On 02/11/20 at 03:44pm, David Hildenbrand wrote:
> On 11.02.20 13:46, Baoquan He wrote:
> > 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@xxxxxxxxxx>
> >>> ---
> >>> 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?
>
> I was looking at
>
> if (nr_pages < PAGES_PER_SECTION && early_section(ms))
> return pfn_to_page(pfn);
>
> and thought that it is also specific to sub-section handling. I wonder
> if we can simply move that into the VMEMMAP variant of
> populate_section_memmap()?
>
> But apart from that I agree that the end result with the current
> approach is also nice.
>
> Can you reshuffle the patches, moving the fixes to the very front so we
> can backport more easily?
Sure, I will move it as the 1st one. Thanks.
