Re: [Qemu-devel] [PULL] xen patches

[Christoph Hellwig]

On Tue, Apr 24, 2012 at 12:28:35PM +0100, Stefano Stabellini wrote:
>       xen_disk: use bdrv_aio_flush instead of bdrv_flush

This one seems completely broken, as it just queues up the flushes and
writes without any ordering between them.  Linux filesystems absolutely
rely on a REQ_FUA request which gets mapped to BLKIF_OP_FLUSH_DISKCACHE
to flush the data it actually sent.

I'm not sure who actually expects the preflush, but the only point
in ever doing it would be to sequence it properly vs the write.