linux-kernel - [PATCH] mm: avoid uninitialized variable in tracepoint

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Date:	Mon, 18 Jan 2016 21:50:26 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Ebru Akagunduz <ebru.akagunduz@...il.com>,
	dan.carpenter@...cle.com, linux-mm@...ck.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] mm: avoid uninitialized variable in tracepoint

A newly added tracepoint in the hugepage code uses a variable in the
error handling that is not initialized at that point:

include/trace/events/huge_memory.h:81:230: error: 'isolated' may be used uninitialized in this function [-Werror=maybe-uninitialized]

The result is relatively harmless, as the trace data will in rare
cases contain incorrect data.

This works around the problem by adding an explicit initialization.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages")

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b2db98136af9..bb3b763b1829 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2320,7 +2320,7 @@ static void collapse_huge_page(struct mm_struct *mm,
 	pgtable_t pgtable;
 	struct page *new_page;
 	spinlock_t *pmd_ptl, *pte_ptl;
-	int isolated, result = 0;
+	int isolated = 0, result = 0;
 	unsigned long hstart, hend;
 	struct mem_cgroup *memcg;
 	unsigned long mmun_start;	/* For mmu_notifiers */