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

From: Eric Blake
Subject: Re: [Qemu-block] [PATCH 1/5] qemu-nbd: Add --pid-file option
Date: Tue, 7 May 2019 14:51:30 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1

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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