reactos/drivers/filesystems/ext2/src/jbd/revoke.c

   1 /*
   2  * linux/fs/jbd/revoke.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 2000
   5  *
   6  * Copyright 2000 Red Hat corp --- 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 revoke routines for the generic filesystem journaling code;
  13  * part of the ext2fs journaling system.
  14  *
  15  * Revoke is the mechanism used to prevent old log records for deleted
  16  * metadata from being replayed on top of newer data using the same
  17  * blocks.  The revoke mechanism is used in two separate places:
  18  *
  19  * + Commit: during commit we write the entire list of the current
  20  *   transaction's revoked blocks to the journal
  21  *
  22  * + Recovery: during recovery we record the transaction ID of all
  23  *   revoked blocks.  If there are multiple revoke records in the log
  24  *   for a single block, only the last one counts, and if there is a log
  25  *   entry for a block beyond the last revoke, then that log entry still
  26  *   gets replayed.
  27  *
  28  * We can get interactions between revokes and new log data within a
  29  * single transaction:
  30  *
  31  * Block is revoked and then journaled:
  32  *   The desired end result is the journaling of the new block, so we
  33  *   cancel the revoke before the transaction commits.
  34  *
  35  * Block is journaled and then revoked:
  36  *   The revoke must take precedence over the write of the block, so we
  37  *   need either to cancel the journal entry or to write the revoke
  38  *   later in the log than the log block.  In this case, we choose the
  39  *   latter: journaling a block cancels any revoke record for that block
  40  *   in the current transaction, so any revoke for that block in the
  41  *   transaction must have happened after the block was journaled and so
  42  *   the revoke must take precedence.
  43  *
  44  * Block is revoked and then written as data:
  45  *   The data write is allowed to succeed, but the revoke is _not_
  46  *   cancelled.  We still need to prevent old log records from
  47  *   overwriting the new data.  We don't even need to clear the revoke
  48  *   bit here.
  49  *
  50  * Revoke information on buffers is a tri-state value:
  51  *
  52  * RevokeValid clear:   no cached revoke status, need to look it up
  53  * RevokeValid set, Revoked clear:
  54  *                      buffer has not been revoked, and cancel_revoke
  55  *                      need do nothing.
  56  * RevokeValid set, Revoked set:
  57  *                      buffer has been revoked.
  58  */
  59
  60 #ifndef __KERNEL__
  61 #include "jfs_user.h"
  62 #else
  63 #include <linux/time.h>
  64 #include <linux/fs.h>
  65 #include <linux/jbd.h>
  66 #include <linux/errno.h>
  67 #include <linux/slab.h>
  68 #include <linux/list.h>
  69 #include <linux/init.h>
  70 #endif
  71 #include <linux/log2.h>
  72
  73 static struct kmem_cache *revoke_record_cache = NULL;
  74 static struct kmem_cache *revoke_table_cache = NULL;
  75
  76 /* Each revoke record represents one single revoked block.  During
  77    journal replay, this involves recording the transaction ID of the
  78    last transaction to revoke this block. */
  79
  80 struct jbd_revoke_record_s
  81 {
  82     struct list_head  hash;
  83     tid_t                 sequence;     /* Used for recovery only */
  84     unsigned long         blocknr;
  85 };
  86
  87
  88 /* The revoke table is just a simple hash table of revoke records. */
  89 struct jbd_revoke_table_s
  90 {
  91     /* It is conceivable that we might want a larger hash table
  92      * for recovery.  Must be a power of two. */
  93     int           hash_size;
  94     int           hash_shift;
  95     struct list_head *hash_table;
  96 };
  97
  98
  99 #ifdef __KERNEL__
 100 static void write_one_revoke_record(journal_t *, transaction_t *,
 101                                     struct journal_head **, int *,
 102                                     struct jbd_revoke_record_s *);
 103 static void flush_descriptor(journal_t *, struct journal_head *, int);
 104 #endif
 105
 106 /* Utility functions to maintain the revoke table */
 107
 108 /* Borrowed from buffer.c: this is a tried and tested block hash function */
 109 static inline int hash(journal_t *journal, unsigned long block)
 110 {
 111     struct jbd_revoke_table_s *table = journal->j_revoke;
 112     int hash_shift = table->hash_shift;
 113
 114     return ((block << (hash_shift - 6)) ^
 115             (block >> 13) ^
 116             (block << (hash_shift - 12))) & (table->hash_size - 1);
 117 }
 118
 119 static int insert_revoke_hash(journal_t *journal, unsigned long blocknr,
 120                               tid_t seq)
 121 {
 122     struct list_head *hash_list;
 123     struct jbd_revoke_record_s *record;
 124
 125 repeat:
 126     record = (struct jbd_revoke_record_s *)
 127              kmem_cache_alloc(revoke_record_cache, GFP_NOFS);
 128     if (!record)
 129         goto oom;
 130
 131     record->sequence = seq;
 132     record->blocknr = blocknr;
 133     hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
 134     spin_lock(&journal->j_revoke_lock);
 135     list_add(&record->hash, hash_list);
 136     spin_unlock(&journal->j_revoke_lock);
 137     return 0;
 138
 139 oom:
 140     if (!journal_oom_retry)
 141         return -ENOMEM;
 142     jbd_debug(1, "ENOMEM in %s, retrying\n", __FUNCTION__);
 143     yield();
 144     goto repeat;
 145 }
 146
 147 /* Find a revoke record in the journal's hash table. */
 148
 149 static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
 150                     unsigned long blocknr)
 151 {
 152     struct list_head *hash_list;
 153     struct jbd_revoke_record_s *record;
 154
 155     hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
 156
 157     spin_lock(&journal->j_revoke_lock);
 158     record = (struct jbd_revoke_record_s *) hash_list->next;
 159     while (&(record->hash) != hash_list) {
 160         if (record->blocknr == blocknr) {
 161             spin_unlock(&journal->j_revoke_lock);
 162             return record;
 163         }
 164         record = (struct jbd_revoke_record_s *) record->hash.next;
 165     }
 166     spin_unlock(&journal->j_revoke_lock);
 167     return NULL;
 168 }
 169
 170 int __init journal_init_revoke_caches(void)
 171 {
 172     revoke_record_cache = kmem_cache_create("revoke_record",
 173                                             sizeof(struct jbd_revoke_record_s),
 174                                             0,
 175                                             SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
 176                                             NULL);
 177     if (revoke_record_cache == 0)
 178         return -ENOMEM;
 179
 180     revoke_table_cache = kmem_cache_create("revoke_table",
 181                                            sizeof(struct jbd_revoke_table_s),
 182                                            0, SLAB_TEMPORARY, NULL);
 183     if (revoke_table_cache == 0) {
 184         kmem_cache_destroy(revoke_record_cache);
 185         revoke_record_cache = NULL;
 186         return -ENOMEM;
 187     }
 188     return 0;
 189 }
 190
 191 void journal_destroy_revoke_caches(void)
 192 {
 193     kmem_cache_destroy(revoke_record_cache);
 194     revoke_record_cache = NULL;
 195     kmem_cache_destroy(revoke_table_cache);
 196     revoke_table_cache = NULL;
 197 }
 198
 199 /* Initialise the revoke table for a given journal to a given size. */
 200
 201 int journal_init_revoke(journal_t *journal, int hash_size)
 202 {
 203     int shift, tmp;
 204
 205     J_ASSERT (journal->j_revoke_table[0] == NULL);
 206
 207     shift = 0;
 208     tmp = hash_size;
 209     while ((tmp >>= 1UL) != 0UL)
 210         shift++;
 211
 212     journal->j_revoke_table[0] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
 213     if (!journal->j_revoke_table[0])
 214         return -ENOMEM;
 215     journal->j_revoke = journal->j_revoke_table[0];
 216
 217     /* Check that the hash_size is a power of two */
 218     J_ASSERT(is_power_of_2(hash_size));
 219
 220     journal->j_revoke->hash_size = hash_size;
 221
 222     journal->j_revoke->hash_shift = shift;
 223
 224     journal->j_revoke->hash_table =
 225         kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
 226     if (!journal->j_revoke->hash_table) {
 227         kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
 228         journal->j_revoke = NULL;
 229         return -ENOMEM;
 230     }
 231
 232     for (tmp = 0; tmp < hash_size; tmp++)
 233         INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
 234
 235     journal->j_revoke_table[1] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
 236     if (!journal->j_revoke_table[1]) {
 237         kfree(journal->j_revoke_table[0]->hash_table);
 238         kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
 239         return -ENOMEM;
 240     }
 241
 242     journal->j_revoke = journal->j_revoke_table[1];
 243
 244     /* Check that the hash_size is a power of two */
 245     J_ASSERT(is_power_of_2(hash_size));
 246
 247     journal->j_revoke->hash_size = hash_size;
 248
 249     journal->j_revoke->hash_shift = shift;
 250
 251     journal->j_revoke->hash_table =
 252         kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
 253     if (!journal->j_revoke->hash_table) {
 254         kfree(journal->j_revoke_table[0]->hash_table);
 255         kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
 256         kmem_cache_free(revoke_table_cache, journal->j_revoke_table[1]);
 257         journal->j_revoke = NULL;
 258         return -ENOMEM;
 259     }
 260
 261     for (tmp = 0; tmp < hash_size; tmp++)
 262         INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
 263
 264     spin_lock_init(&journal->j_revoke_lock);
 265
 266     return 0;
 267 }
 268
 269 /* Destoy a journal's revoke table.  The table must already be empty! */
 270
 271 void journal_destroy_revoke(journal_t *journal)
 272 {
 273     struct jbd_revoke_table_s *table;
 274     struct list_head *hash_list;
 275     int i;
 276
 277     table = journal->j_revoke_table[0];
 278     if (!table)
 279         return;
 280
 281     for (i=0; i<table->hash_size; i++) {
 282         hash_list = &table->hash_table[i];
 283         J_ASSERT (list_empty(hash_list));
 284     }
 285
 286     kfree(table->hash_table);
 287     kmem_cache_free(revoke_table_cache, table);
 288     journal->j_revoke = NULL;
 289
 290     table = journal->j_revoke_table[1];
 291     if (!table)
 292         return;
 293
 294     for (i=0; i<table->hash_size; i++) {
 295         hash_list = &table->hash_table[i];
 296         J_ASSERT (list_empty(hash_list));
 297     }
 298
 299     kfree(table->hash_table);
 300     kmem_cache_free(revoke_table_cache, table);
 301     journal->j_revoke = NULL;
 302 }
 303
 304
 305 #ifdef __KERNEL__
 306
 307 /*
 308  * journal_revoke: revoke a given buffer_head from the journal.  This
 309  * prevents the block from being replayed during recovery if we take a
 310  * crash after this current transaction commits.  Any subsequent
 311  * metadata writes of the buffer in this transaction cancel the
 312  * revoke.
 313  *
 314  * Note that this call may block --- it is up to the caller to make
 315  * sure that there are no further calls to journal_write_metadata
 316  * before the revoke is complete.  In ext3, this implies calling the
 317  * revoke before clearing the block bitmap when we are deleting
 318  * metadata.
 319  *
 320  * Revoke performs a journal_forget on any buffer_head passed in as a
 321  * parameter, but does _not_ forget the buffer_head if the bh was only
 322  * found implicitly.
 323  *
 324  * bh_in may not be a journalled buffer - it may have come off
 325  * the hash tables without an attached journal_head.
 326  *
 327  * If bh_in is non-zero, journal_revoke() will decrement its b_count
 328  * by one.
 329  */
 330
 331 int journal_revoke(handle_t *handle, unsigned long blocknr,
 332                    struct buffer_head *bh_in)
 333 {
 334     struct buffer_head *bh = NULL;
 335     journal_t *journal;
 336     struct block_device *bdev;
 337     int err;
 338
 339     might_sleep();
 340     if (bh_in)
 341         BUFFER_TRACE(bh_in, "enter");
 342
 343     journal = handle->h_transaction->t_journal;
 344     if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)) {
 345         J_ASSERT (!"Cannot set revoke feature!");
 346         return -EINVAL;
 347     }
 348
 349     bdev = journal->j_fs_dev;
 350     bh = bh_in;
 351
 352     if (!bh) {
 353         bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
 354         if (bh)
 355             BUFFER_TRACE(bh, "found on hash");
 356     }
 357 #ifdef JBD_EXPENSIVE_CHECKING
 358     else {
 359         struct buffer_head *bh2;
 360
 361         /* If there is a different buffer_head lying around in
 362          * memory anywhere... */
 363         bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
 364         if (bh2) {
 365             /* ... and it has RevokeValid status... */
 366             if (bh2 != bh && buffer_revokevalid(bh2))
 367                 /* ...then it better be revoked too,
 368                  * since it's illegal to create a revoke
 369                  * record against a buffer_head which is
 370                  * not marked revoked --- that would
 371                  * risk missing a subsequent revoke
 372                  * cancel. */
 373                 J_ASSERT_BH(bh2, buffer_revoked(bh2));
 374             put_bh(bh2);
 375         }
 376     }
 377 #endif
 378
 379     /* We really ought not ever to revoke twice in a row without
 380            first having the revoke cancelled: it's illegal to free a
 381            block twice without allocating it in between! */
 382     if (bh) {
 383         if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
 384                          "inconsistent data on disk")) {
 385             if (!bh_in)
 386                 brelse(bh);
 387             return -EIO;
 388         }
 389         set_buffer_revoked(bh);
 390         set_buffer_revokevalid(bh);
 391         if (bh_in) {
 392             BUFFER_TRACE(bh_in, "call journal_forget");
 393             journal_forget(handle, bh_in);
 394         } else {
 395             BUFFER_TRACE(bh, "call brelse");
 396             __brelse(bh);
 397         }
 398     }
 399
 400     jbd_debug(2, "insert revoke for block %lu, bh_in=%p\n", blocknr, bh_in);
 401     err = insert_revoke_hash(journal, blocknr,
 402                              handle->h_transaction->t_tid);
 403     BUFFER_TRACE(bh_in, "exit");
 404     return err;
 405 }
 406
 407 /*
 408  * Cancel an outstanding revoke.  For use only internally by the
 409  * journaling code (called from journal_get_write_access).
 410  *
 411  * We trust buffer_revoked() on the buffer if the buffer is already
 412  * being journaled: if there is no revoke pending on the buffer, then we
 413  * don't do anything here.
 414  *
 415  * This would break if it were possible for a buffer to be revoked and
 416  * discarded, and then reallocated within the same transaction.  In such
 417  * a case we would have lost the revoked bit, but when we arrived here
 418  * the second time we would still have a pending revoke to cancel.  So,
 419  * do not trust the Revoked bit on buffers unless RevokeValid is also
 420  * set.
 421  *
 422  * The caller must have the journal locked.
 423  */
 424 int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
 425 {
 426     struct jbd_revoke_record_s *record;
 427     journal_t *journal = handle->h_transaction->t_journal;
 428     int need_cancel;
 429     int did_revoke = 0; /* akpm: debug */
 430     struct buffer_head *bh = jh2bh(jh);
 431
 432     jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
 433
 434     /* Is the existing Revoke bit valid?  If so, we trust it, and
 435      * only perform the full cancel if the revoke bit is set.  If
 436      * not, we can't trust the revoke bit, and we need to do the
 437      * full search for a revoke record. */
 438     if (test_set_buffer_revokevalid(bh)) {
 439         need_cancel = test_clear_buffer_revoked(bh);
 440     } else {
 441         need_cancel = 1;
 442         clear_buffer_revoked(bh);
 443     }
 444
 445     if (need_cancel) {
 446         record = find_revoke_record(journal, (unsigned long)bh->b_blocknr);
 447         if (record) {
 448             jbd_debug(4, "cancelled existing revoke on "
 449                       "blocknr %llu\n", (u64)bh->b_blocknr);
 450             spin_lock(&journal->j_revoke_lock);
 451             list_del(&record->hash);
 452             spin_unlock(&journal->j_revoke_lock);
 453             kmem_cache_free(revoke_record_cache, record);
 454             did_revoke = 1;
 455         }
 456     }
 457
 458 #ifdef JBD_EXPENSIVE_CHECKING
 459     /* There better not be one left behind by now! */
 460     record = find_revoke_record(journal, bh->b_blocknr);
 461     J_ASSERT_JH(jh, record == NULL);
 462 #endif
 463
 464     /* Finally, have we just cleared revoke on an unhashed
 465      * buffer_head?  If so, we'd better make sure we clear the
 466      * revoked status on any hashed alias too, otherwise the revoke
 467      * state machine will get very upset later on. */
 468     if (need_cancel) {
 469         struct buffer_head *bh2;
 470         bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
 471         if (bh2) {
 472             if (bh2 != bh)
 473                 clear_buffer_revoked(bh2);
 474             __brelse(bh2);
 475         }
 476     }
 477     return did_revoke;
 478 }
 479
 480 /* journal_switch_revoke table select j_revoke for next transaction
 481  * we do not want to suspend any processing until all revokes are
 482  * written -bzzz
 483  */
 484 void journal_switch_revoke_table(journal_t *journal)
 485 {
 486     int i;
 487
 488     if (journal->j_revoke == journal->j_revoke_table[0])
 489         journal->j_revoke = journal->j_revoke_table[1];
 490     else
 491         journal->j_revoke = journal->j_revoke_table[0];
 492
 493     for (i = 0; i < journal->j_revoke->hash_size; i++)
 494         INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
 495 }
 496
 497 /*
 498  * Write revoke records to the journal for all entries in the current
 499  * revoke hash, deleting the entries as we go.
 500  *
 501  * Called with the journal lock held.
 502  */
 503
 504 void journal_write_revoke_records(journal_t *journal,
 505                                   transaction_t *transaction)
 506 {
 507     struct journal_head *descriptor;
 508     struct jbd_revoke_record_s *record;
 509     struct jbd_revoke_table_s *revoke;
 510     struct list_head *hash_list;
 511     int i, offset, count;
 512
 513     descriptor = NULL;
 514     offset = 0;
 515     count = 0;
 516
 517     /* select revoke table for committing transaction */
 518     revoke = journal->j_revoke == journal->j_revoke_table[0] ?
 519              journal->j_revoke_table[1] : journal->j_revoke_table[0];
 520
 521     for (i = 0; i < revoke->hash_size; i++) {
 522         hash_list = &revoke->hash_table[i];
 523
 524         while (!list_empty(hash_list)) {
 525             record = (struct jbd_revoke_record_s *)
 526                      hash_list->next;
 527             write_one_revoke_record(journal, transaction,
 528                                     &descriptor, &offset,
 529                                     record);
 530             count++;
 531             list_del(&record->hash);
 532             kmem_cache_free(revoke_record_cache, record);
 533         }
 534     }
 535     if (descriptor)
 536         flush_descriptor(journal, descriptor, offset);
 537     jbd_debug(1, "Wrote %d revoke records\n", count);
 538 }
 539
 540 /*
 541  * Write out one revoke record.  We need to create a new descriptor
 542  * block if the old one is full or if we have not already created one.
 543  */
 544
 545 static void write_one_revoke_record(journal_t *journal,
 546                                     transaction_t *transaction,
 547                                     struct journal_head **descriptorp,
 548                                     int *offsetp,
 549                                     struct jbd_revoke_record_s *record)
 550 {
 551     struct journal_head *descriptor;
 552     int offset;
 553     journal_header_t *header;
 554
 555     /* If we are already aborting, this all becomes a noop.  We
 556            still need to go round the loop in
 557            journal_write_revoke_records in order to free all of the
 558            revoke records: only the IO to the journal is omitted. */
 559     if (is_journal_aborted(journal))
 560         return;
 561
 562     descriptor = *descriptorp;
 563     offset = *offsetp;
 564
 565     /* Make sure we have a descriptor with space left for the record */
 566     if (descriptor) {
 567         if (offset == journal->j_blocksize) {
 568             flush_descriptor(journal, descriptor, offset);
 569             descriptor = NULL;
 570         }
 571     }
 572
 573     if (!descriptor) {
 574         descriptor = journal_get_descriptor_buffer(journal);
 575         if (!descriptor)
 576             return;
 577         header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
 578         header->h_magic     = cpu_to_be32(JFS_MAGIC_NUMBER);
 579         header->h_blocktype = cpu_to_be32(JFS_REVOKE_BLOCK);
 580         header->h_sequence  = cpu_to_be32(transaction->t_tid);
 581
 582         /* Record it so that we can wait for IO completion later */
 583         JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
 584         journal_file_buffer(descriptor, transaction, BJ_LogCtl);
 585
 586         offset = sizeof(journal_revoke_header_t);
 587         *descriptorp = descriptor;
 588     }
 589
 590     * ((__be32 *)(&jh2bh(descriptor)->b_data[offset])) =
 591         cpu_to_be32(record->blocknr);
 592     offset += 4;
 593     *offsetp = offset;
 594 }
 595
 596 /*
 597  * Flush a revoke descriptor out to the journal.  If we are aborting,
 598  * this is a noop; otherwise we are generating a buffer which needs to
 599  * be waited for during commit, so it has to go onto the appropriate
 600  * journal buffer list.
 601  */
 602
 603 static void flush_descriptor(journal_t *journal,
 604                              struct journal_head *descriptor,
 605                              int offset)
 606 {
 607     journal_revoke_header_t *header;
 608     struct buffer_head *bh = jh2bh(descriptor);
 609
 610     if (is_journal_aborted(journal)) {
 611         put_bh(bh);
 612         return;
 613     }
 614
 615     header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
 616     header->r_count = cpu_to_be32(offset);
 617     set_buffer_jwrite(bh);
 618     BUFFER_TRACE(bh, "write");
 619     set_buffer_dirty(bh);
 620     ll_rw_block(SWRITE, 1, &bh);
 621 }
 622 #endif
 623
 624 /*
 625  * Revoke support for recovery.
 626  *
 627  * Recovery needs to be able to:
 628  *
 629  *  record all revoke records, including the tid of the latest instance
 630  *  of each revoke in the journal
 631  *
 632  *  check whether a given block in a given transaction should be replayed
 633  *  (ie. has not been revoked by a revoke record in that or a subsequent
 634  *  transaction)
 635  *
 636  *  empty the revoke table after recovery.
 637  */
 638
 639 /*
 640  * First, setting revoke records.  We create a new revoke record for
 641  * every block ever revoked in the log as we scan it for recovery, and
 642  * we update the existing records if we find multiple revokes for a
 643  * single block.
 644  */
 645
 646 int journal_set_revoke(journal_t *journal,
 647                        unsigned long blocknr,
 648                        tid_t sequence)
 649 {
 650     struct jbd_revoke_record_s *record;
 651
 652     record = find_revoke_record(journal, blocknr);
 653     if (record) {
 654         /* If we have multiple occurrences, only record the
 655          * latest sequence number in the hashed record */
 656         if (tid_gt(sequence, record->sequence))
 657             record->sequence = sequence;
 658         return 0;
 659     }
 660     return insert_revoke_hash(journal, blocknr, sequence);
 661 }
 662
 663 /*
 664  * Test revoke records.  For a given block referenced in the log, has
 665  * that block been revoked?  A revoke record with a given transaction
 666  * sequence number revokes all blocks in that transaction and earlier
 667  * ones, but later transactions still need replayed.
 668  */
 669
 670 int journal_test_revoke(journal_t *journal,
 671                         unsigned long blocknr,
 672                         tid_t sequence)
 673 {
 674     struct jbd_revoke_record_s *record;
 675
 676     record = find_revoke_record(journal, blocknr);
 677     if (!record)
 678         return 0;
 679     if (tid_gt(sequence, record->sequence))
 680         return 0;
 681     return 1;
 682 }
 683
 684 /*
 685  * Finally, once recovery is over, we need to clear the revoke table so
 686  * that it can be reused by the running filesystem.
 687  */
 688
 689 void journal_clear_revoke(journal_t *journal)
 690 {
 691     int i;
 692     struct list_head *hash_list;
 693     struct jbd_revoke_record_s *record;
 694     struct jbd_revoke_table_s *revoke;
 695
 696     revoke = journal->j_revoke;
 697
 698     for (i = 0; i < revoke->hash_size; i++) {
 699         hash_list = &revoke->hash_table[i];
 700         while (!list_empty(hash_list)) {
 701             record = (struct jbd_revoke_record_s*) hash_list->next;
 702             list_del(&record->hash);
 703             kmem_cache_free(revoke_record_cache, record);
 704         }
 705     }
 706 }