Use internal storage as network storage

I Have Redmi AC2100 and I saw it has 89 Mb free space

Filesystem                Size      Used Available Use% Mounted on
/dev/root                 3.8M      3.8M         0 100% /rom
tmpfs                    59.7M    248.0K     59.4M   0% /tmp
/dev/ubi0_1              97.3M      3.2M     89.4M   3% /overlay
overlayfs:/overlay       97.3M      3.2M     89.4M   3% /
tmpfs                   512.0K         0    512.0K   0% /dev

I want to share documents to Windows and Android, it possible to allocate 50 Mb of space as Network storage?
if yes, can you give me the direction.


This is not a good idea, unless the files will be written/edited very infrequently, but read with some regularity. The problem is that internal flash memory in most embedded devices has a very limited write-cycle lifetime. This means that if you use it for general file storage it will wear out very quickly and you may find that the storage develops bad blocks and ultimately fails in short order.