Re: [Qemu-devel] [PATCH] block: Flush image after open

[Christoph Hellwig]

On Wed, Mar 09, 2011 at 05:15:53PM +0100, Kevin Wolf wrote:
> Quoting the bug report:
> 
>     qemu ensures that guest writes and qemu metadata writes hit the disk
>     when necessary to prevent data corruption. However, if an image was
>     in host pagecache prior to starting qemu, for example after running
>     qemu-img convert, then nothing prevents writes from reaching the
>     disk out of order, potentially causing corruption.
> 
> I'm not entirely sure if there is a realistic case where we would get
> corruption, but it's probably a case of better safe than sorry.

Except for SCSI with ordered tags (which we don't support) there are not
ordering guarantees in the storage protocols, and as such the above explanation
doesn't make any sense at all.