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SubjectRe: [patch 07/18] v4l: nopage
On Fri, 7 Dec 2007 16:31:42 -0800 Andrew Morton wrote:

> On Wed, 05 Dec 2007 18:15:54 +1100
> npiggin@suse.de wrote:
>
> > +static int
> > +videobuf_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> > {
> > struct page *page;
> >
> > - dprintk(3,"nopage: fault @ %08lx [vma %08lx-%08lx]\n",
> > - vaddr,vma->vm_start,vma->vm_end);
> > - if (vaddr > vma->vm_end)
> > - return NOPAGE_SIGBUS;
> > + dprintk(3,"fault: fault @ %08lx [vma %08lx-%08lx]\n",
> > + (unsigned long)vmf->virtual_address,vma->vm_start,vma->vm_end);
> > page = alloc_page(GFP_USER | __GFP_DMA32);
> > if (!page)
> > - return NOPAGE_OOM;
> > + return VM_FAULT_OOM;
> > clear_user_page(page_address(page), vaddr, page);
>
> This didn't compile on sparc64 because `vaddr' is undefined.
>
>
> Let us see why:
>
> #define clear_user_page(page, vaddr, pg) clear_page(page)
> #define copy_user_page(to, from, vaddr, pg) copy_page(to, from)
>
> #define __alloc_zeroed_user_highpage(movableflags, vma, vaddr) \
> alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO | movableflags, vma, vaddr)
>
> root cause: lack of argument checking on x86 due to stupid macros.

Hm, I would have said that the root cause was that Nick removed the
vaddr parameter from the function parameters:

-static struct page*
-videobuf_vm_nopage(struct vm_area_struct *vma, unsigned long vaddr,
- int *type)
+static int
+videobuf_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{

Should the function now produce 'vaddr' internally?


> Could someone *please* start a little project of extirpating this utter
> brain damage? Convert those macros to typechecked static inlines on x86
> (at least) so this sort of thing (which happens again and again and again)
> is lessened?

Yep, unless someone else is already doing so...

> macros are such miserable things. I wonder if we could get checkpatch to
> help out here?


---
~Randy
Features and documentation: http://lwn.net/Articles/260136/


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