Make the vfs.zfs.vdev.raidz_impl sysctl cross-platform

Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by:	Alan Somers <asomers@gmail.com>
Sponsored by:	ConnectWise
Closes #16980

module/os/freebsd/zfs/sysctl_os.c

@@ -679,6 +679,27 @@ param_set_deadman_failmode(SYSCTL_HANDLER_ARGS)
 	return (-param_set_deadman_failmode_common(buf));
 }
 
+int
+param_set_raidz_impl(SYSCTL_HANDLER_ARGS)
+{
+	const size_t bufsize = 128;
+	char *buf;
+	int rc;
+
+	buf = malloc(bufsize, M_SOLARIS, M_WAITOK | M_ZERO);
+	if (req->newptr == NULL)
+		vdev_raidz_impl_get(buf, bufsize);
+
+	rc = sysctl_handle_string(oidp, buf, bufsize, req);
+	if (rc || req->newptr == NULL) {
+		free(buf, M_SOLARIS);
+		return (rc);
+	}
+	rc = vdev_raidz_impl_set(buf);
+	free(buf, M_SOLARIS);
+	return (rc);
+}
+
 int
 param_set_slop_shift(SYSCTL_HANDLER_ARGS)
 {

module/os/linux/zfs/vdev_raidz.c

@@ -0,0 +1,42 @@
+/*
+ * 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) 2025 ConnectWise */
+
+#include <sys/zfs_context.h>
+#include <sys/spa.h>
+#include <sys/zio.h>
+#include <sys/vdev_impl.h>
+#include <sys/vdev_raidz.h>
+
+int
+param_get_raidz_impl(char *buf, zfs_kernel_param_t *kp)
+{
+	return (vdev_raidz_impl_get(buf, PAGE_SIZE));
+}
+
+int
+param_set_raidz_impl(const char *val, zfs_kernel_param_t *kp)
+{
+	int error;
+
+	error = vdev_raidz_impl_set(val);
+	return (error);
+}