Why does my iPad say storage is full when it isn't?

[iMore Question]

I recently installed an update, I think it was iOS 8. After that, my iPad deleted ALL of my music and videos and won't let me download any of it again. It says my storage is full but obviously it isn't because all of the videos and music that were on it have been deleted!

 

[Jaguarr40]

Look in settings and about to confirm the message. It might have happened during the update and needs to be hard rebooted.
Worst is you may want to do another backup and clean reinstall of the OS...9.0.1.