ismounted.c revision d9039ae0ff3f7929ede576058b3ad3e9c62a47c4 
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=0, file_rdev=0;
50	ino_t		file_ino=0;
51	FILE 		*f;
52	int		fd;
53
54	*mount_flags = 0;
55	if ((f = setmntent (mtab_file, "r")) == NULL)
56		return errno;
57	if (stat(file, &st_buf) == 0) {
58		if (S_ISBLK(st_buf.st_mode)) {
59#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
60			file_rdev = st_buf.st_rdev;
61#endif	/* __GNU__ */
62		} else {
63			file_dev = st_buf.st_dev;
64			file_ino = st_buf.st_ino;
65		}
66	}
67	while ((mnt = getmntent (f)) != NULL) {
68		if (strcmp(file, mnt->mnt_fsname) == 0)
69			break;
70		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
71			if (S_ISBLK(st_buf.st_mode)) {
72#ifndef __GNU__
73				if (file_rdev && (file_rdev == st_buf.st_rdev))
74					break;
75#endif	/* __GNU__ */
76			} else {
77				if (file_dev && ((file_dev == st_buf.st_dev) &&
78						 (file_ino == st_buf.st_ino)))
79					break;
80			}
81		}
82	}
83
84	if (mnt == 0) {
85#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
86		/*
87		 * Do an extra check to see if this is the root device.  We
88		 * can't trust /etc/mtab, and /proc/mounts will only list
89		 * /dev/root for the root filesystem.  Argh.  Instead we
90		 * check if the given device has the same major/minor number
91		 * as the device that the root directory is on.
92		 */
93		if (file_rdev && stat("/", &st_buf) == 0) {
94			if (st_buf.st_dev == file_rdev) {
95				*mount_flags = EXT2_MF_MOUNTED;
96				if (mtpt)
97					strncpy(mtpt, "/", mtlen);
98				goto is_root;
99			}
100		}
101#endif	/* __GNU__ */
102		goto errout;
103	}
104#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
105	/* Validate the entry in case /etc/mtab is out of date */
106	/*
107	 * We need to be paranoid, because some broken distributions
108	 * (read: Slackware) don't initialize /etc/mtab before checking
109	 * all of the non-root filesystems on the disk.
110	 */
111	if (stat(mnt->mnt_dir, &st_buf) < 0) {
112		retval = errno;
113		if (retval == ENOENT) {
114#ifdef DEBUG
115			printf("Bogus entry in %s!  (%s does not exist)\n",
116			       mtab_file, mnt->mnt_dir);
117#endif /* DEBUG */
118			retval = 0;
119		}
120		goto errout;
121	}
122	if (file_rdev && (st_buf.st_dev != file_rdev)) {
123#ifdef DEBUG
124		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
125		       mtab_file, file, mnt->mnt_dir);
126#endif /* DEBUG */
127		goto errout;
128	}
129#endif /* __GNU__ */
130	*mount_flags = EXT2_MF_MOUNTED;
131
132#ifdef MNTOPT_RO
133	/* Check to see if the ro option is set */
134	if (hasmntopt(mnt, MNTOPT_RO))
135		*mount_flags |= EXT2_MF_READONLY;
136#endif
137
138	if (mtpt)
139		strncpy(mtpt, mnt->mnt_dir, mtlen);
140	/*
141	 * Check to see if we're referring to the root filesystem.
142	 * If so, do a manual check to see if we can open /etc/mtab
143	 * read/write, since if the root is mounted read/only, the
144	 * contents of /etc/mtab may not be accurate.
145	 */
146	if (!strcmp(mnt->mnt_dir, "/")) {
147is_root:
148#define TEST_FILE "/.ismount-test-file"
149		*mount_flags |= EXT2_MF_ISROOT;
150		fd = open(TEST_FILE, O_RDWR|O_CREAT);
151		if (fd < 0) {
152			if (errno == EROFS)
153				*mount_flags |= EXT2_MF_READONLY;
154		} else
155			close(fd);
156		(void) unlink(TEST_FILE);
157	}
158	retval = 0;
159errout:
160	endmntent (f);
161	return retval;
162}
163
164static errcode_t check_mntent(const char *file, int *mount_flags,
165			      char *mtpt, int mtlen)
166{
167	errcode_t	retval;
168
169#ifdef DEBUG
170	retval = check_mntent_file("/tmp/mtab", file, mount_flags,
171				   mtpt, mtlen);
172	if (retval == 0)
173		return 0;
174#endif /* DEBUG */
175#ifdef __linux__
176	retval = check_mntent_file("/proc/mounts", file, mount_flags,
177				   mtpt, mtlen);
178	if (retval == 0 && (*mount_flags != 0))
179		return 0;
180#endif /* __linux__ */
181#if defined(MOUNTED) || defined(_PATH_MOUNTED)
182#ifndef MOUNTED
183#define MOUNTED _PATH_MOUNTED
184#endif /* MOUNTED */
185	retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
186	return retval;
187#else
188	*mount_flags = 0;
189	return 0;
190#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
191}
192
193#else
194#if defined(HAVE_GETMNTINFO)
195
196static errcode_t check_getmntinfo(const char *file, int *mount_flags,
197				  char *mtpt, int mtlen)
198{
199	struct statfs *mp;
200        int    len, n;
201        const  char   *s1;
202	char	*s2;
203
204        n = getmntinfo(&mp, MNT_NOWAIT);
205        if (n == 0)
206		return errno;
207
208        len = sizeof(_PATH_DEV) - 1;
209        s1 = file;
210        if (strncmp(_PATH_DEV, s1, len) == 0)
211                s1 += len;
212
213	*mount_flags = 0;
214        while (--n >= 0) {
215                s2 = mp->f_mntfromname;
216                if (strncmp(_PATH_DEV, s2, len) == 0) {
217                        s2 += len - 1;
218                        *s2 = 'r';
219                }
220                if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
221			*mount_flags = EXT2_MF_MOUNTED;
222			break;
223		}
224                ++mp;
225	}
226	if (mtpt)
227		strncpy(mtpt, mp->f_mntonname, mtlen);
228	return 0;
229}
230#endif /* HAVE_GETMNTINFO */
231#endif /* HAVE_MNTENT_H */
232
233/*
234 * Check to see if we're dealing with the swap device.
235 */
236static int is_swap_device(const char *file)
237{
238	FILE		*f;
239	char		buf[1024], *cp;
240	dev_t		file_dev;
241	struct stat	st_buf;
242	int		ret = 0;
243
244	file_dev = 0;
245#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
246	if ((stat(file, &st_buf) == 0) &&
247	    S_ISBLK(st_buf.st_mode))
248		file_dev = st_buf.st_rdev;
249#endif	/* __GNU__ */
250
251	if (!(f = fopen("/proc/swaps", "r")))
252		return 0;
253	/* Skip the first line */
254	if (fgets(buf, sizeof(buf), f))
255	while (fgets(buf, sizeof(buf), f)) {
256		if ((cp = strchr(buf, ' ')) != NULL)
257			*cp = 0;
258		if ((cp = strchr(buf, '\t')) != NULL)
259			*cp = 0;
260		if (strcmp(buf, file) == 0) {
261			ret++;
262			break;
263		}
264#ifndef __GNU__
265		if (file_dev && (stat(buf, &st_buf) == 0) &&
266		    S_ISBLK(st_buf.st_mode) &&
267		    file_dev == st_buf.st_rdev) {
268			ret++;
269			break;
270		}
271#endif 	/* __GNU__ */
272	}
273	fclose(f);
274	return ret;
275}
276
277
278/*
279 * ext2fs_check_mount_point() fills determines if the device is
280 * mounted or otherwise busy, and fills in mount_flags with one or
281 * more of the following flags: EXT2_MF_MOUNTED, EXT2_MF_ISROOT,
282 * EXT2_MF_READONLY, EXT2_MF_SWAP, and EXT2_MF_BUSY.  If mtpt is
283 * non-NULL, the directory where the device is mounted is copied to
284 * where mtpt is pointing, up to mtlen characters.
285 */
286#ifdef __TURBOC__
287 #pragma argsused
288#endif
289errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
290				  char *mtpt, int mtlen)
291{
292	struct stat	st_buf;
293	errcode_t	retval = 0;
294	int		fd;
295
296	if (is_swap_device(device)) {
297		*mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
298		strncpy(mtpt, "<swap>", mtlen);
299	} else {
300#ifdef HAVE_MNTENT_H
301		retval = check_mntent(device, mount_flags, mtpt, mtlen);
302#else
303#ifdef HAVE_GETMNTINFO
304		retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
305#else
306#ifdef __GNUC__
307 #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
308#endif
309		*mount_flags = 0;
310#endif /* HAVE_GETMNTINFO */
311#endif /* HAVE_MNTENT_H */
312	}
313	if (retval)
314		return retval;
315
316#ifdef __linux__ /* This only works on Linux 2.6+ systems */
317	if ((stat(device, &st_buf) != 0) ||
318	    !S_ISBLK(st_buf.st_mode))
319		return 0;
320	fd = open(device, O_RDONLY | O_EXCL);
321	if (fd < 0) {
322		if (errno == EBUSY)
323			*mount_flags |= EXT2_MF_BUSY;
324	} else
325		close(fd);
326#endif
327
328	return 0;
329}
330
331/*
332 * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
333 * EXT2_MF_READONLY, and EXT2_MF_ROOT
334 *
335 */
336errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
337{
338	return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
339}
340
341#ifdef DEBUG
342int main(int argc, char **argv)
343{
344	int	retval, mount_flags;
345	char	mntpt[80];
346
347	if (argc < 2) {
348		fprintf(stderr, "Usage: %s device\n", argv[0]);
349		exit(1);
350	}
351
352	mntpt[0] = 0;
353	retval = ext2fs_check_mount_point(argv[1], &mount_flags,
354					  mntpt, sizeof(mntpt));
355	if (retval) {
356		com_err(argv[0], retval,
357			"while calling ext2fs_check_if_mounted");
358		exit(1);
359	}
360	printf("Device %s reports flags %02x\n", argv[1], mount_flags);
361	if (mount_flags & EXT2_MF_BUSY)
362		printf("\t%s is apparently in use.\n", argv[1]);
363	if (mount_flags & EXT2_MF_MOUNTED)
364		printf("\t%s is mounted.\n", argv[1]);
365	if (mount_flags & EXT2_MF_SWAP)
366		printf("\t%s is a swap device.\n", argv[1]);
367	if (mount_flags & EXT2_MF_READONLY)
368		printf("\t%s is read-only.\n", argv[1]);
369	if (mount_flags & EXT2_MF_ISROOT)
370		printf("\t%s is the root filesystem.\n", argv[1]);
371	if (mntpt[0])
372		printf("\t%s is mounted on %s.\n", argv[1], mntpt);
373	exit(0);
374}
375#endif /* DEBUG */
376