kernel: vm: Add vm_object refcount

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 13 insertions, 0 deletions

diff --git a/sys/include/vm/obj.h b/sys/include/vm/obj.h
index 6129889..c1c2f17 100644
--- a/sys/include/vm/obj.h
+++ b/sys/include/vm/obj.h
@@ -42,9 +42,17 @@ struct vm_object {
     struct vm_pagerops *pgops;      /* Pager operations */
 
     uint8_t is_anon : 1;            /* Is an anonymous mapping */
+    int ref;                        /* Ref count */
     struct vnode *vnode;            /* Only used if `is_anon` is 0 */
 };
 
+#define vm_object_ref(OBJPTR) (++(OBJPTR)->ref)
+#define vm_object_unref(OBJPTR) do {    \
+        if ((OBJPTR)->ref > 1) {        \
+            --(OBJPTR)->ref;            \
+        }                               \
+    } while (0);
+
 int vm_obj_init(struct vm_object **res, struct vnode *vnode);
 int vm_obj_destroy(struct vm_object *obj);
 
diff --git a/sys/vm/vm_obj.c b/sys/vm/vm_obj.c
index 589ca47..7487b47 100644
--- a/sys/vm/vm_obj.c
+++ b/sys/vm/vm_obj.c
@@ -59,6 +59,7 @@ vm_obj_init(struct vm_object **res, struct vnode *vnode)
 
     memset(obj, 0, sizeof(struct vm_object));
     obj->vnode = vnode;
+    obj->ref = 1;
 
     vm_set_pgops(obj, vnode);
     *res = obj;
@@ -73,6 +74,10 @@ vm_obj_destroy(struct vm_object *obj)
     if (vp->vmobj != NULL)
         vp->vmobj = NULL;
 
+    /* Check the ref count */
+    if (obj->ref > 1)
+        return -EBUSY;
+
     dynfree(obj);
     return 0;
 }