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Subject[ 03/10] mm: dont overwrite mm->def_flags in do_mlockall()
Date
3.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gerald Schaefer <gerald.schaefer@de.ibm.com>

commit 9977f0f164d46613288e0b5778eae500dfe06f31 upstream.

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 <gerald.schaefer@de.ibm.com>
Reported-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/mlock.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -517,11 +517,11 @@ SYSCALL_DEFINE2(munlock, unsigned long,
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;




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