Document noasync and nosync.

Clarify the meaning of sync.
Run all the -o keywords through the Cm (keyword emphasis) macro.

sbin/mount/mount.8

@@ -1,4 +1,4 @@
-.\"	$NetBSD: mount.8,v 1.20 1998/04/29 09:49:13 fair Exp $
+.\"	$NetBSD: mount.8,v 1.21 1998/09/14 03:48:30 ross Exp $
 .\"
 .\" Copyright (c) 1980, 1989, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -116,7 +116,7 @@ Options are specified with a
 flag followed by a comma separated string of options.
 The following options are available:
 .Bl -tag -width nocoredump
-.It async
+.It Cm async
 All
 .Tn I/O
 to the file system should be done asynchronously.
@@ -125,24 +125,28 @@ This is a
 flag to set,
 and should not be used unless you are prepared to recreate the file
 system should your system crash.
-.It force
+.It Cm noasync
+Clear
+.Cm async
+mode.
+.It Cm force
 The same as
 .Fl f ;
 forces the revocation of write access when trying to downgrade
 a filesystem mount status from read-write to read-only.
-.It noatime
+.It Cm noatime
 Never update the access time field for files.
 This option is useful for optimizing read performance on filesystems
 that are used as news spools.
-.It noauto
+.It Cm noauto
 This filesystem should be skipped when mount is run with the
 .Fl a
 flag.
-.It nodev
+.It Cm nodev
 Do not interpret character or block special devices on the file system.
 This option is useful for a server that has file systems containing
 special devices for architectures other than its own.
-.It nocoredump
+.It Cm nocoredump
 Do not allow programs to create crash dumps (core files) on the file system.
 This option can be used to help protect sensitive
 data by keeping core files (which may contain sensitive data)
@@ -151,27 +155,32 @@ Only core files that would be created by program crashes are
 prevented by use of this flag; the behavior of
 .Xr savecore 8
 is not affected.
-.It noexec
+.It Cm noexec
 Do not allow execution of any binaries on the mounted file system.
 This option is useful for a server that has file systems containing
 binaries for architectures other than its own.
-.It nosuid
+.It Cm nosuid
 Do not allow set-user-identifier or set-group-identifier bits to take effect.
-.It rdonly
+.It Cm rdonly
 The same as
 .Fl r ;
 mount the file system read-only (even the super-user may not write it).
-.It symperm
+.It Cm symperm
 Recognize permission of symbolic link when reading or traversing link.
-.It sync
+.It Cm sync
 All
 .Tn I/O
-to the file system should be done synchronously.
-.It update
+to the file system should be done synchronously. This is not equivalent to the
+normal mode in which only metadata is written synchronously.
+.It Cm nosync
+Clear
+.Cm sync
+mode.
+.It Cm update
 The same as
 .Fl u ;
 indicate that the status of an already mounted file system should be changed.
-.It union
+.It Cm union
 Causes the namespace at the mount point to appear as the union
 of the mounted filesystem root and the existing directory.
 Lookups will be done in the mounted filesystem first.