From 0effdf461c5789be02d40c1868c70cc02ea24627 Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Fri, 13 May 2022 16:48:56 -0700 Subject: [PATCH] mm: hugetlb_vmemmap: disable hugetlb_optimize_vmemmap when struct page crosses page boundaries Patch series "add hugetlb_optimize_vmemmap sysctl", v11. This series aims to add hugetlb_optimize_vmemmap sysctl to enable or disable the feature of optimizing vmemmap pages associated with HugeTLB pages. This patch (of 4): If the size of "struct page" is not the power of two but with the feature of minimizing overhead of struct page associated with each HugeTLB is enabled, then the vmemmap pages of HugeTLB will be corrupted after remapping (panic is about to happen in theory). But this only exists when !CONFIG_MEMCG && !CONFIG_SLUB on x86_64. However, it is not a conventional configuration nowadays. So it is not a real word issue, just the result of a code review. But we cannot prevent anyone from configuring that combined configure. This hugetlb_optimize_vmemmap should be disable in this case to fix this issue. Link: https://lkml.kernel.org/r/20220512041142.39501-1-songmuchun@bytedance.com Link: https://lkml.kernel.org/r/20220512041142.39501-2-songmuchun@bytedance.com Signed-off-by: Muchun Song Reviewed-by: Mike Kravetz Cc: David Hildenbrand Cc: Iurii Zaikin Cc: Jonathan Corbet Cc: Kees Cook Cc: Luis Chamberlain Cc: Masahiro Yamada Cc: Oscar Salvador Cc: Xiongchun Duan Signed-off-by: Andrew Morton --- mm/hugetlb_vmemmap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index 29554c6ef2ae..6254bb2d4ae5 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -28,12 +28,6 @@ EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key); static int __init hugetlb_vmemmap_early_param(char *buf) { - /* We cannot optimize if a "struct page" crosses page boundaries. */ - if (!is_power_of_2(sizeof(struct page))) { - pr_warn("cannot free vmemmap pages because \"struct page\" crosses page boundaries\n"); - return 0; - } - if (!buf) return -EINVAL; @@ -119,6 +113,12 @@ void __init hugetlb_vmemmap_init(struct hstate *h) if (!hugetlb_optimize_vmemmap_enabled()) return; + if (!is_power_of_2(sizeof(struct page))) { + pr_warn_once("cannot optimize vmemmap pages because \"struct page\" crosses page boundaries\n"); + static_branch_disable(&hugetlb_optimize_vmemmap_key); + return; + } + vmemmap_pages = (nr_pages * sizeof(struct page)) >> PAGE_SHIFT; /* * The head page is not to be freed to buddy allocator, the other tail