[PATCH] writeback: expose cgroup info in trace_writeback_pages_written()

[Yafang Shao]

With cgroup v2 writeback, we can know these pages are written from which
cgroup.
So expose the cgroup_ino for better tracking.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 fs/fs-writeback.c                | 4 ++--
 include/trace/events/writeback.h | 9 ++++++---
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 36855c1..e98a33e 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1973,7 +1973,7 @@ void wb_workfn(struct work_struct *work)
 		 */
 		do {
 			pages_written = wb_do_writeback(wb);
-			trace_writeback_pages_written(pages_written);
+			trace_writeback_pages_written(wb, pages_written);
 		} while (!list_empty(&wb->work_list));
 	} else {
 		/*
@@ -1983,7 +1983,7 @@ void wb_workfn(struct work_struct *work)
 		 */
 		pages_written = writeback_inodes_wb(wb, 1024,
 						    WB_REASON_FORKER_THREAD);
-		trace_writeback_pages_written(pages_written);
+		trace_writeback_pages_written(wb, pages_written);
 	}
 
 	if (!list_empty(&wb->work_list))
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 32db72c..a806713 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -255,15 +255,18 @@ static inline unsigned int __trace_wbc_assign_cgroup(struct writeback_control *w
 DEFINE_WRITEBACK_WORK_EVENT(writeback_wait);
 
 TRACE_EVENT(writeback_pages_written,
-	TP_PROTO(long pages_written),
-	TP_ARGS(pages_written),
+	TP_PROTO(struct bdi_writeback *wb, long pages_written),
+	TP_ARGS(wb, pages_written),
 	TP_STRUCT__entry(
 		__field(long,		pages)
+		__field(unsigned int,	cgroup_ino)
 	),
 	TP_fast_assign(
 		__entry->pages		= pages_written;
+		__entry->cgroup_ino	= __trace_wb_assign_cgroup(wb);
 	),
-	TP_printk("%ld", __entry->pages)
+	TP_printk("pages=%ld cgroup_ino=%u",
+		   __entry->pages, __entry->cgroup_ino)
 );
 
 DECLARE_EVENT_CLASS(writeback_class,
-- 
1.8.3.1