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

[Davidlohr Bueso]

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@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>

Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>

... 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()?