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snapshot.c revision 1.2 
      1 /*	$NetBSD: snapshot.c,v 1.2 2005/04/19 08:10:43 hannken Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2005 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Juergen Hannken-Illjes.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the NetBSD
     21  *	Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/param.h>
     40 #include <sys/ioctl.h>
     41 #include <sys/mount.h>
     42 #include <sys/stat.h>
     43 
     44 #include <dev/fssvar.h>
     45 
     46 #include <errno.h>
     47 #include <fcntl.h>
     48 #include <stdio.h>
     49 #include <stdlib.h>
     50 #include <unistd.h>
     51 
     52 #include "snapshot.h"
     53 
     54 /*
     55  * Create a snapshot of the file system currently mounted on the first argument
     56  * using the second argument as backing store and return an open file
     57  * descriptor for the snapshot.  If the second argument is NULL, use the first
     58  * as backing store.  If the third argument is not NULL, it gets the time the
     59  * snapshot was created.
     60  */
     61 int
     62 snap_open(char *mountpoint, char *backup, time_t *snap_date)
     63 {
     64 	int i, fd, israw, fsinternal, dounlink, flags;
     65 	char path[MAXPATHLEN], fss_dev[14];
     66 	dev_t mountdev;
     67 	struct fss_set fss;
     68 	struct fss_get fsg;
     69 	struct stat sb;
     70 	struct statvfs fsb;
     71 
     72 	dounlink = 0;
     73 	fd = -1;
     74 
     75 	fss.fss_mount = mountpoint;
     76 	fss.fss_bstore = backup ? backup : fss.fss_mount;
     77 	fss.fss_csize = 0;
     78 
     79 	if (stat(fss.fss_mount, &sb) < 0)
     80 		goto fail;
     81 	mountdev = sb.st_dev;
     82 
     83 	/*
     84 	 * Prepare the backing store. `backup' is either a raw device,
     85 	 * a file or a directory.  If it is a file, it must not exist.
     86 	 */
     87 	israw = 0;
     88 	if (stat(fss.fss_bstore, &sb) == 0) {
     89 		if (S_ISDIR(sb.st_mode)) {
     90 			snprintf(path, sizeof(path),
     91 			    "%s/XXXXXXXXXX", fss.fss_bstore);
     92 			fd = mkstemp(path);
     93 			fss.fss_bstore = path;
     94 			dounlink = 1;
     95 		} else if (S_ISCHR(sb.st_mode)) {
     96 			fd = open(fss.fss_bstore, O_RDWR);
     97 			israw = 1;
     98 		} else
     99 			goto fail;
    100 	} else {
    101 		fd = open(fss.fss_bstore, O_CREAT|O_EXCL|O_WRONLY, 0600);
    102 		dounlink = 1;
    103 	}
    104 	if (fd < 0)
    105 		goto fail;
    106 
    107 	if (fstat(fd, &sb) < 0)
    108 		goto fail;
    109 	fsinternal = (!israw && sb.st_dev == mountdev);
    110 
    111 	/*
    112 	 * If the backing store is a plain file and the snapshot
    113 	 * is not file system internal, truncate to file system
    114 	 * free space.
    115 	 */
    116 	if (!israw && !fsinternal) {
    117 		if (statvfs(fss.fss_bstore, &fsb) < 0)
    118 			goto fail;
    119 		if (ftruncate(fd, (off_t)fsb.f_frsize*fsb.f_bavail) < 0)
    120 			goto fail;
    121 	}
    122 
    123 	if (close(fd) < 0)
    124 		goto fail;
    125 
    126 	/*
    127 	 * Create the snapshot on the first free snapshot device.
    128 	 */
    129 	for (i = 0; ; i++) {
    130 		snprintf(fss_dev, sizeof(fss_dev), "/dev/rfss%d", i);
    131 		if ((fd = open(fss_dev, O_RDWR, 0)) < 0)
    132 			goto fail;
    133 
    134 		if (ioctl(fd, FSSIOFGET, &flags) < 0)
    135 			goto fail;
    136 
    137 		if (ioctl(fd, FSSIOCSET, &fss) < 0) {
    138 			if (errno != EBUSY)
    139 				goto fail;
    140 			close(fd);
    141 			fd = -1;
    142 			continue;
    143 		}
    144 
    145 		flags |= FSS_UNCONFIG_ON_CLOSE;
    146 		if (ioctl(fd, FSSIOCGET, &fsg) < 0 ||
    147 		    ioctl(fd, FSSIOFSET, &flags) < 0 ||
    148 		    (!israw && unlink(fss.fss_bstore) < 0)) {
    149 			ioctl(fd, FSSIOCCLR);
    150 			goto fail;
    151 		}
    152 
    153 		if (snap_date != NULL)
    154 			*snap_date = fsg.fsg_time.tv_sec;
    155 		return fd;
    156 	}
    157 
    158 fail:
    159 	if (dounlink)
    160 		unlink(fss.fss_bstore);
    161 	if (fd >= 0)
    162 		close(fd);
    163 
    164 	return -1;
    165 }
    166