mlock: do not munlock pages in __do_fault()

If the page is going to be written to, __do_page needs to break COW.

However, the old page (before breaking COW) was never mapped mapped into
the current pte (__do_fault is only called when the pte is not present),
so vmscan can't have marked the old page as PageMlocked due to being
mapped in __do_fault's VMA.  Therefore, __do_fault() does not need to
worry about clearing PageMlocked() on the old page.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index 32df03c..8e8c183 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3051,12 +3051,6 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                                goto out;
                        }
                        charged = 1;
-                       /*
-                        * Don't let another task, with possibly unlocked vma,
-                        * keep the mlocked page.
-                        */
-                       if (vma->vm_flags & VM_LOCKED)
-                               clear_page_mlock(vmf.page);
                        copy_user_highpage(page, vmf.page, address, vma);
                        __SetPageUptodate(page);
                } else {