[linux-2.6-block.git] / include / linux / journal-head.h

/*
 * include/linux/journal-head.h
 *
 * buffer_head fields for JBD
 *
 * 27 May 2001 Andrew Morton
 *	Created - pulled out of fs.h
 */

#ifndef JOURNAL_HEAD_H_INCLUDED
#define JOURNAL_HEAD_H_INCLUDED

typedef unsigned int		tid_t;		/* Unique transaction ID */
typedef struct transaction_s	transaction_t;	/* Compound transaction type */


struct buffer_head;

struct journal_head {
	/*
	 * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
	 */
	struct buffer_head *b_bh;

	/*
	 * Reference count - see description in journal.c
	 * [jbd_lock_bh_journal_head()]
	 */
	int b_jcount;

	/*
	 * Journalling list for this buffer [jbd_lock_bh_state()]
	 * NOTE: We *cannot* combine this with b_modified into a bitfield
	 * as gcc would then (which the C standard allows but which is
	 * very unuseful) make 64-bit accesses to the bitfield and clobber
	 * b_jcount if its update races with bitfield modification.
	 */
	unsigned b_jlist;

	/*
	 * This flag signals the buffer has been modified by
	 * the currently running transaction
	 * [jbd_lock_bh_state()]
	 */
	unsigned b_modified;

	/*
	 * Copy of the buffer data frozen for writing to the log.
	 * [jbd_lock_bh_state()]
	 */
	char *b_frozen_data;

	/*
	 * Pointer to a saved copy of the buffer containing no uncommitted
	 * deallocation references, so that allocations can avoid overwriting
	 * uncommitted deletes. [jbd_lock_bh_state()]
	 */
	char *b_committed_data;

	/*
	 * Pointer to the compound transaction which owns this buffer's
	 * metadata: either the running transaction or the committing
	 * transaction (if there is one).  Only applies to buffers on a
	 * transaction's data or metadata journaling list.
	 * [j_list_lock] [jbd_lock_bh_state()]
	 * Either of these locks is enough for reading, both are needed for
	 * changes.
	 */
	transaction_t *b_transaction;

	/*
	 * Pointer to the running compound transaction which is currently
	 * modifying the buffer's metadata, if there was already a transaction
	 * committing it when the new transaction touched it.
	 * [t_list_lock] [jbd_lock_bh_state()]
	 */
	transaction_t *b_next_transaction;

	/*
	 * Doubly-linked list of buffers on a transaction's data, metadata or
	 * forget queue. [t_list_lock] [jbd_lock_bh_state()]
	 */
	struct journal_head *b_tnext, *b_tprev;

	/*
	 * Pointer to the compound transaction against which this buffer
	 * is checkpointed.  Only dirty buffers can be checkpointed.
	 * [j_list_lock]
	 */
	transaction_t *b_cp_transaction;

	/*
	 * Doubly-linked list of buffers still remaining to be flushed
	 * before an old transaction can be checkpointed.
	 * [j_list_lock]
	 */
	struct journal_head *b_cpnext, *b_cpprev;

	/* Trigger type */
	struct jbd2_buffer_trigger_type *b_triggers;

	/* Trigger type for the committing transaction's frozen data */
	struct jbd2_buffer_trigger_type *b_frozen_triggers;
};

#endif		/* JOURNAL_HEAD_H_INCLUDED */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* include/linux/journal-head.h
	3	*
	4	* buffer_head fields for JBD
	5	*
e1f8e874	6	* 27 May 2001 Andrew Morton
1da177e4 LT	7	* Created - pulled out of fs.h
	8	*/
	9
	10	#ifndef JOURNAL_HEAD_H_INCLUDED
	11	#define JOURNAL_HEAD_H_INCLUDED
	12
	13	typedef unsigned int tid_t; /* Unique transaction ID */
	14	typedef struct transaction_s transaction_t; /* Compound transaction type */
e06c8227 JB	15
e06c8227 JB	16
1da177e4 LT	17	struct buffer_head;
	18
	19	struct journal_head {
	20	/*
	21	* Points back to our buffer_head. [jbd_lock_bh_journal_head()]
	22	*/
	23	struct buffer_head *b_bh;
	24
	25	/*
	26	* Reference count - see description in journal.c
	27	* [jbd_lock_bh_journal_head()]
	28	*/
	29	int b_jcount;
	30
	31	/*
	32	* Journalling list for this buffer [jbd_lock_bh_state()]
e2555fde JK	33	* NOTE: We cannot combine this with b_modified into a bitfield
	34	* as gcc would then (which the C standard allows but which is
	35	* very unuseful) make 64-bit accesses to the bitfield and clobber
	36	* b_jcount if its update races with bitfield modification.
1da177e4	37	*/
e2555fde	38	unsigned b_jlist;
1da177e4 LT	39
	40	/*
	41	* This flag signals the buffer has been modified by
	42	* the currently running transaction
	43	* [jbd_lock_bh_state()]
	44	*/
e2555fde	45	unsigned b_modified;
c2cc7028	46
1da177e4 LT	47	/*
	48	* Copy of the buffer data frozen for writing to the log.
	49	* [jbd_lock_bh_state()]
	50	*/
	51	char *b_frozen_data;
	52
	53	/*
	54	* Pointer to a saved copy of the buffer containing no uncommitted
	55	* deallocation references, so that allocations can avoid overwriting
	56	* uncommitted deletes. [jbd_lock_bh_state()]
	57	*/
	58	char *b_committed_data;
	59
	60	/*
	61	* Pointer to the compound transaction which owns this buffer's
	62	* metadata: either the running transaction or the committing
	63	* transaction (if there is one). Only applies to buffers on a
	64	* transaction's data or metadata journaling list.
	65	* [j_list_lock] [jbd_lock_bh_state()]
932bb305 JK	66	* Either of these locks is enough for reading, both are needed for
932bb305 JK	67	* changes.
1da177e4 LT	68	*/
	69	transaction_t *b_transaction;
	70
	71	/*
	72	* Pointer to the running compound transaction which is currently
	73	* modifying the buffer's metadata, if there was already a transaction
	74	* committing it when the new transaction touched it.
	75	* [t_list_lock] [jbd_lock_bh_state()]
	76	*/
	77	transaction_t *b_next_transaction;
	78
	79	/*
	80	* Doubly-linked list of buffers on a transaction's data, metadata or
	81	* forget queue. [t_list_lock] [jbd_lock_bh_state()]
	82	*/
	83	struct journal_head b_tnext, b_tprev;
	84
	85	/*
	86	* Pointer to the compound transaction against which this buffer
	87	* is checkpointed. Only dirty buffers can be checkpointed.
	88	* [j_list_lock]
	89	*/
	90	transaction_t *b_cp_transaction;
	91
	92	/*
	93	* Doubly-linked list of buffers still remaining to be flushed
	94	* before an old transaction can be checkpointed.
	95	* [j_list_lock]
	96	*/
	97	struct journal_head b_cpnext, b_cpprev;
e06c8227 JB	98
	99	/* Trigger type */
	100	struct jbd2_buffer_trigger_type *b_triggers;
	101
	102	/* Trigger type for the committing transaction's frozen data */
	103	struct jbd2_buffer_trigger_type *b_frozen_triggers;
1da177e4 LT	104	};
	105
	106	#endif /* JOURNAL_HEAD_H_INCLUDED */