s390/mm: fix flush_tlb_kernel_range()

Our flush_tlb_kernel_range() implementation calls __tlb_flush_mm() with
&init_mm as argument. __tlb_flush_mm() however will only flush tlbs
for the passed in mm if its mm_cpumask is not empty.

For the init_mm however its mm_cpumask has never any bits set. Which in
turn means that our flush_tlb_kernel_range() implementation doesn't
work at all.

This can be easily verified with a vmalloc/vfree loop which allocates
a page, writes to it and then frees the page again. A crash will follow
almost instantly.

To fix this remove the cpumask_empty() check in __tlb_flush_mm() since
there shouldn't be too many mms with a zero mm_cpumask, besides the
init_mm of course.

Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/include/asm/tlbflush.h b/arch/s390/include/asm/tlbflush.h
index 1d8fe2b..6b32af3 100644 (file)
--- a/arch/s390/include/asm/tlbflush.h
+++ b/arch/s390/include/asm/tlbflush.h
@@ -74,8 +74,6 @@ static inline void __tlb_flush_idte(unsigned long asce)
 
 static inline void __tlb_flush_mm(struct mm_struct * mm)
 {
-       if (unlikely(cpumask_empty(mm_cpumask(mm))))
-               return;
        /*
         * If the machine has IDTE we prefer to do a per mm flush
         * on all cpus instead of doing a local flush if the mm