diff --git a/arch/arm/kernel/atags_parse.c b/arch/arm/kernel/atags_parse.c
index 68c6ae0b9e4c..98fbfd235ac8 100644
--- a/arch/arm/kernel/atags_parse.c
+++ b/arch/arm/kernel/atags_parse.c
@@ -18,6 +18,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/initrd.h>
 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/root_dev.h>
@@ -91,8 +92,6 @@ __tagtable(ATAG_VIDEOTEXT, parse_tag_videotext);
 #ifdef CONFIG_BLK_DEV_RAM
 static int __init parse_tag_ramdisk(const struct tag *tag)
 {
-	extern int rd_size, rd_image_start, rd_prompt, rd_doload;
-
 	rd_image_start = tag->u.ramdisk.start;
 	rd_doload = (tag->u.ramdisk.flags & 1) == 0;
 	rd_prompt = (tag->u.ramdisk.flags & 2) == 0;
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 17723fd50a53..104b71c0490d 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/initrd.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/major.h>
diff --git a/include/linux/initrd.h b/include/linux/initrd.h
index 55289d261b4f..bc67b767f9ce 100644
--- a/include/linux/initrd.h
+++ b/include/linux/initrd.h
@@ -10,6 +10,9 @@ extern int rd_prompt;
 /* starting block # of image */
 extern int rd_image_start;
 
+/* size of a single RAM disk */
+extern unsigned long rd_size;
+
 /* 1 if it is not an error if initrd_start < memory_start */
 extern int initrd_below_start_ok;