A process's files, the relation between files in mm_struct and files_struct?

In task_struct, we can find there are:

struct mm_struct *mm, *active_mm;struct files_struct *files;  

files_struct contains pointers to up to 256 file data structures, each one describing a file being used by this process.

struct file * fd_array[NR_OPEN_DEFAULT];

mm_struct contains a vm_area_struct.

struct vm_area_struct * mmap;           /* list of VMAs */

And in vm_area_struct, we can find:

struct file * vm_file;          /* File we map to (can be NULL). */

So my question are:

1. what is the relationship between the files in fd_array and the vm_file?

2. Are all the files shown up in the fd_array will also be mapped in the vm_area_struct in a way similar as shown in the picture? Or, are all the files mapped in the vm_area_struct will show up in the fd_array?

Thanks,

_{(source: duartes.org)}