Linux Babe published a tutorial about how to fix the "can’t read superblock" error on Linux.
How to Fix "can't read superblock" Error on Linux (ext4 & Btrfs)
This tutorial shows you how to fix the can not read superblock error on Linux for ext4 and Btrfs file system.
How to Fix "can't read superblock" Error on Linux (ext4 & Btrfs)