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/20211123140342.32962-1-ran.xiaokai@zte.com.cnSigned-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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();
 }