fs/jbd/revoke.c

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