From 6d7bc938adca9024a6b51cf55d9b0542b653b69c Mon Sep 17 00:00:00 2001 From: Luiz Capitulino Date: Mon, 10 Feb 2025 22:48:56 -0500 Subject: [PATCH] mm: hugetlb: avoid fallback for specific node allocation of 1G pages When using the HugeTLB kernel command-line to allocate 1G pages from a specific node, such as: default_hugepagesz=1G hugepages=1:1 If node 1 happens to not have enough memory for the requested number of 1G pages, the allocation falls back to other nodes. A quick way to reproduce this is by creating a KVM guest with a memory-less node and trying to allocate 1 1G page from it. Instead of failing, the allocation will fallback to other nodes. This defeats the purpose of node specific allocation. Also, specific node allocation for 2M pages don't have this behavior: the allocation will just fail for the pages it can't satisfy. This issue happens because HugeTLB calls memblock_alloc_try_nid_raw() for 1G boot-time allocation as this function falls back to other nodes if the allocation can't be satisfied. Use memblock_alloc_exact_nid_raw() instead, which ensures that the allocation will only be satisfied from the specified node. Link: https://lkml.kernel.org/r/20250211034856.629371-1-luizcap@redhat.com Fixes: b5389086ad7b ("hugetlbfs: extend the definition of hugepages parameter to support node allocation") Signed-off-by: Luiz Capitulino Acked-by: Oscar Salvador Acked-by: David Hildenbrand Cc: "Mike Rapoport (IBM)" Cc: Muchun Song Cc: Zhenguo Yao Cc: Frank van der Linden Signed-off-by: Andrew Morton --- mm/hugetlb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 65068671e460..163190e89ea1 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3145,7 +3145,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid) /* do node specific alloc */ if (nid != NUMA_NO_NODE) { - m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h), + m = memblock_alloc_exact_nid_raw(huge_page_size(h), huge_page_size(h), 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid); if (!m) return 0;