From 81b910ab4a0ef0d0b6cd3a1a636fcbcd050c0245 Mon Sep 17 00:00:00 2001
From: Cheyenne Wills <cwills@sinenomine.net>
Date: Tue, 05 Mar 2024 08:37:47 -0700
Subject: [PATCH] Linux 6.8: Remove ctl_table sentinels

The Linux 6.8 commit 'sysctl: Remove the now superfluous sentinel
elements from ctl_table array' (c8a65501d3) was a clean up commit
that removed the sentinel entry in the ctl_table array (e.g. the
"null" entry at the end of the table).

As of Linux 6.8, including the sentinel entry (.procname =) in the
ctl_table is unnecessary, but doesn't yet break anything.  But it is
likely that including the sentinel will start to cause runtime errors in
future Linux versions very soon, so avoid the sentinel when we can, to
avoid possible problems in the future.

Define a new macro that can be used as the last entry of a ctl_table
that will either add a "null" entry, or nothing.

There is not a specific build test we can use within configure, so we
must explicitly test the Linux version to decide if we need to use a
sentinel or not when defining the macro.  We are selecting 6.8 to match
the version where the Linux kernel is removing the sentinels from the in
kernel filesystems.

Note: See the Linux merge commits 'Merge tag 'sysctl-6.8-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux' (a05aea98d4)
for more details behind the staged removal of the sentinels in the
ctl_table structures and the potential future change for removing the
actual check for the sentinel within the Linux kernel.

Reviewed-on: https://gerrit.openafs.org/15645
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 35c8c1bf0b1cb48178f676ba5bcf16ad59c5a33b)

Change-Id: I34cb7586003e10a6c7438d7205123d57af30585e
---

diff --git a/src/afs/LINUX/osi_sysctl.c b/src/afs/LINUX/osi_sysctl.c
index a0a0398..c1116fc 100644
--- a/src/afs/LINUX/osi_sysctl.c
+++ b/src/afs/LINUX/osi_sysctl.c
@@ -54,6 +54,14 @@
 # define AFS_SYSCTL_INT(num, perms, var) \
 	AFS_SYSCTL_INT2(num, perms, #var, var)
 
+# if LINUX_VERSION_CODE >= KERNEL_VERSION(6,8,0)
+/* end of list sentinel not needed */
+#  define AFS_SYSCTL_SENTINEL
+# else
+/* NULL entry to mark the end of the list */
+#  define AFS_SYSCTL_SENTINEL { .procname = NULL }
+# endif
+
 static struct ctl_table_header *afs_sysctl = NULL;
 
 static struct ctl_table afs_sysctl_table[] = {
@@ -75,9 +83,7 @@
     AFS_SYSCTL_INT( 13, 0644, afs_cacheBlocks),
     AFS_SYSCTL_INT2(14, 0644, "md5inum", afs_md5inum),
 
-    {
-	.procname	= 0
-    }
+    AFS_SYSCTL_SENTINEL
 };
 # if !defined(HAVE_LINUX_REGISTER_SYSCTL)
 static struct ctl_table fs_sysctl_table[] = {
@@ -87,9 +93,7 @@
 	.mode		= 0555,
 	.child		= afs_sysctl_table
     },
-    {
-	.procname	= 0
-    }
+    AFS_SYSCTL_SENTINEL
 };
 # endif
 int