linux-kernel - Re: [PATCH v2 2/2] kfence: Alloc kfence

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Message-ID: <fab45904-585b-0c59-a426-9ebecbd9d26f@linux.alibaba.com>
Date:   Mon, 7 Mar 2022 10:23:51 +0800
From:   Tianchen Ding <dtcccc@...ux.alibaba.com>
To:     Marco Elver <elver@...gle.com>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] kfence: Alloc kfence_pool after system startup

On 2022/3/7 07:52, Marco Elver wrote:
> On Sat, 5 Mar 2022 at 15:49, Tianchen Ding <dtcccc@...ux.alibaba.com> wrote:
> [...]
>> +static int kfence_init_late(void)
>> +{
>> +       const unsigned long nr_pages = KFENCE_POOL_SIZE / PAGE_SIZE;
>> +       struct page *pages;
>> +
>> +       pages = alloc_contig_pages(nr_pages, GFP_KERNEL, first_online_node, NULL);
> 
>> mm/kfence/core.c:836:17: error: implicit declaration of function ‘alloc_contig_pages’ [-Werror=implicit-function-declaration]
> 
> This doesn't build without CMA. See ifdef CONFIG_CONTIG_ALLOC in
> gfp.h, which declares alloc_contig_pages.
> 
> Will alloc_pages() work as you expect? If so, perhaps only use
> alloc_contig_pages() #ifdef CONFIG_CONTIG_ALLOC.
> 

alloc_pages() will be fine. We could free "tail" pages after inited.
Will send v3 soon.

> Thanks,
> -- Marco