Commit 1c59827d authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
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[PATCH] mm: hugetlb truncation fixes 



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: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e03d13e9

mm/hugetlb.c

+21 −14
Original line number Diff line number Diff line
@@ -274,21 +274,22 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, 
{

	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 */

		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);

		addr += HPAGE_SIZE;

		}

		spin_unlock(&src->page_table_lock);

	}

	return 0;
@@ -323,8 +324,8 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start, 


		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);

}
@@ -403,6 +404,7 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, 
	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) {
@@ -415,8 +417,13 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, 
			 * 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)];
@@ -434,7 +441,7 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, 
		--remainder;

		++i;

	}



	spin_unlock(&mm->page_table_lock);

	*length = remainder;

	*position = vaddr;

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