I moved all the data of WhatsApp to
/mnt/media_rw/6333-6461/WhatsApp, where 6333-6461 is my external SD card. I opened WhatsApp to find that I could not open any previously downloaded data. This is expected.
Now, I executed the following commands in Termux:
$ su # mount -o bind /mnt/runtime/write/6333-6461/WhatsApp /mnt/runtime/write/emulated/0/WhatsApp
When I opened WhatsApp, I could see all the data that I had previously downloaded. But now I cannot send or receive anything - all sending fails, camera access from WhatsApp fails, and downloading fails.
Evidently WhatsApp is not being able to write onto the bind mount. Any solution to the problem?
My phone, a Samsung Galaxy On7, Android 6.0.1, is rooted with Magisk 20.1 and running stock ROM.