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, 3 insertions, 4 deletions

diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 224b14235e96..89df70e0caa6 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -388,10 +388,9 @@ slow_irqon:
                 start += nr << PAGE_SHIFT;
                 pages += nr;
 
-                down_read(&mm->mmap_sem);
-                ret = get_user_pages(current, mm, start,
-                        (end - start) >> PAGE_SHIFT, write, 0, pages, NULL);
-                up_read(&mm->mmap_sem);
+                ret = get_user_pages_unlocked(current, mm, start,
+                                              (end - start) >> PAGE_SHIFT,
+                                              write, 0, pages);
 
                 /* Have to be a bit careful with return values */
                 if (nr > 0) {