linux-kernel - Re: [PATCH v4 2/5] mm/sparse.c: introduce a new function clear_subsection

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Date:   Thu, 12 Mar 2020 14:26:49 +0100
From:   Pankaj Gupta <pankaj.gupta.linux@...il.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>, mhocko@...e.com,
        David Hildenbrand <david@...hat.com>,
        richard.weiyang@...il.com, dan.j.williams@...el.com
Subject: Re: [PATCH v4 2/5] mm/sparse.c: introduce a new function clear_subsection_map()

>
> Factor out the code which clear subsection map of one memory region from
> section_deactivate() into clear_subsection_map().
>
> And also add helper function is_subsection_map_empty() to check if
> the current subsection map is empty or not.
>
> Signed-off-by: Baoquan He <bhe@...hat.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/sparse.c | 31 +++++++++++++++++++++++--------
>  1 file changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 5919bc5b1547..0be4d4ed96de 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -726,15 +726,11 @@ static void free_map_bootmem(struct page *memmap)
>  }
>  #endif /* CONFIG_SPARSEMEM_VMEMMAP */
>
> -static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> -               struct vmem_altmap *altmap)
> +static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
>  {
>         DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
>         DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
>         struct mem_section *ms = __pfn_to_section(pfn);
> -       bool section_is_early = early_section(ms);
> -       struct page *memmap = NULL;
> -       bool empty;
>         unsigned long *subsection_map = ms->usage
>                 ? &ms->usage->subsection_map[0] : NULL;
>
> @@ -745,8 +741,28 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>         if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
>                                 "section already deactivated (%#lx + %ld)\n",
>                                 pfn, nr_pages))
> -               return;
> +               return -EINVAL;
>
> +       bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
> +       return 0;
> +}
> +
> +static bool is_subsection_map_empty(struct mem_section *ms)
> +{
> +       return bitmap_empty(&ms->usage->subsection_map[0],
> +                           SUBSECTIONS_PER_SECTION);
> +}
> +
> +static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> +               struct vmem_altmap *altmap)
> +{
> +       struct mem_section *ms = __pfn_to_section(pfn);
> +       bool section_is_early = early_section(ms);
> +       struct page *memmap = NULL;
> +       bool empty;
> +
> +       if (clear_subsection_map(pfn, nr_pages))
> +               return;
>         /*
>          * There are 3 cases to handle across two configurations
>          * (SPARSEMEM_VMEMMAP={y,n}):
> @@ -764,8 +780,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>          *
>          * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
>          */
> -       bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
> -       empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
> +       empty = is_subsection_map_empty(ms);
>         if (empty) {
>                 unsigned long section_nr = pfn_to_section_nr(pfn);
>
> --

Acked-by: Pankaj Gupta <pankaj.gupta.linux@...il.com>

> 2.17.2
>
>