lib/ext2fs/ismounted.c

   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_LINUX_LOOP_H
  25 #include <linux/loop.h>
  26 #include <sys/ioctl.h>
  27 #ifdef HAVE_LINUX_MAJOR_H
  28 #include <linux/major.h>
  29 #endif /* HAVE_LINUX_MAJOR_H */
  30 #endif /* HAVE_LINUX_LOOP_H */
  31 #ifdef HAVE_MNTENT_H
  32 #include <mntent.h>
  33 #endif
  34 #ifdef HAVE_GETMNTINFO
  35 #include <paths.h>
  36 #include <sys/param.h>
  37 #include <sys/mount.h>
  38 #endif /* HAVE_GETMNTINFO */
  39 #include <string.h>
  40 #include <sys/stat.h>
  41
  42 #include "ext2_fs.h"
  43 #include "ext2fs.h"
  44
  45 #ifdef HAVE_SETMNTENT
  46 /*
  47  * Check to see if a regular file is mounted.
  48  * If /etc/mtab/ is a symlink of /proc/mounts, you will need the following check
  49  * because the name in /proc/mounts is a loopback device not a regular file.
  50  */
  51 static int check_loop_mounted(const char *mnt_fsname, dev_t mnt_rdev,
  52                                 dev_t file_dev, ino_t file_ino)
  53 {
  54 #if defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H)
  55         struct loop_info64 loopinfo;
  56         int loop_fd, ret;
  57
  58         if (major(mnt_rdev) == LOOP_MAJOR) {
  59                 loop_fd = open(mnt_fsname, O_RDONLY);
  60                 if (loop_fd < 0)
  61                         return -1;
  62
  63                 ret = ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo);
  64                 close(loop_fd);
  65                 if (ret < 0)
  66                         return -1;
  67
  68                 if (file_dev == loopinfo.lo_device &&
  69                                 file_ino == loopinfo.lo_inode)
  70                         return 1;
  71         }
  72 #endif /* defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H) */
  73         return 0;
  74 }
  75
  76 /*
  77  * Helper function which checks a file in /etc/mtab format to see if a
  78  * filesystem is mounted.  Returns an error if the file doesn't exist
  79  * or can't be opened.
  80  */
  81 static errcode_t check_mntent_file(const char *mtab_file, const char *file,
  82                                    int *mount_flags, char *mtpt, int mtlen)
  83 {
  84         struct mntent   *mnt;
  85         struct stat     st_buf;
  86         errcode_t       retval = 0;
  87         dev_t           file_dev=0, file_rdev=0;
  88         ino_t           file_ino=0;
  89         FILE            *f;
  90         int             fd;
  91
  92         *mount_flags = 0;
  93         if ((f = setmntent (mtab_file, "r")) == NULL) {
  94                 if (errno == ENOENT) {
  95                         if (getenv("EXT2FS_NO_MTAB_OK"))
  96                                 return 0;
  97                         else
  98                                 return EXT2_ET_NO_MTAB_FILE;
  99                 }
 100                 return errno;
 101         }
 102         if (stat(file, &st_buf) == 0) {
 103                 if (S_ISBLK(st_buf.st_mode)) {
 104 #ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
 105                         file_rdev = st_buf.st_rdev;
 106 #endif  /* __GNU__ */
 107                 } else {
 108                         file_dev = st_buf.st_dev;
 109                         file_ino = st_buf.st_ino;
 110                 }
 111         }
 112         while ((mnt = getmntent (f)) != NULL) {
 113                 if (mnt->mnt_fsname[0] != '/')
 114                         continue;
 115                 if (strcmp(file, mnt->mnt_fsname) == 0)
 116                         break;
 117                 if (stat(mnt->mnt_fsname, &st_buf) == 0) {
 118                         if (S_ISBLK(st_buf.st_mode)) {
 119 #ifndef __GNU__
 120                                 if (file_rdev && (file_rdev == st_buf.st_rdev))
 121                                         break;
 122                                 if (check_loop_mounted(mnt->mnt_fsname,
 123                                                 st_buf.st_rdev, file_dev,
 124                                                 file_ino) == 1)
 125                                         break;
 126 #endif  /* __GNU__ */
 127                         } else {
 128                                 if (file_dev && ((file_dev == st_buf.st_dev) &&
 129                                                  (file_ino == st_buf.st_ino)))
 130                                         break;
 131                         }
 132                 }
 133         }
 134
 135         if (mnt == 0) {
 136 #ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
 137                 /*
 138                  * Do an extra check to see if this is the root device.  We
 139                  * can't trust /etc/mtab, and /proc/mounts will only list
 140                  * /dev/root for the root filesystem.  Argh.  Instead we
 141                  * check if the given device has the same major/minor number
 142                  * as the device that the root directory is on.
 143                  */
 144                 if (file_rdev && stat("/", &st_buf) == 0) {
 145                         if (st_buf.st_dev == file_rdev) {
 146                                 *mount_flags = EXT2_MF_MOUNTED;
 147                                 if (mtpt)
 148                                         strncpy(mtpt, "/", mtlen);
 149                                 goto is_root;
 150                         }
 151                 }
 152 #endif  /* __GNU__ */
 153                 goto errout;
 154         }
 155 #ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
 156         /* Validate the entry in case /etc/mtab is out of date */
 157         /*
 158          * We need to be paranoid, because some broken distributions
 159          * (read: Slackware) don't initialize /etc/mtab before checking
 160          * all of the non-root filesystems on the disk.
 161          */
 162         if (stat(mnt->mnt_dir, &st_buf) < 0) {
 163                 retval = errno;
 164                 if (retval == ENOENT) {
 165 #ifdef DEBUG
 166                         printf("Bogus entry in %s!  (%s does not exist)\n",
 167                                mtab_file, mnt->mnt_dir);
 168 #endif /* DEBUG */
 169                         retval = 0;
 170                 }
 171                 goto errout;
 172         }
 173         if (file_rdev && (st_buf.st_dev != file_rdev)) {
 174 #ifdef DEBUG
 175                 printf("Bogus entry in %s!  (%s not mounted on %s)\n",
 176                        mtab_file, file, mnt->mnt_dir);
 177 #endif /* DEBUG */
 178                 goto errout;
 179         }
 180 #endif /* __GNU__ */
 181         *mount_flags = EXT2_MF_MOUNTED;
 182
 183 #ifdef MNTOPT_RO
 184         /* Check to see if the ro option is set */
 185         if (hasmntopt(mnt, MNTOPT_RO))
 186                 *mount_flags |= EXT2_MF_READONLY;
 187 #endif
 188
 189         if (mtpt)
 190                 strncpy(mtpt, mnt->mnt_dir, mtlen);
 191         /*
 192          * Check to see if we're referring to the root filesystem.
 193          * If so, do a manual check to see if we can open /etc/mtab
 194          * read/write, since if the root is mounted read/only, the
 195          * contents of /etc/mtab may not be accurate.
 196          */
 197         if (!strcmp(mnt->mnt_dir, "/")) {
 198 is_root:
 199 #define TEST_FILE "/.ismount-test-file"
 200                 *mount_flags |= EXT2_MF_ISROOT;
 201                 fd = open(TEST_FILE, O_RDWR|O_CREAT, 0600);
 202                 if (fd < 0) {
 203                         if (errno == EROFS)
 204                                 *mount_flags |= EXT2_MF_READONLY;
 205                 } else
 206                         close(fd);
 207                 (void) unlink(TEST_FILE);
 208         }
 209         retval = 0;
 210 errout:
 211         endmntent (f);
 212         return retval;
 213 }
 214
 215 static errcode_t check_mntent(const char *file, int *mount_flags,
 216                               char *mtpt, int mtlen)
 217 {
 218         errcode_t       retval;
 219
 220 #ifdef DEBUG
 221         retval = check_mntent_file("/tmp/mtab", file, mount_flags,
 222                                    mtpt, mtlen);
 223         if (retval == 0)
 224                 return 0;
 225 #endif /* DEBUG */
 226 #ifdef __linux__
 227         retval = check_mntent_file("/proc/mounts", file, mount_flags,
 228                                    mtpt, mtlen);
 229         if (retval == 0 && (*mount_flags != 0))
 230                 return 0;
 231 #endif /* __linux__ */
 232 #if defined(MOUNTED) || defined(_PATH_MOUNTED)
 233 #ifndef MOUNTED
 234 #define MOUNTED _PATH_MOUNTED
 235 #endif /* MOUNTED */
 236         retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
 237         return retval;
 238 #else
 239         *mount_flags = 0;
 240         return 0;
 241 #endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
 242 }
 243
 244 #else
 245 #if defined(HAVE_GETMNTINFO)
 246
 247 static errcode_t check_getmntinfo(const char *file, int *mount_flags,
 248                                   char *mtpt, int mtlen)
 249 {
 250         struct statfs *mp;
 251         int    len, n;
 252         const  char   *s1;
 253         char    *s2;
 254
 255         n = getmntinfo(&mp, MNT_NOWAIT);
 256         if (n == 0)
 257                 return errno;
 258
 259         len = sizeof(_PATH_DEV) - 1;
 260         s1 = file;
 261         if (strncmp(_PATH_DEV, s1, len) == 0)
 262                 s1 += len;
 263
 264         *mount_flags = 0;
 265         while (--n >= 0) {
 266                 s2 = mp->f_mntfromname;
 267                 if (strncmp(_PATH_DEV, s2, len) == 0) {
 268                         s2 += len - 1;
 269                         *s2 = 'r';
 270                 }
 271                 if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
 272                         *mount_flags = EXT2_MF_MOUNTED;
 273                         break;
 274                 }
 275                 ++mp;
 276         }
 277         if (mtpt)
 278                 strncpy(mtpt, mp->f_mntonname, mtlen);
 279         return 0;
 280 }
 281 #endif /* HAVE_GETMNTINFO */
 282 #endif /* HAVE_SETMNTENT */
 283
 284 /*
 285  * Check to see if we're dealing with the swap device.
 286  */
 287 static int is_swap_device(const char *file)
 288 {
 289         FILE            *f;
 290         char            buf[1024], *cp;
 291         dev_t           file_dev;
 292         struct stat     st_buf;
 293         int             ret = 0;
 294
 295         file_dev = 0;
 296 #ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
 297         if ((stat(file, &st_buf) == 0) &&
 298             S_ISBLK(st_buf.st_mode))
 299                 file_dev = st_buf.st_rdev;
 300 #endif  /* __GNU__ */
 301
 302         if (!(f = fopen("/proc/swaps", "r")))
 303                 return 0;
 304         /* Skip the first line */
 305         if (!fgets(buf, sizeof(buf), f))
 306                 goto leave;
 307         if (*buf && strncmp(buf, "Filename\t", 9))
 308                 /* Linux <=2.6.19 contained a bug in the /proc/swaps
 309                  * code where the header would not be displayed
 310                  */
 311                 goto valid_first_line;
 312
 313         while (fgets(buf, sizeof(buf), f)) {
 314 valid_first_line:
 315                 if ((cp = strchr(buf, ' ')) != NULL)
 316                         *cp = 0;
 317                 if ((cp = strchr(buf, '\t')) != NULL)
 318                         *cp = 0;
 319                 if (strcmp(buf, file) == 0) {
 320                         ret++;
 321                         break;
 322                 }
 323 #ifndef __GNU__
 324                 if (file_dev && (stat(buf, &st_buf) == 0) &&
 325                     S_ISBLK(st_buf.st_mode) &&
 326                     file_dev == st_buf.st_rdev) {
 327                         ret++;
 328                         break;
 329                 }
 330 #endif  /* __GNU__ */
 331         }
 332
 333 leave:
 334         fclose(f);
 335         return ret;
 336 }
 337
 338
 339 /*
 340  * ext2fs_check_mount_point() fills determines if the device is
 341  * mounted or otherwise busy, and fills in mount_flags with one or
 342  * more of the following flags: EXT2_MF_MOUNTED, EXT2_MF_ISROOT,
 343  * EXT2_MF_READONLY, EXT2_MF_SWAP, and EXT2_MF_BUSY.  If mtpt is
 344  * non-NULL, the directory where the device is mounted is copied to
 345  * where mtpt is pointing, up to mtlen characters.
 346  */
 347 #ifdef __TURBOC__
 348  #pragma argsused
 349 #endif
 350 errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
 351                                   char *mtpt, int mtlen)
 352 {
 353         errcode_t       retval = 0;
 354
 355         if (is_swap_device(device)) {
 356                 *mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
 357                 strncpy(mtpt, "<swap>", mtlen);
 358         } else {
 359 #ifdef HAVE_SETMNTENT
 360                 retval = check_mntent(device, mount_flags, mtpt, mtlen);
 361 #else
 362 #ifdef HAVE_GETMNTINFO
 363                 retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
 364 #else
 365 #ifdef __GNUC__
 366  #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
 367 #endif
 368                 *mount_flags = 0;
 369 #endif /* HAVE_GETMNTINFO */
 370 #endif /* HAVE_SETMNTENT */
 371         }
 372         if (retval)
 373                 return retval;
 374
 375 #ifdef __linux__ /* This only works on Linux 2.6+ systems */
 376         {
 377                 struct stat st_buf;
 378
 379                 if (stat(device, &st_buf) == 0 && S_ISBLK(st_buf.st_mode)) {
 380                         int fd = open(device, O_RDONLY | O_EXCL);
 381
 382                         if (fd >= 0)
 383                                 close(fd);
 384                         else if (errno == EBUSY)
 385                                 *mount_flags |= EXT2_MF_BUSY;
 386                 }
 387         }
 388 #endif
 389
 390         return 0;
 391 }
 392
 393 /*
 394  * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
 395  * EXT2_MF_READONLY, and EXT2_MF_ROOT
 396  *
 397  */
 398 errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
 399 {
 400         return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
 401 }
 402
 403 #ifdef DEBUG
 404 int main(int argc, char **argv)
 405 {
 406         int     retval, mount_flags;
 407         char    mntpt[80];
 408
 409         if (argc < 2) {
 410                 fprintf(stderr, "Usage: %s device\n", argv[0]);
 411                 exit(1);
 412         }
 413
 414         add_error_table(&et_ext2_error_table);
 415         mntpt[0] = 0;
 416         retval = ext2fs_check_mount_point(argv[1], &mount_flags,
 417                                           mntpt, sizeof(mntpt));
 418         if (retval) {
 419                 com_err(argv[0], retval,
 420                         "while calling ext2fs_check_if_mounted");
 421                 exit(1);
 422         }
 423         printf("Device %s reports flags %02x\n", argv[1], mount_flags);
 424         if (mount_flags & EXT2_MF_BUSY)
 425                 printf("\t%s is apparently in use.\n", argv[1]);
 426         if (mount_flags & EXT2_MF_MOUNTED)
 427                 printf("\t%s is mounted.\n", argv[1]);
 428         if (mount_flags & EXT2_MF_SWAP)
 429                 printf("\t%s is a swap device.\n", argv[1]);
 430         if (mount_flags & EXT2_MF_READONLY)
 431                 printf("\t%s is read-only.\n", argv[1]);
 432         if (mount_flags & EXT2_MF_ISROOT)
 433                 printf("\t%s is the root filesystem.\n", argv[1]);
 434         if (mntpt[0])
 435                 printf("\t%s is mounted on %s.\n", argv[1], mntpt);
 436         exit(0);
 437 }
 438 #endif /* DEBUG */