1 /*
2  * include/linux/journal-head.h
3  *
4  * buffer_head fields for JBD
5  *
6  * 27 May 2001 Andrew Morton <akpm@digeo.com>
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 */
15 struct buffer_head;
16 
17 struct journal_head {
18     /*
19      * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
20      */
21     struct buffer_head *b_bh;
22 
23     /*
24      * Reference count - see description in journal.c
25      * [jbd_lock_bh_journal_head()]
26      */
27     int b_jcount;
28 
29     /*
30      * Journalling list for this buffer [jbd_lock_bh_state()]
31      */
32     unsigned b_jlist;
33 
34     /*
35      * This flag signals the buffer has been modified by
36      * the currently running transaction
37      * [jbd_lock_bh_state()]
38      */
39     unsigned b_modified;
40 
41     /*
42      * Copy of the buffer data frozen for writing to the log.
43      * [jbd_lock_bh_state()]
44      */
45     char *b_frozen_data;
46 
47     /*
48      * Pointer to a saved copy of the buffer containing no uncommitted
49      * deallocation references, so that allocations can avoid overwriting
50      * uncommitted deletes. [jbd_lock_bh_state()]
51      */
52     char *b_committed_data;
53 
54     /*
55      * Pointer to the compound transaction which owns this buffer's
56      * metadata: either the running transaction or the committing
57      * transaction (if there is one).  Only applies to buffers on a
58      * transaction's data or metadata journaling list.
59      * [j_list_lock] [jbd_lock_bh_state()]
60      */
61     transaction_t *b_transaction;
62 
63     /*
64      * Pointer to the running compound transaction which is currently
65      * modifying the buffer's metadata, if there was already a transaction
66      * committing it when the new transaction touched it.
67      * [t_list_lock] [jbd_lock_bh_state()]
68      */
69     transaction_t *b_next_transaction;
70 
71     /*
72      * Doubly-linked list of buffers on a transaction's data, metadata or
73      * forget queue. [t_list_lock] [jbd_lock_bh_state()]
74      */
75     struct journal_head *b_tnext, *b_tprev;
76 
77     /*
78      * Pointer to the compound transaction against which this buffer
79      * is checkpointed.  Only dirty buffers can be checkpointed.
80      * [j_list_lock]
81      */
82     transaction_t *b_cp_transaction;
83 
84     /*
85      * Doubly-linked list of buffers still remaining to be flushed
86      * before an old transaction can be checkpointed.
87      * [j_list_lock]
88      */
89     struct journal_head *b_cpnext, *b_cpprev;
90 };
91 
92 #endif		/* JOURNAL_HEAD_H_INCLUDED */
93