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