From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Tue, 7 Apr 2015 23:43:49 +0000 (+1000)
Subject: mm: numa: disable change protection for vma(VM_HUGETLB)
X-Git-Tag: KARO-TXA5-2015-06-26~18^2~502
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f932357fe6b029046e1d13b1d140d6143a1e9d17;p=karo-tx-linux.git

mm: numa: disable change protection for vma(VM_HUGETLB)

Currently when a process accesses a hugetlb range protected with PROTNONE,
unexpected COWs are triggered, which finally puts the hugetlb subsystem
into a broken/uncontrollable state, where for example h->resv_huge_pages
is subtracted too much and wraps around to a very large number, and the
free hugepage pool is no longer maintainable.

This patch simply stops changing protection for vma(VM_HUGETLB) to fix the
problem.  And this also allows us to avoid useless overhead of minor
faults.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Suggested-by: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bcfe32088b37..241213be507c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2165,8 +2165,10 @@ void task_numa_work(struct callback_head *work)
 		vma = mm->mmap;
 	}
 	for (; vma; vma = vma->vm_next) {
-		if (!vma_migratable(vma) || !vma_policy_mof(vma))
+		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
+			is_vm_hugetlb_page(vma)) {
 			continue;
+		}
 
 		/*
 		 * Shared library pages mapped by multiple processes are not