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 | |