[PATCH 77/81] mm: don't overwrite mm->def_flags in do_mlockall()

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Tue Feb 19 18:49:40 UTC 2013 -stable review patch.  If anyone has any objections, please let me know.


From: Gerald Schaefer <gerald.schaefer at 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 at de.ibm.com>
Reported-by: Vivek Goyal <vgoyal at redhat.com>
Cc: Andrea Arcangeli <aarcange at redhat.com>
Cc: Hugh Dickins <hughd at google.com>
Cc: Martin Schwidefsky <schwidefsky at de.ibm.com>
Cc: Heiko Carstens <heiko.carstens at de.ibm.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 mm/mlock.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/mlock.c b/mm/mlock.c
index ef726e8..3283272 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -524,11 +524,11 @@ 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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