On Thu, Jul 23, 2020 at 08:08:46PM -0700, Andrew Morton wrote: >On Tue, 23 Jun 2020 17:30:18 +0800 Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> wrote: > >> On Tue, Jun 23, 2020 at 09:55:43AM +0200, David Hildenbrand wrote: >> >On 23.06.20 09:39, David Hildenbrand wrote: >> >>> Hmm.. I thought this is the behavior for early section, while it looks current >> >>> code doesn't work like this: >> >>> >> >>> if (section_is_early && memmap) >> >>> free_map_bootmem(memmap); >> >>> else >> >>> depopulate_section_memmap(pfn, nr_pages, altmap); >> >>> >> >>> section_is_early is always "true" for early section, while memmap is not-NULL >> >>> only when sub-section map is empty. >> >>> >> >>> If my understanding is correct, when we remove a sub-section in early section, >> >>> the code would call depopulate_section_memmap(), which in turn free related >> >>> memmap. By removing the memmap, the return value from pfn_to_online_page() is >> >>> not a valid one. >> >> >> >> I think you're right, and pfn_valid() would also return true, as it is >> >> an early section. This looks broken. >> >> >> >>> >> >>> Maybe we want to write the code like this: >> >>> >> >>> if (section_is_early) >> >>> if (memmap) >> >>> free_map_bootmem(memmap); >> >>> else >> >>> depopulate_section_memmap(pfn, nr_pages, altmap); >> >>> >> >> >> >> I guess that should be the way to go >> >> >> >> @Dan, I think what Wei proposes here is correct, right? Or how does it >> >> work in the VMEMMAP case with early sections? >> >> >> > >> >Especially, if you would re-hot-add, section_activate() would assume >> >there is a memmap, it must not be removed. >> > >> >> You are right here. I didn't notice it. >> >> >@Wei, can you send a patch? >> > >> >> Sure, let me prepare for it. > >Still awaiting this, and the v3 patch was identical to this v2 patch. > >It's tagged for -stable, so there's some urgency. Should we just go >ahead with the decently-tested v2? This message is to me right? I thought the fix patch is merged, the patch link may be https://lkml.org/lkml/2020/6/23/380. If I missed something, just let me know. -- Wei Yang Help you, Help me
