pid: Split out pid_types.h

Trimming down sched.h dependencies: we dont't want to include more than
the base types.

Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

drivers/target/target_core_xcopy.c

@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/list.h>
+#include <linux/rculist.h>
 #include <linux/configfs.h>
 #include <linux/ratelimit.h>
 #include <scsi/scsi_proto.h>

include/linux/pid.h

@@ -2,18 +2,10 @@
 #ifndef _LINUX_PID_H
 #define _LINUX_PID_H
 
+#include <linux/pid_types.h>
 #include <linux/rculist.h>
-#include <linux/wait.h>
 #include <linux/refcount.h>
-
-enum pid_type
-{
-	PIDTYPE_PID,
-	PIDTYPE_TGID,
-	PIDTYPE_PGID,
-	PIDTYPE_SID,
-	PIDTYPE_MAX,
-};
+#include <linux/wait.h>
 
 /*
  * What is struct pid?
@@ -110,9 +102,6 @@ extern void exchange_tids(struct task_struct *task, struct task_struct *old);
 extern void transfer_pid(struct task_struct *old, struct task_struct *new,
 			 enum pid_type);
 
-struct pid_namespace;
-extern struct pid_namespace init_pid_ns;
-
 extern int pid_max;
 extern int pid_max_min, pid_max_max;
 

include/linux/pid_types.h

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_PID_TYPES_H
+#define _LINUX_PID_TYPES_H
+
+enum pid_type {
+	PIDTYPE_PID,
+	PIDTYPE_TGID,
+	PIDTYPE_PGID,
+	PIDTYPE_SID,
+	PIDTYPE_MAX,
+};
+
+struct pid_namespace;
+extern struct pid_namespace init_pid_ns;
+
+#endif /* _LINUX_PID_TYPES_H */

include/linux/sched.h

@@ -11,7 +11,7 @@
 
 #include <asm/current.h>
 
-#include <linux/pid.h>
+#include <linux/pid_types.h>
 #include <linux/sem.h>
 #include <linux/shm.h>
 #include <linux/kmsan_types.h>

include/linux/seccomp.h

@@ -126,6 +126,8 @@ static inline long seccomp_get_metadata(struct task_struct *task,
 
 #ifdef CONFIG_SECCOMP_CACHE_DEBUG
 struct seq_file;
+struct pid_namespace;
+struct pid;
 
 int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns,
 			   struct pid *pid, struct task_struct *task);