alq.h revision 139825 
1/*-
2 * Copyright (c) 2002, Jeffrey Roberson <jeff@freebsd.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: head/sys/sys/alq.h 139825 2005-01-07 02:29:27Z imp $
27 *
28 */
29#ifndef _SYS_ALQ_H_
30#define	_SYS_ALQ_H_
31
32/*
33 * Opaque type for the Async. Logging Queue
34 */
35struct alq;
36
37/* The thread for the logging daemon */
38extern struct thread *ald_thread;
39
40/*
41 * Async. Logging Entry
42 */
43struct ale {
44	struct ale	*ae_next;	/* Next Entry */
45	char		*ae_data;	/* Entry buffer */
46	int		ae_flags;	/* Entry flags */
47};
48
49#define	AE_VALID	0x0001		/* Entry has valid data */
50
51
52/* waitok options */
53#define	ALQ_NOWAIT	0x0001
54#define	ALQ_WAITOK	0x0002
55
56/*
57 * alq_open:  Creates a new queue
58 *
59 * Arguments:
60 *	alq	Storage for a pointer to the newly created queue.
61 *	file	The filename to open for logging.
62 *	size	The size of each entry in the queue.
63 *	count	The number of items in the buffer, this should be large enough
64 *		to store items over the period of a disk write.
65 * Returns:
66 *	error from open or 0 on success
67 */
68struct ucred;
69int alq_open(struct alq **, const char *file, struct ucred *cred, int size,
70	    int count);
71
72/*
73 * alq_write:  Write data into the queue
74 *
75 * Arguments:
76 *	alq	The queue we're writing to
77 *	data	The entry to be recorded
78 *	waitok	Are we permitted to wait?
79 *
80 * Returns:
81 *	EWOULDBLOCK if:
82 *		Waitok is ALQ_NOWAIT and the queue is full.
83 *		The system is shutting down.
84 *	0 on success.
85 */
86int alq_write(struct alq *alq, void *data, int waitok);
87
88/*
89 * alq_flush:  Flush the queue out to disk
90 */
91void alq_flush(struct alq *alq);
92
93/*
94 * alq_close:  Flush the queue and free all resources.
95 */
96void alq_close(struct alq *alq);
97
98/*
99 * alq_get:  Return an entry for direct access
100 *
101 * Arguments:
102 *	alq	The queue to retrieve an entry from
103 *	waitok	Are we permitted to wait?
104 *
105 * Returns:
106 *	The next available ale on success.
107 *	NULL if:
108 *		Waitok is ALQ_NOWAIT and the queue is full.
109 *		The system is shutting down.
110 *
111 * This leaves the queue locked until a subsequent alq_post.
112 */
113struct ale *alq_get(struct alq *alq, int waitok);
114
115/*
116 * alq_post:  Schedule the ale retrieved by alq_get for writing.
117 *	alq	The queue to post the entry to.
118 *	ale	An asynch logging entry returned by alq_get.
119 */
120void alq_post(struct alq *, struct ale *);
121
122#endif	/* _SYS_ALQ_H_ */
123