thp: decrement refcount on huge zero page if it is split

The DAX code neglected to put the refcount on the huge zero page.
Also we must notify on splits.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5df0d15..7510b6f 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2978,7 +2978,9 @@ again:
        if (unlikely(!pmd_trans_huge(*pmd)))
                goto unlock;
        if (vma_is_dax(vma)) {
-               pmdp_huge_clear_flush(vma, haddr, pmd);
+               pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+               if (is_huge_zero_pmd(_pmd))
+                       put_huge_zero_page();
        } else if (is_huge_zero_pmd(*pmd)) {
                __split_huge_zero_page_pmd(vma, haddr, pmd);
        } else {