Re: [Xen-devel] xl hangs instead of failing more graciously when the fs is read-only

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-06-12 at 09:47 +0200, Sander Eikelenboom wrote:
> Hi Ian,
> 
> At the moment Iâm having the privilege of thrashing my box and root-fs 
> frequently while testing kernels. This causes the root-fs to be mounted 
> read-only. But init continues to do it's job any way .. so we get to 
> xendomains,
> which in turn uses 'xl'. But 'xl' needs a writable FS and hangs when it's not,
> couldn't and shouldn't this fail more graciously ?

Your logs seem to be showing reads/writes to a xenbus device, which has
nothing to do with the writeablility of your rootfs afaik.

I'm pretty sure xl will correctly error out if it fails to write to a
file on a readonly fs, or at least I see no evidence here that it is
not.

Maybe the issue is that xenstored is blocked or by the rootfs ro-ness
(or not even started due to it) and so attempts to communicate with it
fail?

I think the right answer is to always have a writeable rootfs rather
than glossing over whatever error led to this situation.

But I suppose as a fallback xendomains could try and probe for a usable
xenstored before proceeding, similar to how xencommons does (ideally
with a shared scriptlet somewhere).

Ian.



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