+#define PG_WC PG_arch_1
+PAGEFLAG(WC, WC)
+
+#ifdef CONFIG_X86_PAT
+/*
+ * X86 PAT uses page flags WC and Uncached together to keep track of
+ * memory type of pages that have backing page struct. X86 PAT supports 3
+ * different memory types, _PAGE_CACHE_WB, _PAGE_CACHE_WC and
+ * _PAGE_CACHE_UC_MINUS and fourth state where page's memory type has not
+ * been changed from its default (value of -1 used to denote this).
+ * Note we do not support _PAGE_CACHE_UC here.
+ *
+ * Caller must hold memtype_lock for atomicity.
+ */
+static inline unsigned long get_page_memtype(struct page *pg)
+{
+ if (!PageUncached(pg) && !PageWC(pg))
+ return -1;
+ else if (!PageUncached(pg) && PageWC(pg))
+ return _PAGE_CACHE_WC;
+ else if (PageUncached(pg) && !PageWC(pg))
+ return _PAGE_CACHE_UC_MINUS;
+ else
+ return _PAGE_CACHE_WB;
+}
+
+static inline void set_page_memtype(struct page *pg, unsigned long memtype)
+{
+ switch (memtype) {
+ case _PAGE_CACHE_WC:
+ ClearPageUncached(pg);
+ SetPageWC(pg);
+ break;
+ case _PAGE_CACHE_UC_MINUS:
+ SetPageUncached(pg);
+ ClearPageWC(pg);
+ break;
+ case _PAGE_CACHE_WB:
+ SetPageUncached(pg);
+ SetPageWC(pg);
+ break;
+ default:
+ case -1:
+ ClearPageUncached(pg);
+ ClearPageWC(pg);
+ break;
+ }
+}
+#else
+static inline unsigned long get_page_memtype(struct page *pg) { return -1; }
+static inline void set_page_memtype(struct page *pg, unsigned long memtype) { }
+#endif