[libvirt] [PATCH] virNumaGetHugePageInfo: Return page_avail and page_free as ULL

[Michal Privoznik]

On 04/24/2018 10:42 AM, Daniel P. Berrangé wrote:
> On Mon, Apr 23, 2018 at 05:44:38PM +0200, Michal Privoznik wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1569678
>>
>> On some large systems (with ~400GB of RAM) it is possible for
>> unsigned int to overflow in which case we report invalid number
>> of 4K pages pool size. Switch to unsigned long long.
> 
> It isn't very obvious from the code diff what the actual problem
> is, but it is mentioned in the bug that we hit overflow in
> virNumaGetPages when doing:
> 
>         huge_page_sum += 1024 * page_size * page_avail;
> 
> because although 'huge_page_sum' is an unsigned long long, the
> page_size and page_avail are both unsigned int, so the promotion
> to unsigned long long doesn't happen until the sum has been
> calculated, by which time we've already overflowed.  Can you
> mention that we're specifically solving this huge_page_sum
> overflow in the commit message
> 
> Turning page_avail into a unsigned long long is not strictly
> needed until we need ability to represent more than 2^32
> 4k pages, which IIUC equates to 16 TB of RAM. That's not
> outside the realm of possibility, so makes sense that we
> change it to unsigned long long to avoid future problems.
> Can you also mention that we're solving this limit too
> in the commit message.
> 
> Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>

Adjusted and pushed. Thank you.

Michal