On 01/30/2013 04:56 PM, Dave Hansen wrote: > This code was an optimization for 32-bit NUMA systems. > > It has probably been the cause of a number of subtle bugs over > the years, although the conditions to excite them would have > been hard to trigger. Essentially, we remap part of the kernel > linear mapping area, and then sometimes part of that area gets > freed back in to the bootmem allocator. If those pages get > used by kernel data structures (say mem_map[] or a dentry), > there's no big deal. But, if anyone ever tried to use the > linear mapping for these pages _and_ cared about their physical > address, bad things happen. > > For instance, say you passed __GFP_ZERO to the page allocator > and then happened to get handed one of these pages, it zero the > remapped page, but it would make a pte to the _old_ page. > There are probably a hundred other ways that it could screw > with things. > > We don't need to hang on to performance optimizations for > these old boxes any more. All my 32-bit NUMA systems are long > dead and buried, and I probably had access to more than most > people. > > This code is causing real things to break today: > > https://lkml.org/lkml/2013/1/9/376 > > I looked in to actually fixing this, but it requires surgery > to way too much brittle code, as well as stuff like > per_cpu_ptr_to_phys(). > I get a build failure on i386 allyesconfig with this patch: arch/x86/power/built-in.o: In function `swsusp_arch_resume': (.text+0x14e4): undefined reference to `resume_map_numa_kva' It looks trivial to fix up; I assume resume_map_numa_kva() just goes away like it does in the non-NUMA case, but it would be nice if you could confirm that. -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>