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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
16typedef unsigned int tid_t; /* Unique transaction ID */
17typedef struct transaction_s transaction_t; /* Compound transaction type */
18
19
20struct buffer_head;
21
22struct 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 */
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
13typedef unsigned int tid_t; /* Unique transaction ID */
14typedef struct transaction_s transaction_t; /* Compound transaction type */
15
16
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()]
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 * Either of these locks is enough for reading, both are needed for
70 * changes.
71 */
72 transaction_t *b_transaction;
73
74 /*
75 * Pointer to the running compound transaction which is currently
76 * modifying the buffer's metadata, if there was already a transaction
77 * committing it when the new transaction touched it.
78 * [t_list_lock] [jbd_lock_bh_state()]
79 */
80 transaction_t *b_next_transaction;
81
82 /*
83 * Doubly-linked list of buffers on a transaction's data, metadata or
84 * forget queue. [t_list_lock] [jbd_lock_bh_state()]
85 */
86 struct journal_head *b_tnext, *b_tprev;
87
88 /*
89 * Pointer to the compound transaction against which this buffer
90 * is checkpointed. Only dirty buffers can be checkpointed.
91 * [j_list_lock]
92 */
93 transaction_t *b_cp_transaction;
94
95 /*
96 * Doubly-linked list of buffers still remaining to be flushed
97 * before an old transaction can be checkpointed.
98 * [j_list_lock]
99 */
100 struct journal_head *b_cpnext, *b_cpprev;
101
102 /* Trigger type */
103 struct jbd2_buffer_trigger_type *b_triggers;
104
105 /* Trigger type for the committing transaction's frozen data */
106 struct jbd2_buffer_trigger_type *b_frozen_triggers;
107};
108
109#endif /* JOURNAL_HEAD_H_INCLUDED */