[libvirt] [PATCH 2/3] Implementation deficiency in virInitctlSetRunLevel v2

[Daniel P. Berrange]

On Thu, Dec 19, 2013 at 08:07:50PM +0400, Reco wrote:
> Implement fork & setns for lxcDomainShutdownFlags
> 
> ---
>  src/lxc/lxc_driver.c |   45 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/src/lxc/lxc_driver.c b/src/lxc/lxc_driver.c
> index c499182..9d200b2 100644
> --- a/src/lxc/lxc_driver.c
> +++ b/src/lxc/lxc_driver.c
> @@ -2619,6 +2619,50 @@ lxcDomainShutdownFlags(virDomainPtr dom,
>          goto cleanup;
>      }
>  
> +#ifdef HAVE_SETNS
> +    if (flags == 0 || flags & VIR_DOMAIN_SHUTDOWN_INITCTL) {
> +        int pid = -1;
> +        int status = -1;
> +        int mfd = -1;
> +
> +        if (virAsprintf(&vroot, "/proc/%llu/ns/mnt",
> +                        (unsigned long long)priv->initpid) < 0) {
> +            goto cleanup;
> +        }
> +
> +        if ((mfd = open(vroot, O_RDONLY)) < 0) {
> +            virReportSystemError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> +                                 _("Kernel does not provide mount namespace"));
> +         goto cleanup;
> +        }
> +
> +        switch (pid = fork()) {
> +        case 0:
> +            if (setns(mfd, 0) == -1) {
> +                exit(-1);
> +            }
> +            rc = virInitctlSetRunLevel(VIR_INITCTL_RUNLEVEL_POWEROFF, NULL);
> +            exit(rc);
> +            break;
> +        case -1:
> +            virReportSystemError(VIR_ERR_INTERNAL_ERROR, "%s",
> +                                 _("Fork failed"));
> +            goto cleanup;
> +        default:
> +            if (waitpid(pid, &status, 0) < 0 || status < 0) {
> +                virReportSystemError(errno,
> +                                     _("Sending shutdown failed with status %i"),
> +                                     status);
> +                rc = 0;
> +            } else {
> +                rc = status;
> +            }
> +            close(mfd);
> +        }
> +    } else {
> +        rc = 0;
> +    }

Since this is a fairly tedious large piece of code I think it is
worth hiding it in a helper function. I'd suggest that in the
src/util/virprocess.{c,h} file we create a 

  typedef int (*virProcessNamespaceCallback)(pid_t pid, void *opaque);

  virProcessRunInMountNamespace(pid_t pid,
                                virProcessNamespaceCallback cb,
                                void *opaque)


This lxcDomainShutdownFlags code would then use that and pass a
callback function which does the virInitctlSetRunLevel() API call.
That should reduce the code size significantly, since we also need
to fix all the other places in this file which use /proc/$PID/root.

Daniel
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