4 * Written by Stephen C. Tweedie <sct@redhat.com>, 2000
6 * Copyright 2000 Red Hat corp --- All Rights Reserved
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.
12 * Journal revoke routines for the generic filesystem journaling code;
13 * part of the ext2fs journaling system.
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:
19 * + Commit: during commit we write the entire list of the current
20 * transaction's revoked blocks to the journal
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
28 * We can get interactions between revokes and new log data within a
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.
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.
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
50 * Revoke information on buffers is a tri-state value:
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54 * buffer has not been revoked, and cancel_revoke
56 * RevokeValid set, Revoked set:
57 * buffer has been revoked.
63 #include <linux/time.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>
73 static kmem_cache_t *revoke_record_cache;
74 static kmem_cache_t *revoke_table_cache;
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. */
80 struct jbd_revoke_record_s
82 struct list_head hash;
83 tid_t sequence; /* Used for recovery only */
84 unsigned long blocknr;
88 /* The revoke table is just a simple hash table of revoke records. */
89 struct jbd_revoke_table_s
91 /* It is conceivable that we might want a larger hash table
92 * for recovery. Must be a power of two. */
95 struct list_head *hash_table;
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);
106 /* Utility functions to maintain the revoke table */
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)
111 struct jbd_revoke_table_s *table = journal->j_revoke;
112 int hash_shift = table->hash_shift;
114 return ((block << (hash_shift - 6)) ^
116 (block << (hash_shift - 12))) & (table->hash_size - 1);
119 int insert_revoke_hash(journal_t *journal, unsigned long blocknr, tid_t seq)
121 struct list_head *hash_list;
122 struct jbd_revoke_record_s *record;
125 record = kmem_cache_alloc(revoke_record_cache, GFP_NOFS);
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);
138 if (!journal_oom_retry)
140 jbd_debug(1, "ENOMEM in %s, retrying\n", __FUNCTION__);
145 /* Find a revoke record in the journal's hash table. */
147 static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
148 unsigned long blocknr)
150 struct list_head *hash_list;
151 struct jbd_revoke_record_s *record;
153 hash_list = &journal->j_revoke->hash_table[hash(journal, blocknr)];
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);
162 record = (struct jbd_revoke_record_s *) record->hash.next;
164 spin_unlock(&journal->j_revoke_lock);
168 int __init journal_init_revoke_caches(void)
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)
176 revoke_table_cache = kmem_cache_create("revoke_table",
177 sizeof(struct jbd_revoke_table_s),
179 if (revoke_table_cache == 0) {
180 kmem_cache_destroy(revoke_record_cache);
181 revoke_record_cache = NULL;
187 void journal_destroy_revoke_caches(void)
189 kmem_cache_destroy(revoke_record_cache);
190 revoke_record_cache = 0;
191 kmem_cache_destroy(revoke_table_cache);
192 revoke_table_cache = 0;
195 /* Initialise the revoke table for a given journal to a given size. */
197 int journal_init_revoke(journal_t *journal, int hash_size)
201 J_ASSERT (journal->j_revoke_table[0] == NULL);
205 while((tmp >>= 1UL) != 0UL)
208 journal->j_revoke_table[0] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
209 if (!journal->j_revoke_table[0])
211 journal->j_revoke = journal->j_revoke_table[0];
213 /* Check that the hash_size is a power of two */
214 J_ASSERT ((hash_size & (hash_size-1)) == 0);
216 journal->j_revoke->hash_size = hash_size;
218 journal->j_revoke->hash_shift = shift;
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;
228 for (tmp = 0; tmp < hash_size; tmp++)
229 INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
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]);
238 journal->j_revoke = journal->j_revoke_table[1];
240 /* Check that the hash_size is a power of two */
241 J_ASSERT ((hash_size & (hash_size-1)) == 0);
243 journal->j_revoke->hash_size = hash_size;
245 journal->j_revoke->hash_shift = shift;
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;
257 for (tmp = 0; tmp < hash_size; tmp++)
258 INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
260 spin_lock_init(&journal->j_revoke_lock);
265 /* Destoy a journal's revoke table. The table must already be empty! */
267 void journal_destroy_revoke(journal_t *journal)
269 struct jbd_revoke_table_s *table;
270 struct list_head *hash_list;
273 table = journal->j_revoke_table[0];
277 for (i=0; i<table->hash_size; i++) {
278 hash_list = &table->hash_table[i];
279 J_ASSERT (list_empty(hash_list));
282 kfree(table->hash_table);
283 kmem_cache_free(revoke_table_cache, table);
284 journal->j_revoke = NULL;
286 table = journal->j_revoke_table[1];
290 for (i=0; i<table->hash_size; i++) {
291 hash_list = &table->hash_table[i];
292 J_ASSERT (list_empty(hash_list));
295 kfree(table->hash_table);
296 kmem_cache_free(revoke_table_cache, table);
297 journal->j_revoke = NULL;
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
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
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
320 * bh_in may not be a journalled buffer - it may have come off
321 * the hash tables without an attached journal_head.
323 * If bh_in is non-zero, journal_revoke() will decrement its b_count
327 int journal_revoke(handle_t *handle, unsigned long blocknr,
328 struct buffer_head *bh_in)
330 struct buffer_head *bh = NULL;
332 struct block_device *bdev;
336 BUFFER_TRACE(bh_in, "enter");
338 journal = handle->h_transaction->t_journal;
339 if (!journal_set_features(journal, 0, 0, JFS_FEATURE_INCOMPAT_REVOKE)){
340 J_ASSERT (!"Cannot set revoke feature!");
344 bdev = journal->j_fs_dev;
348 bh = __find_get_block(bdev, blocknr, journal->j_blocksize);
350 BUFFER_TRACE(bh, "found on hash");
352 #ifdef JBD_EXPENSIVE_CHECKING
354 struct buffer_head *bh2;
356 /* If there is a different buffer_head lying around in
357 * memory anywhere... */
358 bh2 = __find_get_block(bdev, blocknr, journal->j_blocksize);
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
368 J_ASSERT_BH(bh2, buffer_revoked(bh2));
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! */
378 J_ASSERT_BH(bh, !buffer_revoked(bh));
379 set_buffer_revoked(bh);
380 set_buffer_revokevalid(bh);
382 BUFFER_TRACE(bh_in, "call journal_forget");
383 journal_forget(handle, bh_in);
385 BUFFER_TRACE(bh, "call brelse");
390 jbd_debug(2, "insert revoke for block %lu, bh_in=%p\n", blocknr, bh_in);
391 err = insert_revoke_hash(journal, blocknr,
392 handle->h_transaction->t_tid);
393 BUFFER_TRACE(bh_in, "exit");
398 * Cancel an outstanding revoke. For use only internally by the
399 * journaling code (called from journal_get_write_access).
401 * We trust buffer_revoked() on the buffer if the buffer is already
402 * being journaled: if there is no revoke pending on the buffer, then we
403 * don't do anything here.
405 * This would break if it were possible for a buffer to be revoked and
406 * discarded, and then reallocated within the same transaction. In such
407 * a case we would have lost the revoked bit, but when we arrived here
408 * the second time we would still have a pending revoke to cancel. So,
409 * do not trust the Revoked bit on buffers unless RevokeValid is also
412 * The caller must have the journal locked.
414 int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
416 struct jbd_revoke_record_s *record;
417 journal_t *journal = handle->h_transaction->t_journal;
419 int did_revoke = 0; /* akpm: debug */
420 struct buffer_head *bh = jh2bh(jh);
422 jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);
424 /* Is the existing Revoke bit valid? If so, we trust it, and
425 * only perform the full cancel if the revoke bit is set. If
426 * not, we can't trust the revoke bit, and we need to do the
427 * full search for a revoke record. */
428 if (test_set_buffer_revokevalid(bh)) {
429 need_cancel = test_clear_buffer_revoked(bh);
432 clear_buffer_revoked(bh);
436 record = find_revoke_record(journal, bh->b_blocknr);
438 jbd_debug(4, "cancelled existing revoke on "
439 "blocknr %llu\n", (unsigned long long)bh->b_blocknr);
440 spin_lock(&journal->j_revoke_lock);
441 list_del(&record->hash);
442 spin_unlock(&journal->j_revoke_lock);
443 kmem_cache_free(revoke_record_cache, record);
448 #ifdef JBD_EXPENSIVE_CHECKING
449 /* There better not be one left behind by now! */
450 record = find_revoke_record(journal, bh->b_blocknr);
451 J_ASSERT_JH(jh, record == NULL);
454 /* Finally, have we just cleared revoke on an unhashed
455 * buffer_head? If so, we'd better make sure we clear the
456 * revoked status on any hashed alias too, otherwise the revoke
457 * state machine will get very upset later on. */
459 struct buffer_head *bh2;
460 bh2 = __find_get_block(bh->b_bdev, bh->b_blocknr, bh->b_size);
463 clear_buffer_revoked(bh2);
470 /* journal_switch_revoke table select j_revoke for next transaction
471 * we do not want to suspend any processing until all revokes are
474 void journal_switch_revoke_table(journal_t *journal)
478 if (journal->j_revoke == journal->j_revoke_table[0])
479 journal->j_revoke = journal->j_revoke_table[1];
481 journal->j_revoke = journal->j_revoke_table[0];
483 for (i = 0; i < journal->j_revoke->hash_size; i++)
484 INIT_LIST_HEAD(&journal->j_revoke->hash_table[i]);
488 * Write revoke records to the journal for all entries in the current
489 * revoke hash, deleting the entries as we go.
491 * Called with the journal lock held.
494 void journal_write_revoke_records(journal_t *journal,
495 transaction_t *transaction)
497 struct journal_head *descriptor;
498 struct jbd_revoke_record_s *record;
499 struct jbd_revoke_table_s *revoke;
500 struct list_head *hash_list;
501 int i, offset, count;
507 /* select revoke table for committing transaction */
508 revoke = journal->j_revoke == journal->j_revoke_table[0] ?
509 journal->j_revoke_table[1] : journal->j_revoke_table[0];
511 for (i = 0; i < revoke->hash_size; i++) {
512 hash_list = &revoke->hash_table[i];
514 while (!list_empty(hash_list)) {
515 record = (struct jbd_revoke_record_s *)
517 write_one_revoke_record(journal, transaction,
518 &descriptor, &offset,
521 list_del(&record->hash);
522 kmem_cache_free(revoke_record_cache, record);
526 flush_descriptor(journal, descriptor, offset);
527 jbd_debug(1, "Wrote %d revoke records\n", count);
531 * Write out one revoke record. We need to create a new descriptor
532 * block if the old one is full or if we have not already created one.
535 static void write_one_revoke_record(journal_t *journal,
536 transaction_t *transaction,
537 struct journal_head **descriptorp,
539 struct jbd_revoke_record_s *record)
541 struct journal_head *descriptor;
543 journal_header_t *header;
545 /* If we are already aborting, this all becomes a noop. We
546 still need to go round the loop in
547 journal_write_revoke_records in order to free all of the
548 revoke records: only the IO to the journal is omitted. */
549 if (is_journal_aborted(journal))
552 descriptor = *descriptorp;
555 /* Make sure we have a descriptor with space left for the record */
557 if (offset == journal->j_blocksize) {
558 flush_descriptor(journal, descriptor, offset);
564 descriptor = journal_get_descriptor_buffer(journal);
567 header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
568 header->h_magic = htonl(JFS_MAGIC_NUMBER);
569 header->h_blocktype = htonl(JFS_REVOKE_BLOCK);
570 header->h_sequence = htonl(transaction->t_tid);
572 /* Record it so that we can wait for IO completion later */
573 JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
574 journal_file_buffer(descriptor, transaction, BJ_LogCtl);
576 offset = sizeof(journal_revoke_header_t);
577 *descriptorp = descriptor;
580 * ((unsigned int *)(&jh2bh(descriptor)->b_data[offset])) =
581 htonl(record->blocknr);
587 * Flush a revoke descriptor out to the journal. If we are aborting,
588 * this is a noop; otherwise we are generating a buffer which needs to
589 * be waited for during commit, so it has to go onto the appropriate
590 * journal buffer list.
593 static void flush_descriptor(journal_t *journal,
594 struct journal_head *descriptor,
597 journal_revoke_header_t *header;
598 struct buffer_head *bh = jh2bh(descriptor);
600 if (is_journal_aborted(journal)) {
605 header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
606 header->r_count = htonl(offset);
607 set_buffer_jwrite(bh);
608 BUFFER_TRACE(bh, "write");
609 set_buffer_uptodate(bh);
610 ll_rw_block(WRITE, 1, &bh);
615 * Revoke support for recovery.
617 * Recovery needs to be able to:
619 * record all revoke records, including the tid of the latest instance
620 * of each revoke in the journal
622 * check whether a given block in a given transaction should be replayed
623 * (ie. has not been revoked by a revoke record in that or a subsequent
626 * empty the revoke table after recovery.
630 * First, setting revoke records. We create a new revoke record for
631 * every block ever revoked in the log as we scan it for recovery, and
632 * we update the existing records if we find multiple revokes for a
636 int journal_set_revoke(journal_t *journal,
637 unsigned long blocknr,
640 struct jbd_revoke_record_s *record;
642 record = find_revoke_record(journal, blocknr);
644 /* If we have multiple occurrences, only record the
645 * latest sequence number in the hashed record */
646 if (tid_gt(sequence, record->sequence))
647 record->sequence = sequence;
650 return insert_revoke_hash(journal, blocknr, sequence);
654 * Test revoke records. For a given block referenced in the log, has
655 * that block been revoked? A revoke record with a given transaction
656 * sequence number revokes all blocks in that transaction and earlier
657 * ones, but later transactions still need replayed.
660 int journal_test_revoke(journal_t *journal,
661 unsigned long blocknr,
664 struct jbd_revoke_record_s *record;
666 record = find_revoke_record(journal, blocknr);
669 if (tid_gt(sequence, record->sequence))
675 * Finally, once recovery is over, we need to clear the revoke table so
676 * that it can be reused by the running filesystem.
679 void journal_clear_revoke(journal_t *journal)
682 struct list_head *hash_list;
683 struct jbd_revoke_record_s *record;
684 struct jbd_revoke_table_s *revoke;
686 revoke = journal->j_revoke;
688 for (i = 0; i < revoke->hash_size; i++) {
689 hash_list = &revoke->hash_table[i];
690 while (!list_empty(hash_list)) {
691 record = (struct jbd_revoke_record_s*) hash_list->next;
692 list_del(&record->hash);
693 kmem_cache_free(revoke_record_cache, record);