static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
	return dax_mkwrite(vma, vmf, ext4_get_block_dax,
				ext4_end_io_unwritten);
}
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.