From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Tue, 7 Apr 2015 21:26:47 +0000 (-0700)
Subject: mm: numa: disable change protection for vma(VM_HUGETLB)
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=6b79c57b92cdd90853002980609af516d14c4f9c;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.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>
Signed-off-by: Linus Torvalds <torvalds@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