release/src/router/busybox/libbb/find_mount_point.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9
  10 #include "libbb.h"
  11 #include <mntent.h>
  12
  13 /*
  14  * Given a block device, find the mount table entry if that block device
  15  * is mounted.
  16  *
  17  * Given any other file (or directory), find the mount table entry for its
  18  * filesystem.
  19  */
  20 struct mntent* FAST_FUNC find_mount_point(const char *name, int subdir_too)
  21 {
  22         struct stat s;
  23         FILE *mtab_fp;
  24         struct mntent *mountEntry;
  25         dev_t devno_of_name;
  26         bool block_dev;
  27
  28         if (stat(name, &s) != 0)
  29                 return NULL;
  30
  31         devno_of_name = s.st_dev;
  32         block_dev = 0;
  33         /* Why S_ISCHR? - UBI volumes use char devices, not block */
  34         if (S_ISBLK(s.st_mode) || S_ISCHR(s.st_mode)) {
  35                 devno_of_name = s.st_rdev;
  36                 block_dev = 1;
  37         }
  38
  39         mtab_fp = setmntent(bb_path_mtab_file, "r");
  40         if (!mtab_fp)
  41                 return NULL;
  42
  43         while ((mountEntry = getmntent(mtab_fp)) != NULL) {
  44                 /* rootfs mount in Linux 2.6 exists always,
  45                  * and it makes sense to always ignore it.
  46                  * Otherwise people can't reference their "real" root! */
  47                 if (ENABLE_FEATURE_SKIP_ROOTFS && strcmp(mountEntry->mnt_fsname, "rootfs") == 0)
  48                         continue;
  49
  50                 if (strcmp(name, mountEntry->mnt_dir) == 0
  51                  || strcmp(name, mountEntry->mnt_fsname) == 0
  52                 ) { /* String match. */
  53                         break;
  54                 }
  55
  56                 if (!(subdir_too || block_dev))
  57                         continue;
  58
  59                 /* Is device's dev_t == name's dev_t? */
  60                 if (stat(mountEntry->mnt_fsname, &s) == 0 && s.st_rdev == devno_of_name)
  61                         break;
  62                 /* Match the directory's mount point. */
  63                 if (stat(mountEntry->mnt_dir, &s) == 0 && s.st_dev == devno_of_name)
  64                         break;
  65         }
  66         endmntent(mtab_fp);
  67
  68         return mountEntry;
  69 }