[RFC PATCH v1 05/30] sysctl: ipc: use sysctl_field in mq_sysctl

[Alexey Gladkov <legion@kernel.org>]

Convert mq_sysctls. The table can now share one static array across ipc
namespaces instead of allocating and rewriting a ctl_table copy for each
registration.

Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
 include/linux/sysctl.h |   2 +
 ipc/mq_sysctl.c        | 100 +++++++++--------------------------------
 2 files changed, 24 insertions(+), 78 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 3c7f2ffab334..e2831190e484 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -38,6 +38,7 @@ struct nsproxy;
 struct ctl_table_root;
 struct ctl_table_header;
 struct ctl_dir;
+struct ipc_namespace;
 struct user_namespace;
 
 /* Keep the same order as in fs/proc/proc_sysctl.c */
@@ -90,6 +91,7 @@ typedef int proc_handler(const struct ctl_table *ctl, int write, void *buffer,
 struct sysctl_context {
 	union {
 		struct user_namespace *user_ns;
+		struct ipc_namespace *ipc_ns;
 	} ns;
 };
 
diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index 0dd12e1c9f53..54e59b9901dd 100644
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -11,7 +11,6 @@
 
 #include <linux/stat.h>
 #include <linux/capability.h>
-#include <linux/slab.h>
 #include <linux/cred.h>
 
 static int msg_max_limit_min = MIN_MSGMAX;
@@ -20,50 +19,24 @@ static int msg_max_limit_max = HARD_MSGMAX;
 static int msg_maxsize_limit_min = MIN_MSGSIZEMAX;
 static int msg_maxsize_limit_max = HARD_MSGSIZEMAX;
 
-static const struct ctl_table mq_sysctls[] = {
-	{
-		.procname	= "queues_max",
-		.data		= &init_ipc_ns.mq_queues_max,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "msg_max",
-		.data		= &init_ipc_ns.mq_msg_max,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &msg_max_limit_min,
-		.extra2		= &msg_max_limit_max,
-	},
-	{
-		.procname	= "msgsize_max",
-		.data		= &init_ipc_ns.mq_msgsize_max,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &msg_maxsize_limit_min,
-		.extra2		= &msg_maxsize_limit_max,
-	},
-	{
-		.procname	= "msg_default",
-		.data		= &init_ipc_ns.mq_msg_default,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &msg_max_limit_min,
-		.extra2		= &msg_max_limit_max,
-	},
-	{
-		.procname	= "msgsize_default",
-		.data		= &init_ipc_ns.mq_msgsize_default,
-		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= &msg_maxsize_limit_min,
-		.extra2		= &msg_maxsize_limit_max,
-	},
+#define MQ_SYSCTL_DATA(name, member)				\
+static int *name ## _data(const struct sysctl_context *ctx)	\
+{								\
+	return &ctx->ns.ipc_ns->member;				\
+}
+
+MQ_SYSCTL_DATA(mq_queues_max, mq_queues_max);
+MQ_SYSCTL_DATA(mq_msg_max, mq_msg_max);
+MQ_SYSCTL_DATA(mq_msgsize_max, mq_msgsize_max);
+MQ_SYSCTL_DATA(mq_msg_default, mq_msg_default);
+MQ_SYSCTL_DATA(mq_msgsize_default, mq_msgsize_default);
+
+static const struct sysctl_field mq_sysctls[] = {
+	SYSCTL_FIELD_INT("queues_max", 0644, mq_queues_max_data),
+	SYSCTL_FIELD_STATIC_INT_MINMAX("msg_max", 0644, mq_msg_max_data, &msg_max_limit_min, &msg_max_limit_max),
+	SYSCTL_FIELD_STATIC_INT_MINMAX("msgsize_max", 0644, mq_msgsize_max_data, &msg_maxsize_limit_min, &msg_maxsize_limit_max),
+	SYSCTL_FIELD_STATIC_INT_MINMAX("msg_default", 0644, mq_msg_default_data, &msg_max_limit_min, &msg_max_limit_max),
+	SYSCTL_FIELD_STATIC_INT_MINMAX("msgsize_default", 0644, mq_msgsize_default_data, &msg_maxsize_limit_min, &msg_maxsize_limit_max),
 };
 
 static struct ctl_table_set *set_lookup(struct ctl_table_root *root)
@@ -116,39 +89,14 @@ static struct ctl_table_root set_root = {
 
 bool setup_mq_sysctls(struct ipc_namespace *ns)
 {
-	struct ctl_table *tbl;
+	struct sysctl_context ctx = {
+		.ns.ipc_ns = ns,
+	};
 
 	setup_sysctl_set(&ns->mq_set, &set_root, set_is_seen);
 
-	tbl = kmemdup(mq_sysctls, sizeof(mq_sysctls), GFP_KERNEL);
-	if (tbl) {
-		int i;
-
-		for (i = 0; i < ARRAY_SIZE(mq_sysctls); i++) {
-			if (tbl[i].data == &init_ipc_ns.mq_queues_max)
-				tbl[i].data = &ns->mq_queues_max;
-
-			else if (tbl[i].data == &init_ipc_ns.mq_msg_max)
-				tbl[i].data = &ns->mq_msg_max;
-
-			else if (tbl[i].data == &init_ipc_ns.mq_msgsize_max)
-				tbl[i].data = &ns->mq_msgsize_max;
-
-			else if (tbl[i].data == &init_ipc_ns.mq_msg_default)
-				tbl[i].data = &ns->mq_msg_default;
-
-			else if (tbl[i].data == &init_ipc_ns.mq_msgsize_default)
-				tbl[i].data = &ns->mq_msgsize_default;
-			else
-				tbl[i].data = NULL;
-		}
-
-		ns->mq_sysctls = __register_sysctl_table(&ns->mq_set,
-							 "fs/mqueue", tbl,
-							 ARRAY_SIZE(mq_sysctls));
-	}
+	ns->mq_sysctls = register_sysctl_fields(&ns->mq_set, "fs/mqueue", mq_sysctls, &ctx);
 	if (!ns->mq_sysctls) {
-		kfree(tbl);
 		retire_sysctl_set(&ns->mq_set);
 		return false;
 	}
@@ -158,10 +106,6 @@ bool setup_mq_sysctls(struct ipc_namespace *ns)
 
 void retire_mq_sysctls(struct ipc_namespace *ns)
 {
-	const struct ctl_table *tbl;
-
-	tbl = ns->mq_sysctls->ctl_table_arg;
 	unregister_sysctl_table(ns->mq_sysctls);
 	retire_sysctl_set(&ns->mq_set);
-	kfree(tbl);
 }
-- 
2.55.0