[libvirt] [PATCH/RFC]: don't ignore errors to save the domain status file

[Daniel P. Berrange]

On Sat, Jan 31, 2009 at 02:32:09PM +0100, Guido G?nther wrote:
> Hi,
> we currently don't report errors to save qemu's domain status file back
> to the caller. That was o.k. as long as the code was there for testing
> but now that the XML is being picked up on daemon restart we must
> handle these.
> The attached patch does that, although I'm not confident that it's
> enough. While we return error on device attach/unattach the device
> actually got attached/unattached already. Same is true for
> suspend/resume.
> A better solution would be to write out the new domain status into a
> temp file and simply call rename(2) on it when the attach/unattach
> succeeds and discard it if it fails. This would minimize the possible
> error conditions like disk full, missing permissions to write into that
> directory etc. Does this sound reasonable?

Yeah, I think that sounds like a reasonable idea

 virPrepareStatusFile()
 virSaveStatusFile()

the former creates the temporary file, and the latter does
the rename().

In the prepare stage, we could also do a access(R_OK)
check on the eventual target, as a sanity check that
we're likely to be able to complete the rename() later.


Daniel
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