journal-head.h

  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 */