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) ((((BTRFS_LEAF_DATA_SIZE(r) - \
  29                                    sizeof(struct btrfs_item) * 2) / \
  30                                   size) - 1))
  31
  32 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
  33                                    sizeof(struct btrfs_ordered_sum)) / \
  34                                    sizeof(struct btrfs_sector_sum) * \
  35                                    (r)->sectorsize - (r)->sectorsize)
  36
  37 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
  38                              struct btrfs_root *root,
  39                              u64 objectid, u64 pos,
  40                              u64 disk_offset, u64 disk_num_bytes,
  41                              u64 num_bytes, u64 offset, u64 ram_bytes,
  42                              u8 compression, u8 encryption, u16 other_encoding)
  43 {
  44         int ret = 0;
  45         struct btrfs_file_extent_item *item;
  46         struct btrfs_key file_key;
  47         struct btrfs_path *path;
  48         struct extent_buffer *leaf;
  49
  50         path = btrfs_alloc_path();
  51         if (!path)
  52                 return -ENOMEM;
  53         file_key.objectid = objectid;
  54         file_key.offset = pos;
  55         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
  56
  57         path->leave_spinning = 1;
  58         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  59                                       sizeof(*item));
  60         if (ret < 0)
  61                 goto out;
  62         BUG_ON(ret);
  63         leaf = path->nodes[0];
  64         item = btrfs_item_ptr(leaf, path->slots[0],
  65                               struct btrfs_file_extent_item);
  66         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
  67         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
  68         btrfs_set_file_extent_offset(leaf, item, offset);
  69         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
  70         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
  71         btrfs_set_file_extent_generation(leaf, item, trans->transid);
  72         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
  73         btrfs_set_file_extent_compression(leaf, item, compression);
  74         btrfs_set_file_extent_encryption(leaf, item, encryption);
  75         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
  76
  77         btrfs_mark_buffer_dirty(leaf);
  78 out:
  79         btrfs_free_path(path);
  80         return ret;
  81 }
  82
  83 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  84                                           struct btrfs_root *root,
  85                                           struct btrfs_path *path,
  86                                           u64 bytenr, int cow)
  87 {
  88         int ret;
  89         struct btrfs_key file_key;
  90         struct btrfs_key found_key;
  91         struct btrfs_csum_item *item;
  92         struct extent_buffer *leaf;
  93         u64 csum_offset = 0;
  94         u16 csum_size =
  95                 btrfs_super_csum_size(&root->fs_info->super_copy);
  96         int csums_in_item;
  97
  98         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  99         file_key.offset = bytenr;
 100         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 101         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 102         if (ret < 0)
 103                 goto fail;
 104         leaf = path->nodes[0];
 105         if (ret > 0) {
 106                 ret = 1;
 107                 if (path->slots[0] == 0)
 108                         goto fail;
 109                 path->slots[0]--;
 110                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 111                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 112                         goto fail;
 113
 114                 csum_offset = (bytenr - found_key.offset) >>
 115                                 root->fs_info->sb->s_blocksize_bits;
 116                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 117                 csums_in_item /= csum_size;
 118
 119                 if (csum_offset >= csums_in_item) {
 120                         ret = -EFBIG;
 121                         goto fail;
 122                 }
 123         }
 124         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 125         item = (struct btrfs_csum_item *)((unsigned char *)item +
 126                                           csum_offset * csum_size);
 127         return item;
 128 fail:
 129         if (ret > 0)
 130                 ret = -ENOENT;
 131         return ERR_PTR(ret);
 132 }
 133
 134
 135 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 136                              struct btrfs_root *root,
 137                              struct btrfs_path *path, u64 objectid,
 138                              u64 offset, int mod)
 139 {
 140         int ret;
 141         struct btrfs_key file_key;
 142         int ins_len = mod < 0 ? -1 : 0;
 143         int cow = mod != 0;
 144
 145         file_key.objectid = objectid;
 146         file_key.offset = offset;
 147         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 148         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 149         return ret;
 150 }
 151
 152
 153 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 154                                    struct inode *inode, struct bio *bio,
 155                                    u64 logical_offset, u32 *dst, int dio)
 156 {
 157         u32 sum;
 158         struct bio_vec *bvec = bio->bi_io_vec;
 159         int bio_index = 0;
 160         u64 offset = 0;
 161         u64 item_start_offset = 0;
 162         u64 item_last_offset = 0;
 163         u64 disk_bytenr;
 164         u32 diff;
 165         u16 csum_size =
 166                 btrfs_super_csum_size(&root->fs_info->super_copy);
 167         int ret;
 168         struct btrfs_path *path;
 169         struct btrfs_csum_item *item = NULL;
 170         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 171
 172         path = btrfs_alloc_path();
 173         if (!path)
 174                 return -ENOMEM;
 175         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 176                 path->reada = 2;
 177
 178         WARN_ON(bio->bi_vcnt <= 0);
 179
 180         /*
 181          * the free space stuff is only read when it hasn't been
 182          * updated in the current transaction.  So, we can safely
 183          * read from the commit root and sidestep a nasty deadlock
 184          * between reading the free space cache and updating the csum tree.
 185          */
 186         if (btrfs_is_free_space_inode(root, inode)) {
 187                 path->search_commit_root = 1;
 188                 path->skip_locking = 1;
 189         }
 190
 191         disk_bytenr = (u64)bio->bi_sector << 9;
 192         if (dio)
 193                 offset = logical_offset;
 194         while (bio_index < bio->bi_vcnt) {
 195                 if (!dio)
 196                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 197                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 198                 if (ret == 0)
 199                         goto found;
 200
 201                 if (!item || disk_bytenr < item_start_offset ||
 202                     disk_bytenr >= item_last_offset) {
 203                         struct btrfs_key found_key;
 204                         u32 item_size;
 205
 206                         if (item)
 207                                 btrfs_release_path(path);
 208                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 209                                                  path, disk_bytenr, 0);
 210                         if (IS_ERR(item)) {
 211                                 ret = PTR_ERR(item);
 212                                 if (ret == -ENOENT || ret == -EFBIG)
 213                                         ret = 0;
 214                                 sum = 0;
 215                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 216                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 217                                         set_extent_bits(io_tree, offset,
 218                                                 offset + bvec->bv_len - 1,
 219                                                 EXTENT_NODATASUM, GFP_NOFS);
 220                                 } else {
 221                                         printk(KERN_INFO "btrfs no csum found "
 222                                                "for inode %llu start %llu\n",
 223                                                (unsigned long long)
 224                                                btrfs_ino(inode),
 225                                                (unsigned long long)offset);
 226                                 }
 227                                 item = NULL;
 228                                 btrfs_release_path(path);
 229                                 goto found;
 230                         }
 231                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 232                                               path->slots[0]);
 233
 234                         item_start_offset = found_key.offset;
 235                         item_size = btrfs_item_size_nr(path->nodes[0],
 236                                                        path->slots[0]);
 237                         item_last_offset = item_start_offset +
 238                                 (item_size / csum_size) *
 239                                 root->sectorsize;
 240                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 241                                               struct btrfs_csum_item);
 242                 }
 243                 /*
 244                  * this byte range must be able to fit inside
 245                  * a single leaf so it will also fit inside a u32
 246                  */
 247                 diff = disk_bytenr - item_start_offset;
 248                 diff = diff / root->sectorsize;
 249                 diff = diff * csum_size;
 250
 251                 read_extent_buffer(path->nodes[0], &sum,
 252                                    ((unsigned long)item) + diff,
 253                                    csum_size);
 254 found:
 255                 if (dst)
 256                         *dst++ = sum;
 257                 else
 258                         set_state_private(io_tree, offset, sum);
 259                 disk_bytenr += bvec->bv_len;
 260                 offset += bvec->bv_len;
 261                 bio_index++;
 262                 bvec++;
 263         }
 264         btrfs_free_path(path);
 265         return 0;
 266 }
 267
 268 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 269                           struct bio *bio, u32 *dst)
 270 {
 271         return __btrfs_lookup_bio_sums(root, inode, bio, 0, dst, 0);
 272 }
 273
 274 int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
 275                               struct bio *bio, u64 offset, u32 *dst)
 276 {
 277         return __btrfs_lookup_bio_sums(root, inode, bio, offset, dst, 1);
 278 }
 279
 280 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 281                              struct list_head *list, int search_commit)
 282 {
 283         struct btrfs_key key;
 284         struct btrfs_path *path;
 285         struct extent_buffer *leaf;
 286         struct btrfs_ordered_sum *sums;
 287         struct btrfs_sector_sum *sector_sum;
 288         struct btrfs_csum_item *item;
 289         unsigned long offset;
 290         int ret;
 291         size_t size;
 292         u64 csum_end;
 293         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
 294
 295         path = btrfs_alloc_path();
 296         if (!path)
 297                 return -ENOMEM;
 298
 299         if (search_commit) {
 300                 path->skip_locking = 1;
 301                 path->reada = 2;
 302                 path->search_commit_root = 1;
 303         }
 304
 305         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 306         key.offset = start;
 307         key.type = BTRFS_EXTENT_CSUM_KEY;
 308
 309         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 310         if (ret < 0)
 311                 goto fail;
 312         if (ret > 0 && path->slots[0] > 0) {
 313                 leaf = path->nodes[0];
 314                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 315                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 316                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 317                         offset = (start - key.offset) >>
 318                                  root->fs_info->sb->s_blocksize_bits;
 319                         if (offset * csum_size <
 320                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 321                                 path->slots[0]--;
 322                 }
 323         }
 324
 325         while (start <= end) {
 326                 leaf = path->nodes[0];
 327                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 328                         ret = btrfs_next_leaf(root, path);
 329                         if (ret < 0)
 330                                 goto fail;
 331                         if (ret > 0)
 332                                 break;
 333                         leaf = path->nodes[0];
 334                 }
 335
 336                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 337                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 338                     key.type != BTRFS_EXTENT_CSUM_KEY)
 339                         break;
 340
 341                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 342                 if (key.offset > end)
 343                         break;
 344
 345                 if (key.offset > start)
 346                         start = key.offset;
 347
 348                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 349                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 350                 if (csum_end <= start) {
 351                         path->slots[0]++;
 352                         continue;
 353                 }
 354
 355                 csum_end = min(csum_end, end + 1);
 356                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 357                                       struct btrfs_csum_item);
 358                 while (start < csum_end) {
 359                         size = min_t(size_t, csum_end - start,
 360                                         MAX_ORDERED_SUM_BYTES(root));
 361                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 362                                         GFP_NOFS);
 363                         BUG_ON(!sums);
 364
 365                         sector_sum = sums->sums;
 366                         sums->bytenr = start;
 367                         sums->len = size;
 368
 369                         offset = (start - key.offset) >>
 370                                 root->fs_info->sb->s_blocksize_bits;
 371                         offset *= csum_size;
 372
 373                         while (size > 0) {
 374                                 read_extent_buffer(path->nodes[0],
 375                                                 &sector_sum->sum,
 376                                                 ((unsigned long)item) +
 377                                                 offset, csum_size);
 378                                 sector_sum->bytenr = start;
 379
 380                                 size -= root->sectorsize;
 381                                 start += root->sectorsize;
 382                                 offset += csum_size;
 383                                 sector_sum++;
 384                         }
 385                         list_add_tail(&sums->list, list);
 386                 }
 387                 path->slots[0]++;
 388         }
 389         ret = 0;
 390 fail:
 391         btrfs_free_path(path);
 392         return ret;
 393 }
 394
 395 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 396                        struct bio *bio, u64 file_start, int contig)
 397 {
 398         struct btrfs_ordered_sum *sums;
 399         struct btrfs_sector_sum *sector_sum;
 400         struct btrfs_ordered_extent *ordered;
 401         char *data;
 402         struct bio_vec *bvec = bio->bi_io_vec;
 403         int bio_index = 0;
 404         unsigned long total_bytes = 0;
 405         unsigned long this_sum_bytes = 0;
 406         u64 offset;
 407         u64 disk_bytenr;
 408
 409         WARN_ON(bio->bi_vcnt <= 0);
 410         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 411         if (!sums)
 412                 return -ENOMEM;
 413
 414         sector_sum = sums->sums;
 415         disk_bytenr = (u64)bio->bi_sector << 9;
 416         sums->len = bio->bi_size;
 417         INIT_LIST_HEAD(&sums->list);
 418
 419         if (contig)
 420                 offset = file_start;
 421         else
 422                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 423
 424         ordered = btrfs_lookup_ordered_extent(inode, offset);
 425         BUG_ON(!ordered);
 426         sums->bytenr = ordered->start;
 427
 428         while (bio_index < bio->bi_vcnt) {
 429                 if (!contig)
 430                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 431
 432                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 433                     offset < ordered->file_offset)) {
 434                         unsigned long bytes_left;
 435                         sums->len = this_sum_bytes;
 436                         this_sum_bytes = 0;
 437                         btrfs_add_ordered_sum(inode, ordered, sums);
 438                         btrfs_put_ordered_extent(ordered);
 439
 440                         bytes_left = bio->bi_size - total_bytes;
 441
 442                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 443                                        GFP_NOFS);
 444                         BUG_ON(!sums);
 445                         sector_sum = sums->sums;
 446                         sums->len = bytes_left;
 447                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 448                         BUG_ON(!ordered);
 449                         sums->bytenr = ordered->start;
 450                 }
 451
 452                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 453                 sector_sum->sum = ~(u32)0;
 454                 sector_sum->sum = btrfs_csum_data(root,
 455                                                   data + bvec->bv_offset,
 456                                                   sector_sum->sum,
 457                                                   bvec->bv_len);
 458                 kunmap_atomic(data, KM_USER0);
 459                 btrfs_csum_final(sector_sum->sum,
 460                                  (char *)&sector_sum->sum);
 461                 sector_sum->bytenr = disk_bytenr;
 462
 463                 sector_sum++;
 464                 bio_index++;
 465                 total_bytes += bvec->bv_len;
 466                 this_sum_bytes += bvec->bv_len;
 467                 disk_bytenr += bvec->bv_len;
 468                 offset += bvec->bv_len;
 469                 bvec++;
 470         }
 471         this_sum_bytes = 0;
 472         btrfs_add_ordered_sum(inode, ordered, sums);
 473         btrfs_put_ordered_extent(ordered);
 474         return 0;
 475 }
 476
 477 /*
 478  * helper function for csum removal, this expects the
 479  * key to describe the csum pointed to by the path, and it expects
 480  * the csum to overlap the range [bytenr, len]
 481  *
 482  * The csum should not be entirely contained in the range and the
 483  * range should not be entirely contained in the csum.
 484  *
 485  * This calls btrfs_truncate_item with the correct args based on the
 486  * overlap, and fixes up the key as required.
 487  */
 488 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 489                                       struct btrfs_root *root,
 490                                       struct btrfs_path *path,
 491                                       struct btrfs_key *key,
 492                                       u64 bytenr, u64 len)
 493 {
 494         struct extent_buffer *leaf;
 495         u16 csum_size =
 496                 btrfs_super_csum_size(&root->fs_info->super_copy);
 497         u64 csum_end;
 498         u64 end_byte = bytenr + len;
 499         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 500         int ret;
 501
 502         leaf = path->nodes[0];
 503         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 504         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 505         csum_end += key->offset;
 506
 507         if (key->offset < bytenr && csum_end <= end_byte) {
 508                 /*
 509                  *         [ bytenr - len ]
 510                  *         [   ]
 511                  *   [csum     ]
 512                  *   A simple truncate off the end of the item
 513                  */
 514                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 515                 new_size *= csum_size;
 516                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 517         } else if (key->offset >= bytenr && csum_end > end_byte &&
 518                    end_byte > key->offset) {
 519                 /*
 520                  *         [ bytenr - len ]
 521                  *                 [ ]
 522                  *                 [csum     ]
 523                  * we need to truncate from the beginning of the csum
 524                  */
 525                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 526                 new_size *= csum_size;
 527
 528                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 529
 530                 key->offset = end_byte;
 531                 ret = btrfs_set_item_key_safe(trans, root, path, key);
 532                 BUG_ON(ret);
 533         } else {
 534                 BUG();
 535         }
 536         return 0;
 537 }
 538
 539 /*
 540  * deletes the csum items from the csum tree for a given
 541  * range of bytes.
 542  */
 543 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 544                     struct btrfs_root *root, u64 bytenr, u64 len)
 545 {
 546         struct btrfs_path *path;
 547         struct btrfs_key key;
 548         u64 end_byte = bytenr + len;
 549         u64 csum_end;
 550         struct extent_buffer *leaf;
 551         int ret;
 552         u16 csum_size =
 553                 btrfs_super_csum_size(&root->fs_info->super_copy);
 554         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 555
 556         root = root->fs_info->csum_root;
 557
 558         path = btrfs_alloc_path();
 559         if (!path)
 560                 return -ENOMEM;
 561
 562         while (1) {
 563                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 564                 key.offset = end_byte - 1;
 565                 key.type = BTRFS_EXTENT_CSUM_KEY;
 566
 567                 path->leave_spinning = 1;
 568                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 569                 if (ret > 0) {
 570                         if (path->slots[0] == 0)
 571                                 break;
 572                         path->slots[0]--;
 573                 } else if (ret < 0) {
 574                         break;
 575                 }
 576
 577                 leaf = path->nodes[0];
 578                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 579
 580                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 581                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 582                         break;
 583                 }
 584
 585                 if (key.offset >= end_byte)
 586                         break;
 587
 588                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 589                 csum_end <<= blocksize_bits;
 590                 csum_end += key.offset;
 591
 592                 /* this csum ends before we start, we're done */
 593                 if (csum_end <= bytenr)
 594                         break;
 595
 596                 /* delete the entire item, it is inside our range */
 597                 if (key.offset >= bytenr && csum_end <= end_byte) {
 598                         ret = btrfs_del_item(trans, root, path);
 599                         if (ret)
 600                                 goto out;
 601                         if (key.offset == bytenr)
 602                                 break;
 603                 } else if (key.offset < bytenr && csum_end > end_byte) {
 604                         unsigned long offset;
 605                         unsigned long shift_len;
 606                         unsigned long item_offset;
 607                         /*
 608                          *        [ bytenr - len ]
 609                          *     [csum                ]
 610                          *
 611                          * Our bytes are in the middle of the csum,
 612                          * we need to split this item and insert a new one.
 613                          *
 614                          * But we can't drop the path because the
 615                          * csum could change, get removed, extended etc.
 616                          *
 617                          * The trick here is the max size of a csum item leaves
 618                          * enough room in the tree block for a single
 619                          * item header.  So, we split the item in place,
 620                          * adding a new header pointing to the existing
 621                          * bytes.  Then we loop around again and we have
 622                          * a nicely formed csum item that we can neatly
 623                          * truncate.
 624                          */
 625                         offset = (bytenr - key.offset) >> blocksize_bits;
 626                         offset *= csum_size;
 627
 628                         shift_len = (len >> blocksize_bits) * csum_size;
 629
 630                         item_offset = btrfs_item_ptr_offset(leaf,
 631                                                             path->slots[0]);
 632
 633                         memset_extent_buffer(leaf, 0, item_offset + offset,
 634                                              shift_len);
 635                         key.offset = bytenr;
 636
 637                         /*
 638                          * btrfs_split_item returns -EAGAIN when the
 639                          * item changed size or key
 640                          */
 641                         ret = btrfs_split_item(trans, root, path, &key, offset);
 642                         BUG_ON(ret && ret != -EAGAIN);
 643
 644                         key.offset = end_byte - 1;
 645                 } else {
 646                         ret = truncate_one_csum(trans, root, path,
 647                                                 &key, bytenr, len);
 648                         BUG_ON(ret);
 649                         if (key.offset < bytenr)
 650                                 break;
 651                 }
 652                 btrfs_release_path(path);
 653         }
 654         ret = 0;
 655 out:
 656         btrfs_free_path(path);
 657         return ret;
 658 }
 659
 660 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 661                            struct btrfs_root *root,
 662                            struct btrfs_ordered_sum *sums)
 663 {
 664         u64 bytenr;
 665         int ret;
 666         struct btrfs_key file_key;
 667         struct btrfs_key found_key;
 668         u64 next_offset;
 669         u64 total_bytes = 0;
 670         int found_next;
 671         struct btrfs_path *path;
 672         struct btrfs_csum_item *item;
 673         struct btrfs_csum_item *item_end;
 674         struct extent_buffer *leaf = NULL;
 675         u64 csum_offset;
 676         struct btrfs_sector_sum *sector_sum;
 677         u32 nritems;
 678         u32 ins_size;
 679         u16 csum_size =
 680                 btrfs_super_csum_size(&root->fs_info->super_copy);
 681
 682         path = btrfs_alloc_path();
 683         if (!path)
 684                 return -ENOMEM;
 685
 686         sector_sum = sums->sums;
 687 again:
 688         next_offset = (u64)-1;
 689         found_next = 0;
 690         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 691         file_key.offset = sector_sum->bytenr;
 692         bytenr = sector_sum->bytenr;
 693         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 694
 695         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 696         if (!IS_ERR(item)) {
 697                 leaf = path->nodes[0];
 698                 ret = 0;
 699                 goto found;
 700         }
 701         ret = PTR_ERR(item);
 702         if (ret != -EFBIG && ret != -ENOENT)
 703                 goto fail_unlock;
 704
 705         if (ret == -EFBIG) {
 706                 u32 item_size;
 707                 /* we found one, but it isn't big enough yet */
 708                 leaf = path->nodes[0];
 709                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 710                 if ((item_size / csum_size) >=
 711                     MAX_CSUM_ITEMS(root, csum_size)) {
 712                         /* already at max size, make a new one */
 713                         goto insert;
 714                 }
 715         } else {
 716                 int slot = path->slots[0] + 1;
 717                 /* we didn't find a csum item, insert one */
 718                 nritems = btrfs_header_nritems(path->nodes[0]);
 719                 if (path->slots[0] >= nritems - 1) {
 720                         ret = btrfs_next_leaf(root, path);
 721                         if (ret == 1)
 722                                 found_next = 1;
 723                         if (ret != 0)
 724                                 goto insert;
 725                         slot = 0;
 726                 }
 727                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 728                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 729                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 730                         found_next = 1;
 731                         goto insert;
 732                 }
 733                 next_offset = found_key.offset;
 734                 found_next = 1;
 735                 goto insert;
 736         }
 737
 738         /*
 739          * at this point, we know the tree has an item, but it isn't big
 740          * enough yet to put our csum in.  Grow it
 741          */
 742         btrfs_release_path(path);
 743         ret = btrfs_search_slot(trans, root, &file_key, path,
 744                                 csum_size, 1);
 745         if (ret < 0)
 746                 goto fail_unlock;
 747
 748         if (ret > 0) {
 749                 if (path->slots[0] == 0)
 750                         goto insert;
 751                 path->slots[0]--;
 752         }
 753
 754         leaf = path->nodes[0];
 755         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 756         csum_offset = (bytenr - found_key.offset) >>
 757                         root->fs_info->sb->s_blocksize_bits;
 758
 759         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 760             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 761             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 762                 goto insert;
 763         }
 764
 765         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 766             csum_size) {
 767                 u32 diff = (csum_offset + 1) * csum_size;
 768
 769                 /*
 770                  * is the item big enough already?  we dropped our lock
 771                  * before and need to recheck
 772                  */
 773                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 774                         goto csum;
 775
 776                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 777                 if (diff != csum_size)
 778                         goto insert;
 779
 780                 ret = btrfs_extend_item(trans, root, path, diff);
 781                 goto csum;
 782         }
 783
 784 insert:
 785         btrfs_release_path(path);
 786         csum_offset = 0;
 787         if (found_next) {
 788                 u64 tmp = total_bytes + root->sectorsize;
 789                 u64 next_sector = sector_sum->bytenr;
 790                 struct btrfs_sector_sum *next = sector_sum + 1;
 791
 792                 while (tmp < sums->len) {
 793                         if (next_sector + root->sectorsize != next->bytenr)
 794                                 break;
 795                         tmp += root->sectorsize;
 796                         next_sector = next->bytenr;
 797                         next++;
 798                 }
 799                 tmp = min(tmp, next_offset - file_key.offset);
 800                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 801                 tmp = max((u64)1, tmp);
 802                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 803                 ins_size = csum_size * tmp;
 804         } else {
 805                 ins_size = csum_size;
 806         }
 807         path->leave_spinning = 1;
 808         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 809                                       ins_size);
 810         path->leave_spinning = 0;
 811         if (ret < 0)
 812                 goto fail_unlock;
 813         if (ret != 0) {
 814                 WARN_ON(1);
 815                 goto fail_unlock;
 816         }
 817 csum:
 818         leaf = path->nodes[0];
 819         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 820         ret = 0;
 821         item = (struct btrfs_csum_item *)((unsigned char *)item +
 822                                           csum_offset * csum_size);
 823 found:
 824         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 825         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 826                                       btrfs_item_size_nr(leaf, path->slots[0]));
 827 next_sector:
 828
 829         write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item, csum_size);
 830
 831         total_bytes += root->sectorsize;
 832         sector_sum++;
 833         if (total_bytes < sums->len) {
 834                 item = (struct btrfs_csum_item *)((char *)item +
 835                                                   csum_size);
 836                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 837                     sector_sum->bytenr) {
 838                         bytenr = sector_sum->bytenr;
 839                         goto next_sector;
 840                 }
 841         }
 842
 843         btrfs_mark_buffer_dirty(path->nodes[0]);
 844         if (total_bytes < sums->len) {
 845                 btrfs_release_path(path);
 846                 cond_resched();
 847                 goto again;
 848         }
 849 out:
 850         btrfs_free_path(path);
 851         return ret;
 852
 853 fail_unlock:
 854         goto out;
 855 }