This is already possible on Linux with certain filesystems (notably xfs and ext4), as long as the size of the data you want to prepend is an integer multiple of

This is already possible on Linux with certain filesystems (notably xfs and ext4), as long as the size of the data you want to prepend is an integer multiple of the filesystem block size. https://lwn.net/Articles/629965/ https://lwn.net/Articles/629965/