From d510bf133d045d6c83742aeda6949bec150f6cbf Mon Sep 17 00:00:00 2001
From: Alexander Motin <mav@FreeBSD.org>
Date: Mon, 22 Feb 2021 17:21:05 -0500
Subject: [PATCH] cxgb(4): Rework my commit 9dc7c250.

The previous implementation was reported to try to coalesce packets
in situations when it should not, that resulted in assertion later.
This implementation better checks the first packet of the chain for
the coallescing elligibility.

MFC after:	3 days
---
 sys/dev/cxgb/cxgb_sge.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/sys/dev/cxgb/cxgb_sge.c b/sys/dev/cxgb/cxgb_sge.c
index 491d1a751f4..f13d2f03180 100644
--- a/sys/dev/cxgb/cxgb_sge.c
+++ b/sys/dev/cxgb/cxgb_sge.c
@@ -312,20 +312,22 @@ set_wr_hdr(struct work_request_hdr *wrp, uint32_t wr_hi, uint32_t wr_lo)
 struct coalesce_info {
 	int count;
 	int nbytes;
+	int noncoal;
 };
 
 static int
 coalesce_check(struct mbuf *m, void *arg)
 {
 	struct coalesce_info *ci = arg;
-	int *count = &ci->count;
-	int *nbytes = &ci->nbytes;
 
-	if ((*nbytes == 0) || ((*nbytes + m->m_len <= 10500) &&
-	    (*count < 7) && (m->m_next == NULL) &&
-	    ((mtod(m, vm_offset_t) & PAGE_MASK) + m->m_len <= PAGE_SIZE))) {
-		*count += 1;
-		*nbytes += m->m_len;
+	if ((m->m_next != NULL) ||
+	    ((mtod(m, vm_offset_t) & PAGE_MASK) + m->m_len > PAGE_SIZE))
+		ci->noncoal = 1;
+
+	if ((ci->count == 0) || (ci->noncoal == 0 && (ci->count < 7) &&
+	    (ci->nbytes + m->m_len <= 10500))) {
+		ci->count++;
+		ci->nbytes += m->m_len;
 		return (1);
 	}
 	return (0);
@@ -342,7 +344,7 @@ cxgb_dequeue(struct sge_qset *qs)
 		return TXQ_RING_DEQUEUE(qs);
 
 	m_head = m_tail = NULL;
-	ci.count = ci.nbytes = 0;
+	ci.count = ci.nbytes = ci.noncoal = 0;
 	do {
 		m = TXQ_RING_DEQUEUE_COND(qs, coalesce_check, &ci);
 		if (m_head == NULL) {