On Mon, Dec 05, 2016 at 03:42:14PM +0000, Ard Biesheuvel wrote: > On 2 December 2016 at 14:49, James Morse <james.mo...@arm.com> wrote: > > Patch "arm64: mm: Fix memmap to be initialized for the entire section" > > changes pfn_valid() in a way that breaks hibernate. These patches fix > > hibernate, and provided struct page's are allocated for nomap pages, > > can be applied before [0]. > > > > Hibernate core code belives 'valid' to mean "I can access this". It > > uses pfn_valid() to test the page if the page is 'valid'. > > > > pfn_valid() needs to be changed so that all struct pages in a numa > > node have the same node-id. Currently 'nomap' pages are skipped, and > > retain their pre-numa node-ids, which leads to a later BUG_ON(). > > > > These patches make hibernate's savable_page() take its escape route > > via 'if (PageReserved(page) && pfn_is_nosave(pfn))'. > > > > This makes me feel slightly uneasy. Robert makes a convincing point, > but I wonder if we can expect more fallout from the ambiguity of > pfn_valid(). Now we are not only forced to assign non-existing (as far > as the OS is concerned) pages to the correct NUMA node, we also need > to set certain page flags.
Yes, I really don't know how to proceed here. Playing whack-a-mole with pfn_valid() users doesn't sounds like an improvement on the current situation to me. Robert -- if we leave pfn_valid() as it is, would a point-hack to memmap_init_zone help, or do you anticipate other problems? Will