On 08/06/2012 11:17 PM, Christoph Hellwig wrote:
On Thu, Aug 02, 2012 at 02:43:04PM +0800, Asias He wrote:
Even if it has a payload waiting is highly suboptimal and it should
use a non-blocking sequencing like it is done in the request layer.
So, for REQ_FLUSH, what we need is that send out the VIRTIO_BLK_T_FLUSH and
not to wait.
If it's REQ_FLUSH without data a VIRTIO_BLK_T_FLUSH should be sent out only,
if it's a REQ_FLUSH that has data a VIRTIO_BLK_T_FLUSH should be sent out,
but instead of waiting for it to finish the I/O completion handler should
then submit the actual write.
We still need to wait until the actual write is finished here?
Like,
REQ_FUA is emulated by:
1. Send the actual write
2. Wait until the actual write is finished
3. Send VIRTIO_BLK_T_FLUSH to device
4. Signal the end of the write to upper layer
Remove step 2 and run step 3 from the I/O completion handler.
Thanks for the explanation. V6 is in flight.
--
Asias
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