Messages in this thread | | | Date | Mon, 6 Aug 2012 17:17:31 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH V5 4/4] virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path |
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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.
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