1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Mini umount implementation for busybox
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4 | *
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5 | * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
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6 | * Copyright (C) 2005 by Rob Landley <rob@landley.net>
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7 | *
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8 | * Licensed under GPLv2, see file LICENSE in this source tree.
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9 | */
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10 |
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11 | //usage:#define umount_trivial_usage
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12 | //usage: "[OPTIONS] FILESYSTEM|DIRECTORY"
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13 | //usage:#define umount_full_usage "\n\n"
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14 | //usage: "Unmount file systems\n"
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15 | //usage: IF_FEATURE_UMOUNT_ALL(
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16 | //usage: "\n -a Unmount all file systems" IF_FEATURE_MTAB_SUPPORT(" in /etc/mtab")
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17 | //usage: )
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18 | //usage: IF_FEATURE_MTAB_SUPPORT(
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19 | //usage: "\n -n Don't erase /etc/mtab entries"
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20 | //usage: )
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21 | //usage: "\n -r Try to remount devices as read-only if mount is busy"
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22 | //usage: "\n -l Lazy umount (detach filesystem)"
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23 | //usage: "\n -f Force umount (i.e., unreachable NFS server)"
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24 | //usage: IF_FEATURE_MOUNT_LOOP(
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25 | //usage: "\n -D Don't free loop device even if it has been used"
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26 | //usage: )
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27 | //usage:
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28 | //usage:#define umount_example_usage
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29 | //usage: "$ umount /dev/hdc1\n"
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30 |
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31 | #include <mntent.h>
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32 | #include <sys/mount.h>
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33 | #ifndef MNT_DETACH
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34 | # define MNT_DETACH 0x00000002
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35 | #endif
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36 | #include "libbb.h"
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37 | #include "common_bufsiz.h"
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38 |
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39 | #if defined(__dietlibc__)
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40 | // TODO: This does not belong here.
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41 | /* 16.12.2006, Sampo Kellomaki (sampo@iki.fi)
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42 | * dietlibc-0.30 does not have implementation of getmntent_r() */
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43 | static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
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44 | char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM)
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45 | {
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46 | struct mntent* ment = getmntent(stream);
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47 | return memcpy(result, ment, sizeof(*ment));
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48 | }
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49 | #endif
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50 |
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51 | /* Ignored: -v -t -i
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52 | * bbox always acts as if -d is present.
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53 | * -D can be used to suppress it (bbox extension).
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54 | * Rationale:
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55 | * (1) util-linux's umount does it if "loop=..." is seen in /etc/mtab:
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56 | * thus, on many systems, bare umount _does_ drop loop devices.
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57 | * (2) many users request this feature.
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58 | */
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59 | #define OPTION_STRING "fldDnra" "vt:i"
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60 | #define OPT_FORCE (1 << 0) // Same as MNT_FORCE
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61 | #define OPT_LAZY (1 << 1) // Same as MNT_DETACH
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62 | //#define OPT_FREE_LOOP (1 << 2) // -d is assumed always present
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63 | #define OPT_DONT_FREE_LOOP (1 << 3)
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64 | #define OPT_NO_MTAB (1 << 4)
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65 | #define OPT_REMOUNT (1 << 5)
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66 | #define OPT_ALL (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 6) : 0)
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67 |
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68 | int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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69 | int umount_main(int argc UNUSED_PARAM, char **argv)
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70 | {
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71 | int doForce;
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72 | struct mntent me;
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73 | FILE *fp;
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74 | char *fstype = NULL;
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75 | int status = EXIT_SUCCESS;
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76 | unsigned opt;
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77 | struct mtab_list {
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78 | char *dir;
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79 | char *device;
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80 | struct mtab_list *next;
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81 | } *mtl, *m;
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82 |
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83 | opt = getopt32(argv, OPTION_STRING, &fstype);
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84 | //argc -= optind;
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85 | argv += optind;
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86 |
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87 | // MNT_FORCE and MNT_DETACH (from linux/fs.h) must match
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88 | // OPT_FORCE and OPT_LAZY.
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89 | BUILD_BUG_ON(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH);
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90 | doForce = opt & (OPT_FORCE|OPT_LAZY);
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91 |
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92 | /* Get a list of mount points from mtab. We read them all in now mostly
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93 | * for umount -a (so we don't have to worry about the list changing while
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94 | * we iterate over it, or about getting stuck in a loop on the same failing
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95 | * entry. Notice that this also naturally reverses the list so that -a
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96 | * umounts the most recent entries first. */
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97 | m = mtl = NULL;
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98 |
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99 | // If we're umounting all, then m points to the start of the list and
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100 | // the argument list should be empty (which will match all).
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101 | fp = setmntent(bb_path_mtab_file, "r");
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102 | if (!fp) {
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103 | if (opt & OPT_ALL)
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104 | bb_error_msg_and_die("can't open '%s'", bb_path_mtab_file);
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105 | } else {
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106 | setup_common_bufsiz();
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107 | while (getmntent_r(fp, &me, bb_common_bufsiz1, COMMON_BUFSIZE)) {
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108 | /* Match fstype if passed */
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109 | if (!match_fstype(&me, fstype))
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110 | continue;
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111 | m = xzalloc(sizeof(*m));
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112 | m->next = mtl;
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113 | m->device = xstrdup(me.mnt_fsname);
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114 | m->dir = xstrdup(me.mnt_dir);
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115 | mtl = m;
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116 | }
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117 | endmntent(fp);
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118 | }
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119 |
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120 | // If we're not umounting all, we need at least one argument.
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121 | if (!(opt & OPT_ALL) && !fstype) {
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122 | if (!argv[0])
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123 | bb_show_usage();
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124 | m = NULL;
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125 | }
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126 |
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127 | // Loop through everything we're supposed to umount, and do so.
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128 | for (;;) {
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129 | int curstat;
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130 | char *zapit = *argv;
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131 | char *path;
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132 |
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133 | // Do we already know what to umount this time through the loop?
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134 | if (m)
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135 | path = xstrdup(m->dir);
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136 | // For umount -a, end of mtab means time to exit.
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137 | else if (opt & OPT_ALL)
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138 | break;
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139 | // Use command line argument (and look it up in mtab list)
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140 | else {
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141 | if (!zapit)
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142 | break;
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143 | argv++;
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144 | path = xmalloc_realpath(zapit);
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145 | if (path) {
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146 | for (m = mtl; m; m = m->next)
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147 | if (strcmp(path, m->dir) == 0 || strcmp(path, m->device) == 0)
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148 | break;
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149 | }
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150 | }
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151 | // If we couldn't find this sucker in /etc/mtab, punt by passing our
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152 | // command line argument straight to the umount syscall. Otherwise,
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153 | // umount the directory even if we were given the block device.
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154 | if (m) zapit = m->dir;
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155 |
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156 | // umount from util-linux 2.22.2 does not do this:
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157 | // umount -f uses umount2(MNT_FORCE) immediately,
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158 | // not trying umount() first.
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159 | // (Strangely, umount -fl ignores -f: it is equivalent to umount -l.
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160 | // We do pass both flags in this case)
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161 | #if 0
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162 | // Let's ask the thing nicely to unmount.
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163 | curstat = umount(zapit);
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164 |
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165 | // Unmount with force and/or lazy flags, if necessary.
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166 | if (curstat && doForce)
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167 | #endif
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168 | curstat = umount2(zapit, doForce);
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169 |
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170 | // If still can't umount, maybe remount read-only?
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171 | if (curstat) {
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172 | if ((opt & OPT_REMOUNT) && errno == EBUSY && m) {
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173 | // Note! Even if we succeed here, later we should not
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174 | // free loop device or erase mtab entry!
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175 | const char *msg = "%s busy - remounted read-only";
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176 | curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL);
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177 | if (curstat) {
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178 | msg = "can't remount %s read-only";
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179 | status = EXIT_FAILURE;
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180 | }
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181 | bb_error_msg(msg, m->device);
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182 | } else {
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183 | status = EXIT_FAILURE;
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184 | bb_perror_msg("can't unmount %s", zapit);
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185 | }
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186 | } else {
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187 | // De-allocate the loop device. This ioctl should be ignored on
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188 | // any non-loop block devices.
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189 | if (ENABLE_FEATURE_MOUNT_LOOP && !(opt & OPT_DONT_FREE_LOOP) && m)
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190 | del_loop(m->device);
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191 | if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
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192 | erase_mtab(m->dir);
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193 | }
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194 |
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195 | // Find next matching mtab entry for -a or umount /dev
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196 | // Note this means that "umount /dev/blah" will unmount all instances
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197 | // of /dev/blah, not just the most recent.
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198 | if (m) {
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199 | while ((m = m->next) != NULL)
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200 | // NB: if m is non-NULL, path is non-NULL as well
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201 | if ((opt & OPT_ALL) || strcmp(path, m->device) == 0)
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202 | break;
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203 | }
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204 | free(path);
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205 | }
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206 |
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207 | // Free mtab list if necessary
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208 | if (ENABLE_FEATURE_CLEAN_UP) {
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209 | while (mtl) {
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210 | m = mtl->next;
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211 | free(mtl->device);
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212 | free(mtl->dir);
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213 | free(mtl);
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214 | mtl = m;
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215 | }
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216 | }
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217 |
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218 | return status;
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219 | }
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