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