Merge branch 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6] / 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
31 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
32                                    sizeof(struct btrfs_ordered_sum)) / \
33                                    sizeof(struct btrfs_sector_sum) * \
34                                    (r)->sectorsize - (r)->sectorsize)
35
36 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
37                              struct btrfs_root *root,
38                              u64 objectid, u64 pos,
39                              u64 disk_offset, u64 disk_num_bytes,
40                              u64 num_bytes, u64 offset, u64 ram_bytes,
41                              u8 compression, u8 encryption, u16 other_encoding)
42 {
43         int ret = 0;
44         struct btrfs_file_extent_item *item;
45         struct btrfs_key file_key;
46         struct btrfs_path *path;
47         struct extent_buffer *leaf;
48
49         path = btrfs_alloc_path();
50         BUG_ON(!path);
51         file_key.objectid = objectid;
52         file_key.offset = pos;
53         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
54
55         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
56                                       sizeof(*item));
57         if (ret < 0)
58                 goto out;
59         BUG_ON(ret);
60         leaf = path->nodes[0];
61         item = btrfs_item_ptr(leaf, path->slots[0],
62                               struct btrfs_file_extent_item);
63         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
64         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
65         btrfs_set_file_extent_offset(leaf, item, offset);
66         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
67         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
68         btrfs_set_file_extent_generation(leaf, item, trans->transid);
69         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
70         btrfs_set_file_extent_compression(leaf, item, compression);
71         btrfs_set_file_extent_encryption(leaf, item, encryption);
72         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
73
74         btrfs_mark_buffer_dirty(leaf);
75 out:
76         btrfs_free_path(path);
77         return ret;
78 }
79
80 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
81                                           struct btrfs_root *root,
82                                           struct btrfs_path *path,
83                                           u64 bytenr, int cow)
84 {
85         int ret;
86         struct btrfs_key file_key;
87         struct btrfs_key found_key;
88         struct btrfs_csum_item *item;
89         struct extent_buffer *leaf;
90         u64 csum_offset = 0;
91         u16 csum_size =
92                 btrfs_super_csum_size(&root->fs_info->super_copy);
93         int csums_in_item;
94
95         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
96         file_key.offset = bytenr;
97         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
98         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
99         if (ret < 0)
100                 goto fail;
101         leaf = path->nodes[0];
102         if (ret > 0) {
103                 ret = 1;
104                 if (path->slots[0] == 0)
105                         goto fail;
106                 path->slots[0]--;
107                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
108                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
109                         goto fail;
110
111                 csum_offset = (bytenr - found_key.offset) >>
112                                 root->fs_info->sb->s_blocksize_bits;
113                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
114                 csums_in_item /= csum_size;
115
116                 if (csum_offset >= csums_in_item) {
117                         ret = -EFBIG;
118                         goto fail;
119                 }
120         }
121         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
122         item = (struct btrfs_csum_item *)((unsigned char *)item +
123                                           csum_offset * csum_size);
124         return item;
125 fail:
126         if (ret > 0)
127                 ret = -ENOENT;
128         return ERR_PTR(ret);
129 }
130
131
132 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
133                              struct btrfs_root *root,
134                              struct btrfs_path *path, u64 objectid,
135                              u64 offset, int mod)
136 {
137         int ret;
138         struct btrfs_key file_key;
139         int ins_len = mod < 0 ? -1 : 0;
140         int cow = mod != 0;
141
142         file_key.objectid = objectid;
143         file_key.offset = offset;
144         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
145         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
146         return ret;
147 }
148
149
150 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
151                           struct bio *bio, u32 *dst)
152 {
153         u32 sum;
154         struct bio_vec *bvec = bio->bi_io_vec;
155         int bio_index = 0;
156         u64 offset;
157         u64 item_start_offset = 0;
158         u64 item_last_offset = 0;
159         u64 disk_bytenr;
160         u32 diff;
161         u16 csum_size =
162                 btrfs_super_csum_size(&root->fs_info->super_copy);
163         int ret;
164         struct btrfs_path *path;
165         struct btrfs_csum_item *item = NULL;
166         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
167
168         path = btrfs_alloc_path();
169         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
170                 path->reada = 2;
171
172         WARN_ON(bio->bi_vcnt <= 0);
173
174         disk_bytenr = (u64)bio->bi_sector << 9;
175         while (bio_index < bio->bi_vcnt) {
176                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
177                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
178                 if (ret == 0)
179                         goto found;
180
181                 if (!item || disk_bytenr < item_start_offset ||
182                     disk_bytenr >= item_last_offset) {
183                         struct btrfs_key found_key;
184                         u32 item_size;
185
186                         if (item)
187                                 btrfs_release_path(root, path);
188                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
189                                                  path, disk_bytenr, 0);
190                         if (IS_ERR(item)) {
191                                 ret = PTR_ERR(item);
192                                 if (ret == -ENOENT || ret == -EFBIG)
193                                         ret = 0;
194                                 sum = 0;
195                                 if (BTRFS_I(inode)->root->root_key.objectid ==
196                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
197                                         set_extent_bits(io_tree, offset,
198                                                 offset + bvec->bv_len - 1,
199                                                 EXTENT_NODATASUM, GFP_NOFS);
200                                 } else {
201                                         printk(KERN_INFO "btrfs no csum found "
202                                                "for inode %lu start %llu\n",
203                                                inode->i_ino,
204                                                (unsigned long long)offset);
205                                 }
206                                 item = NULL;
207                                 btrfs_release_path(root, path);
208                                 goto found;
209                         }
210                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
211                                               path->slots[0]);
212
213                         item_start_offset = found_key.offset;
214                         item_size = btrfs_item_size_nr(path->nodes[0],
215                                                        path->slots[0]);
216                         item_last_offset = item_start_offset +
217                                 (item_size / csum_size) *
218                                 root->sectorsize;
219                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
220                                               struct btrfs_csum_item);
221                 }
222                 /*
223                  * this byte range must be able to fit inside
224                  * a single leaf so it will also fit inside a u32
225                  */
226                 diff = disk_bytenr - item_start_offset;
227                 diff = diff / root->sectorsize;
228                 diff = diff * csum_size;
229
230                 read_extent_buffer(path->nodes[0], &sum,
231                                    ((unsigned long)item) + diff,
232                                    csum_size);
233 found:
234                 if (dst)
235                         *dst++ = sum;
236                 else
237                         set_state_private(io_tree, offset, sum);
238                 disk_bytenr += bvec->bv_len;
239                 bio_index++;
240                 bvec++;
241         }
242         btrfs_free_path(path);
243         return 0;
244 }
245
246 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
247                              struct list_head *list)
248 {
249         struct btrfs_key key;
250         struct btrfs_path *path;
251         struct extent_buffer *leaf;
252         struct btrfs_ordered_sum *sums;
253         struct btrfs_sector_sum *sector_sum;
254         struct btrfs_csum_item *item;
255         unsigned long offset;
256         int ret;
257         size_t size;
258         u64 csum_end;
259         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
260
261         path = btrfs_alloc_path();
262         BUG_ON(!path);
263
264         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
265         key.offset = start;
266         key.type = BTRFS_EXTENT_CSUM_KEY;
267
268         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
269         if (ret < 0)
270                 goto fail;
271         if (ret > 0 && path->slots[0] > 0) {
272                 leaf = path->nodes[0];
273                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
274                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
275                     key.type == BTRFS_EXTENT_CSUM_KEY) {
276                         offset = (start - key.offset) >>
277                                  root->fs_info->sb->s_blocksize_bits;
278                         if (offset * csum_size <
279                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
280                                 path->slots[0]--;
281                 }
282         }
283
284         while (start <= end) {
285                 leaf = path->nodes[0];
286                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
287                         ret = btrfs_next_leaf(root, path);
288                         if (ret < 0)
289                                 goto fail;
290                         if (ret > 0)
291                                 break;
292                         leaf = path->nodes[0];
293                 }
294
295                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
296                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
297                     key.type != BTRFS_EXTENT_CSUM_KEY)
298                         break;
299
300                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
301                 if (key.offset > end)
302                         break;
303
304                 if (key.offset > start)
305                         start = key.offset;
306
307                 size = btrfs_item_size_nr(leaf, path->slots[0]);
308                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
309                 if (csum_end <= start) {
310                         path->slots[0]++;
311                         continue;
312                 }
313
314                 csum_end = min(csum_end, end + 1);
315                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
316                                       struct btrfs_csum_item);
317                 while (start < csum_end) {
318                         size = min_t(size_t, csum_end - start,
319                                         MAX_ORDERED_SUM_BYTES(root));
320                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
321                                         GFP_NOFS);
322                         BUG_ON(!sums);
323
324                         sector_sum = sums->sums;
325                         sums->bytenr = start;
326                         sums->len = size;
327
328                         offset = (start - key.offset) >>
329                                 root->fs_info->sb->s_blocksize_bits;
330                         offset *= csum_size;
331
332                         while (size > 0) {
333                                 read_extent_buffer(path->nodes[0],
334                                                 &sector_sum->sum,
335                                                 ((unsigned long)item) +
336                                                 offset, csum_size);
337                                 sector_sum->bytenr = start;
338
339                                 size -= root->sectorsize;
340                                 start += root->sectorsize;
341                                 offset += csum_size;
342                                 sector_sum++;
343                         }
344                         list_add_tail(&sums->list, list);
345                 }
346                 path->slots[0]++;
347         }
348         ret = 0;
349 fail:
350         btrfs_free_path(path);
351         return ret;
352 }
353
354 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
355                        struct bio *bio, u64 file_start, int contig)
356 {
357         struct btrfs_ordered_sum *sums;
358         struct btrfs_sector_sum *sector_sum;
359         struct btrfs_ordered_extent *ordered;
360         char *data;
361         struct bio_vec *bvec = bio->bi_io_vec;
362         int bio_index = 0;
363         unsigned long total_bytes = 0;
364         unsigned long this_sum_bytes = 0;
365         u64 offset;
366         u64 disk_bytenr;
367
368         WARN_ON(bio->bi_vcnt <= 0);
369         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
370         if (!sums)
371                 return -ENOMEM;
372
373         sector_sum = sums->sums;
374         disk_bytenr = (u64)bio->bi_sector << 9;
375         sums->len = bio->bi_size;
376         INIT_LIST_HEAD(&sums->list);
377
378         if (contig)
379                 offset = file_start;
380         else
381                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
382
383         ordered = btrfs_lookup_ordered_extent(inode, offset);
384         BUG_ON(!ordered);
385         sums->bytenr = ordered->start;
386
387         while (bio_index < bio->bi_vcnt) {
388                 if (!contig)
389                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
390
391                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
392                     offset < ordered->file_offset)) {
393                         unsigned long bytes_left;
394                         sums->len = this_sum_bytes;
395                         this_sum_bytes = 0;
396                         btrfs_add_ordered_sum(inode, ordered, sums);
397                         btrfs_put_ordered_extent(ordered);
398
399                         bytes_left = bio->bi_size - total_bytes;
400
401                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
402                                        GFP_NOFS);
403                         BUG_ON(!sums);
404                         sector_sum = sums->sums;
405                         sums->len = bytes_left;
406                         ordered = btrfs_lookup_ordered_extent(inode, offset);
407                         BUG_ON(!ordered);
408                         sums->bytenr = ordered->start;
409                 }
410
411                 data = kmap_atomic(bvec->bv_page, KM_USER0);
412                 sector_sum->sum = ~(u32)0;
413                 sector_sum->sum = btrfs_csum_data(root,
414                                                   data + bvec->bv_offset,
415                                                   sector_sum->sum,
416                                                   bvec->bv_len);
417                 kunmap_atomic(data, KM_USER0);
418                 btrfs_csum_final(sector_sum->sum,
419                                  (char *)&sector_sum->sum);
420                 sector_sum->bytenr = disk_bytenr;
421
422                 sector_sum++;
423                 bio_index++;
424                 total_bytes += bvec->bv_len;
425                 this_sum_bytes += bvec->bv_len;
426                 disk_bytenr += bvec->bv_len;
427                 offset += bvec->bv_len;
428                 bvec++;
429         }
430         this_sum_bytes = 0;
431         btrfs_add_ordered_sum(inode, ordered, sums);
432         btrfs_put_ordered_extent(ordered);
433         return 0;
434 }
435
436 /*
437  * helper function for csum removal, this expects the
438  * key to describe the csum pointed to by the path, and it expects
439  * the csum to overlap the range [bytenr, len]
440  *
441  * The csum should not be entirely contained in the range and the
442  * range should not be entirely contained in the csum.
443  *
444  * This calls btrfs_truncate_item with the correct args based on the
445  * overlap, and fixes up the key as required.
446  */
447 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
448                                       struct btrfs_root *root,
449                                       struct btrfs_path *path,
450                                       struct btrfs_key *key,
451                                       u64 bytenr, u64 len)
452 {
453         struct extent_buffer *leaf;
454         u16 csum_size =
455                 btrfs_super_csum_size(&root->fs_info->super_copy);
456         u64 csum_end;
457         u64 end_byte = bytenr + len;
458         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
459         int ret;
460
461         leaf = path->nodes[0];
462         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
463         csum_end <<= root->fs_info->sb->s_blocksize_bits;
464         csum_end += key->offset;
465
466         if (key->offset < bytenr && csum_end <= end_byte) {
467                 /*
468                  *         [ bytenr - len ]
469                  *         [   ]
470                  *   [csum     ]
471                  *   A simple truncate off the end of the item
472                  */
473                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
474                 new_size *= csum_size;
475                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
476                 BUG_ON(ret);
477         } else if (key->offset >= bytenr && csum_end > end_byte &&
478                    end_byte > key->offset) {
479                 /*
480                  *         [ bytenr - len ]
481                  *                 [ ]
482                  *                 [csum     ]
483                  * we need to truncate from the beginning of the csum
484                  */
485                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
486                 new_size *= csum_size;
487
488                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
489                 BUG_ON(ret);
490
491                 key->offset = end_byte;
492                 ret = btrfs_set_item_key_safe(trans, root, path, key);
493                 BUG_ON(ret);
494         } else {
495                 BUG();
496         }
497         return 0;
498 }
499
500 /*
501  * deletes the csum items from the csum tree for a given
502  * range of bytes.
503  */
504 int btrfs_del_csums(struct btrfs_trans_handle *trans,
505                     struct btrfs_root *root, u64 bytenr, u64 len)
506 {
507         struct btrfs_path *path;
508         struct btrfs_key key;
509         u64 end_byte = bytenr + len;
510         u64 csum_end;
511         struct extent_buffer *leaf;
512         int ret;
513         u16 csum_size =
514                 btrfs_super_csum_size(&root->fs_info->super_copy);
515         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
516
517         root = root->fs_info->csum_root;
518
519         path = btrfs_alloc_path();
520
521         while (1) {
522                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
523                 key.offset = end_byte - 1;
524                 key.type = BTRFS_EXTENT_CSUM_KEY;
525
526                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
527                 if (ret > 0) {
528                         if (path->slots[0] == 0)
529                                 goto out;
530                         path->slots[0]--;
531                 }
532                 leaf = path->nodes[0];
533                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
534
535                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
536                     key.type != BTRFS_EXTENT_CSUM_KEY) {
537                         break;
538                 }
539
540                 if (key.offset >= end_byte)
541                         break;
542
543                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
544                 csum_end <<= blocksize_bits;
545                 csum_end += key.offset;
546
547                 /* this csum ends before we start, we're done */
548                 if (csum_end <= bytenr)
549                         break;
550
551                 /* delete the entire item, it is inside our range */
552                 if (key.offset >= bytenr && csum_end <= end_byte) {
553                         ret = btrfs_del_item(trans, root, path);
554                         BUG_ON(ret);
555                         if (key.offset == bytenr)
556                                 break;
557                 } else if (key.offset < bytenr && csum_end > end_byte) {
558                         unsigned long offset;
559                         unsigned long shift_len;
560                         unsigned long item_offset;
561                         /*
562                          *        [ bytenr - len ]
563                          *     [csum                ]
564                          *
565                          * Our bytes are in the middle of the csum,
566                          * we need to split this item and insert a new one.
567                          *
568                          * But we can't drop the path because the
569                          * csum could change, get removed, extended etc.
570                          *
571                          * The trick here is the max size of a csum item leaves
572                          * enough room in the tree block for a single
573                          * item header.  So, we split the item in place,
574                          * adding a new header pointing to the existing
575                          * bytes.  Then we loop around again and we have
576                          * a nicely formed csum item that we can neatly
577                          * truncate.
578                          */
579                         offset = (bytenr - key.offset) >> blocksize_bits;
580                         offset *= csum_size;
581
582                         shift_len = (len >> blocksize_bits) * csum_size;
583
584                         item_offset = btrfs_item_ptr_offset(leaf,
585                                                             path->slots[0]);
586
587                         memset_extent_buffer(leaf, 0, item_offset + offset,
588                                              shift_len);
589                         key.offset = bytenr;
590
591                         /*
592                          * btrfs_split_item returns -EAGAIN when the
593                          * item changed size or key
594                          */
595                         ret = btrfs_split_item(trans, root, path, &key, offset);
596                         BUG_ON(ret && ret != -EAGAIN);
597
598                         key.offset = end_byte - 1;
599                 } else {
600                         ret = truncate_one_csum(trans, root, path,
601                                                 &key, bytenr, len);
602                         BUG_ON(ret);
603                         if (key.offset < bytenr)
604                                 break;
605                 }
606                 btrfs_release_path(root, path);
607         }
608 out:
609         btrfs_free_path(path);
610         return 0;
611 }
612
613 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
614                            struct btrfs_root *root,
615                            struct btrfs_ordered_sum *sums)
616 {
617         u64 bytenr;
618         int ret;
619         struct btrfs_key file_key;
620         struct btrfs_key found_key;
621         u64 next_offset;
622         u64 total_bytes = 0;
623         int found_next;
624         struct btrfs_path *path;
625         struct btrfs_csum_item *item;
626         struct btrfs_csum_item *item_end;
627         struct extent_buffer *leaf = NULL;
628         u64 csum_offset;
629         struct btrfs_sector_sum *sector_sum;
630         u32 nritems;
631         u32 ins_size;
632         char *eb_map;
633         char *eb_token;
634         unsigned long map_len;
635         unsigned long map_start;
636         u16 csum_size =
637                 btrfs_super_csum_size(&root->fs_info->super_copy);
638
639         path = btrfs_alloc_path();
640         BUG_ON(!path);
641         sector_sum = sums->sums;
642 again:
643         next_offset = (u64)-1;
644         found_next = 0;
645         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
646         file_key.offset = sector_sum->bytenr;
647         bytenr = sector_sum->bytenr;
648         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
649
650         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
651         if (!IS_ERR(item)) {
652                 leaf = path->nodes[0];
653                 ret = 0;
654                 goto found;
655         }
656         ret = PTR_ERR(item);
657         if (ret == -EFBIG) {
658                 u32 item_size;
659                 /* we found one, but it isn't big enough yet */
660                 leaf = path->nodes[0];
661                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
662                 if ((item_size / csum_size) >=
663                     MAX_CSUM_ITEMS(root, csum_size)) {
664                         /* already at max size, make a new one */
665                         goto insert;
666                 }
667         } else {
668                 int slot = path->slots[0] + 1;
669                 /* we didn't find a csum item, insert one */
670                 nritems = btrfs_header_nritems(path->nodes[0]);
671                 if (path->slots[0] >= nritems - 1) {
672                         ret = btrfs_next_leaf(root, path);
673                         if (ret == 1)
674                                 found_next = 1;
675                         if (ret != 0)
676                                 goto insert;
677                         slot = 0;
678                 }
679                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
680                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
681                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
682                         found_next = 1;
683                         goto insert;
684                 }
685                 next_offset = found_key.offset;
686                 found_next = 1;
687                 goto insert;
688         }
689
690         /*
691          * at this point, we know the tree has an item, but it isn't big
692          * enough yet to put our csum in.  Grow it
693          */
694         btrfs_release_path(root, path);
695         ret = btrfs_search_slot(trans, root, &file_key, path,
696                                 csum_size, 1);
697         if (ret < 0)
698                 goto fail_unlock;
699
700         if (ret > 0) {
701                 if (path->slots[0] == 0)
702                         goto insert;
703                 path->slots[0]--;
704         }
705
706         leaf = path->nodes[0];
707         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
708         csum_offset = (bytenr - found_key.offset) >>
709                         root->fs_info->sb->s_blocksize_bits;
710
711         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
712             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
713             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
714                 goto insert;
715         }
716
717         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
718             csum_size) {
719                 u32 diff = (csum_offset + 1) * csum_size;
720
721                 /*
722                  * is the item big enough already?  we dropped our lock
723                  * before and need to recheck
724                  */
725                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
726                         goto csum;
727
728                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
729                 if (diff != csum_size)
730                         goto insert;
731
732                 ret = btrfs_extend_item(trans, root, path, diff);
733                 BUG_ON(ret);
734                 goto csum;
735         }
736
737 insert:
738         btrfs_release_path(root, path);
739         csum_offset = 0;
740         if (found_next) {
741                 u64 tmp = total_bytes + root->sectorsize;
742                 u64 next_sector = sector_sum->bytenr;
743                 struct btrfs_sector_sum *next = sector_sum + 1;
744
745                 while (tmp < sums->len) {
746                         if (next_sector + root->sectorsize != next->bytenr)
747                                 break;
748                         tmp += root->sectorsize;
749                         next_sector = next->bytenr;
750                         next++;
751                 }
752                 tmp = min(tmp, next_offset - file_key.offset);
753                 tmp >>= root->fs_info->sb->s_blocksize_bits;
754                 tmp = max((u64)1, tmp);
755                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
756                 ins_size = csum_size * tmp;
757         } else {
758                 ins_size = csum_size;
759         }
760         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
761                                       ins_size);
762         if (ret < 0)
763                 goto fail_unlock;
764         if (ret != 0) {
765                 WARN_ON(1);
766                 goto fail_unlock;
767         }
768 csum:
769         leaf = path->nodes[0];
770         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
771         ret = 0;
772         item = (struct btrfs_csum_item *)((unsigned char *)item +
773                                           csum_offset * csum_size);
774 found:
775         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
776         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
777                                       btrfs_item_size_nr(leaf, path->slots[0]));
778         eb_token = NULL;
779         cond_resched();
780 next_sector:
781
782         if (!eb_token ||
783            (unsigned long)item + csum_size >= map_start + map_len) {
784                 int err;
785
786                 if (eb_token)
787                         unmap_extent_buffer(leaf, eb_token, KM_USER1);
788                 eb_token = NULL;
789                 err = map_private_extent_buffer(leaf, (unsigned long)item,
790                                                 csum_size,
791                                                 &eb_token, &eb_map,
792                                                 &map_start, &map_len, KM_USER1);
793                 if (err)
794                         eb_token = NULL;
795         }
796         if (eb_token) {
797                 memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
798                        &sector_sum->sum, csum_size);
799         } else {
800                 write_extent_buffer(leaf, &sector_sum->sum,
801                                     (unsigned long)item, csum_size);
802         }
803
804         total_bytes += root->sectorsize;
805         sector_sum++;
806         if (total_bytes < sums->len) {
807                 item = (struct btrfs_csum_item *)((char *)item +
808                                                   csum_size);
809                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
810                     sector_sum->bytenr) {
811                         bytenr = sector_sum->bytenr;
812                         goto next_sector;
813                 }
814         }
815         if (eb_token) {
816                 unmap_extent_buffer(leaf, eb_token, KM_USER1);
817                 eb_token = NULL;
818         }
819         btrfs_mark_buffer_dirty(path->nodes[0]);
820         cond_resched();
821         if (total_bytes < sums->len) {
822                 btrfs_release_path(root, path);
823                 goto again;
824         }
825 out:
826         btrfs_free_path(path);
827         return ret;
828
829 fail_unlock:
830         goto out;
831 }