[patch 03/18] remap_file_pages protection support: make mprotect skip pagetables on nonuniform

[blaisorblade@yahoo.it]

From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

There is IMHO no reason to support using mprotect on non-uniform VMAs. The
only exception is to change the VMA's default protection (which is used for
non-individually remapped pages), but it must still ignore the page tables, as
done in this patch.

The only unsatisfied need is if I want to change protections without changing
the indexes, which with remap_file_pages you must do one page at a time and
re-specifying the indexes.

It is more reasonable to allow remap_file_pages to change protections on a PTE
range without changing the offsets. I've not implemented this, but if wanted I
can. For sure, UML doesn't currently need this interface.

However, for now I've implemented only this change to mprotect(), I'd like to
get some feedback about this choice.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
---

 linux-2.6.git-paolo/mm/mprotect.c |    3 +++
 1 files changed, 3 insertions(+)

diff -puN mm/mprotect.c~rfp-mprotect-skip-pagetables-on-nonuniform mm/mprotect.c
--- linux-2.6.git/mm/mprotect.c~rfp-mprotect-skip-pagetables-on-nonuniform	2005-08-17 13:36:43.000000000 +0200
+++ linux-2.6.git-paolo/mm/mprotect.c	2005-08-17 13:36:43.000000000 +0200
@@ -86,6 +86,9 @@ static void change_protection(struct vm_
 	unsigned long start = addr;
 
 	BUG_ON(addr >= end);
+	if (vma->vm_flags & VM_NONUNIFORM)
+		return;
+
 	pgd = pgd_offset(mm, addr);
 	flush_cache_range(vma, addr, end);
 	spin_lock(&mm->page_table_lock);
_
-
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