mmap: save some cycles for the shared anonymous mapping

shmem_zero_setup() does not change vm_start, pgoff or vm_flags, only some
drivers change them (such as /driver/video/bfin-t350mcqb-fb.c).

Move these codes to a more proper place to save cycles for shared
anonymous mapping.

Signed-off-by: Huang Shijie <shijie8@gmail.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index b6d74b3dbbc2..1aeef6625e6a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1191,21 +1191,21 @@ munmap_back:
                         goto unmap_and_free_vma;
                 if (vm_flags & VM_EXECUTABLE)
                         added_exe_file_vma(mm);
+
+                /* Can addr have changed??
+                 *
+                 * Answer: Yes, several device drivers can do it in their
+                 *         f_op->mmap method. -DaveM
+                 */
+                addr = vma->vm_start;
+                pgoff = vma->vm_pgoff;
+                vm_flags = vma->vm_flags;
         } else if (vm_flags & VM_SHARED) {
                 error = shmem_zero_setup(vma);
                 if (error)
                         goto free_vma;
         }
 
-        /* Can addr have changed??
-         *
-         * Answer: Yes, several device drivers can do it in their
-         *         f_op->mmap method. -DaveM
-         */
-        addr = vma->vm_start;
-        pgoff = vma->vm_pgoff;
-        vm_flags = vma->vm_flags;
-
         if (vma_wants_writenotify(vma))
                 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);