[patch v12 13/13] task isolation: only TIF_TASK_ISOL if task isolation is enabled

[Marcelo Tosatti <mtosatti@redhat.com>]

This avoids processing of TIF_TASK_ISOL, when returning to userspace,
for tasks which do not have task isolation configured.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: linux-2.6/include/linux/task_isolation.h
===================================================================
--- linux-2.6.orig/include/linux/task_isolation.h
+++ linux-2.6/include/linux/task_isolation.h
@@ -5,6 +5,8 @@
 
 #ifdef CONFIG_TASK_ISOLATION
 
+#include <uapi/linux/prctl.h>
+
 struct task_isol_info {
 	/* Which features have been configured */
 	u64 conf_mask;
@@ -51,6 +53,24 @@ int __copy_task_isol(struct task_struct
 
 void task_isol_exit_to_user_mode(void);
 
+static inline bool task_isol_quiesce_activated(struct task_struct *tsk,
+					       u64 quiesce_mask)
+{
+	struct task_isol_info *i;
+
+	i = tsk->task_isol_info;
+	if (!i)
+		return false;
+
+	if (i->active_mask != ISOL_F_QUIESCE)
+		return false;
+
+	if ((i->quiesce_mask & quiesce_mask) == quiesce_mask)
+		return true;
+
+	return false;
+}
+
 #else
 
 static inline void task_isol_exit_to_user_mode(void)
@@ -105,6 +125,12 @@ static inline int prctl_task_isol_activa
 	return -EOPNOTSUPP;
 }
 
+static inline bool task_isol_quiesce_activated(struct task_struct *tsk,
+					       u64 quiesce_mask)
+{
+	return false;
+}
+
 #endif /* CONFIG_TASK_ISOLATION */
 
 #endif /* __LINUX_TASK_ISOL_H */
Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c
+++ linux-2.6/mm/vmstat.c
@@ -28,6 +28,7 @@
 #include <linux/mm_inline.h>
 #include <linux/page_ext.h>
 #include <linux/page_owner.h>
+#include <linux/task_isolation.h>
 
 #include "internal.h"
 
@@ -344,7 +345,8 @@ static inline void mark_vmstat_dirty(voi
 		return;
 
 	raw_cpu_write(vmstat_dirty, true);
-	set_thread_flag(TIF_TASK_ISOL);
+	if (task_isol_quiesce_activated(current, ISOL_F_QUIESCE_VMSTATS))
+		set_thread_flag(TIF_TASK_ISOL);
 }
 
 void init_sync_vmstat(void)