58 lines
2.0 KiB
Diff
58 lines
2.0 KiB
Diff
From 750e8165f5e87b6a142be953640eabb13a9d350a Mon Sep 17 00:00:00 2001
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From: Hugh Dickins <hughd@google.com>
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Date: Wed, 16 Oct 2013 13:47:08 -0700
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Subject: mm: fix BUG in __split_huge_page_pmd
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From: Hugh Dickins <hughd@google.com>
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commit 750e8165f5e87b6a142be953640eabb13a9d350a upstream.
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Occasionally we hit the BUG_ON(pmd_trans_huge(*pmd)) at the end of
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__split_huge_page_pmd(): seen when doing madvise(,,MADV_DONTNEED).
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It's invalid: we don't always have down_write of mmap_sem there: a racing
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do_huge_pmd_wp_page() might have copied-on-write to another huge page
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before our split_huge_page() got the anon_vma lock.
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Forget the BUG_ON, just go back and try again if this happens.
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Signed-off-by: Hugh Dickins <hughd@google.com>
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Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
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Cc: Andrea Arcangeli <aarcange@redhat.com>
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Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
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Cc: David Rientjes <rientjes@google.com>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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mm/huge_memory.c | 10 +++++++++-
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1 file changed, 9 insertions(+), 1 deletion(-)
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--- a/mm/huge_memory.c
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+++ b/mm/huge_memory.c
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@@ -2709,6 +2709,7 @@ void __split_huge_page_pmd(struct vm_are
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mmun_start = haddr;
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mmun_end = haddr + HPAGE_PMD_SIZE;
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+again:
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mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
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spin_lock(&mm->page_table_lock);
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if (unlikely(!pmd_trans_huge(*pmd))) {
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@@ -2731,7 +2732,14 @@ void __split_huge_page_pmd(struct vm_are
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split_huge_page(page);
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put_page(page);
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- BUG_ON(pmd_trans_huge(*pmd));
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+
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+ /*
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+ * We don't always have down_write of mmap_sem here: a racing
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+ * do_huge_pmd_wp_page() might have copied-on-write to another
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+ * huge page before our split_huge_page() got the anon_vma lock.
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+ */
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+ if (unlikely(pmd_trans_huge(*pmd)))
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+ goto again;
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}
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void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
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