SAFE public projects git trees. - safe/jmp/linux-2.6/blob - fs/btrfs/file-item.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  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/bio.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/highmem.h>
  22 #include "ctree.h"
  23 #include "disk-io.h"
  24 #include "transaction.h"
  25 #include "print-tree.h"
  26
  27 #define MAX_CSUM_ITEMS(r,size) ((((BTRFS_LEAF_DATA_SIZE(r) - \
  28                                    sizeof(struct btrfs_item) * 2) / \
  29                                   size) - 1))
  30 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
  31                              struct btrfs_root *root,
  32                              u64 objectid, u64 pos,
  33                              u64 disk_offset, u64 disk_num_bytes,
  34                              u64 num_bytes, u64 offset, u64 ram_bytes,
  35                              u8 compression, u8 encryption, u16 other_encoding)
  36 {
  37         int ret = 0;
  38         struct btrfs_file_extent_item *item;
  39         struct btrfs_key file_key;
  40         struct btrfs_path *path;
  41         struct extent_buffer *leaf;
  42
  43         path = btrfs_alloc_path();
  44         BUG_ON(!path);
  45         file_key.objectid = objectid;
  46         file_key.offset = pos;
  47         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
  48
  49         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  50                                       sizeof(*item));
  51         if (ret < 0)
  52                 goto out;
  53         BUG_ON(ret);
  54         leaf = path->nodes[0];
  55         item = btrfs_item_ptr(leaf, path->slots[0],
  56                               struct btrfs_file_extent_item);
  57         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
  58         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
  59         btrfs_set_file_extent_offset(leaf, item, offset);
  60         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
  61         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
  62         btrfs_set_file_extent_generation(leaf, item, trans->transid);
  63         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
  64         btrfs_set_file_extent_compression(leaf, item, compression);
  65         btrfs_set_file_extent_encryption(leaf, item, encryption);
  66         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
  67
  68         btrfs_mark_buffer_dirty(leaf);
  69 out:
  70         btrfs_free_path(path);
  71         return ret;
  72 }
  73
  74 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  75                                           struct btrfs_root *root,
  76                                           struct btrfs_path *path,
  77                                           u64 bytenr, int cow)
  78 {
  79         int ret;
  80         struct btrfs_key file_key;
  81         struct btrfs_key found_key;
  82         struct btrfs_csum_item *item;
  83         struct extent_buffer *leaf;
  84         u64 csum_offset = 0;
  85         u16 csum_size =
  86                 btrfs_super_csum_size(&root->fs_info->super_copy);
  87         int csums_in_item;
  88
  89         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  90         file_key.offset = bytenr;
  91         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
  92         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
  93         if (ret < 0)
  94                 goto fail;
  95         leaf = path->nodes[0];
  96         if (ret > 0) {
  97                 ret = 1;
  98                 if (path->slots[0] == 0)
  99                         goto fail;
 100                 path->slots[0]--;
 101                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 102                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 103                         goto fail;
 104
 105                 csum_offset = (bytenr - found_key.offset) >>
 106                                 root->fs_info->sb->s_blocksize_bits;
 107                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 108                 csums_in_item /= csum_size;
 109
 110                 if (csum_offset >= csums_in_item) {
 111                         ret = -EFBIG;
 112                         goto fail;
 113                 }
 114         }
 115         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 116         item = (struct btrfs_csum_item *)((unsigned char *)item +
 117                                           csum_offset * csum_size);
 118         return item;
 119 fail:
 120         if (ret > 0)
 121                 ret = -ENOENT;
 122         return ERR_PTR(ret);
 123 }
 124
 125
 126 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 127                              struct btrfs_root *root,
 128                              struct btrfs_path *path, u64 objectid,
 129                              u64 offset, int mod)
 130 {
 131         int ret;
 132         struct btrfs_key file_key;
 133         int ins_len = mod < 0 ? -1 : 0;
 134         int cow = mod != 0;
 135
 136         file_key.objectid = objectid;
 137         file_key.offset = offset;
 138         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 139         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 140         return ret;
 141 }
 142
 143
 144 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 145                           struct bio *bio, u32 *dst)
 146 {
 147         u32 sum;
 148         struct bio_vec *bvec = bio->bi_io_vec;
 149         int bio_index = 0;
 150         u64 offset;
 151         u64 item_start_offset = 0;
 152         u64 item_last_offset = 0;
 153         u64 disk_bytenr;
 154         u32 diff;
 155         u16 csum_size =
 156                 btrfs_super_csum_size(&root->fs_info->super_copy);
 157         int ret;
 158         struct btrfs_path *path;
 159         struct btrfs_csum_item *item = NULL;
 160         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 161
 162         path = btrfs_alloc_path();
 163         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 164                 path->reada = 2;
 165
 166         WARN_ON(bio->bi_vcnt <= 0);
 167
 168         disk_bytenr = (u64)bio->bi_sector << 9;
 169         while(bio_index < bio->bi_vcnt) {
 170                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 171                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 172                 if (ret == 0)
 173                         goto found;
 174
 175                 if (!item || disk_bytenr < item_start_offset ||
 176                     disk_bytenr >= item_last_offset) {
 177                         struct btrfs_key found_key;
 178                         u32 item_size;
 179
 180                         if (item)
 181                                 btrfs_release_path(root, path);
 182                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 183                                                  path, disk_bytenr, 0);
 184                         if (IS_ERR(item)) {
 185                                 ret = PTR_ERR(item);
 186                                 if (ret == -ENOENT || ret == -EFBIG)
 187                                         ret = 0;
 188                                 sum = 0;
 189                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 190                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 191                                         set_extent_bits(io_tree, offset,
 192                                                 offset + bvec->bv_len - 1,
 193                                                 EXTENT_NODATASUM, GFP_NOFS);
 194                                 } else {
 195                                         printk("no csum found for inode %lu "
 196                                                "start %llu\n", inode->i_ino,
 197                                                (unsigned long long)offset);
 198                                 }
 199                                 item = NULL;
 200                                 btrfs_release_path(root, path);
 201                                 goto found;
 202                         }
 203                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 204                                               path->slots[0]);
 205
 206                         item_start_offset = found_key.offset;
 207                         item_size = btrfs_item_size_nr(path->nodes[0],
 208                                                        path->slots[0]);
 209                         item_last_offset = item_start_offset +
 210                                 (item_size / csum_size) *
 211                                 root->sectorsize;
 212                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 213                                               struct btrfs_csum_item);
 214                 }
 215                 /*
 216                  * this byte range must be able to fit inside
 217                  * a single leaf so it will also fit inside a u32
 218                  */
 219                 diff = disk_bytenr - item_start_offset;
 220                 diff = diff / root->sectorsize;
 221                 diff = diff * csum_size;
 222
 223                 read_extent_buffer(path->nodes[0], &sum,
 224                                    ((unsigned long)item) + diff,
 225                                    csum_size);
 226 found:
 227                 if (dst)
 228                         *dst++ = sum;
 229                 else
 230                         set_state_private(io_tree, offset, sum);
 231                 disk_bytenr += bvec->bv_len;
 232                 bio_index++;
 233                 bvec++;
 234         }
 235         btrfs_free_path(path);
 236         return 0;
 237 }
 238
 239 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 240                              struct list_head *list)
 241 {
 242         struct btrfs_key key;
 243         struct btrfs_path *path;
 244         struct extent_buffer *leaf;
 245         struct btrfs_ordered_sum *sums;
 246         struct btrfs_sector_sum *sector_sum;
 247         struct btrfs_csum_item *item;
 248         unsigned long offset;
 249         int ret;
 250         size_t size;
 251         u64 csum_end;
 252         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
 253
 254         path = btrfs_alloc_path();
 255         BUG_ON(!path);
 256
 257         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 258         key.offset = start;
 259         key.type = BTRFS_EXTENT_CSUM_KEY;
 260
 261         ret = btrfs_search_slot(NULL, root->fs_info->csum_root,
 262                                 &key, path, 0, 0);
 263         if (ret < 0)
 264                 goto fail;
 265         if (ret > 0 && path->slots[0] > 0) {
 266                 leaf = path->nodes[0];
 267                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 268                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 269                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 270                         offset = (start - key.offset) >>
 271                                  root->fs_info->sb->s_blocksize_bits;
 272                         if (offset * csum_size <
 273                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 274                                 path->slots[0]--;
 275                 }
 276         }
 277
 278         while (start <= end) {
 279                 leaf = path->nodes[0];
 280                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 281                         ret = btrfs_next_leaf(root->fs_info->csum_root, path);
 282                         if (ret < 0)
 283                                 goto fail;
 284                         if (ret > 0)
 285                                 break;
 286                         leaf = path->nodes[0];
 287                 }
 288
 289                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 290                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 291                     key.type != BTRFS_EXTENT_CSUM_KEY)
 292                         break;
 293
 294                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 295                 if (key.offset > end)
 296                         break;
 297
 298                 if (key.offset > start)
 299                         start = key.offset;
 300
 301                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 302                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 303                 if (csum_end <= start) {
 304                         path->slots[0]++;
 305                         continue;
 306                 }
 307
 308                 size = min(csum_end, end + 1) - start;
 309                 sums = kzalloc(btrfs_ordered_sum_size(root, size), GFP_NOFS);
 310                 BUG_ON(!sums);
 311
 312                 sector_sum = sums->sums;
 313                 sums->bytenr = start;
 314                 sums->len = size;
 315
 316                 offset = (start - key.offset) >>
 317                          root->fs_info->sb->s_blocksize_bits;
 318                 offset *= csum_size;
 319
 320                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 321                                       struct btrfs_csum_item);
 322                 while (size > 0) {
 323                         read_extent_buffer(path->nodes[0], &sector_sum->sum,
 324                                            ((unsigned long)item) + offset,
 325                                            csum_size);
 326                         sector_sum->bytenr = start;
 327
 328                         size -= root->sectorsize;
 329                         start += root->sectorsize;
 330                         offset += csum_size;
 331                         sector_sum++;
 332                 }
 333                 list_add_tail(&sums->list, list);
 334
 335                 path->slots[0]++;
 336         }
 337         ret = 0;
 338 fail:
 339         btrfs_free_path(path);
 340         return ret;
 341 }
 342
 343 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 344                        struct bio *bio, u64 file_start, int contig)
 345 {
 346         struct btrfs_ordered_sum *sums;
 347         struct btrfs_sector_sum *sector_sum;
 348         struct btrfs_ordered_extent *ordered;
 349         char *data;
 350         struct bio_vec *bvec = bio->bi_io_vec;
 351         int bio_index = 0;
 352         unsigned long total_bytes = 0;
 353         unsigned long this_sum_bytes = 0;
 354         u64 offset;
 355         u64 disk_bytenr;
 356
 357         WARN_ON(bio->bi_vcnt <= 0);
 358         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 359         if (!sums)
 360                 return -ENOMEM;
 361
 362         sector_sum = sums->sums;
 363         disk_bytenr = (u64)bio->bi_sector << 9;
 364         sums->len = bio->bi_size;
 365         INIT_LIST_HEAD(&sums->list);
 366
 367         if (contig)
 368                 offset = file_start;
 369         else
 370                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 371
 372         ordered = btrfs_lookup_ordered_extent(inode, offset);
 373         BUG_ON(!ordered);
 374         sums->bytenr = ordered->start;
 375
 376         while(bio_index < bio->bi_vcnt) {
 377                 if (!contig)
 378                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 379
 380                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 381                     offset < ordered->file_offset)) {
 382                         unsigned long bytes_left;
 383                         sums->len = this_sum_bytes;
 384                         this_sum_bytes = 0;
 385                         btrfs_add_ordered_sum(inode, ordered, sums);
 386                         btrfs_put_ordered_extent(ordered);
 387
 388                         bytes_left = bio->bi_size - total_bytes;
 389
 390                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 391                                        GFP_NOFS);
 392                         BUG_ON(!sums);
 393                         sector_sum = sums->sums;
 394                         sums->len = bytes_left;
 395                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 396                         BUG_ON(!ordered);
 397                         sums->bytenr = ordered->start;
 398                 }
 399
 400                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 401                 sector_sum->sum = ~(u32)0;
 402                 sector_sum->sum = btrfs_csum_data(root,
 403                                                   data + bvec->bv_offset,
 404                                                   sector_sum->sum,
 405                                                   bvec->bv_len);
 406                 kunmap_atomic(data, KM_USER0);
 407                 btrfs_csum_final(sector_sum->sum,
 408                                  (char *)&sector_sum->sum);
 409                 sector_sum->bytenr = disk_bytenr;
 410
 411                 sector_sum++;
 412                 bio_index++;
 413                 total_bytes += bvec->bv_len;
 414                 this_sum_bytes += bvec->bv_len;
 415                 disk_bytenr += bvec->bv_len;
 416                 offset += bvec->bv_len;
 417                 bvec++;
 418         }
 419         this_sum_bytes = 0;
 420         btrfs_add_ordered_sum(inode, ordered, sums);
 421         btrfs_put_ordered_extent(ordered);
 422         return 0;
 423 }
 424
 425 /*
 426  * helper function for csum removal, this expects the
 427  * key to describe the csum pointed to by the path, and it expects
 428  * the csum to overlap the range [bytenr, len]
 429  *
 430  * The csum should not be entirely contained in the range and the
 431  * range should not be entirely contained in the csum.
 432  *
 433  * This calls btrfs_truncate_item with the correct args based on the
 434  * overlap, and fixes up the key as required.
 435  */
 436 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 437                                       struct btrfs_root *root,
 438                                       struct btrfs_path *path,
 439                                       struct btrfs_key *key,
 440                                       u64 bytenr, u64 len)
 441 {
 442         struct extent_buffer *leaf;
 443         u16 csum_size =
 444                 btrfs_super_csum_size(&root->fs_info->super_copy);
 445         u64 csum_end;
 446         u64 end_byte = bytenr + len;
 447         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 448         int ret;
 449
 450         leaf = path->nodes[0];
 451         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 452         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 453         csum_end += key->offset;
 454
 455         if (key->offset < bytenr && csum_end <= end_byte) {
 456                 /*
 457                  *         [ bytenr - len ]
 458                  *         [   ]
 459                  *   [csum     ]
 460                  *   A simple truncate off the end of the item
 461                  */
 462                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 463                 new_size *= csum_size;
 464                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 465                 BUG_ON(ret);
 466         } else if (key->offset >= bytenr && csum_end > end_byte &&
 467                    end_byte > key->offset) {
 468                 /*
 469                  *         [ bytenr - len ]
 470                  *                 [ ]
 471                  *                 [csum     ]
 472                  * we need to truncate from the beginning of the csum
 473                  */
 474                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 475                 new_size *= csum_size;
 476
 477                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 478                 BUG_ON(ret);
 479
 480                 key->offset = end_byte;
 481                 ret = btrfs_set_item_key_safe(trans, root, path, key);
 482                 BUG_ON(ret);
 483         } else {
 484                 BUG();
 485         }
 486         return 0;
 487 }
 488
 489 /*
 490  * deletes the csum items from the csum tree for a given
 491  * range of bytes.
 492  */
 493 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 494                     struct btrfs_root *root, u64 bytenr, u64 len)
 495 {
 496         struct btrfs_path *path;
 497         struct btrfs_key key;
 498         u64 end_byte = bytenr + len;
 499         u64 csum_end;
 500         struct extent_buffer *leaf;
 501         int ret;
 502         u16 csum_size =
 503                 btrfs_super_csum_size(&root->fs_info->super_copy);
 504         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 505
 506         root = root->fs_info->csum_root;
 507
 508         path = btrfs_alloc_path();
 509
 510         while(1) {
 511                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 512                 key.offset = end_byte - 1;
 513                 key.type = BTRFS_EXTENT_CSUM_KEY;
 514
 515                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 516                 if (ret > 0) {
 517                         if (path->slots[0] == 0)
 518                                 goto out;
 519                         path->slots[0]--;
 520                 }
 521                 leaf = path->nodes[0];
 522                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 523
 524                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 525                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 526                         break;
 527                 }
 528
 529                 if (key.offset >= end_byte)
 530                         break;
 531
 532                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 533                 csum_end <<= blocksize_bits;
 534                 csum_end += key.offset;
 535
 536                 /* this csum ends before we start, we're done */
 537                 if (csum_end <= bytenr)
 538                         break;
 539
 540                 /* delete the entire item, it is inside our range */
 541                 if (key.offset >= bytenr && csum_end <= end_byte) {
 542                         ret = btrfs_del_item(trans, root, path);
 543                         BUG_ON(ret);
 544                         if (key.offset == bytenr)
 545                                 break;
 546                 } else if (key.offset < bytenr && csum_end > end_byte) {
 547                         unsigned long offset;
 548                         unsigned long shift_len;
 549                         unsigned long item_offset;
 550                         /*
 551                          *        [ bytenr - len ]
 552                          *     [csum                ]
 553                          *
 554                          * Our bytes are in the middle of the csum,
 555                          * we need to split this item and insert a new one.
 556                          *
 557                          * But we can't drop the path because the
 558                          * csum could change, get removed, extended etc.
 559                          *
 560                          * The trick here is the max size of a csum item leaves
 561                          * enough room in the tree block for a single
 562                          * item header.  So, we split the item in place,
 563                          * adding a new header pointing to the existing
 564                          * bytes.  Then we loop around again and we have
 565                          * a nicely formed csum item that we can neatly
 566                          * truncate.
 567                          */
 568                         offset = (bytenr - key.offset) >> blocksize_bits;
 569                         offset *= csum_size;
 570
 571                         shift_len = (len >> blocksize_bits) * csum_size;
 572
 573                         item_offset = btrfs_item_ptr_offset(leaf,
 574                                                             path->slots[0]);
 575
 576                         memset_extent_buffer(leaf, 0, item_offset + offset,
 577                                              shift_len);
 578                         key.offset = bytenr;
 579
 580                         /*
 581                          * btrfs_split_item returns -EAGAIN when the
 582                          * item changed size or key
 583                          */
 584                         ret = btrfs_split_item(trans, root, path, &key, offset);
 585                         BUG_ON(ret && ret != -EAGAIN);
 586
 587                         key.offset = end_byte - 1;
 588                 } else {
 589                         ret = truncate_one_csum(trans, root, path,
 590                                                 &key, bytenr, len);
 591                         BUG_ON(ret);
 592                         if (key.offset < bytenr)
 593                                 break;
 594                 }
 595                 btrfs_release_path(root, path);
 596         }
 597 out:
 598         btrfs_free_path(path);
 599         return 0;
 600 }
 601
 602 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 603                            struct btrfs_root *root,
 604                            struct btrfs_ordered_sum *sums)
 605 {
 606         u64 bytenr;
 607         int ret;
 608         struct btrfs_key file_key;
 609         struct btrfs_key found_key;
 610         u64 next_offset;
 611         u64 total_bytes = 0;
 612         int found_next;
 613         struct btrfs_path *path;
 614         struct btrfs_csum_item *item;
 615         struct btrfs_csum_item *item_end;
 616         struct extent_buffer *leaf = NULL;
 617         u64 csum_offset;
 618         struct btrfs_sector_sum *sector_sum;
 619         u32 nritems;
 620         u32 ins_size;
 621         char *eb_map;
 622         char *eb_token;
 623         unsigned long map_len;
 624         unsigned long map_start;
 625         u16 csum_size =
 626                 btrfs_super_csum_size(&root->fs_info->super_copy);
 627
 628         path = btrfs_alloc_path();
 629         BUG_ON(!path);
 630         sector_sum = sums->sums;
 631 again:
 632         next_offset = (u64)-1;
 633         found_next = 0;
 634         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 635         file_key.offset = sector_sum->bytenr;
 636         bytenr = sector_sum->bytenr;
 637         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 638
 639         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 640         if (!IS_ERR(item)) {
 641                 leaf = path->nodes[0];
 642                 ret = 0;
 643                 goto found;
 644         }
 645         ret = PTR_ERR(item);
 646         if (ret == -EFBIG) {
 647                 u32 item_size;
 648                 /* we found one, but it isn't big enough yet */
 649                 leaf = path->nodes[0];
 650                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 651                 if ((item_size / csum_size) >=
 652                     MAX_CSUM_ITEMS(root, csum_size)) {
 653                         /* already at max size, make a new one */
 654                         goto insert;
 655                 }
 656         } else {
 657                 int slot = path->slots[0] + 1;
 658                 /* we didn't find a csum item, insert one */
 659                 nritems = btrfs_header_nritems(path->nodes[0]);
 660                 if (path->slots[0] >= nritems - 1) {
 661                         ret = btrfs_next_leaf(root, path);
 662                         if (ret == 1)
 663                                 found_next = 1;
 664                         if (ret != 0)
 665                                 goto insert;
 666                         slot = 0;
 667                 }
 668                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 669                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 670                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 671                         found_next = 1;
 672                         goto insert;
 673                 }
 674                 next_offset = found_key.offset;
 675                 found_next = 1;
 676                 goto insert;
 677         }
 678
 679         /*
 680          * at this point, we know the tree has an item, but it isn't big
 681          * enough yet to put our csum in.  Grow it
 682          */
 683         btrfs_release_path(root, path);
 684         ret = btrfs_search_slot(trans, root, &file_key, path,
 685                                 csum_size, 1);
 686         if (ret < 0)
 687                 goto fail_unlock;
 688
 689         if (ret > 0) {
 690                 if (path->slots[0] == 0)
 691                         goto insert;
 692                 path->slots[0]--;
 693         }
 694
 695         leaf = path->nodes[0];
 696         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 697         csum_offset = (bytenr - found_key.offset) >>
 698                         root->fs_info->sb->s_blocksize_bits;
 699
 700         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 701             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 702             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 703                 goto insert;
 704         }
 705
 706         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 707             csum_size) {
 708                 u32 diff = (csum_offset + 1) * csum_size;
 709
 710                 /*
 711                  * is the item big enough already?  we dropped our lock
 712                  * before and need to recheck
 713                  */
 714                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 715                         goto csum;
 716
 717                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 718                 if (diff != csum_size) {
 719                         goto insert;
 720                 }
 721
 722                 ret = btrfs_extend_item(trans, root, path, diff);
 723                 BUG_ON(ret);
 724                 goto csum;
 725         }
 726
 727 insert:
 728         btrfs_release_path(root, path);
 729         csum_offset = 0;
 730         if (found_next) {
 731                 u64 tmp = total_bytes + root->sectorsize;
 732                 u64 next_sector = sector_sum->bytenr;
 733                 struct btrfs_sector_sum *next = sector_sum + 1;
 734
 735                 while(tmp < sums->len) {
 736                         if (next_sector + root->sectorsize != next->bytenr)
 737                                 break;
 738                         tmp += root->sectorsize;
 739                         next_sector = next->bytenr;
 740                         next++;
 741                 }
 742                 tmp = min(tmp, next_offset - file_key.offset);
 743                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 744                 tmp = max((u64)1, tmp);
 745                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 746                 ins_size = csum_size * tmp;
 747         } else {
 748                 ins_size = csum_size;
 749         }
 750         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 751                                       ins_size);
 752         if (ret < 0)
 753                 goto fail_unlock;
 754         if (ret != 0) {
 755                 WARN_ON(1);
 756                 goto fail_unlock;
 757         }
 758 csum:
 759         leaf = path->nodes[0];
 760         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 761         ret = 0;
 762         item = (struct btrfs_csum_item *)((unsigned char *)item +
 763                                           csum_offset * csum_size);
 764 found:
 765         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 766         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 767                                       btrfs_item_size_nr(leaf, path->slots[0]));
 768         eb_token = NULL;
 769         cond_resched();
 770 next_sector:
 771
 772         if (!eb_token ||
 773            (unsigned long)item + csum_size >= map_start + map_len) {
 774                 int err;
 775
 776                 if (eb_token)
 777                         unmap_extent_buffer(leaf, eb_token, KM_USER1);
 778                 eb_token = NULL;
 779                 err = map_private_extent_buffer(leaf, (unsigned long)item,
 780                                                 csum_size,
 781                                                 &eb_token, &eb_map,
 782                                                 &map_start, &map_len, KM_USER1);
 783                 if (err)
 784                         eb_token = NULL;
 785         }
 786         if (eb_token) {
 787                 memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
 788                        &sector_sum->sum, csum_size);
 789         } else {
 790                 write_extent_buffer(leaf, &sector_sum->sum,
 791                                     (unsigned long)item, csum_size);
 792         }
 793
 794         total_bytes += root->sectorsize;
 795         sector_sum++;
 796         if (total_bytes < sums->len) {
 797                 item = (struct btrfs_csum_item *)((char *)item +
 798                                                   csum_size);
 799                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 800                     sector_sum->bytenr) {
 801                         bytenr = sector_sum->bytenr;
 802                         goto next_sector;
 803                 }
 804         }
 805         if (eb_token) {
 806                 unmap_extent_buffer(leaf, eb_token, KM_USER1);
 807                 eb_token = NULL;
 808         }
 809         btrfs_mark_buffer_dirty(path->nodes[0]);
 810         cond_resched();
 811         if (total_bytes < sums->len) {
 812                 btrfs_release_path(root, path);
 813                 goto again;
 814         }
 815 out:
 816         btrfs_free_path(path);
 817         return ret;
 818
 819 fail_unlock:
 820         goto out;
 821 }