fs/btrfs/relocation.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2009 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/writeback.h>
   9 #include <linux/blkdev.h>
  10 #include <linux/rbtree.h>
  11 #include <linux/slab.h>
  12 #include "ctree.h"
  13 #include "disk-io.h"
  14 #include "transaction.h"
  15 #include "volumes.h"
  16 #include "locking.h"
  17 #include "btrfs_inode.h"
  18 #include "async-thread.h"
  19 #include "free-space-cache.h"
  20 #include "inode-map.h"
  21 #include "qgroup.h"
  22 #include "print-tree.h"
  23 #include "delalloc-space.h"
  24 #include "block-group.h"
  25
  26 /*
  27  * backref_node, mapping_node and tree_block start with this
  28  */
  29 struct tree_entry {
  30         struct rb_node rb_node;
  31         u64 bytenr;
  32 };
  33
  34 /*
  35  * present a tree block in the backref cache
  36  */
  37 struct backref_node {
  38         struct rb_node rb_node;
  39         u64 bytenr;
  40
  41         u64 new_bytenr;
  42         /* objectid of tree block owner, can be not uptodate */
  43         u64 owner;
  44         /* link to pending, changed or detached list */
  45         struct list_head list;
  46         /* list of upper level blocks reference this block */
  47         struct list_head upper;
  48         /* list of child blocks in the cache */
  49         struct list_head lower;
  50         /* NULL if this node is not tree root */
  51         struct btrfs_root *root;
  52         /* extent buffer got by COW the block */
  53         struct extent_buffer *eb;
  54         /* level of tree block */
  55         unsigned int level:8;
  56         /* is the block in non-reference counted tree */
  57         unsigned int cowonly:1;
  58         /* 1 if no child node in the cache */
  59         unsigned int lowest:1;
  60         /* is the extent buffer locked */
  61         unsigned int locked:1;
  62         /* has the block been processed */
  63         unsigned int processed:1;
  64         /* have backrefs of this block been checked */
  65         unsigned int checked:1;
  66         /*
  67          * 1 if corresponding block has been cowed but some upper
  68          * level block pointers may not point to the new location
  69          */
  70         unsigned int pending:1;
  71         /*
  72          * 1 if the backref node isn't connected to any other
  73          * backref node.
  74          */
  75         unsigned int detached:1;
  76 };
  77
  78 /*
  79  * present a block pointer in the backref cache
  80  */
  81 struct backref_edge {
  82         struct list_head list[2];
  83         struct backref_node *node[2];
  84 };
  85
  86 #define LOWER   0
  87 #define UPPER   1
  88 #define RELOCATION_RESERVED_NODES       256
  89
  90 struct backref_cache {
  91         /* red black tree of all backref nodes in the cache */
  92         struct rb_root rb_root;
  93         /* for passing backref nodes to btrfs_reloc_cow_block */
  94         struct backref_node *path[BTRFS_MAX_LEVEL];
  95         /*
  96          * list of blocks that have been cowed but some block
  97          * pointers in upper level blocks may not reflect the
  98          * new location
  99          */
 100         struct list_head pending[BTRFS_MAX_LEVEL];
 101         /* list of backref nodes with no child node */
 102         struct list_head leaves;
 103         /* list of blocks that have been cowed in current transaction */
 104         struct list_head changed;
 105         /* list of detached backref node. */
 106         struct list_head detached;
 107
 108         u64 last_trans;
 109
 110         int nr_nodes;
 111         int nr_edges;
 112 };
 113
 114 /*
 115  * map address of tree root to tree
 116  */
 117 struct mapping_node {
 118         struct rb_node rb_node;
 119         u64 bytenr;
 120         void *data;
 121 };
 122
 123 struct mapping_tree {
 124         struct rb_root rb_root;
 125         spinlock_t lock;
 126 };
 127
 128 /*
 129  * present a tree block to process
 130  */
 131 struct tree_block {
 132         struct rb_node rb_node;
 133         u64 bytenr;
 134         struct btrfs_key key;
 135         unsigned int level:8;
 136         unsigned int key_ready:1;
 137 };
 138
 139 #define MAX_EXTENTS 128
 140
 141 struct file_extent_cluster {
 142         u64 start;
 143         u64 end;
 144         u64 boundary[MAX_EXTENTS];
 145         unsigned int nr;
 146 };
 147
 148 struct reloc_control {
 149         /* block group to relocate */
 150         struct btrfs_block_group *block_group;
 151         /* extent tree */
 152         struct btrfs_root *extent_root;
 153         /* inode for moving data */
 154         struct inode *data_inode;
 155
 156         struct btrfs_block_rsv *block_rsv;
 157
 158         struct backref_cache backref_cache;
 159
 160         struct file_extent_cluster cluster;
 161         /* tree blocks have been processed */
 162         struct extent_io_tree processed_blocks;
 163         /* map start of tree root to corresponding reloc tree */
 164         struct mapping_tree reloc_root_tree;
 165         /* list of reloc trees */
 166         struct list_head reloc_roots;
 167         /* list of subvolume trees that get relocated */
 168         struct list_head dirty_subvol_roots;
 169         /* size of metadata reservation for merging reloc trees */
 170         u64 merging_rsv_size;
 171         /* size of relocated tree nodes */
 172         u64 nodes_relocated;
 173         /* reserved size for block group relocation*/
 174         u64 reserved_bytes;
 175
 176         u64 search_start;
 177         u64 extents_found;
 178
 179         unsigned int stage:8;
 180         unsigned int create_reloc_tree:1;
 181         unsigned int merge_reloc_tree:1;
 182         unsigned int found_file_extent:1;
 183 };
 184
 185 /* stages of data relocation */
 186 #define MOVE_DATA_EXTENTS       0
 187 #define UPDATE_DATA_PTRS        1
 188
 189 static void remove_backref_node(struct backref_cache *cache,
 190                                 struct backref_node *node);
 191 static void __mark_block_processed(struct reloc_control *rc,
 192                                    struct backref_node *node);
 193
 194 static void mapping_tree_init(struct mapping_tree *tree)
 195 {
 196         tree->rb_root = RB_ROOT;
 197         spin_lock_init(&tree->lock);
 198 }
 199
 200 static void backref_cache_init(struct backref_cache *cache)
 201 {
 202         int i;
 203         cache->rb_root = RB_ROOT;
 204         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 205                 INIT_LIST_HEAD(&cache->pending[i]);
 206         INIT_LIST_HEAD(&cache->changed);
 207         INIT_LIST_HEAD(&cache->detached);
 208         INIT_LIST_HEAD(&cache->leaves);
 209 }
 210
 211 static void backref_cache_cleanup(struct backref_cache *cache)
 212 {
 213         struct backref_node *node;
 214         int i;
 215
 216         while (!list_empty(&cache->detached)) {
 217                 node = list_entry(cache->detached.next,
 218                                   struct backref_node, list);
 219                 remove_backref_node(cache, node);
 220         }
 221
 222         while (!list_empty(&cache->leaves)) {
 223                 node = list_entry(cache->leaves.next,
 224                                   struct backref_node, lower);
 225                 remove_backref_node(cache, node);
 226         }
 227
 228         cache->last_trans = 0;
 229
 230         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 231                 ASSERT(list_empty(&cache->pending[i]));
 232         ASSERT(list_empty(&cache->changed));
 233         ASSERT(list_empty(&cache->detached));
 234         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
 235         ASSERT(!cache->nr_nodes);
 236         ASSERT(!cache->nr_edges);
 237 }
 238
 239 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
 240 {
 241         struct backref_node *node;
 242
 243         node = kzalloc(sizeof(*node), GFP_NOFS);
 244         if (node) {
 245                 INIT_LIST_HEAD(&node->list);
 246                 INIT_LIST_HEAD(&node->upper);
 247                 INIT_LIST_HEAD(&node->lower);
 248                 RB_CLEAR_NODE(&node->rb_node);
 249                 cache->nr_nodes++;
 250         }
 251         return node;
 252 }
 253
 254 static void free_backref_node(struct backref_cache *cache,
 255                               struct backref_node *node)
 256 {
 257         if (node) {
 258                 cache->nr_nodes--;
 259                 kfree(node);
 260         }
 261 }
 262
 263 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
 264 {
 265         struct backref_edge *edge;
 266
 267         edge = kzalloc(sizeof(*edge), GFP_NOFS);
 268         if (edge)
 269                 cache->nr_edges++;
 270         return edge;
 271 }
 272
 273 static void free_backref_edge(struct backref_cache *cache,
 274                               struct backref_edge *edge)
 275 {
 276         if (edge) {
 277                 cache->nr_edges--;
 278                 kfree(edge);
 279         }
 280 }
 281
 282 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
 283                                    struct rb_node *node)
 284 {
 285         struct rb_node **p = &root->rb_node;
 286         struct rb_node *parent = NULL;
 287         struct tree_entry *entry;
 288
 289         while (*p) {
 290                 parent = *p;
 291                 entry = rb_entry(parent, struct tree_entry, rb_node);
 292
 293                 if (bytenr < entry->bytenr)
 294                         p = &(*p)->rb_left;
 295                 else if (bytenr > entry->bytenr)
 296                         p = &(*p)->rb_right;
 297                 else
 298                         return parent;
 299         }
 300
 301         rb_link_node(node, parent, p);
 302         rb_insert_color(node, root);
 303         return NULL;
 304 }
 305
 306 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
 307 {
 308         struct rb_node *n = root->rb_node;
 309         struct tree_entry *entry;
 310
 311         while (n) {
 312                 entry = rb_entry(n, struct tree_entry, rb_node);
 313
 314                 if (bytenr < entry->bytenr)
 315                         n = n->rb_left;
 316                 else if (bytenr > entry->bytenr)
 317                         n = n->rb_right;
 318                 else
 319                         return n;
 320         }
 321         return NULL;
 322 }
 323
 324 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
 325 {
 326
 327         struct btrfs_fs_info *fs_info = NULL;
 328         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
 329                                               rb_node);
 330         if (bnode->root)
 331                 fs_info = bnode->root->fs_info;
 332         btrfs_panic(fs_info, errno,
 333                     "Inconsistency in backref cache found at offset %llu",
 334                     bytenr);
 335 }
 336
 337 /*
 338  * walk up backref nodes until reach node presents tree root
 339  */
 340 static struct backref_node *walk_up_backref(struct backref_node *node,
 341                                             struct backref_edge *edges[],
 342                                             int *index)
 343 {
 344         struct backref_edge *edge;
 345         int idx = *index;
 346
 347         while (!list_empty(&node->upper)) {
 348                 edge = list_entry(node->upper.next,
 349                                   struct backref_edge, list[LOWER]);
 350                 edges[idx++] = edge;
 351                 node = edge->node[UPPER];
 352         }
 353         BUG_ON(node->detached);
 354         *index = idx;
 355         return node;
 356 }
 357
 358 /*
 359  * walk down backref nodes to find start of next reference path
 360  */
 361 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
 362                                               int *index)
 363 {
 364         struct backref_edge *edge;
 365         struct backref_node *lower;
 366         int idx = *index;
 367
 368         while (idx > 0) {
 369                 edge = edges[idx - 1];
 370                 lower = edge->node[LOWER];
 371                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 372                         idx--;
 373                         continue;
 374                 }
 375                 edge = list_entry(edge->list[LOWER].next,
 376                                   struct backref_edge, list[LOWER]);
 377                 edges[idx - 1] = edge;
 378                 *index = idx;
 379                 return edge->node[UPPER];
 380         }
 381         *index = 0;
 382         return NULL;
 383 }
 384
 385 static void unlock_node_buffer(struct backref_node *node)
 386 {
 387         if (node->locked) {
 388                 btrfs_tree_unlock(node->eb);
 389                 node->locked = 0;
 390         }
 391 }
 392
 393 static void drop_node_buffer(struct backref_node *node)
 394 {
 395         if (node->eb) {
 396                 unlock_node_buffer(node);
 397                 free_extent_buffer(node->eb);
 398                 node->eb = NULL;
 399         }
 400 }
 401
 402 static void drop_backref_node(struct backref_cache *tree,
 403                               struct backref_node *node)
 404 {
 405         BUG_ON(!list_empty(&node->upper));
 406
 407         drop_node_buffer(node);
 408         list_del(&node->list);
 409         list_del(&node->lower);
 410         if (!RB_EMPTY_NODE(&node->rb_node))
 411                 rb_erase(&node->rb_node, &tree->rb_root);
 412         free_backref_node(tree, node);
 413 }
 414
 415 /*
 416  * remove a backref node from the backref cache
 417  */
 418 static void remove_backref_node(struct backref_cache *cache,
 419                                 struct backref_node *node)
 420 {
 421         struct backref_node *upper;
 422         struct backref_edge *edge;
 423
 424         if (!node)
 425                 return;
 426
 427         BUG_ON(!node->lowest && !node->detached);
 428         while (!list_empty(&node->upper)) {
 429                 edge = list_entry(node->upper.next, struct backref_edge,
 430                                   list[LOWER]);
 431                 upper = edge->node[UPPER];
 432                 list_del(&edge->list[LOWER]);
 433                 list_del(&edge->list[UPPER]);
 434                 free_backref_edge(cache, edge);
 435
 436                 if (RB_EMPTY_NODE(&upper->rb_node)) {
 437                         BUG_ON(!list_empty(&node->upper));
 438                         drop_backref_node(cache, node);
 439                         node = upper;
 440                         node->lowest = 1;
 441                         continue;
 442                 }
 443                 /*
 444                  * add the node to leaf node list if no other
 445                  * child block cached.
 446                  */
 447                 if (list_empty(&upper->lower)) {
 448                         list_add_tail(&upper->lower, &cache->leaves);
 449                         upper->lowest = 1;
 450                 }
 451         }
 452
 453         drop_backref_node(cache, node);
 454 }
 455
 456 static void update_backref_node(struct backref_cache *cache,
 457                                 struct backref_node *node, u64 bytenr)
 458 {
 459         struct rb_node *rb_node;
 460         rb_erase(&node->rb_node, &cache->rb_root);
 461         node->bytenr = bytenr;
 462         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 463         if (rb_node)
 464                 backref_tree_panic(rb_node, -EEXIST, bytenr);
 465 }
 466
 467 /*
 468  * update backref cache after a transaction commit
 469  */
 470 static int update_backref_cache(struct btrfs_trans_handle *trans,
 471                                 struct backref_cache *cache)
 472 {
 473         struct backref_node *node;
 474         int level = 0;
 475
 476         if (cache->last_trans == 0) {
 477                 cache->last_trans = trans->transid;
 478                 return 0;
 479         }
 480
 481         if (cache->last_trans == trans->transid)
 482                 return 0;
 483
 484         /*
 485          * detached nodes are used to avoid unnecessary backref
 486          * lookup. transaction commit changes the extent tree.
 487          * so the detached nodes are no longer useful.
 488          */
 489         while (!list_empty(&cache->detached)) {
 490                 node = list_entry(cache->detached.next,
 491                                   struct backref_node, list);
 492                 remove_backref_node(cache, node);
 493         }
 494
 495         while (!list_empty(&cache->changed)) {
 496                 node = list_entry(cache->changed.next,
 497                                   struct backref_node, list);
 498                 list_del_init(&node->list);
 499                 BUG_ON(node->pending);
 500                 update_backref_node(cache, node, node->new_bytenr);
 501         }
 502
 503         /*
 504          * some nodes can be left in the pending list if there were
 505          * errors during processing the pending nodes.
 506          */
 507         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 508                 list_for_each_entry(node, &cache->pending[level], list) {
 509                         BUG_ON(!node->pending);
 510                         if (node->bytenr == node->new_bytenr)
 511                                 continue;
 512                         update_backref_node(cache, node, node->new_bytenr);
 513                 }
 514         }
 515
 516         cache->last_trans = 0;
 517         return 1;
 518 }
 519
 520 static bool reloc_root_is_dead(struct btrfs_root *root)
 521 {
 522         /*
 523          * Pair with set_bit/clear_bit in clean_dirty_subvols and
 524          * btrfs_update_reloc_root. We need to see the updated bit before
 525          * trying to access reloc_root
 526          */
 527         smp_rmb();
 528         if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
 529                 return true;
 530         return false;
 531 }
 532
 533 /*
 534  * Check if this subvolume tree has valid reloc tree.
 535  *
 536  * Reloc tree after swap is considered dead, thus not considered as valid.
 537  * This is enough for most callers, as they don't distinguish dead reloc root
 538  * from no reloc root.  But should_ignore_root() below is a special case.
 539  */
 540 static bool have_reloc_root(struct btrfs_root *root)
 541 {
 542         if (reloc_root_is_dead(root))
 543                 return false;
 544         if (!root->reloc_root)
 545                 return false;
 546         return true;
 547 }
 548
 549 static int should_ignore_root(struct btrfs_root *root)
 550 {
 551         struct btrfs_root *reloc_root;
 552
 553         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 554                 return 0;
 555
 556         /* This root has been merged with its reloc tree, we can ignore it */
 557         if (reloc_root_is_dead(root))
 558                 return 1;
 559
 560         reloc_root = root->reloc_root;
 561         if (!reloc_root)
 562                 return 0;
 563
 564         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
 565             root->fs_info->running_transaction->transid - 1)
 566                 return 0;
 567         /*
 568          * if there is reloc tree and it was created in previous
 569          * transaction backref lookup can find the reloc tree,
 570          * so backref node for the fs tree root is useless for
 571          * relocation.
 572          */
 573         return 1;
 574 }
 575 /*
 576  * find reloc tree by address of tree root
 577  */
 578 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
 579                                           u64 bytenr)
 580 {
 581         struct rb_node *rb_node;
 582         struct mapping_node *node;
 583         struct btrfs_root *root = NULL;
 584
 585         spin_lock(&rc->reloc_root_tree.lock);
 586         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
 587         if (rb_node) {
 588                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 589                 root = (struct btrfs_root *)node->data;
 590         }
 591         spin_unlock(&rc->reloc_root_tree.lock);
 592         return root;
 593 }
 594
 595 static int is_cowonly_root(u64 root_objectid)
 596 {
 597         if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
 598             root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
 599             root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
 600             root_objectid == BTRFS_DEV_TREE_OBJECTID ||
 601             root_objectid == BTRFS_TREE_LOG_OBJECTID ||
 602             root_objectid == BTRFS_CSUM_TREE_OBJECTID ||
 603             root_objectid == BTRFS_UUID_TREE_OBJECTID ||
 604             root_objectid == BTRFS_QUOTA_TREE_OBJECTID ||
 605             root_objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
 606                 return 1;
 607         return 0;
 608 }
 609
 610 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 611                                         u64 root_objectid)
 612 {
 613         struct btrfs_key key;
 614
 615         key.objectid = root_objectid;
 616         key.type = BTRFS_ROOT_ITEM_KEY;
 617         if (is_cowonly_root(root_objectid))
 618                 key.offset = 0;
 619         else
 620                 key.offset = (u64)-1;
 621
 622         return btrfs_get_fs_root(fs_info, &key, false);
 623 }
 624
 625 static noinline_for_stack
 626 int find_inline_backref(struct extent_buffer *leaf, int slot,
 627                         unsigned long *ptr, unsigned long *end)
 628 {
 629         struct btrfs_key key;
 630         struct btrfs_extent_item *ei;
 631         struct btrfs_tree_block_info *bi;
 632         u32 item_size;
 633
 634         btrfs_item_key_to_cpu(leaf, &key, slot);
 635
 636         item_size = btrfs_item_size_nr(leaf, slot);
 637         if (item_size < sizeof(*ei)) {
 638                 btrfs_print_v0_err(leaf->fs_info);
 639                 btrfs_handle_fs_error(leaf->fs_info, -EINVAL, NULL);
 640                 return 1;
 641         }
 642         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 643         WARN_ON(!(btrfs_extent_flags(leaf, ei) &
 644                   BTRFS_EXTENT_FLAG_TREE_BLOCK));
 645
 646         if (key.type == BTRFS_EXTENT_ITEM_KEY &&
 647             item_size <= sizeof(*ei) + sizeof(*bi)) {
 648                 WARN_ON(item_size < sizeof(*ei) + sizeof(*bi));
 649                 return 1;
 650         }
 651         if (key.type == BTRFS_METADATA_ITEM_KEY &&
 652             item_size <= sizeof(*ei)) {
 653                 WARN_ON(item_size < sizeof(*ei));
 654                 return 1;
 655         }
 656
 657         if (key.type == BTRFS_EXTENT_ITEM_KEY) {
 658                 bi = (struct btrfs_tree_block_info *)(ei + 1);
 659                 *ptr = (unsigned long)(bi + 1);
 660         } else {
 661                 *ptr = (unsigned long)(ei + 1);
 662         }
 663         *end = (unsigned long)ei + item_size;
 664         return 0;
 665 }
 666
 667 /*
 668  * build backref tree for a given tree block. root of the backref tree
 669  * corresponds the tree block, leaves of the backref tree correspond
 670  * roots of b-trees that reference the tree block.
 671  *
 672  * the basic idea of this function is check backrefs of a given block
 673  * to find upper level blocks that reference the block, and then check
 674  * backrefs of these upper level blocks recursively. the recursion stop
 675  * when tree root is reached or backrefs for the block is cached.
 676  *
 677  * NOTE: if we find backrefs for a block are cached, we know backrefs
 678  * for all upper level blocks that directly/indirectly reference the
 679  * block are also cached.
 680  */
 681 static noinline_for_stack
 682 struct backref_node *build_backref_tree(struct reloc_control *rc,
 683                                         struct btrfs_key *node_key,
 684                                         int level, u64 bytenr)
 685 {
 686         struct backref_cache *cache = &rc->backref_cache;
 687         struct btrfs_path *path1; /* For searching extent root */
 688         struct btrfs_path *path2; /* For searching parent of TREE_BLOCK_REF */
 689         struct extent_buffer *eb;
 690         struct btrfs_root *root;
 691         struct backref_node *cur;
 692         struct backref_node *upper;
 693         struct backref_node *lower;
 694         struct backref_node *node = NULL;
 695         struct backref_node *exist = NULL;
 696         struct backref_edge *edge;
 697         struct rb_node *rb_node;
 698         struct btrfs_key key;
 699         unsigned long end;
 700         unsigned long ptr;
 701         LIST_HEAD(list); /* Pending edge list, upper node needs to be checked */
 702         LIST_HEAD(useless);
 703         int cowonly;
 704         int ret;
 705         int err = 0;
 706         bool need_check = true;
 707
 708         path1 = btrfs_alloc_path();
 709         path2 = btrfs_alloc_path();
 710         if (!path1 || !path2) {
 711                 err = -ENOMEM;
 712                 goto out;
 713         }
 714         path1->reada = READA_FORWARD;
 715         path2->reada = READA_FORWARD;
 716
 717         node = alloc_backref_node(cache);
 718         if (!node) {
 719                 err = -ENOMEM;
 720                 goto out;
 721         }
 722
 723         node->bytenr = bytenr;
 724         node->level = level;
 725         node->lowest = 1;
 726         cur = node;
 727 again:
 728         end = 0;
 729         ptr = 0;
 730         key.objectid = cur->bytenr;
 731         key.type = BTRFS_METADATA_ITEM_KEY;
 732         key.offset = (u64)-1;
 733
 734         path1->search_commit_root = 1;
 735         path1->skip_locking = 1;
 736         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path1,
 737                                 0, 0);
 738         if (ret < 0) {
 739                 err = ret;
 740                 goto out;
 741         }
 742         ASSERT(ret);
 743         ASSERT(path1->slots[0]);
 744
 745         path1->slots[0]--;
 746
 747         WARN_ON(cur->checked);
 748         if (!list_empty(&cur->upper)) {
 749                 /*
 750                  * the backref was added previously when processing
 751                  * backref of type BTRFS_TREE_BLOCK_REF_KEY
 752                  */
 753                 ASSERT(list_is_singular(&cur->upper));
 754                 edge = list_entry(cur->upper.next, struct backref_edge,
 755                                   list[LOWER]);
 756                 ASSERT(list_empty(&edge->list[UPPER]));
 757                 exist = edge->node[UPPER];
 758                 /*
 759                  * add the upper level block to pending list if we need
 760                  * check its backrefs
 761                  */
 762                 if (!exist->checked)
 763                         list_add_tail(&edge->list[UPPER], &list);
 764         } else {
 765                 exist = NULL;
 766         }
 767
 768         while (1) {
 769                 cond_resched();
 770                 eb = path1->nodes[0];
 771
 772                 if (ptr >= end) {
 773                         if (path1->slots[0] >= btrfs_header_nritems(eb)) {
 774                                 ret = btrfs_next_leaf(rc->extent_root, path1);
 775                                 if (ret < 0) {
 776                                         err = ret;
 777                                         goto out;
 778                                 }
 779                                 if (ret > 0)
 780                                         break;
 781                                 eb = path1->nodes[0];
 782                         }
 783
 784                         btrfs_item_key_to_cpu(eb, &key, path1->slots[0]);
 785                         if (key.objectid != cur->bytenr) {
 786                                 WARN_ON(exist);
 787                                 break;
 788                         }
 789
 790                         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
 791                             key.type == BTRFS_METADATA_ITEM_KEY) {
 792                                 ret = find_inline_backref(eb, path1->slots[0],
 793                                                           &ptr, &end);
 794                                 if (ret)
 795                                         goto next;
 796                         }
 797                 }
 798
 799                 if (ptr < end) {
 800                         /* update key for inline back ref */
 801                         struct btrfs_extent_inline_ref *iref;
 802                         int type;
 803                         iref = (struct btrfs_extent_inline_ref *)ptr;
 804                         type = btrfs_get_extent_inline_ref_type(eb, iref,
 805                                                         BTRFS_REF_TYPE_BLOCK);
 806                         if (type == BTRFS_REF_TYPE_INVALID) {
 807                                 err = -EUCLEAN;
 808                                 goto out;
 809                         }
 810                         key.type = type;
 811                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
 812
 813                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
 814                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
 815                 }
 816
 817                 /*
 818                  * Parent node found and matches current inline ref, no need to
 819                  * rebuild this node for this inline ref.
 820                  */
 821                 if (exist &&
 822                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
 823                       exist->owner == key.offset) ||
 824                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
 825                       exist->bytenr == key.offset))) {
 826                         exist = NULL;
 827                         goto next;
 828                 }
 829
 830                 /* SHARED_BLOCK_REF means key.offset is the parent bytenr */
 831                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
 832                         if (key.objectid == key.offset) {
 833                                 /*
 834                                  * Only root blocks of reloc trees use backref
 835                                  * pointing to itself.
 836                                  */
 837                                 root = find_reloc_root(rc, cur->bytenr);
 838                                 ASSERT(root);
 839                                 cur->root = root;
 840                                 break;
 841                         }
 842
 843                         edge = alloc_backref_edge(cache);
 844                         if (!edge) {
 845                                 err = -ENOMEM;
 846                                 goto out;
 847                         }
 848                         rb_node = tree_search(&cache->rb_root, key.offset);
 849                         if (!rb_node) {
 850                                 upper = alloc_backref_node(cache);
 851                                 if (!upper) {
 852                                         free_backref_edge(cache, edge);
 853                                         err = -ENOMEM;
 854                                         goto out;
 855                                 }
 856                                 upper->bytenr = key.offset;
 857                                 upper->level = cur->level + 1;
 858                                 /*
 859                                  *  backrefs for the upper level block isn't
 860                                  *  cached, add the block to pending list
 861                                  */
 862                                 list_add_tail(&edge->list[UPPER], &list);
 863                         } else {
 864                                 upper = rb_entry(rb_node, struct backref_node,
 865                                                  rb_node);
 866                                 ASSERT(upper->checked);
 867                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 868                         }
 869                         list_add_tail(&edge->list[LOWER], &cur->upper);
 870                         edge->node[LOWER] = cur;
 871                         edge->node[UPPER] = upper;
 872
 873                         goto next;
 874                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
 875                         err = -EINVAL;
 876                         btrfs_print_v0_err(rc->extent_root->fs_info);
 877                         btrfs_handle_fs_error(rc->extent_root->fs_info, err,
 878                                               NULL);
 879                         goto out;
 880                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
 881                         goto next;
 882                 }
 883
 884                 /*
 885                  * key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref offset
 886                  * means the root objectid. We need to search the tree to get
 887                  * its parent bytenr.
 888                  */
 889                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
 890                 if (IS_ERR(root)) {
 891                         err = PTR_ERR(root);
 892                         goto out;
 893                 }
 894
 895                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 896                         cur->cowonly = 1;
 897
 898                 if (btrfs_root_level(&root->root_item) == cur->level) {
 899                         /* tree root */
 900                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
 901                                cur->bytenr);
 902                         if (should_ignore_root(root))
 903                                 list_add(&cur->list, &useless);
 904                         else
 905                                 cur->root = root;
 906                         break;
 907                 }
 908
 909                 level = cur->level + 1;
 910
 911                 /* Search the tree to find parent blocks referring the block. */
 912                 path2->search_commit_root = 1;
 913                 path2->skip_locking = 1;
 914                 path2->lowest_level = level;
 915                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
 916                 path2->lowest_level = 0;
 917                 if (ret < 0) {
 918                         err = ret;
 919                         goto out;
 920                 }
 921                 if (ret > 0 && path2->slots[level] > 0)
 922                         path2->slots[level]--;
 923
 924                 eb = path2->nodes[level];
 925                 if (btrfs_node_blockptr(eb, path2->slots[level]) !=
 926                     cur->bytenr) {
 927                         btrfs_err(root->fs_info,
 928         "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
 929                                   cur->bytenr, level - 1,
 930                                   root->root_key.objectid,
 931                                   node_key->objectid, node_key->type,
 932                                   node_key->offset);
 933                         err = -ENOENT;
 934                         goto out;
 935                 }
 936                 lower = cur;
 937                 need_check = true;
 938
 939                 /* Add all nodes and edges in the path */
 940                 for (; level < BTRFS_MAX_LEVEL; level++) {
 941                         if (!path2->nodes[level]) {
 942                                 ASSERT(btrfs_root_bytenr(&root->root_item) ==
 943                                        lower->bytenr);
 944                                 if (should_ignore_root(root))
 945                                         list_add(&lower->list, &useless);
 946                                 else
 947                                         lower->root = root;
 948                                 break;
 949                         }
 950
 951                         edge = alloc_backref_edge(cache);
 952                         if (!edge) {
 953                                 err = -ENOMEM;
 954                                 goto out;
 955                         }
 956
 957                         eb = path2->nodes[level];
 958                         rb_node = tree_search(&cache->rb_root, eb->start);
 959                         if (!rb_node) {
 960                                 upper = alloc_backref_node(cache);
 961                                 if (!upper) {
 962                                         free_backref_edge(cache, edge);
 963                                         err = -ENOMEM;
 964                                         goto out;
 965                                 }
 966                                 upper->bytenr = eb->start;
 967                                 upper->owner = btrfs_header_owner(eb);
 968                                 upper->level = lower->level + 1;
 969                                 if (!test_bit(BTRFS_ROOT_REF_COWS,
 970                                               &root->state))
 971                                         upper->cowonly = 1;
 972
 973                                 /*
 974                                  * if we know the block isn't shared
 975                                  * we can void checking its backrefs.
 976                                  */
 977                                 if (btrfs_block_can_be_shared(root, eb))
 978                                         upper->checked = 0;
 979                                 else
 980                                         upper->checked = 1;
 981
 982                                 /*
 983                                  * add the block to pending list if we
 984                                  * need check its backrefs, we only do this once
 985                                  * while walking up a tree as we will catch
 986                                  * anything else later on.
 987                                  */
 988                                 if (!upper->checked && need_check) {
 989                                         need_check = false;
 990                                         list_add_tail(&edge->list[UPPER],
 991                                                       &list);
 992                                 } else {
 993                                         if (upper->checked)
 994                                                 need_check = true;
 995                                         INIT_LIST_HEAD(&edge->list[UPPER]);
 996                                 }
 997                         } else {
 998                                 upper = rb_entry(rb_node, struct backref_node,
 999                                                  rb_node);
1000                                 ASSERT(upper->checked);
1001                                 INIT_LIST_HEAD(&edge->list[UPPER]);
1002                                 if (!upper->owner)
1003                                         upper->owner = btrfs_header_owner(eb);
1004                         }
1005                         list_add_tail(&edge->list[LOWER], &lower->upper);
1006                         edge->node[LOWER] = lower;
1007                         edge->node[UPPER] = upper;
1008
1009                         if (rb_node)
1010                                 break;
1011                         lower = upper;
1012                         upper = NULL;
1013                 }
1014                 btrfs_release_path(path2);
1015 next:
1016                 if (ptr < end) {
1017                         ptr += btrfs_extent_inline_ref_size(key.type);
1018                         if (ptr >= end) {
1019                                 WARN_ON(ptr > end);
1020                                 ptr = 0;
1021                                 end = 0;
1022                         }
1023                 }
1024                 if (ptr >= end)
1025                         path1->slots[0]++;
1026         }
1027         btrfs_release_path(path1);
1028
1029         cur->checked = 1;
1030         WARN_ON(exist);
1031
1032         /* the pending list isn't empty, take the first block to process */
1033         if (!list_empty(&list)) {
1034                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1035                 list_del_init(&edge->list[UPPER]);
1036                 cur = edge->node[UPPER];
1037                 goto again;
1038         }
1039
1040         /*
1041          * everything goes well, connect backref nodes and insert backref nodes
1042          * into the cache.
1043          */
1044         ASSERT(node->checked);
1045         cowonly = node->cowonly;
1046         if (!cowonly) {
1047                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1048                                       &node->rb_node);
1049                 if (rb_node)
1050                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1051                 list_add_tail(&node->lower, &cache->leaves);
1052         }
1053
1054         list_for_each_entry(edge, &node->upper, list[LOWER])
1055                 list_add_tail(&edge->list[UPPER], &list);
1056
1057         while (!list_empty(&list)) {
1058                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1059                 list_del_init(&edge->list[UPPER]);
1060                 upper = edge->node[UPPER];
1061                 if (upper->detached) {
1062                         list_del(&edge->list[LOWER]);
1063                         lower = edge->node[LOWER];
1064                         free_backref_edge(cache, edge);
1065                         if (list_empty(&lower->upper))
1066                                 list_add(&lower->list, &useless);
1067                         continue;
1068                 }
1069
1070                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1071                         if (upper->lowest) {
1072                                 list_del_init(&upper->lower);
1073                                 upper->lowest = 0;
1074                         }
1075
1076                         list_add_tail(&edge->list[UPPER], &upper->lower);
1077                         continue;
1078                 }
1079
1080                 if (!upper->checked) {
1081                         /*
1082                          * Still want to blow up for developers since this is a
1083                          * logic bug.
1084                          */
1085                         ASSERT(0);
1086                         err = -EINVAL;
1087                         goto out;
1088                 }
1089                 if (cowonly != upper->cowonly) {
1090                         ASSERT(0);
1091                         err = -EINVAL;
1092                         goto out;
1093                 }
1094
1095                 if (!cowonly) {
1096                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1097                                               &upper->rb_node);
1098                         if (rb_node)
1099                                 backref_tree_panic(rb_node, -EEXIST,
1100                                                    upper->bytenr);
1101                 }
1102
1103                 list_add_tail(&edge->list[UPPER], &upper->lower);
1104
1105                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1106                         list_add_tail(&edge->list[UPPER], &list);
1107         }
1108         /*
1109          * process useless backref nodes. backref nodes for tree leaves
1110          * are deleted from the cache. backref nodes for upper level
1111          * tree blocks are left in the cache to avoid unnecessary backref
1112          * lookup.
1113          */
1114         while (!list_empty(&useless)) {
1115                 upper = list_entry(useless.next, struct backref_node, list);
1116                 list_del_init(&upper->list);
1117                 ASSERT(list_empty(&upper->upper));
1118                 if (upper == node)
1119                         node = NULL;
1120                 if (upper->lowest) {
1121                         list_del_init(&upper->lower);
1122                         upper->lowest = 0;
1123                 }
1124                 while (!list_empty(&upper->lower)) {
1125                         edge = list_entry(upper->lower.next,
1126                                           struct backref_edge, list[UPPER]);
1127                         list_del(&edge->list[UPPER]);
1128                         list_del(&edge->list[LOWER]);
1129                         lower = edge->node[LOWER];
1130                         free_backref_edge(cache, edge);
1131
1132                         if (list_empty(&lower->upper))
1133                                 list_add(&lower->list, &useless);
1134                 }
1135                 __mark_block_processed(rc, upper);
1136                 if (upper->level > 0) {
1137                         list_add(&upper->list, &cache->detached);
1138                         upper->detached = 1;
1139                 } else {
1140                         rb_erase(&upper->rb_node, &cache->rb_root);
1141                         free_backref_node(cache, upper);
1142                 }
1143         }
1144 out:
1145         btrfs_free_path(path1);
1146         btrfs_free_path(path2);
1147         if (err) {
1148                 while (!list_empty(&useless)) {
1149                         lower = list_entry(useless.next,
1150                                            struct backref_node, list);
1151                         list_del_init(&lower->list);
1152                 }
1153                 while (!list_empty(&list)) {
1154                         edge = list_first_entry(&list, struct backref_edge,
1155                                                 list[UPPER]);
1156                         list_del(&edge->list[UPPER]);
1157                         list_del(&edge->list[LOWER]);
1158                         lower = edge->node[LOWER];
1159                         upper = edge->node[UPPER];
1160                         free_backref_edge(cache, edge);
1161
1162                         /*
1163                          * Lower is no longer linked to any upper backref nodes
1164                          * and isn't in the cache, we can free it ourselves.
1165                          */
1166                         if (list_empty(&lower->upper) &&
1167                             RB_EMPTY_NODE(&lower->rb_node))
1168                                 list_add(&lower->list, &useless);
1169
1170                         if (!RB_EMPTY_NODE(&upper->rb_node))
1171                                 continue;
1172
1173                         /* Add this guy's upper edges to the list to process */
1174                         list_for_each_entry(edge, &upper->upper, list[LOWER])
1175                                 list_add_tail(&edge->list[UPPER], &list);
1176                         if (list_empty(&upper->upper))
1177                                 list_add(&upper->list, &useless);
1178                 }
1179
1180                 while (!list_empty(&useless)) {
1181                         lower = list_entry(useless.next,
1182                                            struct backref_node, list);
1183                         list_del_init(&lower->list);
1184                         if (lower == node)
1185                                 node = NULL;
1186                         free_backref_node(cache, lower);
1187                 }
1188
1189                 free_backref_node(cache, node);
1190                 return ERR_PTR(err);
1191         }
1192         ASSERT(!node || !node->detached);
1193         return node;
1194 }
1195
1196 /*
1197  * helper to add backref node for the newly created snapshot.
1198  * the backref node is created by cloning backref node that
1199  * corresponds to root of source tree
1200  */
1201 static int clone_backref_node(struct btrfs_trans_handle *trans,
1202                               struct reloc_control *rc,
1203                               struct btrfs_root *src,
1204                               struct btrfs_root *dest)
1205 {
1206         struct btrfs_root *reloc_root = src->reloc_root;
1207         struct backref_cache *cache = &rc->backref_cache;
1208         struct backref_node *node = NULL;
1209         struct backref_node *new_node;
1210         struct backref_edge *edge;
1211         struct backref_edge *new_edge;
1212         struct rb_node *rb_node;
1213
1214         if (cache->last_trans > 0)
1215                 update_backref_cache(trans, cache);
1216
1217         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1218         if (rb_node) {
1219                 node = rb_entry(rb_node, struct backref_node, rb_node);
1220                 if (node->detached)
1221                         node = NULL;
1222                 else
1223                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1224         }
1225
1226         if (!node) {
1227                 rb_node = tree_search(&cache->rb_root,
1228                                       reloc_root->commit_root->start);
1229                 if (rb_node) {
1230                         node = rb_entry(rb_node, struct backref_node,
1231                                         rb_node);
1232                         BUG_ON(node->detached);
1233                 }
1234         }
1235
1236         if (!node)
1237                 return 0;
1238
1239         new_node = alloc_backref_node(cache);
1240         if (!new_node)
1241                 return -ENOMEM;
1242
1243         new_node->bytenr = dest->node->start;
1244         new_node->level = node->level;
1245         new_node->lowest = node->lowest;
1246         new_node->checked = 1;
1247         new_node->root = dest;
1248
1249         if (!node->lowest) {
1250                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1251                         new_edge = alloc_backref_edge(cache);
1252                         if (!new_edge)
1253                                 goto fail;
1254
1255                         new_edge->node[UPPER] = new_node;
1256                         new_edge->node[LOWER] = edge->node[LOWER];
1257                         list_add_tail(&new_edge->list[UPPER],
1258                                       &new_node->lower);
1259                 }
1260         } else {
1261                 list_add_tail(&new_node->lower, &cache->leaves);
1262         }
1263
1264         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1265                               &new_node->rb_node);
1266         if (rb_node)
1267                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1268
1269         if (!new_node->lowest) {
1270                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1271                         list_add_tail(&new_edge->list[LOWER],
1272                                       &new_edge->node[LOWER]->upper);
1273                 }
1274         }
1275         return 0;
1276 fail:
1277         while (!list_empty(&new_node->lower)) {
1278                 new_edge = list_entry(new_node->lower.next,
1279                                       struct backref_edge, list[UPPER]);
1280                 list_del(&new_edge->list[UPPER]);
1281                 free_backref_edge(cache, new_edge);
1282         }
1283         free_backref_node(cache, new_node);
1284         return -ENOMEM;
1285 }
1286
1287 /*
1288  * helper to add 'address of tree root -> reloc tree' mapping
1289  */
1290 static int __must_check __add_reloc_root(struct btrfs_root *root)
1291 {
1292         struct btrfs_fs_info *fs_info = root->fs_info;
1293         struct rb_node *rb_node;
1294         struct mapping_node *node;
1295         struct reloc_control *rc = fs_info->reloc_ctl;
1296
1297         node = kmalloc(sizeof(*node), GFP_NOFS);
1298         if (!node)
1299                 return -ENOMEM;
1300
1301         node->bytenr = root->node->start;
1302         node->data = root;
1303
1304         spin_lock(&rc->reloc_root_tree.lock);
1305         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1306                               node->bytenr, &node->rb_node);
1307         spin_unlock(&rc->reloc_root_tree.lock);
1308         if (rb_node) {
1309                 btrfs_panic(fs_info, -EEXIST,
1310                             "Duplicate root found for start=%llu while inserting into relocation tree",
1311                             node->bytenr);
1312         }
1313
1314         list_add_tail(&root->root_list, &rc->reloc_roots);
1315         return 0;
1316 }
1317
1318 /*
1319  * helper to delete the 'address of tree root -> reloc tree'
1320  * mapping
1321  */
1322 static void __del_reloc_root(struct btrfs_root *root)
1323 {
1324         struct btrfs_fs_info *fs_info = root->fs_info;
1325         struct rb_node *rb_node;
1326         struct mapping_node *node = NULL;
1327         struct reloc_control *rc = fs_info->reloc_ctl;
1328
1329         if (rc && root->node) {
1330                 spin_lock(&rc->reloc_root_tree.lock);
1331                 rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1332                                       root->node->start);
1333                 if (rb_node) {
1334                         node = rb_entry(rb_node, struct mapping_node, rb_node);
1335                         rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1336                 }
1337                 spin_unlock(&rc->reloc_root_tree.lock);
1338                 if (!node)
1339                         return;
1340                 BUG_ON((struct btrfs_root *)node->data != root);
1341         }
1342
1343         spin_lock(&fs_info->trans_lock);
1344         list_del_init(&root->root_list);
1345         spin_unlock(&fs_info->trans_lock);
1346         kfree(node);
1347 }
1348
1349 /*
1350  * helper to update the 'address of tree root -> reloc tree'
1351  * mapping
1352  */
1353 static int __update_reloc_root(struct btrfs_root *root, u64 new_bytenr)
1354 {
1355         struct btrfs_fs_info *fs_info = root->fs_info;
1356         struct rb_node *rb_node;
1357         struct mapping_node *node = NULL;
1358         struct reloc_control *rc = fs_info->reloc_ctl;
1359
1360         spin_lock(&rc->reloc_root_tree.lock);
1361         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1362                               root->node->start);
1363         if (rb_node) {
1364                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1365                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1366         }
1367         spin_unlock(&rc->reloc_root_tree.lock);
1368
1369         if (!node)
1370                 return 0;
1371         BUG_ON((struct btrfs_root *)node->data != root);
1372
1373         spin_lock(&rc->reloc_root_tree.lock);
1374         node->bytenr = new_bytenr;
1375         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1376                               node->bytenr, &node->rb_node);
1377         spin_unlock(&rc->reloc_root_tree.lock);
1378         if (rb_node)
1379                 backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1380         return 0;
1381 }
1382
1383 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1384                                         struct btrfs_root *root, u64 objectid)
1385 {
1386         struct btrfs_fs_info *fs_info = root->fs_info;
1387         struct btrfs_root *reloc_root;
1388         struct extent_buffer *eb;
1389         struct btrfs_root_item *root_item;
1390         struct btrfs_key root_key;
1391         int ret;
1392
1393         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1394         BUG_ON(!root_item);
1395
1396         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1397         root_key.type = BTRFS_ROOT_ITEM_KEY;
1398         root_key.offset = objectid;
1399
1400         if (root->root_key.objectid == objectid) {
1401                 u64 commit_root_gen;
1402
1403                 /* called by btrfs_init_reloc_root */
1404                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1405                                       BTRFS_TREE_RELOC_OBJECTID);
1406                 BUG_ON(ret);
1407                 /*
1408                  * Set the last_snapshot field to the generation of the commit
1409                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
1410                  * correctly (returns true) when the relocation root is created
1411                  * either inside the critical section of a transaction commit
1412                  * (through transaction.c:qgroup_account_snapshot()) and when
1413                  * it's created before the transaction commit is started.
1414                  */
1415                 commit_root_gen = btrfs_header_generation(root->commit_root);
1416                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
1417         } else {
1418                 /*
1419                  * called by btrfs_reloc_post_snapshot_hook.
1420                  * the source tree is a reloc tree, all tree blocks
1421                  * modified after it was created have RELOC flag
1422                  * set in their headers. so it's OK to not update
1423                  * the 'last_snapshot'.
1424                  */
1425                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1426                                       BTRFS_TREE_RELOC_OBJECTID);
1427                 BUG_ON(ret);
1428         }
1429
1430         memcpy(root_item, &root->root_item, sizeof(*root_item));
1431         btrfs_set_root_bytenr(root_item, eb->start);
1432         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1433         btrfs_set_root_generation(root_item, trans->transid);
1434
1435         if (root->root_key.objectid == objectid) {
1436                 btrfs_set_root_refs(root_item, 0);
1437                 memset(&root_item->drop_progress, 0,
1438                        sizeof(struct btrfs_disk_key));
1439                 root_item->drop_level = 0;
1440         }
1441
1442         btrfs_tree_unlock(eb);
1443         free_extent_buffer(eb);
1444
1445         ret = btrfs_insert_root(trans, fs_info->tree_root,
1446                                 &root_key, root_item);
1447         BUG_ON(ret);
1448         kfree(root_item);
1449
1450         reloc_root = btrfs_read_fs_root(fs_info->tree_root, &root_key);
1451         BUG_ON(IS_ERR(reloc_root));
1452         reloc_root->last_trans = trans->transid;
1453         return reloc_root;
1454 }
1455
1456 /*
1457  * create reloc tree for a given fs tree. reloc tree is just a
1458  * snapshot of the fs tree with special root objectid.
1459  */
1460 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1461                           struct btrfs_root *root)
1462 {
1463         struct btrfs_fs_info *fs_info = root->fs_info;
1464         struct btrfs_root *reloc_root;
1465         struct reloc_control *rc = fs_info->reloc_ctl;
1466         struct btrfs_block_rsv *rsv;
1467         int clear_rsv = 0;
1468         int ret;
1469
1470         /*
1471          * The subvolume has reloc tree but the swap is finished, no need to
1472          * create/update the dead reloc tree
1473          */
1474         if (reloc_root_is_dead(root))
1475                 return 0;
1476
1477         if (root->reloc_root) {
1478                 reloc_root = root->reloc_root;
1479                 reloc_root->last_trans = trans->transid;
1480                 return 0;
1481         }
1482
1483         if (!rc || !rc->create_reloc_tree ||
1484             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1485                 return 0;
1486
1487         if (!trans->reloc_reserved) {
1488                 rsv = trans->block_rsv;
1489                 trans->block_rsv = rc->block_rsv;
1490                 clear_rsv = 1;
1491         }
1492         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1493         if (clear_rsv)
1494                 trans->block_rsv = rsv;
1495
1496         ret = __add_reloc_root(reloc_root);
1497         BUG_ON(ret < 0);
1498         root->reloc_root = reloc_root;
1499         return 0;
1500 }
1501
1502 /*
1503  * update root item of reloc tree
1504  */
1505 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1506                             struct btrfs_root *root)
1507 {
1508         struct btrfs_fs_info *fs_info = root->fs_info;
1509         struct btrfs_root *reloc_root;
1510         struct btrfs_root_item *root_item;
1511         int ret;
1512
1513         if (!have_reloc_root(root))
1514                 goto out;
1515
1516         reloc_root = root->reloc_root;
1517         root_item = &reloc_root->root_item;
1518
1519         /* root->reloc_root will stay until current relocation finished */
1520         if (fs_info->reloc_ctl->merge_reloc_tree &&
1521             btrfs_root_refs(root_item) == 0) {
1522                 set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
1523                 /*
1524                  * Mark the tree as dead before we change reloc_root so
1525                  * have_reloc_root will not touch it from now on.
1526                  */
1527                 smp_wmb();
1528                 __del_reloc_root(reloc_root);
1529         }
1530
1531         if (reloc_root->commit_root != reloc_root->node) {
1532                 btrfs_set_root_node(root_item, reloc_root->node);
1533                 free_extent_buffer(reloc_root->commit_root);
1534                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1535         }
1536
1537         ret = btrfs_update_root(trans, fs_info->tree_root,
1538                                 &reloc_root->root_key, root_item);
1539         BUG_ON(ret);
1540
1541 out:
1542         return 0;
1543 }
1544
1545 /*
1546  * helper to find first cached inode with inode number >= objectid
1547  * in a subvolume
1548  */
1549 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1550 {
1551         struct rb_node *node;
1552         struct rb_node *prev;
1553         struct btrfs_inode *entry;
1554         struct inode *inode;
1555
1556         spin_lock(&root->inode_lock);
1557 again:
1558         node = root->inode_tree.rb_node;
1559         prev = NULL;
1560         while (node) {
1561                 prev = node;
1562                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1563
1564                 if (objectid < btrfs_ino(entry))
1565                         node = node->rb_left;
1566                 else if (objectid > btrfs_ino(entry))
1567                         node = node->rb_right;
1568                 else
1569                         break;
1570         }
1571         if (!node) {
1572                 while (prev) {
1573                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1574                         if (objectid <= btrfs_ino(entry)) {
1575                                 node = prev;
1576                                 break;
1577                         }
1578                         prev = rb_next(prev);
1579                 }
1580         }
1581         while (node) {
1582                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1583                 inode = igrab(&entry->vfs_inode);
1584                 if (inode) {
1585                         spin_unlock(&root->inode_lock);
1586                         return inode;
1587                 }
1588
1589                 objectid = btrfs_ino(entry) + 1;
1590                 if (cond_resched_lock(&root->inode_lock))
1591                         goto again;
1592
1593                 node = rb_next(node);
1594         }
1595         spin_unlock(&root->inode_lock);
1596         return NULL;
1597 }
1598
1599 static int in_block_group(u64 bytenr, struct btrfs_block_group *block_group)
1600 {
1601         if (bytenr >= block_group->start &&
1602             bytenr < block_group->start + block_group->length)
1603                 return 1;
1604         return 0;
1605 }
1606
1607 /*
1608  * get new location of data
1609  */
1610 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1611                             u64 bytenr, u64 num_bytes)
1612 {
1613         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1614         struct btrfs_path *path;
1615         struct btrfs_file_extent_item *fi;
1616         struct extent_buffer *leaf;
1617         int ret;
1618
1619         path = btrfs_alloc_path();
1620         if (!path)
1621                 return -ENOMEM;
1622
1623         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1624         ret = btrfs_lookup_file_extent(NULL, root, path,
1625                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1626         if (ret < 0)
1627                 goto out;
1628         if (ret > 0) {
1629                 ret = -ENOENT;
1630                 goto out;
1631         }
1632
1633         leaf = path->nodes[0];
1634         fi = btrfs_item_ptr(leaf, path->slots[0],
1635                             struct btrfs_file_extent_item);
1636
1637         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1638                btrfs_file_extent_compression(leaf, fi) ||
1639                btrfs_file_extent_encryption(leaf, fi) ||
1640                btrfs_file_extent_other_encoding(leaf, fi));
1641
1642         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1643                 ret = -EINVAL;
1644                 goto out;
1645         }
1646
1647         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1648         ret = 0;
1649 out:
1650         btrfs_free_path(path);
1651         return ret;
1652 }
1653
1654 /*
1655  * update file extent items in the tree leaf to point to
1656  * the new locations.
1657  */
1658 static noinline_for_stack
1659 int replace_file_extents(struct btrfs_trans_handle *trans,
1660                          struct reloc_control *rc,
1661                          struct btrfs_root *root,
1662                          struct extent_buffer *leaf)
1663 {
1664         struct btrfs_fs_info *fs_info = root->fs_info;
1665         struct btrfs_key key;
1666         struct btrfs_file_extent_item *fi;
1667         struct inode *inode = NULL;
1668         u64 parent;
1669         u64 bytenr;
1670         u64 new_bytenr = 0;
1671         u64 num_bytes;
1672         u64 end;
1673         u32 nritems;
1674         u32 i;
1675         int ret = 0;
1676         int first = 1;
1677         int dirty = 0;
1678
1679         if (rc->stage != UPDATE_DATA_PTRS)
1680                 return 0;
1681
1682         /* reloc trees always use full backref */
1683         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1684                 parent = leaf->start;
1685         else
1686                 parent = 0;
1687
1688         nritems = btrfs_header_nritems(leaf);
1689         for (i = 0; i < nritems; i++) {
1690                 struct btrfs_ref ref = { 0 };
1691
1692                 cond_resched();
1693                 btrfs_item_key_to_cpu(leaf, &key, i);
1694                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1695                         continue;
1696                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1697                 if (btrfs_file_extent_type(leaf, fi) ==
1698                     BTRFS_FILE_EXTENT_INLINE)
1699                         continue;
1700                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1701                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1702                 if (bytenr == 0)
1703                         continue;
1704                 if (!in_block_group(bytenr, rc->block_group))
1705                         continue;
1706
1707                 /*
1708                  * if we are modifying block in fs tree, wait for readpage
1709                  * to complete and drop the extent cache
1710                  */
1711                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1712                         if (first) {
1713                                 inode = find_next_inode(root, key.objectid);
1714                                 first = 0;
1715                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1716                                 btrfs_add_delayed_iput(inode);
1717                                 inode = find_next_inode(root, key.objectid);
1718                         }
1719                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1720                                 end = key.offset +
1721                                       btrfs_file_extent_num_bytes(leaf, fi);
1722                                 WARN_ON(!IS_ALIGNED(key.offset,
1723                                                     fs_info->sectorsize));
1724                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1725                                 end--;
1726                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1727                                                       key.offset, end);
1728                                 if (!ret)
1729                                         continue;
1730
1731                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1732                                                 key.offset,     end, 1);
1733                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1734                                               key.offset, end);
1735                         }
1736                 }
1737
1738                 ret = get_new_location(rc->data_inode, &new_bytenr,
1739                                        bytenr, num_bytes);
1740                 if (ret) {
1741                         /*
1742                          * Don't have to abort since we've not changed anything
1743                          * in the file extent yet.
1744                          */
1745                         break;
1746                 }
1747
1748                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1749                 dirty = 1;
1750
1751                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1752                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1753                                        num_bytes, parent);
1754                 ref.real_root = root->root_key.objectid;
1755                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1756                                     key.objectid, key.offset);
1757                 ret = btrfs_inc_extent_ref(trans, &ref);
1758                 if (ret) {
1759                         btrfs_abort_transaction(trans, ret);
1760                         break;
1761                 }
1762
1763                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
1764                                        num_bytes, parent);
1765                 ref.real_root = root->root_key.objectid;
1766                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1767                                     key.objectid, key.offset);
1768                 ret = btrfs_free_extent(trans, &ref);
1769                 if (ret) {
1770                         btrfs_abort_transaction(trans, ret);
1771                         break;
1772                 }
1773         }
1774         if (dirty)
1775                 btrfs_mark_buffer_dirty(leaf);
1776         if (inode)
1777                 btrfs_add_delayed_iput(inode);
1778         return ret;
1779 }
1780
1781 static noinline_for_stack
1782 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1783                      struct btrfs_path *path, int level)
1784 {
1785         struct btrfs_disk_key key1;
1786         struct btrfs_disk_key key2;
1787         btrfs_node_key(eb, &key1, slot);
1788         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1789         return memcmp(&key1, &key2, sizeof(key1));
1790 }
1791
1792 /*
1793  * try to replace tree blocks in fs tree with the new blocks
1794  * in reloc tree. tree blocks haven't been modified since the
1795  * reloc tree was create can be replaced.
1796  *
1797  * if a block was replaced, level of the block + 1 is returned.
1798  * if no block got replaced, 0 is returned. if there are other
1799  * errors, a negative error number is returned.
1800  */
1801 static noinline_for_stack
1802 int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
1803                  struct btrfs_root *dest, struct btrfs_root *src,
1804                  struct btrfs_path *path, struct btrfs_key *next_key,
1805                  int lowest_level, int max_level)
1806 {
1807         struct btrfs_fs_info *fs_info = dest->fs_info;
1808         struct extent_buffer *eb;
1809         struct extent_buffer *parent;
1810         struct btrfs_ref ref = { 0 };
1811         struct btrfs_key key;
1812         u64 old_bytenr;
1813         u64 new_bytenr;
1814         u64 old_ptr_gen;
1815         u64 new_ptr_gen;
1816         u64 last_snapshot;
1817         u32 blocksize;
1818         int cow = 0;
1819         int level;
1820         int ret;
1821         int slot;
1822
1823         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1824         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1825
1826         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1827 again:
1828         slot = path->slots[lowest_level];
1829         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1830
1831         eb = btrfs_lock_root_node(dest);
1832         btrfs_set_lock_blocking_write(eb);
1833         level = btrfs_header_level(eb);
1834
1835         if (level < lowest_level) {
1836                 btrfs_tree_unlock(eb);
1837                 free_extent_buffer(eb);
1838                 return 0;
1839         }
1840
1841         if (cow) {
1842                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1843                 BUG_ON(ret);
1844         }
1845         btrfs_set_lock_blocking_write(eb);
1846
1847         if (next_key) {
1848                 next_key->objectid = (u64)-1;
1849                 next_key->type = (u8)-1;
1850                 next_key->offset = (u64)-1;
1851         }
1852
1853         parent = eb;
1854         while (1) {
1855                 struct btrfs_key first_key;
1856
1857                 level = btrfs_header_level(parent);
1858                 BUG_ON(level < lowest_level);
1859
1860                 ret = btrfs_bin_search(parent, &key, level, &slot);
1861                 if (ret < 0)
1862                         break;
1863                 if (ret && slot > 0)
1864                         slot--;
1865
1866                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1867                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1868
1869                 old_bytenr = btrfs_node_blockptr(parent, slot);
1870                 blocksize = fs_info->nodesize;
1871                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1872                 btrfs_node_key_to_cpu(parent, &first_key, slot);
1873
1874                 if (level <= max_level) {
1875                         eb = path->nodes[level];
1876                         new_bytenr = btrfs_node_blockptr(eb,
1877                                                         path->slots[level]);
1878                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1879                                                         path->slots[level]);
1880                 } else {
1881                         new_bytenr = 0;
1882                         new_ptr_gen = 0;
1883                 }
1884
1885                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1886                         ret = level;
1887                         break;
1888                 }
1889
1890                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1891                     memcmp_node_keys(parent, slot, path, level)) {
1892                         if (level <= lowest_level) {
1893                                 ret = 0;
1894                                 break;
1895                         }
1896
1897                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen,
1898                                              level - 1, &first_key);
1899                         if (IS_ERR(eb)) {
1900                                 ret = PTR_ERR(eb);
1901                                 break;
1902                         } else if (!extent_buffer_uptodate(eb)) {
1903                                 ret = -EIO;
1904                                 free_extent_buffer(eb);
1905                                 break;
1906                         }
1907                         btrfs_tree_lock(eb);
1908                         if (cow) {
1909                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1910                                                       slot, &eb);
1911                                 BUG_ON(ret);
1912                         }
1913                         btrfs_set_lock_blocking_write(eb);
1914
1915                         btrfs_tree_unlock(parent);
1916                         free_extent_buffer(parent);
1917
1918                         parent = eb;
1919                         continue;
1920                 }
1921
1922                 if (!cow) {
1923                         btrfs_tree_unlock(parent);
1924                         free_extent_buffer(parent);
1925                         cow = 1;
1926                         goto again;
1927                 }
1928
1929                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1930                                       path->slots[level]);
1931                 btrfs_release_path(path);
1932
1933                 path->lowest_level = level;
1934                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1935                 path->lowest_level = 0;
1936                 BUG_ON(ret);
1937
1938                 /*
1939                  * Info qgroup to trace both subtrees.
1940                  *
1941                  * We must trace both trees.
1942                  * 1) Tree reloc subtree
1943                  *    If not traced, we will leak data numbers
1944                  * 2) Fs subtree
1945                  *    If not traced, we will double count old data
1946                  *
1947                  * We don't scan the subtree right now, but only record
1948                  * the swapped tree blocks.
1949                  * The real subtree rescan is delayed until we have new
1950                  * CoW on the subtree root node before transaction commit.
1951                  */
1952                 ret = btrfs_qgroup_add_swapped_blocks(trans, dest,
1953                                 rc->block_group, parent, slot,
1954                                 path->nodes[level], path->slots[level],
1955                                 last_snapshot);
1956                 if (ret < 0)
1957                         break;
1958                 /*
1959                  * swap blocks in fs tree and reloc tree.
1960                  */
1961                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1962                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1963                 btrfs_mark_buffer_dirty(parent);
1964
1965                 btrfs_set_node_blockptr(path->nodes[level],
1966                                         path->slots[level], old_bytenr);
1967                 btrfs_set_node_ptr_generation(path->nodes[level],
1968                                               path->slots[level], old_ptr_gen);
1969                 btrfs_mark_buffer_dirty(path->nodes[level]);
1970
1971                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, old_bytenr,
1972                                        blocksize, path->nodes[level]->start);
1973                 ref.skip_qgroup = true;
1974                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1975                 ret = btrfs_inc_extent_ref(trans, &ref);
1976                 BUG_ON(ret);
1977                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1978                                        blocksize, 0);
1979                 ref.skip_qgroup = true;
1980                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1981                 ret = btrfs_inc_extent_ref(trans, &ref);
1982                 BUG_ON(ret);
1983
1984                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, new_bytenr,
1985                                        blocksize, path->nodes[level]->start);
1986                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1987                 ref.skip_qgroup = true;
1988                 ret = btrfs_free_extent(trans, &ref);
1989                 BUG_ON(ret);
1990
1991                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, old_bytenr,
1992                                        blocksize, 0);
1993                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1994                 ref.skip_qgroup = true;
1995                 ret = btrfs_free_extent(trans, &ref);
1996                 BUG_ON(ret);
1997
1998                 btrfs_unlock_up_safe(path, 0);
1999
2000                 ret = level;
2001                 break;
2002         }
2003         btrfs_tree_unlock(parent);
2004         free_extent_buffer(parent);
2005         return ret;
2006 }
2007
2008 /*
2009  * helper to find next relocated block in reloc tree
2010  */
2011 static noinline_for_stack
2012 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2013                        int *level)
2014 {
2015         struct extent_buffer *eb;
2016         int i;
2017         u64 last_snapshot;
2018         u32 nritems;
2019
2020         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2021
2022         for (i = 0; i < *level; i++) {
2023                 free_extent_buffer(path->nodes[i]);
2024                 path->nodes[i] = NULL;
2025         }
2026
2027         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
2028                 eb = path->nodes[i];
2029                 nritems = btrfs_header_nritems(eb);
2030                 while (path->slots[i] + 1 < nritems) {
2031                         path->slots[i]++;
2032                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
2033                             last_snapshot)
2034                                 continue;
2035
2036                         *level = i;
2037                         return 0;
2038                 }
2039                 free_extent_buffer(path->nodes[i]);
2040                 path->nodes[i] = NULL;
2041         }
2042         return 1;
2043 }
2044
2045 /*
2046  * walk down reloc tree to find relocated block of lowest level
2047  */
2048 static noinline_for_stack
2049 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2050                          int *level)
2051 {
2052         struct btrfs_fs_info *fs_info = root->fs_info;
2053         struct extent_buffer *eb = NULL;
2054         int i;
2055         u64 bytenr;
2056         u64 ptr_gen = 0;
2057         u64 last_snapshot;
2058         u32 nritems;
2059
2060         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2061
2062         for (i = *level; i > 0; i--) {
2063                 struct btrfs_key first_key;
2064
2065                 eb = path->nodes[i];
2066                 nritems = btrfs_header_nritems(eb);
2067                 while (path->slots[i] < nritems) {
2068                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2069                         if (ptr_gen > last_snapshot)
2070                                 break;
2071                         path->slots[i]++;
2072                 }
2073                 if (path->slots[i] >= nritems) {
2074                         if (i == *level)
2075                                 break;
2076                         *level = i + 1;
2077                         return 0;
2078                 }
2079                 if (i == 1) {
2080                         *level = i;
2081                         return 0;
2082                 }
2083
2084                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2085                 btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
2086                 eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
2087                                      &first_key);
2088                 if (IS_ERR(eb)) {
2089                         return PTR_ERR(eb);
2090                 } else if (!extent_buffer_uptodate(eb)) {
2091                         free_extent_buffer(eb);
2092                         return -EIO;
2093                 }
2094                 BUG_ON(btrfs_header_level(eb) != i - 1);
2095                 path->nodes[i - 1] = eb;
2096                 path->slots[i - 1] = 0;
2097         }
2098         return 1;
2099 }
2100
2101 /*
2102  * invalidate extent cache for file extents whose key in range of
2103  * [min_key, max_key)
2104  */
2105 static int invalidate_extent_cache(struct btrfs_root *root,
2106                                    struct btrfs_key *min_key,
2107                                    struct btrfs_key *max_key)
2108 {
2109         struct btrfs_fs_info *fs_info = root->fs_info;
2110         struct inode *inode = NULL;
2111         u64 objectid;
2112         u64 start, end;
2113         u64 ino;
2114
2115         objectid = min_key->objectid;
2116         while (1) {
2117                 cond_resched();
2118                 iput(inode);
2119
2120                 if (objectid > max_key->objectid)
2121                         break;
2122
2123                 inode = find_next_inode(root, objectid);
2124                 if (!inode)
2125                         break;
2126                 ino = btrfs_ino(BTRFS_I(inode));
2127
2128                 if (ino > max_key->objectid) {
2129                         iput(inode);
2130                         break;
2131                 }
2132
2133                 objectid = ino + 1;
2134                 if (!S_ISREG(inode->i_mode))
2135                         continue;
2136
2137                 if (unlikely(min_key->objectid == ino)) {
2138                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2139                                 continue;
2140                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2141                                 start = 0;
2142                         else {
2143                                 start = min_key->offset;
2144                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
2145                         }
2146                 } else {
2147                         start = 0;
2148                 }
2149
2150                 if (unlikely(max_key->objectid == ino)) {
2151                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2152                                 continue;
2153                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2154                                 end = (u64)-1;
2155                         } else {
2156                                 if (max_key->offset == 0)
2157                                         continue;
2158                                 end = max_key->offset;
2159                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
2160                                 end--;
2161                         }
2162                 } else {
2163                         end = (u64)-1;
2164                 }
2165
2166                 /* the lock_extent waits for readpage to complete */
2167                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2168                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
2169                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2170         }
2171         return 0;
2172 }
2173
2174 static int find_next_key(struct btrfs_path *path, int level,
2175                          struct btrfs_key *key)
2176
2177 {
2178         while (level < BTRFS_MAX_LEVEL) {
2179                 if (!path->nodes[level])
2180                         break;
2181                 if (path->slots[level] + 1 <
2182                     btrfs_header_nritems(path->nodes[level])) {
2183                         btrfs_node_key_to_cpu(path->nodes[level], key,
2184                                               path->slots[level] + 1);
2185                         return 0;
2186                 }
2187                 level++;
2188         }
2189         return 1;
2190 }
2191
2192 /*
2193  * Insert current subvolume into reloc_control::dirty_subvol_roots
2194  */
2195 static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
2196                                 struct reloc_control *rc,
2197                                 struct btrfs_root *root)
2198 {
2199         struct btrfs_root *reloc_root = root->reloc_root;
2200         struct btrfs_root_item *reloc_root_item;
2201
2202         /* @root must be a subvolume tree root with a valid reloc tree */
2203         ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
2204         ASSERT(reloc_root);
2205
2206         reloc_root_item = &reloc_root->root_item;
2207         memset(&reloc_root_item->drop_progress, 0,
2208                 sizeof(reloc_root_item->drop_progress));
2209         reloc_root_item->drop_level = 0;
2210         btrfs_set_root_refs(reloc_root_item, 0);
2211         btrfs_update_reloc_root(trans, root);
2212
2213         if (list_empty(&root->reloc_dirty_list)) {
2214                 btrfs_grab_fs_root(root);
2215                 list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
2216         }
2217 }
2218
2219 static int clean_dirty_subvols(struct reloc_control *rc)
2220 {
2221         struct btrfs_root *root;
2222         struct btrfs_root *next;
2223         int ret = 0;
2224         int ret2;
2225
2226         list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
2227                                  reloc_dirty_list) {
2228                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
2229                         /* Merged subvolume, cleanup its reloc root */
2230                         struct btrfs_root *reloc_root = root->reloc_root;
2231
2232                         list_del_init(&root->reloc_dirty_list);
2233                         root->reloc_root = NULL;
2234                         if (reloc_root) {
2235
2236                                 ret2 = btrfs_drop_snapshot(reloc_root, NULL, 0, 1);
2237                                 if (ret2 < 0 && !ret)
2238                                         ret = ret2;
2239                         }
2240                         /*
2241                          * Need barrier to ensure clear_bit() only happens after
2242                          * root->reloc_root = NULL. Pairs with have_reloc_root.
2243                          */
2244                         smp_wmb();
2245                         clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
2246                         btrfs_put_fs_root(root);
2247                 } else {
2248                         /* Orphan reloc tree, just clean it up */
2249                         ret2 = btrfs_drop_snapshot(root, NULL, 0, 1);
2250                         if (ret2 < 0 && !ret)
2251                                 ret = ret2;
2252                 }
2253         }
2254         return ret;
2255 }
2256
2257 /*
2258  * merge the relocated tree blocks in reloc tree with corresponding
2259  * fs tree.
2260  */
2261 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2262                                                struct btrfs_root *root)
2263 {
2264         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2265         struct btrfs_key key;
2266         struct btrfs_key next_key;
2267         struct btrfs_trans_handle *trans = NULL;
2268         struct btrfs_root *reloc_root;
2269         struct btrfs_root_item *root_item;
2270         struct btrfs_path *path;
2271         struct extent_buffer *leaf;
2272         int level;
2273         int max_level;
2274         int replaced = 0;
2275         int ret;
2276         int err = 0;
2277         u32 min_reserved;
2278
2279         path = btrfs_alloc_path();
2280         if (!path)
2281                 return -ENOMEM;
2282         path->reada = READA_FORWARD;
2283
2284         reloc_root = root->reloc_root;
2285         root_item = &reloc_root->root_item;
2286
2287         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2288                 level = btrfs_root_level(root_item);
2289                 atomic_inc(&reloc_root->node->refs);
2290                 path->nodes[level] = reloc_root->node;
2291                 path->slots[level] = 0;
2292         } else {
2293                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2294
2295                 level = root_item->drop_level;
2296                 BUG_ON(level == 0);
2297                 path->lowest_level = level;
2298                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2299                 path->lowest_level = 0;
2300                 if (ret < 0) {
2301                         btrfs_free_path(path);
2302                         return ret;
2303                 }
2304
2305                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2306                                       path->slots[level]);
2307                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2308
2309                 btrfs_unlock_up_safe(path, 0);
2310         }
2311
2312         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2313         memset(&next_key, 0, sizeof(next_key));
2314
2315         while (1) {
2316                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2317                                              BTRFS_RESERVE_FLUSH_ALL);
2318                 if (ret) {
2319                         err = ret;
2320                         goto out;
2321                 }
2322                 trans = btrfs_start_transaction(root, 0);
2323                 if (IS_ERR(trans)) {
2324                         err = PTR_ERR(trans);
2325                         trans = NULL;
2326                         goto out;
2327                 }
2328                 trans->block_rsv = rc->block_rsv;
2329
2330                 replaced = 0;
2331                 max_level = level;
2332
2333                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2334                 if (ret < 0) {
2335                         err = ret;
2336                         goto out;
2337                 }
2338                 if (ret > 0)
2339                         break;
2340
2341                 if (!find_next_key(path, level, &key) &&
2342                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2343                         ret = 0;
2344                 } else {
2345                         ret = replace_path(trans, rc, root, reloc_root, path,
2346                                            &next_key, level, max_level);
2347                 }
2348                 if (ret < 0) {
2349                         err = ret;
2350                         goto out;
2351                 }
2352
2353                 if (ret > 0) {
2354                         level = ret;
2355                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2356                                               path->slots[level]);
2357                         replaced = 1;
2358                 }
2359
2360                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2361                 if (ret > 0)
2362                         break;
2363
2364                 BUG_ON(level == 0);
2365                 /*
2366                  * save the merging progress in the drop_progress.
2367                  * this is OK since root refs == 1 in this case.
2368                  */
2369                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2370                                path->slots[level]);
2371                 root_item->drop_level = level;
2372
2373                 btrfs_end_transaction_throttle(trans);
2374                 trans = NULL;
2375
2376                 btrfs_btree_balance_dirty(fs_info);
2377
2378                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2379                         invalidate_extent_cache(root, &key, &next_key);
2380         }
2381
2382         /*
2383          * handle the case only one block in the fs tree need to be
2384          * relocated and the block is tree root.
2385          */
2386         leaf = btrfs_lock_root_node(root);
2387         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2388         btrfs_tree_unlock(leaf);
2389         free_extent_buffer(leaf);
2390         if (ret < 0)
2391                 err = ret;
2392 out:
2393         btrfs_free_path(path);
2394
2395         if (err == 0)
2396                 insert_dirty_subvol(trans, rc, root);
2397
2398         if (trans)
2399                 btrfs_end_transaction_throttle(trans);
2400
2401         btrfs_btree_balance_dirty(fs_info);
2402
2403         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2404                 invalidate_extent_cache(root, &key, &next_key);
2405
2406         return err;
2407 }
2408
2409 static noinline_for_stack
2410 int prepare_to_merge(struct reloc_control *rc, int err)
2411 {
2412         struct btrfs_root *root = rc->extent_root;
2413         struct btrfs_fs_info *fs_info = root->fs_info;
2414         struct btrfs_root *reloc_root;
2415         struct btrfs_trans_handle *trans;
2416         LIST_HEAD(reloc_roots);
2417         u64 num_bytes = 0;
2418         int ret;
2419
2420         mutex_lock(&fs_info->reloc_mutex);
2421         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2422         rc->merging_rsv_size += rc->nodes_relocated * 2;
2423         mutex_unlock(&fs_info->reloc_mutex);
2424
2425 again:
2426         if (!err) {
2427                 num_bytes = rc->merging_rsv_size;
2428                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2429                                           BTRFS_RESERVE_FLUSH_ALL);
2430                 if (ret)
2431                         err = ret;
2432         }
2433
2434         trans = btrfs_join_transaction(rc->extent_root);
2435         if (IS_ERR(trans)) {
2436                 if (!err)
2437                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2438                                                 num_bytes);
2439                 return PTR_ERR(trans);
2440         }
2441
2442         if (!err) {
2443                 if (num_bytes != rc->merging_rsv_size) {
2444                         btrfs_end_transaction(trans);
2445                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2446                                                 num_bytes);
2447                         goto again;
2448                 }
2449         }
2450
2451         rc->merge_reloc_tree = 1;
2452
2453         while (!list_empty(&rc->reloc_roots)) {
2454                 reloc_root = list_entry(rc->reloc_roots.next,
2455                                         struct btrfs_root, root_list);
2456                 list_del_init(&reloc_root->root_list);
2457
2458                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
2459                 BUG_ON(IS_ERR(root));
2460                 BUG_ON(root->reloc_root != reloc_root);
2461
2462                 /*
2463                  * set reference count to 1, so btrfs_recover_relocation
2464                  * knows it should resumes merging
2465                  */
2466                 if (!err)
2467                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2468                 btrfs_update_reloc_root(trans, root);
2469
2470                 list_add(&reloc_root->root_list, &reloc_roots);
2471         }
2472
2473         list_splice(&reloc_roots, &rc->reloc_roots);
2474
2475         if (!err)
2476                 btrfs_commit_transaction(trans);
2477         else
2478                 btrfs_end_transaction(trans);
2479         return err;
2480 }
2481
2482 static noinline_for_stack
2483 void free_reloc_roots(struct list_head *list)
2484 {
2485         struct btrfs_root *reloc_root;
2486
2487         while (!list_empty(list)) {
2488                 reloc_root = list_entry(list->next, struct btrfs_root,
2489                                         root_list);
2490                 __del_reloc_root(reloc_root);
2491                 free_extent_buffer(reloc_root->node);
2492                 free_extent_buffer(reloc_root->commit_root);
2493                 reloc_root->node = NULL;
2494                 reloc_root->commit_root = NULL;
2495         }
2496 }
2497
2498 static noinline_for_stack
2499 void merge_reloc_roots(struct reloc_control *rc)
2500 {
2501         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2502         struct btrfs_root *root;
2503         struct btrfs_root *reloc_root;
2504         LIST_HEAD(reloc_roots);
2505         int found = 0;
2506         int ret = 0;
2507 again:
2508         root = rc->extent_root;
2509
2510         /*
2511          * this serializes us with btrfs_record_root_in_transaction,
2512          * we have to make sure nobody is in the middle of
2513          * adding their roots to the list while we are
2514          * doing this splice
2515          */
2516         mutex_lock(&fs_info->reloc_mutex);
2517         list_splice_init(&rc->reloc_roots, &reloc_roots);
2518         mutex_unlock(&fs_info->reloc_mutex);
2519
2520         while (!list_empty(&reloc_roots)) {
2521                 found = 1;
2522                 reloc_root = list_entry(reloc_roots.next,
2523                                         struct btrfs_root, root_list);
2524
2525                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2526                         root = read_fs_root(fs_info,
2527                                             reloc_root->root_key.offset);
2528                         BUG_ON(IS_ERR(root));
2529                         BUG_ON(root->reloc_root != reloc_root);
2530
2531                         ret = merge_reloc_root(rc, root);
2532                         if (ret) {
2533                                 if (list_empty(&reloc_root->root_list))
2534                                         list_add_tail(&reloc_root->root_list,
2535                                                       &reloc_roots);
2536                                 goto out;
2537                         }
2538                 } else {
2539                         list_del_init(&reloc_root->root_list);
2540                         /* Don't forget to queue this reloc root for cleanup */
2541                         list_add_tail(&reloc_root->reloc_dirty_list,
2542                                       &rc->dirty_subvol_roots);
2543                 }
2544         }
2545
2546         if (found) {
2547                 found = 0;
2548                 goto again;
2549         }
2550 out:
2551         if (ret) {
2552                 btrfs_handle_fs_error(fs_info, ret, NULL);
2553                 if (!list_empty(&reloc_roots))
2554                         free_reloc_roots(&reloc_roots);
2555
2556                 /* new reloc root may be added */
2557                 mutex_lock(&fs_info->reloc_mutex);
2558                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2559                 mutex_unlock(&fs_info->reloc_mutex);
2560                 if (!list_empty(&reloc_roots))
2561                         free_reloc_roots(&reloc_roots);
2562         }
2563
2564         BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2565 }
2566
2567 static void free_block_list(struct rb_root *blocks)
2568 {
2569         struct tree_block *block;
2570         struct rb_node *rb_node;
2571         while ((rb_node = rb_first(blocks))) {
2572                 block = rb_entry(rb_node, struct tree_block, rb_node);
2573                 rb_erase(rb_node, blocks);
2574                 kfree(block);
2575         }
2576 }
2577
2578 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2579                                       struct btrfs_root *reloc_root)
2580 {
2581         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
2582         struct btrfs_root *root;
2583
2584         if (reloc_root->last_trans == trans->transid)
2585                 return 0;
2586
2587         root = read_fs_root(fs_info, reloc_root->root_key.offset);
2588         BUG_ON(IS_ERR(root));
2589         BUG_ON(root->reloc_root != reloc_root);
2590
2591         return btrfs_record_root_in_trans(trans, root);
2592 }
2593
2594 static noinline_for_stack
2595 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2596                                      struct reloc_control *rc,
2597                                      struct backref_node *node,
2598                                      struct backref_edge *edges[])
2599 {
2600         struct backref_node *next;
2601         struct btrfs_root *root;
2602         int index = 0;
2603
2604         next = node;
2605         while (1) {
2606                 cond_resched();
2607                 next = walk_up_backref(next, edges, &index);
2608                 root = next->root;
2609                 BUG_ON(!root);
2610                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2611
2612                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2613                         record_reloc_root_in_trans(trans, root);
2614                         break;
2615                 }
2616
2617                 btrfs_record_root_in_trans(trans, root);
2618                 root = root->reloc_root;
2619
2620                 if (next->new_bytenr != root->node->start) {
2621                         BUG_ON(next->new_bytenr);
2622                         BUG_ON(!list_empty(&next->list));
2623                         next->new_bytenr = root->node->start;
2624                         next->root = root;
2625                         list_add_tail(&next->list,
2626                                       &rc->backref_cache.changed);
2627                         __mark_block_processed(rc, next);
2628                         break;
2629                 }
2630
2631                 WARN_ON(1);
2632                 root = NULL;
2633                 next = walk_down_backref(edges, &index);
2634                 if (!next || next->level <= node->level)
2635                         break;
2636         }
2637         if (!root)
2638                 return NULL;
2639
2640         next = node;
2641         /* setup backref node path for btrfs_reloc_cow_block */
2642         while (1) {
2643                 rc->backref_cache.path[next->level] = next;
2644                 if (--index < 0)
2645                         break;
2646                 next = edges[index]->node[UPPER];
2647         }
2648         return root;
2649 }
2650
2651 /*
2652  * select a tree root for relocation. return NULL if the block
2653  * is reference counted. we should use do_relocation() in this
2654  * case. return a tree root pointer if the block isn't reference
2655  * counted. return -ENOENT if the block is root of reloc tree.
2656  */
2657 static noinline_for_stack
2658 struct btrfs_root *select_one_root(struct backref_node *node)
2659 {
2660         struct backref_node *next;
2661         struct btrfs_root *root;
2662         struct btrfs_root *fs_root = NULL;
2663         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2664         int index = 0;
2665
2666         next = node;
2667         while (1) {
2668                 cond_resched();
2669                 next = walk_up_backref(next, edges, &index);
2670                 root = next->root;
2671                 BUG_ON(!root);
2672
2673                 /* no other choice for non-references counted tree */
2674                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2675                         return root;
2676
2677                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2678                         fs_root = root;
2679
2680                 if (next != node)
2681                         return NULL;
2682
2683                 next = walk_down_backref(edges, &index);
2684                 if (!next || next->level <= node->level)
2685                         break;
2686         }
2687
2688         if (!fs_root)
2689                 return ERR_PTR(-ENOENT);
2690         return fs_root;
2691 }
2692
2693 static noinline_for_stack
2694 u64 calcu_metadata_size(struct reloc_control *rc,
2695                         struct backref_node *node, int reserve)
2696 {
2697         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2698         struct backref_node *next = node;
2699         struct backref_edge *edge;
2700         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2701         u64 num_bytes = 0;
2702         int index = 0;
2703
2704         BUG_ON(reserve && node->processed);
2705
2706         while (next) {
2707                 cond_resched();
2708                 while (1) {
2709                         if (next->processed && (reserve || next != node))
2710                                 break;
2711
2712                         num_bytes += fs_info->nodesize;
2713
2714                         if (list_empty(&next->upper))
2715                                 break;
2716
2717                         edge = list_entry(next->upper.next,
2718                                           struct backref_edge, list[LOWER]);
2719                         edges[index++] = edge;
2720                         next = edge->node[UPPER];
2721                 }
2722                 next = walk_down_backref(edges, &index);
2723         }
2724         return num_bytes;
2725 }
2726
2727 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2728                                   struct reloc_control *rc,
2729                                   struct backref_node *node)
2730 {
2731         struct btrfs_root *root = rc->extent_root;
2732         struct btrfs_fs_info *fs_info = root->fs_info;
2733         u64 num_bytes;
2734         int ret;
2735         u64 tmp;
2736
2737         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2738
2739         trans->block_rsv = rc->block_rsv;
2740         rc->reserved_bytes += num_bytes;
2741
2742         /*
2743          * We are under a transaction here so we can only do limited flushing.
2744          * If we get an enospc just kick back -EAGAIN so we know to drop the
2745          * transaction and try to refill when we can flush all the things.
2746          */
2747         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2748                                 BTRFS_RESERVE_FLUSH_LIMIT);
2749         if (ret) {
2750                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2751                 while (tmp <= rc->reserved_bytes)
2752                         tmp <<= 1;
2753                 /*
2754                  * only one thread can access block_rsv at this point,
2755                  * so we don't need hold lock to protect block_rsv.
2756                  * we expand more reservation size here to allow enough
2757                  * space for relocation and we will return earlier in
2758                  * enospc case.
2759                  */
2760                 rc->block_rsv->size = tmp + fs_info->nodesize *
2761                                       RELOCATION_RESERVED_NODES;
2762                 return -EAGAIN;
2763         }
2764
2765         return 0;
2766 }
2767
2768 /*
2769  * relocate a block tree, and then update pointers in upper level
2770  * blocks that reference the block to point to the new location.
2771  *
2772  * if called by link_to_upper, the block has already been relocated.
2773  * in that case this function just updates pointers.
2774  */
2775 static int do_relocation(struct btrfs_trans_handle *trans,
2776                          struct reloc_control *rc,
2777                          struct backref_node *node,
2778                          struct btrfs_key *key,
2779                          struct btrfs_path *path, int lowest)
2780 {
2781         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2782         struct backref_node *upper;
2783         struct backref_edge *edge;
2784         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2785         struct btrfs_root *root;
2786         struct extent_buffer *eb;
2787         u32 blocksize;
2788         u64 bytenr;
2789         u64 generation;
2790         int slot;
2791         int ret;
2792         int err = 0;
2793
2794         BUG_ON(lowest && node->eb);
2795
2796         path->lowest_level = node->level + 1;
2797         rc->backref_cache.path[node->level] = node;
2798         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2799                 struct btrfs_key first_key;
2800                 struct btrfs_ref ref = { 0 };
2801
2802                 cond_resched();
2803
2804                 upper = edge->node[UPPER];
2805                 root = select_reloc_root(trans, rc, upper, edges);
2806                 BUG_ON(!root);
2807
2808                 if (upper->eb && !upper->locked) {
2809                         if (!lowest) {
2810                                 ret = btrfs_bin_search(upper->eb, key,
2811                                                        upper->level, &slot);
2812                                 if (ret < 0) {
2813                                         err = ret;
2814                                         goto next;
2815                                 }
2816                                 BUG_ON(ret);
2817                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2818                                 if (node->eb->start == bytenr)
2819                                         goto next;
2820                         }
2821                         drop_node_buffer(upper);
2822                 }
2823
2824                 if (!upper->eb) {
2825                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2826                         if (ret) {
2827                                 if (ret < 0)
2828                                         err = ret;
2829                                 else
2830                                         err = -ENOENT;
2831
2832                                 btrfs_release_path(path);
2833                                 break;
2834                         }
2835
2836                         if (!upper->eb) {
2837                                 upper->eb = path->nodes[upper->level];
2838                                 path->nodes[upper->level] = NULL;
2839                         } else {
2840                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2841                         }
2842
2843                         upper->locked = 1;
2844                         path->locks[upper->level] = 0;
2845
2846                         slot = path->slots[upper->level];
2847                         btrfs_release_path(path);
2848                 } else {
2849                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2850                                                &slot);
2851                         if (ret < 0) {
2852                                 err = ret;
2853                                 goto next;
2854                         }
2855                         BUG_ON(ret);
2856                 }
2857
2858                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2859                 if (lowest) {
2860                         if (bytenr != node->bytenr) {
2861                                 btrfs_err(root->fs_info,
2862                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2863                                           bytenr, node->bytenr, slot,
2864                                           upper->eb->start);
2865                                 err = -EIO;
2866                                 goto next;
2867                         }
2868                 } else {
2869                         if (node->eb->start == bytenr)
2870                                 goto next;
2871                 }
2872
2873                 blocksize = root->fs_info->nodesize;
2874                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2875                 btrfs_node_key_to_cpu(upper->eb, &first_key, slot);
2876                 eb = read_tree_block(fs_info, bytenr, generation,
2877                                      upper->level - 1, &first_key);
2878                 if (IS_ERR(eb)) {
2879                         err = PTR_ERR(eb);
2880                         goto next;
2881                 } else if (!extent_buffer_uptodate(eb)) {
2882                         free_extent_buffer(eb);
2883                         err = -EIO;
2884                         goto next;
2885                 }
2886                 btrfs_tree_lock(eb);
2887                 btrfs_set_lock_blocking_write(eb);
2888
2889                 if (!node->eb) {
2890                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2891                                               slot, &eb);
2892                         btrfs_tree_unlock(eb);
2893                         free_extent_buffer(eb);
2894                         if (ret < 0) {
2895                                 err = ret;
2896                                 goto next;
2897                         }
2898                         BUG_ON(node->eb != eb);
2899                 } else {
2900                         btrfs_set_node_blockptr(upper->eb, slot,
2901                                                 node->eb->start);
2902                         btrfs_set_node_ptr_generation(upper->eb, slot,
2903                                                       trans->transid);
2904                         btrfs_mark_buffer_dirty(upper->eb);
2905
2906                         btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF,
2907                                                node->eb->start, blocksize,
2908                                                upper->eb->start);
2909                         ref.real_root = root->root_key.objectid;
2910                         btrfs_init_tree_ref(&ref, node->level,
2911                                             btrfs_header_owner(upper->eb));
2912                         ret = btrfs_inc_extent_ref(trans, &ref);
2913                         BUG_ON(ret);
2914
2915                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2916                         BUG_ON(ret);
2917                 }
2918 next:
2919                 if (!upper->pending)
2920                         drop_node_buffer(upper);
2921                 else
2922                         unlock_node_buffer(upper);
2923                 if (err)
2924                         break;
2925         }
2926
2927         if (!err && node->pending) {
2928                 drop_node_buffer(node);
2929                 list_move_tail(&node->list, &rc->backref_cache.changed);
2930                 node->pending = 0;
2931         }
2932
2933         path->lowest_level = 0;
2934         BUG_ON(err == -ENOSPC);
2935         return err;
2936 }
2937
2938 static int link_to_upper(struct btrfs_trans_handle *trans,
2939                          struct reloc_control *rc,
2940                          struct backref_node *node,
2941                          struct btrfs_path *path)
2942 {
2943         struct btrfs_key key;
2944
2945         btrfs_node_key_to_cpu(node->eb, &key, 0);
2946         return do_relocation(trans, rc, node, &key, path, 0);
2947 }
2948
2949 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2950                                 struct reloc_control *rc,
2951                                 struct btrfs_path *path, int err)
2952 {
2953         LIST_HEAD(list);
2954         struct backref_cache *cache = &rc->backref_cache;
2955         struct backref_node *node;
2956         int level;
2957         int ret;
2958
2959         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2960                 while (!list_empty(&cache->pending[level])) {
2961                         node = list_entry(cache->pending[level].next,
2962                                           struct backref_node, list);
2963                         list_move_tail(&node->list, &list);
2964                         BUG_ON(!node->pending);
2965
2966                         if (!err) {
2967                                 ret = link_to_upper(trans, rc, node, path);
2968                                 if (ret < 0)
2969                                         err = ret;
2970                         }
2971                 }
2972                 list_splice_init(&list, &cache->pending[level]);
2973         }
2974         return err;
2975 }
2976
2977 static void mark_block_processed(struct reloc_control *rc,
2978                                  u64 bytenr, u32 blocksize)
2979 {
2980         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
2981                         EXTENT_DIRTY);
2982 }
2983
2984 static void __mark_block_processed(struct reloc_control *rc,
2985                                    struct backref_node *node)
2986 {
2987         u32 blocksize;
2988         if (node->level == 0 ||
2989             in_block_group(node->bytenr, rc->block_group)) {
2990                 blocksize = rc->extent_root->fs_info->nodesize;
2991                 mark_block_processed(rc, node->bytenr, blocksize);
2992         }
2993         node->processed = 1;
2994 }
2995
2996 /*
2997  * mark a block and all blocks directly/indirectly reference the block
2998  * as processed.
2999  */
3000 static void update_processed_blocks(struct reloc_control *rc,
3001                                     struct backref_node *node)
3002 {
3003         struct backref_node *next = node;
3004         struct backref_edge *edge;
3005         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
3006         int index = 0;
3007
3008         while (next) {
3009                 cond_resched();
3010                 while (1) {
3011                         if (next->processed)
3012                                 break;
3013
3014                         __mark_block_processed(rc, next);
3015
3016                         if (list_empty(&next->upper))
3017                                 break;
3018
3019                         edge = list_entry(next->upper.next,
3020                                           struct backref_edge, list[LOWER]);
3021                         edges[index++] = edge;
3022                         next = edge->node[UPPER];
3023                 }
3024                 next = walk_down_backref(edges, &index);
3025         }
3026 }
3027
3028 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
3029 {
3030         u32 blocksize = rc->extent_root->fs_info->nodesize;
3031
3032         if (test_range_bit(&rc->processed_blocks, bytenr,
3033                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
3034                 return 1;
3035         return 0;
3036 }
3037
3038 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
3039                               struct tree_block *block)
3040 {
3041         struct extent_buffer *eb;
3042
3043         BUG_ON(block->key_ready);
3044         eb = read_tree_block(fs_info, block->bytenr, block->key.offset,
3045                              block->level, NULL);
3046         if (IS_ERR(eb)) {
3047                 return PTR_ERR(eb);
3048         } else if (!extent_buffer_uptodate(eb)) {
3049                 free_extent_buffer(eb);
3050                 return -EIO;
3051         }
3052         if (block->level == 0)
3053                 btrfs_item_key_to_cpu(eb, &block->key, 0);
3054         else
3055                 btrfs_node_key_to_cpu(eb, &block->key, 0);
3056         free_extent_buffer(eb);
3057         block->key_ready = 1;
3058         return 0;
3059 }
3060
3061 /*
3062  * helper function to relocate a tree block
3063  */
3064 static int relocate_tree_block(struct btrfs_trans_handle *trans,
3065                                 struct reloc_control *rc,
3066                                 struct backref_node *node,
3067                                 struct btrfs_key *key,
3068                                 struct btrfs_path *path)
3069 {
3070         struct btrfs_root *root;
3071         int ret = 0;
3072
3073         if (!node)
3074                 return 0;
3075
3076         BUG_ON(node->processed);
3077         root = select_one_root(node);
3078         if (root == ERR_PTR(-ENOENT)) {
3079                 update_processed_blocks(rc, node);
3080                 goto out;
3081         }
3082
3083         if (!root || test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
3084                 ret = reserve_metadata_space(trans, rc, node);
3085                 if (ret)
3086                         goto out;
3087         }
3088
3089         if (root) {
3090                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
3091                         BUG_ON(node->new_bytenr);
3092                         BUG_ON(!list_empty(&node->list));
3093                         btrfs_record_root_in_trans(trans, root);
3094                         root = root->reloc_root;
3095                         node->new_bytenr = root->node->start;
3096                         node->root = root;
3097                         list_add_tail(&node->list, &rc->backref_cache.changed);
3098                 } else {
3099                         path->lowest_level = node->level;
3100                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
3101                         btrfs_release_path(path);
3102                         if (ret > 0)
3103                                 ret = 0;
3104                 }
3105                 if (!ret)
3106                         update_processed_blocks(rc, node);
3107         } else {
3108                 ret = do_relocation(trans, rc, node, key, path, 1);
3109         }
3110 out:
3111         if (ret || node->level == 0 || node->cowonly)
3112                 remove_backref_node(&rc->backref_cache, node);
3113         return ret;
3114 }
3115
3116 /*
3117  * relocate a list of blocks
3118  */
3119 static noinline_for_stack
3120 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
3121                          struct reloc_control *rc, struct rb_root *blocks)
3122 {
3123         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3124         struct backref_node *node;
3125         struct btrfs_path *path;
3126         struct tree_block *block;
3127         struct tree_block *next;
3128         int ret;
3129         int err = 0;
3130
3131         path = btrfs_alloc_path();
3132         if (!path) {
3133                 err = -ENOMEM;
3134                 goto out_free_blocks;
3135         }
3136
3137         /* Kick in readahead for tree blocks with missing keys */
3138         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3139                 if (!block->key_ready)
3140                         readahead_tree_block(fs_info, block->bytenr);
3141         }
3142
3143         /* Get first keys */
3144         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3145                 if (!block->key_ready) {
3146                         err = get_tree_block_key(fs_info, block);
3147                         if (err)
3148                                 goto out_free_path;
3149                 }
3150         }
3151
3152         /* Do tree relocation */
3153         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3154                 node = build_backref_tree(rc, &block->key,
3155                                           block->level, block->bytenr);
3156                 if (IS_ERR(node)) {
3157                         err = PTR_ERR(node);
3158                         goto out;
3159                 }
3160
3161                 ret = relocate_tree_block(trans, rc, node, &block->key,
3162                                           path);
3163                 if (ret < 0) {
3164                         if (ret != -EAGAIN || &block->rb_node == rb_first(blocks))
3165                                 err = ret;
3166                         goto out;
3167                 }
3168         }
3169 out:
3170         err = finish_pending_nodes(trans, rc, path, err);
3171
3172 out_free_path:
3173         btrfs_free_path(path);
3174 out_free_blocks:
3175         free_block_list(blocks);
3176         return err;
3177 }
3178
3179 static noinline_for_stack
3180 int prealloc_file_extent_cluster(struct inode *inode,
3181                                  struct file_extent_cluster *cluster)
3182 {
3183         u64 alloc_hint = 0;
3184         u64 start;
3185         u64 end;
3186         u64 offset = BTRFS_I(inode)->index_cnt;
3187         u64 num_bytes;
3188         int nr = 0;
3189         int ret = 0;
3190         u64 prealloc_start = cluster->start - offset;
3191         u64 prealloc_end = cluster->end - offset;
3192         u64 cur_offset;
3193         struct extent_changeset *data_reserved = NULL;
3194
3195         BUG_ON(cluster->start != cluster->boundary[0]);
3196         inode_lock(inode);
3197
3198         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
3199                                           prealloc_end + 1 - prealloc_start);
3200         if (ret)
3201                 goto out;
3202
3203         cur_offset = prealloc_start;
3204         while (nr < cluster->nr) {
3205                 start = cluster->boundary[nr] - offset;
3206                 if (nr + 1 < cluster->nr)
3207                         end = cluster->boundary[nr + 1] - 1 - offset;
3208                 else
3209                         end = cluster->end - offset;
3210
3211                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3212                 num_bytes = end + 1 - start;
3213                 if (cur_offset < start)
3214                         btrfs_free_reserved_data_space(inode, data_reserved,
3215                                         cur_offset, start - cur_offset);
3216                 ret = btrfs_prealloc_file_range(inode, 0, start,
3217                                                 num_bytes, num_bytes,
3218                                                 end + 1, &alloc_hint);
3219                 cur_offset = end + 1;
3220                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3221                 if (ret)
3222                         break;
3223                 nr++;
3224         }
3225         if (cur_offset < prealloc_end)
3226                 btrfs_free_reserved_data_space(inode, data_reserved,
3227                                 cur_offset, prealloc_end + 1 - cur_offset);
3228 out:
3229         inode_unlock(inode);
3230         extent_changeset_free(data_reserved);
3231         return ret;
3232 }
3233
3234 static noinline_for_stack
3235 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3236                          u64 block_start)
3237 {
3238         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3239         struct extent_map *em;
3240         int ret = 0;
3241
3242         em = alloc_extent_map();
3243         if (!em)
3244                 return -ENOMEM;
3245
3246         em->start = start;
3247         em->len = end + 1 - start;
3248         em->block_len = em->len;
3249         em->block_start = block_start;
3250         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3251
3252         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3253         while (1) {
3254                 write_lock(&em_tree->lock);
3255                 ret = add_extent_mapping(em_tree, em, 0);
3256                 write_unlock(&em_tree->lock);
3257                 if (ret != -EEXIST) {
3258                         free_extent_map(em);
3259                         break;
3260                 }
3261                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
3262         }
3263         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3264         return ret;
3265 }
3266
3267 static int relocate_file_extent_cluster(struct inode *inode,
3268                                         struct file_extent_cluster *cluster)
3269 {
3270         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3271         u64 page_start;
3272         u64 page_end;
3273         u64 offset = BTRFS_I(inode)->index_cnt;
3274         unsigned long index;
3275         unsigned long last_index;
3276         struct page *page;
3277         struct file_ra_state *ra;
3278         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3279         int nr = 0;
3280         int ret = 0;
3281
3282         if (!cluster->nr)
3283                 return 0;
3284
3285         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3286         if (!ra)
3287                 return -ENOMEM;
3288
3289         ret = prealloc_file_extent_cluster(inode, cluster);
3290         if (ret)
3291                 goto out;
3292
3293         file_ra_state_init(ra, inode->i_mapping);
3294
3295         ret = setup_extent_mapping(inode, cluster->start - offset,
3296                                    cluster->end - offset, cluster->start);
3297         if (ret)
3298                 goto out;
3299
3300         index = (cluster->start - offset) >> PAGE_SHIFT;
3301         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3302         while (index <= last_index) {
3303                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
3304                                 PAGE_SIZE);
3305                 if (ret)
3306                         goto out;
3307
3308                 page = find_lock_page(inode->i_mapping, index);
3309                 if (!page) {
3310                         page_cache_sync_readahead(inode->i_mapping,
3311                                                   ra, NULL, index,
3312                                                   last_index + 1 - index);
3313                         page = find_or_create_page(inode->i_mapping, index,
3314                                                    mask);
3315                         if (!page) {
3316                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3317                                                         PAGE_SIZE, true);
3318                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3319                                                         PAGE_SIZE);
3320                                 ret = -ENOMEM;
3321                                 goto out;
3322                         }
3323                 }
3324
3325                 if (PageReadahead(page)) {
3326                         page_cache_async_readahead(inode->i_mapping,
3327                                                    ra, NULL, page, index,
3328                                                    last_index + 1 - index);
3329                 }
3330
3331                 if (!PageUptodate(page)) {
3332                         btrfs_readpage(NULL, page);
3333                         lock_page(page);
3334                         if (!PageUptodate(page)) {
3335                                 unlock_page(page);
3336                                 put_page(page);
3337                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3338                                                         PAGE_SIZE, true);
3339                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3340                                                                PAGE_SIZE);
3341                                 ret = -EIO;
3342                                 goto out;
3343                         }
3344                 }
3345
3346                 page_start = page_offset(page);
3347                 page_end = page_start + PAGE_SIZE - 1;
3348
3349                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3350
3351                 set_page_extent_mapped(page);
3352
3353                 if (nr < cluster->nr &&
3354                     page_start + offset == cluster->boundary[nr]) {
3355                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3356                                         page_start, page_end,
3357                                         EXTENT_BOUNDARY);
3358                         nr++;
3359                 }
3360
3361                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
3362                                                 NULL);
3363                 if (ret) {
3364                         unlock_page(page);
3365                         put_page(page);
3366                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
3367                                                          PAGE_SIZE, true);
3368                         btrfs_delalloc_release_extents(BTRFS_I(inode),
3369                                                        PAGE_SIZE);
3370
3371                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
3372                                           page_start, page_end,
3373                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
3374                         goto out;
3375
3376                 }
3377                 set_page_dirty(page);
3378
3379                 unlock_extent(&BTRFS_I(inode)->io_tree,
3380                               page_start, page_end);
3381                 unlock_page(page);
3382                 put_page(page);
3383
3384                 index++;
3385                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
3386                 balance_dirty_pages_ratelimited(inode->i_mapping);
3387                 btrfs_throttle(fs_info);
3388         }
3389         WARN_ON(nr != cluster->nr);
3390 out:
3391         kfree(ra);
3392         return ret;
3393 }
3394
3395 static noinline_for_stack
3396 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3397                          struct file_extent_cluster *cluster)
3398 {
3399         int ret;
3400
3401         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3402                 ret = relocate_file_extent_cluster(inode, cluster);
3403                 if (ret)
3404                         return ret;
3405                 cluster->nr = 0;
3406         }
3407
3408         if (!cluster->nr)
3409                 cluster->start = extent_key->objectid;
3410         else
3411                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3412         cluster->end = extent_key->objectid + extent_key->offset - 1;
3413         cluster->boundary[cluster->nr] = extent_key->objectid;
3414         cluster->nr++;
3415
3416         if (cluster->nr >= MAX_EXTENTS) {
3417                 ret = relocate_file_extent_cluster(inode, cluster);
3418                 if (ret)
3419                         return ret;
3420                 cluster->nr = 0;
3421         }
3422         return 0;
3423 }
3424
3425 /*
3426  * helper to add a tree block to the list.
3427  * the major work is getting the generation and level of the block
3428  */
3429 static int add_tree_block(struct reloc_control *rc,
3430                           struct btrfs_key *extent_key,
3431                           struct btrfs_path *path,
3432                           struct rb_root *blocks)
3433 {
3434         struct extent_buffer *eb;
3435         struct btrfs_extent_item *ei;
3436         struct btrfs_tree_block_info *bi;
3437         struct tree_block *block;
3438         struct rb_node *rb_node;
3439         u32 item_size;
3440         int level = -1;
3441         u64 generation;
3442
3443         eb =  path->nodes[0];
3444         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3445
3446         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3447             item_size >= sizeof(*ei) + sizeof(*bi)) {
3448                 ei = btrfs_item_ptr(eb, path->slots[0],
3449                                 struct btrfs_extent_item);
3450                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3451                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3452                         level = btrfs_tree_block_level(eb, bi);
3453                 } else {
3454                         level = (int)extent_key->offset;
3455                 }
3456                 generation = btrfs_extent_generation(eb, ei);
3457         } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
3458                 btrfs_print_v0_err(eb->fs_info);
3459                 btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
3460                 return -EINVAL;
3461         } else {
3462                 BUG();
3463         }
3464
3465         btrfs_release_path(path);
3466
3467         BUG_ON(level == -1);
3468
3469         block = kmalloc(sizeof(*block), GFP_NOFS);
3470         if (!block)
3471                 return -ENOMEM;
3472
3473         block->bytenr = extent_key->objectid;
3474         block->key.objectid = rc->extent_root->fs_info->nodesize;
3475         block->key.offset = generation;
3476         block->level = level;
3477         block->key_ready = 0;
3478
3479         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3480         if (rb_node)
3481                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3482
3483         return 0;
3484 }
3485
3486 /*
3487  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3488  */
3489 static int __add_tree_block(struct reloc_control *rc,
3490                             u64 bytenr, u32 blocksize,
3491                             struct rb_root *blocks)
3492 {
3493         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3494         struct btrfs_path *path;
3495         struct btrfs_key key;
3496         int ret;
3497         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
3498
3499         if (tree_block_processed(bytenr, rc))
3500                 return 0;
3501
3502         if (tree_search(blocks, bytenr))
3503                 return 0;
3504
3505         path = btrfs_alloc_path();
3506         if (!path)
3507                 return -ENOMEM;
3508 again:
3509         key.objectid = bytenr;
3510         if (skinny) {
3511                 key.type = BTRFS_METADATA_ITEM_KEY;
3512                 key.offset = (u64)-1;
3513         } else {
3514                 key.type = BTRFS_EXTENT_ITEM_KEY;
3515                 key.offset = blocksize;
3516         }
3517
3518         path->search_commit_root = 1;
3519         path->skip_locking = 1;
3520         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3521         if (ret < 0)
3522                 goto out;
3523
3524         if (ret > 0 && skinny) {
3525                 if (path->slots[0]) {
3526                         path->slots[0]--;
3527                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3528                                               path->slots[0]);
3529                         if (key.objectid == bytenr &&
3530                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3531                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3532                               key.offset == blocksize)))
3533                                 ret = 0;
3534                 }
3535
3536                 if (ret) {
3537                         skinny = false;
3538                         btrfs_release_path(path);
3539                         goto again;
3540                 }
3541         }
3542         if (ret) {
3543                 ASSERT(ret == 1);
3544                 btrfs_print_leaf(path->nodes[0]);
3545                 btrfs_err(fs_info,
3546              "tree block extent item (%llu) is not found in extent tree",
3547                      bytenr);
3548                 WARN_ON(1);
3549                 ret = -EINVAL;
3550                 goto out;
3551         }
3552
3553         ret = add_tree_block(rc, &key, path, blocks);
3554 out:
3555         btrfs_free_path(path);
3556         return ret;
3557 }
3558
3559 /*
3560  * helper to check if the block use full backrefs for pointers in it
3561  */
3562 static int block_use_full_backref(struct reloc_control *rc,
3563                                   struct extent_buffer *eb)
3564 {
3565         u64 flags;
3566         int ret;
3567
3568         if (btrfs_header_flag(eb, BTRFS_HEADER_FLAG_RELOC) ||
3569             btrfs_header_backref_rev(eb) < BTRFS_MIXED_BACKREF_REV)
3570                 return 1;
3571
3572         ret = btrfs_lookup_extent_info(NULL, rc->extent_root->fs_info,
3573                                        eb->start, btrfs_header_level(eb), 1,
3574                                        NULL, &flags);
3575         BUG_ON(ret);
3576
3577         if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
3578                 ret = 1;
3579         else
3580                 ret = 0;
3581         return ret;
3582 }
3583
3584 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3585                                     struct btrfs_block_group *block_group,
3586                                     struct inode *inode,
3587                                     u64 ino)
3588 {
3589         struct btrfs_key key;
3590         struct btrfs_root *root = fs_info->tree_root;
3591         struct btrfs_trans_handle *trans;
3592         int ret = 0;
3593
3594         if (inode)
3595                 goto truncate;
3596
3597         key.objectid = ino;
3598         key.type = BTRFS_INODE_ITEM_KEY;
3599         key.offset = 0;
3600
3601         inode = btrfs_iget(fs_info->sb, &key, root);
3602         if (IS_ERR(inode))
3603                 return -ENOENT;
3604
3605 truncate:
3606         ret = btrfs_check_trunc_cache_free_space(fs_info,
3607                                                  &fs_info->global_block_rsv);
3608         if (ret)
3609                 goto out;
3610
3611         trans = btrfs_join_transaction(root);
3612         if (IS_ERR(trans)) {
3613                 ret = PTR_ERR(trans);
3614                 goto out;
3615         }
3616
3617         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3618
3619         btrfs_end_transaction(trans);
3620         btrfs_btree_balance_dirty(fs_info);
3621 out:
3622         iput(inode);
3623         return ret;
3624 }
3625
3626 /*
3627  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
3628  * this function scans fs tree to find blocks reference the data extent
3629  */
3630 static int find_data_references(struct reloc_control *rc,
3631                                 struct btrfs_key *extent_key,
3632                                 struct extent_buffer *leaf,
3633                                 struct btrfs_extent_data_ref *ref,
3634                                 struct rb_root *blocks)
3635 {
3636         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3637         struct btrfs_path *path;
3638         struct tree_block *block;
3639         struct btrfs_root *root;
3640         struct btrfs_file_extent_item *fi;
3641         struct rb_node *rb_node;
3642         struct btrfs_key key;
3643         u64 ref_root;
3644         u64 ref_objectid;
3645         u64 ref_offset;
3646         u32 ref_count;
3647         u32 nritems;
3648         int err = 0;
3649         int added = 0;
3650         int counted;
3651         int ret;
3652
3653         ref_root = btrfs_extent_data_ref_root(leaf, ref);
3654         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
3655         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
3656         ref_count = btrfs_extent_data_ref_count(leaf, ref);
3657
3658         /*
3659          * This is an extent belonging to the free space cache, lets just delete
3660          * it and redo the search.
3661          */
3662         if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
3663                 ret = delete_block_group_cache(fs_info, rc->block_group,
3664                                                NULL, ref_objectid);
3665                 if (ret != -ENOENT)
3666                         return ret;
3667                 ret = 0;
3668         }
3669
3670         path = btrfs_alloc_path();
3671         if (!path)
3672                 return -ENOMEM;
3673         path->reada = READA_FORWARD;
3674
3675         root = read_fs_root(fs_info, ref_root);
3676         if (IS_ERR(root)) {
3677                 err = PTR_ERR(root);
3678                 goto out;
3679         }
3680
3681         key.objectid = ref_objectid;
3682         key.type = BTRFS_EXTENT_DATA_KEY;
3683         if (ref_offset > ((u64)-1 << 32))
3684                 key.offset = 0;
3685         else
3686                 key.offset = ref_offset;
3687
3688         path->search_commit_root = 1;
3689         path->skip_locking = 1;
3690         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
3691         if (ret < 0) {
3692                 err = ret;
3693                 goto out;
3694         }
3695
3696         leaf = path->nodes[0];
3697         nritems = btrfs_header_nritems(leaf);
3698         /*
3699          * the references in tree blocks that use full backrefs
3700          * are not counted in
3701          */
3702         if (block_use_full_backref(rc, leaf))
3703                 counted = 0;
3704         else
3705                 counted = 1;
3706         rb_node = tree_search(blocks, leaf->start);
3707         if (rb_node) {
3708                 if (counted)
3709                         added = 1;
3710                 else
3711                         path->slots[0] = nritems;
3712         }
3713
3714         while (ref_count > 0) {
3715                 while (path->slots[0] >= nritems) {
3716                         ret = btrfs_next_leaf(root, path);
3717                         if (ret < 0) {
3718                                 err = ret;
3719                                 goto out;
3720                         }
3721                         if (WARN_ON(ret > 0))
3722                                 goto out;
3723
3724                         leaf = path->nodes[0];
3725                         nritems = btrfs_header_nritems(leaf);
3726                         added = 0;
3727
3728                         if (block_use_full_backref(rc, leaf))
3729                                 counted = 0;
3730                         else
3731                                 counted = 1;
3732                         rb_node = tree_search(blocks, leaf->start);
3733                         if (rb_node) {
3734                                 if (counted)
3735                                         added = 1;
3736                                 else
3737                                         path->slots[0] = nritems;
3738                         }
3739                 }
3740
3741                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3742                 if (WARN_ON(key.objectid != ref_objectid ||
3743                     key.type != BTRFS_EXTENT_DATA_KEY))
3744                         break;
3745
3746                 fi = btrfs_item_ptr(leaf, path->slots[0],
3747                                     struct btrfs_file_extent_item);
3748
3749                 if (btrfs_file_extent_type(leaf, fi) ==
3750                     BTRFS_FILE_EXTENT_INLINE)
3751                         goto next;
3752
3753                 if (btrfs_file_extent_disk_bytenr(leaf, fi) !=
3754                     extent_key->objectid)
3755                         goto next;
3756
3757                 key.offset -= btrfs_file_extent_offset(leaf, fi);
3758                 if (key.offset != ref_offset)
3759                         goto next;
3760
3761                 if (counted)
3762                         ref_count--;
3763                 if (added)
3764                         goto next;
3765
3766                 if (!tree_block_processed(leaf->start, rc)) {
3767                         block = kmalloc(sizeof(*block), GFP_NOFS);
3768                         if (!block) {
3769                                 err = -ENOMEM;
3770                                 break;
3771                         }
3772                         block->bytenr = leaf->start;
3773                         btrfs_item_key_to_cpu(leaf, &block->key, 0);
3774                         block->level = 0;
3775                         block->key_ready = 1;
3776                         rb_node = tree_insert(blocks, block->bytenr,
3777                                               &block->rb_node);
3778                         if (rb_node)
3779                                 backref_tree_panic(rb_node, -EEXIST,
3780                                                    block->bytenr);
3781                 }
3782                 if (counted)
3783                         added = 1;
3784                 else
3785                         path->slots[0] = nritems;
3786 next:
3787                 path->slots[0]++;
3788
3789         }
3790 out:
3791         btrfs_free_path(path);
3792         return err;
3793 }
3794
3795 /*
3796  * helper to find all tree blocks that reference a given data extent
3797  */
3798 static noinline_for_stack
3799 int add_data_references(struct reloc_control *rc,
3800                         struct btrfs_key *extent_key,
3801                         struct btrfs_path *path,
3802                         struct rb_root *blocks)
3803 {
3804         struct btrfs_key key;
3805         struct extent_buffer *eb;
3806         struct btrfs_extent_data_ref *dref;
3807         struct btrfs_extent_inline_ref *iref;
3808         unsigned long ptr;
3809         unsigned long end;
3810         u32 blocksize = rc->extent_root->fs_info->nodesize;
3811         int ret = 0;
3812         int err = 0;
3813
3814         eb = path->nodes[0];
3815         ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
3816         end = ptr + btrfs_item_size_nr(eb, path->slots[0]);
3817         ptr += sizeof(struct btrfs_extent_item);
3818
3819         while (ptr < end) {
3820                 iref = (struct btrfs_extent_inline_ref *)ptr;
3821                 key.type = btrfs_get_extent_inline_ref_type(eb, iref,
3822                                                         BTRFS_REF_TYPE_DATA);
3823                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3824                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3825                         ret = __add_tree_block(rc, key.offset, blocksize,
3826                                                blocks);
3827                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3828                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
3829                         ret = find_data_references(rc, extent_key,
3830                                                    eb, dref, blocks);
3831                 } else {
3832                         ret = -EUCLEAN;
3833                         btrfs_err(rc->extent_root->fs_info,
3834                      "extent %llu slot %d has an invalid inline ref type",
3835                              eb->start, path->slots[0]);
3836                 }
3837                 if (ret) {
3838                         err = ret;
3839                         goto out;
3840                 }
3841                 ptr += btrfs_extent_inline_ref_size(key.type);
3842         }
3843         WARN_ON(ptr > end);
3844
3845         while (1) {
3846                 cond_resched();
3847                 eb = path->nodes[0];
3848                 if (path->slots[0] >= btrfs_header_nritems(eb)) {
3849                         ret = btrfs_next_leaf(rc->extent_root, path);
3850                         if (ret < 0) {
3851                                 err = ret;
3852                                 break;
3853                         }
3854                         if (ret > 0)
3855                                 break;
3856                         eb = path->nodes[0];
3857                 }
3858
3859                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
3860                 if (key.objectid != extent_key->objectid)
3861                         break;
3862
3863                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3864                         ret = __add_tree_block(rc, key.offset, blocksize,
3865                                                blocks);
3866                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3867                         dref = btrfs_item_ptr(eb, path->slots[0],
3868                                               struct btrfs_extent_data_ref);
3869                         ret = find_data_references(rc, extent_key,
3870                                                    eb, dref, blocks);
3871                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
3872                         btrfs_print_v0_err(eb->fs_info);
3873                         btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
3874                         ret = -EINVAL;
3875                 } else {
3876                         ret = 0;
3877                 }
3878                 if (ret) {
3879                         err = ret;
3880                         break;
3881                 }
3882                 path->slots[0]++;
3883         }
3884 out:
3885         btrfs_release_path(path);
3886         if (err)
3887                 free_block_list(blocks);
3888         return err;
3889 }
3890
3891 /*
3892  * helper to find next unprocessed extent
3893  */
3894 static noinline_for_stack
3895 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3896                      struct btrfs_key *extent_key)
3897 {
3898         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3899         struct btrfs_key key;
3900         struct extent_buffer *leaf;
3901         u64 start, end, last;
3902         int ret;
3903
3904         last = rc->block_group->start + rc->block_group->length;
3905         while (1) {
3906                 cond_resched();
3907                 if (rc->search_start >= last) {
3908                         ret = 1;
3909                         break;
3910                 }
3911
3912                 key.objectid = rc->search_start;
3913                 key.type = BTRFS_EXTENT_ITEM_KEY;
3914                 key.offset = 0;
3915
3916                 path->search_commit_root = 1;
3917                 path->skip_locking = 1;
3918                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3919                                         0, 0);
3920                 if (ret < 0)
3921                         break;
3922 next:
3923                 leaf = path->nodes[0];
3924                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3925                         ret = btrfs_next_leaf(rc->extent_root, path);
3926                         if (ret != 0)
3927                                 break;
3928                         leaf = path->nodes[0];
3929                 }
3930
3931                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3932                 if (key.objectid >= last) {
3933                         ret = 1;
3934                         break;
3935                 }
3936
3937                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3938                     key.type != BTRFS_METADATA_ITEM_KEY) {
3939                         path->slots[0]++;
3940                         goto next;
3941                 }
3942
3943                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3944                     key.objectid + key.offset <= rc->search_start) {
3945                         path->slots[0]++;
3946                         goto next;
3947                 }
3948
3949                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3950                     key.objectid + fs_info->nodesize <=
3951                     rc->search_start) {
3952                         path->slots[0]++;
3953                         goto next;
3954                 }
3955
3956                 ret = find_first_extent_bit(&rc->processed_blocks,
3957                                             key.objectid, &start, &end,
3958                                             EXTENT_DIRTY, NULL);
3959
3960                 if (ret == 0 && start <= key.objectid) {
3961                         btrfs_release_path(path);
3962                         rc->search_start = end + 1;
3963                 } else {
3964                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3965                                 rc->search_start = key.objectid + key.offset;
3966                         else
3967                                 rc->search_start = key.objectid +
3968                                         fs_info->nodesize;
3969                         memcpy(extent_key, &key, sizeof(key));
3970                         return 0;
3971                 }
3972         }
3973         btrfs_release_path(path);
3974         return ret;
3975 }
3976
3977 static void set_reloc_control(struct reloc_control *rc)
3978 {
3979         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3980
3981         mutex_lock(&fs_info->reloc_mutex);
3982         fs_info->reloc_ctl = rc;
3983         mutex_unlock(&fs_info->reloc_mutex);
3984 }
3985
3986 static void unset_reloc_control(struct reloc_control *rc)
3987 {
3988         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3989
3990         mutex_lock(&fs_info->reloc_mutex);
3991         fs_info->reloc_ctl = NULL;
3992         mutex_unlock(&fs_info->reloc_mutex);
3993 }
3994
3995 static int check_extent_flags(u64 flags)
3996 {
3997         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3998             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3999                 return 1;
4000         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
4001             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
4002                 return 1;
4003         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
4004             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
4005                 return 1;
4006         return 0;
4007 }
4008
4009 static noinline_for_stack
4010 int prepare_to_relocate(struct reloc_control *rc)
4011 {
4012         struct btrfs_trans_handle *trans;
4013         int ret;
4014
4015         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
4016                                               BTRFS_BLOCK_RSV_TEMP);
4017         if (!rc->block_rsv)
4018                 return -ENOMEM;
4019
4020         memset(&rc->cluster, 0, sizeof(rc->cluster));
4021         rc->search_start = rc->block_group->start;
4022         rc->extents_found = 0;
4023         rc->nodes_relocated = 0;
4024         rc->merging_rsv_size = 0;
4025         rc->reserved_bytes = 0;
4026         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
4027                               RELOCATION_RESERVED_NODES;
4028         ret = btrfs_block_rsv_refill(rc->extent_root,
4029                                      rc->block_rsv, rc->block_rsv->size,
4030                                      BTRFS_RESERVE_FLUSH_ALL);
4031         if (ret)
4032                 return ret;
4033
4034         rc->create_reloc_tree = 1;
4035         set_reloc_control(rc);
4036
4037         trans = btrfs_join_transaction(rc->extent_root);
4038         if (IS_ERR(trans)) {
4039                 unset_reloc_control(rc);
4040                 /*
4041                  * extent tree is not a ref_cow tree and has no reloc_root to
4042                  * cleanup.  And callers are responsible to free the above
4043                  * block rsv.
4044                  */
4045                 return PTR_ERR(trans);
4046         }
4047         btrfs_commit_transaction(trans);
4048         return 0;
4049 }
4050
4051 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
4052 {
4053         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
4054         struct rb_root blocks = RB_ROOT;
4055         struct btrfs_key key;
4056         struct btrfs_trans_handle *trans = NULL;
4057         struct btrfs_path *path;
4058         struct btrfs_extent_item *ei;
4059         u64 flags;
4060         u32 item_size;
4061         int ret;
4062         int err = 0;
4063         int progress = 0;
4064
4065         path = btrfs_alloc_path();
4066         if (!path)
4067                 return -ENOMEM;
4068         path->reada = READA_FORWARD;
4069
4070         ret = prepare_to_relocate(rc);
4071         if (ret) {
4072                 err = ret;
4073                 goto out_free;
4074         }
4075
4076         while (1) {
4077                 rc->reserved_bytes = 0;
4078                 ret = btrfs_block_rsv_refill(rc->extent_root,
4079                                         rc->block_rsv, rc->block_rsv->size,
4080                                         BTRFS_RESERVE_FLUSH_ALL);
4081                 if (ret) {
4082                         err = ret;
4083                         break;
4084                 }
4085                 progress++;
4086                 trans = btrfs_start_transaction(rc->extent_root, 0);
4087                 if (IS_ERR(trans)) {
4088                         err = PTR_ERR(trans);
4089                         trans = NULL;
4090                         break;
4091                 }
4092 restart:
4093                 if (update_backref_cache(trans, &rc->backref_cache)) {
4094                         btrfs_end_transaction(trans);
4095                         trans = NULL;
4096                         continue;
4097                 }
4098
4099                 ret = find_next_extent(rc, path, &key);
4100                 if (ret < 0)
4101                         err = ret;
4102                 if (ret != 0)
4103                         break;
4104
4105                 rc->extents_found++;
4106
4107                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4108                                     struct btrfs_extent_item);
4109                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4110                 if (item_size >= sizeof(*ei)) {
4111                         flags = btrfs_extent_flags(path->nodes[0], ei);
4112                         ret = check_extent_flags(flags);
4113                         BUG_ON(ret);
4114                 } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
4115                         err = -EINVAL;
4116                         btrfs_print_v0_err(trans->fs_info);
4117                         btrfs_abort_transaction(trans, err);
4118                         break;
4119                 } else {
4120                         BUG();
4121                 }
4122
4123                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4124                         ret = add_tree_block(rc, &key, path, &blocks);
4125                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4126                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4127                         ret = add_data_references(rc, &key, path, &blocks);
4128                 } else {
4129                         btrfs_release_path(path);
4130                         ret = 0;
4131                 }
4132                 if (ret < 0) {
4133                         err = ret;
4134                         break;
4135                 }
4136
4137                 if (!RB_EMPTY_ROOT(&blocks)) {
4138                         ret = relocate_tree_blocks(trans, rc, &blocks);
4139                         if (ret < 0) {
4140                                 /*
4141                                  * if we fail to relocate tree blocks, force to update
4142                                  * backref cache when committing transaction.
4143                                  */
4144                                 rc->backref_cache.last_trans = trans->transid - 1;
4145
4146                                 if (ret != -EAGAIN) {
4147                                         err = ret;
4148                                         break;
4149                                 }
4150                                 rc->extents_found--;
4151                                 rc->search_start = key.objectid;
4152                         }
4153                 }
4154
4155                 btrfs_end_transaction_throttle(trans);
4156                 btrfs_btree_balance_dirty(fs_info);
4157                 trans = NULL;
4158
4159                 if (rc->stage == MOVE_DATA_EXTENTS &&
4160                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4161                         rc->found_file_extent = 1;
4162                         ret = relocate_data_extent(rc->data_inode,
4163                                                    &key, &rc->cluster);
4164                         if (ret < 0) {
4165                                 err = ret;
4166                                 break;
4167                         }
4168                 }
4169         }
4170         if (trans && progress && err == -ENOSPC) {
4171                 ret = btrfs_force_chunk_alloc(trans, rc->block_group->flags);
4172                 if (ret == 1) {
4173                         err = 0;
4174                         progress = 0;
4175                         goto restart;
4176                 }
4177         }
4178
4179         btrfs_release_path(path);
4180         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4181
4182         if (trans) {
4183                 btrfs_end_transaction_throttle(trans);
4184                 btrfs_btree_balance_dirty(fs_info);
4185         }
4186
4187         if (!err) {
4188                 ret = relocate_file_extent_cluster(rc->data_inode,
4189                                                    &rc->cluster);
4190                 if (ret < 0)
4191                         err = ret;
4192         }
4193
4194         rc->create_reloc_tree = 0;
4195         set_reloc_control(rc);
4196
4197         backref_cache_cleanup(&rc->backref_cache);
4198         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4199
4200         err = prepare_to_merge(rc, err);
4201
4202         merge_reloc_roots(rc);
4203
4204         rc->merge_reloc_tree = 0;
4205         unset_reloc_control(rc);
4206         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4207
4208         /* get rid of pinned extents */
4209         trans = btrfs_join_transaction(rc->extent_root);
4210         if (IS_ERR(trans)) {
4211                 err = PTR_ERR(trans);
4212                 goto out_free;
4213         }
4214         btrfs_commit_transaction(trans);
4215         ret = clean_dirty_subvols(rc);
4216         if (ret < 0 && !err)
4217                 err = ret;
4218 out_free:
4219         btrfs_free_block_rsv(fs_info, rc->block_rsv);
4220         btrfs_free_path(path);
4221         return err;
4222 }
4223
4224 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4225                                  struct btrfs_root *root, u64 objectid)
4226 {
4227         struct btrfs_path *path;
4228         struct btrfs_inode_item *item;
4229         struct extent_buffer *leaf;
4230         int ret;
4231
4232         path = btrfs_alloc_path();
4233         if (!path)
4234                 return -ENOMEM;
4235
4236         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4237         if (ret)
4238                 goto out;
4239
4240         leaf = path->nodes[0];
4241         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4242         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
4243         btrfs_set_inode_generation(leaf, item, 1);
4244         btrfs_set_inode_size(leaf, item, 0);
4245         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4246         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4247                                           BTRFS_INODE_PREALLOC);
4248         btrfs_mark_buffer_dirty(leaf);
4249 out:
4250         btrfs_free_path(path);
4251         return ret;
4252 }
4253
4254 /*
4255  * helper to create inode for data relocation.
4256  * the inode is in data relocation tree and its link count is 0
4257  */
4258 static noinline_for_stack
4259 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4260                                  struct btrfs_block_group *group)
4261 {
4262         struct inode *inode = NULL;
4263         struct btrfs_trans_handle *trans;
4264         struct btrfs_root *root;
4265         struct btrfs_key key;
4266         u64 objectid;
4267         int err = 0;
4268
4269         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4270         if (IS_ERR(root))
4271                 return ERR_CAST(root);
4272
4273         trans = btrfs_start_transaction(root, 6);
4274         if (IS_ERR(trans))
4275                 return ERR_CAST(trans);
4276
4277         err = btrfs_find_free_objectid(root, &objectid);
4278         if (err)
4279                 goto out;
4280
4281         err = __insert_orphan_inode(trans, root, objectid);
4282         BUG_ON(err);
4283
4284         key.objectid = objectid;
4285         key.type = BTRFS_INODE_ITEM_KEY;
4286         key.offset = 0;
4287         inode = btrfs_iget(fs_info->sb, &key, root);
4288         BUG_ON(IS_ERR(inode));
4289         BTRFS_I(inode)->index_cnt = group->start;
4290
4291         err = btrfs_orphan_add(trans, BTRFS_I(inode));
4292 out:
4293         btrfs_end_transaction(trans);
4294         btrfs_btree_balance_dirty(fs_info);
4295         if (err) {
4296                 if (inode)
4297                         iput(inode);
4298                 inode = ERR_PTR(err);
4299         }
4300         return inode;
4301 }
4302
4303 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4304 {
4305         struct reloc_control *rc;
4306
4307         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4308         if (!rc)
4309                 return NULL;
4310
4311         INIT_LIST_HEAD(&rc->reloc_roots);
4312         INIT_LIST_HEAD(&rc->dirty_subvol_roots);
4313         backref_cache_init(&rc->backref_cache);
4314         mapping_tree_init(&rc->reloc_root_tree);
4315         extent_io_tree_init(fs_info, &rc->processed_blocks,
4316                             IO_TREE_RELOC_BLOCKS, NULL);
4317         return rc;
4318 }
4319
4320 /*
4321  * Print the block group being relocated
4322  */
4323 static void describe_relocation(struct btrfs_fs_info *fs_info,
4324                                 struct btrfs_block_group *block_group)
4325 {
4326         char buf[128] = {'\0'};
4327
4328         btrfs_describe_block_groups(block_group->flags, buf, sizeof(buf));
4329
4330         btrfs_info(fs_info,
4331                    "relocating block group %llu flags %s",
4332                    block_group->start, buf);
4333 }
4334
4335 static const char *stage_to_string(int stage)
4336 {
4337         if (stage == MOVE_DATA_EXTENTS)
4338                 return "move data extents";
4339         if (stage == UPDATE_DATA_PTRS)
4340                 return "update data pointers";
4341         return "unknown";
4342 }
4343
4344 /*
4345  * function to relocate all extents in a block group.
4346  */
4347 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
4348 {
4349         struct btrfs_block_group *bg;
4350         struct btrfs_root *extent_root = fs_info->extent_root;
4351         struct reloc_control *rc;
4352         struct inode *inode;
4353         struct btrfs_path *path;
4354         int ret;
4355         int rw = 0;
4356         int err = 0;
4357
4358         bg = btrfs_lookup_block_group(fs_info, group_start);
4359         if (!bg)
4360                 return -ENOENT;
4361
4362         if (btrfs_pinned_by_swapfile(fs_info, bg)) {
4363                 btrfs_put_block_group(bg);
4364                 return -ETXTBSY;
4365         }
4366
4367         rc = alloc_reloc_control(fs_info);
4368         if (!rc) {
4369                 btrfs_put_block_group(bg);
4370                 return -ENOMEM;
4371         }
4372
4373         rc->extent_root = extent_root;
4374         rc->block_group = bg;
4375
4376         ret = btrfs_inc_block_group_ro(rc->block_group, true);
4377         if (ret) {
4378                 err = ret;
4379                 goto out;
4380         }
4381         rw = 1;
4382
4383         path = btrfs_alloc_path();
4384         if (!path) {
4385                 err = -ENOMEM;
4386                 goto out;
4387         }
4388
4389         inode = lookup_free_space_inode(rc->block_group, path);
4390         btrfs_free_path(path);
4391
4392         if (!IS_ERR(inode))
4393                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4394         else
4395                 ret = PTR_ERR(inode);
4396
4397         if (ret && ret != -ENOENT) {
4398                 err = ret;
4399                 goto out;
4400         }
4401
4402         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4403         if (IS_ERR(rc->data_inode)) {
4404                 err = PTR_ERR(rc->data_inode);
4405                 rc->data_inode = NULL;
4406                 goto out;
4407         }
4408
4409         describe_relocation(fs_info, rc->block_group);
4410
4411         btrfs_wait_block_group_reservations(rc->block_group);
4412         btrfs_wait_nocow_writers(rc->block_group);
4413         btrfs_wait_ordered_roots(fs_info, U64_MAX,
4414                                  rc->block_group->start,
4415                                  rc->block_group->length);
4416
4417         while (1) {
4418                 int finishes_stage;
4419
4420                 mutex_lock(&fs_info->cleaner_mutex);
4421                 ret = relocate_block_group(rc);
4422                 mutex_unlock(&fs_info->cleaner_mutex);
4423                 if (ret < 0)
4424                         err = ret;
4425
4426                 finishes_stage = rc->stage;
4427                 /*
4428                  * We may have gotten ENOSPC after we already dirtied some
4429                  * extents.  If writeout happens while we're relocating a
4430                  * different block group we could end up hitting the
4431                  * BUG_ON(rc->stage == UPDATE_DATA_PTRS) in
4432                  * btrfs_reloc_cow_block.  Make sure we write everything out
4433                  * properly so we don't trip over this problem, and then break
4434                  * out of the loop if we hit an error.
4435                  */
4436                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4437                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4438                                                        (u64)-1);
4439                         if (ret)
4440                                 err = ret;
4441                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4442                                                  0, -1);
4443                         rc->stage = UPDATE_DATA_PTRS;
4444                 }
4445
4446                 if (err < 0)
4447                         goto out;
4448
4449                 if (rc->extents_found == 0)
4450                         break;
4451
4452                 btrfs_info(fs_info, "found %llu extents, stage: %s",
4453                            rc->extents_found, stage_to_string(finishes_stage));
4454         }
4455
4456         WARN_ON(rc->block_group->pinned > 0);
4457         WARN_ON(rc->block_group->reserved > 0);
4458         WARN_ON(rc->block_group->used > 0);
4459 out:
4460         if (err && rw)
4461                 btrfs_dec_block_group_ro(rc->block_group);
4462         iput(rc->data_inode);
4463         btrfs_put_block_group(rc->block_group);
4464         kfree(rc);
4465         return err;
4466 }
4467
4468 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4469 {
4470         struct btrfs_fs_info *fs_info = root->fs_info;
4471         struct btrfs_trans_handle *trans;
4472         int ret, err;
4473
4474         trans = btrfs_start_transaction(fs_info->tree_root, 0);
4475         if (IS_ERR(trans))
4476                 return PTR_ERR(trans);
4477
4478         memset(&root->root_item.drop_progress, 0,
4479                 sizeof(root->root_item.drop_progress));
4480         root->root_item.drop_level = 0;
4481         btrfs_set_root_refs(&root->root_item, 0);
4482         ret = btrfs_update_root(trans, fs_info->tree_root,
4483                                 &root->root_key, &root->root_item);
4484
4485         err = btrfs_end_transaction(trans);
4486         if (err)
4487                 return err;
4488         return ret;
4489 }
4490
4491 /*
4492  * recover relocation interrupted by system crash.
4493  *
4494  * this function resumes merging reloc trees with corresponding fs trees.
4495  * this is important for keeping the sharing of tree blocks
4496  */
4497 int btrfs_recover_relocation(struct btrfs_root *root)
4498 {
4499         struct btrfs_fs_info *fs_info = root->fs_info;
4500         LIST_HEAD(reloc_roots);
4501         struct btrfs_key key;
4502         struct btrfs_root *fs_root;
4503         struct btrfs_root *reloc_root;
4504         struct btrfs_path *path;
4505         struct extent_buffer *leaf;
4506         struct reloc_control *rc = NULL;
4507         struct btrfs_trans_handle *trans;
4508         int ret;
4509         int err = 0;
4510
4511         path = btrfs_alloc_path();
4512         if (!path)
4513                 return -ENOMEM;
4514         path->reada = READA_BACK;
4515
4516         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4517         key.type = BTRFS_ROOT_ITEM_KEY;
4518         key.offset = (u64)-1;
4519
4520         while (1) {
4521                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
4522                                         path, 0, 0);
4523                 if (ret < 0) {
4524                         err = ret;
4525                         goto out;
4526                 }
4527                 if (ret > 0) {
4528                         if (path->slots[0] == 0)
4529                                 break;
4530                         path->slots[0]--;
4531                 }
4532                 leaf = path->nodes[0];
4533                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4534                 btrfs_release_path(path);
4535
4536                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4537                     key.type != BTRFS_ROOT_ITEM_KEY)
4538                         break;
4539
4540                 reloc_root = btrfs_read_fs_root(root, &key);
4541                 if (IS_ERR(reloc_root)) {
4542                         err = PTR_ERR(reloc_root);
4543                         goto out;
4544                 }
4545
4546                 list_add(&reloc_root->root_list, &reloc_roots);
4547
4548                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4549                         fs_root = read_fs_root(fs_info,
4550                                                reloc_root->root_key.offset);
4551                         if (IS_ERR(fs_root)) {
4552                                 ret = PTR_ERR(fs_root);
4553                                 if (ret != -ENOENT) {
4554                                         err = ret;
4555                                         goto out;
4556                                 }
4557                                 ret = mark_garbage_root(reloc_root);
4558                                 if (ret < 0) {
4559                                         err = ret;
4560                                         goto out;
4561                                 }
4562                         }
4563                 }
4564
4565                 if (key.offset == 0)
4566                         break;
4567
4568                 key.offset--;
4569         }
4570         btrfs_release_path(path);
4571
4572         if (list_empty(&reloc_roots))
4573                 goto out;
4574
4575         rc = alloc_reloc_control(fs_info);
4576         if (!rc) {
4577                 err = -ENOMEM;
4578                 goto out;
4579         }
4580
4581         rc->extent_root = fs_info->extent_root;
4582
4583         set_reloc_control(rc);
4584
4585         trans = btrfs_join_transaction(rc->extent_root);
4586         if (IS_ERR(trans)) {
4587                 unset_reloc_control(rc);
4588                 err = PTR_ERR(trans);
4589                 goto out_free;
4590         }
4591
4592         rc->merge_reloc_tree = 1;
4593
4594         while (!list_empty(&reloc_roots)) {
4595                 reloc_root = list_entry(reloc_roots.next,
4596                                         struct btrfs_root, root_list);
4597                 list_del(&reloc_root->root_list);
4598
4599                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4600                         list_add_tail(&reloc_root->root_list,
4601                                       &rc->reloc_roots);
4602                         continue;
4603                 }
4604
4605                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
4606                 if (IS_ERR(fs_root)) {
4607                         err = PTR_ERR(fs_root);
4608                         list_add_tail(&reloc_root->root_list, &reloc_roots);
4609                         goto out_free;
4610                 }
4611
4612                 err = __add_reloc_root(reloc_root);
4613                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4614                 fs_root->reloc_root = reloc_root;
4615         }
4616
4617         err = btrfs_commit_transaction(trans);
4618         if (err)
4619                 goto out_free;
4620
4621         merge_reloc_roots(rc);
4622
4623         unset_reloc_control(rc);
4624
4625         trans = btrfs_join_transaction(rc->extent_root);
4626         if (IS_ERR(trans)) {
4627                 err = PTR_ERR(trans);
4628                 goto out_free;
4629         }
4630         err = btrfs_commit_transaction(trans);
4631
4632         ret = clean_dirty_subvols(rc);
4633         if (ret < 0 && !err)
4634                 err = ret;
4635 out_free:
4636         kfree(rc);
4637 out:
4638         if (!list_empty(&reloc_roots))
4639                 free_reloc_roots(&reloc_roots);
4640
4641         btrfs_free_path(path);
4642
4643         if (err == 0) {
4644                 /* cleanup orphan inode in data relocation tree */
4645                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4646                 if (IS_ERR(fs_root))
4647                         err = PTR_ERR(fs_root);
4648                 else
4649                         err = btrfs_orphan_cleanup(fs_root);
4650         }
4651         return err;
4652 }
4653
4654 /*
4655  * helper to add ordered checksum for data relocation.
4656  *
4657  * cloning checksum properly handles the nodatasum extents.
4658  * it also saves CPU time to re-calculate the checksum.
4659  */
4660 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4661 {
4662         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
4663         struct btrfs_ordered_sum *sums;
4664         struct btrfs_ordered_extent *ordered;
4665         int ret;
4666         u64 disk_bytenr;
4667         u64 new_bytenr;
4668         LIST_HEAD(list);
4669
4670         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4671         BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
4672
4673         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4674         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
4675                                        disk_bytenr + len - 1, &list, 0);
4676         if (ret)
4677                 goto out;
4678
4679         while (!list_empty(&list)) {
4680                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4681                 list_del_init(&sums->list);
4682
4683                 /*
4684                  * We need to offset the new_bytenr based on where the csum is.
4685                  * We need to do this because we will read in entire prealloc
4686                  * extents but we may have written to say the middle of the
4687                  * prealloc extent, so we need to make sure the csum goes with
4688                  * the right disk offset.
4689                  *
4690                  * We can do this because the data reloc inode refers strictly
4691                  * to the on disk bytes, so we don't have to worry about
4692                  * disk_len vs real len like with real inodes since it's all
4693                  * disk length.
4694                  */
4695                 new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
4696                 sums->bytenr = new_bytenr;
4697
4698                 btrfs_add_ordered_sum(ordered, sums);
4699         }
4700 out:
4701         btrfs_put_ordered_extent(ordered);
4702         return ret;
4703 }
4704
4705 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4706                           struct btrfs_root *root, struct extent_buffer *buf,
4707                           struct extent_buffer *cow)
4708 {
4709         struct btrfs_fs_info *fs_info = root->fs_info;
4710         struct reloc_control *rc;
4711         struct backref_node *node;
4712         int first_cow = 0;
4713         int level;
4714         int ret = 0;
4715
4716         rc = fs_info->reloc_ctl;
4717         if (!rc)
4718                 return 0;
4719
4720         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4721                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4722
4723         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
4724                 if (buf == root->node)
4725                         __update_reloc_root(root, cow->start);
4726         }
4727
4728         level = btrfs_header_level(buf);
4729         if (btrfs_header_generation(buf) <=
4730             btrfs_root_last_snapshot(&root->root_item))
4731                 first_cow = 1;
4732
4733         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4734             rc->create_reloc_tree) {
4735                 WARN_ON(!first_cow && level == 0);
4736
4737                 node = rc->backref_cache.path[level];
4738                 BUG_ON(node->bytenr != buf->start &&
4739                        node->new_bytenr != buf->start);
4740
4741                 drop_node_buffer(node);
4742                 atomic_inc(&cow->refs);
4743                 node->eb = cow;
4744                 node->new_bytenr = cow->start;
4745
4746                 if (!node->pending) {
4747                         list_move_tail(&node->list,
4748                                        &rc->backref_cache.pending[level]);
4749                         node->pending = 1;
4750                 }
4751
4752                 if (first_cow)
4753                         __mark_block_processed(rc, node);
4754
4755                 if (first_cow && level > 0)
4756                         rc->nodes_relocated += buf->len;
4757         }
4758
4759         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4760                 ret = replace_file_extents(trans, rc, root, cow);
4761         return ret;
4762 }
4763
4764 /*
4765  * called before creating snapshot. it calculates metadata reservation
4766  * required for relocating tree blocks in the snapshot
4767  */
4768 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4769                               u64 *bytes_to_reserve)
4770 {
4771         struct btrfs_root *root = pending->root;
4772         struct reloc_control *rc = root->fs_info->reloc_ctl;
4773
4774         if (!rc || !have_reloc_root(root))
4775                 return;
4776
4777         if (!rc->merge_reloc_tree)
4778                 return;
4779
4780         root = root->reloc_root;
4781         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4782         /*
4783          * relocation is in the stage of merging trees. the space
4784          * used by merging a reloc tree is twice the size of
4785          * relocated tree nodes in the worst case. half for cowing
4786          * the reloc tree, half for cowing the fs tree. the space
4787          * used by cowing the reloc tree will be freed after the
4788          * tree is dropped. if we create snapshot, cowing the fs
4789          * tree may use more space than it frees. so we need
4790          * reserve extra space.
4791          */
4792         *bytes_to_reserve += rc->nodes_relocated;
4793 }
4794
4795 /*
4796  * called after snapshot is created. migrate block reservation
4797  * and create reloc root for the newly created snapshot
4798  */
4799 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4800                                struct btrfs_pending_snapshot *pending)
4801 {
4802         struct btrfs_root *root = pending->root;
4803         struct btrfs_root *reloc_root;
4804         struct btrfs_root *new_root;
4805         struct reloc_control *rc = root->fs_info->reloc_ctl;
4806         int ret;
4807
4808         if (!rc || !have_reloc_root(root))
4809                 return 0;
4810
4811         rc = root->fs_info->reloc_ctl;
4812         rc->merging_rsv_size += rc->nodes_relocated;
4813
4814         if (rc->merge_reloc_tree) {
4815                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4816                                               rc->block_rsv,
4817                                               rc->nodes_relocated, true);
4818                 if (ret)
4819                         return ret;
4820         }
4821
4822         new_root = pending->snap;
4823         reloc_root = create_reloc_root(trans, root->reloc_root,
4824                                        new_root->root_key.objectid);
4825         if (IS_ERR(reloc_root))
4826                 return PTR_ERR(reloc_root);
4827
4828         ret = __add_reloc_root(reloc_root);
4829         BUG_ON(ret < 0);
4830         new_root->reloc_root = reloc_root;
4831
4832         if (rc->create_reloc_tree)
4833                 ret = clone_backref_node(trans, rc, root, reloc_root);
4834         return ret;
4835 }