Re: [Xen-devel] blkif discard attributes

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.07.14 at 12:17, <david.vrabel@xxxxxxxxxx> wrote:
> On 03/07/14 11:08, Jan Beulich wrote:
>>>>> On 03.07.14 at 11:43, <david.vrabel@xxxxxxxxxx> wrote:
>>> On 03/07/14 08:59, Jan Beulich wrote:
>>>> discard_zeroes_data also be communicated from backend to frontend?
>>>
>>> Perhaps. But how would you handle a guest that used to have
>>> discard_zeroes_data but is restored with different storage that no
>>> longer has this property?
>> 
>> Don't these attributes gets re-evaluated after restore anyway?
> 
> I don't see how that helps.  What if a discard request was submitted
> before the suspend, expecting the discard to zero and on restore the
> requests is queued for the new backend which then might not zero.

Hmm, good point. So it's then indeed better to not communicate this.
Albeit similar issues arise with the existing attributes we communicate:
What if the new backend doesn't satisfy the assumptions on the old
one? Possibly the request may get failed, but possibly it may also get
executed wrongly. Neither of which is very desirable.

Jan


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