Revert of:

commit 730d22dbca18c6488ee11d40c1456ce5722191fc
Author: mlelstv <mlelstv@NetBSD.org>
Date:   Fri Apr 26 17:24:23 2019 +0000

    Handle half-closed pipes in FIONWRITE and FIONSPACE.

commit c07acfde1776881558ea5c9de165a136d7f03eb1
Author: mlelstv <mlelstv@NetBSD.org>
Date:   Fri Apr 26 17:20:49 2019 +0000

    Clean up pipe structure before recycling it.

Index: sys_pipe.c
===================================================================
RCS file: /cvsroot/src/sys/kern/sys_pipe.c,v
retrieving revision 1.148
diff -u -r1.148 sys_pipe.c
--- sys_pipe.c	26 Apr 2019 17:24:23 -0000	1.148
+++ sys_pipe.c	6 May 2020 10:09:00 -0000
@@ -1,4 +1,4 @@
-/*	$NetBSD: sys_pipe.c,v 1.148 2019/04/26 17:24:23 mlelstv Exp $	*/
+/*	$NetBSD: sys_pipe.c,v 1.147 2019/04/26 17:20:49 mlelstv Exp $	*/
 
 /*-
  * Copyright (c) 2003, 2007, 2008, 2009 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_pipe.c,v 1.148 2019/04/26 17:24:23 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_pipe.c,v 1.147 2019/04/26 17:20:49 mlelstv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1096,12 +1096,10 @@
 
 	case FIONWRITE:
 		/* Look at other side */
-		mutex_enter(lock);
 		pipe = pipe->pipe_peer;
-		if (pipe == NULL)
-			*(int *)data = 0;
+		mutex_enter(lock);
 #ifndef PIPE_NODIRECT
-		else if (pipe->pipe_state & PIPE_DIRECTW)
+		if (pipe->pipe_state & PIPE_DIRECTW)
 			*(int *)data = pipe->pipe_map.cnt;
 		else
 #endif
@@ -1111,11 +1109,8 @@
 
 	case FIONSPACE:
 		/* Look at other side */
-		mutex_enter(lock);
 		pipe = pipe->pipe_peer;
-		if (pipe == NULL)
-			*(int *)data = 0;
-		else
+		mutex_enter(lock);
 #ifndef PIPE_NODIRECT
 		/*
 		 * If we're in direct-mode, we don't really have a
@@ -1336,8 +1331,6 @@
     free_resources:
 	pipe->pipe_pgid = 0;
 	pipe->pipe_state = PIPE_SIGNALR;
-	pipe->pipe_peer = NULL;
-	pipe->pipe_lock = NULL;
 	pipe_free_kmem(pipe);
 	if (pipe->pipe_kmem != 0) {
 		pool_cache_put(pipe_rd_cache, pipe);