FSCTL_ADD_OVERLAY control code
The FSCTL_ADD_OVERLAY control code adds a new external backing source to a volume’s namespace. This backing source can be a Windows Image Format (WIM) file.
To perform this operation, call FltFsControlFile or ZwFsControlFile with the following parameters.
Parameters
Instance [in]: FltFsControlFile only. An opaque instance pointer for the caller. This parameter is required and cannot be NULL.
FileObject: [in]: FltFsControlFile only. The file pointer object of the volume for which the overlay is added to. This parameter is required and cannot be NULL.
FileHandle [in]: ZwFsControlFile only. The handle of the volume for which the overlay is added to. This parameter is required and cannot be NULL.
FsControlCode [in]: The control code for the operation. Use FSCTL_ADD_OVERLAY for this operation.
InputBuffer [in]: A pointer to the input buffer, which must contain a WOF_EXTERNAL_INFO structure. When required, additional provider specific data is included immediately after WOF_EXTERNAL_INFO.
InputBufferLength [in]: Set to sizeof(WOF_EXTERNAL_INFO) plus the size of any additional provider input data.
OutputBuffer [out]: A pointer to the output buffer, which contains any resultant information from the add operation.
OutputBufferLength [out]: Size of the buffer pointed to by OutputBuffer.
Status block
FltFsControlFile or ZwFsControlFile returns STATUS_SUCCESS if the operation succeeds. Otherwise, the appropriate function might return one of the following NTSTATUS values.
| Code | Meaning |
|---|---|
| STATUS_ACCESS_DENIED | The requestor does not have administrative privileges. |
| STATUS_BUFFER_TOO_SMALL | The length of the output buffer pointed to by OutputBuffer, and specified by OutputBufferLength, is too small. |
| STATUS_INTERNAL_ERROR | The requested volume is not accessible. |
| STATUS_INVALID_DEVICE_REQUEST | The backing service is not present or not started. |
Remarks
When the backing source added is a Windows Imaging Format (WIM) file, the input buffer will contain a WOF_EXTERNAL_INFO structure followed by a WIM_PROVIDER_ADD_OVERLAY_INPUT structure. The InputBufferLength in this case will be sizeof(WOF_EXTERNAL_INFO) + sizeof(WIM_PROVIDER_ADD_OVERLAY_INPUT). On completion of the request, the data pointed to by OutputBuffer contains a single LARGE_INTEGER value which is the new data source identifier for the WIM file.
Other backing providers will define their own specific input parameter structures and output data types.
Requirements
| Requirement type | Requirement |
|---|---|
| Minimum supported client | Windows 8.1 Update |
| Header | Ntifs.h (include Ntifs.h or Fltkernel.h) |