make kfree loop same as kalloc

kalloc.c

@@ -93,18 +93,15 @@ char*
 kalloc(int n)
 {
   char *p;
-  struct run *r, **rr;
+  struct run *r, **rp;
 
   if(n % PAGE || n <= 0)
     panic("kalloc");
 
   acquire(&kalloc_lock);
-
-  rr = &freelist;
-  while(*rr){
-    r = *rr;
+  for(rp=&freelist; (r=*rp) != 0; rp=&r->next){
     if(r->len == n){
-      *rr = r->next;
+      *rp = r->next;
       release(&kalloc_lock);
       return (char*)r;
     }
@@ -114,9 +111,9 @@ kalloc(int n)
       release(&kalloc_lock);
       return p;
     }
-    rr = &(*rr)->next;
   }
   release(&kalloc_lock);
+
   cprintf("kalloc: out of memory\n");
   return 0;
 }