replay.c

可以在不启动LINUX的情况下直接访问EXT2和EXT3格式的磁盘

	journal->j_max_transaction_buffers = journal->j_maxlen / 4;

	/* Add the dynamic fields and write it to disk. */
	journal_update_superblock(journal, 1);
	return 0;
}

/**
 * int journal_load() - Read journal from disk.
 * @journal: Journal to act on.
 *
 * Given a journal_t structure which tells us which disk blocks contain
 * a journal, read the journal from disk to initialise the in-memory
 * structures.
 */
int journal_load(journal_t *journal)
{
	int err;
	journal_superblock_t *sb;

	err = load_superblock(journal);
	if (err)
		return err;

	sb = journal->j_superblock;
	/* If this is a V2 superblock, then we have to check the
	 * features flags on it. */

	if (journal->j_format_version >= 2) {
		if ((sb->s_feature_ro_compat &
		     ~cpu_to_be32(JFS_KNOWN_ROCOMPAT_FEATURES)) ||
		    (sb->s_feature_incompat &
		     ~cpu_to_be32(JFS_KNOWN_INCOMPAT_FEATURES))) {
			printk (KERN_WARNING
				"JBD: Unrecognised features on journal\n");
			return -EINVAL;
		}
	}

	/* Let the recovery code check whether it needs to recover any
	 * data from the journal. */
	if (journal_recover(journal))
		goto recovery_error;

	/* OK, we've finished with the dynamic journal bits:
	 * reinitialise the dynamic contents of the superblock in memory
	 * and reset them on disk. */
	if (journal_reset(journal))
		goto recovery_error;

	journal->j_flags &= ~JFS_ABORT;
	journal->j_flags |= JFS_LOADED;
	return 0;

recovery_error:
	printk (KERN_WARNING "JBD: recovery failed\n");
	return -EIO;
}


//
// transactions routines
//


/*
 *
 * List management code snippets: various functions for manipulating the
 * transaction buffer lists.
 *
 */

/*
 * Append a buffer to a transaction list, given the transaction's list head
 * pointer.
 *
 * j_list_lock is held.
 *
 * jbd_lock_bh_state(jh2bh(jh)) is held.
 */

static inline void
__blist_add_buffer(struct journal_head **list, struct journal_head *jh)
{
	if (!*list) {
		jh->b_tnext = jh->b_tprev = jh;
		*list = jh;
	} else {
		/* Insert at the tail of the list to preserve order */
		struct journal_head *first = *list, *last = first->b_tprev;
		jh->b_tprev = last;
		jh->b_tnext = first;
		last->b_tnext = first->b_tprev = jh;
	}
}

/*
 * Remove a buffer from a transaction list, given the transaction's list
 * head pointer.
 *
 * Called with j_list_lock held, and the journal may not be locked.
 *
 * jbd_lock_bh_state(jh2bh(jh)) is held.
 */

static inline void
__blist_del_buffer(struct journal_head **list, struct journal_head *jh)
{
	if (*list == jh) {
		*list = jh->b_tnext;
		if (*list == jh)
			*list = NULL;
	}
	jh->b_tprev->b_tnext = jh->b_tnext;
	jh->b_tnext->b_tprev = jh->b_tprev;
}

/*
 * Remove a buffer from the appropriate transaction list.
 *
 * Note that this function can *change* the value of
 * bh->b_transaction->t_sync_datalist, t_buffers, t_forget,
 * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list.  If the caller
 * is holding onto a copy of one of thee pointers, it could go bad.
 * Generally the caller needs to re-read the pointer from the transaction_t.
 *
 * Called under j_list_lock.  The journal may not be locked.
 */
static void __journal_temp_unlink_buffer(struct journal_head *jh)
{
	struct journal_head **list = NULL;
	transaction_t *transaction;
	struct buffer_head *bh = jh2bh(jh);

	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
	transaction = jh->b_transaction;
	if (transaction)
		assert_spin_locked(&transaction->t_journal->j_list_lock);

	J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
	if (jh->b_jlist != BJ_None)
		J_ASSERT_JH(jh, transaction != NULL);

	switch (jh->b_jlist) {
	case BJ_None:
		return;
	case BJ_SyncData:
		list = &transaction->t_sync_datalist;
		break;
	case BJ_Metadata:
		transaction->t_nr_buffers--;
		J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0);
		list = &transaction->t_buffers;
		break;
	case BJ_Forget:
		list = &transaction->t_forget;
		break;
	case BJ_IO:
		list = &transaction->t_iobuf_list;
		break;
	case BJ_Shadow:
		list = &transaction->t_shadow_list;
		break;
	case BJ_LogCtl:
		list = &transaction->t_log_list;
		break;
	case BJ_Reserved:
		list = &transaction->t_reserved_list;
		break;
	case BJ_Locked:
		list = &transaction->t_locked_list;
		break;
	}

	__blist_del_buffer(list, jh);
	jh->b_jlist = BJ_None;
	if (test_clear_buffer_jbddirty(bh))
		mark_buffer_dirty(bh);	/* Expose it to the VM */
}

void __journal_unfile_buffer(struct journal_head *jh)
{
	__journal_temp_unlink_buffer(jh);
	jh->b_transaction = NULL;
}

void journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
{
	jbd_lock_bh_state(jh2bh(jh));
	spin_lock(&journal->j_list_lock);
	__journal_unfile_buffer(jh);
	spin_unlock(&journal->j_list_lock);
	jbd_unlock_bh_state(jh2bh(jh));
}

/*
 * This buffer is no longer needed.  If it is on an older transaction's
 * checkpoint list we need to record it on this transaction's forget list
 * to pin this buffer (and hence its checkpointing transaction) down until
 * this transaction commits.  If the buffer isn't on a checkpoint list, we
 * release it.
 * Returns non-zero if JBD no longer has an interest in the buffer.
 *
 * Called under j_list_lock.
 *
 * Called under jbd_lock_bh_state(bh).
 */
static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction)
{
	int may_free = 1;
	struct buffer_head *bh = jh2bh(jh);

	__journal_unfile_buffer(jh);

	if (jh->b_cp_transaction) {
		JBUFFER_TRACE(jh, "on running+cp transaction");
		__journal_file_buffer(jh, transaction, BJ_Forget);
		clear_buffer_jbddirty(bh);
		may_free = 0;
	} else {
		JBUFFER_TRACE(jh, "on running transaction");
		journal_remove_journal_head(bh);
		__brelse(bh);
	}
	return may_free;
}


/*
 * File a buffer on the given transaction list.
 */
void __journal_file_buffer(struct journal_head *jh,
			transaction_t *transaction, int jlist)
{
	struct journal_head **list = NULL;
	int was_dirty = 0;
	struct buffer_head *bh = jh2bh(jh);

	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
	assert_spin_locked(&transaction->t_journal->j_list_lock);

	J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
	J_ASSERT_JH(jh, jh->b_transaction == transaction ||
				jh->b_transaction == NULL);

	if (jh->b_transaction && jh->b_jlist == (unsigned) jlist)
		return;

	/* The following list of buffer states needs to be consistent
	 * with __jbd_unexpected_dirty_buffer()'s handling of dirty
	 * state. */

	if (jlist == BJ_Metadata || jlist == BJ_Reserved ||
	    jlist == BJ_Shadow || jlist == BJ_Forget) {
		if (test_clear_buffer_dirty(bh) ||
		    test_clear_buffer_jbddirty(bh))
			was_dirty = 1;
	}

	if (jh->b_transaction)
		__journal_temp_unlink_buffer(jh);
	jh->b_transaction = transaction;

	switch (jlist) {
	case BJ_None:
		J_ASSERT_JH(jh, !jh->b_committed_data);
		J_ASSERT_JH(jh, !jh->b_frozen_data);
		return;
	case BJ_SyncData:
		list = &transaction->t_sync_datalist;
		break;
	case BJ_Metadata:
		transaction->t_nr_buffers++;
		list = &transaction->t_buffers;
		break;
	case BJ_Forget:
		list = &transaction->t_forget;
		break;
	case BJ_IO:
		list = &transaction->t_iobuf_list;
		break;
	case BJ_Shadow:
		list = &transaction->t_shadow_list;
		break;
	case BJ_LogCtl:
		list = &transaction->t_log_list;
		break;
	case BJ_Reserved:
		list = &transaction->t_reserved_list;
		break;
	case BJ_Locked:
		list =  &transaction->t_locked_list;
		break;
	}

	__blist_add_buffer(list, jh);
	jh->b_jlist = jlist;

	if (was_dirty)
		set_buffer_jbddirty(bh);
}

void journal_file_buffer(struct journal_head *jh,
				transaction_t *transaction, int jlist)
{
	jbd_lock_bh_state(jh2bh(jh));
	spin_lock(&transaction->t_journal->j_list_lock);
	__journal_file_buffer(jh, transaction, jlist);
	spin_unlock(&transaction->t_journal->j_list_lock);
	jbd_unlock_bh_state(jh2bh(jh));
}


/*
 * journal_release_buffer: undo a get_write_access without any buffer
 * updates, if the update decided in the end that it didn't need access.
 *
 */
void
journal_release_buffer(handle_t *handle, struct buffer_head *bh)
{
	BUFFER_TRACE(bh, "entry");
}

/**
 * void journal_forget() - bforget() for potentially-journaled buffers.
 * @handle: transaction handle
 * @bh:     bh to 'forget'
 *
 * We can only do the bforget if there are no commits pending against the
 * buffer.  If the buffer is dirty in the current running transaction we
 * can safely unlink it.
 *
 * bh may not be a journalled buffer at all - it may be a non-JBD
 * buffer which came off the hashtable.  Check for this.
 *
 * Decrements bh->b_count by one.
 *
 * Allow this call even if the handle has aborted --- it may be part of
 * the caller's cleanup after an abort.
 */
int journal_forget (handle_t *handle, struct buffer_head *bh)
{
	transaction_t *transaction = handle->h_transaction;
	journal_t *journal = transaction->t_journal;
	struct journal_head *jh;
	int drop_reserve = 0;
	int err = 0;

	BUFFER_TRACE(bh, "entry");

	jbd_lock_bh_state(bh);
	spin_lock(&journal->j_list_lock);

	if (!buffer_jbd(bh))
		goto not_jbd;
	jh = bh2jh(bh);

	/* Critical error: attempting to delete a bitmap buffer, maybe?
	 * Don't do any jbd operations, and return an error. */
	if (!J_EXPECT_JH(jh, !jh->b_committed_data,
			 "inconsistent data on disk")) {
		err = -EIO;
		goto not_jbd;
	}

	/*
	 * The buffer's going from the transaction, we must drop
	 * all references -bzzz
	 */
	jh->b_modified = 0;

	if (jh->b_transaction == handle->h_transaction) {
		J_ASSERT_JH(jh, !jh->b_frozen_data);

		/* If we are forgetting a buffer which is already part
		 * of this transaction, then we can just drop it from
		 * the transaction immediately. */
		clear_buffer_dirty(bh);
		clear_buffer_jbddirty(bh);

		JBUFFER_TRACE(jh, "belongs to current transaction: unfile");

		drop_reserve = 1;

		/*
		 * We are no longer going to journal this buffer.
		 * However, the commit of this transaction is still
		 * important to the buffer: the delete that we are now
		 * processing might obsolete an old log entry, so by
		 * committing, we can satisfy the buffer's checkpoint.
		 *
		 * So, if we have a checkpoint on the buffer, we should
		 * now refile the buffer on our BJ_Forget list so that
		 * we know to remove the checkpoint after we commit.
		 */

		if (jh->b_cp_transaction) {
			__journal_temp_unlink_buffer(jh);
			__journal_file_buffer(jh, transaction, BJ_Forget);
		} else {
			__journal_unfile_buffer(jh);
			journal_remove_journal_head(bh);
			__brelse(bh);
			if (!buffer_jbd(bh)) {
				spin_unlock(&journal->j_list_lock);
				jbd_unlock_bh_state(bh);
				__bforget(bh);
				goto drop;
			}
		}
	} else if (jh->b_transaction) {
		J_ASSERT_JH(jh, (jh->b_transaction ==
				 journal->j_committing_transaction));
		/* However, if the buffer is still owned by a prior
		 * (committing) transaction, we can't drop it yet... */
		JBUFFER_TRACE(jh, "belongs to older transaction");
		/* ... but we CAN drop it from the new transaction if we
		 * have also modified it since the original commit. */

		if (jh->b_next_transaction) {
			J_ASSERT(jh->b_next_transaction == transaction);
			jh->b_next_transaction = NULL;
			drop_reserve = 1;
		}
	}

not_jbd:
	spin_unlock(&journal->j_list_lock);
	jbd_unlock_bh_state(bh);
	__brelse(bh);
drop:
	if (drop_reserve) {
		/* no need to reserve log space for this block -bzzz */
		handle->h_buffer_credits++;
	}
	return err;
}

/*
 * debugfs tunables
 */
#ifdef CONFIG_JBD_DEBUG

u8 journal_enable_debug __read_mostly;
EXPORT_SYMBOL(journal_enable_debug);

static struct dentry *jbd_debugfs_dir;
static struct dentry *jbd_debug;

static void __init jbd_create_debugfs_entry(void)
{
	jbd_debugfs_dir = debugfs_create_dir("jbd", NULL);
	if (jbd_debugfs_dir)
		jbd_debug = debugfs_create_u8("jbd-debug", S_IRUGO,
					       jbd_debugfs_dir,
					       &journal_enable_debug);
}

static void __exit jbd_remove_debugfs_entry(void)
{
	debugfs_remove(jbd_debug);
	debugfs_remove(jbd_debugfs_dir);
}

#else

static inline void jbd_create_debugfs_entry(void)
{
}

static inline void jbd_remove_debugfs_entry(void)
{
}

#endif

struct kmem_cache *jbd_handle_cache = NULL;

static int __init journal_init_handle_cache(void)
{
	jbd_handle_cache = kmem_cache_create("journal_handle",
				sizeof(handle_t),
				0,		/* offset */
				SLAB_TEMPORARY,	/* flags */
				NULL);		/* ctor */
	if (jbd_handle_cache == NULL) {
		printk(KERN_EMERG "JBD: failed to create handle cache\n");
		return -ENOMEM;
	}
	return 0;
}

static void journal_destroy_handle_cache(void)
{
	if (jbd_handle_cache)
		kmem_cache_destroy(jbd_handle_cache);
}

/*
 * Module startup and shutdown
 */

static int __init journal_init_caches(void)
{
	int ret;

	ret = journal_init_revoke_caches();
	if (ret == 0)
		ret = journal_init_journal_head_cache();
	if (ret == 0)
		ret = journal_init_handle_cache();
	return ret;
}

static void journal_destroy_caches(void)
{
	journal_destroy_revoke_caches();
	journal_destroy_journal_head_cache();
	journal_destroy_handle_cache();
}

static int __init journal_init(void)
{
	int ret;

	J_ASSERT(sizeof(struct journal_superblock_s) == 1024);

	ret = journal_init_caches();
	if (ret != 0)
		journal_destroy_caches();
	jbd_create_debugfs_entry();
	return ret;
}

static void __exit journal_exit(void)
{
#ifdef CONFIG_JBD_DEBUG
	int n = atomic_read(&nr_journal_heads);
	if (n)
		printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
#endif
	jbd_remove_debugfs_entry();
	journal_destroy_caches();
}

MODULE_LICENSE("GPL");
module_init(journal_init);
module_exit(journal_exit);