Re: [PATCH v3 1/4] hugetlb: Fix wrong use of nr_online_nodes

[Davidlohr Bueso <dave@stgolabs.net>]

On Wed, 13 Apr 2022, Peng Liu wrote:

>Certain systems are designed to have sparse/discontiguous nodes. In
>this case, nr_online_nodes can not be used to walk through numa node.
>Also, a valid node may be greater than nr_online_nodes.
>
>However, in hugetlb, it is assumed that nodes are contiguous. Recheck
>all the places that use nr_online_nodes, and repair them one by one.
>
>Suggested-by: David Hildenbrand <david@redhat.com>
>Fixes: 4178158ef8ca ("hugetlbfs: fix issue of preallocation of gigantic pages can't work")
>Fixes: b5389086ad7b ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
>Fixes: e79ce9832316 ("hugetlbfs: fix a truncation issue in hugepages parameter")
>Fixes: f9317f77a6e0 ("hugetlb: clean up potential spectre issue warnings")
>Signed-off-by: Peng Liu <liupeng256@huawei.com>
>Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>

... but

>---
> mm/hugetlb.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
>diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>index b34f50156f7e..5b5a2a5a742f 100644
>--- a/mm/hugetlb.c
>+++ b/mm/hugetlb.c
>@@ -2979,7 +2979,7 @@ int __alloc_bootmem_huge_page(struct hstate *h, int nid)
>	struct huge_bootmem_page *m = NULL; /* initialize for clang */
>	int nr_nodes, node;
>
>-	if (nid != NUMA_NO_NODE && nid >= nr_online_nodes)
>+	if (nid != NUMA_NO_NODE && !node_online(nid))

afaict null_blk could also use this, actually the whole thing wants a
helper - node_valid()?