Re: [Xen-devel] BUG 4.2.2: xl cd-insert corrupts xenstore state

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 01/05/13 16:59, Ian Jackson wrote:
> George Dunlap writes ("Re: BUG 4.2.2: xl cd-insert corrupts xenstore state"):
> > Turns out I already fixed this once!
> >
> > commit c3556e2a1aee3c9b7dda5d57e85e8867fff1b9da
> > Author: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> > Commit: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> Here's the backport, which was nearly trivial.
>
> I'll push this to 4.2 staging unless someone objevts.
FYI, I'm pretty sure the effect this will have is to change the failure 
I was seeing in 4.2 (xl crashing) to the failure Fabio and I were seeing 
in 4.3 with cd-eject and cd-insert.
I think the situation without this patch is:
* cd-eject messes up xenstore, causes future block commands to crash
* cd-insert works
With this patch, I think what happen sis:
* cd-eject fails but does not mess up xenstore
* cd-insert also fails

It should be noted that this is only true *if blktap is available*; if 
blktap is not available, libxl uses qdev and everything works fine.
(And I should emphasize, this is prediction based on my recent 
experience with unstable, and hasn't been verified by testing.)
The problem actually turns out to be that if blktap is available, that 
libxl will choose it for cdroms, but the cd-insert and cd-eject stuff 
don't work with blktap.  I think I'm going to submit a patch for 4.3 
that prevents blktap from being used for cdroms -- you may want to wait 
and backport them both.
 -George

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