ismounted.c revision 18a1444b4f1e6a0948fd38fa0de382d86cfe04de 
1/*
2 * ismounted.c --- Check to see if the filesystem was mounted
3 *
4 * Copyright (C) 1995,1996,1997,1998,1999,2000,2008 Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Public
8 * License.
9 * %End-Header%
10 */
11
12#include <stdio.h>
13#if HAVE_UNISTD_H
14#include <unistd.h>
15#endif
16#ifdef HAVE_STDLIB_H
17#include <stdlib.h>
18#endif
19#if HAVE_ERRNO_H
20#include <errno.h>
21#endif
22#include <fcntl.h>
23#ifdef HAVE_LINUX_FD_H
24#include <linux/fd.h>
25#endif
26#ifdef HAVE_MNTENT_H
27#include <mntent.h>
28#endif
29#include <string.h>
30#include <sys/stat.h>
31#include <ctype.h>
32
33#include "fsck.h"
34
35/*
36 * ext2fs_check_if_mounted flags
37 */
38#define MF_MOUNTED		1
39
40#include "et/com_err.h"
41
42#ifdef HAVE_SETMNTENT
43static char *skip_over_blank(char *cp)
44{
45	while (*cp && isspace(*cp))
46		cp++;
47	return cp;
48}
49
50static char *skip_over_word(char *cp)
51{
52	while (*cp && !isspace(*cp))
53		cp++;
54	return cp;
55}
56
57static char *parse_word(char **buf)
58{
59	char *word, *next;
60
61	word = *buf;
62	if (*word == 0)
63		return 0;
64
65	word = skip_over_blank(word);
66	next = skip_over_word(word);
67	if (*next)
68		*next++ = 0;
69	*buf = next;
70	return word;
71}
72#endif
73
74/*
75 * Helper function which checks a file in /etc/mtab format to see if a
76 * filesystem is mounted.  Returns an error if the file doesn't exist
77 * or can't be opened.
78 */
79static errcode_t check_mntent_file(const char *mtab_file, const char *file,
80				   int *mount_flags)
81{
82#ifdef HAVE_SETMNTENT
83	struct stat	st_buf;
84	errcode_t	retval = 0;
85	dev_t		file_dev=0, file_rdev=0;
86	ino_t		file_ino=0;
87	FILE 		*f;
88	char		buf[1024], *device = 0, *mnt_dir = 0, *cp;
89
90	*mount_flags = 0;
91	if ((f = setmntent (mtab_file, "r")) == NULL)
92		return errno;
93	if (stat(file, &st_buf) == 0) {
94		if (S_ISBLK(st_buf.st_mode)) {
95#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
96			file_rdev = st_buf.st_rdev;
97#endif	/* __GNU__ */
98		} else {
99			file_dev = st_buf.st_dev;
100			file_ino = st_buf.st_ino;
101		}
102	}
103	while (1) {
104		if (!fgets(buf, sizeof(buf), f)) {
105			device = mnt_dir = 0;
106			break;
107		}
108		buf[sizeof(buf)-1] = 0;
109
110		cp = buf;
111		device = parse_word(&cp);
112		if (!device || *device == '#')
113			return 0;	/* Ignore blank lines and comments */
114		mnt_dir = parse_word(&cp);
115
116		if (device[0] != '/')
117			continue;
118
119		if (strcmp(file, device) == 0)
120			break;
121		if (stat(device, &st_buf) == 0) {
122			if (S_ISBLK(st_buf.st_mode)) {
123#ifndef __GNU__
124				if (file_rdev && (file_rdev == st_buf.st_rdev))
125					break;
126#endif	/* __GNU__ */
127			} else {
128				if (file_dev && ((file_dev == st_buf.st_dev) &&
129						 (file_ino == st_buf.st_ino)))
130					break;
131			}
132		}
133	}
134
135	if (mnt_dir == 0) {
136#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
137		/*
138		 * Do an extra check to see if this is the root device.  We
139		 * can't trust /etc/mtab, and /proc/mounts will only list
140		 * /dev/root for the root filesystem.  Argh.  Instead we
141		 * check if the given device has the same major/minor number
142		 * as the device that the root directory is on.
143		 */
144		if (file_rdev && (stat("/", &st_buf) == 0) &&
145		    (st_buf.st_dev == file_rdev))
146			*mount_flags = MF_MOUNTED;
147#endif	/* __GNU__ */
148		goto errout;
149	}
150#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
151	/* Validate the entry in case /etc/mtab is out of date */
152	/*
153	 * We need to be paranoid, because some broken distributions
154	 * (read: Slackware) don't initialize /etc/mtab before checking
155	 * all of the non-root filesystems on the disk.
156	 */
157	if (stat(mnt_dir, &st_buf) < 0) {
158		retval = errno;
159		if (retval == ENOENT) {
160#ifdef DEBUG
161			printf("Bogus entry in %s!  (%s does not exist)\n",
162			       mtab_file, mnt_dir);
163#endif /* DEBUG */
164			retval = 0;
165		}
166		goto errout;
167	}
168	if (file_rdev && (st_buf.st_dev != file_rdev)) {
169#ifdef DEBUG
170		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
171		       mtab_file, file, mnt_dir);
172#endif /* DEBUG */
173		goto errout;
174	}
175#endif /* __GNU__ */
176	*mount_flags = MF_MOUNTED;
177
178	retval = 0;
179errout:
180	endmntent (f);
181	return retval;
182#else /* !HAVE_SETMNTENT */
183	return 0;
184#endif /* HAVE_MNTENT_H */
185}
186
187int is_mounted(const char *file)
188{
189	errcode_t	retval;
190	int		mount_flags = 0;
191
192#ifdef __linux__
193	retval = check_mntent_file("/proc/mounts", file, &mount_flags);
194	if (retval)
195		return 0;
196	if (mount_flags)
197		return 1;
198#endif /* __linux__ */
199	retval = check_mntent_file("/etc/mtab", file, &mount_flags);
200	if (retval)
201		return 0;
202	return (mount_flags);
203}
204
205#ifdef DEBUG
206int main(int argc, char **argv)
207{
208	if (argc < 2) {
209		fprintf(stderr, "Usage: %s device\n", argv[0]);
210		exit(1);
211	}
212
213	if (is_mounted(argv[1]))
214		printf("\t%s is mounted.\n", argv[1]);
215	exit(0);
216}
217#endif /* DEBUG */
218