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    SubjectRe: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()
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    On 09.03.20 14:32, Baoquan He wrote:
    > On 03/09/20 at 09:59am, David Hildenbrand wrote:
    >> On 07.03.20 09:42, Baoquan He wrote:
    >>> Factor out the code 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 | 31 ++++++++++++++++++++++++-------
    >>> 1 file changed, 24 insertions(+), 7 deletions(-)
    >>>
    >>> diff --git a/mm/sparse.c b/mm/sparse.c
    >>> index e37c0abcdc89..d9dcd58d5c1d 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 = false;
    >>> unsigned long *subsection_map = ms->usage
    >>> ? &ms->usage->subsection_map[0] : NULL;
    >>>
    >>> @@ -745,8 +741,31 @@ 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 -EINVAL;
    >>> +
    >>> + bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
    >>> +
    >>
    >> Nit: I'd drop this line.
    >
    > It's fine to me. I usually keep one line for the returning. I will
    > remove it when update.
    >
    >>
    >>> + 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 = false;
    >>
    >> Nit: No need to initialize empty.
    >
    > This is inherited from patch 1.
    >
    >>
    >>> +
    >>> + if (clear_subsection_map(pfn, nr_pages))
    >>> return;
    >>>
    >>
    >> Nit: I'd drop this empty line.
    >>
    >>> + empty = is_subsection_map_empty(ms);
    >>> /*
    >>> * There are 3 cases to handle across two configurations
    >>> * (SPARSEMEM_VMEMMAP={y,n}):
    >>> @@ -764,8 +783,6 @@ 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);
    >>
    >> I do wonder why you moved this up the comment?
    >
    > Since this empty will cover two places of handling, so moved it up,
    > seems this is what I was thinking. Can move it back here.

    You're moving the whole comment later, was just wondering (makes it
    slightly harder to review).


    --
    Thanks,

    David / dhildenb

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