/* 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.
 */
//config:config UMOUNT
//config:       bool "umount (5.1 kb)"
//config:       default y
//config:       help
//config:       When you want to remove a mounted filesystem from its current mount
//config:       point, for example when you are shutting down the system, the
//config:       'umount' utility is the tool to use. If you enabled the 'mount'
//config:       utility, you almost certainly also want to enable 'umount'.
//config:
//config:config FEATURE_UMOUNT_ALL
//config:       bool "Support -a (unmount all)"
//config:       default y
//config:       depends on UMOUNT
//config:       help
//config:       Support -a option to unmount all currently mounted filesystems.

//applet:IF_UMOUNT(APPLET_NOEXEC(umount, umount, BB_DIR_BIN, BB_SUID_DROP, umount))
/*
 * On one hand, in some weird situations you'd want umount
 * to not do anything surprising, to behave as a usual fork+execed executable.
 *
 * OTOH, there can be situations where execing would not succeed, or even hang
 * (say, if executable is on a filesystem which is in trouble and accesses to it
 * block in kernel).
 * In this case, you might be actually happy if your standalone bbox shell
 * does not fork+exec, but only forks and calls umount_main() which it already has!
 * Let's go with NOEXEC.
 *
 * bb_common_bufsiz1 usage here is safe wrt NOEXEC: not expecting it to be zeroed.
 */

//kbuild:lib-$(CONFIG_UMOUNT) += umount.o

//usage:#define umount_trivial_usage
//usage:       "[-rlf"IF_FEATURE_MTAB_SUPPORT("m")IF_FEATURE_MOUNT_LOOP("d")IF_FEATURE_UMOUNT_ALL("a")"] [-t FSTYPE] FILESYSTEM|DIRECTORY"
//usage:#define umount_full_usage "\n\n"
//usage:       "Unmount filesystems\n"
//usage:        IF_FEATURE_UMOUNT_ALL(
//usage:     "\n        -a      Unmount all filesystems" 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      Remount devices 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      Free loop device if it has been used"
//usage:        )
//usage:     "\n        -t FSTYPE[,...] Unmount only these filesystem type(s)"
//usage:
//usage:#define umount_example_usage
//usage:       "$ umount /dev/hdc1\n"

#include <mntent.h>
#include <sys/mount.h>
#ifndef MNT_DETACH
# define MNT_DETACH 0x00000002
#endif
#include "libbb.h"
#include "common_bufsiz.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: -c -v -i */
#define OPTION_STRING           "fldnrat:" "cvi"
#define OPT_FORCE               (1 << 0) // Same as MNT_FORCE
#define OPT_LAZY                (1 << 1) // Same as MNT_DETACH
#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)

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.
        BUILD_BUG_ON(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH);
        doForce = opt & (OPT_FORCE|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 {
                setup_common_bufsiz();
                while (getmntent_r(fp, &me, bb_common_bufsiz1, COMMON_BUFSIZE)) {
                        /* Match fstype (fstype==NULL matches always) */
                        if (!fstype_matches(me.mnt_type, 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.
        // Note: "-t FSTYPE" does not imply -a.
        if (!(opt & OPT_ALL)) {
                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;

// umount from util-linux 2.22.2 does not do this:
// umount -f uses umount2(MNT_FORCE) immediately,
// not trying umount() first.
// (Strangely, umount -fl ignores -f: it is equivalent to umount -l.
// We do pass both flags in this case)
#if 0
                // Let's ask the thing nicely to unmount.
                curstat = umount(zapit);

                // Unmount with force and/or lazy flags, if necessary.
                if (curstat && doForce)
#endif
                        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 unmount %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_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)
                                // 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;
}