mm: move oom_kill sysctls to their own file

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we just
care about the core logic.

So move the oom_kill sysctls to their own file, mm/oom_kill.c

[sfr@canb.auug.org.au: null-terminate the array]
  Link: https://lkml.kernel.org/r/20220216193202.28838626@canb.auug.org.au

Link: https://lkml.kernel.org/r/20220215093203.31032-1-sujiaxun@uniontech.com
Signed-off-by: sujiaxun <sujiaxun@uniontech.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Kees Cook <keescook@chromium.org>
Cc: Iurii Zaikin <yzaikin@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

3 files changed, 35 insertions, 30 deletions

diff --git a/include/linux/oom.h b/include/linux/oom.h
index 2db9a1432511..02d1e7bbd8cd 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -123,8 +123,4 @@ extern void oom_killer_enable(void);
 
 extern struct task_struct *find_lock_task_mm(struct task_struct *p);
 
-/* sysctls */
-extern int sysctl_oom_dump_tasks;
-extern int sysctl_oom_kill_allocating_task;
-extern int sysctl_panic_on_oom;
 #endif /* _INCLUDE_LINUX_OOM_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5e43569ce2be..a21c0ea396f3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2242,29 +2242,6 @@ static struct ctl_table vm_table[] = {
 		.extra2		= SYSCTL_TWO,
 	},
 	{
-		.procname	= "panic_on_oom",
-		.data		= &sysctl_panic_on_oom,
-		.maxlen		= sizeof(sysctl_panic_on_oom),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_TWO,
-	},
-	{
-		.procname	= "oom_kill_allocating_task",
-		.data		= &sysctl_oom_kill_allocating_task,
-		.maxlen		= sizeof(sysctl_oom_kill_allocating_task),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "oom_dump_tasks",
-		.data		= &sysctl_oom_dump_tasks,
-		.maxlen		= sizeof(sysctl_oom_dump_tasks),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
 		.procname	= "overcommit_ratio",
 		.data		= &sysctl_overcommit_ratio,
 		.maxlen		= sizeof(sysctl_overcommit_ratio),
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7ec38194f8e1..7cc338a9e9e4 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -52,9 +52,38 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/oom.h>
 
-int sysctl_panic_on_oom;
-int sysctl_oom_kill_allocating_task;
-int sysctl_oom_dump_tasks = 1;
+static int sysctl_panic_on_oom;
+static int sysctl_oom_kill_allocating_task;
+static int sysctl_oom_dump_tasks = 1;
+
+#ifdef CONFIG_SYSCTL
+static struct ctl_table vm_oom_kill_table[] = {
+	{
+		.procname	= "panic_on_oom",
+		.data		= &sysctl_panic_on_oom,
+		.maxlen		= sizeof(sysctl_panic_on_oom),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
+	{
+		.procname	= "oom_kill_allocating_task",
+		.data		= &sysctl_oom_kill_allocating_task,
+		.maxlen		= sizeof(sysctl_oom_kill_allocating_task),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "oom_dump_tasks",
+		.data		= &sysctl_oom_dump_tasks,
+		.maxlen		= sizeof(sysctl_oom_dump_tasks),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{}
+};
+#endif
 
 /*
  * Serializes oom killer invocations (out_of_memory()) from all contexts to
@@ -677,6 +706,9 @@ static void wake_oom_reaper(struct task_struct *tsk)
 static int __init oom_init(void)
 {
 	oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
+#ifdef CONFIG_SYSCTL
+	register_sysctl_init("vm", vm_oom_kill_table);
+#endif
 	return 0;
 }
 subsys_initcall(oom_init)