/*
* 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 */