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Date:   Mon, 18 Apr 2022 21:03:52 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Peng Liu <liupeng256@huawei.com>
Cc:     <mike.kravetz@oracle.com>, <david@redhat.com>,
        <yaozhenguo1@gmail.com>, <baolin.wang@linux.alibaba.com>,
        <songmuchun@bytedance.com>, <liuyuntao10@huawei.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        <wangkefeng.wang@huawei.com>, <dave@stgolabs.net>
Subject: Re: [PATCH v4] hugetlb: Fix wrong use of nr_online_nodes
Message-Id: <20220418210352.1d1d90aeba477d598bd6f0be@linux-foundation.org>
In-Reply-To: <20220416103526.3287348-1-liupeng256@huawei.com>
References: <20220413032915.251254-2-liupeng256@huawei.com>
        <20220416103526.3287348-1-liupeng256@huawei.com>
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On Sat, 16 Apr 2022 10:35:26 +0000 Peng Liu <liupeng256@huawei.com> 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.

oops.

What are the user-visible runtime effects of this flaw?