From a5fdba1185eeb1b6596e656a3e6bf3ef39b87ea3 Mon Sep 17 00:00:00 2001
From: Brian Atkinson <batkinson@lanl.gov>
Date: Tue, 1 Aug 2023 17:48:19 -0400
Subject: [PATCH] Revert "Linux 6.5 compat: register_sysctl_table removed"

This reverts commit b35374fd6474603170fd9a3c7503da6eb13ac712 as there
are error messages when loading the SPL module. Errors seemed to be tied
to duplicate a duplicate entry.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #15134
---
 config/kernel-register_sysctl_table.m4 | 27 --------------------------
 config/kernel.m4                       |  2 --
 module/os/linux/spl/spl-proc.c         | 26 +++----------------------
 3 files changed, 3 insertions(+), 52 deletions(-)
 delete mode 100644 config/kernel-register_sysctl_table.m4

diff --git a/config/kernel-register_sysctl_table.m4 b/config/kernel-register_sysctl_table.m4
deleted file mode 100644
index f18316b32b6d..000000000000
--- a/config/kernel-register_sysctl_table.m4
+++ /dev/null
@@ -1,27 +0,0 @@
-dnl #
-dnl # Linux 6.5 removes register_sysctl_table
-dnl #
-AC_DEFUN([ZFS_AC_KERNEL_SRC_REGISTER_SYSCTL_TABLE], [
-	ZFS_LINUX_TEST_SRC([has_register_sysctl_table], [
-		#include <linux/sysctl.h>
-
-		static struct ctl_table dummy_table[] = {
-			{}
-		};
-
-    ],[
-		struct ctl_table_header *h
-			__attribute((unused)) = register_sysctl_table(dummy_table);
-    ])
-])
-
-AC_DEFUN([ZFS_AC_KERNEL_REGISTER_SYSCTL_TABLE], [
-	AC_MSG_CHECKING([whether register_sysctl_table exists])
-	ZFS_LINUX_TEST_RESULT([has_register_sysctl_table], [
-		AC_MSG_RESULT([yes])
-		AC_DEFINE(HAVE_SYSCTL_REGISTER_TABLE, 1,
-			[sysctl_register_table exists])
-	],[
-		AC_MSG_RESULT([no])
-	])
-])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 28bd361d33ff..1487fa2e7793 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -160,7 +160,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_SRC], [
 	ZFS_AC_KERNEL_SRC_FILEMAP
 	ZFS_AC_KERNEL_SRC_WRITEPAGE_T
 	ZFS_AC_KERNEL_SRC_RECLAIMED
-	ZFS_AC_KERNEL_SRC_REGISTER_SYSCTL_TABLE
 	case "$host_cpu" in
 		powerpc*)
 			ZFS_AC_KERNEL_SRC_CPU_HAS_FEATURE
@@ -300,7 +299,6 @@ AC_DEFUN([ZFS_AC_KERNEL_TEST_RESULT], [
 	ZFS_AC_KERNEL_FILEMAP
 	ZFS_AC_KERNEL_WRITEPAGE_T
 	ZFS_AC_KERNEL_RECLAIMED
-	ZFS_AC_KERNEL_REGISTER_SYSCTL_TABLE
 	case "$host_cpu" in
 		powerpc*)
 			ZFS_AC_KERNEL_CPU_HAS_FEATURE
diff --git a/module/os/linux/spl/spl-proc.c b/module/os/linux/spl/spl-proc.c
index bcc356ae55b6..01f5619e1893 100644
--- a/module/os/linux/spl/spl-proc.c
+++ b/module/os/linux/spl/spl-proc.c
@@ -624,7 +624,6 @@ static struct ctl_table spl_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dohostid,
 	},
-#ifdef HAVE_REGISTER_SYSCTL_TABLE
 	{
 		.procname	= "kmem",
 		.mode		= 0555,
@@ -635,11 +634,9 @@ static struct ctl_table spl_table[] = {
 		.mode		= 0555,
 		.child		= spl_kstat_table,
 	},
-#endif
 	{},
 };
 
-#ifdef HAVE_REGISTER_SYSCTL_TABLE
 static struct ctl_table spl_dir[] = {
 	{
 		.procname	= "spl",
@@ -651,38 +648,21 @@ static struct ctl_table spl_dir[] = {
 
 static struct ctl_table spl_root[] = {
 	{
-		.procname	= "kernel",
-		.mode		= 0555,
-		.child		= spl_dir,
+	.procname = "kernel",
+	.mode = 0555,
+	.child = spl_dir,
 	},
 	{}
 };
-#endif
 
 int
 spl_proc_init(void)
 {
 	int rc = 0;
 
-#ifdef HAVE_REGISTER_SYSCTL_TABLE
 	spl_header = register_sysctl_table(spl_root);
 	if (spl_header == NULL)
 		return (-EUNATCH);
-#else
-	spl_header = register_sysctl("kernel/spl", spl_table);
-	if (spl_header == NULL)
-		return (-EUNATCH);
-
-	if (register_sysctl("kernel/spl/kmem", spl_kmem_table) == NULL) {
-		rc = -EUNATCH;
-		goto out;
-	}
-
-	if (register_sysctl("kernel/spl/kstat", spl_kstat_table) == NULL) {
-		rc = -EUNATCH;
-		goto out;
-	}
-#endif
 
 	proc_spl = proc_mkdir("spl", NULL);
 	if (proc_spl == NULL) {