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/*
 * include/linux/journal-head.h
 *
 * buffer_head fields for JBD
 *
 * 27 May 2001 Andrew Morton <akpm@digeo.com>
 *      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()]
         */
        unsigned b_jlist;

        /*
         * 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()]
         */
        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;
};

#endif          /* JOURNAL_HEAD_H_INCLUDED */