On Thu 01-08-19 09:39:57, Michal Hocko wrote: > On Thu 01-08-19 09:31:09, David Hildenbrand wrote: > > On 01.08.19 09:26, David Hildenbrand wrote: > [...] > > > I am not sure about the implications of having > > > pfn_valid()/pfn_present()/pfn_online() return true but accessing it > > > results in crashes. (suspend, kdump, whatever other technology touches > > > online memory) > > > > (oneidea: we could of course go ahead and mark the pages PG_offline > > before unmapping the pfn range to work around these issues) > > PG_reserved and an elevated reference count should be enough to drive > any pfn walker out. Pfn walkers shouldn't touch any page unless they > know and recognize their type. Btw. this shouldn't be much different from DEBUG_PAGE_ALLOC in principle. The memory is valid, but not mapped to the kernel virtual space. Nobody should be really touching it anyway. -- Michal Hocko SUSE Labs
