On 01/09/2017 08:57 AM, Jerome Glisse wrote:
> On Mon, Jan 09, 2017 at 08:21:25AM -0800, Dave Hansen wrote:
>> On 01/09/2017 01:19 AM, Balbir Singh wrote:
>>>> + /*
>>>> + * This should never happen ! Page from ZONE_DEVICE always must have an
>>>> + * active refcount. Complain about it and try to restore the refcount.
>>>> + */
>>>> + if (is_zone_device_page(page)) {
>>>> + VM_BUG_ON_PAGE(is_zone_device_page(page), page);
>>> This can be VM_BUG_ON_PAGE(1, page), hopefully the compiler does the right thing
>>> here. I suspect this should be a BUG_ON, independent of CONFIG_DEBUG_VM
>> BUG_ON() means "kill the machine dead". Do we really want a guaranteed
>> dead machine if someone screws up their refcounting?
> VM_BUG_ON_PAGE ok with you ? It is just a safety net, i can simply drop that
> patch if people have too much feeling about it.
Enough distros turn on DEBUG_VM that there's basically no difference
between VM_BUG_ON() and BUG_ON().
I also think it would be much nicer if you buried the check in the
allocator in a slow path somewhere instead of sticking it in one of the
hottest paths in the whole kernel.
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