[PATCH] ptep_establish smp race x86 PAE >4G

This avoid userspace mm corruption during COWs with threads (i.e. 
malloc;fork;clone) on x86 PAE with >4G of ram
Signed-Off-By: Andrea Arcangeli <andrea@novell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-generic/pgtable.h

@@ -13,11 +13,19 @@
  * Note: the old pte is known to not be writable, so we don't need to
  * worry about dirty bits etc getting lost.
  */
+#ifndef __HAVE_ARCH_SET_PTE_ATOMIC
 #define ptep_establish(__vma, __address, __ptep, __entry)		\
 do {				  					\
 	set_pte(__ptep, __entry);					\
 	flush_tlb_page(__vma, __address);				\
 } while (0)
+#else /* __HAVE_ARCH_SET_PTE_ATOMIC */
+#define ptep_establish(__vma, __address, __ptep, __entry)		\
+do {				  					\
+	set_pte_atomic(__ptep, __entry);				\
+	flush_tlb_page(__vma, __address);				\
+} while (0)
+#endif /* __HAVE_ARCH_SET_PTE_ATOMIC */
 #endif
 
 #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS

include/asm-i386/pgtable-3level.h

@@ -54,6 +54,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
 	smp_wmb();
 	ptep->pte_low = pte.pte_low;
 }
+#define __HAVE_ARCH_SET_PTE_ATOMIC
 #define set_pte_atomic(pteptr,pteval) \
 		set_64bit((unsigned long long *)(pteptr),pte_val(pteval))
 #define set_pmd(pmdptr,pmdval) \