write_all nitpicking

[divinity76]

1: write_all always returned a bogus 0, so it might as well return nothing, also the return value was never used for anything. 2: bytes_written should be ssize_t not int

could also mention that i'm not happy with the >0 check being just an assert but i don't address that here

[acozzette]

@divinity76 Thank you for the pull request but actually this project was something I did a while ago in college and am no longer working on it or maintaining it. I think if you want to use it or contribute to it you would probably be better off finding a fork that is actively maintained.

[nixomose]

if it's any help, I've been working on a similar project:

https://github.com/nixomose/zosbd2

I used buse originally but nbd caused me all sorts of grief so I wrote something a bit more built-to-purpose.