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mm: fix BUG in __split_huge_page_pmd

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commit 750e8165f5 upstream.

Occasionally we hit the BUG_ON(pmd_trans_huge(*pmd)) at the end of
__split_huge_page_pmd(): seen when doing madvise(,,MADV_DONTNEED).

It's invalid: we don't always have down_write of mmap_sem there: a racing
do_huge_pmd_wp_page() might have copied-on-write to another huge page
before our split_huge_page() got the anon_vma lock.

Forget the BUG_ON, just go back and try again if this happens.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hugh Dickins
2013-10-16 13:47:08 -07:00
committed by Greg Kroah-Hartman
parent fe0051d83c
commit 7ed008638e
1 changed files with 9 additions and 1 deletions
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10
mm/huge_memory.c
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@@ -2699,6 +2699,7 @@ void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
mmun_start = haddr;
mmun_end = haddr + HPAGE_PMD_SIZE;
again:
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_trans_huge(*pmd))) {
@@ -2721,7 +2722,14 @@ void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
split_huge_page(page);
put_page(page);
BUG_ON(pmd_trans_huge(*pmd));
/*
* We don't always have down_write of mmap_sem here: a racing
* do_huge_pmd_wp_page() might have copied-on-write to another
* huge page before our split_huge_page() got the anon_vma lock.
*/
if (unlikely(pmd_trans_huge(*pmd)))
goto again;
}
void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,