Re: [PATCH] kvm-userland mm count skew

[Andrea Arcangeli <andrea-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

On Tue, Jan 22, 2008 at 03:41:02PM +0200, Avi Kivity wrote:
> Andrea Arcangeli wrote:
>> I still can't see how it could be possibly make a difference for the
>> mm_count if the kvm module is compiled inside the kernel or as an
>> external module, the reference counting there hasn't changed since
>> ages. The mmdrop fires only in the first overflow so even if I'm right
>> it probably wasn't much destabilizing to go negative given it happened
>> at mm destruction time.
>>
>>   
>
> It's this bit:

Ok. But the atomic_inc removal isn't conditional to < 2.6.25, so it
still doesn't look good to me. it would look better if we would
unconditionally define mmdrop to nop in the external module
compile. The other problem is that I don't see why atomic_inc/mmdrop
are needed at all if the external module is safe, so why don't we drop
them? In ->release->kvm_destroy_vm it seems the kvm->mm is never used
anyway.

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