Let's consolidate the mapcount logic to make it easier to understand and
to prepare for further changes.
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
mm/huge_memory.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e5483347291c..4751d03947da 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2101,21 +2101,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
pte = pte_offset_map(&_pmd, addr);
BUG_ON(!pte_none(*pte));
set_pte_at(mm, addr, pte, entry);
- if (!pmd_migration)
- atomic_inc(&page[i]._mapcount);
pte_unmap(pte);
}
if (!pmd_migration) {
+ /* Sub-page mapcount accounting for above small mappings. */
+ int val = 1;
+
/*
* Set PG_double_map before dropping compound_mapcount to avoid
* false-negative page_mapped().
+ *
+ * The first to set PageDoubleMap() has to increment all
+ * sub-page mapcounts by one.
*/
- if (compound_mapcount(page) > 1 &&
- !TestSetPageDoubleMap(page)) {
- for (i = 0; i < HPAGE_PMD_NR; i++)
- atomic_inc(&page[i]._mapcount);
- }
+ if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page))
+ val++;
+
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ atomic_add(val, &page[i]._mapcount);
lock_page_memcg(page);
if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
--
2.31.1
