diff --git a/fs/xfs/libxfs/xfs_rtgroup.c b/fs/xfs/libxfs/xfs_rtgroup.c
index 325e4eb8f8781..173297f582e00 100644
--- a/fs/xfs/libxfs/xfs_rtgroup.c
+++ b/fs/xfs/libxfs/xfs_rtgroup.c
@@ -419,3 +419,120 @@ xfs_rtgroup_log_super(
 	xfs_rtgroup_update_super(rtsb_bp, sb_bp);
 	xfs_trans_ordered_buf(tp, rtsb_bp);
 }
+
+/* Initialize a secondary realtime superblock. */
+static int
+xfs_rtgroup_init_secondary_super(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno,
+	struct xfs_buf		**bpp)
+{
+	struct xfs_buf		*bp;
+	struct xfs_rtsb		*rsb;
+	xfs_rtblock_t		rtbno;
+	int			error;
+
+	ASSERT(rgno != 0);
+
+	error = xfs_buf_get_uncached(mp->m_rtdev_targp, XFS_FSB_TO_BB(mp, 1),
+			0, &bp);
+	if (error)
+		return error;
+
+	rtbno = xfs_rgbno_to_rtb(mp, rgno, 0);
+	bp->b_maps[0].bm_bn = xfs_rtb_to_daddr(mp, rtbno);
+	bp->b_ops = &xfs_rtsb_buf_ops;
+	xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
+
+	rsb = bp->b_addr;
+	rsb->rsb_magicnum = cpu_to_be32(XFS_RTSB_MAGIC);
+	rsb->rsb_blocksize = cpu_to_be32(mp->m_sb.sb_blocksize);
+	rsb->rsb_rblocks = cpu_to_be64(mp->m_sb.sb_rblocks);
+
+	rsb->rsb_rextents = cpu_to_be64(mp->m_sb.sb_rextents);
+
+	memcpy(&rsb->rsb_uuid, &mp->m_sb.sb_uuid, sizeof(rsb->rsb_uuid));
+
+	rsb->rsb_rgcount = cpu_to_be32(mp->m_sb.sb_rgcount);
+	memcpy(&rsb->rsb_fname, &mp->m_sb.sb_fname, XFSLABEL_MAX);
+
+	rsb->rsb_rextsize = cpu_to_be32(mp->m_sb.sb_rextsize);
+	rsb->rsb_rbmblocks = cpu_to_be32(mp->m_sb.sb_rbmblocks);
+
+	rsb->rsb_rgblocks = cpu_to_be32(mp->m_sb.sb_rgblocks);
+	rsb->rsb_blocklog = mp->m_sb.sb_blocklog;
+	rsb->rsb_sectlog = mp->m_sb.sb_sectlog;
+	rsb->rsb_rextslog = mp->m_sb.sb_rextslog;
+
+	memcpy(&rsb->rsb_meta_uuid, &mp->m_sb.sb_meta_uuid,
+			sizeof(rsb->rsb_meta_uuid));
+
+	*bpp = bp;
+	return 0;
+}
+
+/*
+ * Update all the realtime superblocks to match the new state of the primary.
+ * Because we are completely overwriting all the existing fields in the
+ * secondary superblock buffers, there is no need to read them in from disk.
+ * Just get a new buffer, stamp it and write it.
+ *
+ * The rt super buffers do not need to be kept them in memory once they are
+ * written so we mark them as a one-shot buffer.
+ */
+int
+xfs_rtgroup_update_secondary_sbs(
+	struct xfs_mount	*mp)
+{
+	LIST_HEAD		(buffer_list);
+	struct xfs_rtgroup	*rtg;
+	xfs_rgnumber_t		start_rgno = 1;
+	int			saved_error = 0;
+	int			error = 0;
+
+	for_each_rtgroup_from(mp, start_rgno, rtg) {
+		struct xfs_buf		*bp;
+
+		error = xfs_rtgroup_init_secondary_super(mp, rtg->rtg_rgno,
+				&bp);
+		/*
+		 * If we get an error reading or writing alternate superblocks,
+		 * continue.  If we break early, we'll leave more superblocks
+		 * un-updated than updated.
+		 */
+		if (error) {
+			xfs_warn(mp,
+		"error allocating secondary superblock for rt group %d",
+				rtg->rtg_rgno);
+			if (!saved_error)
+				saved_error = error;
+			continue;
+		}
+
+		xfs_buf_oneshot(bp);
+		xfs_buf_delwri_queue(bp, &buffer_list);
+		xfs_buf_relse(bp);
+
+		/* don't hold too many buffers at once */
+		if (rtg->rtg_rgno % 16)
+			continue;
+
+		error = xfs_buf_delwri_submit(&buffer_list);
+		if (error) {
+			xfs_warn(mp,
+	"write error %d updating a secondary superblock near rt group %u",
+				error, rtg->rtg_rgno);
+			if (!saved_error)
+				saved_error = error;
+			continue;
+		}
+	}
+	error = xfs_buf_delwri_submit(&buffer_list);
+	if (error) {
+		xfs_warn(mp,
+	"write error %d updating a secondary superblock near rt group %u",
+			error, start_rgno);
+	}
+
+	return saved_error ? saved_error : error;
+}
diff --git a/fs/xfs/libxfs/xfs_rtgroup.h b/fs/xfs/libxfs/xfs_rtgroup.h
index 83bbd43f7271a..2d0422c6712da 100644
--- a/fs/xfs/libxfs/xfs_rtgroup.h
+++ b/fs/xfs/libxfs/xfs_rtgroup.h
@@ -212,10 +212,12 @@ xfs_rgblock_t xfs_rtgroup_block_count(struct xfs_mount *mp,
 void xfs_rtgroup_update_super(struct xfs_buf *rtsb_bp,
 		const struct xfs_buf *sb_bp);
 void xfs_rtgroup_log_super(struct xfs_trans *tp, const struct xfs_buf *sb_bp);
+int xfs_rtgroup_update_secondary_sbs(struct xfs_mount *mp);
 #else
 # define xfs_rtgroup_block_count(mp, rgno)	(0)
 # define xfs_rtgroup_update_super(bp, sb_bp)	((void)0)
 # define xfs_rtgroup_log_super(tp, sb_bp)	((void)0)
+# define xfs_rtgroup_update_secondary_sbs(mp)	(0)
 #endif /* CONFIG_XFS_RT */
 
 #endif /* __LIBXFS_RTGROUP_H */
