Adjust discussion of blkno's units to describe the units for

blkno for non-special files. Per comments from yamt at.

share/man/man9/buffercache.9

@@ -1,4 +1,4 @@
-.\"     $NetBSD: buffercache.9,v 1.15 2005/09/10 22:45:45 wiz Exp $
+.\"     $NetBSD: buffercache.9,v 1.16 2005/10/27 00:05:03 wrstuden Exp $
 .\"
 .\" Copyright (c)2003 YAMAMOTO Takashi,
 .\" All rights reserved.
@@ -101,7 +101,7 @@
 .\"
 .\"
 .\" ------------------------------------------------------------
-.Dd September 8, 2005
+.Dd October 26, 2005
 .Dt BUFFERCACHE 9
 .Os
 .Sh NAME
@@ -181,14 +181,26 @@ and
 .Fa blkno .
 The buffer is returned via
 .Fa bpp .
+The units of
+.Fa blkno
+are specifically the units used by the
+.Fn VOP_STRATEGY
+routine for the
+.Fa vp
+vnode.
+For device special files,
 .Fa blkno
 is in units of
-.Dv DEV_BSIZE .
-Both
+.Dv DEV_BSIZE
+and both
 .Fa blkno
 and
 .Fa size
 must be multiples of the underlying device's block size.
+For other files,
+.Fa blkno
+is in units of file system blocks for the file system containing
+.Fa vp .
 .Pp
 If the buffer is not found (i.e. the block is not cached in memory),
 .Fn bread