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 Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Library
8 * General Public License, version 2.
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_LINUX_LOOP_H
24#include <linux/loop.h>
25#include <sys/ioctl.h>
26#ifdef HAVE_LINUX_MAJOR_H
27#include <linux/major.h>
28#endif /* HAVE_LINUX_MAJOR_H */
29#endif /* HAVE_LINUX_LOOP_H */
30#ifdef HAVE_MNTENT_H
31#include <mntent.h>
32#endif
33#ifdef HAVE_GETMNTINFO
34#include <paths.h>
35#include <sys/param.h>
36#include <sys/mount.h>
37#endif /* HAVE_GETMNTINFO */
38#include <string.h>
39#include <sys/stat.h>
40
41#include "ext2_fs.h"
42#include "ext2fs.h"
43
44/*
45 * Check to see if a regular file is mounted.
46 * If /etc/mtab/ is a symlink of /proc/mounts, you will need the following check
47 * because the name in /proc/mounts is a loopback device not a regular file.
48 */
49static int check_loop_mounted(const char *mnt_fsname, dev_t mnt_rdev,
50				dev_t file_dev, ino_t file_ino)
51{
52#if defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H)
53	struct loop_info64 loopinfo;
54	int loop_fd, ret;
55
56	if (major(mnt_rdev) == LOOP_MAJOR) {
57		loop_fd = open(mnt_fsname, O_RDONLY);
58		if (loop_fd < 0)
59			return -1;
60
61		ret = ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo);
62		close(loop_fd);
63		if (ret < 0)
64			return -1;
65
66		if (file_dev == loopinfo.lo_device &&
67				file_ino == loopinfo.lo_inode)
68			return 1;
69	}
70#endif /* defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H) */
71	return 0;
72}
73
74#ifdef HAVE_SETMNTENT
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, char *mtpt, int mtlen)
82{
83	struct mntent 	*mnt;
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	int		fd;
90
91	*mount_flags = 0;
92	if ((f = setmntent (mtab_file, "r")) == NULL) {
93		if (errno == ENOENT) {
94			if (getenv("EXT2FS_NO_MTAB_OK"))
95				return 0;
96			else
97				return EXT2_ET_NO_MTAB_FILE;
98		}
99		return errno;
100	}
101	if (stat(file, &st_buf) == 0) {
102		if (S_ISBLK(st_buf.st_mode)) {
103#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
104			file_rdev = st_buf.st_rdev;
105#endif	/* __GNU__ */
106		} else {
107			file_dev = st_buf.st_dev;
108			file_ino = st_buf.st_ino;
109		}
110	}
111	while ((mnt = getmntent (f)) != NULL) {
112		if (mnt->mnt_fsname[0] != '/')
113			continue;
114		if (strcmp(file, mnt->mnt_fsname) == 0)
115			break;
116		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
117			if (S_ISBLK(st_buf.st_mode)) {
118#ifndef __GNU__
119				if (file_rdev && (file_rdev == st_buf.st_rdev))
120					break;
121				if (check_loop_mounted(mnt->mnt_fsname,
122						st_buf.st_rdev, file_dev,
123						file_ino) == 1)
124					break;
125#endif	/* __GNU__ */
126			} else {
127				if (file_dev && ((file_dev == st_buf.st_dev) &&
128						 (file_ino == st_buf.st_ino)))
129					break;
130			}
131		}
132	}
133
134	if (mnt == 0) {
135#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
136		/*
137		 * Do an extra check to see if this is the root device.  We
138		 * can't trust /etc/mtab, and /proc/mounts will only list
139		 * /dev/root for the root filesystem.  Argh.  Instead we
140		 * check if the given device has the same major/minor number
141		 * as the device that the root directory is on.
142		 */
143		if (file_rdev && stat("/", &st_buf) == 0) {
144			if (st_buf.st_dev == file_rdev) {
145				*mount_flags = EXT2_MF_MOUNTED;
146				if (mtpt)
147					strncpy(mtpt, "/", mtlen);
148				goto is_root;
149			}
150		}
151#endif	/* __GNU__ */
152		goto errout;
153	}
154#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
155	/* Validate the entry in case /etc/mtab is out of date */
156	/*
157	 * We need to be paranoid, because some broken distributions
158	 * (read: Slackware) don't initialize /etc/mtab before checking
159	 * all of the non-root filesystems on the disk.
160	 */
161	if (stat(mnt->mnt_dir, &st_buf) < 0) {
162		retval = errno;
163		if (retval == ENOENT) {
164#ifdef DEBUG
165			printf("Bogus entry in %s!  (%s does not exist)\n",
166			       mtab_file, mnt->mnt_dir);
167#endif /* DEBUG */
168			retval = 0;
169		}
170		goto errout;
171	}
172	if (file_rdev && (st_buf.st_dev != file_rdev)) {
173#ifdef DEBUG
174		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
175		       mtab_file, file, mnt->mnt_dir);
176#endif /* DEBUG */
177		goto errout;
178	}
179#endif /* __GNU__ */
180	*mount_flags = EXT2_MF_MOUNTED;
181
182#ifdef MNTOPT_RO
183	/* Check to see if the ro option is set */
184	if (hasmntopt(mnt, MNTOPT_RO))
185		*mount_flags |= EXT2_MF_READONLY;
186#endif
187
188	if (mtpt)
189		strncpy(mtpt, mnt->mnt_dir, mtlen);
190	/*
191	 * Check to see if we're referring to the root filesystem.
192	 * If so, do a manual check to see if we can open /etc/mtab
193	 * read/write, since if the root is mounted read/only, the
194	 * contents of /etc/mtab may not be accurate.
195	 */
196	if (!strcmp(mnt->mnt_dir, "/")) {
197is_root:
198#define TEST_FILE "/.ismount-test-file"
199		*mount_flags |= EXT2_MF_ISROOT;
200		fd = open(TEST_FILE, O_RDWR|O_CREAT, 0600);
201		if (fd < 0) {
202			if (errno == EROFS)
203				*mount_flags |= EXT2_MF_READONLY;
204		} else
205			close(fd);
206		(void) unlink(TEST_FILE);
207	}
208	retval = 0;
209errout:
210	endmntent (f);
211	return retval;
212}
213
214static errcode_t check_mntent(const char *file, int *mount_flags,
215			      char *mtpt, int mtlen)
216{
217	errcode_t	retval;
218
219#ifdef DEBUG
220	retval = check_mntent_file("/tmp/mtab", file, mount_flags,
221				   mtpt, mtlen);
222	if (retval == 0)
223		return 0;
224#endif /* DEBUG */
225#ifdef __linux__
226	retval = check_mntent_file("/proc/mounts", file, mount_flags,
227				   mtpt, mtlen);
228	if (retval == 0 && (*mount_flags != 0))
229		return 0;
230#endif /* __linux__ */
231#if defined(MOUNTED) || defined(_PATH_MOUNTED)
232#ifndef MOUNTED
233#define MOUNTED _PATH_MOUNTED
234#endif /* MOUNTED */
235	retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
236	return retval;
237#else
238	*mount_flags = 0;
239	return 0;
240#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
241}
242
243#else
244#if defined(HAVE_GETMNTINFO)
245
246static errcode_t check_getmntinfo(const char *file, int *mount_flags,
247				  char *mtpt, int mtlen)
248{
249	struct statfs *mp;
250        int    len, n;
251        const  char   *s1;
252	char	*s2;
253
254        n = getmntinfo(&mp, MNT_NOWAIT);
255        if (n == 0)
256		return errno;
257
258        len = sizeof(_PATH_DEV) - 1;
259        s1 = file;
260        if (strncmp(_PATH_DEV, s1, len) == 0)
261                s1 += len;
262
263	*mount_flags = 0;
264        while (--n >= 0) {
265                s2 = mp->f_mntfromname;
266                if (strncmp(_PATH_DEV, s2, len) == 0) {
267                        s2 += len - 1;
268                        *s2 = 'r';
269                }
270                if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
271			*mount_flags = EXT2_MF_MOUNTED;
272			break;
273		}
274                ++mp;
275	}
276	if (mtpt)
277		strncpy(mtpt, mp->f_mntonname, mtlen);
278	return 0;
279}
280#endif /* HAVE_GETMNTINFO */
281#endif /* HAVE_SETMNTENT */
282
283/*
284 * Check to see if we're dealing with the swap device.
285 */
286static int is_swap_device(const char *file)
287{
288	FILE		*f;
289	char		buf[1024], *cp;
290	dev_t		file_dev;
291	struct stat	st_buf;
292	int		ret = 0;
293
294	file_dev = 0;
295#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
296	if ((stat(file, &st_buf) == 0) &&
297	    S_ISBLK(st_buf.st_mode))
298		file_dev = st_buf.st_rdev;
299#endif	/* __GNU__ */
300
301	if (!(f = fopen("/proc/swaps", "r")))
302		return 0;
303	/* Skip the first line */
304	if (!fgets(buf, sizeof(buf), f))
305		goto leave;
306	if (*buf && strncmp(buf, "Filename\t", 9))
307		/* Linux <=2.6.19 contained a bug in the /proc/swaps
308		 * code where the header would not be displayed
309		 */
310		goto valid_first_line;
311
312	while (fgets(buf, sizeof(buf), f)) {
313valid_first_line:
314		if ((cp = strchr(buf, ' ')) != NULL)
315			*cp = 0;
316		if ((cp = strchr(buf, '\t')) != NULL)
317			*cp = 0;
318		if (strcmp(buf, file) == 0) {
319			ret++;
320			break;
321		}
322#ifndef __GNU__
323		if (file_dev && (stat(buf, &st_buf) == 0) &&
324		    S_ISBLK(st_buf.st_mode) &&
325		    file_dev == st_buf.st_rdev) {
326			ret++;
327			break;
328		}
329#endif 	/* __GNU__ */
330	}
331
332leave:
333	fclose(f);
334	return ret;
335}
336
337
338/*
339 * ext2fs_check_mount_point() fills determines if the device is
340 * mounted or otherwise busy, and fills in mount_flags with one or
341 * more of the following flags: EXT2_MF_MOUNTED, EXT2_MF_ISROOT,
342 * EXT2_MF_READONLY, EXT2_MF_SWAP, and EXT2_MF_BUSY.  If mtpt is
343 * non-NULL, the directory where the device is mounted is copied to
344 * where mtpt is pointing, up to mtlen characters.
345 */
346#ifdef __TURBOC__
347 #pragma argsused
348#endif
349errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
350				  char *mtpt, int mtlen)
351{
352	errcode_t	retval = 0;
353
354	if (is_swap_device(device)) {
355		*mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
356		strncpy(mtpt, "<swap>", mtlen);
357	} else {
358#ifdef HAVE_SETMNTENT
359		retval = check_mntent(device, mount_flags, mtpt, mtlen);
360#else
361#ifdef HAVE_GETMNTINFO
362		retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
363#else
364#ifdef __GNUC__
365 #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
366#endif
367		*mount_flags = 0;
368#endif /* HAVE_GETMNTINFO */
369#endif /* HAVE_SETMNTENT */
370	}
371	if (retval)
372		return retval;
373
374#ifdef __linux__ /* This only works on Linux 2.6+ systems */
375	{
376		struct stat st_buf;
377
378		if (stat(device, &st_buf) == 0 && S_ISBLK(st_buf.st_mode)) {
379			int fd = open(device, O_RDONLY | O_EXCL);
380
381			if (fd >= 0)
382				close(fd);
383			else if (errno == EBUSY)
384				*mount_flags |= EXT2_MF_BUSY;
385		}
386	}
387#endif
388
389	return 0;
390}
391
392/*
393 * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
394 * EXT2_MF_READONLY, and EXT2_MF_ROOT
395 *
396 */
397errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
398{
399	return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
400}
401
402#ifdef DEBUG
403int main(int argc, char **argv)
404{
405	int	retval, mount_flags;
406	char	mntpt[80];
407
408	if (argc < 2) {
409		fprintf(stderr, "Usage: %s device\n", argv[0]);
410		exit(1);
411	}
412
413	add_error_table(&et_ext2_error_table);
414	mntpt[0] = 0;
415	retval = ext2fs_check_mount_point(argv[1], &mount_flags,
416					  mntpt, sizeof(mntpt));
417	if (retval) {
418		com_err(argv[0], retval,
419			"while calling ext2fs_check_if_mounted");
420		exit(1);
421	}
422	printf("Device %s reports flags %02x\n", argv[1], mount_flags);
423	if (mount_flags & EXT2_MF_BUSY)
424		printf("\t%s is apparently in use.\n", argv[1]);
425	if (mount_flags & EXT2_MF_MOUNTED)
426		printf("\t%s is mounted.\n", argv[1]);
427	if (mount_flags & EXT2_MF_SWAP)
428		printf("\t%s is a swap device.\n", argv[1]);
429	if (mount_flags & EXT2_MF_READONLY)
430		printf("\t%s is read-only.\n", argv[1]);
431	if (mount_flags & EXT2_MF_ISROOT)
432		printf("\t%s is the root filesystem.\n", argv[1]);
433	if (mntpt[0])
434		printf("\t%s is mounted on %s.\n", argv[1], mntpt);
435	exit(0);
436}
437#endif /* DEBUG */
438