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[linux-2.6.git] / include / linux / journal-head.h
1 /*
2  * include/linux/journal-head.h
3  *
4  * buffer_head fields for JBD
5  *
6  * 27 May 2001 Andrew Morton
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
16
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()]
33          */
34         unsigned b_jlist;
35
36         /*
37          * This flag signals the buffer has been modified by
38          * the currently running transaction
39          * [jbd_lock_bh_state()]
40          */
41         unsigned b_modified;
42
43         /*
44          * This feild tracks the last transaction id in which this buffer
45          * has been cowed
46          * [jbd_lock_bh_state()]
47          */
48         tid_t b_cow_tid;
49
50         /*
51          * Copy of the buffer data frozen for writing to the log.
52          * [jbd_lock_bh_state()]
53          */
54         char *b_frozen_data;
55
56         /*
57          * Pointer to a saved copy of the buffer containing no uncommitted
58          * deallocation references, so that allocations can avoid overwriting
59          * uncommitted deletes. [jbd_lock_bh_state()]
60          */
61         char *b_committed_data;
62
63         /*
64          * Pointer to the compound transaction which owns this buffer's
65          * metadata: either the running transaction or the committing
66          * transaction (if there is one).  Only applies to buffers on a
67          * transaction's data or metadata journaling list.
68          * [j_list_lock] [jbd_lock_bh_state()]
69          */
70         transaction_t *b_transaction;
71
72         /*
73          * Pointer to the running compound transaction which is currently
74          * modifying the buffer's metadata, if there was already a transaction
75          * committing it when the new transaction touched it.
76          * [t_list_lock] [jbd_lock_bh_state()]
77          */
78         transaction_t *b_next_transaction;
79
80         /*
81          * Doubly-linked list of buffers on a transaction's data, metadata or
82          * forget queue. [t_list_lock] [jbd_lock_bh_state()]
83          */
84         struct journal_head *b_tnext, *b_tprev;
85
86         /*
87          * Pointer to the compound transaction against which this buffer
88          * is checkpointed.  Only dirty buffers can be checkpointed.
89          * [j_list_lock]
90          */
91         transaction_t *b_cp_transaction;
92
93         /*
94          * Doubly-linked list of buffers still remaining to be flushed
95          * before an old transaction can be checkpointed.
96          * [j_list_lock]
97          */
98         struct journal_head *b_cpnext, *b_cpprev;
99
100         /* Trigger type */
101         struct jbd2_buffer_trigger_type *b_triggers;
102
103         /* Trigger type for the committing transaction's frozen data */
104         struct jbd2_buffer_trigger_type *b_frozen_triggers;
105 };
106
107 #endif          /* JOURNAL_HEAD_H_INCLUDED */