[PATCH v5 1/8] net: Remove the now superfluous sentinel elements from ctl_table array

[Joel Granados via B4 Relay <devnull+j.granados.samsung.com@kernel.org>]

From: Joel Granados <j.granados@samsung.com>

This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

* Remove sentinel element from ctl_table structs.
* Remove the zeroing out of an array element (to make it look like a
  sentinel) in neigh_sysctl_register and lowpan_frags_ns_sysctl_register
  This is not longer needed and is safe after commit c899710fe7f9
  ("networking: Update to register_net_sysctl_sz") added the array size
  to the ctl_table registration.
* Replace the for loop stop condition in sysctl_core_net_init that tests
  for procname == NULL with one that depends on array size
* Removed the "-1" in mpls_net_init that adjusted for having an extra
  empty element when looping over ctl_table arrays
* Use a table_size variable to keep the value of ARRAY_SIZE

Signed-off-by: Joel Granados <j.granados@samsung.com>
---
 net/core/neighbour.c                |  5 +----
 net/core/sysctl_net_core.c          | 12 +++++-------
 net/dccp/sysctl.c                   |  2 --
 net/ieee802154/6lowpan/reassembly.c |  6 +-----
 net/mpls/af_mpls.c                  | 12 ++++++------
 net/unix/sysctl_net_unix.c          |  1 -
 6 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 552719c3bbc3..b0327402b3e6 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -3728,7 +3728,7 @@ static int neigh_proc_base_reachable_time(struct ctl_table *ctl, int write,
 
 static struct neigh_sysctl_table {
 	struct ctl_table_header *sysctl_header;
-	struct ctl_table neigh_vars[NEIGH_VAR_MAX + 1];
+	struct ctl_table neigh_vars[NEIGH_VAR_MAX];
 } neigh_sysctl_template __read_mostly = {
 	.neigh_vars = {
 		NEIGH_SYSCTL_ZERO_INTMAX_ENTRY(MCAST_PROBES, "mcast_solicit"),
@@ -3779,7 +3779,6 @@ static struct neigh_sysctl_table {
 			.extra2		= SYSCTL_INT_MAX,
 			.proc_handler	= proc_dointvec_minmax,
 		},
-		{},
 	},
 };
 
@@ -3807,8 +3806,6 @@ int neigh_sysctl_register(struct net_device *dev, struct neigh_parms *p,
 	if (dev) {
 		dev_name_source = dev->name;
 		/* Terminate the table early */
-		memset(&t->neigh_vars[NEIGH_VAR_GC_INTERVAL], 0,
-		       sizeof(t->neigh_vars[NEIGH_VAR_GC_INTERVAL]));
 		neigh_vars_size = NEIGH_VAR_BASE_REACHABLE_TIME_MS + 1;
 	} else {
 		struct neigh_table *tbl = p->tbl;
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 6973dda3abda..a84690b13bb9 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -660,7 +660,6 @@ static struct ctl_table net_core_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
 	},
-	{ }
 };
 
 static struct ctl_table netns_core_table[] = {
@@ -697,7 +696,6 @@ static struct ctl_table netns_core_table[] = {
 		.extra2		= SYSCTL_ONE,
 		.proc_handler	= proc_dou8vec_minmax,
 	},
-	{ }
 };
 
 static int __init fb_tunnels_only_for_init_net_sysctl_setup(char *str)
@@ -715,7 +713,8 @@ __setup("fb_tunnels=", fb_tunnels_only_for_init_net_sysctl_setup);
 
 static __net_init int sysctl_core_net_init(struct net *net)
 {
-	struct ctl_table *tbl, *tmp;
+	size_t table_size = ARRAY_SIZE(netns_core_table);
+	struct ctl_table *tbl;
 
 	tbl = netns_core_table;
 	if (!net_eq(net, &init_net)) {
@@ -723,12 +722,11 @@ static __net_init int sysctl_core_net_init(struct net *net)
 		if (tbl == NULL)
 			goto err_dup;
 
-		for (tmp = tbl; tmp->procname; tmp++)
-			tmp->data += (char *)net - (char *)&init_net;
+		for (int i = 0; i < table_size; ++i)
+			(tbl + i)->data += (char *)net - (char *)&init_net;
 	}
 
-	net->core.sysctl_hdr = register_net_sysctl_sz(net, "net/core", tbl,
-						      ARRAY_SIZE(netns_core_table));
+	net->core.sysctl_hdr = register_net_sysctl_sz(net, "net/core", tbl, table_size);
 	if (net->core.sysctl_hdr == NULL)
 		goto err_reg;
 
diff --git a/net/dccp/sysctl.c b/net/dccp/sysctl.c
index ee8d4f5afa72..3fc474d6e57d 100644
--- a/net/dccp/sysctl.c
+++ b/net/dccp/sysctl.c
@@ -90,8 +90,6 @@ static struct ctl_table dccp_default_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_ms_jiffies,
 	},
-
-	{ }
 };
 
 static struct ctl_table_header *dccp_table_header;
diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
index 6dd960ec558c..09b18ee6df00 100644
--- a/net/ieee802154/6lowpan/reassembly.c
+++ b/net/ieee802154/6lowpan/reassembly.c
@@ -338,7 +338,6 @@ static struct ctl_table lowpan_frags_ns_ctl_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_jiffies,
 	},
-	{ }
 };
 
 /* secret interval has been deprecated */
@@ -351,7 +350,6 @@ static struct ctl_table lowpan_frags_ctl_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_jiffies,
 	},
-	{ }
 };
 
 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
@@ -370,10 +368,8 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
 			goto err_alloc;
 
 		/* Don't export sysctls to unprivileged users */
-		if (net->user_ns != &init_user_ns) {
-			table[0].procname = NULL;
+		if (net->user_ns != &init_user_ns)
 			table_size = 0;
-		}
 	}
 
 	table[0].data	= &ieee802154_lowpan->fqdir->high_thresh;
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 6dab883a08dd..ecc849678e7b 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -1393,13 +1393,13 @@ static const struct ctl_table mpls_dev_table[] = {
 		.proc_handler	= mpls_conf_proc,
 		.data		= MPLS_PERDEV_SYSCTL_OFFSET(input_enabled),
 	},
-	{ }
 };
 
 static int mpls_dev_sysctl_register(struct net_device *dev,
 				    struct mpls_dev *mdev)
 {
 	char path[sizeof("net/mpls/conf/") + IFNAMSIZ];
+	size_t table_size = ARRAY_SIZE(mpls_dev_table);
 	struct net *net = dev_net(dev);
 	struct ctl_table *table;
 	int i;
@@ -1411,7 +1411,7 @@ static int mpls_dev_sysctl_register(struct net_device *dev,
 	/* Table data contains only offsets relative to the base of
 	 * the mdev at this point, so make them absolute.
 	 */
-	for (i = 0; i < ARRAY_SIZE(mpls_dev_table); i++) {
+	for (i = 0; i < table_size; i++) {
 		table[i].data = (char *)mdev + (uintptr_t)table[i].data;
 		table[i].extra1 = mdev;
 		table[i].extra2 = net;
@@ -1419,8 +1419,7 @@ static int mpls_dev_sysctl_register(struct net_device *dev,
 
 	snprintf(path, sizeof(path), "net/mpls/conf/%s", dev->name);
 
-	mdev->sysctl = register_net_sysctl_sz(net, path, table,
-					      ARRAY_SIZE(mpls_dev_table));
+	mdev->sysctl = register_net_sysctl_sz(net, path, table, table_size);
 	if (!mdev->sysctl)
 		goto free;
 
@@ -2674,6 +2673,7 @@ static const struct ctl_table mpls_table[] = {
 
 static int mpls_net_init(struct net *net)
 {
+	size_t table_size = ARRAY_SIZE(mpls_table);
 	struct ctl_table *table;
 	int i;
 
@@ -2689,11 +2689,11 @@ static int mpls_net_init(struct net *net)
 	/* Table data contains only offsets relative to the base of
 	 * the mdev at this point, so make them absolute.
 	 */
-	for (i = 0; i < ARRAY_SIZE(mpls_table) - 1; i++)
+	for (i = 0; i < table_size; i++)
 		table[i].data = (char *)net + (uintptr_t)table[i].data;
 
 	net->mpls.ctl = register_net_sysctl_sz(net, "net/mpls", table,
-					       ARRAY_SIZE(mpls_table));
+					       table_size);
 	if (net->mpls.ctl == NULL) {
 		kfree(table);
 		return -ENOMEM;
diff --git a/net/unix/sysctl_net_unix.c b/net/unix/sysctl_net_unix.c
index 3e84b31c355a..ae45d4cfac39 100644
--- a/net/unix/sysctl_net_unix.c
+++ b/net/unix/sysctl_net_unix.c
@@ -19,7 +19,6 @@ static struct ctl_table unix_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
-	{ }
 };
 
 int __net_init unix_sysctl_register(struct net *net)

-- 
2.43.0