ismounted.c revision 1d6fd6d0c3766a8165e69284c75812574a29c804 
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 "config.h"
13#include <stdio.h>
14#if HAVE_UNISTD_H
15#include <unistd.h>
16#endif
17#ifdef HAVE_STDLIB_H
18#include <stdlib.h>
19#endif
20#if HAVE_ERRNO_H
21#include <errno.h>
22#endif
23#include <fcntl.h>
24#ifdef HAVE_LINUX_FD_H
25#include <linux/fd.h>
26#endif
27#ifdef HAVE_MNTENT_H
28#include <mntent.h>
29#endif
30#include <string.h>
31#include <sys/stat.h>
32#include <ctype.h>
33
34#include "fsck.h"
35
36/*
37 * ext2fs_check_if_mounted flags
38 */
39#define MF_MOUNTED		1
40
41#include "et/com_err.h"
42
43#ifdef HAVE_SETMNTENT
44static char *skip_over_blank(char *cp)
45{
46	while (*cp && isspace(*cp))
47		cp++;
48	return cp;
49}
50
51static char *skip_over_word(char *cp)
52{
53	while (*cp && !isspace(*cp))
54		cp++;
55	return cp;
56}
57
58static char *parse_word(char **buf)
59{
60	char *word, *next;
61
62	word = *buf;
63	if (*word == 0)
64		return 0;
65
66	word = skip_over_blank(word);
67	next = skip_over_word(word);
68	if (*next)
69		*next++ = 0;
70	*buf = next;
71	return word;
72}
73#endif
74
75/*
76 * Helper function which checks a file in /etc/mtab format to see if a
77 * filesystem is mounted.  Returns an error if the file doesn't exist
78 * or can't be opened.
79 */
80static errcode_t check_mntent_file(const char *mtab_file, const char *file,
81				   int *mount_flags)
82{
83#ifdef HAVE_SETMNTENT
84	struct stat	st_buf;
85	errcode_t	retval = 0;
86	dev_t		file_dev=0, file_rdev=0;
87	ino_t		file_ino=0;
88	FILE 		*f;
89	char		buf[1024], *device = 0, *mnt_dir = 0, *cp;
90
91	*mount_flags = 0;
92	if ((f = setmntent (mtab_file, "r")) == NULL)
93		return errno;
94	if (stat(file, &st_buf) == 0) {
95		if (S_ISBLK(st_buf.st_mode)) {
96#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
97			file_rdev = st_buf.st_rdev;
98#endif	/* __GNU__ */
99		} else {
100			file_dev = st_buf.st_dev;
101			file_ino = st_buf.st_ino;
102		}
103	}
104	while (1) {
105		if (!fgets(buf, sizeof(buf), f)) {
106			device = mnt_dir = 0;
107			break;
108		}
109		buf[sizeof(buf)-1] = 0;
110
111		cp = buf;
112		device = parse_word(&cp);
113		if (!device || *device == '#')
114			return 0;	/* Ignore blank lines and comments */
115		mnt_dir = parse_word(&cp);
116
117		if (device[0] != '/')
118			continue;
119
120		if (strcmp(file, device) == 0)
121			break;
122		if (stat(device, &st_buf) == 0) {
123			if (S_ISBLK(st_buf.st_mode)) {
124#ifndef __GNU__
125				if (file_rdev && (file_rdev == st_buf.st_rdev))
126					break;
127#endif	/* __GNU__ */
128			} else {
129				if (file_dev && ((file_dev == st_buf.st_dev) &&
130						 (file_ino == st_buf.st_ino)))
131					break;
132			}
133		}
134	}
135
136	if (mnt_dir == 0) {
137#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
138		/*
139		 * Do an extra check to see if this is the root device.  We
140		 * can't trust /etc/mtab, and /proc/mounts will only list
141		 * /dev/root for the root filesystem.  Argh.  Instead we
142		 * check if the given device has the same major/minor number
143		 * as the device that the root directory is on.
144		 */
145		if (file_rdev && (stat("/", &st_buf) == 0) &&
146		    (st_buf.st_dev == file_rdev))
147			*mount_flags = MF_MOUNTED;
148#endif	/* __GNU__ */
149		goto errout;
150	}
151#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
152	/* Validate the entry in case /etc/mtab is out of date */
153	/*
154	 * We need to be paranoid, because some broken distributions
155	 * (read: Slackware) don't initialize /etc/mtab before checking
156	 * all of the non-root filesystems on the disk.
157	 */
158	if (stat(mnt_dir, &st_buf) < 0) {
159		retval = errno;
160		if (retval == ENOENT) {
161#ifdef DEBUG
162			printf("Bogus entry in %s!  (%s does not exist)\n",
163			       mtab_file, mnt_dir);
164#endif /* DEBUG */
165			retval = 0;
166		}
167		goto errout;
168	}
169	if (file_rdev && (st_buf.st_dev != file_rdev)) {
170#ifdef DEBUG
171		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
172		       mtab_file, file, mnt_dir);
173#endif /* DEBUG */
174		goto errout;
175	}
176#endif /* __GNU__ */
177	*mount_flags = MF_MOUNTED;
178
179	retval = 0;
180errout:
181	endmntent (f);
182	return retval;
183#else /* !HAVE_SETMNTENT */
184	return 0;
185#endif /* HAVE_MNTENT_H */
186}
187
188int is_mounted(const char *file)
189{
190	errcode_t	retval;
191	int		mount_flags = 0;
192
193#ifdef __linux__
194	retval = check_mntent_file("/proc/mounts", file, &mount_flags);
195	if (retval)
196		return 0;
197	if (mount_flags)
198		return 1;
199#endif /* __linux__ */
200	retval = check_mntent_file("/etc/mtab", file, &mount_flags);
201	if (retval)
202		return 0;
203	return (mount_flags);
204}
205
206#ifdef DEBUG
207int main(int argc, char **argv)
208{
209	if (argc < 2) {
210		fprintf(stderr, "Usage: %s device\n", argv[0]);
211		exit(1);
212	}
213
214	if (is_mounted(argv[1]))
215		printf("\t%s is mounted.\n", argv[1]);
216	exit(0);
217}
218#endif /* DEBUG */
219