9p: Check for NULL fid in v9fs_dir_release()

NULL fid should be handled in cases where we endup calling v9fs_dir_release()
before even we instantiate the fid in filp.
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/vfs_dir.c

@@ -292,9 +292,11 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 
 	fid = filp->private_data;
 	P9_DPRINTK(P9_DEBUG_VFS,
-			"inode: %p filp: %p fid: %d\n", inode, filp, fid->fid);
+			"v9fs_dir_release: inode: %p filp: %p fid: %d\n",
+			inode, filp, fid ? fid->fid : -1);
 	filemap_write_and_wait(inode->i_mapping);
-	p9_client_clunk(fid);
+	if (fid)
+		p9_client_clunk(fid);
 	return 0;
 }