mm: gup: use get_user_pages_unlocked within get_user_pages_fast

This allows the get_user_pages_fast slow path to release the mmap_sem
before blocking.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 639fce464008..5c586c78ca8d 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -235,10 +235,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
         /* Try to get the remaining pages with get_user_pages */
         start += nr << PAGE_SHIFT;
         pages += nr;
-        down_read(&mm->mmap_sem);
-        ret = get_user_pages(current, mm, start,
-                             nr_pages - nr, write, 0, pages, NULL);
-        up_read(&mm->mmap_sem);
+        ret = get_user_pages_unlocked(current, mm, start,
+                             nr_pages - nr, write, 0, pages);
         /* Have to be a bit careful with return values */
         if (nr > 0)
                 ret = (ret < 0) ? nr : ret + nr;