ismounted.c revision 07cefe7a7051e32f14b93d9003a6dbb308597bd3 
1/*
2 * ismounted.c --- Check to see if the filesystem was mounted
3 *
4 * Copyright (C) 1995,1996,1997,1998,1999,2000 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#if HAVE_ERRNO_H
17#include <errno.h>
18#endif
19#include <fcntl.h>
20#ifdef HAVE_LINUX_FD_H
21#include <linux/fd.h>
22#endif
23#ifdef HAVE_MNTENT_H
24#include <mntent.h>
25#endif
26#ifdef HAVE_GETMNTINFO
27#include <paths.h>
28#include <sys/param.h>
29#include <sys/mount.h>
30#endif /* HAVE_GETMNTINFO */
31#include <string.h>
32#include <sys/stat.h>
33
34#include "ext2_fs.h"
35#include "ext2fs.h"
36
37#ifdef HAVE_MNTENT_H
38/*
39 * Helper function which checks a file in /etc/mtab format to see if a
40 * filesystem is mounted.  Returns an error if the file doesn't exist
41 * or can't be opened.
42 */
43static errcode_t check_mntent_file(const char *mtab_file, const char *file,
44				   int *mount_flags, char *mtpt, int mtlen)
45{
46	struct mntent 	*mnt;
47	struct stat	st_buf;
48	errcode_t	retval = 0;
49	dev_t		file_dev;
50	FILE 		*f;
51	int		fd;
52
53	*mount_flags = 0;
54	if ((f = setmntent (mtab_file, "r")) == NULL)
55		return errno;
56	file_dev = 0;
57#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
58	if (stat(file, &st_buf) == 0)
59		file_dev = st_buf.st_rdev;
60#endif
61	while ((mnt = getmntent (f)) != NULL) {
62		if (strcmp(file, mnt->mnt_fsname) == 0)
63			break;
64#ifndef __GNU__
65		if (file_dev && (stat(mnt->mnt_fsname, &st_buf) == 0) &&
66		    file_dev == st_buf.st_rdev)
67			break;
68#endif
69	}
70
71	if (mnt == 0) {
72#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
73		/*
74		 * Do an extra check to see if this is the root device.  We
75		 * can't trust /etc/mtab, and /proc/mounts will only list
76		 * /dev/root for the root filesystem.  Argh.  Instead we
77		 * check if the given device has the same major/minor number
78		 * as the device that the root directory is on.
79		 */
80		if (file_dev && stat("/", &st_buf) == 0) {
81			if (st_buf.st_dev == file_dev) {
82				*mount_flags = EXT2_MF_MOUNTED;
83				if (mtpt)
84					strncpy(mtpt, "/", mtlen);
85				goto is_root;
86			}
87		}
88#endif
89		goto exit;
90	}
91#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
92	/* Validate the entry in case /etc/mtab is out of date */
93	/*
94	 * We need to be paranoid, because some broken distributions
95	 * (read: Slackware) don't initialize /etc/mtab before checking
96	 * all of the non-root filesystems on the disk.
97	 */
98	if (stat(mnt->mnt_dir, &st_buf) < 0) {
99		retval = errno;
100		if (retval == ENOENT) {
101#ifdef DEBUG
102			printf("Bogus entry in %s!  (%s does not exist)\n",
103			       mtab_file, mnt->mnt_dir);
104#endif
105			retval = 0;
106		}
107		goto exit;
108	}
109	if (file_dev && (st_buf.st_dev != file_dev)) {
110#ifdef DEBUG
111		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
112		       mtab_file, file, mnt->mnt_dir);
113#endif
114		goto exit;
115	}
116#endif
117	*mount_flags = EXT2_MF_MOUNTED;
118
119	/* Check to see if the ro option is set */
120	if (hasmntopt(mnt, MNTOPT_RO))
121		*mount_flags |= EXT2_MF_READONLY;
122
123	if (mtpt)
124		strncpy(mtpt, mnt->mnt_dir, mtlen);
125	/*
126	 * Check to see if we're referring to the root filesystem.
127	 * If so, do a manual check to see if we can open /etc/mtab
128	 * read/write, since if the root is mounted read/only, the
129	 * contents of /etc/mtab may not be accurate.
130	 */
131	if (!strcmp(mnt->mnt_dir, "/")) {
132is_root:
133#define TEST_FILE "/.ismount-test-file"
134		*mount_flags |= EXT2_MF_ISROOT;
135		fd = open(TEST_FILE, O_RDWR|O_CREAT);
136		if (fd < 0) {
137			if (errno == EROFS)
138				*mount_flags |= EXT2_MF_READONLY;
139		} else
140			close(fd);
141		(void) unlink(TEST_FILE);
142	}
143	retval = 0;
144exit:
145	endmntent (f);
146	return retval;
147}
148
149/*
150 * Check to see if we're dealing with the swap device.
151 */
152static int is_swap_device(const char *file)
153{
154	FILE		*f;
155	char		buf[1024], *cp;
156	dev_t		file_dev;
157	struct stat	st_buf;
158
159	file_dev = 0;
160#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
161	if (stat(file, &st_buf) == 0)
162		file_dev = st_buf.st_rdev;
163#endif
164
165	f = fopen("/proc/swaps", "r");
166	if (!f)
167		return;
168	/* Skip the first line */
169	fgets(buf, sizeof(buf), f);
170	while (!feof(f)) {
171		if (!fgets(buf, sizeof(buf), f))
172			break;
173		if ((cp = strchr(buf, ' ')) != NULL)
174			*cp = 0;
175		if ((cp = strchr(buf, '\t')) != NULL)
176			*cp = 0;
177		if (strcmp(buf, file) == 0)
178			return 1;
179#ifndef __GNU__
180		if (file_dev && (stat(buf, &st_buf) == 0) &&
181		    file_dev == st_buf.st_rdev)
182			return 1;
183#endif
184	}
185	return 0;
186}
187
188static errcode_t check_mntent(const char *file, int *mount_flags,
189			      char *mtpt, int mtlen)
190{
191	errcode_t	retval;
192
193#ifdef DEBUG
194	retval = check_mntent_file("/tmp/mtab", file, mount_flags,
195				   mtpt, mtlen);
196	if (retval == 0)
197		return 0;
198#endif
199#ifdef __linux__
200	retval = check_mntent_file("/proc/mounts", file, mount_flags,
201				   mtpt, mtlen);
202	if (retval == 0)
203		return 0;
204#endif
205	retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
206	return retval;
207}
208
209#elif defined(HAVE_GETMNTINFO)
210
211static errcode_t check_getmntinfo(const char *file, int *mount_flags,
212				  char *mtpt, int mtlen)
213{
214	struct statfs *mp;
215        int    len, n;
216        const  char   *s1;
217	char	*s2;
218
219        n = getmntinfo(&mp, MNT_NOWAIT);
220        if (n == 0)
221		return errno;
222
223        len = sizeof(_PATH_DEV) - 1;
224        s1 = file;
225        if (strncmp(_PATH_DEV, s1, len) == 0)
226                s1 += len;
227
228	*mount_flags = 0;
229        while (--n >= 0) {
230                s2 = mp->f_mntfromname;
231                if (strncmp(_PATH_DEV, s2, len) == 0) {
232                        s2 += len - 1;
233                        *s2 = 'r';
234                }
235                if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
236			*mount_flags = EXT2_MF_MOUNTED;
237			break;
238		}
239                ++mp;
240	}
241	if (mtpt)
242		strncpy(mtpt, mp->f_mntonname, mtlen);
243	return 0;
244}
245#endif /* HAVE_GETMNTINFO */
246
247/*
248 * ext2fs_check_mount_point() returns 1 if the device is mounted, 0
249 * otherwise.  If mtpt is non-NULL, the directory where the device is
250 * mounted is copied to where mtpt is pointing, up to mtlen
251 * characters.
252 */
253#ifdef __TURBOC__
254 #pragma argsused
255#endif
256errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
257				  char *mtpt, int mtlen)
258{
259	if (is_swap_device(device)) {
260		*mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
261		strncpy(mtpt, "<swap>", mtlen);
262		return 0;
263	}
264#ifdef HAVE_MNTENT_H
265	return check_mntent(device, mount_flags, mtpt, mtlen);
266#else
267#ifdef HAVE_GETMNTINFO
268	return check_getmntinfo(device, mount_flags, mtpt, mtlen);
269#else
270#warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
271	*mount_flags = 0;
272	return 0;
273#endif /* HAVE_GETMNTINFO */
274#endif /* HAVE_MNTENT_H */
275}
276
277/*
278 * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
279 * EXT2_MF_READONLY, and EXT2_MF_ROOT
280 *
281 */
282errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
283{
284	return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
285}
286
287#ifdef DEBUG
288int main(int argc, char **argv)
289{
290	int	retval, mount_flags;
291	char	mntpt[80];
292
293	if (argc < 2) {
294		fprintf(stderr, "Usage: %s device\n", argv[0]);
295		exit(1);
296	}
297
298	mntpt[0] = 0;
299	retval = ext2fs_check_mount_point(argv[1], &mount_flags,
300					  mntpt, sizeof(mntpt));
301	if (retval) {
302		com_err(argv[0], retval,
303			"while calling ext2fs_check_if_mounted");
304		exit(1);
305	}
306	printf("Device %s reports flags %02x\n", argv[1], mount_flags);
307	if (mount_flags & EXT2_MF_MOUNTED)
308		printf("\t%s is mounted.\n", argv[1]);
309
310	if (mount_flags & EXT2_MF_SWAP)
311		printf("\t%s is a swap device.\n", argv[1]);
312
313	if (mount_flags & EXT2_MF_READONLY)
314		printf("\t%s is read-only.\n", argv[1]);
315
316	if (mount_flags & EXT2_MF_ISROOT)
317		printf("\t%s is the root filesystem.\n", argv[1]);
318	if (mntpt[0])
319		printf("\t%s is mounted on %s.\n", argv[1], mntpt);
320
321	exit(0);
322}
323#endif
324