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@linux.alibaba.com 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.