Re: [PATCH V3 3/3] virtio-blk: Add bio-based IO path for virtio-blk

From: Christoph Hellwig
Date: Mon Jul 30 2012 - 09:51:18 EST


On Mon, Jul 30, 2012 at 09:31:06AM +0200, Paolo Bonzini wrote:
> You only need to add REQ_FLUSH support. The virtio-blk protocol does
> not support REQ_FUA, because there's no easy way to do it in userspace.

A bio-based driver needs to handle both REQ_FLUSH and REQ_FUA as it does
not get the sequencing of REQ_FUA into REQ_FLUSH that request based drivers
can request. To what the REQ_FUA request gets translated is a different story.
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