From: William Lee Irwin III <wli@holomorphy.com>
follow_hugetlb_page() drops out of the loop prematurely and fails to take the
appropriate refcounts if its starting address was not hugepage-aligned.
It looked a bit unclean too, so I rewrote it. This fixes a bug, and more
importantly, makes the thing readable by something other than a compiler
(e.g. programmers).
arch/i386/mm/hugetlbpage.c | 52 +++++++++++++++++++++++++--------------------
1 files changed, 30 insertions(+), 22 deletions(-)
diff -puN arch/i386/mm/hugetlbpage.c~follow_hugetlb_page-fix arch/i386/mm/hugetlbpage.c
--- 25/arch/i386/mm/hugetlbpage.c~follow_hugetlb_page-fix 2003-04-15 19:50:24.000000000 -0700
+++ 25-akpm/arch/i386/mm/hugetlbpage.c 2003-04-15 19:50:24.000000000 -0700
@@ -129,37 +129,45 @@ nomem:
int
follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
struct page **pages, struct vm_area_struct **vmas,
- unsigned long *st, int *length, int i)
+ unsigned long *position, int *length, int i)
{
- pte_t *ptep, pte;
- unsigned long start = *st;
- unsigned long pstart;
- int len = *length;
- struct page *page;
+ unsigned long vpfn, vaddr = *position;
+ int remainder = *length;
+
+ WARN_ON(!is_vm_hugetlb_page(vma));
- do {
- pstart = start;
- ptep = huge_pte_offset(mm, start);
- pte = *ptep;
+ vpfn = vaddr/PAGE_SIZE;
+ while (vaddr < vma->vm_end && remainder) {
-back1:
- page = pte_page(pte);
if (pages) {
- page += ((start & ~HPAGE_MASK) >> PAGE_SHIFT);
+ pte_t *pte;
+ struct page *page;
+
+ pte = huge_pte_offset(mm, vaddr);
+
+ /* hugetlb should be locked, and hence, prefaulted */
+ WARN_ON(!pte || pte_none(*pte));
+
+ page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
+
+ WARN_ON(!PageCompound(page));
+
get_page(page);
pages[i] = page;
}
+
if (vmas)
vmas[i] = vma;
- i++;
- len--;
- start += PAGE_SIZE;
- if (((start & HPAGE_MASK) == pstart) && len &&
- (start < vma->vm_end))
- goto back1;
- } while (len && start < vma->vm_end);
- *length = len;
- *st = start;
+
+ vaddr += PAGE_SIZE;
+ ++vpfn;
+ --remainder;
+ ++i;
+ }
+
+ *length = remainder;
+ *position = vaddr;
+
return i;
}
_