Re: [Xen-devel] [PATCH] xencommons: Attempt to load blktap driver

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.05.12 at 18:40, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
> On 15/05/12 17:36, Jan Beulich wrote:
>>>>> On 15.05.12 at 18:21, George Dunlap<george.dunlap@xxxxxxxxxxxxx>  wrote:
>>>   But if not, I suggest we accept this patch, and I'll come
>>> back and try to write a proper one before the 4.2 release.  I think it's
>>> really important we do something before 4.2, as it causes pretty serious
>>> problems on systems which are affected (almost always a host crash,
>>> possibly with some disk corruption).
>> A host crash because of a driver not loaded? That would suggest
>> bugs elsewhere...
> Yes -- a bug in the AIO implementation for foreign pages, as the 
> description states.

But if there's no backend driver, there shouldn't be any I/O at all,
and hence no crash? Or are you saying that in the absence of the
driver another (qdisk?) backend gets selected (which doesn't match
my own observations, at least not as far as local attach to Dom0
is concerned, and I would hope [expect] that backend selection
doesn't depend on which domain the frontend lives in)?

Finally, loading "blktap" here is the right thing for pvops, but
wrong for legacy/forward ported kernels - blktap2 would be
the right module name there afaict. Perhaps, if this really is to
go in (temporarily), loading an alias (devname: or xen-backend:,
though the latter apears to be missing from the pvops driver)
would be better here?

Jan


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