On 9/14/2022 1:49 PM, Andrew Morton wrote:
On Wed, 14 Sep 2022 12:09:17 -0700 Doug Berger opendmb@gmail.com wrote:
With gigantic pages it may not be true that struct page structures are contiguous across the entire gigantic page. The nth_page macro is used here in place of direct pointer arithmetic to correct for this.
What were the user-visible runtime effects of this bug?
As Mike said this would only conceptually be a problem for systems with CONFIG_SPARSEMEM && !CONFIG_SPARSEMEM_VMEMMAP, and could cause kernel address exceptions or memory corruption with unpredictable side effects.
However, I am unaware of a system other than perhaps the PS3 that uses the classic sparse addressing, so the odds of such a system also using gigantic hugetlbfs pages that it wants to demote is likely quite small.
Thanks, -Doug