diff --git a/fs/xfs/libxfs/xfs_log_format.h b/fs/xfs/libxfs/xfs_log_format.h
index a6eed43fa7cd5d7898c7d15c8823bdd4874dec2b..fc5eef85d61ea7d865a571482f44cfac2695e81a 100644
--- a/fs/xfs/libxfs/xfs_log_format.h
+++ b/fs/xfs/libxfs/xfs_log_format.h
@@ -647,9 +647,17 @@ struct xfs_rui_log_format {
 	__uint16_t		rui_size;	/* size of this item */
 	__uint32_t		rui_nextents;	/* # extents to free */
 	__uint64_t		rui_id;		/* rui identifier */
-	struct xfs_map_extent	rui_extents[1];	/* array of extents to rmap */
+	struct xfs_map_extent	rui_extents[];	/* array of extents to rmap */
 };
 
+static inline size_t
+xfs_rui_log_format_sizeof(
+	unsigned int		nr)
+{
+	return sizeof(struct xfs_rui_log_format) +
+			nr * sizeof(struct xfs_map_extent);
+}
+
 /*
  * This is the structure used to lay out an rud log item in the
  * log.  The rud_extents array is a variable size array whose
diff --git a/fs/xfs/xfs_rmap_item.c b/fs/xfs/xfs_rmap_item.c
index 2500f28689d5b1d25e9bcd6d64fabe047dc7b1fb..0432a459871c6e086db5928bddfc4460d14562e6 100644
--- a/fs/xfs/xfs_rmap_item.c
+++ b/fs/xfs/xfs_rmap_item.c
@@ -51,28 +51,16 @@ xfs_rui_item_free(
 		kmem_zone_free(xfs_rui_zone, ruip);
 }
 
-/*
- * This returns the number of iovecs needed to log the given rui item.
- * We only need 1 iovec for an rui item.  It just logs the rui_log_format
- * structure.
- */
-static inline int
-xfs_rui_item_sizeof(
-	struct xfs_rui_log_item *ruip)
-{
-	return sizeof(struct xfs_rui_log_format) +
-			(ruip->rui_format.rui_nextents - 1) *
-			sizeof(struct xfs_map_extent);
-}
-
 STATIC void
 xfs_rui_item_size(
 	struct xfs_log_item	*lip,
 	int			*nvecs,
 	int			*nbytes)
 {
+	struct xfs_rui_log_item	*ruip = RUI_ITEM(lip);
+
 	*nvecs += 1;
-	*nbytes += xfs_rui_item_sizeof(RUI_ITEM(lip));
+	*nbytes += xfs_rui_log_format_sizeof(ruip->rui_format.rui_nextents);
 }
 
 /*
@@ -97,7 +85,7 @@ xfs_rui_item_format(
 	ruip->rui_format.rui_size = 1;
 
 	xlog_copy_iovec(lv, &vecp, XLOG_REG_TYPE_RUI_FORMAT, &ruip->rui_format,
-			xfs_rui_item_sizeof(ruip));
+			xfs_rui_log_format_sizeof(ruip->rui_format.rui_nextents));
 }
 
 /*
@@ -205,16 +193,12 @@ xfs_rui_init(
 
 {
 	struct xfs_rui_log_item		*ruip;
-	uint				size;
 
 	ASSERT(nextents > 0);
-	if (nextents > XFS_RUI_MAX_FAST_EXTENTS) {
-		size = (uint)(sizeof(struct xfs_rui_log_item) +
-			((nextents - 1) * sizeof(struct xfs_map_extent)));
-		ruip = kmem_zalloc(size, KM_SLEEP);
-	} else {
+	if (nextents > XFS_RUI_MAX_FAST_EXTENTS)
+		ruip = kmem_zalloc(xfs_rui_log_item_sizeof(nextents), KM_SLEEP);
+	else
 		ruip = kmem_zone_zalloc(xfs_rui_zone, KM_SLEEP);
-	}
 
 	xfs_log_item_init(mp, &ruip->rui_item, XFS_LI_RUI, &xfs_rui_item_ops);
 	ruip->rui_format.rui_nextents = nextents;
@@ -239,14 +223,12 @@ xfs_rui_copy_format(
 	uint				len;
 
 	src_rui_fmt = buf->i_addr;
-	len = sizeof(struct xfs_rui_log_format) +
-			(src_rui_fmt->rui_nextents - 1) *
-			sizeof(struct xfs_map_extent);
+	len = xfs_rui_log_format_sizeof(src_rui_fmt->rui_nextents);
 
 	if (buf->i_len != len)
 		return -EFSCORRUPTED;
 
-	memcpy((char *)dst_rui_fmt, (char *)src_rui_fmt, len);
+	memcpy(dst_rui_fmt, src_rui_fmt, len);
 	return 0;
 }
 
diff --git a/fs/xfs/xfs_rmap_item.h b/fs/xfs/xfs_rmap_item.h
index aefcc3a318a593a24f6efe000456cbf5395e65ee..340c968e1f9c047f5c12eacafc215e55cc5129ad 100644
--- a/fs/xfs/xfs_rmap_item.h
+++ b/fs/xfs/xfs_rmap_item.h
@@ -70,6 +70,14 @@ struct xfs_rui_log_item {
 	struct xfs_rui_log_format	rui_format;
 };
 
+static inline size_t
+xfs_rui_log_item_sizeof(
+	unsigned int		nr)
+{
+	return offsetof(struct xfs_rui_log_item, rui_format) +
+			xfs_rui_log_format_sizeof(nr);
+}
+
 /*
  * This is the "rmap update done" log item.  It is used to log the fact that
  * some rmapbt updates mentioned in an earlier rui item have been performed.
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index fd6be45b3a1e01c81bfe179d67818bafc9f6ec92..340975392e9185b8378c7046ec9ad02677acbb67 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1782,9 +1782,8 @@ xfs_init_zones(void)
 	if (!xfs_rud_zone)
 		goto out_destroy_icreate_zone;
 
-	xfs_rui_zone = kmem_zone_init((sizeof(struct xfs_rui_log_item) +
-			((XFS_RUI_MAX_FAST_EXTENTS - 1) *
-				sizeof(struct xfs_map_extent))),
+	xfs_rui_zone = kmem_zone_init(
+			xfs_rui_log_item_sizeof(XFS_RUI_MAX_FAST_EXTENTS),
 			"xfs_rui_item");
 	if (!xfs_rui_zone)
 		goto out_destroy_rud_zone;