arc_os: split userspace and Linux kernel code

The Linux arc_os.c carries userspace and kernel code, with very little
overlap between the two. This lifts the userspace parts out into a
separate arc_os.c for libzpool and removes it from the Linux side.

Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #16492

lib/libzpool/Makefile.am

@@ -12,6 +12,7 @@ CPPCHECKTARGETS += libzpool.la
 
 dist_libzpool_la_SOURCES = \
 	%D%/abd_os.c \
+	%D%/arc_os.c \
 	%D%/kernel.c \
 	%D%/taskq.c \
 	%D%/util.c
@@ -42,7 +43,6 @@ nodist_libzpool_la_SOURCES = \
 	module/lua/lvm.c \
 	module/lua/lzio.c \
 	\
-	module/os/linux/zfs/arc_os.c \
 	module/os/linux/zfs/trace.c \
 	module/os/linux/zfs/vdev_file.c \
 	module/os/linux/zfs/vdev_label_os.c \

lib/libzpool/arc_os.c

@@ -0,0 +1,87 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or https://opensource.org/licenses/CDDL-1.0.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, Joyent, Inc.
+ * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+ * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
+ * Copyright 2017 Nexenta Systems, Inc.  All rights reserved.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/arc_impl.h>
+
+/*
+ * Return a default max arc size based on the amount of physical memory.
+ * This may be overridden by tuning the zfs_arc_max module parameter.
+ */
+uint64_t
+arc_default_max(uint64_t min, uint64_t allmem)
+{
+	uint64_t size;
+
+	if (allmem >= 1 << 30)
+		size = allmem - (1 << 30);
+	else
+		size = min;
+	return (MAX(allmem * 5 / 8, size));
+}
+
+int64_t
+arc_available_memory(void)
+{
+	int64_t lowest = INT64_MAX;
+
+	/* Every 100 calls, free a small amount */
+	if (random_in_range(100) == 0)
+		lowest = -1024;
+
+	return (lowest);
+}
+
+int
+arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
+{
+	(void) spa, (void) reserve, (void) txg;
+	return (0);
+}
+
+uint64_t
+arc_all_memory(void)
+{
+	return (ptob(physmem) / 2);
+}
+
+uint64_t
+arc_free_memory(void)
+{
+	return (random_in_range(arc_all_memory() * 20 / 100));
+}
+
+void
+arc_register_hotplug(void)
+{
+}
+
+void
+arc_unregister_hotplug(void)
+{
+}