x86, pat: Generalize the use of page flag PG_uncached

Only IA64 was using PG_uncached as of now. We now intend to use this bit
in x86 as well, to keep track of memory type of those addresses that
have page struct for them. So, generalize the use of that bit across
ia64 and x86.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/ia64/Kconfig

@@ -112,6 +112,10 @@ config IA64_UNCACHED_ALLOCATOR
 	bool
 	select GENERIC_ALLOCATOR
 
+config ARCH_USES_PG_UNCACHED
+	def_bool y
+	depends on IA64_UNCACHED_ALLOCATOR
+
 config AUDIT_ARCH
 	bool
 	default y

arch/x86/Kconfig

@@ -1414,6 +1414,10 @@ config X86_PAT
 
 	  If unsure, say Y.
 
+config ARCH_USES_PG_UNCACHED
+	def_bool y
+	depends on X86_PAT
+
 config EFI
 	bool "EFI runtime service support"
 	depends on ACPI

include/linux/page-flags.h

@@ -99,7 +99,7 @@ enum pageflags {
 #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
 	PG_mlocked,		/* Page is vma mlocked */
 #endif
-#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
 	PG_uncached,		/* Page has been mapped as uncached */
 #endif
 	__NR_PAGEFLAGS,
@@ -257,7 +257,7 @@ PAGEFLAG_FALSE(Mlocked)
 	SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
 #endif
 
-#ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
+#ifdef CONFIG_ARCH_USES_PG_UNCACHED
 PAGEFLAG(Uncached, uncached)
 #else
 PAGEFLAG_FALSE(Uncached)