powerpc/hugetlb: Call mm_dec_nr_pmds() in hugetlb_free_pmd_range()

Commit dc6c9a35b66b5 ("mm: account pmd page tables to the process")
added a counter that is incremented whenever a PMD is allocated and
decremented whenever a PMD is freed.  For hugepages on PPC, common code
is used to allocated PMDs, but arch-specific code is used to free PMDs.

This results in kernel output such as "BUG: non-zero nr_pmds on freeing
mm: 1" when using hugepages.

Update the PPC hugepage PMD freeing code to decrement the count, just
as the above commit did for free_pmd_range().

Fixes: dc6c9a35b66b5 ("mm: account pmd page tables to the process")
Signed-off-by: Scott Wood <scottwood@freescale.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # 4.0.x

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 7e408bfc7948..cecbe00cee24 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -581,6 +581,7 @@ static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
         pmd = pmd_offset(pud, start);
         pud_clear(pud);
         pmd_free_tlb(tlb, pmd, start);
+        mm_dec_nr_pmds(tlb->mm);
 }
 
 static void hugetlb_free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,