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 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 "config.h"
13#include <stdio.h>
14#if HAVE_UNISTD_H
15#include <unistd.h>
16#endif
17#if HAVE_ERRNO_H
18#include <errno.h>
19#endif
20#include <fcntl.h>
21#ifdef HAVE_LINUX_FD_H
22#include <linux/fd.h>
23#endif
24#ifdef HAVE_MNTENT_H
25#include <mntent.h>
26#endif
27#ifdef HAVE_GETMNTINFO
28#include <paths.h>
29#include <sys/param.h>
30#include <sys/mount.h>
31#endif /* HAVE_GETMNTINFO */
32#include <string.h>
33#include <sys/stat.h>
34
35#include "ext2_fs.h"
36#include "ext2fs.h"
37
38#ifdef HAVE_SETMNTENT
39/*
40 * Helper function which checks a file in /etc/mtab format to see if a
41 * filesystem is mounted.  Returns an error if the file doesn't exist
42 * or can't be opened.
43 */
44static errcode_t check_mntent_file(const char *mtab_file, const char *file,
45				   int *mount_flags, char *mtpt, int mtlen)
46{
47	struct mntent 	*mnt;
48	struct stat	st_buf;
49	errcode_t	retval = 0;
50	dev_t		file_dev=0, file_rdev=0;
51	ino_t		file_ino=0;
52	FILE 		*f;
53	int		fd;
54
55	*mount_flags = 0;
56	if ((f = setmntent (mtab_file, "r")) == NULL)
57		return (errno == ENOENT ? EXT2_NO_MTAB_FILE : errno);
58	if (stat(file, &st_buf) == 0) {
59		if (S_ISBLK(st_buf.st_mode)) {
60#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
61			file_rdev = st_buf.st_rdev;
62#endif	/* __GNU__ */
63		} else {
64			file_dev = st_buf.st_dev;
65			file_ino = st_buf.st_ino;
66		}
67	}
68	while ((mnt = getmntent (f)) != NULL) {
69		if (mnt->mnt_fsname[0] != '/')
70			continue;
71		if (strcmp(file, mnt->mnt_fsname) == 0)
72			break;
73		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
74			if (S_ISBLK(st_buf.st_mode)) {
75#ifndef __GNU__
76				if (file_rdev && (file_rdev == st_buf.st_rdev))
77					break;
78#endif	/* __GNU__ */
79			} else {
80				if (file_dev && ((file_dev == st_buf.st_dev) &&
81						 (file_ino == st_buf.st_ino)))
82					break;
83			}
84		}
85	}
86
87	if (mnt == 0) {
88#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
89		/*
90		 * Do an extra check to see if this is the root device.  We
91		 * can't trust /etc/mtab, and /proc/mounts will only list
92		 * /dev/root for the root filesystem.  Argh.  Instead we
93		 * check if the given device has the same major/minor number
94		 * as the device that the root directory is on.
95		 */
96		if (file_rdev && stat("/", &st_buf) == 0) {
97			if (st_buf.st_dev == file_rdev) {
98				*mount_flags = EXT2_MF_MOUNTED;
99				if (mtpt)
100					strncpy(mtpt, "/", mtlen);
101				goto is_root;
102			}
103		}
104#endif	/* __GNU__ */
105		goto errout;
106	}
107#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
108	/* Validate the entry in case /etc/mtab is out of date */
109	/*
110	 * We need to be paranoid, because some broken distributions
111	 * (read: Slackware) don't initialize /etc/mtab before checking
112	 * all of the non-root filesystems on the disk.
113	 */
114	if (stat(mnt->mnt_dir, &st_buf) < 0) {
115		retval = errno;
116		if (retval == ENOENT) {
117#ifdef DEBUG
118			printf("Bogus entry in %s!  (%s does not exist)\n",
119			       mtab_file, mnt->mnt_dir);
120#endif /* DEBUG */
121			retval = 0;
122		}
123		goto errout;
124	}
125	if (file_rdev && (st_buf.st_dev != file_rdev)) {
126#ifdef DEBUG
127		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
128		       mtab_file, file, mnt->mnt_dir);
129#endif /* DEBUG */
130		goto errout;
131	}
132#endif /* __GNU__ */
133	*mount_flags = EXT2_MF_MOUNTED;
134
135#ifdef MNTOPT_RO
136	/* Check to see if the ro option is set */
137	if (hasmntopt(mnt, MNTOPT_RO))
138		*mount_flags |= EXT2_MF_READONLY;
139#endif
140
141	if (mtpt)
142		strncpy(mtpt, mnt->mnt_dir, mtlen);
143	/*
144	 * Check to see if we're referring to the root filesystem.
145	 * If so, do a manual check to see if we can open /etc/mtab
146	 * read/write, since if the root is mounted read/only, the
147	 * contents of /etc/mtab may not be accurate.
148	 */
149	if (!strcmp(mnt->mnt_dir, "/")) {
150is_root:
151#define TEST_FILE "/.ismount-test-file"
152		*mount_flags |= EXT2_MF_ISROOT;
153		fd = open(TEST_FILE, O_RDWR|O_CREAT, 0600);
154		if (fd < 0) {
155			if (errno == EROFS)
156				*mount_flags |= EXT2_MF_READONLY;
157		} else
158			close(fd);
159		(void) unlink(TEST_FILE);
160	}
161	retval = 0;
162errout:
163	endmntent (f);
164	return retval;
165}
166
167static errcode_t check_mntent(const char *file, int *mount_flags,
168			      char *mtpt, int mtlen)
169{
170	errcode_t	retval;
171
172#ifdef DEBUG
173	retval = check_mntent_file("/tmp/mtab", file, mount_flags,
174				   mtpt, mtlen);
175	if (retval == 0)
176		return 0;
177#endif /* DEBUG */
178#ifdef __linux__
179	retval = check_mntent_file("/proc/mounts", file, mount_flags,
180				   mtpt, mtlen);
181	if (retval == 0 && (*mount_flags != 0))
182		return 0;
183#endif /* __linux__ */
184#if defined(MOUNTED) || defined(_PATH_MOUNTED)
185#ifndef MOUNTED
186#define MOUNTED _PATH_MOUNTED
187#endif /* MOUNTED */
188	retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
189	return retval;
190#else
191	*mount_flags = 0;
192	return 0;
193#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
194}
195
196#else
197#if defined(HAVE_GETMNTINFO)
198
199static errcode_t check_getmntinfo(const char *file, int *mount_flags,
200				  char *mtpt, int mtlen)
201{
202	struct statfs *mp;
203        int    len, n;
204        const  char   *s1;
205	char	*s2;
206
207        n = getmntinfo(&mp, MNT_NOWAIT);
208        if (n == 0)
209		return errno;
210
211        len = sizeof(_PATH_DEV) - 1;
212        s1 = file;
213        if (strncmp(_PATH_DEV, s1, len) == 0)
214                s1 += len;
215
216	*mount_flags = 0;
217        while (--n >= 0) {
218                s2 = mp->f_mntfromname;
219                if (strncmp(_PATH_DEV, s2, len) == 0) {
220                        s2 += len - 1;
221                        *s2 = 'r';
222                }
223                if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
224			*mount_flags = EXT2_MF_MOUNTED;
225			break;
226		}
227                ++mp;
228	}
229	if (mtpt)
230		strncpy(mtpt, mp->f_mntonname, mtlen);
231	return 0;
232}
233#endif /* HAVE_GETMNTINFO */
234#endif /* HAVE_SETMNTENT */
235
236/*
237 * Check to see if we're dealing with the swap device.
238 */
239static int is_swap_device(const char *file)
240{
241	FILE		*f;
242	char		buf[1024], *cp;
243	dev_t		file_dev;
244	struct stat	st_buf;
245	int		ret = 0;
246
247	file_dev = 0;
248#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
249	if ((stat(file, &st_buf) == 0) &&
250	    S_ISBLK(st_buf.st_mode))
251		file_dev = st_buf.st_rdev;
252#endif	/* __GNU__ */
253
254	if (!(f = fopen("/proc/swaps", "r")))
255		return 0;
256	/* Skip the first line */
257	if (!fgets(buf, sizeof(buf), f))
258		goto leave;
259	if (*buf && strncmp(buf, "Filename\t", 9))
260		/* Linux <=2.6.19 contained a bug in the /proc/swaps
261		 * code where the header would not be displayed
262		 */
263		goto valid_first_line;
264
265	while (fgets(buf, sizeof(buf), f)) {
266valid_first_line:
267		if ((cp = strchr(buf, ' ')) != NULL)
268			*cp = 0;
269		if ((cp = strchr(buf, '\t')) != NULL)
270			*cp = 0;
271		if (strcmp(buf, file) == 0) {
272			ret++;
273			break;
274		}
275#ifndef __GNU__
276		if (file_dev && (stat(buf, &st_buf) == 0) &&
277		    S_ISBLK(st_buf.st_mode) &&
278		    file_dev == st_buf.st_rdev) {
279			ret++;
280			break;
281		}
282#endif 	/* __GNU__ */
283	}
284
285leave:
286	fclose(f);
287	return ret;
288}
289
290
291/*
292 * ext2fs_check_mount_point() fills determines if the device is
293 * mounted or otherwise busy, and fills in mount_flags with one or
294 * more of the following flags: EXT2_MF_MOUNTED, EXT2_MF_ISROOT,
295 * EXT2_MF_READONLY, EXT2_MF_SWAP, and EXT2_MF_BUSY.  If mtpt is
296 * non-NULL, the directory where the device is mounted is copied to
297 * where mtpt is pointing, up to mtlen characters.
298 */
299#ifdef __TURBOC__
300 #pragma argsused
301#endif
302errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
303				  char *mtpt, int mtlen)
304{
305	errcode_t	retval = 0;
306
307	if (is_swap_device(device)) {
308		*mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
309		strncpy(mtpt, "<swap>", mtlen);
310	} else {
311#ifdef HAVE_SETMNTENT
312		retval = check_mntent(device, mount_flags, mtpt, mtlen);
313#else
314#ifdef HAVE_GETMNTINFO
315		retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
316#else
317#ifdef __GNUC__
318 #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
319#endif
320		*mount_flags = 0;
321#endif /* HAVE_GETMNTINFO */
322#endif /* HAVE_SETMNTENT */
323	}
324	if (retval)
325		return retval;
326
327#ifdef __linux__ /* This only works on Linux 2.6+ systems */
328	{
329		struct stat st_buf;
330
331		if (stat(device, &st_buf) == 0 && S_ISBLK(st_buf.st_mode)) {
332			int fd = open(device, O_RDONLY | O_EXCL);
333
334			if (fd >= 0)
335				close(fd);
336			else if (errno == EBUSY)
337				*mount_flags |= EXT2_MF_BUSY;
338		}
339	}
340#endif
341
342	return 0;
343}
344
345/*
346 * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
347 * EXT2_MF_READONLY, and EXT2_MF_ROOT
348 *
349 */
350errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
351{
352	return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
353}
354
355#ifdef DEBUG
356int main(int argc, char **argv)
357{
358	int	retval, mount_flags;
359	char	mntpt[80];
360
361	if (argc < 2) {
362		fprintf(stderr, "Usage: %s device\n", argv[0]);
363		exit(1);
364	}
365
366	add_error_table(&et_ext2_error_table);
367	mntpt[0] = 0;
368	retval = ext2fs_check_mount_point(argv[1], &mount_flags,
369					  mntpt, sizeof(mntpt));
370	if (retval) {
371		com_err(argv[0], retval,
372			"while calling ext2fs_check_if_mounted");
373		exit(1);
374	}
375	printf("Device %s reports flags %02x\n", argv[1], mount_flags);
376	if (mount_flags & EXT2_MF_BUSY)
377		printf("\t%s is apparently in use.\n", argv[1]);
378	if (mount_flags & EXT2_MF_MOUNTED)
379		printf("\t%s is mounted.\n", argv[1]);
380	if (mount_flags & EXT2_MF_SWAP)
381		printf("\t%s is a swap device.\n", argv[1]);
382	if (mount_flags & EXT2_MF_READONLY)
383		printf("\t%s is read-only.\n", argv[1]);
384	if (mount_flags & EXT2_MF_ISROOT)
385		printf("\t%s is the root filesystem.\n", argv[1]);
386	if (mntpt[0])
387		printf("\t%s is mounted on %s.\n", argv[1], mntpt);
388	exit(0);
389}
390#endif /* DEBUG */
391