ismounted.c revision 5f91561ae7e08d79b6a5feca167259fd7634713f 
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 == ENOENT ? EXT2_NO_MTAB_FILE : 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 (mnt->mnt_fsname[0] != '/')
69			continue;
70		if (strcmp(file, mnt->mnt_fsname) == 0)
71			break;
72		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
73			if (S_ISBLK(st_buf.st_mode)) {
74#ifndef __GNU__
75				if (file_rdev && (file_rdev == st_buf.st_rdev))
76					break;
77#endif	/* __GNU__ */
78			} else {
79				if (file_dev && ((file_dev == st_buf.st_dev) &&
80						 (file_ino == st_buf.st_ino)))
81					break;
82			}
83		}
84	}
85
86	if (mnt == 0) {
87#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
88		/*
89		 * Do an extra check to see if this is the root device.  We
90		 * can't trust /etc/mtab, and /proc/mounts will only list
91		 * /dev/root for the root filesystem.  Argh.  Instead we
92		 * check if the given device has the same major/minor number
93		 * as the device that the root directory is on.
94		 */
95		if (file_rdev && stat("/", &st_buf) == 0) {
96			if (st_buf.st_dev == file_rdev) {
97				*mount_flags = EXT2_MF_MOUNTED;
98				if (mtpt)
99					strncpy(mtpt, "/", mtlen);
100				goto is_root;
101			}
102		}
103#endif	/* __GNU__ */
104		goto errout;
105	}
106#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
107	/* Validate the entry in case /etc/mtab is out of date */
108	/*
109	 * We need to be paranoid, because some broken distributions
110	 * (read: Slackware) don't initialize /etc/mtab before checking
111	 * all of the non-root filesystems on the disk.
112	 */
113	if (stat(mnt->mnt_dir, &st_buf) < 0) {
114		retval = errno;
115		if (retval == ENOENT) {
116#ifdef DEBUG
117			printf("Bogus entry in %s!  (%s does not exist)\n",
118			       mtab_file, mnt->mnt_dir);
119#endif /* DEBUG */
120			retval = 0;
121		}
122		goto errout;
123	}
124	if (file_rdev && (st_buf.st_dev != file_rdev)) {
125#ifdef DEBUG
126		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
127		       mtab_file, file, mnt->mnt_dir);
128#endif /* DEBUG */
129		goto errout;
130	}
131#endif /* __GNU__ */
132	*mount_flags = EXT2_MF_MOUNTED;
133
134#ifdef MNTOPT_RO
135	/* Check to see if the ro option is set */
136	if (hasmntopt(mnt, MNTOPT_RO))
137		*mount_flags |= EXT2_MF_READONLY;
138#endif
139
140	if (mtpt)
141		strncpy(mtpt, mnt->mnt_dir, mtlen);
142	/*
143	 * Check to see if we're referring to the root filesystem.
144	 * If so, do a manual check to see if we can open /etc/mtab
145	 * read/write, since if the root is mounted read/only, the
146	 * contents of /etc/mtab may not be accurate.
147	 */
148	if (!strcmp(mnt->mnt_dir, "/")) {
149is_root:
150#define TEST_FILE "/.ismount-test-file"
151		*mount_flags |= EXT2_MF_ISROOT;
152		fd = open(TEST_FILE, O_RDWR|O_CREAT, 0600);
153		if (fd < 0) {
154			if (errno == EROFS)
155				*mount_flags |= EXT2_MF_READONLY;
156		} else
157			close(fd);
158		(void) unlink(TEST_FILE);
159	}
160	retval = 0;
161errout:
162	endmntent (f);
163	return retval;
164}
165
166static errcode_t check_mntent(const char *file, int *mount_flags,
167			      char *mtpt, int mtlen)
168{
169	errcode_t	retval;
170
171#ifdef DEBUG
172	retval = check_mntent_file("/tmp/mtab", file, mount_flags,
173				   mtpt, mtlen);
174	if (retval == 0)
175		return 0;
176#endif /* DEBUG */
177#ifdef __linux__
178	retval = check_mntent_file("/proc/mounts", file, mount_flags,
179				   mtpt, mtlen);
180	if (retval == 0 && (*mount_flags != 0))
181		return 0;
182#endif /* __linux__ */
183#if defined(MOUNTED) || defined(_PATH_MOUNTED)
184#ifndef MOUNTED
185#define MOUNTED _PATH_MOUNTED
186#endif /* MOUNTED */
187	retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
188	return retval;
189#else
190	*mount_flags = 0;
191	return 0;
192#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
193}
194
195#else
196#if defined(HAVE_GETMNTINFO)
197
198static errcode_t check_getmntinfo(const char *file, int *mount_flags,
199				  char *mtpt, int mtlen)
200{
201	struct statfs *mp;
202        int    len, n;
203        const  char   *s1;
204	char	*s2;
205
206        n = getmntinfo(&mp, MNT_NOWAIT);
207        if (n == 0)
208		return errno;
209
210        len = sizeof(_PATH_DEV) - 1;
211        s1 = file;
212        if (strncmp(_PATH_DEV, s1, len) == 0)
213                s1 += len;
214
215	*mount_flags = 0;
216        while (--n >= 0) {
217                s2 = mp->f_mntfromname;
218                if (strncmp(_PATH_DEV, s2, len) == 0) {
219                        s2 += len - 1;
220                        *s2 = 'r';
221                }
222                if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
223			*mount_flags = EXT2_MF_MOUNTED;
224			break;
225		}
226                ++mp;
227	}
228	if (mtpt)
229		strncpy(mtpt, mp->f_mntonname, mtlen);
230	return 0;
231}
232#endif /* HAVE_GETMNTINFO */
233#endif /* HAVE_MNTENT_H */
234
235/*
236 * Check to see if we're dealing with the swap device.
237 */
238static int is_swap_device(const char *file)
239{
240	FILE		*f;
241	char		buf[1024], *cp;
242	dev_t		file_dev;
243	struct stat	st_buf;
244	int		ret = 0;
245
246	file_dev = 0;
247#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
248	if ((stat(file, &st_buf) == 0) &&
249	    S_ISBLK(st_buf.st_mode))
250		file_dev = st_buf.st_rdev;
251#endif	/* __GNU__ */
252
253	if (!(f = fopen("/proc/swaps", "r")))
254		return 0;
255	/* Skip the first line */
256	if (!fgets(buf, sizeof(buf), f))
257		goto leave;
258	if (*buf && strncmp(buf, "Filename\t", 9))
259		/* Linux <=2.6.19 contained a bug in the /proc/swaps
260		 * code where the header would not be displayed
261		 */
262		goto valid_first_line;
263
264	while (fgets(buf, sizeof(buf), f)) {
265valid_first_line:
266		if ((cp = strchr(buf, ' ')) != NULL)
267			*cp = 0;
268		if ((cp = strchr(buf, '\t')) != NULL)
269			*cp = 0;
270		if (strcmp(buf, file) == 0) {
271			ret++;
272			break;
273		}
274#ifndef __GNU__
275		if (file_dev && (stat(buf, &st_buf) == 0) &&
276		    S_ISBLK(st_buf.st_mode) &&
277		    file_dev == st_buf.st_rdev) {
278			ret++;
279			break;
280		}
281#endif 	/* __GNU__ */
282	}
283
284leave:
285	fclose(f);
286	return ret;
287}
288
289
290/*
291 * ext2fs_check_mount_point() fills determines if the device is
292 * mounted or otherwise busy, and fills in mount_flags with one or
293 * more of the following flags: EXT2_MF_MOUNTED, EXT2_MF_ISROOT,
294 * EXT2_MF_READONLY, EXT2_MF_SWAP, and EXT2_MF_BUSY.  If mtpt is
295 * non-NULL, the directory where the device is mounted is copied to
296 * where mtpt is pointing, up to mtlen characters.
297 */
298#ifdef __TURBOC__
299 #pragma argsused
300#endif
301errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
302				  char *mtpt, int mtlen)
303{
304	struct stat	st_buf;
305	errcode_t	retval = 0;
306	int		fd;
307
308	if (is_swap_device(device)) {
309		*mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
310		strncpy(mtpt, "<swap>", mtlen);
311	} else {
312#ifdef HAVE_MNTENT_H
313		retval = check_mntent(device, mount_flags, mtpt, mtlen);
314#else
315#ifdef HAVE_GETMNTINFO
316		retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
317#else
318#ifdef __GNUC__
319 #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
320#endif
321		*mount_flags = 0;
322#endif /* HAVE_GETMNTINFO */
323#endif /* HAVE_MNTENT_H */
324	}
325	if (retval)
326		return retval;
327
328#ifdef __linux__ /* This only works on Linux 2.6+ systems */
329	if ((stat(device, &st_buf) != 0) ||
330	    !S_ISBLK(st_buf.st_mode))
331		return 0;
332	fd = open(device, O_RDONLY | O_EXCL);
333	if (fd < 0) {
334		if (errno == EBUSY)
335			*mount_flags |= EXT2_MF_BUSY;
336	} else
337		close(fd);
338#endif
339
340	return 0;
341}
342
343/*
344 * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
345 * EXT2_MF_READONLY, and EXT2_MF_ROOT
346 *
347 */
348errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
349{
350	return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
351}
352
353#ifdef DEBUG
354int main(int argc, char **argv)
355{
356	int	retval, mount_flags;
357	char	mntpt[80];
358
359	if (argc < 2) {
360		fprintf(stderr, "Usage: %s device\n", argv[0]);
361		exit(1);
362	}
363
364	add_error_table(&et_ext2_error_table);
365	mntpt[0] = 0;
366	retval = ext2fs_check_mount_point(argv[1], &mount_flags,
367					  mntpt, sizeof(mntpt));
368	if (retval) {
369		com_err(argv[0], retval,
370			"while calling ext2fs_check_if_mounted");
371		exit(1);
372	}
373	printf("Device %s reports flags %02x\n", argv[1], mount_flags);
374	if (mount_flags & EXT2_MF_BUSY)
375		printf("\t%s is apparently in use.\n", argv[1]);
376	if (mount_flags & EXT2_MF_MOUNTED)
377		printf("\t%s is mounted.\n", argv[1]);
378	if (mount_flags & EXT2_MF_SWAP)
379		printf("\t%s is a swap device.\n", argv[1]);
380	if (mount_flags & EXT2_MF_READONLY)
381		printf("\t%s is read-only.\n", argv[1]);
382	if (mount_flags & EXT2_MF_ISROOT)
383		printf("\t%s is the root filesystem.\n", argv[1]);
384	if (mntpt[0])
385		printf("\t%s is mounted on %s.\n", argv[1], mntpt);
386	exit(0);
387}
388#endif /* DEBUG */
389