Commit 6cda7204 authored Aug 06, 2020 by Wei Yang Committed by Linus Torvalds Aug 07, 2020

mm/sparse: only sub-section aligned range would be populated



There are two code path which invoke __populate_section_memmap()

  * sparse_init_nid()
  * sparse_add_section()

For both case, we are sure the memory range is sub-section aligned.

  * we pass PAGES_PER_SECTION to sparse_init_nid()
  * we check range by check_pfn_span() before calling
    sparse_add_section()

Also, the counterpart of __populate_section_memmap(), we don't do such
calculation and check since the range is checked by check_pfn_span() in
__remove_pages().

Clear the calculation and check to keep it simple and comply with its
counterpart.

Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand <david@redhat.com>
Link: http://lkml.kernel.org/r/20200703031828.14645-1-richard.weiyang@linux.alibaba.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent ef69bc9f

mm/sparse-vmemmap.c

+6 −14

Original line number	Diff line number	Diff line
		@@ -251,20 +251,12 @@ int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
		struct page * __meminit __populate_section_memmap(unsigned long pfn,
		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
		{
		unsigned long start;
		unsigned long end;
		unsigned long start = (unsigned long) pfn_to_page(pfn);
		unsigned long end = start + nr_pages * sizeof(struct page);

		/*
		* The minimum granularity of memmap extensions is
		* PAGES_PER_SUBSECTION as allocations are tracked in the
		* 'subsection_map' bitmap of the section.
		*/
		end = ALIGN(pfn + nr_pages, PAGES_PER_SUBSECTION);
		pfn &= PAGE_SUBSECTION_MASK;
		nr_pages = end - pfn;

		start = (unsigned long) pfn_to_page(pfn);
		end = start + nr_pages * sizeof(struct page);
		if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) \|\|
		!IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
		return NULL;

		if (vmemmap_populate(start, end, nid, altmap))
		return NULL;

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