jbd.h

可以在不启动LINUX的情况下直接访问EXT2和EXT3格式的磁盘

 * @h_jdata: flag to force data journaling
 * @h_aborted: flag indicating fatal error on handle
 * @h_lockdep_map: lockdep info for debugging lock problems
 **/

/* Docbook can't yet cope with the bit fields, but will leave the documentation
 * in so it can be fixed later.
 */

struct handle_s
{
	/* Which compound transaction is this update a part of? */
	transaction_t		*h_transaction;

	/* Number of remaining buffers we are allowed to dirty: */
	int			h_buffer_credits;

	/* Reference count on this handle */
	int			h_ref;

	/* Field for caller's use to track errors through large fs */
	/* operations */
	int			h_err;

	/* Flags [no locking] */
	unsigned int	h_sync:		1;	/* sync-on-close */
	unsigned int	h_jdata:	1;	/* force data journaling */
	unsigned int	h_aborted:	1;	/* fatal error on handle */

#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map	h_lockdep_map;
#endif
};


/* The transaction_t type is the guts of the journaling mechanism.  It
 * tracks a compound transaction through its various states:
 *
 * RUNNING:	accepting new updates
 * LOCKED:	Updates still running but we don't accept new ones
 * RUNDOWN:	Updates are tidying up but have finished requesting
 *		new buffers to modify (state not used for now)
 * FLUSH:       All updates complete, but we are still writing to disk
 * COMMIT:      All data on disk, writing commit record
 * FINISHED:	We still have to keep the transaction for checkpointing.
 *
 * The transaction keeps track of all of the buffers modified by a
 * running transaction, and all of the buffers committed but not yet
 * flushed to home for finished transactions.
 */

/*
 * Lock ranking:
 *
 *    j_list_lock
 *      ->jbd_lock_bh_journal_head()	(This is "innermost")
 *
 *    j_state_lock
 *    ->jbd_lock_bh_state()
 *
 *    jbd_lock_bh_state()
 *    ->j_list_lock
 *
 *    j_state_lock
 *    ->t_handle_lock
 *
 *    j_state_lock
 *    ->j_list_lock			(journal_unmap_buffer)
 *
 */

struct transaction_s
{
	/* Pointer to the journal for this transaction. [no locking] */
	journal_t		*t_journal;

	/* Sequence number for this transaction [no locking] */
	tid_t			t_tid;

	/*
	 * Transaction's current state
	 * [no locking - only kjournald alters this]
	 * [j_list_lock] guards transition of a transaction into T_FINISHED
	 * state and subsequent call of __journal_drop_transaction()
	 * FIXME: needs barriers
	 * KLUDGE: [use j_state_lock]
	 */
	enum {
		T_RUNNING,
		T_LOCKED,
		T_RUNDOWN,
		T_FLUSH,
		T_COMMIT,
		T_FINISHED
	}			t_state;

	/*
	 * Where in the log does this transaction's commit start? [no locking]
	 */
	unsigned long		t_log_start;

	/* Number of buffers on the t_buffers list [j_list_lock] */
	int			t_nr_buffers;

	/*
	 * Doubly-linked circular list of all buffers reserved but not yet
	 * modified by this transaction [j_list_lock]
	 */
	struct journal_head	*t_reserved_list;

	/*
	 * Doubly-linked circular list of all buffers under writeout during
	 * commit [j_list_lock]
	 */
	struct journal_head	*t_locked_list;

	/*
	 * Doubly-linked circular list of all metadata buffers owned by this
	 * transaction [j_list_lock]
	 */
	struct journal_head	*t_buffers;

	/*
	 * Doubly-linked circular list of all data buffers still to be
	 * flushed before this transaction can be committed [j_list_lock]
	 */
	struct journal_head	*t_sync_datalist;

	/*
	 * Doubly-linked circular list of all forget buffers (superseded
	 * buffers which we can un-checkpoint once this transaction commits)
	 * [j_list_lock]
	 */
	struct journal_head	*t_forget;

	/*
	 * Doubly-linked circular list of all buffers still to be flushed before
	 * this transaction can be checkpointed. [j_list_lock]
	 */
	struct journal_head	*t_checkpoint_list;

	/*
	 * Doubly-linked circular list of all buffers submitted for IO while
	 * checkpointing. [j_list_lock]
	 */
	struct journal_head	*t_checkpoint_io_list;

	/*
	 * Doubly-linked circular list of temporary buffers currently undergoing
	 * IO in the log [j_list_lock]
	 */
	struct journal_head	*t_iobuf_list;

	/*
	 * Doubly-linked circular list of metadata buffers being shadowed by log
	 * IO.  The IO buffers on the iobuf list and the shadow buffers on this
	 * list match each other one for one at all times. [j_list_lock]
	 */
	struct journal_head	*t_shadow_list;

	/*
	 * Doubly-linked circular list of control buffers being written to the
	 * log. [j_list_lock]
	 */
	struct journal_head	*t_log_list;

	/*
	 * Protects info related to handles
	 */
	spinlock_t		t_handle_lock;

	/*
	 * Number of outstanding updates running on this transaction
	 * [t_handle_lock]
	 */
	int			t_updates;

	/*
	 * Number of buffers reserved for use by all handles in this transaction
	 * handle but not yet modified. [t_handle_lock]
	 */
	int			t_outstanding_credits;

	/*
	 * Forward and backward links for the circular list of all transactions
	 * awaiting checkpoint. [j_list_lock]
	 */
	transaction_t		*t_cpnext, *t_cpprev;

	/*
	 * When will the transaction expire (become due for commit), in jiffies?
	 * [no locking]
	 */
	unsigned long		t_expires;

	/*
	 * How many handles used this transaction? [t_handle_lock]
	 */
	int t_handle_count;

};

/**
 * struct journal_s - The journal_s type is the concrete type associated with
 *     journal_t.
 * @j_flags:  General journaling state flags
 * @j_errno:  Is there an outstanding uncleared error on the journal (from a
 *     prior abort)?
 * @j_sb_buffer: First part of superblock buffer
 * @j_superblock: Second part of superblock buffer
 * @j_format_version: Version of the superblock format
 * @j_state_lock: Protect the various scalars in the journal
 * @j_barrier_count:  Number of processes waiting to create a barrier lock
 * @j_barrier: The barrier lock itself
 * @j_running_transaction: The current running transaction..
 * @j_committing_transaction: the transaction we are pushing to disk
 * @j_checkpoint_transactions: a linked circular list of all transactions
 *  waiting for checkpointing
 * @j_wait_transaction_locked: Wait queue for waiting for a locked transaction
 *  to start committing, or for a barrier lock to be released
 * @j_wait_logspace: Wait queue for waiting for checkpointing to complete
 * @j_wait_done_commit: Wait queue for waiting for commit to complete
 * @j_wait_checkpoint:  Wait queue to trigger checkpointing
 * @j_wait_commit: Wait queue to trigger commit
 * @j_wait_updates: Wait queue to wait for updates to complete
 * @j_checkpoint_mutex: Mutex for locking against concurrent checkpoints
 * @j_head: Journal head - identifies the first unused block in the journal
 * @j_tail: Journal tail - identifies the oldest still-used block in the
 *  journal.
 * @j_free: Journal free - how many free blocks are there in the journal?
 * @j_first: The block number of the first usable block
 * @j_last: The block number one beyond the last usable block
 * @j_dev: Device where we store the journal
 * @j_blocksize: blocksize for the location where we store the journal.
 * @j_blk_offset: starting block offset for into the device where we store the
 *     journal
 * @j_fs_dev: Device which holds the client fs.  For internal journal this will
 *     be equal to j_dev
 * @j_maxlen: Total maximum capacity of the journal region on disk.
 * @j_list_lock: Protects the buffer lists and internal buffer state.
 * @j_inode: Optional inode where we store the journal.  If present, all journal
 *     block numbers are mapped into this inode via bmap().
 * @j_tail_sequence:  Sequence number of the oldest transaction in the log
 * @j_transaction_sequence: Sequence number of the next transaction to grant
 * @j_commit_sequence: Sequence number of the most recently committed
 *  transaction
 * @j_commit_request: Sequence number of the most recent transaction wanting
 *     commit
 * @j_uuid: Uuid of client object.
 * @j_task: Pointer to the current commit thread for this journal
 * @j_max_transaction_buffers:  Maximum number of metadata buffers to allow in a
 *     single compound commit transaction
 * @j_commit_interval: What is the maximum transaction lifetime before we begin
 *  a commit?
 * @j_commit_timer:  The timer used to wakeup the commit thread
 * @j_revoke_lock: Protect the revoke table
 * @j_revoke: The revoke table - maintains the list of revoked blocks in the
 *     current transaction.
 * @j_revoke_table: alternate revoke tables for j_revoke
 * @j_wbuf: array of buffer_heads for journal_commit_transaction
 * @j_wbufsize: maximum number of buffer_heads allowed in j_wbuf, the
 *	number that will fit in j_blocksize
 * @j_last_sync_writer: most recent pid which did a synchronous write
 * @j_private: An opaque pointer to fs-private information.
 */

struct journal_s
{
	/* General journaling state flags [j_state_lock] */
	unsigned long		j_flags;

	/*
	 * Is there an outstanding uncleared error on the journal (from a prior
	 * abort)? [j_state_lock]
	 */
	int			j_errno;

	/* The superblock buffer */
	struct buffer_head	*j_sb_buffer;
	journal_superblock_t	*j_superblock;

	/* Version of the superblock format */
	int			j_format_version;

	/*
	 * Protect the various scalars in the journal
	 */
	spinlock_t		j_state_lock;

	/*
	 * Number of processes waiting to create a barrier lock [j_state_lock]
	 */
	int			j_barrier_count;

	/* The barrier lock itself */
	struct mutex		j_barrier;

	/*
	 * Transactions: The current running transaction...
	 * [j_state_lock] [caller holding open handle]
	 */
	transaction_t		*j_running_transaction;

	/*
	 * the transaction we are pushing to disk
	 * [j_state_lock] [caller holding open handle]
	 */
	transaction_t		*j_committing_transaction;

	/*
	 * ... and a linked circular list of all transactions waiting for
	 * checkpointing. [j_list_lock]
	 */
	transaction_t		*j_checkpoint_transactions;

	/*
	 * Wait queue for waiting for a locked transaction to start committing,
	 * or for a barrier lock to be released
	 */
	wait_queue_head_t	j_wait_transaction_locked;

	/* Wait queue for waiting for checkpointing to complete */
	wait_queue_head_t	j_wait_logspace;

	/* Wait queue for waiting for commit to complete */
	wait_queue_head_t	j_wait_done_commit;

	/* Wait queue to trigger checkpointing */
	wait_queue_head_t	j_wait_checkpoint;

	/* Wait queue to trigger commit */
	wait_queue_head_t	j_wait_commit;

	/* Wait queue to wait for updates to complete */
	wait_queue_head_t	j_wait_updates;

	/* Semaphore for locking against concurrent checkpoints */
	struct mutex		j_checkpoint_mutex;

	/*
	 * Journal head: identifies the first unused block in the journal.
	 * [j_state_lock]
	 */
	unsigned long		j_head;

	/*
	 * Journal tail: identifies the oldest still-used block in the journal.
	 * [j_state_lock]
	 */
	unsigned long		j_tail;

	/*
	 * Journal free: how many free blocks are there in the journal?
	 * [j_state_lock]
	 */
	unsigned long		j_free;

	/*
	 * Journal start and end: the block numbers of the first usable block
	 * and one beyond the last usable block in the journal. [j_state_lock]
	 */
	unsigned long		j_first;
	unsigned long		j_last;

	/*
	 * Device, blocksize and starting block offset for the location where we
	 * store the journal.
	 */
	struct block_device	*j_dev;