diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index c5f153c3693f..53e130f803b1 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -468,6 +468,8 @@ STATIC int
 xfs_check_summary_counts(
 	struct xfs_mount	*mp)
 {
+	int			error = 0;
+
 	/*
 	 * The AG0 superblock verifier rejects in-progress filesystems,
 	 * so we should never see the flag set this far into mounting.
@@ -506,11 +508,32 @@ xfs_check_summary_counts(
 	 * superblock to be correct and we don't need to do anything here.
 	 * Otherwise, recalculate the summary counters.
 	 */
-	if ((!xfs_has_lazysbcount(mp) || xfs_is_clean(mp)) &&
-	    !xfs_fs_has_sickness(mp, XFS_SICK_FS_COUNTERS))
-		return 0;
+	if ((xfs_has_lazysbcount(mp) && !xfs_is_clean(mp)) ||
+	    xfs_fs_has_sickness(mp, XFS_SICK_FS_COUNTERS)) {
+		error = xfs_initialize_perag_data(mp, mp->m_sb.sb_agcount);
+		if (error)
+			return error;
+	}
 
-	return xfs_initialize_perag_data(mp, mp->m_sb.sb_agcount);
+	/*
+	 * Older kernels misused sb_frextents to reflect both incore
+	 * reservations made by running transactions and the actual count of
+	 * free rt extents in the ondisk metadata.  Transactions committed
+	 * during runtime can therefore contain a superblock update that
+	 * undercounts the number of free rt extents tracked in the rt bitmap.
+	 * A clean unmount record will have the correct frextents value since
+	 * there can be no other transactions running at that point.
+	 *
+	 * If we're mounting the rt volume after recovering the log, recompute
+	 * frextents from the rtbitmap file to fix the inconsistency.
+	 */
+	if (xfs_has_realtime(mp) && !xfs_is_clean(mp)) {
+		error = xfs_rtalloc_reinit_frextents(mp);
+		if (error)
+			return error;
+	}
+
+	return 0;
 }
 
 /*
@@ -784,11 +807,6 @@ xfs_mountfs(
 		goto out_inodegc_shrinker;
 	}
 
-	/* Make sure the summary counts are ok. */
-	error = xfs_check_summary_counts(mp);
-	if (error)
-		goto out_log_dealloc;
-
 	/* Enable background inode inactivation workers. */
 	xfs_inodegc_start(mp);
 	xfs_blockgc_start(mp);
@@ -844,6 +862,11 @@ xfs_mountfs(
 		goto out_rele_rip;
 	}
 
+	/* Make sure the summary counts are ok. */
+	error = xfs_check_summary_counts(mp);
+	if (error)
+		goto out_rtunmount;
+
 	/*
 	 * If this is a read-only mount defer the superblock updates until
 	 * the next remount into writeable mode.  Otherwise we would never
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index b8c79ee791af..76f50e75f99c 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -1284,6 +1284,43 @@ xfs_rtmount_init(
 	return 0;
 }
 
+static int
+xfs_rtalloc_count_frextent(
+	struct xfs_mount		*mp,
+	struct xfs_trans		*tp,
+	const struct xfs_rtalloc_rec	*rec,
+	void				*priv)
+{
+	uint64_t			*valp = priv;
+
+	*valp += rec->ar_extcount;
+	return 0;
+}
+
+/*
+ * Reinitialize the number of free realtime extents from the realtime bitmap.
+ * Callers must ensure that there is no other activity in the filesystem.
+ */
+int
+xfs_rtalloc_reinit_frextents(
+	struct xfs_mount	*mp)
+{
+	uint64_t		val = 0;
+	int			error;
+
+	xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
+	error = xfs_rtalloc_query_all(mp, NULL, xfs_rtalloc_count_frextent,
+			&val);
+	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_EXCL);
+	if (error)
+		return error;
+
+	spin_lock(&mp->m_sb_lock);
+	mp->m_sb.sb_frextents = val;
+	spin_unlock(&mp->m_sb_lock);
+	return 0;
+}
+
 /*
  * Get the bitmap and summary inodes and the summary cache into the mount
  * structure at mount time.
diff --git a/fs/xfs/xfs_rtalloc.h b/fs/xfs/xfs_rtalloc.h
index 539d134f4f25..62c7ad79cbb6 100644
--- a/fs/xfs/xfs_rtalloc.h
+++ b/fs/xfs/xfs_rtalloc.h
@@ -135,6 +135,7 @@ bool xfs_verify_rtbno(struct xfs_mount *mp, xfs_rtblock_t rtbno);
 int xfs_rtalloc_extent_is_free(struct xfs_mount *mp, struct xfs_trans *tp,
 			       xfs_rtblock_t start, xfs_extlen_t len,
 			       bool *is_free);
+int xfs_rtalloc_reinit_frextents(struct xfs_mount *mp);
 #else
 # define xfs_rtallocate_extent(t,b,min,max,l,f,p,rb)    (ENOSYS)
 # define xfs_rtfree_extent(t,b,l)                       (ENOSYS)
@@ -145,6 +146,7 @@ int xfs_rtalloc_extent_is_free(struct xfs_mount *mp, struct xfs_trans *tp,
 # define xfs_rtbuf_get(m,t,b,i,p)                       (ENOSYS)
 # define xfs_verify_rtbno(m, r)			(false)
 # define xfs_rtalloc_extent_is_free(m,t,s,l,i)          (ENOSYS)
+# define xfs_rtalloc_reinit_frextents(m)                (0)
 static inline int		/* error */
 xfs_rtmount_init(
 	xfs_mount_t	*mp)	/* file system mount structure */