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 */
115