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