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mm: don't overwrite mm->def_flags in do_mlockall()

With commit 8e72033 ("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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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gerald-schaefer authored and torvalds committed Feb 12, 2013
1 parent 3399cfb commit 9977f0f164d46613288e0b5778eae500dfe06f31
Showing with 3 additions and 3 deletions.
  1. +3 −3 mm/mlock.c
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@@ -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;

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