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From:   Alexey Makhalov <amakhalov@vmware.com>
To:     David Hildenbrand <david@redhat.com>
CC:     Michal Hocko <mhocko@suse.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        Oscar Salvador <OSalvador@suse.com>
Subject: Re: [PATCH] mm: fix panic in __alloc_pages
Thread-Topic: [PATCH] mm: fix panic in __alloc_pages
Thread-Index: AQHXz1zvSxS/i+mFgUadpM+6bJvGtavv3QcAgAAG4YD//5TPAIAAec8AgAAFsICAABNmgIAAB32AgAAMNwCAAAX9AIAJCxiA
Date:   Mon, 8 Nov 2021 06:12:11 +0000
Message-ID: <86BDA7AC-3E7A-4779-9388-9DF7BA7230AA@vmware.com>
References: <20211101201312.11589-1-amakhalov@vmware.com>
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I=E2=80=99m going to send patch v2, with node_online check moved to =
caller (pcpu_alloc_pages() function)
as was suggested by David. It seems as it is only one place which passes =
present but offlined
node to alloc-pages_node(). Moving node online check to the caller keeps =
hot path (alloc_pages)
simple and performant.

> diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
> index 2054c9213c43..c21ff5bb91dc 100644
> --- a/mm/percpu-vm.c
> +++ b/mm/percpu-vm.c
> @@ -84,15 +84,19 @@ static int pcpu_alloc_pages(struct pcpu_chunk =
*chunk,
>                           gfp_t gfp)
> {
>       unsigned int cpu, tcpu;
> -       int i;
> +       int i, nid;
>=20
>       gfp |=3D __GFP_HIGHMEM;
>=20
>       for_each_possible_cpu(cpu) {
> +               nid =3D cpu_to_node(cpu);
> +
> +               if (nid =3D=3D NUMA_NO_NODE || !node_online(nid))
> +                       nid =3D numa_mem_id();
>               for (i =3D page_start; i < page_end; i++) {
>                       struct page **pagep =3D =
&pages[pcpu_page_idx(cpu, i)];
>=20
> -                       *pagep =3D alloc_pages_node(cpu_to_node(cpu), =
gfp, 0);
> +                       *pagep =3D alloc_pages_node(nid, gfp, 0);
>                       if (!*pagep)
>                               goto err;
>               }
>=20

Thanks,
=E2=80=94Alexey


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