commit: 9977f0f164d46613288e0b5778eae500dfe06f31
From: Gerald Schaefer <[email protected]>
Date: Tue, 12 Feb 2013 13:46:20 -0800
Subject: mm: don't overwrite mm->def_flags in do_mlockall()

With commit 8e72033f2a48 ("thp: make MADV_HUGEPAGE check for
mm->def_flags") the VM_NOHUGEPAGE flag may be set on s390 in
mm->def_flags for certain processes, to prevent future thp mappings.
This would be overwritten by do_mlockall(), which sets it back to 0 with
an optional VM_LOCKED flag set.

To fix this, instead of overwriting mm->def_flags in do_mlockall(), only
the VM_LOCKED flag should be set or cleared.

Signed-off-by: Gerald Schaefer <[email protected]>
Reported-by: Vivek Goyal <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
 mm/mlock.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index f0b9ce5..c9bd528 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -517,11 +517,11 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, 
len)
 static int do_mlockall(int flags)
 {
        struct vm_area_struct * vma, * prev = NULL;
-       unsigned int def_flags = 0;
 
        if (flags & MCL_FUTURE)
-               def_flags = VM_LOCKED;
-       current->mm->def_flags = def_flags;
+               current->mm->def_flags |= VM_LOCKED;
+       else
+               current->mm->def_flags &= ~VM_LOCKED;
        if (flags == MCL_FUTURE)
                goto out;
 
-- 
1.7.10.4
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