Re: [libvirt] [PATCH 09/14] qemu: Start PR daemons on domain startup

On Mon, Feb 12, 2018 at 05:54:19PM +0100, Peter Krempa wrote: > On Thu, Jan 18, 2018 at 17:04:41 +0100, Michal Privoznik wrote: > > Before we exec() qemu we have to spawn pr-helper processes for > > all managed reservations (well, technically there can only one). > > The only caveat there is that we should place the process into > > the same namespace and cgroup as qemu (so that it shares the same > > view of the system). But we can do that only after we've forked. > > That means calling the setup function between fork() and exec(). > > > > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > > --- > > src/qemu/qemu_process.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 151 insertions(+) > > > > diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c > > index 25ec464d3..02608c1f3 100644 > > --- a/src/qemu/qemu_process.c > > +++ b/src/qemu/qemu_process.c > > @@ -2507,6 +2507,151 @@ qemuProcessSetupEmulator(virDomainObjPtr vm) > > } > > > > > > +static int > > +qemuProcessSetupOnePRDaemonHook(void *opaque) > > +{ > > + virDomainObjPtr vm = opaque; > > + size_t i, nfds = 0; > > + int *fds = NULL; > > + int ret = -1; > > + > > + if (virProcessGetNamespaces(vm->pid, &nfds, &fds) < 0) > > If this detects '0' namespaces ... > > > + return ret; > > + > > + if (virProcessSetNamespaces(nfds, fds) < 0) > > ... this call will be unhappy. Namespaces have been around since at least RHEL-5 vintage so I reckon we can assume non-zero number of namespaces. In fact perhaps we should just make virProcessGetNamespaces() return an explicit error in the unlikely case it finds zero namespaces.