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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 */ |