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
 304                 size = min(csum_end, end + 1) - start;
 305                 sums = kzalloc(btrfs_ordered_sum_size(root, size), GFP_NOFS);
 306                 BUG_ON(!sums);
 307
 308                 sector_sum = sums->sums;
 309                 sums->bytenr = start;
 310                 sums->len = size;
 311
 312                 offset = (start - key.offset) >>
 313                          root->fs_info->sb->s_blocksize_bits;
 314                 offset *= csum_size;
 315
 316                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 317                                       struct btrfs_csum_item);
 318                 while (size > 0) {
 319                         read_extent_buffer(path->nodes[0], &sector_sum->sum,
 320                                            ((unsigned long)item) + offset,
 321                                            csum_size);
 322                         sector_sum->bytenr = start;
 323
 324                         size -= root->sectorsize;
 325                         start += root->sectorsize;
 326                         offset += csum_size;
 327                         sector_sum++;
 328                 }
 329                 list_add_tail(&sums->list, list);
 330
 331                 path->slots[0]++;
 332         }
 333         ret = 0;
 334 fail:
 335         btrfs_free_path(path);
 336         return ret;
 337 }
 338
 339 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 340                        struct bio *bio, u64 file_start, int contig)
 341 {
 342         struct btrfs_ordered_sum *sums;
 343         struct btrfs_sector_sum *sector_sum;
 344         struct btrfs_ordered_extent *ordered;
 345         char *data;
 346         struct bio_vec *bvec = bio->bi_io_vec;
 347         int bio_index = 0;
 348         unsigned long total_bytes = 0;
 349         unsigned long this_sum_bytes = 0;
 350         u64 offset;
 351         u64 disk_bytenr;
 352
 353         WARN_ON(bio->bi_vcnt <= 0);
 354         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 355         if (!sums)
 356                 return -ENOMEM;
 357
 358         sector_sum = sums->sums;
 359         disk_bytenr = (u64)bio->bi_sector << 9;
 360         sums->len = bio->bi_size;
 361         INIT_LIST_HEAD(&sums->list);
 362
 363         if (contig)
 364                 offset = file_start;
 365         else
 366                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 367
 368         ordered = btrfs_lookup_ordered_extent(inode, offset);
 369         BUG_ON(!ordered);
 370         sums->bytenr = ordered->start;
 371
 372         while(bio_index < bio->bi_vcnt) {
 373                 if (!contig)
 374                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 375
 376                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 377                     offset < ordered->file_offset)) {
 378                         unsigned long bytes_left;
 379                         sums->len = this_sum_bytes;
 380                         this_sum_bytes = 0;
 381                         btrfs_add_ordered_sum(inode, ordered, sums);
 382                         btrfs_put_ordered_extent(ordered);
 383
 384                         bytes_left = bio->bi_size - total_bytes;
 385
 386                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 387                                        GFP_NOFS);
 388                         BUG_ON(!sums);
 389                         sector_sum = sums->sums;
 390                         sums->len = bytes_left;
 391                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 392                         BUG_ON(!ordered);
 393                         sums->bytenr = ordered->start;
 394                 }
 395
 396                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 397                 sector_sum->sum = ~(u32)0;
 398                 sector_sum->sum = btrfs_csum_data(root,
 399                                                   data + bvec->bv_offset,
 400                                                   sector_sum->sum,
 401                                                   bvec->bv_len);
 402                 kunmap_atomic(data, KM_USER0);
 403                 btrfs_csum_final(sector_sum->sum,
 404                                  (char *)&sector_sum->sum);
 405                 sector_sum->bytenr = disk_bytenr;
 406
 407                 sector_sum++;
 408                 bio_index++;
 409                 total_bytes += bvec->bv_len;
 410                 this_sum_bytes += bvec->bv_len;
 411                 disk_bytenr += bvec->bv_len;
 412                 offset += bvec->bv_len;
 413                 bvec++;
 414         }
 415         this_sum_bytes = 0;
 416         btrfs_add_ordered_sum(inode, ordered, sums);
 417         btrfs_put_ordered_extent(ordered);
 418         return 0;
 419 }
 420
 421 /*
 422  * helper function for csum removal, this expects the
 423  * key to describe the csum pointed to by the path, and it expects
 424  * the csum to overlap the range [bytenr, len]
 425  *
 426  * The csum should not be entirely contained in the range and the
 427  * range should not be entirely contained in the csum.
 428  *
 429  * This calls btrfs_truncate_item with the correct args based on the
 430  * overlap, and fixes up the key as required.
 431  */
 432 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 433                                       struct btrfs_root *root,
 434                                       struct btrfs_path *path,
 435                                       struct btrfs_key *key,
 436                                       u64 bytenr, u64 len)
 437 {
 438         struct extent_buffer *leaf;
 439         u16 csum_size =
 440                 btrfs_super_csum_size(&root->fs_info->super_copy);
 441         u64 csum_end;
 442         u64 end_byte = bytenr + len;
 443         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 444         int ret;
 445
 446         leaf = path->nodes[0];
 447         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 448         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 449         csum_end += key->offset;
 450
 451         if (key->offset < bytenr && csum_end <= end_byte) {
 452                 /*
 453                  *         [ bytenr - len ]
 454                  *         [   ]
 455                  *   [csum     ]
 456                  *   A simple truncate off the end of the item
 457                  */
 458                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 459                 new_size *= csum_size;
 460                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 461                 BUG_ON(ret);
 462         } else if (key->offset >= bytenr && csum_end > end_byte &&
 463                    end_byte > key->offset) {
 464                 /*
 465                  *         [ bytenr - len ]
 466                  *                 [ ]
 467                  *                 [csum     ]
 468                  * we need to truncate from the beginning of the csum
 469                  */
 470                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 471                 new_size *= csum_size;
 472
 473                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 474                 BUG_ON(ret);
 475
 476                 key->offset = end_byte;
 477                 ret = btrfs_set_item_key_safe(trans, root, path, key);
 478                 BUG_ON(ret);
 479         } else {
 480                 BUG();
 481         }
 482         return 0;
 483 }
 484
 485 /*
 486  * deletes the csum items from the csum tree for a given
 487  * range of bytes.
 488  */
 489 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 490                     struct btrfs_root *root, u64 bytenr, u64 len)
 491 {
 492         struct btrfs_path *path;
 493         struct btrfs_key key;
 494         u64 end_byte = bytenr + len;
 495         u64 csum_end;
 496         struct extent_buffer *leaf;
 497         int ret;
 498         u16 csum_size =
 499                 btrfs_super_csum_size(&root->fs_info->super_copy);
 500         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 501
 502         root = root->fs_info->csum_root;
 503
 504         path = btrfs_alloc_path();
 505
 506         while(1) {
 507                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 508                 key.offset = end_byte - 1;
 509                 key.type = BTRFS_EXTENT_CSUM_KEY;
 510
 511                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 512                 if (ret > 0) {
 513                         if (path->slots[0] == 0)
 514                                 goto out;
 515                         path->slots[0]--;
 516                 }
 517                 leaf = path->nodes[0];
 518                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 519
 520                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 521                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 522                         break;
 523                 }
 524
 525                 if (key.offset >= end_byte)
 526                         break;
 527
 528                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 529                 csum_end <<= blocksize_bits;
 530                 csum_end += key.offset;
 531
 532                 /* this csum ends before we start, we're done */
 533                 if (csum_end <= bytenr)
 534                         break;
 535
 536                 /* delete the entire item, it is inside our range */
 537                 if (key.offset >= bytenr && csum_end <= end_byte) {
 538                         ret = btrfs_del_item(trans, root, path);
 539                         BUG_ON(ret);
 540                         if (key.offset == bytenr)
 541                                 break;
 542                 } else if (key.offset < bytenr && csum_end > end_byte) {
 543                         unsigned long offset;
 544                         unsigned long shift_len;
 545                         unsigned long item_offset;
 546                         /*
 547                          *        [ bytenr - len ]
 548                          *     [csum                ]
 549                          *
 550                          * Our bytes are in the middle of the csum,
 551                          * we need to split this item and insert a new one.
 552                          *
 553                          * But we can't drop the path because the
 554                          * csum could change, get removed, extended etc.
 555                          *
 556                          * The trick here is the max size of a csum item leaves
 557                          * enough room in the tree block for a single
 558                          * item header.  So, we split the item in place,
 559                          * adding a new header pointing to the existing
 560                          * bytes.  Then we loop around again and we have
 561                          * a nicely formed csum item that we can neatly
 562                          * truncate.
 563                          */
 564                         offset = (bytenr - key.offset) >> blocksize_bits;
 565                         offset *= csum_size;
 566
 567                         shift_len = (len >> blocksize_bits) * csum_size;
 568
 569                         item_offset = btrfs_item_ptr_offset(leaf,
 570                                                             path->slots[0]);
 571
 572                         memset_extent_buffer(leaf, 0, item_offset + offset,
 573                                              shift_len);
 574                         key.offset = bytenr;
 575
 576                         /*
 577                          * btrfs_split_item returns -EAGAIN when the
 578                          * item changed size or key
 579                          */
 580                         ret = btrfs_split_item(trans, root, path, &key, offset);
 581                         BUG_ON(ret && ret != -EAGAIN);
 582
 583                         key.offset = end_byte - 1;
 584                 } else {
 585                         ret = truncate_one_csum(trans, root, path,
 586                                                 &key, bytenr, len);
 587                         BUG_ON(ret);
 588                         if (key.offset < bytenr)
 589                                 break;
 590                 }
 591                 btrfs_release_path(root, path);
 592         }
 593 out:
 594         btrfs_free_path(path);
 595         return 0;
 596 }
 597
 598 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 599                            struct btrfs_root *root,
 600                            struct btrfs_ordered_sum *sums)
 601 {
 602         u64 bytenr;
 603         int ret;
 604         struct btrfs_key file_key;
 605         struct btrfs_key found_key;
 606         u64 next_offset;
 607         u64 total_bytes = 0;
 608         int found_next;
 609         struct btrfs_path *path;
 610         struct btrfs_csum_item *item;
 611         struct btrfs_csum_item *item_end;
 612         struct extent_buffer *leaf = NULL;
 613         u64 csum_offset;
 614         struct btrfs_sector_sum *sector_sum;
 615         u32 nritems;
 616         u32 ins_size;
 617         char *eb_map;
 618         char *eb_token;
 619         unsigned long map_len;
 620         unsigned long map_start;
 621         u16 csum_size =
 622                 btrfs_super_csum_size(&root->fs_info->super_copy);
 623
 624         path = btrfs_alloc_path();
 625         BUG_ON(!path);
 626         sector_sum = sums->sums;
 627 again:
 628         next_offset = (u64)-1;
 629         found_next = 0;
 630         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 631         file_key.offset = sector_sum->bytenr;
 632         bytenr = sector_sum->bytenr;
 633         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 634
 635         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 636         if (!IS_ERR(item)) {
 637                 leaf = path->nodes[0];
 638                 ret = 0;
 639                 goto found;
 640         }
 641         ret = PTR_ERR(item);
 642         if (ret == -EFBIG) {
 643                 u32 item_size;
 644                 /* we found one, but it isn't big enough yet */
 645                 leaf = path->nodes[0];
 646                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 647                 if ((item_size / csum_size) >=
 648                     MAX_CSUM_ITEMS(root, csum_size)) {
 649                         /* already at max size, make a new one */
 650                         goto insert;
 651                 }
 652         } else {
 653                 int slot = path->slots[0] + 1;
 654                 /* we didn't find a csum item, insert one */
 655                 nritems = btrfs_header_nritems(path->nodes[0]);
 656                 if (path->slots[0] >= nritems - 1) {
 657                         ret = btrfs_next_leaf(root, path);
 658                         if (ret == 1)
 659                                 found_next = 1;
 660                         if (ret != 0)
 661                                 goto insert;
 662                         slot = 0;
 663                 }
 664                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 665                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 666                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 667                         found_next = 1;
 668                         goto insert;
 669                 }
 670                 next_offset = found_key.offset;
 671                 found_next = 1;
 672                 goto insert;
 673         }
 674
 675         /*
 676          * at this point, we know the tree has an item, but it isn't big
 677          * enough yet to put our csum in.  Grow it
 678          */
 679         btrfs_release_path(root, path);
 680         ret = btrfs_search_slot(trans, root, &file_key, path,
 681                                 csum_size, 1);
 682         if (ret < 0)
 683                 goto fail_unlock;
 684
 685         if (ret > 0) {
 686                 if (path->slots[0] == 0)
 687                         goto insert;
 688                 path->slots[0]--;
 689         }
 690
 691         leaf = path->nodes[0];
 692         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 693         csum_offset = (bytenr - found_key.offset) >>
 694                         root->fs_info->sb->s_blocksize_bits;
 695
 696         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 697             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 698             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 699                 goto insert;
 700         }
 701
 702         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 703             csum_size) {
 704                 u32 diff = (csum_offset + 1) * csum_size;
 705
 706                 /*
 707                  * is the item big enough already?  we dropped our lock
 708                  * before and need to recheck
 709                  */
 710                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 711                         goto csum;
 712
 713                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 714                 if (diff != csum_size) {
 715                         goto insert;
 716                 }
 717
 718                 ret = btrfs_extend_item(trans, root, path, diff);
 719                 BUG_ON(ret);
 720                 goto csum;
 721         }
 722
 723 insert:
 724         btrfs_release_path(root, path);
 725         csum_offset = 0;
 726         if (found_next) {
 727                 u64 tmp = total_bytes + root->sectorsize;
 728                 u64 next_sector = sector_sum->bytenr;
 729                 struct btrfs_sector_sum *next = sector_sum + 1;
 730
 731                 while(tmp < sums->len) {
 732                         if (next_sector + root->sectorsize != next->bytenr)
 733                                 break;
 734                         tmp += root->sectorsize;
 735                         next_sector = next->bytenr;
 736                         next++;
 737                 }
 738                 tmp = min(tmp, next_offset - file_key.offset);
 739                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 740                 tmp = max((u64)1, tmp);
 741                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 742                 ins_size = csum_size * tmp;
 743         } else {
 744                 ins_size = csum_size;
 745         }
 746         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 747                                       ins_size);
 748         if (ret < 0)
 749                 goto fail_unlock;
 750         if (ret != 0) {
 751                 WARN_ON(1);
 752                 goto fail_unlock;
 753         }
 754 csum:
 755         leaf = path->nodes[0];
 756         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 757         ret = 0;
 758         item = (struct btrfs_csum_item *)((unsigned char *)item +
 759                                           csum_offset * csum_size);
 760 found:
 761         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 762         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 763                                       btrfs_item_size_nr(leaf, path->slots[0]));
 764         eb_token = NULL;
 765         cond_resched();
 766 next_sector:
 767
 768         if (!eb_token ||
 769            (unsigned long)item + csum_size >= map_start + map_len) {
 770                 int err;
 771
 772                 if (eb_token)
 773                         unmap_extent_buffer(leaf, eb_token, KM_USER1);
 774                 eb_token = NULL;
 775                 err = map_private_extent_buffer(leaf, (unsigned long)item,
 776                                                 csum_size,
 777                                                 &eb_token, &eb_map,
 778                                                 &map_start, &map_len, KM_USER1);
 779                 if (err)
 780                         eb_token = NULL;
 781         }
 782         if (eb_token) {
 783                 memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
 784                        &sector_sum->sum, csum_size);
 785         } else {
 786                 write_extent_buffer(leaf, &sector_sum->sum,
 787                                     (unsigned long)item, csum_size);
 788         }
 789
 790         total_bytes += root->sectorsize;
 791         sector_sum++;
 792         if (total_bytes < sums->len) {
 793                 item = (struct btrfs_csum_item *)((char *)item +
 794                                                   csum_size);
 795                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 796                     sector_sum->bytenr) {
 797                         bytenr = sector_sum->bytenr;
 798                         goto next_sector;
 799                 }
 800         }
 801         if (eb_token) {
 802                 unmap_extent_buffer(leaf, eb_token, KM_USER1);
 803                 eb_token = NULL;
 804         }
 805         btrfs_mark_buffer_dirty(path->nodes[0]);
 806         cond_resched();
 807         if (total_bytes < sums->len) {
 808                 btrfs_release_path(root, path);
 809                 goto again;
 810         }
 811 out:
 812         btrfs_free_path(path);
 813         return ret;
 814
 815 fail_unlock:
 816         goto out;
 817 }