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Re: [Xen-devel] domU oom -> xvda1 read-only without any notice?

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] domU oom -> xvda1 read-only without any notice?
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Wed, 31 Mar 2010 09:54:59 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Josip Rodin <joy@xxxxxxxxxxxxxx>
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On Wed, 2010-03-31 at 09:45 +0100, Keir Fraser wrote:
> 
> AFAIK that means that the read-only-ness is not being propagated up to
> domU block layer by the xen_blockfront driver. I'm not sure exactly
> what other possibilities there are, but if the kernel has been OOMing
> processes then perhaps you're in a runlevel or mode, or even a kenrel
> bug, in which rootfs is forced read-only for other reasons? There have
> been bugs around OOM in the past, and really it's a kernel path that's
> obviously best avoided! Any idea why the OOM occurred in the first
> place?

Root filesystems are often mounted with the "errors=remount-ro" option
(is it the Debian default?). So it's possible this is a domU decision to
go read-only, but the question remains as to what happened in the domU
to trigger this decision, can an OOM do that? There might be something
earlier in the domU dmesg?

Ian.



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