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
  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 */
  20struct 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}
  70