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Date: Sat, 19 Jan 2013 02:06:11 +0800
From: Liu Yuan <namei.unix@gmail.com>
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Subject: Re: [Qemu-devel] bdrv_co_flush_to_disk() don't flush as expected
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Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>

On 01/18/2013 11:43 PM, Liu Yuan wrote:
>  # start up the guest
>  $ qemu-system-x86_64 --enable-kvm -drive
> file=~/images/test1,if=virtio,cache=writeback -smp 2 -cpu host -m 1024
> -drive file=sheepdog:test,if=virtio,cache=writeback
>  # write to the /dev/vdb of the guest
>  # sudo dd if=/dev/urandom of=/dev/vdb bs=4M count=1 oflag=direct,sync
> 
> This doesn't trigger flush for vdb device. I also write a small program
> to call fsync(2) to the device, no flush neither.
> 
> Only the poweroff of the guest will trigger the flush request for vdb.
> So is this expected behavior and I am missing something?

Oops, it is something wrong in the Guest. I created a new guest and it
works like a charm. Sorry for the false alarm.

Thanks,
Yuan