root/fs/jbd2/revoke.c

DEFINITIONS

1. hash
2. insert_revoke_hash
3. find_revoke_record
4. jbd2_journal_destroy_revoke_record_cache
5. jbd2_journal_destroy_revoke_table_cache
6. jbd2_journal_init_revoke_record_cache
7. jbd2_journal_init_revoke_table_cache
8. jbd2_journal_init_revoke_table
9. jbd2_journal_destroy_revoke_table
10. jbd2_journal_init_revoke
11. jbd2_journal_destroy_revoke
12. jbd2_journal_revoke
13. jbd2_journal_cancel_revoke
14. jbd2_clear_buffer_revoked_flags
15. jbd2_journal_switch_revoke_table
16. jbd2_journal_write_revoke_records
17. write_one_revoke_record
18. flush_descriptor
19. jbd2_journal_set_revoke
20. jbd2_journal_test_revoke
21. jbd2_journal_clear_revoke

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * linux/fs/jbd2/revoke.c
   4  *
   5  * Written by Stephen C. Tweedie <sct@redhat.com>, 2000
   6  *
   7  * Copyright 2000 Red Hat corp --- All Rights Reserved
   8  *
   9  * Journal revoke routines for the generic filesystem journaling code;
  10  * part of the ext2fs journaling system.
  11  *
  12  * Revoke is the mechanism used to prevent old log records for deleted
  13  * metadata from being replayed on top of newer data using the same
  14  * blocks.  The revoke mechanism is used in two separate places:
  15  *
  16  * + Commit: during commit we write the entire list of the current
  17  *   transaction's revoked blocks to the journal
  18  *
  19  * + Recovery: during recovery we record the transaction ID of all
  20  *   revoked blocks.  If there are multiple revoke records in the log
  21  *   for a single block, only the last one counts, and if there is a log
  22  *   entry for a block beyond the last revoke, then that log entry still
  23  *   gets replayed.
  24  *
  25  * We can get interactions between revokes and new log data within a
  26  * single transaction:
  27  *
  28  * Block is revoked and then journaled:
  29  *   The desired end result is the journaling of the new block, so we
  30  *   cancel the revoke before the transaction commits.
  31  *
  32  * Block is journaled and then revoked:
  33  *   The revoke must take precedence over the write of the block, so we
  34  *   need either to cancel the journal entry or to write the revoke
  35  *   later in the log than the log block.  In this case, we choose the
  36  *   latter: journaling a block cancels any revoke record for that block
  37  *   in the current transaction, so any revoke for that block in the
  38  *   transaction must have happened after the block was journaled and so
  39  *   the revoke must take precedence.
  40  *
  41  * Block is revoked and then written as data:
  42  *   The data write is allowed to succeed, but the revoke is _not_
  43  *   cancelled.  We still need to prevent old log records from
  44  *   overwriting the new data.  We don't even need to clear the revoke
  45  *   bit here.
  46  *
  47  * We cache revoke status of a buffer in the current transaction in b_states
  48  * bits.  As the name says, revokevalid flag indicates that the cached revoke
  49  * status of a buffer is valid and we can rely on the cached status.
  50  *
  51  * Revoke information on buffers is a tri-state value:
  52  *
  53  * RevokeValid clear:   no cached revoke status, need to look it up
  54  * RevokeValid set, Revoked clear:
  55  *                      buffer has not been revoked, and cancel_revoke
  56  *                      need do nothing.
  57  * RevokeValid set, Revoked set:
  58  *                      buffer has been revoked.
  59  *
  60  * Locking rules:
  61  * We keep two hash tables of revoke records. One hashtable belongs to the
  62  * running transaction (is pointed to by journal->j_revoke), the other one
  63  * belongs to the committing transaction. Accesses to the second hash table
  64  * happen only from the kjournald and no other thread touches this table.  Also
  65  * journal_switch_revoke_table() which switches which hashtable belongs to the
  66  * running and which to the committing transaction is called only from
  67  * kjournald. Therefore we need no locks when accessing the hashtable belonging
  68  * to the committing transaction.
  69  *
  70  * All users operating on the hash table belonging to the running transaction
  71  * have a handle to the transaction. Therefore they are safe from kjournald
  72  * switching hash tables under them. For operations on the lists of entries in
  73  * the hash table j_revoke_lock is used.
  74  *
  75  * Finally, also replay code uses the hash tables but at this moment no one else
  76  * can touch them (filesystem isn't mounted yet) and hence no locking is
  77  * needed.
  78  */
  79 
  80 #ifndef __KERNEL__
  81 #include "jfs_user.h"
  82 #else
  83 #include <linux/time.h>
  84 #include <linux/fs.h>
  85 #include <linux/jbd2.h>
  86 #include <linux/errno.h>
  87 #include <linux/slab.h>
  88 #include <linux/list.h>
  89 #include <linux/init.h>
  90 #include <linux/bio.h>
  91 #include <linux/log2.h>
  92 #include <linux/hash.h>
  93 #endif
  94 
  95 static struct kmem_cache *jbd2_revoke_record_cache;
  96 static struct kmem_cache *jbd2_revoke_table_cache;
  97 
  98 /* Each revoke record represents one single revoked block.  During
  99    journal replay, this involves recording the transaction ID of the
 100    last transaction to revoke this block. */
 101 
 102 struct jbd2_revoke_record_s
 103 {
 104         struct list_head  hash;
 105         tid_t             sequence;     /* Used for recovery only */
 106         unsigned long long        blocknr;
 107 };
 108 
 109 
 110 /* The revoke table is just a simple hash table of revoke records. */
 111 struct jbd2_revoke_table_s
 112 {
 113         /* It is conceivable that we might want a larger hash table
 114          * for recovery.  Must be a power of two. */
 115         int               hash_size;
 116         int               hash_shift;
 117         struct list_head *hash_table;
 118 };
 119 
 120 
 121 #ifdef __KERNEL__
 122 static void write_one_revoke_record(transaction_t *,
 123                                     struct list_head *,
 124                                     struct buffer_head **, int *,
 125                                     struct jbd2_revoke_record_s *);
 126 static void flush_descriptor(journal_t *, struct buffer_head *, int);
 127 #endif
 128 
 129 /* Utility functions to maintain the revoke table */
 130 
 131 static inline int hash(journal_t *journal, unsigned long long block)
 132 {
 133         return hash_64(block, journal->j_revoke->hash_shift);
 134 }
 135 
 136 static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,
 137                               tid_t seq)
 138 {
 139         struct list_head *hash_list;
 140         struct jbd2_revoke_record_s *record;
 141         gfp_t gfp_mask = GFP_NOFS;
 142 
 143         if (journal_oom_retry)
 144                 gfp_mask |= __GFP_NOFAIL;
 145         record = kmem_cache_alloc(jbd2_revoke_record_cache, gfp_mask);
 146         if (!record)
 147                 return -ENOMEM;
 148 
 149         record->sequence = seq;
 150         record->blocknr = blocknr;
 151         hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
 152         spin_lock(&journal->j_revoke_lock);
 153         list_add(&record->hash, hash_list);
 154         spin_unlock(&journal->j_revoke_lock);
 155         return 0;
 156 }
 157 
 158 /* Find a revoke record in the journal's hash table. */
 159 
 160 static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
 161                                                       unsigned long long blocknr)
 162 {
 163         struct list_head *hash_list;
 164         struct jbd2_revoke_record_s *record;
 165 
 166         hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
 167 
 168         spin_lock(&journal->j_revoke_lock);
 169         record = (struct jbd2_revoke_record_s *) hash_list->next;
 170         while (&(record->hash) != hash_list) {
 171                 if (record->blocknr == blocknr) {
 172                         spin_unlock(&journal->j_revoke_lock);
 173                         return record;
 174                 }
 175                 record = (struct jbd2_revoke_record_s *) record->hash.next;
 176         }
 177         spin_unlock(&journal->j_revoke_lock);
 178         return NULL;
 179 }
 180 
 181 void jbd2_journal_destroy_revoke_record_cache(void)
 182 {
 183         kmem_cache_destroy(jbd2_revoke_record_cache);
 184         jbd2_revoke_record_cache = NULL;
 185 }
 186 
 187 void jbd2_journal_destroy_revoke_table_cache(void)
 188 {
 189         kmem_cache_destroy(jbd2_revoke_table_cache);
 190         jbd2_revoke_table_cache = NULL;
 191 }
 192 
 193 int __init jbd2_journal_init_revoke_record_cache(void)
 194 {
 195         J_ASSERT(!jbd2_revoke_record_cache);
 196         jbd2_revoke_record_cache = KMEM_CACHE(jbd2_revoke_record_s,
 197                                         SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY);
 198 
 199         if (!jbd2_revoke_record_cache) {
 200                 pr_emerg("JBD2: failed to create revoke_record cache\n");
 201                 return -ENOMEM;
 202         }
 203         return 0;
 204 }
 205 
 206 int __init jbd2_journal_init_revoke_table_cache(void)
 207 {
 208         J_ASSERT(!jbd2_revoke_table_cache);
 209         jbd2_revoke_table_cache = KMEM_CACHE(jbd2_revoke_table_s,
 210                                              SLAB_TEMPORARY);
 211         if (!jbd2_revoke_table_cache) {
 212                 pr_emerg("JBD2: failed to create revoke_table cache\n");
 213                 return -ENOMEM;
 214         }
 215         return 0;
 216 }
 217 
 218 static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
 219 {
 220         int shift = 0;
 221         int tmp = hash_size;
 222         struct jbd2_revoke_table_s *table;
 223 
 224         table = kmem_cache_alloc(jbd2_revoke_table_cache, GFP_KERNEL);
 225         if (!table)
 226                 goto out;
 227 
 228         while((tmp >>= 1UL) != 0UL)
 229                 shift++;
 230 
 231         table->hash_size = hash_size;
 232         table->hash_shift = shift;
 233         table->hash_table =
 234                 kmalloc_array(hash_size, sizeof(struct list_head), GFP_KERNEL);
 235         if (!table->hash_table) {
 236                 kmem_cache_free(jbd2_revoke_table_cache, table);
 237                 table = NULL;
 238                 goto out;
 239         }
 240 
 241         for (tmp = 0; tmp < hash_size; tmp++)
 242                 INIT_LIST_HEAD(&table->hash_table[tmp]);
 243 
 244 out:
 245         return table;
 246 }
 247 
 248 static void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
 249 {
 250         int i;
 251         struct list_head *hash_list;
 252 
 253         for (i = 0; i < table->hash_size; i++) {
 254                 hash_list = &table->hash_table[i];
 255                 J_ASSERT(list_empty(hash_list));
 256         }
 257 
 258         kfree(table->hash_table);
 259         kmem_cache_free(jbd2_revoke_table_cache, table);
 260 }
 261 
 262 /* Initialise the revoke table for a given journal to a given size. */
 263 int jbd2_journal_init_revoke(journal_t *journal, int hash_size)
 264 {
 265         J_ASSERT(journal->j_revoke_table[0] == NULL);
 266         J_ASSERT(is_power_of_2(hash_size));
 267 
 268         journal->j_revoke_table[0] = jbd2_journal_init_revoke_table(hash_size);
 269         if (!journal->j_revoke_table[0])
 270                 goto fail0;
 271 
 272         journal->j_revoke_table[1] = jbd2_journal_init_revoke_table(hash_size);
 273         if (!journal->j_revoke_table[1])
 274                 goto fail1;
 275 
 276         journal->j_revoke = journal->j_revoke_table[1];
 277 
 278         spin_lock_init(&journal->j_revoke_lock);
 279 
 280         return 0;
 281 
 282 fail1:
 283         jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
 284         journal->j_revoke_table[0] = NULL;
 285 fail0:
 286         return -ENOMEM;
 287 }
 288 
 289 /* Destroy a journal's revoke table.  The table must already be empty! */
 290 void jbd2_journal_destroy_revoke(journal_t *journal)
 291 {
 292         journal->j_revoke = NULL;
 293         if (journal->j_revoke_table[0])
 294                 jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
 295         if (journal->j_revoke_table[1])
 296                 jbd2_journal_destroy_revoke_table(journal->j_revoke_table[1]);
 297 }
 298 
 299 
 300 #ifdef __KERNEL__
 301 
 302 /*
 303  * jbd2_journal_revoke: revoke a given buffer_head from the journal.  This
 304  * prevents the block from being replayed during recovery if we take a
 305  * crash after this current transaction commits.  Any subsequent
 306  * metadata writes of the buffer in this transaction cancel the
 307  * revoke.
 308  *
 309  * Note that this call may block --- it is up to the caller to make
 310  * sure that there are no further calls to journal_write_metadata
 311  * before the revoke is complete.  In ext3, this implies calling the
 312  * revoke before clearing the block bitmap when we are deleting
 313  * metadata.
 314  *
 315  * Revoke performs a jbd2_journal_forget on any buffer_head passed in as a
 316  * parameter, but does _not_ forget the buffer_head if the bh was only
 317  * found implicitly.
 318  *
 319  * bh_in may not be a journalled buffer - it may have come off
 320  * the hash tables without an attached journal_head.
 321  *
 322  * If bh_in is non-zero, jbd2_journal_revoke() will decrement its b_count
 323  * by one.
 324  */
 325 
 326 int jbd2_journal_revoke(handle_t *handle, unsigned long long blocknr,
 327                    struct buffer_head *bh_in)
 328 {
 329         struct buffer_head *bh = NULL;
 330         journal_t *journal;
 331         struct block_device *bdev;
 332         int err;
 333 
 334         might_sleep();
 335         if (bh_in)
 336                 BUFFER_TRACE(bh_in, "enter");
 337 
 338         journal = handle->h_transaction->t_journal;
 339         if (!jbd2_journal_set_features(journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE)){
 340                 J_ASSERT (!"Cannot set revoke feature!");
 341                 return -EINVAL;
 342         }
 343 
 344         bdev = journal->j_fs_dev;
 345         bh = bh_in;
 346 
 347         if (!bh) {
 348                 bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
 349                 if (bh)
 350                         BUFFER_TRACE(bh, "found on hash");
 351         }
 352 #ifdef JBD2_EXPENSIVE_CHECKING
 353         else {
 354                 struct buffer_head *bh2;
 355 
 356                 /* If there is a different buffer_head lying around in
 357                  * memory anywhere... */
 358                 bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
 359                 if (bh2) {
 360                         /* ... and it has RevokeValid status... */
 361                         if (bh2 != bh && buffer_revokevalid(bh2))
 362                                 /* ...then it better be revoked too,
 363                                  * since it's illegal to create a revoke
 364                                  * record against a buffer_head which is
 365                                  * not marked revoked --- that would
 366                                  * risk missing a subsequent revoke
 367                                  * cancel. */
 368                                 J_ASSERT_BH(bh2, buffer_revoked(bh2));
 369                         put_bh(bh2);
 370                 }
 371         }
 372 #endif
 373 
 374         /* We really ought not ever to revoke twice in a row without
 375            first having the revoke cancelled: it's illegal to free a
 376            block twice without allocating it in between! */
 377         if (bh) {
 378                 if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
 379                                  "inconsistent data on disk")) {
 380                         if (!bh_in)
 381                                 brelse(bh);
 382                         return -EIO;
 383                 }
 384                 set_buffer_revoked(bh);
 385                 set_buffer_revokevalid(bh);
 386                 if (bh_in) {
 387                         BUFFER_TRACE(bh_in, "call jbd2_journal_forget");
 388                         jbd2_journal_forget(handle, bh_in);
 389                 } else {
 390                         BUFFER_TRACE(bh, "call brelse");
 391                         __brelse(bh);
 392                 }
 393         }
 394 
 395         jbd_debug(2, "insert revoke for block %llu, bh_in=%p\n",blocknr, bh_in);
 396         err = insert_revoke_hash(journal, blocknr,
 397                                 handle->h_transaction->t_tid);
 398         BUFFER_TRACE(bh_in, "exit");
 399         return err;
 400 }
 401 
 402 /*
 403  * Cancel an outstanding revoke.  For use only internally by the
 404  * journaling code (called from jbd2_journal_get_write_access).
 405  *
 406  * We trust buffer_revoked() on the buffer if the buffer is already
 407  * being journaled: if there is no revoke pending on the buffer, then we
 408  * don't do anything here.
 409  *
 410  * This would break if it were possible for a buffer to be revoked and
 411  * discarded, and then reallocated within the same transaction.  In such
 412  * a case we would have lost the revoked bit, but when we arrived here
 413  * the second time we would still have a pending revoke to cancel.  So,
 414  * do not trust the Revoked bit on buffers unless RevokeValid is also
 415  * set.
 416  */
 417 int jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
 418 {
 419         struct jbd2_revoke_record_s *record;
 420         journal_t *journal = handle->h_transaction->t_journal;
 421         int need_cancel;
 422         int did_revoke = 0;     /* akpm: debug */
 423         struct buffer_head *bh = jh2bh(jh);
 424 
 425         jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
 426 
 427         /* Is the existing Revoke bit valid?  If so, we trust it, and
 428          * only perform the full cancel if the revoke bit is set.  If
 429          * not, we can't trust the revoke bit, and we need to do the
 430          * full search for a revoke record. */
 431         if (test_set_buffer_revokevalid(bh)) {
 432                 need_cancel = test_clear_buffer_revoked(bh);
 433         } else {
 434                 need_cancel = 1;
 435                 clear_buffer_revoked(bh);
 436         }
 437 
 438         if (need_cancel) {
 439                 record = find_revoke_record(journal, bh->b_blocknr);
 440                 if (record) {
 441                         jbd_debug(4, "cancelled existing revoke on "
 442                                   "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
 443                         spin_lock(&journal->j_revoke_lock);
 444                         list_del(&record->hash);
 445                         spin_unlock(&journal->j_revoke_lock);
 446                         kmem_cache_free(jbd2_revoke_record_cache, record);
 447                         did_revoke = 1;
 448                 }
 449         }
 450 
 451 #ifdef JBD2_EXPENSIVE_CHECKING
 452         /* There better not be one left behind by now! */
 453         record = find_revoke_record(journal, bh->b_blocknr);
 454         J_ASSERT_JH(jh, record == NULL);
 455 #endif
 456 
 457         /* Finally, have we just cleared revoke on an unhashed
 458          * buffer_head?  If so, we'd better make sure we clear the
 459          * revoked status on any hashed alias too, otherwise the revoke
 460          * state machine will get very upset later on. */
 461         if (need_cancel) {
 462                 struct buffer_head *bh2;
 463                 bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
 464                 if (bh2) {
 465                         if (bh2 != bh)
 466                                 clear_buffer_revoked(bh2);
 467                         __brelse(bh2);
 468                 }
 469         }
 470         return did_revoke;
 471 }
 472 
 473 /*
 474  * journal_clear_revoked_flag clears revoked flag of buffers in
 475  * revoke table to reflect there is no revoked buffers in the next
 476  * transaction which is going to be started.
 477  */
 478 void jbd2_clear_buffer_revoked_flags(journal_t *journal)
 479 {
 480         struct jbd2_revoke_table_s *revoke = journal->j_revoke;
 481         int i = 0;
 482 
 483         for (i = 0; i < revoke->hash_size; i++) {
 484                 struct list_head *hash_list;
 485                 struct list_head *list_entry;
 486                 hash_list = &revoke->hash_table[i];
 487 
 488                 list_for_each(list_entry, hash_list) {
 489                         struct jbd2_revoke_record_s *record;
 490                         struct buffer_head *bh;
 491                         record = (struct jbd2_revoke_record_s *)list_entry;
 492                         bh = __find_get_block(journal->j_fs_dev,
 493                                               record->blocknr,
 494                                               journal->j_blocksize);
 495                         if (bh) {
 496                                 clear_buffer_revoked(bh);
 497                                 __brelse(bh);
 498                         }
 499                 }
 500         }
 501 }
 502 
 503 /* journal_switch_revoke table select j_revoke for next transaction
 504  * we do not want to suspend any processing until all revokes are
 505  * written -bzzz
 506  */
 507 void jbd2_journal_switch_revoke_table(journal_t *journal)
 508 {
 509         int i;
 510 
 511         if (journal->j_revoke == journal->j_revoke_table[0])
 512                 journal->j_revoke = journal->j_revoke_table[1];
 513         else
 514                 journal->j_revoke = journal->j_revoke_table[0];
 515 
 516         for (i = 0; i < journal->j_revoke->hash_size; i++)
 517                 INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
 518 }
 519 
 520 /*
 521  * Write revoke records to the journal for all entries in the current
 522  * revoke hash, deleting the entries as we go.
 523  */
 524 void jbd2_journal_write_revoke_records(transaction_t *transaction,
 525                                        struct list_head *log_bufs)
 526 {
 527         journal_t *journal = transaction->t_journal;
 528         struct buffer_head *descriptor;
 529         struct jbd2_revoke_record_s *record;
 530         struct jbd2_revoke_table_s *revoke;
 531         struct list_head *hash_list;
 532         int i, offset, count;
 533 
 534         descriptor = NULL;
 535         offset = 0;
 536         count = 0;
 537 
 538         /* select revoke table for committing transaction */
 539         revoke = journal->j_revoke == journal->j_revoke_table[0] ?
 540                 journal->j_revoke_table[1] : journal->j_revoke_table[0];
 541 
 542         for (i = 0; i < revoke->hash_size; i++) {
 543                 hash_list = &revoke->hash_table[i];
 544 
 545                 while (!list_empty(hash_list)) {
 546                         record = (struct jbd2_revoke_record_s *)
 547                                 hash_list->next;
 548                         write_one_revoke_record(transaction, log_bufs,
 549                                                 &descriptor, &offset, record);
 550                         count++;
 551                         list_del(&record->hash);
 552                         kmem_cache_free(jbd2_revoke_record_cache, record);
 553                 }
 554         }
 555         if (descriptor)
 556                 flush_descriptor(journal, descriptor, offset);
 557         jbd_debug(1, "Wrote %d revoke records\n", count);
 558 }
 559 
 560 /*
 561  * Write out one revoke record.  We need to create a new descriptor
 562  * block if the old one is full or if we have not already created one.
 563  */
 564 
 565 static void write_one_revoke_record(transaction_t *transaction,
 566                                     struct list_head *log_bufs,
 567                                     struct buffer_head **descriptorp,
 568                                     int *offsetp,
 569                                     struct jbd2_revoke_record_s *record)
 570 {
 571         journal_t *journal = transaction->t_journal;
 572         int csum_size = 0;
 573         struct buffer_head *descriptor;
 574         int sz, offset;
 575 
 576         /* If we are already aborting, this all becomes a noop.  We
 577            still need to go round the loop in
 578            jbd2_journal_write_revoke_records in order to free all of the
 579            revoke records: only the IO to the journal is omitted. */
 580         if (is_journal_aborted(journal))
 581                 return;
 582 
 583         descriptor = *descriptorp;
 584         offset = *offsetp;
 585 
 586         /* Do we need to leave space at the end for a checksum? */
 587         if (jbd2_journal_has_csum_v2or3(journal))
 588                 csum_size = sizeof(struct jbd2_journal_block_tail);
 589 
 590         if (jbd2_has_feature_64bit(journal))
 591                 sz = 8;
 592         else
 593                 sz = 4;
 594 
 595         /* Make sure we have a descriptor with space left for the record */
 596         if (descriptor) {
 597                 if (offset + sz > journal->j_blocksize - csum_size) {
 598                         flush_descriptor(journal, descriptor, offset);
 599                         descriptor = NULL;
 600                 }
 601         }
 602 
 603         if (!descriptor) {
 604                 descriptor = jbd2_journal_get_descriptor_buffer(transaction,
 605                                                         JBD2_REVOKE_BLOCK);
 606                 if (!descriptor)
 607                         return;
 608 
 609                 /* Record it so that we can wait for IO completion later */
 610                 BUFFER_TRACE(descriptor, "file in log_bufs");
 611                 jbd2_file_log_bh(log_bufs, descriptor);
 612 
 613                 offset = sizeof(jbd2_journal_revoke_header_t);
 614                 *descriptorp = descriptor;
 615         }
 616 
 617         if (jbd2_has_feature_64bit(journal))
 618                 * ((__be64 *)(&descriptor->b_data[offset])) =
 619                         cpu_to_be64(record->blocknr);
 620         else
 621                 * ((__be32 *)(&descriptor->b_data[offset])) =
 622                         cpu_to_be32(record->blocknr);
 623         offset += sz;
 624 
 625         *offsetp = offset;
 626 }
 627 
 628 /*
 629  * Flush a revoke descriptor out to the journal.  If we are aborting,
 630  * this is a noop; otherwise we are generating a buffer which needs to
 631  * be waited for during commit, so it has to go onto the appropriate
 632  * journal buffer list.
 633  */
 634 
 635 static void flush_descriptor(journal_t *journal,
 636                              struct buffer_head *descriptor,
 637                              int offset)
 638 {
 639         jbd2_journal_revoke_header_t *header;
 640 
 641         if (is_journal_aborted(journal))
 642                 return;
 643 
 644         header = (jbd2_journal_revoke_header_t *)descriptor->b_data;
 645         header->r_count = cpu_to_be32(offset);
 646         jbd2_descriptor_block_csum_set(journal, descriptor);
 647 
 648         set_buffer_jwrite(descriptor);
 649         BUFFER_TRACE(descriptor, "write");
 650         set_buffer_dirty(descriptor);
 651         write_dirty_buffer(descriptor, REQ_SYNC);
 652 }
 653 #endif
 654 
 655 /*
 656  * Revoke support for recovery.
 657  *
 658  * Recovery needs to be able to:
 659  *
 660  *  record all revoke records, including the tid of the latest instance
 661  *  of each revoke in the journal
 662  *
 663  *  check whether a given block in a given transaction should be replayed
 664  *  (ie. has not been revoked by a revoke record in that or a subsequent
 665  *  transaction)
 666  *
 667  *  empty the revoke table after recovery.
 668  */
 669 
 670 /*
 671  * First, setting revoke records.  We create a new revoke record for
 672  * every block ever revoked in the log as we scan it for recovery, and
 673  * we update the existing records if we find multiple revokes for a
 674  * single block.
 675  */
 676 
 677 int jbd2_journal_set_revoke(journal_t *journal,
 678                        unsigned long long blocknr,
 679                        tid_t sequence)
 680 {
 681         struct jbd2_revoke_record_s *record;
 682 
 683         record = find_revoke_record(journal, blocknr);
 684         if (record) {
 685                 /* If we have multiple occurrences, only record the
 686                  * latest sequence number in the hashed record */
 687                 if (tid_gt(sequence, record->sequence))
 688                         record->sequence = sequence;
 689                 return 0;
 690         }
 691         return insert_revoke_hash(journal, blocknr, sequence);
 692 }
 693 
 694 /*
 695  * Test revoke records.  For a given block referenced in the log, has
 696  * that block been revoked?  A revoke record with a given transaction
 697  * sequence number revokes all blocks in that transaction and earlier
 698  * ones, but later transactions still need replayed.
 699  */
 700 
 701 int jbd2_journal_test_revoke(journal_t *journal,
 702                         unsigned long long blocknr,
 703                         tid_t sequence)
 704 {
 705         struct jbd2_revoke_record_s *record;
 706 
 707         record = find_revoke_record(journal, blocknr);
 708         if (!record)
 709                 return 0;
 710         if (tid_gt(sequence, record->sequence))
 711                 return 0;
 712         return 1;
 713 }
 714 
 715 /*
 716  * Finally, once recovery is over, we need to clear the revoke table so
 717  * that it can be reused by the running filesystem.
 718  */
 719 
 720 void jbd2_journal_clear_revoke(journal_t *journal)
 721 {
 722         int i;
 723         struct list_head *hash_list;
 724         struct jbd2_revoke_record_s *record;
 725         struct jbd2_revoke_table_s *revoke;
 726 
 727         revoke = journal->j_revoke;
 728 
 729         for (i = 0; i < revoke->hash_size; i++) {
 730                 hash_list = &revoke->hash_table[i];
 731                 while (!list_empty(hash_list)) {
 732                         record = (struct jbd2_revoke_record_s*) hash_list->next;
 733                         list_del(&record->hash);
 734                         kmem_cache_free(jbd2_revoke_record_cache, record);
 735                 }
 736         }
 737 }