revoke.c

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							  bh2->b_state));
			__brelse(bh2);
		}
	}
#endif

	/* We really ought not ever to revoke twice in a row without
           first having the revoke cancelled: it's illegal to free a
           block twice without allocating it in between! */
	if (bh) {
		J_ASSERT_BH(bh, !test_bit(BH_Revoked, &bh->b_state));
		set_bit(BH_Revoked, &bh->b_state);
		set_bit(BH_RevokeValid, &bh->b_state);
		if (bh_in) {
			BUFFER_TRACE(bh_in, "call journal_forget");
			journal_forget(handle, bh_in);
		} else {
			BUFFER_TRACE(bh, "call brelse");
			__brelse(bh);
		}
	}

	lock_journal(journal);
	jbd_debug(2, "insert revoke for block %lu, bh_in=%p\n", blocknr, bh_in);
	err = insert_revoke_hash(journal, blocknr,
				handle->h_transaction->t_tid);
	unlock_journal(journal);
	BUFFER_TRACE(bh_in, "exit");
	return err;
}

/*
 * Cancel an outstanding revoke.  For use only internally by the
 * journaling code (called from journal_get_write_access).
 *
 * We trust the BH_Revoked bit on the buffer if the buffer is already
 * being journaled: if there is no revoke pending on the buffer, then we
 * don't do anything here.
 *
 * This would break if it were possible for a buffer to be revoked and
 * discarded, and then reallocated within the same transaction.  In such
 * a case we would have lost the revoked bit, but when we arrived here
 * the second time we would still have a pending revoke to cancel.  So,
 * do not trust the Revoked bit on buffers unless RevokeValid is also
 * set.
 *
 * The caller must have the journal locked.
 */
int journal_cancel_revoke(handle_t *handle, struct journal_head *jh)
{
	struct jbd_revoke_record_s *record;
	journal_t *journal = handle->h_transaction->t_journal;
	int need_cancel;
	int did_revoke = 0;	/* akpm: debug */
	struct buffer_head *bh = jh2bh(jh);
	
	jbd_debug(4, "journal_head %p, cancelling revoke\n", jh);

	/* Is the existing Revoke bit valid?  If so, we trust it, and
	 * only perform the full cancel if the revoke bit is set.  If
	 * not, we can't trust the revoke bit, and we need to do the
	 * full search for a revoke record. */
	if (test_and_set_bit(BH_RevokeValid, &bh->b_state))
		need_cancel = (test_and_clear_bit(BH_Revoked, &bh->b_state));
	else {
		need_cancel = 1;
		clear_bit(BH_Revoked, &bh->b_state);
	}

	if (need_cancel) {
		record = find_revoke_record(journal, bh->b_blocknr);
		if (record) {
			jbd_debug(4, "cancelled existing revoke on "
				  "blocknr %lu\n", bh->b_blocknr);
			list_del(&record->hash);
			kmem_cache_free(revoke_record_cache, record);
			did_revoke = 1;
		}
	}

#ifdef JBD_EXPENSIVE_CHECKING
	/* There better not be one left behind by now! */
	record = find_revoke_record(journal, bh->b_blocknr);
	J_ASSERT_JH(jh, record == NULL);
#endif

	/* Finally, have we just cleared revoke on an unhashed
	 * buffer_head?  If so, we'd better make sure we clear the
	 * revoked status on any hashed alias too, otherwise the revoke
	 * state machine will get very upset later on. */
	if (need_cancel && !bh->b_pprev) {
		struct buffer_head *bh2;
		bh2 = get_hash_table(bh->b_dev, bh->b_blocknr, bh->b_size);
		if (bh2) {
			clear_bit(BH_Revoked, &bh2->b_state);
			__brelse(bh2);
		}
	}
	
	return did_revoke;
}


/*
 * Write revoke records to the journal for all entries in the current
 * revoke hash, deleting the entries as we go.
 *
 * Called with the journal lock held.
 */

void journal_write_revoke_records(journal_t *journal, 
				  transaction_t *transaction)
{
	struct journal_head *descriptor;
	struct jbd_revoke_record_s *record;
	struct jbd_revoke_table_s *revoke;
	struct list_head *hash_list;
	int i, offset, count;

	descriptor = NULL; 
	offset = 0;
	count = 0;
	revoke = journal->j_revoke;
	
	for (i = 0; i < revoke->hash_size; i++) {
		hash_list = &revoke->hash_table[i];

		while (!list_empty(hash_list)) {
			record = (struct jbd_revoke_record_s *) 
				hash_list->next;
			write_one_revoke_record(journal, transaction,
						&descriptor, &offset, 
						record);
			count++;
			list_del(&record->hash);
			kmem_cache_free(revoke_record_cache, record);
		}
	}
	if (descriptor) 
		flush_descriptor(journal, descriptor, offset);
	jbd_debug(1, "Wrote %d revoke records\n", count);
}

/* 
 * Write out one revoke record.  We need to create a new descriptor
 * block if the old one is full or if we have not already created one.  
 */

static void write_one_revoke_record(journal_t *journal, 
				    transaction_t *transaction,
				    struct journal_head **descriptorp, 
				    int *offsetp,
				    struct jbd_revoke_record_s *record)
{
	struct journal_head *descriptor;
	int offset;
	journal_header_t *header;

	/* If we are already aborting, this all becomes a noop.  We
           still need to go round the loop in
           journal_write_revoke_records in order to free all of the
           revoke records: only the IO to the journal is omitted. */
	if (is_journal_aborted(journal))
		return;

	descriptor = *descriptorp;
	offset = *offsetp;

	/* Make sure we have a descriptor with space left for the record */
	if (descriptor) {
		if (offset == journal->j_blocksize) {
			flush_descriptor(journal, descriptor, offset);
			descriptor = NULL;
		}
	}
	
	if (!descriptor) {
		descriptor = journal_get_descriptor_buffer(journal);
		if (!descriptor)
			return;
		header = (journal_header_t *) &jh2bh(descriptor)->b_data[0];
		header->h_magic     = htonl(JFS_MAGIC_NUMBER);
		header->h_blocktype = htonl(JFS_REVOKE_BLOCK);
		header->h_sequence  = htonl(transaction->t_tid);

		/* Record it so that we can wait for IO completion later */
		JBUFFER_TRACE(descriptor, "file as BJ_LogCtl");
		journal_file_buffer(descriptor, transaction, BJ_LogCtl);

		offset = sizeof(journal_revoke_header_t);
		*descriptorp = descriptor;
	}
	
	* ((unsigned int *)(&jh2bh(descriptor)->b_data[offset])) = 
		htonl(record->blocknr);
	offset += 4;
	*offsetp = offset;
}

/* 
 * Flush a revoke descriptor out to the journal.  If we are aborting,
 * this is a noop; otherwise we are generating a buffer which needs to
 * be waited for during commit, so it has to go onto the appropriate
 * journal buffer list.
 */

static void flush_descriptor(journal_t *journal, 
			     struct journal_head *descriptor, 
			     int offset)
{
	journal_revoke_header_t *header;

	if (is_journal_aborted(journal)) {
		JBUFFER_TRACE(descriptor, "brelse");
		unlock_buffer(jh2bh(descriptor));
		__brelse(jh2bh(descriptor));
		return;
	}
	
	header = (journal_revoke_header_t *) jh2bh(descriptor)->b_data;
	header->r_count = htonl(offset);
	set_bit(BH_JWrite, &jh2bh(descriptor)->b_state);
	{
		struct buffer_head *bh = jh2bh(descriptor);
		BUFFER_TRACE(bh, "write");
		clear_bit(BH_Dirty, &bh->b_state);
		bh->b_end_io = journal_end_buffer_io_sync;
		submit_bh(WRITE, bh);
	}
}

#endif

/* 
 * Revoke support for recovery.
 *
 * Recovery needs to be able to:
 *
 *  record all revoke records, including the tid of the latest instance
 *  of each revoke in the journal
 *
 *  check whether a given block in a given transaction should be replayed
 *  (ie. has not been revoked by a revoke record in that or a subsequent
 *  transaction)
 * 
 *  empty the revoke table after recovery.
 */

/*
 * First, setting revoke records.  We create a new revoke record for
 * every block ever revoked in the log as we scan it for recovery, and
 * we update the existing records if we find multiple revokes for a
 * single block. 
 */

int journal_set_revoke(journal_t *journal, 
		       unsigned long blocknr, 
		       tid_t sequence)
{
	struct jbd_revoke_record_s *record;
	
	record = find_revoke_record(journal, blocknr);
	if (record) {
		/* If we have multiple occurences, only record the
		 * latest sequence number in the hashed record */
		if (tid_gt(sequence, record->sequence))
			record->sequence = sequence;
		return 0;
	} 
	return insert_revoke_hash(journal, blocknr, sequence);
}

/* 
 * Test revoke records.  For a given block referenced in the log, has
 * that block been revoked?  A revoke record with a given transaction
 * sequence number revokes all blocks in that transaction and earlier
 * ones, but later transactions still need replayed.
 */

int journal_test_revoke(journal_t *journal, 
			unsigned long blocknr,
			tid_t sequence)
{
	struct jbd_revoke_record_s *record;
	
	record = find_revoke_record(journal, blocknr);
	if (!record)
		return 0;
	if (tid_gt(sequence, record->sequence))
		return 0;
	return 1;
}

/*
 * Finally, once recovery is over, we need to clear the revoke table so
 * that it can be reused by the running filesystem.
 */

void journal_clear_revoke(journal_t *journal)
{
	int i;
	struct list_head *hash_list;
	struct jbd_revoke_record_s *record;
	struct jbd_revoke_table_s *revoke;
	
	revoke = journal->j_revoke;
	
	for (i = 0; i < revoke->hash_size; i++) {
		hash_list = &revoke->hash_table[i];
		while (!list_empty(hash_list)) {
			record = (struct jbd_revoke_record_s*) hash_list->next;
			list_del(&record->hash);
			kmem_cache_free(revoke_record_cache, record);
		}
	}
}