[Q] Help for mount bind folders topic

A simple question
---> doesn't work

Code:

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mount -o bind /mnt/test /storage/emulated/0/test

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--->worked

Code:

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mount -o bind /mnt/storage/emulsted/0/test /mnt/test

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I just want to extend my internal sdcard via a mounted samba.
It seems that sdcard filesystem is not been supported.
Somebody have any idea ?