fs/jbd/recovery.c

   1 /*
   2  * linux/fs/jbd/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/jbd.h>
  22 #include <linux/errno.h>
  23 #endif
  24
  25 /*
  26  * Maintain information about the progress of the recovery job, so that
  27  * the different passes can carry information between them.
  28  */
  29 struct recovery_info
  30 {
  31         tid_t           start_transaction;
  32         tid_t           end_transaction;
  33
  34         int             nr_replays;
  35         int             nr_revokes;
  36         int             nr_revoke_hits;
  37 };
  38
  39 enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  40 static int do_one_pass(journal_t *journal,
  41                                 struct recovery_info *info, enum passtype pass);
  42 static int scan_revoke_records(journal_t *, struct buffer_head *,
  43                                 tid_t, struct recovery_info *);
  44
  45 #ifdef __KERNEL__
  46
  47 /* Release readahead buffers after use */
  48 static void journal_brelse_array(struct buffer_head *b[], int n)
  49 {
  50         while (--n >= 0)
  51                 brelse (b[n]);
  52 }
  53
  54
  55 /*
  56  * When reading from the journal, we are going through the block device
  57  * layer directly and so there is no readahead being done for us.  We
  58  * need to implement any readahead ourselves if we want it to happen at
  59  * all.  Recovery is basically one long sequential read, so make sure we
  60  * do the IO in reasonably large chunks.
  61  *
  62  * This is not so critical that we need to be enormously clever about
  63  * the readahead size, though.  128K is a purely arbitrary, good-enough
  64  * fixed value.
  65  */
  66
  67 #define MAXBUF 8
  68 static int do_readahead(journal_t *journal, unsigned int start)
  69 {
  70         int err;
  71         unsigned int max, nbufs, next;
  72         unsigned int blocknr;
  73         struct buffer_head *bh;
  74
  75         struct buffer_head * bufs[MAXBUF];
  76
  77         /* Do up to 128K of readahead */
  78         max = start + (128 * 1024 / journal->j_blocksize);
  79         if (max > journal->j_maxlen)
  80                 max = journal->j_maxlen;
  81
  82         /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
  83          * a time to the block device IO layer. */
  84
  85         nbufs = 0;
  86
  87         for (next = start; next < max; next++) {
  88                 err = journal_bmap(journal, next, &blocknr);
  89
  90                 if (err) {
  91                         printk (KERN_ERR "JBD: bad block at offset %u\n",
  92                                 next);
  93                         goto failed;
  94                 }
  95
  96                 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  97                 if (!bh) {
  98                         err = -ENOMEM;
  99                         goto failed;
 100                 }
 101
 102                 if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
 103                         bufs[nbufs++] = bh;
 104                         if (nbufs == MAXBUF) {
 105                                 ll_rw_block(READ, nbufs, bufs);
 106                                 journal_brelse_array(bufs, nbufs);
 107                                 nbufs = 0;
 108                         }
 109                 } else
 110                         brelse(bh);
 111         }
 112
 113         if (nbufs)
 114                 ll_rw_block(READ, nbufs, bufs);
 115         err = 0;
 116
 117 failed:
 118         if (nbufs)
 119                 journal_brelse_array(bufs, nbufs);
 120         return err;
 121 }
 122
 123 #endif /* __KERNEL__ */
 124
 125
 126 /*
 127  * Read a block from the journal
 128  */
 129
 130 static int jread(struct buffer_head **bhp, journal_t *journal,
 131                  unsigned int offset)
 132 {
 133         int err;
 134         unsigned int blocknr;
 135         struct buffer_head *bh;
 136
 137         *bhp = NULL;
 138
 139         if (offset >= journal->j_maxlen) {
 140                 printk(KERN_ERR "JBD: corrupted journal superblock\n");
 141                 return -EIO;
 142         }
 143
 144         err = journal_bmap(journal, offset, &blocknr);
 145
 146         if (err) {
 147                 printk (KERN_ERR "JBD: bad block at offset %u\n",
 148                         offset);
 149                 return err;
 150         }
 151
 152         bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
 153         if (!bh)
 154                 return -ENOMEM;
 155
 156         if (!buffer_uptodate(bh)) {
 157                 /* If this is a brand new buffer, start readahead.
 158                    Otherwise, we assume we are already reading it.  */
 159                 if (!buffer_req(bh))
 160                         do_readahead(journal, offset);
 161                 wait_on_buffer(bh);
 162         }
 163
 164         if (!buffer_uptodate(bh)) {
 165                 printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
 166                         offset);
 167                 brelse(bh);
 168                 return -EIO;
 169         }
 170
 171         *bhp = bh;
 172         return 0;
 173 }
 174
 175
 176 /*
 177  * Count the number of in-use tags in a journal descriptor block.
 178  */
 179
 180 static int count_tags(struct buffer_head *bh, int size)
 181 {
 182         char *                  tagp;
 183         journal_block_tag_t *   tag;
 184         int                     nr = 0;
 185
 186         tagp = &bh->b_data[sizeof(journal_header_t)];
 187
 188         while ((tagp - bh->b_data + sizeof(journal_block_tag_t)) <= size) {
 189                 tag = (journal_block_tag_t *) tagp;
 190
 191                 nr++;
 192                 tagp += sizeof(journal_block_tag_t);
 193                 if (!(tag->t_flags & cpu_to_be32(JFS_FLAG_SAME_UUID)))
 194                         tagp += 16;
 195
 196                 if (tag->t_flags & cpu_to_be32(JFS_FLAG_LAST_TAG))
 197                         break;
 198         }
 199
 200         return nr;
 201 }
 202
 203
 204 /* Make sure we wrap around the log correctly! */
 205 #define wrap(journal, var)                                              \
 206 do {                                                                    \
 207         if (var >= (journal)->j_last)                                   \
 208                 var -= ((journal)->j_last - (journal)->j_first);        \
 209 } while (0)
 210
 211 /**
 212  * journal_recover - recovers a on-disk journal
 213  * @journal: the journal to recover
 214  *
 215  * The primary function for recovering the log contents when mounting a
 216  * journaled device.
 217  *
 218  * Recovery is done in three passes.  In the first pass, we look for the
 219  * end of the log.  In the second, we assemble the list of revoke
 220  * blocks.  In the third and final pass, we replay any un-revoked blocks
 221  * in the log.
 222  */
 223 int journal_recover(journal_t *journal)
 224 {
 225         int                     err, err2;
 226         journal_superblock_t *  sb;
 227
 228         struct recovery_info    info;
 229
 230         memset(&info, 0, sizeof(info));
 231         sb = journal->j_superblock;
 232
 233         /*
 234          * The journal superblock's s_start field (the current log head)
 235          * is always zero if, and only if, the journal was cleanly
 236          * unmounted.
 237          */
 238
 239         if (!sb->s_start) {
 240                 jbd_debug(1, "No recovery required, last transaction %d\n",
 241                           be32_to_cpu(sb->s_sequence));
 242                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
 243                 return 0;
 244         }
 245
 246         err = do_one_pass(journal, &info, PASS_SCAN);
 247         if (!err)
 248                 err = do_one_pass(journal, &info, PASS_REVOKE);
 249         if (!err)
 250                 err = do_one_pass(journal, &info, PASS_REPLAY);
 251
 252         jbd_debug(1, "JBD: recovery, exit status %d, "
 253                   "recovered transactions %u to %u\n",
 254                   err, info.start_transaction, info.end_transaction);
 255         jbd_debug(1, "JBD: Replayed %d and revoked %d/%d blocks\n",
 256                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
 257
 258         /* Restart the log at the next transaction ID, thus invalidating
 259          * any existing commit records in the log. */
 260         journal->j_transaction_sequence = ++info.end_transaction;
 261
 262         journal_clear_revoke(journal);
 263         err2 = sync_blockdev(journal->j_fs_dev);
 264         if (!err)
 265                 err = err2;
 266
 267         return err;
 268 }
 269
 270 /**
 271  * 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 journal_skip_recovery(journal_t *journal)
 284 {
 285         int                     err;
 286         struct recovery_info    info;
 287
 288         memset (&info, 0, sizeof(info));
 289
 290         err = do_one_pass(journal, &info, PASS_SCAN);
 291
 292         if (err) {
 293                 printk(KERN_ERR "JBD: error %d scanning journal\n", err);
 294                 ++journal->j_transaction_sequence;
 295         } else {
 296 #ifdef CONFIG_JBD_DEBUG
 297                 int dropped = info.end_transaction -
 298                               be32_to_cpu(journal->j_superblock->s_sequence);
 299                 jbd_debug(1,
 300                           "JBD: ignoring %d transaction%s from the journal.\n",
 301                           dropped, (dropped == 1) ? "" : "s");
 302 #endif
 303                 journal->j_transaction_sequence = ++info.end_transaction;
 304         }
 305
 306         journal->j_tail = 0;
 307         return err;
 308 }
 309
 310 static int do_one_pass(journal_t *journal,
 311                         struct recovery_info *info, enum passtype pass)
 312 {
 313         unsigned int            first_commit_ID, next_commit_ID;
 314         unsigned int            next_log_block;
 315         int                     err, success = 0;
 316         journal_superblock_t *  sb;
 317         journal_header_t *      tmp;
 318         struct buffer_head *    bh;
 319         unsigned int            sequence;
 320         int                     blocktype;
 321
 322         /*
 323          * First thing is to establish what we expect to find in the log
 324          * (in terms of transaction IDs), and where (in terms of log
 325          * block offsets): query the superblock.
 326          */
 327
 328         sb = journal->j_superblock;
 329         next_commit_ID = be32_to_cpu(sb->s_sequence);
 330         next_log_block = be32_to_cpu(sb->s_start);
 331
 332         first_commit_ID = next_commit_ID;
 333         if (pass == PASS_SCAN)
 334                 info->start_transaction = first_commit_ID;
 335
 336         jbd_debug(1, "Starting recovery pass %d\n", pass);
 337
 338         /*
 339          * Now we walk through the log, transaction by transaction,
 340          * making sure that each transaction has a commit block in the
 341          * expected place.  Each complete transaction gets replayed back
 342          * into the main filesystem.
 343          */
 344
 345         while (1) {
 346                 int                     flags;
 347                 char *                  tagp;
 348                 journal_block_tag_t *   tag;
 349                 struct buffer_head *    obh;
 350                 struct buffer_head *    nbh;
 351
 352                 cond_resched();
 353
 354                 /* If we already know where to stop the log traversal,
 355                  * check right now that we haven't gone past the end of
 356                  * the log. */
 357
 358                 if (pass != PASS_SCAN)
 359                         if (tid_geq(next_commit_ID, info->end_transaction))
 360                                 break;
 361
 362                 jbd_debug(2, "Scanning for sequence ID %u at %u/%u\n",
 363                           next_commit_ID, next_log_block, journal->j_last);
 364
 365                 /* Skip over each chunk of the transaction looking
 366                  * either the next descriptor block or the final commit
 367                  * record. */
 368
 369                 jbd_debug(3, "JBD: checking block %u\n", next_log_block);
 370                 err = jread(&bh, journal, next_log_block);
 371                 if (err)
 372                         goto failed;
 373
 374                 next_log_block++;
 375                 wrap(journal, next_log_block);
 376
 377                 /* What kind of buffer is it?
 378                  *
 379                  * If it is a descriptor block, check that it has the
 380                  * expected sequence number.  Otherwise, we're all done
 381                  * here. */
 382
 383                 tmp = (journal_header_t *)bh->b_data;
 384
 385                 if (tmp->h_magic != cpu_to_be32(JFS_MAGIC_NUMBER)) {
 386                         brelse(bh);
 387                         break;
 388                 }
 389
 390                 blocktype = be32_to_cpu(tmp->h_blocktype);
 391                 sequence = be32_to_cpu(tmp->h_sequence);
 392                 jbd_debug(3, "Found magic %d, sequence %d\n",
 393                           blocktype, sequence);
 394
 395                 if (sequence != next_commit_ID) {
 396                         brelse(bh);
 397                         break;
 398                 }
 399
 400                 /* OK, we have a valid descriptor block which matches
 401                  * all of the sequence number checks.  What are we going
 402                  * to do with it?  That depends on the pass... */
 403
 404                 switch(blocktype) {
 405                 case JFS_DESCRIPTOR_BLOCK:
 406                         /* If it is a valid descriptor block, replay it
 407                          * in pass REPLAY; otherwise, just skip over the
 408                          * blocks it describes. */
 409                         if (pass != PASS_REPLAY) {
 410                                 next_log_block +=
 411                                         count_tags(bh, journal->j_blocksize);
 412                                 wrap(journal, next_log_block);
 413                                 brelse(bh);
 414                                 continue;
 415                         }
 416
 417                         /* A descriptor block: we can now write all of
 418                          * the data blocks.  Yay, useful work is finally
 419                          * getting done here! */
 420
 421                         tagp = &bh->b_data[sizeof(journal_header_t)];
 422                         while ((tagp - bh->b_data +sizeof(journal_block_tag_t))
 423                                <= journal->j_blocksize) {
 424                                 unsigned int io_block;
 425
 426                                 tag = (journal_block_tag_t *) tagp;
 427                                 flags = be32_to_cpu(tag->t_flags);
 428
 429                                 io_block = next_log_block++;
 430                                 wrap(journal, next_log_block);
 431                                 err = jread(&obh, journal, io_block);
 432                                 if (err) {
 433                                         /* Recover what we can, but
 434                                          * report failure at the end. */
 435                                         success = err;
 436                                         printk (KERN_ERR
 437                                                 "JBD: IO error %d recovering "
 438                                                 "block %u in log\n",
 439                                                 err, io_block);
 440                                 } else {
 441                                         unsigned int blocknr;
 442
 443                                         J_ASSERT(obh != NULL);
 444                                         blocknr = be32_to_cpu(tag->t_blocknr);
 445
 446                                         /* If the block has been
 447                                          * revoked, then we're all done
 448                                          * here. */
 449                                         if (journal_test_revoke
 450                                             (journal, blocknr,
 451                                              next_commit_ID)) {
 452                                                 brelse(obh);
 453                                                 ++info->nr_revoke_hits;
 454                                                 goto skip_write;
 455                                         }
 456
 457                                         /* Find a buffer for the new
 458                                          * data being restored */
 459                                         nbh = __getblk(journal->j_fs_dev,
 460                                                         blocknr,
 461                                                         journal->j_blocksize);
 462                                         if (nbh == NULL) {
 463                                                 printk(KERN_ERR
 464                                                        "JBD: Out of memory "
 465                                                        "during recovery.\n");
 466                                                 err = -ENOMEM;
 467                                                 brelse(bh);
 468                                                 brelse(obh);
 469                                                 goto failed;
 470                                         }
 471
 472                                         lock_buffer(nbh);
 473                                         memcpy(nbh->b_data, obh->b_data,
 474                                                         journal->j_blocksize);
 475                                         if (flags & JFS_FLAG_ESCAPE) {
 476                                                 *((__be32 *)nbh->b_data) =
 477                                                 cpu_to_be32(JFS_MAGIC_NUMBER);
 478                                         }
 479
 480                                         BUFFER_TRACE(nbh, "marking dirty");
 481                                         set_buffer_uptodate(nbh);
 482                                         mark_buffer_dirty(nbh);
 483                                         BUFFER_TRACE(nbh, "marking uptodate");
 484                                         ++info->nr_replays;
 485                                         /* ll_rw_block(WRITE, 1, &nbh); */
 486                                         unlock_buffer(nbh);
 487                                         brelse(obh);
 488                                         brelse(nbh);
 489                                 }
 490
 491                         skip_write:
 492                                 tagp += sizeof(journal_block_tag_t);
 493                                 if (!(flags & JFS_FLAG_SAME_UUID))
 494                                         tagp += 16;
 495
 496                                 if (flags & JFS_FLAG_LAST_TAG)
 497                                         break;
 498                         }
 499
 500                         brelse(bh);
 501                         continue;
 502
 503                 case JFS_COMMIT_BLOCK:
 504                         /* Found an expected commit block: not much to
 505                          * do other than move on to the next sequence
 506                          * number. */
 507                         brelse(bh);
 508                         next_commit_ID++;
 509                         continue;
 510
 511                 case JFS_REVOKE_BLOCK:
 512                         /* If we aren't in the REVOKE pass, then we can
 513                          * just skip over this block. */
 514                         if (pass != PASS_REVOKE) {
 515                                 brelse(bh);
 516                                 continue;
 517                         }
 518
 519                         err = scan_revoke_records(journal, bh,
 520                                                   next_commit_ID, info);
 521                         brelse(bh);
 522                         if (err)
 523                                 goto failed;
 524                         continue;
 525
 526                 default:
 527                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 528                                   blocktype);
 529                         brelse(bh);
 530                         goto done;
 531                 }
 532         }
 533
 534  done:
 535         /*
 536          * We broke out of the log scan loop: either we came to the
 537          * known end of the log or we found an unexpected block in the
 538          * log.  If the latter happened, then we know that the "current"
 539          * transaction marks the end of the valid log.
 540          */
 541
 542         if (pass == PASS_SCAN)
 543                 info->end_transaction = next_commit_ID;
 544         else {
 545                 /* It's really bad news if different passes end up at
 546                  * different places (but possible due to IO errors). */
 547                 if (info->end_transaction != next_commit_ID) {
 548                         printk (KERN_ERR "JBD: recovery pass %d ended at "
 549                                 "transaction %u, expected %u\n",
 550                                 pass, next_commit_ID, info->end_transaction);
 551                         if (!success)
 552                                 success = -EIO;
 553                 }
 554         }
 555
 556         return success;
 557
 558  failed:
 559         return err;
 560 }
 561
 562
 563 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 564
 565 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 566                                tid_t sequence, struct recovery_info *info)
 567 {
 568         journal_revoke_header_t *header;
 569         int offset, max;
 570
 571         header = (journal_revoke_header_t *) bh->b_data;
 572         offset = sizeof(journal_revoke_header_t);
 573         max = be32_to_cpu(header->r_count);
 574
 575         while (offset < max) {
 576                 unsigned int blocknr;
 577                 int err;
 578
 579                 blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 580                 offset += 4;
 581                 err = journal_set_revoke(journal, blocknr, sequence);
 582                 if (err)
 583                         return err;
 584                 ++info->nr_revokes;
 585         }
 586         return 0;
 587 }