Re: [PATCH] virtio_blk: support barriers without FLUSH feature

From: Rusty Russell
Date: Tue Jun 15 2010 - 21:56:42 EST

On Tue, 15 Jun 2010 10:13:48 pm Christoph Hellwig wrote:
> If we want to support barriers with the cache=writethrough mode in qemu
> we need to tell the block layer that we only need queue drains to
> implement a barrier. Follow the model set by SCSI and IDE and assume
> that there is no volatile write cache if the host doesn't advertize it.
> While this might imply working barriers on old qemu versions or other
> hypervisors that actually have a volatile write cache this is only a
> cosmetic issue - these hypervisors don't guarantee any data integrity
> with or without this patch, but with the patch we at least provide
> data ordering.
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Thanks, applied.

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