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authorHugh Dickins <hugh@veritas.com>2005-10-19 21:23:43 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-19 23:04:30 -0700
commit1c59827d1da9bcd6970800d4f8a031b5859e8b4c (patch)
tree768e771e4da8f8f5a84d38b4b91d2fb852a4123a
parente03d13e985d48ac4885382c9e3b1510c78bd047f (diff)
downloadop-kernel-dev-1c59827d1da9bcd6970800d4f8a031b5859e8b4c.zip
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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: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--mm/hugetlb.c35
1 files changed, 21 insertions, 14 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 901ac52..a1b30d4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -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 */
- 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;
@@ -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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