lib/vdso: Make __arch_update_vdso_data() logic understandable

The function name suggests that this is a boolean checking whether the
architecture asks for an update of the VDSO data, but it works the other
way round. To spare further confusion invert the logic.

Fixes: 44f57d78 ("timekeeping: Provide a generic update_vsyscall() implementation")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200114185946.656652824@linutronix.de

arch/arm/include/asm/vdso/vsyscall.h

@@ -34,9 +34,9 @@ struct vdso_data *__arm_get_k_vdso_data(void)
 #define __arch_get_k_vdso_data __arm_get_k_vdso_data
 
 static __always_inline
-int __arm_update_vdso_data(void)
+bool __arm_update_vdso_data(void)
 {
-	return !cntvct_ok;
+	return cntvct_ok;
 }
 #define __arch_update_vdso_data __arm_update_vdso_data
 

include/asm-generic/vdso/vsyscall.h

@@ -12,9 +12,9 @@ static __always_inline struct vdso_data *__arch_get_k_vdso_data(void)
 #endif /* __arch_get_k_vdso_data */
 
 #ifndef __arch_update_vdso_data
-static __always_inline int __arch_update_vdso_data(void)
+static __always_inline bool __arch_update_vdso_data(void)
 {
-	return 0;
+	return true;
 }
 #endif /* __arch_update_vdso_data */
 

kernel/time/vsyscall.c

@@ -84,7 +84,7 @@ void update_vsyscall(struct timekeeper *tk)
 	struct vdso_timestamp *vdso_ts;
 	u64 nsec;
 
-	if (__arch_update_vdso_data()) {
+	if (!__arch_update_vdso_data()) {
 		/*
 		 * Some architectures might want to skip the update of the
 		 * data page.