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.