Rationale for memmap vs memmap2

1

What is the story behind https://crates.io/crates/memmap vs https://crates.io/crates/memmap2 ? What 'flaws' in memmap is memmap2 correcting ?

2

https://github.com/danburkert/memmap-rs/issues/90

3

Also https://github.com/RazrFalcon/memmap2-rs/issues/7