Re: Bug 220102 - struct taskstats breaks backward compatibility since version 15

[Boian Bonev]

On Sat, 2025-05-10 at 13:23 -0700, Andrew Morton wrote:
> > > > https://bugzilla.kernel.org/show_bug.cgi?id=220102
> > 
> > My patch was attached in the bugzilla above.
> 
> We barely use bugzilla at all for kernel development.  I think I wish
> that kernel bugzilla was simply shut down, replaced with a page to
> help people to email their bug reports.

I am not sure if my patch is up to standards, PFA

> 
> > I also see that Wang Yaxin
> > <wang.yaxin@xxxxxxxxxx> has already sent a different but working
> > patch...
> 
> Cool.  Except I cannot find that patch.  Help?

That one was on email.
diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h
index 95762232e018..7f169c65b16e 100644
--- a/include/uapi/linux/taskstats.h
+++ b/include/uapi/linux/taskstats.h
@@ -34,7 +34,7 @@
  */
 
 
-#define TASKSTATS_VERSION	15
+#define TASKSTATS_VERSION	16
 #define TS_COMM_LEN		32	/* should be >= TASK_COMM_LEN
 					 * in linux/sched.h */
 
@@ -72,8 +72,6 @@ struct taskstats {
 	 */
 	__u64	cpu_count __attribute__((aligned(8)));
 	__u64	cpu_delay_total;
-	__u64	cpu_delay_max;
-	__u64	cpu_delay_min;
 
 	/* Following four fields atomically updated using task->delays->lock */
 
@@ -82,14 +80,10 @@ struct taskstats {
 	 */
 	__u64	blkio_count;
 	__u64	blkio_delay_total;
-	__u64	blkio_delay_max;
-	__u64	blkio_delay_min;
 
 	/* Delay waiting for page fault I/O (swap in only) */
 	__u64	swapin_count;
 	__u64	swapin_delay_total;
-	__u64	swapin_delay_max;
-	__u64	swapin_delay_min;
 
 	/* cpu "wall-clock" running time
 	 * On some architectures, value will adjust for cpu time stolen
@@ -161,8 +155,8 @@ struct taskstats {
 	__u64	write_bytes;		/* bytes of write I/O */
 	__u64	cancelled_write_bytes;	/* bytes of cancelled write I/O */
 
-	__u64  nvcsw;			/* voluntary_ctxt_switches */
-	__u64  nivcsw;			/* nonvoluntary_ctxt_switches */
+	__u64   nvcsw;			/* voluntary_ctxt_switches */
+	__u64   nivcsw;			/* nonvoluntary_ctxt_switches */
 
 	/* time accounting for SMT machines */
 	__u64	ac_utimescaled;		/* utime scaled on frequency etc */
@@ -172,14 +166,10 @@ struct taskstats {
 	/* Delay waiting for memory reclaim */
 	__u64	freepages_count;
 	__u64	freepages_delay_total;
-	__u64	freepages_delay_max;
-	__u64	freepages_delay_min;
 
 	/* Delay waiting for thrashing page */
 	__u64	thrashing_count;
 	__u64	thrashing_delay_total;
-	__u64	thrashing_delay_max;
-	__u64	thrashing_delay_min;
 
 	/* v10: 64-bit btime to avoid overflow */
 	__u64	ac_btime64;		/* 64-bit begin time */
@@ -187,8 +177,6 @@ struct taskstats {
 	/* v11: Delay waiting for memory compact */
 	__u64	compact_count;
 	__u64	compact_delay_total;
-	__u64	compact_delay_max;
-	__u64	compact_delay_min;
 
 	/* v12 begin */
 	__u32   ac_tgid;	/* thread group ID */
@@ -208,17 +196,30 @@ struct taskstats {
 	/* v12 end */
 
 	/* v13: Delay waiting for write-protect copy */
-	__u64    wpcopy_count;
-	__u64    wpcopy_delay_total;
-	__u64    wpcopy_delay_max;
-	__u64    wpcopy_delay_min;
+	__u64   wpcopy_count;
+	__u64   wpcopy_delay_total;
 
 	/* v14: Delay waiting for IRQ/SOFTIRQ */
-	__u64    irq_count;
-	__u64    irq_delay_total;
-	__u64    irq_delay_max;
-	__u64    irq_delay_min;
-	/* v15: add Delay max */
+	__u64   irq_count;
+	__u64   irq_delay_total;
+	/* v15: broken compatibility */
+	/* v16: add Delay min/max */
+	__u64	cpu_delay_min;
+	__u64	cpu_delay_max;
+	__u64	blkio_delay_min;
+	__u64	blkio_delay_max;
+	__u64	swapin_delay_min;
+	__u64	swapin_delay_max;
+	__u64	freepages_delay_min;
+	__u64	freepages_delay_max;
+	__u64	thrashing_delay_min;
+	__u64	thrashing_delay_max;
+	__u64	compact_delay_min;
+	__u64	compact_delay_max;
+	__u64   wpcopy_delay_min;
+	__u64   wpcopy_delay_max;
+	__u64   irq_delay_min;
+	__u64   irq_delay_max;
 };