Merge tag 'for-linus-20160523' of git://git.infradead.org/linux-mtd
[linux-2.6-block.git] / include / linux / journal-head.h
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1/*
2 * include/linux/journal-head.h
3 *
4 * buffer_head fields for JBD
5 *
e1f8e874 6 * 27 May 2001 Andrew Morton
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7 * Created - pulled out of fs.h
8 */
9
10#ifndef JOURNAL_HEAD_H_INCLUDED
11#define JOURNAL_HEAD_H_INCLUDED
12
13typedef unsigned int tid_t; /* Unique transaction ID */
14typedef struct transaction_s transaction_t; /* Compound transaction type */
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15
16
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17struct buffer_head;
18
19struct 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()]
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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;
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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
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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()]
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66 * Either of these locks is enough for reading, both are needed for
67 * changes.
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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;
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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;
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104};
105
106#endif /* JOURNAL_HEAD_H_INCLUDED */