1 files changed, 81 insertions, 0 deletions
diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h
new file mode 100644
index 000000000..b6efb0c64
--- /dev/null
+++ b/include/linux/flex_array.h
@@ -0,0 +1,81 @@
+#ifndef _FLEX_ARRAY_H
+#define _FLEX_ARRAY_H
+
+#include <linux/types.h>
+#include <linux/reciprocal_div.h>
+#include <asm/page.h>
+
+#define FLEX_ARRAY_PART_SIZE PAGE_SIZE
+#define FLEX_ARRAY_BASE_SIZE PAGE_SIZE
+
+struct flex_array_part;
+
+/*
+ * This is meant to replace cases where an array-like
+ * structure has gotten too big to fit into kmalloc()
+ * and the developer is getting tempted to use
+ * vmalloc().
+ */
+
+struct flex_array {
+	union {
+		struct {
+			int element_size;
+			int total_nr_elements;
+			int elems_per_part;
+			struct reciprocal_value reciprocal_elems;
+			struct flex_array_part *parts[];
+		};
+		/*
+		 * This little trick makes sure that
+		 * sizeof(flex_array) == PAGE_SIZE
+		 */
+		char padding[FLEX_ARRAY_BASE_SIZE];
+	};
+};
+
+/* Number of bytes left in base struct flex_array, excluding metadata */
+#define FLEX_ARRAY_BASE_BYTES_LEFT					\
+	(FLEX_ARRAY_BASE_SIZE - offsetof(struct flex_array, parts))
+
+/* Number of pointers in base to struct flex_array_part pages */
+#define FLEX_ARRAY_NR_BASE_PTRS						\
+	(FLEX_ARRAY_BASE_BYTES_LEFT / sizeof(struct flex_array_part *))
+
+/* Number of elements of size that fit in struct flex_array_part */
+#define FLEX_ARRAY_ELEMENTS_PER_PART(size)				\
+	(FLEX_ARRAY_PART_SIZE / size)
+
+/*
+ * Defines a statically allocated flex array and ensures its parameters are
+ * valid.
+ */
+#define DEFINE_FLEX_ARRAY(__arrayname, __element_size, __total)		\
+	struct flex_array __arrayname = { { {				\
+		.element_size = (__element_size),			\
+		.total_nr_elements = (__total),				\
+	} } };								\
+	static inline void __arrayname##_invalid_parameter(void)	\
+	{								\
+		BUILD_BUG_ON((__total) > FLEX_ARRAY_NR_BASE_PTRS *	\
+			FLEX_ARRAY_ELEMENTS_PER_PART(__element_size));	\
+	}
+
+struct flex_array *flex_array_alloc(int element_size, unsigned int total,
+		gfp_t flags);
+int flex_array_prealloc(struct flex_array *fa, unsigned int start,
+		unsigned int nr_elements, gfp_t flags);
+void flex_array_free(struct flex_array *fa);
+void flex_array_free_parts(struct flex_array *fa);
+int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
+		gfp_t flags);
+int flex_array_clear(struct flex_array *fa, unsigned int element_nr);
+void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
+int flex_array_shrink(struct flex_array *fa);
+
+#define flex_array_put_ptr(fa, nr, src, gfp) \
+	flex_array_put(fa, nr, (void *)&(src), gfp)
+
+void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr);
+
+#endif /* _FLEX_ARRAY_H */