[libvirt] [PATCH 2/4] qemu: introduce CHECK_STREQ_NULLABLE in qemuDomainDiskChangeSupported

[Laine Stump]

On 3/28/19 10:34 AM, Ján Tomko wrote:
> A marco for comparing string fields of the disk.


Polo'ed-by: Laine Stump <laine at laine.org>


(seriously, though - s/marco/macro/ :-)


>
> https://bugzilla.redhat.com/show_bug.cgi?id=1601677
>
> Signed-off-by: Ján Tomko <jtomko at redhat.com>
> ---
>   src/qemu/qemu_domain.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index bb3a672d47..72e322d6a7 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -9322,6 +9322,18 @@ qemuDomainDiskChangeSupported(virDomainDiskDefPtr disk,
>           } \
>       } while (0)
>   
> +#define CHECK_STREQ_NULLABLE(field, field_name) \
> +    do { \
> +        if (!disk->field) \
> +            break; \


So is a missing value in the updated XML equal to "no change"? Or Does a 
missing value actually mean "this should be un-set if it has been set to 
something"?


(I'm asking this because in the case of MTU for <interface>, if the 
existing interface has an mtu set (even to 1500), and the updated XML 
has no MTU, we consider that a change (and don't allow it).


Reviewed-by: Laine Stump <laine at laine.org>


once the commit message typo is fixed, and if the meaning of "not 
specified" for a field in the update truly is meant to be "don't change" 
rather than "remove any previous setting of this field and return it to 
default".


> +        if (STRNEQ_NULLABLE(disk->field, orig_disk->field)) { \
> +            virReportError(VIR_ERR_OPERATION_UNSUPPORTED, \
> +                           _("cannot modify field '%s' of the disk"), \
> +                           field_name); \
> +            return false; \
> +        } \
> +    } while (0)
> +
>       CHECK_EQ(device, "device", false);
>       CHECK_EQ(bus, "bus", false);
>       if (STRNEQ(disk->dst, orig_disk->dst)) {
> @@ -9469,6 +9481,7 @@ qemuDomainDiskChangeSupported(virDomainDiskDefPtr disk,
>       }
>   
>   #undef CHECK_EQ
> +#undef CHECK_STREQ_NULLABLE
>   
>       return true;
>   }