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

[William Lee Irwin III <wli@holomorphy.com>]

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);
 	}