s390/mm: fix per vma lock fault handling

With per-vma locks, handle_mm_fault() may return non-fatal error
flags. In this case the code should reset the fault flags before
returning.

Fixes: e06f47a1 ("s390/mm: try VMA lock-based page fault handling first")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/mm/fault.c

@@ -421,6 +421,8 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
 	vma_end_read(vma);
 	if (!(fault & VM_FAULT_RETRY)) {
 		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		if (likely(!(fault & VM_FAULT_ERROR)))
+			fault = 0;
 		goto out;
 	}
 	count_vm_vma_lock_event(VMA_LOCK_RETRY);