1 files changed, 73 insertions, 0 deletions

diff --git a/include/linux/flex_array.h b/include/linux/flex_array.h
new file mode 100644
index 000000000000..1d747f72298b
--- /dev/null
+++ b/include/linux/flex_array.h
@@ -0,0 +1,73 @@
+#ifndef _FLEX_ARRAY_H
+#define _FLEX_ARRAY_H
+
+#include <linux/types.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;
+                        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 end, 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);
+
+#endif /* _FLEX_ARRAY_H */