Messages in this thread Patch in this message |  | | | Date | Sun, 25 Sep 2005 16:47:33 +0100 (BST) | | From | Hugh Dickins <> | | Subject | [PATCH 01/21] mm: hugetlb truncation fixes |
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hugetlbfs allows truncation of its files (should it?), but hugetlb.c often forgets that: crashes and misaccounting ensue.
copy_hugetlb_page_range better grab the src page_table_lock since we don't want to guess what happens if concurrently truncated. unmap_hugepage_range rss accounting must not assume the full range was mapped. follow_hugetlb_page must guard with page_table_lock and be prepared to exit early.
Restyle copy_hugetlb_page_range with a for loop like the others there.
Signed-off-by: Hugh Dickins <hugh@veritas.com> --- mm/hugetlb.c | 35 +++++++++++++++++++++-------------- 1 files changed, 21 insertions(+), 14 deletions(-) --- 2.6.14-rc2/mm/hugetlb.c 2005-09-22 12:32:03.000000000 +0100 +++ mm01/mm/hugetlb.c 2005-09-24 19:26:24.000000000 +0100 @@ -273,21 +273,22 @@ int copy_hugetlb_page_range(struct mm_st { pte_t *src_pte, *dst_pte, entry; struct page *ptepage; - unsigned long addr = vma->vm_start; - unsigned long end = vma->vm_end; + unsigned long addr; - while (addr < end) { + for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) { dst_pte = huge_pte_alloc(dst, addr); if (!dst_pte) goto nomem; + spin_lock(&src->page_table_lock); src_pte = huge_pte_offset(src, addr); - BUG_ON(!src_pte || pte_none(*src_pte)); /* prefaulted */ - entry = *src_pte; - ptepage = pte_page(entry); - get_page(ptepage); - add_mm_counter(dst, rss, HPAGE_SIZE / PAGE_SIZE); - set_huge_pte_at(dst, addr, dst_pte, entry); - addr += HPAGE_SIZE; + if (src_pte && !pte_none(*src_pte)) { + entry = *src_pte; + ptepage = pte_page(entry); + get_page(ptepage); + add_mm_counter(dst, rss, HPAGE_SIZE / PAGE_SIZE); + set_huge_pte_at(dst, addr, dst_pte, entry); + } + spin_unlock(&src->page_table_lock); } return 0; @@ -322,8 +323,8 @@ void unmap_hugepage_range(struct vm_area page = pte_page(pte); put_page(page); + add_mm_counter(mm, rss, - (HPAGE_SIZE / PAGE_SIZE)); } - add_mm_counter(mm, rss, -((end - start) >> PAGE_SHIFT)); flush_tlb_range(vma, start, end); } @@ -402,6 +403,7 @@ int follow_hugetlb_page(struct mm_struct BUG_ON(!is_vm_hugetlb_page(vma)); vpfn = vaddr/PAGE_SIZE; + spin_lock(&mm->page_table_lock); while (vaddr < vma->vm_end && remainder) { if (pages) { @@ -414,8 +416,13 @@ int follow_hugetlb_page(struct mm_struct * indexing below to work. */ pte = huge_pte_offset(mm, vaddr & HPAGE_MASK); - /* hugetlb should be locked, and hence, prefaulted */ - WARN_ON(!pte || pte_none(*pte)); + /* the hugetlb file might have been truncated */ + if (!pte || pte_none(*pte)) { + remainder = 0; + if (!i) + i = -EFAULT; + break; + } page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)]; @@ -433,7 +440,7 @@ int follow_hugetlb_page(struct mm_struct --remainder; ++i; } - + spin_unlock(&mm->page_table_lock); *length = remainder; *position = vaddr; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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