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revoke.c
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1 /*
2  * linux/fs/jbd2/revoke.c
3  *
4  * Written by Stephen C. Tweedie <[email protected]>, 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/jbd2.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 
97 static struct kmem_cache *jbd2_revoke_record_cache;
98 static struct kmem_cache *jbd2_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 
105 {
106  struct list_head hash;
107  tid_t sequence; /* Used for recovery only */
108  unsigned long long blocknr;
109 };
110 
111 
112 /* The revoke table is just a simple hash table of revoke records. */
114 {
115  /* It is conceivable that we might want a larger hash table
116  * for recovery. Must be a power of two. */
120 };
121 
122 
123 #ifdef __KERNEL__
124 static void write_one_revoke_record(journal_t *, transaction_t *,
125  struct journal_head **, int *,
126  struct jbd2_revoke_record_s *, int);
127 static 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 */
133 static inline int hash(journal_t *journal, unsigned long long block)
134 {
135  struct jbd2_revoke_table_s *table = journal->j_revoke;
136  int hash_shift = table->hash_shift;
137  int hash = (int)block ^ (int)((block >> 31) >> 1);
138 
139  return ((hash << (hash_shift - 6)) ^
140  (hash >> 13) ^
141  (hash << (hash_shift - 12))) & (table->hash_size - 1);
142 }
143 
144 static int insert_revoke_hash(journal_t *journal, unsigned long long blocknr,
145  tid_t seq)
146 {
147  struct list_head *hash_list;
149 
150 repeat:
151  record = kmem_cache_alloc(jbd2_revoke_record_cache, GFP_NOFS);
152  if (!record)
153  goto oom;
154 
155  record->sequence = seq;
156  record->blocknr = blocknr;
157  hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
158  spin_lock(&journal->j_revoke_lock);
159  list_add(&record->hash, hash_list);
160  spin_unlock(&journal->j_revoke_lock);
161  return 0;
162 
163 oom:
164  if (!journal_oom_retry)
165  return -ENOMEM;
166  jbd_debug(1, "ENOMEM in %s, retrying\n", __func__);
167  yield();
168  goto repeat;
169 }
170 
171 /* Find a revoke record in the journal's hash table. */
172 
173 static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
174  unsigned long long blocknr)
175 {
176  struct list_head *hash_list;
178 
179  hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
180 
181  spin_lock(&journal->j_revoke_lock);
182  record = (struct jbd2_revoke_record_s *) hash_list->next;
183  while (&(record->hash) != hash_list) {
184  if (record->blocknr == blocknr) {
185  spin_unlock(&journal->j_revoke_lock);
186  return record;
187  }
188  record = (struct jbd2_revoke_record_s *) record->hash.next;
189  }
190  spin_unlock(&journal->j_revoke_lock);
191  return NULL;
192 }
193 
195 {
196  if (jbd2_revoke_record_cache) {
197  kmem_cache_destroy(jbd2_revoke_record_cache);
198  jbd2_revoke_record_cache = NULL;
199  }
200  if (jbd2_revoke_table_cache) {
201  kmem_cache_destroy(jbd2_revoke_table_cache);
202  jbd2_revoke_table_cache = NULL;
203  }
204 }
205 
207 {
208  J_ASSERT(!jbd2_revoke_record_cache);
209  J_ASSERT(!jbd2_revoke_table_cache);
210 
211  jbd2_revoke_record_cache = KMEM_CACHE(jbd2_revoke_record_s,
213  if (!jbd2_revoke_record_cache)
214  goto record_cache_failure;
215 
216  jbd2_revoke_table_cache = KMEM_CACHE(jbd2_revoke_table_s,
218  if (!jbd2_revoke_table_cache)
219  goto table_cache_failure;
220  return 0;
221 table_cache_failure:
223 record_cache_failure:
224  return -ENOMEM;
225 }
226 
227 static struct jbd2_revoke_table_s *jbd2_journal_init_revoke_table(int hash_size)
228 {
229  int shift = 0;
230  int tmp = hash_size;
231  struct jbd2_revoke_table_s *table;
232 
233  table = kmem_cache_alloc(jbd2_revoke_table_cache, GFP_KERNEL);
234  if (!table)
235  goto out;
236 
237  while((tmp >>= 1UL) != 0UL)
238  shift++;
239 
240  table->hash_size = hash_size;
241  table->hash_shift = shift;
242  table->hash_table =
243  kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
244  if (!table->hash_table) {
245  kmem_cache_free(jbd2_revoke_table_cache, table);
246  table = NULL;
247  goto out;
248  }
249 
250  for (tmp = 0; tmp < hash_size; tmp++)
251  INIT_LIST_HEAD(&table->hash_table[tmp]);
252 
253 out:
254  return table;
255 }
256 
257 static void jbd2_journal_destroy_revoke_table(struct jbd2_revoke_table_s *table)
258 {
259  int i;
260  struct list_head *hash_list;
261 
262  for (i = 0; i < table->hash_size; i++) {
263  hash_list = &table->hash_table[i];
264  J_ASSERT(list_empty(hash_list));
265  }
266 
267  kfree(table->hash_table);
268  kmem_cache_free(jbd2_revoke_table_cache, table);
269 }
270 
271 /* Initialise the revoke table for a given journal to a given size. */
272 int jbd2_journal_init_revoke(journal_t *journal, int hash_size)
273 {
274  J_ASSERT(journal->j_revoke_table[0] == NULL);
275  J_ASSERT(is_power_of_2(hash_size));
276 
277  journal->j_revoke_table[0] = jbd2_journal_init_revoke_table(hash_size);
278  if (!journal->j_revoke_table[0])
279  goto fail0;
280 
281  journal->j_revoke_table[1] = jbd2_journal_init_revoke_table(hash_size);
282  if (!journal->j_revoke_table[1])
283  goto fail1;
284 
285  journal->j_revoke = journal->j_revoke_table[1];
286 
287  spin_lock_init(&journal->j_revoke_lock);
288 
289  return 0;
290 
291 fail1:
292  jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
293 fail0:
294  return -ENOMEM;
295 }
296 
297 /* Destroy a journal's revoke table. The table must already be empty! */
298 void jbd2_journal_destroy_revoke(journal_t *journal)
299 {
300  journal->j_revoke = NULL;
301  if (journal->j_revoke_table[0])
302  jbd2_journal_destroy_revoke_table(journal->j_revoke_table[0]);
303  if (journal->j_revoke_table[1])
304  jbd2_journal_destroy_revoke_table(journal->j_revoke_table[1]);
305 }
306 
307 
308 #ifdef __KERNEL__
309 
310 /*
311  * jbd2_journal_revoke: revoke a given buffer_head from the journal. This
312  * prevents the block from being replayed during recovery if we take a
313  * crash after this current transaction commits. Any subsequent
314  * metadata writes of the buffer in this transaction cancel the
315  * revoke.
316  *
317  * Note that this call may block --- it is up to the caller to make
318  * sure that there are no further calls to journal_write_metadata
319  * before the revoke is complete. In ext3, this implies calling the
320  * revoke before clearing the block bitmap when we are deleting
321  * metadata.
322  *
323  * Revoke performs a jbd2_journal_forget on any buffer_head passed in as a
324  * parameter, but does _not_ forget the buffer_head if the bh was only
325  * found implicitly.
326  *
327  * bh_in may not be a journalled buffer - it may have come off
328  * the hash tables without an attached journal_head.
329  *
330  * If bh_in is non-zero, jbd2_journal_revoke() will decrement its b_count
331  * by one.
332  */
333 
334 int jbd2_journal_revoke(handle_t *handle, unsigned long long blocknr,
335  struct buffer_head *bh_in)
336 {
337  struct buffer_head *bh = NULL;
338  journal_t *journal;
339  struct block_device *bdev;
340  int err;
341 
342  might_sleep();
343  if (bh_in)
344  BUFFER_TRACE(bh_in, "enter");
345 
346  journal = handle->h_transaction->t_journal;
348  J_ASSERT (!"Cannot set revoke feature!");
349  return -EINVAL;
350  }
351 
352  bdev = journal->j_fs_dev;
353  bh = bh_in;
354 
355  if (!bh) {
356  bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
357  if (bh)
358  BUFFER_TRACE(bh, "found on hash");
359  }
360 #ifdef JBD2_EXPENSIVE_CHECKING
361  else {
362  struct buffer_head *bh2;
363 
364  /* If there is a different buffer_head lying around in
365  * memory anywhere... */
366  bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
367  if (bh2) {
368  /* ... and it has RevokeValid status... */
369  if (bh2 != bh && buffer_revokevalid(bh2))
370  /* ...then it better be revoked too,
371  * since it's illegal to create a revoke
372  * record against a buffer_head which is
373  * not marked revoked --- that would
374  * risk missing a subsequent revoke
375  * cancel. */
376  J_ASSERT_BH(bh2, buffer_revoked(bh2));
377  put_bh(bh2);
378  }
379  }
380 #endif
381 
382  /* We really ought not ever to revoke twice in a row without
383  first having the revoke cancelled: it's illegal to free a
384  block twice without allocating it in between! */
385  if (bh) {
386  if (!J_EXPECT_BH(bh, !buffer_revoked(bh),
387  "inconsistent data on disk")) {
388  if (!bh_in)
389  brelse(bh);
390  return -EIO;
391  }
392  set_buffer_revoked(bh);
393  set_buffer_revokevalid(bh);
394  if (bh_in) {
395  BUFFER_TRACE(bh_in, "call jbd2_journal_forget");
396  jbd2_journal_forget(handle, bh_in);
397  } else {
398  BUFFER_TRACE(bh, "call brelse");
399  __brelse(bh);
400  }
401  }
402 
403  jbd_debug(2, "insert revoke for block %llu, bh_in=%p\n",blocknr, bh_in);
404  err = insert_revoke_hash(journal, blocknr,
405  handle->h_transaction->t_tid);
406  BUFFER_TRACE(bh_in, "exit");
407  return err;
408 }
409 
410 /*
411  * Cancel an outstanding revoke. For use only internally by the
412  * journaling code (called from jbd2_journal_get_write_access).
413  *
414  * We trust buffer_revoked() on the buffer if the buffer is already
415  * being journaled: if there is no revoke pending on the buffer, then we
416  * don't do anything here.
417  *
418  * This would break if it were possible for a buffer to be revoked and
419  * discarded, and then reallocated within the same transaction. In such
420  * a case we would have lost the revoked bit, but when we arrived here
421  * the second time we would still have a pending revoke to cancel. So,
422  * do not trust the Revoked bit on buffers unless RevokeValid is also
423  * set.
424  */
425 int jbd2_journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
426 {
428  journal_t *journal = handle->h_transaction->t_journal;
429  int need_cancel;
430  int did_revoke = 0; /* akpm: debug */
431  struct buffer_head *bh = jh2bh(jh);
432 
433  jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
434 
435  /* Is the existing Revoke bit valid? If so, we trust it, and
436  * only perform the full cancel if the revoke bit is set. If
437  * not, we can't trust the revoke bit, and we need to do the
438  * full search for a revoke record. */
439  if (test_set_buffer_revokevalid(bh)) {
440  need_cancel = test_clear_buffer_revoked(bh);
441  } else {
442  need_cancel = 1;
443  clear_buffer_revoked(bh);
444  }
445 
446  if (need_cancel) {
447  record = find_revoke_record(journal, bh->b_blocknr);
448  if (record) {
449  jbd_debug(4, "cancelled existing revoke on "
450  "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
451  spin_lock(&journal->j_revoke_lock);
452  list_del(&record->hash);
453  spin_unlock(&journal->j_revoke_lock);
454  kmem_cache_free(jbd2_revoke_record_cache, record);
455  did_revoke = 1;
456  }
457  }
458 
459 #ifdef JBD2_EXPENSIVE_CHECKING
460  /* There better not be one left behind by now! */
461  record = find_revoke_record(journal, bh->b_blocknr);
462  J_ASSERT_JH(jh, record == NULL);
463 #endif
464 
465  /* Finally, have we just cleared revoke on an unhashed
466  * buffer_head? If so, we'd better make sure we clear the
467  * revoked status on any hashed alias too, otherwise the revoke
468  * state machine will get very upset later on. */
469  if (need_cancel) {
470  struct buffer_head *bh2;
471  bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
472  if (bh2) {
473  if (bh2 != bh)
474  clear_buffer_revoked(bh2);
475  __brelse(bh2);
476  }
477  }
478  return did_revoke;
479 }
480 
481 /*
482  * journal_clear_revoked_flag clears revoked flag of buffers in
483  * revoke table to reflect there is no revoked buffers in the next
484  * transaction which is going to be started.
485  */
486 void jbd2_clear_buffer_revoked_flags(journal_t *journal)
487 {
488  struct jbd2_revoke_table_s *revoke = journal->j_revoke;
489  int i = 0;
490 
491  for (i = 0; i < revoke->hash_size; i++) {
492  struct list_head *hash_list;
493  struct list_head *list_entry;
494  hash_list = &revoke->hash_table[i];
495 
496  list_for_each(list_entry, hash_list) {
498  struct buffer_head *bh;
499  record = (struct jbd2_revoke_record_s *)list_entry;
500  bh = __find_get_block(journal->j_fs_dev,
501  record->blocknr,
502  journal->j_blocksize);
503  if (bh) {
504  clear_buffer_revoked(bh);
505  __brelse(bh);
506  }
507  }
508  }
509 }
510 
511 /* journal_switch_revoke table select j_revoke for next transaction
512  * we do not want to suspend any processing until all revokes are
513  * written -bzzz
514  */
515 void jbd2_journal_switch_revoke_table(journal_t *journal)
516 {
517  int i;
518 
519  if (journal->j_revoke == journal->j_revoke_table[0])
520  journal->j_revoke = journal->j_revoke_table[1];
521  else
522  journal->j_revoke = journal->j_revoke_table[0];
523 
524  for (i = 0; i < journal->j_revoke->hash_size; i++)
525  INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
526 }
527 
528 /*
529  * Write revoke records to the journal for all entries in the current
530  * revoke hash, deleting the entries as we go.
531  */
532 void jbd2_journal_write_revoke_records(journal_t *journal,
534  int write_op)
535 {
536  struct journal_head *descriptor;
538  struct jbd2_revoke_table_s *revoke;
539  struct list_head *hash_list;
540  int i, offset, count;
541 
542  descriptor = NULL;
543  offset = 0;
544  count = 0;
545 
546  /* select revoke table for committing transaction */
547  revoke = journal->j_revoke == journal->j_revoke_table[0] ?
548  journal->j_revoke_table[1] : journal->j_revoke_table[0];
549 
550  for (i = 0; i < revoke->hash_size; i++) {
551  hash_list = &revoke->hash_table[i];
552 
553  while (!list_empty(hash_list)) {
554  record = (struct jbd2_revoke_record_s *)
555  hash_list->next;
556  write_one_revoke_record(journal, transaction,
557  &descriptor, &offset,
558  record, write_op);
559  count++;
560  list_del(&record->hash);
561  kmem_cache_free(jbd2_revoke_record_cache, record);
562  }
563  }
564  if (descriptor)
565  flush_descriptor(journal, descriptor, offset, write_op);
566  jbd_debug(1, "Wrote %d revoke records\n", count);
567 }
568 
569 /*
570  * Write out one revoke record. We need to create a new descriptor
571  * block if the old one is full or if we have not already created one.
572  */
573 
574 static void write_one_revoke_record(journal_t *journal,
575  transaction_t *transaction,
576  struct journal_head **descriptorp,
577  int *offsetp,
578  struct jbd2_revoke_record_s *record,
579  int write_op)
580 {
581  int csum_size = 0;
582  struct journal_head *descriptor;
583  int offset;
585 
586  /* If we are already aborting, this all becomes a noop. We
587  still need to go round the loop in
588  jbd2_journal_write_revoke_records in order to free all of the
589  revoke records: only the IO to the journal is omitted. */
590  if (is_journal_aborted(journal))
591  return;
592 
593  descriptor = *descriptorp;
594  offset = *offsetp;
595 
596  /* Do we need to leave space at the end for a checksum? */
598  csum_size = sizeof(struct jbd2_journal_revoke_tail);
599 
600  /* Make sure we have a descriptor with space left for the record */
601  if (descriptor) {
602  if (offset >= journal->j_blocksize - csum_size) {
603  flush_descriptor(journal, descriptor, offset, write_op);
604  descriptor = NULL;
605  }
606  }
607 
608  if (!descriptor) {
609  descriptor = jbd2_journal_get_descriptor_buffer(journal);
610  if (!descriptor)
611  return;
612  header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
615  header->h_sequence = cpu_to_be32(transaction->t_tid);
616 
617  /* Record it so that we can wait for IO completion later */
618  JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
619  jbd2_journal_file_buffer(descriptor, transaction, BJ_LogCtl);
620 
621  offset = sizeof(jbd2_journal_revoke_header_t);
622  *descriptorp = descriptor;
623  }
624 
626  * ((__be64 *)(&jh2bh(descriptor)->b_data[offset])) =
627  cpu_to_be64(record->blocknr);
628  offset += 8;
629 
630  } else {
631  * ((__be32 *)(&jh2bh(descriptor)->b_data[offset])) =
632  cpu_to_be32(record->blocknr);
633  offset += 4;
634  }
635 
636  *offsetp = offset;
637 }
638 
639 static void jbd2_revoke_csum_set(journal_t *j,
640  struct journal_head *descriptor)
641 {
643  __u32 csum;
644 
646  return;
647 
648  tail = (struct jbd2_journal_revoke_tail *)
649  (jh2bh(descriptor)->b_data + j->j_blocksize -
650  sizeof(struct jbd2_journal_revoke_tail));
651  tail->r_checksum = 0;
652  csum = jbd2_chksum(j, j->j_csum_seed, jh2bh(descriptor)->b_data,
653  j->j_blocksize);
654  tail->r_checksum = cpu_to_be32(csum);
655 }
656 
657 /*
658  * Flush a revoke descriptor out to the journal. If we are aborting,
659  * this is a noop; otherwise we are generating a buffer which needs to
660  * be waited for during commit, so it has to go onto the appropriate
661  * journal buffer list.
662  */
663 
664 static void flush_descriptor(journal_t *journal,
665  struct journal_head *descriptor,
666  int offset, int write_op)
667 {
669  struct buffer_head *bh = jh2bh(descriptor);
670 
671  if (is_journal_aborted(journal)) {
672  put_bh(bh);
673  return;
674  }
675 
676  header = (jbd2_journal_revoke_header_t *) jh2bh(descriptor)->b_data;
677  header->r_count = cpu_to_be32(offset);
678  jbd2_revoke_csum_set(journal, descriptor);
679 
680  set_buffer_jwrite(bh);
681  BUFFER_TRACE(bh, "write");
682  set_buffer_dirty(bh);
683  write_dirty_buffer(bh, write_op);
684 }
685 #endif
686 
687 /*
688  * Revoke support for recovery.
689  *
690  * Recovery needs to be able to:
691  *
692  * record all revoke records, including the tid of the latest instance
693  * of each revoke in the journal
694  *
695  * check whether a given block in a given transaction should be replayed
696  * (ie. has not been revoked by a revoke record in that or a subsequent
697  * transaction)
698  *
699  * empty the revoke table after recovery.
700  */
701 
702 /*
703  * First, setting revoke records. We create a new revoke record for
704  * every block ever revoked in the log as we scan it for recovery, and
705  * we update the existing records if we find multiple revokes for a
706  * single block.
707  */
708 
709 int jbd2_journal_set_revoke(journal_t *journal,
710  unsigned long long blocknr,
711  tid_t sequence)
712 {
714 
715  record = find_revoke_record(journal, blocknr);
716  if (record) {
717  /* If we have multiple occurrences, only record the
718  * latest sequence number in the hashed record */
719  if (tid_gt(sequence, record->sequence))
720  record->sequence = sequence;
721  return 0;
722  }
723  return insert_revoke_hash(journal, blocknr, sequence);
724 }
725 
726 /*
727  * Test revoke records. For a given block referenced in the log, has
728  * that block been revoked? A revoke record with a given transaction
729  * sequence number revokes all blocks in that transaction and earlier
730  * ones, but later transactions still need replayed.
731  */
732 
733 int jbd2_journal_test_revoke(journal_t *journal,
734  unsigned long long blocknr,
735  tid_t sequence)
736 {
738 
739  record = find_revoke_record(journal, blocknr);
740  if (!record)
741  return 0;
742  if (tid_gt(sequence, record->sequence))
743  return 0;
744  return 1;
745 }
746 
747 /*
748  * Finally, once recovery is over, we need to clear the revoke table so
749  * that it can be reused by the running filesystem.
750  */
751 
752 void jbd2_journal_clear_revoke(journal_t *journal)
753 {
754  int i;
755  struct list_head *hash_list;
757  struct jbd2_revoke_table_s *revoke;
758 
759  revoke = journal->j_revoke;
760 
761  for (i = 0; i < revoke->hash_size; i++) {
762  hash_list = &revoke->hash_table[i];
763  while (!list_empty(hash_list)) {
764  record = (struct jbd2_revoke_record_s*) hash_list->next;
765  list_del(&record->hash);
766  kmem_cache_free(jbd2_revoke_record_cache, record);
767  }
768  }
769 }