Re: [patch, feature] nonlinear mappings, prefaulting support, 2.5.42-F8
From: William Lee Irwin III <hidden>
Date: 2002-10-14 21:18:36
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On Mon, Oct 14, 2002 at 06:02:30PM +0200, Ingo Molnar wrote:
quoted
if this is really an issue then we could force vma->vm_page_prot to PROT_NONE within remap_file_pages(), so at least all subsequent faults will be PROT_NONE and the user would have to explicitly re-mprotect() the vma again to change this.i've added this to the -G1 patch at: http://redhat.com/~mingo/remap-file-pages-patches/ Ingo
Also, this may be relaxed when the file offsets match. Against unpatched -G1: Bill
--- 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); } --
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