Re: [PATCH vOther2 1/1] qemu-nbd: Restore "qemu-nbd -v --fork" output

[Michael Tokarev]

25.08.2023 23:08, Denis V. Lunev wrote:
> +            /* Remember parent's stderr if we will be restoring it. */
> +            if (verbose /* fork_process is set */) {
> +                opts.stderr = dup(STDERR_FILENO);
> +                if (opts.stderr < 0) {
> +                    error_report("Could not dup stdedd: %s", strerror(errno));
> +                    exit(EXIT_FAILURE);
> +                }
> +            }
> +
>               ret = qemu_daemon(1, 0);

I haven't looked closely to this development.

To me it all looks.. backwards.

Instead of saving stderr around qemu_daemon() call, it might be more
productive to tell qemu_daemon() to stop redirecting stderr (and maybe
instrumenting it to do so).

Besides, qemu has 2 daemon implementations, one is qemu_daemon()
in util/oslib-posix.c and another is os_daemonize() in os-posix.c.
Note os_daemonize() does the right thing wrt logging already, -

        /* In case -D is given do not redirect stderr to /dev/null */
        if (!qemu_log_enabled()) {
            dup2(fd, 2);
        }

but I guess nbd does not use qemu_log_enabled() et al.

Also, qemu-nbd can benefit from using -runas/-chroot too.

Ideally this whole thing should be consolidated.  I already took a
step towards this by moving softmmu-specific stuff from os-posix.c
to softmmu/, this work should continue. When it's done, we can
revert this band-aid change for a real solution.

Thanks,

/mjt