fs/btrfs/relocation.c

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