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/slab.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/highmem.h>
  23 #include "ctree.h"
  24 #include "disk-io.h"
  25 #include "transaction.h"
  26 #include "print-tree.h"
  27
  28 #define __MAX_CSUM_ITEMS(r, size) ((unsigned long)(((BTRFS_LEAF_DATA_SIZE(r) - \
  29                                    sizeof(struct btrfs_item) * 2) / \
  30                                   size) - 1))
  31
  32 #define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
  33                                        PAGE_CACHE_SIZE))
  34
  35 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
  36                                    sizeof(struct btrfs_ordered_sum)) / \
  37                                    sizeof(struct btrfs_sector_sum) * \
  38                                    (r)->sectorsize - (r)->sectorsize)
  39
  40 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
  41                              struct btrfs_root *root,
  42                              u64 objectid, u64 pos,
  43                              u64 disk_offset, u64 disk_num_bytes,
  44                              u64 num_bytes, u64 offset, u64 ram_bytes,
  45                              u8 compression, u8 encryption, u16 other_encoding)
  46 {
  47         int ret = 0;
  48         struct btrfs_file_extent_item *item;
  49         struct btrfs_key file_key;
  50         struct btrfs_path *path;
  51         struct extent_buffer *leaf;
  52
  53         path = btrfs_alloc_path();
  54         if (!path)
  55                 return -ENOMEM;
  56         file_key.objectid = objectid;
  57         file_key.offset = pos;
  58         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
  59
  60         path->leave_spinning = 1;
  61         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  62                                       sizeof(*item));
  63         if (ret < 0)
  64                 goto out;
  65         BUG_ON(ret); /* Can't happen */
  66         leaf = path->nodes[0];
  67         item = btrfs_item_ptr(leaf, path->slots[0],
  68                               struct btrfs_file_extent_item);
  69         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
  70         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
  71         btrfs_set_file_extent_offset(leaf, item, offset);
  72         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
  73         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
  74         btrfs_set_file_extent_generation(leaf, item, trans->transid);
  75         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
  76         btrfs_set_file_extent_compression(leaf, item, compression);
  77         btrfs_set_file_extent_encryption(leaf, item, encryption);
  78         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
  79
  80         btrfs_mark_buffer_dirty(leaf);
  81 out:
  82         btrfs_free_path(path);
  83         return ret;
  84 }
  85
  86 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  87                                           struct btrfs_root *root,
  88                                           struct btrfs_path *path,
  89                                           u64 bytenr, int cow)
  90 {
  91         int ret;
  92         struct btrfs_key file_key;
  93         struct btrfs_key found_key;
  94         struct btrfs_csum_item *item;
  95         struct extent_buffer *leaf;
  96         u64 csum_offset = 0;
  97         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
  98         int csums_in_item;
  99
 100         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 101         file_key.offset = bytenr;
 102         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 103         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 104         if (ret < 0)
 105                 goto fail;
 106         leaf = path->nodes[0];
 107         if (ret > 0) {
 108                 ret = 1;
 109                 if (path->slots[0] == 0)
 110                         goto fail;
 111                 path->slots[0]--;
 112                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 113                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 114                         goto fail;
 115
 116                 csum_offset = (bytenr - found_key.offset) >>
 117                                 root->fs_info->sb->s_blocksize_bits;
 118                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 119                 csums_in_item /= csum_size;
 120
 121                 if (csum_offset >= csums_in_item) {
 122                         ret = -EFBIG;
 123                         goto fail;
 124                 }
 125         }
 126         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 127         item = (struct btrfs_csum_item *)((unsigned char *)item +
 128                                           csum_offset * csum_size);
 129         return item;
 130 fail:
 131         if (ret > 0)
 132                 ret = -ENOENT;
 133         return ERR_PTR(ret);
 134 }
 135
 136
 137 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 138                              struct btrfs_root *root,
 139                              struct btrfs_path *path, u64 objectid,
 140                              u64 offset, int mod)
 141 {
 142         int ret;
 143         struct btrfs_key file_key;
 144         int ins_len = mod < 0 ? -1 : 0;
 145         int cow = mod != 0;
 146
 147         file_key.objectid = objectid;
 148         file_key.offset = offset;
 149         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 150         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 151         return ret;
 152 }
 153
 154
 155 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 156                                    struct inode *inode, struct bio *bio,
 157                                    u64 logical_offset, u32 *dst, int dio)
 158 {
 159         u32 sum;
 160         struct bio_vec *bvec = bio->bi_io_vec;
 161         int bio_index = 0;
 162         u64 offset = 0;
 163         u64 item_start_offset = 0;
 164         u64 item_last_offset = 0;
 165         u64 disk_bytenr;
 166         u32 diff;
 167         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 168         int ret;
 169         struct btrfs_path *path;
 170         struct btrfs_csum_item *item = NULL;
 171         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 172
 173         path = btrfs_alloc_path();
 174         if (!path)
 175                 return -ENOMEM;
 176         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 177                 path->reada = 2;
 178
 179         WARN_ON(bio->bi_vcnt <= 0);
 180
 181         /*
 182          * the free space stuff is only read when it hasn't been
 183          * updated in the current transaction.  So, we can safely
 184          * read from the commit root and sidestep a nasty deadlock
 185          * between reading the free space cache and updating the csum tree.
 186          */
 187         if (btrfs_is_free_space_inode(inode)) {
 188                 path->search_commit_root = 1;
 189                 path->skip_locking = 1;
 190         }
 191
 192         disk_bytenr = (u64)bio->bi_sector << 9;
 193         if (dio)
 194                 offset = logical_offset;
 195         while (bio_index < bio->bi_vcnt) {
 196                 if (!dio)
 197                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 198                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 199                 if (ret == 0)
 200                         goto found;
 201
 202                 if (!item || disk_bytenr < item_start_offset ||
 203                     disk_bytenr >= item_last_offset) {
 204                         struct btrfs_key found_key;
 205                         u32 item_size;
 206
 207                         if (item)
 208                                 btrfs_release_path(path);
 209                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 210                                                  path, disk_bytenr, 0);
 211                         if (IS_ERR(item)) {
 212                                 ret = PTR_ERR(item);
 213                                 if (ret == -ENOENT || ret == -EFBIG)
 214                                         ret = 0;
 215                                 sum = 0;
 216                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 217                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 218                                         set_extent_bits(io_tree, offset,
 219                                                 offset + bvec->bv_len - 1,
 220                                                 EXTENT_NODATASUM, GFP_NOFS);
 221                                 } else {
 222                                         printk(KERN_INFO "btrfs no csum found "
 223                                                "for inode %llu start %llu\n",
 224                                                (unsigned long long)
 225                                                btrfs_ino(inode),
 226                                                (unsigned long long)offset);
 227                                 }
 228                                 item = NULL;
 229                                 btrfs_release_path(path);
 230                                 goto found;
 231                         }
 232                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 233                                               path->slots[0]);
 234
 235                         item_start_offset = found_key.offset;
 236                         item_size = btrfs_item_size_nr(path->nodes[0],
 237                                                        path->slots[0]);
 238                         item_last_offset = item_start_offset +
 239                                 (item_size / csum_size) *
 240                                 root->sectorsize;
 241                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 242                                               struct btrfs_csum_item);
 243                 }
 244                 /*
 245                  * this byte range must be able to fit inside
 246                  * a single leaf so it will also fit inside a u32
 247                  */
 248                 diff = disk_bytenr - item_start_offset;
 249                 diff = diff / root->sectorsize;
 250                 diff = diff * csum_size;
 251
 252                 read_extent_buffer(path->nodes[0], &sum,
 253                                    ((unsigned long)item) + diff,
 254                                    csum_size);
 255 found:
 256                 if (dst)
 257                         *dst++ = sum;
 258                 else
 259                         set_state_private(io_tree, offset, sum);
 260                 disk_bytenr += bvec->bv_len;
 261                 offset += bvec->bv_len;
 262                 bio_index++;
 263                 bvec++;
 264         }
 265         btrfs_free_path(path);
 266         return 0;
 267 }
 268
 269 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 270                           struct bio *bio, u32 *dst)
 271 {
 272         return __btrfs_lookup_bio_sums(root, inode, bio, 0, dst, 0);
 273 }
 274
 275 int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
 276                               struct bio *bio, u64 offset)
 277 {
 278         return __btrfs_lookup_bio_sums(root, inode, bio, offset, NULL, 1);
 279 }
 280
 281 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 282                              struct list_head *list, int search_commit)
 283 {
 284         struct btrfs_key key;
 285         struct btrfs_path *path;
 286         struct extent_buffer *leaf;
 287         struct btrfs_ordered_sum *sums;
 288         struct btrfs_sector_sum *sector_sum;
 289         struct btrfs_csum_item *item;
 290         LIST_HEAD(tmplist);
 291         unsigned long offset;
 292         int ret;
 293         size_t size;
 294         u64 csum_end;
 295         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 296
 297         path = btrfs_alloc_path();
 298         if (!path)
 299                 return -ENOMEM;
 300
 301         if (search_commit) {
 302                 path->skip_locking = 1;
 303                 path->reada = 2;
 304                 path->search_commit_root = 1;
 305         }
 306
 307         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 308         key.offset = start;
 309         key.type = BTRFS_EXTENT_CSUM_KEY;
 310
 311         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 312         if (ret < 0)
 313                 goto fail;
 314         if (ret > 0 && path->slots[0] > 0) {
 315                 leaf = path->nodes[0];
 316                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 317                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 318                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 319                         offset = (start - key.offset) >>
 320                                  root->fs_info->sb->s_blocksize_bits;
 321                         if (offset * csum_size <
 322                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 323                                 path->slots[0]--;
 324                 }
 325         }
 326
 327         while (start <= end) {
 328                 leaf = path->nodes[0];
 329                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 330                         ret = btrfs_next_leaf(root, path);
 331                         if (ret < 0)
 332                                 goto fail;
 333                         if (ret > 0)
 334                                 break;
 335                         leaf = path->nodes[0];
 336                 }
 337
 338                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 339                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 340                     key.type != BTRFS_EXTENT_CSUM_KEY)
 341                         break;
 342
 343                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 344                 if (key.offset > end)
 345                         break;
 346
 347                 if (key.offset > start)
 348                         start = key.offset;
 349
 350                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 351                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 352                 if (csum_end <= start) {
 353                         path->slots[0]++;
 354                         continue;
 355                 }
 356
 357                 csum_end = min(csum_end, end + 1);
 358                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 359                                       struct btrfs_csum_item);
 360                 while (start < csum_end) {
 361                         size = min_t(size_t, csum_end - start,
 362                                         MAX_ORDERED_SUM_BYTES(root));
 363                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 364                                         GFP_NOFS);
 365                         if (!sums) {
 366                                 ret = -ENOMEM;
 367                                 goto fail;
 368                         }
 369
 370                         sector_sum = sums->sums;
 371                         sums->bytenr = start;
 372                         sums->len = size;
 373
 374                         offset = (start - key.offset) >>
 375                                 root->fs_info->sb->s_blocksize_bits;
 376                         offset *= csum_size;
 377
 378                         while (size > 0) {
 379                                 read_extent_buffer(path->nodes[0],
 380                                                 &sector_sum->sum,
 381                                                 ((unsigned long)item) +
 382                                                 offset, csum_size);
 383                                 sector_sum->bytenr = start;
 384
 385                                 size -= root->sectorsize;
 386                                 start += root->sectorsize;
 387                                 offset += csum_size;
 388                                 sector_sum++;
 389                         }
 390                         list_add_tail(&sums->list, &tmplist);
 391                 }
 392                 path->slots[0]++;
 393         }
 394         ret = 0;
 395 fail:
 396         while (ret < 0 && !list_empty(&tmplist)) {
 397                 sums = list_entry(&tmplist, struct btrfs_ordered_sum, list);
 398                 list_del(&sums->list);
 399                 kfree(sums);
 400         }
 401         list_splice_tail(&tmplist, list);
 402
 403         btrfs_free_path(path);
 404         return ret;
 405 }
 406
 407 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 408                        struct bio *bio, u64 file_start, int contig)
 409 {
 410         struct btrfs_ordered_sum *sums;
 411         struct btrfs_sector_sum *sector_sum;
 412         struct btrfs_ordered_extent *ordered;
 413         char *data;
 414         struct bio_vec *bvec = bio->bi_io_vec;
 415         int bio_index = 0;
 416         unsigned long total_bytes = 0;
 417         unsigned long this_sum_bytes = 0;
 418         u64 offset;
 419         u64 disk_bytenr;
 420
 421         WARN_ON(bio->bi_vcnt <= 0);
 422         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 423         if (!sums)
 424                 return -ENOMEM;
 425
 426         sector_sum = sums->sums;
 427         disk_bytenr = (u64)bio->bi_sector << 9;
 428         sums->len = bio->bi_size;
 429         INIT_LIST_HEAD(&sums->list);
 430
 431         if (contig)
 432                 offset = file_start;
 433         else
 434                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 435
 436         ordered = btrfs_lookup_ordered_extent(inode, offset);
 437         BUG_ON(!ordered); /* Logic error */
 438         sums->bytenr = ordered->start;
 439
 440         while (bio_index < bio->bi_vcnt) {
 441                 if (!contig)
 442                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 443
 444                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 445                     offset < ordered->file_offset)) {
 446                         unsigned long bytes_left;
 447                         sums->len = this_sum_bytes;
 448                         this_sum_bytes = 0;
 449                         btrfs_add_ordered_sum(inode, ordered, sums);
 450                         btrfs_put_ordered_extent(ordered);
 451
 452                         bytes_left = bio->bi_size - total_bytes;
 453
 454                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 455                                        GFP_NOFS);
 456                         BUG_ON(!sums); /* -ENOMEM */
 457                         sector_sum = sums->sums;
 458                         sums->len = bytes_left;
 459                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 460                         BUG_ON(!ordered); /* Logic error */
 461                         sums->bytenr = ordered->start;
 462                 }
 463
 464                 data = kmap_atomic(bvec->bv_page);
 465                 sector_sum->sum = ~(u32)0;
 466                 sector_sum->sum = btrfs_csum_data(root,
 467                                                   data + bvec->bv_offset,
 468                                                   sector_sum->sum,
 469                                                   bvec->bv_len);
 470                 kunmap_atomic(data);
 471                 btrfs_csum_final(sector_sum->sum,
 472                                  (char *)&sector_sum->sum);
 473                 sector_sum->bytenr = disk_bytenr;
 474
 475                 sector_sum++;
 476                 bio_index++;
 477                 total_bytes += bvec->bv_len;
 478                 this_sum_bytes += bvec->bv_len;
 479                 disk_bytenr += bvec->bv_len;
 480                 offset += bvec->bv_len;
 481                 bvec++;
 482         }
 483         this_sum_bytes = 0;
 484         btrfs_add_ordered_sum(inode, ordered, sums);
 485         btrfs_put_ordered_extent(ordered);
 486         return 0;
 487 }
 488
 489 /*
 490  * helper function for csum removal, this expects the
 491  * key to describe the csum pointed to by the path, and it expects
 492  * the csum to overlap the range [bytenr, len]
 493  *
 494  * The csum should not be entirely contained in the range and the
 495  * range should not be entirely contained in the csum.
 496  *
 497  * This calls btrfs_truncate_item with the correct args based on the
 498  * overlap, and fixes up the key as required.
 499  */
 500 static noinline void truncate_one_csum(struct btrfs_trans_handle *trans,
 501                                        struct btrfs_root *root,
 502                                        struct btrfs_path *path,
 503                                        struct btrfs_key *key,
 504                                        u64 bytenr, u64 len)
 505 {
 506         struct extent_buffer *leaf;
 507         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 508         u64 csum_end;
 509         u64 end_byte = bytenr + len;
 510         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 511
 512         leaf = path->nodes[0];
 513         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 514         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 515         csum_end += key->offset;
 516
 517         if (key->offset < bytenr && csum_end <= end_byte) {
 518                 /*
 519                  *         [ bytenr - len ]
 520                  *         [   ]
 521                  *   [csum     ]
 522                  *   A simple truncate off the end of the item
 523                  */
 524                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 525                 new_size *= csum_size;
 526                 btrfs_truncate_item(trans, root, path, new_size, 1);
 527         } else if (key->offset >= bytenr && csum_end > end_byte &&
 528                    end_byte > key->offset) {
 529                 /*
 530                  *         [ bytenr - len ]
 531                  *                 [ ]
 532                  *                 [csum     ]
 533                  * we need to truncate from the beginning of the csum
 534                  */
 535                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 536                 new_size *= csum_size;
 537
 538                 btrfs_truncate_item(trans, root, path, new_size, 0);
 539
 540                 key->offset = end_byte;
 541                 btrfs_set_item_key_safe(trans, root, path, key);
 542         } else {
 543                 BUG();
 544         }
 545 }
 546
 547 /*
 548  * deletes the csum items from the csum tree for a given
 549  * range of bytes.
 550  */
 551 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 552                     struct btrfs_root *root, u64 bytenr, u64 len)
 553 {
 554         struct btrfs_path *path;
 555         struct btrfs_key key;
 556         u64 end_byte = bytenr + len;
 557         u64 csum_end;
 558         struct extent_buffer *leaf;
 559         int ret;
 560         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 561         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 562
 563         root = root->fs_info->csum_root;
 564
 565         path = btrfs_alloc_path();
 566         if (!path)
 567                 return -ENOMEM;
 568
 569         while (1) {
 570                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 571                 key.offset = end_byte - 1;
 572                 key.type = BTRFS_EXTENT_CSUM_KEY;
 573
 574                 path->leave_spinning = 1;
 575                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 576                 if (ret > 0) {
 577                         if (path->slots[0] == 0)
 578                                 break;
 579                         path->slots[0]--;
 580                 } else if (ret < 0) {
 581                         break;
 582                 }
 583
 584                 leaf = path->nodes[0];
 585                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 586
 587                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 588                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 589                         break;
 590                 }
 591
 592                 if (key.offset >= end_byte)
 593                         break;
 594
 595                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 596                 csum_end <<= blocksize_bits;
 597                 csum_end += key.offset;
 598
 599                 /* this csum ends before we start, we're done */
 600                 if (csum_end <= bytenr)
 601                         break;
 602
 603                 /* delete the entire item, it is inside our range */
 604                 if (key.offset >= bytenr && csum_end <= end_byte) {
 605                         ret = btrfs_del_item(trans, root, path);
 606                         if (ret)
 607                                 goto out;
 608                         if (key.offset == bytenr)
 609                                 break;
 610                 } else if (key.offset < bytenr && csum_end > end_byte) {
 611                         unsigned long offset;
 612                         unsigned long shift_len;
 613                         unsigned long item_offset;
 614                         /*
 615                          *        [ bytenr - len ]
 616                          *     [csum                ]
 617                          *
 618                          * Our bytes are in the middle of the csum,
 619                          * we need to split this item and insert a new one.
 620                          *
 621                          * But we can't drop the path because the
 622                          * csum could change, get removed, extended etc.
 623                          *
 624                          * The trick here is the max size of a csum item leaves
 625                          * enough room in the tree block for a single
 626                          * item header.  So, we split the item in place,
 627                          * adding a new header pointing to the existing
 628                          * bytes.  Then we loop around again and we have
 629                          * a nicely formed csum item that we can neatly
 630                          * truncate.
 631                          */
 632                         offset = (bytenr - key.offset) >> blocksize_bits;
 633                         offset *= csum_size;
 634
 635                         shift_len = (len >> blocksize_bits) * csum_size;
 636
 637                         item_offset = btrfs_item_ptr_offset(leaf,
 638                                                             path->slots[0]);
 639
 640                         memset_extent_buffer(leaf, 0, item_offset + offset,
 641                                              shift_len);
 642                         key.offset = bytenr;
 643
 644                         /*
 645                          * btrfs_split_item returns -EAGAIN when the
 646                          * item changed size or key
 647                          */
 648                         ret = btrfs_split_item(trans, root, path, &key, offset);
 649                         if (ret && ret != -EAGAIN) {
 650                                 btrfs_abort_transaction(trans, root, ret);
 651                                 goto out;
 652                         }
 653
 654                         key.offset = end_byte - 1;
 655                 } else {
 656                         truncate_one_csum(trans, root, path, &key, bytenr, len);
 657                         if (key.offset < bytenr)
 658                                 break;
 659                 }
 660                 btrfs_release_path(path);
 661         }
 662         ret = 0;
 663 out:
 664         btrfs_free_path(path);
 665         return ret;
 666 }
 667
 668 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 669                            struct btrfs_root *root,
 670                            struct btrfs_ordered_sum *sums)
 671 {
 672         u64 bytenr;
 673         int ret;
 674         struct btrfs_key file_key;
 675         struct btrfs_key found_key;
 676         u64 next_offset;
 677         u64 total_bytes = 0;
 678         int found_next;
 679         struct btrfs_path *path;
 680         struct btrfs_csum_item *item;
 681         struct btrfs_csum_item *item_end;
 682         struct extent_buffer *leaf = NULL;
 683         u64 csum_offset;
 684         struct btrfs_sector_sum *sector_sum;
 685         u32 nritems;
 686         u32 ins_size;
 687         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 688
 689         path = btrfs_alloc_path();
 690         if (!path)
 691                 return -ENOMEM;
 692
 693         sector_sum = sums->sums;
 694         trans->adding_csums = 1;
 695 again:
 696         next_offset = (u64)-1;
 697         found_next = 0;
 698         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 699         file_key.offset = sector_sum->bytenr;
 700         bytenr = sector_sum->bytenr;
 701         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 702
 703         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 704         if (!IS_ERR(item)) {
 705                 leaf = path->nodes[0];
 706                 ret = 0;
 707                 goto found;
 708         }
 709         ret = PTR_ERR(item);
 710         if (ret != -EFBIG && ret != -ENOENT)
 711                 goto fail_unlock;
 712
 713         if (ret == -EFBIG) {
 714                 u32 item_size;
 715                 /* we found one, but it isn't big enough yet */
 716                 leaf = path->nodes[0];
 717                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 718                 if ((item_size / csum_size) >=
 719                     MAX_CSUM_ITEMS(root, csum_size)) {
 720                         /* already at max size, make a new one */
 721                         goto insert;
 722                 }
 723         } else {
 724                 int slot = path->slots[0] + 1;
 725                 /* we didn't find a csum item, insert one */
 726                 nritems = btrfs_header_nritems(path->nodes[0]);
 727                 if (path->slots[0] >= nritems - 1) {
 728                         ret = btrfs_next_leaf(root, path);
 729                         if (ret == 1)
 730                                 found_next = 1;
 731                         if (ret != 0)
 732                                 goto insert;
 733                         slot = 0;
 734                 }
 735                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 736                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 737                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 738                         found_next = 1;
 739                         goto insert;
 740                 }
 741                 next_offset = found_key.offset;
 742                 found_next = 1;
 743                 goto insert;
 744         }
 745
 746         /*
 747          * at this point, we know the tree has an item, but it isn't big
 748          * enough yet to put our csum in.  Grow it
 749          */
 750         btrfs_release_path(path);
 751         ret = btrfs_search_slot(trans, root, &file_key, path,
 752                                 csum_size, 1);
 753         if (ret < 0)
 754                 goto fail_unlock;
 755
 756         if (ret > 0) {
 757                 if (path->slots[0] == 0)
 758                         goto insert;
 759                 path->slots[0]--;
 760         }
 761
 762         leaf = path->nodes[0];
 763         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 764         csum_offset = (bytenr - found_key.offset) >>
 765                         root->fs_info->sb->s_blocksize_bits;
 766
 767         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 768             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 769             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 770                 goto insert;
 771         }
 772
 773         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 774             csum_size) {
 775                 u32 diff = (csum_offset + 1) * csum_size;
 776
 777                 /*
 778                  * is the item big enough already?  we dropped our lock
 779                  * before and need to recheck
 780                  */
 781                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 782                         goto csum;
 783
 784                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 785                 if (diff != csum_size)
 786                         goto insert;
 787
 788                 btrfs_extend_item(trans, root, path, diff);
 789                 goto csum;
 790         }
 791
 792 insert:
 793         btrfs_release_path(path);
 794         csum_offset = 0;
 795         if (found_next) {
 796                 u64 tmp = total_bytes + root->sectorsize;
 797                 u64 next_sector = sector_sum->bytenr;
 798                 struct btrfs_sector_sum *next = sector_sum + 1;
 799
 800                 while (tmp < sums->len) {
 801                         if (next_sector + root->sectorsize != next->bytenr)
 802                                 break;
 803                         tmp += root->sectorsize;
 804                         next_sector = next->bytenr;
 805                         next++;
 806                 }
 807                 tmp = min(tmp, next_offset - file_key.offset);
 808                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 809                 tmp = max((u64)1, tmp);
 810                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 811                 ins_size = csum_size * tmp;
 812         } else {
 813                 ins_size = csum_size;
 814         }
 815         path->leave_spinning = 1;
 816         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 817                                       ins_size);
 818         path->leave_spinning = 0;
 819         if (ret < 0)
 820                 goto fail_unlock;
 821         if (ret != 0) {
 822                 WARN_ON(1);
 823                 goto fail_unlock;
 824         }
 825 csum:
 826         leaf = path->nodes[0];
 827         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 828         ret = 0;
 829         item = (struct btrfs_csum_item *)((unsigned char *)item +
 830                                           csum_offset * csum_size);
 831 found:
 832         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 833         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 834                                       btrfs_item_size_nr(leaf, path->slots[0]));
 835 next_sector:
 836
 837         write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item, csum_size);
 838
 839         total_bytes += root->sectorsize;
 840         sector_sum++;
 841         if (total_bytes < sums->len) {
 842                 item = (struct btrfs_csum_item *)((char *)item +
 843                                                   csum_size);
 844                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 845                     sector_sum->bytenr) {
 846                         bytenr = sector_sum->bytenr;
 847                         goto next_sector;
 848                 }
 849         }
 850
 851         btrfs_mark_buffer_dirty(path->nodes[0]);
 852         if (total_bytes < sums->len) {
 853                 btrfs_release_path(path);
 854                 cond_resched();
 855                 goto again;
 856         }
 857 out:
 858         trans->adding_csums = 0;
 859         btrfs_free_path(path);
 860         return ret;
 861
 862 fail_unlock:
 863         goto out;
 864 }