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?
