Can't create a new lusf file on tmpfs(Linux)

[shinnya]

It may be impossible to create a new lusf file on tmpfs because tmpfs doesn't support O_DIRECT. This issue makes cannyls(or frugalos) crash.

I checked the behavior of tmpfs by the following code:

#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <errno.h> // errno
#include <string.h> // strerror

int main(int argc, char** argv)
{
    int result = open("/tmp/foo.txt", O_CREAT | O_RDONLY | O_DIRECT);

    if (result == -1) {
        printf("%s\n", strerror(errno));
        return -1;
    }

    printf("ok\n");

    return 0;
}

Then run:

$ gcc -o main main.c ; ./main
Invalid argument

environment

$ uname -a
Linux quad 4.18.6-arch1-1-ARCH #1 SMP PREEMPT Wed Sep 5 11:54:09 UTC 2018 x86_64 GNU/Linux

$ cargo -V
cargo 1.30.0 (a1a4ad372 2018-11-02)

how to reproduce

Make sure that /tmp is mounted as tmpfs.

$ git clone https://github.com/frugalos/kanils.git
$ cd kanils
$ cargo run -- Create --storage /tmp/foo.lusf --capacity=1024
    Finished dev [unoptimized + debuginfo] target(s) in 0.07s
     Running `target/debug/kanils Create --storage /tmp/foo.lusf --capacity=1024`
passed data region size = 1024
thread 'main' panicked at '
EXPRESSION: FileNvm::create(opt.storage_path, total_size)
ERROR: Other (cause; File exists (os error 17))
HISTORY:
  [0] at /home/shinnya/.cargo/registry/src/github.com-1ecc6299db9ec823/cannyls-0.9.1/src/nvm/file.rs:163
  [1] at src/main.rs:212

[yuezato]

I think this is a problem of KaNiLs rather than CannyLS:
https://github.com/frugalos/kanils/blob/3fffa9a5641f4f5153f174264e3f88e35ad60ffe/src/main.rs#L212-L217