Re: [Xen-devel] [PATCH 0 of 2] xl: fix localhost migration after 25733:353bc0801b11

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-08-07 at 12:02 +0100, Ian Campbell wrote:

> # HG changeset patch
> # User Ian Campbell <ian.campbell@xxxxxxxxxx>
> # Date 1344337292 -3600
> # Node ID c5f673d8b330d6195e2aa3bbf63bb594b4bc99ee
> # Parent  a7ad22e5525831dd491d7ee1fe538b7543404ac7
> libxl: write physical-device node if user did not supply a block script
> 
> This reverts one of the intentional changes from 25733:353bc0801b11.
> That change exposed an issue with the xl migration protocol, which
> although safe triggers the hotplug scripts device sharing logic.
> 
> For 4.2 we disable this logic by writing the physical-device xenstore
> node ourselves if a user did not supply a script. If the user did
> supply a script then we continue to rely on it to write the
> physical-device node (not least because the script may create the
> device and therefore it is not available before we run the script).
> 
> This means that to support localhost migration a block hotplug script
> needs to be robust against adding a device twice and should not
> deactivate the device until it has been removed twice.
> 
> This should be revisted for 4.3.
                     ^i
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Ian J acked this IRL so I have committed.

Our reasoning is that at this stage in the release it is better to go
back to the previous behaviour, which although strictly speaking wrong
is harmless and has no API implications, rather than try to invent new
correct APIs on short notice etc.

Ian.


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