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 GPL version 2, see file LICENSE in this tarball for details.
9 */
10
11#include <mntent.h>
12#include <getopt.h>
13#include "libbb.h"
14
15#define OPTION_STRING		"flDnravdt:"
16#define OPT_FORCE			1
17#define OPT_LAZY			2
18#define OPT_DONTFREELOOP	4
19#define OPT_NO_MTAB			8
20#define OPT_REMOUNT			16
21#define OPT_ALL				(ENABLE_FEATURE_UMOUNT_ALL ? 32 : 0)
22
23int umount_main(int argc, char **argv);
24int umount_main(int argc, char **argv)
25{
26	int doForce;
27	char path[2*PATH_MAX];
28	struct mntent me;
29	FILE *fp;
30	char *fstype = 0;
31	int status = EXIT_SUCCESS;
32	unsigned opt;
33	struct mtab_list {
34		char *dir;
35		char *device;
36		struct mtab_list *next;
37	} *mtl, *m;
38
39	/* Parse any options */
40
41	opt = getopt32(argv, OPTION_STRING, &fstype);
42
43	argc -= optind;
44	argv += optind;
45
46	doForce = MAX((opt & OPT_FORCE), (opt & OPT_LAZY));
47
48	/* Get a list of mount points from mtab.  We read them all in now mostly
49	 * for umount -a (so we don't have to worry about the list changing while
50	 * we iterate over it, or about getting stuck in a loop on the same failing
51	 * entry.  Notice that this also naturally reverses the list so that -a
52	 * umounts the most recent entries first. */
53
54	m = mtl = 0;
55
56	/* If we're umounting all, then m points to the start of the list and
57	 * the argument list should be empty (which will match all). */
58
59	fp = setmntent(bb_path_mtab_file, "r");
60	if (!fp) {
61		if (opt & OPT_ALL)
62			bb_error_msg_and_die("cannot open %s", bb_path_mtab_file);
63	} else {
64		while (getmntent_r(fp, &me, path, sizeof(path))) {
65			/* Match fstype if passed */
66			if (fstype && match_fstype(&me, fstype))
67				continue;
68			m = xmalloc(sizeof(struct mtab_list));
69			m->next = mtl;
70			m->device = xstrdup(me.mnt_fsname);
71			m->dir = xstrdup(me.mnt_dir);
72			mtl = m;
73		}
74		endmntent(fp);
75	}
76
77	/* If we're not umounting all, we need at least one argument. */
78	if (!(opt & OPT_ALL) && !fstype) {
79		m = 0;
80		if (!argc) bb_show_usage();
81	}
82
83	// Loop through everything we're supposed to umount, and do so.
84	for (;;) {
85		int curstat;
86		char *zapit = *argv;
87
88		// Do we already know what to umount this time through the loop?
89		if (m) safe_strncpy(path, m->dir, PATH_MAX);
90		// For umount -a, end of mtab means time to exit.
91		else if (opt & OPT_ALL) break;
92		// Get next command line argument (and look it up in mtab list)
93		else if (!argc--) break;
94		else {
95			argv++;
96			realpath(zapit, path);
97			for (m = mtl; m; m = m->next)
98				if (!strcmp(path, m->dir) || !strcmp(path, m->device))
99					break;
100		}
101		// If we couldn't find this sucker in /etc/mtab, punt by passing our
102		// command line argument straight to the umount syscall.  Otherwise,
103		// umount the directory even if we were given the block device.
104		if (m) zapit = m->dir;
105
106		// Let's ask the thing nicely to unmount.
107		curstat = umount(zapit);
108
109		// Force the unmount, if necessary.
110		if (curstat && doForce) {
111			curstat = umount2(zapit, doForce);
112			if (curstat)
113				bb_error_msg("forced umount of %s failed!", zapit);
114		}
115
116		// If still can't umount, maybe remount read-only?
117		if (curstat && (opt & OPT_REMOUNT) && errno == EBUSY && m) {
118			curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL);
119			bb_error_msg(curstat ? "cannot remount %s read-only" :
120						 "%s busy - remounted read-only", m->device);
121		}
122
123		if (curstat) {
124			status = EXIT_FAILURE;
125			bb_perror_msg("cannot umount %s", zapit);
126		} else {
127			/* De-allocate the loop device.  This ioctl should be ignored on
128			 * any non-loop block devices. */
129			if (ENABLE_FEATURE_MOUNT_LOOP && !(opt & OPT_DONTFREELOOP) && m)
130				del_loop(m->device);
131			if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
132				erase_mtab(m->dir);
133		}
134
135		// Find next matching mtab entry for -a or umount /dev
136		// Note this means that "umount /dev/blah" will unmount all instances
137		// of /dev/blah, not just the most recent.
138		while (m && (m = m->next))
139			if ((opt & OPT_ALL) || !strcmp(path, m->device))
140				break;
141	}
142
143	// Free mtab list if necessary
144
145	if (ENABLE_FEATURE_CLEAN_UP) {
146		while (mtl) {
147			m = mtl->next;
148			free(mtl->device);
149			free(mtl->dir);
150			free(mtl);
151			mtl = m;
152		}
153	}
154
155	return status;
156}
157