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   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 #include <linux/slab.h>
  24 #endif
  25
  26 /*
  27  * Maintain information about the progress of the recovery job, so that
  28  * the different passes can carry information between them.
  29  */
  30 struct recovery_info
  31 {
  32         tid_t           start_transaction;
  33         tid_t           end_transaction;
  34
  35         int             nr_replays;
  36         int             nr_revokes;
  37         int             nr_revoke_hits;
  38 };
  39
  40 enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  41 static int do_one_pass(journal_t *journal,
  42                                 struct recovery_info *info, enum passtype pass);
  43 static int scan_revoke_records(journal_t *, struct buffer_head *,
  44                                 tid_t, struct recovery_info *);
  45
  46 #ifdef __KERNEL__
  47
  48 /* Release readahead buffers after use */
  49 static void journal_brelse_array(struct buffer_head *b[], int n)
  50 {
  51         while (--n >= 0)
  52                 brelse (b[n]);
  53 }
  54
  55
  56 /*
  57  * When reading from the journal, we are going through the block device
  58  * layer directly and so there is no readahead being done for us.  We
  59  * need to implement any readahead ourselves if we want it to happen at
  60  * all.  Recovery is basically one long sequential read, so make sure we
  61  * do the IO in reasonably large chunks.
  62  *
  63  * This is not so critical that we need to be enormously clever about
  64  * the readahead size, though.  128K is a purely arbitrary, good-enough
  65  * fixed value.
  66  */
  67
  68 #define MAXBUF 8
  69 static int do_readahead(journal_t *journal, unsigned int start)
  70 {
  71         int err;
  72         unsigned int max, nbufs, next;
  73         unsigned long blocknr;
  74         struct buffer_head *bh;
  75
  76         struct buffer_head * bufs[MAXBUF];
  77
  78         /* Do up to 128K of readahead */
  79         max = start + (128 * 1024 / journal->j_blocksize);
  80         if (max > journal->j_maxlen)
  81                 max = journal->j_maxlen;
  82
  83         /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
  84          * a time to the block device IO layer. */
  85
  86         nbufs = 0;
  87
  88         for (next = start; next < max; next++) {
  89                 err = journal_bmap(journal, next, &blocknr);
  90
  91                 if (err) {
  92                         printk (KERN_ERR "JBD: bad block at offset %u\n",
  93                                 next);
  94                         goto failed;
  95                 }
  96
  97                 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  98                 if (!bh) {
  99                         err = -ENOMEM;
 100                         goto failed;
 101                 }
 102
 103                 if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
 104                         bufs[nbufs++] = bh;
 105                         if (nbufs == MAXBUF) {
 106                                 ll_rw_block(READ, nbufs, bufs);
 107                                 journal_brelse_array(bufs, nbufs);
 108                                 nbufs = 0;
 109                         }
 110                 } else
 111                         brelse(bh);
 112         }
 113
 114         if (nbufs)
 115                 ll_rw_block(READ, nbufs, bufs);
 116         err = 0;
 117
 118 failed:
 119         if (nbufs)
 120                 journal_brelse_array(bufs, nbufs);
 121         return err;
 122 }
 123
 124 #endif /* __KERNEL__ */
 125
 126
 127 /*
 128  * Read a block from the journal
 129  */
 130
 131 static int jread(struct buffer_head **bhp, journal_t *journal,
 132                  unsigned int offset)
 133 {
 134         int err;
 135         unsigned long blocknr;
 136         struct buffer_head *bh;
 137
 138         *bhp = NULL;
 139
 140         if (offset >= journal->j_maxlen) {
 141                 printk(KERN_ERR "JBD: corrupted journal superblock\n");
 142                 return -EIO;
 143         }
 144
 145         err = journal_bmap(journal, offset, &blocknr);
 146
 147         if (err) {
 148                 printk (KERN_ERR "JBD: bad block at offset %u\n",
 149                         offset);
 150                 return err;
 151         }
 152
 153         bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
 154         if (!bh)
 155                 return -ENOMEM;
 156
 157         if (!buffer_uptodate(bh)) {
 158                 /* If this is a brand new buffer, start readahead.
 159                    Otherwise, we assume we are already reading it.  */
 160                 if (!buffer_req(bh))
 161                         do_readahead(journal, offset);
 162                 wait_on_buffer(bh);
 163         }
 164
 165         if (!buffer_uptodate(bh)) {
 166                 printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
 167                         offset);
 168                 brelse(bh);
 169                 return -EIO;
 170         }
 171
 172         *bhp = bh;
 173         return 0;
 174 }
 175
 176
 177 /*
 178  * Count the number of in-use tags in a journal descriptor block.
 179  */
 180
 181 static int count_tags(struct buffer_head *bh, int size)
 182 {
 183         char *                  tagp;
 184         journal_block_tag_t *   tag;
 185         int                     nr = 0;
 186
 187         tagp = &bh->b_data[sizeof(journal_header_t)];
 188
 189         while ((tagp - bh->b_data + sizeof(journal_block_tag_t)) <= size) {
 190                 tag = (journal_block_tag_t *) tagp;
 191
 192                 nr++;
 193                 tagp += sizeof(journal_block_tag_t);
 194                 if (!(tag->t_flags & cpu_to_be32(JFS_FLAG_SAME_UUID)))
 195                         tagp += 16;
 196
 197                 if (tag->t_flags & cpu_to_be32(JFS_FLAG_LAST_TAG))
 198                         break;
 199         }
 200
 201         return nr;
 202 }
 203
 204
 205 /* Make sure we wrap around the log correctly! */
 206 #define wrap(journal, var)                                              \
 207 do {                                                                    \
 208         if (var >= (journal)->j_last)                                   \
 209                 var -= ((journal)->j_last - (journal)->j_first);        \
 210 } while (0)
 211
 212 /**
 213  * journal_recover - recovers a on-disk journal
 214  * @journal: the journal to recover
 215  *
 216  * The primary function for recovering the log contents when mounting a
 217  * journaled device.
 218  *
 219  * Recovery is done in three passes.  In the first pass, we look for the
 220  * end of the log.  In the second, we assemble the list of revoke
 221  * blocks.  In the third and final pass, we replay any un-revoked blocks
 222  * in the log.
 223  */
 224 int journal_recover(journal_t *journal)
 225 {
 226         int                     err, err2;
 227         journal_superblock_t *  sb;
 228
 229         struct recovery_info    info;
 230
 231         memset(&info, 0, sizeof(info));
 232         sb = journal->j_superblock;
 233
 234         /*
 235          * The journal superblock's s_start field (the current log head)
 236          * is always zero if, and only if, the journal was cleanly
 237          * unmounted.
 238          */
 239
 240         if (!sb->s_start) {
 241                 jbd_debug(1, "No recovery required, last transaction %d\n",
 242                           be32_to_cpu(sb->s_sequence));
 243                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
 244                 return 0;
 245         }
 246
 247         err = do_one_pass(journal, &info, PASS_SCAN);
 248         if (!err)
 249                 err = do_one_pass(journal, &info, PASS_REVOKE);
 250         if (!err)
 251                 err = do_one_pass(journal, &info, PASS_REPLAY);
 252
 253         jbd_debug(1, "JBD: recovery, exit status %d, "
 254                   "recovered transactions %u to %u\n",
 255                   err, info.start_transaction, info.end_transaction);
 256         jbd_debug(1, "JBD: Replayed %d and revoked %d/%d blocks\n",
 257                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
 258
 259         /* Restart the log at the next transaction ID, thus invalidating
 260          * any existing commit records in the log. */
 261         journal->j_transaction_sequence = ++info.end_transaction;
 262
 263         journal_clear_revoke(journal);
 264         err2 = sync_blockdev(journal->j_fs_dev);
 265         if (!err)
 266                 err = err2;
 267
 268         return err;
 269 }
 270
 271 /**
 272  * journal_skip_recovery - Start journal and wipe exiting records
 273  * @journal: journal to startup
 274  *
 275  * Locate any valid recovery information from the journal and set up the
 276  * journal structures in memory to ignore it (presumably because the
 277  * caller has evidence that it is out of date).
 278  * This function does'nt appear to be exorted..
 279  *
 280  * We perform one pass over the journal to allow us to tell the user how
 281  * much recovery information is being erased, and to let us initialise
 282  * the journal transaction sequence numbers to the next unused ID.
 283  */
 284 int journal_skip_recovery(journal_t *journal)
 285 {
 286         int                     err;
 287         journal_superblock_t *  sb;
 288
 289         struct recovery_info    info;
 290
 291         memset (&info, 0, sizeof(info));
 292         sb = journal->j_superblock;
 293
 294         err = do_one_pass(journal, &info, PASS_SCAN);
 295
 296         if (err) {
 297                 printk(KERN_ERR "JBD: error %d scanning journal\n", err);
 298                 ++journal->j_transaction_sequence;
 299         } else {
 300 #ifdef CONFIG_JBD_DEBUG
 301                 int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
 302 #endif
 303                 jbd_debug(1,
 304                           "JBD: ignoring %d transaction%s from the journal.\n",
 305                           dropped, (dropped == 1) ? "" : "s");
 306                 journal->j_transaction_sequence = ++info.end_transaction;
 307         }
 308
 309         journal->j_tail = 0;
 310         return err;
 311 }
 312
 313 static int do_one_pass(journal_t *journal,
 314                         struct recovery_info *info, enum passtype pass)
 315 {
 316         unsigned int            first_commit_ID, next_commit_ID;
 317         unsigned long           next_log_block;
 318         int                     err, success = 0;
 319         journal_superblock_t *  sb;
 320         journal_header_t *      tmp;
 321         struct buffer_head *    bh;
 322         unsigned int            sequence;
 323         int                     blocktype;
 324
 325         /* Precompute the maximum metadata descriptors in a descriptor block */
 326         int                     MAX_BLOCKS_PER_DESC;
 327         MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
 328                                / sizeof(journal_block_tag_t));
 329
 330         /*
 331          * First thing is to establish what we expect to find in the log
 332          * (in terms of transaction IDs), and where (in terms of log
 333          * block offsets): query the superblock.
 334          */
 335
 336         sb = journal->j_superblock;
 337         next_commit_ID = be32_to_cpu(sb->s_sequence);
 338         next_log_block = be32_to_cpu(sb->s_start);
 339
 340         first_commit_ID = next_commit_ID;
 341         if (pass == PASS_SCAN)
 342                 info->start_transaction = first_commit_ID;
 343
 344         jbd_debug(1, "Starting recovery pass %d\n", pass);
 345
 346         /*
 347          * Now we walk through the log, transaction by transaction,
 348          * making sure that each transaction has a commit block in the
 349          * expected place.  Each complete transaction gets replayed back
 350          * into the main filesystem.
 351          */
 352
 353         while (1) {
 354                 int                     flags;
 355                 char *                  tagp;
 356                 journal_block_tag_t *   tag;
 357                 struct buffer_head *    obh;
 358                 struct buffer_head *    nbh;
 359
 360                 cond_resched();
 361
 362                 /* If we already know where to stop the log traversal,
 363                  * check right now that we haven't gone past the end of
 364                  * the log. */
 365
 366                 if (pass != PASS_SCAN)
 367                         if (tid_geq(next_commit_ID, info->end_transaction))
 368                                 break;
 369
 370                 jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
 371                           next_commit_ID, next_log_block, journal->j_last);
 372
 373                 /* Skip over each chunk of the transaction looking
 374                  * either the next descriptor block or the final commit
 375                  * record. */
 376
 377                 jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
 378                 err = jread(&bh, journal, next_log_block);
 379                 if (err)
 380                         goto failed;
 381
 382                 next_log_block++;
 383                 wrap(journal, next_log_block);
 384
 385                 /* What kind of buffer is it?
 386                  *
 387                  * If it is a descriptor block, check that it has the
 388                  * expected sequence number.  Otherwise, we're all done
 389                  * here. */
 390
 391                 tmp = (journal_header_t *)bh->b_data;
 392
 393                 if (tmp->h_magic != cpu_to_be32(JFS_MAGIC_NUMBER)) {
 394                         brelse(bh);
 395                         break;
 396                 }
 397
 398                 blocktype = be32_to_cpu(tmp->h_blocktype);
 399                 sequence = be32_to_cpu(tmp->h_sequence);
 400                 jbd_debug(3, "Found magic %d, sequence %d\n",
 401                           blocktype, sequence);
 402
 403                 if (sequence != next_commit_ID) {
 404                         brelse(bh);
 405                         break;
 406                 }
 407
 408                 /* OK, we have a valid descriptor block which matches
 409                  * all of the sequence number checks.  What are we going
 410                  * to do with it?  That depends on the pass... */
 411
 412                 switch(blocktype) {
 413                 case JFS_DESCRIPTOR_BLOCK:
 414                         /* If it is a valid descriptor block, replay it
 415                          * in pass REPLAY; otherwise, just skip over the
 416                          * blocks it describes. */
 417                         if (pass != PASS_REPLAY) {
 418                                 next_log_block +=
 419                                         count_tags(bh, journal->j_blocksize);
 420                                 wrap(journal, next_log_block);
 421                                 brelse(bh);
 422                                 continue;
 423                         }
 424
 425                         /* A descriptor block: we can now write all of
 426                          * the data blocks.  Yay, useful work is finally
 427                          * getting done here! */
 428
 429                         tagp = &bh->b_data[sizeof(journal_header_t)];
 430                         while ((tagp - bh->b_data +sizeof(journal_block_tag_t))
 431                                <= journal->j_blocksize) {
 432                                 unsigned long io_block;
 433
 434                                 tag = (journal_block_tag_t *) tagp;
 435                                 flags = be32_to_cpu(tag->t_flags);
 436
 437                                 io_block = next_log_block++;
 438                                 wrap(journal, next_log_block);
 439                                 err = jread(&obh, journal, io_block);
 440                                 if (err) {
 441                                         /* Recover what we can, but
 442                                          * report failure at the end. */
 443                                         success = err;
 444                                         printk (KERN_ERR
 445                                                 "JBD: IO error %d recovering "
 446                                                 "block %ld in log\n",
 447                                                 err, io_block);
 448                                 } else {
 449                                         unsigned long blocknr;
 450
 451                                         J_ASSERT(obh != NULL);
 452                                         blocknr = be32_to_cpu(tag->t_blocknr);
 453
 454                                         /* If the block has been
 455                                          * revoked, then we're all done
 456                                          * here. */
 457                                         if (journal_test_revoke
 458                                             (journal, blocknr,
 459                                              next_commit_ID)) {
 460                                                 brelse(obh);
 461                                                 ++info->nr_revoke_hits;
 462                                                 goto skip_write;
 463                                         }
 464
 465                                         /* Find a buffer for the new
 466                                          * data being restored */
 467                                         nbh = __getblk(journal->j_fs_dev,
 468                                                         blocknr,
 469                                                         journal->j_blocksize);
 470                                         if (nbh == NULL) {
 471                                                 printk(KERN_ERR
 472                                                        "JBD: Out of memory "
 473                                                        "during recovery.\n");
 474                                                 err = -ENOMEM;
 475                                                 brelse(bh);
 476                                                 brelse(obh);
 477                                                 goto failed;
 478                                         }
 479
 480                                         lock_buffer(nbh);
 481                                         memcpy(nbh->b_data, obh->b_data,
 482                                                         journal->j_blocksize);
 483                                         if (flags & JFS_FLAG_ESCAPE) {
 484                                                 *((__be32 *)nbh->b_data) =
 485                                                 cpu_to_be32(JFS_MAGIC_NUMBER);
 486                                         }
 487
 488                                         BUFFER_TRACE(nbh, "marking dirty");
 489                                         set_buffer_uptodate(nbh);
 490                                         mark_buffer_dirty(nbh);
 491                                         BUFFER_TRACE(nbh, "marking uptodate");
 492                                         ++info->nr_replays;
 493                                         /* ll_rw_block(WRITE, 1, &nbh); */
 494                                         unlock_buffer(nbh);
 495                                         brelse(obh);
 496                                         brelse(nbh);
 497                                 }
 498
 499                         skip_write:
 500                                 tagp += sizeof(journal_block_tag_t);
 501                                 if (!(flags & JFS_FLAG_SAME_UUID))
 502                                         tagp += 16;
 503
 504                                 if (flags & JFS_FLAG_LAST_TAG)
 505                                         break;
 506                         }
 507
 508                         brelse(bh);
 509                         continue;
 510
 511                 case JFS_COMMIT_BLOCK:
 512                         /* Found an expected commit block: not much to
 513                          * do other than move on to the next sequence
 514                          * number. */
 515                         brelse(bh);
 516                         next_commit_ID++;
 517                         continue;
 518
 519                 case JFS_REVOKE_BLOCK:
 520                         /* If we aren't in the REVOKE pass, then we can
 521                          * just skip over this block. */
 522                         if (pass != PASS_REVOKE) {
 523                                 brelse(bh);
 524                                 continue;
 525                         }
 526
 527                         err = scan_revoke_records(journal, bh,
 528                                                   next_commit_ID, info);
 529                         brelse(bh);
 530                         if (err)
 531                                 goto failed;
 532                         continue;
 533
 534                 default:
 535                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 536                                   blocktype);
 537                         brelse(bh);
 538                         goto done;
 539                 }
 540         }
 541
 542  done:
 543         /*
 544          * We broke out of the log scan loop: either we came to the
 545          * known end of the log or we found an unexpected block in the
 546          * log.  If the latter happened, then we know that the "current"
 547          * transaction marks the end of the valid log.
 548          */
 549
 550         if (pass == PASS_SCAN)
 551                 info->end_transaction = next_commit_ID;
 552         else {
 553                 /* It's really bad news if different passes end up at
 554                  * different places (but possible due to IO errors). */
 555                 if (info->end_transaction != next_commit_ID) {
 556                         printk (KERN_ERR "JBD: recovery pass %d ended at "
 557                                 "transaction %u, expected %u\n",
 558                                 pass, next_commit_ID, info->end_transaction);
 559                         if (!success)
 560                                 success = -EIO;
 561                 }
 562         }
 563
 564         return success;
 565
 566  failed:
 567         return err;
 568 }
 569
 570
 571 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 572
 573 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 574                                tid_t sequence, struct recovery_info *info)
 575 {
 576         journal_revoke_header_t *header;
 577         int offset, max;
 578
 579         header = (journal_revoke_header_t *) bh->b_data;
 580         offset = sizeof(journal_revoke_header_t);
 581         max = be32_to_cpu(header->r_count);
 582
 583         while (offset < max) {
 584                 unsigned long blocknr;
 585                 int err;
 586
 587                 blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 588                 offset += 4;
 589                 err = journal_set_revoke(journal, blocknr, sequence);
 590                 if (err)
 591                         return err;
 592                 ++info->nr_revokes;
 593         }
 594         return 0;
 595 }