Re: [Qemu-devel] [PATCH] qemu-img: let qemu-img behave as the manual advertise

[Kevin Wolf]

Am 11.04.2012 12:05, schrieb Liu Yuan:
> On 04/11/2012 03:49 PM, Kevin Wolf wrote:
> 
>> I don't agree with this patch. If the documentation says that qemu-img
>> always uses writeback, then the documentation must be fixed.
>>
>> We really don't care about flushes during an image conversion. It should
>> just go as fast as it can. If any error happens in the middle, you'll
>> have to throw the image away anyway, because it contains only half of
>> what you need. So not having flushed doesn't really make any difference.
>>
>> As soon as a guest begins using the image with data that we really care
>> about, it's probably running in a VM with non-unsafe mode, and then it
>> gets flushed.
> 
> 
> But we can set cache mode for qemu-img convert. So at least if we set
> explicitly with other modes(for e.g, writeback) that ask to flush the
> dirty bits, I think we should call brdv_flush().
> 
> If you agree, I'll update the patch with this modification.

Yes, adding the flush is fine, I just wouldn't change the default cache
mode.

Kevin