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 (5.1 kb)" 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 -a (unmount all)" 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_NOEXEC(umount, umount, BB_DIR_BIN, BB_SUID_DROP, umount)) 28/* 29 * On one hand, in some weird situations you'd want umount 30 * to not do anything surprising, to behave as a usual fork+execed executable. 31 * 32 * OTOH, there can be situations where execing would not succeed, or even hang 33 * (say, if executable is on a filesystem which is in trouble and accesses to it 34 * block in kernel). 35 * In this case, you might be actually happy if your standalone bbox shell 36 * does not fork+exec, but only forks and calls umount_main() which it already has! 37 * Let's go with NOEXEC. 38 * 39 * bb_common_bufsiz1 usage here is safe wrt NOEXEC: not expecting it to be zeroed. 40 */ 41 42//kbuild:lib-$(CONFIG_UMOUNT) += umount.o 43 44//usage:#define umount_trivial_usage 45//usage: "[OPTIONS] FILESYSTEM|DIRECTORY" 46//usage:#define umount_full_usage "\n\n" 47//usage: "Unmount file systems\n" 48//usage: IF_FEATURE_UMOUNT_ALL( 49//usage: "\n -a Unmount all file systems" IF_FEATURE_MTAB_SUPPORT(" in /etc/mtab") 50//usage: ) 51//usage: IF_FEATURE_MTAB_SUPPORT( 52//usage: "\n -n Don't erase /etc/mtab entries" 53//usage: ) 54//usage: "\n -r Try to remount devices as read-only if mount is busy" 55//usage: "\n -l Lazy umount (detach filesystem)" 56//usage: "\n -f Force umount (i.e., unreachable NFS server)" 57//usage: IF_FEATURE_MOUNT_LOOP( 58//usage: "\n -d Free loop device if it has been used" 59//usage: ) 60//usage: "\n -t FSTYPE[,...] Unmount only these filesystem type(s)" 61//usage: 62//usage:#define umount_example_usage 63//usage: "$ umount /dev/hdc1\n" 64 65#include <mntent.h> 66#include <sys/mount.h> 67#ifndef MNT_DETACH 68# define MNT_DETACH 0x00000002 69#endif 70#include "libbb.h" 71#include "common_bufsiz.h" 72 73#if defined(__dietlibc__) 74// TODO: This does not belong here. 75/* 16.12.2006, Sampo Kellomaki (sampo@iki.fi) 76 * dietlibc-0.30 does not have implementation of getmntent_r() */ 77static struct mntent *getmntent_r(FILE* stream, struct mntent* result, 78 char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM) 79{ 80 struct mntent* ment = getmntent(stream); 81 return memcpy(result, ment, sizeof(*ment)); 82} 83#endif 84 85/* ignored: -c -v -i */ 86#define OPTION_STRING "fldnrat:" "cvi" 87#define OPT_FORCE (1 << 0) // Same as MNT_FORCE 88#define OPT_LAZY (1 << 1) // Same as MNT_DETACH 89#define OPT_FREELOOP (1 << 2) 90#define OPT_NO_MTAB (1 << 3) 91#define OPT_REMOUNT (1 << 4) 92#define OPT_ALL (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 5) : 0) 93 94int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; 95int umount_main(int argc UNUSED_PARAM, char **argv) 96{ 97 int doForce; 98 struct mntent me; 99 FILE *fp; 100 char *fstype = NULL; 101 int status = EXIT_SUCCESS; 102 unsigned opt; 103 struct mtab_list { 104 char *dir; 105 char *device; 106 struct mtab_list *next; 107 } *mtl, *m; 108 109 opt = getopt32(argv, OPTION_STRING, &fstype); 110 //argc -= optind; 111 argv += optind; 112 113 // MNT_FORCE and MNT_DETACH (from linux/fs.h) must match 114 // OPT_FORCE and OPT_LAZY. 115 BUILD_BUG_ON(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH); 116 doForce = opt & (OPT_FORCE|OPT_LAZY); 117 118 /* Get a list of mount points from mtab. We read them all in now mostly 119 * for umount -a (so we don't have to worry about the list changing while 120 * we iterate over it, or about getting stuck in a loop on the same failing 121 * entry. Notice that this also naturally reverses the list so that -a 122 * umounts the most recent entries first. */ 123 m = mtl = NULL; 124 125 // If we're umounting all, then m points to the start of the list and 126 // the argument list should be empty (which will match all). 127 fp = setmntent(bb_path_mtab_file, "r"); 128 if (!fp) { 129 if (opt & OPT_ALL) 130 bb_error_msg_and_die("can't open '%s'", bb_path_mtab_file); 131 } else { 132 setup_common_bufsiz(); 133 while (getmntent_r(fp, &me, bb_common_bufsiz1, COMMON_BUFSIZE)) { 134 /* Match fstype (fstype==NULL matches always) */ 135 if (!fstype_matches(me.mnt_type, fstype)) 136 continue; 137 m = xzalloc(sizeof(*m)); 138 m->next = mtl; 139 m->device = xstrdup(me.mnt_fsname); 140 m->dir = xstrdup(me.mnt_dir); 141 mtl = m; 142 } 143 endmntent(fp); 144 } 145 146 // If we're not umounting all, we need at least one argument. 147 // Note: "-t FSTYPE" does not imply -a. 148 if (!(opt & OPT_ALL)) { 149 if (!argv[0]) 150 bb_show_usage(); 151 m = NULL; 152 } 153 154 // Loop through everything we're supposed to umount, and do so. 155 for (;;) { 156 int curstat; 157 char *zapit = *argv; 158 char *path; 159 160 // Do we already know what to umount this time through the loop? 161 if (m) 162 path = xstrdup(m->dir); 163 // For umount -a, end of mtab means time to exit. 164 else if (opt & OPT_ALL) 165 break; 166 // Use command line argument (and look it up in mtab list) 167 else { 168 if (!zapit) 169 break; 170 argv++; 171 path = xmalloc_realpath(zapit); 172 if (path) { 173 for (m = mtl; m; m = m->next) 174 if (strcmp(path, m->dir) == 0 || strcmp(path, m->device) == 0) 175 break; 176 } 177 } 178 // If we couldn't find this sucker in /etc/mtab, punt by passing our 179 // command line argument straight to the umount syscall. Otherwise, 180 // umount the directory even if we were given the block device. 181 if (m) zapit = m->dir; 182 183// umount from util-linux 2.22.2 does not do this: 184// umount -f uses umount2(MNT_FORCE) immediately, 185// not trying umount() first. 186// (Strangely, umount -fl ignores -f: it is equivalent to umount -l. 187// We do pass both flags in this case) 188#if 0 189 // Let's ask the thing nicely to unmount. 190 curstat = umount(zapit); 191 192 // Unmount with force and/or lazy flags, if necessary. 193 if (curstat && doForce) 194#endif 195 curstat = umount2(zapit, doForce); 196 197 // If still can't umount, maybe remount read-only? 198 if (curstat) { 199 if ((opt & OPT_REMOUNT) && errno == EBUSY && m) { 200 // Note! Even if we succeed here, later we should not 201 // free loop device or erase mtab entry! 202 const char *msg = "%s busy - remounted read-only"; 203 curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL); 204 if (curstat) { 205 msg = "can't remount %s read-only"; 206 status = EXIT_FAILURE; 207 } 208 bb_error_msg(msg, m->device); 209 } else { 210 status = EXIT_FAILURE; 211 bb_perror_msg("can't unmount %s", zapit); 212 } 213 } else { 214 // De-allocate the loop device. This ioctl should be ignored on 215 // any non-loop block devices. 216 if (ENABLE_FEATURE_MOUNT_LOOP && (opt & OPT_FREELOOP) && m) 217 del_loop(m->device); 218 if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m) 219 erase_mtab(m->dir); 220 } 221 222 // Find next matching mtab entry for -a or umount /dev 223 // Note this means that "umount /dev/blah" will unmount all instances 224 // of /dev/blah, not just the most recent. 225 if (m) { 226 while ((m = m->next) != NULL) 227 // NB: if m is non-NULL, path is non-NULL as well 228 if ((opt & OPT_ALL) || strcmp(path, m->device) == 0) 229 break; 230 } 231 free(path); 232 } 233 234 // Free mtab list if necessary 235 if (ENABLE_FEATURE_CLEAN_UP) { 236 while (mtl) { 237 m = mtl->next; 238 free(mtl->device); 239 free(mtl->dir); 240 free(mtl); 241 mtl = m; 242 } 243 } 244 245 return status; 246} 247