[libvirt] [PATCH] virsh: report 0-length active block-commit job status

[John Ferlan]

On 01/12/2015 05:54 PM, Eric Blake wrote:
> At least with live block commit, it is possible to have a block
> job that reports 0 status: namely, when the active image contains
> no sectors that differ from the backing image it is being committed
> into [1].  I'm not sure if that represents a qemu bug, but it leads
> to weird virsh output where 'virsh blockjob $dom vda' has no output
> during a no-op commit job.  It appears that the special case for
> a zero total was first introduced for migration, where it does sort
> of make sense (when we do storage migration, the job is broken up
> into two pieces where the first half of migrating storage has no
> clue what the total length of the second phase will be, and where
> qemu migration always reports a non-zero total length but only once
> we complete the first phase to start actual migration), but it
> doesn't seem to make sense for any of the block jobs.
> 
> [1] https://www.redhat.com/archives/libvir-list/2015-January/msg00348.html
> 
> * tools/virsh-domain.c (vshPrintJobProgress): Move special-case of
> 0 total...
> (vshWatchJob): ...into lone caller where it matters.
> 
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
>  tools/virsh-domain.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
> index 6733cfa..ec62aae 100644
> --- a/tools/virsh-domain.c
> +++ b/tools/virsh-domain.c
> @@ -1,7 +1,7 @@
>  /*
>   * virsh-domain.c: Commands to manage domain
>   *
> - * Copyright (C) 2005, 2007-2014 Red Hat, Inc.
> + * Copyright (C) 2005, 2007-2015 Red Hat, Inc.
>   *
>   * This library is free software; you can redistribute it and/or
>   * modify it under the terms of the GNU Lesser General Public
> @@ -1678,10 +1678,6 @@ vshPrintJobProgress(const char *label, unsigned long long remaining,
>  {
>      int progress;
> 
> -    if (total == 0)
> -        /* migration has not been started */
> -        return;
> -

Would it be necessarily true that remaining was zero at this point?
Because if it wasn't then, the else condition will divide by zero if
total == 0...  More than 1 caller to this function...

Perhaps safer to say if "remaining == 0 || total == 0"?

I was just reviewing Michal's patch from last week:

http://www.redhat.com/archives/libvir-list/2015-January/msg00230.html

where it seems a zero could imply some sort of failure.  If you did the
total == 0 check, then the && jobinfo.dataTotal isn't necessary...  I
would suppose that an error would mean we're 100% done...


John
>      if (remaining == 0) {
>          /* migration has completed */
>          progress = 100;
> @@ -4189,7 +4185,7 @@ vshWatchJob(vshControl *ctl,
>              ret = virDomainGetJobInfo(dom, &jobinfo);
>              pthread_sigmask(SIG_SETMASK, &oldsigmask, NULL);
>              if (ret == 0) {
> -                if (verbose)
> +                if (verbose && jobinfo.dataTotal)
>                      vshPrintJobProgress(label, jobinfo.dataRemaining,
>                                          jobinfo.dataTotal);
>