diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index b1bcd36ca963db3fbed33583dcfc0f30d540606c..958865445f0643a07184de100a3921d4289e3fdf 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -212,7 +212,7 @@ static void bitmap_checkfree(struct bitmap *bitmap, unsigned long page)
  */
 
 /* IO operations when bitmap is stored near all superblocks */
-static struct page *read_sb_page(mddev_t *mddev, long offset,
+static struct page *read_sb_page(mddev_t *mddev, loff_t offset,
 				 struct page *page,
 				 unsigned long index, int size)
 {
@@ -287,14 +287,22 @@ static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
 
 	while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
 			int size = PAGE_SIZE;
-			long offset = mddev->bitmap_info.offset;
+			loff_t offset = mddev->bitmap_info.offset;
 			if (page->index == bitmap->file_pages-1)
 				size = roundup(bitmap->last_page_size,
 					       bdev_logical_block_size(rdev->bdev));
 			/* Just make sure we aren't corrupting data or
 			 * metadata
 			 */
-			if (offset < 0) {
+			if (mddev->external) {
+				/* Bitmap could be anywhere. */
+				if (rdev->sb_start + offset + (page->index *(PAGE_SIZE/512)) >
+				    rdev->data_offset &&
+				    rdev->sb_start + offset < 
+				    rdev->data_offset + mddev->dev_sectors +
+				    (PAGE_SIZE/512))
+					goto bad_alignment;
+			} else if (offset < 0) {
 				/* DATA  BITMAP METADATA  */
 				if (offset
 				    + (long)(page->index * (PAGE_SIZE/512))
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 4b07e0ab3841b5794b3da0fe2f945af5913c5f69..df692953a12faba98121fcc386e23a0d178c0db6 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -282,11 +282,13 @@ struct mddev_s
 	struct bitmap                   *bitmap; /* the bitmap for the device */
 	struct {
 		struct file		*file; /* the bitmap file */
-		long			offset; /* offset from superblock of
+		loff_t			offset; /* offset from superblock of
 						 * start of bitmap. May be
 						 * negative, but not '0'
+						 * For external metadata, offset
+						 * from start of device. 
 						 */
-		long			default_offset; /* this is the offset to use when
+		loff_t			default_offset; /* this is the offset to use when
 							 * hot-adding a bitmap.  It should
 							 * eventually be settable by sysfs.
 							 */