On Mon, Jul 31, 2017 at 08:41:16AM +0200, Michal Hocko wrote: > On Fri 28-07-17 15:41:47, Greg KH wrote: > > On Fri, Jul 28, 2017 at 03:53:35PM +0200, Michal Hocko wrote: > > > JFYI. We have encountered a regression after applying this patch on a > > > large ppc machine. While the patch is the right thing to do it doesn't > > > work well with the current vmalloc area size on ppc and large machines > > > where NUMA nodes are very far from each other. Just for the reference > > > the boot fails on such a machine with bunch of warning preceeding it. > > > See http://lkml.kernel.org/r/20170724134240.GL25221@xxxxxxxxxxxxxx > > > > > > It seems the right thing to do is to enlarge the vmalloc space on ppc > > > but this is not the case in the upstream kernel yet AFAIK. It is also > > > questionable whether that is a stable material but I will decision on > > > you here. > > > > > > We have reverted this patch from our 4.4 based kernel. > > > > But all is fine on newer kernels? That is odd. > > Newer kernels do not have enlarged vmalloc space yet AFAIK so they won't > work properly eiter. This bug is quite rare though because you need a > specific HW configuration to trigger the issue - namely NUMA nodes have > to be far away from each other in the physical memory space. > > > I'll be glad to drop it, but should it be dropped from all stable trees? > > Yes from all stable backports. Ok, now all reverted, thanks. greg k-h