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SubjectRe: [PATCH 1/7] mm/sparse.c: Introduce new function fill_subsection_map()
On 02/10/20 at 10:49am, David Hildenbrand wrote:
> On 09.02.20 11:48, Baoquan He wrote:
> > Wrap the codes filling subsection map in section_activate() into
> > fill_subsection_map(), this makes section_activate() cleaner and
> > easier to follow.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> > mm/sparse.c | 45 ++++++++++++++++++++++++++++++++++-----------
> > 1 file changed, 34 insertions(+), 11 deletions(-)
> >
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index c184b69460b7..9ad741ccbeb6 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -788,24 +788,28 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> > depopulate_section_memmap(pfn, nr_pages, altmap);
> > }
> >
> > -static struct page * __meminit section_activate(int nid, unsigned long pfn,
> > - unsigned long nr_pages, struct vmem_altmap *altmap)
> > +/**
> > + * fill_subsection_map - fill subsection map of a memory region
> > + * @pfn - start pfn of the memory range
> > + * @nr_pages - number of pfns to add in the region
> > + *
> > + * This clears the related subsection map inside one section, and only
> > + * intended for hotplug.
> > + *
> > + * Return:
> > + * * 0 - On success.
> > + * * -EINVAL - Invalid memory region.
> > + * * -EEXIST - Subsection map has been set.
> > + */
> > +static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
> > {
> > - DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> > struct mem_section *ms = __pfn_to_section(pfn);
> > - struct mem_section_usage *usage = NULL;
> > + DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> > unsigned long *subsection_map;
> > - struct page *memmap;
> > int rc = 0;
> >
> > subsection_mask_set(map, pfn, nr_pages);
> >
> > - if (!ms->usage) {
> > - usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
> > - if (!usage)
> > - return ERR_PTR(-ENOMEM);
> > - ms->usage = usage;
> > - }
> > subsection_map = &ms->usage->subsection_map[0];
> >
> > if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
> > @@ -816,6 +820,25 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
> > bitmap_or(subsection_map, map, subsection_map,
> > SUBSECTIONS_PER_SECTION);
> >
> > + return rc;
> > +}
> > +
> > +static struct page * __meminit section_activate(int nid, unsigned long pfn,
> > + unsigned long nr_pages, struct vmem_altmap *altmap)
> > +{
> > + struct mem_section *ms = __pfn_to_section(pfn);
> > + struct mem_section_usage *usage = NULL;
> > + struct page *memmap;
> > + int rc = 0;
> > +
> > + if (!ms->usage) {
> > + usage = kzalloc(mem_section_usage_size(), GFP_KERNEL);
> > + if (!usage)
> > + return ERR_PTR(-ENOMEM);
> > + ms->usage = usage;
> > + }
> > +
> > + rc = fill_subsection_map(pfn, nr_pages);
> > if (rc) {
> > if (usage)
> > ms->usage = NULL;
> >
>
> What about having two variants of
> section_activate()/section_deactivate() instead? Then we don't have any
> subsection related stuff in !subsection code.

Thanks for looking into this, David.

Having two variants of section_activate()/section_deactivate() is also
good. Just not like memmap handling which is very different between classic
sparse and vmemmap, makes having two variants very attractive, the code
and logic in section_activate()/section_deactivate() is not too much,
and both of them basically can share the most of code, these make the
variants way not so necessary. I personally prefer the current way, what
do you think?

Thanks
Baoquan

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