linux/fs/jbd/recovery.c
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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/blkdev.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 */
  30struct 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
  40enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  41static int do_one_pass(journal_t *journal,
  42                                struct recovery_info *info, enum passtype pass);
  43static 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 */
  49static 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
  69static int do_readahead(journal_t *journal, unsigned int start)
  70{
  71        int err;
  72        unsigned int max, nbufs, next;
  73        unsigned int 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
 118failed:
 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
 131static int jread(struct buffer_head **bhp, journal_t *journal,
 132                 unsigned int offset)
 133{
 134        int err;
 135        unsigned int 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
 181static 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)                                              \
 207do {                                                                    \
 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 */
 224int 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        /* Flush disk caches to get replayed data on the permanent storage */
 268        if (journal->j_flags & JFS_BARRIER) {
 269                err2 = blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
 270                if (!err)
 271                        err = err2;
 272        }
 273
 274        return err;
 275}
 276
 277/**
 278 * journal_skip_recovery - Start journal and wipe exiting records
 279 * @journal: journal to startup
 280 *
 281 * Locate any valid recovery information from the journal and set up the
 282 * journal structures in memory to ignore it (presumably because the
 283 * caller has evidence that it is out of date).
 284 * This function does'nt appear to be exorted..
 285 *
 286 * We perform one pass over the journal to allow us to tell the user how
 287 * much recovery information is being erased, and to let us initialise
 288 * the journal transaction sequence numbers to the next unused ID.
 289 */
 290int journal_skip_recovery(journal_t *journal)
 291{
 292        int                     err;
 293        struct recovery_info    info;
 294
 295        memset (&info, 0, sizeof(info));
 296
 297        err = do_one_pass(journal, &info, PASS_SCAN);
 298
 299        if (err) {
 300                printk(KERN_ERR "JBD: error %d scanning journal\n", err);
 301                ++journal->j_transaction_sequence;
 302        } else {
 303#ifdef CONFIG_JBD_DEBUG
 304                int dropped = info.end_transaction -
 305                              be32_to_cpu(journal->j_superblock->s_sequence);
 306                jbd_debug(1,
 307                          "JBD: ignoring %d transaction%s from the journal.\n",
 308                          dropped, (dropped == 1) ? "" : "s");
 309#endif
 310                journal->j_transaction_sequence = ++info.end_transaction;
 311        }
 312
 313        journal->j_tail = 0;
 314        return err;
 315}
 316
 317static int do_one_pass(journal_t *journal,
 318                        struct recovery_info *info, enum passtype pass)
 319{
 320        unsigned int            first_commit_ID, next_commit_ID;
 321        unsigned int            next_log_block;
 322        int                     err, success = 0;
 323        journal_superblock_t *  sb;
 324        journal_header_t *      tmp;
 325        struct buffer_head *    bh;
 326        unsigned int            sequence;
 327        int                     blocktype;
 328
 329        /*
 330         * First thing is to establish what we expect to find in the log
 331         * (in terms of transaction IDs), and where (in terms of log
 332         * block offsets): query the superblock.
 333         */
 334
 335        sb = journal->j_superblock;
 336        next_commit_ID = be32_to_cpu(sb->s_sequence);
 337        next_log_block = be32_to_cpu(sb->s_start);
 338
 339        first_commit_ID = next_commit_ID;
 340        if (pass == PASS_SCAN)
 341                info->start_transaction = first_commit_ID;
 342
 343        jbd_debug(1, "Starting recovery pass %d\n", pass);
 344
 345        /*
 346         * Now we walk through the log, transaction by transaction,
 347         * making sure that each transaction has a commit block in the
 348         * expected place.  Each complete transaction gets replayed back
 349         * into the main filesystem.
 350         */
 351
 352        while (1) {
 353                int                     flags;
 354                char *                  tagp;
 355                journal_block_tag_t *   tag;
 356                struct buffer_head *    obh;
 357                struct buffer_head *    nbh;
 358
 359                cond_resched();
 360
 361                /* If we already know where to stop the log traversal,
 362                 * check right now that we haven't gone past the end of
 363                 * the log. */
 364
 365                if (pass != PASS_SCAN)
 366                        if (tid_geq(next_commit_ID, info->end_transaction))
 367                                break;
 368
 369                jbd_debug(2, "Scanning for sequence ID %u at %u/%u\n",
 370                          next_commit_ID, next_log_block, journal->j_last);
 371
 372                /* Skip over each chunk of the transaction looking
 373                 * either the next descriptor block or the final commit
 374                 * record. */
 375
 376                jbd_debug(3, "JBD: checking block %u\n", next_log_block);
 377                err = jread(&bh, journal, next_log_block);
 378                if (err)
 379                        goto failed;
 380
 381                next_log_block++;
 382                wrap(journal, next_log_block);
 383
 384                /* What kind of buffer is it?
 385                 *
 386                 * If it is a descriptor block, check that it has the
 387                 * expected sequence number.  Otherwise, we're all done
 388                 * here. */
 389
 390                tmp = (journal_header_t *)bh->b_data;
 391
 392                if (tmp->h_magic != cpu_to_be32(JFS_MAGIC_NUMBER)) {
 393                        brelse(bh);
 394                        break;
 395                }
 396
 397                blocktype = be32_to_cpu(tmp->h_blocktype);
 398                sequence = be32_to_cpu(tmp->h_sequence);
 399                jbd_debug(3, "Found magic %d, sequence %d\n",
 400                          blocktype, sequence);
 401
 402                if (sequence != next_commit_ID) {
 403                        brelse(bh);
 404                        break;
 405                }
 406
 407                /* OK, we have a valid descriptor block which matches
 408                 * all of the sequence number checks.  What are we going
 409                 * to do with it?  That depends on the pass... */
 410
 411                switch(blocktype) {
 412                case JFS_DESCRIPTOR_BLOCK:
 413                        /* If it is a valid descriptor block, replay it
 414                         * in pass REPLAY; otherwise, just skip over the
 415                         * blocks it describes. */
 416                        if (pass != PASS_REPLAY) {
 417                                next_log_block +=
 418                                        count_tags(bh, journal->j_blocksize);
 419                                wrap(journal, next_log_block);
 420                                brelse(bh);
 421                                continue;
 422                        }
 423
 424                        /* A descriptor block: we can now write all of
 425                         * the data blocks.  Yay, useful work is finally
 426                         * getting done here! */
 427
 428                        tagp = &bh->b_data[sizeof(journal_header_t)];
 429                        while ((tagp - bh->b_data +sizeof(journal_block_tag_t))
 430                               <= journal->j_blocksize) {
 431                                unsigned int io_block;
 432
 433                                tag = (journal_block_tag_t *) tagp;
 434                                flags = be32_to_cpu(tag->t_flags);
 435
 436                                io_block = next_log_block++;
 437                                wrap(journal, next_log_block);
 438                                err = jread(&obh, journal, io_block);
 439                                if (err) {
 440                                        /* Recover what we can, but
 441                                         * report failure at the end. */
 442                                        success = err;
 443                                        printk (KERN_ERR
 444                                                "JBD: IO error %d recovering "
 445                                                "block %u in log\n",
 446                                                err, io_block);
 447                                } else {
 448                                        unsigned int blocknr;
 449
 450                                        J_ASSERT(obh != NULL);
 451                                        blocknr = be32_to_cpu(tag->t_blocknr);
 452
 453                                        /* If the block has been
 454                                         * revoked, then we're all done
 455                                         * here. */
 456                                        if (journal_test_revoke
 457                                            (journal, blocknr,
 458                                             next_commit_ID)) {
 459                                                brelse(obh);
 460                                                ++info->nr_revoke_hits;
 461                                                goto skip_write;
 462                                        }
 463
 464                                        /* Find a buffer for the new
 465                                         * data being restored */
 466                                        nbh = __getblk(journal->j_fs_dev,
 467                                                        blocknr,
 468                                                        journal->j_blocksize);
 469                                        if (nbh == NULL) {
 470                                                printk(KERN_ERR
 471                                                       "JBD: Out of memory "
 472                                                       "during recovery.\n");
 473                                                err = -ENOMEM;
 474                                                brelse(bh);
 475                                                brelse(obh);
 476                                                goto failed;
 477                                        }
 478
 479                                        lock_buffer(nbh);
 480                                        memcpy(nbh->b_data, obh->b_data,
 481                                                        journal->j_blocksize);
 482                                        if (flags & JFS_FLAG_ESCAPE) {
 483                                                *((__be32 *)nbh->b_data) =
 484                                                cpu_to_be32(JFS_MAGIC_NUMBER);
 485                                        }
 486
 487                                        BUFFER_TRACE(nbh, "marking dirty");
 488                                        set_buffer_uptodate(nbh);
 489                                        mark_buffer_dirty(nbh);
 490                                        BUFFER_TRACE(nbh, "marking uptodate");
 491                                        ++info->nr_replays;
 492                                        /* ll_rw_block(WRITE, 1, &nbh); */
 493                                        unlock_buffer(nbh);
 494                                        brelse(obh);
 495                                        brelse(nbh);
 496                                }
 497
 498                        skip_write:
 499                                tagp += sizeof(journal_block_tag_t);
 500                                if (!(flags & JFS_FLAG_SAME_UUID))
 501                                        tagp += 16;
 502
 503                                if (flags & JFS_FLAG_LAST_TAG)
 504                                        break;
 505                        }
 506
 507                        brelse(bh);
 508                        continue;
 509
 510                case JFS_COMMIT_BLOCK:
 511                        /* Found an expected commit block: not much to
 512                         * do other than move on to the next sequence
 513                         * number. */
 514                        brelse(bh);
 515                        next_commit_ID++;
 516                        continue;
 517
 518                case JFS_REVOKE_BLOCK:
 519                        /* If we aren't in the REVOKE pass, then we can
 520                         * just skip over this block. */
 521                        if (pass != PASS_REVOKE) {
 522                                brelse(bh);
 523                                continue;
 524                        }
 525
 526                        err = scan_revoke_records(journal, bh,
 527                                                  next_commit_ID, info);
 528                        brelse(bh);
 529                        if (err)
 530                                goto failed;
 531                        continue;
 532
 533                default:
 534                        jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 535                                  blocktype);
 536                        brelse(bh);
 537                        goto done;
 538                }
 539        }
 540
 541 done:
 542        /*
 543         * We broke out of the log scan loop: either we came to the
 544         * known end of the log or we found an unexpected block in the
 545         * log.  If the latter happened, then we know that the "current"
 546         * transaction marks the end of the valid log.
 547         */
 548
 549        if (pass == PASS_SCAN)
 550                info->end_transaction = next_commit_ID;
 551        else {
 552                /* It's really bad news if different passes end up at
 553                 * different places (but possible due to IO errors). */
 554                if (info->end_transaction != next_commit_ID) {
 555                        printk (KERN_ERR "JBD: recovery pass %d ended at "
 556                                "transaction %u, expected %u\n",
 557                                pass, next_commit_ID, info->end_transaction);
 558                        if (!success)
 559                                success = -EIO;
 560                }
 561        }
 562
 563        return success;
 564
 565 failed:
 566        return err;
 567}
 568
 569
 570/* Scan a revoke record, marking all blocks mentioned as revoked. */
 571
 572static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 573                               tid_t sequence, struct recovery_info *info)
 574{
 575        journal_revoke_header_t *header;
 576        int offset, max;
 577
 578        header = (journal_revoke_header_t *) bh->b_data;
 579        offset = sizeof(journal_revoke_header_t);
 580        max = be32_to_cpu(header->r_count);
 581
 582        while (offset < max) {
 583                unsigned int blocknr;
 584                int err;
 585
 586                blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 587                offset += 4;
 588                err = journal_set_revoke(journal, blocknr, sequence);
 589                if (err)
 590                        return err;
 591                ++info->nr_revokes;
 592        }
 593        return 0;
 594}
 595
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