[PATCH 3/6] prctl: introduce PR_THP_POLICY_SYSTEM for the process

[Usama Arif <usamaarif642@gmail.com>]

This is set via the new PR_SET_THP_POLICY prctl.
This will clear both the MMF2_THP_VMA_DEFAULT_NOHUGE and
MMF2_THP_VMA_DEFAULT_HUGE process flags which will make
the VMA behaviour of the process the same as system.

Signed-off-by: Usama Arif <usamaarif642@gmail.com>
---
 include/uapi/linux/prctl.h                         | 1 +
 kernel/sys.c                                       | 6 ++++++
 tools/include/uapi/linux/prctl.h                   | 1 +
 tools/perf/trace/beauty/include/uapi/linux/prctl.h | 1 +
 4 files changed, 9 insertions(+)

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index d25458f4db9e..340d5ff769a9 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -368,5 +368,6 @@ struct prctl_mm_map {
 #define PR_GET_THP_POLICY		79
 #define PR_THP_POLICY_DEFAULT_HUGE	0
 #define PR_THP_POLICY_DEFAULT_NOHUGE	1
+#define PR_THP_POLICY_SYSTEM		2
 
 #endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index d91203e6dd0d..d556cdea97c4 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2665,6 +2665,8 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			error = PR_THP_POLICY_DEFAULT_HUGE;
 		else if (!!test_bit(MMF2_THP_VMA_DEFAULT_NOHUGE, &me->mm->flags2))
 			error = PR_THP_POLICY_DEFAULT_NOHUGE;
+		else
+			error = PR_THP_POLICY_SYSTEM;
 		break;
 	case PR_SET_THP_POLICY:
 		if (arg3 || arg4 || arg5)
@@ -2682,6 +2684,10 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 			set_bit(MMF2_THP_VMA_DEFAULT_NOHUGE, &me->mm->flags2);
 			process_vmas_thp_default_nohuge(me->mm);
 			break;
+		case PR_THP_POLICY_SYSTEM:
+			clear_bit(MMF2_THP_VMA_DEFAULT_HUGE, &me->mm->flags2);
+			clear_bit(MMF2_THP_VMA_DEFAULT_NOHUGE, &me->mm->flags2);
+			break;
 		default:
 			return -EINVAL;
 		}
diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h
index e03d0ed890c5..cc209c9a8afb 100644
--- a/tools/include/uapi/linux/prctl.h
+++ b/tools/include/uapi/linux/prctl.h
@@ -332,5 +332,6 @@ struct prctl_mm_map {
 #define PR_GET_THP_POLICY		79
 #define PR_THP_POLICY_DEFAULT_HUGE	0
 #define PR_THP_POLICY_DEFAULT_NOHUGE	1
+#define PR_THP_POLICY_SYSTEM		2
 
 #endif /* _LINUX_PRCTL_H */
diff --git a/tools/perf/trace/beauty/include/uapi/linux/prctl.h b/tools/perf/trace/beauty/include/uapi/linux/prctl.h
index d25458f4db9e..340d5ff769a9 100644
--- a/tools/perf/trace/beauty/include/uapi/linux/prctl.h
+++ b/tools/perf/trace/beauty/include/uapi/linux/prctl.h
@@ -368,5 +368,6 @@ struct prctl_mm_map {
 #define PR_GET_THP_POLICY		79
 #define PR_THP_POLICY_DEFAULT_HUGE	0
 #define PR_THP_POLICY_DEFAULT_NOHUGE	1
+#define PR_THP_POLICY_SYSTEM		2
 
 #endif /* _LINUX_PRCTL_H */
-- 
2.47.1