ismounted.c revision a6ce1349539f866334ef3d5758bc2ee44a454acd 
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
42static char *skip_over_blank(char *cp)
43{
44	while (*cp && isspace(*cp))
45		cp++;
46	return cp;
47}
48
49static char *skip_over_word(char *cp)
50{
51	while (*cp && !isspace(*cp))
52		cp++;
53	return cp;
54}
55
56static char *parse_word(char **buf)
57{
58	char *word, *next;
59
60	word = *buf;
61	if (*word == 0)
62		return 0;
63
64	word = skip_over_blank(word);
65	next = skip_over_word(word);
66	if (*next)
67		*next++ = 0;
68	*buf = next;
69	return word;
70}
71
72/*
73 * Helper function which checks a file in /etc/mtab format to see if a
74 * filesystem is mounted.  Returns an error if the file doesn't exist
75 * or can't be opened.
76 */
77static errcode_t check_mntent_file(const char *mtab_file, const char *file,
78				   int *mount_flags)
79{
80#ifdef HAVE_MNTENT_H
81	struct stat	st_buf;
82	errcode_t	retval = 0;
83	dev_t		file_dev=0, file_rdev=0;
84	ino_t		file_ino=0;
85	FILE 		*f;
86	char		buf[1024], *device = 0, *mnt_dir = 0, *cp;
87
88	*mount_flags = 0;
89	if ((f = setmntent (mtab_file, "r")) == NULL)
90		return errno;
91	if (stat(file, &st_buf) == 0) {
92		if (S_ISBLK(st_buf.st_mode)) {
93#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
94			file_rdev = st_buf.st_rdev;
95#endif	/* __GNU__ */
96		} else {
97			file_dev = st_buf.st_dev;
98			file_ino = st_buf.st_ino;
99		}
100	}
101	while (1) {
102		if (!fgets(buf, sizeof(buf), f)) {
103			device = mnt_dir = 0;
104			break;
105		}
106		buf[sizeof(buf)-1] = 0;
107
108		cp = buf;
109		device = parse_word(&cp);
110		if (!device || *device == '#')
111			return 0;	/* Ignore blank lines and comments */
112		mnt_dir = parse_word(&cp);
113
114		if (device[0] != '/')
115			continue;
116
117		if (strcmp(file, device) == 0)
118			break;
119		if (stat(device, &st_buf) == 0) {
120			if (S_ISBLK(st_buf.st_mode)) {
121#ifndef __GNU__
122				if (file_rdev && (file_rdev == st_buf.st_rdev))
123					break;
124#endif	/* __GNU__ */
125			} else {
126				if (file_dev && ((file_dev == st_buf.st_dev) &&
127						 (file_ino == st_buf.st_ino)))
128					break;
129			}
130		}
131	}
132
133	if (mnt_dir == 0) {
134#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
135		/*
136		 * Do an extra check to see if this is the root device.  We
137		 * can't trust /etc/mtab, and /proc/mounts will only list
138		 * /dev/root for the root filesystem.  Argh.  Instead we
139		 * check if the given device has the same major/minor number
140		 * as the device that the root directory is on.
141		 */
142		if (file_rdev && (stat("/", &st_buf) == 0) &&
143		    (st_buf.st_dev == file_rdev))
144			*mount_flags = MF_MOUNTED;
145#endif	/* __GNU__ */
146		goto errout;
147	}
148#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
149	/* Validate the entry in case /etc/mtab is out of date */
150	/*
151	 * We need to be paranoid, because some broken distributions
152	 * (read: Slackware) don't initialize /etc/mtab before checking
153	 * all of the non-root filesystems on the disk.
154	 */
155	if (stat(mnt_dir, &st_buf) < 0) {
156		retval = errno;
157		if (retval == ENOENT) {
158#ifdef DEBUG
159			printf("Bogus entry in %s!  (%s does not exist)\n",
160			       mtab_file, mnt_dir);
161#endif /* DEBUG */
162			retval = 0;
163		}
164		goto errout;
165	}
166	if (file_rdev && (st_buf.st_dev != file_rdev)) {
167#ifdef DEBUG
168		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
169		       mtab_file, file, mnt_dir);
170#endif /* DEBUG */
171		goto errout;
172	}
173#endif /* __GNU__ */
174	*mount_flags = MF_MOUNTED;
175
176	retval = 0;
177errout:
178	endmntent (f);
179	return retval;
180#else /* !HAVE_MNTENT_H */
181	return 0;
182#endif /* HAVE_MNTENT_H */
183}
184
185int is_mounted(const char *file)
186{
187	errcode_t	retval;
188	int		mount_flags = 0;
189
190#ifdef __linux__
191	retval = check_mntent_file("/proc/mounts", file, &mount_flags);
192	if (retval)
193		return 0;
194	if (mount_flags)
195		return 1;
196#endif /* __linux__ */
197	retval = check_mntent_file("/etc/mtab", file, &mount_flags);
198	if (retval)
199		return 0;
200	return (mount_flags);
201}
202
203#ifdef DEBUG
204int main(int argc, char **argv)
205{
206	if (argc < 2) {
207		fprintf(stderr, "Usage: %s device\n", argv[0]);
208		exit(1);
209	}
210
211	if (is_mounted(argv[1]))
212		printf("\t%s is mounted.\n", argv[1]);
213	exit(0);
214}
215#endif /* DEBUG */
216