Commit 6b79c57b authored Apr 07, 2015 by Naoya Horiguchi Committed by Linus Torvalds Apr 07, 2015

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>

parent ce66b032

kernel/sched/fair.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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

Admin message