LXR busybox/libbb/find_mount

   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#include "libbb.h"
  10#include <mntent.h>
  11
  12/*
  13 * Given a block device, find the mount table entry if that block device
  14 * is mounted.
  15 *
  16 * Given any other file (or directory), find the mount table entry for its
  17 * filesystem.
  18 */
  19struct mntent* FAST_FUNC find_mount_point(const char *name, int subdir_too)
  20{
  21        struct stat s;
  22        FILE *mtab_fp;
  23        struct mntent *mountEntry;
  24        dev_t devno_of_name;
  25        bool block_dev;
  26
  27        if (stat(name, &s) != 0)
  28                return NULL;
  29
  30        devno_of_name = s.st_dev;
  31        block_dev = 0;
  32        /* Why S_ISCHR? - UBI volumes use char devices, not block */
  33        if (S_ISBLK(s.st_mode) || S_ISCHR(s.st_mode)) {
  34                devno_of_name = s.st_rdev;
  35                block_dev = 1;
  36        }
  37
  38        mtab_fp = setmntent(bb_path_mtab_file, "r");
  39        if (!mtab_fp)
  40                return NULL;
  41
  42        while ((mountEntry = getmntent(mtab_fp)) != NULL) {
  43                /* rootfs mount in Linux 2.6 exists always,
  44                 * and it makes sense to always ignore it.
  45                 * Otherwise people can't reference their "real" root! */
  46                if (ENABLE_FEATURE_SKIP_ROOTFS && strcmp(mountEntry->mnt_fsname, "rootfs") == 0)
  47                        continue;
  48
  49                if (strcmp(name, mountEntry->mnt_dir) == 0
  50                 || strcmp(name, mountEntry->mnt_fsname) == 0
  51                ) { /* String match. */
  52                        break;
  53                }
  54
  55                if (!(subdir_too || block_dev))
  56                        continue;
  57
  58                /* Is device's dev_t == name's dev_t? */
  59                if (mountEntry->mnt_fsname[0] == '/'
  60                /* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  61                 * avoid stat'ing "sysfs", "proc", "none" and such,
  62                 * useless at best, can stat unrelated files at worst.
  63                 */
  64                 && stat(mountEntry->mnt_fsname, &s) == 0
  65                 && s.st_rdev == devno_of_name
  66                ) {
  67                        break;
  68                }
  69                /* Match the directory's mount point. */
  70                if (stat(mountEntry->mnt_dir, &s) == 0
  71                 && s.st_dev == devno_of_name
  72                ) {
  73                        break;
  74                }
  75        }
  76        endmntent(mtab_fp);
  77
  78        return mountEntry;
  79}
  80