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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 | * 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. |
37 | */ |
38 | unsigned b_jlist; |
39 | |
40 | /* |
41 | * This flag signals the buffer has been modified by |
42 | * the currently running transaction |
43 | * [jbd_lock_bh_state()] |
44 | */ |
45 | unsigned b_modified; |
46 | |
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()] |
66 | * Either of these locks is enough for reading, both are needed for |
67 | * changes. |
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; |
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; |
104 | }; |
105 | |
106 | #endif /* JOURNAL_HEAD_H_INCLUDED */ |
107 |
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