fs/btrfs/extent-tree.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include "kerncompat.h"
   4 #include "radix-tree.h"
   5 #include "ctree.h"
   6 #include "disk-io.h"
   7 #include "print-tree.h"
   8 #include "transaction.h"
   9
  10 static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
  11                             *orig_root, u64 num_blocks, u64 search_start, u64
  12                             search_end, struct btrfs_key *ins);
  13 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
  14                                  btrfs_root *extent_root);
  15 static int run_pending(struct btrfs_trans_handle *trans, struct btrfs_root
  16                        *extent_root);
  17
  18 /*
  19  * pending extents are blocks that we're trying to allocate in the extent
  20  * map while trying to grow the map because of other allocations.  To avoid
  21  * recursing, they are tagged in the radix tree and cleaned up after
  22  * other allocations are done.  The pending tag is also used in the same
  23  * manner for deletes.
  24  */
  25 #define CTREE_EXTENT_PENDING_DEL 0
  26
  27 static int inc_block_ref(struct btrfs_trans_handle *trans, struct btrfs_root
  28                          *root, u64 blocknr)
  29 {
  30         struct btrfs_path path;
  31         int ret;
  32         struct btrfs_key key;
  33         struct btrfs_leaf *l;
  34         struct btrfs_extent_item *item;
  35         struct btrfs_key ins;
  36         u32 refs;
  37
  38         find_free_extent(trans, root->extent_root, 0, 0, (u64)-1, &ins);
  39         btrfs_init_path(&path);
  40         key.objectid = blocknr;
  41         key.flags = 0;
  42         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
  43         key.offset = 1;
  44         ret = btrfs_search_slot(trans, root->extent_root, &key, &path, 0, 1);
  45         if (ret != 0)
  46                 BUG();
  47         BUG_ON(ret != 0);
  48         l = &path.nodes[0]->leaf;
  49         item = btrfs_item_ptr(l, path.slots[0], struct btrfs_extent_item);
  50         refs = btrfs_extent_refs(item);
  51         btrfs_set_extent_refs(item, refs + 1);
  52
  53         BUG_ON(list_empty(&path.nodes[0]->dirty));
  54         btrfs_release_path(root->extent_root, &path);
  55         finish_current_insert(trans, root->extent_root);
  56         run_pending(trans, root->extent_root);
  57         return 0;
  58 }
  59
  60 static int lookup_block_ref(struct btrfs_trans_handle *trans, struct btrfs_root
  61                             *root, u64 blocknr, u32 *refs)
  62 {
  63         struct btrfs_path path;
  64         int ret;
  65         struct btrfs_key key;
  66         struct btrfs_leaf *l;
  67         struct btrfs_extent_item *item;
  68         btrfs_init_path(&path);
  69         key.objectid = blocknr;
  70         key.offset = 1;
  71         key.flags = 0;
  72         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
  73         ret = btrfs_search_slot(trans, root->extent_root, &key, &path, 0, 0);
  74         if (ret != 0)
  75                 BUG();
  76         l = &path.nodes[0]->leaf;
  77         item = btrfs_item_ptr(l, path.slots[0], struct btrfs_extent_item);
  78         *refs = btrfs_extent_refs(item);
  79         btrfs_release_path(root->extent_root, &path);
  80         return 0;
  81 }
  82
  83 int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  84                   struct btrfs_buffer *buf)
  85 {
  86         u64 blocknr;
  87         int i;
  88
  89         if (!root->ref_cows)
  90                 return 0;
  91         if (btrfs_is_leaf(&buf->node))
  92                 return 0;
  93
  94         for (i = 0; i < btrfs_header_nritems(&buf->node.header); i++) {
  95                 blocknr = btrfs_node_blockptr(&buf->node, i);
  96                 inc_block_ref(trans, root, blocknr);
  97         }
  98         return 0;
  99 }
 100
 101 int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans, struct
 102                                btrfs_root *root)
 103 {
 104         unsigned long gang[8];
 105         u64 first = 0;
 106         int ret;
 107         int i;
 108
 109         while(1) {
 110                 ret = radix_tree_gang_lookup(&root->pinned_radix,
 111                                                  (void **)gang, 0,
 112                                                  ARRAY_SIZE(gang));
 113                 if (!ret)
 114                         break;
 115                 if (!first)
 116                         first = gang[0];
 117                 for (i = 0; i < ret; i++) {
 118                         radix_tree_delete(&root->pinned_radix, gang[i]);
 119                 }
 120         }
 121         root->last_insert.objectid = first;
 122         root->last_insert.offset = 0;
 123         return 0;
 124 }
 125
 126 static int finish_current_insert(struct btrfs_trans_handle *trans, struct
 127                                  btrfs_root *extent_root)
 128 {
 129         struct btrfs_key ins;
 130         struct btrfs_extent_item extent_item;
 131         int i;
 132         int ret;
 133
 134         btrfs_set_extent_refs(&extent_item, 1);
 135         btrfs_set_extent_owner(&extent_item,
 136                 btrfs_header_parentid(&extent_root->node->node.header));
 137         ins.offset = 1;
 138         ins.flags = 0;
 139         btrfs_set_key_type(&ins, BTRFS_EXTENT_ITEM_KEY);
 140
 141         for (i = 0; i < extent_root->current_insert.flags; i++) {
 142                 ins.objectid = extent_root->current_insert.objectid + i;
 143                 ret = btrfs_insert_item(trans, extent_root, &ins, &extent_item,
 144                                         sizeof(extent_item));
 145                 BUG_ON(ret);
 146         }
 147         extent_root->current_insert.offset = 0;
 148         return 0;
 149 }
 150
 151 /*
 152  * remove an extent from the root, returns 0 on success
 153  */
 154 static int __free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 155                          *root, u64 blocknr, u64 num_blocks, int pin)
 156 {
 157         struct btrfs_path path;
 158         struct btrfs_key key;
 159         struct btrfs_root *extent_root = root->extent_root;
 160         int ret;
 161         struct btrfs_extent_item *ei;
 162         struct btrfs_key ins;
 163         u32 refs;
 164
 165         BUG_ON(pin && num_blocks != 1);
 166         key.objectid = blocknr;
 167         key.flags = 0;
 168         btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
 169         key.offset = num_blocks;
 170
 171         find_free_extent(trans, root, 0, 0, (u64)-1, &ins);
 172         btrfs_init_path(&path);
 173         ret = btrfs_search_slot(trans, extent_root, &key, &path, -1, 1);
 174         if (ret) {
 175                 printf("failed to find %Lu\n", key.objectid);
 176                 btrfs_print_tree(extent_root, extent_root->node);
 177                 printf("failed to find %Lu\n", key.objectid);
 178                 BUG();
 179         }
 180         ei = btrfs_item_ptr(&path.nodes[0]->leaf, path.slots[0],
 181                             struct btrfs_extent_item);
 182         BUG_ON(ei->refs == 0);
 183         refs = btrfs_extent_refs(ei) - 1;
 184         btrfs_set_extent_refs(ei, refs);
 185         if (refs == 0) {
 186                 if (pin) {
 187                         int err;
 188                         radix_tree_preload(GFP_KERNEL);
 189                         err = radix_tree_insert(&extent_root->pinned_radix,
 190                                           blocknr, (void *)blocknr);
 191                         BUG_ON(err);
 192                         radix_tree_preload_end();
 193                 }
 194                 ret = btrfs_del_item(trans, extent_root, &path);
 195                 if (!pin && extent_root->last_insert.objectid > blocknr)
 196                         extent_root->last_insert.objectid = blocknr;
 197                 if (ret)
 198                         BUG();
 199         }
 200         btrfs_release_path(extent_root, &path);
 201         finish_current_insert(trans, extent_root);
 202         return ret;
 203 }
 204
 205 /*
 206  * find all the blocks marked as pending in the radix tree and remove
 207  * them from the extent map
 208  */
 209 static int del_pending_extents(struct btrfs_trans_handle *trans, struct
 210                                btrfs_root *extent_root)
 211 {
 212         int ret;
 213         struct btrfs_buffer *gang[4];
 214         int i;
 215
 216         while(1) {
 217                 ret = radix_tree_gang_lookup_tag(&extent_root->cache_radix,
 218                                                  (void **)gang, 0,
 219                                                  ARRAY_SIZE(gang),
 220                                                  CTREE_EXTENT_PENDING_DEL);
 221                 if (!ret)
 222                         break;
 223                 for (i = 0; i < ret; i++) {
 224                         ret = __free_extent(trans, extent_root,
 225                                             gang[i]->blocknr, 1, 1);
 226                         radix_tree_tag_clear(&extent_root->cache_radix,
 227                                                 gang[i]->blocknr,
 228                                                 CTREE_EXTENT_PENDING_DEL);
 229                         btrfs_block_release(extent_root, gang[i]);
 230                 }
 231         }
 232         return 0;
 233 }
 234
 235 static int run_pending(struct btrfs_trans_handle *trans, struct btrfs_root
 236                        *extent_root)
 237 {
 238         while(radix_tree_tagged(&extent_root->cache_radix,
 239                                 CTREE_EXTENT_PENDING_DEL))
 240                 del_pending_extents(trans, extent_root);
 241         return 0;
 242 }
 243
 244
 245 /*
 246  * remove an extent from the root, returns 0 on success
 247  */
 248 int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 249                       *root, u64 blocknr, u64 num_blocks, int pin)
 250 {
 251         struct btrfs_root *extent_root = root->extent_root;
 252         struct btrfs_buffer *t;
 253         int pending_ret;
 254         int ret;
 255
 256         if (root == extent_root) {
 257                 t = find_tree_block(root, blocknr);
 258                 radix_tree_tag_set(&root->cache_radix, blocknr,
 259                                    CTREE_EXTENT_PENDING_DEL);
 260                 return 0;
 261         }
 262         ret = __free_extent(trans, root, blocknr, num_blocks, pin);
 263         pending_ret = run_pending(trans, root->extent_root);
 264         return ret ? ret : pending_ret;
 265 }
 266
 267 /*
 268  * walks the btree of allocated extents and find a hole of a given size.
 269  * The key ins is changed to record the hole:
 270  * ins->objectid == block start
 271  * ins->flags = BTRFS_EXTENT_ITEM_KEY
 272  * ins->offset == number of blocks
 273  * Any available blocks before search_start are skipped.
 274  */
 275 static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 276                             *orig_root, u64 num_blocks, u64 search_start, u64
 277                             search_end, struct btrfs_key *ins)
 278 {
 279         struct btrfs_path path;
 280         struct btrfs_key key;
 281         int ret;
 282         u64 hole_size = 0;
 283         int slot = 0;
 284         u64 last_block;
 285         u64 test_block;
 286         int start_found;
 287         struct btrfs_leaf *l;
 288         struct btrfs_root * root = orig_root->extent_root;
 289         int total_needed = num_blocks;
 290
 291         total_needed += (btrfs_header_level(&root->node->node.header) + 1) * 3;
 292         if (root->last_insert.objectid > search_start)
 293                 search_start = root->last_insert.objectid;
 294
 295         ins->flags = 0;
 296         btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY);
 297
 298 check_failed:
 299         btrfs_init_path(&path);
 300         ins->objectid = search_start;
 301         ins->offset = 0;
 302         start_found = 0;
 303         ret = btrfs_search_slot(trans, root, ins, &path, 0, 0);
 304         if (ret < 0)
 305                 goto error;
 306
 307         if (path.slots[0] > 0)
 308                 path.slots[0]--;
 309
 310         while (1) {
 311                 l = &path.nodes[0]->leaf;
 312                 slot = path.slots[0];
 313                 if (slot >= btrfs_header_nritems(&l->header)) {
 314                         ret = btrfs_next_leaf(root, &path);
 315                         if (ret == 0)
 316                                 continue;
 317                         if (ret < 0)
 318                                 goto error;
 319                         if (!start_found) {
 320                                 ins->objectid = search_start;
 321                                 ins->offset = (u64)-1;
 322                                 start_found = 1;
 323                                 goto check_pending;
 324                         }
 325                         ins->objectid = last_block > search_start ?
 326                                         last_block : search_start;
 327                         ins->offset = (u64)-1;
 328                         goto check_pending;
 329                 }
 330                 btrfs_disk_key_to_cpu(&key, &l->items[slot].key);
 331                 if (key.objectid >= search_start) {
 332                         if (start_found) {
 333                                 if (last_block < search_start)
 334                                         last_block = search_start;
 335                                 hole_size = key.objectid - last_block;
 336                                 if (hole_size > total_needed) {
 337                                         ins->objectid = last_block;
 338                                         ins->offset = hole_size;
 339                                         goto check_pending;
 340                                 }
 341                         }
 342                 }
 343                 start_found = 1;
 344                 last_block = key.objectid + key.offset;
 345                 path.slots[0]++;
 346         }
 347         // FIXME -ENOSPC
 348 check_pending:
 349         /* we have to make sure we didn't find an extent that has already
 350          * been allocated by the map tree or the original allocation
 351          */
 352         btrfs_release_path(root, &path);
 353         BUG_ON(ins->objectid < search_start);
 354         for (test_block = ins->objectid;
 355              test_block < ins->objectid + total_needed; test_block++) {
 356                 if (radix_tree_lookup(&root->pinned_radix, test_block)) {
 357                         search_start = test_block + 1;
 358                         goto check_failed;
 359                 }
 360         }
 361         BUG_ON(root->current_insert.offset);
 362         root->current_insert.offset = total_needed - num_blocks;
 363         root->current_insert.objectid = ins->objectid + num_blocks;
 364         root->current_insert.flags = 0;
 365         root->last_insert.objectid = ins->objectid;
 366         ins->offset = num_blocks;
 367         return 0;
 368 error:
 369         btrfs_release_path(root, &path);
 370         return ret;
 371 }
 372
 373 /*
 374  * finds a free extent and does all the dirty work required for allocation
 375  * returns the key for the extent through ins, and a tree buffer for
 376  * the first block of the extent through buf.
 377  *
 378  * returns 0 if everything worked, non-zero otherwise.
 379  */
 380 static int alloc_extent(struct btrfs_trans_handle *trans, struct btrfs_root
 381                         *root, u64 num_blocks, u64 search_start, u64
 382                         search_end, u64 owner, struct btrfs_key *ins)
 383 {
 384         int ret;
 385         int pending_ret;
 386         struct btrfs_root *extent_root = root->extent_root;
 387         struct btrfs_extent_item extent_item;
 388
 389         btrfs_set_extent_refs(&extent_item, 1);
 390         btrfs_set_extent_owner(&extent_item, owner);
 391
 392         if (root == extent_root) {
 393                 BUG_ON(extent_root->current_insert.offset == 0);
 394                 BUG_ON(num_blocks != 1);
 395                 BUG_ON(extent_root->current_insert.flags ==
 396                        extent_root->current_insert.offset);
 397                 ins->offset = 1;
 398                 ins->objectid = extent_root->current_insert.objectid +
 399                                 extent_root->current_insert.flags++;
 400                 return 0;
 401         }
 402         ret = find_free_extent(trans, root, num_blocks, search_start,
 403                                search_end, ins);
 404         if (ret)
 405                 return ret;
 406
 407         ret = btrfs_insert_item(trans, extent_root, ins, &extent_item,
 408                                 sizeof(extent_item));
 409
 410         finish_current_insert(trans, extent_root);
 411         pending_ret = run_pending(trans, extent_root);
 412         if (ret)
 413                 return ret;
 414         if (pending_ret)
 415                 return pending_ret;
 416         return 0;
 417 }
 418
 419 /*
 420  * helper function to allocate a block for a given tree
 421  * returns the tree buffer or NULL.
 422  */
 423 struct btrfs_buffer *btrfs_alloc_free_block(struct btrfs_trans_handle *trans,
 424                                             struct btrfs_root *root)
 425 {
 426         struct btrfs_key ins;
 427         int ret;
 428         struct btrfs_buffer *buf;
 429
 430         ret = alloc_extent(trans, root, 1, 0, (unsigned long)-1,
 431                            btrfs_header_parentid(&root->node->node.header),
 432                            &ins);
 433         if (ret) {
 434                 BUG();
 435                 return NULL;
 436         }
 437         buf = find_tree_block(root, ins.objectid);
 438         dirty_tree_block(trans, root, buf);
 439         return buf;
 440 }
 441
 442 /*
 443  * helper function for drop_snapshot, this walks down the tree dropping ref
 444  * counts as it goes.
 445  */
 446 static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
 447                           *root, struct btrfs_path *path, int *level)
 448 {
 449         struct btrfs_buffer *next;
 450         struct btrfs_buffer *cur;
 451         u64 blocknr;
 452         int ret;
 453         u32 refs;
 454
 455         ret = lookup_block_ref(trans, root, path->nodes[*level]->blocknr,
 456                                &refs);
 457         BUG_ON(ret);
 458         if (refs > 1)
 459                 goto out;
 460         /*
 461          * walk down to the last node level and free all the leaves
 462          */
 463         while(*level > 0) {
 464                 cur = path->nodes[*level];
 465                 if (path->slots[*level] >=
 466                     btrfs_header_nritems(&cur->node.header))
 467                         break;
 468                 blocknr = btrfs_node_blockptr(&cur->node, path->slots[*level]);
 469                 ret = lookup_block_ref(trans, root, blocknr, &refs);
 470                 if (refs != 1 || *level == 1) {
 471                         path->slots[*level]++;
 472                         ret = btrfs_free_extent(trans, root, blocknr, 1, 1);
 473                         BUG_ON(ret);
 474                         continue;
 475                 }
 476                 BUG_ON(ret);
 477                 next = read_tree_block(root, blocknr);
 478                 if (path->nodes[*level-1])
 479                         btrfs_block_release(root, path->nodes[*level-1]);
 480                 path->nodes[*level-1] = next;
 481                 *level = btrfs_header_level(&next->node.header);
 482                 path->slots[*level] = 0;
 483         }
 484 out:
 485         ret = btrfs_free_extent(trans, root, path->nodes[*level]->blocknr, 1,
 486                                 1);
 487         btrfs_block_release(root, path->nodes[*level]);
 488         path->nodes[*level] = NULL;
 489         *level += 1;
 490         BUG_ON(ret);
 491         return 0;
 492 }
 493
 494 /*
 495  * helper for dropping snapshots.  This walks back up the tree in the path
 496  * to find the first node higher up where we haven't yet gone through
 497  * all the slots
 498  */
 499 static int walk_up_tree(struct btrfs_trans_handle *trans, struct btrfs_root
 500                         *root, struct btrfs_path *path, int *level)
 501 {
 502         int i;
 503         int slot;
 504         int ret;
 505         for(i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
 506                 slot = path->slots[i];
 507                 if (slot <
 508                     btrfs_header_nritems(&path->nodes[i]->node.header)- 1) {
 509                         path->slots[i]++;
 510                         *level = i;
 511                         return 0;
 512                 } else {
 513                         ret = btrfs_free_extent(trans, root,
 514                                                 path->nodes[*level]->blocknr,
 515                                                 1, 1);
 516                         btrfs_block_release(root, path->nodes[*level]);
 517                         path->nodes[*level] = NULL;
 518                         *level = i + 1;
 519                         BUG_ON(ret);
 520                 }
 521         }
 522         return 1;
 523 }
 524
 525 /*
 526  * drop the reference count on the tree rooted at 'snap'.  This traverses
 527  * the tree freeing any blocks that have a ref count of zero after being
 528  * decremented.
 529  */
 530 int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
 531                         *root, struct btrfs_buffer *snap)
 532 {
 533         int ret = 0;
 534         int wret;
 535         int level;
 536         struct btrfs_path path;
 537         int i;
 538         int orig_level;
 539
 540         btrfs_init_path(&path);
 541
 542         level = btrfs_header_level(&snap->node.header);
 543         orig_level = level;
 544         path.nodes[level] = snap;
 545         path.slots[level] = 0;
 546         while(1) {
 547                 wret = walk_down_tree(trans, root, &path, &level);
 548                 if (wret > 0)
 549                         break;
 550                 if (wret < 0)
 551                         ret = wret;
 552
 553                 wret = walk_up_tree(trans, root, &path, &level);
 554                 if (wret > 0)
 555                         break;
 556                 if (wret < 0)
 557                         ret = wret;
 558         }
 559         for (i = 0; i <= orig_level; i++) {
 560                 if (path.nodes[i]) {
 561                         btrfs_block_release(root, path.nodes[i]);
 562                 }
 563         }
 564         return ret;
 565 }