1 /* vi: set sw=4 ts=4: */
2 /*
3 * Mini umount implementation for busybox
4 *
5 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
6 * Copyright (C) 2005 by Rob Landley <rob@landley.net>
7 *
8 * Licensed under GPLv2, see file LICENSE in this source tree.
9 */
10 //config:config UMOUNT
11 //config: bool "umount"
12 //config: default y
13 //config: select PLATFORM_LINUX
14 //config: help
15 //config: When you want to remove a mounted filesystem from its current mount
16 //config: point, for example when you are shutting down the system, the
17 //config: 'umount' utility is the tool to use. If you enabled the 'mount'
18 //config: utility, you almost certainly also want to enable 'umount'.
19 //config:
20 //config:config FEATURE_UMOUNT_ALL
21 //config: bool "Support option -a"
22 //config: default y
23 //config: depends on UMOUNT
24 //config: help
25 //config: Support -a option to unmount all currently mounted filesystems.
26
27 //applet:IF_UMOUNT(APPLET(umount, BB_DIR_BIN, BB_SUID_DROP))
28
29 //kbuild:lib-$(CONFIG_UMOUNT) += umount.o
30
31 //usage:#define umount_trivial_usage
32 //usage: "[OPTIONS] FILESYSTEM|DIRECTORY"
33 //usage:#define umount_full_usage "\n\n"
34 //usage: "Unmount file systems\n"
35 //usage: IF_FEATURE_UMOUNT_ALL(
36 //usage: "\n -a Unmount all file systems" IF_FEATURE_MTAB_SUPPORT(" in /etc/mtab")
37 //usage: )
38 //usage: IF_FEATURE_MTAB_SUPPORT(
39 //usage: "\n -n Don't erase /etc/mtab entries"
40 //usage: )
41 //usage: "\n -r Try to remount devices as read-only if mount is busy"
42 //usage: "\n -l Lazy umount (detach filesystem)"
43 //usage: "\n -f Force umount (i.e., unreachable NFS server)"
44 //usage: IF_FEATURE_MOUNT_LOOP(
45 //usage: "\n -D Don't free loop device even if it has been used"
46 //usage: )
47 //usage:
48 //usage:#define umount_example_usage
49 //usage: "$ umount /dev/hdc1\n"
50
51 #include <mntent.h>
52 #include <sys/mount.h>
53 #ifndef MNT_DETACH
54 # define MNT_DETACH 0x00000002
55 #endif
56 #include "libbb.h"
57 #include "common_bufsiz.h"
58
59 #if defined(__dietlibc__)
60 // TODO: This does not belong here.
61 /* 16.12.2006, Sampo Kellomaki (sampo@iki.fi)
62 * dietlibc-0.30 does not have implementation of getmntent_r() */
getmntent_r(FILE * stream,struct mntent * result,char * buffer UNUSED_PARAM,int bufsize UNUSED_PARAM)63 static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
64 char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM)
65 {
66 struct mntent* ment = getmntent(stream);
67 return memcpy(result, ment, sizeof(*ment));
68 }
69 #endif
70
71 /* Ignored: -v -t -i
72 * bbox always acts as if -d is present.
73 * -D can be used to suppress it (bbox extension).
74 * Rationale:
75 * (1) util-linux's umount does it if "loop=..." is seen in /etc/mtab:
76 * thus, on many systems, bare umount _does_ drop loop devices.
77 * (2) many users request this feature.
78 */
79 #define OPTION_STRING "fldDnra" "vt:i"
80 #define OPT_FORCE (1 << 0) // Same as MNT_FORCE
81 #define OPT_LAZY (1 << 1) // Same as MNT_DETACH
82 //#define OPT_FREE_LOOP (1 << 2) // -d is assumed always present
83 #define OPT_DONT_FREE_LOOP (1 << 3)
84 #define OPT_NO_MTAB (1 << 4)
85 #define OPT_REMOUNT (1 << 5)
86 #define OPT_ALL (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 6) : 0)
87
88 int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
umount_main(int argc UNUSED_PARAM,char ** argv)89 int umount_main(int argc UNUSED_PARAM, char **argv)
90 {
91 int doForce;
92 struct mntent me;
93 FILE *fp;
94 char *fstype = NULL;
95 int status = EXIT_SUCCESS;
96 unsigned opt;
97 struct mtab_list {
98 char *dir;
99 char *device;
100 struct mtab_list *next;
101 } *mtl, *m;
102
103 opt = getopt32(argv, OPTION_STRING, &fstype);
104 //argc -= optind;
105 argv += optind;
106
107 // MNT_FORCE and MNT_DETACH (from linux/fs.h) must match
108 // OPT_FORCE and OPT_LAZY.
109 BUILD_BUG_ON(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH);
110 doForce = opt & (OPT_FORCE|OPT_LAZY);
111
112 /* Get a list of mount points from mtab. We read them all in now mostly
113 * for umount -a (so we don't have to worry about the list changing while
114 * we iterate over it, or about getting stuck in a loop on the same failing
115 * entry. Notice that this also naturally reverses the list so that -a
116 * umounts the most recent entries first. */
117 m = mtl = NULL;
118
119 // If we're umounting all, then m points to the start of the list and
120 // the argument list should be empty (which will match all).
121 fp = setmntent(bb_path_mtab_file, "r");
122 if (!fp) {
123 if (opt & OPT_ALL)
124 bb_error_msg_and_die("can't open '%s'", bb_path_mtab_file);
125 } else {
126 setup_common_bufsiz();
127 while (getmntent_r(fp, &me, bb_common_bufsiz1, COMMON_BUFSIZE)) {
128 /* Match fstype if passed */
129 if (!match_fstype(&me, fstype))
130 continue;
131 m = xzalloc(sizeof(*m));
132 m->next = mtl;
133 m->device = xstrdup(me.mnt_fsname);
134 m->dir = xstrdup(me.mnt_dir);
135 mtl = m;
136 }
137 endmntent(fp);
138 }
139
140 // If we're not umounting all, we need at least one argument.
141 if (!(opt & OPT_ALL) && !fstype) {
142 if (!argv[0])
143 bb_show_usage();
144 m = NULL;
145 }
146
147 // Loop through everything we're supposed to umount, and do so.
148 for (;;) {
149 int curstat;
150 char *zapit = *argv;
151 char *path;
152
153 // Do we already know what to umount this time through the loop?
154 if (m)
155 path = xstrdup(m->dir);
156 // For umount -a, end of mtab means time to exit.
157 else if (opt & OPT_ALL)
158 break;
159 // Use command line argument (and look it up in mtab list)
160 else {
161 if (!zapit)
162 break;
163 argv++;
164 path = xmalloc_realpath(zapit);
165 if (path) {
166 for (m = mtl; m; m = m->next)
167 if (strcmp(path, m->dir) == 0 || strcmp(path, m->device) == 0)
168 break;
169 }
170 }
171 // If we couldn't find this sucker in /etc/mtab, punt by passing our
172 // command line argument straight to the umount syscall. Otherwise,
173 // umount the directory even if we were given the block device.
174 if (m) zapit = m->dir;
175
176 // umount from util-linux 2.22.2 does not do this:
177 // umount -f uses umount2(MNT_FORCE) immediately,
178 // not trying umount() first.
179 // (Strangely, umount -fl ignores -f: it is equivalent to umount -l.
180 // We do pass both flags in this case)
181 #if 0
182 // Let's ask the thing nicely to unmount.
183 curstat = umount(zapit);
184
185 // Unmount with force and/or lazy flags, if necessary.
186 if (curstat && doForce)
187 #endif
188 curstat = umount2(zapit, doForce);
189
190 // If still can't umount, maybe remount read-only?
191 if (curstat) {
192 if ((opt & OPT_REMOUNT) && errno == EBUSY && m) {
193 // Note! Even if we succeed here, later we should not
194 // free loop device or erase mtab entry!
195 const char *msg = "%s busy - remounted read-only";
196 curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL);
197 if (curstat) {
198 msg = "can't remount %s read-only";
199 status = EXIT_FAILURE;
200 }
201 bb_error_msg(msg, m->device);
202 } else {
203 status = EXIT_FAILURE;
204 bb_perror_msg("can't unmount %s", zapit);
205 }
206 } else {
207 // De-allocate the loop device. This ioctl should be ignored on
208 // any non-loop block devices.
209 if (ENABLE_FEATURE_MOUNT_LOOP && !(opt & OPT_DONT_FREE_LOOP) && m)
210 del_loop(m->device);
211 if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
212 erase_mtab(m->dir);
213 }
214
215 // Find next matching mtab entry for -a or umount /dev
216 // Note this means that "umount /dev/blah" will unmount all instances
217 // of /dev/blah, not just the most recent.
218 if (m) {
219 while ((m = m->next) != NULL)
220 // NB: if m is non-NULL, path is non-NULL as well
221 if ((opt & OPT_ALL) || strcmp(path, m->device) == 0)
222 break;
223 }
224 free(path);
225 }
226
227 // Free mtab list if necessary
228 if (ENABLE_FEATURE_CLEAN_UP) {
229 while (mtl) {
230 m = mtl->next;
231 free(mtl->device);
232 free(mtl->dir);
233 free(mtl);
234 mtl = m;
235 }
236 }
237
238 return status;
239 }
240