1 files changed, 5 insertions, 2 deletions

diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 8c7c620bfe9b..afa8c72d8a3d 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -473,8 +473,11 @@ union mcluster {
 /*
  * Check if we can write to an mbuf.
  */
+#define M_EXT_WRITABLE(m)	\
+    ((m)->m_ext.ext_free == NULL && mclrefcnt[mtocl((m)->m_ext.ext_buf)] == 1)
+
 #define M_WRITABLE(m) (!((m)->m_flags & M_EXT) || \
-    ((m)->m_ext.ext_free == NULL && mclrefcnt[mtocl((m)->m_ext.ext_buf)] == 1))
+    M_EXT_WRITABLE(m) )
 
 /*
  * Compute the amount of space available
@@ -482,7 +485,7 @@ union mcluster {
  */
 #define	M_LEADINGSPACE(m)						\
 	((m)->m_flags & M_EXT ?						\
-	    /* (m)->m_data - (m)->m_ext.ext_buf */ 0 :			\
+	    (M_EXT_WRITABLE(m) ? (m)->m_data - (m)->m_ext.ext_buf : 0):	\
 	    (m)->m_flags & M_PKTHDR ? (m)->m_data - (m)->m_pktdat :	\
 	    (m)->m_data - (m)->m_dat)