[patch 119/163] mm/sparse: only sub-section aligned range would be populated

Andrew Morton
2020-08-07T06:24:02Z

From: Wei Yang <richard.weiyang@linux.alibaba.com>
Subject: 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.

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

mm/sparse-vmemmap.c | 18 +++++-------------
1 file changed, 5 insertions(+), 13 deletions(-)

--- a/mm/sparse-vmemmap.c~mm-sparse-only-sub-section-aligned-range-would-be-populated
+++ a/mm/sparse-vmemmap.c
@@ -251,20 +251,12 @@ int __meminit vmemmap_populate_basepages
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;
_