RE: [Xen-devel] RE: Window VM hit blue screen when dom0 uses ext4 with extent enabled

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Thu, 2011-07-14 at 09:41 +0100, MaoXiaoyun wrote:
> 
>  
> > 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 2.6.32.36 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.
> Meanwhile, there are quite a lot ext4 patches in upstream, I'm afried 
> some of them are also needed for stable ext4, well, not sure.
>  
> Could someone kindly backport e9e3bcecf44c04b9e6b505fd8e2eb9cea58fb94d
> for me? 

I think would be a good idea to ping the ext4 developers about this and
suggest that this might be a candidate for an upstream stable backport.
If not then it would be good to know why not instead of blindly taking
it into our stable tree...

Ian.

>  
> Many thanks.
> 
> > Ian.
> > 
> > 
> > 
> 



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