Re: [Xen-devel] [PATCHv3] QEMU(upstream): Disable xen's use of O_DIRECT by default as it results in crashes.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 20 Mar 2013, Paolo Bonzini wrote:
> Il 20/03/2013 09:33, Alex Bligh ha scritto:
> > Stefano,
> > 
> > --On 19 March 2013 15:13:29 +0000 Stefano Stabellini
> > <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > 
> >> Therefore I think that the current change is not safe, but it is pretty
> >> easy to make it safe.
> >> You just need to move the call to blk_open from blk_init to blk_connect.
> >> Actually you can move most of blk_init to blk_connect, you just need to
> >> keep the 4 xenstore_write_be_int at the end of the function.
> > 
> > The final of these 4 writes in blk_init is:
> > 
> >    xenstore_write_be_int(&blkdev->xendev, "sectors",
> >                          blkdev->file_size / blkdev->file_blk);
> > 
> > and blkdev->filesize comes from bdrv_getlength(blkdev->bs), and that
> > requires (I think) bdrv_open to have been called. Can these
> > 4 writes move safely to blk_connect? Or can we write the sectors
> > count as (say) 0 here and fix it later in blk_connect? The remainder
> > look ok.
> 
> I think so.  blkfront reads "sectors" when QEMU moves to
> XenbusStateConnected, in blkfront_connect.
> 
> blk_connect is called from xen_be_try_initialise, which moves to
> XenbusStateConnected on success.  So, QEMU's blk_connect will always be
> called before blkfront's blkfront_connect.

Alex, do you have any updates on this patch?

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