[Qemu-devel] Re: [PATCH +stable] block: don't attempt to merge overlapping requests

[Avi Kivity]

On 05/18/2010 10:22 PM, Stefan Hajnoczi wrote:
> On Tue, May 18, 2010 at 6:18 PM, Avi Kivity<address@hidden>  wrote:
>    
> > The block multiwrite code pretends to be able to merge overlapping requests,
> > but doesn't do so in fact.  This leads to I/O errors (for example on mkfs
> > of a large virtio disk).
> >      
> Are overlapping write requests correct guest behavior?  I thought the
> ordering semantics require a flush between overlapping writes to
> ensure A is written before B.
>
> What cache= mode are you running?
>    

writeback.

--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.