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TOMOYO Linux Cross Reference
Linux/fs/jbd2/recovery.c

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  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/crc32.h>
 24 #include <linux/blkdev.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 "JBD2: 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(REQ_OP_READ, 0, 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(REQ_OP_READ, 0, 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 "JBD2: corrupted journal superblock\n");
143                 return -EFSCORRUPTED;
144         }
145 
146         err = jbd2_journal_bmap(journal, offset, &blocknr);
147 
148         if (err) {
149                 printk(KERN_ERR "JBD2: 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 "JBD2: 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 static int jbd2_descriptor_block_csum_verify(journal_t *j, void *buf)
178 {
179         struct jbd2_journal_block_tail *tail;
180         __be32 provided;
181         __u32 calculated;
182 
183         if (!jbd2_journal_has_csum_v2or3(j))
184                 return 1;
185 
186         tail = (struct jbd2_journal_block_tail *)(buf + j->j_blocksize -
187                         sizeof(struct jbd2_journal_block_tail));
188         provided = tail->t_checksum;
189         tail->t_checksum = 0;
190         calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
191         tail->t_checksum = provided;
192 
193         return provided == cpu_to_be32(calculated);
194 }
195 
196 /*
197  * Count the number of in-use tags in a journal descriptor block.
198  */
199 
200 static int count_tags(journal_t *journal, struct buffer_head *bh)
201 {
202         char *                  tagp;
203         journal_block_tag_t *   tag;
204         int                     nr = 0, size = journal->j_blocksize;
205         int                     tag_bytes = journal_tag_bytes(journal);
206 
207         if (jbd2_journal_has_csum_v2or3(journal))
208                 size -= sizeof(struct jbd2_journal_block_tail);
209 
210         tagp = &bh->b_data[sizeof(journal_header_t)];
211 
212         while ((tagp - bh->b_data + tag_bytes) <= size) {
213                 tag = (journal_block_tag_t *) tagp;
214 
215                 nr++;
216                 tagp += tag_bytes;
217                 if (!(tag->t_flags & cpu_to_be16(JBD2_FLAG_SAME_UUID)))
218                         tagp += 16;
219 
220                 if (tag->t_flags & cpu_to_be16(JBD2_FLAG_LAST_TAG))
221                         break;
222         }
223 
224         return nr;
225 }
226 
227 
228 /* Make sure we wrap around the log correctly! */
229 #define wrap(journal, var)                                              \
230 do {                                                                    \
231         if (var >= (journal)->j_last)                                   \
232                 var -= ((journal)->j_last - (journal)->j_first);        \
233 } while (0)
234 
235 /**
236  * jbd2_journal_recover - recovers a on-disk journal
237  * @journal: the journal to recover
238  *
239  * The primary function for recovering the log contents when mounting a
240  * journaled device.
241  *
242  * Recovery is done in three passes.  In the first pass, we look for the
243  * end of the log.  In the second, we assemble the list of revoke
244  * blocks.  In the third and final pass, we replay any un-revoked blocks
245  * in the log.
246  */
247 int jbd2_journal_recover(journal_t *journal)
248 {
249         int                     err, err2;
250         journal_superblock_t *  sb;
251 
252         struct recovery_info    info;
253 
254         memset(&info, 0, sizeof(info));
255         sb = journal->j_superblock;
256 
257         /*
258          * The journal superblock's s_start field (the current log head)
259          * is always zero if, and only if, the journal was cleanly
260          * unmounted.
261          */
262 
263         if (!sb->s_start) {
264                 jbd_debug(1, "No recovery required, last transaction %d\n",
265                           be32_to_cpu(sb->s_sequence));
266                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
267                 return 0;
268         }
269 
270         err = do_one_pass(journal, &info, PASS_SCAN);
271         if (!err)
272                 err = do_one_pass(journal, &info, PASS_REVOKE);
273         if (!err)
274                 err = do_one_pass(journal, &info, PASS_REPLAY);
275 
276         jbd_debug(1, "JBD2: recovery, exit status %d, "
277                   "recovered transactions %u to %u\n",
278                   err, info.start_transaction, info.end_transaction);
279         jbd_debug(1, "JBD2: Replayed %d and revoked %d/%d blocks\n",
280                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
281 
282         /* Restart the log at the next transaction ID, thus invalidating
283          * any existing commit records in the log. */
284         journal->j_transaction_sequence = ++info.end_transaction;
285 
286         jbd2_journal_clear_revoke(journal);
287         err2 = sync_blockdev(journal->j_fs_dev);
288         if (!err)
289                 err = err2;
290         /* Make sure all replayed data is on permanent storage */
291         if (journal->j_flags & JBD2_BARRIER) {
292                 err2 = blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
293                 if (!err)
294                         err = err2;
295         }
296         return err;
297 }
298 
299 /**
300  * jbd2_journal_skip_recovery - Start journal and wipe exiting records
301  * @journal: journal to startup
302  *
303  * Locate any valid recovery information from the journal and set up the
304  * journal structures in memory to ignore it (presumably because the
305  * caller has evidence that it is out of date).
306  * This function doesn't appear to be exported..
307  *
308  * We perform one pass over the journal to allow us to tell the user how
309  * much recovery information is being erased, and to let us initialise
310  * the journal transaction sequence numbers to the next unused ID.
311  */
312 int jbd2_journal_skip_recovery(journal_t *journal)
313 {
314         int                     err;
315 
316         struct recovery_info    info;
317 
318         memset (&info, 0, sizeof(info));
319 
320         err = do_one_pass(journal, &info, PASS_SCAN);
321 
322         if (err) {
323                 printk(KERN_ERR "JBD2: error %d scanning journal\n", err);
324                 ++journal->j_transaction_sequence;
325         } else {
326 #ifdef CONFIG_JBD2_DEBUG
327                 int dropped = info.end_transaction - 
328                         be32_to_cpu(journal->j_superblock->s_sequence);
329                 jbd_debug(1,
330                           "JBD2: ignoring %d transaction%s from the journal.\n",
331                           dropped, (dropped == 1) ? "" : "s");
332 #endif
333                 journal->j_transaction_sequence = ++info.end_transaction;
334         }
335 
336         journal->j_tail = 0;
337         return err;
338 }
339 
340 static inline unsigned long long read_tag_block(journal_t *journal,
341                                                 journal_block_tag_t *tag)
342 {
343         unsigned long long block = be32_to_cpu(tag->t_blocknr);
344         if (jbd2_has_feature_64bit(journal))
345                 block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
346         return block;
347 }
348 
349 /*
350  * calc_chksums calculates the checksums for the blocks described in the
351  * descriptor block.
352  */
353 static int calc_chksums(journal_t *journal, struct buffer_head *bh,
354                         unsigned long *next_log_block, __u32 *crc32_sum)
355 {
356         int i, num_blks, err;
357         unsigned long io_block;
358         struct buffer_head *obh;
359 
360         num_blks = count_tags(journal, bh);
361         /* Calculate checksum of the descriptor block. */
362         *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
363 
364         for (i = 0; i < num_blks; i++) {
365                 io_block = (*next_log_block)++;
366                 wrap(journal, *next_log_block);
367                 err = jread(&obh, journal, io_block);
368                 if (err) {
369                         printk(KERN_ERR "JBD2: IO error %d recovering block "
370                                 "%lu in log\n", err, io_block);
371                         return 1;
372                 } else {
373                         *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
374                                      obh->b_size);
375                 }
376                 put_bh(obh);
377         }
378         return 0;
379 }
380 
381 static int jbd2_commit_block_csum_verify(journal_t *j, void *buf)
382 {
383         struct commit_header *h;
384         __be32 provided;
385         __u32 calculated;
386 
387         if (!jbd2_journal_has_csum_v2or3(j))
388                 return 1;
389 
390         h = buf;
391         provided = h->h_chksum[0];
392         h->h_chksum[0] = 0;
393         calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
394         h->h_chksum[0] = provided;
395 
396         return provided == cpu_to_be32(calculated);
397 }
398 
399 static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag,
400                                       void *buf, __u32 sequence)
401 {
402         journal_block_tag3_t *tag3 = (journal_block_tag3_t *)tag;
403         __u32 csum32;
404         __be32 seq;
405 
406         if (!jbd2_journal_has_csum_v2or3(j))
407                 return 1;
408 
409         seq = cpu_to_be32(sequence);
410         csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
411         csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize);
412 
413         if (jbd2_has_feature_csum3(j))
414                 return tag3->t_checksum == cpu_to_be32(csum32);
415         else
416                 return tag->t_checksum == cpu_to_be16(csum32);
417 }
418 
419 static int do_one_pass(journal_t *journal,
420                         struct recovery_info *info, enum passtype pass)
421 {
422         unsigned int            first_commit_ID, next_commit_ID;
423         unsigned long           next_log_block;
424         int                     err, success = 0;
425         journal_superblock_t *  sb;
426         journal_header_t *      tmp;
427         struct buffer_head *    bh;
428         unsigned int            sequence;
429         int                     blocktype;
430         int                     tag_bytes = journal_tag_bytes(journal);
431         __u32                   crc32_sum = ~0; /* Transactional Checksums */
432         int                     descr_csum_size = 0;
433         int                     block_error = 0;
434 
435         /*
436          * First thing is to establish what we expect to find in the log
437          * (in terms of transaction IDs), and where (in terms of log
438          * block offsets): query the superblock.
439          */
440 
441         sb = journal->j_superblock;
442         next_commit_ID = be32_to_cpu(sb->s_sequence);
443         next_log_block = be32_to_cpu(sb->s_start);
444 
445         first_commit_ID = next_commit_ID;
446         if (pass == PASS_SCAN)
447                 info->start_transaction = first_commit_ID;
448 
449         jbd_debug(1, "Starting recovery pass %d\n", pass);
450 
451         /*
452          * Now we walk through the log, transaction by transaction,
453          * making sure that each transaction has a commit block in the
454          * expected place.  Each complete transaction gets replayed back
455          * into the main filesystem.
456          */
457 
458         while (1) {
459                 int                     flags;
460                 char *                  tagp;
461                 journal_block_tag_t *   tag;
462                 struct buffer_head *    obh;
463                 struct buffer_head *    nbh;
464 
465                 cond_resched();
466 
467                 /* If we already know where to stop the log traversal,
468                  * check right now that we haven't gone past the end of
469                  * the log. */
470 
471                 if (pass != PASS_SCAN)
472                         if (tid_geq(next_commit_ID, info->end_transaction))
473                                 break;
474 
475                 jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
476                           next_commit_ID, next_log_block, journal->j_last);
477 
478                 /* Skip over each chunk of the transaction looking
479                  * either the next descriptor block or the final commit
480                  * record. */
481 
482                 jbd_debug(3, "JBD2: checking block %ld\n", next_log_block);
483                 err = jread(&bh, journal, next_log_block);
484                 if (err)
485                         goto failed;
486 
487                 next_log_block++;
488                 wrap(journal, next_log_block);
489 
490                 /* What kind of buffer is it?
491                  *
492                  * If it is a descriptor block, check that it has the
493                  * expected sequence number.  Otherwise, we're all done
494                  * here. */
495 
496                 tmp = (journal_header_t *)bh->b_data;
497 
498                 if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
499                         brelse(bh);
500                         break;
501                 }
502 
503                 blocktype = be32_to_cpu(tmp->h_blocktype);
504                 sequence = be32_to_cpu(tmp->h_sequence);
505                 jbd_debug(3, "Found magic %d, sequence %d\n",
506                           blocktype, sequence);
507 
508                 if (sequence != next_commit_ID) {
509                         brelse(bh);
510                         break;
511                 }
512 
513                 /* OK, we have a valid descriptor block which matches
514                  * all of the sequence number checks.  What are we going
515                  * to do with it?  That depends on the pass... */
516 
517                 switch(blocktype) {
518                 case JBD2_DESCRIPTOR_BLOCK:
519                         /* Verify checksum first */
520                         if (jbd2_journal_has_csum_v2or3(journal))
521                                 descr_csum_size =
522                                         sizeof(struct jbd2_journal_block_tail);
523                         if (descr_csum_size > 0 &&
524                             !jbd2_descriptor_block_csum_verify(journal,
525                                                                bh->b_data)) {
526                                 printk(KERN_ERR "JBD2: Invalid checksum "
527                                        "recovering block %lu in log\n",
528                                        next_log_block);
529                                 err = -EFSBADCRC;
530                                 brelse(bh);
531                                 goto failed;
532                         }
533 
534                         /* If it is a valid descriptor block, replay it
535                          * in pass REPLAY; if journal_checksums enabled, then
536                          * calculate checksums in PASS_SCAN, otherwise,
537                          * just skip over the blocks it describes. */
538                         if (pass != PASS_REPLAY) {
539                                 if (pass == PASS_SCAN &&
540                                     jbd2_has_feature_checksum(journal) &&
541                                     !info->end_transaction) {
542                                         if (calc_chksums(journal, bh,
543                                                         &next_log_block,
544                                                         &crc32_sum)) {
545                                                 put_bh(bh);
546                                                 break;
547                                         }
548                                         put_bh(bh);
549                                         continue;
550                                 }
551                                 next_log_block += count_tags(journal, bh);
552                                 wrap(journal, next_log_block);
553                                 put_bh(bh);
554                                 continue;
555                         }
556 
557                         /* A descriptor block: we can now write all of
558                          * the data blocks.  Yay, useful work is finally
559                          * getting done here! */
560 
561                         tagp = &bh->b_data[sizeof(journal_header_t)];
562                         while ((tagp - bh->b_data + tag_bytes)
563                                <= journal->j_blocksize - descr_csum_size) {
564                                 unsigned long io_block;
565 
566                                 tag = (journal_block_tag_t *) tagp;
567                                 flags = be16_to_cpu(tag->t_flags);
568 
569                                 io_block = next_log_block++;
570                                 wrap(journal, next_log_block);
571                                 err = jread(&obh, journal, io_block);
572                                 if (err) {
573                                         /* Recover what we can, but
574                                          * report failure at the end. */
575                                         success = err;
576                                         printk(KERN_ERR
577                                                 "JBD2: IO error %d recovering "
578                                                 "block %ld in log\n",
579                                                 err, io_block);
580                                 } else {
581                                         unsigned long long blocknr;
582 
583                                         J_ASSERT(obh != NULL);
584                                         blocknr = read_tag_block(journal,
585                                                                  tag);
586 
587                                         /* If the block has been
588                                          * revoked, then we're all done
589                                          * here. */
590                                         if (jbd2_journal_test_revoke
591                                             (journal, blocknr,
592                                              next_commit_ID)) {
593                                                 brelse(obh);
594                                                 ++info->nr_revoke_hits;
595                                                 goto skip_write;
596                                         }
597 
598                                         /* Look for block corruption */
599                                         if (!jbd2_block_tag_csum_verify(
600                                                 journal, tag, obh->b_data,
601                                                 be32_to_cpu(tmp->h_sequence))) {
602                                                 brelse(obh);
603                                                 success = -EFSBADCRC;
604                                                 printk(KERN_ERR "JBD2: Invalid "
605                                                        "checksum recovering "
606                                                        "block %llu in log\n",
607                                                        blocknr);
608                                                 block_error = 1;
609                                                 goto skip_write;
610                                         }
611 
612                                         /* Find a buffer for the new
613                                          * data being restored */
614                                         nbh = __getblk(journal->j_fs_dev,
615                                                         blocknr,
616                                                         journal->j_blocksize);
617                                         if (nbh == NULL) {
618                                                 printk(KERN_ERR
619                                                        "JBD2: Out of memory "
620                                                        "during recovery.\n");
621                                                 err = -ENOMEM;
622                                                 brelse(bh);
623                                                 brelse(obh);
624                                                 goto failed;
625                                         }
626 
627                                         lock_buffer(nbh);
628                                         memcpy(nbh->b_data, obh->b_data,
629                                                         journal->j_blocksize);
630                                         if (flags & JBD2_FLAG_ESCAPE) {
631                                                 *((__be32 *)nbh->b_data) =
632                                                 cpu_to_be32(JBD2_MAGIC_NUMBER);
633                                         }
634 
635                                         BUFFER_TRACE(nbh, "marking dirty");
636                                         set_buffer_uptodate(nbh);
637                                         mark_buffer_dirty(nbh);
638                                         BUFFER_TRACE(nbh, "marking uptodate");
639                                         ++info->nr_replays;
640                                         /* ll_rw_block(WRITE, 1, &nbh); */
641                                         unlock_buffer(nbh);
642                                         brelse(obh);
643                                         brelse(nbh);
644                                 }
645 
646                         skip_write:
647                                 tagp += tag_bytes;
648                                 if (!(flags & JBD2_FLAG_SAME_UUID))
649                                         tagp += 16;
650 
651                                 if (flags & JBD2_FLAG_LAST_TAG)
652                                         break;
653                         }
654 
655                         brelse(bh);
656                         continue;
657 
658                 case JBD2_COMMIT_BLOCK:
659                         /*     How to differentiate between interrupted commit
660                          *               and journal corruption ?
661                          *
662                          * {nth transaction}
663                          *        Checksum Verification Failed
664                          *                       |
665                          *               ____________________
666                          *              |                    |
667                          *      async_commit             sync_commit
668                          *              |                    |
669                          *              | GO TO NEXT    "Journal Corruption"
670                          *              | TRANSACTION
671                          *              |
672                          * {(n+1)th transanction}
673                          *              |
674                          *       _______|______________
675                          *      |                     |
676                          * Commit block found   Commit block not found
677                          *      |                     |
678                          * "Journal Corruption"       |
679                          *               _____________|_________
680                          *              |                       |
681                          *      nth trans corrupt       OR   nth trans
682                          *      and (n+1)th interrupted     interrupted
683                          *      before commit block
684                          *      could reach the disk.
685                          *      (Cannot find the difference in above
686                          *       mentioned conditions. Hence assume
687                          *       "Interrupted Commit".)
688                          */
689 
690                         /* Found an expected commit block: if checksums
691                          * are present verify them in PASS_SCAN; else not
692                          * much to do other than move on to the next sequence
693                          * number. */
694                         if (pass == PASS_SCAN &&
695                             jbd2_has_feature_checksum(journal)) {
696                                 int chksum_err, chksum_seen;
697                                 struct commit_header *cbh =
698                                         (struct commit_header *)bh->b_data;
699                                 unsigned found_chksum =
700                                         be32_to_cpu(cbh->h_chksum[0]);
701 
702                                 chksum_err = chksum_seen = 0;
703 
704                                 if (info->end_transaction) {
705                                         journal->j_failed_commit =
706                                                 info->end_transaction;
707                                         brelse(bh);
708                                         break;
709                                 }
710 
711                                 if (crc32_sum == found_chksum &&
712                                     cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
713                                     cbh->h_chksum_size ==
714                                                 JBD2_CRC32_CHKSUM_SIZE)
715                                        chksum_seen = 1;
716                                 else if (!(cbh->h_chksum_type == 0 &&
717                                              cbh->h_chksum_size == 0 &&
718                                              found_chksum == 0 &&
719                                              !chksum_seen))
720                                 /*
721                                  * If fs is mounted using an old kernel and then
722                                  * kernel with journal_chksum is used then we
723                                  * get a situation where the journal flag has
724                                  * checksum flag set but checksums are not
725                                  * present i.e chksum = 0, in the individual
726                                  * commit blocks.
727                                  * Hence to avoid checksum failures, in this
728                                  * situation, this extra check is added.
729                                  */
730                                                 chksum_err = 1;
731 
732                                 if (chksum_err) {
733                                         info->end_transaction = next_commit_ID;
734 
735                                         if (!jbd2_has_feature_async_commit(journal)) {
736                                                 journal->j_failed_commit =
737                                                         next_commit_ID;
738                                                 brelse(bh);
739                                                 break;
740                                         }
741                                 }
742                                 crc32_sum = ~0;
743                         }
744                         if (pass == PASS_SCAN &&
745                             !jbd2_commit_block_csum_verify(journal,
746                                                            bh->b_data)) {
747                                 info->end_transaction = next_commit_ID;
748 
749                                 if (!jbd2_has_feature_async_commit(journal)) {
750                                         journal->j_failed_commit =
751                                                 next_commit_ID;
752                                         brelse(bh);
753                                         break;
754                                 }
755                         }
756                         brelse(bh);
757                         next_commit_ID++;
758                         continue;
759 
760                 case JBD2_REVOKE_BLOCK:
761                         /* If we aren't in the REVOKE pass, then we can
762                          * just skip over this block. */
763                         if (pass != PASS_REVOKE) {
764                                 brelse(bh);
765                                 continue;
766                         }
767 
768                         err = scan_revoke_records(journal, bh,
769                                                   next_commit_ID, info);
770                         brelse(bh);
771                         if (err)
772                                 goto failed;
773                         continue;
774 
775                 default:
776                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
777                                   blocktype);
778                         brelse(bh);
779                         goto done;
780                 }
781         }
782 
783  done:
784         /*
785          * We broke out of the log scan loop: either we came to the
786          * known end of the log or we found an unexpected block in the
787          * log.  If the latter happened, then we know that the "current"
788          * transaction marks the end of the valid log.
789          */
790 
791         if (pass == PASS_SCAN) {
792                 if (!info->end_transaction)
793                         info->end_transaction = next_commit_ID;
794         } else {
795                 /* It's really bad news if different passes end up at
796                  * different places (but possible due to IO errors). */
797                 if (info->end_transaction != next_commit_ID) {
798                         printk(KERN_ERR "JBD2: recovery pass %d ended at "
799                                 "transaction %u, expected %u\n",
800                                 pass, next_commit_ID, info->end_transaction);
801                         if (!success)
802                                 success = -EIO;
803                 }
804         }
805         if (block_error && success == 0)
806                 success = -EIO;
807         return success;
808 
809  failed:
810         return err;
811 }
812 
813 /* Scan a revoke record, marking all blocks mentioned as revoked. */
814 
815 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
816                                tid_t sequence, struct recovery_info *info)
817 {
818         jbd2_journal_revoke_header_t *header;
819         int offset, max;
820         int csum_size = 0;
821         __u32 rcount;
822         int record_len = 4;
823 
824         header = (jbd2_journal_revoke_header_t *) bh->b_data;
825         offset = sizeof(jbd2_journal_revoke_header_t);
826         rcount = be32_to_cpu(header->r_count);
827 
828         if (!jbd2_descriptor_block_csum_verify(journal, header))
829                 return -EFSBADCRC;
830 
831         if (jbd2_journal_has_csum_v2or3(journal))
832                 csum_size = sizeof(struct jbd2_journal_block_tail);
833         if (rcount > journal->j_blocksize - csum_size)
834                 return -EINVAL;
835         max = rcount;
836 
837         if (jbd2_has_feature_64bit(journal))
838                 record_len = 8;
839 
840         while (offset + record_len <= max) {
841                 unsigned long long blocknr;
842                 int err;
843 
844                 if (record_len == 4)
845                         blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
846                 else
847                         blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
848                 offset += record_len;
849                 err = jbd2_journal_set_revoke(journal, blocknr, sequence);
850                 if (err)
851                         return err;
852                 ++info->nr_revokes;
853         }
854         return 0;
855 }
856 

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