Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 3.8 81/81] mm: fix BUG in __split_huge_page_pmd | Date | Tue, 29 Oct 2013 11:04:42 -0700 |
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3.8.13.12 -stable review patch. If anyone has any objections, please let me know.
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From: Hugh Dickins <hughd@google.com>
commit 750e8165f5e87b6a142be953640eabb13a9d350a 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: Kamal Mostafa <kamal@canonical.com> --- mm/huge_memory.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e9308d3..a057a7d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2740,6 +2740,7 @@ 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))) { @@ -2762,7 +2763,14 @@ 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, -- 1.8.1.2
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