diff --git a/drivers/md/md.c b/drivers/md/md.c
index dc99d95a1b6d..df1230af02cd 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -658,11 +658,14 @@ static unsigned int calc_sb_csum(mdp_super_t * sb)
  */
 
 struct super_type  {
-	char 		*name;
-	struct module	*owner;
-	int		(*load_super)(mdk_rdev_t *rdev, mdk_rdev_t *refdev, int minor_version);
-	int		(*validate_super)(mddev_t *mddev, mdk_rdev_t *rdev);
-	void		(*sync_super)(mddev_t *mddev, mdk_rdev_t *rdev);
+	char		    *name;
+	struct module	    *owner;
+	int		    (*load_super)(mdk_rdev_t *rdev, mdk_rdev_t *refdev,
+					  int minor_version);
+	int		    (*validate_super)(mddev_t *mddev, mdk_rdev_t *rdev);
+	void		    (*sync_super)(mddev_t *mddev, mdk_rdev_t *rdev);
+	unsigned long long  (*rdev_size_change)(mdk_rdev_t *rdev,
+						unsigned long long size);
 };
 
 /*
@@ -1003,6 +1006,27 @@ static void super_90_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 	sb->sb_csum = calc_sb_csum(sb);
 }
 
+/*
+ * rdev_size_change for 0.90.0
+ */
+static unsigned long long
+super_90_rdev_size_change(mdk_rdev_t *rdev, unsigned long long size)
+{
+	if (size && size < rdev->mddev->size)
+		return 0; /* component must fit device */
+	size *= 2; /* convert to sectors */
+	if (rdev->mddev->bitmap_offset)
+		return 0; /* can't move bitmap */
+	rdev->sb_offset = calc_dev_sboffset(rdev->bdev);
+	if (!size || size > rdev->sb_offset*2)
+		size = rdev->sb_offset*2;
+	md_super_write(rdev->mddev, rdev, rdev->sb_offset << 1, rdev->sb_size,
+		       rdev->sb_page);
+	md_super_wait(rdev->mddev);
+	return size/2; /* kB for sysfs */
+}
+
+
 /*
  * version 1 superblock
  */
@@ -1328,21 +1352,59 @@ static void super_1_sync(mddev_t *mddev, mdk_rdev_t *rdev)
 	sb->sb_csum = calc_sb_1_csum(sb);
 }
 
+static unsigned long long
+super_1_rdev_size_change(mdk_rdev_t *rdev, unsigned long long size)
+{
+	struct mdp_superblock_1 *sb;
+	unsigned long long max_size;
+	if (size && size < rdev->mddev->size)
+		return 0; /* component must fit device */
+	size *= 2; /* convert to sectors */
+	if (rdev->sb_offset < rdev->data_offset/2) {
+		/* minor versions 1 and 2; superblock before data */
+		max_size = (rdev->bdev->bd_inode->i_size >> 9);
+		max_size -= rdev->data_offset;
+		if (!size || size > max_size)
+			size = max_size;
+	} else if (rdev->mddev->bitmap_offset) {
+		/* minor version 0 with bitmap we can't move */
+		return 0;
+	} else {
+		/* minor version 0; superblock after data */
+		sector_t sb_offset;
+		sb_offset = (rdev->bdev->bd_inode->i_size >> 9) - 8*2;
+		sb_offset &= ~(sector_t)(4*2 - 1);
+		max_size = rdev->size*2 + sb_offset - rdev->sb_offset*2;
+		if (!size || size > max_size)
+			size = max_size;
+		rdev->sb_offset = sb_offset/2;
+	}
+	sb = (struct mdp_superblock_1 *) page_address(rdev->sb_page);
+	sb->data_size = cpu_to_le64(size);
+	sb->super_offset = rdev->sb_offset*2;
+	sb->sb_csum = calc_sb_1_csum(sb);
+	md_super_write(rdev->mddev, rdev, rdev->sb_offset << 1, rdev->sb_size,
+		       rdev->sb_page);
+	md_super_wait(rdev->mddev);
+	return size/2; /* kB for sysfs */
+}
 
 static struct super_type super_types[] = {
 	[0] = {
 		.name	= "0.90.0",
 		.owner	= THIS_MODULE,
-		.load_super	= super_90_load,
-		.validate_super	= super_90_validate,
-		.sync_super	= super_90_sync,
+		.load_super	    = super_90_load,
+		.validate_super	    = super_90_validate,
+		.sync_super	    = super_90_sync,
+		.rdev_size_change   = super_90_rdev_size_change,
 	},
 	[1] = {
 		.name	= "md-1",
 		.owner	= THIS_MODULE,
-		.load_super	= super_1_load,
-		.validate_super	= super_1_validate,
-		.sync_super	= super_1_sync,
+		.load_super	    = super_1_load,
+		.validate_super	    = super_1_validate,
+		.sync_super	    = super_1_sync,
+		.rdev_size_change   = super_1_rdev_size_change,
 	},
 };
 
@@ -2060,8 +2122,20 @@ rdev_size_store(mdk_rdev_t *rdev, const char *buf, size_t len)
 
 	if (e==buf || (*e && *e != '\n'))
 		return -EINVAL;
-	if (my_mddev->pers && rdev->raid_disk >= 0)
-		return -EBUSY;
+	if (my_mddev->pers && rdev->raid_disk >= 0) {
+		if (rdev->mddev->persistent) {
+			size = super_types[rdev->mddev->major_version].
+				rdev_size_change(rdev, size);
+			if (!size)
+				return -EBUSY;
+		} else if (!size) {
+			size = (rdev->bdev->bd_inode->i_size >> 10);
+			size -= rdev->data_offset/2;
+		}
+		if (size < rdev->mddev->size)
+			return -EINVAL; /* component must fit device */
+	}
+
 	rdev->size = size;
 	if (size > oldsize && rdev->mddev->external) {
 		/* need to check that all other rdevs with the same ->bdev