Re: [PATCH v2 3/7] mm/sparse.c: introduce a new function clear_subsection_map()

David Hildenbrand
2020-02-28T14:37:06Z

On 20.02.20 05:33, Baoquan He wrote:
> Wrap the codes which clear subsection map of one memory region from
> section_deactivate() into clear_subsection_map().
>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
> mm/sparse.c | 46 ++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 38 insertions(+), 8 deletions(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 977b47acd38d..df857ee9330c 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -726,14 +726,25 @@ 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)
> +/**
> + * clear_subsection_map - Clear subsection map of one memory region
> + *
> + * @pfn - start pfn of the memory range
> + * @nr_pages - number of pfns to add in the region
> + *
> + * This is only intended for hotplug, and clear the related subsection
> + * map inside one section.
> + *
> + * Return:
> + * * -EINVAL - Section already deactived.
> + * * 0 - Subsection map is emptied.
> + * * 1 - Subsection map is not empty.
> + */

Less verbose please (in my preference: none and simplify return handling)

> +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;
> unsigned long *subsection_map = ms->usage
> ? &ms->usage->subsection_map[0] : NULL;
>
> @@ -744,8 +755,28 @@ 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);
>
> + if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
> + return 0;
> +

Can we please just have a

subsection_map_empty() instead and handle that in the caller?
(you can then always return true in the !VMEMMAP variant)

I dislike the "rc" handling in the caller.

> + return 1;
> +}
> +
> +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;
> + int rc;
> +
> +

one superfluous empty line

> + rc = clear_subsection_map(pfn, nr_pages);
> + if (IS_ERR_VALUE((unsigned long)rc))

huh? "if (rc < 0)" ? or am I missing something?

> + return;
> /*
> * There are 3 cases to handle across two configurations
> * (SPARSEMEM_VMEMMAP={y,n}):
> @@ -763,8 +794,7 @@ 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);
> - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
> + if (!rc) {
> unsigned long section_nr = pfn_to_section_nr(pfn);
>
> /*
> @@ -786,7 +816,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> else
> depopulate_section_memmap(pfn, nr_pages, altmap);
>
> - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
> + if (!rc)

I don't really like that handling.

Either

s/rc/section_empty/

or use a separate subsection_map_empty()

> ms->section_mem_map = (unsigned long)NULL;
> }
>
>

Thanks!

--
Thanks,

David / dhildenb