1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * include/linux/journal-head.h
4 *
5 * buffer_head fields for JBD
6 *
7 * 27 May 2001 Andrew Morton
8 * Created - pulled out of fs.h
9 */
10
11 #ifndef JOURNAL_HEAD_H_INCLUDED
12 #define JOURNAL_HEAD_H_INCLUDED
13
14 #include <linux/spinlock.h>
15
16 typedef unsigned int tid_t; /* Unique transaction ID */
17 typedef struct transaction_s transaction_t; /* Compound transaction type */
18
19
20 struct buffer_head;
21
22 struct journal_head {
23 /*
24 * Points back to our buffer_head. [jbd_lock_bh_journal_head()]
25 */
26 struct buffer_head *b_bh;
27
28 /*
29 * Protect the buffer head state
30 */
31 spinlock_t b_state_lock;
32
33 /*
34 * Reference count - see description in journal.c
35 * [jbd_lock_bh_journal_head()]
36 */
37 int b_jcount;
38
39 /*
40 * Journalling list for this buffer [b_state_lock]
41 * NOTE: We *cannot* combine this with b_modified into a bitfield
42 * as gcc would then (which the C standard allows but which is
43 * very unuseful) make 64-bit accesses to the bitfield and clobber
44 * b_jcount if its update races with bitfield modification.
45 */
46 unsigned b_jlist;
47
48 /*
49 * This flag signals the buffer has been modified by
50 * the currently running transaction
51 * [b_state_lock]
52 */
53 unsigned b_modified;
54
55 /*
56 * Copy of the buffer data frozen for writing to the log.
57 * [b_state_lock]
58 */
59 char *b_frozen_data;
60
61 /*
62 * Pointer to a saved copy of the buffer containing no uncommitted
63 * deallocation references, so that allocations can avoid overwriting
64 * uncommitted deletes. [b_state_lock]
65 */
66 char *b_committed_data;
67
68 /*
69 * Pointer to the compound transaction which owns this buffer's
70 * metadata: either the running transaction or the committing
71 * transaction (if there is one). Only applies to buffers on a
72 * transaction's data or metadata journaling list.
73 * [j_list_lock] [b_state_lock]
74 * Either of these locks is enough for reading, both are needed for
75 * changes.
76 */
77 transaction_t *b_transaction;
78
79 /*
80 * Pointer to the running compound transaction which is currently
81 * modifying the buffer's metadata, if there was already a transaction
82 * committing it when the new transaction touched it.
83 * [t_list_lock] [b_state_lock]
84 */
85 transaction_t *b_next_transaction;
86
87 /*
88 * Doubly-linked list of buffers on a transaction's data, metadata or
89 * forget queue. [t_list_lock] [b_state_lock]
90 */
91 struct journal_head *b_tnext, *b_tprev;
92
93 /*
94 * Pointer to the compound transaction against which this buffer
95 * is checkpointed. Only dirty buffers can be checkpointed.
96 * [j_list_lock]
97 */
98 transaction_t *b_cp_transaction;
99
100 /*
101 * Doubly-linked list of buffers still remaining to be flushed
102 * before an old transaction can be checkpointed.
103 * [j_list_lock]
104 */
105 struct journal_head *b_cpnext, *b_cpprev;
106
107 /* Trigger type */
108 struct jbd2_buffer_trigger_type *b_triggers;
109
110 /* Trigger type for the committing transaction's frozen data */
111 struct jbd2_buffer_trigger_type *b_frozen_triggers;
112 };
113
114 #endif /* JOURNAL_HEAD_H_INCLUDED */
115
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