Re: [PATCH for xen-4.4] libxl: add option for discard support to xl disk configuration

[George Dunlap <george.dunlap@eu.citrix.com>]

On 02/04/2014 04:22 PM, Ian Campbell wrote:
> On Thu, 2014-01-30 at 18:30 +0100, Olaf Hering wrote:
>
> George, any thoughts on:
>
>>> TBH -- if you (==suse I guess?) are contemplating carrying this as a
>>> backport even before 4.4 is out the door we should probably be at least
>>> considering a freeze exception for 4.4. George CCd for input. (I
>>> appreciate that "backport=>freeze exception" is a potentially slippery
>>> slope/ripe for abuse...)
>> It will make less work for SUSE if this change would be incorporated
>> into 4.4, and later replaced with the "final" version I sent out today.
>> However, its small and will be easy to port forward to 4.4.X.
>>
>> The risk of including such change is small as it requires a patched qemu
>> which actually does discard (1.7?), a patched frontend driver (pvops
>> 3.15?) before the codepaths it enables are actually executed.

Well it looks like in order to keep ABI compatibility (which I don't 
think we ever promised), you're introducing this weird hack with 
overloading a putative boolean value with a magic number?

I think the patch is really ugly.  I assume the reason you're attemping 
to avoid breaking ABI compatibility is because we're so close to the 
release? But if so, adding an ugly hack like this is worse, IMHO.

  -George