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Re: [libvirt] [PATCH] qemu: Add missing VIR_DOMAIN_BLOCK_COMMIT_DELETE flags



On 08/27/13 11:37, Michal Privoznik wrote:
> On 27.08.2013 10:58, Alex Jia wrote:
>> On 08/27/2013 04:47 PM, Peter Krempa wrote:
>>> On 08/27/13 09:53, Alex Jia wrote:
>>>> The flag "VIR_DOMAIN_BLOCK_COMMIT_DELETE" is missed by
>>>> qemuDomainBlockCommit(),
>>>> and then will hit error "unsupported flags (0x2) in function
>>>> qemuDomainBlockCommit" if users run 'virsh blockcommit' with
>>>> '--delete' option.
>>>>
>>>> RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1001475
>>>>
>>>> Signed-off-by: Alex Jia<ajia redhat com>
>>>> ---
>>>>   src/qemu/qemu_driver.c |    3 ++-
>>>>   1 files changed, 2 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>>>> index ed29373..8863124 100644
>>>> --- a/src/qemu/qemu_driver.c
>>>> +++ b/src/qemu/qemu_driver.c
>>>> @@ -14444,7 +14444,8 @@ qemuDomainBlockCommit(virDomainPtr dom, const
>>>> char *path, const char *base,
>>>>       const char *base_canon = NULL;
>>>>       bool clean_access = false;
>>>>
>>>> -    virCheckFlags(VIR_DOMAIN_BLOCK_COMMIT_SHALLOW, -1);
>>>> +    virCheckFlags(VIR_DOMAIN_BLOCK_COMMIT_SHALLOW |
>>>> +                  VIR_DOMAIN_BLOCK_COMMIT_DELETE, -1);
>>>>
>>>>       if (!(vm = qemuDomObjFromDomain(dom)))
>>>>           goto cleanup;
>>>>
>>> The code doesn't seem to support the BLOCK_COMMIT_DELETE flag. It was
>>
>> Yes, the codes haven't any implementation for BLOCK_COMMIT_DELETE flag
>> now, maybe, only need to raise a friendly error message in here instead
>> of "unsupported flags (0x2) xxxx".
> 
> I agree that this error message is not user-friendly. Bare virsh users
> know nothing about our flags and their numerical expression. However, I
> don't think there is a way how to produce "Unsupported flag
> VIR_DOMAIN_BLOCK_COMMIT_DELETE" instead of "Unsupported flag 0x2" since
> all we see in the qemuDomainBlockCommit() function is just number. I
> mean, mapping of flag onto numeric value is not one-to-one function (aka
> injective function). That is, a value 0x2 can express
> VIR_DOMAIN_BLOCK_COMMIT_DELETE, VIR_DOMAIN_START_AUTODESTROY,
> VIR_DUMP_DESTROY, etc. (git grep "1 << 1," include/).
> 
> If we want to make it work, we have to introduce an injective function,
> e.g. virUnsupportedFlags(), which would accept a list (not an ORed
> value) of all flags that are not supported. Too much effort for not much
> outcome.

Additionally this would require updating the list of unsupported flags
at each function when adding a new flag to keep them in sync or add a
way to autogenerate the list automagically.

It would be nice to have this automatic, but I think that Alex was
suggesting something like

if (flags & VIR_DOMAIN_BLOCK_COMMIT_DELETE) {
virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "we don't support this yet");
goto cleanup;
}

Peter

> 
> Michal
> 

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