delayacct: fix incomplete disable operation when switch enable to disable

When a task is created after delayacct is enabled, kernel will do all
the delay accountings for that task.  The problems is if user disables
delayacct by set /proc/sys/kernel/task_delayacct to zero, only blkio
delay accounting is disabled.

Now disable all the kinds of delay accountings when
/proc/sys/kernel/task_delayacct sets to zero.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Yang Yang <[email protected]>
Reported-by: Zeal Robot <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: yangyang20220519

include/linux/delayacct.h

@@ -131,36 +131,54 @@ static inline __u64 delayacct_blkio_ticks(struct task_struct *tsk)
 
 static inline void delayacct_freepages_start(void)
 {
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
 	if (current->delays)
 		__delayacct_freepages_start();
 }
 
 static inline void delayacct_freepages_end(void)
 {
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
 	if (current->delays)
 		__delayacct_freepages_end();
 }
 
 static inline void delayacct_thrashing_start(void)
 {
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
 	if (current->delays)
 		__delayacct_thrashing_start();
 }
 
 static inline void delayacct_thrashing_end(void)
 {
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
 	if (current->delays)
 		__delayacct_thrashing_end();
 }
 
 static inline void delayacct_swapin_start(void)
 {
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
 	if (current->delays)
 		__delayacct_swapin_start();
 }
 
 static inline void delayacct_swapin_end(void)
 {
+	if (!static_branch_unlikely(&delayacct_key))
+		return;
+
 	if (current->delays)
 		__delayacct_swapin_end();
 }