linux-kernel - Re: [PATCH v4] hugetlb: Fix wrong use of nr_online

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Date:   Mon, 18 Apr 2022 13:53:25 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Peng Liu <liupeng256@...wei.com>, <mike.kravetz@...cle.com>,
        <david@...hat.com>, <akpm@...ux-foundation.org>,
        <yaozhenguo1@...il.com>, <baolin.wang@...ux.alibaba.com>,
        <songmuchun@...edance.com>, <liuyuntao10@...wei.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <dave@...olabs.net>
Subject: Re: [PATCH v4] hugetlb: Fix wrong use of nr_online_nodes


On 2022/4/16 18:35, 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@...hat.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@...wei.com>
> ---
> v3->v4:
>   Make sure nid is valid before use node_online, and __alloc_bootmem_huge_page
>   is no need to check node_online, which is suggested by Kefeng.
  Reviewed-by: Kefeng Wang <wangkefeng.wang@...wei.com>

>   mm/hugetlb.c | 12 +++++-------
>   1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index b34f50156f7e..a386c5f94932 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2979,8 +2979,6 @@ 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)
> -		return 0;
>   	/* do node specific alloc */
>   	if (nid != NUMA_NO_NODE) {
>   		m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
> @@ -3088,7 +3086,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>   	}
>   
>   	/* do node specific alloc */
> -	for (i = 0; i < nr_online_nodes; i++) {
> +	for_each_online_node(i) {
>   		if (h->max_huge_pages_node[i] > 0) {
>   			hugetlb_hstate_alloc_pages_onenode(h, i);
>   			node_specific_alloc = true;
> @@ -4049,7 +4047,7 @@ static int __init hugetlb_init(void)
>   			default_hstate.max_huge_pages =
>   				default_hstate_max_huge_pages;
>   
> -			for (i = 0; i < nr_online_nodes; i++)
> +			for_each_online_node(i)
>   				default_hstate.max_huge_pages_node[i] =
>   					default_hugepages_in_node[i];
>   		}
> @@ -4164,9 +4162,9 @@ static int __init hugepages_setup(char *s)
>   				pr_warn("HugeTLB: architecture can't support node specific alloc, ignoring!\n");
>   				return 0;
>   			}
> -			if (tmp >= nr_online_nodes)
> +			if (tmp >= MAX_NUMNODES || !node_online(tmp))
>   				goto invalid;
> -			node = array_index_nospec(tmp, nr_online_nodes);
> +			node = array_index_nospec(tmp, MAX_NUMNODES);
>   			p += count + 1;
>   			/* Parse hugepages */
>   			if (sscanf(p, "%lu%n", &tmp, &count) != 1)
> @@ -4294,7 +4292,7 @@ static int __init default_hugepagesz_setup(char *s)
>   	 */
>   	if (default_hstate_max_huge_pages) {
>   		default_hstate.max_huge_pages = default_hstate_max_huge_pages;
> -		for (i = 0; i < nr_online_nodes; i++)
> +		for_each_online_node(i)
>   			default_hstate.max_huge_pages_node[i] =
>   				default_hugepages_in_node[i];
>   		if (hstate_is_gigantic(&default_hstate))