lustre: instantiate negative dentry

In the atomic_open callback. We should instantiate
negative dentry. Else will got sanity:183 failed.

Signed-off-by: yang sheng <yang.sheng@intel.com>
Reviewed-on: http://review.whamcloud.com/8110
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3228
Reviewed-by: Peng Tao <bergwolf@gmail.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/namei.c

@@ -468,6 +468,12 @@ int ll_lookup_it_finish(struct ptlrpc_request *request,
 		if (IS_ERR(alias))
 			return PTR_ERR(alias);
 		*de = alias;
+	} else if (!it_disposition(it, DISP_LOOKUP_NEG)  &&
+		   !it_disposition(it, DISP_OPEN_CREATE)) {
+		/* With DISP_OPEN_CREATE dentry will
+		   instantiated in ll_create_it. */
+		LASSERT((*de)->d_inode == NULL);
+		d_instantiate(*de, inode);
 	}
 
 	if (!it_disposition(it, DISP_LOOKUP_NEG)) {