Re: [Qemu-devel] [PATCH 1/5] qemu-nbd: Add --pid-file option

[Eric Blake]

On 5/7/19 2:39 PM, Max Reitz wrote:
> On 07.05.19 21:30, Eric Blake wrote:
>> On 5/7/19 1:36 PM, Max Reitz wrote:
>>> --fork is a bit boring if there is no way to get the child's PID.  This
>>> option helps.
>>>
>>> Signed-off-by: Max Reitz <address@hidden>
>>> ---
>>>  qemu-nbd.c    | 29 +++++++++++++++++++++++++++++
>>>  qemu-nbd.texi |  2 ++
>>>  2 files changed, 31 insertions(+)
>>>
>>
>>> @@ -111,6 +112,7 @@ static void usage(const char *name)
>>>  "                            specify tracing options\n"
>>>  "  --fork                    fork off the server process and exit the 
>>> parent\n"
>>>  "                            once the server is running\n"
>>> +"  --pid-file=PATH           store the server's process ID in the given 
>>> file\n"
>>
>> Should --pid-file imply --fork, or be an error if --fork was not
>> supplied? As coded, it writes a pid file regardless of --fork, even
>> though it is less obvious that it is useful in that case. I don't have a
>> strong preference (there doesn't seem to be a useful consensus on what
>> forking daemons should do), but it would at least be worth documenting
>> the intended action (even if that implies a tweak to the patch to match
>> the intent).
> 
> I think the documentation is pretty clear.  It stores the server's PID,
> whether it has been forked or not.
> 
> I don't think we would gain anything from forbidding --pid-file without
> --fork, would we?

I can't think of any reason to forbid it. So it sounds like we are
intentional, this writes the pid into --pid-file regardless of whether
that pid can be learned by other means as well.


>>> +    const char *pid_path = NULL;
>>
>> Bikeshedding: pid_name is nicer (path makes me think of $PATH and other
>> colon-separated lists, which this is not).
> 
> I'd prefer pid_filename myself, then, because pid_name sounds like a
> weird way to say "process name". O:-)

Works for me, even if it is longer. Do you want to respin, or just have
me touch it up when folding it into my NBD tree?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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