From 0dc294f717d41bfbafc746a7a96a7bc0f114c20c Mon Sep 17 00:00:00 2001
From: Arseny Solokha <asolokha@kb.kras.ru>
Date: Fri, 30 Jan 2015 19:08:27 +0700
Subject: [PATCH] powerpc/mm: bail out early when flushing TLB page

MMU_NO_CONTEXT is conditionally defined as 0 or (unsigned int)-1. However,
in __flush_tlb_page() a corresponding variable is only tested for open
coded 0, which can cause NULL pointer dereference if `mm' argument was
legitimately passed as such.

Bail out early in case the first argument is NULL, thus eliminate confusion
between different values of MMU_NO_CONTEXT and avoid disabling and then
re-enabling preemption unnecessarily.

Signed-off-by: Arseny Solokha <asolokha@kb.kras.ru>
Signed-off-by: Scott Wood <scottwood@freescale.com>
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