Re: [Xen-devel] [PATCH v2] xen-blkfront: remove type check from blkfront_setup_discard

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 13.01.14 at 14:45, David Vrabel <david.vrabel@citrix.com> wrote:
>> On 13/01/14 13:16, Jan Beulich wrote:
>>>>>> On 13.01.14 at 14:00, Ian Campbell <Ian.Campbell@citrix.com>
>wrote:
>>>> On Mon, 2014-01-13 at 12:34 +0000, Jan Beulich wrote:
>>>>>>>> On 13.01.14 at 13:01, Olaf Hering <olaf@aepfle.de> wrote:
>>>>>> On Mon, Jan 13, Jan Beulich wrote:
>>>>>>
>>>>>>> You can't do this in one go - the first two and the last one may
>be
>>>>>>> set independently (and are independent in their meaning), and
>>>>>>> hence need to be queried independently (xenbus_gather() fails
>>>>>>> on the first absent value).
>>>>>>
>>>>>> Yes, thats the purpose. Since the properties are required its an
>all or
>>>>>> nothing thing. If they are truly optional then blkif.h should be
>updated
>>>>>> to say that.
>>>>>
>>>>> They _are_ optional.
>>>>
>>>> But is it true that either they are all present or they are all
>absent?
>>> 
>>> No, it's not. discard-secure is independent of the other two (but
>>> those other two are tied together).
>> 
>> Can we have a patch to blkif.h that clarifies this?
>> 
>> e.g.,
>> 
>> feature-discard
>> 
>>    ...
>> 
>>    discard-granularity and discard-offset must also be present if
>>    feature-discard is enabled
>
>It would be "may" here too afaict. But I'll defer to Konrad, who
>has done more work in this area...
>
>Jan
>
>>    discard-secure may also be present if feature-discard is enabled.
>> 
>> David
>
>
>
>
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It is all 'may'. If there is just 'feature-discard' without any other options that is OK.