linux-kernel - [PATCH 1/4] mm: thp: Return the correct value for change_huge

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Date:	Sat,  7 Mar 2015 15:20:48 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Dave Chinner <david@...morbit.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>, xfs@....sgi.com,
	linuxppc-dev@...ts.ozlabs.org, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 1/4] mm: thp: Return the correct value for change_huge_pmd

The wrong value is being returned by change_huge_pmd since commit
10c1045f28e8 ("mm: numa: avoid unnecessary TLB flushes when setting
NUMA hinting entries") which allows a fallthrough that tries to adjust
non-existent PTEs. This patch corrects it.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/huge_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index fc00c8cb5a82..194c0f019774 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1482,6 +1482,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 
 	if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
 		pmd_t entry;
+		ret = 1;
 
 		/*
 		 * Avoid trapping faults against the zero page. The read-only
@@ -1490,11 +1491,10 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		 */
 		if (prot_numa && is_huge_zero_pmd(*pmd)) {
 			spin_unlock(ptl);
-			return 0;
+			return ret;
 		}
 
 		if (!prot_numa || !pmd_protnone(*pmd)) {
-			ret = 1;
 			entry = pmdp_get_and_clear_notify(mm, addr, pmd);
 			entry = pmd_modify(entry, newprot);
 			ret = HPAGE_PMD_NR;
-- 
2.1.2

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