fs/jbd/recovery.c

   1 /*
   2  * linux/fs/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 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 & htonl(JFS_FLAG_SAME_UUID)))
 195                         tagp += 16;
 196
 197                 if (tag->t_flags & htonl(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  * int journal_recover(journal_t *journal) - 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;
 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                           ntohl(sb->s_sequence));
 243                 journal->j_transaction_sequence = ntohl(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(0, "JBD: recovery, exit status %d, "
 254                   "recovered transactions %u to %u\n",
 255                   err, info.start_transaction, info.end_transaction);
 256         jbd_debug(0, "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         sync_blockdev(journal->j_fs_dev);
 265         return err;
 266 }
 267
 268 /**
 269  * int journal_skip_recovery() - Start journal and wipe exiting records
 270  * @journal: journal to startup
 271  *
 272  * Locate any valid recovery information from the journal and set up the
 273  * journal structures in memory to ignore it (presumably because the
 274  * caller has evidence that it is out of date).
 275  * This function does'nt appear to be exorted..
 276  *
 277  * We perform one pass over the journal to allow us to tell the user how
 278  * much recovery information is being erased, and to let us initialise
 279  * the journal transaction sequence numbers to the next unused ID.
 280  */
 281 int journal_skip_recovery(journal_t *journal)
 282 {
 283         int                     err;
 284         journal_superblock_t *  sb;
 285
 286         struct recovery_info    info;
 287
 288         memset (&info, 0, sizeof(info));
 289         sb = journal->j_superblock;
 290
 291         err = do_one_pass(journal, &info, PASS_SCAN);
 292
 293         if (err) {
 294                 printk(KERN_ERR "JBD: error %d scanning journal\n", err);
 295                 ++journal->j_transaction_sequence;
 296         } else {
 297 #ifdef CONFIG_JBD_DEBUG
 298                 int dropped = info.end_transaction - ntohl(sb->s_sequence);
 299 #endif
 300                 jbd_debug(0,
 301                           "JBD: ignoring %d transaction%s from the journal.\n",
 302                           dropped, (dropped == 1) ? "" : "s");
 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 long           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         /* Precompute the maximum metadata descriptors in a descriptor block */
 323         int                     MAX_BLOCKS_PER_DESC;
 324         MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
 325                                / sizeof(journal_block_tag_t));
 326
 327         /*
 328          * First thing is to establish what we expect to find in the log
 329          * (in terms of transaction IDs), and where (in terms of log
 330          * block offsets): query the superblock.
 331          */
 332
 333         sb = journal->j_superblock;
 334         next_commit_ID = ntohl(sb->s_sequence);
 335         next_log_block = ntohl(sb->s_start);
 336
 337         first_commit_ID = next_commit_ID;
 338         if (pass == PASS_SCAN)
 339                 info->start_transaction = first_commit_ID;
 340
 341         jbd_debug(1, "Starting recovery pass %d\n", pass);
 342
 343         /*
 344          * Now we walk through the log, transaction by transaction,
 345          * making sure that each transaction has a commit block in the
 346          * expected place.  Each complete transaction gets replayed back
 347          * into the main filesystem.
 348          */
 349
 350         while (1) {
 351                 int                     flags;
 352                 char *                  tagp;
 353                 journal_block_tag_t *   tag;
 354                 struct buffer_head *    obh;
 355                 struct buffer_head *    nbh;
 356
 357                 /* If we already know where to stop the log traversal,
 358                  * check right now that we haven't gone past the end of
 359                  * the log. */
 360
 361                 if (pass != PASS_SCAN)
 362                         if (tid_geq(next_commit_ID, info->end_transaction))
 363                                 break;
 364
 365                 jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
 366                           next_commit_ID, next_log_block, journal->j_last);
 367
 368                 /* Skip over each chunk of the transaction looking
 369                  * either the next descriptor block or the final commit
 370                  * record. */
 371
 372                 jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
 373                 err = jread(&bh, journal, next_log_block);
 374                 if (err)
 375                         goto failed;
 376
 377                 next_log_block++;
 378                 wrap(journal, next_log_block);
 379
 380                 /* What kind of buffer is it?
 381                  *
 382                  * If it is a descriptor block, check that it has the
 383                  * expected sequence number.  Otherwise, we're all done
 384                  * here. */
 385
 386                 tmp = (journal_header_t *)bh->b_data;
 387
 388                 if (tmp->h_magic != htonl(JFS_MAGIC_NUMBER)) {
 389                         brelse(bh);
 390                         break;
 391                 }
 392
 393                 blocktype = ntohl(tmp->h_blocktype);
 394                 sequence = ntohl(tmp->h_sequence);
 395                 jbd_debug(3, "Found magic %d, sequence %d\n",
 396                           blocktype, sequence);
 397
 398                 if (sequence != next_commit_ID) {
 399                         brelse(bh);
 400                         break;
 401                 }
 402
 403                 /* OK, we have a valid descriptor block which matches
 404                  * all of the sequence number checks.  What are we going
 405                  * to do with it?  That depends on the pass... */
 406
 407                 switch(blocktype) {
 408                 case JFS_DESCRIPTOR_BLOCK:
 409                         /* If it is a valid descriptor block, replay it
 410                          * in pass REPLAY; otherwise, just skip over the
 411                          * blocks it describes. */
 412                         if (pass != PASS_REPLAY) {
 413                                 next_log_block +=
 414                                         count_tags(bh, journal->j_blocksize);
 415                                 wrap(journal, next_log_block);
 416                                 brelse(bh);
 417                                 continue;
 418                         }
 419
 420                         /* A descriptor block: we can now write all of
 421                          * the data blocks.  Yay, useful work is finally
 422                          * getting done here! */
 423
 424                         tagp = &bh->b_data[sizeof(journal_header_t)];
 425                         while ((tagp - bh->b_data +sizeof(journal_block_tag_t))
 426                                <= journal->j_blocksize) {
 427                                 unsigned long io_block;
 428
 429                                 tag = (journal_block_tag_t *) tagp;
 430                                 flags = ntohl(tag->t_flags);
 431
 432                                 io_block = next_log_block++;
 433                                 wrap(journal, next_log_block);
 434                                 err = jread(&obh, journal, io_block);
 435                                 if (err) {
 436                                         /* Recover what we can, but
 437                                          * report failure at the end. */
 438                                         success = err;
 439                                         printk (KERN_ERR
 440                                                 "JBD: IO error %d recovering "
 441                                                 "block %ld in log\n",
 442                                                 err, io_block);
 443                                 } else {
 444                                         unsigned long blocknr;
 445
 446                                         J_ASSERT(obh != NULL);
 447                                         blocknr = ntohl(tag->t_blocknr);
 448
 449                                         /* If the block has been
 450                                          * revoked, then we're all done
 451                                          * here. */
 452                                         if (journal_test_revoke
 453                                             (journal, blocknr,
 454                                              next_commit_ID)) {
 455                                                 brelse(obh);
 456                                                 ++info->nr_revoke_hits;
 457                                                 goto skip_write;
 458                                         }
 459
 460                                         /* Find a buffer for the new
 461                                          * data being restored */
 462                                         nbh = __getblk(journal->j_fs_dev,
 463                                                         blocknr,
 464                                                         journal->j_blocksize);
 465                                         if (nbh == NULL) {
 466                                                 printk(KERN_ERR
 467                                                        "JBD: Out of memory "
 468                                                        "during recovery.\n");
 469                                                 err = -ENOMEM;
 470                                                 brelse(bh);
 471                                                 brelse(obh);
 472                                                 goto failed;
 473                                         }
 474
 475                                         lock_buffer(nbh);
 476                                         memcpy(nbh->b_data, obh->b_data,
 477                                                         journal->j_blocksize);
 478                                         if (flags & JFS_FLAG_ESCAPE) {
 479                                                 *((unsigned int *)bh->b_data) =
 480                                                         htonl(JFS_MAGIC_NUMBER);
 481                                         }
 482
 483                                         BUFFER_TRACE(nbh, "marking dirty");
 484                                         set_buffer_uptodate(nbh);
 485                                         mark_buffer_dirty(nbh);
 486                                         BUFFER_TRACE(nbh, "marking uptodate");
 487                                         ++info->nr_replays;
 488                                         /* ll_rw_block(WRITE, 1, &nbh); */
 489                                         unlock_buffer(nbh);
 490                                         brelse(obh);
 491                                         brelse(nbh);
 492                                 }
 493
 494                         skip_write:
 495                                 tagp += sizeof(journal_block_tag_t);
 496                                 if (!(flags & JFS_FLAG_SAME_UUID))
 497                                         tagp += 16;
 498
 499                                 if (flags & JFS_FLAG_LAST_TAG)
 500                                         break;
 501                         }
 502
 503                         brelse(bh);
 504                         continue;
 505
 506                 case JFS_COMMIT_BLOCK:
 507                         /* Found an expected commit block: not much to
 508                          * do other than move on to the next sequence
 509                          * number. */
 510                         brelse(bh);
 511                         next_commit_ID++;
 512                         continue;
 513
 514                 case JFS_REVOKE_BLOCK:
 515                         /* If we aren't in the REVOKE pass, then we can
 516                          * just skip over this block. */
 517                         if (pass != PASS_REVOKE) {
 518                                 brelse(bh);
 519                                 continue;
 520                         }
 521
 522                         err = scan_revoke_records(journal, bh,
 523                                                   next_commit_ID, info);
 524                         brelse(bh);
 525                         if (err)
 526                                 goto failed;
 527                         continue;
 528
 529                 default:
 530                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 531                                   blocktype);
 532                         goto done;
 533                 }
 534         }
 535
 536  done:
 537         /*
 538          * We broke out of the log scan loop: either we came to the
 539          * known end of the log or we found an unexpected block in the
 540          * log.  If the latter happened, then we know that the "current"
 541          * transaction marks the end of the valid log.
 542          */
 543
 544         if (pass == PASS_SCAN)
 545                 info->end_transaction = next_commit_ID;
 546         else {
 547                 /* It's really bad news if different passes end up at
 548                  * different places (but possible due to IO errors). */
 549                 if (info->end_transaction != next_commit_ID) {
 550                         printk (KERN_ERR "JBD: recovery pass %d ended at "
 551                                 "transaction %u, expected %u\n",
 552                                 pass, next_commit_ID, info->end_transaction);
 553                         if (!success)
 554                                 success = -EIO;
 555                 }
 556         }
 557
 558         return success;
 559
 560  failed:
 561         return err;
 562 }
 563
 564
 565 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 566
 567 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 568                                tid_t sequence, struct recovery_info *info)
 569 {
 570         journal_revoke_header_t *header;
 571         int offset, max;
 572
 573         header = (journal_revoke_header_t *) bh->b_data;
 574         offset = sizeof(journal_revoke_header_t);
 575         max = ntohl(header->r_count);
 576
 577         while (offset < max) {
 578                 unsigned long blocknr;
 579                 int err;
 580
 581                 blocknr = ntohl(* ((unsigned int *) (bh->b_data+offset)));
 582                 offset += 4;
 583                 err = journal_set_revoke(journal, blocknr, sequence);
 584                 if (err)
 585                         return err;
 586                 ++info->nr_revokes;
 587         }
 588         return 0;
 589 }