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 <linux/error-injection.h>
  13 #include "ctree.h"
  14 #include "disk-io.h"
  15 #include "transaction.h"
  16 #include "volumes.h"
  17 #include "locking.h"
  18 #include "btrfs_inode.h"
  19 #include "async-thread.h"
  20 #include "free-space-cache.h"
  21 #include "inode-map.h"
  22 #include "qgroup.h"
  23 #include "print-tree.h"
  24 #include "delalloc-space.h"
  25 #include "block-group.h"
  26 #include "backref.h"
  27 #include "misc.h"
  28
  29 /*
  30  * Relocation overview
  31  *
  32  * [What does relocation do]
  33  *
  34  * The objective of relocation is to relocate all extents of the target block
  35  * group to other block groups.
  36  * This is utilized by resize (shrink only), profile converting, compacting
  37  * space, or balance routine to spread chunks over devices.
  38  *
  39  *              Before          |               After
  40  * ------------------------------------------------------------------
  41  *  BG A: 10 data extents       | BG A: deleted
  42  *  BG B:  2 data extents       | BG B: 10 data extents (2 old + 8 relocated)
  43  *  BG C:  1 extents            | BG C:  3 data extents (1 old + 2 relocated)
  44  *
  45  * [How does relocation work]
  46  *
  47  * 1.   Mark the target block group read-only
  48  *      New extents won't be allocated from the target block group.
  49  *
  50  * 2.1  Record each extent in the target block group
  51  *      To build a proper map of extents to be relocated.
  52  *
  53  * 2.2  Build data reloc tree and reloc trees
  54  *      Data reloc tree will contain an inode, recording all newly relocated
  55  *      data extents.
  56  *      There will be only one data reloc tree for one data block group.
  57  *
  58  *      Reloc tree will be a special snapshot of its source tree, containing
  59  *      relocated tree blocks.
  60  *      Each tree referring to a tree block in target block group will get its
  61  *      reloc tree built.
  62  *
  63  * 2.3  Swap source tree with its corresponding reloc tree
  64  *      Each involved tree only refers to new extents after swap.
  65  *
  66  * 3.   Cleanup reloc trees and data reloc tree.
  67  *      As old extents in the target block group are still referenced by reloc
  68  *      trees, we need to clean them up before really freeing the target block
  69  *      group.
  70  *
  71  * The main complexity is in steps 2.2 and 2.3.
  72  *
  73  * The entry point of relocation is relocate_block_group() function.
  74  */
  75
  76 #define RELOCATION_RESERVED_NODES       256
  77 /*
  78  * map address of tree root to tree
  79  */
  80 struct mapping_node {
  81         struct {
  82                 struct rb_node rb_node;
  83                 u64 bytenr;
  84         }; /* Use rb_simle_node for search/insert */
  85         void *data;
  86 };
  87
  88 struct mapping_tree {
  89         struct rb_root rb_root;
  90         spinlock_t lock;
  91 };
  92
  93 /*
  94  * present a tree block to process
  95  */
  96 struct tree_block {
  97         struct {
  98                 struct rb_node rb_node;
  99                 u64 bytenr;
 100         }; /* Use rb_simple_node for search/insert */
 101         struct btrfs_key key;
 102         unsigned int level:8;
 103         unsigned int key_ready:1;
 104 };
 105
 106 #define MAX_EXTENTS 128
 107
 108 struct file_extent_cluster {
 109         u64 start;
 110         u64 end;
 111         u64 boundary[MAX_EXTENTS];
 112         unsigned int nr;
 113 };
 114
 115 struct reloc_control {
 116         /* block group to relocate */
 117         struct btrfs_block_group *block_group;
 118         /* extent tree */
 119         struct btrfs_root *extent_root;
 120         /* inode for moving data */
 121         struct inode *data_inode;
 122
 123         struct btrfs_block_rsv *block_rsv;
 124
 125         struct btrfs_backref_cache backref_cache;
 126
 127         struct file_extent_cluster cluster;
 128         /* tree blocks have been processed */
 129         struct extent_io_tree processed_blocks;
 130         /* map start of tree root to corresponding reloc tree */
 131         struct mapping_tree reloc_root_tree;
 132         /* list of reloc trees */
 133         struct list_head reloc_roots;
 134         /* list of subvolume trees that get relocated */
 135         struct list_head dirty_subvol_roots;
 136         /* size of metadata reservation for merging reloc trees */
 137         u64 merging_rsv_size;
 138         /* size of relocated tree nodes */
 139         u64 nodes_relocated;
 140         /* reserved size for block group relocation*/
 141         u64 reserved_bytes;
 142
 143         u64 search_start;
 144         u64 extents_found;
 145
 146         unsigned int stage:8;
 147         unsigned int create_reloc_tree:1;
 148         unsigned int merge_reloc_tree:1;
 149         unsigned int found_file_extent:1;
 150 };
 151
 152 /* stages of data relocation */
 153 #define MOVE_DATA_EXTENTS       0
 154 #define UPDATE_DATA_PTRS        1
 155
 156 static void mark_block_processed(struct reloc_control *rc,
 157                                  struct btrfs_backref_node *node)
 158 {
 159         u32 blocksize;
 160
 161         if (node->level == 0 ||
 162             in_range(node->bytenr, rc->block_group->start,
 163                      rc->block_group->length)) {
 164                 blocksize = rc->extent_root->fs_info->nodesize;
 165                 set_extent_bits(&rc->processed_blocks, node->bytenr,
 166                                 node->bytenr + blocksize - 1, EXTENT_DIRTY);
 167         }
 168         node->processed = 1;
 169 }
 170
 171
 172 static void mapping_tree_init(struct mapping_tree *tree)
 173 {
 174         tree->rb_root = RB_ROOT;
 175         spin_lock_init(&tree->lock);
 176 }
 177
 178 /*
 179  * walk up backref nodes until reach node presents tree root
 180  */
 181 static struct btrfs_backref_node *walk_up_backref(
 182                 struct btrfs_backref_node *node,
 183                 struct btrfs_backref_edge *edges[], int *index)
 184 {
 185         struct btrfs_backref_edge *edge;
 186         int idx = *index;
 187
 188         while (!list_empty(&node->upper)) {
 189                 edge = list_entry(node->upper.next,
 190                                   struct btrfs_backref_edge, list[LOWER]);
 191                 edges[idx++] = edge;
 192                 node = edge->node[UPPER];
 193         }
 194         BUG_ON(node->detached);
 195         *index = idx;
 196         return node;
 197 }
 198
 199 /*
 200  * walk down backref nodes to find start of next reference path
 201  */
 202 static struct btrfs_backref_node *walk_down_backref(
 203                 struct btrfs_backref_edge *edges[], int *index)
 204 {
 205         struct btrfs_backref_edge *edge;
 206         struct btrfs_backref_node *lower;
 207         int idx = *index;
 208
 209         while (idx > 0) {
 210                 edge = edges[idx - 1];
 211                 lower = edge->node[LOWER];
 212                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 213                         idx--;
 214                         continue;
 215                 }
 216                 edge = list_entry(edge->list[LOWER].next,
 217                                   struct btrfs_backref_edge, list[LOWER]);
 218                 edges[idx - 1] = edge;
 219                 *index = idx;
 220                 return edge->node[UPPER];
 221         }
 222         *index = 0;
 223         return NULL;
 224 }
 225
 226 static void update_backref_node(struct btrfs_backref_cache *cache,
 227                                 struct btrfs_backref_node *node, u64 bytenr)
 228 {
 229         struct rb_node *rb_node;
 230         rb_erase(&node->rb_node, &cache->rb_root);
 231         node->bytenr = bytenr;
 232         rb_node = rb_simple_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 233         if (rb_node)
 234                 btrfs_backref_panic(cache->fs_info, bytenr, -EEXIST);
 235 }
 236
 237 /*
 238  * update backref cache after a transaction commit
 239  */
 240 static int update_backref_cache(struct btrfs_trans_handle *trans,
 241                                 struct btrfs_backref_cache *cache)
 242 {
 243         struct btrfs_backref_node *node;
 244         int level = 0;
 245
 246         if (cache->last_trans == 0) {
 247                 cache->last_trans = trans->transid;
 248                 return 0;
 249         }
 250
 251         if (cache->last_trans == trans->transid)
 252                 return 0;
 253
 254         /*
 255          * detached nodes are used to avoid unnecessary backref
 256          * lookup. transaction commit changes the extent tree.
 257          * so the detached nodes are no longer useful.
 258          */
 259         while (!list_empty(&cache->detached)) {
 260                 node = list_entry(cache->detached.next,
 261                                   struct btrfs_backref_node, list);
 262                 btrfs_backref_cleanup_node(cache, node);
 263         }
 264
 265         while (!list_empty(&cache->changed)) {
 266                 node = list_entry(cache->changed.next,
 267                                   struct btrfs_backref_node, list);
 268                 list_del_init(&node->list);
 269                 BUG_ON(node->pending);
 270                 update_backref_node(cache, node, node->new_bytenr);
 271         }
 272
 273         /*
 274          * some nodes can be left in the pending list if there were
 275          * errors during processing the pending nodes.
 276          */
 277         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 278                 list_for_each_entry(node, &cache->pending[level], list) {
 279                         BUG_ON(!node->pending);
 280                         if (node->bytenr == node->new_bytenr)
 281                                 continue;
 282                         update_backref_node(cache, node, node->new_bytenr);
 283                 }
 284         }
 285
 286         cache->last_trans = 0;
 287         return 1;
 288 }
 289
 290 static bool reloc_root_is_dead(struct btrfs_root *root)
 291 {
 292         /*
 293          * Pair with set_bit/clear_bit in clean_dirty_subvols and
 294          * btrfs_update_reloc_root. We need to see the updated bit before
 295          * trying to access reloc_root
 296          */
 297         smp_rmb();
 298         if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
 299                 return true;
 300         return false;
 301 }
 302
 303 /*
 304  * Check if this subvolume tree has valid reloc tree.
 305  *
 306  * Reloc tree after swap is considered dead, thus not considered as valid.
 307  * This is enough for most callers, as they don't distinguish dead reloc root
 308  * from no reloc root.  But btrfs_should_ignore_reloc_root() below is a
 309  * special case.
 310  */
 311 static bool have_reloc_root(struct btrfs_root *root)
 312 {
 313         if (reloc_root_is_dead(root))
 314                 return false;
 315         if (!root->reloc_root)
 316                 return false;
 317         return true;
 318 }
 319
 320 int btrfs_should_ignore_reloc_root(struct btrfs_root *root)
 321 {
 322         struct btrfs_root *reloc_root;
 323
 324         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
 325                 return 0;
 326
 327         /* This root has been merged with its reloc tree, we can ignore it */
 328         if (reloc_root_is_dead(root))
 329                 return 1;
 330
 331         reloc_root = root->reloc_root;
 332         if (!reloc_root)
 333                 return 0;
 334
 335         if (btrfs_header_generation(reloc_root->commit_root) ==
 336             root->fs_info->running_transaction->transid)
 337                 return 0;
 338         /*
 339          * if there is reloc tree and it was created in previous
 340          * transaction backref lookup can find the reloc tree,
 341          * so backref node for the fs tree root is useless for
 342          * relocation.
 343          */
 344         return 1;
 345 }
 346
 347 /*
 348  * find reloc tree by address of tree root
 349  */
 350 struct btrfs_root *find_reloc_root(struct btrfs_fs_info *fs_info, u64 bytenr)
 351 {
 352         struct reloc_control *rc = fs_info->reloc_ctl;
 353         struct rb_node *rb_node;
 354         struct mapping_node *node;
 355         struct btrfs_root *root = NULL;
 356
 357         ASSERT(rc);
 358         spin_lock(&rc->reloc_root_tree.lock);
 359         rb_node = rb_simple_search(&rc->reloc_root_tree.rb_root, bytenr);
 360         if (rb_node) {
 361                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 362                 root = (struct btrfs_root *)node->data;
 363         }
 364         spin_unlock(&rc->reloc_root_tree.lock);
 365         return btrfs_grab_root(root);
 366 }
 367
 368 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 369                                         u64 root_objectid)
 370 {
 371         struct btrfs_key key;
 372
 373         key.objectid = root_objectid;
 374         key.type = BTRFS_ROOT_ITEM_KEY;
 375         key.offset = (u64)-1;
 376
 377         return btrfs_get_fs_root(fs_info, &key, false);
 378 }
 379
 380 /*
 381  * For useless nodes, do two major clean ups:
 382  *
 383  * - Cleanup the children edges and nodes
 384  *   If child node is also orphan (no parent) during cleanup, then the child
 385  *   node will also be cleaned up.
 386  *
 387  * - Freeing up leaves (level 0), keeps nodes detached
 388  *   For nodes, the node is still cached as "detached"
 389  *
 390  * Return false if @node is not in the @useless_nodes list.
 391  * Return true if @node is in the @useless_nodes list.
 392  */
 393 static bool handle_useless_nodes(struct reloc_control *rc,
 394                                  struct btrfs_backref_node *node)
 395 {
 396         struct btrfs_backref_cache *cache = &rc->backref_cache;
 397         struct list_head *useless_node = &cache->useless_node;
 398         bool ret = false;
 399
 400         while (!list_empty(useless_node)) {
 401                 struct btrfs_backref_node *cur;
 402
 403                 cur = list_first_entry(useless_node, struct btrfs_backref_node,
 404                                  list);
 405                 list_del_init(&cur->list);
 406
 407                 /* Only tree root nodes can be added to @useless_nodes */
 408                 ASSERT(list_empty(&cur->upper));
 409
 410                 if (cur == node)
 411                         ret = true;
 412
 413                 /* The node is the lowest node */
 414                 if (cur->lowest) {
 415                         list_del_init(&cur->lower);
 416                         cur->lowest = 0;
 417                 }
 418
 419                 /* Cleanup the lower edges */
 420                 while (!list_empty(&cur->lower)) {
 421                         struct btrfs_backref_edge *edge;
 422                         struct btrfs_backref_node *lower;
 423
 424                         edge = list_entry(cur->lower.next,
 425                                         struct btrfs_backref_edge, list[UPPER]);
 426                         list_del(&edge->list[UPPER]);
 427                         list_del(&edge->list[LOWER]);
 428                         lower = edge->node[LOWER];
 429                         btrfs_backref_free_edge(cache, edge);
 430
 431                         /* Child node is also orphan, queue for cleanup */
 432                         if (list_empty(&lower->upper))
 433                                 list_add(&lower->list, useless_node);
 434                 }
 435                 /* Mark this block processed for relocation */
 436                 mark_block_processed(rc, cur);
 437
 438                 /*
 439                  * Backref nodes for tree leaves are deleted from the cache.
 440                  * Backref nodes for upper level tree blocks are left in the
 441                  * cache to avoid unnecessary backref lookup.
 442                  */
 443                 if (cur->level > 0) {
 444                         list_add(&cur->list, &cache->detached);
 445                         cur->detached = 1;
 446                 } else {
 447                         rb_erase(&cur->rb_node, &cache->rb_root);
 448                         btrfs_backref_free_node(cache, cur);
 449                 }
 450         }
 451         return ret;
 452 }
 453
 454 /*
 455  * Build backref tree for a given tree block. Root of the backref tree
 456  * corresponds the tree block, leaves of the backref tree correspond roots of
 457  * b-trees that reference the tree block.
 458  *
 459  * The basic idea of this function is check backrefs of a given block to find
 460  * upper level blocks that reference the block, and then check backrefs of
 461  * these upper level blocks recursively. The recursion stops when tree root is
 462  * reached or backrefs for the block is cached.
 463  *
 464  * NOTE: if we find that backrefs for a block are cached, we know backrefs for
 465  * all upper level blocks that directly/indirectly reference the block are also
 466  * cached.
 467  */
 468 static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 469                         struct reloc_control *rc, struct btrfs_key *node_key,
 470                         int level, u64 bytenr)
 471 {
 472         struct btrfs_backref_iter *iter;
 473         struct btrfs_backref_cache *cache = &rc->backref_cache;
 474         /* For searching parent of TREE_BLOCK_REF */
 475         struct btrfs_path *path;
 476         struct btrfs_backref_node *cur;
 477         struct btrfs_backref_node *node = NULL;
 478         struct btrfs_backref_edge *edge;
 479         int ret;
 480         int err = 0;
 481
 482         iter = btrfs_backref_iter_alloc(rc->extent_root->fs_info, GFP_NOFS);
 483         if (!iter)
 484                 return ERR_PTR(-ENOMEM);
 485         path = btrfs_alloc_path();
 486         if (!path) {
 487                 err = -ENOMEM;
 488                 goto out;
 489         }
 490
 491         node = btrfs_backref_alloc_node(cache, bytenr, level);
 492         if (!node) {
 493                 err = -ENOMEM;
 494                 goto out;
 495         }
 496
 497         node->lowest = 1;
 498         cur = node;
 499
 500         /* Breadth-first search to build backref cache */
 501         do {
 502                 ret = btrfs_backref_add_tree_node(cache, path, iter, node_key,
 503                                                   cur);
 504                 if (ret < 0) {
 505                         err = ret;
 506                         goto out;
 507                 }
 508                 edge = list_first_entry_or_null(&cache->pending_edge,
 509                                 struct btrfs_backref_edge, list[UPPER]);
 510                 /*
 511                  * The pending list isn't empty, take the first block to
 512                  * process
 513                  */
 514                 if (edge) {
 515                         list_del_init(&edge->list[UPPER]);
 516                         cur = edge->node[UPPER];
 517                 }
 518         } while (edge);
 519
 520         /* Finish the upper linkage of newly added edges/nodes */
 521         ret = btrfs_backref_finish_upper_links(cache, node);
 522         if (ret < 0) {
 523                 err = ret;
 524                 goto out;
 525         }
 526
 527         if (handle_useless_nodes(rc, node))
 528                 node = NULL;
 529 out:
 530         btrfs_backref_iter_free(iter);
 531         btrfs_free_path(path);
 532         if (err) {
 533                 btrfs_backref_error_cleanup(cache, node);
 534                 return ERR_PTR(err);
 535         }
 536         ASSERT(!node || !node->detached);
 537         ASSERT(list_empty(&cache->useless_node) &&
 538                list_empty(&cache->pending_edge));
 539         return node;
 540 }
 541
 542 /*
 543  * helper to add backref node for the newly created snapshot.
 544  * the backref node is created by cloning backref node that
 545  * corresponds to root of source tree
 546  */
 547 static int clone_backref_node(struct btrfs_trans_handle *trans,
 548                               struct reloc_control *rc,
 549                               struct btrfs_root *src,
 550                               struct btrfs_root *dest)
 551 {
 552         struct btrfs_root *reloc_root = src->reloc_root;
 553         struct btrfs_backref_cache *cache = &rc->backref_cache;
 554         struct btrfs_backref_node *node = NULL;
 555         struct btrfs_backref_node *new_node;
 556         struct btrfs_backref_edge *edge;
 557         struct btrfs_backref_edge *new_edge;
 558         struct rb_node *rb_node;
 559
 560         if (cache->last_trans > 0)
 561                 update_backref_cache(trans, cache);
 562
 563         rb_node = rb_simple_search(&cache->rb_root, src->commit_root->start);
 564         if (rb_node) {
 565                 node = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
 566                 if (node->detached)
 567                         node = NULL;
 568                 else
 569                         BUG_ON(node->new_bytenr != reloc_root->node->start);
 570         }
 571
 572         if (!node) {
 573                 rb_node = rb_simple_search(&cache->rb_root,
 574                                            reloc_root->commit_root->start);
 575                 if (rb_node) {
 576                         node = rb_entry(rb_node, struct btrfs_backref_node,
 577                                         rb_node);
 578                         BUG_ON(node->detached);
 579                 }
 580         }
 581
 582         if (!node)
 583                 return 0;
 584
 585         new_node = btrfs_backref_alloc_node(cache, dest->node->start,
 586                                             node->level);
 587         if (!new_node)
 588                 return -ENOMEM;
 589
 590         new_node->lowest = node->lowest;
 591         new_node->checked = 1;
 592         new_node->root = btrfs_grab_root(dest);
 593         ASSERT(new_node->root);
 594
 595         if (!node->lowest) {
 596                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
 597                         new_edge = btrfs_backref_alloc_edge(cache);
 598                         if (!new_edge)
 599                                 goto fail;
 600
 601                         btrfs_backref_link_edge(new_edge, edge->node[LOWER],
 602                                                 new_node, LINK_UPPER);
 603                 }
 604         } else {
 605                 list_add_tail(&new_node->lower, &cache->leaves);
 606         }
 607
 608         rb_node = rb_simple_insert(&cache->rb_root, new_node->bytenr,
 609                                    &new_node->rb_node);
 610         if (rb_node)
 611                 btrfs_backref_panic(trans->fs_info, new_node->bytenr, -EEXIST);
 612
 613         if (!new_node->lowest) {
 614                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
 615                         list_add_tail(&new_edge->list[LOWER],
 616                                       &new_edge->node[LOWER]->upper);
 617                 }
 618         }
 619         return 0;
 620 fail:
 621         while (!list_empty(&new_node->lower)) {
 622                 new_edge = list_entry(new_node->lower.next,
 623                                       struct btrfs_backref_edge, list[UPPER]);
 624                 list_del(&new_edge->list[UPPER]);
 625                 btrfs_backref_free_edge(cache, new_edge);
 626         }
 627         btrfs_backref_free_node(cache, new_node);
 628         return -ENOMEM;
 629 }
 630
 631 /*
 632  * helper to add 'address of tree root -> reloc tree' mapping
 633  */
 634 static int __must_check __add_reloc_root(struct btrfs_root *root)
 635 {
 636         struct btrfs_fs_info *fs_info = root->fs_info;
 637         struct rb_node *rb_node;
 638         struct mapping_node *node;
 639         struct reloc_control *rc = fs_info->reloc_ctl;
 640
 641         node = kmalloc(sizeof(*node), GFP_NOFS);
 642         if (!node)
 643                 return -ENOMEM;
 644
 645         node->bytenr = root->commit_root->start;
 646         node->data = root;
 647
 648         spin_lock(&rc->reloc_root_tree.lock);
 649         rb_node = rb_simple_insert(&rc->reloc_root_tree.rb_root,
 650                                    node->bytenr, &node->rb_node);
 651         spin_unlock(&rc->reloc_root_tree.lock);
 652         if (rb_node) {
 653                 btrfs_panic(fs_info, -EEXIST,
 654                             "Duplicate root found for start=%llu while inserting into relocation tree",
 655                             node->bytenr);
 656         }
 657
 658         list_add_tail(&root->root_list, &rc->reloc_roots);
 659         return 0;
 660 }
 661
 662 /*
 663  * helper to delete the 'address of tree root -> reloc tree'
 664  * mapping
 665  */
 666 static void __del_reloc_root(struct btrfs_root *root)
 667 {
 668         struct btrfs_fs_info *fs_info = root->fs_info;
 669         struct rb_node *rb_node;
 670         struct mapping_node *node = NULL;
 671         struct reloc_control *rc = fs_info->reloc_ctl;
 672         bool put_ref = false;
 673
 674         if (rc && root->node) {
 675                 spin_lock(&rc->reloc_root_tree.lock);
 676                 rb_node = rb_simple_search(&rc->reloc_root_tree.rb_root,
 677                                            root->commit_root->start);
 678                 if (rb_node) {
 679                         node = rb_entry(rb_node, struct mapping_node, rb_node);
 680                         rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
 681                         RB_CLEAR_NODE(&node->rb_node);
 682                 }
 683                 spin_unlock(&rc->reloc_root_tree.lock);
 684                 if (!node)
 685                         return;
 686                 BUG_ON((struct btrfs_root *)node->data != root);
 687         }
 688
 689         /*
 690          * We only put the reloc root here if it's on the list.  There's a lot
 691          * of places where the pattern is to splice the rc->reloc_roots, process
 692          * the reloc roots, and then add the reloc root back onto
 693          * rc->reloc_roots.  If we call __del_reloc_root while it's off of the
 694          * list we don't want the reference being dropped, because the guy
 695          * messing with the list is in charge of the reference.
 696          */
 697         spin_lock(&fs_info->trans_lock);
 698         if (!list_empty(&root->root_list)) {
 699                 put_ref = true;
 700                 list_del_init(&root->root_list);
 701         }
 702         spin_unlock(&fs_info->trans_lock);
 703         if (put_ref)
 704                 btrfs_put_root(root);
 705         kfree(node);
 706 }
 707
 708 /*
 709  * helper to update the 'address of tree root -> reloc tree'
 710  * mapping
 711  */
 712 static int __update_reloc_root(struct btrfs_root *root)
 713 {
 714         struct btrfs_fs_info *fs_info = root->fs_info;
 715         struct rb_node *rb_node;
 716         struct mapping_node *node = NULL;
 717         struct reloc_control *rc = fs_info->reloc_ctl;
 718
 719         spin_lock(&rc->reloc_root_tree.lock);
 720         rb_node = rb_simple_search(&rc->reloc_root_tree.rb_root,
 721                                    root->commit_root->start);
 722         if (rb_node) {
 723                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 724                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
 725         }
 726         spin_unlock(&rc->reloc_root_tree.lock);
 727
 728         if (!node)
 729                 return 0;
 730         BUG_ON((struct btrfs_root *)node->data != root);
 731
 732         spin_lock(&rc->reloc_root_tree.lock);
 733         node->bytenr = root->node->start;
 734         rb_node = rb_simple_insert(&rc->reloc_root_tree.rb_root,
 735                                    node->bytenr, &node->rb_node);
 736         spin_unlock(&rc->reloc_root_tree.lock);
 737         if (rb_node)
 738                 btrfs_backref_panic(fs_info, node->bytenr, -EEXIST);
 739         return 0;
 740 }
 741
 742 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
 743                                         struct btrfs_root *root, u64 objectid)
 744 {
 745         struct btrfs_fs_info *fs_info = root->fs_info;
 746         struct btrfs_root *reloc_root;
 747         struct extent_buffer *eb;
 748         struct btrfs_root_item *root_item;
 749         struct btrfs_key root_key;
 750         int ret;
 751
 752         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
 753         BUG_ON(!root_item);
 754
 755         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
 756         root_key.type = BTRFS_ROOT_ITEM_KEY;
 757         root_key.offset = objectid;
 758
 759         if (root->root_key.objectid == objectid) {
 760                 u64 commit_root_gen;
 761
 762                 /* called by btrfs_init_reloc_root */
 763                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
 764                                       BTRFS_TREE_RELOC_OBJECTID);
 765                 BUG_ON(ret);
 766                 /*
 767                  * Set the last_snapshot field to the generation of the commit
 768                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
 769                  * correctly (returns true) when the relocation root is created
 770                  * either inside the critical section of a transaction commit
 771                  * (through transaction.c:qgroup_account_snapshot()) and when
 772                  * it's created before the transaction commit is started.
 773                  */
 774                 commit_root_gen = btrfs_header_generation(root->commit_root);
 775                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
 776         } else {
 777                 /*
 778                  * called by btrfs_reloc_post_snapshot_hook.
 779                  * the source tree is a reloc tree, all tree blocks
 780                  * modified after it was created have RELOC flag
 781                  * set in their headers. so it's OK to not update
 782                  * the 'last_snapshot'.
 783                  */
 784                 ret = btrfs_copy_root(trans, root, root->node, &eb,
 785                                       BTRFS_TREE_RELOC_OBJECTID);
 786                 BUG_ON(ret);
 787         }
 788
 789         memcpy(root_item, &root->root_item, sizeof(*root_item));
 790         btrfs_set_root_bytenr(root_item, eb->start);
 791         btrfs_set_root_level(root_item, btrfs_header_level(eb));
 792         btrfs_set_root_generation(root_item, trans->transid);
 793
 794         if (root->root_key.objectid == objectid) {
 795                 btrfs_set_root_refs(root_item, 0);
 796                 memset(&root_item->drop_progress, 0,
 797                        sizeof(struct btrfs_disk_key));
 798                 root_item->drop_level = 0;
 799         }
 800
 801         btrfs_tree_unlock(eb);
 802         free_extent_buffer(eb);
 803
 804         ret = btrfs_insert_root(trans, fs_info->tree_root,
 805                                 &root_key, root_item);
 806         BUG_ON(ret);
 807         kfree(root_item);
 808
 809         reloc_root = btrfs_read_tree_root(fs_info->tree_root, &root_key);
 810         BUG_ON(IS_ERR(reloc_root));
 811         set_bit(BTRFS_ROOT_SHAREABLE, &reloc_root->state);
 812         reloc_root->last_trans = trans->transid;
 813         return reloc_root;
 814 }
 815
 816 /*
 817  * create reloc tree for a given fs tree. reloc tree is just a
 818  * snapshot of the fs tree with special root objectid.
 819  *
 820  * The reloc_root comes out of here with two references, one for
 821  * root->reloc_root, and another for being on the rc->reloc_roots list.
 822  */
 823 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
 824                           struct btrfs_root *root)
 825 {
 826         struct btrfs_fs_info *fs_info = root->fs_info;
 827         struct btrfs_root *reloc_root;
 828         struct reloc_control *rc = fs_info->reloc_ctl;
 829         struct btrfs_block_rsv *rsv;
 830         int clear_rsv = 0;
 831         int ret;
 832
 833         if (!rc)
 834                 return 0;
 835
 836         /*
 837          * The subvolume has reloc tree but the swap is finished, no need to
 838          * create/update the dead reloc tree
 839          */
 840         if (reloc_root_is_dead(root))
 841                 return 0;
 842
 843         /*
 844          * This is subtle but important.  We do not do
 845          * record_root_in_transaction for reloc roots, instead we record their
 846          * corresponding fs root, and then here we update the last trans for the
 847          * reloc root.  This means that we have to do this for the entire life
 848          * of the reloc root, regardless of which stage of the relocation we are
 849          * in.
 850          */
 851         if (root->reloc_root) {
 852                 reloc_root = root->reloc_root;
 853                 reloc_root->last_trans = trans->transid;
 854                 return 0;
 855         }
 856
 857         /*
 858          * We are merging reloc roots, we do not need new reloc trees.  Also
 859          * reloc trees never need their own reloc tree.
 860          */
 861         if (!rc->create_reloc_tree ||
 862             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
 863                 return 0;
 864
 865         if (!trans->reloc_reserved) {
 866                 rsv = trans->block_rsv;
 867                 trans->block_rsv = rc->block_rsv;
 868                 clear_rsv = 1;
 869         }
 870         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
 871         if (clear_rsv)
 872                 trans->block_rsv = rsv;
 873
 874         ret = __add_reloc_root(reloc_root);
 875         BUG_ON(ret < 0);
 876         root->reloc_root = btrfs_grab_root(reloc_root);
 877         return 0;
 878 }
 879
 880 /*
 881  * update root item of reloc tree
 882  */
 883 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
 884                             struct btrfs_root *root)
 885 {
 886         struct btrfs_fs_info *fs_info = root->fs_info;
 887         struct btrfs_root *reloc_root;
 888         struct btrfs_root_item *root_item;
 889         int ret;
 890
 891         if (!have_reloc_root(root))
 892                 goto out;
 893
 894         reloc_root = root->reloc_root;
 895         root_item = &reloc_root->root_item;
 896
 897         /*
 898          * We are probably ok here, but __del_reloc_root() will drop its ref of
 899          * the root.  We have the ref for root->reloc_root, but just in case
 900          * hold it while we update the reloc root.
 901          */
 902         btrfs_grab_root(reloc_root);
 903
 904         /* root->reloc_root will stay until current relocation finished */
 905         if (fs_info->reloc_ctl->merge_reloc_tree &&
 906             btrfs_root_refs(root_item) == 0) {
 907                 set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
 908                 /*
 909                  * Mark the tree as dead before we change reloc_root so
 910                  * have_reloc_root will not touch it from now on.
 911                  */
 912                 smp_wmb();
 913                 __del_reloc_root(reloc_root);
 914         }
 915
 916         if (reloc_root->commit_root != reloc_root->node) {
 917                 __update_reloc_root(reloc_root);
 918                 btrfs_set_root_node(root_item, reloc_root->node);
 919                 free_extent_buffer(reloc_root->commit_root);
 920                 reloc_root->commit_root = btrfs_root_node(reloc_root);
 921         }
 922
 923         ret = btrfs_update_root(trans, fs_info->tree_root,
 924                                 &reloc_root->root_key, root_item);
 925         BUG_ON(ret);
 926         btrfs_put_root(reloc_root);
 927 out:
 928         return 0;
 929 }
 930
 931 /*
 932  * helper to find first cached inode with inode number >= objectid
 933  * in a subvolume
 934  */
 935 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
 936 {
 937         struct rb_node *node;
 938         struct rb_node *prev;
 939         struct btrfs_inode *entry;
 940         struct inode *inode;
 941
 942         spin_lock(&root->inode_lock);
 943 again:
 944         node = root->inode_tree.rb_node;
 945         prev = NULL;
 946         while (node) {
 947                 prev = node;
 948                 entry = rb_entry(node, struct btrfs_inode, rb_node);
 949
 950                 if (objectid < btrfs_ino(entry))
 951                         node = node->rb_left;
 952                 else if (objectid > btrfs_ino(entry))
 953                         node = node->rb_right;
 954                 else
 955                         break;
 956         }
 957         if (!node) {
 958                 while (prev) {
 959                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
 960                         if (objectid <= btrfs_ino(entry)) {
 961                                 node = prev;
 962                                 break;
 963                         }
 964                         prev = rb_next(prev);
 965                 }
 966         }
 967         while (node) {
 968                 entry = rb_entry(node, struct btrfs_inode, rb_node);
 969                 inode = igrab(&entry->vfs_inode);
 970                 if (inode) {
 971                         spin_unlock(&root->inode_lock);
 972                         return inode;
 973                 }
 974
 975                 objectid = btrfs_ino(entry) + 1;
 976                 if (cond_resched_lock(&root->inode_lock))
 977                         goto again;
 978
 979                 node = rb_next(node);
 980         }
 981         spin_unlock(&root->inode_lock);
 982         return NULL;
 983 }
 984
 985 /*
 986  * get new location of data
 987  */
 988 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
 989                             u64 bytenr, u64 num_bytes)
 990 {
 991         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
 992         struct btrfs_path *path;
 993         struct btrfs_file_extent_item *fi;
 994         struct extent_buffer *leaf;
 995         int ret;
 996
 997         path = btrfs_alloc_path();
 998         if (!path)
 999                 return -ENOMEM;
1000
1001         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1002         ret = btrfs_lookup_file_extent(NULL, root, path,
1003                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1004         if (ret < 0)
1005                 goto out;
1006         if (ret > 0) {
1007                 ret = -ENOENT;
1008                 goto out;
1009         }
1010
1011         leaf = path->nodes[0];
1012         fi = btrfs_item_ptr(leaf, path->slots[0],
1013                             struct btrfs_file_extent_item);
1014
1015         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1016                btrfs_file_extent_compression(leaf, fi) ||
1017                btrfs_file_extent_encryption(leaf, fi) ||
1018                btrfs_file_extent_other_encoding(leaf, fi));
1019
1020         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1021                 ret = -EINVAL;
1022                 goto out;
1023         }
1024
1025         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1026         ret = 0;
1027 out:
1028         btrfs_free_path(path);
1029         return ret;
1030 }
1031
1032 /*
1033  * update file extent items in the tree leaf to point to
1034  * the new locations.
1035  */
1036 static noinline_for_stack
1037 int replace_file_extents(struct btrfs_trans_handle *trans,
1038                          struct reloc_control *rc,
1039                          struct btrfs_root *root,
1040                          struct extent_buffer *leaf)
1041 {
1042         struct btrfs_fs_info *fs_info = root->fs_info;
1043         struct btrfs_key key;
1044         struct btrfs_file_extent_item *fi;
1045         struct inode *inode = NULL;
1046         u64 parent;
1047         u64 bytenr;
1048         u64 new_bytenr = 0;
1049         u64 num_bytes;
1050         u64 end;
1051         u32 nritems;
1052         u32 i;
1053         int ret = 0;
1054         int first = 1;
1055         int dirty = 0;
1056
1057         if (rc->stage != UPDATE_DATA_PTRS)
1058                 return 0;
1059
1060         /* reloc trees always use full backref */
1061         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1062                 parent = leaf->start;
1063         else
1064                 parent = 0;
1065
1066         nritems = btrfs_header_nritems(leaf);
1067         for (i = 0; i < nritems; i++) {
1068                 struct btrfs_ref ref = { 0 };
1069
1070                 cond_resched();
1071                 btrfs_item_key_to_cpu(leaf, &key, i);
1072                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1073                         continue;
1074                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1075                 if (btrfs_file_extent_type(leaf, fi) ==
1076                     BTRFS_FILE_EXTENT_INLINE)
1077                         continue;
1078                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1079                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1080                 if (bytenr == 0)
1081                         continue;
1082                 if (!in_range(bytenr, rc->block_group->start,
1083                               rc->block_group->length))
1084                         continue;
1085
1086                 /*
1087                  * if we are modifying block in fs tree, wait for readpage
1088                  * to complete and drop the extent cache
1089                  */
1090                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1091                         if (first) {
1092                                 inode = find_next_inode(root, key.objectid);
1093                                 first = 0;
1094                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1095                                 btrfs_add_delayed_iput(inode);
1096                                 inode = find_next_inode(root, key.objectid);
1097                         }
1098                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1099                                 end = key.offset +
1100                                       btrfs_file_extent_num_bytes(leaf, fi);
1101                                 WARN_ON(!IS_ALIGNED(key.offset,
1102                                                     fs_info->sectorsize));
1103                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1104                                 end--;
1105                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1106                                                       key.offset, end);
1107                                 if (!ret)
1108                                         continue;
1109
1110                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1111                                                 key.offset,     end, 1);
1112                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1113                                               key.offset, end);
1114                         }
1115                 }
1116
1117                 ret = get_new_location(rc->data_inode, &new_bytenr,
1118                                        bytenr, num_bytes);
1119                 if (ret) {
1120                         /*
1121                          * Don't have to abort since we've not changed anything
1122                          * in the file extent yet.
1123                          */
1124                         break;
1125                 }
1126
1127                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1128                 dirty = 1;
1129
1130                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1131                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1132                                        num_bytes, parent);
1133                 ref.real_root = root->root_key.objectid;
1134                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1135                                     key.objectid, key.offset);
1136                 ret = btrfs_inc_extent_ref(trans, &ref);
1137                 if (ret) {
1138                         btrfs_abort_transaction(trans, ret);
1139                         break;
1140                 }
1141
1142                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
1143                                        num_bytes, parent);
1144                 ref.real_root = root->root_key.objectid;
1145                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1146                                     key.objectid, key.offset);
1147                 ret = btrfs_free_extent(trans, &ref);
1148                 if (ret) {
1149                         btrfs_abort_transaction(trans, ret);
1150                         break;
1151                 }
1152         }
1153         if (dirty)
1154                 btrfs_mark_buffer_dirty(leaf);
1155         if (inode)
1156                 btrfs_add_delayed_iput(inode);
1157         return ret;
1158 }
1159
1160 static noinline_for_stack
1161 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1162                      struct btrfs_path *path, int level)
1163 {
1164         struct btrfs_disk_key key1;
1165         struct btrfs_disk_key key2;
1166         btrfs_node_key(eb, &key1, slot);
1167         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1168         return memcmp(&key1, &key2, sizeof(key1));
1169 }
1170
1171 /*
1172  * try to replace tree blocks in fs tree with the new blocks
1173  * in reloc tree. tree blocks haven't been modified since the
1174  * reloc tree was create can be replaced.
1175  *
1176  * if a block was replaced, level of the block + 1 is returned.
1177  * if no block got replaced, 0 is returned. if there are other
1178  * errors, a negative error number is returned.
1179  */
1180 static noinline_for_stack
1181 int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
1182                  struct btrfs_root *dest, struct btrfs_root *src,
1183                  struct btrfs_path *path, struct btrfs_key *next_key,
1184                  int lowest_level, int max_level)
1185 {
1186         struct btrfs_fs_info *fs_info = dest->fs_info;
1187         struct extent_buffer *eb;
1188         struct extent_buffer *parent;
1189         struct btrfs_ref ref = { 0 };
1190         struct btrfs_key key;
1191         u64 old_bytenr;
1192         u64 new_bytenr;
1193         u64 old_ptr_gen;
1194         u64 new_ptr_gen;
1195         u64 last_snapshot;
1196         u32 blocksize;
1197         int cow = 0;
1198         int level;
1199         int ret;
1200         int slot;
1201
1202         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1203         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1204
1205         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1206 again:
1207         slot = path->slots[lowest_level];
1208         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1209
1210         eb = btrfs_lock_root_node(dest);
1211         btrfs_set_lock_blocking_write(eb);
1212         level = btrfs_header_level(eb);
1213
1214         if (level < lowest_level) {
1215                 btrfs_tree_unlock(eb);
1216                 free_extent_buffer(eb);
1217                 return 0;
1218         }
1219
1220         if (cow) {
1221                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1222                 BUG_ON(ret);
1223         }
1224         btrfs_set_lock_blocking_write(eb);
1225
1226         if (next_key) {
1227                 next_key->objectid = (u64)-1;
1228                 next_key->type = (u8)-1;
1229                 next_key->offset = (u64)-1;
1230         }
1231
1232         parent = eb;
1233         while (1) {
1234                 struct btrfs_key first_key;
1235
1236                 level = btrfs_header_level(parent);
1237                 BUG_ON(level < lowest_level);
1238
1239                 ret = btrfs_bin_search(parent, &key, &slot);
1240                 if (ret < 0)
1241                         break;
1242                 if (ret && slot > 0)
1243                         slot--;
1244
1245                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1246                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1247
1248                 old_bytenr = btrfs_node_blockptr(parent, slot);
1249                 blocksize = fs_info->nodesize;
1250                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1251                 btrfs_node_key_to_cpu(parent, &first_key, slot);
1252
1253                 if (level <= max_level) {
1254                         eb = path->nodes[level];
1255                         new_bytenr = btrfs_node_blockptr(eb,
1256                                                         path->slots[level]);
1257                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1258                                                         path->slots[level]);
1259                 } else {
1260                         new_bytenr = 0;
1261                         new_ptr_gen = 0;
1262                 }
1263
1264                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1265                         ret = level;
1266                         break;
1267                 }
1268
1269                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1270                     memcmp_node_keys(parent, slot, path, level)) {
1271                         if (level <= lowest_level) {
1272                                 ret = 0;
1273                                 break;
1274                         }
1275
1276                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen,
1277                                              level - 1, &first_key);
1278                         if (IS_ERR(eb)) {
1279                                 ret = PTR_ERR(eb);
1280                                 break;
1281                         } else if (!extent_buffer_uptodate(eb)) {
1282                                 ret = -EIO;
1283                                 free_extent_buffer(eb);
1284                                 break;
1285                         }
1286                         btrfs_tree_lock(eb);
1287                         if (cow) {
1288                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1289                                                       slot, &eb);
1290                                 BUG_ON(ret);
1291                         }
1292                         btrfs_set_lock_blocking_write(eb);
1293
1294                         btrfs_tree_unlock(parent);
1295                         free_extent_buffer(parent);
1296
1297                         parent = eb;
1298                         continue;
1299                 }
1300
1301                 if (!cow) {
1302                         btrfs_tree_unlock(parent);
1303                         free_extent_buffer(parent);
1304                         cow = 1;
1305                         goto again;
1306                 }
1307
1308                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1309                                       path->slots[level]);
1310                 btrfs_release_path(path);
1311
1312                 path->lowest_level = level;
1313                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1314                 path->lowest_level = 0;
1315                 BUG_ON(ret);
1316
1317                 /*
1318                  * Info qgroup to trace both subtrees.
1319                  *
1320                  * We must trace both trees.
1321                  * 1) Tree reloc subtree
1322                  *    If not traced, we will leak data numbers
1323                  * 2) Fs subtree
1324                  *    If not traced, we will double count old data
1325                  *
1326                  * We don't scan the subtree right now, but only record
1327                  * the swapped tree blocks.
1328                  * The real subtree rescan is delayed until we have new
1329                  * CoW on the subtree root node before transaction commit.
1330                  */
1331                 ret = btrfs_qgroup_add_swapped_blocks(trans, dest,
1332                                 rc->block_group, parent, slot,
1333                                 path->nodes[level], path->slots[level],
1334                                 last_snapshot);
1335                 if (ret < 0)
1336                         break;
1337                 /*
1338                  * swap blocks in fs tree and reloc tree.
1339                  */
1340                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1341                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1342                 btrfs_mark_buffer_dirty(parent);
1343
1344                 btrfs_set_node_blockptr(path->nodes[level],
1345                                         path->slots[level], old_bytenr);
1346                 btrfs_set_node_ptr_generation(path->nodes[level],
1347                                               path->slots[level], old_ptr_gen);
1348                 btrfs_mark_buffer_dirty(path->nodes[level]);
1349
1350                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, old_bytenr,
1351                                        blocksize, path->nodes[level]->start);
1352                 ref.skip_qgroup = true;
1353                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1354                 ret = btrfs_inc_extent_ref(trans, &ref);
1355                 BUG_ON(ret);
1356                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1357                                        blocksize, 0);
1358                 ref.skip_qgroup = true;
1359                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1360                 ret = btrfs_inc_extent_ref(trans, &ref);
1361                 BUG_ON(ret);
1362
1363                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, new_bytenr,
1364                                        blocksize, path->nodes[level]->start);
1365                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1366                 ref.skip_qgroup = true;
1367                 ret = btrfs_free_extent(trans, &ref);
1368                 BUG_ON(ret);
1369
1370                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, old_bytenr,
1371                                        blocksize, 0);
1372                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1373                 ref.skip_qgroup = true;
1374                 ret = btrfs_free_extent(trans, &ref);
1375                 BUG_ON(ret);
1376
1377                 btrfs_unlock_up_safe(path, 0);
1378
1379                 ret = level;
1380                 break;
1381         }
1382         btrfs_tree_unlock(parent);
1383         free_extent_buffer(parent);
1384         return ret;
1385 }
1386
1387 /*
1388  * helper to find next relocated block in reloc tree
1389  */
1390 static noinline_for_stack
1391 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1392                        int *level)
1393 {
1394         struct extent_buffer *eb;
1395         int i;
1396         u64 last_snapshot;
1397         u32 nritems;
1398
1399         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1400
1401         for (i = 0; i < *level; i++) {
1402                 free_extent_buffer(path->nodes[i]);
1403                 path->nodes[i] = NULL;
1404         }
1405
1406         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
1407                 eb = path->nodes[i];
1408                 nritems = btrfs_header_nritems(eb);
1409                 while (path->slots[i] + 1 < nritems) {
1410                         path->slots[i]++;
1411                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
1412                             last_snapshot)
1413                                 continue;
1414
1415                         *level = i;
1416                         return 0;
1417                 }
1418                 free_extent_buffer(path->nodes[i]);
1419                 path->nodes[i] = NULL;
1420         }
1421         return 1;
1422 }
1423
1424 /*
1425  * walk down reloc tree to find relocated block of lowest level
1426  */
1427 static noinline_for_stack
1428 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1429                          int *level)
1430 {
1431         struct btrfs_fs_info *fs_info = root->fs_info;
1432         struct extent_buffer *eb = NULL;
1433         int i;
1434         u64 bytenr;
1435         u64 ptr_gen = 0;
1436         u64 last_snapshot;
1437         u32 nritems;
1438
1439         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1440
1441         for (i = *level; i > 0; i--) {
1442                 struct btrfs_key first_key;
1443
1444                 eb = path->nodes[i];
1445                 nritems = btrfs_header_nritems(eb);
1446                 while (path->slots[i] < nritems) {
1447                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
1448                         if (ptr_gen > last_snapshot)
1449                                 break;
1450                         path->slots[i]++;
1451                 }
1452                 if (path->slots[i] >= nritems) {
1453                         if (i == *level)
1454                                 break;
1455                         *level = i + 1;
1456                         return 0;
1457                 }
1458                 if (i == 1) {
1459                         *level = i;
1460                         return 0;
1461                 }
1462
1463                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
1464                 btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
1465                 eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
1466                                      &first_key);
1467                 if (IS_ERR(eb)) {
1468                         return PTR_ERR(eb);
1469                 } else if (!extent_buffer_uptodate(eb)) {
1470                         free_extent_buffer(eb);
1471                         return -EIO;
1472                 }
1473                 BUG_ON(btrfs_header_level(eb) != i - 1);
1474                 path->nodes[i - 1] = eb;
1475                 path->slots[i - 1] = 0;
1476         }
1477         return 1;
1478 }
1479
1480 /*
1481  * invalidate extent cache for file extents whose key in range of
1482  * [min_key, max_key)
1483  */
1484 static int invalidate_extent_cache(struct btrfs_root *root,
1485                                    struct btrfs_key *min_key,
1486                                    struct btrfs_key *max_key)
1487 {
1488         struct btrfs_fs_info *fs_info = root->fs_info;
1489         struct inode *inode = NULL;
1490         u64 objectid;
1491         u64 start, end;
1492         u64 ino;
1493
1494         objectid = min_key->objectid;
1495         while (1) {
1496                 cond_resched();
1497                 iput(inode);
1498
1499                 if (objectid > max_key->objectid)
1500                         break;
1501
1502                 inode = find_next_inode(root, objectid);
1503                 if (!inode)
1504                         break;
1505                 ino = btrfs_ino(BTRFS_I(inode));
1506
1507                 if (ino > max_key->objectid) {
1508                         iput(inode);
1509                         break;
1510                 }
1511
1512                 objectid = ino + 1;
1513                 if (!S_ISREG(inode->i_mode))
1514                         continue;
1515
1516                 if (unlikely(min_key->objectid == ino)) {
1517                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
1518                                 continue;
1519                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
1520                                 start = 0;
1521                         else {
1522                                 start = min_key->offset;
1523                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
1524                         }
1525                 } else {
1526                         start = 0;
1527                 }
1528
1529                 if (unlikely(max_key->objectid == ino)) {
1530                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
1531                                 continue;
1532                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
1533                                 end = (u64)-1;
1534                         } else {
1535                                 if (max_key->offset == 0)
1536                                         continue;
1537                                 end = max_key->offset;
1538                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1539                                 end--;
1540                         }
1541                 } else {
1542                         end = (u64)-1;
1543                 }
1544
1545                 /* the lock_extent waits for readpage to complete */
1546                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
1547                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
1548                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
1549         }
1550         return 0;
1551 }
1552
1553 static int find_next_key(struct btrfs_path *path, int level,
1554                          struct btrfs_key *key)
1555
1556 {
1557         while (level < BTRFS_MAX_LEVEL) {
1558                 if (!path->nodes[level])
1559                         break;
1560                 if (path->slots[level] + 1 <
1561                     btrfs_header_nritems(path->nodes[level])) {
1562                         btrfs_node_key_to_cpu(path->nodes[level], key,
1563                                               path->slots[level] + 1);
1564                         return 0;
1565                 }
1566                 level++;
1567         }
1568         return 1;
1569 }
1570
1571 /*
1572  * Insert current subvolume into reloc_control::dirty_subvol_roots
1573  */
1574 static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
1575                                 struct reloc_control *rc,
1576                                 struct btrfs_root *root)
1577 {
1578         struct btrfs_root *reloc_root = root->reloc_root;
1579         struct btrfs_root_item *reloc_root_item;
1580
1581         /* @root must be a subvolume tree root with a valid reloc tree */
1582         ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1583         ASSERT(reloc_root);
1584
1585         reloc_root_item = &reloc_root->root_item;
1586         memset(&reloc_root_item->drop_progress, 0,
1587                 sizeof(reloc_root_item->drop_progress));
1588         reloc_root_item->drop_level = 0;
1589         btrfs_set_root_refs(reloc_root_item, 0);
1590         btrfs_update_reloc_root(trans, root);
1591
1592         if (list_empty(&root->reloc_dirty_list)) {
1593                 btrfs_grab_root(root);
1594                 list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
1595         }
1596 }
1597
1598 static int clean_dirty_subvols(struct reloc_control *rc)
1599 {
1600         struct btrfs_root *root;
1601         struct btrfs_root *next;
1602         int ret = 0;
1603         int ret2;
1604
1605         list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
1606                                  reloc_dirty_list) {
1607                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1608                         /* Merged subvolume, cleanup its reloc root */
1609                         struct btrfs_root *reloc_root = root->reloc_root;
1610
1611                         list_del_init(&root->reloc_dirty_list);
1612                         root->reloc_root = NULL;
1613                         /*
1614                          * Need barrier to ensure clear_bit() only happens after
1615                          * root->reloc_root = NULL. Pairs with have_reloc_root.
1616                          */
1617                         smp_wmb();
1618                         clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
1619                         if (reloc_root) {
1620                                 /*
1621                                  * btrfs_drop_snapshot drops our ref we hold for
1622                                  * ->reloc_root.  If it fails however we must
1623                                  * drop the ref ourselves.
1624                                  */
1625                                 ret2 = btrfs_drop_snapshot(reloc_root, 0, 1);
1626                                 if (ret2 < 0) {
1627                                         btrfs_put_root(reloc_root);
1628                                         if (!ret)
1629                                                 ret = ret2;
1630                                 }
1631                         }
1632                         btrfs_put_root(root);
1633                 } else {
1634                         /* Orphan reloc tree, just clean it up */
1635                         ret2 = btrfs_drop_snapshot(root, 0, 1);
1636                         if (ret2 < 0) {
1637                                 btrfs_put_root(root);
1638                                 if (!ret)
1639                                         ret = ret2;
1640                         }
1641                 }
1642         }
1643         return ret;
1644 }
1645
1646 /*
1647  * merge the relocated tree blocks in reloc tree with corresponding
1648  * fs tree.
1649  */
1650 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
1651                                                struct btrfs_root *root)
1652 {
1653         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
1654         struct btrfs_key key;
1655         struct btrfs_key next_key;
1656         struct btrfs_trans_handle *trans = NULL;
1657         struct btrfs_root *reloc_root;
1658         struct btrfs_root_item *root_item;
1659         struct btrfs_path *path;
1660         struct extent_buffer *leaf;
1661         int level;
1662         int max_level;
1663         int replaced = 0;
1664         int ret;
1665         int err = 0;
1666         u32 min_reserved;
1667
1668         path = btrfs_alloc_path();
1669         if (!path)
1670                 return -ENOMEM;
1671         path->reada = READA_FORWARD;
1672
1673         reloc_root = root->reloc_root;
1674         root_item = &reloc_root->root_item;
1675
1676         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
1677                 level = btrfs_root_level(root_item);
1678                 atomic_inc(&reloc_root->node->refs);
1679                 path->nodes[level] = reloc_root->node;
1680                 path->slots[level] = 0;
1681         } else {
1682                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
1683
1684                 level = root_item->drop_level;
1685                 BUG_ON(level == 0);
1686                 path->lowest_level = level;
1687                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
1688                 path->lowest_level = 0;
1689                 if (ret < 0) {
1690                         btrfs_free_path(path);
1691                         return ret;
1692                 }
1693
1694                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
1695                                       path->slots[level]);
1696                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
1697
1698                 btrfs_unlock_up_safe(path, 0);
1699         }
1700
1701         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
1702         memset(&next_key, 0, sizeof(next_key));
1703
1704         while (1) {
1705                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
1706                                              BTRFS_RESERVE_FLUSH_ALL);
1707                 if (ret) {
1708                         err = ret;
1709                         goto out;
1710                 }
1711                 trans = btrfs_start_transaction(root, 0);
1712                 if (IS_ERR(trans)) {
1713                         err = PTR_ERR(trans);
1714                         trans = NULL;
1715                         goto out;
1716                 }
1717
1718                 /*
1719                  * At this point we no longer have a reloc_control, so we can't
1720                  * depend on btrfs_init_reloc_root to update our last_trans.
1721                  *
1722                  * But that's ok, we started the trans handle on our
1723                  * corresponding fs_root, which means it's been added to the
1724                  * dirty list.  At commit time we'll still call
1725                  * btrfs_update_reloc_root() and update our root item
1726                  * appropriately.
1727                  */
1728                 reloc_root->last_trans = trans->transid;
1729                 trans->block_rsv = rc->block_rsv;
1730
1731                 replaced = 0;
1732                 max_level = level;
1733
1734                 ret = walk_down_reloc_tree(reloc_root, path, &level);
1735                 if (ret < 0) {
1736                         err = ret;
1737                         goto out;
1738                 }
1739                 if (ret > 0)
1740                         break;
1741
1742                 if (!find_next_key(path, level, &key) &&
1743                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
1744                         ret = 0;
1745                 } else {
1746                         ret = replace_path(trans, rc, root, reloc_root, path,
1747                                            &next_key, level, max_level);
1748                 }
1749                 if (ret < 0) {
1750                         err = ret;
1751                         goto out;
1752                 }
1753
1754                 if (ret > 0) {
1755                         level = ret;
1756                         btrfs_node_key_to_cpu(path->nodes[level], &key,
1757                                               path->slots[level]);
1758                         replaced = 1;
1759                 }
1760
1761                 ret = walk_up_reloc_tree(reloc_root, path, &level);
1762                 if (ret > 0)
1763                         break;
1764
1765                 BUG_ON(level == 0);
1766                 /*
1767                  * save the merging progress in the drop_progress.
1768                  * this is OK since root refs == 1 in this case.
1769                  */
1770                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
1771                                path->slots[level]);
1772                 root_item->drop_level = level;
1773
1774                 btrfs_end_transaction_throttle(trans);
1775                 trans = NULL;
1776
1777                 btrfs_btree_balance_dirty(fs_info);
1778
1779                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
1780                         invalidate_extent_cache(root, &key, &next_key);
1781         }
1782
1783         /*
1784          * handle the case only one block in the fs tree need to be
1785          * relocated and the block is tree root.
1786          */
1787         leaf = btrfs_lock_root_node(root);
1788         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
1789         btrfs_tree_unlock(leaf);
1790         free_extent_buffer(leaf);
1791         if (ret < 0)
1792                 err = ret;
1793 out:
1794         btrfs_free_path(path);
1795
1796         if (err == 0)
1797                 insert_dirty_subvol(trans, rc, root);
1798
1799         if (trans)
1800                 btrfs_end_transaction_throttle(trans);
1801
1802         btrfs_btree_balance_dirty(fs_info);
1803
1804         if (replaced && rc->stage == UPDATE_DATA_PTRS)
1805                 invalidate_extent_cache(root, &key, &next_key);
1806
1807         return err;
1808 }
1809
1810 static noinline_for_stack
1811 int prepare_to_merge(struct reloc_control *rc, int err)
1812 {
1813         struct btrfs_root *root = rc->extent_root;
1814         struct btrfs_fs_info *fs_info = root->fs_info;
1815         struct btrfs_root *reloc_root;
1816         struct btrfs_trans_handle *trans;
1817         LIST_HEAD(reloc_roots);
1818         u64 num_bytes = 0;
1819         int ret;
1820
1821         mutex_lock(&fs_info->reloc_mutex);
1822         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
1823         rc->merging_rsv_size += rc->nodes_relocated * 2;
1824         mutex_unlock(&fs_info->reloc_mutex);
1825
1826 again:
1827         if (!err) {
1828                 num_bytes = rc->merging_rsv_size;
1829                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
1830                                           BTRFS_RESERVE_FLUSH_ALL);
1831                 if (ret)
1832                         err = ret;
1833         }
1834
1835         trans = btrfs_join_transaction(rc->extent_root);
1836         if (IS_ERR(trans)) {
1837                 if (!err)
1838                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
1839                                                 num_bytes, NULL);
1840                 return PTR_ERR(trans);
1841         }
1842
1843         if (!err) {
1844                 if (num_bytes != rc->merging_rsv_size) {
1845                         btrfs_end_transaction(trans);
1846                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
1847                                                 num_bytes, NULL);
1848                         goto again;
1849                 }
1850         }
1851
1852         rc->merge_reloc_tree = 1;
1853
1854         while (!list_empty(&rc->reloc_roots)) {
1855                 reloc_root = list_entry(rc->reloc_roots.next,
1856                                         struct btrfs_root, root_list);
1857                 list_del_init(&reloc_root->root_list);
1858
1859                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
1860                 BUG_ON(IS_ERR(root));
1861                 BUG_ON(root->reloc_root != reloc_root);
1862
1863                 /*
1864                  * set reference count to 1, so btrfs_recover_relocation
1865                  * knows it should resumes merging
1866                  */
1867                 if (!err)
1868                         btrfs_set_root_refs(&reloc_root->root_item, 1);
1869                 btrfs_update_reloc_root(trans, root);
1870
1871                 list_add(&reloc_root->root_list, &reloc_roots);
1872                 btrfs_put_root(root);
1873         }
1874
1875         list_splice(&reloc_roots, &rc->reloc_roots);
1876
1877         if (!err)
1878                 btrfs_commit_transaction(trans);
1879         else
1880                 btrfs_end_transaction(trans);
1881         return err;
1882 }
1883
1884 static noinline_for_stack
1885 void free_reloc_roots(struct list_head *list)
1886 {
1887         struct btrfs_root *reloc_root, *tmp;
1888
1889         list_for_each_entry_safe(reloc_root, tmp, list, root_list)
1890                 __del_reloc_root(reloc_root);
1891 }
1892
1893 static noinline_for_stack
1894 void merge_reloc_roots(struct reloc_control *rc)
1895 {
1896         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
1897         struct btrfs_root *root;
1898         struct btrfs_root *reloc_root;
1899         LIST_HEAD(reloc_roots);
1900         int found = 0;
1901         int ret = 0;
1902 again:
1903         root = rc->extent_root;
1904
1905         /*
1906          * this serializes us with btrfs_record_root_in_transaction,
1907          * we have to make sure nobody is in the middle of
1908          * adding their roots to the list while we are
1909          * doing this splice
1910          */
1911         mutex_lock(&fs_info->reloc_mutex);
1912         list_splice_init(&rc->reloc_roots, &reloc_roots);
1913         mutex_unlock(&fs_info->reloc_mutex);
1914
1915         while (!list_empty(&reloc_roots)) {
1916                 found = 1;
1917                 reloc_root = list_entry(reloc_roots.next,
1918                                         struct btrfs_root, root_list);
1919
1920                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
1921                         root = read_fs_root(fs_info,
1922                                             reloc_root->root_key.offset);
1923                         BUG_ON(IS_ERR(root));
1924                         BUG_ON(root->reloc_root != reloc_root);
1925
1926                         ret = merge_reloc_root(rc, root);
1927                         btrfs_put_root(root);
1928                         if (ret) {
1929                                 if (list_empty(&reloc_root->root_list))
1930                                         list_add_tail(&reloc_root->root_list,
1931                                                       &reloc_roots);
1932                                 goto out;
1933                         }
1934                 } else {
1935                         list_del_init(&reloc_root->root_list);
1936                         /* Don't forget to queue this reloc root for cleanup */
1937                         list_add_tail(&reloc_root->reloc_dirty_list,
1938                                       &rc->dirty_subvol_roots);
1939                 }
1940         }
1941
1942         if (found) {
1943                 found = 0;
1944                 goto again;
1945         }
1946 out:
1947         if (ret) {
1948                 btrfs_handle_fs_error(fs_info, ret, NULL);
1949                 free_reloc_roots(&reloc_roots);
1950
1951                 /* new reloc root may be added */
1952                 mutex_lock(&fs_info->reloc_mutex);
1953                 list_splice_init(&rc->reloc_roots, &reloc_roots);
1954                 mutex_unlock(&fs_info->reloc_mutex);
1955                 free_reloc_roots(&reloc_roots);
1956         }
1957
1958         /*
1959          * We used to have
1960          *
1961          * BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
1962          *
1963          * here, but it's wrong.  If we fail to start the transaction in
1964          * prepare_to_merge() we will have only 0 ref reloc roots, none of which
1965          * have actually been removed from the reloc_root_tree rb tree.  This is
1966          * fine because we're bailing here, and we hold a reference on the root
1967          * for the list that holds it, so these roots will be cleaned up when we
1968          * do the reloc_dirty_list afterwards.  Meanwhile the root->reloc_root
1969          * will be cleaned up on unmount.
1970          *
1971          * The remaining nodes will be cleaned up by free_reloc_control.
1972          */
1973 }
1974
1975 static void free_block_list(struct rb_root *blocks)
1976 {
1977         struct tree_block *block;
1978         struct rb_node *rb_node;
1979         while ((rb_node = rb_first(blocks))) {
1980                 block = rb_entry(rb_node, struct tree_block, rb_node);
1981                 rb_erase(rb_node, blocks);
1982                 kfree(block);
1983         }
1984 }
1985
1986 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
1987                                       struct btrfs_root *reloc_root)
1988 {
1989         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
1990         struct btrfs_root *root;
1991         int ret;
1992
1993         if (reloc_root->last_trans == trans->transid)
1994                 return 0;
1995
1996         root = read_fs_root(fs_info, reloc_root->root_key.offset);
1997         BUG_ON(IS_ERR(root));
1998         BUG_ON(root->reloc_root != reloc_root);
1999         ret = btrfs_record_root_in_trans(trans, root);
2000         btrfs_put_root(root);
2001
2002         return ret;
2003 }
2004
2005 static noinline_for_stack
2006 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2007                                      struct reloc_control *rc,
2008                                      struct btrfs_backref_node *node,
2009                                      struct btrfs_backref_edge *edges[])
2010 {
2011         struct btrfs_backref_node *next;
2012         struct btrfs_root *root;
2013         int index = 0;
2014
2015         next = node;
2016         while (1) {
2017                 cond_resched();
2018                 next = walk_up_backref(next, edges, &index);
2019                 root = next->root;
2020                 BUG_ON(!root);
2021                 BUG_ON(!test_bit(BTRFS_ROOT_SHAREABLE, &root->state));
2022
2023                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2024                         record_reloc_root_in_trans(trans, root);
2025                         break;
2026                 }
2027
2028                 btrfs_record_root_in_trans(trans, root);
2029                 root = root->reloc_root;
2030
2031                 if (next->new_bytenr != root->node->start) {
2032                         BUG_ON(next->new_bytenr);
2033                         BUG_ON(!list_empty(&next->list));
2034                         next->new_bytenr = root->node->start;
2035                         btrfs_put_root(next->root);
2036                         next->root = btrfs_grab_root(root);
2037                         ASSERT(next->root);
2038                         list_add_tail(&next->list,
2039                                       &rc->backref_cache.changed);
2040                         mark_block_processed(rc, next);
2041                         break;
2042                 }
2043
2044                 WARN_ON(1);
2045                 root = NULL;
2046                 next = walk_down_backref(edges, &index);
2047                 if (!next || next->level <= node->level)
2048                         break;
2049         }
2050         if (!root)
2051                 return NULL;
2052
2053         next = node;
2054         /* setup backref node path for btrfs_reloc_cow_block */
2055         while (1) {
2056                 rc->backref_cache.path[next->level] = next;
2057                 if (--index < 0)
2058                         break;
2059                 next = edges[index]->node[UPPER];
2060         }
2061         return root;
2062 }
2063
2064 /*
2065  * Select a tree root for relocation.
2066  *
2067  * Return NULL if the block is not shareable. We should use do_relocation() in
2068  * this case.
2069  *
2070  * Return a tree root pointer if the block is shareable.
2071  * Return -ENOENT if the block is root of reloc tree.
2072  */
2073 static noinline_for_stack
2074 struct btrfs_root *select_one_root(struct btrfs_backref_node *node)
2075 {
2076         struct btrfs_backref_node *next;
2077         struct btrfs_root *root;
2078         struct btrfs_root *fs_root = NULL;
2079         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2080         int index = 0;
2081
2082         next = node;
2083         while (1) {
2084                 cond_resched();
2085                 next = walk_up_backref(next, edges, &index);
2086                 root = next->root;
2087                 BUG_ON(!root);
2088
2089                 /* No other choice for non-shareable tree */
2090                 if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
2091                         return root;
2092
2093                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2094                         fs_root = root;
2095
2096                 if (next != node)
2097                         return NULL;
2098
2099                 next = walk_down_backref(edges, &index);
2100                 if (!next || next->level <= node->level)
2101                         break;
2102         }
2103
2104         if (!fs_root)
2105                 return ERR_PTR(-ENOENT);
2106         return fs_root;
2107 }
2108
2109 static noinline_for_stack
2110 u64 calcu_metadata_size(struct reloc_control *rc,
2111                         struct btrfs_backref_node *node, int reserve)
2112 {
2113         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2114         struct btrfs_backref_node *next = node;
2115         struct btrfs_backref_edge *edge;
2116         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2117         u64 num_bytes = 0;
2118         int index = 0;
2119
2120         BUG_ON(reserve && node->processed);
2121
2122         while (next) {
2123                 cond_resched();
2124                 while (1) {
2125                         if (next->processed && (reserve || next != node))
2126                                 break;
2127
2128                         num_bytes += fs_info->nodesize;
2129
2130                         if (list_empty(&next->upper))
2131                                 break;
2132
2133                         edge = list_entry(next->upper.next,
2134                                         struct btrfs_backref_edge, list[LOWER]);
2135                         edges[index++] = edge;
2136                         next = edge->node[UPPER];
2137                 }
2138                 next = walk_down_backref(edges, &index);
2139         }
2140         return num_bytes;
2141 }
2142
2143 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2144                                   struct reloc_control *rc,
2145                                   struct btrfs_backref_node *node)
2146 {
2147         struct btrfs_root *root = rc->extent_root;
2148         struct btrfs_fs_info *fs_info = root->fs_info;
2149         u64 num_bytes;
2150         int ret;
2151         u64 tmp;
2152
2153         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2154
2155         trans->block_rsv = rc->block_rsv;
2156         rc->reserved_bytes += num_bytes;
2157
2158         /*
2159          * We are under a transaction here so we can only do limited flushing.
2160          * If we get an enospc just kick back -EAGAIN so we know to drop the
2161          * transaction and try to refill when we can flush all the things.
2162          */
2163         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2164                                 BTRFS_RESERVE_FLUSH_LIMIT);
2165         if (ret) {
2166                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2167                 while (tmp <= rc->reserved_bytes)
2168                         tmp <<= 1;
2169                 /*
2170                  * only one thread can access block_rsv at this point,
2171                  * so we don't need hold lock to protect block_rsv.
2172                  * we expand more reservation size here to allow enough
2173                  * space for relocation and we will return earlier in
2174                  * enospc case.
2175                  */
2176                 rc->block_rsv->size = tmp + fs_info->nodesize *
2177                                       RELOCATION_RESERVED_NODES;
2178                 return -EAGAIN;
2179         }
2180
2181         return 0;
2182 }
2183
2184 /*
2185  * relocate a block tree, and then update pointers in upper level
2186  * blocks that reference the block to point to the new location.
2187  *
2188  * if called by link_to_upper, the block has already been relocated.
2189  * in that case this function just updates pointers.
2190  */
2191 static int do_relocation(struct btrfs_trans_handle *trans,
2192                          struct reloc_control *rc,
2193                          struct btrfs_backref_node *node,
2194                          struct btrfs_key *key,
2195                          struct btrfs_path *path, int lowest)
2196 {
2197         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2198         struct btrfs_backref_node *upper;
2199         struct btrfs_backref_edge *edge;
2200         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2201         struct btrfs_root *root;
2202         struct extent_buffer *eb;
2203         u32 blocksize;
2204         u64 bytenr;
2205         u64 generation;
2206         int slot;
2207         int ret;
2208         int err = 0;
2209
2210         BUG_ON(lowest && node->eb);
2211
2212         path->lowest_level = node->level + 1;
2213         rc->backref_cache.path[node->level] = node;
2214         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2215                 struct btrfs_key first_key;
2216                 struct btrfs_ref ref = { 0 };
2217
2218                 cond_resched();
2219
2220                 upper = edge->node[UPPER];
2221                 root = select_reloc_root(trans, rc, upper, edges);
2222                 BUG_ON(!root);
2223
2224                 if (upper->eb && !upper->locked) {
2225                         if (!lowest) {
2226                                 ret = btrfs_bin_search(upper->eb, key, &slot);
2227                                 if (ret < 0) {
2228                                         err = ret;
2229                                         goto next;
2230                                 }
2231                                 BUG_ON(ret);
2232                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2233                                 if (node->eb->start == bytenr)
2234                                         goto next;
2235                         }
2236                         btrfs_backref_drop_node_buffer(upper);
2237                 }
2238
2239                 if (!upper->eb) {
2240                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2241                         if (ret) {
2242                                 if (ret < 0)
2243                                         err = ret;
2244                                 else
2245                                         err = -ENOENT;
2246
2247                                 btrfs_release_path(path);
2248                                 break;
2249                         }
2250
2251                         if (!upper->eb) {
2252                                 upper->eb = path->nodes[upper->level];
2253                                 path->nodes[upper->level] = NULL;
2254                         } else {
2255                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2256                         }
2257
2258                         upper->locked = 1;
2259                         path->locks[upper->level] = 0;
2260
2261                         slot = path->slots[upper->level];
2262                         btrfs_release_path(path);
2263                 } else {
2264                         ret = btrfs_bin_search(upper->eb, key, &slot);
2265                         if (ret < 0) {
2266                                 err = ret;
2267                                 goto next;
2268                         }
2269                         BUG_ON(ret);
2270                 }
2271
2272                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2273                 if (lowest) {
2274                         if (bytenr != node->bytenr) {
2275                                 btrfs_err(root->fs_info,
2276                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2277                                           bytenr, node->bytenr, slot,
2278                                           upper->eb->start);
2279                                 err = -EIO;
2280                                 goto next;
2281                         }
2282                 } else {
2283                         if (node->eb->start == bytenr)
2284                                 goto next;
2285                 }
2286
2287                 blocksize = root->fs_info->nodesize;
2288                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2289                 btrfs_node_key_to_cpu(upper->eb, &first_key, slot);
2290                 eb = read_tree_block(fs_info, bytenr, generation,
2291                                      upper->level - 1, &first_key);
2292                 if (IS_ERR(eb)) {
2293                         err = PTR_ERR(eb);
2294                         goto next;
2295                 } else if (!extent_buffer_uptodate(eb)) {
2296                         free_extent_buffer(eb);
2297                         err = -EIO;
2298                         goto next;
2299                 }
2300                 btrfs_tree_lock(eb);
2301                 btrfs_set_lock_blocking_write(eb);
2302
2303                 if (!node->eb) {
2304                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2305                                               slot, &eb);
2306                         btrfs_tree_unlock(eb);
2307                         free_extent_buffer(eb);
2308                         if (ret < 0) {
2309                                 err = ret;
2310                                 goto next;
2311                         }
2312                         BUG_ON(node->eb != eb);
2313                 } else {
2314                         btrfs_set_node_blockptr(upper->eb, slot,
2315                                                 node->eb->start);
2316                         btrfs_set_node_ptr_generation(upper->eb, slot,
2317                                                       trans->transid);
2318                         btrfs_mark_buffer_dirty(upper->eb);
2319
2320                         btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF,
2321                                                node->eb->start, blocksize,
2322                                                upper->eb->start);
2323                         ref.real_root = root->root_key.objectid;
2324                         btrfs_init_tree_ref(&ref, node->level,
2325                                             btrfs_header_owner(upper->eb));
2326                         ret = btrfs_inc_extent_ref(trans, &ref);
2327                         BUG_ON(ret);
2328
2329                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2330                         BUG_ON(ret);
2331                 }
2332 next:
2333                 if (!upper->pending)
2334                         btrfs_backref_drop_node_buffer(upper);
2335                 else
2336                         btrfs_backref_unlock_node_buffer(upper);
2337                 if (err)
2338                         break;
2339         }
2340
2341         if (!err && node->pending) {
2342                 btrfs_backref_drop_node_buffer(node);
2343                 list_move_tail(&node->list, &rc->backref_cache.changed);
2344                 node->pending = 0;
2345         }
2346
2347         path->lowest_level = 0;
2348         BUG_ON(err == -ENOSPC);
2349         return err;
2350 }
2351
2352 static int link_to_upper(struct btrfs_trans_handle *trans,
2353                          struct reloc_control *rc,
2354                          struct btrfs_backref_node *node,
2355                          struct btrfs_path *path)
2356 {
2357         struct btrfs_key key;
2358
2359         btrfs_node_key_to_cpu(node->eb, &key, 0);
2360         return do_relocation(trans, rc, node, &key, path, 0);
2361 }
2362
2363 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2364                                 struct reloc_control *rc,
2365                                 struct btrfs_path *path, int err)
2366 {
2367         LIST_HEAD(list);
2368         struct btrfs_backref_cache *cache = &rc->backref_cache;
2369         struct btrfs_backref_node *node;
2370         int level;
2371         int ret;
2372
2373         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2374                 while (!list_empty(&cache->pending[level])) {
2375                         node = list_entry(cache->pending[level].next,
2376                                           struct btrfs_backref_node, list);
2377                         list_move_tail(&node->list, &list);
2378                         BUG_ON(!node->pending);
2379
2380                         if (!err) {
2381                                 ret = link_to_upper(trans, rc, node, path);
2382                                 if (ret < 0)
2383                                         err = ret;
2384                         }
2385                 }
2386                 list_splice_init(&list, &cache->pending[level]);
2387         }
2388         return err;
2389 }
2390
2391 /*
2392  * mark a block and all blocks directly/indirectly reference the block
2393  * as processed.
2394  */
2395 static void update_processed_blocks(struct reloc_control *rc,
2396                                     struct btrfs_backref_node *node)
2397 {
2398         struct btrfs_backref_node *next = node;
2399         struct btrfs_backref_edge *edge;
2400         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2401         int index = 0;
2402
2403         while (next) {
2404                 cond_resched();
2405                 while (1) {
2406                         if (next->processed)
2407                                 break;
2408
2409                         mark_block_processed(rc, next);
2410
2411                         if (list_empty(&next->upper))
2412                                 break;
2413
2414                         edge = list_entry(next->upper.next,
2415                                         struct btrfs_backref_edge, list[LOWER]);
2416                         edges[index++] = edge;
2417                         next = edge->node[UPPER];
2418                 }
2419                 next = walk_down_backref(edges, &index);
2420         }
2421 }
2422
2423 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
2424 {
2425         u32 blocksize = rc->extent_root->fs_info->nodesize;
2426
2427         if (test_range_bit(&rc->processed_blocks, bytenr,
2428                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2429                 return 1;
2430         return 0;
2431 }
2432
2433 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
2434                               struct tree_block *block)
2435 {
2436         struct extent_buffer *eb;
2437
2438         eb = read_tree_block(fs_info, block->bytenr, block->key.offset,
2439                              block->level, NULL);
2440         if (IS_ERR(eb)) {
2441                 return PTR_ERR(eb);
2442         } else if (!extent_buffer_uptodate(eb)) {
2443                 free_extent_buffer(eb);
2444                 return -EIO;
2445         }
2446         if (block->level == 0)
2447                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2448         else
2449                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2450         free_extent_buffer(eb);
2451         block->key_ready = 1;
2452         return 0;
2453 }
2454
2455 /*
2456  * helper function to relocate a tree block
2457  */
2458 static int relocate_tree_block(struct btrfs_trans_handle *trans,
2459                                 struct reloc_control *rc,
2460                                 struct btrfs_backref_node *node,
2461                                 struct btrfs_key *key,
2462                                 struct btrfs_path *path)
2463 {
2464         struct btrfs_root *root;
2465         int ret = 0;
2466
2467         if (!node)
2468                 return 0;
2469
2470         /*
2471          * If we fail here we want to drop our backref_node because we are going
2472          * to start over and regenerate the tree for it.
2473          */
2474         ret = reserve_metadata_space(trans, rc, node);
2475         if (ret)
2476                 goto out;
2477
2478         BUG_ON(node->processed);
2479         root = select_one_root(node);
2480         if (root == ERR_PTR(-ENOENT)) {
2481                 update_processed_blocks(rc, node);
2482                 goto out;
2483         }
2484
2485         if (root) {
2486                 if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) {
2487                         BUG_ON(node->new_bytenr);
2488                         BUG_ON(!list_empty(&node->list));
2489                         btrfs_record_root_in_trans(trans, root);
2490                         root = root->reloc_root;
2491                         node->new_bytenr = root->node->start;
2492                         btrfs_put_root(node->root);
2493                         node->root = btrfs_grab_root(root);
2494                         ASSERT(node->root);
2495                         list_add_tail(&node->list, &rc->backref_cache.changed);
2496                 } else {
2497                         path->lowest_level = node->level;
2498                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2499                         btrfs_release_path(path);
2500                         if (ret > 0)
2501                                 ret = 0;
2502                 }
2503                 if (!ret)
2504                         update_processed_blocks(rc, node);
2505         } else {
2506                 ret = do_relocation(trans, rc, node, key, path, 1);
2507         }
2508 out:
2509         if (ret || node->level == 0 || node->cowonly)
2510                 btrfs_backref_cleanup_node(&rc->backref_cache, node);
2511         return ret;
2512 }
2513
2514 /*
2515  * relocate a list of blocks
2516  */
2517 static noinline_for_stack
2518 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
2519                          struct reloc_control *rc, struct rb_root *blocks)
2520 {
2521         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2522         struct btrfs_backref_node *node;
2523         struct btrfs_path *path;
2524         struct tree_block *block;
2525         struct tree_block *next;
2526         int ret;
2527         int err = 0;
2528
2529         path = btrfs_alloc_path();
2530         if (!path) {
2531                 err = -ENOMEM;
2532                 goto out_free_blocks;
2533         }
2534
2535         /* Kick in readahead for tree blocks with missing keys */
2536         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
2537                 if (!block->key_ready)
2538                         readahead_tree_block(fs_info, block->bytenr);
2539         }
2540
2541         /* Get first keys */
2542         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
2543                 if (!block->key_ready) {
2544                         err = get_tree_block_key(fs_info, block);
2545                         if (err)
2546                                 goto out_free_path;
2547                 }
2548         }
2549
2550         /* Do tree relocation */
2551         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
2552                 node = build_backref_tree(rc, &block->key,
2553                                           block->level, block->bytenr);
2554                 if (IS_ERR(node)) {
2555                         err = PTR_ERR(node);
2556                         goto out;
2557                 }
2558
2559                 ret = relocate_tree_block(trans, rc, node, &block->key,
2560                                           path);
2561                 if (ret < 0) {
2562                         err = ret;
2563                         break;
2564                 }
2565         }
2566 out:
2567         err = finish_pending_nodes(trans, rc, path, err);
2568
2569 out_free_path:
2570         btrfs_free_path(path);
2571 out_free_blocks:
2572         free_block_list(blocks);
2573         return err;
2574 }
2575
2576 static noinline_for_stack
2577 int prealloc_file_extent_cluster(struct inode *inode,
2578                                  struct file_extent_cluster *cluster)
2579 {
2580         u64 alloc_hint = 0;
2581         u64 start;
2582         u64 end;
2583         u64 offset = BTRFS_I(inode)->index_cnt;
2584         u64 num_bytes;
2585         int nr = 0;
2586         int ret = 0;
2587         u64 prealloc_start = cluster->start - offset;
2588         u64 prealloc_end = cluster->end - offset;
2589         u64 cur_offset;
2590         struct extent_changeset *data_reserved = NULL;
2591
2592         BUG_ON(cluster->start != cluster->boundary[0]);
2593         inode_lock(inode);
2594
2595         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
2596                                           prealloc_end + 1 - prealloc_start);
2597         if (ret)
2598                 goto out;
2599
2600         cur_offset = prealloc_start;
2601         while (nr < cluster->nr) {
2602                 start = cluster->boundary[nr] - offset;
2603                 if (nr + 1 < cluster->nr)
2604                         end = cluster->boundary[nr + 1] - 1 - offset;
2605                 else
2606                         end = cluster->end - offset;
2607
2608                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2609                 num_bytes = end + 1 - start;
2610                 if (cur_offset < start)
2611                         btrfs_free_reserved_data_space(inode, data_reserved,
2612                                         cur_offset, start - cur_offset);
2613                 ret = btrfs_prealloc_file_range(inode, 0, start,
2614                                                 num_bytes, num_bytes,
2615                                                 end + 1, &alloc_hint);
2616                 cur_offset = end + 1;
2617                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2618                 if (ret)
2619                         break;
2620                 nr++;
2621         }
2622         if (cur_offset < prealloc_end)
2623                 btrfs_free_reserved_data_space(inode, data_reserved,
2624                                 cur_offset, prealloc_end + 1 - cur_offset);
2625 out:
2626         inode_unlock(inode);
2627         extent_changeset_free(data_reserved);
2628         return ret;
2629 }
2630
2631 static noinline_for_stack
2632 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
2633                          u64 block_start)
2634 {
2635         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
2636         struct extent_map *em;
2637         int ret = 0;
2638
2639         em = alloc_extent_map();
2640         if (!em)
2641                 return -ENOMEM;
2642
2643         em->start = start;
2644         em->len = end + 1 - start;
2645         em->block_len = em->len;
2646         em->block_start = block_start;
2647         set_bit(EXTENT_FLAG_PINNED, &em->flags);
2648
2649         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2650         while (1) {
2651                 write_lock(&em_tree->lock);
2652                 ret = add_extent_mapping(em_tree, em, 0);
2653                 write_unlock(&em_tree->lock);
2654                 if (ret != -EEXIST) {
2655                         free_extent_map(em);
2656                         break;
2657                 }
2658                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
2659         }
2660         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2661         return ret;
2662 }
2663
2664 /*
2665  * Allow error injection to test balance cancellation
2666  */
2667 int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info)
2668 {
2669         return atomic_read(&fs_info->balance_cancel_req);
2670 }
2671 ALLOW_ERROR_INJECTION(btrfs_should_cancel_balance, TRUE);
2672
2673 static int relocate_file_extent_cluster(struct inode *inode,
2674                                         struct file_extent_cluster *cluster)
2675 {
2676         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2677         u64 page_start;
2678         u64 page_end;
2679         u64 offset = BTRFS_I(inode)->index_cnt;
2680         unsigned long index;
2681         unsigned long last_index;
2682         struct page *page;
2683         struct file_ra_state *ra;
2684         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
2685         int nr = 0;
2686         int ret = 0;
2687
2688         if (!cluster->nr)
2689                 return 0;
2690
2691         ra = kzalloc(sizeof(*ra), GFP_NOFS);
2692         if (!ra)
2693                 return -ENOMEM;
2694
2695         ret = prealloc_file_extent_cluster(inode, cluster);
2696         if (ret)
2697                 goto out;
2698
2699         file_ra_state_init(ra, inode->i_mapping);
2700
2701         ret = setup_extent_mapping(inode, cluster->start - offset,
2702                                    cluster->end - offset, cluster->start);
2703         if (ret)
2704                 goto out;
2705
2706         index = (cluster->start - offset) >> PAGE_SHIFT;
2707         last_index = (cluster->end - offset) >> PAGE_SHIFT;
2708         while (index <= last_index) {
2709                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
2710                                 PAGE_SIZE);
2711                 if (ret)
2712                         goto out;
2713
2714                 page = find_lock_page(inode->i_mapping, index);
2715                 if (!page) {
2716                         page_cache_sync_readahead(inode->i_mapping,
2717                                                   ra, NULL, index,
2718                                                   last_index + 1 - index);
2719                         page = find_or_create_page(inode->i_mapping, index,
2720                                                    mask);
2721                         if (!page) {
2722                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
2723                                                         PAGE_SIZE, true);
2724                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
2725                                                         PAGE_SIZE);
2726                                 ret = -ENOMEM;
2727                                 goto out;
2728                         }
2729                 }
2730
2731                 if (PageReadahead(page)) {
2732                         page_cache_async_readahead(inode->i_mapping,
2733                                                    ra, NULL, page, index,
2734                                                    last_index + 1 - index);
2735                 }
2736
2737                 if (!PageUptodate(page)) {
2738                         btrfs_readpage(NULL, page);
2739                         lock_page(page);
2740                         if (!PageUptodate(page)) {
2741                                 unlock_page(page);
2742                                 put_page(page);
2743                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
2744                                                         PAGE_SIZE, true);
2745                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
2746                                                                PAGE_SIZE);
2747                                 ret = -EIO;
2748                                 goto out;
2749                         }
2750                 }
2751
2752                 page_start = page_offset(page);
2753                 page_end = page_start + PAGE_SIZE - 1;
2754
2755                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
2756
2757                 set_page_extent_mapped(page);
2758
2759                 if (nr < cluster->nr &&
2760                     page_start + offset == cluster->boundary[nr]) {
2761                         set_extent_bits(&BTRFS_I(inode)->io_tree,
2762                                         page_start, page_end,
2763                                         EXTENT_BOUNDARY);
2764                         nr++;
2765                 }
2766
2767                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
2768                                                 NULL);
2769                 if (ret) {
2770                         unlock_page(page);
2771                         put_page(page);
2772                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
2773                                                          PAGE_SIZE, true);
2774                         btrfs_delalloc_release_extents(BTRFS_I(inode),
2775                                                        PAGE_SIZE);
2776
2777                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
2778                                           page_start, page_end,
2779                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
2780                         goto out;
2781
2782                 }
2783                 set_page_dirty(page);
2784
2785                 unlock_extent(&BTRFS_I(inode)->io_tree,
2786                               page_start, page_end);
2787                 unlock_page(page);
2788                 put_page(page);
2789
2790                 index++;
2791                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
2792                 balance_dirty_pages_ratelimited(inode->i_mapping);
2793                 btrfs_throttle(fs_info);
2794                 if (btrfs_should_cancel_balance(fs_info)) {
2795                         ret = -ECANCELED;
2796                         goto out;
2797                 }
2798         }
2799         WARN_ON(nr != cluster->nr);
2800 out:
2801         kfree(ra);
2802         return ret;
2803 }
2804
2805 static noinline_for_stack
2806 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
2807                          struct file_extent_cluster *cluster)
2808 {
2809         int ret;
2810
2811         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
2812                 ret = relocate_file_extent_cluster(inode, cluster);
2813                 if (ret)
2814                         return ret;
2815                 cluster->nr = 0;
2816         }
2817
2818         if (!cluster->nr)
2819                 cluster->start = extent_key->objectid;
2820         else
2821                 BUG_ON(cluster->nr >= MAX_EXTENTS);
2822         cluster->end = extent_key->objectid + extent_key->offset - 1;
2823         cluster->boundary[cluster->nr] = extent_key->objectid;
2824         cluster->nr++;
2825
2826         if (cluster->nr >= MAX_EXTENTS) {
2827                 ret = relocate_file_extent_cluster(inode, cluster);
2828                 if (ret)
2829                         return ret;
2830                 cluster->nr = 0;
2831         }
2832         return 0;
2833 }
2834
2835 /*
2836  * helper to add a tree block to the list.
2837  * the major work is getting the generation and level of the block
2838  */
2839 static int add_tree_block(struct reloc_control *rc,
2840                           struct btrfs_key *extent_key,
2841                           struct btrfs_path *path,
2842                           struct rb_root *blocks)
2843 {
2844         struct extent_buffer *eb;
2845         struct btrfs_extent_item *ei;
2846         struct btrfs_tree_block_info *bi;
2847         struct tree_block *block;
2848         struct rb_node *rb_node;
2849         u32 item_size;
2850         int level = -1;
2851         u64 generation;
2852
2853         eb =  path->nodes[0];
2854         item_size = btrfs_item_size_nr(eb, path->slots[0]);
2855
2856         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
2857             item_size >= sizeof(*ei) + sizeof(*bi)) {
2858                 ei = btrfs_item_ptr(eb, path->slots[0],
2859                                 struct btrfs_extent_item);
2860                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
2861                         bi = (struct btrfs_tree_block_info *)(ei + 1);
2862                         level = btrfs_tree_block_level(eb, bi);
2863                 } else {
2864                         level = (int)extent_key->offset;
2865                 }
2866                 generation = btrfs_extent_generation(eb, ei);
2867         } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
2868                 btrfs_print_v0_err(eb->fs_info);
2869                 btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
2870                 return -EINVAL;
2871         } else {
2872                 BUG();
2873         }
2874
2875         btrfs_release_path(path);
2876
2877         BUG_ON(level == -1);
2878
2879         block = kmalloc(sizeof(*block), GFP_NOFS);
2880         if (!block)
2881                 return -ENOMEM;
2882
2883         block->bytenr = extent_key->objectid;
2884         block->key.objectid = rc->extent_root->fs_info->nodesize;
2885         block->key.offset = generation;
2886         block->level = level;
2887         block->key_ready = 0;
2888
2889         rb_node = rb_simple_insert(blocks, block->bytenr, &block->rb_node);
2890         if (rb_node)
2891                 btrfs_backref_panic(rc->extent_root->fs_info, block->bytenr,
2892                                     -EEXIST);
2893
2894         return 0;
2895 }
2896
2897 /*
2898  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
2899  */
2900 static int __add_tree_block(struct reloc_control *rc,
2901                             u64 bytenr, u32 blocksize,
2902                             struct rb_root *blocks)
2903 {
2904         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2905         struct btrfs_path *path;
2906         struct btrfs_key key;
2907         int ret;
2908         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
2909
2910         if (tree_block_processed(bytenr, rc))
2911                 return 0;
2912
2913         if (rb_simple_search(blocks, bytenr))
2914                 return 0;
2915
2916         path = btrfs_alloc_path();
2917         if (!path)
2918                 return -ENOMEM;
2919 again:
2920         key.objectid = bytenr;
2921         if (skinny) {
2922                 key.type = BTRFS_METADATA_ITEM_KEY;
2923                 key.offset = (u64)-1;
2924         } else {
2925                 key.type = BTRFS_EXTENT_ITEM_KEY;
2926                 key.offset = blocksize;
2927         }
2928
2929         path->search_commit_root = 1;
2930         path->skip_locking = 1;
2931         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
2932         if (ret < 0)
2933                 goto out;
2934
2935         if (ret > 0 && skinny) {
2936                 if (path->slots[0]) {
2937                         path->slots[0]--;
2938                         btrfs_item_key_to_cpu(path->nodes[0], &key,
2939                                               path->slots[0]);
2940                         if (key.objectid == bytenr &&
2941                             (key.type == BTRFS_METADATA_ITEM_KEY ||
2942                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
2943                               key.offset == blocksize)))
2944                                 ret = 0;
2945                 }
2946
2947                 if (ret) {
2948                         skinny = false;
2949                         btrfs_release_path(path);
2950                         goto again;
2951                 }
2952         }
2953         if (ret) {
2954                 ASSERT(ret == 1);
2955                 btrfs_print_leaf(path->nodes[0]);
2956                 btrfs_err(fs_info,
2957              "tree block extent item (%llu) is not found in extent tree",
2958                      bytenr);
2959                 WARN_ON(1);
2960                 ret = -EINVAL;
2961                 goto out;
2962         }
2963
2964         ret = add_tree_block(rc, &key, path, blocks);
2965 out:
2966         btrfs_free_path(path);
2967         return ret;
2968 }
2969
2970 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
2971                                     struct btrfs_block_group *block_group,
2972                                     struct inode *inode,
2973                                     u64 ino)
2974 {
2975         struct btrfs_key key;
2976         struct btrfs_root *root = fs_info->tree_root;
2977         struct btrfs_trans_handle *trans;
2978         int ret = 0;
2979
2980         if (inode)
2981                 goto truncate;
2982
2983         key.objectid = ino;
2984         key.type = BTRFS_INODE_ITEM_KEY;
2985         key.offset = 0;
2986
2987         inode = btrfs_iget(fs_info->sb, &key, root);
2988         if (IS_ERR(inode))
2989                 return -ENOENT;
2990
2991 truncate:
2992         ret = btrfs_check_trunc_cache_free_space(fs_info,
2993                                                  &fs_info->global_block_rsv);
2994         if (ret)
2995                 goto out;
2996
2997         trans = btrfs_join_transaction(root);
2998         if (IS_ERR(trans)) {
2999                 ret = PTR_ERR(trans);
3000                 goto out;
3001         }
3002
3003         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3004
3005         btrfs_end_transaction(trans);
3006         btrfs_btree_balance_dirty(fs_info);
3007 out:
3008         iput(inode);
3009         return ret;
3010 }
3011
3012 /*
3013  * Locate the free space cache EXTENT_DATA in root tree leaf and delete the
3014  * cache inode, to avoid free space cache data extent blocking data relocation.
3015  */
3016 static int delete_v1_space_cache(struct extent_buffer *leaf,
3017                                  struct btrfs_block_group *block_group,
3018                                  u64 data_bytenr)
3019 {
3020         u64 space_cache_ino;
3021         struct btrfs_file_extent_item *ei;
3022         struct btrfs_key key;
3023         bool found = false;
3024         int i;
3025         int ret;
3026
3027         if (btrfs_header_owner(leaf) != BTRFS_ROOT_TREE_OBJECTID)
3028                 return 0;
3029
3030         for (i = 0; i < btrfs_header_nritems(leaf); i++) {
3031                 btrfs_item_key_to_cpu(leaf, &key, i);
3032                 if (key.type != BTRFS_EXTENT_DATA_KEY)
3033                         continue;
3034                 ei = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
3035                 if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_REG &&
3036                     btrfs_file_extent_disk_bytenr(leaf, ei) == data_bytenr) {
3037                         found = true;
3038                         space_cache_ino = key.objectid;
3039                         break;
3040                 }
3041         }
3042         if (!found)
3043                 return -ENOENT;
3044         ret = delete_block_group_cache(leaf->fs_info, block_group, NULL,
3045                                         space_cache_ino);
3046         return ret;
3047 }
3048
3049 /*
3050  * helper to find all tree blocks that reference a given data extent
3051  */
3052 static noinline_for_stack
3053 int add_data_references(struct reloc_control *rc,
3054                         struct btrfs_key *extent_key,
3055                         struct btrfs_path *path,
3056                         struct rb_root *blocks)
3057 {
3058         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3059         struct ulist *leaves = NULL;
3060         struct ulist_iterator leaf_uiter;
3061         struct ulist_node *ref_node = NULL;
3062         const u32 blocksize = fs_info->nodesize;
3063         int ret = 0;
3064
3065         btrfs_release_path(path);
3066         ret = btrfs_find_all_leafs(NULL, fs_info, extent_key->objectid,
3067                                    0, &leaves, NULL, true);
3068         if (ret < 0)
3069                 return ret;
3070
3071         ULIST_ITER_INIT(&leaf_uiter);
3072         while ((ref_node = ulist_next(leaves, &leaf_uiter))) {
3073                 struct extent_buffer *eb;
3074
3075                 eb = read_tree_block(fs_info, ref_node->val, 0, 0, NULL);
3076                 if (IS_ERR(eb)) {
3077                         ret = PTR_ERR(eb);
3078                         break;
3079                 }
3080                 ret = delete_v1_space_cache(eb, rc->block_group,
3081                                             extent_key->objectid);
3082                 free_extent_buffer(eb);
3083                 if (ret < 0)
3084                         break;
3085                 ret = __add_tree_block(rc, ref_node->val, blocksize, blocks);
3086                 if (ret < 0)
3087                         break;
3088         }
3089         if (ret < 0)
3090                 free_block_list(blocks);
3091         ulist_free(leaves);
3092         return ret;
3093 }
3094
3095 /*
3096  * helper to find next unprocessed extent
3097  */
3098 static noinline_for_stack
3099 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3100                      struct btrfs_key *extent_key)
3101 {
3102         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3103         struct btrfs_key key;
3104         struct extent_buffer *leaf;
3105         u64 start, end, last;
3106         int ret;
3107
3108         last = rc->block_group->start + rc->block_group->length;
3109         while (1) {
3110                 cond_resched();
3111                 if (rc->search_start >= last) {
3112                         ret = 1;
3113                         break;
3114                 }
3115
3116                 key.objectid = rc->search_start;
3117                 key.type = BTRFS_EXTENT_ITEM_KEY;
3118                 key.offset = 0;
3119
3120                 path->search_commit_root = 1;
3121                 path->skip_locking = 1;
3122                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3123                                         0, 0);
3124                 if (ret < 0)
3125                         break;
3126 next:
3127                 leaf = path->nodes[0];
3128                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3129                         ret = btrfs_next_leaf(rc->extent_root, path);
3130                         if (ret != 0)
3131                                 break;
3132                         leaf = path->nodes[0];
3133                 }
3134
3135                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3136                 if (key.objectid >= last) {
3137                         ret = 1;
3138                         break;
3139                 }
3140
3141                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3142                     key.type != BTRFS_METADATA_ITEM_KEY) {
3143                         path->slots[0]++;
3144                         goto next;
3145                 }
3146
3147                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3148                     key.objectid + key.offset <= rc->search_start) {
3149                         path->slots[0]++;
3150                         goto next;
3151                 }
3152
3153                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3154                     key.objectid + fs_info->nodesize <=
3155                     rc->search_start) {
3156                         path->slots[0]++;
3157                         goto next;
3158                 }
3159
3160                 ret = find_first_extent_bit(&rc->processed_blocks,
3161                                             key.objectid, &start, &end,
3162                                             EXTENT_DIRTY, NULL);
3163
3164                 if (ret == 0 && start <= key.objectid) {
3165                         btrfs_release_path(path);
3166                         rc->search_start = end + 1;
3167                 } else {
3168                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3169                                 rc->search_start = key.objectid + key.offset;
3170                         else
3171                                 rc->search_start = key.objectid +
3172                                         fs_info->nodesize;
3173                         memcpy(extent_key, &key, sizeof(key));
3174                         return 0;
3175                 }
3176         }
3177         btrfs_release_path(path);
3178         return ret;
3179 }
3180
3181 static void set_reloc_control(struct reloc_control *rc)
3182 {
3183         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3184
3185         mutex_lock(&fs_info->reloc_mutex);
3186         fs_info->reloc_ctl = rc;
3187         mutex_unlock(&fs_info->reloc_mutex);
3188 }
3189
3190 static void unset_reloc_control(struct reloc_control *rc)
3191 {
3192         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3193
3194         mutex_lock(&fs_info->reloc_mutex);
3195         fs_info->reloc_ctl = NULL;
3196         mutex_unlock(&fs_info->reloc_mutex);
3197 }
3198
3199 static int check_extent_flags(u64 flags)
3200 {
3201         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3202             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3203                 return 1;
3204         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3205             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3206                 return 1;
3207         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3208             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3209                 return 1;
3210         return 0;
3211 }
3212
3213 static noinline_for_stack
3214 int prepare_to_relocate(struct reloc_control *rc)
3215 {
3216         struct btrfs_trans_handle *trans;
3217         int ret;
3218
3219         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3220                                               BTRFS_BLOCK_RSV_TEMP);
3221         if (!rc->block_rsv)
3222                 return -ENOMEM;
3223
3224         memset(&rc->cluster, 0, sizeof(rc->cluster));
3225         rc->search_start = rc->block_group->start;
3226         rc->extents_found = 0;
3227         rc->nodes_relocated = 0;
3228         rc->merging_rsv_size = 0;
3229         rc->reserved_bytes = 0;
3230         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
3231                               RELOCATION_RESERVED_NODES;
3232         ret = btrfs_block_rsv_refill(rc->extent_root,
3233                                      rc->block_rsv, rc->block_rsv->size,
3234                                      BTRFS_RESERVE_FLUSH_ALL);
3235         if (ret)
3236                 return ret;
3237
3238         rc->create_reloc_tree = 1;
3239         set_reloc_control(rc);
3240
3241         trans = btrfs_join_transaction(rc->extent_root);
3242         if (IS_ERR(trans)) {
3243                 unset_reloc_control(rc);
3244                 /*
3245                  * extent tree is not a ref_cow tree and has no reloc_root to
3246                  * cleanup.  And callers are responsible to free the above
3247                  * block rsv.
3248                  */
3249                 return PTR_ERR(trans);
3250         }
3251         btrfs_commit_transaction(trans);
3252         return 0;
3253 }
3254
3255 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
3256 {
3257         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3258         struct rb_root blocks = RB_ROOT;
3259         struct btrfs_key key;
3260         struct btrfs_trans_handle *trans = NULL;
3261         struct btrfs_path *path;
3262         struct btrfs_extent_item *ei;
3263         u64 flags;
3264         u32 item_size;
3265         int ret;
3266         int err = 0;
3267         int progress = 0;
3268
3269         path = btrfs_alloc_path();
3270         if (!path)
3271                 return -ENOMEM;
3272         path->reada = READA_FORWARD;
3273
3274         ret = prepare_to_relocate(rc);
3275         if (ret) {
3276                 err = ret;
3277                 goto out_free;
3278         }
3279
3280         while (1) {
3281                 rc->reserved_bytes = 0;
3282                 ret = btrfs_block_rsv_refill(rc->extent_root,
3283                                         rc->block_rsv, rc->block_rsv->size,
3284                                         BTRFS_RESERVE_FLUSH_ALL);
3285                 if (ret) {
3286                         err = ret;
3287                         break;
3288                 }
3289                 progress++;
3290                 trans = btrfs_start_transaction(rc->extent_root, 0);
3291                 if (IS_ERR(trans)) {
3292                         err = PTR_ERR(trans);
3293                         trans = NULL;
3294                         break;
3295                 }
3296 restart:
3297                 if (update_backref_cache(trans, &rc->backref_cache)) {
3298                         btrfs_end_transaction(trans);
3299                         trans = NULL;
3300                         continue;
3301                 }
3302
3303                 ret = find_next_extent(rc, path, &key);
3304                 if (ret < 0)
3305                         err = ret;
3306                 if (ret != 0)
3307                         break;
3308
3309                 rc->extents_found++;
3310
3311                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
3312                                     struct btrfs_extent_item);
3313                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
3314                 if (item_size >= sizeof(*ei)) {
3315                         flags = btrfs_extent_flags(path->nodes[0], ei);
3316                         ret = check_extent_flags(flags);
3317                         BUG_ON(ret);
3318                 } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
3319                         err = -EINVAL;
3320                         btrfs_print_v0_err(trans->fs_info);
3321                         btrfs_abort_transaction(trans, err);
3322                         break;
3323                 } else {
3324                         BUG();
3325                 }
3326
3327                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
3328                         ret = add_tree_block(rc, &key, path, &blocks);
3329                 } else if (rc->stage == UPDATE_DATA_PTRS &&
3330                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
3331                         ret = add_data_references(rc, &key, path, &blocks);
3332                 } else {
3333                         btrfs_release_path(path);
3334                         ret = 0;
3335                 }
3336                 if (ret < 0) {
3337                         err = ret;
3338                         break;
3339                 }
3340
3341                 if (!RB_EMPTY_ROOT(&blocks)) {
3342                         ret = relocate_tree_blocks(trans, rc, &blocks);
3343                         if (ret < 0) {
3344                                 if (ret != -EAGAIN) {
3345                                         err = ret;
3346                                         break;
3347                                 }
3348                                 rc->extents_found--;
3349                                 rc->search_start = key.objectid;
3350                         }
3351                 }
3352
3353                 btrfs_end_transaction_throttle(trans);
3354                 btrfs_btree_balance_dirty(fs_info);
3355                 trans = NULL;
3356
3357                 if (rc->stage == MOVE_DATA_EXTENTS &&
3358                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
3359                         rc->found_file_extent = 1;
3360                         ret = relocate_data_extent(rc->data_inode,
3361                                                    &key, &rc->cluster);
3362                         if (ret < 0) {
3363                                 err = ret;
3364                                 break;
3365                         }
3366                 }
3367                 if (btrfs_should_cancel_balance(fs_info)) {
3368                         err = -ECANCELED;
3369                         break;
3370                 }
3371         }
3372         if (trans && progress && err == -ENOSPC) {
3373                 ret = btrfs_force_chunk_alloc(trans, rc->block_group->flags);
3374                 if (ret == 1) {
3375                         err = 0;
3376                         progress = 0;
3377                         goto restart;
3378                 }
3379         }
3380
3381         btrfs_release_path(path);
3382         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
3383
3384         if (trans) {
3385                 btrfs_end_transaction_throttle(trans);
3386                 btrfs_btree_balance_dirty(fs_info);
3387         }
3388
3389         if (!err) {
3390                 ret = relocate_file_extent_cluster(rc->data_inode,
3391                                                    &rc->cluster);
3392                 if (ret < 0)
3393                         err = ret;
3394         }
3395
3396         rc->create_reloc_tree = 0;
3397         set_reloc_control(rc);
3398
3399         btrfs_backref_release_cache(&rc->backref_cache);
3400         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
3401
3402         /*
3403          * Even in the case when the relocation is cancelled, we should all go
3404          * through prepare_to_merge() and merge_reloc_roots().
3405          *
3406          * For error (including cancelled balance), prepare_to_merge() will
3407          * mark all reloc trees orphan, then queue them for cleanup in
3408          * merge_reloc_roots()
3409          */
3410         err = prepare_to_merge(rc, err);
3411
3412         merge_reloc_roots(rc);
3413
3414         rc->merge_reloc_tree = 0;
3415         unset_reloc_control(rc);
3416         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
3417
3418         /* get rid of pinned extents */
3419         trans = btrfs_join_transaction(rc->extent_root);
3420         if (IS_ERR(trans)) {
3421                 err = PTR_ERR(trans);
3422                 goto out_free;
3423         }
3424         btrfs_commit_transaction(trans);
3425 out_free:
3426         ret = clean_dirty_subvols(rc);
3427         if (ret < 0 && !err)
3428                 err = ret;
3429         btrfs_free_block_rsv(fs_info, rc->block_rsv);
3430         btrfs_free_path(path);
3431         return err;
3432 }
3433
3434 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
3435                                  struct btrfs_root *root, u64 objectid)
3436 {
3437         struct btrfs_path *path;
3438         struct btrfs_inode_item *item;
3439         struct extent_buffer *leaf;
3440         int ret;
3441
3442         path = btrfs_alloc_path();
3443         if (!path)
3444                 return -ENOMEM;
3445
3446         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
3447         if (ret)
3448                 goto out;
3449
3450         leaf = path->nodes[0];
3451         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
3452         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
3453         btrfs_set_inode_generation(leaf, item, 1);
3454         btrfs_set_inode_size(leaf, item, 0);
3455         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
3456         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
3457                                           BTRFS_INODE_PREALLOC);
3458         btrfs_mark_buffer_dirty(leaf);
3459 out:
3460         btrfs_free_path(path);
3461         return ret;
3462 }
3463
3464 /*
3465  * helper to create inode for data relocation.
3466  * the inode is in data relocation tree and its link count is 0
3467  */
3468 static noinline_for_stack
3469 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
3470                                  struct btrfs_block_group *group)
3471 {
3472         struct inode *inode = NULL;
3473         struct btrfs_trans_handle *trans;
3474         struct btrfs_root *root;
3475         struct btrfs_key key;
3476         u64 objectid;
3477         int err = 0;
3478
3479         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
3480         if (IS_ERR(root))
3481                 return ERR_CAST(root);
3482
3483         trans = btrfs_start_transaction(root, 6);
3484         if (IS_ERR(trans)) {
3485                 btrfs_put_root(root);
3486                 return ERR_CAST(trans);
3487         }
3488
3489         err = btrfs_find_free_objectid(root, &objectid);
3490         if (err)
3491                 goto out;
3492
3493         err = __insert_orphan_inode(trans, root, objectid);
3494         BUG_ON(err);
3495
3496         key.objectid = objectid;
3497         key.type = BTRFS_INODE_ITEM_KEY;
3498         key.offset = 0;
3499         inode = btrfs_iget(fs_info->sb, &key, root);
3500         BUG_ON(IS_ERR(inode));
3501         BTRFS_I(inode)->index_cnt = group->start;
3502
3503         err = btrfs_orphan_add(trans, BTRFS_I(inode));
3504 out:
3505         btrfs_put_root(root);
3506         btrfs_end_transaction(trans);
3507         btrfs_btree_balance_dirty(fs_info);
3508         if (err) {
3509                 if (inode)
3510                         iput(inode);
3511                 inode = ERR_PTR(err);
3512         }
3513         return inode;
3514 }
3515
3516 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
3517 {
3518         struct reloc_control *rc;
3519
3520         rc = kzalloc(sizeof(*rc), GFP_NOFS);
3521         if (!rc)
3522                 return NULL;
3523
3524         INIT_LIST_HEAD(&rc->reloc_roots);
3525         INIT_LIST_HEAD(&rc->dirty_subvol_roots);
3526         btrfs_backref_init_cache(fs_info, &rc->backref_cache, 1);
3527         mapping_tree_init(&rc->reloc_root_tree);
3528         extent_io_tree_init(fs_info, &rc->processed_blocks,
3529                             IO_TREE_RELOC_BLOCKS, NULL);
3530         return rc;
3531 }
3532
3533 static void free_reloc_control(struct reloc_control *rc)
3534 {
3535         struct mapping_node *node, *tmp;
3536
3537         free_reloc_roots(&rc->reloc_roots);
3538         rbtree_postorder_for_each_entry_safe(node, tmp,
3539                         &rc->reloc_root_tree.rb_root, rb_node)
3540                 kfree(node);
3541
3542         kfree(rc);
3543 }
3544
3545 /*
3546  * Print the block group being relocated
3547  */
3548 static void describe_relocation(struct btrfs_fs_info *fs_info,
3549                                 struct btrfs_block_group *block_group)
3550 {
3551         char buf[128] = {'\0'};
3552
3553         btrfs_describe_block_groups(block_group->flags, buf, sizeof(buf));
3554
3555         btrfs_info(fs_info,
3556                    "relocating block group %llu flags %s",
3557                    block_group->start, buf);
3558 }
3559
3560 static const char *stage_to_string(int stage)
3561 {
3562         if (stage == MOVE_DATA_EXTENTS)
3563                 return "move data extents";
3564         if (stage == UPDATE_DATA_PTRS)
3565                 return "update data pointers";
3566         return "unknown";
3567 }
3568
3569 /*
3570  * function to relocate all extents in a block group.
3571  */
3572 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
3573 {
3574         struct btrfs_block_group *bg;
3575         struct btrfs_root *extent_root = fs_info->extent_root;
3576         struct reloc_control *rc;
3577         struct inode *inode;
3578         struct btrfs_path *path;
3579         int ret;
3580         int rw = 0;
3581         int err = 0;
3582
3583         bg = btrfs_lookup_block_group(fs_info, group_start);
3584         if (!bg)
3585                 return -ENOENT;
3586
3587         if (btrfs_pinned_by_swapfile(fs_info, bg)) {
3588                 btrfs_put_block_group(bg);
3589                 return -ETXTBSY;
3590         }
3591
3592         rc = alloc_reloc_control(fs_info);
3593         if (!rc) {
3594                 btrfs_put_block_group(bg);
3595                 return -ENOMEM;
3596         }
3597
3598         rc->extent_root = extent_root;
3599         rc->block_group = bg;
3600
3601         ret = btrfs_inc_block_group_ro(rc->block_group, true);
3602         if (ret) {
3603                 err = ret;
3604                 goto out;
3605         }
3606         rw = 1;
3607
3608         path = btrfs_alloc_path();
3609         if (!path) {
3610                 err = -ENOMEM;
3611                 goto out;
3612         }
3613
3614         inode = lookup_free_space_inode(rc->block_group, path);
3615         btrfs_free_path(path);
3616
3617         if (!IS_ERR(inode))
3618                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
3619         else
3620                 ret = PTR_ERR(inode);
3621
3622         if (ret && ret != -ENOENT) {
3623                 err = ret;
3624                 goto out;
3625         }
3626
3627         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
3628         if (IS_ERR(rc->data_inode)) {
3629                 err = PTR_ERR(rc->data_inode);
3630                 rc->data_inode = NULL;
3631                 goto out;
3632         }
3633
3634         describe_relocation(fs_info, rc->block_group);
3635
3636         btrfs_wait_block_group_reservations(rc->block_group);
3637         btrfs_wait_nocow_writers(rc->block_group);
3638         btrfs_wait_ordered_roots(fs_info, U64_MAX,
3639                                  rc->block_group->start,
3640                                  rc->block_group->length);
3641
3642         while (1) {
3643                 int finishes_stage;
3644
3645                 mutex_lock(&fs_info->cleaner_mutex);
3646                 ret = relocate_block_group(rc);
3647                 mutex_unlock(&fs_info->cleaner_mutex);
3648                 if (ret < 0)
3649                         err = ret;
3650
3651                 finishes_stage = rc->stage;
3652                 /*
3653                  * We may have gotten ENOSPC after we already dirtied some
3654                  * extents.  If writeout happens while we're relocating a
3655                  * different block group we could end up hitting the
3656                  * BUG_ON(rc->stage == UPDATE_DATA_PTRS) in
3657                  * btrfs_reloc_cow_block.  Make sure we write everything out
3658                  * properly so we don't trip over this problem, and then break
3659                  * out of the loop if we hit an error.
3660                  */
3661                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
3662                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
3663                                                        (u64)-1);
3664                         if (ret)
3665                                 err = ret;
3666                         invalidate_mapping_pages(rc->data_inode->i_mapping,
3667                                                  0, -1);
3668                         rc->stage = UPDATE_DATA_PTRS;
3669                 }
3670
3671                 if (err < 0)
3672                         goto out;
3673
3674                 if (rc->extents_found == 0)
3675                         break;
3676
3677                 btrfs_info(fs_info, "found %llu extents, stage: %s",
3678                            rc->extents_found, stage_to_string(finishes_stage));
3679         }
3680
3681         WARN_ON(rc->block_group->pinned > 0);
3682         WARN_ON(rc->block_group->reserved > 0);
3683         WARN_ON(rc->block_group->used > 0);
3684 out:
3685         if (err && rw)
3686                 btrfs_dec_block_group_ro(rc->block_group);
3687         iput(rc->data_inode);
3688         btrfs_put_block_group(rc->block_group);
3689         free_reloc_control(rc);
3690         return err;
3691 }
3692
3693 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
3694 {
3695         struct btrfs_fs_info *fs_info = root->fs_info;
3696         struct btrfs_trans_handle *trans;
3697         int ret, err;
3698
3699         trans = btrfs_start_transaction(fs_info->tree_root, 0);
3700         if (IS_ERR(trans))
3701                 return PTR_ERR(trans);
3702
3703         memset(&root->root_item.drop_progress, 0,
3704                 sizeof(root->root_item.drop_progress));
3705         root->root_item.drop_level = 0;
3706         btrfs_set_root_refs(&root->root_item, 0);
3707         ret = btrfs_update_root(trans, fs_info->tree_root,
3708                                 &root->root_key, &root->root_item);
3709
3710         err = btrfs_end_transaction(trans);
3711         if (err)
3712                 return err;
3713         return ret;
3714 }
3715
3716 /*
3717  * recover relocation interrupted by system crash.
3718  *
3719  * this function resumes merging reloc trees with corresponding fs trees.
3720  * this is important for keeping the sharing of tree blocks
3721  */
3722 int btrfs_recover_relocation(struct btrfs_root *root)
3723 {
3724         struct btrfs_fs_info *fs_info = root->fs_info;
3725         LIST_HEAD(reloc_roots);
3726         struct btrfs_key key;
3727         struct btrfs_root *fs_root;
3728         struct btrfs_root *reloc_root;
3729         struct btrfs_path *path;
3730         struct extent_buffer *leaf;
3731         struct reloc_control *rc = NULL;
3732         struct btrfs_trans_handle *trans;
3733         int ret;
3734         int err = 0;
3735
3736         path = btrfs_alloc_path();
3737         if (!path)
3738                 return -ENOMEM;
3739         path->reada = READA_BACK;
3740
3741         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
3742         key.type = BTRFS_ROOT_ITEM_KEY;
3743         key.offset = (u64)-1;
3744
3745         while (1) {
3746                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
3747                                         path, 0, 0);
3748                 if (ret < 0) {
3749                         err = ret;
3750                         goto out;
3751                 }
3752                 if (ret > 0) {
3753                         if (path->slots[0] == 0)
3754                                 break;
3755                         path->slots[0]--;
3756                 }
3757                 leaf = path->nodes[0];
3758                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3759                 btrfs_release_path(path);
3760
3761                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
3762                     key.type != BTRFS_ROOT_ITEM_KEY)
3763                         break;
3764
3765                 reloc_root = btrfs_read_tree_root(root, &key);
3766                 if (IS_ERR(reloc_root)) {
3767                         err = PTR_ERR(reloc_root);
3768                         goto out;
3769                 }
3770
3771                 set_bit(BTRFS_ROOT_SHAREABLE, &reloc_root->state);
3772                 list_add(&reloc_root->root_list, &reloc_roots);
3773
3774                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
3775                         fs_root = read_fs_root(fs_info,
3776                                                reloc_root->root_key.offset);
3777                         if (IS_ERR(fs_root)) {
3778                                 ret = PTR_ERR(fs_root);
3779                                 if (ret != -ENOENT) {
3780                                         err = ret;
3781                                         goto out;
3782                                 }
3783                                 ret = mark_garbage_root(reloc_root);
3784                                 if (ret < 0) {
3785                                         err = ret;
3786                                         goto out;
3787                                 }
3788                         } else {
3789                                 btrfs_put_root(fs_root);
3790                         }
3791                 }
3792
3793                 if (key.offset == 0)
3794                         break;
3795
3796                 key.offset--;
3797         }
3798         btrfs_release_path(path);
3799
3800         if (list_empty(&reloc_roots))
3801                 goto out;
3802
3803         rc = alloc_reloc_control(fs_info);
3804         if (!rc) {
3805                 err = -ENOMEM;
3806                 goto out;
3807         }
3808
3809         rc->extent_root = fs_info->extent_root;
3810
3811         set_reloc_control(rc);
3812
3813         trans = btrfs_join_transaction(rc->extent_root);
3814         if (IS_ERR(trans)) {
3815                 err = PTR_ERR(trans);
3816                 goto out_unset;
3817         }
3818
3819         rc->merge_reloc_tree = 1;
3820
3821         while (!list_empty(&reloc_roots)) {
3822                 reloc_root = list_entry(reloc_roots.next,
3823                                         struct btrfs_root, root_list);
3824                 list_del(&reloc_root->root_list);
3825
3826                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
3827                         list_add_tail(&reloc_root->root_list,
3828                                       &rc->reloc_roots);
3829                         continue;
3830                 }
3831
3832                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
3833                 if (IS_ERR(fs_root)) {
3834                         err = PTR_ERR(fs_root);
3835                         list_add_tail(&reloc_root->root_list, &reloc_roots);
3836                         btrfs_end_transaction(trans);
3837                         goto out_unset;
3838                 }
3839
3840                 err = __add_reloc_root(reloc_root);
3841                 BUG_ON(err < 0); /* -ENOMEM or logic error */
3842                 fs_root->reloc_root = btrfs_grab_root(reloc_root);
3843                 btrfs_put_root(fs_root);
3844         }
3845
3846         err = btrfs_commit_transaction(trans);
3847         if (err)
3848                 goto out_unset;
3849
3850         merge_reloc_roots(rc);
3851
3852         unset_reloc_control(rc);
3853
3854         trans = btrfs_join_transaction(rc->extent_root);
3855         if (IS_ERR(trans)) {
3856                 err = PTR_ERR(trans);
3857                 goto out_clean;
3858         }
3859         err = btrfs_commit_transaction(trans);
3860 out_clean:
3861         ret = clean_dirty_subvols(rc);
3862         if (ret < 0 && !err)
3863                 err = ret;
3864 out_unset:
3865         unset_reloc_control(rc);
3866         free_reloc_control(rc);
3867 out:
3868         free_reloc_roots(&reloc_roots);
3869
3870         btrfs_free_path(path);
3871
3872         if (err == 0) {
3873                 /* cleanup orphan inode in data relocation tree */
3874                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
3875                 if (IS_ERR(fs_root)) {
3876                         err = PTR_ERR(fs_root);
3877                 } else {
3878                         err = btrfs_orphan_cleanup(fs_root);
3879                         btrfs_put_root(fs_root);
3880                 }
3881         }
3882         return err;
3883 }
3884
3885 /*
3886  * helper to add ordered checksum for data relocation.
3887  *
3888  * cloning checksum properly handles the nodatasum extents.
3889  * it also saves CPU time to re-calculate the checksum.
3890  */
3891 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
3892 {
3893         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3894         struct btrfs_ordered_sum *sums;
3895         struct btrfs_ordered_extent *ordered;
3896         int ret;
3897         u64 disk_bytenr;
3898         u64 new_bytenr;
3899         LIST_HEAD(list);
3900
3901         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
3902         BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
3903
3904         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
3905         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
3906                                        disk_bytenr + len - 1, &list, 0);
3907         if (ret)
3908                 goto out;
3909
3910         while (!list_empty(&list)) {
3911                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
3912                 list_del_init(&sums->list);
3913
3914                 /*
3915                  * We need to offset the new_bytenr based on where the csum is.
3916                  * We need to do this because we will read in entire prealloc
3917                  * extents but we may have written to say the middle of the
3918                  * prealloc extent, so we need to make sure the csum goes with
3919                  * the right disk offset.
3920                  *
3921                  * We can do this because the data reloc inode refers strictly
3922                  * to the on disk bytes, so we don't have to worry about
3923                  * disk_len vs real len like with real inodes since it's all
3924                  * disk length.
3925                  */
3926                 new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
3927                 sums->bytenr = new_bytenr;
3928
3929                 btrfs_add_ordered_sum(ordered, sums);
3930         }
3931 out:
3932         btrfs_put_ordered_extent(ordered);
3933         return ret;
3934 }
3935
3936 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
3937                           struct btrfs_root *root, struct extent_buffer *buf,
3938                           struct extent_buffer *cow)
3939 {
3940         struct btrfs_fs_info *fs_info = root->fs_info;
3941         struct reloc_control *rc;
3942         struct btrfs_backref_node *node;
3943         int first_cow = 0;
3944         int level;
3945         int ret = 0;
3946
3947         rc = fs_info->reloc_ctl;
3948         if (!rc)
3949                 return 0;
3950
3951         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
3952                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
3953
3954         level = btrfs_header_level(buf);
3955         if (btrfs_header_generation(buf) <=
3956             btrfs_root_last_snapshot(&root->root_item))
3957                 first_cow = 1;
3958
3959         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
3960             rc->create_reloc_tree) {
3961                 WARN_ON(!first_cow && level == 0);
3962
3963                 node = rc->backref_cache.path[level];
3964                 BUG_ON(node->bytenr != buf->start &&
3965                        node->new_bytenr != buf->start);
3966
3967                 btrfs_backref_drop_node_buffer(node);
3968                 atomic_inc(&cow->refs);
3969                 node->eb = cow;
3970                 node->new_bytenr = cow->start;
3971
3972                 if (!node->pending) {
3973                         list_move_tail(&node->list,
3974                                        &rc->backref_cache.pending[level]);
3975                         node->pending = 1;
3976                 }
3977
3978                 if (first_cow)
3979                         mark_block_processed(rc, node);
3980
3981                 if (first_cow && level > 0)
3982                         rc->nodes_relocated += buf->len;
3983         }
3984
3985         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
3986                 ret = replace_file_extents(trans, rc, root, cow);
3987         return ret;
3988 }
3989
3990 /*
3991  * called before creating snapshot. it calculates metadata reservation
3992  * required for relocating tree blocks in the snapshot
3993  */
3994 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
3995                               u64 *bytes_to_reserve)
3996 {
3997         struct btrfs_root *root = pending->root;
3998         struct reloc_control *rc = root->fs_info->reloc_ctl;
3999
4000         if (!rc || !have_reloc_root(root))
4001                 return;
4002
4003         if (!rc->merge_reloc_tree)
4004                 return;
4005
4006         root = root->reloc_root;
4007         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4008         /*
4009          * relocation is in the stage of merging trees. the space
4010          * used by merging a reloc tree is twice the size of
4011          * relocated tree nodes in the worst case. half for cowing
4012          * the reloc tree, half for cowing the fs tree. the space
4013          * used by cowing the reloc tree will be freed after the
4014          * tree is dropped. if we create snapshot, cowing the fs
4015          * tree may use more space than it frees. so we need
4016          * reserve extra space.
4017          */
4018         *bytes_to_reserve += rc->nodes_relocated;
4019 }
4020
4021 /*
4022  * called after snapshot is created. migrate block reservation
4023  * and create reloc root for the newly created snapshot
4024  *
4025  * This is similar to btrfs_init_reloc_root(), we come out of here with two
4026  * references held on the reloc_root, one for root->reloc_root and one for
4027  * rc->reloc_roots.
4028  */
4029 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4030                                struct btrfs_pending_snapshot *pending)
4031 {
4032         struct btrfs_root *root = pending->root;
4033         struct btrfs_root *reloc_root;
4034         struct btrfs_root *new_root;
4035         struct reloc_control *rc = root->fs_info->reloc_ctl;
4036         int ret;
4037
4038         if (!rc || !have_reloc_root(root))
4039                 return 0;
4040
4041         rc = root->fs_info->reloc_ctl;
4042         rc->merging_rsv_size += rc->nodes_relocated;
4043
4044         if (rc->merge_reloc_tree) {
4045                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4046                                               rc->block_rsv,
4047                                               rc->nodes_relocated, true);
4048                 if (ret)
4049                         return ret;
4050         }
4051
4052         new_root = pending->snap;
4053         reloc_root = create_reloc_root(trans, root->reloc_root,
4054                                        new_root->root_key.objectid);
4055         if (IS_ERR(reloc_root))
4056                 return PTR_ERR(reloc_root);
4057
4058         ret = __add_reloc_root(reloc_root);
4059         BUG_ON(ret < 0);
4060         new_root->reloc_root = btrfs_grab_root(reloc_root);
4061
4062         if (rc->create_reloc_tree)
4063                 ret = clone_backref_node(trans, rc, root, reloc_root);
4064         return ret;
4065 }