sched/headers: Move in_vfork() from <linux/sched.h> to <linux/sched/mm.h>

The in_vfork() function deals with task->mm, so it better belongs
into <linux/sched/mm.h>.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -1242,32 +1242,6 @@ static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
 #define TNF_FAULT_LOCAL	0x08
 #define TNF_MIGRATE_FAIL 0x10
 
-static inline bool in_vfork(struct task_struct *tsk)
-{
-	bool ret;
-
-	/*
-	 * need RCU to access ->real_parent if CLONE_VM was used along with
-	 * CLONE_PARENT.
-	 *
-	 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
-	 * imply CLONE_VM
-	 *
-	 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
-	 * ->real_parent is not necessarily the task doing vfork(), so in
-	 * theory we can't rely on task_lock() if we want to dereference it.
-	 *
-	 * And in this case we can't trust the real_parent->mm == tsk->mm
-	 * check, it can be false negative. But we do not care, if init or
-	 * another oom-unkillable task does this it should blame itself.
-	 */
-	rcu_read_lock();
-	ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
-	rcu_read_unlock();
-
-	return ret;
-}
-
 #ifdef CONFIG_NUMA_BALANCING
 extern void task_numa_fault(int last_node, int node, int pages, int flags);
 extern pid_t task_numa_group_id(struct task_struct *p);

include/linux/sched/mm.h

@@ -121,4 +121,30 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
 #endif
 
+static inline bool in_vfork(struct task_struct *tsk)
+{
+	bool ret;
+
+	/*
+	 * need RCU to access ->real_parent if CLONE_VM was used along with
+	 * CLONE_PARENT.
+	 *
+	 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
+	 * imply CLONE_VM
+	 *
+	 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
+	 * ->real_parent is not necessarily the task doing vfork(), so in
+	 * theory we can't rely on task_lock() if we want to dereference it.
+	 *
+	 * And in this case we can't trust the real_parent->mm == tsk->mm
+	 * check, it can be false negative. But we do not care, if init or
+	 * another oom-unkillable task does this it should blame itself.
+	 */
+	rcu_read_lock();
+	ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
+	rcu_read_unlock();
+
+	return ret;
+}
+
 #endif /* _LINUX_SCHED_MM_H */