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Message-ID: <20200212112641.GJ26758@MiWiFi-R3L-srv>
Date: Wed, 12 Feb 2020 19:26:41 +0800
From: Baoquan He <bhe@...hat.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
akpm@...ux-foundation.org, dan.j.williams@...el.com,
richardw.yang@...ux.intel.com
Subject: Re: [PATCH 3/7] mm/sparse.c: only use subsection map in VMEMMAP case
On 02/11/20 at 03:43pm, David Hildenbrand wrote:
> On 09.02.20 11:48, Baoquan He wrote:
> > Currently, subsection map is used when SPARSEMEM is enabled, including
> > VMEMMAP case and !VMEMMAP case. However, subsection hotplug is not
> > supported at all in SPARSEMEM|!VMEMMAP case, subsection map is unnecessary
> > and misleading. Let's adjust code to only allow subsection map being
> > used in SPARSEMEM|VMEMMAP case.
> >
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> > ---
> > include/linux/mmzone.h | 2 +
> > mm/sparse.c | 231 ++++++++++++++++++++++-------------------
> > 2 files changed, 124 insertions(+), 109 deletions(-)
> >
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index 462f6873905a..fc0de3a9a51e 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -1185,7 +1185,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
> > #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
> >
> > struct mem_section_usage {
> > +#ifdef CONFIG_SPARSEMEM_VMEMMAP
> > DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
> > +#endif
> > /* See declaration of similar field in struct zone */
> > unsigned long pageblock_flags[0];
> > };
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index 696f6b9f706e..cf55d272d0a9 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -209,41 +209,6 @@ static inline unsigned long first_present_section_nr(void)
> > return next_present_section_nr(-1);
> > }
> >
> > -static void subsection_mask_set(unsigned long *map, unsigned long pfn,
> > - unsigned long nr_pages)
> > -{
> > - int idx = subsection_map_index(pfn);
> > - int end = subsection_map_index(pfn + nr_pages - 1);
> > -
> > - bitmap_set(map, idx, end - idx + 1);
> > -}
> > -
> > -void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
> > -{
> > - int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
> > - unsigned long nr, start_sec = pfn_to_section_nr(pfn);
> > -
> > - if (!nr_pages)
> > - return;
> > -
> > - for (nr = start_sec; nr <= end_sec; nr++) {
> > - struct mem_section *ms;
> > - unsigned long pfns;
> > -
> > - pfns = min(nr_pages, PAGES_PER_SECTION
> > - - (pfn & ~PAGE_SECTION_MASK));
> > - ms = __nr_to_section(nr);
> > - subsection_mask_set(ms->usage->subsection_map, pfn, pfns);
> > -
> > - pr_debug("%s: sec: %lu pfns: %lu set(%d, %d)\n", __func__, nr,
> > - pfns, subsection_map_index(pfn),
> > - subsection_map_index(pfn + pfns - 1));
> > -
> > - pfn += pfns;
> > - nr_pages -= pfns;
> > - }
> > -}
> > -
> > /* Record a memory area against a node. */
> > void __init memory_present(int nid, unsigned long start, unsigned long end)
> > {
> > @@ -432,12 +397,134 @@ static unsigned long __init section_map_size(void)
> > return ALIGN(sizeof(struct page) * PAGES_PER_SECTION, PMD_SIZE);
> > }
> >
> > +static void subsection_mask_set(unsigned long *map, unsigned long pfn,
> > + unsigned long nr_pages)
> > +{
> > + int idx = subsection_map_index(pfn);
> > + int end = subsection_map_index(pfn + nr_pages - 1);
> > +
> > + bitmap_set(map, idx, end - idx + 1);
> > +}
> > +
> > +void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
> > +{
> > + int end_sec = pfn_to_section_nr(pfn + nr_pages - 1);
> > + unsigned long nr, start_sec = pfn_to_section_nr(pfn);
> > +
> > + if (!nr_pages)
> > + return;
> > +
> > + for (nr = start_sec; nr <= end_sec; nr++) {
> > + struct mem_section *ms;
> > + unsigned long pfns;
> > +
> > + pfns = min(nr_pages, PAGES_PER_SECTION
> > + - (pfn & ~PAGE_SECTION_MASK));
> > + ms = __nr_to_section(nr);
> > + subsection_mask_set(ms->usage->subsection_map, pfn, pfns);
> > +
> > + pr_debug("%s: sec: %lu pfns: %lu set(%d, %d)\n", __func__, nr,
> > + pfns, subsection_map_index(pfn),
> > + subsection_map_index(pfn + pfns - 1));
> > +
> > + pfn += pfns;
> > + nr_pages -= pfns;
> > + }
> > +}
> > +
> > +/**
> > + * 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.
> > + */
> > +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);
> > + unsigned long *subsection_map = ms->usage
> > + ? &ms->usage->subsection_map[0] : NULL;
> > +
> > + subsection_mask_set(map, pfn, nr_pages);
> > + if (subsection_map)
> > + bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
> > +
> > + 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);
> > +
> > + if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
> > + return 0;
> > +
> > + return 1;
> > +}
> > +
> > +/**
> > + * 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)
> > +{
> > + struct mem_section *ms = __pfn_to_section(pfn);
> > + DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> > + unsigned long *subsection_map;
> > + int rc = 0;
> > +
> > + subsection_mask_set(map, pfn, nr_pages);
> > +
> > + subsection_map = &ms->usage->subsection_map[0];
> > +
> > + if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
> > + rc = -EINVAL;
> > + else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
> > + rc = -EEXIST;
> > + else
> > + bitmap_or(subsection_map, map, subsection_map,
> > + SUBSECTIONS_PER_SECTION);
> > +
> > + return rc;
> > +}
> > +
> > #else
> > static unsigned long __init section_map_size(void)
> > {
> > return PAGE_ALIGN(sizeof(struct page) * PAGES_PER_SECTION);
> > }
> >
> > +void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
> > +{
> > +}
> > +
> > +static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
> > +{
> > + return 0;
> > +}
> > +static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
> > +{
> > + return 0;
> > +}
> > +
> > struct page __init *__populate_section_memmap(unsigned long pfn,
> > unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
> > {
> > @@ -726,45 +813,6 @@ static void free_map_bootmem(struct page *memmap)
> > }
> > #endif /* CONFIG_SPARSEMEM_VMEMMAP */
> >
> > -/**
> > - * 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.
> > - */
> > -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);
> > - unsigned long *subsection_map = ms->usage
> > - ? &ms->usage->subsection_map[0] : NULL;
> > -
> > - subsection_mask_set(map, pfn, nr_pages);
> > - if (subsection_map)
> > - bitmap_and(tmp, map, subsection_map, SUBSECTIONS_PER_SECTION);
> > -
> > - 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);
> > -
> > - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION))
> > - return 0;
> > -
> > - return 1;
> > -}
> > -
> > static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> > struct vmem_altmap *altmap)
> > {
> > @@ -818,41 +866,6 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> > depopulate_section_memmap(pfn, nr_pages, 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)
> > -{
> > - struct mem_section *ms = __pfn_to_section(pfn);
> > - DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> > - unsigned long *subsection_map;
> > - int rc = 0;
> > -
> > - subsection_mask_set(map, pfn, nr_pages);
> > -
> > - subsection_map = &ms->usage->subsection_map[0];
> > -
> > - if (bitmap_empty(map, SUBSECTIONS_PER_SECTION))
> > - rc = -EINVAL;
> > - else if (bitmap_intersects(map, subsection_map, SUBSECTIONS_PER_SECTION))
> > - rc = -EEXIST;
> > - else
> > - 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)
> > {
> >
>
> I'd prefer adding more ifdefs to avoid heavy code movement. Would make
> it much easier to review :)
OK, I did it in the first place. Later I think putting all subsectin
related handling into one place makes code look better. Now I understand
it may make patch format messy. I will adjust the place to make
reviewing easier. Thanks for your great suggestion.
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