Re: 2.5.67-mm3

William Lee Irwin III
2003-04-16T02:21:54Z

On Mon, Apr 14, 2003 at 01:53:13AM -0700, Andrew Morton wrote:
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.5/2.5.67/2.5.67-mm3/
>
> A bunch of new fixes, and a framebuffer update. This should work a bit
> better than -mm2.

follow_hugetlb_page() behaved improperly 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).

diff -urpN linux-2.5.67-bk6/arch/i386/mm/hugetlbpage.c htlb-2.5.67-bk6-1/arch/i386/mm/hugetlbpage.c
--- linux-2.5.67-bk6/arch/i386/mm/hugetlbpage.c 2003-04-07 10:32:49.000000000 -0700
+++ htlb-2.5.67-bk6-1/arch/i386/mm/hugetlbpage.c 2003-04-15 18:58:07.000000000 -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;
}