;
 581         if (is_cowonly_root(root_objectid))
 582                 key.offset = 0;
 583         else
 584                 key.offset = (u64)-1;
 585
 586         return btrfs_get_fs_root(fs_info, &key, false);
 587 }
 588
 589 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 590 static noinline_for_stack
 591 struct btrfs_root *find_tree_root(struct reloc_control *rc,
 592                                   struct extent_buffer *leaf,
 593                                   struct btrfs_extent_ref_v0 *ref0)
 594 {
 595         struct btrfs_root *root;
 596         u64 root_objectid = btrfs_ref_root_v0(leaf, ref0);
 597         u64 generation = btrfs_ref_generation_v0(leaf, ref0);
 598
 599         BUG_ON(root_objectid == BTRFS_TREE_RELOC_OBJECTID);
 600
 601         root = read_fs_root(rc->extent_root->fs_info, root_objectid);
 602         BUG_ON(IS_ERR(root));
 603
 604         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 605             generation != btrfs_root_generation(&root->root_item))
 606                 return NULL;
 607
 608         return root;
 609 }
 610 #endif
 611
 612 static noinline_for_stack
 613 int find_inline_backref(struct extent_buffer *leaf, int slot,
 614                         unsigned long *ptr, unsigned long *end)
 615 {
 616         struct btrfs_key key;
 617         struct btrfs_extent_item *ei;
 618         struct btrfs_tree_block_info *bi;
 619         u32 item_size;
 620
 621         btrfs_item_key_to_cpu(leaf, &key, slot);
 622
 623         item_size = btrfs_item_size_nr(leaf, slot);
 624 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 625         if (item_size < sizeof(*ei)) {
 626                 WARN_ON(item_size != sizeof(struct btrfs_extent_item_v0));
 627                 return 1;
 628         }
 629 #endif
 630         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 631         WARN_ON(!(btrfs_extent_flags(leaf, ei) &
 632                   BTRFS_EXTENT_FLAG_TREE_BLOCK));
 633
 634         if (key.type == BTRFS_EXTENT_ITEM_KEY &&
 635             item_size <= sizeof(*ei) + sizeof(*bi)) {
 636                 WARN_ON(item_size < sizeof(*ei) + sizeof(*bi));
 637                 return 1;
 638         }
 639         if (key.type == BTRFS_METADATA_ITEM_KEY &&
 640             item_size <= sizeof(*ei)) {
 641                 WARN_ON(item_size < sizeof(*ei));
 642                 return 1;
 643         }
 644
 645         if (key.type == BTRFS_EXTENT_ITEM_KEY) {
 646                 bi = (struct btrfs_tree_block_info *)(ei + 1);
 647                 *ptr = (unsigned long)(bi + 1);
 648         } else {
 649                 *ptr = (unsigned long)(ei + 1);
 650         }
 651         *end = (unsigned long)ei + item_size;
 652         return 0;
 653 }
 654
 655 /*
 656  * build backref tree for a given tree block. root of the backref tree
 657  * corresponds the tree block, leaves of the backref tree correspond
 658  * roots of b-trees that reference the tree block.
 659  *
 660  * the basic idea of this function is check backrefs of a given block
 661  * to find upper level blocks that reference the block, and then check
 662  * backrefs of these upper level blocks recursively. the recursion stop
 663  * when tree root is reached or backrefs for the block is cached.
 664  *
 665  * NOTE: if we find backrefs for a block are cached, we know backrefs
 666  * for all upper level blocks that directly/indirectly reference the
 667  * block are also cached.
 668  */
 669 static noinline_for_stack
 670 struct backref_node *build_backref_tree(struct reloc_control *rc,
 671                                         struct btrfs_key *node_key,
 672                                         int level, u64 bytenr)
 673 {
 674         struct backref_cache *cache = &rc->backref_cache;
 675         struct btrfs_path *path1;
 676         struct btrfs_path *path2;
 677         struct extent_buffer *eb;
 678         struct btrfs_root *root;
 679         struct backref_node *cur;
 680         struct backref_node *upper;
 681         struct backref_node *lower;
 682         struct backref_node *node = NULL;
 683         struct backref_node *exist = NULL;
 684         struct backref_edge *edge;
 685         struct rb_node *rb_node;
 686         struct btrfs_key key;
 687         unsigned long end;
 688         unsigned long ptr;
 689         LIST_HEAD(list);
 690         LIST_HEAD(useless);
 691         int cowonly;
 692         int ret;
 693         int err = 0;
 694         bool need_check = true;
 695
 696         path1 = btrfs_alloc_path();
 697         path2 = btrfs_alloc_path();
 698         if (!path1 || !path2) {
 699                 err = -ENOMEM;
 700                 goto out;
 701         }
 702         path1->reada = READA_FORWARD;
 703         path2->reada = READA_FORWARD;
 704
 705         node = alloc_backref_node(cache);
 706         if (!node) {
 707                 err = -ENOMEM;
 708                 goto out;
 709         }
 710
 711         node->bytenr = bytenr;
 712         node->level = level;
 713         node->lowest = 1;
 714         cur = node;
 715 again:
 716         end = 0;
 717         ptr = 0;
 718         key.objectid = cur->bytenr;
 719         key.type = BTRFS_METADATA_ITEM_KEY;
 720         key.offset = (u64)-1;
 721
 722         path1->search_commit_root = 1;
 723         path1->skip_locking = 1;
 724         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path1,
 725                                 0, 0);
 726         if (ret < 0) {
 727                 err = ret;
 728                 goto out;
 729         }
 730         ASSERT(ret);
 731         ASSERT(path1->slots[0]);
 732
 733         path1->slots[0]--;
 734
 735         WARN_ON(cur->checked);
 736         if (!list_empty(&cur->upper)) {
 737                 /*
 738                  * the backref was added previously when processing
 739                  * backref of type BTRFS_TREE_BLOCK_REF_KEY
 740                  */
 741                 ASSERT(list_is_singular(&cur->upper));
 742                 edge = list_entry(cur->upper.next, struct backref_edge,
 743                                   list[LOWER]);
 744                 ASSERT(list_empty(&edge->list[UPPER]));
 745                 exist = edge->node[UPPER];
 746                 /*
 747                  * add the upper level block to pending list if we need
 748                  * check its backrefs
 749                  */
 750                 if (!exist->checked)
 751                         list_add_tail(&edge->list[UPPER], &list);
 752         } else {
 753                 exist = NULL;
 754         }
 755
 756         while (1) {
 757                 cond_resched();
 758                 eb = path1->nodes[0];
 759
 760                 if (ptr >= end) {
 761                         if (path1->slots[0] >= btrfs_header_nritems(eb)) {
 762                                 ret = btrfs_next_leaf(rc->extent_root, path1);
 763                                 if (ret < 0) {
 764                                         err = ret;
 765                                         goto out;
 766                                 }
 767                                 if (ret > 0)
 768                                         break;
 769                                 eb = path1->nodes[0];
 770                         }
 771
 772                         btrfs_item_key_to_cpu(eb, &key, path1->slots[0]);
 773                         if (key.objectid != cur->bytenr) {
 774                                 WARN_ON(exist);
 775                                 break;
 776                         }
 777
 778                         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
 779                             key.type == BTRFS_METADATA_ITEM_KEY) {
 780                                 ret = find_inline_backref(eb, path1->slots[0],
 781                                                           &ptr, &end);
 782                                 if (ret)
 783                                         goto next;
 784                         }
 785                 }
 786
 787                 if (ptr < end) {
 788                         /* update key for inline back ref */
 789                         struct btrfs_extent_inline_ref *iref;
 790                         int type;
 791                         iref = (struct btrfs_extent_inline_ref *)ptr;
 792                         type = btrfs_get_extent_inline_ref_type(eb, iref,
 793                                                         BTRFS_REF_TYPE_BLOCK);
 794                         if (type == BTRFS_REF_TYPE_INVALID) {
 795                                 err = -EINVAL;
 796                                 goto out;
 797                         }
 798                         key.type = type;
 799                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
 800
 801                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
 802                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
 803                 }
 804
 805                 if (exist &&
 806                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
 807                       exist->owner == key.offset) ||
 808                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
 809                       exist->bytenr == key.offset))) {
 810                         exist = NULL;
 811                         goto next;
 812                 }
 813
 814 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 815                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY ||
 816                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
 817                         if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
 818                                 struct btrfs_extent_ref_v0 *ref0;
 819                                 ref0 = btrfs_item_ptr(eb, path1->slots[0],
 820                                                 struct btrfs_extent_ref_v0);
 821                                 if (key.objectid == key.offset) {
 822                                         root = find_tree_root(rc, eb, ref0);
 823                                         if (root && !should_ignore_root(root))
 824                                                 cur->root = root;
 825                                         else
 826                                                 list_add(&cur->list, &useless);
 827                                         break;
 828                                 }
 829                                 if (is_cowonly_root(btrfs_ref_root_v0(eb,
 830                                                                       ref0)))
 831                                         cur->cowonly = 1;
 832                         }
 833 #else
 834                 ASSERT(key.type != BTRFS_EXTENT_REF_V0_KEY);
 835                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
 836 #endif
 837                         if (key.objectid == key.offset) {
 838                                 /*
 839                                  * only root blocks of reloc trees use
 840                                  * backref of this type.
 841                                  */
 842                                 root = find_reloc_root(rc, cur->bytenr);
 843                                 ASSERT(root);
 844                                 cur->root = root;
 845                                 break;
 846                         }
 847
 848                         edge = alloc_backref_edge(cache);
 849                         if (!edge) {
 850                                 err = -ENOMEM;
 851                                 goto out;
 852                         }
 853                         rb_node = tree_search(&cache->rb_root, key.offset);
 854                         if (!rb_node) {
 855                                 upper = alloc_backref_node(cache);
 856                                 if (!upper) {
 857                                         free_backref_edge(cache, edge);
 858                                         err = -ENOMEM;
 859                                         goto out;
 860                                 }
 861                                 upper->bytenr = key.offset;
 862                                 upper->level = cur->level + 1;
 863                                 /*
 864                                  *  backrefs for the upper level block isn't
 865                                  *  cached, add the block to pending list
 866                                  */
 867                                 list_add_tail(&edge->list[UPPER], &list);
 868                         } else {
 869                                 upper = rb_entry(rb_node, struct backref_node,
 870                                                  rb_node);
 871                                 ASSERT(upper->checked);
 872                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 873                         }
 874                         list_add_tail(&edge->list[LOWER], &cur->upper);
 875                         edge->node[LOWER] = cur;
 876                         edge->node[UPPER] = upper;
 877
 878                         goto next;
 879                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
 880                         goto next;
 881                 }
 882
 883                 /* key.type == BTRFS_TREE_BLOCK_REF_KEY */
 884                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
 885                 if (IS_ERR(root)) {
 886                         err = PTR_ERR(root);
 887                         goto out;
 888                 }
 889
 890                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 891                         cur->cowonly = 1;
 892
 893                 if (btrfs_root_level(&root->root_item) == cur->level) {
 894                         /* tree root */
 895                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
 896                                cur->bytenr);
 897                         if (should_ignore_root(root))
 898                                 list_add(&cur->list, &useless);
 899                         else
 900                                 cur->root = root;
 901                         break;
 902                 }
 903
 904                 level = cur->level + 1;
 905
 906                 /*
 907                  * searching the tree to find upper level blocks
 908                  * reference the block.
 909                  */
 910                 path2->search_commit_root = 1;
 911                 path2->skip_locking = 1;
 912                 path2->lowest_level = level;
 913                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
 914                 path2->lowest_level = 0;
 915                 if (ret < 0) {
 916                         err = ret;
 917                         goto out;
 918                 }
 919                 if (ret > 0 && path2->slots[level] > 0)
 920                         path2->slots[level]--;
 921
 922                 eb = path2->nodes[level];
 923                 if (btrfs_node_blockptr(eb, path2->slots[level]) !=
 924                     cur->bytenr) {
 925                         btrfs_err(root->fs_info,
 926         "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
 927                                   cur->bytenr, level - 1, root->objectid,
 928                                   node_key->objectid, node_key->type,
 929                                   node_key->offset);
 930                         err = -ENOENT;
 931                         goto out;
 932                 }
 933                 lower = cur;
 934                 need_check = true;
 935                 for (; level < BTRFS_MAX_LEVEL; level++) {
 936                         if (!path2->nodes[level]) {
 937                                 ASSERT(btrfs_root_bytenr(&root->root_item) ==
 938                                        lower->bytenr);
 939                                 if (should_ignore_root(root))
 940                                         list_add(&lower->list, &useless);
 941                                 else
 942                                         lower->root = root;
 943                                 break;
 944                         }
 945
 946                         edge = alloc_backref_edge(cache);
 947                         if (!edge) {
 948                                 err = -ENOMEM;
 949                                 goto out;
 950                         }
 951
 952                         eb = path2->nodes[level];
 953                         rb_node = tree_search(&cache->rb_root, eb->start);
 954                         if (!rb_node) {
 955                                 upper = alloc_backref_node(cache);
 956                                 if (!upper) {
 957                                         free_backref_edge(cache, edge);
 958                                         err = -ENOMEM;
 959                                         goto out;
 960                                 }
 961                                 upper->bytenr = eb->start;
 962                                 upper->owner = btrfs_header_owner(eb);
 963                                 upper->level = lower->level + 1;
 964                                 if (!test_bit(BTRFS_ROOT_REF_COWS,
 965                                               &root->state))
 966                                         upper->cowonly = 1;
 967
 968                                 /*
 969                                  * if we know the block isn't shared
 970                                  * we can void checking its backrefs.
 971                                  */
 972                                 if (btrfs_block_can_be_shared(root, eb))
 973                                         upper->checked = 0;
 974                                 else
 975                                         upper->checked = 1;
 976
 977                                 /*
 978                                  * add the block to pending list if we
 979                                  * need check its backrefs, we only do this once
 980                                  * while walking up a tree as we will catch
 981                                  * anything else later on.
 982                                  */
 983                                 if (!upper->checked && need_check) {
 984                                         need_check = false;
 985                                         list_add_tail(&edge->list[UPPER],
 986                                                       &list);
 987                                 } else {
 988                                         if (upper->checked)
 989                                                 need_check = true;
 990                                         INIT_LIST_HEAD(&edge->list[UPPER]);
 991                                 }
 992                         } else {
 993                                 upper = rb_entry(rb_node, struct backref_node,
 994                                                  rb_node);
 995                                 ASSERT(upper->checked);
 996                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 997                                 if (!upper->owner)
 998                                         upper->owner = btrfs_header_owner(eb);
 999                         }
1000                         list_add_tail(&edge->list[LOWER], &lower->upper);
1001                         edge->node[LOWER] = lower;
1002                         edge->node[UPPER] = upper;
1003
1004                         if (rb_node)
1005                                 break;
1006                         lower = upper;
1007                         upper = NULL;
1008                 }
1009                 btrfs_release_path(path2);
1010 next:
1011                 if (ptr < end) {
1012                         ptr += btrfs_extent_inline_ref_size(key.type);
1013                         if (ptr >= end) {
1014                                 WARN_ON(ptr > end);
1015                                 ptr = 0;
1016                                 end = 0;
1017                         }
1018                 }
1019                 if (ptr >= end)
1020                         path1->slots[0]++;
1021         }
1022         btrfs_release_path(path1);
1023
1024         cur->checked = 1;
1025         WARN_ON(exist);
1026
1027         /* the pending list isn't empty, take the first block to process */
1028         if (!list_empty(&list)) {
1029                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1030                 list_del_init(&edge->list[UPPER]);
1031                 cur = edge->node[UPPER];
1032                 goto again;
1033         }
1034
1035         /*
1036          * everything goes well, connect backref nodes and insert backref nodes
1037          * into the cache.
1038          */
1039         ASSERT(node->checked);
1040         cowonly = node->cowonly;
1041         if (!cowonly) {
1042                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1043                                       &node->rb_node);
1044                 if (rb_node)
1045                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1046                 list_add_tail(&node->lower, &cache->leaves);
1047         }
1048
1049         list_for_each_entry(edge, &node->upper, list[LOWER])
1050                 list_add_tail(&edge->list[UPPER], &list);
1051
1052         while (!list_empty(&list)) {
1053                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1054                 list_del_init(&edge->list[UPPER]);
1055                 upper = edge->node[UPPER];
1056                 if (upper->detached) {
1057                         list_del(&edge->list[LOWER]);
1058                         lower = edge->node[LOWER];
1059                         free_backref_edge(cache, edge);
1060                         if (list_empty(&lower->upper))
1061                                 list_add(&lower->list, &useless);
1062                         continue;
1063                 }
1064
1065                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1066                         if (upper->lowest) {
1067                                 list_del_init(&upper->lower);
1068                                 upper->lowest = 0;
1069                         }
1070
1071                         list_add_tail(&edge->list[UPPER], &upper->lower);
1072                         continue;
1073                 }
1074
1075                 if (!upper->checked) {
1076                         /*
1077                          * Still want to blow up for developers since this is a
1078                          * logic bug.
1079                          */
1080                         ASSERT(0);
1081                         err = -EINVAL;
1082                         goto out;
1083                 }
1084                 if (cowonly != upper->cowonly) {
1085                         ASSERT(0);
1086                         err = -EINVAL;
1087                         goto out;
1088                 }
1089
1090                 if (!cowonly) {
1091                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1092                                               &upper->rb_node);
1093                         if (rb_node)
1094                                 backref_tree_panic(rb_node, -EEXIST,
1095                                                    upper->bytenr);
1096                 }
1097
1098                 list_add_tail(&edge->list[UPPER], &upper->lower);
1099
1100                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1101                         list_add_tail(&edge->list[UPPER], &list);
1102         }
1103         /*
1104          * process useless backref nodes. backref nodes for tree leaves
1105          * are deleted from the cache. backref nodes for upper level
1106          * tree blocks are left in the cache to avoid unnecessary backref
1107          * lookup.
1108          */
1109         while (!list_empty(&useless)) {
1110                 upper = list_entry(useless.next, struct backref_node, list);
1111                 list_del_init(&upper->list);
1112                 ASSERT(list_empty(&upper->upper));
1113                 if (upper == node)
1114                         node = NULL;
1115                 if (upper->lowest) {
1116                         list_del_init(&upper->lower);
1117                         upper->lowest = 0;
1118                 }
1119                 while (!list_empty(&upper->lower)) {
1120                         edge = list_entry(upper->lower.next,
1121                                           struct backref_edge, list[UPPER]);
1122                         list_del(&edge->list[UPPER]);
1123                         list_del(&edge->list[LOWER]);
1124                         lower = edge->node[LOWER];
1125                         free_backref_edge(cache, edge);
1126
1127                         if (list_empty(&lower->upper))
1128                                 list_add(&lower->list, &useless);
1129                 }
1130                 __mark_block_processed(rc, upper);
1131                 if (upper->level > 0) {
1132                         list_add(&upper->list, &cache->detached);
1133                         upper->detached = 1;
1134                 } else {
1135                         rb_erase(&upper->rb_node, &cache->rb_root);
1136                         free_backref_node(cache, upper);
1137                 }
1138         }
1139 out:
1140         btrfs_free_path(path1);
1141         btrfs_free_path(path2);
1142         if (err) {
1143                 while (!list_empty(&useless)) {
1144                         lower = list_entry(useless.next,
1145                                            struct backref_node, list);
1146                         list_del_init(&lower->list);
1147                 }
1148                 while (!list_empty(&list)) {
1149                         edge = list_first_entry(&list, struct backref_edge,
1150                                                 list[UPPER]);
1151                         list_del(&edge->list[UPPER]);
1152                         list_del(&edge->list[LOWER]);
1153                         lower = edge->node[LOWER];
1154                         upper = edge->node[UPPER];
1155                         free_backref_edge(cache, edge);
1156
1157                         /*
1158                          * Lower is no longer linked to any upper backref nodes
1159                          * and isn't in the cache, we can free it ourselves.
1160                          */
1161                         if (list_empty(&lower->upper) &&
1162                             RB_EMPTY_NODE(&lower->rb_node))
1163                                 list_add(&lower->list, &useless);
1164
1165                         if (!RB_EMPTY_NODE(&upper->rb_node))
1166                                 continue;
1167
1168                         /* Add this guy's upper edges to the list to process */
1169                         list_for_each_entry(edge, &upper->upper, list[LOWER])
1170                                 list_add_tail(&edge->list[UPPER], &list);
1171                         if (list_empty(&upper->upper))
1172                                 list_add(&upper->list, &useless);
1173                 }
1174
1175                 while (!list_empty(&useless)) {
1176                         lower = list_entry(useless.next,
1177                                            struct backref_node, list);
1178                         list_del_init(&lower->list);
1179                         if (lower == node)
1180                                 node = NULL;
1181                         free_backref_node(cache, lower);
1182                 }
1183
1184                 free_backref_node(cache, node);
1185                 return ERR_PTR(err);
1186         }
1187         ASSERT(!node || !node->detached);
1188         return node;
1189 }
1190
1191 /*
1192  * helper to add backref node for the newly created snapshot.
1193  * the backref node is created by cloning backref node that
1194  * corresponds to root of source tree
1195  */
1196 static int clone_backref_node(struct btrfs_trans_handle *trans,
1197                               struct reloc_control *rc,
1198                               struct btrfs_root *src,
1199                               struct btrfs_root *dest)
1200 {
1201         struct btrfs_root *reloc_root = src->reloc_root;
1202         struct backref_cache *cache = &rc->backref_cache;
1203         struct backref_node *node = NULL;
1204         struct backref_node *new_node;
1205         struct backref_edge *edge;
1206         struct backref_edge *new_edge;
1207         struct rb_node *rb_node;
1208
1209         if (cache->last_trans > 0)
1210                 update_backref_cache(trans, cache);
1211
1212         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1213         if (rb_node) {
1214                 node = rb_entry(rb_node, struct backref_node, rb_node);
1215                 if (node->detached)
1216                         node = NULL;
1217                 else
1218                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1219         }
1220
1221         if (!node) {
1222                 rb_node = tree_search(&cache->rb_root,
1223                                       reloc_root->commit_root->start);
1224                 if (rb_node) {
1225                         node = rb_entry(rb_node, struct backref_node,
1226                                         rb_node);
1227                         BUG_ON(node->detached);
1228                 }
1229         }
1230
1231         if (!node)
1232                 return 0;
1233
1234         new_node = alloc_backref_node(cache);
1235         if (!new_node)
1236                 return -ENOMEM;
1237
1238         new_node->bytenr = dest->node->start;
1239         new_node->level = node->level;
1240         new_node->lowest = node->lowest;
1241         new_node->checked = 1;
1242         new_node->root = dest;
1243
1244         if (!node->lowest) {
1245                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1246                         new_edge = alloc_backref_edge(cache);
1247                         if (!new_edge)
1248                                 goto fail;
1249
1250                         new_edge->node[UPPER] = new_node;
1251                         new_edge->node[LOWER] = edge->node[LOWER];
1252                         list_add_tail(&new_edge->list[UPPER],
1253                                       &new_node->lower);
1254                 }
1255         } else {
1256                 list_add_tail(&new_node->lower, &cache->leaves);
1257         }
1258
1259         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1260                               &new_node->rb_node);
1261         if (rb_node)
1262                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1263
1264         if (!new_node->lowest) {
1265                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1266                         list_add_tail(&new_edge->list[LOWER],
1267                                       &new_edge->node[LOWER]->upper);
1268                 }
1269         }
1270         return 0;
1271 fail:
1272         while (!list_empty(&new_node->lower)) {
1273                 new_edge = list_entry(new_node->lower.next,
1274                                       struct backref_edge, list[UPPER]);
1275                 list_del(&new_edge->list[UPPER]);
1276                 free_backref_edge(cache, new_edge);
1277         }
1278         free_backref_node(cache, new_node);
1279         return -ENOMEM;
1280 }
1281
1282 /*
1283  * helper to add 'address of tree root -> reloc tree' mapping
1284  */
1285 static int __must_check __add_reloc_root(struct btrfs_root *root)
1286 {
1287         struct btrfs_fs_info *fs_info = root->fs_info;
1288         struct rb_node *rb_node;
1289         struct mapping_node *node;
1290         struct reloc_control *rc = fs_info->reloc_ctl;
1291
1292         node = kmalloc(sizeof(*node), GFP_NOFS);
1293         if (!node)
1294                 return -ENOMEM;
1295
1296         node->bytenr = root->node->start;
1297         node->data = root;
1298
1299         spin_lock(&rc->reloc_root_tree.lock);
1300         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1301                               node->bytenr, &node->rb_node);
1302         spin_unlock(&rc->reloc_root_tree.lock);
1303         if (rb_node) {
1304                 btrfs_panic(fs_info, -EEXIST,
1305                             "Duplicate root found for start=%llu while inserting into relocation tree",
1306                             node->bytenr);
1307         }
1308
1309         list_add_tail(&root->root_list, &rc->reloc_roots);
1310         return 0;
1311 }
1312
1313 /*
1314  * helper to delete the 'address of tree root -> reloc tree'
1315  * mapping
1316  */
1317 static void __del_reloc_root(struct btrfs_root *root)
1318 {
1319         struct btrfs_fs_info *fs_info = root->fs_info;
1320         struct rb_node *rb_node;
1321         struct mapping_node *node = NULL;
1322         struct reloc_control *rc = fs_info->reloc_ctl;
1323
1324         spin_lock(&rc->reloc_root_tree.lock);
1325         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1326                               root->node->start);
1327         if (rb_node) {
1328                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1329                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1330         }
1331         spin_unlock(&rc->reloc_root_tree.lock);
1332
1333         if (!node)
1334                 return;
1335         BUG_ON((struct btrfs_root *)node->data != root);
1336
1337         spin_lock(&fs_info->trans_lock);
1338         list_del_init(&root->root_list);
1339         spin_unlock(&fs_info->trans_lock);
1340         kfree(node);
1341 }
1342
1343 /*
1344  * helper to update the 'address of tree root -> reloc tree'
1345  * mapping
1346  */
1347 static int __update_reloc_root(struct btrfs_root *root, u64 new_bytenr)
1348 {
1349         struct btrfs_fs_info *fs_info = root->fs_info;
1350         struct rb_node *rb_node;
1351         struct mapping_node *node = NULL;
1352         struct reloc_control *rc = fs_info->reloc_ctl;
1353
1354         spin_lock(&rc->reloc_root_tree.lock);
1355         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1356                               root->node->start);
1357         if (rb_node) {
1358                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1359                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1360         }
1361         spin_unlock(&rc->reloc_root_tree.lock);
1362
1363         if (!node)
1364                 return 0;
1365         BUG_ON((struct btrfs_root *)node->data != root);
1366
1367         spin_lock(&rc->reloc_root_tree.lock);
1368         node->bytenr = new_bytenr;
1369         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1370                               node->bytenr, &node->rb_node);
1371         spin_unlock(&rc->reloc_root_tree.lock);
1372         if (rb_node)
1373                 backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1374         return 0;
1375 }
1376
1377 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1378                                         struct btrfs_root *root, u64 objectid)
1379 {
1380         struct btrfs_fs_info *fs_info = root->fs_info;
1381         struct btrfs_root *reloc_root;
1382         struct extent_buffer *eb;
1383         struct btrfs_root_item *root_item;
1384         struct btrfs_key root_key;
1385         int ret;
1386
1387         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1388         BUG_ON(!root_item);
1389
1390         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1391         root_key.type = BTRFS_ROOT_ITEM_KEY;
1392         root_key.offset = objectid;
1393
1394         if (root->root_key.objectid == objectid) {
1395                 u64 commit_root_gen;
1396
1397                 /* called by btrfs_init_reloc_root */
1398                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1399                                       BTRFS_TREE_RELOC_OBJECTID);
1400                 BUG_ON(ret);
1401                 /*
1402                  * Set the last_snapshot field to the generation of the commit
1403                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
1404                  * correctly (returns true) when the relocation root is created
1405                  * either inside the critical section of a transaction commit
1406                  * (through transaction.c:qgroup_account_snapshot()) and when
1407                  * it's created before the transaction commit is started.
1408                  */
1409                 commit_root_gen = btrfs_header_generation(root->commit_root);
1410                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
1411         } else {
1412                 /*
1413                  * called by btrfs_reloc_post_snapshot_hook.
1414                  * the source tree is a reloc tree, all tree blocks
1415                  * modified after it was created have RELOC flag
1416                  * set in their headers. so it's OK to not update
1417                  * the 'last_snapshot'.
1418                  */
1419                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1420                                       BTRFS_TREE_RELOC_OBJECTID);
1421                 BUG_ON(ret);
1422         }
1423
1424         memcpy(root_item, &root->root_item, sizeof(*root_item));
1425         btrfs_set_root_bytenr(root_item, eb->start);
1426         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1427         btrfs_set_root_generation(root_item, trans->transid);
1428
1429         if (root->root_key.objectid == objectid) {
1430                 btrfs_set_root_refs(root_item, 0);
1431                 memset(&root_item->drop_progress, 0,
1432                        sizeof(struct btrfs_disk_key));
1433                 root_item->drop_level = 0;
1434         }
1435
1436         btrfs_tree_unlock(eb);
1437         free_extent_buffer(eb);
1438
1439         ret = btrfs_insert_root(trans, fs_info->tree_root,
1440                                 &root_key, root_item);
1441         BUG_ON(ret);
1442         kfree(root_item);
1443
1444         reloc_root = btrfs_read_fs_root(fs_info->tree_root, &root_key);
1445         BUG_ON(IS_ERR(reloc_root));
1446         reloc_root->last_trans = trans->transid;
1447         return reloc_root;
1448 }
1449
1450 /*
1451  * create reloc tree for a given fs tree. reloc tree is just a
1452  * snapshot of the fs tree with special root objectid.
1453  */
1454 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1455                           struct btrfs_root *root)
1456 {
1457         struct btrfs_fs_info *fs_info = root->fs_info;
1458         struct btrfs_root *reloc_root;
1459         struct reloc_control *rc = fs_info->reloc_ctl;
1460         struct btrfs_block_rsv *rsv;
1461         int clear_rsv = 0;
1462         int ret;
1463
1464         if (root->reloc_root) {
1465                 reloc_root = root->reloc_root;
1466                 reloc_root->last_trans = trans->transid;
1467                 return 0;
1468         }
1469
1470         if (!rc || !rc->create_reloc_tree ||
1471             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1472                 return 0;
1473
1474         if (!trans->reloc_reserved) {
1475                 rsv = trans->block_rsv;
1476                 trans->block_rsv = rc->block_rsv;
1477                 clear_rsv = 1;
1478         }
1479         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1480         if (clear_rsv)
1481                 trans->block_rsv = rsv;
1482
1483         ret = __add_reloc_root(reloc_root);
1484         BUG_ON(ret < 0);
1485         root->reloc_root = reloc_root;
1486         return 0;
1487 }
1488
1489 /*
1490  * update root item of reloc tree
1491  */
1492 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1493                             struct btrfs_root *root)
1494 {
1495         struct btrfs_fs_info *fs_info = root->fs_info;
1496         struct btrfs_root *reloc_root;
1497         struct btrfs_root_item *root_item;
1498         int ret;
1499
1500         if (!root->reloc_root)
1501                 goto out;
1502
1503         reloc_root = root->reloc_root;
1504         root_item = &reloc_root->root_item;
1505
1506         if (fs_info->reloc_ctl->merge_reloc_tree &&
1507             btrfs_root_refs(root_item) == 0) {
1508                 root->reloc_root = NULL;
1509                 __del_reloc_root(reloc_root);
1510         }
1511
1512         if (reloc_root->commit_root != reloc_root->node) {
1513                 btrfs_set_root_node(root_item, reloc_root->node);
1514                 free_extent_buffer(reloc_root->commit_root);
1515                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1516         }
1517
1518         ret = btrfs_update_root(trans, fs_info->tree_root,
1519                                 &reloc_root->root_key, root_item);
1520         BUG_ON(ret);
1521
1522 out:
1523         return 0;
1524 }
1525
1526 /*
1527  * helper to find first cached inode with inode number >= objectid
1528  * in a subvolume
1529  */
1530 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1531 {
1532         struct rb_node *node;
1533         struct rb_node *prev;
1534         struct btrfs_inode *entry;
1535         struct inode *inode;
1536
1537         spin_lock(&root->inode_lock);
1538 again:
1539         node = root->inode_tree.rb_node;
1540         prev = NULL;
1541         while (node) {
1542                 prev = node;
1543                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1544
1545                 if (objectid < btrfs_ino(entry))
1546                         node = node->rb_left;
1547                 else if (objectid > btrfs_ino(entry))
1548                         node = node->rb_right;
1549                 else
1550                         break;
1551         }
1552         if (!node) {
1553                 while (prev) {
1554                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1555                         if (objectid <= btrfs_ino(entry)) {
1556                                 node = prev;
1557                                 break;
1558                         }
1559                         prev = rb_next(prev);
1560                 }
1561         }
1562         while (node) {
1563                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1564                 inode = igrab(&entry->vfs_inode);
1565                 if (inode) {
1566                         spin_unlock(&root->inode_lock);
1567                         return inode;
1568                 }
1569
1570                 objectid = btrfs_ino(entry) + 1;
1571                 if (cond_resched_lock(&root->inode_lock))
1572                         goto again;
1573
1574                 node = rb_next(node);
1575         }
1576         spin_unlock(&root->inode_lock);
1577         return NULL;
1578 }
1579
1580 static int in_block_group(u64 bytenr,
1581                           struct btrfs_block_group_cache *block_group)
1582 {
1583         if (bytenr >= block_group->key.objectid &&
1584             bytenr < block_group->key.objectid + block_group->key.offset)
1585                 return 1;
1586         return 0;
1587 }
1588
1589 /*
1590  * get new location of data
1591  */
1592 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1593                             u64 bytenr, u64 num_bytes)
1594 {
1595         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1596         struct btrfs_path *path;
1597         struct btrfs_file_extent_item *fi;
1598         struct extent_buffer *leaf;
1599         int ret;
1600
1601         path = btrfs_alloc_path();
1602         if (!path)
1603                 return -ENOMEM;
1604
1605         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1606         ret = btrfs_lookup_file_extent(NULL, root, path,
1607                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1608         if (ret < 0)
1609                 goto out;
1610         if (ret > 0) {
1611                 ret = -ENOENT;
1612                 goto out;
1613         }
1614
1615         leaf = path->nodes[0];
1616         fi = btrfs_item_ptr(leaf, path->slots[0],
1617                             struct btrfs_file_extent_item);
1618
1619         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1620                btrfs_file_extent_compression(leaf, fi) ||
1621                btrfs_file_extent_encryption(leaf, fi) ||
1622                btrfs_file_extent_other_encoding(leaf, fi));
1623
1624         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1625                 ret = -EINVAL;
1626                 goto out;
1627         }
1628
1629         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1630         ret = 0;
1631 out:
1632         btrfs_free_path(path);
1633         return ret;
1634 }
1635
1636 /*
1637  * update file extent items in the tree leaf to point to
1638  * the new locations.
1639  */
1640 static noinline_for_stack
1641 int replace_file_extents(struct btrfs_trans_handle *trans,
1642                          struct reloc_control *rc,
1643                          struct btrfs_root *root,
1644                          struct extent_buffer *leaf)
1645 {
1646         struct btrfs_fs_info *fs_info = root->fs_info;
1647         struct btrfs_key key;
1648         struct btrfs_file_extent_item *fi;
1649         struct inode *inode = NULL;
1650         u64 parent;
1651         u64 bytenr;
1652         u64 new_bytenr = 0;
1653         u64 num_bytes;
1654         u64 end;
1655         u32 nritems;
1656         u32 i;
1657         int ret = 0;
1658         int first = 1;
1659         int dirty = 0;
1660
1661         if (rc->stage != UPDATE_DATA_PTRS)
1662                 return 0;
1663
1664         /* reloc trees always use full backref */
1665         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1666                 parent = leaf->start;
1667         else
1668                 parent = 0;
1669
1670         nritems = btrfs_header_nritems(leaf);
1671         for (i = 0; i < nritems; i++) {
1672                 cond_resched();
1673                 btrfs_item_key_to_cpu(leaf, &key, i);
1674                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1675                         continue;
1676                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1677                 if (btrfs_file_extent_type(leaf, fi) ==
1678                     BTRFS_FILE_EXTENT_INLINE)
1679                         continue;
1680                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1681                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1682                 if (bytenr == 0)
1683                         continue;
1684                 if (!in_block_group(bytenr, rc->block_group))
1685                         continue;
1686
1687                 /*
1688                  * if we are modifying block in fs tree, wait for readpage
1689                  * to complete and drop the extent cache
1690                  */
1691                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1692                         if (first) {
1693                                 inode = find_next_inode(root, key.objectid);
1694                                 first = 0;
1695                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1696                                 btrfs_add_delayed_iput(inode);
1697                                 inode = find_next_inode(root, key.objectid);
1698                         }
1699                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1700                                 end = key.offset +
1701                                       btrfs_file_extent_num_bytes(leaf, fi);
1702                                 WARN_ON(!IS_ALIGNED(key.offset,
1703                                                     fs_info->sectorsize));
1704                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1705                                 end--;
1706                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1707                                                       key.offset, end);
1708                                 if (!ret)
1709                                         continue;
1710
1711                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1712                                                 key.offset,     end, 1);
1713                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1714                                               key.offset, end);
1715                         }
1716                 }
1717
1718                 ret = get_new_location(rc->data_inode, &new_bytenr,
1719                                        bytenr, num_bytes);
1720                 if (ret) {
1721                         /*
1722                          * Don't have to abort since we've not changed anything
1723                          * in the file extent yet.
1724                          */
1725                         break;
1726                 }
1727
1728                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1729                 dirty = 1;
1730
1731                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1732                 ret = btrfs_inc_extent_ref(trans, root, new_bytenr,
1733                                            num_bytes, parent,
1734                                            btrfs_header_owner(leaf),
1735                                            key.objectid, key.offset);
1736                 if (ret) {
1737                         btrfs_abort_transaction(trans, ret);
1738                         break;
1739                 }
1740
1741                 ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
1742                                         parent, btrfs_header_owner(leaf),
1743                                         key.objectid, key.offset);
1744                 if (ret) {
1745                         btrfs_abort_transaction(trans, ret);
1746                         break;
1747                 }
1748         }
1749         if (dirty)
1750                 btrfs_mark_buffer_dirty(leaf);
1751         if (inode)
1752                 btrfs_add_delayed_iput(inode);
1753         return ret;
1754 }
1755
1756 static noinline_for_stack
1757 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1758                      struct btrfs_path *path, int level)
1759 {
1760         struct btrfs_disk_key key1;
1761         struct btrfs_disk_key key2;
1762         btrfs_node_key(eb, &key1, slot);
1763         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1764         return memcmp(&key1, &key2, sizeof(key1));
1765 }
1766
1767 /*
1768  * try to replace tree blocks in fs tree with the new blocks
1769  * in reloc tree. tree blocks haven't been modified since the
1770  * reloc tree was create can be replaced.
1771  *
1772  * if a block was replaced, level of the block + 1 is returned.
1773  * if no block got replaced, 0 is returned. if there are other
1774  * errors, a negative error number is returned.
1775  */
1776 static noinline_for_stack
1777 int replace_path(struct btrfs_trans_handle *trans,
1778                  struct btrfs_root *dest, struct btrfs_root *src,
1779                  struct btrfs_path *path, struct btrfs_key *next_key,
1780                  int lowest_level, int max_level)
1781 {
1782         struct btrfs_fs_info *fs_info = dest->fs_info;
1783         struct extent_buffer *eb;
1784         struct extent_buffer *parent;
1785         struct btrfs_key key;
1786         u64 old_bytenr;
1787         u64 new_bytenr;
1788         u64 old_ptr_gen;
1789         u64 new_ptr_gen;
1790         u64 last_snapshot;
1791         u32 blocksize;
1792         int cow = 0;
1793         int level;
1794         int ret;
1795         int slot;
1796
1797         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1798         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1799
1800         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1801 again:
1802         slot = path->slots[lowest_level];
1803         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1804
1805         eb = btrfs_lock_root_node(dest);
1806         btrfs_set_lock_blocking(eb);
1807         level = btrfs_header_level(eb);
1808
1809         if (level < lowest_level) {
1810                 btrfs_tree_unlock(eb);
1811                 free_extent_buffer(eb);
1812                 return 0;
1813         }
1814
1815         if (cow) {
1816                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1817                 BUG_ON(ret);
1818         }
1819         btrfs_set_lock_blocking(eb);
1820
1821         if (next_key) {
1822                 next_key->objectid = (u64)-1;
1823                 next_key->type = (u8)-1;
1824                 next_key->offset = (u64)-1;
1825         }
1826
1827         parent = eb;
1828         while (1) {
1829                 struct btrfs_key first_key;
1830
1831                 level = btrfs_header_level(parent);
1832                 BUG_ON(level < lowest_level);
1833
1834                 ret = btrfs_bin_search(parent, &key, level, &slot);
1835                 if (ret && slot > 0)
1836                         slot--;
1837
1838                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1839                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1840
1841                 old_bytenr = btrfs_node_blockptr(parent, slot);
1842                 blocksize = fs_info->nodesize;
1843                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1844                 btrfs_node_key_to_cpu(parent, &first_key, slot);
1845
1846                 if (level <= max_level) {
1847                         eb = path->nodes[level];
1848                         new_bytenr = btrfs_node_blockptr(eb,
1849                                                         path->slots[level]);
1850                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1851                                                         path->slots[level]);
1852                 } else {
1853                         new_bytenr = 0;
1854                         new_ptr_gen = 0;
1855                 }
1856
1857                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1858                         ret = level;
1859                         break;
1860                 }
1861
1862                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1863                     memcmp_node_keys(parent, slot, path, level)) {
1864                         if (level <= lowest_level) {
1865                                 ret = 0;
1866                                 break;
1867                         }
1868
1869                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen,
1870                                              level - 1, &first_key);
1871                         if (IS_ERR(eb)) {
1872                                 ret = PTR_ERR(eb);
1873                                 break;
1874                         } else if (!extent_buffer_uptodate(eb)) {
1875                                 ret = -EIO;
1876                                 free_extent_buffer(eb);
1877                                 break;
1878                         }
1879                         btrfs_tree_lock(eb);
1880                         if (cow) {
1881                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1882                                                       slot, &eb);
1883                                 BUG_ON(ret);
1884                         }
1885                         btrfs_set_lock_blocking(eb);
1886
1887                         btrfs_tree_unlock(parent);
1888                         free_extent_buffer(parent);
1889
1890                         parent = eb;
1891                         continue;
1892                 }
1893
1894                 if (!cow) {
1895                         btrfs_tree_unlock(parent);
1896                         free_extent_buffer(parent);
1897                         cow = 1;
1898                         goto again;
1899                 }
1900
1901                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1902                                       path->slots[level]);
1903                 btrfs_release_path(path);
1904
1905                 path->lowest_level = level;
1906                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1907                 path->lowest_level = 0;
1908                 BUG_ON(ret);
1909
1910                 /*
1911                  * Info qgroup to trace both subtrees.
1912                  *
1913                  * We must trace both trees.
1914                  * 1) Tree reloc subtree
1915                  *    If not traced, we will leak data numbers
1916                  * 2) Fs subtree
1917                  *    If not traced, we will double count old data
1918                  *    and tree block numbers, if current trans doesn't free
1919                  *    data reloc tree inode.
1920                  */
1921                 ret = btrfs_qgroup_trace_subtree(trans, src, parent,
1922                                 btrfs_header_generation(parent),
1923                                 btrfs_header_level(parent));
1924                 if (ret < 0)
1925                         break;
1926                 ret = btrfs_qgroup_trace_subtree(trans, dest,
1927                                 path->nodes[level],
1928                                 btrfs_header_generation(path->nodes[level]),
1929                                 btrfs_header_level(path->nodes[level]));
1930                 if (ret < 0)
1931                         break;
1932
1933                 /*
1934                  * swap blocks in fs tree and reloc tree.
1935                  */
1936                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1937                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1938                 btrfs_mark_buffer_dirty(parent);
1939
1940                 btrfs_set_node_blockptr(path->nodes[level],
1941                                         path->slots[level], old_bytenr);
1942                 btrfs_set_node_ptr_generation(path->nodes[level],
1943                                               path->slots[level], old_ptr_gen);
1944                 btrfs_mark_buffer_dirty(path->nodes[level]);
1945
1946                 ret = btrfs_inc_extent_ref(trans, src, old_bytenr,
1947                                         blocksize, path->nodes[level]->start,
1948                                         src->root_key.objectid, level - 1, 0);
1949                 BUG_ON(ret);
1950                 ret = btrfs_inc_extent_ref(trans, dest, new_bytenr,
1951                                         blocksize, 0, dest->root_key.objectid,
1952                                         level - 1, 0);
1953                 BUG_ON(ret);
1954
1955                 ret = btrfs_free_extent(trans, src, new_bytenr, blocksize,
1956                                         path->nodes[level]->start,
1957                                         src->root_key.objectid, level - 1, 0);
1958                 BUG_ON(ret);
1959
1960                 ret = btrfs_free_extent(trans, dest, old_bytenr, blocksize,
1961                                         0, dest->root_key.objectid, level - 1,
1962                                         0);
1963                 BUG_ON(ret);
1964
1965                 btrfs_unlock_up_safe(path, 0);
1966
1967                 ret = level;
1968                 break;
1969         }
1970         btrfs_tree_unlock(parent);
1971         free_extent_buffer(parent);
1972         return ret;
1973 }
1974
1975 /*
1976  * helper to find next relocated block in reloc tree
1977  */
1978 static noinline_for_stack
1979 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1980                        int *level)
1981 {
1982         struct extent_buffer *eb;
1983         int i;
1984         u64 last_snapshot;
1985         u32 nritems;
1986
1987         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1988
1989         for (i = 0; i < *level; i++) {
1990                 free_extent_buffer(path->nodes[i]);
1991                 path->nodes[i] = NULL;
1992         }
1993
1994         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
1995                 eb = path->nodes[i];
1996                 nritems = btrfs_header_nritems(eb);
1997                 while (path->slots[i] + 1 < nritems) {
1998                         path->slots[i]++;
1999                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
2000                             last_snapshot)
2001                                 continue;
2002
2003                         *level = i;
2004                         return 0;
2005                 }
2006                 free_extent_buffer(path->nodes[i]);
2007                 path->nodes[i] = NULL;
2008         }
2009         return 1;
2010 }
2011
2012 /*
2013  * walk down reloc tree to find relocated block of lowest level
2014  */
2015 static noinline_for_stack
2016 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2017                          int *level)
2018 {
2019         struct btrfs_fs_info *fs_info = root->fs_info;
2020         struct extent_buffer *eb = NULL;
2021         int i;
2022         u64 bytenr;
2023         u64 ptr_gen = 0;
2024         u64 last_snapshot;
2025         u32 nritems;
2026
2027         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2028
2029         for (i = *level; i > 0; i--) {
2030                 struct btrfs_key first_key;
2031
2032                 eb = path->nodes[i];
2033                 nritems = btrfs_header_nritems(eb);
2034                 while (path->slots[i] < nritems) {
2035                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2036                         if (ptr_gen > last_snapshot)
2037                                 break;
2038                         path->slots[i]++;
2039                 }
2040                 if (path->slots[i] >= nritems) {
2041                         if (i == *level)
2042                                 break;
2043                         *level = i + 1;
2044                         return 0;
2045                 }
2046                 if (i == 1) {
2047                         *level = i;
2048                         return 0;
2049                 }
2050
2051                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2052                 btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
2053                 eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
2054                                      &first_key);
2055                 if (IS_ERR(eb)) {
2056                         return PTR_ERR(eb);
2057                 } else if (!extent_buffer_uptodate(eb)) {
2058                         free_extent_buffer(eb);
2059                         return -EIO;
2060                 }
2061                 BUG_ON(btrfs_header_level(eb) != i - 1);
2062                 path->nodes[i - 1] = eb;
2063                 path->slots[i - 1] = 0;
2064         }
2065         return 1;
2066 }
2067
2068 /*
2069  * invalidate extent cache for file extents whose key in range of
2070  * [min_key, max_key)
2071  */
2072 static int invalidate_extent_cache(struct btrfs_root *root,
2073                                    struct btrfs_key *min_key,
2074                                    struct btrfs_key *max_key)
2075 {
2076         struct btrfs_fs_info *fs_info = root->fs_info;
2077         struct inode *inode = NULL;
2078         u64 objectid;
2079         u64 start, end;
2080         u64 ino;
2081
2082         objectid = min_key->objectid;
2083         while (1) {
2084                 cond_resched();
2085                 iput(inode);
2086
2087                 if (objectid > max_key->objectid)
2088                         break;
2089
2090                 inode = find_next_inode(root, objectid);
2091                 if (!inode)
2092                         break;
2093                 ino = btrfs_ino(BTRFS_I(inode));
2094
2095                 if (ino > max_key->objectid) {
2096                         iput(inode);
2097                         break;
2098                 }
2099
2100                 objectid = ino + 1;
2101                 if (!S_ISREG(inode->i_mode))
2102                         continue;
2103
2104                 if (unlikely(min_key->objectid == ino)) {
2105                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2106                                 continue;
2107                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2108                                 start = 0;
2109                         else {
2110                                 start = min_key->offset;
2111                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
2112                         }
2113                 } else {
2114                         start = 0;
2115                 }
2116
2117                 if (unlikely(max_key->objectid == ino)) {
2118                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2119                                 continue;
2120                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2121                                 end = (u64)-1;
2122                         } else {
2123                                 if (max_key->offset == 0)
2124                                         continue;
2125                                 end = max_key->offset;
2126                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
2127                                 end--;
2128                         }
2129                 } else {
2130                         end = (u64)-1;
2131                 }
2132
2133                 /* the lock_extent waits for readpage to complete */
2134                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2135                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
2136                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2137         }
2138         return 0;
2139 }
2140
2141 static int find_next_key(struct btrfs_path *path, int level,
2142                          struct btrfs_key *key)
2143
2144 {
2145         while (level < BTRFS_MAX_LEVEL) {
2146                 if (!path->nodes[level])
2147                         break;
2148                 if (path->slots[level] + 1 <
2149                     btrfs_header_nritems(path->nodes[level])) {
2150                         btrfs_node_key_to_cpu(path->nodes[level], key,
2151                                               path->slots[level] + 1);
2152                         return 0;
2153                 }
2154                 level++;
2155         }
2156         return 1;
2157 }
2158
2159 /*
2160  * merge the relocated tree blocks in reloc tree with corresponding
2161  * fs tree.
2162  */
2163 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2164                                                struct btrfs_root *root)
2165 {
2166         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2167         LIST_HEAD(inode_list);
2168         struct btrfs_key key;
2169         struct btrfs_key next_key;
2170         struct btrfs_trans_handle *trans = NULL;
2171         struct btrfs_root *reloc_root;
2172         struct btrfs_root_item *root_item;
2173         struct btrfs_path *path;
2174         struct extent_buffer *leaf;
2175         int level;
2176         int max_level;
2177         int replaced = 0;
2178         int ret;
2179         int err = 0;
2180         u32 min_reserved;
2181
2182         path = btrfs_alloc_path();
2183         if (!path)
2184                 return -ENOMEM;
2185         path->reada = READA_FORWARD;
2186
2187         reloc_root = root->reloc_root;
2188         root_item = &reloc_root->root_item;
2189
2190         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2191                 level = btrfs_root_level(root_item);
2192                 extent_buffer_get(reloc_root->node);
2193                 path->nodes[level] = reloc_root->node;
2194                 path->slots[level] = 0;
2195         } else {
2196                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2197
2198                 level = root_item->drop_level;
2199                 BUG_ON(level == 0);
2200                 path->lowest_level = level;
2201                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2202                 path->lowest_level = 0;
2203                 if (ret < 0) {
2204                         btrfs_free_path(path);
2205                         return ret;
2206                 }
2207
2208                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2209                                       path->slots[level]);
2210                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2211
2212                 btrfs_unlock_up_safe(path, 0);
2213         }
2214
2215         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2216         memset(&next_key, 0, sizeof(next_key));
2217
2218         while (1) {
2219                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2220                                              BTRFS_RESERVE_FLUSH_ALL);
2221                 if (ret) {
2222                         err = ret;
2223                         goto out;
2224                 }
2225                 trans = btrfs_start_transaction(root, 0);
2226                 if (IS_ERR(trans)) {
2227                         err = PTR_ERR(trans);
2228                         trans = NULL;
2229                         goto out;
2230                 }
2231                 trans->block_rsv = rc->block_rsv;
2232
2233                 replaced = 0;
2234                 max_level = level;
2235
2236                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2237                 if (ret < 0) {
2238                         err = ret;
2239                         goto out;
2240                 }
2241                 if (ret > 0)
2242                         break;
2243
2244                 if (!find_next_key(path, level, &key) &&
2245                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2246                         ret = 0;
2247                 } else {
2248                         ret = replace_path(trans, root, reloc_root, path,
2249                                            &next_key, level, max_level);
2250                 }
2251                 if (ret < 0) {
2252                         err = ret;
2253                         goto out;
2254                 }
2255
2256                 if (ret > 0) {
2257                         level = ret;
2258                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2259                                               path->slots[level]);
2260                         replaced = 1;
2261                 }
2262
2263                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2264                 if (ret > 0)
2265                         break;
2266
2267                 BUG_ON(level == 0);
2268                 /*
2269                  * save the merging progress in the drop_progress.
2270                  * this is OK since root refs == 1 in this case.
2271                  */
2272                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2273                                path->slots[level]);
2274                 root_item->drop_level = level;
2275
2276                 btrfs_end_transaction_throttle(trans);
2277                 trans = NULL;
2278
2279                 btrfs_btree_balance_dirty(fs_info);
2280
2281                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2282                         invalidate_extent_cache(root, &key, &next_key);
2283         }
2284
2285         /*
2286          * handle the case only one block in the fs tree need to be
2287          * relocated and the block is tree root.
2288          */
2289         leaf = btrfs_lock_root_node(root);
2290         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2291         btrfs_tree_unlock(leaf);
2292         free_extent_buffer(leaf);
2293         if (ret < 0)
2294                 err = ret;
2295 out:
2296         btrfs_free_path(path);
2297
2298         if (err == 0) {
2299                 memset(&root_item->drop_progress, 0,
2300                        sizeof(root_item->drop_progress));
2301                 root_item->drop_level = 0;
2302                 btrfs_set_root_refs(root_item, 0);
2303                 btrfs_update_reloc_root(trans, root);
2304         }
2305
2306         if (trans)
2307                 btrfs_end_transaction_throttle(trans);
2308
2309         btrfs_btree_balance_dirty(fs_info);
2310
2311         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2312                 invalidate_extent_cache(root, &key, &next_key);
2313
2314         return err;
2315 }
2316
2317 static noinline_for_stack
2318 int prepare_to_merge(struct reloc_control *rc, int err)
2319 {
2320         struct btrfs_root *root = rc->extent_root;
2321         struct btrfs_fs_info *fs_info = root->fs_info;
2322         struct btrfs_root *reloc_root;
2323         struct btrfs_trans_handle *trans;
2324         LIST_HEAD(reloc_roots);
2325         u64 num_bytes = 0;
2326         int ret;
2327
2328         mutex_lock(&fs_info->reloc_mutex);
2329         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2330         rc->merging_rsv_size += rc->nodes_relocated * 2;
2331         mutex_unlock(&fs_info->reloc_mutex);
2332
2333 again:
2334         if (!err) {
2335                 num_bytes = rc->merging_rsv_size;
2336                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2337                                           BTRFS_RESERVE_FLUSH_ALL);
2338                 if (ret)
2339                         err = ret;
2340         }
2341
2342         trans = btrfs_join_transaction(rc->extent_root);
2343         if (IS_ERR(trans)) {
2344                 if (!err)
2345                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2346                                                 num_bytes);
2347                 return PTR_ERR(trans);
2348         }
2349
2350         if (!err) {
2351                 if (num_bytes != rc->merging_rsv_size) {
2352                         btrfs_end_transaction(trans);
2353                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2354                                                 num_bytes);
2355                         goto again;
2356                 }
2357         }
2358
2359         rc->merge_reloc_tree = 1;
2360
2361         while (!list_empty(&rc->reloc_roots)) {
2362                 reloc_root = list_entry(rc->reloc_roots.next,
2363                                         struct btrfs_root, root_list);
2364                 list_del_init(&reloc_root->root_list);
2365
2366                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
2367                 BUG_ON(IS_ERR(root));
2368                 BUG_ON(root->reloc_root != reloc_root);
2369
2370                 /*
2371                  * set reference count to 1, so btrfs_recover_relocation
2372                  * knows it should resumes merging
2373                  */
2374                 if (!err)
2375                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2376                 btrfs_update_reloc_root(trans, root);
2377
2378                 list_add(&reloc_root->root_list, &reloc_roots);
2379         }
2380
2381         list_splice(&reloc_roots, &rc->reloc_roots);
2382
2383         if (!err)
2384                 btrfs_commit_transaction(trans);
2385         else
2386                 btrfs_end_transaction(trans);
2387         return err;
2388 }
2389
2390 static noinline_for_stack
2391 void free_reloc_roots(struct list_head *list)
2392 {
2393         struct btrfs_root *reloc_root;
2394
2395         while (!list_empty(list)) {
2396                 reloc_root = list_entry(list->next, struct btrfs_root,
2397                                         root_list);
2398                 __del_reloc_root(reloc_root);
2399                 free_extent_buffer(reloc_root->node);
2400                 free_extent_buffer(reloc_root->commit_root);
2401                 reloc_root->node = NULL;
2402                 reloc_root->commit_root = NULL;
2403         }
2404 }
2405
2406 static noinline_for_stack
2407 void merge_reloc_roots(struct reloc_control *rc)
2408 {
2409         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2410         struct btrfs_root *root;
2411         struct btrfs_root *reloc_root;
2412         LIST_HEAD(reloc_roots);
2413         int found = 0;
2414         int ret = 0;
2415 again:
2416         root = rc->extent_root;
2417
2418         /*
2419          * this serializes us with btrfs_record_root_in_transaction,
2420          * we have to make sure nobody is in the middle of
2421          * adding their roots to the list while we are
2422          * doing this splice
2423          */
2424         mutex_lock(&fs_info->reloc_mutex);
2425         list_splice_init(&rc->reloc_roots, &reloc_roots);
2426         mutex_unlock(&fs_info->reloc_mutex);
2427
2428         while (!list_empty(&reloc_roots)) {
2429                 found = 1;
2430                 reloc_root = list_entry(reloc_roots.next,
2431                                         struct btrfs_root, root_list);
2432
2433                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2434                         root = read_fs_root(fs_info,
2435                                             reloc_root->root_key.offset);
2436                         BUG_ON(IS_ERR(root));
2437                         BUG_ON(root->reloc_root != reloc_root);
2438
2439                         ret = merge_reloc_root(rc, root);
2440                         if (ret) {
2441                                 if (list_empty(&reloc_root->root_list))
2442                                         list_add_tail(&reloc_root->root_list,
2443                                                       &reloc_roots);
2444                                 goto out;
2445                         }
2446                 } else {
2447                         list_del_init(&reloc_root->root_list);
2448                 }
2449
2450                 ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);
2451                 if (ret < 0) {
2452                         if (list_empty(&reloc_root->root_list))
2453                                 list_add_tail(&reloc_root->root_list,
2454                                               &reloc_roots);
2455                         goto out;
2456                 }
2457         }
2458
2459         if (found) {
2460                 found = 0;
2461                 goto again;
2462         }
2463 out:
2464         if (ret) {
2465                 btrfs_handle_fs_error(fs_info, ret, NULL);
2466                 if (!list_empty(&reloc_roots))
2467                         free_reloc_roots(&reloc_roots);
2468
2469                 /* new reloc root may be added */
2470                 mutex_lock(&fs_info->reloc_mutex);
2471                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2472                 mutex_unlock(&fs_info->reloc_mutex);
2473                 if (!list_empty(&reloc_roots))
2474                         free_reloc_roots(&reloc_roots);
2475         }
2476
2477         BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2478 }
2479
2480 static void free_block_list(struct rb_root *blocks)
2481 {
2482         struct tree_block *block;
2483         struct rb_node *rb_node;
2484         while ((rb_node = rb_first(blocks))) {
2485                 block = rb_entry(rb_node, struct tree_block, rb_node);
2486                 rb_erase(rb_node, blocks);
2487                 kfree(block);
2488         }
2489 }
2490
2491 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2492                                       struct btrfs_root *reloc_root)
2493 {
2494         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
2495         struct btrfs_root *root;
2496
2497         if (reloc_root->last_trans == trans->transid)
2498                 return 0;
2499
2500         root = read_fs_root(fs_info, reloc_root->root_key.offset);
2501         BUG_ON(IS_ERR(root));
2502         BUG_ON(root->reloc_root != reloc_root);
2503
2504         return btrfs_record_root_in_trans(trans, root);
2505 }
2506
2507 static noinline_for_stack
2508 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2509                                      struct reloc_control *rc,
2510                                      struct backref_node *node,
2511                                      struct backref_edge *edges[])
2512 {
2513         struct backref_node *next;
2514         struct btrfs_root *root;
2515         int index = 0;
2516
2517         next = node;
2518         while (1) {
2519                 cond_resched();
2520                 next = walk_up_backref(next, edges, &index);
2521                 root = next->root;
2522                 BUG_ON(!root);
2523                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2524
2525                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2526                         record_reloc_root_in_trans(trans, root);
2527                         break;
2528                 }
2529
2530                 btrfs_record_root_in_trans(trans, root);
2531                 root = root->reloc_root;
2532
2533                 if (next->new_bytenr != root->node->start) {
2534                         BUG_ON(next->new_bytenr);
2535                         BUG_ON(!list_empty(&next->list));
2536                         next->new_bytenr = root->node->start;
2537                         next->root = root;
2538                         list_add_tail(&next->list,
2539                                       &rc->backref_cache.changed);
2540                         __mark_block_processed(rc, next);
2541                         break;
2542                 }
2543
2544                 WARN_ON(1);
2545                 root = NULL;
2546                 next = walk_down_backref(edges, &index);
2547                 if (!next || next->level <= node->level)
2548                         break;
2549         }
2550         if (!root)
2551                 return NULL;
2552
2553         next = node;
2554         /* setup backref node path for btrfs_reloc_cow_block */
2555         while (1) {
2556                 rc->backref_cache.path[next->level] = next;
2557                 if (--index < 0)
2558                         break;
2559                 next = edges[index]->node[UPPER];
2560         }
2561         return root;
2562 }
2563
2564 /*
2565  * select a tree root for relocation. return NULL if the block
2566  * is reference counted. we should use do_relocation() in this
2567  * case. return a tree root pointer if the block isn't reference
2568  * counted. return -ENOENT if the block is root of reloc tree.
2569  */
2570 static noinline_for_stack
2571 struct btrfs_root *select_one_root(struct backref_node *node)
2572 {
2573         struct backref_node *next;
2574         struct btrfs_root *root;
2575         struct btrfs_root *fs_root = NULL;
2576         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2577         int index = 0;
2578
2579         next = node;
2580         while (1) {
2581                 cond_resched();
2582                 next = walk_up_backref(next, edges, &index);
2583                 root = next->root;
2584                 BUG_ON(!root);
2585
2586                 /* no other choice for non-references counted tree */
2587                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2588                         return root;
2589
2590                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2591                         fs_root = root;
2592
2593                 if (next != node)
2594                         return NULL;
2595
2596                 next = walk_down_backref(edges, &index);
2597                 if (!next || next->level <= node->level)
2598                         break;
2599         }
2600
2601         if (!fs_root)
2602                 return ERR_PTR(-ENOENT);
2603         return fs_root;
2604 }
2605
2606 static noinline_for_stack
2607 u64 calcu_metadata_size(struct reloc_control *rc,
2608                         struct backref_node *node, int reserve)
2609 {
2610         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2611         struct backref_node *next = node;
2612         struct backref_edge *edge;
2613         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2614         u64 num_bytes = 0;
2615         int index = 0;
2616
2617         BUG_ON(reserve && node->processed);
2618
2619         while (next) {
2620                 cond_resched();
2621                 while (1) {
2622                         if (next->processed && (reserve || next != node))
2623                                 break;
2624
2625                         num_bytes += fs_info->nodesize;
2626
2627                         if (list_empty(&next->upper))
2628                                 break;
2629
2630                         edge = list_entry(next->upper.next,
2631                                           struct backref_edge, list[LOWER]);
2632                         edges[index++] = edge;
2633                         next = edge->node[UPPER];
2634                 }
2635                 next = walk_down_backref(edges, &index);
2636         }
2637         return num_bytes;
2638 }
2639
2640 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2641                                   struct reloc_control *rc,
2642                                   struct backref_node *node)
2643 {
2644         struct btrfs_root *root = rc->extent_root;
2645         struct btrfs_fs_info *fs_info = root->fs_info;
2646         u64 num_bytes;
2647         int ret;
2648         u64 tmp;
2649
2650         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2651
2652         trans->block_rsv = rc->block_rsv;
2653         rc->reserved_bytes += num_bytes;
2654
2655         /*
2656          * We are under a transaction here so we can only do limited flushing.
2657          * If we get an enospc just kick back -EAGAIN so we know to drop the
2658          * transaction and try to refill when we can flush all the things.
2659          */
2660         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2661                                 BTRFS_RESERVE_FLUSH_LIMIT);
2662         if (ret) {
2663                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2664                 while (tmp <= rc->reserved_bytes)
2665                         tmp <<= 1;
2666                 /*
2667                  * only one thread can access block_rsv at this point,
2668                  * so we don't need hold lock to protect block_rsv.
2669                  * we expand more reservation size here to allow enough
2670                  * space for relocation and we will return eailer in
2671                  * enospc case.
2672                  */
2673                 rc->block_rsv->size = tmp + fs_info->nodesize *
2674                                       RELOCATION_RESERVED_NODES;
2675                 return -EAGAIN;
2676         }
2677
2678         return 0;
2679 }
2680
2681 /*
2682  * relocate a block tree, and then update pointers in upper level
2683  * blocks that reference the block to point to the new location.
2684  *
2685  * if called by link_to_upper, the block has already been relocated.
2686  * in that case this function just updates pointers.
2687  */
2688 static int do_relocation(struct btrfs_trans_handle *trans,
2689                          struct reloc_control *rc,
2690                          struct backref_node *node,
2691                          struct btrfs_key *key,
2692                          struct btrfs_path *path, int lowest)
2693 {
2694         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2695         struct backref_node *upper;
2696         struct backref_edge *edge;
2697         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2698         struct btrfs_root *root;
2699         struct extent_buffer *eb;
2700         u32 blocksize;
2701         u64 bytenr;
2702         u64 generation;
2703         int slot;
2704         int ret;
2705         int err = 0;
2706
2707         BUG_ON(lowest && node->eb);
2708
2709         path->lowest_level = node->level + 1;
2710         rc->backref_cache.path[node->level] = node;
2711         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2712                 struct btrfs_key first_key;
2713
2714                 cond_resched();
2715
2716                 upper = edge->node[UPPER];
2717                 root = select_reloc_root(trans, rc, upper, edges);
2718                 BUG_ON(!root);
2719
2720                 if (upper->eb && !upper->locked) {
2721                         if (!lowest) {
2722                                 ret = btrfs_bin_search(upper->eb, key,
2723                                                        upper->level, &slot);
2724                                 BUG_ON(ret);
2725                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2726                                 if (node->eb->start == bytenr)
2727                                         goto next;
2728                         }
2729                         drop_node_buffer(upper);
2730                 }
2731
2732                 if (!upper->eb) {
2733                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2734                         if (ret) {
2735                                 if (ret < 0)
2736                                         err = ret;
2737                                 else
2738                                         err = -ENOENT;
2739
2740                                 btrfs_release_path(path);
2741                                 break;
2742                         }
2743
2744                         if (!upper->eb) {
2745                                 upper->eb = path->nodes[upper->level];
2746                                 path->nodes[upper->level] = NULL;
2747                         } else {
2748                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2749                         }
2750
2751                         upper->locked = 1;
2752                         path->locks[upper->level] = 0;
2753
2754                         slot = path->slots[upper->level];
2755                         btrfs_release_path(path);
2756                 } else {
2757                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2758                                                &slot);
2759                         BUG_ON(ret);
2760                 }
2761
2762                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2763                 if (lowest) {
2764                         if (bytenr != node->bytenr) {
2765                                 btrfs_err(root->fs_info,
2766                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2767                                           bytenr, node->bytenr, slot,
2768                                           upper->eb->start);
2769                                 err = -EIO;
2770                                 goto next;
2771                         }
2772                 } else {
2773                         if (node->eb->start == bytenr)
2774                                 goto next;
2775                 }
2776
2777                 blocksize = root->fs_info->nodesize;
2778                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2779                 btrfs_node_key_to_cpu(upper->eb, &first_key, slot);
2780                 eb = read_tree_block(fs_info, bytenr, generation,
2781                                      upper->level - 1, &first_key);
2782                 if (IS_ERR(eb)) {
2783                         err = PTR_ERR(eb);
2784                         goto next;
2785                 } else if (!extent_buffer_uptodate(eb)) {
2786                         free_extent_buffer(eb);
2787                         err = -EIO;
2788                         goto next;
2789                 }
2790                 btrfs_tree_lock(eb);
2791                 btrfs_set_lock_blocking(eb);
2792
2793                 if (!node->eb) {
2794                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2795                                               slot, &eb);
2796                         btrfs_tree_unlock(eb);
2797                         free_extent_buffer(eb);
2798                         if (ret < 0) {
2799                                 err = ret;
2800                                 goto next;
2801                         }
2802                         BUG_ON(node->eb != eb);
2803                 } else {
2804                         btrfs_set_node_blockptr(upper->eb, slot,
2805                                                 node->eb->start);
2806                         btrfs_set_node_ptr_generation(upper->eb, slot,
2807                                                       trans->transid);
2808                         btrfs_mark_buffer_dirty(upper->eb);
2809
2810                         ret = btrfs_inc_extent_ref(trans, root,
2811                                                 node->eb->start, blocksize,
2812                                                 upper->eb->start,
2813                                                 btrfs_header_owner(upper->eb),
2814                                                 node->level, 0);
2815                         BUG_ON(ret);
2816
2817                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2818                         BUG_ON(ret);
2819                 }
2820 next:
2821                 if (!upper->pending)
2822                         drop_node_buffer(upper);
2823                 else
2824                         unlock_node_buffer(upper);
2825                 if (err)
2826                         break;
2827         }
2828
2829         if (!err && node->pending) {
2830                 drop_node_buffer(node);
2831                 list_move_tail(&node->list, &rc->backref_cache.changed);
2832                 node->pending = 0;
2833         }
2834
2835         path->lowest_level = 0;
2836         BUG_ON(err == -ENOSPC);
2837         return err;
2838 }
2839
2840 static int link_to_upper(struct btrfs_trans_handle *trans,
2841                          struct reloc_control *rc,
2842                          struct backref_node *node,
2843                          struct btrfs_path *path)
2844 {
2845         struct btrfs_key key;
2846
2847         btrfs_node_key_to_cpu(node->eb, &key, 0);
2848         return do_relocation(trans, rc, node, &key, path, 0);
2849 }
2850
2851 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2852                                 struct reloc_control *rc,
2853                                 struct btrfs_path *path, int err)
2854 {
2855         LIST_HEAD(list);
2856         struct backref_cache *cache = &rc->backref_cache;
2857         struct backref_node *node;
2858         int level;
2859         int ret;
2860
2861         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2862                 while (!list_empty(&cache->pending[level])) {
2863                         node = list_entry(cache->pending[level].next,
2864                                           struct backref_node, list);
2865                         list_move_tail(&node->list, &list);
2866                         BUG_ON(!node->pending);
2867
2868                         if (!err) {
2869                                 ret = link_to_upper(trans, rc, node, path);
2870                                 if (ret < 0)
2871                                         err = ret;
2872                         }
2873                 }
2874                 list_splice_init(&list, &cache->pending[level]);
2875         }
2876         return err;
2877 }
2878
2879 static void mark_block_processed(struct reloc_control *rc,
2880                                  u64 bytenr, u32 blocksize)
2881 {
2882         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
2883                         EXTENT_DIRTY);
2884 }
2885
2886 static void __mark_block_processed(struct reloc_control *rc,
2887                                    struct backref_node *node)
2888 {
2889         u32 blocksize;
2890         if (node->level == 0 ||
2891             in_block_group(node->bytenr, rc->block_group)) {
2892                 blocksize = rc->extent_root->fs_info->nodesize;
2893                 mark_block_processed(rc, node->bytenr, blocksize);
2894         }
2895         node->processed = 1;
2896 }
2897
2898 /*
2899  * mark a block and all blocks directly/indirectly reference the block
2900  * as processed.
2901  */
2902 static void update_processed_blocks(struct reloc_control *rc,
2903                                     struct backref_node *node)
2904 {
2905         struct backref_node *next = node;
2906         struct backref_edge *edge;
2907         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2908         int index = 0;
2909
2910         while (next) {
2911                 cond_resched();
2912                 while (1) {
2913                         if (next->processed)
2914                                 break;
2915
2916                         __mark_block_processed(rc, next);
2917
2918                         if (list_empty(&next->upper))
2919                                 break;
2920
2921                         edge = list_entry(next->upper.next,
2922                                           struct backref_edge, list[LOWER]);
2923                         edges[index++] = edge;
2924                         next = edge->node[UPPER];
2925                 }
2926                 next = walk_down_backref(edges, &index);
2927         }
2928 }
2929
2930 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
2931 {
2932         u32 blocksize = rc->extent_root->fs_info->nodesize;
2933
2934         if (test_range_bit(&rc->processed_blocks, bytenr,
2935                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2936                 return 1;
2937         return 0;
2938 }
2939
2940 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
2941                               struct tree_block *block)
2942 {
2943         struct extent_buffer *eb;
2944
2945         BUG_ON(block->key_ready);
2946         eb = read_tree_block(fs_info, block->bytenr, block->key.offset,
2947                              block->level, NULL);
2948         if (IS_ERR(eb)) {
2949                 return PTR_ERR(eb);
2950         } else if (!extent_buffer_uptodate(eb)) {
2951                 free_extent_buffer(eb);
2952                 return -EIO;
2953         }
2954         WARN_ON(btrfs_header_level(eb) != block->level);
2955         if (block->level == 0)
2956                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2957         else
2958                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2959         free_extent_buffer(eb);
2960         block->key_ready = 1;
2961         return 0;
2962 }
2963
2964 /*
2965  * helper function to relocate a tree block
2966  */
2967 static int relocate_tree_block(struct btrfs_trans_handle *trans,
2968                                 struct reloc_control *rc,
2969                                 struct backref_node *node,
2970                                 struct btrfs_key *key,
2971                                 struct btrfs_path *path)
2972 {
2973         struct btrfs_root *root;
2974         int ret = 0;
2975
2976         if (!node)
2977                 return 0;
2978
2979         BUG_ON(node->processed);
2980         root = select_one_root(node);
2981         if (root == ERR_PTR(-ENOENT)) {
2982                 update_processed_blocks(rc, node);
2983                 goto out;
2984         }
2985
2986         if (!root || test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
2987                 ret = reserve_metadata_space(trans, rc, node);
2988                 if (ret)
2989                         goto out;
2990         }
2991
2992         if (root) {
2993                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
2994                         BUG_ON(node->new_bytenr);
2995                         BUG_ON(!list_empty(&node->list));
2996                         btrfs_record_root_in_trans(trans, root);
2997                         root = root->reloc_root;
2998                         node->new_bytenr = root->node->start;
2999                         node->root = root;
3000                         list_add_tail(&node->list, &rc->backref_cache.changed);
3001                 } else {
3002                         path->lowest_level = node->level;
3003                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
3004                         btrfs_release_path(path);
3005                         if (ret > 0)
3006                                 ret = 0;
3007                 }
3008                 if (!ret)
3009                         update_processed_blocks(rc, node);
3010         } else {
3011                 ret = do_relocation(trans, rc, node, key, path, 1);
3012         }
3013 out:
3014         if (ret || node->level == 0 || node->cowonly)
3015                 remove_backref_node(&rc->backref_cache, node);
3016         return ret;
3017 }
3018
3019 /*
3020  * relocate a list of blocks
3021  */
3022 static noinline_for_stack
3023 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
3024                          struct reloc_control *rc, struct rb_root *blocks)
3025 {
3026         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3027         struct backref_node *node;
3028         struct btrfs_path *path;
3029         struct tree_block *block;
3030         struct rb_node *rb_node;
3031         int ret;
3032         int err = 0;
3033
3034         path = btrfs_alloc_path();
3035         if (!path) {
3036                 err = -ENOMEM;
3037                 goto out_free_blocks;
3038         }
3039
3040         rb_node = rb_first(blocks);
3041         while (rb_node) {
3042                 block = rb_entry(rb_node, struct tree_block, rb_node);
3043                 if (!block->key_ready)
3044                         readahead_tree_block(fs_info, block->bytenr);
3045                 rb_node = rb_next(rb_node);
3046         }
3047
3048         rb_node = rb_first(blocks);
3049         while (rb_node) {
3050                 block = rb_entry(rb_node, struct tree_block, rb_node);
3051                 if (!block->key_ready) {
3052                         err = get_tree_block_key(fs_info, block);
3053                         if (err)
3054                                 goto out_free_path;
3055                 }
3056                 rb_node = rb_next(rb_node);
3057         }
3058
3059         rb_node = rb_first(blocks);
3060         while (rb_node) {
3061                 block = rb_entry(rb_node, struct tree_block, rb_node);
3062
3063                 node = build_backref_tree(rc, &block->key,
3064                                           block->level, block->bytenr);
3065                 if (IS_ERR(node)) {
3066                         err = PTR_ERR(node);
3067                         goto out;
3068                 }
3069
3070                 ret = relocate_tree_block(trans, rc, node, &block->key,
3071                                           path);
3072                 if (ret < 0) {
3073                         if (ret != -EAGAIN || rb_node == rb_first(blocks))
3074                                 err = ret;
3075                         goto out;
3076                 }
3077                 rb_node = rb_next(rb_node);
3078         }
3079 out:
3080         err = finish_pending_nodes(trans, rc, path, err);
3081
3082 out_free_path:
3083         btrfs_free_path(path);
3084 out_free_blocks:
3085         free_block_list(blocks);
3086         return err;
3087 }
3088
3089 static noinline_for_stack
3090 int prealloc_file_extent_cluster(struct inode *inode,
3091                                  struct file_extent_cluster *cluster)
3092 {
3093         u64 alloc_hint = 0;
3094         u64 start;
3095         u64 end;
3096         u64 offset = BTRFS_I(inode)->index_cnt;
3097         u64 num_bytes;
3098         int nr = 0;
3099         int ret = 0;
3100         u64 prealloc_start = cluster->start - offset;
3101         u64 prealloc_end = cluster->end - offset;
3102         u64 cur_offset;
3103         struct extent_changeset *data_reserved = NULL;
3104
3105         BUG_ON(cluster->start != cluster->boundary[0]);
3106         inode_lock(inode);
3107
3108         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
3109                                           prealloc_end + 1 - prealloc_start);
3110         if (ret)
3111                 goto out;
3112
3113         cur_offset = prealloc_start;
3114         while (nr < cluster->nr) {
3115                 start = cluster->boundary[nr] - offset;
3116                 if (nr + 1 < cluster->nr)
3117                         end = cluster->boundary[nr + 1] - 1 - offset;
3118                 else
3119                         end = cluster->end - offset;
3120
3121                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3122                 num_bytes = end + 1 - start;
3123                 if (cur_offset < start)
3124                         btrfs_free_reserved_data_space(inode, data_reserved,
3125                                         cur_offset, start - cur_offset);
3126                 ret = btrfs_prealloc_file_range(inode, 0, start,
3127                                                 num_bytes, num_bytes,
3128                                                 end + 1, &alloc_hint);
3129                 cur_offset = end + 1;
3130                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3131                 if (ret)
3132                         break;
3133                 nr++;
3134         }
3135         if (cur_offset < prealloc_end)
3136                 btrfs_free_reserved_data_space(inode, data_reserved,
3137                                 cur_offset, prealloc_end + 1 - cur_offset);
3138 out:
3139         inode_unlock(inode);
3140         extent_changeset_free(data_reserved);
3141         return ret;
3142 }
3143
3144 static noinline_for_stack
3145 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3146                          u64 block_start)
3147 {
3148         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3149         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3150         struct extent_map *em;
3151         int ret = 0;
3152
3153         em = alloc_extent_map();
3154         if (!em)
3155                 return -ENOMEM;
3156
3157         em->start = start;
3158         em->len = end + 1 - start;
3159         em->block_len = em->len;
3160         em->block_start = block_start;
3161         em->bdev = fs_info->fs_devices->latest_bdev;
3162         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3163
3164         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3165         while (1) {
3166                 write_lock(&em_tree->lock);
3167                 ret = add_extent_mapping(em_tree, em, 0);
3168                 write_unlock(&em_tree->lock);
3169                 if (ret != -EEXIST) {
3170                         free_extent_map(em);
3171                         break;
3172                 }
3173                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
3174         }
3175         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3176         return ret;
3177 }
3178
3179 static int relocate_file_extent_cluster(struct inode *inode,
3180                                         struct file_extent_cluster *cluster)
3181 {
3182         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3183         u64 page_start;
3184         u64 page_end;
3185         u64 offset = BTRFS_I(inode)->index_cnt;
3186         unsigned long index;
3187         unsigned long last_index;
3188         struct page *page;
3189         struct file_ra_state *ra;
3190         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3191         int nr = 0;
3192         int ret = 0;
3193
3194         if (!cluster->nr)
3195                 return 0;
3196
3197         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3198         if (!ra)
3199                 return -ENOMEM;
3200
3201         ret = prealloc_file_extent_cluster(inode, cluster);
3202         if (ret)
3203                 goto out;
3204
3205         file_ra_state_init(ra, inode->i_mapping);
3206
3207         ret = setup_extent_mapping(inode, cluster->start - offset,
3208                                    cluster->end - offset, cluster->start);
3209         if (ret)
3210                 goto out;
3211
3212         index = (cluster->start - offset) >> PAGE_SHIFT;
3213         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3214         while (index <= last_index) {
3215                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
3216                                 PAGE_SIZE);
3217                 if (ret)
3218                         goto out;
3219
3220                 page = find_lock_page(inode->i_mapping, index);
3221                 if (!page) {
3222                         page_cache_sync_readahead(inode->i_mapping,
3223                                                   ra, NULL, index,
3224                                                   last_index + 1 - index);
3225                         page = find_or_create_page(inode->i_mapping, index,
3226                                                    mask);
3227                         if (!page) {
3228                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3229                                                         PAGE_SIZE, true);
3230                                 ret = -ENOMEM;
3231                                 goto out;
3232                         }
3233                 }
3234
3235                 if (PageReadahead(page)) {
3236                         page_cache_async_readahead(inode->i_mapping,
3237                                                    ra, NULL, page, index,
3238                                                    last_index + 1 - index);
3239                 }
3240
3241                 if (!PageUptodate(page)) {
3242                         btrfs_readpage(NULL, page);
3243                         lock_page(page);
3244                         if (!PageUptodate(page)) {
3245                                 unlock_page(page);
3246                                 put_page(page);
3247                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3248                                                         PAGE_SIZE, true);
3249                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3250                                                                PAGE_SIZE, true);
3251                                 ret = -EIO;
3252                                 goto out;
3253                         }
3254                 }
3255
3256                 page_start = page_offset(page);
3257                 page_end = page_start + PAGE_SIZE - 1;
3258
3259                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3260
3261                 set_page_extent_mapped(page);
3262
3263                 if (nr < cluster->nr &&
3264                     page_start + offset == cluster->boundary[nr]) {
3265                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3266                                         page_start, page_end,
3267                                         EXTENT_BOUNDARY);
3268                         nr++;
3269                 }
3270
3271                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
3272                                                 NULL, 0);
3273                 if (ret) {
3274                         unlock_page(page);
3275                         put_page(page);
3276                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
3277                                                          PAGE_SIZE, true);
3278                         btrfs_delalloc_release_extents(BTRFS_I(inode),
3279                                                        PAGE_SIZE, true);
3280
3281                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
3282                                           page_start, page_end,
3283                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
3284                         goto out;
3285
3286                 }
3287                 set_page_dirty(page);
3288
3289                 unlock_extent(&BTRFS_I(inode)->io_tree,
3290                               page_start, page_end);
3291                 unlock_page(page);
3292                 put_page(page);
3293
3294                 index++;
3295                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE,
3296                                                false);
3297                 balance_dirty_pages_ratelimited(inode->i_mapping);
3298                 btrfs_throttle(fs_info);
3299         }
3300         WARN_ON(nr != cluster->nr);
3301 out:
3302         kfree(ra);
3303         return ret;
3304 }
3305
3306 static noinline_for_stack
3307 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3308                          struct file_extent_cluster *cluster)
3309 {
3310         int ret;
3311
3312         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3313                 ret = relocate_file_extent_cluster(inode, cluster);
3314                 if (ret)
3315                         return ret;
3316                 cluster->nr = 0;
3317         }
3318
3319         if (!cluster->nr)
3320                 cluster->start = extent_key->objectid;
3321         else
3322                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3323         cluster->end = extent_key->objectid + extent_key->offset - 1;
3324         cluster->boundary[cluster->nr] = extent_key->objectid;
3325         cluster->nr++;
3326
3327         if (cluster->nr >= MAX_EXTENTS) {
3328                 ret = relocate_file_extent_cluster(inode, cluster);
3329                 if (ret)
3330                         return ret;
3331                 cluster->nr = 0;
3332         }
3333         return 0;
3334 }
3335
3336 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3337 static int get_ref_objectid_v0(struct reloc_control *rc,
3338                                struct btrfs_path *path,
3339                                struct btrfs_key *extent_key,
3340                                u64 *ref_objectid, int *path_change)
3341 {
3342         struct btrfs_key key;
3343         struct extent_buffer *leaf;
3344         struct btrfs_extent_ref_v0 *ref0;
3345         int ret;
3346         int slot;
3347
3348         leaf = path->nodes[0];
3349         slot = path->slots[0];
3350         while (1) {
3351                 if (slot >= btrfs_header_nritems(leaf)) {
3352                         ret = btrfs_next_leaf(rc->extent_root, path);
3353                         if (ret < 0)
3354                                 return ret;
3355                         BUG_ON(ret > 0);
3356                         leaf = path->nodes[0];
3357                         slot = path->slots[0];
3358                         if (path_change)
3359                                 *path_change = 1;
3360                 }
3361                 btrfs_item_key_to_cpu(leaf, &key, slot);
3362                 if (key.objectid != extent_key->objectid)
3363                         return -ENOENT;
3364
3365                 if (key.type != BTRFS_EXTENT_REF_V0_KEY) {
3366                         slot++;
3367                         continue;
3368                 }
3369                 ref0 = btrfs_item_ptr(leaf, slot,
3370                                 struct btrfs_extent_ref_v0);
3371                 *ref_objectid = btrfs_ref_objectid_v0(leaf, ref0);
3372                 break;
3373         }
3374         return 0;
3375 }
3376 #endif
3377
3378 /*
3379  * helper to add a tree block to the list.
3380  * the major work is getting the generation and level of the block
3381  */
3382 static int add_tree_block(struct reloc_control *rc,
3383                           struct btrfs_key *extent_key,
3384                           struct btrfs_path *path,
3385                           struct rb_root *blocks)
3386 {
3387         struct extent_buffer *eb;
3388         struct btrfs_extent_item *ei;
3389         struct btrfs_tree_block_info *bi;
3390         struct tree_block *block;
3391         struct rb_node *rb_node;
3392         u32 item_size;
3393         int level = -1;
3394         u64 generation;
3395
3396         eb =  path->nodes[0];
3397         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3398
3399         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3400             item_size >= sizeof(*ei) + sizeof(*bi)) {
3401                 ei = btrfs_item_ptr(eb, path->slots[0],
3402                                 struct btrfs_extent_item);
3403                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3404                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3405                         level = btrfs_tree_block_level(eb, bi);
3406                 } else {
3407                         level = (int)extent_key->offset;
3408                 }
3409                 generation = btrfs_extent_generation(eb, ei);
3410         } else {
3411 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3412                 u64 ref_owner;
3413                 int ret;
3414
3415                 BUG_ON(item_size != sizeof(struct btrfs_extent_item_v0));
3416                 ret = get_ref_objectid_v0(rc, path, extent_key,
3417                                           &ref_owner, NULL);
3418                 if (ret < 0)
3419                         return ret;
3420                 BUG_ON(ref_owner >= BTRFS_MAX_LEVEL);
3421                 level = (int)ref_owner;
3422                 /* FIXME: get real generation */
3423                 generation = 0;
3424 #else
3425                 BUG();
3426 #endif
3427         }
3428
3429         btrfs_release_path(path);
3430
3431         BUG_ON(level == -1);
3432
3433         block = kmalloc(sizeof(*block), GFP_NOFS);
3434         if (!block)
3435                 return -ENOMEM;
3436
3437         block->bytenr = extent_key->objectid;
3438         block->key.objectid = rc->extent_root->fs_info->nodesize;
3439         block->key.offset = generation;
3440         block->level = level;
3441         block->key_ready = 0;
3442
3443         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3444         if (rb_node)
3445                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3446
3447         return 0;
3448 }
3449
3450 /*
3451  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3452  */
3453 static int __add_tree_block(struct reloc_control *rc,
3454                             u64 bytenr, u32 blocksize,
3455                             struct rb_root *blocks)
3456 {
3457         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3458         struct btrfs_path *path;
3459         struct btrfs_key key;
3460         int ret;
3461         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
3462
3463         if (tree_block_processed(bytenr, rc))
3464                 return 0;
3465
3466         if (tree_search(blocks, bytenr))
3467                 return 0;
3468
3469         path = btrfs_alloc_path();
3470         if (!path)
3471                 return -ENOMEM;
3472 again:
3473         key.objectid = bytenr;
3474         if (skinny) {
3475                 key.type = BTRFS_METADATA_ITEM_KEY;
3476                 key.offset = (u64)-1;
3477         } else {
3478                 key.type = BTRFS_EXTENT_ITEM_KEY;
3479                 key.offset = blocksize;
3480         }
3481
3482         path->search_commit_root = 1;
3483         path->skip_locking = 1;
3484         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3485         if (ret < 0)
3486                 goto out;
3487
3488         if (ret > 0 && skinny) {
3489                 if (path->slots[0]) {
3490                         path->slots[0]--;
3491                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3492                                               path->slots[0]);
3493                         if (key.objectid == bytenr &&
3494                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3495                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3496                               key.offset == blocksize)))
3497                                 ret = 0;
3498                 }
3499
3500                 if (ret) {
3501                         skinny = false;
3502                         btrfs_release_path(path);
3503                         goto again;
3504                 }
3505         }
3506         if (ret) {
3507                 ASSERT(ret == 1);
3508                 btrfs_print_leaf(path->nodes[0]);
3509                 btrfs_err(fs_info,
3510              "tree block extent item (%llu) is not found in extent tree",
3511                      bytenr);
3512                 WARN_ON(1);
3513                 ret = -EINVAL;
3514                 goto out;
3515         }
3516
3517         ret = add_tree_block(rc, &key, path, blocks);
3518 out:
3519         btrfs_free_path(path);
3520         return ret;
3521 }
3522
3523 /*
3524  * helper to check if the block use full backrefs for pointers in it
3525  */
3526 static int block_use_full_backref(struct reloc_control *rc,
3527                                   struct extent_buffer *eb)
3528 {
3529         u64 flags;
3530         int ret;
3531
3532         if (btrfs_header_flag(eb, BTRFS_HEADER_FLAG_RELOC) ||
3533             btrfs_header_backref_rev(eb) < BTRFS_MIXED_BACKREF_REV)
3534                 return 1;
3535
3536         ret = btrfs_lookup_extent_info(NULL, rc->extent_root->fs_info,
3537                                        eb->start, btrfs_header_level(eb), 1,
3538                                        NULL, &flags);
3539         BUG_ON(ret);
3540
3541         if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
3542                 ret = 1;
3543         else
3544                 ret = 0;
3545         return ret;
3546 }
3547
3548 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3549                                     struct btrfs_block_group_cache *block_group,
3550                                     struct inode *inode,
3551                                     u64 ino)
3552 {
3553         struct btrfs_key key;
3554         struct btrfs_root *root = fs_info->tree_root;
3555         struct btrfs_trans_handle *trans;
3556         int ret = 0;
3557
3558         if (inode)
3559                 goto truncate;
3560
3561         key.objectid = ino;
3562         key.type = BTRFS_INODE_ITEM_KEY;
3563         key.offset = 0;
3564
3565         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
3566         if (IS_ERR(inode) || is_bad_inode(inode)) {
3567                 if (!IS_ERR(inode))
3568                         iput(inode);
3569                 return -ENOENT;
3570         }
3571
3572 truncate:
3573         ret = btrfs_check_trunc_cache_free_space(fs_info,
3574                                                  &fs_info->global_block_rsv);
3575         if (ret)
3576                 goto out;
3577
3578         trans = btrfs_join_transaction(root);
3579         if (IS_ERR(trans)) {
3580                 ret = PTR_ERR(trans);
3581                 goto out;
3582         }
3583
3584         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3585
3586         btrfs_end_transaction(trans);
3587         btrfs_btree_balance_dirty(fs_info);
3588 out:
3589         iput(inode);
3590         return ret;
3591 }
3592
3593 /*
3594  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
3595  * this function scans fs tree to find blocks reference the data extent
3596  */
3597 static int find_data_references(struct reloc_control *rc,
3598                                 struct btrfs_key *extent_key,
3599                                 struct extent_buffer *leaf,
3600                                 struct btrfs_extent_data_ref *ref,
3601                                 struct rb_root *blocks)
3602 {
3603         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3604         struct btrfs_path *path;
3605         struct tree_block *block;
3606         struct btrfs_root *root;
3607         struct btrfs_file_extent_item *fi;
3608         struct rb_node *rb_node;
3609         struct btrfs_key key;
3610         u64 ref_root;
3611         u64 ref_objectid;
3612         u64 ref_offset;
3613         u32 ref_count;
3614         u32 nritems;
3615         int err = 0;
3616         int added = 0;
3617         int counted;
3618         int ret;
3619
3620         ref_root = btrfs_extent_data_ref_root(leaf, ref);
3621         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
3622         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
3623         ref_count = btrfs_extent_data_ref_count(leaf, ref);
3624
3625         /*
3626          * This is an extent belonging to the free space cache, lets just delete
3627          * it and redo the search.
3628          */
3629         if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
3630                 ret = delete_block_group_cache(fs_info, rc->block_group,
3631                                                NULL, ref_objectid);
3632                 if (ret != -ENOENT)
3633                         return ret;
3634                 ret = 0;
3635         }
3636
3637         path = btrfs_alloc_path();
3638         if (!path)
3639                 return -ENOMEM;
3640         path->reada = READA_FORWARD;
3641
3642         root = read_fs_root(fs_info, ref_root);
3643         if (IS_ERR(root)) {
3644                 err = PTR_ERR(root);
3645                 goto out;
3646         }
3647
3648         key.objectid = ref_objectid;
3649         key.type = BTRFS_EXTENT_DATA_KEY;
3650         if (ref_offset > ((u64)-1 << 32))
3651                 key.offset = 0;
3652         else
3653                 key.offset = ref_offset;
3654
3655         path->search_commit_root = 1;
3656         path->skip_locking = 1;
3657         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
3658         if (ret < 0) {
3659                 err = ret;
3660                 goto out;
3661         }
3662
3663         leaf = path->nodes[0];
3664         nritems = btrfs_header_nritems(leaf);
3665         /*
3666          * the references in tree blocks that use full backrefs
3667          * are not counted in
3668          */
3669         if (block_use_full_backref(rc, leaf))
3670                 counted = 0;
3671         else
3672                 counted = 1;
3673         rb_node = tree_search(blocks, leaf->start);
3674         if (rb_node) {
3675                 if (counted)
3676                         added = 1;
3677                 else
3678                         path->slots[0] = nritems;
3679         }
3680
3681         while (ref_count > 0) {
3682                 while (path->slots[0] >= nritems) {
3683                         ret = btrfs_next_leaf(root, path);
3684                         if (ret < 0) {
3685                                 err = ret;
3686                                 goto out;
3687                         }
3688                         if (WARN_ON(ret > 0))
3689                                 goto out;
3690
3691                         leaf = path->nodes[0];
3692                         nritems = btrfs_header_nritems(leaf);
3693                         added = 0;
3694
3695                         if (block_use_full_backref(rc, leaf))
3696                                 counted = 0;
3697                         else
3698                                 counted = 1;
3699                         rb_node = tree_search(blocks, leaf->start);
3700                         if (rb_node) {
3701                                 if (counted)
3702                                         added = 1;
3703                                 else
3704                                         path->slots[0] = nritems;
3705                         }
3706                 }
3707
3708                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3709                 if (WARN_ON(key.objectid != ref_objectid ||
3710                     key.type != BTRFS_EXTENT_DATA_KEY))
3711                         break;
3712
3713                 fi = btrfs_item_ptr(leaf, path->slots[0],
3714                                     struct btrfs_file_extent_item);
3715
3716                 if (btrfs_file_extent_type(leaf, fi) ==
3717                     BTRFS_FILE_EXTENT_INLINE)
3718                         goto next;
3719
3720                 if (btrfs_file_extent_disk_bytenr(leaf, fi) !=
3721                     extent_key->objectid)
3722                         goto next;
3723
3724                 key.offset -= btrfs_file_extent_offset(leaf, fi);
3725                 if (key.offset != ref_offset)
3726                         goto next;
3727
3728                 if (counted)
3729                         ref_count--;
3730                 if (added)
3731                         goto next;
3732
3733                 if (!tree_block_processed(leaf->start, rc)) {
3734                         block = kmalloc(sizeof(*block), GFP_NOFS);
3735                         if (!block) {
3736                                 err = -ENOMEM;
3737                                 break;
3738                         }
3739                         block->bytenr = leaf->start;
3740                         btrfs_item_key_to_cpu(leaf, &block->key, 0);
3741                         block->level = 0;
3742                         block->key_ready = 1;
3743                         rb_node = tree_insert(blocks, block->bytenr,
3744                                               &block->rb_node);
3745                         if (rb_node)
3746                                 backref_tree_panic(rb_node, -EEXIST,
3747                                                    block->bytenr);
3748                 }
3749                 if (counted)
3750                         added = 1;
3751                 else
3752                         path->slots[0] = nritems;
3753 next:
3754                 path->slots[0]++;
3755
3756         }
3757 out:
3758         btrfs_free_path(path);
3759         return err;
3760 }
3761
3762 /*
3763  * helper to find all tree blocks that reference a given data extent
3764  */
3765 static noinline_for_stack
3766 int add_data_references(struct reloc_control *rc,
3767                         struct btrfs_key *extent_key,
3768                         struct btrfs_path *path,
3769                         struct rb_root *blocks)
3770 {
3771         struct btrfs_key key;
3772         struct extent_buffer *eb;
3773         struct btrfs_extent_data_ref *dref;
3774         struct btrfs_extent_inline_ref *iref;
3775         unsigned long ptr;
3776         unsigned long end;
3777         u32 blocksize = rc->extent_root->fs_info->nodesize;
3778         int ret = 0;
3779         int err = 0;
3780
3781         eb = path->nodes[0];
3782         ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
3783         end = ptr + btrfs_item_size_nr(eb, path->slots[0]);
3784 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3785         if (ptr + sizeof(struct btrfs_extent_item_v0) == end)
3786                 ptr = end;
3787         else
3788 #endif
3789                 ptr += sizeof(struct btrfs_extent_item);
3790
3791         while (ptr < end) {
3792                 iref = (struct btrfs_extent_inline_ref *)ptr;
3793                 key.type = btrfs_get_extent_inline_ref_type(eb, iref,
3794                                                         BTRFS_REF_TYPE_DATA);
3795                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3796                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3797                         ret = __add_tree_block(rc, key.offset, blocksize,
3798                                                blocks);
3799                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3800                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
3801                         ret = find_data_references(rc, extent_key,
3802                                                    eb, dref, blocks);
3803                 } else {
3804                         ret = -EINVAL;
3805                         btrfs_err(rc->extent_root->fs_info,
3806                      "extent %llu slot %d has an invalid inline ref type",
3807                              eb->start, path->slots[0]);
3808                 }
3809                 if (ret) {
3810                         err = ret;
3811                         goto out;
3812                 }
3813                 ptr += btrfs_extent_inline_ref_size(key.type);
3814         }
3815         WARN_ON(ptr > end);
3816
3817         while (1) {
3818                 cond_resched();
3819                 eb = path->nodes[0];
3820                 if (path->slots[0] >= btrfs_header_nritems(eb)) {
3821                         ret = btrfs_next_leaf(rc->extent_root, path);
3822                         if (ret < 0) {
3823                                 err = ret;
3824                                 break;
3825                         }
3826                         if (ret > 0)
3827                                 break;
3828                         eb = path->nodes[0];
3829                 }
3830
3831                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
3832                 if (key.objectid != extent_key->objectid)
3833                         break;
3834
3835 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3836                 if (key.type == BTRFS_SHARED_DATA_REF_KEY ||
3837                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
3838 #else
3839                 BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
3840                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3841 #endif
3842                         ret = __add_tree_block(rc, key.offset, blocksize,
3843                                                blocks);
3844                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3845                         dref = btrfs_item_ptr(eb, path->slots[0],
3846                                               struct btrfs_extent_data_ref);
3847                         ret = find_data_references(rc, extent_key,
3848                                                    eb, dref, blocks);
3849                 } else {
3850                         ret = 0;
3851                 }
3852                 if (ret) {
3853                         err = ret;
3854                         break;
3855                 }
3856                 path->slots[0]++;
3857         }
3858 out:
3859         btrfs_release_path(path);
3860         if (err)
3861                 free_block_list(blocks);
3862         return err;
3863 }
3864
3865 /*
3866  * helper to find next unprocessed extent
3867  */
3868 static noinline_for_stack
3869 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3870                      struct btrfs_key *extent_key)
3871 {
3872         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3873         struct btrfs_key key;
3874         struct extent_buffer *leaf;
3875         u64 start, end, last;
3876         int ret;
3877
3878         last = rc->block_group->key.objectid + rc->block_group->key.offset;
3879         while (1) {
3880                 cond_resched();
3881                 if (rc->search_start >= last) {
3882                         ret = 1;
3883                         break;
3884                 }
3885
3886                 key.objectid = rc->search_start;
3887                 key.type = BTRFS_EXTENT_ITEM_KEY;
3888                 key.offset = 0;
3889
3890                 path->search_commit_root = 1;
3891                 path->skip_locking = 1;
3892                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3893                                         0, 0);
3894                 if (ret < 0)
3895                         break;
3896 next:
3897                 leaf = path->nodes[0];
3898                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3899                         ret = btrfs_next_leaf(rc->extent_root, path);
3900                         if (ret != 0)
3901                                 break;
3902                         leaf = path->nodes[0];
3903                 }
3904
3905                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3906                 if (key.objectid >= last) {
3907                         ret = 1;
3908                         break;
3909                 }
3910
3911                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3912                     key.type != BTRFS_METADATA_ITEM_KEY) {
3913                         path->slots[0]++;
3914                         goto next;
3915                 }
3916
3917                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3918                     key.objectid + key.offset <= rc->search_start) {
3919                         path->slots[0]++;
3920                         goto next;
3921                 }
3922
3923                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3924                     key.objectid + fs_info->nodesize <=
3925                     rc->search_start) {
3926                         path->slots[0]++;
3927                         goto next;
3928                 }
3929
3930                 ret = find_first_extent_bit(&rc->processed_blocks,
3931                                             key.objectid, &start, &end,
3932                                             EXTENT_DIRTY, NULL);
3933
3934                 if (ret == 0 && start <= key.objectid) {
3935                         btrfs_release_path(path);
3936                         rc->search_start = end + 1;
3937                 } else {
3938                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3939                                 rc->search_start = key.objectid + key.offset;
3940                         else
3941                                 rc->search_start = key.objectid +
3942                                         fs_info->nodesize;
3943                         memcpy(extent_key, &key, sizeof(key));
3944                         return 0;
3945                 }
3946         }
3947         btrfs_release_path(path);
3948         return ret;
3949 }
3950
3951 static void set_reloc_control(struct reloc_control *rc)
3952 {
3953         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3954
3955         mutex_lock(&fs_info->reloc_mutex);
3956         fs_info->reloc_ctl = rc;
3957         mutex_unlock(&fs_info->reloc_mutex);
3958 }
3959
3960 static void unset_reloc_control(struct reloc_control *rc)
3961 {
3962         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3963
3964         mutex_lock(&fs_info->reloc_mutex);
3965         fs_info->reloc_ctl = NULL;
3966         mutex_unlock(&fs_info->reloc_mutex);
3967 }
3968
3969 static int check_extent_flags(u64 flags)
3970 {
3971         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3972             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3973                 return 1;
3974         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3975             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3976                 return 1;
3977         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3978             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3979                 return 1;
3980         return 0;
3981 }
3982
3983 static noinline_for_stack
3984 int prepare_to_relocate(struct reloc_control *rc)
3985 {
3986         struct btrfs_trans_handle *trans;
3987         int ret;
3988
3989         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3990                                               BTRFS_BLOCK_RSV_TEMP);
3991         if (!rc->block_rsv)
3992                 return -ENOMEM;
3993
3994         memset(&rc->cluster, 0, sizeof(rc->cluster));
3995         rc->search_start = rc->block_group->key.objectid;
3996         rc->extents_found = 0;
3997         rc->nodes_relocated = 0;
3998         rc->merging_rsv_size = 0;
3999         rc->reserved_bytes = 0;
4000         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
4001                               RELOCATION_RESERVED_NODES;
4002         ret = btrfs_block_rsv_refill(rc->extent_root,
4003                                      rc->block_rsv, rc->block_rsv->size,
4004                                      BTRFS_RESERVE_FLUSH_ALL);
4005         if (ret)
4006                 return ret;
4007
4008         rc->create_reloc_tree = 1;
4009         set_reloc_control(rc);
4010
4011         trans = btrfs_join_transaction(rc->extent_root);
4012         if (IS_ERR(trans)) {
4013                 unset_reloc_control(rc);
4014                 /*
4015                  * extent tree is not a ref_cow tree and has no reloc_root to
4016                  * cleanup.  And callers are responsible to free the above
4017                  * block rsv.
4018                  */
4019                 return PTR_ERR(trans);
4020         }
4021         btrfs_commit_transaction(trans);
4022         return 0;
4023 }
4024
4025 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
4026 {
4027         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
4028         struct rb_root blocks = RB_ROOT;
4029         struct btrfs_key key;
4030         struct btrfs_trans_handle *trans = NULL;
4031         struct btrfs_path *path;
4032         struct btrfs_extent_item *ei;
4033         u64 flags;
4034         u32 item_size;
4035         int ret;
4036         int err = 0;
4037         int progress = 0;
4038
4039         path = btrfs_alloc_path();
4040         if (!path)
4041                 return -ENOMEM;
4042         path->reada = READA_FORWARD;
4043
4044         ret = prepare_to_relocate(rc);
4045         if (ret) {
4046                 err = ret;
4047                 goto out_free;
4048         }
4049
4050         while (1) {
4051                 rc->reserved_bytes = 0;
4052                 ret = btrfs_block_rsv_refill(rc->extent_root,
4053                                         rc->block_rsv, rc->block_rsv->size,
4054                                         BTRFS_RESERVE_FLUSH_ALL);
4055                 if (ret) {
4056                         err = ret;
4057                         break;
4058                 }
4059                 progress++;
4060                 trans = btrfs_start_transaction(rc->extent_root, 0);
4061                 if (IS_ERR(trans)) {
4062                         err = PTR_ERR(trans);
4063                         trans = NULL;
4064                         break;
4065                 }
4066 restart:
4067                 if (update_backref_cache(trans, &rc->backref_cache)) {
4068                         btrfs_end_transaction(trans);
4069                         continue;
4070                 }
4071
4072                 ret = find_next_extent(rc, path, &key);
4073                 if (ret < 0)
4074                         err = ret;
4075                 if (ret != 0)
4076                         break;
4077
4078                 rc->extents_found++;
4079
4080                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4081                                     struct btrfs_extent_item);
4082                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4083                 if (item_size >= sizeof(*ei)) {
4084                         flags = btrfs_extent_flags(path->nodes[0], ei);
4085                         ret = check_extent_flags(flags);
4086                         BUG_ON(ret);
4087
4088                 } else {
4089 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
4090                         u64 ref_owner;
4091                         int path_change = 0;
4092
4093                         BUG_ON(item_size !=
4094                                sizeof(struct btrfs_extent_item_v0));
4095                         ret = get_ref_objectid_v0(rc, path, &key, &ref_owner,
4096                                                   &path_change);
4097                         if (ret < 0) {
4098                                 err = ret;
4099                                 break;
4100                         }
4101                         if (ref_owner < BTRFS_FIRST_FREE_OBJECTID)
4102                                 flags = BTRFS_EXTENT_FLAG_TREE_BLOCK;
4103                         else
4104                                 flags = BTRFS_EXTENT_FLAG_DATA;
4105
4106                         if (path_change) {
4107                                 btrfs_release_path(path);
4108
4109                                 path->search_commit_root = 1;
4110                                 path->skip_locking = 1;
4111                                 ret = btrfs_search_slot(NULL, rc->extent_root,
4112                                                         &key, path, 0, 0);
4113                                 if (ret < 0) {
4114                                         err = ret;
4115                                         break;
4116                                 }
4117                                 BUG_ON(ret > 0);
4118                         }
4119 #else
4120                         BUG();
4121 #endif
4122                 }
4123
4124                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4125                         ret = add_tree_block(rc, &key, path, &blocks);
4126                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4127                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4128                         ret = add_data_references(rc, &key, path, &blocks);
4129                 } else {
4130                         btrfs_release_path(path);
4131                         ret = 0;
4132                 }
4133                 if (ret < 0) {
4134                         err = ret;
4135                         break;
4136                 }
4137
4138                 if (!RB_EMPTY_ROOT(&blocks)) {
4139                         ret = relocate_tree_blocks(trans, rc, &blocks);
4140                         if (ret < 0) {
4141                                 /*
4142                                  * if we fail to relocate tree blocks, force to update
4143                                  * backref cache when committing transaction.
4144                                  */
4145                                 rc->backref_cache.last_trans = trans->transid - 1;
4146
4147                                 if (ret != -EAGAIN) {
4148                                         err = ret;
4149                                         break;
4150                                 }
4151                                 rc->extents_found--;
4152                                 rc->search_start = key.objectid;
4153                         }
4154                 }
4155
4156                 btrfs_end_transaction_throttle(trans);
4157                 btrfs_btree_balance_dirty(fs_info);
4158                 trans = NULL;
4159
4160                 if (rc->stage == MOVE_DATA_EXTENTS &&
4161                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4162                         rc->found_file_extent = 1;
4163                         ret = relocate_data_extent(rc->data_inode,
4164                                                    &key, &rc->cluster);
4165                         if (ret < 0) {
4166                                 err = ret;
4167                                 break;
4168                         }
4169                 }
4170         }
4171         if (trans && progress && err == -ENOSPC) {
4172                 ret = btrfs_force_chunk_alloc(trans, fs_info,
4173                                               rc->block_group->flags);
4174                 if (ret == 1) {
4175                         err = 0;
4176                         progress = 0;
4177                         goto restart;
4178                 }
4179         }
4180
4181         btrfs_release_path(path);
4182         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4183
4184         if (trans) {
4185                 btrfs_end_transaction_throttle(trans);
4186                 btrfs_btree_balance_dirty(fs_info);
4187         }
4188
4189         if (!err) {
4190                 ret = relocate_file_extent_cluster(rc->data_inode,
4191                                                    &rc->cluster);
4192                 if (ret < 0)
4193                         err = ret;
4194         }
4195
4196         rc->create_reloc_tree = 0;
4197         set_reloc_control(rc);
4198
4199         backref_cache_cleanup(&rc->backref_cache);
4200         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4201
4202         err = prepare_to_merge(rc, err);
4203
4204         merge_reloc_roots(rc);
4205
4206         rc->merge_reloc_tree = 0;
4207         unset_reloc_control(rc);
4208         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4209
4210         /* get rid of pinned extents */
4211         trans = btrfs_join_transaction(rc->extent_root);
4212         if (IS_ERR(trans)) {
4213                 err = PTR_ERR(trans);
4214                 goto out_free;
4215         }
4216         btrfs_commit_transaction(trans);
4217 out_free:
4218         btrfs_free_block_rsv(fs_info, rc->block_rsv);
4219         btrfs_free_path(path);
4220         return err;
4221 }
4222
4223 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4224                                  struct btrfs_root *root, u64 objectid)
4225 {
4226         struct btrfs_path *path;
4227         struct btrfs_inode_item *item;
4228         struct extent_buffer *leaf;
4229         int ret;
4230
4231         path = btrfs_alloc_path();
4232         if (!path)
4233                 return -ENOMEM;
4234
4235         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4236         if (ret)
4237                 goto out;
4238
4239         leaf = path->nodes[0];
4240         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4241         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
4242         btrfs_set_inode_generation(leaf, item, 1);
4243         btrfs_set_inode_size(leaf, item, 0);
4244         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4245         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4246                                           BTRFS_INODE_PREALLOC);
4247         btrfs_mark_buffer_dirty(leaf);
4248 out:
4249         btrfs_free_path(path);
4250         return ret;
4251 }
4252
4253 /*
4254  * helper to create inode for data relocation.
4255  * the inode is in data relocation tree and its link count is 0
4256  */
4257 static noinline_for_stack
4258 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4259                                  struct btrfs_block_group_cache *group)
4260 {
4261         struct inode *inode = NULL;
4262         struct btrfs_trans_handle *trans;
4263         struct btrfs_root *root;
4264         struct btrfs_key key;
4265         u64 objectid;
4266         int err = 0;
4267
4268         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4269         if (IS_ERR(root))
4270                 return ERR_CAST(root);
4271
4272         trans = btrfs_start_transaction(root, 6);
4273         if (IS_ERR(trans))
4274                 return ERR_CAST(trans);
4275
4276         err = btrfs_find_free_objectid(root, &objectid);
4277         if (err)
4278                 goto out;
4279
4280         err = __insert_orphan_inode(trans, root, objectid);
4281         BUG_ON(err);
4282
4283         key.objectid = objectid;
4284         key.type = BTRFS_INODE_ITEM_KEY;
4285         key.offset = 0;
4286         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
4287         BUG_ON(IS_ERR(inode) || is_bad_inode(inode));
4288         BTRFS_I(inode)->index_cnt = group->key.objectid;
4289
4290         err = btrfs_orphan_add(trans, BTRFS_I(inode));
4291 out:
4292         btrfs_end_transaction(trans);
4293         btrfs_btree_balance_dirty(fs_info);
4294         if (err) {
4295                 if (inode)
4296                         iput(inode);
4297                 inode = ERR_PTR(err);
4298         }
4299         return inode;
4300 }
4301
4302 static struct reloc_control *alloc_reloc_control(void)
4303 {
4304         struct reloc_control *rc;
4305
4306         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4307         if (!rc)
4308                 return NULL;
4309
4310         INIT_LIST_HEAD(&rc->reloc_roots);
4311         backref_cache_init(&rc->backref_cache);
4312         mapping_tree_init(&rc->reloc_root_tree);
4313         extent_io_tree_init(&rc->processed_blocks, NULL);
4314         return rc;
4315 }
4316
4317 /*
4318  * Print the block group being relocated
4319  */
4320 static void describe_relocation(struct btrfs_fs_info *fs_info,
4321                                 struct btrfs_block_group_cache *block_group)
4322 {
4323         char buf[128];          /* prefixed by a '|' that'll be dropped */
4324         u64 flags = block_group->flags;
4325
4326         /* Shouldn't happen */
4327         if (!flags) {
4328                 strcpy(buf, "|NONE");
4329         } else {
4330                 char *bp = buf;
4331
4332 #define DESCRIBE_FLAG(f, d) \
4333                 if (flags & BTRFS_BLOCK_GROUP_##f) { \
4334                         bp += snprintf(bp, buf - bp + sizeof(buf), "|%s", d); \
4335                         flags &= ~BTRFS_BLOCK_GROUP_##f; \
4336                 }
4337                 DESCRIBE_FLAG(DATA,     "data");
4338                 DESCRIBE_FLAG(SYSTEM,   "system");
4339                 DESCRIBE_FLAG(METADATA, "metadata");
4340                 DESCRIBE_FLAG(RAID0,    "raid0");
4341                 DESCRIBE_FLAG(RAID1,    "raid1");
4342                 DESCRIBE_FLAG(DUP,      "dup");
4343                 DESCRIBE_FLAG(RAID10,   "raid10");
4344                 DESCRIBE_FLAG(RAID5,    "raid5");
4345                 DESCRIBE_FLAG(RAID6,    "raid6");
4346                 if (flags)
4347                         snprintf(buf, buf - bp + sizeof(buf), "|0x%llx", flags);
4348 #undef DESCRIBE_FLAG
4349         }
4350
4351         btrfs_info(fs_info,
4352                    "relocating block group %llu flags %s",
4353                    block_group->key.objectid, buf + 1);
4354 }
4355
4356 /*
4357  * function to relocate all extents in a block group.
4358  */
4359 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
4360 {
4361         struct btrfs_root *extent_root = fs_info->extent_root;
4362         struct reloc_control *rc;
4363         struct inode *inode;
4364         struct btrfs_path *path;
4365         int ret;
4366         int rw = 0;
4367         int err = 0;
4368
4369         rc = alloc_reloc_control();
4370         if (!rc)
4371                 return -ENOMEM;
4372
4373         rc->extent_root = extent_root;
4374
4375         rc->block_group = btrfs_lookup_block_group(fs_info, group_start);
4376         BUG_ON(!rc->block_group);
4377
4378         ret = btrfs_inc_block_group_ro(fs_info, rc->block_group);
4379         if (ret) {
4380                 err = ret;
4381                 goto out;
4382         }
4383         rw = 1;
4384
4385         path = btrfs_alloc_path();
4386         if (!path) {
4387                 err = -ENOMEM;
4388                 goto out;
4389         }
4390
4391         inode = lookup_free_space_inode(fs_info, rc->block_group, path);
4392         btrfs_free_path(path);
4393
4394         if (!IS_ERR(inode))
4395                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4396         else
4397                 ret = PTR_ERR(inode);
4398
4399         if (ret && ret != -ENOENT) {
4400                 err = ret;
4401                 goto out;
4402         }
4403
4404         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4405         if (IS_ERR(rc->data_inode)) {
4406                 err = PTR_ERR(rc->data_inode);
4407                 rc->data_inode = NULL;
4408                 goto out;
4409         }
4410
4411         describe_relocation(fs_info, rc->block_group);
4412
4413         btrfs_wait_block_group_reservations(rc->block_group);
4414         btrfs_wait_nocow_writers(rc->block_group);
4415         btrfs_wait_ordered_roots(fs_info, U64_MAX,
4416                                  rc->block_group->key.objectid,
4417                                  rc->block_group->key.offset);
4418
4419         while (1) {
4420                 mutex_lock(&fs_info->cleaner_mutex);
4421                 ret = relocate_block_group(rc);
4422                 mutex_unlock(&fs_info->cleaner_mutex);
4423                 if (ret < 0) {
4424                         err = ret;
4425                         goto out;
4426                 }
4427
4428                 if (rc->extents_found == 0)
4429                         break;
4430
4431                 btrfs_info(fs_info, "found %llu extents", rc->extents_found);
4432
4433                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4434                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4435                                                        (u64)-1);
4436                         if (ret) {
4437                                 err = ret;
4438                                 goto out;
4439                         }
4440                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4441                                                  0, -1);
4442                         rc->stage = UPDATE_DATA_PTRS;
4443                 }
4444         }
4445
4446         WARN_ON(rc->block_group->pinned > 0);
4447         WARN_ON(rc->block_group->reserved > 0);
4448         WARN_ON(btrfs_block_group_used(&rc->block_group->item) > 0);
4449 out:
4450         if (err && rw)
4451                 btrfs_dec_block_group_ro(rc->block_group);
4452         iput(rc->data_inode);
4453         btrfs_put_block_group(rc->block_group);
4454         kfree(rc);
4455         return err;
4456 }
4457
4458 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4459 {
4460         struct btrfs_fs_info *fs_info = root->fs_info;
4461         struct btrfs_trans_handle *trans;
4462         int ret, err;
4463
4464         trans = btrfs_start_transaction(fs_info->tree_root, 0);
4465         if (IS_ERR(trans))
4466                 return PTR_ERR(trans);
4467
4468         memset(&root->root_item.drop_progress, 0,
4469                 sizeof(root->root_item.drop_progress));
4470         root->root_item.drop_level = 0;
4471         btrfs_set_root_refs(&root->root_item, 0);
4472         ret = btrfs_update_root(trans, fs_info->tree_root,
4473                                 &root->root_key, &root->root_item);
4474
4475         err = btrfs_end_transaction(trans);
4476         if (err)
4477                 return err;
4478         return ret;
4479 }
4480
4481 /*
4482  * recover relocation interrupted by system crash.
4483  *
4484  * this function resumes merging reloc trees with corresponding fs trees.
4485  * this is important for keeping the sharing of tree blocks
4486  */
4487 int btrfs_recover_relocation(struct btrfs_root *root)
4488 {
4489         struct btrfs_fs_info *fs_info = root->fs_info;
4490         LIST_HEAD(reloc_roots);
4491         struct btrfs_key key;
4492         struct btrfs_root *fs_root;
4493         struct btrfs_root *reloc_root;
4494         struct btrfs_path *path;
4495         struct extent_buffer *leaf;
4496         struct reloc_control *rc = NULL;
4497         struct btrfs_trans_handle *trans;
4498         int ret;
4499         int err = 0;
4500
4501         path = btrfs_alloc_path();
4502         if (!path)
4503                 return -ENOMEM;
4504         path->reada = READA_BACK;
4505
4506         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4507         key.type = BTRFS_ROOT_ITEM_KEY;
4508         key.offset = (u64)-1;
4509
4510         while (1) {
4511                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
4512                                         path, 0, 0);
4513                 if (ret < 0) {
4514                         err = ret;
4515                         goto out;
4516                 }
4517                 if (ret > 0) {
4518                         if (path->slots[0] == 0)
4519                                 break;
4520                         path->slots[0]--;
4521                 }
4522                 leaf = path->nodes[0];
4523                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4524                 btrfs_release_path(path);
4525
4526                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4527                     key.type != BTRFS_ROOT_ITEM_KEY)
4528                         break;
4529
4530                 reloc_root = btrfs_read_fs_root(root, &key);
4531                 if (IS_ERR(reloc_root)) {
4532                         err = PTR_ERR(reloc_root);
4533                         goto out;
4534                 }
4535
4536                 list_add(&reloc_root->root_list, &reloc_roots);
4537
4538                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4539                         fs_root = read_fs_root(fs_info,
4540                                                reloc_root->root_key.offset);
4541                         if (IS_ERR(fs_root)) {
4542                                 ret = PTR_ERR(fs_root);
4543                                 if (ret != -ENOENT) {
4544                                         err = ret;
4545                                         goto out;
4546                                 }
4547                                 ret = mark_garbage_root(reloc_root);
4548                                 if (ret < 0) {
4549                                         err = ret;
4550                                         goto out;
4551                                 }
4552                         }
4553                 }
4554
4555                 if (key.offset == 0)
4556                         break;
4557
4558                 key.offset--;
4559         }
4560         btrfs_release_path(path);
4561
4562         if (list_empty(&reloc_roots))
4563                 goto out;
4564
4565         rc = alloc_reloc_control();
4566         if (!rc) {
4567                 err = -ENOMEM;
4568                 goto out;
4569         }
4570
4571         rc->extent_root = fs_info->extent_root;
4572
4573         set_reloc_control(rc);
4574
4575         trans = btrfs_join_transaction(rc->extent_root);
4576         if (IS_ERR(trans)) {
4577                 unset_reloc_control(rc);
4578                 err = PTR_ERR(trans);
4579                 goto out_free;
4580         }
4581
4582         rc->merge_reloc_tree = 1;
4583
4584         while (!list_empty(&reloc_roots)) {
4585                 reloc_root = list_entry(reloc_roots.next,
4586                                         struct btrfs_root, root_list);
4587                 list_del(&reloc_root->root_list);
4588
4589                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4590                         list_add_tail(&reloc_root->root_list,
4591                                       &rc->reloc_roots);
4592                         continue;
4593                 }
4594
4595                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
4596                 if (IS_ERR(fs_root)) {
4597                         err = PTR_ERR(fs_root);
4598                         goto out_free;
4599                 }
4600
4601                 err = __add_reloc_root(reloc_root);
4602                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4603                 fs_root->reloc_root = reloc_root;
4604         }
4605
4606         err = btrfs_commit_transaction(trans);
4607         if (err)
4608                 goto out_free;
4609
4610         merge_reloc_roots(rc);
4611
4612         unset_reloc_control(rc);
4613
4614         trans = btrfs_join_transaction(rc->extent_root);
4615         if (IS_ERR(trans)) {
4616                 err = PTR_ERR(trans);
4617                 goto out_free;
4618         }
4619         err = btrfs_commit_transaction(trans);
4620 out_free:
4621         kfree(rc);
4622 out:
4623         if (!list_empty(&reloc_roots))
4624                 free_reloc_roots(&reloc_roots);
4625
4626         btrfs_free_path(path);
4627
4628         if (err == 0) {
4629                 /* cleanup orphan inode in data relocation tree */
4630                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4631                 if (IS_ERR(fs_root))
4632                         err = PTR_ERR(fs_root);
4633                 else
4634                         err = btrfs_orphan_cleanup(fs_root);
4635         }
4636         return err;
4637 }
4638
4639 /*
4640  * helper to add ordered checksum for data relocation.
4641  *
4642  * cloning checksum properly handles the nodatasum extents.
4643  * it also saves CPU time to re-calculate the checksum.
4644  */
4645 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4646 {
4647         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
4648         struct btrfs_ordered_sum *sums;
4649         struct btrfs_ordered_extent *ordered;
4650         int ret;
4651         u64 disk_bytenr;
4652         u64 new_bytenr;
4653         LIST_HEAD(list);
4654
4655         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4656         BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
4657
4658         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4659         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
4660                                        disk_bytenr + len - 1, &list, 0);
4661         if (ret)
4662                 goto out;
4663
4664         while (!list_empty(&list)) {
4665                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4666                 list_del_init(&sums->list);
4667
4668                 /*
4669                  * We need to offset the new_bytenr based on where the csum is.
4670                  * We need to do this because we will read in entire prealloc
4671                  * extents but we may have written to say the middle of the
4672                  * prealloc extent, so we need to make sure the csum goes with
4673                  * the right disk offset.
4674                  *
4675                  * We can do this because the data reloc inode refers strictly
4676                  * to the on disk bytes, so we don't have to worry about
4677                  * disk_len vs real len like with real inodes since it's all
4678                  * disk length.
4679                  */
4680                 new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
4681                 sums->bytenr = new_bytenr;
4682
4683                 btrfs_add_ordered_sum(inode, ordered, sums);
4684         }
4685 out:
4686         btrfs_put_ordered_extent(ordered);
4687         return ret;
4688 }
4689
4690 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4691                           struct btrfs_root *root, struct extent_buffer *buf,
4692                           struct extent_buffer *cow)
4693 {
4694         struct btrfs_fs_info *fs_info = root->fs_info;
4695         struct reloc_control *rc;
4696         struct backref_node *node;
4697         int first_cow = 0;
4698         int level;
4699         int ret = 0;
4700
4701         rc = fs_info->reloc_ctl;
4702         if (!rc)
4703                 return 0;
4704
4705         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4706                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4707
4708         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
4709                 if (buf == root->node)
4710                         __update_reloc_root(root, cow->start);
4711         }
4712
4713         level = btrfs_header_level(buf);
4714         if (btrfs_header_generation(buf) <=
4715             btrfs_root_last_snapshot(&root->root_item))
4716                 first_cow = 1;
4717
4718         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4719             rc->create_reloc_tree) {
4720                 WARN_ON(!first_cow && level == 0);
4721
4722                 node = rc->backref_cache.path[level];
4723                 BUG_ON(node->bytenr != buf->start &&
4724                        node->new_bytenr != buf->start);
4725
4726                 drop_node_buffer(node);
4727                 extent_buffer_get(cow);
4728                 node->eb = cow;
4729                 node->new_bytenr = cow->start;
4730
4731                 if (!node->pending) {
4732                         list_move_tail(&node->list,
4733                                        &rc->backref_cache.pending[level]);
4734                         node->pending = 1;
4735                 }
4736
4737                 if (first_cow)
4738                         __mark_block_processed(rc, node);
4739
4740                 if (first_cow && level > 0)
4741                         rc->nodes_relocated += buf->len;
4742         }
4743
4744         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4745                 ret = replace_file_extents(trans, rc, root, cow);
4746         return ret;
4747 }
4748
4749 /*
4750  * called before creating snapshot. it calculates metadata reservation
4751  * required for relocating tree blocks in the snapshot
4752  */
4753 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4754                               u64 *bytes_to_reserve)
4755 {
4756         struct btrfs_root *root;
4757         struct reloc_control *rc;
4758
4759         root = pending->root;
4760         if (!root->reloc_root)
4761                 return;
4762
4763         rc = root->fs_info->reloc_ctl;
4764         if (!rc->merge_reloc_tree)
4765                 return;
4766
4767         root = root->reloc_root;
4768         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4769         /*
4770          * relocation is in the stage of merging trees. the space
4771          * used by merging a reloc tree is twice the size of
4772          * relocated tree nodes in the worst case. half for cowing
4773          * the reloc tree, half for cowing the fs tree. the space
4774          * used by cowing the reloc tree will be freed after the
4775          * tree is dropped. if we create snapshot, cowing the fs
4776          * tree may use more space than it frees. so we need
4777          * reserve extra space.
4778          */
4779         *bytes_to_reserve += rc->nodes_relocated;
4780 }
4781
4782 /*
4783  * called after snapshot is created. migrate block reservation
4784  * and create reloc root for the newly created snapshot
4785  */
4786 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4787                                struct btrfs_pending_snapshot *pending)
4788 {
4789         struct btrfs_root *root = pending->root;
4790         struct btrfs_root *reloc_root;
4791         struct btrfs_root *new_root;
4792         struct reloc_control *rc;
4793         int ret;
4794
4795         if (!root->reloc_root)
4796                 return 0;
4797
4798         rc = root->fs_info->reloc_ctl;
4799         rc->merging_rsv_size += rc->nodes_relocated;
4800
4801         if (rc->merge_reloc_tree) {
4802                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4803                                               rc->block_rsv,
4804                                               rc->nodes_relocated, 1);
4805                 if (ret)
4806                         return ret;
4807         }
4808
4809         new_root = pending->snap;
4810         reloc_root = create_reloc_root(trans, root->reloc_root,
4811                                        new_root->root_key.objectid);
4812         if (IS_ERR(reloc_root))
4813                 return PTR_ERR(reloc_root);
4814
4815         ret = __add_reloc_root(reloc_root);
4816         BUG_ON(ret < 0);
4817         new_root->reloc_root = reloc_root;
4818
4819         if (rc->create_reloc_tree)
4820                 ret = clone_backref_node(trans, rc, root, reloc_root);
4821         return ret;
4822 }