Re: [patch, feature] nonlinear mappings, prefaulting support, 2.5.42-F8

William Lee Irwin III
2002-10-14T21:25:14Z

On Mon, Oct 14, 2002 at 02:20:45PM -0700, William Lee Irwin III wrote:
+ offset = (start - vma->vm_start) >> PAGE_CACHE_SHIFT
+ + vma->vm_pgoff;

I'm not so old I should be forgetting C already.

--- mpop-2.5.42/mm/fremap.c 2002-10-14 11:43:03.000000000 -0700
+++ wlipop-2.5.42/mm/fremap.c 2002-10-14 14:17:11.000000000 -0700
@@ -129,10 +129,16 @@
end > start && start >= vma->vm_start &&
end <= vma->vm_end) {
/*
- * Change the default protection to PROT_NONE:
+ * Change the default protection to PROT_NONE if
+ * the file offset doesn't coincide with the vma's:
*/
- if (pgprot_val(vma->vm_page_prot) != pgprot_val(__S000))
- vma->vm_page_prot = __S000;
+ if (pgprot_val(vma->vm_page_prot) != pgprot_val(__S000)) {
+ unsigned long offset;
+ offset = ((start - vma->vm_start) >> PAGE_CACHE_SHIFT)
+ + vma->vm_pgoff;
+ if (offset != pgoff)
+ vma->vm_page_prot = __S000;
+ }
err = vma->vm_ops->populate(vma, start, size, prot,
pgoff, flags & MAP_NONBLOCK);
}