From 1cf62785d11ca9c07893c67d4d9285f2ae96951a Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Fri, 29 Mar 1996 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1996-03-29

---
 port/cache.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/port/cache.c b/port/cache.c
index f9b5f20e0db38125c67378823edad80c9d686308..a98ba635e0b6e30f8b262409e5eb6171c8c6d68d 100644
--- a/port/cache.c
+++ b/port/cache.c
@@ -526,23 +526,19 @@ cwrite(Chan* c, uchar *buf, int len, ulong offset)
 		p = f;		
 	}
 
-	if(f != 0) {
+	if(f != 0 && offset < f->start+f->len) {
 		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;
-				}
-			}	
+		n = f->len - o;
+		if(n > len)
+			n = len;
+		if(cpgmove(f, buf, o, n)) {
+			len -= n;
+			if(len == 0) {
+				qunlock(m);
+				return;
+			}
+			offset += n;
+			buf += n;
 		}
 	}