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Re: [libvirt] [PATCH] Don't overwrite virRun error messages



On 03/08/2011 11:50 AM, Cole Robinson wrote:
> virRun gives pretty useful error output, let's not overwrite it unless there
> is a good reason. Some places were providing more information about what
> the commands were _attempting_ to do, however that's usually less useful from
> a debugging POV than what actually happened.
> ---
>  src/lxc/veth.c                        |   45 +++------------------------------
>  src/openvz/openvz_driver.c            |   20 --------------
>  src/qemu/qemu_driver.c                |    4 ---
>  src/storage/storage_backend.c         |    3 --
>  src/storage/storage_backend_logical.c |    3 --
>  src/vmware/vmware_driver.c            |    2 -
>  6 files changed, 4 insertions(+), 73 deletions(-)

Hmm, I wonder if we should be using virCommand instead of virRun.  But
that's a question for a separate patch.  Meanwhile, I agree with your
argument that virRun's diagnosis is usually better.

> @@ -122,13 +121,7 @@ int vethCreate(char** veth1, char** veth2)
>      argv[8] = *veth2;
>  
>      VIR_DEBUG("veth1: %s veth2: %s", *veth1, *veth2);
> -    rc = virRun(argv, &cmdResult);
> -
> -    if (rc != 0 ||
> -        (WIFEXITED(cmdResult) && WEXITSTATUS(cmdResult) != 0)) {
> -        vethError(VIR_ERR_INTERNAL_ERROR,
> -                  _("Failed to create veth device pair '%s', '%s': %d"),
> -                  *veth1, *veth2, WEXITSTATUS(cmdResult));
> +    if (virRun(argv, NULL) < 0) {

Not to mention that it fixes real bugs! Here, in the old code, rc can be
0 (we successfully waited on the child), while WIFEXITED(cmdResult) is
false (such as if the child command had a bug, and died due to a signal
such as SIGSEGV [that never happens, right?]) - but in that situation we
didn't report vethError or take the cleanup path.  In the new code,
virRun() refuses to return 0 if the child does not exit normally, so we
always diagnose failure, whether due to non-zero status or to a signal.

ACK!

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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