From: Hugh Dickins <[email protected]> Subject: mm: fix BUG in __split_huge_page_pmd
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 <[email protected]> Acked-by: Kirill A. Shutemov <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Naoya Horiguchi <[email protected]> Cc: David Rientjes <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> --- mm/huge_memory.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff -puN mm/huge_memory.c~mm-fix-bug-in-__split_huge_page_pmd mm/huge_memory.c --- a/mm/huge_memory.c~mm-fix-bug-in-__split_huge_page_pmd +++ a/mm/huge_memory.c @@ -2697,6 +2697,7 @@ void __split_huge_page_pmd(struct vm_are 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))) { @@ -2719,7 +2720,14 @@ void __split_huge_page_pmd(struct vm_are 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, _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
