- Move from mount(2) to nmount(2). This should allow to convert MNT_SNAPSHOT

flag from a mount flag to FS-specific flag.
- Simplify usage. Instead of 'mksnap_ffs /mnt/foo /mnt/foo/snap' allow to
  give only one argument: 'mksnap_ffs /mnt/foo/snap'. Old usage is also
  accepted for now.
- Add an example of how to mount a snapshot.

sbin/mksnap_ffs/Makefile

@@ -1,8 +1,13 @@
 # $FreeBSD$
 
+.PATH:	${.CURDIR}/../mount
+
 PROG=	mksnap_ffs
+SRCS=	mksnap_ffs.c getmntopts.c
 MAN=	mksnap_ffs.8
 
+CFLAGS+=-I${.CURDIR}/../mount
+
 .if defined(NOSUID)
 BINMODE=550
 .else

sbin/mksnap_ffs/mksnap_ffs.8

@@ -34,7 +34,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 19, 2003
+.Dd May 29, 2009
 .Dt MKSNAP_FFS 8
 .Os
 .Sh NAME
@@ -42,19 +42,12 @@
 .Nd take a file system snapshot
 .Sh SYNOPSIS
 .Nm
-.Ar mountpoint
 .Ar snapshot_name
 .Sh DESCRIPTION
 The
 .Nm
 utility creates a snapshot named
-.Ar snapshot_name
-on the file system mounted at
-.Ar mountpoint .
-The
-.Ar snapshot_name
-argument must be contained within the file system mounted at
-.Ar mountpoint .
+.Ar snapshot_name .
 .Pp
 The group ownership of the file is set to
 .Dq Li operator ;
@@ -64,9 +57,19 @@ The mode of the snapshot is set to be readable by the owner
 or members of the
 .Dq Li operator
 group.
+.Sh EXAMPLES
+Create a snapshot of
+.Pa /usr/home
+file system and mount the snapshot elsewhere:
+.Bd -literal -offset indent
+mksnap_ffs /usr/home/snapshot
+mdconfig -a -t vnode -o readonly -f /usr/home/snapshot
+mount -o ro /dev/md0 /mnt/
+.Ed
 .Sh SEE ALSO
 .Xr chmod 2 ,
 .Xr chown 8 ,
+.Xr mdconfig 8,
 .Xr mount 8
 .Sh CAVEATS
 The disk full situation is not handled gracefully and may

sbin/mksnap_ffs/mksnap_ffs.c

@@ -44,31 +44,38 @@
 #include <fcntl.h>
 #include <grp.h>
 #include <limits.h>
+#include <mntopts.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sysexits.h>
 #include <unistd.h>
 
-void usage(void);
+static void
+usage(void)
+{
+
+	errx(EX_USAGE, "usage: mksnap_ffs snapshot_name");
+}
 
 int
 main(int argc, char **argv)
 {
-	char *dir, *cp, path[PATH_MAX];
+	char errmsg[255], path[PATH_MAX];
+	char *cp, *snapname;
 	struct statfs stfsbuf;
-	struct ufs_args args;
 	struct group *grp;
 	struct stat stbuf;
-	int fd;
+	struct iovec *iov;
+	int fd, iovlen;
 
-	if (argc != 3)
+	if (argc == 2)
+		snapname = argv[1];
+	else if (argc == 3)
+		snapname = argv[2];	/* Old usage. */
+	else
 		usage();
 
-	dir = argv[1];
-	memset(&args, 0, sizeof args);
-	args.fspec = argv[2];
-
 	/*
 	 * Check that the user running this program has permission
 	 * to create and remove a snapshot file from the directory
@@ -77,15 +84,15 @@ main(int argc, char **argv)
 	 * will not be able to remove the snapshot when they are
 	 * done with it.
 	 */
-	if (strlen(args.fspec) >= PATH_MAX)
-		errx(1, "pathname too long %s", args.fspec);
-	cp = strrchr(args.fspec, '/');
+	if (strlen(snapname) >= PATH_MAX)
+		errx(1, "pathname too long %s", snapname);
+	cp = strrchr(snapname, '/');
 	if (cp == NULL) {
 		strlcpy(path, ".", PATH_MAX);
-	} else if (cp == args.fspec) {
+	} else if (cp == snapname) {
 		strlcpy(path, "/", PATH_MAX);
 	} else {
-		strlcpy(path, args.fspec, cp - args.fspec + 1);
+		strlcpy(path, snapname, cp - snapname + 1);
 	}
 	if (statfs(path, &stfsbuf) < 0)
 		err(1, "%s", path);
@@ -104,27 +111,26 @@ main(int argc, char **argv)
 	 */
 	if ((grp = getgrnam("operator")) == NULL)
 		errx(1, "Cannot retrieve operator gid");
-	if (mount("ufs", dir, MNT_UPDATE | MNT_SNAPSHOT | stfsbuf.f_flags,
-	    &args) < 0)
-		err(1, "Cannot create %s", args.fspec);
-	if ((fd = open(args.fspec, O_RDONLY)) < 0)
-		err(1, "Cannot open %s", args.fspec);
+
+	build_iovec(&iov, &iovlen, "fstype", "ffs", 4);
+	build_iovec(&iov, &iovlen, "from", snapname, (size_t)-1);
+	build_iovec(&iov, &iovlen, "fspath", stfsbuf.f_mntonname, (size_t)-1);
+	build_iovec(&iov, &iovlen, "errmsg", errmsg, sizeof(errmsg));
+	build_iovec(&iov, &iovlen, "update", NULL, 0);
+	build_iovec(&iov, &iovlen, "snapshot", NULL, 0);
+
+	if (nmount(iov, iovlen, stfsbuf.f_flags) < 0)
+		err(1, "Cannot create snapshot %s: %s", snapname, errmsg);
+	if ((fd = open(snapname, O_RDONLY)) < 0)
+		err(1, "Cannot open %s", snapname);
 	if (fstat(fd, &stbuf) != 0)
-		err(1, "Cannot stat %s", args.fspec);
+		err(1, "Cannot stat %s", snapname);
 	if ((stbuf.st_flags & SF_SNAPSHOT) == 0)
-		errx(1, "File %s is not a snapshot", args.fspec);
+		errx(1, "File %s is not a snapshot", snapname);
 	if (fchown(fd, -1, grp->gr_gid) != 0)
-		err(1, "Cannot chown %s", args.fspec);
+		err(1, "Cannot chown %s", snapname);
 	if (fchmod(fd, S_IRUSR | S_IRGRP) != 0)
-		err(1, "Cannot chmod %s", args.fspec);
+		err(1, "Cannot chmod %s", snapname);
 
 	exit(EXIT_SUCCESS);
 }
-
-void
-usage()
-{
-
-	fprintf(stderr, "usage: mksnap_ffs mountpoint snapshot_name\n");
-	exit(EX_USAGE);
-}