fs/btrfs/backref.c

   1 /*
   2  * Copyright (C) 2011 STRATO.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/vmalloc.h>
  20 #include "ctree.h"
  21 #include "disk-io.h"
  22 #include "backref.h"
  23 #include "ulist.h"
  24 #include "transaction.h"
  25 #include "delayed-ref.h"
  26 #include "locking.h"
  27
  28 struct extent_inode_elem {
  29         u64 inum;
  30         u64 offset;
  31         struct extent_inode_elem *next;
  32 };
  33
  34 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
  35                                 struct btrfs_file_extent_item *fi,
  36                                 u64 extent_item_pos,
  37                                 struct extent_inode_elem **eie)
  38 {
  39         u64 offset = 0;
  40         struct extent_inode_elem *e;
  41
  42         if (!btrfs_file_extent_compression(eb, fi) &&
  43             !btrfs_file_extent_encryption(eb, fi) &&
  44             !btrfs_file_extent_other_encoding(eb, fi)) {
  45                 u64 data_offset;
  46                 u64 data_len;
  47
  48                 data_offset = btrfs_file_extent_offset(eb, fi);
  49                 data_len = btrfs_file_extent_num_bytes(eb, fi);
  50
  51                 if (extent_item_pos < data_offset ||
  52                     extent_item_pos >= data_offset + data_len)
  53                         return 1;
  54                 offset = extent_item_pos - data_offset;
  55         }
  56
  57         e = kmalloc(sizeof(*e), GFP_NOFS);
  58         if (!e)
  59                 return -ENOMEM;
  60
  61         e->next = *eie;
  62         e->inum = key->objectid;
  63         e->offset = key->offset + offset;
  64         *eie = e;
  65
  66         return 0;
  67 }
  68
  69 static void free_inode_elem_list(struct extent_inode_elem *eie)
  70 {
  71         struct extent_inode_elem *eie_next;
  72
  73         for (; eie; eie = eie_next) {
  74                 eie_next = eie->next;
  75                 kfree(eie);
  76         }
  77 }
  78
  79 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
  80                                 u64 extent_item_pos,
  81                                 struct extent_inode_elem **eie)
  82 {
  83         u64 disk_byte;
  84         struct btrfs_key key;
  85         struct btrfs_file_extent_item *fi;
  86         int slot;
  87         int nritems;
  88         int extent_type;
  89         int ret;
  90
  91         /*
  92          * from the shared data ref, we only have the leaf but we need
  93          * the key. thus, we must look into all items and see that we
  94          * find one (some) with a reference to our extent item.
  95          */
  96         nritems = btrfs_header_nritems(eb);
  97         for (slot = 0; slot < nritems; ++slot) {
  98                 btrfs_item_key_to_cpu(eb, &key, slot);
  99                 if (key.type != BTRFS_EXTENT_DATA_KEY)
 100                         continue;
 101                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 102                 extent_type = btrfs_file_extent_type(eb, fi);
 103                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
 104                         continue;
 105                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
 106                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 107                 if (disk_byte != wanted_disk_byte)
 108                         continue;
 109
 110                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
 111                 if (ret < 0)
 112                         return ret;
 113         }
 114
 115         return 0;
 116 }
 117
 118 /*
 119  * this structure records all encountered refs on the way up to the root
 120  */
 121 struct __prelim_ref {
 122         struct list_head list;
 123         u64 root_id;
 124         struct btrfs_key key_for_search;
 125         int level;
 126         int count;
 127         struct extent_inode_elem *inode_list;
 128         u64 parent;
 129         u64 wanted_disk_byte;
 130 };
 131
 132 static struct kmem_cache *btrfs_prelim_ref_cache;
 133
 134 int __init btrfs_prelim_ref_init(void)
 135 {
 136         btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
 137                                         sizeof(struct __prelim_ref),
 138                                         0,
 139                                         SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
 140                                         NULL);
 141         if (!btrfs_prelim_ref_cache)
 142                 return -ENOMEM;
 143         return 0;
 144 }
 145
 146 void btrfs_prelim_ref_exit(void)
 147 {
 148         if (btrfs_prelim_ref_cache)
 149                 kmem_cache_destroy(btrfs_prelim_ref_cache);
 150 }
 151
 152 /*
 153  * the rules for all callers of this function are:
 154  * - obtaining the parent is the goal
 155  * - if you add a key, you must know that it is a correct key
 156  * - if you cannot add the parent or a correct key, then we will look into the
 157  *   block later to set a correct key
 158  *
 159  * delayed refs
 160  * ============
 161  *        backref type | shared | indirect | shared | indirect
 162  * information         |   tree |     tree |   data |     data
 163  * --------------------+--------+----------+--------+----------
 164  *      parent logical |    y   |     -    |    -   |     -
 165  *      key to resolve |    -   |     y    |    y   |     y
 166  *  tree block logical |    -   |     -    |    -   |     -
 167  *  root for resolving |    y   |     y    |    y   |     y
 168  *
 169  * - column 1:       we've the parent -> done
 170  * - column 2, 3, 4: we use the key to find the parent
 171  *
 172  * on disk refs (inline or keyed)
 173  * ==============================
 174  *        backref type | shared | indirect | shared | indirect
 175  * information         |   tree |     tree |   data |     data
 176  * --------------------+--------+----------+--------+----------
 177  *      parent logical |    y   |     -    |    y   |     -
 178  *      key to resolve |    -   |     -    |    -   |     y
 179  *  tree block logical |    y   |     y    |    y   |     y
 180  *  root for resolving |    -   |     y    |    y   |     y
 181  *
 182  * - column 1, 3: we've the parent -> done
 183  * - column 2:    we take the first key from the block to find the parent
 184  *                (see __add_missing_keys)
 185  * - column 4:    we use the key to find the parent
 186  *
 187  * additional information that's available but not required to find the parent
 188  * block might help in merging entries to gain some speed.
 189  */
 190
 191 static int __add_prelim_ref(struct list_head *head, u64 root_id,
 192                             struct btrfs_key *key, int level,
 193                             u64 parent, u64 wanted_disk_byte, int count,
 194                             gfp_t gfp_mask)
 195 {
 196         struct __prelim_ref *ref;
 197
 198         if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
 199                 return 0;
 200
 201         ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
 202         if (!ref)
 203                 return -ENOMEM;
 204
 205         ref->root_id = root_id;
 206         if (key)
 207                 ref->key_for_search = *key;
 208         else
 209                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
 210
 211         ref->inode_list = NULL;
 212         ref->level = level;
 213         ref->count = count;
 214         ref->parent = parent;
 215         ref->wanted_disk_byte = wanted_disk_byte;
 216         list_add_tail(&ref->list, head);
 217
 218         return 0;
 219 }
 220
 221 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
 222                            struct ulist *parents, struct __prelim_ref *ref,
 223                            int level, u64 time_seq, const u64 *extent_item_pos)
 224 {
 225         int ret = 0;
 226         int slot;
 227         struct extent_buffer *eb;
 228         struct btrfs_key key;
 229         struct btrfs_key *key_for_search = &ref->key_for_search;
 230         struct btrfs_file_extent_item *fi;
 231         struct extent_inode_elem *eie = NULL, *old = NULL;
 232         u64 disk_byte;
 233         u64 wanted_disk_byte = ref->wanted_disk_byte;
 234         u64 count = 0;
 235
 236         if (level != 0) {
 237                 eb = path->nodes[level];
 238                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
 239                 if (ret < 0)
 240                         return ret;
 241                 return 0;
 242         }
 243
 244         /*
 245          * We normally enter this function with the path already pointing to
 246          * the first item to check. But sometimes, we may enter it with
 247          * slot==nritems. In that case, go to the next leaf before we continue.
 248          */
 249         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
 250                 ret = btrfs_next_old_leaf(root, path, time_seq);
 251
 252         while (!ret && count < ref->count) {
 253                 eb = path->nodes[0];
 254                 slot = path->slots[0];
 255
 256                 btrfs_item_key_to_cpu(eb, &key, slot);
 257
 258                 if (key.objectid != key_for_search->objectid ||
 259                     key.type != BTRFS_EXTENT_DATA_KEY)
 260                         break;
 261
 262                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 263                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 264
 265                 if (disk_byte == wanted_disk_byte) {
 266                         eie = NULL;
 267                         old = NULL;
 268                         count++;
 269                         if (extent_item_pos) {
 270                                 ret = check_extent_in_eb(&key, eb, fi,
 271                                                 *extent_item_pos,
 272                                                 &eie);
 273                                 if (ret < 0)
 274                                         break;
 275                         }
 276                         if (ret > 0)
 277                                 goto next;
 278                         ret = ulist_add_merge(parents, eb->start,
 279                                               (uintptr_t)eie,
 280                                               (u64 *)&old, GFP_NOFS);
 281                         if (ret < 0)
 282                                 break;
 283                         if (!ret && extent_item_pos) {
 284                                 while (old->next)
 285                                         old = old->next;
 286                                 old->next = eie;
 287                         }
 288                         eie = NULL;
 289                 }
 290 next:
 291                 ret = btrfs_next_old_item(root, path, time_seq);
 292         }
 293
 294         if (ret > 0)
 295                 ret = 0;
 296         else if (ret < 0)
 297                 free_inode_elem_list(eie);
 298         return ret;
 299 }
 300
 301 /*
 302  * resolve an indirect backref in the form (root_id, key, level)
 303  * to a logical address
 304  */
 305 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 306                                   struct btrfs_path *path, u64 time_seq,
 307                                   struct __prelim_ref *ref,
 308                                   struct ulist *parents,
 309                                   const u64 *extent_item_pos)
 310 {
 311         struct btrfs_root *root;
 312         struct btrfs_key root_key;
 313         struct extent_buffer *eb;
 314         int ret = 0;
 315         int root_level;
 316         int level = ref->level;
 317         int index;
 318
 319         root_key.objectid = ref->root_id;
 320         root_key.type = BTRFS_ROOT_ITEM_KEY;
 321         root_key.offset = (u64)-1;
 322
 323         index = srcu_read_lock(&fs_info->subvol_srcu);
 324
 325         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
 326         if (IS_ERR(root)) {
 327                 srcu_read_unlock(&fs_info->subvol_srcu, index);
 328                 ret = PTR_ERR(root);
 329                 goto out;
 330         }
 331
 332         root_level = btrfs_old_root_level(root, time_seq);
 333
 334         if (root_level + 1 == level) {
 335                 srcu_read_unlock(&fs_info->subvol_srcu, index);
 336                 goto out;
 337         }
 338
 339         path->lowest_level = level;
 340         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
 341
 342         /* root node has been locked, we can release @subvol_srcu safely here */
 343         srcu_read_unlock(&fs_info->subvol_srcu, index);
 344
 345         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
 346                  "%d for key (%llu %u %llu)\n",
 347                  ref->root_id, level, ref->count, ret,
 348                  ref->key_for_search.objectid, ref->key_for_search.type,
 349                  ref->key_for_search.offset);
 350         if (ret < 0)
 351                 goto out;
 352
 353         eb = path->nodes[level];
 354         while (!eb) {
 355                 if (WARN_ON(!level)) {
 356                         ret = 1;
 357                         goto out;
 358                 }
 359                 level--;
 360                 eb = path->nodes[level];
 361         }
 362
 363         ret = add_all_parents(root, path, parents, ref, level, time_seq,
 364                               extent_item_pos);
 365 out:
 366         path->lowest_level = 0;
 367         btrfs_release_path(path);
 368         return ret;
 369 }
 370
 371 /*
 372  * resolve all indirect backrefs from the list
 373  */
 374 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 375                                    struct btrfs_path *path, u64 time_seq,
 376                                    struct list_head *head,
 377                                    const u64 *extent_item_pos)
 378 {
 379         int err;
 380         int ret = 0;
 381         struct __prelim_ref *ref;
 382         struct __prelim_ref *ref_safe;
 383         struct __prelim_ref *new_ref;
 384         struct ulist *parents;
 385         struct ulist_node *node;
 386         struct ulist_iterator uiter;
 387
 388         parents = ulist_alloc(GFP_NOFS);
 389         if (!parents)
 390                 return -ENOMEM;
 391
 392         /*
 393          * _safe allows us to insert directly after the current item without
 394          * iterating over the newly inserted items.
 395          * we're also allowed to re-assign ref during iteration.
 396          */
 397         list_for_each_entry_safe(ref, ref_safe, head, list) {
 398                 if (ref->parent)        /* already direct */
 399                         continue;
 400                 if (ref->count == 0)
 401                         continue;
 402                 err = __resolve_indirect_ref(fs_info, path, time_seq, ref,
 403                                              parents, extent_item_pos);
 404                 /*
 405                  * we can only tolerate ENOENT,otherwise,we should catch error
 406                  * and return directly.
 407                  */
 408                 if (err == -ENOENT) {
 409                         continue;
 410                 } else if (err) {
 411                         ret = err;
 412                         goto out;
 413                 }
 414
 415                 /* we put the first parent into the ref at hand */
 416                 ULIST_ITER_INIT(&uiter);
 417                 node = ulist_next(parents, &uiter);
 418                 ref->parent = node ? node->val : 0;
 419                 ref->inode_list = node ?
 420                         (struct extent_inode_elem *)(uintptr_t)node->aux : NULL;
 421
 422                 /* additional parents require new refs being added here */
 423                 while ((node = ulist_next(parents, &uiter))) {
 424                         new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
 425                                                    GFP_NOFS);
 426                         if (!new_ref) {
 427                                 ret = -ENOMEM;
 428                                 goto out;
 429                         }
 430                         memcpy(new_ref, ref, sizeof(*ref));
 431                         new_ref->parent = node->val;
 432                         new_ref->inode_list = (struct extent_inode_elem *)
 433                                                         (uintptr_t)node->aux;
 434                         list_add(&new_ref->list, &ref->list);
 435                 }
 436                 ulist_reinit(parents);
 437         }
 438 out:
 439         ulist_free(parents);
 440         return ret;
 441 }
 442
 443 static inline int ref_for_same_block(struct __prelim_ref *ref1,
 444                                      struct __prelim_ref *ref2)
 445 {
 446         if (ref1->level != ref2->level)
 447                 return 0;
 448         if (ref1->root_id != ref2->root_id)
 449                 return 0;
 450         if (ref1->key_for_search.type != ref2->key_for_search.type)
 451                 return 0;
 452         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
 453                 return 0;
 454         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
 455                 return 0;
 456         if (ref1->parent != ref2->parent)
 457                 return 0;
 458
 459         return 1;
 460 }
 461
 462 /*
 463  * read tree blocks and add keys where required.
 464  */
 465 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
 466                               struct list_head *head)
 467 {
 468         struct list_head *pos;
 469         struct extent_buffer *eb;
 470
 471         list_for_each(pos, head) {
 472                 struct __prelim_ref *ref;
 473                 ref = list_entry(pos, struct __prelim_ref, list);
 474
 475                 if (ref->parent)
 476                         continue;
 477                 if (ref->key_for_search.type)
 478                         continue;
 479                 BUG_ON(!ref->wanted_disk_byte);
 480                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
 481                                      fs_info->tree_root->leafsize, 0);
 482                 if (!eb || !extent_buffer_uptodate(eb)) {
 483                         free_extent_buffer(eb);
 484                         return -EIO;
 485                 }
 486                 btrfs_tree_read_lock(eb);
 487                 if (btrfs_header_level(eb) == 0)
 488                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 489                 else
 490                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 491                 btrfs_tree_read_unlock(eb);
 492                 free_extent_buffer(eb);
 493         }
 494         return 0;
 495 }
 496
 497 /*
 498  * merge two lists of backrefs and adjust counts accordingly
 499  *
 500  * mode = 1: merge identical keys, if key is set
 501  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
 502  *           additionally, we could even add a key range for the blocks we
 503  *           looked into to merge even more (-> replace unresolved refs by those
 504  *           having a parent).
 505  * mode = 2: merge identical parents
 506  */
 507 static void __merge_refs(struct list_head *head, int mode)
 508 {
 509         struct list_head *pos1;
 510
 511         list_for_each(pos1, head) {
 512                 struct list_head *n2;
 513                 struct list_head *pos2;
 514                 struct __prelim_ref *ref1;
 515
 516                 ref1 = list_entry(pos1, struct __prelim_ref, list);
 517
 518                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
 519                      pos2 = n2, n2 = pos2->next) {
 520                         struct __prelim_ref *ref2;
 521                         struct __prelim_ref *xchg;
 522                         struct extent_inode_elem *eie;
 523
 524                         ref2 = list_entry(pos2, struct __prelim_ref, list);
 525
 526                         if (mode == 1) {
 527                                 if (!ref_for_same_block(ref1, ref2))
 528                                         continue;
 529                                 if (!ref1->parent && ref2->parent) {
 530                                         xchg = ref1;
 531                                         ref1 = ref2;
 532                                         ref2 = xchg;
 533                                 }
 534                         } else {
 535                                 if (ref1->parent != ref2->parent)
 536                                         continue;
 537                         }
 538
 539                         eie = ref1->inode_list;
 540                         while (eie && eie->next)
 541                                 eie = eie->next;
 542                         if (eie)
 543                                 eie->next = ref2->inode_list;
 544                         else
 545                                 ref1->inode_list = ref2->inode_list;
 546                         ref1->count += ref2->count;
 547
 548                         list_del(&ref2->list);
 549                         kmem_cache_free(btrfs_prelim_ref_cache, ref2);
 550                 }
 551
 552         }
 553 }
 554
 555 /*
 556  * add all currently queued delayed refs from this head whose seq nr is
 557  * smaller or equal that seq to the list
 558  */
 559 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 560                               struct list_head *prefs)
 561 {
 562         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 563         struct rb_node *n = &head->node.rb_node;
 564         struct btrfs_key key;
 565         struct btrfs_key op_key = {0};
 566         int sgn;
 567         int ret = 0;
 568
 569         if (extent_op && extent_op->update_key)
 570                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
 571
 572         spin_lock(&head->lock);
 573         n = rb_first(&head->ref_root);
 574         while (n) {
 575                 struct btrfs_delayed_ref_node *node;
 576                 node = rb_entry(n, struct btrfs_delayed_ref_node,
 577                                 rb_node);
 578                 n = rb_next(n);
 579                 if (node->seq > seq)
 580                         continue;
 581
 582                 switch (node->action) {
 583                 case BTRFS_ADD_DELAYED_EXTENT:
 584                 case BTRFS_UPDATE_DELAYED_HEAD:
 585                         WARN_ON(1);
 586                         continue;
 587                 case BTRFS_ADD_DELAYED_REF:
 588                         sgn = 1;
 589                         break;
 590                 case BTRFS_DROP_DELAYED_REF:
 591                         sgn = -1;
 592                         break;
 593                 default:
 594                         BUG_ON(1);
 595                 }
 596                 switch (node->type) {
 597                 case BTRFS_TREE_BLOCK_REF_KEY: {
 598                         struct btrfs_delayed_tree_ref *ref;
 599
 600                         ref = btrfs_delayed_node_to_tree_ref(node);
 601                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
 602                                                ref->level + 1, 0, node->bytenr,
 603                                                node->ref_mod * sgn, GFP_ATOMIC);
 604                         break;
 605                 }
 606                 case BTRFS_SHARED_BLOCK_REF_KEY: {
 607                         struct btrfs_delayed_tree_ref *ref;
 608
 609                         ref = btrfs_delayed_node_to_tree_ref(node);
 610                         ret = __add_prelim_ref(prefs, ref->root, NULL,
 611                                                ref->level + 1, ref->parent,
 612                                                node->bytenr,
 613                                                node->ref_mod * sgn, GFP_ATOMIC);
 614                         break;
 615                 }
 616                 case BTRFS_EXTENT_DATA_REF_KEY: {
 617                         struct btrfs_delayed_data_ref *ref;
 618                         ref = btrfs_delayed_node_to_data_ref(node);
 619
 620                         key.objectid = ref->objectid;
 621                         key.type = BTRFS_EXTENT_DATA_KEY;
 622                         key.offset = ref->offset;
 623                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
 624                                                node->bytenr,
 625                                                node->ref_mod * sgn, GFP_ATOMIC);
 626                         break;
 627                 }
 628                 case BTRFS_SHARED_DATA_REF_KEY: {
 629                         struct btrfs_delayed_data_ref *ref;
 630
 631                         ref = btrfs_delayed_node_to_data_ref(node);
 632
 633                         key.objectid = ref->objectid;
 634                         key.type = BTRFS_EXTENT_DATA_KEY;
 635                         key.offset = ref->offset;
 636                         ret = __add_prelim_ref(prefs, ref->root, &key, 0,
 637                                                ref->parent, node->bytenr,
 638                                                node->ref_mod * sgn, GFP_ATOMIC);
 639                         break;
 640                 }
 641                 default:
 642                         WARN_ON(1);
 643                 }
 644                 if (ret)
 645                         break;
 646         }
 647         spin_unlock(&head->lock);
 648         return ret;
 649 }
 650
 651 /*
 652  * add all inline backrefs for bytenr to the list
 653  */
 654 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
 655                              struct btrfs_path *path, u64 bytenr,
 656                              int *info_level, struct list_head *prefs)
 657 {
 658         int ret = 0;
 659         int slot;
 660         struct extent_buffer *leaf;
 661         struct btrfs_key key;
 662         struct btrfs_key found_key;
 663         unsigned long ptr;
 664         unsigned long end;
 665         struct btrfs_extent_item *ei;
 666         u64 flags;
 667         u64 item_size;
 668
 669         /*
 670          * enumerate all inline refs
 671          */
 672         leaf = path->nodes[0];
 673         slot = path->slots[0];
 674
 675         item_size = btrfs_item_size_nr(leaf, slot);
 676         BUG_ON(item_size < sizeof(*ei));
 677
 678         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 679         flags = btrfs_extent_flags(leaf, ei);
 680         btrfs_item_key_to_cpu(leaf, &found_key, slot);
 681
 682         ptr = (unsigned long)(ei + 1);
 683         end = (unsigned long)ei + item_size;
 684
 685         if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
 686             flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 687                 struct btrfs_tree_block_info *info;
 688
 689                 info = (struct btrfs_tree_block_info *)ptr;
 690                 *info_level = btrfs_tree_block_level(leaf, info);
 691                 ptr += sizeof(struct btrfs_tree_block_info);
 692                 BUG_ON(ptr > end);
 693         } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
 694                 *info_level = found_key.offset;
 695         } else {
 696                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 697         }
 698
 699         while (ptr < end) {
 700                 struct btrfs_extent_inline_ref *iref;
 701                 u64 offset;
 702                 int type;
 703
 704                 iref = (struct btrfs_extent_inline_ref *)ptr;
 705                 type = btrfs_extent_inline_ref_type(leaf, iref);
 706                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
 707
 708                 switch (type) {
 709                 case BTRFS_SHARED_BLOCK_REF_KEY:
 710                         ret = __add_prelim_ref(prefs, 0, NULL,
 711                                                 *info_level + 1, offset,
 712                                                 bytenr, 1, GFP_NOFS);
 713                         break;
 714                 case BTRFS_SHARED_DATA_REF_KEY: {
 715                         struct btrfs_shared_data_ref *sdref;
 716                         int count;
 717
 718                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
 719                         count = btrfs_shared_data_ref_count(leaf, sdref);
 720                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
 721                                                bytenr, count, GFP_NOFS);
 722                         break;
 723                 }
 724                 case BTRFS_TREE_BLOCK_REF_KEY:
 725                         ret = __add_prelim_ref(prefs, offset, NULL,
 726                                                *info_level + 1, 0,
 727                                                bytenr, 1, GFP_NOFS);
 728                         break;
 729                 case BTRFS_EXTENT_DATA_REF_KEY: {
 730                         struct btrfs_extent_data_ref *dref;
 731                         int count;
 732                         u64 root;
 733
 734                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
 735                         count = btrfs_extent_data_ref_count(leaf, dref);
 736                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 737                                                                       dref);
 738                         key.type = BTRFS_EXTENT_DATA_KEY;
 739                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 740                         root = btrfs_extent_data_ref_root(leaf, dref);
 741                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 742                                                bytenr, count, GFP_NOFS);
 743                         break;
 744                 }
 745                 default:
 746                         WARN_ON(1);
 747                 }
 748                 if (ret)
 749                         return ret;
 750                 ptr += btrfs_extent_inline_ref_size(type);
 751         }
 752
 753         return 0;
 754 }
 755
 756 /*
 757  * add all non-inline backrefs for bytenr to the list
 758  */
 759 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
 760                             struct btrfs_path *path, u64 bytenr,
 761                             int info_level, struct list_head *prefs)
 762 {
 763         struct btrfs_root *extent_root = fs_info->extent_root;
 764         int ret;
 765         int slot;
 766         struct extent_buffer *leaf;
 767         struct btrfs_key key;
 768
 769         while (1) {
 770                 ret = btrfs_next_item(extent_root, path);
 771                 if (ret < 0)
 772                         break;
 773                 if (ret) {
 774                         ret = 0;
 775                         break;
 776                 }
 777
 778                 slot = path->slots[0];
 779                 leaf = path->nodes[0];
 780                 btrfs_item_key_to_cpu(leaf, &key, slot);
 781
 782                 if (key.objectid != bytenr)
 783                         break;
 784                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
 785                         continue;
 786                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
 787                         break;
 788
 789                 switch (key.type) {
 790                 case BTRFS_SHARED_BLOCK_REF_KEY:
 791                         ret = __add_prelim_ref(prefs, 0, NULL,
 792                                                 info_level + 1, key.offset,
 793                                                 bytenr, 1, GFP_NOFS);
 794                         break;
 795                 case BTRFS_SHARED_DATA_REF_KEY: {
 796                         struct btrfs_shared_data_ref *sdref;
 797                         int count;
 798
 799                         sdref = btrfs_item_ptr(leaf, slot,
 800                                               struct btrfs_shared_data_ref);
 801                         count = btrfs_shared_data_ref_count(leaf, sdref);
 802                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
 803                                                 bytenr, count, GFP_NOFS);
 804                         break;
 805                 }
 806                 case BTRFS_TREE_BLOCK_REF_KEY:
 807                         ret = __add_prelim_ref(prefs, key.offset, NULL,
 808                                                info_level + 1, 0,
 809                                                bytenr, 1, GFP_NOFS);
 810                         break;
 811                 case BTRFS_EXTENT_DATA_REF_KEY: {
 812                         struct btrfs_extent_data_ref *dref;
 813                         int count;
 814                         u64 root;
 815
 816                         dref = btrfs_item_ptr(leaf, slot,
 817                                               struct btrfs_extent_data_ref);
 818                         count = btrfs_extent_data_ref_count(leaf, dref);
 819                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 820                                                                       dref);
 821                         key.type = BTRFS_EXTENT_DATA_KEY;
 822                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 823                         root = btrfs_extent_data_ref_root(leaf, dref);
 824                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 825                                                bytenr, count, GFP_NOFS);
 826                         break;
 827                 }
 828                 default:
 829                         WARN_ON(1);
 830                 }
 831                 if (ret)
 832                         return ret;
 833
 834         }
 835
 836         return ret;
 837 }
 838
 839 /*
 840  * this adds all existing backrefs (inline backrefs, backrefs and delayed
 841  * refs) for the given bytenr to the refs list, merges duplicates and resolves
 842  * indirect refs to their parent bytenr.
 843  * When roots are found, they're added to the roots list
 844  *
 845  * FIXME some caching might speed things up
 846  */
 847 static int find_parent_nodes(struct btrfs_trans_handle *trans,
 848                              struct btrfs_fs_info *fs_info, u64 bytenr,
 849                              u64 time_seq, struct ulist *refs,
 850                              struct ulist *roots, const u64 *extent_item_pos)
 851 {
 852         struct btrfs_key key;
 853         struct btrfs_path *path;
 854         struct btrfs_delayed_ref_root *delayed_refs = NULL;
 855         struct btrfs_delayed_ref_head *head;
 856         int info_level = 0;
 857         int ret;
 858         struct list_head prefs_delayed;
 859         struct list_head prefs;
 860         struct __prelim_ref *ref;
 861         struct extent_inode_elem *eie = NULL;
 862
 863         INIT_LIST_HEAD(&prefs);
 864         INIT_LIST_HEAD(&prefs_delayed);
 865
 866         key.objectid = bytenr;
 867         key.offset = (u64)-1;
 868         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
 869                 key.type = BTRFS_METADATA_ITEM_KEY;
 870         else
 871                 key.type = BTRFS_EXTENT_ITEM_KEY;
 872
 873         path = btrfs_alloc_path();
 874         if (!path)
 875                 return -ENOMEM;
 876         if (!trans)
 877                 path->search_commit_root = 1;
 878
 879         /*
 880          * grab both a lock on the path and a lock on the delayed ref head.
 881          * We need both to get a consistent picture of how the refs look
 882          * at a specified point in time
 883          */
 884 again:
 885         head = NULL;
 886
 887         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
 888         if (ret < 0)
 889                 goto out;
 890         BUG_ON(ret == 0);
 891
 892         if (trans) {
 893                 /*
 894                  * look if there are updates for this ref queued and lock the
 895                  * head
 896                  */
 897                 delayed_refs = &trans->transaction->delayed_refs;
 898                 spin_lock(&delayed_refs->lock);
 899                 head = btrfs_find_delayed_ref_head(trans, bytenr);
 900                 if (head) {
 901                         if (!mutex_trylock(&head->mutex)) {
 902                                 atomic_inc(&head->node.refs);
 903                                 spin_unlock(&delayed_refs->lock);
 904
 905                                 btrfs_release_path(path);
 906
 907                                 /*
 908                                  * Mutex was contended, block until it's
 909                                  * released and try again
 910                                  */
 911                                 mutex_lock(&head->mutex);
 912                                 mutex_unlock(&head->mutex);
 913                                 btrfs_put_delayed_ref(&head->node);
 914                                 goto again;
 915                         }
 916                         spin_unlock(&delayed_refs->lock);
 917                         ret = __add_delayed_refs(head, time_seq,
 918                                                  &prefs_delayed);
 919                         mutex_unlock(&head->mutex);
 920                         if (ret)
 921                                 goto out;
 922                 } else {
 923                         spin_unlock(&delayed_refs->lock);
 924                 }
 925         }
 926
 927         if (path->slots[0]) {
 928                 struct extent_buffer *leaf;
 929                 int slot;
 930
 931                 path->slots[0]--;
 932                 leaf = path->nodes[0];
 933                 slot = path->slots[0];
 934                 btrfs_item_key_to_cpu(leaf, &key, slot);
 935                 if (key.objectid == bytenr &&
 936                     (key.type == BTRFS_EXTENT_ITEM_KEY ||
 937                      key.type == BTRFS_METADATA_ITEM_KEY)) {
 938                         ret = __add_inline_refs(fs_info, path, bytenr,
 939                                                 &info_level, &prefs);
 940                         if (ret)
 941                                 goto out;
 942                         ret = __add_keyed_refs(fs_info, path, bytenr,
 943                                                info_level, &prefs);
 944                         if (ret)
 945                                 goto out;
 946                 }
 947         }
 948         btrfs_release_path(path);
 949
 950         list_splice_init(&prefs_delayed, &prefs);
 951
 952         ret = __add_missing_keys(fs_info, &prefs);
 953         if (ret)
 954                 goto out;
 955
 956         __merge_refs(&prefs, 1);
 957
 958         ret = __resolve_indirect_refs(fs_info, path, time_seq, &prefs,
 959                                       extent_item_pos);
 960         if (ret)
 961                 goto out;
 962
 963         __merge_refs(&prefs, 2);
 964
 965         while (!list_empty(&prefs)) {
 966                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
 967                 WARN_ON(ref->count < 0);
 968                 if (ref->count && ref->root_id && ref->parent == 0) {
 969                         /* no parent == root of tree */
 970                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
 971                         if (ret < 0)
 972                                 goto out;
 973                 }
 974                 if (ref->count && ref->parent) {
 975                         if (extent_item_pos && !ref->inode_list &&
 976                             ref->level == 0) {
 977                                 u32 bsz;
 978                                 struct extent_buffer *eb;
 979                                 bsz = btrfs_level_size(fs_info->extent_root,
 980                                                         ref->level);
 981                                 eb = read_tree_block(fs_info->extent_root,
 982                                                            ref->parent, bsz, 0);
 983                                 if (!eb || !extent_buffer_uptodate(eb)) {
 984                                         free_extent_buffer(eb);
 985                                         ret = -EIO;
 986                                         goto out;
 987                                 }
 988                                 ret = find_extent_in_eb(eb, bytenr,
 989                                                         *extent_item_pos, &eie);
 990                                 free_extent_buffer(eb);
 991                                 if (ret < 0)
 992                                         goto out;
 993                                 ref->inode_list = eie;
 994                         }
 995                         ret = ulist_add_merge(refs, ref->parent,
 996                                               (uintptr_t)ref->inode_list,
 997                                               (u64 *)&eie, GFP_NOFS);
 998                         if (ret < 0)
 999                                 goto out;
1000                         if (!ret && extent_item_pos) {
1001                                 /*
1002                                  * we've recorded that parent, so we must extend
1003                                  * its inode list here
1004                                  */
1005                                 BUG_ON(!eie);
1006                                 while (eie->next)
1007                                         eie = eie->next;
1008                                 eie->next = ref->inode_list;
1009                         }
1010                         eie = NULL;
1011                 }
1012                 list_del(&ref->list);
1013                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1014         }
1015
1016 out:
1017         btrfs_free_path(path);
1018         while (!list_empty(&prefs)) {
1019                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
1020                 list_del(&ref->list);
1021                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1022         }
1023         while (!list_empty(&prefs_delayed)) {
1024                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
1025                                        list);
1026                 list_del(&ref->list);
1027                 kmem_cache_free(btrfs_prelim_ref_cache, ref);
1028         }
1029         if (ret < 0)
1030                 free_inode_elem_list(eie);
1031         return ret;
1032 }
1033
1034 static void free_leaf_list(struct ulist *blocks)
1035 {
1036         struct ulist_node *node = NULL;
1037         struct extent_inode_elem *eie;
1038         struct ulist_iterator uiter;
1039
1040         ULIST_ITER_INIT(&uiter);
1041         while ((node = ulist_next(blocks, &uiter))) {
1042                 if (!node->aux)
1043                         continue;
1044                 eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
1045                 free_inode_elem_list(eie);
1046                 node->aux = 0;
1047         }
1048
1049         ulist_free(blocks);
1050 }
1051
1052 /*
1053  * Finds all leafs with a reference to the specified combination of bytenr and
1054  * offset. key_list_head will point to a list of corresponding keys (caller must
1055  * free each list element). The leafs will be stored in the leafs ulist, which
1056  * must be freed with ulist_free.
1057  *
1058  * returns 0 on success, <0 on error
1059  */
1060 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
1061                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1062                                 u64 time_seq, struct ulist **leafs,
1063                                 const u64 *extent_item_pos)
1064 {
1065         struct ulist *tmp;
1066         int ret;
1067
1068         tmp = ulist_alloc(GFP_NOFS);
1069         if (!tmp)
1070                 return -ENOMEM;
1071         *leafs = ulist_alloc(GFP_NOFS);
1072         if (!*leafs) {
1073                 ulist_free(tmp);
1074                 return -ENOMEM;
1075         }
1076
1077         ret = find_parent_nodes(trans, fs_info, bytenr,
1078                                 time_seq, *leafs, tmp, extent_item_pos);
1079         ulist_free(tmp);
1080
1081         if (ret < 0 && ret != -ENOENT) {
1082                 free_leaf_list(*leafs);
1083                 return ret;
1084         }
1085
1086         return 0;
1087 }
1088
1089 /*
1090  * walk all backrefs for a given extent to find all roots that reference this
1091  * extent. Walking a backref means finding all extents that reference this
1092  * extent and in turn walk the backrefs of those, too. Naturally this is a
1093  * recursive process, but here it is implemented in an iterative fashion: We
1094  * find all referencing extents for the extent in question and put them on a
1095  * list. In turn, we find all referencing extents for those, further appending
1096  * to the list. The way we iterate the list allows adding more elements after
1097  * the current while iterating. The process stops when we reach the end of the
1098  * list. Found roots are added to the roots list.
1099  *
1100  * returns 0 on success, < 0 on error.
1101  */
1102 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1103                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1104                                 u64 time_seq, struct ulist **roots)
1105 {
1106         struct ulist *tmp;
1107         struct ulist_node *node = NULL;
1108         struct ulist_iterator uiter;
1109         int ret;
1110
1111         tmp = ulist_alloc(GFP_NOFS);
1112         if (!tmp)
1113                 return -ENOMEM;
1114         *roots = ulist_alloc(GFP_NOFS);
1115         if (!*roots) {
1116                 ulist_free(tmp);
1117                 return -ENOMEM;
1118         }
1119
1120         ULIST_ITER_INIT(&uiter);
1121         while (1) {
1122                 ret = find_parent_nodes(trans, fs_info, bytenr,
1123                                         time_seq, tmp, *roots, NULL);
1124                 if (ret < 0 && ret != -ENOENT) {
1125                         ulist_free(tmp);
1126                         ulist_free(*roots);
1127                         return ret;
1128                 }
1129                 node = ulist_next(tmp, &uiter);
1130                 if (!node)
1131                         break;
1132                 bytenr = node->val;
1133                 cond_resched();
1134         }
1135
1136         ulist_free(tmp);
1137         return 0;
1138 }
1139
1140 /*
1141  * this makes the path point to (inum INODE_ITEM ioff)
1142  */
1143 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1144                         struct btrfs_path *path)
1145 {
1146         struct btrfs_key key;
1147         return btrfs_find_item(fs_root, path, inum, ioff,
1148                         BTRFS_INODE_ITEM_KEY, &key);
1149 }
1150
1151 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1152                                 struct btrfs_path *path,
1153                                 struct btrfs_key *found_key)
1154 {
1155         return btrfs_find_item(fs_root, path, inum, ioff,
1156                         BTRFS_INODE_REF_KEY, found_key);
1157 }
1158
1159 int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1160                           u64 start_off, struct btrfs_path *path,
1161                           struct btrfs_inode_extref **ret_extref,
1162                           u64 *found_off)
1163 {
1164         int ret, slot;
1165         struct btrfs_key key;
1166         struct btrfs_key found_key;
1167         struct btrfs_inode_extref *extref;
1168         struct extent_buffer *leaf;
1169         unsigned long ptr;
1170
1171         key.objectid = inode_objectid;
1172         btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
1173         key.offset = start_off;
1174
1175         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1176         if (ret < 0)
1177                 return ret;
1178
1179         while (1) {
1180                 leaf = path->nodes[0];
1181                 slot = path->slots[0];
1182                 if (slot >= btrfs_header_nritems(leaf)) {
1183                         /*
1184                          * If the item at offset is not found,
1185                          * btrfs_search_slot will point us to the slot
1186                          * where it should be inserted. In our case
1187                          * that will be the slot directly before the
1188                          * next INODE_REF_KEY_V2 item. In the case
1189                          * that we're pointing to the last slot in a
1190                          * leaf, we must move one leaf over.
1191                          */
1192                         ret = btrfs_next_leaf(root, path);
1193                         if (ret) {
1194                                 if (ret >= 1)
1195                                         ret = -ENOENT;
1196                                 break;
1197                         }
1198                         continue;
1199                 }
1200
1201                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
1202
1203                 /*
1204                  * Check that we're still looking at an extended ref key for
1205                  * this particular objectid. If we have different
1206                  * objectid or type then there are no more to be found
1207                  * in the tree and we can exit.
1208                  */
1209                 ret = -ENOENT;
1210                 if (found_key.objectid != inode_objectid)
1211                         break;
1212                 if (btrfs_key_type(&found_key) != BTRFS_INODE_EXTREF_KEY)
1213                         break;
1214
1215                 ret = 0;
1216                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1217                 extref = (struct btrfs_inode_extref *)ptr;
1218                 *ret_extref = extref;
1219                 if (found_off)
1220                         *found_off = found_key.offset;
1221                 break;
1222         }
1223
1224         return ret;
1225 }
1226
1227 /*
1228  * this iterates to turn a name (from iref/extref) into a full filesystem path.
1229  * Elements of the path are separated by '/' and the path is guaranteed to be
1230  * 0-terminated. the path is only given within the current file system.
1231  * Therefore, it never starts with a '/'. the caller is responsible to provide
1232  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1233  * the start point of the resulting string is returned. this pointer is within
1234  * dest, normally.
1235  * in case the path buffer would overflow, the pointer is decremented further
1236  * as if output was written to the buffer, though no more output is actually
1237  * generated. that way, the caller can determine how much space would be
1238  * required for the path to fit into the buffer. in that case, the returned
1239  * value will be smaller than dest. callers must check this!
1240  */
1241 char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1242                         u32 name_len, unsigned long name_off,
1243                         struct extent_buffer *eb_in, u64 parent,
1244                         char *dest, u32 size)
1245 {
1246         int slot;
1247         u64 next_inum;
1248         int ret;
1249         s64 bytes_left = ((s64)size) - 1;
1250         struct extent_buffer *eb = eb_in;
1251         struct btrfs_key found_key;
1252         int leave_spinning = path->leave_spinning;
1253         struct btrfs_inode_ref *iref;
1254
1255         if (bytes_left >= 0)
1256                 dest[bytes_left] = '\0';
1257
1258         path->leave_spinning = 1;
1259         while (1) {
1260                 bytes_left -= name_len;
1261                 if (bytes_left >= 0)
1262                         read_extent_buffer(eb, dest + bytes_left,
1263                                            name_off, name_len);
1264                 if (eb != eb_in) {
1265                         btrfs_tree_read_unlock_blocking(eb);
1266                         free_extent_buffer(eb);
1267                 }
1268                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1269                 if (ret > 0)
1270                         ret = -ENOENT;
1271                 if (ret)
1272                         break;
1273
1274                 next_inum = found_key.offset;
1275
1276                 /* regular exit ahead */
1277                 if (parent == next_inum)
1278                         break;
1279
1280                 slot = path->slots[0];
1281                 eb = path->nodes[0];
1282                 /* make sure we can use eb after releasing the path */
1283                 if (eb != eb_in) {
1284                         atomic_inc(&eb->refs);
1285                         btrfs_tree_read_lock(eb);
1286                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1287                 }
1288                 btrfs_release_path(path);
1289                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1290
1291                 name_len = btrfs_inode_ref_name_len(eb, iref);
1292                 name_off = (unsigned long)(iref + 1);
1293
1294                 parent = next_inum;
1295                 --bytes_left;
1296                 if (bytes_left >= 0)
1297                         dest[bytes_left] = '/';
1298         }
1299
1300         btrfs_release_path(path);
1301         path->leave_spinning = leave_spinning;
1302
1303         if (ret)
1304                 return ERR_PTR(ret);
1305
1306         return dest + bytes_left;
1307 }
1308
1309 /*
1310  * this makes the path point to (logical EXTENT_ITEM *)
1311  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1312  * tree blocks and <0 on error.
1313  */
1314 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1315                         struct btrfs_path *path, struct btrfs_key *found_key,
1316                         u64 *flags_ret)
1317 {
1318         int ret;
1319         u64 flags;
1320         u64 size = 0;
1321         u32 item_size;
1322         struct extent_buffer *eb;
1323         struct btrfs_extent_item *ei;
1324         struct btrfs_key key;
1325
1326         if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
1327                 key.type = BTRFS_METADATA_ITEM_KEY;
1328         else
1329                 key.type = BTRFS_EXTENT_ITEM_KEY;
1330         key.objectid = logical;
1331         key.offset = (u64)-1;
1332
1333         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1334         if (ret < 0)
1335                 return ret;
1336
1337         while (1) {
1338                 u32 nritems;
1339                 if (path->slots[0] == 0) {
1340                         btrfs_set_path_blocking(path);
1341                         ret = btrfs_prev_leaf(fs_info->extent_root, path);
1342                         if (ret != 0) {
1343                                 if (ret > 0) {
1344                                         pr_debug("logical %llu is not within "
1345                                                  "any extent\n", logical);
1346                                         ret = -ENOENT;
1347                                 }
1348                                 return ret;
1349                         }
1350                 } else {
1351                         path->slots[0]--;
1352                 }
1353                 nritems = btrfs_header_nritems(path->nodes[0]);
1354                 if (nritems == 0) {
1355                         pr_debug("logical %llu is not within any extent\n",
1356                                  logical);
1357                         return -ENOENT;
1358                 }
1359                 if (path->slots[0] == nritems)
1360                         path->slots[0]--;
1361
1362                 btrfs_item_key_to_cpu(path->nodes[0], found_key,
1363                                       path->slots[0]);
1364                 if (found_key->type == BTRFS_EXTENT_ITEM_KEY ||
1365                     found_key->type == BTRFS_METADATA_ITEM_KEY)
1366                         break;
1367         }
1368
1369         if (found_key->type == BTRFS_METADATA_ITEM_KEY)
1370                 size = fs_info->extent_root->leafsize;
1371         else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
1372                 size = found_key->offset;
1373
1374         if (found_key->objectid > logical ||
1375             found_key->objectid + size <= logical) {
1376                 pr_debug("logical %llu is not within any extent\n", logical);
1377                 return -ENOENT;
1378         }
1379
1380         eb = path->nodes[0];
1381         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1382         BUG_ON(item_size < sizeof(*ei));
1383
1384         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1385         flags = btrfs_extent_flags(eb, ei);
1386
1387         pr_debug("logical %llu is at position %llu within the extent (%llu "
1388                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1389                  logical, logical - found_key->objectid, found_key->objectid,
1390                  found_key->offset, flags, item_size);
1391
1392         WARN_ON(!flags_ret);
1393         if (flags_ret) {
1394                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1395                         *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1396                 else if (flags & BTRFS_EXTENT_FLAG_DATA)
1397                         *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1398                 else
1399                         BUG_ON(1);
1400                 return 0;
1401         }
1402
1403         return -EIO;
1404 }
1405
1406 /*
1407  * helper function to iterate extent inline refs. ptr must point to a 0 value
1408  * for the first call and may be modified. it is used to track state.
1409  * if more refs exist, 0 is returned and the next call to
1410  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1411  * next ref. after the last ref was processed, 1 is returned.
1412  * returns <0 on error
1413  */
1414 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1415                                    struct btrfs_key *key,
1416                                    struct btrfs_extent_item *ei, u32 item_size,
1417                                    struct btrfs_extent_inline_ref **out_eiref,
1418                                    int *out_type)
1419 {
1420         unsigned long end;
1421         u64 flags;
1422         struct btrfs_tree_block_info *info;
1423
1424         if (!*ptr) {
1425                 /* first call */
1426                 flags = btrfs_extent_flags(eb, ei);
1427                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1428                         if (key->type == BTRFS_METADATA_ITEM_KEY) {
1429                                 /* a skinny metadata extent */
1430                                 *out_eiref =
1431                                      (struct btrfs_extent_inline_ref *)(ei + 1);
1432                         } else {
1433                                 WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
1434                                 info = (struct btrfs_tree_block_info *)(ei + 1);
1435                                 *out_eiref =
1436                                    (struct btrfs_extent_inline_ref *)(info + 1);
1437                         }
1438                 } else {
1439                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1440                 }
1441                 *ptr = (unsigned long)*out_eiref;
1442                 if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
1443                         return -ENOENT;
1444         }
1445
1446         end = (unsigned long)ei + item_size;
1447         *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
1448         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1449
1450         *ptr += btrfs_extent_inline_ref_size(*out_type);
1451         WARN_ON(*ptr > end);
1452         if (*ptr == end)
1453                 return 1; /* last */
1454
1455         return 0;
1456 }
1457
1458 /*
1459  * reads the tree block backref for an extent. tree level and root are returned
1460  * through out_level and out_root. ptr must point to a 0 value for the first
1461  * call and may be modified (see __get_extent_inline_ref comment).
1462  * returns 0 if data was provided, 1 if there was no more data to provide or
1463  * <0 on error.
1464  */
1465 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1466                             struct btrfs_key *key, struct btrfs_extent_item *ei,
1467                             u32 item_size, u64 *out_root, u8 *out_level)
1468 {
1469         int ret;
1470         int type;
1471         struct btrfs_tree_block_info *info;
1472         struct btrfs_extent_inline_ref *eiref;
1473
1474         if (*ptr == (unsigned long)-1)
1475                 return 1;
1476
1477         while (1) {
1478                 ret = __get_extent_inline_ref(ptr, eb, key, ei, item_size,
1479                                               &eiref, &type);
1480                 if (ret < 0)
1481                         return ret;
1482
1483                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1484                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1485                         break;
1486
1487                 if (ret == 1)
1488                         return 1;
1489         }
1490
1491         /* we can treat both ref types equally here */
1492         info = (struct btrfs_tree_block_info *)(ei + 1);
1493         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1494         *out_level = btrfs_tree_block_level(eb, info);
1495
1496         if (ret == 1)
1497                 *ptr = (unsigned long)-1;
1498
1499         return 0;
1500 }
1501
1502 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1503                                 u64 root, u64 extent_item_objectid,
1504                                 iterate_extent_inodes_t *iterate, void *ctx)
1505 {
1506         struct extent_inode_elem *eie;
1507         int ret = 0;
1508
1509         for (eie = inode_list; eie; eie = eie->next) {
1510                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1511                          "root %llu\n", extent_item_objectid,
1512                          eie->inum, eie->offset, root);
1513                 ret = iterate(eie->inum, eie->offset, root, ctx);
1514                 if (ret) {
1515                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1516                                  extent_item_objectid, ret);
1517                         break;
1518                 }
1519         }
1520
1521         return ret;
1522 }
1523
1524 /*
1525  * calls iterate() for every inode that references the extent identified by
1526  * the given parameters.
1527  * when the iterator function returns a non-zero value, iteration stops.
1528  */
1529 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1530                                 u64 extent_item_objectid, u64 extent_item_pos,
1531                                 int search_commit_root,
1532                                 iterate_extent_inodes_t *iterate, void *ctx)
1533 {
1534         int ret;
1535         struct btrfs_trans_handle *trans = NULL;
1536         struct ulist *refs = NULL;
1537         struct ulist *roots = NULL;
1538         struct ulist_node *ref_node = NULL;
1539         struct ulist_node *root_node = NULL;
1540         struct seq_list tree_mod_seq_elem = {};
1541         struct ulist_iterator ref_uiter;
1542         struct ulist_iterator root_uiter;
1543
1544         pr_debug("resolving all inodes for extent %llu\n",
1545                         extent_item_objectid);
1546
1547         if (!search_commit_root) {
1548                 trans = btrfs_join_transaction(fs_info->extent_root);
1549                 if (IS_ERR(trans))
1550                         return PTR_ERR(trans);
1551                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1552         }
1553
1554         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1555                                    tree_mod_seq_elem.seq, &refs,
1556                                    &extent_item_pos);
1557         if (ret)
1558                 goto out;
1559
1560         ULIST_ITER_INIT(&ref_uiter);
1561         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1562                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1563                                            tree_mod_seq_elem.seq, &roots);
1564                 if (ret)
1565                         break;
1566                 ULIST_ITER_INIT(&root_uiter);
1567                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1568                         pr_debug("root %llu references leaf %llu, data list "
1569                                  "%#llx\n", root_node->val, ref_node->val,
1570                                  ref_node->aux);
1571                         ret = iterate_leaf_refs((struct extent_inode_elem *)
1572                                                 (uintptr_t)ref_node->aux,
1573                                                 root_node->val,
1574                                                 extent_item_objectid,
1575                                                 iterate, ctx);
1576                 }
1577                 ulist_free(roots);
1578         }
1579
1580         free_leaf_list(refs);
1581 out:
1582         if (!search_commit_root) {
1583                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1584                 btrfs_end_transaction(trans, fs_info->extent_root);
1585         }
1586
1587         return ret;
1588 }
1589
1590 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1591                                 struct btrfs_path *path,
1592                                 iterate_extent_inodes_t *iterate, void *ctx)
1593 {
1594         int ret;
1595         u64 extent_item_pos;
1596         u64 flags = 0;
1597         struct btrfs_key found_key;
1598         int search_commit_root = path->search_commit_root;
1599
1600         ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1601         btrfs_release_path(path);
1602         if (ret < 0)
1603                 return ret;
1604         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1605                 return -EINVAL;
1606
1607         extent_item_pos = logical - found_key.objectid;
1608         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1609                                         extent_item_pos, search_commit_root,
1610                                         iterate, ctx);
1611
1612         return ret;
1613 }
1614
1615 typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1616                               struct extent_buffer *eb, void *ctx);
1617
1618 static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1619                               struct btrfs_path *path,
1620                               iterate_irefs_t *iterate, void *ctx)
1621 {
1622         int ret = 0;
1623         int slot;
1624         u32 cur;
1625         u32 len;
1626         u32 name_len;
1627         u64 parent = 0;
1628         int found = 0;
1629         struct extent_buffer *eb;
1630         struct btrfs_item *item;
1631         struct btrfs_inode_ref *iref;
1632         struct btrfs_key found_key;
1633
1634         while (!ret) {
1635                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1636                                      &found_key);
1637                 if (ret < 0)
1638                         break;
1639                 if (ret) {
1640                         ret = found ? 0 : -ENOENT;
1641                         break;
1642                 }
1643                 ++found;
1644
1645                 parent = found_key.offset;
1646                 slot = path->slots[0];
1647                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1648                 if (!eb) {
1649                         ret = -ENOMEM;
1650                         break;
1651                 }
1652                 extent_buffer_get(eb);
1653                 btrfs_tree_read_lock(eb);
1654                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1655                 btrfs_release_path(path);
1656
1657                 item = btrfs_item_nr(slot);
1658                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1659
1660                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1661                         name_len = btrfs_inode_ref_name_len(eb, iref);
1662                         /* path must be released before calling iterate()! */
1663                         pr_debug("following ref at offset %u for inode %llu in "
1664                                  "tree %llu\n", cur, found_key.objectid,
1665                                  fs_root->objectid);
1666                         ret = iterate(parent, name_len,
1667                                       (unsigned long)(iref + 1), eb, ctx);
1668                         if (ret)
1669                                 break;
1670                         len = sizeof(*iref) + name_len;
1671                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1672                 }
1673                 btrfs_tree_read_unlock_blocking(eb);
1674                 free_extent_buffer(eb);
1675         }
1676
1677         btrfs_release_path(path);
1678
1679         return ret;
1680 }
1681
1682 static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1683                                  struct btrfs_path *path,
1684                                  iterate_irefs_t *iterate, void *ctx)
1685 {
1686         int ret;
1687         int slot;
1688         u64 offset = 0;
1689         u64 parent;
1690         int found = 0;
1691         struct extent_buffer *eb;
1692         struct btrfs_inode_extref *extref;
1693         struct extent_buffer *leaf;
1694         u32 item_size;
1695         u32 cur_offset;
1696         unsigned long ptr;
1697
1698         while (1) {
1699                 ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1700                                             &offset);
1701                 if (ret < 0)
1702                         break;
1703                 if (ret) {
1704                         ret = found ? 0 : -ENOENT;
1705                         break;
1706                 }
1707                 ++found;
1708
1709                 slot = path->slots[0];
1710                 eb = btrfs_clone_extent_buffer(path->nodes[0]);
1711                 if (!eb) {
1712                         ret = -ENOMEM;
1713                         break;
1714                 }
1715                 extent_buffer_get(eb);
1716
1717                 btrfs_tree_read_lock(eb);
1718                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1719                 btrfs_release_path(path);
1720
1721                 leaf = path->nodes[0];
1722                 item_size = btrfs_item_size_nr(leaf, slot);
1723                 ptr = btrfs_item_ptr_offset(leaf, slot);
1724                 cur_offset = 0;
1725
1726                 while (cur_offset < item_size) {
1727                         u32 name_len;
1728
1729                         extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1730                         parent = btrfs_inode_extref_parent(eb, extref);
1731                         name_len = btrfs_inode_extref_name_len(eb, extref);
1732                         ret = iterate(parent, name_len,
1733                                       (unsigned long)&extref->name, eb, ctx);
1734                         if (ret)
1735                                 break;
1736
1737                         cur_offset += btrfs_inode_extref_name_len(leaf, extref);
1738                         cur_offset += sizeof(*extref);
1739                 }
1740                 btrfs_tree_read_unlock_blocking(eb);
1741                 free_extent_buffer(eb);
1742
1743                 offset++;
1744         }
1745
1746         btrfs_release_path(path);
1747
1748         return ret;
1749 }
1750
1751 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1752                          struct btrfs_path *path, iterate_irefs_t *iterate,
1753                          void *ctx)
1754 {
1755         int ret;
1756         int found_refs = 0;
1757
1758         ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1759         if (!ret)
1760                 ++found_refs;
1761         else if (ret != -ENOENT)
1762                 return ret;
1763
1764         ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1765         if (ret == -ENOENT && found_refs)
1766                 return 0;
1767
1768         return ret;
1769 }
1770
1771 /*
1772  * returns 0 if the path could be dumped (probably truncated)
1773  * returns <0 in case of an error
1774  */
1775 static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1776                          struct extent_buffer *eb, void *ctx)
1777 {
1778         struct inode_fs_paths *ipath = ctx;
1779         char *fspath;
1780         char *fspath_min;
1781         int i = ipath->fspath->elem_cnt;
1782         const int s_ptr = sizeof(char *);
1783         u32 bytes_left;
1784
1785         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1786                                         ipath->fspath->bytes_left - s_ptr : 0;
1787
1788         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1789         fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1790                                    name_off, eb, inum, fspath_min, bytes_left);
1791         if (IS_ERR(fspath))
1792                 return PTR_ERR(fspath);
1793
1794         if (fspath > fspath_min) {
1795                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1796                 ++ipath->fspath->elem_cnt;
1797                 ipath->fspath->bytes_left = fspath - fspath_min;
1798         } else {
1799                 ++ipath->fspath->elem_missed;
1800                 ipath->fspath->bytes_missing += fspath_min - fspath;
1801                 ipath->fspath->bytes_left = 0;
1802         }
1803
1804         return 0;
1805 }
1806
1807 /*
1808  * this dumps all file system paths to the inode into the ipath struct, provided
1809  * is has been created large enough. each path is zero-terminated and accessed
1810  * from ipath->fspath->val[i].
1811  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1812  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1813  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1814  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1815  * have been needed to return all paths.
1816  */
1817 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1818 {
1819         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1820                              inode_to_path, ipath);
1821 }
1822
1823 struct btrfs_data_container *init_data_container(u32 total_bytes)
1824 {
1825         struct btrfs_data_container *data;
1826         size_t alloc_bytes;
1827
1828         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1829         data = vmalloc(alloc_bytes);
1830         if (!data)
1831                 return ERR_PTR(-ENOMEM);
1832
1833         if (total_bytes >= sizeof(*data)) {
1834                 data->bytes_left = total_bytes - sizeof(*data);
1835                 data->bytes_missing = 0;
1836         } else {
1837                 data->bytes_missing = sizeof(*data) - total_bytes;
1838                 data->bytes_left = 0;
1839         }
1840
1841         data->elem_cnt = 0;
1842         data->elem_missed = 0;
1843
1844         return data;
1845 }
1846
1847 /*
1848  * allocates space to return multiple file system paths for an inode.
1849  * total_bytes to allocate are passed, note that space usable for actual path
1850  * information will be total_bytes - sizeof(struct inode_fs_paths).
1851  * the returned pointer must be freed with free_ipath() in the end.
1852  */
1853 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1854                                         struct btrfs_path *path)
1855 {
1856         struct inode_fs_paths *ifp;
1857         struct btrfs_data_container *fspath;
1858
1859         fspath = init_data_container(total_bytes);
1860         if (IS_ERR(fspath))
1861                 return (void *)fspath;
1862
1863         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1864         if (!ifp) {
1865                 kfree(fspath);
1866                 return ERR_PTR(-ENOMEM);
1867         }
1868
1869         ifp->btrfs_path = path;
1870         ifp->fspath = fspath;
1871         ifp->fs_root = fs_root;
1872
1873         return ifp;
1874 }
1875
1876 void free_ipath(struct inode_fs_paths *ipath)
1877 {
1878         if (!ipath)
1879                 return;
1880         vfree(ipath->fspath);
1881         kfree(ipath);
1882 }