diff --git a/share/man/man9/buffercache.9 b/share/man/man9/buffercache.9
index ae401f7b5b36..70673d368001 100644
--- a/share/man/man9/buffercache.9
+++ b/share/man/man9/buffercache.9
@@ -1,4 +1,4 @@
-.\"     $NetBSD: buffercache.9,v 1.11 2003/11/04 13:45:52 keihan Exp $
+.\"     $NetBSD: buffercache.9,v 1.12 2004/06/17 13:13:41 yamt Exp $
 .\"
 .\" Copyright (c)2003 YAMAMOTO Takashi,
 .\" All rights reserved.
@@ -101,7 +101,7 @@
 .\"
 .\"
 .\" ------------------------------------------------------------
-.Dd September 15, 2003
+.Dd June 17, 2004
 .Dt BUFFERCACHE 9
 .Os
 .Sh NAME
@@ -148,7 +148,7 @@
 .Ft struct buf *
 .Fn incore "struct vnode *vp" "daddr_t blkno"
 .Ft void
-.Fn allocbuf "struct buf *bp" "int size"
+.Fn allocbuf "struct buf *bp" "int size" "int preserve"
 .Ft void
 .Fn brelse "struct buf *bp"
 .Ft void
@@ -290,10 +290,14 @@ Note that
 doesn't busy the buffer unlike
 .Fn getblk .
 .\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-.It Fn allocbuf "bp" "size"
+.It Fn allocbuf "bp" "size" "preserve"
 Expand or contract the actual memory allocated to a buffer.
-If the buffer shrinks, data is lost, so it's up to the caller to have written
-it out *first*; this routine will not start a write.
+If
+.Fa preserve
+is zero, entire data in the buffer will be lost.
+Otherwise, if the buffer shrinks, truncated part of data is lost,
+so it's up to the caller to have written
+it out *first* if needed; this routine will not start a write.
 If the buffer grows, it's the callers responsibility to fill out
 the buffer's additional contents.
 .\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -