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

[Daniel P . Berrangé]

On Tue, May 07, 2019 at 09:39:01PM +0200, 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?

Indeed, use of --pid-file should be independant of --fork, as a mgmt app
may have already forked it into the background, and merely want to get
the pidfile

Regards,
Daniel
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