> Subject: Re: [Xen-devel] RE: Window VM hit blue screen when dom0 uses ext4 with extent enabled
> From: Ian.Campbell@xxxxxxxxxx
> To: tinnycloud@xxxxxxxxxxx
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx; jeremy@xxxxxxxx; konrad.wilk@xxxxxxxxxx
> Date: Thu, 14 Jul 2011 09:02:06 +0100
> On Thu, 2011-07-14 at 06:44 +0100, MaoXiaoyun wrote:
> > I think the 18.104.22.168 ext4 needs to backport this patch much likely.
> > Otherwise it will hit the problem I met.
> > http://patchwork.ozlabs.org/patch/79880/
> That version is still in state NEW but something appears to have been
> committed upstream as e9e3bcecf44c04b9e6b505fd8e2eb9cea58fb94d:
> ext4: serialize unaligned asynchronous DIO
> ext4 has a data corruption case when doing non-block-aligned
> asynchronous direct IO into a sparse file, as demonstrated
> by xfstest 240.
> Seems like a reasonable enough thing to backport to me (for what that's
> worth). Although:
> It is also quite a lot slower
> (14 min for package installs, vs. 8 min for well-aligned)
> but I'll take slow correctness over fast corruption any day.
> Mingming suggested that we can track outstanding
> conversions, and wait on those so that non-sparse
> files won't be affected, and I've implemented that here;
> unaligned AIO to nonsparse files won't take a perf hit.
> Something to bear in mind if you are deploying anything based on sparse
> files on ext4.
That's right. Since we use VHD as our base image.
We are trying to backport this patch, but isn't easy for me.
some of them are also needed for stable ext4, well, not sure.