document the flush routines

lib/libpuffs/puffs_flush.3

@@ -1,4 +1,4 @@
-.\"	$NetBSD: puffs_flush.3,v 1.2 2007/04/06 16:44:01 pooka Exp $
+.\"	$NetBSD: puffs_flush.3,v 1.3 2007/04/06 17:55:10 pooka Exp $
 .\"
 .\" Copyright (c) 2007 Antti Kantee.  All rights reserved.
 .\"
@@ -43,6 +43,12 @@
 .Fo puffs_inval_pagecache_node_range
 .Fa "struct puffs_usermoint *pu" "void *cookie" "off_t start" "off_t end"
 .Fc
+.Ft int
+.Fn puffs_flush_pagecache_node "struct puffs_usermoint *pu" "void *cookie"
+.Ft int
+.Fo puffs_flush_pagecache_node_range
+.Fa "struct puffs_usermoint *pu" "void *cookie" "off_t start" "off_t end"
+.Fc
 .Sh DESCRIPTION
 .Em IMPORTANT NOTE!
 This document describes interfaces which are not yet guaranteed to be
@@ -93,8 +99,16 @@ invalidate data in the "read cache", but also data in the "write back"
 cache (conceptually speaking; in reality they are the same cache), which
 has not yet been flushed to the file server.
 Therefore any unflushed data will be lost.
+.Pp
+The counterparts of the invalidation routines are the flushing routines
+.Fn puffs_flush_pagecache_node
+and
+.Fn puffs_flush_pagecache_node_range ,
+which force unwritten data from the kernel page cache to be written.
+For the flush range version, the same range rules as with the
+invalidation routine apply.
+The data is flushed asynchronously, i.e. if the routine returns
+succesfully, all the caller knows is that the data has been queued
+for writing.
 .Sh SEE ALSO
 .Xr puffs 3
-.Sh BUGS
-Routines for forcing a flush of the page cache for a node are not
-yet implemented.