thp: change pmd_trans_huge_lock() interface to return ptl

After THP refcounting rework we have only two possible return values
from pmd_trans_huge_lock(): success and failure.  Return-by-pointer for
ptl doesn't make much sense in this case.

Let's convert pmd_trans_huge_lock() to return ptl on success and NULL on
failure.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ca052f2a4a0b..d06cae2de783 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4638,7 +4638,8 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
         pte_t *pte;
         spinlock_t *ptl;
 
-        if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
+        ptl = pmd_trans_huge_lock(pmd, vma);
+        if (ptl) {
                 if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
                         mc.precharge += HPAGE_PMD_NR;
                 spin_unlock(ptl);
@@ -4826,7 +4827,8 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
         union mc_target target;
         struct page *page;
 
-        if (pmd_trans_huge_lock(pmd, vma, &ptl)) {
+        ptl = pmd_trans_huge_lock(pmd, vma);
+        if (ptl) {
                 if (mc.precharge < HPAGE_PMD_NR) {
                         spin_unlock(ptl);
                         return 0;