kernel: duppage checking

1 files changed, 9 insertions, 10 deletions

diff --git a/sys/src/9/port/fault.c b/sys/src/9/port/fault.c
index 5ab0c9f2e..b5c59d80f 100644
--- a/sys/src/9/port/fault.c
+++ b/sys/src/9/port/fault.c
@@ -140,14 +140,20 @@ fixfault(Segment *s, ulong addr, int read, int doputmmu)
 
 		lkp = *pg;
 		lock(lkp);
-
+		if(lkp->ref <= 0)
+			panic("fault: lkp->ref %d <= 0", lkp->ref);
 		if(lkp->image == &swapimage)
 			ref = lkp->ref + swapcount(lkp->daddr);
 		else
 			ref = lkp->ref;
-		if(ref > 1) {
-			unlock(lkp);
+		if(ref == 1 && lkp->image){
+			/* save a copy of the original for the image cache */
+			duppage(lkp);
 
+			ref = lkp->ref;
+		}
+		unlock(lkp);
+		if(ref > 1){
 			new = newpage(0, &s, addr);
 			if(s == 0)
 				return -1;
@@ -155,13 +161,6 @@ fixfault(Segment *s, ulong addr, int read, int doputmmu)
 			copypage(lkp, *pg);
 			putpage(lkp);
 		}
-		else {
-			/* save a copy of the original for the image cache */
-			if(lkp->image)
-				duppage(lkp);
-
-			unlock(lkp);
-		}
 		mmuphys = PPN((*pg)->pa) | PTEWRITE | PTEVALID;
 		(*pg)->modref = PG_MOD|PG_REF;
 		break;