/*      $NetBSD: snapshot.c,v 1.7 2019/02/03 12:17:14 mrg Exp $ */

/*-
 * Copyright (c) 2005 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Juergen Hannken-Illjes.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/stat.h>

#include <dev/fssvar.h>

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "snapshot.h"

/*
 * Create a snapshot of the file system currently mounted on the first argument
 * using the second argument as backing store and return an open file
 * descriptor for the snapshot.  If the second argument is NULL, use the first
 * as backing store.  If the third argument is not NULL, it gets the time the
 * snapshot was created.  If the fourth argument is not NULL, it gets the
 * snapshot device path.
 */
int
snap_open(char *file, char *backup, time_t *snap_date, char **snap_dev)
{
        int i, n, fd, israw, fsinternal, dounlink;
        char path[MAXPATHLEN], fss_dev[20], *cp;
        dev_t mountdev;
        struct fss_set fss;
        struct fss_get fsg;
        struct stat sb;
        struct statvfs *mntbuf, *fs, fsb;

        dounlink = 0;
        fd = -1;
        mntbuf = NULL;

        /*
         * Lookup the mount point. `file' is either a directory or a raw
         * character device.
         */
        if (lstat(file, &sb) < 0)
                goto fail;
        fss.fss_mount = NULL;
        if (S_ISCHR(sb.st_mode)) {
                if ((cp = strrchr(file, '/')) == NULL || cp[1] != 'r') {
                        errno = EINVAL;
                        goto fail;
                }
                snprintf(path, sizeof(path), "%.*s/%s",
                    (int)(cp - file), file, cp + 2);
                n = getmntinfo(&mntbuf, MNT_NOWAIT);
                for (fs = mntbuf, i = 0; i < n; i++, fs++) {
                        if (strcmp(fs->f_mntfromname, path) == 0) {
                                fss.fss_mount = fs->f_mntonname;
                                if (stat(fss.fss_mount, &sb) < 0)
                                        goto fail;
                                break;
                        }
                }
        } else if (S_ISDIR(sb.st_mode))
                fss.fss_mount = file;
        if (fss.fss_mount == NULL) {
                errno = EINVAL;
                goto fail;
        }
        fss.fss_bstore = backup ? backup : fss.fss_mount;
        fss.fss_csize = 0;
        mountdev = sb.st_dev;

        /*
         * Prepare the backing store. `backup' is either a raw device,
         * a file or a directory.  If it is a file, it must not exist.
         */
        israw = 0;
        if (stat(fss.fss_bstore, &sb) == 0) {
                if (S_ISDIR(sb.st_mode)) {
                        snprintf(path, sizeof(path),
                            "%s/XXXXXXXXXX", fss.fss_bstore);
                        fd = mkstemp(path);
                        fss.fss_bstore = path;
                        dounlink = 1;
                } else if (S_ISCHR(sb.st_mode)) {
                        fd = open(fss.fss_bstore, O_RDWR);
                        israw = 1;
                } else
                        goto fail;
        } else {
                fd = open(fss.fss_bstore, O_CREAT|O_EXCL|O_WRONLY, 0600);
                dounlink = 1;
        }
        if (fd < 0)
                goto fail;

        if (fstat(fd, &sb) < 0)
                goto fail;
        fsinternal = (!israw && sb.st_dev == mountdev);

        /*
         * If the backing store is a plain file and the snapshot
         * is not file system internal, truncate to file system
         * free space.
         */
        if (!israw && !fsinternal) {
                if (statvfs(fss.fss_bstore, &fsb) < 0)
                        goto fail;
                if (ftruncate(fd, (off_t)fsb.f_frsize*fsb.f_bavail) < 0)
                        goto fail;
        }

        if (close(fd) < 0)
                goto fail;

        fss.fss_flags = FSS_UNCONFIG_ON_CLOSE;
        if (dounlink)
                fss.fss_flags |= FSS_UNLINK_ON_CREATE;
        /*
         * Create the snapshot on the first free snapshot device.
         */
        for (i = 0; ; i++) {
                snprintf(fss_dev, sizeof(fss_dev), "/dev/rfss%d", i);
                if ((fd = open(fss_dev, O_RDWR, 0)) < 0)
                        goto fail;

                if (ioctl(fd, FSSIOCSET, &fss) < 0) {
                        if (errno != EBUSY)
                                goto fail;
                        close(fd);
                        fd = -1;
                        continue;
                }
                dounlink = 0;

                if (snap_dev != NULL) {
                        *snap_dev = strdup(fss_dev);
                        if (*snap_dev == NULL) {
                                ioctl(fd, FSSIOCCLR);
                                goto fail;
                        }
                }

                if (ioctl(fd, FSSIOCGET, &fsg) < 0) {
                        ioctl(fd, FSSIOCCLR);
                        goto fail;
                }

                if (mntbuf)
                        free(mntbuf);
                if (snap_date != NULL)
                        *snap_date = fsg.fsg_time.tv_sec;
                return fd;
        }

fail:
        if (mntbuf)
                free(mntbuf);
        if (dounlink)
                unlink(fss.fss_bstore);
        if (fd >= 0)
                close(fd);

        return -1;
}