kernel: vfs: Add vnode refcount

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

2 files changed, 23 insertions, 0 deletions

diff --git a/sys/include/sys/vnode.h b/sys/include/sys/vnode.h
index 545fa2f..3f3b011 100644
--- a/sys/include/sys/vnode.h
+++ b/sys/include/sys/vnode.h
@@ -31,6 +31,7 @@
 #define _SYS_VNODE_H_
 
 #include <sys/types.h>
+#include <sys/atomic.h>
 #include <sys/sio.h>
 
 #if defined(_KERNEL)
@@ -42,8 +43,11 @@ struct vnode {
     int flags;
     void *data;
     const struct vops *vops;
+    uint32_t refcount;
 };
 
+#define vfs_vref(VP) (atomic_inc_int(&(VP)->refcount))
+
 /* Vnode type flags */
 #define VNON    0x00    /* Uninitialized */
 #define VREG    0x01    /* Regular file */
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index b732cb4..0d4be72 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -30,6 +30,7 @@
 #include <sys/vnode.h>
 #include <sys/errno.h>
 #include <sys/mount.h>
+#include <sys/syslog.h>
 #include <vm/dynalloc.h>
 #include <string.h>
 
@@ -46,6 +47,7 @@ vfs_alloc_vnode(struct vnode **res, int type)
 
     memset(vp, 0, sizeof(*vp));
     vp->type = type;
+    vp->refcount = 1;
     *res = vp;
     return 0;
 }
@@ -83,6 +85,23 @@ vfs_release_vnode(struct vnode *vp)
 
     if (vp == NULL)
         return -EINVAL;
+
+    /*
+     * The refcount cannot be zero before we decrement it,
+     * something is quite wrong if this happens.
+     */
+    if (vp->refcount == 0) {
+        kprintf("Cannot release vnode, bad refcount\n");
+        return -EIO;
+    }
+
+    /*
+     * Drop the reference and don't destroy the vnode
+     * if it's still not zero.
+     */
+    if (atomic_dec_int(&vp->refcount) > 0)
+        return 0;
+
     if (vops->reclaim != NULL)
         status = vops->reclaim(vp);
     if (status != 0)