fs/btrfs/relocation.c

   1 /*
   2  * Copyright (C) 2009 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/sched.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/writeback.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/rbtree.h>
  24 #include <linux/slab.h>
  25 #include "ctree.h"
  26 #include "disk-io.h"
  27 #include "transaction.h"
  28 #include "volumes.h"
  29 #include "locking.h"
  30 #include "btrfs_inode.h"
  31 #include "async-thread.h"
  32 #include "free-space-cache.h"
  33 #include "inode-map.h"
  34 #include "qgroup.h"
  35
  36 /*
  37  * backref_node, mapping_node and tree_block start with this
  38  */
  39 struct tree_entry {
  40         struct rb_node rb_node;
  41         u64 bytenr;
  42 };
  43
  44 /*
  45  * present a tree block in the backref cache
  46  */
  47 struct backref_node {
  48         struct rb_node rb_node;
  49         u64 bytenr;
  50
  51         u64 new_bytenr;
  52         /* objectid of tree block owner, can be not uptodate */
  53         u64 owner;
  54         /* link to pending, changed or detached list */
  55         struct list_head list;
  56         /* list of upper level blocks reference this block */
  57         struct list_head upper;
  58         /* list of child blocks in the cache */
  59         struct list_head lower;
  60         /* NULL if this node is not tree root */
  61         struct btrfs_root *root;
  62         /* extent buffer got by COW the block */
  63         struct extent_buffer *eb;
  64         /* level of tree block */
  65         unsigned int level:8;
  66         /* is the block in non-reference counted tree */
  67         unsigned int cowonly:1;
  68         /* 1 if no child node in the cache */
  69         unsigned int lowest:1;
  70         /* is the extent buffer locked */
  71         unsigned int locked:1;
  72         /* has the block been processed */
  73         unsigned int processed:1;
  74         /* have backrefs of this block been checked */
  75         unsigned int checked:1;
  76         /*
  77          * 1 if corresponding block has been cowed but some upper
  78          * level block pointers may not point to the new location
  79          */
  80         unsigned int pending:1;
  81         /*
  82          * 1 if the backref node isn't connected to any other
  83          * backref node.
  84          */
  85         unsigned int detached:1;
  86 };
  87
  88 /*
  89  * present a block pointer in the backref cache
  90  */
  91 struct backref_edge {
  92         struct list_head list[2];
  93         struct backref_node *node[2];
  94 };
  95
  96 #define LOWER   0
  97 #define UPPER   1
  98 #define RELOCATION_RESERVED_NODES       256
  99
 100 struct backref_cache {
 101         /* red black tree of all backref nodes in the cache */
 102         struct rb_root rb_root;
 103         /* for passing backref nodes to btrfs_reloc_cow_block */
 104         struct backref_node *path[BTRFS_MAX_LEVEL];
 105         /*
 106          * list of blocks that have been cowed but some block
 107          * pointers in upper level blocks may not reflect the
 108          * new location
 109          */
 110         struct list_head pending[BTRFS_MAX_LEVEL];
 111         /* list of backref nodes with no child node */
 112         struct list_head leaves;
 113         /* list of blocks that have been cowed in current transaction */
 114         struct list_head changed;
 115         /* list of detached backref node. */
 116         struct list_head detached;
 117
 118         u64 last_trans;
 119
 120         int nr_nodes;
 121         int nr_edges;
 122 };
 123
 124 /*
 125  * map address of tree root to tree
 126  */
 127 struct mapping_node {
 128         struct rb_node rb_node;
 129         u64 bytenr;
 130         void *data;
 131 };
 132
 133 struct mapping_tree {
 134         struct rb_root rb_root;
 135         spinlock_t lock;
 136 };
 137
 138 /*
 139  * present a tree block to process
 140  */
 141 struct tree_block {
 142         struct rb_node rb_node;
 143         u64 bytenr;
 144         struct btrfs_key key;
 145         unsigned int level:8;
 146         unsigned int key_ready:1;
 147 };
 148
 149 #define MAX_EXTENTS 128
 150
 151 struct file_extent_cluster {
 152         u64 start;
 153         u64 end;
 154         u64 boundary[MAX_EXTENTS];
 155         unsigned int nr;
 156 };
 157
 158 struct reloc_control {
 159         /* block group to relocate */
 160         struct btrfs_block_group_cache *block_group;
 161         /* extent tree */
 162         struct btrfs_root *extent_root;
 163         /* inode for moving data */
 164         struct inode *data_inode;
 165
 166         struct btrfs_block_rsv *block_rsv;
 167
 168         struct backref_cache backref_cache;
 169
 170         struct file_extent_cluster cluster;
 171         /* tree blocks have been processed */
 172         struct extent_io_tree processed_blocks;
 173         /* map start of tree root to corresponding reloc tree */
 174         struct mapping_tree reloc_root_tree;
 175         /* list of reloc trees */
 176         struct list_head reloc_roots;
 177         /* size of metadata reservation for merging reloc trees */
 178         u64 merging_rsv_size;
 179         /* size of relocated tree nodes */
 180         u64 nodes_relocated;
 181         /* reserved size for block group relocation*/
 182         u64 reserved_bytes;
 183
 184         u64 search_start;
 185         u64 extents_found;
 186
 187         unsigned int stage:8;
 188         unsigned int create_reloc_tree:1;
 189         unsigned int merge_reloc_tree:1;
 190         unsigned int found_file_extent:1;
 191 };
 192
 193 /* stages of data relocation */
 194 #define MOVE_DATA_EXTENTS       0
 195 #define UPDATE_DATA_PTRS        1
 196
 197 static void remove_backref_node(struct backref_cache *cache,
 198                                 struct backref_node *node);
 199 static void __mark_block_processed(struct reloc_control *rc,
 200                                    struct backref_node *node);
 201
 202 static void mapping_tree_init(struct mapping_tree *tree)
 203 {
 204         tree->rb_root = RB_ROOT;
 205         spin_lock_init(&tree->lock);
 206 }
 207
 208 static void backref_cache_init(struct backref_cache *cache)
 209 {
 210         int i;
 211         cache->rb_root = RB_ROOT;
 212         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 213                 INIT_LIST_HEAD(&cache->pending[i]);
 214         INIT_LIST_HEAD(&cache->changed);
 215         INIT_LIST_HEAD(&cache->detached);
 216         INIT_LIST_HEAD(&cache->leaves);
 217 }
 218
 219 static void backref_cache_cleanup(struct backref_cache *cache)
 220 {
 221         struct backref_node *node;
 222         int i;
 223
 224         while (!list_empty(&cache->detached)) {
 225                 node = list_entry(cache->detached.next,
 226                                   struct backref_node, list);
 227                 remove_backref_node(cache, node);
 228         }
 229
 230         while (!list_empty(&cache->leaves)) {
 231                 node = list_entry(cache->leaves.next,
 232                                   struct backref_node, lower);
 233                 remove_backref_node(cache, node);
 234         }
 235
 236         cache->last_trans = 0;
 237
 238         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 239                 ASSERT(list_empty(&cache->pending[i]));
 240         ASSERT(list_empty(&cache->changed));
 241         ASSERT(list_empty(&cache->detached));
 242         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
 243         ASSERT(!cache->nr_nodes);
 244         ASSERT(!cache->nr_edges);
 245 }
 246
 247 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
 248 {
 249         struct backref_node *node;
 250
 251         node = kzalloc(sizeof(*node), GFP_NOFS);
 252         if (node) {
 253                 INIT_LIST_HEAD(&node->list);
 254                 INIT_LIST_HEAD(&node->upper);
 255                 INIT_LIST_HEAD(&node->lower);
 256                 RB_CLEAR_NODE(&node->rb_node);
 257                 cache->nr_nodes++;
 258         }
 259         return node;
 260 }
 261
 262 static void free_backref_node(struct backref_cache *cache,
 263                               struct backref_node *node)
 264 {
 265         if (node) {
 266                 cache->nr_nodes--;
 267                 kfree(node);
 268         }
 269 }
 270
 271 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
 272 {
 273         struct backref_edge *edge;
 274
 275         edge = kzalloc(sizeof(*edge), GFP_NOFS);
 276         if (edge)
 277                 cache->nr_edges++;
 278         return edge;
 279 }
 280
 281 static void free_backref_edge(struct backref_cache *cache,
 282                               struct backref_edge *edge)
 283 {
 284         if (edge) {
 285                 cache->nr_edges--;
 286                 kfree(edge);
 287         }
 288 }
 289
 290 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
 291                                    struct rb_node *node)
 292 {
 293         struct rb_node **p = &root->rb_node;
 294         struct rb_node *parent = NULL;
 295         struct tree_entry *entry;
 296
 297         while (*p) {
 298                 parent = *p;
 299                 entry = rb_entry(parent, struct tree_entry, rb_node);
 300
 301                 if (bytenr < entry->bytenr)
 302                         p = &(*p)->rb_left;
 303                 else if (bytenr > entry->bytenr)
 304                         p = &(*p)->rb_right;
 305                 else
 306                         return parent;
 307         }
 308
 309         rb_link_node(node, parent, p);
 310         rb_insert_color(node, root);
 311         return NULL;
 312 }
 313
 314 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
 315 {
 316         struct rb_node *n = root->rb_node;
 317         struct tree_entry *entry;
 318
 319         while (n) {
 320                 entry = rb_entry(n, struct tree_entry, rb_node);
 321
 322                 if (bytenr < entry->bytenr)
 323                         n = n->rb_left;
 324                 else if (bytenr > entry->bytenr)
 325                         n = n->rb_right;
 326                 else
 327                         return n;
 328         }
 329         return NULL;
 330 }
 331
 332 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
 333 {
 334
 335         struct btrfs_fs_info *fs_info = NULL;
 336         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
 337                                               rb_node);
 338         if (bnode->root)
 339                 fs_info = bnode->root->fs_info;
 340         btrfs_panic(fs_info, errno,
 341                     "Inconsistency in backref cache found at offset %llu",
 342                     bytenr);
 343 }
 344
 345 /*
 346  * walk up backref nodes until reach node presents tree root
 347  */
 348 static struct backref_node *walk_up_backref(struct backref_node *node,
 349                                             struct backref_edge *edges[],
 350                                             int *index)
 351 {
 352         struct backref_edge *edge;
 353         int idx = *index;
 354
 355         while (!list_empty(&node->upper)) {
 356                 edge = list_entry(node->upper.next,
 357                                   struct backref_edge, list[LOWER]);
 358                 edges[idx++] = edge;
 359                 node = edge->node[UPPER];
 360         }
 361         BUG_ON(node->detached);
 362         *index = idx;
 363         return node;
 364 }
 365
 366 /*
 367  * walk down backref nodes to find start of next reference path
 368  */
 369 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
 370                                               int *index)
 371 {
 372         struct backref_edge *edge;
 373         struct backref_node *lower;
 374         int idx = *index;
 375
 376         while (idx > 0) {
 377                 edge = edges[idx - 1];
 378                 lower = edge->node[LOWER];
 379                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 380                         idx--;
 381                         continue;
 382                 }
 383                 edge = list_entry(edge->list[LOWER].next,
 384                                   struct backref_edge, list[LOWER]);
 385                 edges[idx - 1] = edge;
 386                 *index = idx;
 387                 return edge->node[UPPER];
 388         }
 389         *index = 0;
 390         return NULL;
 391 }
 392
 393 static void unlock_node_buffer(struct backref_node *node)
 394 {
 395         if (node->locked) {
 396                 btrfs_tree_unlock(node->eb);
 397                 node->locked = 0;
 398         }
 399 }
 400
 401 static void drop_node_buffer(struct backref_node *node)
 402 {
 403         if (node->eb) {
 404                 unlock_node_buffer(node);
 405                 free_extent_buffer(node->eb);
 406                 node->eb = NULL;
 407         }
 408 }
 409
 410 static void drop_backref_node(struct backref_cache *tree,
 411                               struct backref_node *node)
 412 {
 413         BUG_ON(!list_empty(&node->upper));
 414
 415         drop_node_buffer(node);
 416         list_del(&node->list);
 417         list_del(&node->lower);
 418         if (!RB_EMPTY_NODE(&node->rb_node))
 419                 rb_erase(&node->rb_node, &tree->rb_root);
 420         free_backref_node(tree, node);
 421 }
 422
 423 /*
 424  * remove a backref node from the backref cache
 425  */
 426 static void remove_backref_node(struct backref_cache *cache,
 427                                 struct backref_node *node)
 428 {
 429         struct backref_node *upper;
 430         struct backref_edge *edge;
 431
 432         if (!node)
 433                 return;
 434
 435         BUG_ON(!node->lowest && !node->detached);
 436         while (!list_empty(&node->upper)) {
 437                 edge = list_entry(node->upper.next, struct backref_edge,
 438                                   list[LOWER]);
 439                 upper = edge->node[UPPER];
 440                 list_del(&edge->list[LOWER]);
 441                 list_del(&edge->list[UPPER]);
 442                 free_backref_edge(cache, edge);
 443
 444                 if (RB_EMPTY_NODE(&upper->rb_node)) {
 445                         BUG_ON(!list_empty(&node->upper));
 446                         drop_backref_node(cache, node);
 447                         node = upper;
 448                         node->lowest = 1;
 449                         continue;
 450                 }
 451                 /*
 452                  * add the node to leaf node list if no other
 453                  * child block cached.
 454                  */
 455                 if (list_empty(&upper->lower)) {
 456                         list_add_tail(&upper->lower, &cache->leaves);
 457                         upper->lowest = 1;
 458                 }
 459         }
 460
 461         drop_backref_node(cache, node);
 462 }
 463
 464 static void update_backref_node(struct backref_cache *cache,
 465                                 struct backref_node *node, u64 bytenr)
 466 {
 467         struct rb_node *rb_node;
 468         rb_erase(&node->rb_node, &cache->rb_root);
 469         node->bytenr = bytenr;
 470         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 471         if (rb_node)
 472                 backref_tree_panic(rb_node, -EEXIST, bytenr);
 473 }
 474
 475 /*
 476  * update backref cache after a transaction commit
 477  */
 478 static int update_backref_cache(struct btrfs_trans_handle *trans,
 479                                 struct backref_cache *cache)
 480 {
 481         struct backref_node *node;
 482         int level = 0;
 483
 484         if (cache->last_trans == 0) {
 485                 cache->last_trans = trans->transid;
 486                 return 0;
 487         }
 488
 489         if (cache->last_trans == trans->transid)
 490                 return 0;
 491
 492         /*
 493          * detached nodes are used to avoid unnecessary backref
 494          * lookup. transaction commit changes the extent tree.
 495          * so the detached nodes are no longer useful.
 496          */
 497         while (!list_empty(&cache->detached)) {
 498                 node = list_entry(cache->detached.next,
 499                                   struct backref_node, list);
 500                 remove_backref_node(cache, node);
 501         }
 502
 503         while (!list_empty(&cache->changed)) {
 504                 node = list_entry(cache->changed.next,
 505                                   struct backref_node, list);
 506                 list_del_init(&node->list);
 507                 BUG_ON(node->pending);
 508                 update_backref_node(cache, node, node->new_bytenr);
 509         }
 510
 511         /*
 512          * some nodes can be left in the pending list if there were
 513          * errors during processing the pending nodes.
 514          */
 515         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 516                 list_for_each_entry(node, &cache->pending[level], list) {
 517                         BUG_ON(!node->pending);
 518                         if (node->bytenr == node->new_bytenr)
 519                                 continue;
 520                         update_backref_node(cache, node, node->new_bytenr);
 521                 }
 522         }
 523
 524         cache->last_trans = 0;
 525         return 1;
 526 }
 527
 528
 529 static int should_ignore_root(struct btrfs_root *root)
 530 {
 531         struct btrfs_root *reloc_root;
 532
 533         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 534                 return 0;
 535
 536         reloc_root = root->reloc_root;
 537         if (!reloc_root)
 538                 return 0;
 539
 540         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
 541             root->fs_info->running_transaction->transid - 1)
 542                 return 0;
 543         /*
 544          * if there is reloc tree and it was created in previous
 545          * transaction backref lookup can find the reloc tree,
 546          * so backref node for the fs tree root is useless for
 547          * relocation.
 548          */
 549         return 1;
 550 }
 551 /*
 552  * find reloc tree by address of tree root
 553  */
 554 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
 555                                           u64 bytenr)
 556 {
 557         struct rb_node *rb_node;
 558         struct mapping_node *node;
 559         struct btrfs_root *root = NULL;
 560
 561         spin_lock(&rc->reloc_root_tree.lock);
 562         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
 563         if (rb_node) {
 564                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 565                 root = (struct btrfs_root *)node->data;
 566         }
 567         spin_unlock(&rc->reloc_root_tree.lock);
 568         return root;
 569 }
 570
 571 static int is_cowonly_root(u64 root_objectid)
 572 {
 573         if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
 574             root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
 575             root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
 576             root_objectid == BTRFS_DEV_TREE_OBJECTID ||
 577             root_objectid == BTRFS_TREE_LOG_OBJECTID ||
 578             root_objectid == BTRFS_CSUM_TREE_OBJECTID ||
 579             root_objectid == BTRFS_UUID_TREE_OBJECTID ||
 580             root_objectid == BTRFS_QUOTA_TREE_OBJECTID ||
 581             root_objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
 582                 return 1;
 583         return 0;
 584 }
 585
 586 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 587                                         u64 root_objectid)
 588 {
 589         struct btrfs_key key;
 590
 591         key.objectid = root_objectid;
 592         key.type = BTRFS_ROOT_ITEM_KEY;
 593         if (is_cowonly_root(root_objectid))
 594                 key.offset = 0;
 595         else
 596                 key.offset = (u64)-1;
 597
 598         return btrfs_get_fs_root(fs_info, &key, false);
 599 }
 600
 601 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 602 static noinline_for_stack
 603 struct btrfs_root *find_tree_root(struct reloc_control *rc,
 604                                   struct extent_buffer *leaf,
 605                                   struct btrfs_extent_ref_v0 *ref0)
 606 {
 607         struct btrfs_root *root;
 608         u64 root_objectid = btrfs_ref_root_v0(leaf, ref0);
 609         u64 generation = btrfs_ref_generation_v0(leaf, ref0);
 610
 611         BUG_ON(root_objectid == BTRFS_TREE_RELOC_OBJECTID);
 612
 613         root = read_fs_root(rc->extent_root->fs_info, root_objectid);
 614         BUG_ON(IS_ERR(root));
 615
 616         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 617             generation != btrfs_root_generation(&root->root_item))
 618                 return NULL;
 619
 620         return root;
 621 }
 622 #endif
 623
 624 static noinline_for_stack
 625 int find_inline_backref(struct extent_buffer *leaf, int slot,
 626                         unsigned long *ptr, unsigned long *end)
 627 {
 628         struct btrfs_key key;
 629         struct btrfs_extent_item *ei;
 630         struct btrfs_tree_block_info *bi;
 631         u32 item_size;
 632
 633         btrfs_item_key_to_cpu(leaf, &key, slot);
 634
 635         item_size = btrfs_item_size_nr(leaf, slot);
 636 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 637         if (item_size < sizeof(*ei)) {
 638                 WARN_ON(item_size != sizeof(struct btrfs_extent_item_v0));
 639                 return 1;
 640         }
 641 #endif
 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;
 688         struct btrfs_path *path2;
 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);
 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                         iref = (struct btrfs_extent_inline_ref *)ptr;
 803                         key.type = btrfs_extent_inline_ref_type(eb, iref);
 804                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
 805                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
 806                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
 807                 }
 808
 809                 if (exist &&
 810                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
 811                       exist->owner == key.offset) ||
 812                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
 813                       exist->bytenr == key.offset))) {
 814                         exist = NULL;
 815                         goto next;
 816                 }
 817
 818 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
 819                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY ||
 820                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
 821                         if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
 822                                 struct btrfs_extent_ref_v0 *ref0;
 823                                 ref0 = btrfs_item_ptr(eb, path1->slots[0],
 824                                                 struct btrfs_extent_ref_v0);
 825                                 if (key.objectid == key.offset) {
 826                                         root = find_tree_root(rc, eb, ref0);
 827                                         if (root && !should_ignore_root(root))
 828                                                 cur->root = root;
 829                                         else
 830                                                 list_add(&cur->list, &useless);
 831                                         break;
 832                                 }
 833                                 if (is_cowonly_root(btrfs_ref_root_v0(eb,
 834                                                                       ref0)))
 835                                         cur->cowonly = 1;
 836                         }
 837 #else
 838                 ASSERT(key.type != BTRFS_EXTENT_REF_V0_KEY);
 839                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
 840 #endif
 841                         if (key.objectid == key.offset) {
 842                                 /*
 843                                  * only root blocks of reloc trees use
 844                                  * backref of this type.
 845                                  */
 846                                 root = find_reloc_root(rc, cur->bytenr);
 847                                 ASSERT(root);
 848                                 cur->root = root;
 849                                 break;
 850                         }
 851
 852                         edge = alloc_backref_edge(cache);
 853                         if (!edge) {
 854                                 err = -ENOMEM;
 855                                 goto out;
 856                         }
 857                         rb_node = tree_search(&cache->rb_root, key.offset);
 858                         if (!rb_node) {
 859                                 upper = alloc_backref_node(cache);
 860                                 if (!upper) {
 861                                         free_backref_edge(cache, edge);
 862                                         err = -ENOMEM;
 863                                         goto out;
 864                                 }
 865                                 upper->bytenr = key.offset;
 866                                 upper->level = cur->level + 1;
 867                                 /*
 868                                  *  backrefs for the upper level block isn't
 869                                  *  cached, add the block to pending list
 870                                  */
 871                                 list_add_tail(&edge->list[UPPER], &list);
 872                         } else {
 873                                 upper = rb_entry(rb_node, struct backref_node,
 874                                                  rb_node);
 875                                 ASSERT(upper->checked);
 876                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 877                         }
 878                         list_add_tail(&edge->list[LOWER], &cur->upper);
 879                         edge->node[LOWER] = cur;
 880                         edge->node[UPPER] = upper;
 881
 882                         goto next;
 883                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
 884                         goto next;
 885                 }
 886
 887                 /* key.type == BTRFS_TREE_BLOCK_REF_KEY */
 888                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
 889                 if (IS_ERR(root)) {
 890                         err = PTR_ERR(root);
 891                         goto out;
 892                 }
 893
 894                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 895                         cur->cowonly = 1;
 896
 897                 if (btrfs_root_level(&root->root_item) == cur->level) {
 898                         /* tree root */
 899                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
 900                                cur->bytenr);
 901                         if (should_ignore_root(root))
 902                                 list_add(&cur->list, &useless);
 903                         else
 904                                 cur->root = root;
 905                         break;
 906                 }
 907
 908                 level = cur->level + 1;
 909
 910                 /*
 911                  * searching the tree to find upper level blocks
 912                  * reference the block.
 913                  */
 914                 path2->search_commit_root = 1;
 915                 path2->skip_locking = 1;
 916                 path2->lowest_level = level;
 917                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
 918                 path2->lowest_level = 0;
 919                 if (ret < 0) {
 920                         err = ret;
 921                         goto out;
 922                 }
 923                 if (ret > 0 && path2->slots[level] > 0)
 924                         path2->slots[level]--;
 925
 926                 eb = path2->nodes[level];
 927                 if (btrfs_node_blockptr(eb, path2->slots[level]) !=
 928                     cur->bytenr) {
 929                         btrfs_err(root->fs_info,
 930         "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
 931                                   cur->bytenr, level - 1, root->objectid,
 932                                   node_key->objectid, node_key->type,
 933                                   node_key->offset);
 934                         err = -ENOENT;
 935                         goto out;
 936                 }
 937                 lower = cur;
 938                 need_check = true;
 939                 for (; level < BTRFS_MAX_LEVEL; level++) {
 940                         if (!path2->nodes[level]) {
 941                                 ASSERT(btrfs_root_bytenr(&root->root_item) ==
 942                                        lower->bytenr);
 943                                 if (should_ignore_root(root))
 944                                         list_add(&lower->list, &useless);
 945                                 else
 946                                         lower->root = root;
 947                                 break;
 948                         }
 949
 950                         edge = alloc_backref_edge(cache);
 951                         if (!edge) {
 952                                 err = -ENOMEM;
 953                                 goto out;
 954                         }
 955
 956                         eb = path2->nodes[level];
 957                         rb_node = tree_search(&cache->rb_root, eb->start);
 958                         if (!rb_node) {
 959                                 upper = alloc_backref_node(cache);
 960                                 if (!upper) {
 961                                         free_backref_edge(cache, edge);
 962                                         err = -ENOMEM;
 963                                         goto out;
 964                                 }
 965                                 upper->bytenr = eb->start;
 966                                 upper->owner = btrfs_header_owner(eb);
 967                                 upper->level = lower->level + 1;
 968                                 if (!test_bit(BTRFS_ROOT_REF_COWS,
 969                                               &root->state))
 970                                         upper->cowonly = 1;
 971
 972                                 /*
 973                                  * if we know the block isn't shared
 974                                  * we can void checking its backrefs.
 975                                  */
 976                                 if (btrfs_block_can_be_shared(root, eb))
 977                                         upper->checked = 0;
 978                                 else
 979                                         upper->checked = 1;
 980
 981                                 /*
 982                                  * add the block to pending list if we
 983                                  * need check its backrefs, we only do this once
 984                                  * while walking up a tree as we will catch
 985                                  * anything else later on.
 986                                  */
 987                                 if (!upper->checked && need_check) {
 988                                         need_check = false;
 989                                         list_add_tail(&edge->list[UPPER],
 990                                                       &list);
 991                                 } else {
 992                                         if (upper->checked)
 993                                                 need_check = true;
 994                                         INIT_LIST_HEAD(&edge->list[UPPER]);
 995                                 }
 996                         } else {
 997                                 upper = rb_entry(rb_node, struct backref_node,
 998                                                  rb_node);
 999                                 ASSERT(upper->checked);
1000                                 INIT_LIST_HEAD(&edge->list[UPPER]);
1001                                 if (!upper->owner)
1002                                         upper->owner = btrfs_header_owner(eb);
1003                         }
1004                         list_add_tail(&edge->list[LOWER], &lower->upper);
1005                         edge->node[LOWER] = lower;
1006                         edge->node[UPPER] = upper;
1007
1008                         if (rb_node)
1009                                 break;
1010                         lower = upper;
1011                         upper = NULL;
1012                 }
1013                 btrfs_release_path(path2);
1014 next:
1015                 if (ptr < end) {
1016                         ptr += btrfs_extent_inline_ref_size(key.type);
1017                         if (ptr >= end) {
1018                                 WARN_ON(ptr > end);
1019                                 ptr = 0;
1020                                 end = 0;
1021                         }
1022                 }
1023                 if (ptr >= end)
1024                         path1->slots[0]++;
1025         }
1026         btrfs_release_path(path1);
1027
1028         cur->checked = 1;
1029         WARN_ON(exist);
1030
1031         /* the pending list isn't empty, take the first block to process */
1032         if (!list_empty(&list)) {
1033                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1034                 list_del_init(&edge->list[UPPER]);
1035                 cur = edge->node[UPPER];
1036                 goto again;
1037         }
1038
1039         /*
1040          * everything goes well, connect backref nodes and insert backref nodes
1041          * into the cache.
1042          */
1043         ASSERT(node->checked);
1044         cowonly = node->cowonly;
1045         if (!cowonly) {
1046                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1047                                       &node->rb_node);
1048                 if (rb_node)
1049                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1050                 list_add_tail(&node->lower, &cache->leaves);
1051         }
1052
1053         list_for_each_entry(edge, &node->upper, list[LOWER])
1054                 list_add_tail(&edge->list[UPPER], &list);
1055
1056         while (!list_empty(&list)) {
1057                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1058                 list_del_init(&edge->list[UPPER]);
1059                 upper = edge->node[UPPER];
1060                 if (upper->detached) {
1061                         list_del(&edge->list[LOWER]);
1062                         lower = edge->node[LOWER];
1063                         free_backref_edge(cache, edge);
1064                         if (list_empty(&lower->upper))
1065                                 list_add(&lower->list, &useless);
1066                         continue;
1067                 }
1068
1069                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1070                         if (upper->lowest) {
1071                                 list_del_init(&upper->lower);
1072                                 upper->lowest = 0;
1073                         }
1074
1075                         list_add_tail(&edge->list[UPPER], &upper->lower);
1076                         continue;
1077                 }
1078
1079                 if (!upper->checked) {
1080                         /*
1081                          * Still want to blow up for developers since this is a
1082                          * logic bug.
1083                          */
1084                         ASSERT(0);
1085                         err = -EINVAL;
1086                         goto out;
1087                 }
1088                 if (cowonly != upper->cowonly) {
1089                         ASSERT(0);
1090                         err = -EINVAL;
1091                         goto out;
1092                 }
1093
1094                 if (!cowonly) {
1095                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1096                                               &upper->rb_node);
1097                         if (rb_node)
1098                                 backref_tree_panic(rb_node, -EEXIST,
1099                                                    upper->bytenr);
1100                 }
1101
1102                 list_add_tail(&edge->list[UPPER], &upper->lower);
1103
1104                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1105                         list_add_tail(&edge->list[UPPER], &list);
1106         }
1107         /*
1108          * process useless backref nodes. backref nodes for tree leaves
1109          * are deleted from the cache. backref nodes for upper level
1110          * tree blocks are left in the cache to avoid unnecessary backref
1111          * lookup.
1112          */
1113         while (!list_empty(&useless)) {
1114                 upper = list_entry(useless.next, struct backref_node, list);
1115                 list_del_init(&upper->list);
1116                 ASSERT(list_empty(&upper->upper));
1117                 if (upper == node)
1118                         node = NULL;
1119                 if (upper->lowest) {
1120                         list_del_init(&upper->lower);
1121                         upper->lowest = 0;
1122                 }
1123                 while (!list_empty(&upper->lower)) {
1124                         edge = list_entry(upper->lower.next,
1125                                           struct backref_edge, list[UPPER]);
1126                         list_del(&edge->list[UPPER]);
1127                         list_del(&edge->list[LOWER]);
1128                         lower = edge->node[LOWER];
1129                         free_backref_edge(cache, edge);
1130
1131                         if (list_empty(&lower->upper))
1132                                 list_add(&lower->list, &useless);
1133                 }
1134                 __mark_block_processed(rc, upper);
1135                 if (upper->level > 0) {
1136                         list_add(&upper->list, &cache->detached);
1137                         upper->detached = 1;
1138                 } else {
1139                         rb_erase(&upper->rb_node, &cache->rb_root);
1140                         free_backref_node(cache, upper);
1141                 }
1142         }
1143 out:
1144         btrfs_free_path(path1);
1145         btrfs_free_path(path2);
1146         if (err) {
1147                 while (!list_empty(&useless)) {
1148                         lower = list_entry(useless.next,
1149                                            struct backref_node, list);
1150                         list_del_init(&lower->list);
1151                 }
1152                 while (!list_empty(&list)) {
1153                         edge = list_first_entry(&list, struct backref_edge,
1154                                                 list[UPPER]);
1155                         list_del(&edge->list[UPPER]);
1156                         list_del(&edge->list[LOWER]);
1157                         lower = edge->node[LOWER];
1158                         upper = edge->node[UPPER];
1159                         free_backref_edge(cache, edge);
1160
1161                         /*
1162                          * Lower is no longer linked to any upper backref nodes
1163                          * and isn't in the cache, we can free it ourselves.
1164                          */
1165                         if (list_empty(&lower->upper) &&
1166                             RB_EMPTY_NODE(&lower->rb_node))
1167                                 list_add(&lower->list, &useless);
1168
1169                         if (!RB_EMPTY_NODE(&upper->rb_node))
1170                                 continue;
1171
1172                         /* Add this guy's upper edges to the list to process */
1173                         list_for_each_entry(edge, &upper->upper, list[LOWER])
1174                                 list_add_tail(&edge->list[UPPER], &list);
1175                         if (list_empty(&upper->upper))
1176                                 list_add(&upper->list, &useless);
1177                 }
1178
1179                 while (!list_empty(&useless)) {
1180                         lower = list_entry(useless.next,
1181                                            struct backref_node, list);
1182                         list_del_init(&lower->list);
1183                         if (lower == node)
1184                                 node = NULL;
1185                         free_backref_node(cache, lower);
1186                 }
1187
1188                 free_backref_node(cache, node);
1189                 return ERR_PTR(err);
1190         }
1191         ASSERT(!node || !node->detached);
1192         return node;
1193 }
1194
1195 /*
1196  * helper to add backref node for the newly created snapshot.
1197  * the backref node is created by cloning backref node that
1198  * corresponds to root of source tree
1199  */
1200 static int clone_backref_node(struct btrfs_trans_handle *trans,
1201                               struct reloc_control *rc,
1202                               struct btrfs_root *src,
1203                               struct btrfs_root *dest)
1204 {
1205         struct btrfs_root *reloc_root = src->reloc_root;
1206         struct backref_cache *cache = &rc->backref_cache;
1207         struct backref_node *node = NULL;
1208         struct backref_node *new_node;
1209         struct backref_edge *edge;
1210         struct backref_edge *new_edge;
1211         struct rb_node *rb_node;
1212
1213         if (cache->last_trans > 0)
1214                 update_backref_cache(trans, cache);
1215
1216         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1217         if (rb_node) {
1218                 node = rb_entry(rb_node, struct backref_node, rb_node);
1219                 if (node->detached)
1220                         node = NULL;
1221                 else
1222                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1223         }
1224
1225         if (!node) {
1226                 rb_node = tree_search(&cache->rb_root,
1227                                       reloc_root->commit_root->start);
1228                 if (rb_node) {
1229                         node = rb_entry(rb_node, struct backref_node,
1230                                         rb_node);
1231                         BUG_ON(node->detached);
1232                 }
1233         }
1234
1235         if (!node)
1236                 return 0;
1237
1238         new_node = alloc_backref_node(cache);
1239         if (!new_node)
1240                 return -ENOMEM;
1241
1242         new_node->bytenr = dest->node->start;
1243         new_node->level = node->level;
1244         new_node->lowest = node->lowest;
1245         new_node->checked = 1;
1246         new_node->root = dest;
1247
1248         if (!node->lowest) {
1249                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1250                         new_edge = alloc_backref_edge(cache);
1251                         if (!new_edge)
1252                                 goto fail;
1253
1254                         new_edge->node[UPPER] = new_node;
1255                         new_edge->node[LOWER] = edge->node[LOWER];
1256                         list_add_tail(&new_edge->list[UPPER],
1257                                       &new_node->lower);
1258                 }
1259         } else {
1260                 list_add_tail(&new_node->lower, &cache->leaves);
1261         }
1262
1263         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1264                               &new_node->rb_node);
1265         if (rb_node)
1266                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1267
1268         if (!new_node->lowest) {
1269                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1270                         list_add_tail(&new_edge->list[LOWER],
1271                                       &new_edge->node[LOWER]->upper);
1272                 }
1273         }
1274         return 0;
1275 fail:
1276         while (!list_empty(&new_node->lower)) {
1277                 new_edge = list_entry(new_node->lower.next,
1278                                       struct backref_edge, list[UPPER]);
1279                 list_del(&new_edge->list[UPPER]);
1280                 free_backref_edge(cache, new_edge);
1281         }
1282         free_backref_node(cache, new_node);
1283         return -ENOMEM;
1284 }
1285
1286 /*
1287  * helper to add 'address of tree root -> reloc tree' mapping
1288  */
1289 static int __must_check __add_reloc_root(struct btrfs_root *root)
1290 {
1291         struct rb_node *rb_node;
1292         struct mapping_node *node;
1293         struct reloc_control *rc = root->fs_info->reloc_ctl;
1294
1295         node = kmalloc(sizeof(*node), GFP_NOFS);
1296         if (!node)
1297                 return -ENOMEM;
1298
1299         node->bytenr = root->node->start;
1300         node->data = root;
1301
1302         spin_lock(&rc->reloc_root_tree.lock);
1303         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1304                               node->bytenr, &node->rb_node);
1305         spin_unlock(&rc->reloc_root_tree.lock);
1306         if (rb_node) {
1307                 btrfs_panic(root->fs_info, -EEXIST,
1308                             "Duplicate root found for start=%llu while inserting into relocation tree",
1309                             node->bytenr);
1310                 kfree(node);
1311                 return -EEXIST;
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 rb_node *rb_node;
1325         struct mapping_node *node = NULL;
1326         struct reloc_control *rc = root->fs_info->reloc_ctl;
1327
1328         spin_lock(&rc->reloc_root_tree.lock);
1329         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1330                               root->node->start);
1331         if (rb_node) {
1332                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1333                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1334         }
1335         spin_unlock(&rc->reloc_root_tree.lock);
1336
1337         if (!node)
1338                 return;
1339         BUG_ON((struct btrfs_root *)node->data != root);
1340
1341         spin_lock(&root->fs_info->trans_lock);
1342         list_del_init(&root->root_list);
1343         spin_unlock(&root->fs_info->trans_lock);
1344         kfree(node);
1345 }
1346
1347 /*
1348  * helper to update the 'address of tree root -> reloc tree'
1349  * mapping
1350  */
1351 static int __update_reloc_root(struct btrfs_root *root, u64 new_bytenr)
1352 {
1353         struct rb_node *rb_node;
1354         struct mapping_node *node = NULL;
1355         struct reloc_control *rc = root->fs_info->reloc_ctl;
1356
1357         spin_lock(&rc->reloc_root_tree.lock);
1358         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1359                               root->node->start);
1360         if (rb_node) {
1361                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1362                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1363         }
1364         spin_unlock(&rc->reloc_root_tree.lock);
1365
1366         if (!node)
1367                 return 0;
1368         BUG_ON((struct btrfs_root *)node->data != root);
1369
1370         spin_lock(&rc->reloc_root_tree.lock);
1371         node->bytenr = new_bytenr;
1372         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1373                               node->bytenr, &node->rb_node);
1374         spin_unlock(&rc->reloc_root_tree.lock);
1375         if (rb_node)
1376                 backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1377         return 0;
1378 }
1379
1380 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1381                                         struct btrfs_root *root, u64 objectid)
1382 {
1383         struct btrfs_root *reloc_root;
1384         struct extent_buffer *eb;
1385         struct btrfs_root_item *root_item;
1386         struct btrfs_key root_key;
1387         u64 last_snap = 0;
1388         int ret;
1389
1390         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1391         BUG_ON(!root_item);
1392
1393         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1394         root_key.type = BTRFS_ROOT_ITEM_KEY;
1395         root_key.offset = objectid;
1396
1397         if (root->root_key.objectid == objectid) {
1398                 /* called by btrfs_init_reloc_root */
1399                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1400                                       BTRFS_TREE_RELOC_OBJECTID);
1401                 BUG_ON(ret);
1402
1403                 last_snap = btrfs_root_last_snapshot(&root->root_item);
1404                 btrfs_set_root_last_snapshot(&root->root_item,
1405                                              trans->transid - 1);
1406         } else {
1407                 /*
1408                  * called by btrfs_reloc_post_snapshot_hook.
1409                  * the source tree is a reloc tree, all tree blocks
1410                  * modified after it was created have RELOC flag
1411                  * set in their headers. so it's OK to not update
1412                  * the 'last_snapshot'.
1413                  */
1414                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1415                                       BTRFS_TREE_RELOC_OBJECTID);
1416                 BUG_ON(ret);
1417         }
1418
1419         memcpy(root_item, &root->root_item, sizeof(*root_item));
1420         btrfs_set_root_bytenr(root_item, eb->start);
1421         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1422         btrfs_set_root_generation(root_item, trans->transid);
1423
1424         if (root->root_key.objectid == objectid) {
1425                 btrfs_set_root_refs(root_item, 0);
1426                 memset(&root_item->drop_progress, 0,
1427                        sizeof(struct btrfs_disk_key));
1428                 root_item->drop_level = 0;
1429                 /*
1430                  * abuse rtransid, it is safe because it is impossible to
1431                  * receive data into a relocation tree.
1432                  */
1433                 btrfs_set_root_rtransid(root_item, last_snap);
1434                 btrfs_set_root_otransid(root_item, trans->transid);
1435         }
1436
1437         btrfs_tree_unlock(eb);
1438         free_extent_buffer(eb);
1439
1440         ret = btrfs_insert_root(trans, root->fs_info->tree_root,
1441                                 &root_key, root_item);
1442         BUG_ON(ret);
1443         kfree(root_item);
1444
1445         reloc_root = btrfs_read_fs_root(root->fs_info->tree_root, &root_key);
1446         BUG_ON(IS_ERR(reloc_root));
1447         reloc_root->last_trans = trans->transid;
1448         return reloc_root;
1449 }
1450
1451 /*
1452  * create reloc tree for a given fs tree. reloc tree is just a
1453  * snapshot of the fs tree with special root objectid.
1454  */
1455 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1456                           struct btrfs_root *root)
1457 {
1458         struct btrfs_root *reloc_root;
1459         struct reloc_control *rc = root->fs_info->reloc_ctl;
1460         struct btrfs_block_rsv *rsv;
1461         int clear_rsv = 0;
1462         int ret;
1463
1464         if (root->reloc_root) {
1465                 reloc_root = root->reloc_root;
1466                 reloc_root->last_trans = trans->transid;
1467                 return 0;
1468         }
1469
1470         if (!rc || !rc->create_reloc_tree ||
1471             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1472                 return 0;
1473
1474         if (!trans->reloc_reserved) {
1475                 rsv = trans->block_rsv;
1476                 trans->block_rsv = rc->block_rsv;
1477                 clear_rsv = 1;
1478         }
1479         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1480         if (clear_rsv)
1481                 trans->block_rsv = rsv;
1482
1483         ret = __add_reloc_root(reloc_root);
1484         BUG_ON(ret < 0);
1485         root->reloc_root = reloc_root;
1486         return 0;
1487 }
1488
1489 /*
1490  * update root item of reloc tree
1491  */
1492 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1493                             struct btrfs_root *root)
1494 {
1495         struct btrfs_root *reloc_root;
1496         struct btrfs_root_item *root_item;
1497         int ret;
1498
1499         if (!root->reloc_root)
1500                 goto out;
1501
1502         reloc_root = root->reloc_root;
1503         root_item = &reloc_root->root_item;
1504
1505         if (root->fs_info->reloc_ctl->merge_reloc_tree &&
1506             btrfs_root_refs(root_item) == 0) {
1507                 root->reloc_root = NULL;
1508                 __del_reloc_root(reloc_root);
1509         }
1510
1511         if (reloc_root->commit_root != reloc_root->node) {
1512                 btrfs_set_root_node(root_item, reloc_root->node);
1513                 free_extent_buffer(reloc_root->commit_root);
1514                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1515         }
1516
1517         ret = btrfs_update_root(trans, root->fs_info->tree_root,
1518                                 &reloc_root->root_key, root_item);
1519         BUG_ON(ret);
1520
1521 out:
1522         return 0;
1523 }
1524
1525 /*
1526  * helper to find first cached inode with inode number >= objectid
1527  * in a subvolume
1528  */
1529 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1530 {
1531         struct rb_node *node;
1532         struct rb_node *prev;
1533         struct btrfs_inode *entry;
1534         struct inode *inode;
1535
1536         spin_lock(&root->inode_lock);
1537 again:
1538         node = root->inode_tree.rb_node;
1539         prev = NULL;
1540         while (node) {
1541                 prev = node;
1542                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1543
1544                 if (objectid < btrfs_ino(&entry->vfs_inode))
1545                         node = node->rb_left;
1546                 else if (objectid > btrfs_ino(&entry->vfs_inode))
1547                         node = node->rb_right;
1548                 else
1549                         break;
1550         }
1551         if (!node) {
1552                 while (prev) {
1553                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1554                         if (objectid <= btrfs_ino(&entry->vfs_inode)) {
1555                                 node = prev;
1556                                 break;
1557                         }
1558                         prev = rb_next(prev);
1559                 }
1560         }
1561         while (node) {
1562                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1563                 inode = igrab(&entry->vfs_inode);
1564                 if (inode) {
1565                         spin_unlock(&root->inode_lock);
1566                         return inode;
1567                 }
1568
1569                 objectid = btrfs_ino(&entry->vfs_inode) + 1;
1570                 if (cond_resched_lock(&root->inode_lock))
1571                         goto again;
1572
1573                 node = rb_next(node);
1574         }
1575         spin_unlock(&root->inode_lock);
1576         return NULL;
1577 }
1578
1579 static int in_block_group(u64 bytenr,
1580                           struct btrfs_block_group_cache *block_group)
1581 {
1582         if (bytenr >= block_group->key.objectid &&
1583             bytenr < block_group->key.objectid + block_group->key.offset)
1584                 return 1;
1585         return 0;
1586 }
1587
1588 /*
1589  * get new location of data
1590  */
1591 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1592                             u64 bytenr, u64 num_bytes)
1593 {
1594         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1595         struct btrfs_path *path;
1596         struct btrfs_file_extent_item *fi;
1597         struct extent_buffer *leaf;
1598         int ret;
1599
1600         path = btrfs_alloc_path();
1601         if (!path)
1602                 return -ENOMEM;
1603
1604         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1605         ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(reloc_inode),
1606                                        bytenr, 0);
1607         if (ret < 0)
1608                 goto out;
1609         if (ret > 0) {
1610                 ret = -ENOENT;
1611                 goto out;
1612         }
1613
1614         leaf = path->nodes[0];
1615         fi = btrfs_item_ptr(leaf, path->slots[0],
1616                             struct btrfs_file_extent_item);
1617
1618         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1619                btrfs_file_extent_compression(leaf, fi) ||
1620                btrfs_file_extent_encryption(leaf, fi) ||
1621                btrfs_file_extent_other_encoding(leaf, fi));
1622
1623         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1624                 ret = -EINVAL;
1625                 goto out;
1626         }
1627
1628         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1629         ret = 0;
1630 out:
1631         btrfs_free_path(path);
1632         return ret;
1633 }
1634
1635 /*
1636  * update file extent items in the tree leaf to point to
1637  * the new locations.
1638  */
1639 static noinline_for_stack
1640 int replace_file_extents(struct btrfs_trans_handle *trans,
1641                          struct reloc_control *rc,
1642                          struct btrfs_root *root,
1643                          struct extent_buffer *leaf)
1644 {
1645         struct btrfs_key key;
1646         struct btrfs_file_extent_item *fi;
1647         struct inode *inode = NULL;
1648         u64 parent;
1649         u64 bytenr;
1650         u64 new_bytenr = 0;
1651         u64 num_bytes;
1652         u64 end;
1653         u32 nritems;
1654         u32 i;
1655         int ret = 0;
1656         int first = 1;
1657         int dirty = 0;
1658
1659         if (rc->stage != UPDATE_DATA_PTRS)
1660                 return 0;
1661
1662         /* reloc trees always use full backref */
1663         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1664                 parent = leaf->start;
1665         else
1666                 parent = 0;
1667
1668         nritems = btrfs_header_nritems(leaf);
1669         for (i = 0; i < nritems; i++) {
1670                 cond_resched();
1671                 btrfs_item_key_to_cpu(leaf, &key, i);
1672                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1673                         continue;
1674                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1675                 if (btrfs_file_extent_type(leaf, fi) ==
1676                     BTRFS_FILE_EXTENT_INLINE)
1677                         continue;
1678                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1679                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1680                 if (bytenr == 0)
1681                         continue;
1682                 if (!in_block_group(bytenr, rc->block_group))
1683                         continue;
1684
1685                 /*
1686                  * if we are modifying block in fs tree, wait for readpage
1687                  * to complete and drop the extent cache
1688                  */
1689                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1690                         if (first) {
1691                                 inode = find_next_inode(root, key.objectid);
1692                                 first = 0;
1693                         } else if (inode && btrfs_ino(inode) < key.objectid) {
1694                                 btrfs_add_delayed_iput(inode);
1695                                 inode = find_next_inode(root, key.objectid);
1696                         }
1697                         if (inode && btrfs_ino(inode) == key.objectid) {
1698                                 end = key.offset +
1699                                       btrfs_file_extent_num_bytes(leaf, fi);
1700                                 WARN_ON(!IS_ALIGNED(key.offset,
1701                                                     root->sectorsize));
1702                                 WARN_ON(!IS_ALIGNED(end, root->sectorsize));
1703                                 end--;
1704                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1705                                                       key.offset, end);
1706                                 if (!ret)
1707                                         continue;
1708
1709                                 btrfs_drop_extent_cache(inode, key.offset, end,
1710                                                         1);
1711                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1712                                               key.offset, end);
1713                         }
1714                 }
1715
1716                 ret = get_new_location(rc->data_inode, &new_bytenr,
1717                                        bytenr, num_bytes);
1718                 if (ret) {
1719                         /*
1720                          * Don't have to abort since we've not changed anything
1721                          * in the file extent yet.
1722                          */
1723                         break;
1724                 }
1725
1726                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1727                 dirty = 1;
1728
1729                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1730                 ret = btrfs_inc_extent_ref(trans, root, new_bytenr,
1731                                            num_bytes, parent,
1732                                            btrfs_header_owner(leaf),
1733                                            key.objectid, key.offset);
1734                 if (ret) {
1735                         btrfs_abort_transaction(trans, ret);
1736                         break;
1737                 }
1738
1739                 ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
1740                                         parent, btrfs_header_owner(leaf),
1741                                         key.objectid, key.offset);
1742                 if (ret) {
1743                         btrfs_abort_transaction(trans, ret);
1744                         break;
1745                 }
1746         }
1747         if (dirty)
1748                 btrfs_mark_buffer_dirty(leaf);
1749         if (inode)
1750                 btrfs_add_delayed_iput(inode);
1751         return ret;
1752 }
1753
1754 static noinline_for_stack
1755 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1756                      struct btrfs_path *path, int level)
1757 {
1758         struct btrfs_disk_key key1;
1759         struct btrfs_disk_key key2;
1760         btrfs_node_key(eb, &key1, slot);
1761         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1762         return memcmp(&key1, &key2, sizeof(key1));
1763 }
1764
1765 /*
1766  * try to replace tree blocks in fs tree with the new blocks
1767  * in reloc tree. tree blocks haven't been modified since the
1768  * reloc tree was create can be replaced.
1769  *
1770  * if a block was replaced, level of the block + 1 is returned.
1771  * if no block got replaced, 0 is returned. if there are other
1772  * errors, a negative error number is returned.
1773  */
1774 static noinline_for_stack
1775 int replace_path(struct btrfs_trans_handle *trans,
1776                  struct btrfs_root *dest, struct btrfs_root *src,
1777                  struct btrfs_path *path, struct btrfs_key *next_key,
1778                  int lowest_level, int max_level)
1779 {
1780         struct extent_buffer *eb;
1781         struct extent_buffer *parent;
1782         struct btrfs_key key;
1783         u64 old_bytenr;
1784         u64 new_bytenr;
1785         u64 old_ptr_gen;
1786         u64 new_ptr_gen;
1787         u64 last_snapshot;
1788         u32 blocksize;
1789         int cow = 0;
1790         int level;
1791         int ret;
1792         int slot;
1793
1794         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1795         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1796
1797         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1798 again:
1799         slot = path->slots[lowest_level];
1800         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1801
1802         eb = btrfs_lock_root_node(dest);
1803         btrfs_set_lock_blocking(eb);
1804         level = btrfs_header_level(eb);
1805
1806         if (level < lowest_level) {
1807                 btrfs_tree_unlock(eb);
1808                 free_extent_buffer(eb);
1809                 return 0;
1810         }
1811
1812         if (cow) {
1813                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1814                 BUG_ON(ret);
1815         }
1816         btrfs_set_lock_blocking(eb);
1817
1818         if (next_key) {
1819                 next_key->objectid = (u64)-1;
1820                 next_key->type = (u8)-1;
1821                 next_key->offset = (u64)-1;
1822         }
1823
1824         parent = eb;
1825         while (1) {
1826                 level = btrfs_header_level(parent);
1827                 BUG_ON(level < lowest_level);
1828
1829                 ret = btrfs_bin_search(parent, &key, level, &slot);
1830                 if (ret && slot > 0)
1831                         slot--;
1832
1833                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1834                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1835
1836                 old_bytenr = btrfs_node_blockptr(parent, slot);
1837                 blocksize = dest->nodesize;
1838                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1839
1840                 if (level <= max_level) {
1841                         eb = path->nodes[level];
1842                         new_bytenr = btrfs_node_blockptr(eb,
1843                                                         path->slots[level]);
1844                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1845                                                         path->slots[level]);
1846                 } else {
1847                         new_bytenr = 0;
1848                         new_ptr_gen = 0;
1849                 }
1850
1851                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1852                         ret = level;
1853                         break;
1854                 }
1855
1856                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1857                     memcmp_node_keys(parent, slot, path, level)) {
1858                         if (level <= lowest_level) {
1859                                 ret = 0;
1860                                 break;
1861                         }
1862
1863                         eb = read_tree_block(dest, old_bytenr, old_ptr_gen);
1864                         if (IS_ERR(eb)) {
1865                                 ret = PTR_ERR(eb);
1866                                 break;
1867                         } else if (!extent_buffer_uptodate(eb)) {
1868                                 ret = -EIO;
1869                                 free_extent_buffer(eb);
1870                                 break;
1871                         }
1872                         btrfs_tree_lock(eb);
1873                         if (cow) {
1874                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1875                                                       slot, &eb);
1876                                 BUG_ON(ret);
1877                         }
1878                         btrfs_set_lock_blocking(eb);
1879
1880                         btrfs_tree_unlock(parent);
1881                         free_extent_buffer(parent);
1882
1883                         parent = eb;
1884                         continue;
1885                 }
1886
1887                 if (!cow) {
1888                         btrfs_tree_unlock(parent);
1889                         free_extent_buffer(parent);
1890                         cow = 1;
1891                         goto again;
1892                 }
1893
1894                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1895                                       path->slots[level]);
1896                 btrfs_release_path(path);
1897
1898                 path->lowest_level = level;
1899                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1900                 path->lowest_level = 0;
1901                 BUG_ON(ret);
1902
1903                 /*
1904                  * swap blocks in fs tree and reloc tree.
1905                  */
1906                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1907                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1908                 btrfs_mark_buffer_dirty(parent);
1909
1910                 btrfs_set_node_blockptr(path->nodes[level],
1911                                         path->slots[level], old_bytenr);
1912                 btrfs_set_node_ptr_generation(path->nodes[level],
1913                                               path->slots[level], old_ptr_gen);
1914                 btrfs_mark_buffer_dirty(path->nodes[level]);
1915
1916                 ret = btrfs_inc_extent_ref(trans, src, old_bytenr, blocksize,
1917                                         path->nodes[level]->start,
1918                                         src->root_key.objectid, level - 1, 0);
1919                 BUG_ON(ret);
1920                 ret = btrfs_inc_extent_ref(trans, dest, new_bytenr, blocksize,
1921                                         0, dest->root_key.objectid, level - 1,
1922                                         0);
1923                 BUG_ON(ret);
1924
1925                 ret = btrfs_free_extent(trans, src, new_bytenr, blocksize,
1926                                         path->nodes[level]->start,
1927                                         src->root_key.objectid, level - 1, 0);
1928                 BUG_ON(ret);
1929
1930                 ret = btrfs_free_extent(trans, dest, old_bytenr, blocksize,
1931                                         0, dest->root_key.objectid, level - 1,
1932                                         0);
1933                 BUG_ON(ret);
1934
1935                 btrfs_unlock_up_safe(path, 0);
1936
1937                 ret = level;
1938                 break;
1939         }
1940         btrfs_tree_unlock(parent);
1941         free_extent_buffer(parent);
1942         return ret;
1943 }
1944
1945 /*
1946  * helper to find next relocated block in reloc tree
1947  */
1948 static noinline_for_stack
1949 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1950                        int *level)
1951 {
1952         struct extent_buffer *eb;
1953         int i;
1954         u64 last_snapshot;
1955         u32 nritems;
1956
1957         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1958
1959         for (i = 0; i < *level; i++) {
1960                 free_extent_buffer(path->nodes[i]);
1961                 path->nodes[i] = NULL;
1962         }
1963
1964         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
1965                 eb = path->nodes[i];
1966                 nritems = btrfs_header_nritems(eb);
1967                 while (path->slots[i] + 1 < nritems) {
1968                         path->slots[i]++;
1969                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
1970                             last_snapshot)
1971                                 continue;
1972
1973                         *level = i;
1974                         return 0;
1975                 }
1976                 free_extent_buffer(path->nodes[i]);
1977                 path->nodes[i] = NULL;
1978         }
1979         return 1;
1980 }
1981
1982 /*
1983  * walk down reloc tree to find relocated block of lowest level
1984  */
1985 static noinline_for_stack
1986 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1987                          int *level)
1988 {
1989         struct extent_buffer *eb = NULL;
1990         int i;
1991         u64 bytenr;
1992         u64 ptr_gen = 0;
1993         u64 last_snapshot;
1994         u32 nritems;
1995
1996         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1997
1998         for (i = *level; i > 0; i--) {
1999                 eb = path->nodes[i];
2000                 nritems = btrfs_header_nritems(eb);
2001                 while (path->slots[i] < nritems) {
2002                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2003                         if (ptr_gen > last_snapshot)
2004                                 break;
2005                         path->slots[i]++;
2006                 }
2007                 if (path->slots[i] >= nritems) {
2008                         if (i == *level)
2009                                 break;
2010                         *level = i + 1;
2011                         return 0;
2012                 }
2013                 if (i == 1) {
2014                         *level = i;
2015                         return 0;
2016                 }
2017
2018                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2019                 eb = read_tree_block(root, bytenr, ptr_gen);
2020                 if (IS_ERR(eb)) {
2021                         return PTR_ERR(eb);
2022                 } else if (!extent_buffer_uptodate(eb)) {
2023                         free_extent_buffer(eb);
2024                         return -EIO;
2025                 }
2026                 BUG_ON(btrfs_header_level(eb) != i - 1);
2027                 path->nodes[i - 1] = eb;
2028                 path->slots[i - 1] = 0;
2029         }
2030         return 1;
2031 }
2032
2033 /*
2034  * invalidate extent cache for file extents whose key in range of
2035  * [min_key, max_key)
2036  */
2037 static int invalidate_extent_cache(struct btrfs_root *root,
2038                                    struct btrfs_key *min_key,
2039                                    struct btrfs_key *max_key)
2040 {
2041         struct inode *inode = NULL;
2042         u64 objectid;
2043         u64 start, end;
2044         u64 ino;
2045
2046         objectid = min_key->objectid;
2047         while (1) {
2048                 cond_resched();
2049                 iput(inode);
2050
2051                 if (objectid > max_key->objectid)
2052                         break;
2053
2054                 inode = find_next_inode(root, objectid);
2055                 if (!inode)
2056                         break;
2057                 ino = btrfs_ino(inode);
2058
2059                 if (ino > max_key->objectid) {
2060                         iput(inode);
2061                         break;
2062                 }
2063
2064                 objectid = ino + 1;
2065                 if (!S_ISREG(inode->i_mode))
2066                         continue;
2067
2068                 if (unlikely(min_key->objectid == ino)) {
2069                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2070                                 continue;
2071                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2072                                 start = 0;
2073                         else {
2074                                 start = min_key->offset;
2075                                 WARN_ON(!IS_ALIGNED(start, root->sectorsize));
2076                         }
2077                 } else {
2078                         start = 0;
2079                 }
2080
2081                 if (unlikely(max_key->objectid == ino)) {
2082                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2083                                 continue;
2084                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2085                                 end = (u64)-1;
2086                         } else {
2087                                 if (max_key->offset == 0)
2088                                         continue;
2089                                 end = max_key->offset;
2090                                 WARN_ON(!IS_ALIGNED(end, root->sectorsize));
2091                                 end--;
2092                         }
2093                 } else {
2094                         end = (u64)-1;
2095                 }
2096
2097                 /* the lock_extent waits for readpage to complete */
2098                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2099                 btrfs_drop_extent_cache(inode, start, end, 1);
2100                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2101         }
2102         return 0;
2103 }
2104
2105 static int find_next_key(struct btrfs_path *path, int level,
2106                          struct btrfs_key *key)
2107
2108 {
2109         while (level < BTRFS_MAX_LEVEL) {
2110                 if (!path->nodes[level])
2111                         break;
2112                 if (path->slots[level] + 1 <
2113                     btrfs_header_nritems(path->nodes[level])) {
2114                         btrfs_node_key_to_cpu(path->nodes[level], key,
2115                                               path->slots[level] + 1);
2116                         return 0;
2117                 }
2118                 level++;
2119         }
2120         return 1;
2121 }
2122
2123 /*
2124  * merge the relocated tree blocks in reloc tree with corresponding
2125  * fs tree.
2126  */
2127 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2128                                                struct btrfs_root *root)
2129 {
2130         LIST_HEAD(inode_list);
2131         struct btrfs_key key;
2132         struct btrfs_key next_key;
2133         struct btrfs_trans_handle *trans = NULL;
2134         struct btrfs_root *reloc_root;
2135         struct btrfs_root_item *root_item;
2136         struct btrfs_path *path;
2137         struct extent_buffer *leaf;
2138         int level;
2139         int max_level;
2140         int replaced = 0;
2141         int ret;
2142         int err = 0;
2143         u32 min_reserved;
2144
2145         path = btrfs_alloc_path();
2146         if (!path)
2147                 return -ENOMEM;
2148         path->reada = READA_FORWARD;
2149
2150         reloc_root = root->reloc_root;
2151         root_item = &reloc_root->root_item;
2152
2153         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2154                 level = btrfs_root_level(root_item);
2155                 extent_buffer_get(reloc_root->node);
2156                 path->nodes[level] = reloc_root->node;
2157                 path->slots[level] = 0;
2158         } else {
2159                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2160
2161                 level = root_item->drop_level;
2162                 BUG_ON(level == 0);
2163                 path->lowest_level = level;
2164                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2165                 path->lowest_level = 0;
2166                 if (ret < 0) {
2167                         btrfs_free_path(path);
2168                         return ret;
2169                 }
2170
2171                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2172                                       path->slots[level]);
2173                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2174
2175                 btrfs_unlock_up_safe(path, 0);
2176         }
2177
2178         min_reserved = root->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2179         memset(&next_key, 0, sizeof(next_key));
2180
2181         while (1) {
2182                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2183                                              BTRFS_RESERVE_FLUSH_ALL);
2184                 if (ret) {
2185                         err = ret;
2186                         goto out;
2187                 }
2188                 trans = btrfs_start_transaction(root, 0);
2189                 if (IS_ERR(trans)) {
2190                         err = PTR_ERR(trans);
2191                         trans = NULL;
2192                         goto out;
2193                 }
2194                 trans->block_rsv = rc->block_rsv;
2195
2196                 replaced = 0;
2197                 max_level = level;
2198
2199                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2200                 if (ret < 0) {
2201                         err = ret;
2202                         goto out;
2203                 }
2204                 if (ret > 0)
2205                         break;
2206
2207                 if (!find_next_key(path, level, &key) &&
2208                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2209                         ret = 0;
2210                 } else {
2211                         ret = replace_path(trans, root, reloc_root, path,
2212                                            &next_key, level, max_level);
2213                 }
2214                 if (ret < 0) {
2215                         err = ret;
2216                         goto out;
2217                 }
2218
2219                 if (ret > 0) {
2220                         level = ret;
2221                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2222                                               path->slots[level]);
2223                         replaced = 1;
2224                 }
2225
2226                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2227                 if (ret > 0)
2228                         break;
2229
2230                 BUG_ON(level == 0);
2231                 /*
2232                  * save the merging progress in the drop_progress.
2233                  * this is OK since root refs == 1 in this case.
2234                  */
2235                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2236                                path->slots[level]);
2237                 root_item->drop_level = level;
2238
2239                 btrfs_end_transaction_throttle(trans, root);
2240                 trans = NULL;
2241
2242                 btrfs_btree_balance_dirty(root);
2243
2244                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2245                         invalidate_extent_cache(root, &key, &next_key);
2246         }
2247
2248         /*
2249          * handle the case only one block in the fs tree need to be
2250          * relocated and the block is tree root.
2251          */
2252         leaf = btrfs_lock_root_node(root);
2253         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2254         btrfs_tree_unlock(leaf);
2255         free_extent_buffer(leaf);
2256         if (ret < 0)
2257                 err = ret;
2258 out:
2259         btrfs_free_path(path);
2260
2261         if (err == 0) {
2262                 memset(&root_item->drop_progress, 0,
2263                        sizeof(root_item->drop_progress));
2264                 root_item->drop_level = 0;
2265                 btrfs_set_root_refs(root_item, 0);
2266                 btrfs_update_reloc_root(trans, root);
2267         }
2268
2269         if (trans)
2270                 btrfs_end_transaction_throttle(trans, root);
2271
2272         btrfs_btree_balance_dirty(root);
2273
2274         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2275                 invalidate_extent_cache(root, &key, &next_key);
2276
2277         return err;
2278 }
2279
2280 static noinline_for_stack
2281 int prepare_to_merge(struct reloc_control *rc, int err)
2282 {
2283         struct btrfs_root *root = rc->extent_root;
2284         struct btrfs_root *reloc_root;
2285         struct btrfs_trans_handle *trans;
2286         LIST_HEAD(reloc_roots);
2287         u64 num_bytes = 0;
2288         int ret;
2289
2290         mutex_lock(&root->fs_info->reloc_mutex);
2291         rc->merging_rsv_size += root->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2292         rc->merging_rsv_size += rc->nodes_relocated * 2;
2293         mutex_unlock(&root->fs_info->reloc_mutex);
2294
2295 again:
2296         if (!err) {
2297                 num_bytes = rc->merging_rsv_size;
2298                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2299                                           BTRFS_RESERVE_FLUSH_ALL);
2300                 if (ret)
2301                         err = ret;
2302         }
2303
2304         trans = btrfs_join_transaction(rc->extent_root);
2305         if (IS_ERR(trans)) {
2306                 if (!err)
2307                         btrfs_block_rsv_release(rc->extent_root,
2308                                                 rc->block_rsv, num_bytes);
2309                 return PTR_ERR(trans);
2310         }
2311
2312         if (!err) {
2313                 if (num_bytes != rc->merging_rsv_size) {
2314                         btrfs_end_transaction(trans, rc->extent_root);
2315                         btrfs_block_rsv_release(rc->extent_root,
2316                                                 rc->block_rsv, num_bytes);
2317                         goto again;
2318                 }
2319         }
2320
2321         rc->merge_reloc_tree = 1;
2322
2323         while (!list_empty(&rc->reloc_roots)) {
2324                 reloc_root = list_entry(rc->reloc_roots.next,
2325                                         struct btrfs_root, root_list);
2326                 list_del_init(&reloc_root->root_list);
2327
2328                 root = read_fs_root(reloc_root->fs_info,
2329                                     reloc_root->root_key.offset);
2330                 BUG_ON(IS_ERR(root));
2331                 BUG_ON(root->reloc_root != reloc_root);
2332
2333                 /*
2334                  * set reference count to 1, so btrfs_recover_relocation
2335                  * knows it should resumes merging
2336                  */
2337                 if (!err)
2338                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2339                 btrfs_update_reloc_root(trans, root);
2340
2341                 list_add(&reloc_root->root_list, &reloc_roots);
2342         }
2343
2344         list_splice(&reloc_roots, &rc->reloc_roots);
2345
2346         if (!err)
2347                 btrfs_commit_transaction(trans, rc->extent_root);
2348         else
2349                 btrfs_end_transaction(trans, rc->extent_root);
2350         return err;
2351 }
2352
2353 static noinline_for_stack
2354 void free_reloc_roots(struct list_head *list)
2355 {
2356         struct btrfs_root *reloc_root;
2357
2358         while (!list_empty(list)) {
2359                 reloc_root = list_entry(list->next, struct btrfs_root,
2360                                         root_list);
2361                 free_extent_buffer(reloc_root->node);
2362                 free_extent_buffer(reloc_root->commit_root);
2363                 reloc_root->node = NULL;
2364                 reloc_root->commit_root = NULL;
2365                 __del_reloc_root(reloc_root);
2366         }
2367 }
2368
2369 static noinline_for_stack
2370 void merge_reloc_roots(struct reloc_control *rc)
2371 {
2372         struct btrfs_root *root;
2373         struct btrfs_root *reloc_root;
2374         u64 last_snap;
2375         u64 otransid;
2376         u64 objectid;
2377         LIST_HEAD(reloc_roots);
2378         int found = 0;
2379         int ret = 0;
2380 again:
2381         root = rc->extent_root;
2382
2383         /*
2384          * this serializes us with btrfs_record_root_in_transaction,
2385          * we have to make sure nobody is in the middle of
2386          * adding their roots to the list while we are
2387          * doing this splice
2388          */
2389         mutex_lock(&root->fs_info->reloc_mutex);
2390         list_splice_init(&rc->reloc_roots, &reloc_roots);
2391         mutex_unlock(&root->fs_info->reloc_mutex);
2392
2393         while (!list_empty(&reloc_roots)) {
2394                 found = 1;
2395                 reloc_root = list_entry(reloc_roots.next,
2396                                         struct btrfs_root, root_list);
2397
2398                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2399                         root = read_fs_root(reloc_root->fs_info,
2400                                             reloc_root->root_key.offset);
2401                         BUG_ON(IS_ERR(root));
2402                         BUG_ON(root->reloc_root != reloc_root);
2403
2404                         ret = merge_reloc_root(rc, root);
2405                         if (ret) {
2406                                 if (list_empty(&reloc_root->root_list))
2407                                         list_add_tail(&reloc_root->root_list,
2408                                                       &reloc_roots);
2409                                 goto out;
2410                         }
2411                 } else {
2412                         list_del_init(&reloc_root->root_list);
2413                 }
2414
2415                 /*
2416                  * we keep the old last snapshot transid in rtranid when we
2417                  * created the relocation tree.
2418                  */
2419                 last_snap = btrfs_root_rtransid(&reloc_root->root_item);
2420                 otransid = btrfs_root_otransid(&reloc_root->root_item);
2421                 objectid = reloc_root->root_key.offset;
2422
2423                 ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);
2424                 if (ret < 0) {
2425                         if (list_empty(&reloc_root->root_list))
2426                                 list_add_tail(&reloc_root->root_list,
2427                                               &reloc_roots);
2428                         goto out;
2429                 }
2430         }
2431
2432         if (found) {
2433                 found = 0;
2434                 goto again;
2435         }
2436 out:
2437         if (ret) {
2438                 btrfs_handle_fs_error(root->fs_info, ret, NULL);
2439                 if (!list_empty(&reloc_roots))
2440                         free_reloc_roots(&reloc_roots);
2441
2442                 /* new reloc root may be added */
2443                 mutex_lock(&root->fs_info->reloc_mutex);
2444                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2445                 mutex_unlock(&root->fs_info->reloc_mutex);
2446                 if (!list_empty(&reloc_roots))
2447                         free_reloc_roots(&reloc_roots);
2448         }
2449
2450         BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2451 }
2452
2453 static void free_block_list(struct rb_root *blocks)
2454 {
2455         struct tree_block *block;
2456         struct rb_node *rb_node;
2457         while ((rb_node = rb_first(blocks))) {
2458                 block = rb_entry(rb_node, struct tree_block, rb_node);
2459                 rb_erase(rb_node, blocks);
2460                 kfree(block);
2461         }
2462 }
2463
2464 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2465                                       struct btrfs_root *reloc_root)
2466 {
2467         struct btrfs_root *root;
2468
2469         if (reloc_root->last_trans == trans->transid)
2470                 return 0;
2471
2472         root = read_fs_root(reloc_root->fs_info, reloc_root->root_key.offset);
2473         BUG_ON(IS_ERR(root));
2474         BUG_ON(root->reloc_root != reloc_root);
2475
2476         return btrfs_record_root_in_trans(trans, root);
2477 }
2478
2479 static noinline_for_stack
2480 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2481                                      struct reloc_control *rc,
2482                                      struct backref_node *node,
2483                                      struct backref_edge *edges[])
2484 {
2485         struct backref_node *next;
2486         struct btrfs_root *root;
2487         int index = 0;
2488
2489         next = node;
2490         while (1) {
2491                 cond_resched();
2492                 next = walk_up_backref(next, edges, &index);
2493                 root = next->root;
2494                 BUG_ON(!root);
2495                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2496
2497                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2498                         record_reloc_root_in_trans(trans, root);
2499                         break;
2500                 }
2501
2502                 btrfs_record_root_in_trans(trans, root);
2503                 root = root->reloc_root;
2504
2505                 if (next->new_bytenr != root->node->start) {
2506                         BUG_ON(next->new_bytenr);
2507                         BUG_ON(!list_empty(&next->list));
2508                         next->new_bytenr = root->node->start;
2509                         next->root = root;
2510                         list_add_tail(&next->list,
2511                                       &rc->backref_cache.changed);
2512                         __mark_block_processed(rc, next);
2513                         break;
2514                 }
2515
2516                 WARN_ON(1);
2517                 root = NULL;
2518                 next = walk_down_backref(edges, &index);
2519                 if (!next || next->level <= node->level)
2520                         break;
2521         }
2522         if (!root)
2523                 return NULL;
2524
2525         next = node;
2526         /* setup backref node path for btrfs_reloc_cow_block */
2527         while (1) {
2528                 rc->backref_cache.path[next->level] = next;
2529                 if (--index < 0)
2530                         break;
2531                 next = edges[index]->node[UPPER];
2532         }
2533         return root;
2534 }
2535
2536 /*
2537  * select a tree root for relocation. return NULL if the block
2538  * is reference counted. we should use do_relocation() in this
2539  * case. return a tree root pointer if the block isn't reference
2540  * counted. return -ENOENT if the block is root of reloc tree.
2541  */
2542 static noinline_for_stack
2543 struct btrfs_root *select_one_root(struct backref_node *node)
2544 {
2545         struct backref_node *next;
2546         struct btrfs_root *root;
2547         struct btrfs_root *fs_root = NULL;
2548         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2549         int index = 0;
2550
2551         next = node;
2552         while (1) {
2553                 cond_resched();
2554                 next = walk_up_backref(next, edges, &index);
2555                 root = next->root;
2556                 BUG_ON(!root);
2557
2558                 /* no other choice for non-references counted tree */
2559                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2560                         return root;
2561
2562                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2563                         fs_root = root;
2564
2565                 if (next != node)
2566                         return NULL;
2567
2568                 next = walk_down_backref(edges, &index);
2569                 if (!next || next->level <= node->level)
2570                         break;
2571         }
2572
2573         if (!fs_root)
2574                 return ERR_PTR(-ENOENT);
2575         return fs_root;
2576 }
2577
2578 static noinline_for_stack
2579 u64 calcu_metadata_size(struct reloc_control *rc,
2580                         struct backref_node *node, int reserve)
2581 {
2582         struct backref_node *next = node;
2583         struct backref_edge *edge;
2584         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2585         u64 num_bytes = 0;
2586         int index = 0;
2587
2588         BUG_ON(reserve && node->processed);
2589
2590         while (next) {
2591                 cond_resched();
2592                 while (1) {
2593                         if (next->processed && (reserve || next != node))
2594                                 break;
2595
2596                         num_bytes += rc->extent_root->nodesize;
2597
2598                         if (list_empty(&next->upper))
2599                                 break;
2600
2601                         edge = list_entry(next->upper.next,
2602                                           struct backref_edge, list[LOWER]);
2603                         edges[index++] = edge;
2604                         next = edge->node[UPPER];
2605                 }
2606                 next = walk_down_backref(edges, &index);
2607         }
2608         return num_bytes;
2609 }
2610
2611 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2612                                   struct reloc_control *rc,
2613                                   struct backref_node *node)
2614 {
2615         struct btrfs_root *root = rc->extent_root;
2616         u64 num_bytes;
2617         int ret;
2618         u64 tmp;
2619
2620         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2621
2622         trans->block_rsv = rc->block_rsv;
2623         rc->reserved_bytes += num_bytes;
2624
2625         /*
2626          * We are under a transaction here so we can only do limited flushing.
2627          * If we get an enospc just kick back -EAGAIN so we know to drop the
2628          * transaction and try to refill when we can flush all the things.
2629          */
2630         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2631                                 BTRFS_RESERVE_FLUSH_LIMIT);
2632         if (ret) {
2633                 tmp = rc->extent_root->nodesize * RELOCATION_RESERVED_NODES;
2634                 while (tmp <= rc->reserved_bytes)
2635                         tmp <<= 1;
2636                 /*
2637                  * only one thread can access block_rsv at this point,
2638                  * so we don't need hold lock to protect block_rsv.
2639                  * we expand more reservation size here to allow enough
2640                  * space for relocation and we will return eailer in
2641                  * enospc case.
2642                  */
2643                 rc->block_rsv->size = tmp + rc->extent_root->nodesize *
2644                         RELOCATION_RESERVED_NODES;
2645                 return -EAGAIN;
2646         }
2647
2648         return 0;
2649 }
2650
2651 /*
2652  * relocate a block tree, and then update pointers in upper level
2653  * blocks that reference the block to point to the new location.
2654  *
2655  * if called by link_to_upper, the block has already been relocated.
2656  * in that case this function just updates pointers.
2657  */
2658 static int do_relocation(struct btrfs_trans_handle *trans,
2659                          struct reloc_control *rc,
2660                          struct backref_node *node,
2661                          struct btrfs_key *key,
2662                          struct btrfs_path *path, int lowest)
2663 {
2664         struct backref_node *upper;
2665         struct backref_edge *edge;
2666         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2667         struct btrfs_root *root;
2668         struct extent_buffer *eb;
2669         u32 blocksize;
2670         u64 bytenr;
2671         u64 generation;
2672         int slot;
2673         int ret;
2674         int err = 0;
2675
2676         BUG_ON(lowest && node->eb);
2677
2678         path->lowest_level = node->level + 1;
2679         rc->backref_cache.path[node->level] = node;
2680         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2681                 cond_resched();
2682
2683                 upper = edge->node[UPPER];
2684                 root = select_reloc_root(trans, rc, upper, edges);
2685                 BUG_ON(!root);
2686
2687                 if (upper->eb && !upper->locked) {
2688                         if (!lowest) {
2689                                 ret = btrfs_bin_search(upper->eb, key,
2690                                                        upper->level, &slot);
2691                                 BUG_ON(ret);
2692                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2693                                 if (node->eb->start == bytenr)
2694                                         goto next;
2695                         }
2696                         drop_node_buffer(upper);
2697                 }
2698
2699                 if (!upper->eb) {
2700                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2701                         if (ret) {
2702                                 if (ret < 0)
2703                                         err = ret;
2704                                 else
2705                                         err = -ENOENT;
2706
2707                                 btrfs_release_path(path);
2708                                 break;
2709                         }
2710
2711                         if (!upper->eb) {
2712                                 upper->eb = path->nodes[upper->level];
2713                                 path->nodes[upper->level] = NULL;
2714                         } else {
2715                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2716                         }
2717
2718                         upper->locked = 1;
2719                         path->locks[upper->level] = 0;
2720
2721                         slot = path->slots[upper->level];
2722                         btrfs_release_path(path);
2723                 } else {
2724                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2725                                                &slot);
2726                         BUG_ON(ret);
2727                 }
2728
2729                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2730                 if (lowest) {
2731                         BUG_ON(bytenr != node->bytenr);
2732                 } else {
2733                         if (node->eb->start == bytenr)
2734                                 goto next;
2735                 }
2736
2737                 blocksize = root->nodesize;
2738                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2739                 eb = read_tree_block(root, bytenr, generation);
2740                 if (IS_ERR(eb)) {
2741                         err = PTR_ERR(eb);
2742                         goto next;
2743                 } else if (!extent_buffer_uptodate(eb)) {
2744                         free_extent_buffer(eb);
2745                         err = -EIO;
2746                         goto next;
2747                 }
2748                 btrfs_tree_lock(eb);
2749                 btrfs_set_lock_blocking(eb);
2750
2751                 if (!node->eb) {
2752                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2753                                               slot, &eb);
2754                         btrfs_tree_unlock(eb);
2755                         free_extent_buffer(eb);
2756                         if (ret < 0) {
2757                                 err = ret;
2758                                 goto next;
2759                         }
2760                         BUG_ON(node->eb != eb);
2761                 } else {
2762                         btrfs_set_node_blockptr(upper->eb, slot,
2763                                                 node->eb->start);
2764                         btrfs_set_node_ptr_generation(upper->eb, slot,
2765                                                       trans->transid);
2766                         btrfs_mark_buffer_dirty(upper->eb);
2767
2768                         ret = btrfs_inc_extent_ref(trans, root,
2769                                                 node->eb->start, blocksize,
2770                                                 upper->eb->start,
2771                                                 btrfs_header_owner(upper->eb),
2772                                                 node->level, 0);
2773                         BUG_ON(ret);
2774
2775                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2776                         BUG_ON(ret);
2777                 }
2778 next:
2779                 if (!upper->pending)
2780                         drop_node_buffer(upper);
2781                 else
2782                         unlock_node_buffer(upper);
2783                 if (err)
2784                         break;
2785         }
2786
2787         if (!err && node->pending) {
2788                 drop_node_buffer(node);
2789                 list_move_tail(&node->list, &rc->backref_cache.changed);
2790                 node->pending = 0;
2791         }
2792
2793         path->lowest_level = 0;
2794         BUG_ON(err == -ENOSPC);
2795         return err;
2796 }
2797
2798 static int link_to_upper(struct btrfs_trans_handle *trans,
2799                          struct reloc_control *rc,
2800                          struct backref_node *node,
2801                          struct btrfs_path *path)
2802 {
2803         struct btrfs_key key;
2804
2805         btrfs_node_key_to_cpu(node->eb, &key, 0);
2806         return do_relocation(trans, rc, node, &key, path, 0);
2807 }
2808
2809 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2810                                 struct reloc_control *rc,
2811                                 struct btrfs_path *path, int err)
2812 {
2813         LIST_HEAD(list);
2814         struct backref_cache *cache = &rc->backref_cache;
2815         struct backref_node *node;
2816         int level;
2817         int ret;
2818
2819         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2820                 while (!list_empty(&cache->pending[level])) {
2821                         node = list_entry(cache->pending[level].next,
2822                                           struct backref_node, list);
2823                         list_move_tail(&node->list, &list);
2824                         BUG_ON(!node->pending);
2825
2826                         if (!err) {
2827                                 ret = link_to_upper(trans, rc, node, path);
2828                                 if (ret < 0)
2829                                         err = ret;
2830                         }
2831                 }
2832                 list_splice_init(&list, &cache->pending[level]);
2833         }
2834         return err;
2835 }
2836
2837 static void mark_block_processed(struct reloc_control *rc,
2838                                  u64 bytenr, u32 blocksize)
2839 {
2840         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
2841                         EXTENT_DIRTY);
2842 }
2843
2844 static void __mark_block_processed(struct reloc_control *rc,
2845                                    struct backref_node *node)
2846 {
2847         u32 blocksize;
2848         if (node->level == 0 ||
2849             in_block_group(node->bytenr, rc->block_group)) {
2850                 blocksize = rc->extent_root->nodesize;
2851                 mark_block_processed(rc, node->bytenr, blocksize);
2852         }
2853         node->processed = 1;
2854 }
2855
2856 /*
2857  * mark a block and all blocks directly/indirectly reference the block
2858  * as processed.
2859  */
2860 static void update_processed_blocks(struct reloc_control *rc,
2861                                     struct backref_node *node)
2862 {
2863         struct backref_node *next = node;
2864         struct backref_edge *edge;
2865         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2866         int index = 0;
2867
2868         while (next) {
2869                 cond_resched();
2870                 while (1) {
2871                         if (next->processed)
2872                                 break;
2873
2874                         __mark_block_processed(rc, next);
2875
2876                         if (list_empty(&next->upper))
2877                                 break;
2878
2879                         edge = list_entry(next->upper.next,
2880                                           struct backref_edge, list[LOWER]);
2881                         edges[index++] = edge;
2882                         next = edge->node[UPPER];
2883                 }
2884                 next = walk_down_backref(edges, &index);
2885         }
2886 }
2887
2888 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
2889 {
2890         u32 blocksize = rc->extent_root->nodesize;
2891
2892         if (test_range_bit(&rc->processed_blocks, bytenr,
2893                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2894                 return 1;
2895         return 0;
2896 }
2897
2898 static int get_tree_block_key(struct reloc_control *rc,
2899                               struct tree_block *block)
2900 {
2901         struct extent_buffer *eb;
2902
2903         BUG_ON(block->key_ready);
2904         eb = read_tree_block(rc->extent_root, block->bytenr,
2905                              block->key.offset);
2906         if (IS_ERR(eb)) {
2907                 return PTR_ERR(eb);
2908         } else if (!extent_buffer_uptodate(eb)) {
2909                 free_extent_buffer(eb);
2910                 return -EIO;
2911         }
2912         WARN_ON(btrfs_header_level(eb) != block->level);
2913         if (block->level == 0)
2914                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2915         else
2916                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2917         free_extent_buffer(eb);
2918         block->key_ready = 1;
2919         return 0;
2920 }
2921
2922 /*
2923  * helper function to relocate a tree block
2924  */
2925 static int relocate_tree_block(struct btrfs_trans_handle *trans,
2926                                 struct reloc_control *rc,
2927                                 struct backref_node *node,
2928                                 struct btrfs_key *key,
2929                                 struct btrfs_path *path)
2930 {
2931         struct btrfs_root *root;
2932         int ret = 0;
2933
2934         if (!node)
2935                 return 0;
2936
2937         BUG_ON(node->processed);
2938         root = select_one_root(node);
2939         if (root == ERR_PTR(-ENOENT)) {
2940                 update_processed_blocks(rc, node);
2941                 goto out;
2942         }
2943
2944         if (!root || test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
2945                 ret = reserve_metadata_space(trans, rc, node);
2946                 if (ret)
2947                         goto out;
2948         }
2949
2950         if (root) {
2951                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
2952                         BUG_ON(node->new_bytenr);
2953                         BUG_ON(!list_empty(&node->list));
2954                         btrfs_record_root_in_trans(trans, root);
2955                         root = root->reloc_root;
2956                         node->new_bytenr = root->node->start;
2957                         node->root = root;
2958                         list_add_tail(&node->list, &rc->backref_cache.changed);
2959                 } else {
2960                         path->lowest_level = node->level;
2961                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2962                         btrfs_release_path(path);
2963                         if (ret > 0)
2964                                 ret = 0;
2965                 }
2966                 if (!ret)
2967                         update_processed_blocks(rc, node);
2968         } else {
2969                 ret = do_relocation(trans, rc, node, key, path, 1);
2970         }
2971 out:
2972         if (ret || node->level == 0 || node->cowonly)
2973                 remove_backref_node(&rc->backref_cache, node);
2974         return ret;
2975 }
2976
2977 /*
2978  * relocate a list of blocks
2979  */
2980 static noinline_for_stack
2981 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
2982                          struct reloc_control *rc, struct rb_root *blocks)
2983 {
2984         struct backref_node *node;
2985         struct btrfs_path *path;
2986         struct tree_block *block;
2987         struct rb_node *rb_node;
2988         int ret;
2989         int err = 0;
2990
2991         path = btrfs_alloc_path();
2992         if (!path) {
2993                 err = -ENOMEM;
2994                 goto out_free_blocks;
2995         }
2996
2997         rb_node = rb_first(blocks);
2998         while (rb_node) {
2999                 block = rb_entry(rb_node, struct tree_block, rb_node);
3000                 if (!block->key_ready)
3001                         readahead_tree_block(rc->extent_root, block->bytenr);
3002                 rb_node = rb_next(rb_node);
3003         }
3004
3005         rb_node = rb_first(blocks);
3006         while (rb_node) {
3007                 block = rb_entry(rb_node, struct tree_block, rb_node);
3008                 if (!block->key_ready) {
3009                         err = get_tree_block_key(rc, block);
3010                         if (err)
3011                                 goto out_free_path;
3012                 }
3013                 rb_node = rb_next(rb_node);
3014         }
3015
3016         rb_node = rb_first(blocks);
3017         while (rb_node) {
3018                 block = rb_entry(rb_node, struct tree_block, rb_node);
3019
3020                 node = build_backref_tree(rc, &block->key,
3021                                           block->level, block->bytenr);
3022                 if (IS_ERR(node)) {
3023                         err = PTR_ERR(node);
3024                         goto out;
3025                 }
3026
3027                 ret = relocate_tree_block(trans, rc, node, &block->key,
3028                                           path);
3029                 if (ret < 0) {
3030                         if (ret != -EAGAIN || rb_node == rb_first(blocks))
3031                                 err = ret;
3032                         goto out;
3033                 }
3034                 rb_node = rb_next(rb_node);
3035         }
3036 out:
3037         err = finish_pending_nodes(trans, rc, path, err);
3038
3039 out_free_path:
3040         btrfs_free_path(path);
3041 out_free_blocks:
3042         free_block_list(blocks);
3043         return err;
3044 }
3045
3046 static noinline_for_stack
3047 int prealloc_file_extent_cluster(struct inode *inode,
3048                                  struct file_extent_cluster *cluster)
3049 {
3050         u64 alloc_hint = 0;
3051         u64 start;
3052         u64 end;
3053         u64 offset = BTRFS_I(inode)->index_cnt;
3054         u64 num_bytes;
3055         int nr = 0;
3056         int ret = 0;
3057         u64 prealloc_start = cluster->start - offset;
3058         u64 prealloc_end = cluster->end - offset;
3059         u64 cur_offset;
3060
3061         BUG_ON(cluster->start != cluster->boundary[0]);
3062         inode_lock(inode);
3063
3064         ret = btrfs_check_data_free_space(inode, prealloc_start,
3065                                           prealloc_end + 1 - prealloc_start);
3066         if (ret)
3067                 goto out;
3068
3069         cur_offset = prealloc_start;
3070         while (nr < cluster->nr) {
3071                 start = cluster->boundary[nr] - offset;
3072                 if (nr + 1 < cluster->nr)
3073                         end = cluster->boundary[nr + 1] - 1 - offset;
3074                 else
3075                         end = cluster->end - offset;
3076
3077                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3078                 num_bytes = end + 1 - start;
3079                 if (cur_offset < start)
3080                         btrfs_free_reserved_data_space(inode, cur_offset,
3081                                         start - cur_offset);
3082                 ret = btrfs_prealloc_file_range(inode, 0, start,
3083                                                 num_bytes, num_bytes,
3084                                                 end + 1, &alloc_hint);
3085                 cur_offset = end + 1;
3086                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3087                 if (ret)
3088                         break;
3089                 nr++;
3090         }
3091         if (cur_offset < prealloc_end)
3092                 btrfs_free_reserved_data_space(inode, cur_offset,
3093                                        prealloc_end + 1 - cur_offset);
3094 out:
3095         inode_unlock(inode);
3096         return ret;
3097 }
3098
3099 static noinline_for_stack
3100 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3101                          u64 block_start)
3102 {
3103         struct btrfs_root *root = BTRFS_I(inode)->root;
3104         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3105         struct extent_map *em;
3106         int ret = 0;
3107
3108         em = alloc_extent_map();
3109         if (!em)
3110                 return -ENOMEM;
3111
3112         em->start = start;
3113         em->len = end + 1 - start;
3114         em->block_len = em->len;
3115         em->block_start = block_start;
3116         em->bdev = root->fs_info->fs_devices->latest_bdev;
3117         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3118
3119         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3120         while (1) {
3121                 write_lock(&em_tree->lock);
3122                 ret = add_extent_mapping(em_tree, em, 0);
3123                 write_unlock(&em_tree->lock);
3124                 if (ret != -EEXIST) {
3125                         free_extent_map(em);
3126                         break;
3127                 }
3128                 btrfs_drop_extent_cache(inode, start, end, 0);
3129         }
3130         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3131         return ret;
3132 }
3133
3134 static int relocate_file_extent_cluster(struct inode *inode,
3135                                         struct file_extent_cluster *cluster)
3136 {
3137         u64 page_start;
3138         u64 page_end;
3139         u64 offset = BTRFS_I(inode)->index_cnt;
3140         unsigned long index;
3141         unsigned long last_index;
3142         struct page *page;
3143         struct file_ra_state *ra;
3144         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3145         int nr = 0;
3146         int ret = 0;
3147
3148         if (!cluster->nr)
3149                 return 0;
3150
3151         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3152         if (!ra)
3153                 return -ENOMEM;
3154
3155         ret = prealloc_file_extent_cluster(inode, cluster);
3156         if (ret)
3157                 goto out;
3158
3159         file_ra_state_init(ra, inode->i_mapping);
3160
3161         ret = setup_extent_mapping(inode, cluster->start - offset,
3162                                    cluster->end - offset, cluster->start);
3163         if (ret)
3164                 goto out;
3165
3166         index = (cluster->start - offset) >> PAGE_SHIFT;
3167         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3168         while (index <= last_index) {
3169                 ret = btrfs_delalloc_reserve_metadata(inode, PAGE_SIZE);
3170                 if (ret)
3171                         goto out;
3172
3173                 page = find_lock_page(inode->i_mapping, index);
3174                 if (!page) {
3175                         page_cache_sync_readahead(inode->i_mapping,
3176                                                   ra, NULL, index,
3177                                                   last_index + 1 - index);
3178                         page = find_or_create_page(inode->i_mapping, index,
3179                                                    mask);
3180                         if (!page) {
3181                                 btrfs_delalloc_release_metadata(inode,
3182                                                         PAGE_SIZE);
3183                                 ret = -ENOMEM;
3184                                 goto out;
3185                         }
3186                 }
3187
3188                 if (PageReadahead(page)) {
3189                         page_cache_async_readahead(inode->i_mapping,
3190                                                    ra, NULL, page, index,
3191                                                    last_index + 1 - index);
3192                 }
3193
3194                 if (!PageUptodate(page)) {
3195                         btrfs_readpage(NULL, page);
3196                         lock_page(page);
3197                         if (!PageUptodate(page)) {
3198                                 unlock_page(page);
3199                                 put_page(page);
3200                                 btrfs_delalloc_release_metadata(inode,
3201                                                         PAGE_SIZE);
3202                                 ret = -EIO;
3203                                 goto out;
3204                         }
3205                 }
3206
3207                 page_start = page_offset(page);
3208                 page_end = page_start + PAGE_SIZE - 1;
3209
3210                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3211
3212                 set_page_extent_mapped(page);
3213
3214                 if (nr < cluster->nr &&
3215                     page_start + offset == cluster->boundary[nr]) {
3216                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3217                                         page_start, page_end,
3218                                         EXTENT_BOUNDARY);
3219                         nr++;
3220                 }
3221
3222                 btrfs_set_extent_delalloc(inode, page_start, page_end, NULL, 0);
3223                 set_page_dirty(page);
3224
3225                 unlock_extent(&BTRFS_I(inode)->io_tree,
3226                               page_start, page_end);
3227                 unlock_page(page);
3228                 put_page(page);
3229
3230                 index++;
3231                 balance_dirty_pages_ratelimited(inode->i_mapping);
3232                 btrfs_throttle(BTRFS_I(inode)->root);
3233         }
3234         WARN_ON(nr != cluster->nr);
3235 out:
3236         kfree(ra);
3237         return ret;
3238 }
3239
3240 static noinline_for_stack
3241 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3242                          struct file_extent_cluster *cluster)
3243 {
3244         int ret;
3245
3246         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3247                 ret = relocate_file_extent_cluster(inode, cluster);
3248                 if (ret)
3249                         return ret;
3250                 cluster->nr = 0;
3251         }
3252
3253         if (!cluster->nr)
3254                 cluster->start = extent_key->objectid;
3255         else
3256                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3257         cluster->end = extent_key->objectid + extent_key->offset - 1;
3258         cluster->boundary[cluster->nr] = extent_key->objectid;
3259         cluster->nr++;
3260
3261         if (cluster->nr >= MAX_EXTENTS) {
3262                 ret = relocate_file_extent_cluster(inode, cluster);
3263                 if (ret)
3264                         return ret;
3265                 cluster->nr = 0;
3266         }
3267         return 0;
3268 }
3269
3270 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3271 static int get_ref_objectid_v0(struct reloc_control *rc,
3272                                struct btrfs_path *path,
3273                                struct btrfs_key *extent_key,
3274                                u64 *ref_objectid, int *path_change)
3275 {
3276         struct btrfs_key key;
3277         struct extent_buffer *leaf;
3278         struct btrfs_extent_ref_v0 *ref0;
3279         int ret;
3280         int slot;
3281
3282         leaf = path->nodes[0];
3283         slot = path->slots[0];
3284         while (1) {
3285                 if (slot >= btrfs_header_nritems(leaf)) {
3286                         ret = btrfs_next_leaf(rc->extent_root, path);
3287                         if (ret < 0)
3288                                 return ret;
3289                         BUG_ON(ret > 0);
3290                         leaf = path->nodes[0];
3291                         slot = path->slots[0];
3292                         if (path_change)
3293                                 *path_change = 1;
3294                 }
3295                 btrfs_item_key_to_cpu(leaf, &key, slot);
3296                 if (key.objectid != extent_key->objectid)
3297                         return -ENOENT;
3298
3299                 if (key.type != BTRFS_EXTENT_REF_V0_KEY) {
3300                         slot++;
3301                         continue;
3302                 }
3303                 ref0 = btrfs_item_ptr(leaf, slot,
3304                                 struct btrfs_extent_ref_v0);
3305                 *ref_objectid = btrfs_ref_objectid_v0(leaf, ref0);
3306                 break;
3307         }
3308         return 0;
3309 }
3310 #endif
3311
3312 /*
3313  * helper to add a tree block to the list.
3314  * the major work is getting the generation and level of the block
3315  */
3316 static int add_tree_block(struct reloc_control *rc,
3317                           struct btrfs_key *extent_key,
3318                           struct btrfs_path *path,
3319                           struct rb_root *blocks)
3320 {
3321         struct extent_buffer *eb;
3322         struct btrfs_extent_item *ei;
3323         struct btrfs_tree_block_info *bi;
3324         struct tree_block *block;
3325         struct rb_node *rb_node;
3326         u32 item_size;
3327         int level = -1;
3328         u64 generation;
3329
3330         eb =  path->nodes[0];
3331         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3332
3333         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3334             item_size >= sizeof(*ei) + sizeof(*bi)) {
3335                 ei = btrfs_item_ptr(eb, path->slots[0],
3336                                 struct btrfs_extent_item);
3337                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3338                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3339                         level = btrfs_tree_block_level(eb, bi);
3340                 } else {
3341                         level = (int)extent_key->offset;
3342                 }
3343                 generation = btrfs_extent_generation(eb, ei);
3344         } else {
3345 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3346                 u64 ref_owner;
3347                 int ret;
3348
3349                 BUG_ON(item_size != sizeof(struct btrfs_extent_item_v0));
3350                 ret = get_ref_objectid_v0(rc, path, extent_key,
3351                                           &ref_owner, NULL);
3352                 if (ret < 0)
3353                         return ret;
3354                 BUG_ON(ref_owner >= BTRFS_MAX_LEVEL);
3355                 level = (int)ref_owner;
3356                 /* FIXME: get real generation */
3357                 generation = 0;
3358 #else
3359                 BUG();
3360 #endif
3361         }
3362
3363         btrfs_release_path(path);
3364
3365         BUG_ON(level == -1);
3366
3367         block = kmalloc(sizeof(*block), GFP_NOFS);
3368         if (!block)
3369                 return -ENOMEM;
3370
3371         block->bytenr = extent_key->objectid;
3372         block->key.objectid = rc->extent_root->nodesize;
3373         block->key.offset = generation;
3374         block->level = level;
3375         block->key_ready = 0;
3376
3377         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3378         if (rb_node)
3379                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3380
3381         return 0;
3382 }
3383
3384 /*
3385  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3386  */
3387 static int __add_tree_block(struct reloc_control *rc,
3388                             u64 bytenr, u32 blocksize,
3389                             struct rb_root *blocks)
3390 {
3391         struct btrfs_path *path;
3392         struct btrfs_key key;
3393         int ret;
3394         bool skinny = btrfs_fs_incompat(rc->extent_root->fs_info,
3395                                         SKINNY_METADATA);
3396
3397         if (tree_block_processed(bytenr, rc))
3398                 return 0;
3399
3400         if (tree_search(blocks, bytenr))
3401                 return 0;
3402
3403         path = btrfs_alloc_path();
3404         if (!path)
3405                 return -ENOMEM;
3406 again:
3407         key.objectid = bytenr;
3408         if (skinny) {
3409                 key.type = BTRFS_METADATA_ITEM_KEY;
3410                 key.offset = (u64)-1;
3411         } else {
3412                 key.type = BTRFS_EXTENT_ITEM_KEY;
3413                 key.offset = blocksize;
3414         }
3415
3416         path->search_commit_root = 1;
3417         path->skip_locking = 1;
3418         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3419         if (ret < 0)
3420                 goto out;
3421
3422         if (ret > 0 && skinny) {
3423                 if (path->slots[0]) {
3424                         path->slots[0]--;
3425                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3426                                               path->slots[0]);
3427                         if (key.objectid == bytenr &&
3428                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3429                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3430                               key.offset == blocksize)))
3431                                 ret = 0;
3432                 }
3433
3434                 if (ret) {
3435                         skinny = false;
3436                         btrfs_release_path(path);
3437                         goto again;
3438                 }
3439         }
3440         BUG_ON(ret);
3441
3442         ret = add_tree_block(rc, &key, path, blocks);
3443 out:
3444         btrfs_free_path(path);
3445         return ret;
3446 }
3447
3448 /*
3449  * helper to check if the block use full backrefs for pointers in it
3450  */
3451 static int block_use_full_backref(struct reloc_control *rc,
3452                                   struct extent_buffer *eb)
3453 {
3454         u64 flags;
3455         int ret;
3456
3457         if (btrfs_header_flag(eb, BTRFS_HEADER_FLAG_RELOC) ||
3458             btrfs_header_backref_rev(eb) < BTRFS_MIXED_BACKREF_REV)
3459                 return 1;
3460
3461         ret = btrfs_lookup_extent_info(NULL, rc->extent_root,
3462                                        eb->start, btrfs_header_level(eb), 1,
3463                                        NULL, &flags);
3464         BUG_ON(ret);
3465
3466         if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
3467                 ret = 1;
3468         else
3469                 ret = 0;
3470         return ret;
3471 }
3472
3473 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3474                                     struct btrfs_block_group_cache *block_group,
3475                                     struct inode *inode,
3476                                     u64 ino)
3477 {
3478         struct btrfs_key key;
3479         struct btrfs_root *root = fs_info->tree_root;
3480         struct btrfs_trans_handle *trans;
3481         int ret = 0;
3482
3483         if (inode)
3484                 goto truncate;
3485
3486         key.objectid = ino;
3487         key.type = BTRFS_INODE_ITEM_KEY;
3488         key.offset = 0;
3489
3490         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
3491         if (IS_ERR(inode) || is_bad_inode(inode)) {
3492                 if (!IS_ERR(inode))
3493                         iput(inode);
3494                 return -ENOENT;
3495         }
3496
3497 truncate:
3498         ret = btrfs_check_trunc_cache_free_space(root,
3499                                                  &fs_info->global_block_rsv);
3500         if (ret)
3501                 goto out;
3502
3503         trans = btrfs_join_transaction(root);
3504         if (IS_ERR(trans)) {
3505                 ret = PTR_ERR(trans);
3506                 goto out;
3507         }
3508
3509         ret = btrfs_truncate_free_space_cache(root, trans, block_group, inode);
3510
3511         btrfs_end_transaction(trans, root);
3512         btrfs_btree_balance_dirty(root);
3513 out:
3514         iput(inode);
3515         return ret;
3516 }
3517
3518 /*
3519  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
3520  * this function scans fs tree to find blocks reference the data extent
3521  */
3522 static int find_data_references(struct reloc_control *rc,
3523                                 struct btrfs_key *extent_key,
3524                                 struct extent_buffer *leaf,
3525                                 struct btrfs_extent_data_ref *ref,
3526                                 struct rb_root *blocks)
3527 {
3528         struct btrfs_path *path;
3529         struct tree_block *block;
3530         struct btrfs_root *root;
3531         struct btrfs_file_extent_item *fi;
3532         struct rb_node *rb_node;
3533         struct btrfs_key key;
3534         u64 ref_root;
3535         u64 ref_objectid;
3536         u64 ref_offset;
3537         u32 ref_count;
3538         u32 nritems;
3539         int err = 0;
3540         int added = 0;
3541         int counted;
3542         int ret;
3543
3544         ref_root = btrfs_extent_data_ref_root(leaf, ref);
3545         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
3546         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
3547         ref_count = btrfs_extent_data_ref_count(leaf, ref);
3548
3549         /*
3550          * This is an extent belonging to the free space cache, lets just delete
3551          * it and redo the search.
3552          */
3553         if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
3554                 ret = delete_block_group_cache(rc->extent_root->fs_info,
3555                                                rc->block_group,
3556                                                NULL, ref_objectid);
3557                 if (ret != -ENOENT)
3558                         return ret;
3559                 ret = 0;
3560         }
3561
3562         path = btrfs_alloc_path();
3563         if (!path)
3564                 return -ENOMEM;
3565         path->reada = READA_FORWARD;
3566
3567         root = read_fs_root(rc->extent_root->fs_info, ref_root);
3568         if (IS_ERR(root)) {
3569                 err = PTR_ERR(root);
3570                 goto out;
3571         }
3572
3573         key.objectid = ref_objectid;
3574         key.type = BTRFS_EXTENT_DATA_KEY;
3575         if (ref_offset > ((u64)-1 << 32))
3576                 key.offset = 0;
3577         else
3578                 key.offset = ref_offset;
3579
3580         path->search_commit_root = 1;
3581         path->skip_locking = 1;
3582         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
3583         if (ret < 0) {
3584                 err = ret;
3585                 goto out;
3586         }
3587
3588         leaf = path->nodes[0];
3589         nritems = btrfs_header_nritems(leaf);
3590         /*
3591          * the references in tree blocks that use full backrefs
3592          * are not counted in
3593          */
3594         if (block_use_full_backref(rc, leaf))
3595                 counted = 0;
3596         else
3597                 counted = 1;
3598         rb_node = tree_search(blocks, leaf->start);
3599         if (rb_node) {
3600                 if (counted)
3601                         added = 1;
3602                 else
3603                         path->slots[0] = nritems;
3604         }
3605
3606         while (ref_count > 0) {
3607                 while (path->slots[0] >= nritems) {
3608                         ret = btrfs_next_leaf(root, path);
3609                         if (ret < 0) {
3610                                 err = ret;
3611                                 goto out;
3612                         }
3613                         if (WARN_ON(ret > 0))
3614                                 goto out;
3615
3616                         leaf = path->nodes[0];
3617                         nritems = btrfs_header_nritems(leaf);
3618                         added = 0;
3619
3620                         if (block_use_full_backref(rc, leaf))
3621                                 counted = 0;
3622                         else
3623                                 counted = 1;
3624                         rb_node = tree_search(blocks, leaf->start);
3625                         if (rb_node) {
3626                                 if (counted)
3627                                         added = 1;
3628                                 else
3629                                         path->slots[0] = nritems;
3630                         }
3631                 }
3632
3633                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3634                 if (WARN_ON(key.objectid != ref_objectid ||
3635                     key.type != BTRFS_EXTENT_DATA_KEY))
3636                         break;
3637
3638                 fi = btrfs_item_ptr(leaf, path->slots[0],
3639                                     struct btrfs_file_extent_item);
3640
3641                 if (btrfs_file_extent_type(leaf, fi) ==
3642                     BTRFS_FILE_EXTENT_INLINE)
3643                         goto next;
3644
3645                 if (btrfs_file_extent_disk_bytenr(leaf, fi) !=
3646                     extent_key->objectid)
3647                         goto next;
3648
3649                 key.offset -= btrfs_file_extent_offset(leaf, fi);
3650                 if (key.offset != ref_offset)
3651                         goto next;
3652
3653                 if (counted)
3654                         ref_count--;
3655                 if (added)
3656                         goto next;
3657
3658                 if (!tree_block_processed(leaf->start, rc)) {
3659                         block = kmalloc(sizeof(*block), GFP_NOFS);
3660                         if (!block) {
3661                                 err = -ENOMEM;
3662                                 break;
3663                         }
3664                         block->bytenr = leaf->start;
3665                         btrfs_item_key_to_cpu(leaf, &block->key, 0);
3666                         block->level = 0;
3667                         block->key_ready = 1;
3668                         rb_node = tree_insert(blocks, block->bytenr,
3669                                               &block->rb_node);
3670                         if (rb_node)
3671                                 backref_tree_panic(rb_node, -EEXIST,
3672                                                    block->bytenr);
3673                 }
3674                 if (counted)
3675                         added = 1;
3676                 else
3677                         path->slots[0] = nritems;
3678 next:
3679                 path->slots[0]++;
3680
3681         }
3682 out:
3683         btrfs_free_path(path);
3684         return err;
3685 }
3686
3687 /*
3688  * helper to find all tree blocks that reference a given data extent
3689  */
3690 static noinline_for_stack
3691 int add_data_references(struct reloc_control *rc,
3692                         struct btrfs_key *extent_key,
3693                         struct btrfs_path *path,
3694                         struct rb_root *blocks)
3695 {
3696         struct btrfs_key key;
3697         struct extent_buffer *eb;
3698         struct btrfs_extent_data_ref *dref;
3699         struct btrfs_extent_inline_ref *iref;
3700         unsigned long ptr;
3701         unsigned long end;
3702         u32 blocksize = rc->extent_root->nodesize;
3703         int ret = 0;
3704         int err = 0;
3705
3706         eb = path->nodes[0];
3707         ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
3708         end = ptr + btrfs_item_size_nr(eb, path->slots[0]);
3709 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3710         if (ptr + sizeof(struct btrfs_extent_item_v0) == end)
3711                 ptr = end;
3712         else
3713 #endif
3714                 ptr += sizeof(struct btrfs_extent_item);
3715
3716         while (ptr < end) {
3717                 iref = (struct btrfs_extent_inline_ref *)ptr;
3718                 key.type = btrfs_extent_inline_ref_type(eb, iref);
3719                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3720                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3721                         ret = __add_tree_block(rc, key.offset, blocksize,
3722                                                blocks);
3723                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3724                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
3725                         ret = find_data_references(rc, extent_key,
3726                                                    eb, dref, blocks);
3727                 } else {
3728                         BUG();
3729                 }
3730                 if (ret) {
3731                         err = ret;
3732                         goto out;
3733                 }
3734                 ptr += btrfs_extent_inline_ref_size(key.type);
3735         }
3736         WARN_ON(ptr > end);
3737
3738         while (1) {
3739                 cond_resched();
3740                 eb = path->nodes[0];
3741                 if (path->slots[0] >= btrfs_header_nritems(eb)) {
3742                         ret = btrfs_next_leaf(rc->extent_root, path);
3743                         if (ret < 0) {
3744                                 err = ret;
3745                                 break;
3746                         }
3747                         if (ret > 0)
3748                                 break;
3749                         eb = path->nodes[0];
3750                 }
3751
3752                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
3753                 if (key.objectid != extent_key->objectid)
3754                         break;
3755
3756 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3757                 if (key.type == BTRFS_SHARED_DATA_REF_KEY ||
3758                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
3759 #else
3760                 BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
3761                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3762 #endif
3763                         ret = __add_tree_block(rc, key.offset, blocksize,
3764                                                blocks);
3765                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3766                         dref = btrfs_item_ptr(eb, path->slots[0],
3767                                               struct btrfs_extent_data_ref);
3768                         ret = find_data_references(rc, extent_key,
3769                                                    eb, dref, blocks);
3770                 } else {
3771                         ret = 0;
3772                 }
3773                 if (ret) {
3774                         err = ret;
3775                         break;
3776                 }
3777                 path->slots[0]++;
3778         }
3779 out:
3780         btrfs_release_path(path);
3781         if (err)
3782                 free_block_list(blocks);
3783         return err;
3784 }
3785
3786 /*
3787  * helper to find next unprocessed extent
3788  */
3789 static noinline_for_stack
3790 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3791                      struct btrfs_key *extent_key)
3792 {
3793         struct btrfs_key key;
3794         struct extent_buffer *leaf;
3795         u64 start, end, last;
3796         int ret;
3797
3798         last = rc->block_group->key.objectid + rc->block_group->key.offset;
3799         while (1) {
3800                 cond_resched();
3801                 if (rc->search_start >= last) {
3802                         ret = 1;
3803                         break;
3804                 }
3805
3806                 key.objectid = rc->search_start;
3807                 key.type = BTRFS_EXTENT_ITEM_KEY;
3808                 key.offset = 0;
3809
3810                 path->search_commit_root = 1;
3811                 path->skip_locking = 1;
3812                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3813                                         0, 0);
3814                 if (ret < 0)
3815                         break;
3816 next:
3817                 leaf = path->nodes[0];
3818                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3819                         ret = btrfs_next_leaf(rc->extent_root, path);
3820                         if (ret != 0)
3821                                 break;
3822                         leaf = path->nodes[0];
3823                 }
3824
3825                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3826                 if (key.objectid >= last) {
3827                         ret = 1;
3828                         break;
3829                 }
3830
3831                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3832                     key.type != BTRFS_METADATA_ITEM_KEY) {
3833                         path->slots[0]++;
3834                         goto next;
3835                 }
3836
3837                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3838                     key.objectid + key.offset <= rc->search_start) {
3839                         path->slots[0]++;
3840                         goto next;
3841                 }
3842
3843                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3844                     key.objectid + rc->extent_root->nodesize <=
3845                     rc->search_start) {
3846                         path->slots[0]++;
3847                         goto next;
3848                 }
3849
3850                 ret = find_first_extent_bit(&rc->processed_blocks,
3851                                             key.objectid, &start, &end,
3852                                             EXTENT_DIRTY, NULL);
3853
3854                 if (ret == 0 && start <= key.objectid) {
3855                         btrfs_release_path(path);
3856                         rc->search_start = end + 1;
3857                 } else {
3858                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3859                                 rc->search_start = key.objectid + key.offset;
3860                         else
3861                                 rc->search_start = key.objectid +
3862                                         rc->extent_root->nodesize;
3863                         memcpy(extent_key, &key, sizeof(key));
3864                         return 0;
3865                 }
3866         }
3867         btrfs_release_path(path);
3868         return ret;
3869 }
3870
3871 static void set_reloc_control(struct reloc_control *rc)
3872 {
3873         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3874
3875         mutex_lock(&fs_info->reloc_mutex);
3876         fs_info->reloc_ctl = rc;
3877         mutex_unlock(&fs_info->reloc_mutex);
3878 }
3879
3880 static void unset_reloc_control(struct reloc_control *rc)
3881 {
3882         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3883
3884         mutex_lock(&fs_info->reloc_mutex);
3885         fs_info->reloc_ctl = NULL;
3886         mutex_unlock(&fs_info->reloc_mutex);
3887 }
3888
3889 static int check_extent_flags(u64 flags)
3890 {
3891         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3892             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3893                 return 1;
3894         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3895             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3896                 return 1;
3897         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3898             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3899                 return 1;
3900         return 0;
3901 }
3902
3903 static noinline_for_stack
3904 int prepare_to_relocate(struct reloc_control *rc)
3905 {
3906         struct btrfs_trans_handle *trans;
3907         int ret;
3908
3909         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root,
3910                                               BTRFS_BLOCK_RSV_TEMP);
3911         if (!rc->block_rsv)
3912                 return -ENOMEM;
3913
3914         memset(&rc->cluster, 0, sizeof(rc->cluster));
3915         rc->search_start = rc->block_group->key.objectid;
3916         rc->extents_found = 0;
3917         rc->nodes_relocated = 0;
3918         rc->merging_rsv_size = 0;
3919         rc->reserved_bytes = 0;
3920         rc->block_rsv->size = rc->extent_root->nodesize *
3921                               RELOCATION_RESERVED_NODES;
3922         ret = btrfs_block_rsv_refill(rc->extent_root,
3923                                      rc->block_rsv, rc->block_rsv->size,
3924                                      BTRFS_RESERVE_FLUSH_ALL);
3925         if (ret)
3926                 return ret;
3927
3928         rc->create_reloc_tree = 1;
3929         set_reloc_control(rc);
3930
3931         trans = btrfs_join_transaction(rc->extent_root);
3932         if (IS_ERR(trans)) {
3933                 unset_reloc_control(rc);
3934                 /*
3935                  * extent tree is not a ref_cow tree and has no reloc_root to
3936                  * cleanup.  And callers are responsible to free the above
3937                  * block rsv.
3938                  */
3939                 return PTR_ERR(trans);
3940         }
3941         btrfs_commit_transaction(trans, rc->extent_root);
3942         return 0;
3943 }
3944
3945 /*
3946  * Qgroup fixer for data chunk relocation.
3947  * The data relocation is done in the following steps
3948  * 1) Copy data extents into data reloc tree
3949  * 2) Create tree reloc tree(special snapshot) for related subvolumes
3950  * 3) Modify file extents in tree reloc tree
3951  * 4) Merge tree reloc tree with original fs tree, by swapping tree blocks
3952  *
3953  * The problem is, data and tree reloc tree are not accounted to qgroup,
3954  * and 4) will only info qgroup to track tree blocks change, not file extents
3955  * in the tree blocks.
3956  *
3957  * The good news is, related data extents are all in data reloc tree, so we
3958  * only need to info qgroup to track all file extents in data reloc tree
3959  * before commit trans.
3960  */
3961 static int qgroup_fix_relocated_data_extents(struct btrfs_trans_handle *trans,
3962                                              struct reloc_control *rc)
3963 {
3964         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3965         struct inode *inode = rc->data_inode;
3966         struct btrfs_root *data_reloc_root = BTRFS_I(inode)->root;
3967         struct btrfs_path *path;
3968         struct btrfs_key key;
3969         int ret = 0;
3970
3971         if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
3972                 return 0;
3973
3974         /*
3975          * Only for stage where we update data pointers the qgroup fix is
3976          * valid.
3977          * For MOVING_DATA stage, we will miss the timing of swapping tree
3978          * blocks, and won't fix it.
3979          */
3980         if (!(rc->stage == UPDATE_DATA_PTRS && rc->extents_found))
3981                 return 0;
3982
3983         path = btrfs_alloc_path();
3984         if (!path)
3985                 return -ENOMEM;
3986         key.objectid = btrfs_ino(inode);
3987         key.type = BTRFS_EXTENT_DATA_KEY;
3988         key.offset = 0;
3989
3990         ret = btrfs_search_slot(NULL, data_reloc_root, &key, path, 0, 0);
3991         if (ret < 0)
3992                 goto out;
3993
3994         lock_extent(&BTRFS_I(inode)->io_tree, 0, (u64)-1);
3995         while (1) {
3996                 struct btrfs_file_extent_item *fi;
3997
3998                 btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
3999                 if (key.objectid > btrfs_ino(inode))
4000                         break;
4001                 if (key.type != BTRFS_EXTENT_DATA_KEY)
4002                         goto next;
4003                 fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
4004                                     struct btrfs_file_extent_item);
4005                 if (btrfs_file_extent_type(path->nodes[0], fi) !=
4006                                 BTRFS_FILE_EXTENT_REG)
4007                         goto next;
4008                 ret = btrfs_qgroup_insert_dirty_extent(trans, fs_info,
4009                         btrfs_file_extent_disk_bytenr(path->nodes[0], fi),
4010                         btrfs_file_extent_disk_num_bytes(path->nodes[0], fi),
4011                         GFP_NOFS);
4012                 if (ret < 0)
4013                         break;
4014 next:
4015                 ret = btrfs_next_item(data_reloc_root, path);
4016                 if (ret < 0)
4017                         break;
4018                 if (ret > 0) {
4019                         ret = 0;
4020                         break;
4021                 }
4022         }
4023         unlock_extent(&BTRFS_I(inode)->io_tree, 0 , (u64)-1);
4024 out:
4025         btrfs_free_path(path);
4026         return ret;
4027 }
4028
4029 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
4030 {
4031         struct rb_root blocks = RB_ROOT;
4032         struct btrfs_key key;
4033         struct btrfs_trans_handle *trans = NULL;
4034         struct btrfs_path *path;
4035         struct btrfs_extent_item *ei;
4036         u64 flags;
4037         u32 item_size;
4038         int ret;
4039         int err = 0;
4040         int progress = 0;
4041
4042         path = btrfs_alloc_path();
4043         if (!path)
4044                 return -ENOMEM;
4045         path->reada = READA_FORWARD;
4046
4047         ret = prepare_to_relocate(rc);
4048         if (ret) {
4049                 err = ret;
4050                 goto out_free;
4051         }
4052
4053         while (1) {
4054                 rc->reserved_bytes = 0;
4055                 ret = btrfs_block_rsv_refill(rc->extent_root,
4056                                         rc->block_rsv, rc->block_rsv->size,
4057                                         BTRFS_RESERVE_FLUSH_ALL);
4058                 if (ret) {
4059                         err = ret;
4060                         break;
4061                 }
4062                 progress++;
4063                 trans = btrfs_start_transaction(rc->extent_root, 0);
4064                 if (IS_ERR(trans)) {
4065                         err = PTR_ERR(trans);
4066                         trans = NULL;
4067                         break;
4068                 }
4069 restart:
4070                 if (update_backref_cache(trans, &rc->backref_cache)) {
4071                         btrfs_end_transaction(trans, rc->extent_root);
4072                         continue;
4073                 }
4074
4075                 ret = find_next_extent(rc, path, &key);
4076                 if (ret < 0)
4077                         err = ret;
4078                 if (ret != 0)
4079                         break;
4080
4081                 rc->extents_found++;
4082
4083                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4084                                     struct btrfs_extent_item);
4085                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4086                 if (item_size >= sizeof(*ei)) {
4087                         flags = btrfs_extent_flags(path->nodes[0], ei);
4088                         ret = check_extent_flags(flags);
4089                         BUG_ON(ret);
4090
4091                 } else {
4092 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
4093                         u64 ref_owner;
4094                         int path_change = 0;
4095
4096                         BUG_ON(item_size !=
4097                                sizeof(struct btrfs_extent_item_v0));
4098                         ret = get_ref_objectid_v0(rc, path, &key, &ref_owner,
4099                                                   &path_change);
4100                         if (ret < 0) {
4101                                 err = ret;
4102                                 break;
4103                         }
4104                         if (ref_owner < BTRFS_FIRST_FREE_OBJECTID)
4105                                 flags = BTRFS_EXTENT_FLAG_TREE_BLOCK;
4106                         else
4107                                 flags = BTRFS_EXTENT_FLAG_DATA;
4108
4109                         if (path_change) {
4110                                 btrfs_release_path(path);
4111
4112                                 path->search_commit_root = 1;
4113                                 path->skip_locking = 1;
4114                                 ret = btrfs_search_slot(NULL, rc->extent_root,
4115                                                         &key, path, 0, 0);
4116                                 if (ret < 0) {
4117                                         err = ret;
4118                                         break;
4119                                 }
4120                                 BUG_ON(ret > 0);
4121                         }
4122 #else
4123                         BUG();
4124 #endif
4125                 }
4126
4127                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4128                         ret = add_tree_block(rc, &key, path, &blocks);
4129                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4130                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4131                         ret = add_data_references(rc, &key, path, &blocks);
4132                 } else {
4133                         btrfs_release_path(path);
4134                         ret = 0;
4135                 }
4136                 if (ret < 0) {
4137                         err = ret;
4138                         break;
4139                 }
4140
4141                 if (!RB_EMPTY_ROOT(&blocks)) {
4142                         ret = relocate_tree_blocks(trans, rc, &blocks);
4143                         if (ret < 0) {
4144                                 /*
4145                                  * if we fail to relocate tree blocks, force to update
4146                                  * backref cache when committing transaction.
4147                                  */
4148                                 rc->backref_cache.last_trans = trans->transid - 1;
4149
4150                                 if (ret != -EAGAIN) {
4151                                         err = ret;
4152                                         break;
4153                                 }
4154                                 rc->extents_found--;
4155                                 rc->search_start = key.objectid;
4156                         }
4157                 }
4158
4159                 btrfs_end_transaction_throttle(trans, rc->extent_root);
4160                 btrfs_btree_balance_dirty(rc->extent_root);
4161                 trans = NULL;
4162
4163                 if (rc->stage == MOVE_DATA_EXTENTS &&
4164                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4165                         rc->found_file_extent = 1;
4166                         ret = relocate_data_extent(rc->data_inode,
4167                                                    &key, &rc->cluster);
4168                         if (ret < 0) {
4169                                 err = ret;
4170                                 break;
4171                         }
4172                 }
4173         }
4174         if (trans && progress && err == -ENOSPC) {
4175                 ret = btrfs_force_chunk_alloc(trans, rc->extent_root,
4176                                               rc->block_group->flags);
4177                 if (ret == 1) {
4178                         err = 0;
4179                         progress = 0;
4180                         goto restart;
4181                 }
4182         }
4183
4184         btrfs_release_path(path);
4185         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4186
4187         if (trans) {
4188                 btrfs_end_transaction_throttle(trans, rc->extent_root);
4189                 btrfs_btree_balance_dirty(rc->extent_root);
4190         }
4191
4192         if (!err) {
4193                 ret = relocate_file_extent_cluster(rc->data_inode,
4194                                                    &rc->cluster);
4195                 if (ret < 0)
4196                         err = ret;
4197         }
4198
4199         rc->create_reloc_tree = 0;
4200         set_reloc_control(rc);
4201
4202         backref_cache_cleanup(&rc->backref_cache);
4203         btrfs_block_rsv_release(rc->extent_root, rc->block_rsv, (u64)-1);
4204
4205         err = prepare_to_merge(rc, err);
4206
4207         merge_reloc_roots(rc);
4208
4209         rc->merge_reloc_tree = 0;
4210         unset_reloc_control(rc);
4211         btrfs_block_rsv_release(rc->extent_root, rc->block_rsv, (u64)-1);
4212
4213         /* get rid of pinned extents */
4214         trans = btrfs_join_transaction(rc->extent_root);
4215         if (IS_ERR(trans)) {
4216                 err = PTR_ERR(trans);
4217                 goto out_free;
4218         }
4219         ret = qgroup_fix_relocated_data_extents(trans, rc);
4220         if (ret < 0) {
4221                 btrfs_abort_transaction(trans, ret);
4222                 if (!err)
4223                         err = ret;
4224                 goto out_free;
4225         }
4226         btrfs_commit_transaction(trans, rc->extent_root);
4227 out_free:
4228         btrfs_free_block_rsv(rc->extent_root, rc->block_rsv);
4229         btrfs_free_path(path);
4230         return err;
4231 }
4232
4233 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4234                                  struct btrfs_root *root, u64 objectid)
4235 {
4236         struct btrfs_path *path;
4237         struct btrfs_inode_item *item;
4238         struct extent_buffer *leaf;
4239         int ret;
4240
4241         path = btrfs_alloc_path();
4242         if (!path)
4243                 return -ENOMEM;
4244
4245         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4246         if (ret)
4247                 goto out;
4248
4249         leaf = path->nodes[0];
4250         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4251         memset_extent_buffer(leaf, 0, (unsigned long)item, sizeof(*item));
4252         btrfs_set_inode_generation(leaf, item, 1);
4253         btrfs_set_inode_size(leaf, item, 0);
4254         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4255         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4256                                           BTRFS_INODE_PREALLOC);
4257         btrfs_mark_buffer_dirty(leaf);
4258 out:
4259         btrfs_free_path(path);
4260         return ret;
4261 }
4262
4263 /*
4264  * helper to create inode for data relocation.
4265  * the inode is in data relocation tree and its link count is 0
4266  */
4267 static noinline_for_stack
4268 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4269                                  struct btrfs_block_group_cache *group)
4270 {
4271         struct inode *inode = NULL;
4272         struct btrfs_trans_handle *trans;
4273         struct btrfs_root *root;
4274         struct btrfs_key key;
4275         u64 objectid;
4276         int err = 0;
4277
4278         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4279         if (IS_ERR(root))
4280                 return ERR_CAST(root);
4281
4282         trans = btrfs_start_transaction(root, 6);
4283         if (IS_ERR(trans))
4284                 return ERR_CAST(trans);
4285
4286         err = btrfs_find_free_objectid(root, &objectid);
4287         if (err)
4288                 goto out;
4289
4290         err = __insert_orphan_inode(trans, root, objectid);
4291         BUG_ON(err);
4292
4293         key.objectid = objectid;
4294         key.type = BTRFS_INODE_ITEM_KEY;
4295         key.offset = 0;
4296         inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
4297         BUG_ON(IS_ERR(inode) || is_bad_inode(inode));
4298         BTRFS_I(inode)->index_cnt = group->key.objectid;
4299
4300         err = btrfs_orphan_add(trans, inode);
4301 out:
4302         btrfs_end_transaction(trans, root);
4303         btrfs_btree_balance_dirty(root);
4304         if (err) {
4305                 if (inode)
4306                         iput(inode);
4307                 inode = ERR_PTR(err);
4308         }
4309         return inode;
4310 }
4311
4312 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4313 {
4314         struct reloc_control *rc;
4315
4316         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4317         if (!rc)
4318                 return NULL;
4319
4320         INIT_LIST_HEAD(&rc->reloc_roots);
4321         backref_cache_init(&rc->backref_cache);
4322         mapping_tree_init(&rc->reloc_root_tree);
4323         extent_io_tree_init(&rc->processed_blocks,
4324                             fs_info->btree_inode->i_mapping);
4325         return rc;
4326 }
4327
4328 /*
4329  * function to relocate all extents in a block group.
4330  */
4331 int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
4332 {
4333         struct btrfs_fs_info *fs_info = extent_root->fs_info;
4334         struct reloc_control *rc;
4335         struct inode *inode;
4336         struct btrfs_path *path;
4337         int ret;
4338         int rw = 0;
4339         int err = 0;
4340
4341         rc = alloc_reloc_control(fs_info);
4342         if (!rc)
4343                 return -ENOMEM;
4344
4345         rc->extent_root = extent_root;
4346
4347         rc->block_group = btrfs_lookup_block_group(fs_info, group_start);
4348         BUG_ON(!rc->block_group);
4349
4350         ret = btrfs_inc_block_group_ro(extent_root, rc->block_group);
4351         if (ret) {
4352                 err = ret;
4353                 goto out;
4354         }
4355         rw = 1;
4356
4357         path = btrfs_alloc_path();
4358         if (!path) {
4359                 err = -ENOMEM;
4360                 goto out;
4361         }
4362
4363         inode = lookup_free_space_inode(fs_info->tree_root, rc->block_group,
4364                                         path);
4365         btrfs_free_path(path);
4366
4367         if (!IS_ERR(inode))
4368                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4369         else
4370                 ret = PTR_ERR(inode);
4371
4372         if (ret && ret != -ENOENT) {
4373                 err = ret;
4374                 goto out;
4375         }
4376
4377         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4378         if (IS_ERR(rc->data_inode)) {
4379                 err = PTR_ERR(rc->data_inode);
4380                 rc->data_inode = NULL;
4381                 goto out;
4382         }
4383
4384         btrfs_info(extent_root->fs_info,
4385                    "relocating block group %llu flags %llu",
4386                    rc->block_group->key.objectid, rc->block_group->flags);
4387
4388         btrfs_wait_block_group_reservations(rc->block_group);
4389         btrfs_wait_nocow_writers(rc->block_group);
4390         btrfs_wait_ordered_roots(fs_info, -1,
4391                                  rc->block_group->key.objectid,
4392                                  rc->block_group->key.offset);
4393
4394         while (1) {
4395                 mutex_lock(&fs_info->cleaner_mutex);
4396                 ret = relocate_block_group(rc);
4397                 mutex_unlock(&fs_info->cleaner_mutex);
4398                 if (ret < 0) {
4399                         err = ret;
4400                         goto out;
4401                 }
4402
4403                 if (rc->extents_found == 0)
4404                         break;
4405
4406                 btrfs_info(extent_root->fs_info, "found %llu extents",
4407                         rc->extents_found);
4408
4409                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4410                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4411                                                        (u64)-1);
4412                         if (ret) {
4413                                 err = ret;
4414                                 goto out;
4415                         }
4416                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4417                                                  0, -1);
4418                         rc->stage = UPDATE_DATA_PTRS;
4419                 }
4420         }
4421
4422         WARN_ON(rc->block_group->pinned > 0);
4423         WARN_ON(rc->block_group->reserved > 0);
4424         WARN_ON(btrfs_block_group_used(&rc->block_group->item) > 0);
4425 out:
4426         if (err && rw)
4427                 btrfs_dec_block_group_ro(extent_root, rc->block_group);
4428         iput(rc->data_inode);
4429         btrfs_put_block_group(rc->block_group);
4430         kfree(rc);
4431         return err;
4432 }
4433
4434 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4435 {
4436         struct btrfs_trans_handle *trans;
4437         int ret, err;
4438
4439         trans = btrfs_start_transaction(root->fs_info->tree_root, 0);
4440         if (IS_ERR(trans))
4441                 return PTR_ERR(trans);
4442
4443         memset(&root->root_item.drop_progress, 0,
4444                 sizeof(root->root_item.drop_progress));
4445         root->root_item.drop_level = 0;
4446         btrfs_set_root_refs(&root->root_item, 0);
4447         ret = btrfs_update_root(trans, root->fs_info->tree_root,
4448                                 &root->root_key, &root->root_item);
4449
4450         err = btrfs_end_transaction(trans, root->fs_info->tree_root);
4451         if (err)
4452                 return err;
4453         return ret;
4454 }
4455
4456 /*
4457  * recover relocation interrupted by system crash.
4458  *
4459  * this function resumes merging reloc trees with corresponding fs trees.
4460  * this is important for keeping the sharing of tree blocks
4461  */
4462 int btrfs_recover_relocation(struct btrfs_root *root)
4463 {
4464         LIST_HEAD(reloc_roots);
4465         struct btrfs_key key;
4466         struct btrfs_root *fs_root;
4467         struct btrfs_root *reloc_root;
4468         struct btrfs_path *path;
4469         struct extent_buffer *leaf;
4470         struct reloc_control *rc = NULL;
4471         struct btrfs_trans_handle *trans;
4472         int ret;
4473         int err = 0;
4474
4475         path = btrfs_alloc_path();
4476         if (!path)
4477                 return -ENOMEM;
4478         path->reada = READA_BACK;
4479
4480         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4481         key.type = BTRFS_ROOT_ITEM_KEY;
4482         key.offset = (u64)-1;
4483
4484         while (1) {
4485                 ret = btrfs_search_slot(NULL, root->fs_info->tree_root, &key,
4486                                         path, 0, 0);
4487                 if (ret < 0) {
4488                         err = ret;
4489                         goto out;
4490                 }
4491                 if (ret > 0) {
4492                         if (path->slots[0] == 0)
4493                                 break;
4494                         path->slots[0]--;
4495                 }
4496                 leaf = path->nodes[0];
4497                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4498                 btrfs_release_path(path);
4499
4500                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4501                     key.type != BTRFS_ROOT_ITEM_KEY)
4502                         break;
4503
4504                 reloc_root = btrfs_read_fs_root(root, &key);
4505                 if (IS_ERR(reloc_root)) {
4506                         err = PTR_ERR(reloc_root);
4507                         goto out;
4508                 }
4509
4510                 list_add(&reloc_root->root_list, &reloc_roots);
4511
4512                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4513                         fs_root = read_fs_root(root->fs_info,
4514                                                reloc_root->root_key.offset);
4515                         if (IS_ERR(fs_root)) {
4516                                 ret = PTR_ERR(fs_root);
4517                                 if (ret != -ENOENT) {
4518                                         err = ret;
4519                                         goto out;
4520                                 }
4521                                 ret = mark_garbage_root(reloc_root);
4522                                 if (ret < 0) {
4523                                         err = ret;
4524                                         goto out;
4525                                 }
4526                         }
4527                 }
4528
4529                 if (key.offset == 0)
4530                         break;
4531
4532                 key.offset--;
4533         }
4534         btrfs_release_path(path);
4535
4536         if (list_empty(&reloc_roots))
4537                 goto out;
4538
4539         rc = alloc_reloc_control(root->fs_info);
4540         if (!rc) {
4541                 err = -ENOMEM;
4542                 goto out;
4543         }
4544
4545         rc->extent_root = root->fs_info->extent_root;
4546
4547         set_reloc_control(rc);
4548
4549         trans = btrfs_join_transaction(rc->extent_root);
4550         if (IS_ERR(trans)) {
4551                 unset_reloc_control(rc);
4552                 err = PTR_ERR(trans);
4553                 goto out_free;
4554         }
4555
4556         rc->merge_reloc_tree = 1;
4557
4558         while (!list_empty(&reloc_roots)) {
4559                 reloc_root = list_entry(reloc_roots.next,
4560                                         struct btrfs_root, root_list);
4561                 list_del(&reloc_root->root_list);
4562
4563                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4564                         list_add_tail(&reloc_root->root_list,
4565                                       &rc->reloc_roots);
4566                         continue;
4567                 }
4568
4569                 fs_root = read_fs_root(root->fs_info,
4570                                        reloc_root->root_key.offset);
4571                 if (IS_ERR(fs_root)) {
4572                         err = PTR_ERR(fs_root);
4573                         goto out_free;
4574                 }
4575
4576                 err = __add_reloc_root(reloc_root);
4577                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4578                 fs_root->reloc_root = reloc_root;
4579         }
4580
4581         err = btrfs_commit_transaction(trans, rc->extent_root);
4582         if (err)
4583                 goto out_free;
4584
4585         merge_reloc_roots(rc);
4586
4587         unset_reloc_control(rc);
4588
4589         trans = btrfs_join_transaction(rc->extent_root);
4590         if (IS_ERR(trans)) {
4591                 err = PTR_ERR(trans);
4592                 goto out_free;
4593         }
4594         err = qgroup_fix_relocated_data_extents(trans, rc);
4595         if (err < 0) {
4596                 btrfs_abort_transaction(trans, err);
4597                 goto out_free;
4598         }
4599         err = btrfs_commit_transaction(trans, rc->extent_root);
4600 out_free:
4601         kfree(rc);
4602 out:
4603         if (!list_empty(&reloc_roots))
4604                 free_reloc_roots(&reloc_roots);
4605
4606         btrfs_free_path(path);
4607
4608         if (err == 0) {
4609                 /* cleanup orphan inode in data relocation tree */
4610                 fs_root = read_fs_root(root->fs_info,
4611                                        BTRFS_DATA_RELOC_TREE_OBJECTID);
4612                 if (IS_ERR(fs_root))
4613                         err = PTR_ERR(fs_root);
4614                 else
4615                         err = btrfs_orphan_cleanup(fs_root);
4616         }
4617         return err;
4618 }
4619
4620 /*
4621  * helper to add ordered checksum for data relocation.
4622  *
4623  * cloning checksum properly handles the nodatasum extents.
4624  * it also saves CPU time to re-calculate the checksum.
4625  */
4626 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4627 {
4628         struct btrfs_ordered_sum *sums;
4629         struct btrfs_ordered_extent *ordered;
4630         struct btrfs_root *root = BTRFS_I(inode)->root;
4631         int ret;
4632         u64 disk_bytenr;
4633         u64 new_bytenr;
4634         LIST_HEAD(list);
4635
4636         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4637         BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
4638
4639         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4640         ret = btrfs_lookup_csums_range(root->fs_info->csum_root, disk_bytenr,
4641                                        disk_bytenr + len - 1, &list, 0);
4642         if (ret)
4643                 goto out;
4644
4645         while (!list_empty(&list)) {
4646                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4647                 list_del_init(&sums->list);
4648
4649                 /*
4650                  * We need to offset the new_bytenr based on where the csum is.
4651                  * We need to do this because we will read in entire prealloc
4652                  * extents but we may have written to say the middle of the
4653                  * prealloc extent, so we need to make sure the csum goes with
4654                  * the right disk offset.
4655                  *
4656                  * We can do this because the data reloc inode refers strictly
4657                  * to the on disk bytes, so we don't have to worry about
4658                  * disk_len vs real len like with real inodes since it's all
4659                  * disk length.
4660                  */
4661                 new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
4662                 sums->bytenr = new_bytenr;
4663
4664                 btrfs_add_ordered_sum(inode, ordered, sums);
4665         }
4666 out:
4667         btrfs_put_ordered_extent(ordered);
4668         return ret;
4669 }
4670
4671 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4672                           struct btrfs_root *root, struct extent_buffer *buf,
4673                           struct extent_buffer *cow)
4674 {
4675         struct reloc_control *rc;
4676         struct backref_node *node;
4677         int first_cow = 0;
4678         int level;
4679         int ret = 0;
4680
4681         rc = root->fs_info->reloc_ctl;
4682         if (!rc)
4683                 return 0;
4684
4685         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4686                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4687
4688         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
4689                 if (buf == root->node)
4690                         __update_reloc_root(root, cow->start);
4691         }
4692
4693         level = btrfs_header_level(buf);
4694         if (btrfs_header_generation(buf) <=
4695             btrfs_root_last_snapshot(&root->root_item))
4696                 first_cow = 1;
4697
4698         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4699             rc->create_reloc_tree) {
4700                 WARN_ON(!first_cow && level == 0);
4701
4702                 node = rc->backref_cache.path[level];
4703                 BUG_ON(node->bytenr != buf->start &&
4704                        node->new_bytenr != buf->start);
4705
4706                 drop_node_buffer(node);
4707                 extent_buffer_get(cow);
4708                 node->eb = cow;
4709                 node->new_bytenr = cow->start;
4710
4711                 if (!node->pending) {
4712                         list_move_tail(&node->list,
4713                                        &rc->backref_cache.pending[level]);
4714                         node->pending = 1;
4715                 }
4716
4717                 if (first_cow)
4718                         __mark_block_processed(rc, node);
4719
4720                 if (first_cow && level > 0)
4721                         rc->nodes_relocated += buf->len;
4722         }
4723
4724         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4725                 ret = replace_file_extents(trans, rc, root, cow);
4726         return ret;
4727 }
4728
4729 /*
4730  * called before creating snapshot. it calculates metadata reservation
4731  * required for relocating tree blocks in the snapshot
4732  */
4733 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4734                               u64 *bytes_to_reserve)
4735 {
4736         struct btrfs_root *root;
4737         struct reloc_control *rc;
4738
4739         root = pending->root;
4740         if (!root->reloc_root)
4741                 return;
4742
4743         rc = root->fs_info->reloc_ctl;
4744         if (!rc->merge_reloc_tree)
4745                 return;
4746
4747         root = root->reloc_root;
4748         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4749         /*
4750          * relocation is in the stage of merging trees. the space
4751          * used by merging a reloc tree is twice the size of
4752          * relocated tree nodes in the worst case. half for cowing
4753          * the reloc tree, half for cowing the fs tree. the space
4754          * used by cowing the reloc tree will be freed after the
4755          * tree is dropped. if we create snapshot, cowing the fs
4756          * tree may use more space than it frees. so we need
4757          * reserve extra space.
4758          */
4759         *bytes_to_reserve += rc->nodes_relocated;
4760 }
4761
4762 /*
4763  * called after snapshot is created. migrate block reservation
4764  * and create reloc root for the newly created snapshot
4765  */
4766 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4767                                struct btrfs_pending_snapshot *pending)
4768 {
4769         struct btrfs_root *root = pending->root;
4770         struct btrfs_root *reloc_root;
4771         struct btrfs_root *new_root;
4772         struct reloc_control *rc;
4773         int ret;
4774
4775         if (!root->reloc_root)
4776                 return 0;
4777
4778         rc = root->fs_info->reloc_ctl;
4779         rc->merging_rsv_size += rc->nodes_relocated;
4780
4781         if (rc->merge_reloc_tree) {
4782                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4783                                               rc->block_rsv,
4784                                               rc->nodes_relocated, 1);
4785                 if (ret)
4786                         return ret;
4787         }
4788
4789         new_root = pending->snap;
4790         reloc_root = create_reloc_root(trans, root->reloc_root,
4791                                        new_root->root_key.objectid);
4792         if (IS_ERR(reloc_root))
4793                 return PTR_ERR(reloc_root);
4794
4795         ret = __add_reloc_root(reloc_root);
4796         BUG_ON(ret < 0);
4797         new_root->reloc_root = reloc_root;
4798
4799         if (rc->create_reloc_tree)
4800                 ret = clone_backref_node(trans, rc, root, reloc_root);
4801         return ret;
4802 }