Messages in this thread | | | Date | Mon, 30 Jul 2012 12:43:12 +0800 | From | Asias He <> | Subject | Re: [PATCH V3 3/3] virtio-blk: Add bio-based IO path for virtio-blk |
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On 07/28/2012 02:42 PM, Paolo Bonzini wrote: >>> I'm not sure what the correct behavior for bio & cacheflush is, if >>> any. >> >> REQ_FLUSH is not supported in the bio path. > > Ouch, that's correct: > > @@ -414,7 +529,7 @@ static void virtblk_update_cache_mode(struct virtio_device *vdev) > u8 writeback = virtblk_get_cache_mode(vdev); > struct virtio_blk *vblk = vdev->priv; > > - if (writeback) > + if (writeback && !use_bio) > blk_queue_flush(vblk->disk->queue, REQ_FLUSH); > else > blk_queue_flush(vblk->disk->queue, 0); > > then it is not safe against power losses.
Yes. Something like this:
qemu -drive file=foo.img,cache=writeback/unsafe
is not safe against power losses also?
I think we can add REQ_FLUSH & REQ_FUA support to bio path and that deserves another patch.
-- Asias
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