1 /* $NetBSD: snapshot.c,v 1.7 2019/02/03 12:17:14 mrg Exp $ */
2
3 /*-
4 * Copyright (c) 2005 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Juergen Hannken-Illjes.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 #include <sys/param.h>
33 #include <sys/ioctl.h>
34 #include <sys/mount.h>
35 #include <sys/stat.h>
36
37 #include <dev/fssvar.h>
38
39 #include <errno.h>
40 #include <fcntl.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <unistd.h>
45
46 #include "snapshot.h"
47
48 /*
49 * Create a snapshot of the file system currently mounted on the first argument
50 * using the second argument as backing store and return an open file
51 * descriptor for the snapshot. If the second argument is NULL, use the first
52 * as backing store. If the third argument is not NULL, it gets the time the
53 * snapshot was created. If the fourth argument is not NULL, it gets the
54 * snapshot device path.
55 */
56 int
snap_open(char * file,char * backup,time_t * snap_date,char ** snap_dev)57 snap_open(char *file, char *backup, time_t *snap_date, char **snap_dev)
58 {
59 int i, n, fd, israw, fsinternal, dounlink;
60 char path[MAXPATHLEN], fss_dev[20], *cp;
61 dev_t mountdev;
62 struct fss_set fss;
63 struct fss_get fsg;
64 struct stat sb;
65 struct statvfs *mntbuf, *fs, fsb;
66
67 dounlink = 0;
68 fd = -1;
69 mntbuf = NULL;
70
71 /*
72 * Lookup the mount point. `file' is either a directory or a raw
73 * character device.
74 */
75 if (lstat(file, &sb) < 0)
76 goto fail;
77 fss.fss_mount = NULL;
78 if (S_ISCHR(sb.st_mode)) {
79 if ((cp = strrchr(file, '/')) == NULL || cp[1] != 'r') {
80 errno = EINVAL;
81 goto fail;
82 }
83 snprintf(path, sizeof(path), "%.*s/%s",
84 (int)(cp - file), file, cp + 2);
85 n = getmntinfo(&mntbuf, MNT_NOWAIT);
86 for (fs = mntbuf, i = 0; i < n; i++, fs++) {
87 if (strcmp(fs->f_mntfromname, path) == 0) {
88 fss.fss_mount = fs->f_mntonname;
89 if (stat(fss.fss_mount, &sb) < 0)
90 goto fail;
91 break;
92 }
93 }
94 } else if (S_ISDIR(sb.st_mode))
95 fss.fss_mount = file;
96 if (fss.fss_mount == NULL) {
97 errno = EINVAL;
98 goto fail;
99 }
100 fss.fss_bstore = backup ? backup : fss.fss_mount;
101 fss.fss_csize = 0;
102 mountdev = sb.st_dev;
103
104 /*
105 * Prepare the backing store. `backup' is either a raw device,
106 * a file or a directory. If it is a file, it must not exist.
107 */
108 israw = 0;
109 if (stat(fss.fss_bstore, &sb) == 0) {
110 if (S_ISDIR(sb.st_mode)) {
111 snprintf(path, sizeof(path),
112 "%s/XXXXXXXXXX", fss.fss_bstore);
113 fd = mkstemp(path);
114 fss.fss_bstore = path;
115 dounlink = 1;
116 } else if (S_ISCHR(sb.st_mode)) {
117 fd = open(fss.fss_bstore, O_RDWR);
118 israw = 1;
119 } else
120 goto fail;
121 } else {
122 fd = open(fss.fss_bstore, O_CREAT|O_EXCL|O_WRONLY, 0600);
123 dounlink = 1;
124 }
125 if (fd < 0)
126 goto fail;
127
128 if (fstat(fd, &sb) < 0)
129 goto fail;
130 fsinternal = (!israw && sb.st_dev == mountdev);
131
132 /*
133 * If the backing store is a plain file and the snapshot
134 * is not file system internal, truncate to file system
135 * free space.
136 */
137 if (!israw && !fsinternal) {
138 if (statvfs(fss.fss_bstore, &fsb) < 0)
139 goto fail;
140 if (ftruncate(fd, (off_t)fsb.f_frsize*fsb.f_bavail) < 0)
141 goto fail;
142 }
143
144 if (close(fd) < 0)
145 goto fail;
146
147 fss.fss_flags = FSS_UNCONFIG_ON_CLOSE;
148 if (dounlink)
149 fss.fss_flags |= FSS_UNLINK_ON_CREATE;
150 /*
151 * Create the snapshot on the first free snapshot device.
152 */
153 for (i = 0; ; i++) {
154 snprintf(fss_dev, sizeof(fss_dev), "/dev/rfss%d", i);
155 if ((fd = open(fss_dev, O_RDWR, 0)) < 0)
156 goto fail;
157
158 if (ioctl(fd, FSSIOCSET, &fss) < 0) {
159 if (errno != EBUSY)
160 goto fail;
161 close(fd);
162 fd = -1;
163 continue;
164 }
165 dounlink = 0;
166
167 if (snap_dev != NULL) {
168 *snap_dev = strdup(fss_dev);
169 if (*snap_dev == NULL) {
170 ioctl(fd, FSSIOCCLR);
171 goto fail;
172 }
173 }
174
175 if (ioctl(fd, FSSIOCGET, &fsg) < 0) {
176 ioctl(fd, FSSIOCCLR);
177 goto fail;
178 }
179
180 if (mntbuf)
181 free(mntbuf);
182 if (snap_date != NULL)
183 *snap_date = fsg.fsg_time.tv_sec;
184 return fd;
185 }
186
187 fail:
188 if (mntbuf)
189 free(mntbuf);
190 if (dounlink)
191 unlink(fss.fss_bstore);
192 if (fd >= 0)
193 close(fd);
194
195 return -1;
196 }
197