From ae76db6206afa100bdbee39669a69dbc77601f5f Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Tue, 26 Mar 1996 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1996-03-26

---
 port/cache.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/port/cache.c b/port/cache.c
index 35c164aff1dc051b340fa91e97ac1b16afb39a39..f9b5f20e0db38125c67378823edad80c9d686308 100644
--- a/port/cache.c
+++ b/port/cache.c
@@ -498,7 +498,7 @@ cupdate(Chan *c, uchar *buf, int len, ulong offset)
 void
 cwrite(Chan* c, uchar *buf, int len, ulong offset)
 {
-	int o;
+	int o, n;
 	Mntcache *m;
 	ulong eblock, ee;
 	Extent *p, *f, *e, *tail;
@@ -526,6 +526,26 @@ cwrite(Chan* c, uchar *buf, int len, ulong offset)
 		p = f;		
 	}
 
+	if(f != 0) {
+		o = offset - f->start;
+		if(o >= 0) {
+			n = f->len - o;
+			if(n > len)
+				n = len;
+			if(n > 0) {
+				if(cpgmove(f, buf, o, n)) {
+					buf += n;
+					len -= n;
+					offset += n;
+				}
+				if(len == 0) {
+					qunlock(m);
+					return;
+				}
+			}	
+		}
+	}
+
 	if(p != 0) {
 		ee = p->start+p->len;
 		if(ee > offset) {