On 23/10/15 20:32, Anna Schumaker wrote:
> +    len = stat.st_size;
> +
> +    fd_out = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC, 0644);
> +    if (fd_out == \-1) {
> +        perror("open (argv[2])");
> +        exit(EXIT_FAILURE);
> +    }
> +
> +    do {
> +        ret = copy_file_range(fd_in, NULL, fd_out, NULL, len, 0);
> +        if (ret == \-1) {
> +            perror("copy_file_range");
> +            exit(EXIT_FAILURE);
> +        }
> +
> +        len \-= ret;
> +    } while (len > 0);

Is this an infinite loop if len decreases before the copy completes?
Perhaps this should be: while (len && ret);

Otherwise this set looks good.

I'm a bit worried about the sparse expansion and default reflinking
which might preclude cp(1) from using this call in most cases, but I will
test and try to use it. coreutils has heuristics for determining if files
are remote, which we might use to restrict to that use case.

thanks,
Pádraig.
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