g_zero.c revision 260385 
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: stable/10/sys/geom/zero/g_zero.c 260385 2014-01-07 01:32:23Z scottl $");
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
44static int	g_zero_clear_sysctl(SYSCTL_HANDLER_ARGS);
45
46SYSCTL_DECL(_kern_geom);
47static SYSCTL_NODE(_kern_geom, OID_AUTO, zero, CTLFLAG_RW, 0,
48    "GEOM_ZERO stuff");
49static int g_zero_clear = 1;
50SYSCTL_PROC(_kern_geom_zero, OID_AUTO, clear, CTLTYPE_INT|CTLFLAG_RW,
51    &g_zero_clear, 0, g_zero_clear_sysctl, "I", "Clear read data buffer");
52static int g_zero_byte = 0;
53SYSCTL_INT(_kern_geom_zero, OID_AUTO, byte, CTLFLAG_RW, &g_zero_byte, 0,
54    "Byte (octet) value to clear the buffers with");
55
56static struct g_provider *gpp;
57
58static int
59g_zero_clear_sysctl(SYSCTL_HANDLER_ARGS)
60{
61	int error;
62
63	error = sysctl_handle_int(oidp, &g_zero_clear, 0, req);
64	if (error != 0 || req->newptr == NULL)
65		return (error);
66	if (gpp == NULL)
67		return (ENXIO);
68	if (g_zero_clear)
69		gpp->flags &= ~G_PF_ACCEPT_UNMAPPED;
70	else
71		gpp->flags |= G_PF_ACCEPT_UNMAPPED;
72	return (0);
73}
74
75static void
76g_zero_start(struct bio *bp)
77{
78	int error = ENXIO;
79
80	switch (bp->bio_cmd) {
81	case BIO_READ:
82		if (g_zero_clear && (bp->bio_flags & BIO_UNMAPPED) == 0)
83			memset(bp->bio_data, g_zero_byte, bp->bio_length);
84		/* FALLTHROUGH */
85	case BIO_DELETE:
86	case BIO_WRITE:
87		bp->bio_completed = bp->bio_length;
88		error = 0;
89		break;
90	case BIO_GETATTR:
91	default:
92		error = EOPNOTSUPP;
93		break;
94	}
95	g_io_deliver(bp, error);
96}
97
98static void
99g_zero_init(struct g_class *mp)
100{
101	struct g_geom *gp;
102	struct g_provider *pp;
103
104	g_topology_assert();
105	gp = g_new_geomf(mp, "gzero");
106	gp->start = g_zero_start;
107	gp->access = g_std_access;
108	gpp = pp = g_new_providerf(gp, "%s", gp->name);
109	pp->flags |= G_PF_DIRECT_SEND | G_PF_DIRECT_RECEIVE;
110	if (!g_zero_clear)
111		pp->flags |= G_PF_ACCEPT_UNMAPPED;
112	pp->mediasize = 1152921504606846976LLU;
113	pp->sectorsize = 512;
114	g_error_provider(pp, 0);
115}
116
117static int
118g_zero_destroy_geom(struct gctl_req *req __unused, struct g_class *mp __unused,
119    struct g_geom *gp)
120{
121	struct g_provider *pp;
122
123	g_topology_assert();
124	if (gp == NULL)
125		return (0);
126	pp = LIST_FIRST(&gp->provider);
127	if (pp == NULL)
128		return (0);
129	if (pp->acr > 0 || pp->acw > 0 || pp->ace > 0)
130		return (EBUSY);
131	gpp = NULL;
132	g_wither_geom(gp, ENXIO);
133	return (0);
134}
135
136static struct g_class g_zero_class = {
137	.name = G_ZERO_CLASS_NAME,
138	.version = G_VERSION,
139	.init = g_zero_init,
140	.destroy_geom = g_zero_destroy_geom
141};
142
143DECLARE_GEOM_CLASS(g_zero_class, g_zero);
144