Re: [Qemu-devel] [PATCH] qcow2: Metadata preallocation

[Kevin Wolf]

Jamie Lokier schrieb:
> Filip Navara wrote:
>> FILE_ATTRIBUTE_SPARSE_FILE? You can't actually set it when
>> opening/creating the file, a separate call to
>> DeviceIoControl/FSCTL_SET_SPARSE is needed.
> 
> I see that you increase the file size by writing zeros to the end.
> 
> Can't you use the Windows equivalent of unix ftruncate() to extend the
> file instead, after FSCTL_SET_SPARSE?

There actually exists a bdrv_truncate(). I wasn't aware of that. If you
prefer, I can resend the patch with bdrv_truncate instead of a zero write.

Kevin