mm, thp: drop page_table_lock to uncharge memcg pages

mm->page_table_lock is hotly contested for page fault tests and isn't
necessary to do mem_cgroup_uncharge_page() in do_huge_pmd_wp_page().

Signed-off-by: David Rientjes <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Reviewed-by: Andrea Arcangeli <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index edfeb8cb23df27ad77716408962687ceed4ba342..d0def42c121bb570315d084b75d38083f53597c3 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -973,8 +973,10 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
        spin_lock(&mm->page_table_lock);
        put_page(page);
        if (unlikely(!pmd_same(*pmd, orig_pmd))) {
+               spin_unlock(&mm->page_table_lock);
                mem_cgroup_uncharge_page(new_page);
                put_page(new_page);
+               goto out;
        } else {
                pmd_t entry;
                VM_BUG_ON(!PageHead(page));