source: MondoRescue/branches/stable/mindi-busybox/util-linux/umount.c@ 902

/* 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>
 *
 * This program is licensed under the GNU General Public license (GPL)
 * version 2 or later, see http://www.fsf.org/licensing/licenses/gpl.html
 * or the file "LICENSE" in the busybox source tarball for the full text.
 *
 */

#include "busybox.h"
#include <mntent.h>
#include <errno.h>
#include <getopt.h>

#define OPTION_STRING       "flDnravd"
#define OPT_FORCE           1
#define OPT_LAZY            2
#define OPT_DONTFREELOOP    4
#define OPT_NO_MTAB         8
#define OPT_REMOUNT         16
#define OPT_ALL             (ENABLE_FEATURE_UMOUNT_ALL ? 32 : 0)

int umount_main(int argc, char **argv)
{
    int doForce;
    char path[2*PATH_MAX];
    struct mntent me;
    FILE *fp;
    int status = EXIT_SUCCESS;
    unsigned long opt;
    struct mtab_list {
        char *dir;
        char *device;
        struct mtab_list *next;
    } *mtl, *m;

    /* Parse any options */

    opt = bb_getopt_ulflags(argc, argv, OPTION_STRING);

    argc -= optind;
    argv += optind;

    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 = 0;

    /* 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). */

    if (!(fp = setmntent(bb_path_mtab_file, "r"))) {
        if (opt & OPT_ALL)
            bb_error_msg_and_die("Cannot open %s", bb_path_mtab_file);
    } else while (getmntent_r(fp,&me,path,sizeof(path))) {
        m = xmalloc(sizeof(struct mtab_list));
        m->next = mtl;
        m->device = bb_xstrdup(me.mnt_fsname);
        m->dir = bb_xstrdup(me.mnt_dir);
        mtl = m;
    }
    endmntent(fp);

    /* If we're not mounting all, we need at least one argument. */
    if (!(opt & OPT_ALL)) {
        m = 0;
        if (!argc) bb_show_usage();
    }
    
    // Loop through everything we're supposed to umount, and do so.
    for (;;) {
        int curstat;
        char *zapit = *argv;

        // Do we already know what to umount this time through the loop?
        if (m) safe_strncpy(path, m->dir, PATH_MAX);
        // For umount -a, end of mtab means time to exit.
        else if (opt & OPT_ALL) break;
        // Get next command line argument (and look it up in mtab list)
        else if (!argc--) break;
        else {
            argv++;
            realpath(zapit, path);
            for (m = mtl; m; m = m->next)
                if (!strcmp(path, m->dir) || !strcmp(path, m->device))
                    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 (curstat)
                bb_error_msg_and_die("forced umount of %s failed!", zapit);
        }

        // If still can't umount, maybe remount read-only?
        if (curstat && (opt & OPT_REMOUNT) && errno == EBUSY && m) {
            curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL);
            bb_error_msg(curstat ? "Cannot remount %s read-only" :
                         "%s busy - remounted read-only", m->device);
        }

        if (curstat) {
            status = EXIT_FAILURE;
            bb_perror_msg("Couldn't umount %s", 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_DONTFREELOOP) && 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.
        while (m && (m = m->next))
            if ((opt & OPT_ALL) || !strcmp(path,m->device))
                break;
    }

    // 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;
}