diff --git a/sys/dev/cxgbe/tom/t4_cpl_io.c b/sys/dev/cxgbe/tom/t4_cpl_io.c
--- a/sys/dev/cxgbe/tom/t4_cpl_io.c
+++ b/sys/dev/cxgbe/tom/t4_cpl_io.c
@@ -703,7 +703,7 @@
 		for (m = sndptr; m != NULL; m = m->m_next) {
 			int n;
 
-			if ((m->m_flags & M_NOTAVAIL) != 0)
+			if ((m->m_flags & M_NOTREADY) != 0)
 				break;
 			if (m->m_flags & M_EXTPG) {
 #ifdef KERN_TLS
@@ -787,7 +787,7 @@
 
 		/* nothing to send */
 		if (plen == 0) {
-			KASSERT(m == NULL || (m->m_flags & M_NOTAVAIL) != 0,
+			KASSERT(m == NULL || (m->m_flags & M_NOTREADY) != 0,
 			    ("%s: nothing to send, but m != NULL is ready",
 			    __func__));
 			break;
@@ -880,7 +880,7 @@
 		toep->txsd_avail--;
 
 		t4_l2t_send(sc, wr, toep->l2te);
-	} while (m != NULL && (m->m_flags & M_NOTAVAIL) == 0);
+	} while (m != NULL && (m->m_flags & M_NOTREADY) == 0);
 
 	/* Send a FIN if requested, but only if there's no more data to send */
 	if (m == NULL && toep->flags & TPF_SEND_FIN)
diff --git a/sys/dev/cxgbe/tom/t4_tls.c b/sys/dev/cxgbe/tom/t4_tls.c
--- a/sys/dev/cxgbe/tom/t4_tls.c
+++ b/sys/dev/cxgbe/tom/t4_tls.c
@@ -563,7 +563,7 @@
 		 * If there is no ready data to send, wait until more
 		 * data arrives.
 		 */
-		if (m == NULL || (m->m_flags & M_NOTAVAIL) != 0) {
+		if (m == NULL || (m->m_flags & M_NOTREADY) != 0) {
 			if (sowwakeup)
 				sowwakeup_locked(so);
 			else
@@ -614,7 +614,7 @@
 
 		/* Shove if there is no additional data pending. */
 		shove = ((m->m_next == NULL ||
-		    (m->m_next->m_flags & M_NOTAVAIL) != 0)) &&
+		    (m->m_next->m_flags & M_NOTREADY) != 0)) &&
 		    (tp->t_flags & TF_MORETOCOME) == 0;
 
 		if (sb->sb_flags & SB_AUTOSIZE &&
diff --git a/sys/kern/uipc_ktls.c b/sys/kern/uipc_ktls.c
--- a/sys/kern/uipc_ktls.c
+++ b/sys/kern/uipc_ktls.c
@@ -1207,7 +1207,7 @@
 	for (; m != NULL; m = m->m_next) {
 		KASSERT(m->m_nextpkt == NULL, ("%s: m_nextpkt != NULL",
 		    __func__));
-		KASSERT((m->m_flags & M_NOTAVAIL) == 0, ("%s: mbuf not avail",
+		KASSERT((m->m_flags & M_NOTREADY) == 0, ("%s: mbuf not ready",
 		    __func__));
 		KASSERT(sb->sb_acc >= m->m_len, ("%s: sb_acc < m->m_len",
 		    __func__));
diff --git a/sys/kern/uipc_sockbuf.c b/sys/kern/uipc_sockbuf.c
--- a/sys/kern/uipc_sockbuf.c
+++ b/sys/kern/uipc_sockbuf.c
@@ -195,14 +195,14 @@
 sbready(struct sockbuf *sb, struct mbuf *m0, int count)
 {
 	struct mbuf *m;
-	u_int blocker;
+	bool blocker;
 
 	SOCKBUF_LOCK_ASSERT(sb);
 	KASSERT(sb->sb_fnrdy != NULL, ("%s: sb %p NULL fnrdy", __func__, sb));
 	KASSERT(count > 0, ("%s: invalid count %d", __func__, count));
 
 	m = m0;
-	blocker = (sb->sb_fnrdy == m) ? M_BLOCKED : 0;
+	blocker = (sb->sb_fnrdy == m);
 
 	while (count > 0) {
 		KASSERT(m->m_flags & M_NOTREADY,
@@ -217,8 +217,7 @@
 			m->m_epg_nrdy = 0;
 		} else
 			count--;
-
-		m->m_flags &= ~(M_NOTREADY | blocker);
+		m->m_flags &= ~M_NOTREADY;
 		if (blocker)
 			sb->sb_acc += m->m_len;
 		m = m->m_next;
@@ -240,12 +239,8 @@
 	}
 
 	/* This one was blocking all the queue. */
-	for (; m && (m->m_flags & M_NOTREADY) == 0; m = m->m_next) {
-		KASSERT(m->m_flags & M_BLOCKED,
-		    ("%s: m %p !M_BLOCKED", __func__, m));
-		m->m_flags &= ~M_BLOCKED;
+	for (; m && (m->m_flags & M_NOTREADY) == 0; m = m->m_next)
 		sb->sb_acc += m->m_len;
-	}
 
 	sb->sb_fnrdy = m;
 	sbready_compress(sb, m0, m);
@@ -269,8 +264,7 @@
 			sb->sb_fnrdy = m;
 		else
 			sb->sb_acc += m->m_len;
-	} else
-		m->m_flags |= M_BLOCKED;
+	}
 
 	if (m->m_type != MT_DATA && m->m_type != MT_OOBDATA)
 		sb->sb_ctl += m->m_len;
@@ -287,29 +281,29 @@
 void
 sbfree(struct sockbuf *sb, struct mbuf *m)
 {
+	struct mbuf *n;
 
 #if 0	/* XXX: not yet: soclose() call path comes here w/o lock. */
 	SOCKBUF_LOCK_ASSERT(sb);
 #endif
-
 	sb->sb_ccc -= m->m_len;
 
-	if (!(m->m_flags & M_NOTAVAIL))
-		sb->sb_acc -= m->m_len;
-
 	if (m == sb->sb_fnrdy) {
-		struct mbuf *n;
-
 		KASSERT(m->m_flags & M_NOTREADY,
 		    ("%s: m %p !M_NOTREADY", __func__, m));
 
 		n = m->m_next;
 		while (n != NULL && !(n->m_flags & M_NOTREADY)) {
-			n->m_flags &= ~M_BLOCKED;
 			sb->sb_acc += n->m_len;
 			n = n->m_next;
 		}
 		sb->sb_fnrdy = n;
+	} else {
+		/* Assert that mbuf is not behind sb_fnrdy. */
+		for (n = sb->sb_fnrdy; n != NULL; n = n->m_next)
+			KASSERT(n != m, ("%s: sb %p freeing %p behind sb_fnrdy",
+			    __func__, sb, m));
+		sb->sb_acc -= m->m_len;
 	}
 
 	if (m->m_type != MT_DATA && m->m_type != MT_OOBDATA)
@@ -1129,13 +1123,7 @@
 			}
 			fnrdy = m;
 		}
-		if (fnrdy) {
-			if (!(m->m_flags & M_NOTAVAIL)) {
-				printf("sb %p: fnrdy %p, m %p is avail\n",
-				    sb, sb->sb_fnrdy, m);
-				goto fail;
-			}
-		} else
+		if (fnrdy == NULL)
 			acc += m->m_len;
 		ccc += m->m_len;
 		mbcnt += MSIZE;
@@ -1602,8 +1590,8 @@
 			next = m->m_nextpkt;
 		}
 		if (m->m_len > len) {
-			KASSERT(!(m->m_flags & M_NOTAVAIL),
-			    ("%s: m %p M_NOTAVAIL", __func__, m));
+			KASSERT(!(m->m_flags & M_NOTREADY),
+			    ("%s: m %p M_NOTREADY", __func__, m));
 			m->m_len -= len;
 			m->m_data += len;
 			sb->sb_ccc -= len;
diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -3342,7 +3342,7 @@
 			for (m = sb->sb_mb;
 			     m != NULL && m->m_len <= len;
 			     m = m->m_next) {
-				KASSERT(!(m->m_flags & M_NOTAVAIL),
+				KASSERT(!(m->m_flags & M_NOTREADY),
 				    ("%s: m %p not available", __func__, m));
 				len -= m->m_len;
 				uio->uio_resid -= m->m_len;
diff --git a/sys/sys/sockbuf.h b/sys/sys/sockbuf.h
--- a/sys/sys/sockbuf.h
+++ b/sys/sys/sockbuf.h
@@ -210,8 +210,6 @@
  * Socket buffer private mbuf(9) flags.
  */
 #define	M_NOTREADY	M_PROTO1	/* m_data not populated yet */
-#define	M_BLOCKED	M_PROTO2	/* M_NOTREADY in front of m */
-#define	M_NOTAVAIL	(M_NOTREADY | M_BLOCKED)
 
 void	sbappend(struct sockbuf *sb, struct mbuf *m, int flags);
 void	sbappend_locked(struct sockbuf *sb, struct mbuf *m, int flags);