source: MondoRescue/branches/3.2/mindi-busybox/util-linux/umount.c@ 3232

/* vi: set sw=4 ts=4: */
/*
 * Mini umount implementation for busybox
 *
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 * Copyright (C) 2005 by Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 */

//usage:#define umount_trivial_usage
//usage:       "[OPTIONS] FILESYSTEM|DIRECTORY"
//usage:#define umount_full_usage "\n\n"
//usage:       "Unmount file systems\n"
//usage:    IF_FEATURE_UMOUNT_ALL(
//usage:     "\n    -a  Unmount all file systems" IF_FEATURE_MTAB_SUPPORT(" in /etc/mtab")
//usage:    )
//usage:    IF_FEATURE_MTAB_SUPPORT(
//usage:     "\n    -n  Don't erase /etc/mtab entries"
//usage:    )
//usage:     "\n    -r  Try to remount devices as read-only if mount is busy"
//usage:     "\n    -l  Lazy umount (detach filesystem)"
//usage:     "\n    -f  Force umount (i.e., unreachable NFS server)"
//usage:    IF_FEATURE_MOUNT_LOOP(
//usage:     "\n    -D  Don't free loop device even if it has been used"
//usage:    )
//usage:
//usage:#define umount_example_usage
//usage:       "$ umount /dev/hdc1\n"

#include <mntent.h>
#include <sys/mount.h>
#include "libbb.h"

#if defined(__dietlibc__)
// TODO: This does not belong here.
/* 16.12.2006, Sampo Kellomaki (sampo@iki.fi)
 * dietlibc-0.30 does not have implementation of getmntent_r() */
static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
        char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM)
{
    struct mntent* ment = getmntent(stream);
    return memcpy(result, ment, sizeof(*ment));
}
#endif

/* Ignored: -v -t -i
 * bbox always acts as if -d is present.
 * -D can be used to suppress it (bbox extension).
 * Rationale:
 * (1) util-linux's umount does it if "loop=..." is seen in /etc/mtab:
 * thus, on many systems, bare umount _does_ drop loop devices.
 * (2) many users request this feature.
 */
#define OPTION_STRING           "fldDnra" "vt:i"
#define OPT_FORCE               (1 << 0) // Same as MNT_FORCE
#define OPT_LAZY                (1 << 1) // Same as MNT_DETACH
//#define OPT_FREE_LOOP           (1 << 2) // -d is assumed always present
#define OPT_DONT_FREE_LOOP      (1 << 3)
#define OPT_NO_MTAB             (1 << 4)
#define OPT_REMOUNT             (1 << 5)
#define OPT_ALL                 (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 6) : 0)

int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int umount_main(int argc UNUSED_PARAM, char **argv)
{
    int doForce;
    struct mntent me;
    FILE *fp;
    char *fstype = NULL;
    int status = EXIT_SUCCESS;
    unsigned opt;
    struct mtab_list {
        char *dir;
        char *device;
        struct mtab_list *next;
    } *mtl, *m;

    opt = getopt32(argv, OPTION_STRING, &fstype);
    //argc -= optind;
    argv += optind;

    // MNT_FORCE and MNT_DETACH (from linux/fs.h) must match
    // OPT_FORCE and OPT_LAZY, otherwise this trick won't work:
    doForce = MAX((opt & OPT_FORCE), (opt & OPT_LAZY));

    /* Get a list of mount points from mtab.  We read them all in now mostly
     * for umount -a (so we don't have to worry about the list changing while
     * we iterate over it, or about getting stuck in a loop on the same failing
     * entry.  Notice that this also naturally reverses the list so that -a
     * umounts the most recent entries first. */
    m = mtl = NULL;

    // If we're umounting all, then m points to the start of the list and
    // the argument list should be empty (which will match all).
    fp = setmntent(bb_path_mtab_file, "r");
    if (!fp) {
        if (opt & OPT_ALL)
            bb_error_msg_and_die("can't open '%s'", bb_path_mtab_file);
    } else {
        while (getmntent_r(fp, &me, bb_common_bufsiz1, sizeof(bb_common_bufsiz1))) {
            /* Match fstype if passed */
            if (!match_fstype(&me, fstype))
                continue;
            m = xzalloc(sizeof(*m));
            m->next = mtl;
            m->device = xstrdup(me.mnt_fsname);
            m->dir = xstrdup(me.mnt_dir);
            mtl = m;
        }
        endmntent(fp);
    }

    // If we're not umounting all, we need at least one argument.
    if (!(opt & OPT_ALL) && !fstype) {
        if (!argv[0])
            bb_show_usage();
        m = NULL;
    }

    // Loop through everything we're supposed to umount, and do so.
    for (;;) {
        int curstat;
        char *zapit = *argv;
        char *path;

        // Do we already know what to umount this time through the loop?
        if (m)
            path = xstrdup(m->dir);
        // For umount -a, end of mtab means time to exit.
        else if (opt & OPT_ALL)
            break;
        // Use command line argument (and look it up in mtab list)
        else {
            if (!zapit)
                break;
            argv++;
            path = xmalloc_realpath(zapit);
            if (path) {
                for (m = mtl; m; m = m->next)
                    if (strcmp(path, m->dir) == 0 || strcmp(path, m->device) == 0)
                        break;
            }
        }
        // If we couldn't find this sucker in /etc/mtab, punt by passing our
        // command line argument straight to the umount syscall.  Otherwise,
        // umount the directory even if we were given the block device.
        if (m) zapit = m->dir;

        // Let's ask the thing nicely to unmount.
        curstat = umount(zapit);

        // Force the unmount, if necessary.
        if (curstat && doForce)
            curstat = umount2(zapit, doForce);

        // If still can't umount, maybe remount read-only?
        if (curstat) {
            if ((opt & OPT_REMOUNT) && errno == EBUSY && m) {
                // Note! Even if we succeed here, later we should not
                // free loop device or erase mtab entry!
                const char *msg = "%s busy - remounted read-only";
                curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL);
                if (curstat) {
                    msg = "can't remount %s read-only";
                    status = EXIT_FAILURE;
                }
                bb_error_msg(msg, m->device);
            } else {
                status = EXIT_FAILURE;
                bb_perror_msg("can't %sumount %s", (doForce ? "forcibly " : ""), zapit);
            }
        } else {
            // De-allocate the loop device.  This ioctl should be ignored on
            // any non-loop block devices.
            if (ENABLE_FEATURE_MOUNT_LOOP && !(opt & OPT_DONT_FREE_LOOP) && m)
                del_loop(m->device);
            if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
                erase_mtab(m->dir);
        }

        // Find next matching mtab entry for -a or umount /dev
        // Note this means that "umount /dev/blah" will unmount all instances
        // of /dev/blah, not just the most recent.
        if (m) {
            while ((m = m->next) != NULL)
                // NB: if m is non-NULL, path is non-NULL as well
                if ((opt & OPT_ALL) || strcmp(path, m->device) == 0)
                    break;
        }
        free(path);
    }

    // Free mtab list if necessary
    if (ENABLE_FEATURE_CLEAN_UP) {
        while (mtl) {
            m = mtl->next;
            free(mtl->device);
            free(mtl->dir);
            free(mtl);
            mtl = m;
        }
    }

    return status;
}