From 652a6417046de7d102a1520fee11a30d91ad7f2f Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Mon, 27 Jul 2015 06:42:41 +0200
Subject: [PATCH] kernel: clunk the cache when removing cache flag on a
 channel, only call cread() chen CCACHE flag is set

to avoid double caching, attachimage() and setswapchan() clear
the CCACHE flag on the channel but this keeps the read ahread
state of the cache arround (until the chan gets closed), so also
call cclunk() to detach the mcp and free the read ahead state.

avoid the call to cread() when CCACHE flag is clear.
---
 sys/src/9/port/devmnt.c  | 2 +-
 sys/src/9/port/segment.c | 4 +++-
 sys/src/9/port/swap.c    | 1 +
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/sys/src/9/port/devmnt.c b/sys/src/9/port/devmnt.c
index 63f235ebb..9f6728a4b 100644
--- a/sys/src/9/port/devmnt.c
+++ b/sys/src/9/port/devmnt.c
@@ -706,7 +706,7 @@ mntrdwr(int type, Chan *c, void *buf, long n, vlong off)
 		if(nreq > c->iounit)
 			nreq = c->iounit;
 
-		if(type == Tread) {
+		if(type == Tread && (c->flag&CCACHE) != 0) {
 			nr = cread(c, (uchar*)uba, nreq, off);
 			if(nr > 0) {
 				nreq = nr;
diff --git a/sys/src/9/port/segment.c b/sys/src/9/port/segment.c
index 987f984cc..d7124caef 100644
--- a/sys/src/9/port/segment.c
+++ b/sys/src/9/port/segment.c
@@ -232,6 +232,9 @@ attachimage(int type, Chan *c, uintptr base, ulong len)
 {
 	Image *i, **l;
 
+	c->flag &= ~CCACHE;
+	cclunk(c);
+
 	lock(&imagealloc);
 
 	/*
@@ -272,7 +275,6 @@ found:
 	unlock(&imagealloc);
 	if(i->c == nil){
 		i->c = c;
-		c->flag &= ~CCACHE;
 		incref(c);
 	}
 
diff --git a/sys/src/9/port/swap.c b/sys/src/9/port/swap.c
index c5e249732..9d492257e 100644
--- a/sys/src/9/port/swap.c
+++ b/sys/src/9/port/swap.c
@@ -424,6 +424,7 @@ setswapchan(Chan *c)
 		}
 	}
 	c->flag &= ~CCACHE;
+	cclunk(c);
 	swapimage.c = c;
 	poperror();
 }