g_zero.c revision 154473 
1/*-
2 * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@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, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/sys/geom/zero/g_zero.c 154473 2006-01-17 11:48:16Z pjd $");
29
30#include <sys/param.h>
31#include <sys/bio.h>
32#include <sys/kernel.h>
33#include <sys/limits.h>
34#include <sys/malloc.h>
35#include <sys/queue.h>
36#include <sys/sysctl.h>
37#include <sys/systm.h>
38
39#include <geom/geom.h>
40
41
42#define	G_ZERO_CLASS_NAME	"ZERO"
43
44SYSCTL_DECL(_kern_geom);
45SYSCTL_NODE(_kern_geom, OID_AUTO, zero, CTLFLAG_RW, 0, "GEOM_ZERO stuff");
46static int g_zero_clear = 1;
47SYSCTL_INT(_kern_geom_zero, OID_AUTO, clear, CTLFLAG_RW, &g_zero_clear, 0,
48    "Clear read data buffer");
49static int g_zero_byte = 0;
50SYSCTL_INT(_kern_geom_zero, OID_AUTO, byte, CTLFLAG_RW, &g_zero_byte, 0,
51    "Byte (octet) value to clear the buffers with");
52
53static void
54g_zero_start(struct bio *bp)
55{
56	int error = ENXIO;
57
58	switch (bp->bio_cmd) {
59	case BIO_READ:
60		if (g_zero_clear)
61			memset(bp->bio_data, g_zero_byte, bp->bio_length);
62		/* FALLTHROUGH */
63	case BIO_DELETE:
64	case BIO_WRITE:
65		bp->bio_completed = bp->bio_length;
66		error = 0;
67		break;
68	case BIO_GETATTR:
69	default:
70		error = EOPNOTSUPP;
71		break;
72	}
73	g_io_deliver(bp, error);
74}
75
76static void
77g_zero_init(struct g_class *mp)
78{
79	struct g_geom *gp;
80	struct g_provider *pp;
81
82	g_topology_assert();
83	gp = g_new_geomf(mp, "gzero");
84	gp->start = g_zero_start;
85	gp->access = g_std_access;
86	pp = g_new_providerf(gp, "%s", gp->name);
87	pp->mediasize = 1152921504606846976LLU;
88	pp->sectorsize = 512;
89	g_error_provider(pp, 0);
90}
91
92static int
93g_zero_destroy_geom(struct gctl_req *req __unused, struct g_class *mp __unused,
94    struct g_geom *gp)
95{
96	struct g_provider *pp;
97
98	g_topology_assert();
99	if (gp == NULL)
100		return (0);
101	pp = LIST_FIRST(&gp->provider);
102	if (pp == NULL)
103		return (0);
104	if (pp->acr > 0 || pp->acw > 0 || pp->ace > 0)
105		return (EBUSY);
106	g_wither_geom(gp, ENXIO);
107	return (EBUSY);
108}
109
110static struct g_class g_zero_class = {
111	.name = G_ZERO_CLASS_NAME,
112	.version = G_VERSION,
113	.init = g_zero_init,
114	.destroy_geom = g_zero_destroy_geom
115};
116
117DECLARE_GEOM_CLASS(g_zero_class, g_zero);
118