[src/trunk]: src/sys/kern Revert my rev1.190, remove the M_READO...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/af39d6c03bad
branches:  trunk
changeset: 318686:af39d6c03bad
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu May 03 07:46:17 2018 +0000
description:
Revert my rev1.190, remove the M_READONLY check. The initial code was
correct: what is read-only is the mbuf storage, not the mbuf itself. The
storage contains the packet payload, and never has anything related to
mbufs. So it is fine to remove M_PKTHDR on mbufs that have a read-only
storage.

In fact it was kind of obvious, since several places already manually
remove M_PKTHDR without taking care of the external storage.

diffstat:

 sys/kern/uipc_mbuf.c |  9 ++-------
 1 files changed, 2 insertions(+), 7 deletions(-)

diffs (30 lines):

diff -r 3205fb969f92 -r af39d6c03bad sys/kern/uipc_mbuf.c
--- a/sys/kern/uipc_mbuf.c      Thu May 03 07:28:43 2018 +0000
+++ b/sys/kern/uipc_mbuf.c      Thu May 03 07:46:17 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uipc_mbuf.c,v 1.213 2018/05/03 07:25:50 maxv Exp $     */
+/*     $NetBSD: uipc_mbuf.c,v 1.214 2018/05/03 07:46:17 maxv Exp $     */
 
 /*
  * Copyright (c) 1999, 2001 The NetBSD Foundation, Inc.
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.213 2018/05/03 07:25:50 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.214 2018/05/03 07:46:17 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_mbuftrace.h"
@@ -1538,11 +1538,6 @@
 {
        KASSERT(m->m_flags & M_PKTHDR);
 
-       if (M_READONLY(m)) {
-               /* Nothing we can do. */
-               return;
-       }
-
        m_tag_delete_chain(m, NULL);
        m->m_flags &= ~M_PKTHDR;
        memset(&m->m_pkthdr, 0, sizeof(m->m_pkthdr));