jbd2: correctly unescape journal data blocks
[sfrench/cifs-2.6.git] / fs / jbd2 / recovery.c
1 /*
2  * linux/fs/jbd2/recovery.c
3  *
4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
5  *
6  * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
7  *
8  * This file is part of the Linux kernel and is made available under
9  * the terms of the GNU General Public License, version 2, or at your
10  * option, any later version, incorporated herein by reference.
11  *
12  * Journal recovery routines for the generic filesystem journaling code;
13  * part of the ext2fs journaling system.
14  */
15
16 #ifndef __KERNEL__
17 #include "jfs_user.h"
18 #else
19 #include <linux/time.h>
20 #include <linux/fs.h>
21 #include <linux/jbd2.h>
22 #include <linux/errno.h>
23 #include <linux/slab.h>
24 #include <linux/crc32.h>
25 #endif
26
27 /*
28  * Maintain information about the progress of the recovery job, so that
29  * the different passes can carry information between them.
30  */
31 struct recovery_info
32 {
33         tid_t           start_transaction;
34         tid_t           end_transaction;
35
36         int             nr_replays;
37         int             nr_revokes;
38         int             nr_revoke_hits;
39 };
40
41 enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
42 static int do_one_pass(journal_t *journal,
43                                 struct recovery_info *info, enum passtype pass);
44 static int scan_revoke_records(journal_t *, struct buffer_head *,
45                                 tid_t, struct recovery_info *);
46
47 #ifdef __KERNEL__
48
49 /* Release readahead buffers after use */
50 static void journal_brelse_array(struct buffer_head *b[], int n)
51 {
52         while (--n >= 0)
53                 brelse (b[n]);
54 }
55
56
57 /*
58  * When reading from the journal, we are going through the block device
59  * layer directly and so there is no readahead being done for us.  We
60  * need to implement any readahead ourselves if we want it to happen at
61  * all.  Recovery is basically one long sequential read, so make sure we
62  * do the IO in reasonably large chunks.
63  *
64  * This is not so critical that we need to be enormously clever about
65  * the readahead size, though.  128K is a purely arbitrary, good-enough
66  * fixed value.
67  */
68
69 #define MAXBUF 8
70 static int do_readahead(journal_t *journal, unsigned int start)
71 {
72         int err;
73         unsigned int max, nbufs, next;
74         unsigned long long blocknr;
75         struct buffer_head *bh;
76
77         struct buffer_head * bufs[MAXBUF];
78
79         /* Do up to 128K of readahead */
80         max = start + (128 * 1024 / journal->j_blocksize);
81         if (max > journal->j_maxlen)
82                 max = journal->j_maxlen;
83
84         /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
85          * a time to the block device IO layer. */
86
87         nbufs = 0;
88
89         for (next = start; next < max; next++) {
90                 err = jbd2_journal_bmap(journal, next, &blocknr);
91
92                 if (err) {
93                         printk (KERN_ERR "JBD: bad block at offset %u\n",
94                                 next);
95                         goto failed;
96                 }
97
98                 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
99                 if (!bh) {
100                         err = -ENOMEM;
101                         goto failed;
102                 }
103
104                 if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
105                         bufs[nbufs++] = bh;
106                         if (nbufs == MAXBUF) {
107                                 ll_rw_block(READ, nbufs, bufs);
108                                 journal_brelse_array(bufs, nbufs);
109                                 nbufs = 0;
110                         }
111                 } else
112                         brelse(bh);
113         }
114
115         if (nbufs)
116                 ll_rw_block(READ, nbufs, bufs);
117         err = 0;
118
119 failed:
120         if (nbufs)
121                 journal_brelse_array(bufs, nbufs);
122         return err;
123 }
124
125 #endif /* __KERNEL__ */
126
127
128 /*
129  * Read a block from the journal
130  */
131
132 static int jread(struct buffer_head **bhp, journal_t *journal,
133                  unsigned int offset)
134 {
135         int err;
136         unsigned long long blocknr;
137         struct buffer_head *bh;
138
139         *bhp = NULL;
140
141         if (offset >= journal->j_maxlen) {
142                 printk(KERN_ERR "JBD: corrupted journal superblock\n");
143                 return -EIO;
144         }
145
146         err = jbd2_journal_bmap(journal, offset, &blocknr);
147
148         if (err) {
149                 printk (KERN_ERR "JBD: bad block at offset %u\n",
150                         offset);
151                 return err;
152         }
153
154         bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
155         if (!bh)
156                 return -ENOMEM;
157
158         if (!buffer_uptodate(bh)) {
159                 /* If this is a brand new buffer, start readahead.
160                    Otherwise, we assume we are already reading it.  */
161                 if (!buffer_req(bh))
162                         do_readahead(journal, offset);
163                 wait_on_buffer(bh);
164         }
165
166         if (!buffer_uptodate(bh)) {
167                 printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
168                         offset);
169                 brelse(bh);
170                 return -EIO;
171         }
172
173         *bhp = bh;
174         return 0;
175 }
176
177
178 /*
179  * Count the number of in-use tags in a journal descriptor block.
180  */
181
182 static int count_tags(journal_t *journal, struct buffer_head *bh)
183 {
184         char *                  tagp;
185         journal_block_tag_t *   tag;
186         int                     nr = 0, size = journal->j_blocksize;
187         int                     tag_bytes = journal_tag_bytes(journal);
188
189         tagp = &bh->b_data[sizeof(journal_header_t)];
190
191         while ((tagp - bh->b_data + tag_bytes) <= size) {
192                 tag = (journal_block_tag_t *) tagp;
193
194                 nr++;
195                 tagp += tag_bytes;
196                 if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))
197                         tagp += 16;
198
199                 if (tag->t_flags & cpu_to_be32(JBD2_FLAG_LAST_TAG))
200                         break;
201         }
202
203         return nr;
204 }
205
206
207 /* Make sure we wrap around the log correctly! */
208 #define wrap(journal, var)                                              \
209 do {                                                                    \
210         if (var >= (journal)->j_last)                                   \
211                 var -= ((journal)->j_last - (journal)->j_first);        \
212 } while (0)
213
214 /**
215  * jbd2_journal_recover - recovers a on-disk journal
216  * @journal: the journal to recover
217  *
218  * The primary function for recovering the log contents when mounting a
219  * journaled device.
220  *
221  * Recovery is done in three passes.  In the first pass, we look for the
222  * end of the log.  In the second, we assemble the list of revoke
223  * blocks.  In the third and final pass, we replay any un-revoked blocks
224  * in the log.
225  */
226 int jbd2_journal_recover(journal_t *journal)
227 {
228         int                     err;
229         journal_superblock_t *  sb;
230
231         struct recovery_info    info;
232
233         memset(&info, 0, sizeof(info));
234         sb = journal->j_superblock;
235
236         /*
237          * The journal superblock's s_start field (the current log head)
238          * is always zero if, and only if, the journal was cleanly
239          * unmounted.
240          */
241
242         if (!sb->s_start) {
243                 jbd_debug(1, "No recovery required, last transaction %d\n",
244                           be32_to_cpu(sb->s_sequence));
245                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
246                 return 0;
247         }
248
249         err = do_one_pass(journal, &info, PASS_SCAN);
250         if (!err)
251                 err = do_one_pass(journal, &info, PASS_REVOKE);
252         if (!err)
253                 err = do_one_pass(journal, &info, PASS_REPLAY);
254
255         jbd_debug(1, "JBD: recovery, exit status %d, "
256                   "recovered transactions %u to %u\n",
257                   err, info.start_transaction, info.end_transaction);
258         jbd_debug(1, "JBD: Replayed %d and revoked %d/%d blocks\n",
259                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
260
261         /* Restart the log at the next transaction ID, thus invalidating
262          * any existing commit records in the log. */
263         journal->j_transaction_sequence = ++info.end_transaction;
264
265         jbd2_journal_clear_revoke(journal);
266         sync_blockdev(journal->j_fs_dev);
267         return err;
268 }
269
270 /**
271  * jbd2_journal_skip_recovery - Start journal and wipe exiting records
272  * @journal: journal to startup
273  *
274  * Locate any valid recovery information from the journal and set up the
275  * journal structures in memory to ignore it (presumably because the
276  * caller has evidence that it is out of date).
277  * This function does'nt appear to be exorted..
278  *
279  * We perform one pass over the journal to allow us to tell the user how
280  * much recovery information is being erased, and to let us initialise
281  * the journal transaction sequence numbers to the next unused ID.
282  */
283 int jbd2_journal_skip_recovery(journal_t *journal)
284 {
285         int                     err;
286         journal_superblock_t *  sb;
287
288         struct recovery_info    info;
289
290         memset (&info, 0, sizeof(info));
291         sb = journal->j_superblock;
292
293         err = do_one_pass(journal, &info, PASS_SCAN);
294
295         if (err) {
296                 printk(KERN_ERR "JBD: error %d scanning journal\n", err);
297                 ++journal->j_transaction_sequence;
298         } else {
299 #ifdef CONFIG_JBD2_DEBUG
300                 int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
301 #endif
302                 jbd_debug(1,
303                           "JBD: ignoring %d transaction%s from the journal.\n",
304                           dropped, (dropped == 1) ? "" : "s");
305                 journal->j_transaction_sequence = ++info.end_transaction;
306         }
307
308         journal->j_tail = 0;
309         return err;
310 }
311
312 static inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag_t *tag)
313 {
314         unsigned long long block = be32_to_cpu(tag->t_blocknr);
315         if (tag_bytes > JBD2_TAG_SIZE32)
316                 block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
317         return block;
318 }
319
320 /*
321  * calc_chksums calculates the checksums for the blocks described in the
322  * descriptor block.
323  */
324 static int calc_chksums(journal_t *journal, struct buffer_head *bh,
325                         unsigned long *next_log_block, __u32 *crc32_sum)
326 {
327         int i, num_blks, err;
328         unsigned long io_block;
329         struct buffer_head *obh;
330
331         num_blks = count_tags(journal, bh);
332         /* Calculate checksum of the descriptor block. */
333         *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
334
335         for (i = 0; i < num_blks; i++) {
336                 io_block = (*next_log_block)++;
337                 wrap(journal, *next_log_block);
338                 err = jread(&obh, journal, io_block);
339                 if (err) {
340                         printk(KERN_ERR "JBD: IO error %d recovering block "
341                                 "%lu in log\n", err, io_block);
342                         return 1;
343                 } else {
344                         *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
345                                      obh->b_size);
346                 }
347         }
348         return 0;
349 }
350
351 static int do_one_pass(journal_t *journal,
352                         struct recovery_info *info, enum passtype pass)
353 {
354         unsigned int            first_commit_ID, next_commit_ID;
355         unsigned long           next_log_block;
356         int                     err, success = 0;
357         journal_superblock_t *  sb;
358         journal_header_t *      tmp;
359         struct buffer_head *    bh;
360         unsigned int            sequence;
361         int                     blocktype;
362         int                     tag_bytes = journal_tag_bytes(journal);
363         __u32                   crc32_sum = ~0; /* Transactional Checksums */
364
365         /* Precompute the maximum metadata descriptors in a descriptor block */
366         int                     MAX_BLOCKS_PER_DESC;
367         MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
368                                / tag_bytes);
369
370         /*
371          * First thing is to establish what we expect to find in the log
372          * (in terms of transaction IDs), and where (in terms of log
373          * block offsets): query the superblock.
374          */
375
376         sb = journal->j_superblock;
377         next_commit_ID = be32_to_cpu(sb->s_sequence);
378         next_log_block = be32_to_cpu(sb->s_start);
379
380         first_commit_ID = next_commit_ID;
381         if (pass == PASS_SCAN)
382                 info->start_transaction = first_commit_ID;
383
384         jbd_debug(1, "Starting recovery pass %d\n", pass);
385
386         /*
387          * Now we walk through the log, transaction by transaction,
388          * making sure that each transaction has a commit block in the
389          * expected place.  Each complete transaction gets replayed back
390          * into the main filesystem.
391          */
392
393         while (1) {
394                 int                     flags;
395                 char *                  tagp;
396                 journal_block_tag_t *   tag;
397                 struct buffer_head *    obh;
398                 struct buffer_head *    nbh;
399
400                 cond_resched();
401
402                 /* If we already know where to stop the log traversal,
403                  * check right now that we haven't gone past the end of
404                  * the log. */
405
406                 if (pass != PASS_SCAN)
407                         if (tid_geq(next_commit_ID, info->end_transaction))
408                                 break;
409
410                 jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
411                           next_commit_ID, next_log_block, journal->j_last);
412
413                 /* Skip over each chunk of the transaction looking
414                  * either the next descriptor block or the final commit
415                  * record. */
416
417                 jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
418                 err = jread(&bh, journal, next_log_block);
419                 if (err)
420                         goto failed;
421
422                 next_log_block++;
423                 wrap(journal, next_log_block);
424
425                 /* What kind of buffer is it?
426                  *
427                  * If it is a descriptor block, check that it has the
428                  * expected sequence number.  Otherwise, we're all done
429                  * here. */
430
431                 tmp = (journal_header_t *)bh->b_data;
432
433                 if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
434                         brelse(bh);
435                         break;
436                 }
437
438                 blocktype = be32_to_cpu(tmp->h_blocktype);
439                 sequence = be32_to_cpu(tmp->h_sequence);
440                 jbd_debug(3, "Found magic %d, sequence %d\n",
441                           blocktype, sequence);
442
443                 if (sequence != next_commit_ID) {
444                         brelse(bh);
445                         break;
446                 }
447
448                 /* OK, we have a valid descriptor block which matches
449                  * all of the sequence number checks.  What are we going
450                  * to do with it?  That depends on the pass... */
451
452                 switch(blocktype) {
453                 case JBD2_DESCRIPTOR_BLOCK:
454                         /* If it is a valid descriptor block, replay it
455                          * in pass REPLAY; if journal_checksums enabled, then
456                          * calculate checksums in PASS_SCAN, otherwise,
457                          * just skip over the blocks it describes. */
458                         if (pass != PASS_REPLAY) {
459                                 if (pass == PASS_SCAN &&
460                                     JBD2_HAS_COMPAT_FEATURE(journal,
461                                             JBD2_FEATURE_COMPAT_CHECKSUM) &&
462                                     !info->end_transaction) {
463                                         if (calc_chksums(journal, bh,
464                                                         &next_log_block,
465                                                         &crc32_sum)) {
466                                                 put_bh(bh);
467                                                 break;
468                                         }
469                                         put_bh(bh);
470                                         continue;
471                                 }
472                                 next_log_block += count_tags(journal, bh);
473                                 wrap(journal, next_log_block);
474                                 put_bh(bh);
475                                 continue;
476                         }
477
478                         /* A descriptor block: we can now write all of
479                          * the data blocks.  Yay, useful work is finally
480                          * getting done here! */
481
482                         tagp = &bh->b_data[sizeof(journal_header_t)];
483                         while ((tagp - bh->b_data + tag_bytes)
484                                <= journal->j_blocksize) {
485                                 unsigned long io_block;
486
487                                 tag = (journal_block_tag_t *) tagp;
488                                 flags = be32_to_cpu(tag->t_flags);
489
490                                 io_block = next_log_block++;
491                                 wrap(journal, next_log_block);
492                                 err = jread(&obh, journal, io_block);
493                                 if (err) {
494                                         /* Recover what we can, but
495                                          * report failure at the end. */
496                                         success = err;
497                                         printk (KERN_ERR
498                                                 "JBD: IO error %d recovering "
499                                                 "block %ld in log\n",
500                                                 err, io_block);
501                                 } else {
502                                         unsigned long long blocknr;
503
504                                         J_ASSERT(obh != NULL);
505                                         blocknr = read_tag_block(tag_bytes,
506                                                                  tag);
507
508                                         /* If the block has been
509                                          * revoked, then we're all done
510                                          * here. */
511                                         if (jbd2_journal_test_revoke
512                                             (journal, blocknr,
513                                              next_commit_ID)) {
514                                                 brelse(obh);
515                                                 ++info->nr_revoke_hits;
516                                                 goto skip_write;
517                                         }
518
519                                         /* Find a buffer for the new
520                                          * data being restored */
521                                         nbh = __getblk(journal->j_fs_dev,
522                                                         blocknr,
523                                                         journal->j_blocksize);
524                                         if (nbh == NULL) {
525                                                 printk(KERN_ERR
526                                                        "JBD: Out of memory "
527                                                        "during recovery.\n");
528                                                 err = -ENOMEM;
529                                                 brelse(bh);
530                                                 brelse(obh);
531                                                 goto failed;
532                                         }
533
534                                         lock_buffer(nbh);
535                                         memcpy(nbh->b_data, obh->b_data,
536                                                         journal->j_blocksize);
537                                         if (flags & JBD2_FLAG_ESCAPE) {
538                                                 *((__be32 *)nbh->b_data) =
539                                                 cpu_to_be32(JBD2_MAGIC_NUMBER);
540                                         }
541
542                                         BUFFER_TRACE(nbh, "marking dirty");
543                                         set_buffer_uptodate(nbh);
544                                         mark_buffer_dirty(nbh);
545                                         BUFFER_TRACE(nbh, "marking uptodate");
546                                         ++info->nr_replays;
547                                         /* ll_rw_block(WRITE, 1, &nbh); */
548                                         unlock_buffer(nbh);
549                                         brelse(obh);
550                                         brelse(nbh);
551                                 }
552
553                         skip_write:
554                                 tagp += tag_bytes;
555                                 if (!(flags & JBD2_FLAG_SAME_UUID))
556                                         tagp += 16;
557
558                                 if (flags & JBD2_FLAG_LAST_TAG)
559                                         break;
560                         }
561
562                         brelse(bh);
563                         continue;
564
565                 case JBD2_COMMIT_BLOCK:
566                         /*     How to differentiate between interrupted commit
567                          *               and journal corruption ?
568                          *
569                          * {nth transaction}
570                          *        Checksum Verification Failed
571                          *                       |
572                          *               ____________________
573                          *              |                    |
574                          *      async_commit             sync_commit
575                          *              |                    |
576                          *              | GO TO NEXT    "Journal Corruption"
577                          *              | TRANSACTION
578                          *              |
579                          * {(n+1)th transanction}
580                          *              |
581                          *       _______|______________
582                          *      |                     |
583                          * Commit block found   Commit block not found
584                          *      |                     |
585                          * "Journal Corruption"       |
586                          *               _____________|_________
587                          *              |                       |
588                          *      nth trans corrupt       OR   nth trans
589                          *      and (n+1)th interrupted     interrupted
590                          *      before commit block
591                          *      could reach the disk.
592                          *      (Cannot find the difference in above
593                          *       mentioned conditions. Hence assume
594                          *       "Interrupted Commit".)
595                          */
596
597                         /* Found an expected commit block: if checksums
598                          * are present verify them in PASS_SCAN; else not
599                          * much to do other than move on to the next sequence
600                          * number. */
601                         if (pass == PASS_SCAN &&
602                             JBD2_HAS_COMPAT_FEATURE(journal,
603                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
604                                 int chksum_err, chksum_seen;
605                                 struct commit_header *cbh =
606                                         (struct commit_header *)bh->b_data;
607                                 unsigned found_chksum =
608                                         be32_to_cpu(cbh->h_chksum[0]);
609
610                                 chksum_err = chksum_seen = 0;
611
612                                 if (info->end_transaction) {
613                                         printk(KERN_ERR "JBD: Transaction %u "
614                                                 "found to be corrupt.\n",
615                                                 next_commit_ID - 1);
616                                         brelse(bh);
617                                         break;
618                                 }
619
620                                 if (crc32_sum == found_chksum &&
621                                     cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
622                                     cbh->h_chksum_size ==
623                                                 JBD2_CRC32_CHKSUM_SIZE)
624                                        chksum_seen = 1;
625                                 else if (!(cbh->h_chksum_type == 0 &&
626                                              cbh->h_chksum_size == 0 &&
627                                              found_chksum == 0 &&
628                                              !chksum_seen))
629                                 /*
630                                  * If fs is mounted using an old kernel and then
631                                  * kernel with journal_chksum is used then we
632                                  * get a situation where the journal flag has
633                                  * checksum flag set but checksums are not
634                                  * present i.e chksum = 0, in the individual
635                                  * commit blocks.
636                                  * Hence to avoid checksum failures, in this
637                                  * situation, this extra check is added.
638                                  */
639                                                 chksum_err = 1;
640
641                                 if (chksum_err) {
642                                         info->end_transaction = next_commit_ID;
643
644                                         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
645                                            JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){
646                                                 printk(KERN_ERR
647                                                        "JBD: Transaction %u "
648                                                        "found to be corrupt.\n",
649                                                        next_commit_ID);
650                                                 brelse(bh);
651                                                 break;
652                                         }
653                                 }
654                                 crc32_sum = ~0;
655                         }
656                         brelse(bh);
657                         next_commit_ID++;
658                         continue;
659
660                 case JBD2_REVOKE_BLOCK:
661                         /* If we aren't in the REVOKE pass, then we can
662                          * just skip over this block. */
663                         if (pass != PASS_REVOKE) {
664                                 brelse(bh);
665                                 continue;
666                         }
667
668                         err = scan_revoke_records(journal, bh,
669                                                   next_commit_ID, info);
670                         brelse(bh);
671                         if (err)
672                                 goto failed;
673                         continue;
674
675                 default:
676                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
677                                   blocktype);
678                         brelse(bh);
679                         goto done;
680                 }
681         }
682
683  done:
684         /*
685          * We broke out of the log scan loop: either we came to the
686          * known end of the log or we found an unexpected block in the
687          * log.  If the latter happened, then we know that the "current"
688          * transaction marks the end of the valid log.
689          */
690
691         if (pass == PASS_SCAN) {
692                 if (!info->end_transaction)
693                         info->end_transaction = next_commit_ID;
694         } else {
695                 /* It's really bad news if different passes end up at
696                  * different places (but possible due to IO errors). */
697                 if (info->end_transaction != next_commit_ID) {
698                         printk (KERN_ERR "JBD: recovery pass %d ended at "
699                                 "transaction %u, expected %u\n",
700                                 pass, next_commit_ID, info->end_transaction);
701                         if (!success)
702                                 success = -EIO;
703                 }
704         }
705
706         return success;
707
708  failed:
709         return err;
710 }
711
712
713 /* Scan a revoke record, marking all blocks mentioned as revoked. */
714
715 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
716                                tid_t sequence, struct recovery_info *info)
717 {
718         jbd2_journal_revoke_header_t *header;
719         int offset, max;
720         int record_len = 4;
721
722         header = (jbd2_journal_revoke_header_t *) bh->b_data;
723         offset = sizeof(jbd2_journal_revoke_header_t);
724         max = be32_to_cpu(header->r_count);
725
726         if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
727                 record_len = 8;
728
729         while (offset + record_len <= max) {
730                 unsigned long long blocknr;
731                 int err;
732
733                 if (record_len == 4)
734                         blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
735                 else
736                         blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
737                 offset += record_len;
738                 err = jbd2_journal_set_revoke(journal, blocknr, sequence);
739                 if (err)
740                         return err;
741                 ++info->nr_revokes;
742         }
743         return 0;
744 }