Re: [Qemu-devel] [PATCH] Introduce cache images for the QCOW2 format

[Alex Bligh]

On 15 Aug 2013, at 01:53, Fam Zheng wrote:

> On Wed, 08/14 13:03, Alex Bligh wrote:
>> 
>> On 14 Aug 2013, at 12:52, Fam Zheng wrote:
>> 
>>> Yes, this one sounds good to have. VMDK and VHDX have this kind of
>>> backing file status validation.
>> 
>> ... though I'd prefer something safer than looking at mtime, for
>> instance a sequence number that is incremented prior to any
>> bdrv_close if a write has been done since bdrv_open.
>> 
> It should be incremented prior to any write for each r/w open, in case
> program crashes after write but before close.

Yup - well prior to the first write anyway.

-- 
Alex Bligh