time/namespace: Prepare introduction of struct vdso_clock

To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.

To prepare for the rework of the data structures, replace the struct
vdso_time_data pointer with a struct vdso_clock pointer where applicable.

No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-14-c1b5c69a166f@linutronix.de

Author: anna-marialx

kernel/time/namespace.c

@@ -165,26 +165,26 @@ static struct timens_offset offset_from_ts(struct timespec64 off)
  *     HVCLOCK
  *     VVAR
  *
- * The check for vdso_time_data->clock_mode is in the unlikely path of
+ * The check for vdso_clock->clock_mode is in the unlikely path of
  * the seq begin magic. So for the non-timens case most of the time
  * 'seq' is even, so the branch is not taken.
  *
  * If 'seq' is odd, i.e. a concurrent update is in progress, the extra check
- * for vdso_time_data->clock_mode is a non-issue. The task is spin waiting for the
+ * for vdso_clock->clock_mode is a non-issue. The task is spin waiting for the
  * update to finish and for 'seq' to become even anyway.
  *
- * Timens page has vdso_time_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which
+ * Timens page has vdso_clock->clock_mode set to VDSO_CLOCKMODE_TIMENS which
  * enforces the time namespace handling path.
  */
-static void timens_setup_vdso_clock_data(struct vdso_time_data *vdata,
+static void timens_setup_vdso_clock_data(struct vdso_clock *vc,
 					 struct time_namespace *ns)
 {
-	struct timens_offset *offset = vdata->offset;
+	struct timens_offset *offset = vc->offset;
 	struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic);
 	struct timens_offset boottime = offset_from_ts(ns->offsets.boottime);
 
-	vdata->seq			= 1;
-	vdata->clock_mode		= VDSO_CLOCKMODE_TIMENS;
+	vc->seq				= 1;
+	vc->clock_mode			= VDSO_CLOCKMODE_TIMENS;
 	offset[CLOCK_MONOTONIC]		= monotonic;
 	offset[CLOCK_MONOTONIC_RAW]	= monotonic;
 	offset[CLOCK_MONOTONIC_COARSE]	= monotonic;
@@ -220,6 +220,7 @@ static void timens_set_vvar_page(struct task_struct *task,
 				struct time_namespace *ns)
 {
 	struct vdso_time_data *vdata;
+	struct vdso_clock *vc;
 	unsigned int i;
 
 	if (ns == &init_time_ns)
@@ -236,9 +237,10 @@ static void timens_set_vvar_page(struct task_struct *task,
 
 	ns->frozen_offsets = true;
 	vdata = page_address(ns->vvar_page);
+	vc = vdata;
 
 	for (i = 0; i < CS_BASES; i++)
-		timens_setup_vdso_clock_data(&vdata[i], ns);
+		timens_setup_vdso_clock_data(&vc[i], ns);
 
 out:
 	mutex_unlock(&offset_lock);