1 files changed, 93 insertions, 0 deletions
diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h
index e4b48a0dda24..76c817162d2f 100644
--- a/include/linux/page_ext.h
+++ b/include/linux/page_ext.h
@@ -3,6 +3,7 @@
 #define __LINUX_PAGE_EXT_H
 
 #include <linux/types.h>
+#include <linux/mmzone.h>
 #include <linux/stacktrace.h>
 
 struct pglist_data;
@@ -69,16 +70,31 @@ extern void page_ext_init(void);
 static inline void page_ext_init_flatmem_late(void)
 {
 }
+
+static inline bool page_ext_iter_next_fast_possible(unsigned long next_pfn)
+{
+	/*
+	 * page_ext is allocated per memory section. Once we cross a
+	 * memory section, we have to fetch the new pointer.
+	 */
+	return next_pfn % PAGES_PER_SECTION;
+}
 #else
 extern void page_ext_init_flatmem(void);
 extern void page_ext_init_flatmem_late(void);
 static inline void page_ext_init(void)
 {
 }
+
+static inline bool page_ext_iter_next_fast_possible(unsigned long next_pfn)
+{
+	return true;
+}
 #endif
 
 extern struct page_ext *page_ext_get(const struct page *page);
 extern void page_ext_put(struct page_ext *page_ext);
+extern struct page_ext *page_ext_lookup(unsigned long pfn);
 
 static inline void *page_ext_data(struct page_ext *page_ext,
 				  struct page_ext_operations *ops)
@@ -93,6 +109,83 @@ static inline struct page_ext *page_ext_next(struct page_ext *curr)
 	return next;
 }
 
+struct page_ext_iter {
+	unsigned long index;
+	unsigned long start_pfn;
+	struct page_ext *page_ext;
+};
+
+/**
+ * page_ext_iter_begin() - Prepare for iterating through page extensions.
+ * @iter: page extension iterator.
+ * @pfn: PFN of the page we're interested in.
+ *
+ * Must be called with RCU read lock taken.
+ *
+ * Return: NULL if no page_ext exists for this page.
+ */
+static inline struct page_ext *page_ext_iter_begin(struct page_ext_iter *iter,
+						unsigned long pfn)
+{
+	iter->index = 0;
+	iter->start_pfn = pfn;
+	iter->page_ext = page_ext_lookup(pfn);
+
+	return iter->page_ext;
+}
+
+/**
+ * page_ext_iter_next() - Get next page extension
+ * @iter: page extension iterator.
+ *
+ * Must be called with RCU read lock taken.
+ *
+ * Return: NULL if no next page_ext exists.
+ */
+static inline struct page_ext *page_ext_iter_next(struct page_ext_iter *iter)
+{
+	unsigned long pfn;
+
+	if (WARN_ON_ONCE(!iter->page_ext))
+		return NULL;
+
+	iter->index++;
+	pfn = iter->start_pfn + iter->index;
+
+	if (page_ext_iter_next_fast_possible(pfn))
+		iter->page_ext = page_ext_next(iter->page_ext);
+	else
+		iter->page_ext = page_ext_lookup(pfn);
+
+	return iter->page_ext;
+}
+
+/**
+ * page_ext_iter_get() - Get current page extension
+ * @iter: page extension iterator.
+ *
+ * Return: NULL if no page_ext exists for this iterator.
+ */
+static inline struct page_ext *page_ext_iter_get(const struct page_ext_iter *iter)
+{
+	return iter->page_ext;
+}
+
+/**
+ * for_each_page_ext(): iterate through page_ext objects.
+ * @__page: the page we're interested in
+ * @__pgcount: how many pages to iterate through
+ * @__page_ext: struct page_ext pointer where the current page_ext
+ *              object is returned
+ * @__iter: struct page_ext_iter object (defined in the stack)
+ *
+ * IMPORTANT: must be called with RCU read lock taken.
+ */
+#define for_each_page_ext(__page, __pgcount, __page_ext, __iter) \
+	for (__page_ext = page_ext_iter_begin(&__iter, page_to_pfn(__page));\
+		__page_ext && __iter.index < __pgcount;          \
+		__page_ext = page_ext_iter_next(&__iter))
+
 #else /* !CONFIG_PAGE_EXTENSION */
 struct page_ext;