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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-03-11 at 14:42 +0000, George Dunlap wrote:
> On 11/03/13 14:02, Alex Bligh wrote:
> >
> > --On 8 March 2013 12:54:16 +0000 George Dunlap
> > <George.Dunlap@xxxxxxxxxxxxx> wrote:
> >
> >> On Fri, Mar 8, 2013 at 11:40 AM, Alex Bligh <alex@xxxxxxxxxxx> wrote:
> >>> Due to what is almost certainly a kernel bug, writes with
> >>> O_DIRECT may continue to reference the page after the write
> >>> has been marked as completed, particularly in the case of
> >>> TCP retransmit. In other scenarios, this "merely" risks
> >>> data corruption on the write, but with Xen pages from domU
> >>> are only transiently mapped into dom0's memory, resulting
> >>> in kernel panics when they are subsequently accessed.
> >>>
> >>> This brings PV devices in line with emulated devices. Removing
> >>> O_DIRECT is safe as barrier operations are now correctly passed
> >>> through.
> >> Not qualified to comment on the technical merits of the patch, but re
> >> the commit message:
> >>
> >> Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> > Any further thoughts on this one?
> 
> I believe that Stefano is the person to commit it, but he's on holiday 
> for two weeks.

I don't think its that long -- IIRC he's due back tomorrow (although
perhaps not in the office until Thursday).

Ian.



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