/*
* ismounted.c --- Check to see if the filesystem was mounted
*
* Copyright (C) 1995,1996,1997,1998,1999,2000,2008 Theodore Ts'o.
*
* This file may be redistributed under the terms of the GNU Public
* License.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_MNTENT_H
#include <mntent.h>
#endif
#include <string.h>
#include <sys/stat.h>
#include <ctype.h>
#include <sys/param.h>
#ifdef __APPLE__
#include <sys/ucred.h>
#include <sys/mount.h>
#endif
#include "pathnames.h"
#include "ismounted.h"
#include "c.h"
#ifdef __linux__
# include "loopdev.h"
#endif
#ifdef HAVE_MNTENT_H
/*
* Helper function which checks a file in /etc/mtab format to see if a
* filesystem is mounted. Returns an error if the file doesn't exist
* or can't be opened.
*/
static int check_mntent_file(const char *mtab_file, const char *file,
int *mount_flags, char *mtpt, int mtlen)
{
struct mntent *mnt;
struct stat st_buf;
int retval = 0;
dev_t file_dev=0, file_rdev=0;
ino_t file_ino=0;
FILE *f;
int fd;
*mount_flags = 0;
if ((f = setmntent (mtab_file, "r")) == NULL)
return errno;
if (stat(file, &st_buf) == 0) {
if (S_ISBLK(st_buf.st_mode)) {
#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
file_rdev = st_buf.st_rdev;
#endif /* __GNU__ */
} else {
file_dev = st_buf.st_dev;
file_ino = st_buf.st_ino;
}
}
while ((mnt = getmntent (f)) != NULL) {
if (mnt->mnt_fsname[0] != '/')
continue;
if (strcmp(file, mnt->mnt_fsname) == 0)
break;
if (stat(mnt->mnt_fsname, &st_buf) != 0)
continue;
if (S_ISBLK(st_buf.st_mode)) {
#ifndef __GNU__
if (file_rdev && file_rdev == st_buf.st_rdev)
break;
#ifdef __linux__
/* maybe the file is loopdev backing file */
if (file_dev
&& major(st_buf.st_rdev) == LOOPDEV_MAJOR
&& loopdev_is_used(mnt->mnt_fsname, file, 0, 0))
break;
#endif /* __linux__ */
#endif /* __GNU__ */
} else {
if (file_dev && ((file_dev == st_buf.st_dev) &&
(file_ino == st_buf.st_ino)))
break;
}
}
if (mnt == NULL) {
#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
/*
* Do an extra check to see if this is the root device. We
* can't trust /etc/mtab, and /proc/mounts will only list
* /dev/root for the root filesystem. Argh. Instead we
* check if the given device has the same major/minor number
* as the device that the root directory is on.
*/
if (file_rdev && stat("/", &st_buf) == 0 &&
st_buf.st_dev == file_rdev) {
*mount_flags = MF_MOUNTED;
if (mtpt)
strncpy(mtpt, "/", mtlen);
goto is_root;
}
#endif /* __GNU__ */
goto errout;
}
#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
/* Validate the entry in case /etc/mtab is out of date */
/*
* We need to be paranoid, because some broken distributions
* (read: Slackware) don't initialize /etc/mtab before checking
* all of the non-root filesystems on the disk.
*/
if (stat(mnt->mnt_dir, &st_buf) < 0) {
retval = errno;
if (retval == ENOENT) {
#ifdef DEBUG
printf("Bogus entry in %s! (%s does not exist)\n",
mtab_file, mnt->mnt_dir);
#endif /* DEBUG */
retval = 0;
}
goto errout;
}
if (file_rdev && (st_buf.st_dev != file_rdev)) {
#ifdef DEBUG
printf("Bogus entry in %s! (%s not mounted on %s)\n",
mtab_file, file, mnt->mnt_dir);
#endif /* DEBUG */
goto errout;
}
#endif /* __GNU__ */
*mount_flags = MF_MOUNTED;
#ifdef MNTOPT_RO
/* Check to see if the ro option is set */
if (hasmntopt(mnt, MNTOPT_RO))
*mount_flags |= MF_READONLY;
#endif
if (mtpt)
strncpy(mtpt, mnt->mnt_dir, mtlen);
/*
* Check to see if we're referring to the root filesystem.
* If so, do a manual check to see if we can open /etc/mtab
* read/write, since if the root is mounted read/only, the
* contents of /etc/mtab may not be accurate.
*/
if (!strcmp(mnt->mnt_dir, "/")) {
is_root:
#define TEST_FILE "/.ismount-test-file"
*mount_flags |= MF_ISROOT;
fd = open(TEST_FILE, O_RDWR|O_CREAT, 0600);
if (fd < 0) {
if (errno == EROFS)
*mount_flags |= MF_READONLY;
} else
close(fd);
(void) unlink(TEST_FILE);
}
retval = 0;
errout:
endmntent (f);
return retval;
}
static int check_mntent(const char *file, int *mount_flags,
char *mtpt, int mtlen)
{
int retval;
#ifdef DEBUG
retval = check_mntent_file("/tmp/mtab", file, mount_flags,
mtpt, mtlen);
if (retval == 0)
return 0;
#endif /* DEBUG */
#ifdef __linux__
retval = check_mntent_file("/proc/mounts", file, mount_flags,
mtpt, mtlen);
if (retval == 0 && (*mount_flags != 0))
return 0;
if (access("/proc/mounts", R_OK) == 0) {
*mount_flags = 0;
return retval;
}
#endif /* __linux__ */
#if defined(MOUNTED) || defined(_PATH_MOUNTED)
#ifndef MOUNTED
#define MOUNTED _PATH_MOUNTED
#endif /* MOUNTED */
retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
return retval;
#else
*mount_flags = 0;
return 0;
#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
}
#else
#if defined(HAVE_GETMNTINFO)
static int check_getmntinfo(const char *file, int *mount_flags,
char *mtpt, int mtlen)
{
struct statfs *mp;
int len, n;
const char *s1;
char *s2;
n = getmntinfo(&mp, MNT_NOWAIT);
if (n == 0)
return errno;
len = sizeof(_PATH_DEV) - 1;
s1 = file;
if (strncmp(_PATH_DEV, s1, len) == 0)
s1 += len;
*mount_flags = 0;
while (--n >= 0) {
s2 = mp->f_mntfromname;
if (strncmp(_PATH_DEV, s2, len) == 0) {
s2 += len - 1;
*s2 = 'r';
}
if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
*mount_flags = MF_MOUNTED;
break;
}
++mp;
}
if (mtpt)
strncpy(mtpt, mp->f_mntonname, mtlen);
return 0;
}
#endif /* HAVE_GETMNTINFO */
#endif /* HAVE_MNTENT_H */
/*
* Check to see if we're dealing with the swap device.
*/
static int is_swap_device(const char *file)
{
FILE *f;
char buf[1024], *cp;
dev_t file_dev;
struct stat st_buf;
int ret = 0;
file_dev = 0;
#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
if ((stat(file, &st_buf) == 0) &&
S_ISBLK(st_buf.st_mode))
file_dev = st_buf.st_rdev;
#endif /* __GNU__ */
if (!(f = fopen("/proc/swaps", "r")))
return 0;
/* Skip the first line */
if (!fgets(buf, sizeof(buf), f))
goto leave;
if (*buf && strncmp(buf, "Filename\t", 9))
/* Linux <=2.6.19 contained a bug in the /proc/swaps
* code where the header would not be displayed
*/
goto valid_first_line;
while (fgets(buf, sizeof(buf), f)) {
valid_first_line:
if ((cp = strchr(buf, ' ')) != NULL)
*cp = 0;
if ((cp = strchr(buf, '\t')) != NULL)
*cp = 0;
if (strcmp(buf, file) == 0) {
ret++;
break;
}
#ifndef __GNU__
if (file_dev && (stat(buf, &st_buf) == 0) &&
S_ISBLK(st_buf.st_mode) &&
file_dev == st_buf.st_rdev) {
ret++;
break;
}
#endif /* __GNU__ */
}
leave:
fclose(f);
return ret;
}
/*
* check_mount_point() fills determines if the device is mounted or otherwise
* busy, and fills in mount_flags with one or more of the following flags:
* MF_MOUNTED, MF_ISROOT, MF_READONLY, MF_SWAP, and MF_BUSY. If mtpt is
* non-NULL, the directory where the device is mounted is copied to where mtpt
* is pointing, up to mtlen characters.
*/
#ifdef __TURBOC__
#pragma argsused
#endif
int check_mount_point(const char *device, int *mount_flags,
char *mtpt, int mtlen)
{
struct stat st_buf;
int retval = 0;
int fd;
if (is_swap_device(device)) {
*mount_flags = MF_MOUNTED | MF_SWAP;
strncpy(mtpt, "<swap>", mtlen);
} else {
#ifdef HAVE_MNTENT_H
retval = check_mntent(device, mount_flags, mtpt, mtlen);
#else
#ifdef HAVE_GETMNTINFO
retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
#else
#ifdef __GNUC__
#warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
#endif
*mount_flags = 0;
#endif /* HAVE_GETMNTINFO */
#endif /* HAVE_MNTENT_H */
}
if (retval)
return retval;
#ifdef __linux__ /* This only works on Linux 2.6+ systems */
if ((stat(device, &st_buf) != 0) ||
!S_ISBLK(st_buf.st_mode))
return 0;
fd = open(device, O_RDONLY | O_EXCL);
if (fd < 0) {
if (errno == EBUSY)
*mount_flags |= MF_BUSY;
} else
close(fd);
#endif
return 0;
}
int is_mounted(const char *file)
{
int retval;
int mount_flags = 0;
retval = check_mount_point(file, &mount_flags, NULL, 0);
if (retval)
return 0;
return mount_flags & MF_MOUNTED;
}
#ifdef TEST_PROGRAM
int main(int argc, char **argv)
{
int flags = 0;
char devname[PATH_MAX];
if (argc < 2) {
fprintf(stderr, "Usage: %s device\n", argv[0]);
return EXIT_FAILURE;
}
if (check_mount_point(argv[1], &flags, devname, sizeof(devname)) == 0 &&
(flags & MF_MOUNTED)) {
if (flags & MF_SWAP)
printf("used swap device\n");
else
printf("mounted on %s\n", devname);
return EXIT_SUCCESS;
}
printf("not mounted\n");
return EXIT_FAILURE;
}
#endif /* DEBUG */
