linux/fs/jbd/revoke.c
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   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 * We cache revoke status of a buffer in the current transaction in b_states
  51 * bits.  As the name says, revokevalid flag indicates that the cached revoke
  52 * status of a buffer is valid and we can rely on the cached status.
  53 *
  54 * Revoke information on buffers is a tri-state value:
  55 *
  56 * RevokeValid clear:   no cached revoke status, need to look it up
  57 * RevokeValid set, Revoked clear:
  58 *                      buffer has not been revoked, and cancel_revoke
  59 *                      need do nothing.
  60 * RevokeValid set, Revoked set:
  61 *                      buffer has been revoked.
  62 *
  63 * Locking rules:
  64 * We keep two hash tables of revoke records. One hashtable belongs to the
  65 * running transaction (is pointed to by journal->j_revoke), the other one
  66 * belongs to the committing transaction. Accesses to the second hash table
  67 * happen only from the kjournald and no other thread touches this table.  Also
  68 * journal_switch_revoke_table() which switches which hashtable belongs to the
  69 * running and which to the committing transaction is called only from
  70 * kjournald. Therefore we need no locks when accessing the hashtable belonging
  71 * to the committing transaction.
  72 *
  73 * All users operating on the hash table belonging to the running transaction
  74 * have a handle to the transaction. Therefore they are safe from kjournald
  75 * switching hash tables under them. For operations on the lists of entries in
  76 * the hash table j_revoke_lock is used.
  77 *
  78 * Finally, also replay code uses the hash tables but at this moment no one else
  79 * can touch them (filesystem isn't mounted yet) and hence no locking is
  80 * needed.
  81 */
  82
  83#ifndef __KERNEL__
  84#include "jfs_user.h"
  85#else
  86#include <linux/time.h>
  87#include <linux/fs.h>
  88#include <linux/jbd.h>
  89#include <linux/errno.h>
  90#include <linux/slab.h>
  91#include <linux/list.h>
  92#include <linux/init.h>
  93#include <linux/bio.h>
  94#endif
  95#include <linux/log2.h>
  96
  97static struct kmem_cache *revoke_record_cache;
  98static struct kmem_cache *revoke_table_cache;
  99
 100/* Each revoke record represents one single revoked block.  During
 101   journal replay, this involves recording the transaction ID of the
 102   last transaction to revoke this block. */
 103
 104struct jbd_revoke_record_s
 105{
 106        struct list_head  hash;
 107        tid_t             sequence;     /* Used for recovery only */
 108        unsigned int      blocknr;
 109};
 110
 111
 112/* The revoke table is just a simple hash table of revoke records. */
 113struct jbd_revoke_table_s
 114{
 115        /* It is conceivable that we might want a larger hash table
 116         * for recovery.  Must be a power of two. */
 117        int               hash_size;
 118        int               hash_shift;
 119        struct list_head *hash_table;
 120};
 121
 122
 123#ifdef __KERNEL__
 124static void write_one_revoke_record(journal_t *, transaction_t *,
 125                                    struct journal_head **, int *,
 126                                    struct jbd_revoke_record_s *, int);
 127static void flush_descriptor(journal_t *, struct journal_head *, int, int);
 128#endif
 129
 130/* Utility functions to maintain the revoke table */
 131
 132/* Borrowed from buffer.c: this is a tried and tested block hash function */
 133static inline int hash(journal_t *journal, unsigned int block)
 134{
 135        struct jbd_revoke_table_s *table = journal->j_revoke;
 136        int hash_shift = table->hash_shift;
 137
 138        return ((block << (hash_shift - 6)) ^
 139                (block >> 13) ^
 140                (block << (hash_shift - 12))) & (table->hash_size - 1);
 141}
 142
 143static int insert_revoke_hash(journal_t *journal, unsigned int blocknr,
 144                              tid_t seq)
 145{
 146        struct list_head *hash_list;
 147        struct jbd_revoke_record_s *record;
 148
 149repeat:
 150        record = kmem_cache_alloc(revoke_record_cache, GFP_NOFS);
 151        if (!record)
 152                goto oom;
 153
 154        record->sequence = seq;
 155        record->blocknr = blocknr;
 156        hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
 157        spin_lock(&journal->j_revoke_lock);
 158        list_add(&record->hash, hash_list);
 159        spin_unlock(&journal->j_revoke_lock);
 160        return 0;
 161
 162oom:
 163        if (!journal_oom_retry)
 164                return -ENOMEM;
 165        jbd_debug(1, "ENOMEM in %s, retrying\n", __func__);
 166        yield();
 167        goto repeat;
 168}
 169
 170/* Find a revoke record in the journal's hash table. */
 171
 172static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
 173                                                      unsigned int blocknr)
 174{
 175        struct list_head *hash_list;
 176        struct jbd_revoke_record_s *record;
 177
 178        hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
 179
 180        spin_lock(&journal->j_revoke_lock);
 181        record = (struct jbd_revoke_record_s *) hash_list->next;
 182        while (&(record->hash) != hash_list) {
 183                if (record->blocknr == blocknr) {
 184                        spin_unlock(&journal->j_revoke_lock);
 185                        return record;
 186                }
 187                record = (struct jbd_revoke_record_s *) record->hash.next;
 188        }
 189        spin_unlock(&journal->j_revoke_lock);
 190        return NULL;
 191}
 192
 193void journal_destroy_revoke_caches(void)
 194{
 195        if (revoke_record_cache) {
 196                kmem_cache_destroy(revoke_record_cache);
 197                revoke_record_cache = NULL;
 198        }
 199        if (revoke_table_cache) {
 200                kmem_cache_destroy(revoke_table_cache);
 201                revoke_table_cache = NULL;
 202        }
 203}
 204
 205int __init journal_init_revoke_caches(void)
 206{
 207        J_ASSERT(!revoke_record_cache);
 208        J_ASSERT(!revoke_table_cache);
 209
 210        revoke_record_cache = kmem_cache_create("revoke_record",
 211                                           sizeof(struct jbd_revoke_record_s),
 212                                           0,
 213                                           SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
 214                                           NULL);
 215        if (!revoke_record_cache)
 216                goto record_cache_failure;
 217
 218        revoke_table_cache = kmem_cache_create("revoke_table",
 219                                           sizeof(struct jbd_revoke_table_s),
 220                                           0, SLAB_TEMPORARY, NULL);
 221        if (!revoke_table_cache)
 222                goto table_cache_failure;
 223
 224        return 0;
 225
 226table_cache_failure:
 227        journal_destroy_revoke_caches();
 228record_cache_failure:
 229        return -ENOMEM;
 230}
 231
 232static struct jbd_revoke_table_s *journal_init_revoke_table(int hash_size)
 233{
 234        int shift = 0;
 235        int tmp = hash_size;
 236        struct jbd_revoke_table_s *table;
 237
 238        table = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
 239        if (!table)
 240                goto out;
 241
 242        while((tmp >>= 1UL) != 0UL)
 243                shift++;
 244
 245        table->hash_size = hash_size;
 246        table->hash_shift = shift;
 247        table->hash_table =
 248                kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
 249        if (!table->hash_table) {
 250                kmem_cache_free(revoke_table_cache, table);
 251                table = NULL;
 252                goto out;
 253        }
 254
 255        for (tmp = 0; tmp < hash_size; tmp++)
 256                INIT_LIST_HEAD(&table->hash_table[tmp]);
 257
 258out:
 259        return table;
 260}
 261
 262static void journal_destroy_revoke_table(struct jbd_revoke_table_s *table)
 263{
 264        int i;
 265        struct list_head *hash_list;
 266
 267        for (i = 0; i < table->hash_size; i++) {
 268                hash_list = &table->hash_table[i];
 269                J_ASSERT(list_empty(hash_list));
 270        }
 271
 272        kfree(table->hash_table);
 273        kmem_cache_free(revoke_table_cache, table);
 274}
 275
 276/* Initialise the revoke table for a given journal to a given size. */
 277int journal_init_revoke(journal_t *journal, int hash_size)
 278{
 279        J_ASSERT(journal->j_revoke_table[0] == NULL);
 280        J_ASSERT(is_power_of_2(hash_size));
 281
 282        journal->j_revoke_table[0] = journal_init_revoke_table(hash_size);
 283        if (!journal->j_revoke_table[0])
 284                goto fail0;
 285
 286        journal->j_revoke_table[1] = journal_init_revoke_table(hash_size);
 287        if (!journal->j_revoke_table[1])
 288                goto fail1;
 289
 290        journal->j_revoke = journal->j_revoke_table[1];
 291
 292        spin_lock_init(&journal->j_revoke_lock);
 293
 294        return 0;
 295
 296fail1:
 297        journal_destroy_revoke_table(journal->j_revoke_table[0]);
 298fail0:
 299        return -ENOMEM;
 300}
 301
 302/* Destroy a journal's revoke table.  The table must already be empty! */
 303void journal_destroy_revoke(journal_t *journal)
 304{
 305        journal->j_revoke = NULL;
 306        if (journal->j_revoke_table[0])
 307                journal_destroy_revoke_table(journal->j_revoke_table[0]);
 308        if (journal->j_revoke_table[1])
 309                journal_destroy_revoke_table(journal->j_revoke_table[1]);
 310}
 311
 312
 313#ifdef __KERNEL__
 314
 315/*
 316 * journal_revoke: revoke a given buffer_head from the journal.  This
 317 * prevents the block from being replayed during recovery if we take a
 318 * crash after this current transaction commits.  Any subsequent
 319 * metadata writes of the buffer in this transaction cancel the
 320 * revoke.
 321 *
 322 * Note that this call may block --- it is up to the caller to make
 323 * sure that there are no further calls to journal_write_metadata
 324 * before the revoke is complete.  In ext3, this implies calling the
 325 * revoke before clearing the block bitmap when we are deleting
 326 * metadata.
 327 *
 328 * Revoke performs a journal_forget on any buffer_head passed in as a
 329 * parameter, but does _not_ forget the buffer_head if the bh was only
 330 * found implicitly.
 331 *
 332 * bh_in may not be a journalled buffer - it may have come off
 333 * the hash tables without an attached journal_head.
 334 *
 335 * If bh_in is non-zero, journal_revoke() will decrement its b_count
 336 * by one.
 337 */
 338
 339int journal_revoke(handle_t *handle, unsigned int blocknr,
 340                   struct buffer_head *bh_in)
 341{
 342        struct buffer_head *bh = NULL;
 343        journal_t *journal;
 344        struct block_device *bdev;
 345        int err;
 346
 347        might_sleep();
 348        if (bh_in)
 349                BUFFER_TRACE(bh_in, "enter");
 350
 351        journal = handle->h_transaction->t_journal;
 352        if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)){
 353                J_ASSERT (!"Cannot set revoke feature!");
 354                return -EINVAL;
 355        }
 356
 357        bdev = journal->j_fs_dev;
 358        bh = bh_in;
 359
 360        if (!bh) {
 361                bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
 362                if (bh)
 363                        BUFFER_TRACE(bh, "found on hash");
 364        }
 365#ifdef JBD_EXPENSIVE_CHECKING
 366        else {
 367                struct buffer_head *bh2;
 368
 369                /* If there is a different buffer_head lying around in
 370                 * memory anywhere... */
 371                bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
 372                if (bh2) {
 373                        /* ... and it has RevokeValid status... */
 374                        if (bh2 != bh && buffer_revokevalid(bh2))
 375                                /* ...then it better be revoked too,
 376                                 * since it's illegal to create a revoke
 377                                 * record against a buffer_head which is
 378                                 * not marked revoked --- that would
 379                                 * risk missing a subsequent revoke
 380                                 * cancel. */
 381                                J_ASSERT_BH(bh2, buffer_revoked(bh2));
 382                        put_bh(bh2);
 383                }
 384        }
 385#endif
 386
 387        /* We really ought not ever to revoke twice in a row without
 388           first having the revoke cancelled: it's illegal to free a
 389           block twice without allocating it in between! */
 390        if (bh) {
 391                if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
 392                                 "inconsistent data on disk")) {
 393                        if (!bh_in)
 394                                brelse(bh);
 395                        return -EIO;
 396                }
 397                set_buffer_revoked(bh);
 398                set_buffer_revokevalid(bh);
 399                if (bh_in) {
 400                        BUFFER_TRACE(bh_in, "call journal_forget");
 401                        journal_forget(handle, bh_in);
 402                } else {
 403                        BUFFER_TRACE(bh, "call brelse");
 404                        __brelse(bh);
 405                }
 406        }
 407
 408        jbd_debug(2, "insert revoke for block %u, bh_in=%p\n", blocknr, bh_in);
 409        err = insert_revoke_hash(journal, blocknr,
 410                                handle->h_transaction->t_tid);
 411        BUFFER_TRACE(bh_in, "exit");
 412        return err;
 413}
 414
 415/*
 416 * Cancel an outstanding revoke.  For use only internally by the
 417 * journaling code (called from journal_get_write_access).
 418 *
 419 * We trust buffer_revoked() on the buffer if the buffer is already
 420 * being journaled: if there is no revoke pending on the buffer, then we
 421 * don't do anything here.
 422 *
 423 * This would break if it were possible for a buffer to be revoked and
 424 * discarded, and then reallocated within the same transaction.  In such
 425 * a case we would have lost the revoked bit, but when we arrived here
 426 * the second time we would still have a pending revoke to cancel.  So,
 427 * do not trust the Revoked bit on buffers unless RevokeValid is also
 428 * set.
 429 */
 430int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
 431{
 432        struct jbd_revoke_record_s *record;
 433        journal_t *journal = handle->h_transaction->t_journal;
 434        int need_cancel;
 435        int did_revoke = 0;     /* akpm: debug */
 436        struct buffer_head *bh = jh2bh(jh);
 437
 438        jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
 439
 440        /* Is the existing Revoke bit valid?  If so, we trust it, and
 441         * only perform the full cancel if the revoke bit is set.  If
 442         * not, we can't trust the revoke bit, and we need to do the
 443         * full search for a revoke record. */
 444        if (test_set_buffer_revokevalid(bh)) {
 445                need_cancel = test_clear_buffer_revoked(bh);
 446        } else {
 447                need_cancel = 1;
 448                clear_buffer_revoked(bh);
 449        }
 450
 451        if (need_cancel) {
 452                record = find_revoke_record(journal, bh->b_blocknr);
 453                if (record) {
 454                        jbd_debug(4, "cancelled existing revoke on "
 455                                  "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
 456                        spin_lock(&journal->j_revoke_lock);
 457                        list_del(&record->hash);
 458                        spin_unlock(&journal->j_revoke_lock);
 459                        kmem_cache_free(revoke_record_cache, record);
 460                        did_revoke = 1;
 461                }
 462        }
 463
 464#ifdef JBD_EXPENSIVE_CHECKING
 465        /* There better not be one left behind by now! */
 466        record = find_revoke_record(journal, bh->b_blocknr);
 467        J_ASSERT_JH(jh, record == NULL);
 468#endif
 469
 470        /* Finally, have we just cleared revoke on an unhashed
 471         * buffer_head?  If so, we'd better make sure we clear the
 472         * revoked status on any hashed alias too, otherwise the revoke
 473         * state machine will get very upset later on. */
 474        if (need_cancel) {
 475                struct buffer_head *bh2;
 476                bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
 477                if (bh2) {
 478                        if (bh2 != bh)
 479                                clear_buffer_revoked(bh2);
 480                        __brelse(bh2);
 481                }
 482        }
 483        return did_revoke;
 484}
 485
 486/*
 487 * journal_clear_revoked_flags clears revoked flag of buffers in
 488 * revoke table to reflect there is no revoked buffer in the next
 489 * transaction which is going to be started.
 490 */
 491void journal_clear_buffer_revoked_flags(journal_t *journal)
 492{
 493        struct jbd_revoke_table_s *revoke = journal->j_revoke;
 494        int i = 0;
 495
 496        for (i = 0; i < revoke->hash_size; i++) {
 497                struct list_head *hash_list;
 498                struct list_head *list_entry;
 499                hash_list = &revoke->hash_table[i];
 500
 501                list_for_each(list_entry, hash_list) {
 502                        struct jbd_revoke_record_s *record;
 503                        struct buffer_head *bh;
 504                        record = (struct jbd_revoke_record_s *)list_entry;
 505                        bh = __find_get_block(journal->j_fs_dev,
 506                                              record->blocknr,
 507                                              journal->j_blocksize);
 508                        if (bh) {
 509                                clear_buffer_revoked(bh);
 510                                __brelse(bh);
 511                        }
 512                }
 513        }
 514}
 515
 516/* journal_switch_revoke table select j_revoke for next transaction
 517 * we do not want to suspend any processing until all revokes are
 518 * written -bzzz
 519 */
 520void journal_switch_revoke_table(journal_t *journal)
 521{
 522        int i;
 523
 524        if (journal->j_revoke == journal->j_revoke_table[0])
 525                journal->j_revoke = journal->j_revoke_table[1];
 526        else
 527                journal->j_revoke = journal->j_revoke_table[0];
 528
 529        for (i = 0; i < journal->j_revoke->hash_size; i++)
 530                INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
 531}
 532
 533/*
 534 * Write revoke records to the journal for all entries in the current
 535 * revoke hash, deleting the entries as we go.
 536 */
 537void journal_write_revoke_records(journal_t *journal,
 538                                  transaction_t *transaction, int write_op)
 539{
 540        struct journal_head *descriptor;
 541        struct jbd_revoke_record_s *record;
 542        struct jbd_revoke_table_s *revoke;
 543        struct list_head *hash_list;
 544        int i, offset, count;
 545
 546        descriptor = NULL;
 547        offset = 0;
 548        count = 0;
 549
 550        /* select revoke table for committing transaction */
 551        revoke = journal->j_revoke == journal->j_revoke_table[0] ?
 552                journal->j_revoke_table[1] : journal->j_revoke_table[0];
 553
 554        for (i = 0; i < revoke->hash_size; i++) {
 555                hash_list = &revoke->hash_table[i];
 556
 557                while (!list_empty(hash_list)) {
 558                        record = (struct jbd_revoke_record_s *)
 559                                hash_list->next;
 560                        write_one_revoke_record(journal, transaction,
 561                                                &descriptor, &offset,
 562                                                record, write_op);
 563                        count++;
 564                        list_del(&record->hash);
 565                        kmem_cache_free(revoke_record_cache, record);
 566                }
 567        }
 568        if (descriptor)
 569                flush_descriptor(journal, descriptor, offset, write_op);
 570        jbd_debug(1, "Wrote %d revoke records\n", count);
 571}
 572
 573/*
 574 * Write out one revoke record.  We need to create a new descriptor
 575 * block if the old one is full or if we have not already created one.
 576 */
 577
 578static void write_one_revoke_record(journal_t *journal,
 579                                    transaction_t *transaction,
 580                                    struct journal_head **descriptorp,
 581                                    int *offsetp,
 582                                    struct jbd_revoke_record_s *record,
 583                                    int write_op)
 584{
 585        struct journal_head *descriptor;
 586        int offset;
 587        journal_header_t *header;
 588
 589        /* If we are already aborting, this all becomes a noop.  We
 590           still need to go round the loop in
 591           journal_write_revoke_records in order to free all of the
 592           revoke records: only the IO to the journal is omitted. */
 593        if (is_journal_aborted(journal))
 594                return;
 595
 596        descriptor = *descriptorp;
 597        offset = *offsetp;
 598
 599        /* Make sure we have a descriptor with space left for the record */
 600        if (descriptor) {
 601                if (offset == journal->j_blocksize) {
 602                        flush_descriptor(journal, descriptor, offset, write_op);
 603                        descriptor = NULL;
 604                }
 605        }
 606
 607        if (!descriptor) {
 608                descriptor = journal_get_descriptor_buffer(journal);
 609                if (!descriptor)
 610                        return;
 611                header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
 612                header->h_magic     = cpu_to_be32(JFS_MAGIC_NUMBER);
 613                header->h_blocktype = cpu_to_be32(JFS_REVOKE_BLOCK);
 614                header->h_sequence  = cpu_to_be32(transaction->t_tid);
 615
 616                /* Record it so that we can wait for IO completion later */
 617                JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
 618                journal_file_buffer(descriptor, transaction, BJ_LogCtl);
 619
 620                offset = sizeof(journal_revoke_header_t);
 621                *descriptorp = descriptor;
 622        }
 623
 624        * ((__be32 *)(&jh2bh(descriptor)->b_data[offset])) =
 625                cpu_to_be32(record->blocknr);
 626        offset += 4;
 627        *offsetp = offset;
 628}
 629
 630/*
 631 * Flush a revoke descriptor out to the journal.  If we are aborting,
 632 * this is a noop; otherwise we are generating a buffer which needs to
 633 * be waited for during commit, so it has to go onto the appropriate
 634 * journal buffer list.
 635 */
 636
 637static void flush_descriptor(journal_t *journal,
 638                             struct journal_head *descriptor,
 639                             int offset, int write_op)
 640{
 641        journal_revoke_header_t *header;
 642        struct buffer_head *bh = jh2bh(descriptor);
 643
 644        if (is_journal_aborted(journal)) {
 645                put_bh(bh);
 646                return;
 647        }
 648
 649        header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
 650        header->r_count = cpu_to_be32(offset);
 651        set_buffer_jwrite(bh);
 652        BUFFER_TRACE(bh, "write");
 653        set_buffer_dirty(bh);
 654        write_dirty_buffer(bh, write_op);
 655}
 656#endif
 657
 658/*
 659 * Revoke support for recovery.
 660 *
 661 * Recovery needs to be able to:
 662 *
 663 *  record all revoke records, including the tid of the latest instance
 664 *  of each revoke in the journal
 665 *
 666 *  check whether a given block in a given transaction should be replayed
 667 *  (ie. has not been revoked by a revoke record in that or a subsequent
 668 *  transaction)
 669 *
 670 *  empty the revoke table after recovery.
 671 */
 672
 673/*
 674 * First, setting revoke records.  We create a new revoke record for
 675 * every block ever revoked in the log as we scan it for recovery, and
 676 * we update the existing records if we find multiple revokes for a
 677 * single block.
 678 */
 679
 680int journal_set_revoke(journal_t *journal,
 681                       unsigned int blocknr,
 682                       tid_t sequence)
 683{
 684        struct jbd_revoke_record_s *record;
 685
 686        record = find_revoke_record(journal, blocknr);
 687        if (record) {
 688                /* If we have multiple occurrences, only record the
 689                 * latest sequence number in the hashed record */
 690                if (tid_gt(sequence, record->sequence))
 691                        record->sequence = sequence;
 692                return 0;
 693        }
 694        return insert_revoke_hash(journal, blocknr, sequence);
 695}
 696
 697/*
 698 * Test revoke records.  For a given block referenced in the log, has
 699 * that block been revoked?  A revoke record with a given transaction
 700 * sequence number revokes all blocks in that transaction and earlier
 701 * ones, but later transactions still need replayed.
 702 */
 703
 704int journal_test_revoke(journal_t *journal,
 705                        unsigned int blocknr,
 706                        tid_t sequence)
 707{
 708        struct jbd_revoke_record_s *record;
 709
 710        record = find_revoke_record(journal, blocknr);
 711        if (!record)
 712                return 0;
 713        if (tid_gt(sequence, record->sequence))
 714                return 0;
 715        return 1;
 716}
 717
 718/*
 719 * Finally, once recovery is over, we need to clear the revoke table so
 720 * that it can be reused by the running filesystem.
 721 */
 722
 723void journal_clear_revoke(journal_t *journal)
 724{
 725        int i;
 726        struct list_head *hash_list;
 727        struct jbd_revoke_record_s *record;
 728        struct jbd_revoke_table_s *revoke;
 729
 730        revoke = journal->j_revoke;
 731
 732        for (i = 0; i < revoke->hash_size; i++) {
 733                hash_list = &revoke->hash_table[i];
 734                while (!list_empty(hash_list)) {
 735                        record = (struct jbd_revoke_record_s*) hash_list->next;
 736                        list_del(&record->hash);
 737                        kmem_cache_free(revoke_record_cache, record);
 738                }
 739        }
 740}
 741
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