/* 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 GPL version 2, see file LICENSE in this tarball for details.
 */

#include <mntent.h>
#include "libbb.h"

#if defined(__dietlibc__)
/* 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 -d -t -i */
#define OPTION_STRING           "fldnra" "vdt:i"
#define OPT_FORCE               (1 << 0)
#define OPT_LAZY                (1 << 1)
#define OPT_FREELOOP            (1 << 2)
#define OPT_NO_MTAB             (1 << 3)
#define OPT_REMOUNT             (1 << 4)
#define OPT_ALL                 (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 5) : 0)

// These constants from linux/fs.h must match OPT_FORCE and OPT_LAZY,
// otherwise "doForce" trick below won't work!
//#define MNT_FORCE  0x00000001 /* Attempt to forcibly umount */
//#define MNT_DETACH 0x00000002 /* Just detach from the tree */

int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int umount_main(int argc UNUSED_PARAM, char **argv)
{
        int doForce;
        char *const path = xmalloc(PATH_MAX + 2); /* to save stack */
        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;
        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, path, PATH_MAX)) {
                        /* 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;

                // 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;
                // Use command line argument (and look it up in mtab list)
                else {
                        if (!zapit)
                                break;
                        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 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_FREELOOP) && 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)
                        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;
                }
                free(path);
        }

        return status;
}