os: vnode: Add refcounts to vnodes

Keep track of how many referencing are on a vnode so one isn't freed
early while another object is still using it.

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

2 files changed, 10 insertions, 0 deletions

diff --git a/src/sys/include/os/vnode.h b/src/sys/include/os/vnode.h
index ed98206..354c73c 100644
--- a/src/sys/include/os/vnode.h
+++ b/src/sys/include/os/vnode.h
@@ -31,6 +31,7 @@
 #define _OS_VNODE_H_ 1
 
 #include <sys/types.h>
+#include <sys/atomic.h>
 
 /* Forward declarations */
 struct vnode;
@@ -82,16 +83,20 @@ struct vop {
  * [V]  Set up by VFS
  * [F/V]: Both F and V
  *
+ * @refcount: How many objects have a reference
  * @type: Vnode type  [F/V]
  * @vops:  Vnode operations hooks [F]
  * @data: Filesystem specific data [F]
  */
 struct vnode {
+    int refcount;
     vtype_t type;
     struct vop *vops;
     void *data;
 };
 
+#define vnode_ref(VP) (atomic_inc_int(&(VP)->refcount))
+
 /*
  * Allocate a new vnode
  *
diff --git a/src/sys/os/vfs_subr.c b/src/sys/os/vfs_subr.c
index 6cb542c..64c7492 100644
--- a/src/sys/os/vfs_subr.c
+++ b/src/sys/os/vfs_subr.c
@@ -29,6 +29,7 @@
 
 #include <sys/types.h>
 #include <sys/errno.h>
+#include <sys/atomic.h>
 #include <os/vnode.h>
 #include <os/kalloc.h>
 #include <os/vfs.h>
@@ -77,6 +78,7 @@ vfs_valloc(struct vnode **resp, vtype_t type, int flags)
     }
 
     memset(vp, 0, sizeof(*vp));
+    vp->refcount = 1;
     vp->type = type;
     *resp = vp;
     return 0;
@@ -89,6 +91,9 @@ vfs_vrel(struct vnode *vp, int flags)
         return -EINVAL;
     }
 
+    if (atomic_dec_int(&vp->refcount) > 1) {
+        return 0;
+    }
     kfree(vp);
     return 0;
 }