2007-08-15 17:43:38

by Dean Nelson

Subject: [PATCH] calculation of pgoff in do_linear_fault() uses mixed units

The calculation of pgoff in do_linear_fault() should use PAGE_SHIFT and not
PAGE_CACHE_SHIFT since vma->vm_pgoff is in units of PAGE_SIZE and not
PAGE_CACHE_SIZE. At the moment linux/pagemap.h has PAGE_CACHE_SHIFT defined
as PAGE_SHIFT, but should that ever change this calculation would break.

Signed-off-by: Dean Nelson <[email protected]>


Index: linux-2.6/mm/memory.c
===================================================================
--- linux-2.6.orig/mm/memory.c 2007-08-14 06:42:18.322378070 -0500
+++ linux-2.6/mm/memory.c 2007-08-15 12:30:51.621604739 -0500
@@ -2465,7 +2465,7 @@
int write_access, pte_t orig_pte)
{
pgoff_t pgoff = (((address & PAGE_MASK)
- - vma->vm_start) >> PAGE_CACHE_SHIFT) + vma->vm_pgoff;
+ - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0);

return __do_fault(mm, vma, address, page_table, pmd, pgoff,

2007-08-16 02:52:32

by Nick Piggin

Subject: Re: [PATCH] calculation of pgoff in do_linear_fault() uses mixed units

On Wed, Aug 15, 2007 at 12:43:26PM -0500, Dean Nelson wrote:
> The calculation of pgoff in do_linear_fault() should use PAGE_SHIFT and not
> PAGE_CACHE_SHIFT since vma->vm_pgoff is in units of PAGE_SIZE and not
> PAGE_CACHE_SIZE. At the moment linux/pagemap.h has PAGE_CACHE_SHIFT defined
> as PAGE_SHIFT, but should that ever change this calculation would break.
>
> Signed-off-by: Dean Nelson <[email protected]>
>

Acked-by: Nick Piggin <[email protected]>

>
> Index: linux-2.6/mm/memory.c
> ===================================================================
> --- linux-2.6.orig/mm/memory.c 2007-08-14 06:42:18.322378070 -0500
> +++ linux-2.6/mm/memory.c 2007-08-15 12:30:51.621604739 -0500
> @@ -2465,7 +2465,7 @@
> int write_access, pte_t orig_pte)
> {
> pgoff_t pgoff = (((address & PAGE_MASK)
> - - vma->vm_start) >> PAGE_CACHE_SHIFT) + vma->vm_pgoff;
> + - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
> unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0);
>
> return __do_fault(mm, vma, address, page_table, pmd, pgoff,