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SubjectRe: [PATCH v3 3/7] mm/sparse.c: introduce a new function clear_subsection_map()
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.

>
> > if (empty) {
> > unsigned long section_nr = pfn_to_section_nr(pfn);
> >
> >
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
>
> --
> Thanks,
>
> David / dhildenb

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